NON-METALLIC FERROMAGNETIC MATERIALS AND DEVICES -- DR. NATHAN SCHVARTZ WADC TR 57-123

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• Collection: General CIA Records
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• Document Page Count: 76
• Document Creation Date: December 23, 2016
• Document Release Date: February 5, 2014
• Sequence Number: 3
• Publication Date: October 10, 1958
• Content Type: REPORT

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NONMETALLIC FERROMAGNETIC
MATERIALS AND DEVICES
JOHN M. BLANK
ROBERT W. JOHNSTON
HAROLD IV KATZ
GERALD G. PALMER
NATHAN SCHWARTZ
GENERAL ELECTRIC COMPANY
OCTOBER 1957
WRIGHT AIR DEVELOPMENT CENTER
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ABSTRACT
This report covers research and development performed on the
study of nonmetallic ferromagnetic materials and devices by the Electronics
Laboratory of the General Electric Company during the contract period.
The work presented in this report describes the effort expended
in the various areas of ferrite development covered by the subject contract.
These areas include the development of ferrite materials for high power
applications, low signal applications, and dynamic magnetostrictive appli-
cations for operation in the temperature range -65?C to +250?C; and a high
frequency, narrow band (30 mc) modulated delay line.
PUBLICATION REVIEW
?
The publication of this report does not constitute approval by,
the Air Force of the findings or conclusions contained herein. It is pub-
lished only for the exchange and stimulation of ideas.
ill
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4.1
TABLE OF CONTENTS
Section
Page
I
INTRODUCTION
1
II
MATT3RIALSFOR HIGH PMER APPLICATIONS
3
Objective
3
Approach
3
Compositions and Materials Preparation
5
Magnetic Evaluation
6
Compositional Control
21
Domain Wall Relaxation and Dispersion
26
Conclusions and Recommendations
39
III
MATERIALS FOR LOW SIGNAL APPLICATIONS
40
Objective
40
Approach
40
Ferrite Compositions
41
Results of Magnetic Evaluation
142
Processing of Low Loss, Low Signal Ferrites
55
Low Temperature Evaluation
65
Differential Thermal Analysis. . .
75
Conclusions and Recommendations
88
IV
HIGH FREQUENCY NARROW BAND MODULATED DELAY LINES
89
Introduction
89
Objective
89
General Considerations
90
Materials Preparation and Initial Evaluation
90
Testing of Delay-Lines
93
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Section
TABLE OF CONTENTS (Contd)
and Recommendations
MATERIALS AND APPLICATIONS
Page
Figure
LIST OF ILLUSTRATIONS
High Frequency Hysteresigraph
B-H Curves for Toroid 704 F 158-1SB
Page
112
114
7
8
V
Conclusions
MAGNETOSTRICTIVE
1
2
Objective
114
3
B-H Curves - Toroid 704 F 158-1SB 25?C in water; 25?C
in Air
9
Material Parameters
114
4
B-H Curves - Toroid 704 F 158-1SB 25?C in Air;
The Equivalent Circuit of a Freely Vibrating Sample.
250?C in Air
10
Method of Measurement
117
5
B-H Curves - Toroid 704 F 158-1SB 25?C in Water;
250?C in Air
11
Materials
120
Results of Measurements
120
6
B-H Curves - Toroid 704 F 158-1SB -65?C in Air;
250?C in Air
12
Conclusions and Recommendations
129
7
B-H Curves - Toroid 590 F 114-2
25?C in Water; 25?C in Air
13
VI
CONCLUSIONS
130
-8
B-H Curves - Toroid 690 F 114-2
Bibliography
25?C in Water; 250?C in Air
14
Distribution List
9
B-H Curves - Toroid 690 F 114-2
25?C in Air; 250?C in Air
15
Io
B-H Curves - Toroid 690 F 114-2
-65?C in Air; 250?C in Air
16
11
B-H Curves - Toroid 723 F 189-1
25?C in Water; 250?C in Air
17
12
B-H Curves - Toroid 723 F 189-1
-65?C in Air; 250?C in Air
18
13
B-H Curves - Toroid 724 F 188-1
25?C in Water; 250?C in Air
19
14
Core Loss in Watts/cm3 for Toroid 704 F 158-1SB
as Function of Bmax with Frequency as Parameter . ? ? ?
22
15
Core Loss in Ergs/cm3 per cycle for Toroid 704 F 158-1SB
as Function of Bmax with Frequency as Parameter . . . .
22
16
Core Loss in Ergs/cm3 per cycle for Toroid 704 F 158-1SB
as Function of Frequency with Bmax as Parameter . . .
23
vi
17
Permeability of Toroid 704 F 158-1SB as Function of
Frequency with Bmax as Parameter
23
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LIST OF ILLUSTRATIONS (Contd)
Figure
18 Composition 704. B for H = 1 Oersted vs.
Fe2+ Content by Analysis
19 Typical Dispersion Curves at Two Values of H
20 Dispersion Curves at H = 0.7 Oersteds and H = 1.4 Oersteds
,21 Dispersion Curves at H = 0.7 Oersteds and H = 1.4 Oersteds
22 Dispersion Curves at H = 0.7 Oersteds and H = 1.4 Oersteds
23 Dispersion Curves at H = 0.7 Oersteds and H = 1.4 Oersteds 36
24 Dispersion Curves for Toroid 704 F 158-1SB in water at
25?C
30
33
34
35
25 Dispersion Curves for Toroid 730A F 245-1 in water at
25?C
26 Temperature Variation of ? and Q for Toroid 67.52.
f = 1.5 mc
27 Temperature Variation of g and Q for Toroid 67.24.
f = 1.5 mc
28 Temperature Variation of ? and Q for Toroid 67.54.
fl= 1.5 mc
29 Temperature Variation of ? and Q for Toroid 84.7.
f = 1.5 mc
30 Temperature Variation of ? and Q for Toroid 84.11.
f = 1.5 mc
31 Dependence of Permeability
32 Frequency Spectrum of Qt
and Material Q on Driving Field
for Selected Samples
33 Frequency Spectrum of Initial Permeability
34 Frequency Spectrum of p.Q for Two Selected Samples ? ? ? ?
35 Initial Permeability, Q, and ?Q vs. Calcine Temperature ?
36 ?Q vs. Rise Rate
37 ?Q and g vs. Ramming Pressure for Composition 84
38 ?Q vs. Ramming Pressure for Composition 84
viii
37
38
45
46
47
48.
49
51
52
53
54
56
62
63
64
LIST OF ILLUSTRATIONS (Contd)
Figure
Block Diagram of Cryostat
Photograph of Cryostat
Photograph of Equipment Used in Conjunction with Cryostat
Block Diagram of Circuit Used to Determine Initial Permea-
Page.
39
4o
41
42
67
69
70
bility and Q
71
43
Series and Parallel Equivalent Circuits of Coil
73
44
Permeability vs. Temperature for Toroid .75HQ67.23 . ? ?
74
45
DTA Furnace
77
46
Fire Brick Door Carrying Sample Holders
78
47
Differential Thermograms
80
48
Schematic Diagram of DTA Furnace No. 3
82
49
DTA Test Sample Arrangement
84
50
DTA. Composition 84 vs. A1203
85
51
DTA Furnace Assembly
86
52
Temperature and Differential Temperature Recorders for DTA
87
53
Permeameter Schematic for ? vs. Bias
91
54
Permeability vs. Driving Field for Sample .75HQ84.10 .
92
55
Ferrite Delay Line
94
56
Ferrite Delay Line Mounted in Ferrite Yoke
96
57
Block Diagram for Modulated Delay Evaluation
97
58
Time Delay vs. Frequency for Ferrite Delay Line with
Various Biasing Fields
98
59
Block Diagram for Visual Presentation
99
60
Time Delay vs. Frequency for Delay Lines Patched with
Indium Amalgam. Lines III and IV
102
61
Change in Delay vs. D.C. Modulation Current. Line V. ? ?
103
62
Change in Delay vs. D.C. Modulation Current at 10 mc.
Line VII
105
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Z:$
Figure
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LIST OF ILLUSTRATIONS (Contd)
Variation in RF Output Amplitude vs. Variation in Time
Delay at 10 mc. Line VII
64 Change in Delay vs. D.C. Modulation Current with Tempera-
ture as Parameter. Line VIII
65 Change in Delay vs. D.C. Modulation Current
66 change in Delay vs. D.C. Modulation Current
67 Photograph of Modulated Delay Line
68 Equivalent Circuit of Freely Vibrating Sample
69 Circuit for Measuring fa, f, Za and Zr for Sample at a
Given Magnetic Operating Point
70 Magnetizing and Demagnetizing Sources
71 Voltage vs. Frequency for a Magnetically Driven Vibrating
Toroidal Sample
72 Voltage vs. Frequency for Sample 285.38 Vibrating Radially
with Remanent Flux as Parameter
73
74
75
76
Temperature Variation of Er and fa for Toroid 285.38 .
Temperature Variation of fr and fa for Toroid 285.52 . .
106
118
119
121
122
125
126
Variation of fr, fa and k with Bias Current for Toroid 285.52 121
Voltage-Frequency Characteristic for Tol.oid 285.56 . . .
.
Table
1
2
3
4
5
6
7
8
9
lo
LIST OF TABLES
Mol% Fe304 calculated from ferrous iron analysis in
solution withComposition 164 ferrite at several
temperatures during cooling from 1400?C at 100?C
per hour
Description of Compositions used in the development of
high power ferrites
Effect of firing time and temperature
Composition: 48 mol% Fe2O3, 25 mok%1
0.5 moll% v205
Description of
applications
on magnetic Q.
Zn0, 26.5 mol% NiO,
ferrite compositions for low signal
Effect of high
and 84
humidity on p. and Q for Compositions 67
Effect of high
84.11
Description of
humidity on permeability and Q of Toroid
compositions
Processing of test bodies for low signal applications
Effect of calcination temperature on shrinkage, go, and Q
Toroids fired at 1100?C for 10 minutes
Effect of 0.5 mol% vanadium pentoxide for 10 minute firing
at 1100?C
128 11
12
Magnetic Properties of Composition No. 84 prepared with
different iron oxides
Compamison of brands and effects of heating and cooling
rates on Composition No. 84
13
Effect of ramming pressure on tie and Q
14
Effect of rise rates on tie and Q
15
Comparison of air and oxygen atmosphere firings
16
Physical characteristics of delay lines
17
Magnetic and electrical evaluation of delay lines
?
?
? ?
18
Test information for Line No. 10A
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57
59
60
61
61
66
100
101
107
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LIST OF TABLES (Contd)
Table
19 Delay line fabrication data 109
20 Resonant frequency, fe,; electrostatic modulation, E;
electromechanical couaing coefficient, k; and observed
mechanical Q, Qm, for Composition 285 and processing
treatment as indicated . . q 123
Page
4
SECTION I
INTRODUCTION
This report is being submitted as a summary of the effort ex-
pended to date under Contract No. AF 33(616)-3339. The objectives of the
investigation carried out during the present contract period are:
1. To develop ferrite materials for applications in the temperature
range -65?C to +250?C.
2. To develop a narrow band, high frequency ferrite delay line, the
delay of which can be varied by a biasing magnetic field.
Under objective 1 above, the specific types of materials to be
considered are:
a. Materials for high power applications in the frequency range
20 kc to 1000 kc.
b. Materials for low signal applications with high ?Q product,
low temperature coefficient of permeability, and whose
characteristics are not affected by prolonged exposure to
high humidity.
c. Materials for magnetos trictive applications. Such materials
are to be suitable for use in filters and oscillators over
the frequency range 455 kc to 1000 kc, and have a maximum
temperature coefficient of resonant frequency of 10 ppm per
C? over the temperature range of interest.
Under objective 2, the present goal is to achieve a total delay
of approximately 0.5 microseconds in a line of reasonable length (3 inches)
and a change in delay of 0.1 microseconds at 30 mc.
Section II of this report covers the work on the development of
materials for high power application. In this section, the processing and
methods of compositional control are described for materials of this type.
The choice of materials is governed by the high temperature requirements.
The anticipated operating frequency range is such that a study of the dis-
persion in high signal permeability of these materials forma a basic as-
pect of the problem. Atmosphere conditions during firing are used as a
compositional control agency. Superior transformer materials require a
high degree of homogeneity throughout the volume of the material in a given
configuration. Also, atmosphere firing conditions help determine the ul-
timate cation distribution and the valence state of the.iron ions in the
material. The percentage Fe'+ ions incorporated in the final composition
determines to a great extent the shape of the hysteresis loop, the coercive
force and the ultimate high signal permeability. Detailed discussion of
Manuscript released by the author 1 Aar 1957 for publication as a
WADC Technical Report
1
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these various aspects of the overall problem are given and recommendations
are made for producing the most satisfactory material in the present ferrite
system of interest.
Section III covers the work on the development of materials for
low signal applications. The broad objectives of this program were such
to give considerable latitude to the type of investigation. The results
of this work indicate that a series of materials for low Signal applica-
tions can be obtained with low loss and perform satisfactorily over the
temperature range of interest, -65?C to +250?C. Data are presented which
show the results of measurement at temperatures as low as -175?C. The
significant successes of this broad development were: (1) The fabrica-
tion of materials with high ?Q products, and (2) The development of
materials with low temperature coefficient of permeability in the tempera-
ture interval -65?C to +25?C.
In the course of the current development, differential thermal
analysis (DTA) was applied to the binder burnoff problem and carried into
the temperature region of calcining and sintering.
A further important conclusion from this work resulted from ob-
servations made on ferrite systems in which various sources of iron oxide
are used in the fabrication procedure. The difference in impurity content
among these various sources of tron oxide affect the ultimate magnetic
properties of these low fired, partially sintered materials. The results
of these various investigations, the processing of the various significant
compositions and the magnetic evaluation are presented in Section III.
Section IV of this report covers the work on the development of
a modulated ferrite delay line. The initial objective of a 30 mc line
with a +0.1 variation in delay has not been achieved. However, a com-
pletely satisfactory 10 mc line has been developed which exhibits suffic-
ient time delay variation for the intended application. The processing
of the necessary materials and the method of line construction are described
in detail in Section IV.
Section V contains the work performed in the investigation of
ferrite materials for magnetostrictive applications. No large effort was
expended on this project because of the overriding importance of other
phases included in the total effort. However, the tentative conclusion
is that the desired coefficient of resonant frequency, 10 parts per million
per degree centigrade, cannot be obtained readily over the wide temperature
interval, -65?C to +250?C.
In Section VI a review is given of the important conclusions and
results derived from the investigations carried out in the areas of interest
included in the scope of Contract No. AF 33(616)-3339.
2
SECTION II
MATERIALS FOR HIGH POWER APPLICATIONS
Objective
The purpose of this development is to provide ferrite materials
having low losses at high flux density over the frequency range 20 kc to
1000 kc and over the temperature range -65?C to 250?C.
Approach
Previous work carried out at the Electronics Laboratory of the
General Electric Company in the field of ferrite materials for high power
applications led to the development of Composition 164, a 30-20 Ni-Zn fer-
rite. This work was described in WADC Technical Report TR-56-274, Part II.
The development of Composition 164 was an attempt to compromise
the many conflicting demands on a high temperature, high saturation, low
loss ferrite. This material consisted of 50 mol% Fe2031 30 mol% NiO, and
20 mol% ZnO, and represented a compromise among saturation magnetization,
exchange energy, and magnetocrystalline anisotropy.
When a composition is chosen, saturation magnetization, magneto-
crystalline anisotropy, exchange energy, and saturation magnetostriction
are essentially fixed, give or take a few percent depending on small changes
which vary with firing temperature and time, rate of cool, etc. These are
the properties which determine the energy per unit area of domain walls,
the density of magnetic poles at surfaces of magnetic discontinuity, the
direction of preferred magnetization and the ease or difficulty of rotating'
the direction of magnetization away from the preferred direction. The grain
size and shape, the density and size of defects such as inclusions, voids,
lamellar precipitates, and the conditions of internal stress are the seats
from which the above characteristics operate to determine magnetic response
in the hysteresis loop.
In the development reported here, the proposed scheme included
the introduction of magnetite into Composition 164 ferrite. This was
attractive for many reasons. Magnetite is known to form solid solutions
with nickel ferrite. It is reasonable to expect that magnetite will also
be soluble in Composition 164. Magnetite has a higher saturation magnetiza-
tion than nickel ferrite, so that the addition of magnetite to Composition
164 should increase the saturation magnetization. Since magnetite has a
positive magnetostriction and Composition 164 a negative magnetostriction,
the addition of magnetite should reduce the saturation magnetostriction of
the solution and thus raise the permeability. It should be remembered,
however, that magnetite has a much lower resistivity than nickel ferrite
and therefore may be detrimental to magnetic performance at frequencies
above 20 kc.
In proceeding with the planned approach, it was necessary to
learn how to add magnetite to Composition 164. Merely adding Reagent Grade
3
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magnetite to the other ingredients or to the calcine does not necessarily
accomplish the desired result. On heating, magnetite converts to ferric
oxide at about 500?C. Also, ferric oxide converts back to magnetite by
losing oxygen at higher temperatures.
The range of temperatures for which ferric oxide converts to
magnetite is lower than the sintering range of temperatures used in fabri-
cating high power ferrites. As a result, magnetite additions to Composi-
tion 164 can be achieved by simply adding ferric oxide in excess of the
amount needed to make the nickel-zinc portion of the solution. The prob-
lem does not end there. On cooling: the ferrite-magnetite solution accepts
oxygen and precipitates ferric oxide. Two things can be done to prevent
this. The solution can be cooled so quickly that the acceptance of oxygen
and the resulting precipitation will not have time to occur; or, the solu-
tion can be protected from oxidation by a protective atmosphere such as
nitrogen, argon, helium, carbon dioxide, or steam.
A preliminary experiment was carried out to determine the feasi-
bility of introducing magnetite by the method described above. A new
composition, Composition 690, was prepared containing
52.7 mol% Fe203
28.4 mol% NiO
18.9 mol% ZnO
which amounted to adding 5.4 mol% extra ferric oxide to Composition 164.
When converted, 5.4 mol% Fe203 makes 3.6 mol% Fe3041 magnetite.
Eight 1/4 inch cubes of this composition were placed in a tube
furnace and heated at 94?C per hour to 1400?C for 3 hours. One cube was
then withdrawn from the tube and quenched into water. The furnace was set
to cool 100?C per hour. Cubes were pulled and water quenched at about 50?C
intervals. These cubes were examined for precipitation of ferric oxide.
None showed precipitation. The cubes were then crushed and analyzed for
ferrous iron from which the magnetite content can be calculated. The re-
sults are shown in Table I.
TABLE I
MOL% Fe3O4 CALCULATED FROM FERROUS IRON ANALYSIS
IN SOLUTION WITH COMPOSITION 164 FERRITE AT SEVERAL
TEMPERATURES DURING COOLING FROM 1400?C at 100?C
PER HOUR
Temperature from
which quenched
Weight % Fe
by analysis
Mol% FeR04
calculated
1400?C
1350
1293
1250
1190
1150
1100
1045
1.13
1.13
0.81
0.81
0.81
1.19
0.95
0.91
5.1
5.1
3.8
3.8
3.8
5.4
4.3
4.1
4
f4,
The average for the series is 4.5 +0.7 mol% Fe304. It is clear
that this treatment produces the desired solution of magnetite in Composi-
tion 164. The control of the desired amount of magnetite leaves something
to be desired in that aiming for 3.6 mol%, a value closer to 4.5 mol% was
obtained. All the values are higher than anticipated. This was probably
due to the presence of a greater effective amount of extra Fe20.1 than in-
tended. It is not unlikely that ZnO is lost by volatilization during the
heat treatments, which would lead to a proportional increase of excess
iron.
Within the range of temperatures examined, there seemed to be no
tendency to take on oxygen as confirmed by the absence of precipitated Fe203.
Rapid cooling or atmosphere protection from 1000?C downward is adequate for
maintaining solid solution in this ferrite. Thus, this preliminary experi-
ment proved the feasibility of the method and served as a guide for prepara-
tion of the desired range of new compositions.
Compositions and Materials Preparation
Table II gives the ferrite compositions
investigations.
TABLE II
used in the course of the
DESCRIPTION OF COMPOSITIONS USED
IN THE DEVELOPMENT OF HIGH POWER FERRITES,
Composition
Mol% Fe203
Nol% NiO
Mol% ZnO
164
50.0
30.0
20.0
690
52.7
28.4
18.9
704
54.6
27.2
18.2
716
57.5
25.5
17.0
723
50.0
30.0
20.0
724
50.0
35.0
15.0
737
53.6
27.9
18.5
730A
52.7
28.4
18.9
731
51.2
29.3
19.5
These materials were prepared in accordance with standard ceramic
practice. The procedure in each case was as follows:
Reagent grade oxides were used. These materials satisfy the specifi-
cations set by the American Chemical Society for this classification.
The oxides were weighed with an accuracy of plus or minus 0.05
grams to make up a "batch" of total weight approximately equal to 2 kilograms.
The batch was ball milled for 16 hours in 3 liters af water in a
1 gallon size iron mill containing 10 pounds of 1" diameter steel balls and
15 pounds of 7/16n diameter steel balls. The slurry was separated from the
balls by screening. No additional water was added to thin the slurry and
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wash out the mill as the slurry when properly prepared did not separate
into a liquid and solid portion. The slurry was dried in pyrex trays at
90?C, and the dry .cake forced through a 10 mesh screen.
The entire batch was placed in a 2 x 5 x 10 inch mullite sagge.
box and calcined 3 hours at 900?C (variations in the calcine are indica ad
where appropriate in the body of the text.)
The calcined powder was ball milled for 15 hours in the same ball
mill as before with 1 liter of water per kilogram of powder. (Water may
be added after the milling operation to facilitate removing the slurry.)
Drying then followed in pyrex trays at 90?C after which the dried cake was
forced through a 10 mesh screen.
Polyvinyl alcohol was used as a binder being employed in a solu-
tion of 15 gm polyvinyl alcohol to 100 ml of water. The binder and powder
were blended using a mortar and pestle. It was convenient to blend binder
into at most 500 grams of powder at a time. Twenty milliliters of solution
were used for 100 grams of powder.
The blended powder was then forced through a 40 mesh screen and
pressed in toroid dies at 27,000 pounds per square inch pressure. The
toroids were dried overnight at 80?C.
The toroids were set on mullite tile coated with 1/8 inch of
Chemically Pure alumina powder. A typical sintering included a soak of 3
hours at 1400?C and a 129?C/hr rate of rise and rate of fall. The binder
burned off satisfactorily at the above rate of rise.
This procedure achieved a fired density of 5.10 to 5.20 gm/cm3
with negligible surface porosity.
Magnetic Evaluation
Below are given the results of magnetic measurements for selected
samples. Magnetization curves (B-H curves) are presented as functions of
frequency and temperature. Core loss in Composition 704 as a function of
maximum flux density and frequency is given for operation at 30?C.
Magnetization curves (B-H curves). Magnetization curves were
obtained using the high frequency hysteresigraph developed under Contract
No. AF 33(616)-2009 and reported in WADC Technical Report TR-56-274, Part VI.
Figure 1 is a photograph of the hysteresigraph in operation. The sample
for which the hysteresigram is shown on the oscilloscope is contained in
the Dewar flask which houses a -65?C air chamber. The magnetization data
at a given frequency were obtained by measuring the peak driving field for
a given maximum flux density. These maximum values were read from the
hysteresigraph display.
Magnetization curves are presented in Figures 2 through 13 for
samples of Compositions 704, 690, 723, and 724. A typical set of curves
with frequency of operation as parameter is shown in Figure 2 for toroid
704 F158-1SB (Composition 704). The data for Figure 2 were obtained with
the sam le in water at 30?C.
6
Figure 1. High Frequency Hysteresigraph
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7
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Figure 3. B-H Curves - Toroid 701i F 158-1SB 25?C in Water;
25?C in Air
9
STAT
STAT
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
in
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Figure 3. B-H Curves - Toroid 70h F 158-18B 25?C in Water;
25?C in Air
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9
STAT
STAT
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Figure 4. B-H Curves - Toroid 704 F 158-1SB 25?C in Air;
250?C in Air
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
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10
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figure 7. B-H Curves - Toroid 690 F 114-2 2500 in Water;
25?C in kir
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13
1,4
STAT
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
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LO 1.2
Figure 9. B-H Curves - Toroid 690 F 114-2 -65?C in
Air; 250?C in Air
1.5
STAT
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Declassified in Part - Sanitized Copy Approved for Release @ 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
)0
B-H CURVES
690F1 14 2
? --
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250?C
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Figure 11. B-H Curves - Toroid 723 F 189-1 25?C in Water; 250?C in Air
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Declassified in Part - Sanitized Copy Approved for Release @ 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
.f?
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B-H CURVES
723F189 - I
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Figure 13. B-H Curves - Toroid 724 F 188-1 25?C in Water; 250?C in Air
1 A
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STAT
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The data shown in Figures 3 through 13 were obtained in a series
of experiments carried out to determine the behavior of Compositions 690,
704, 723, and 724 which encompass a ZnO content from 15 mol% to 20 mol%
and a Fe203 content from 50 mol % to 54.6 mol%. The curves were obtained
by measuring the peak H values required to drive the test sample to peak
B values of 100, 300, 500, 700 and 1000 gauss at five frequencies, 50, 100,
200, 400 and 1000 kc.
Four different temperature situations were employed: (1) the
sample was immersed in water at 25?C in an effort to find the properties
of the sample at 25?C; (2) the sample was suspended in still air at 25?C
and allowed to reach a steady state temperature distribution in equilibrium
with the air; (3) the sample was suspended in a tube furnace in still air
at 250?C and allowed to reach steady state temperature distribution in
equilibrium with the air. The temperature rise above ambient may have been
as much as 100?C in the high loss situations; (4) the sample was suspended
in still air at -65?C and allowed to reach a steady state.
Further comment should be made regarding the low temperature
measurements. The low temperature chamber was a brass test tube immersed
in a methyl alcohol bath, the temperature of which was adjusted to keep
the temperature of the brass wall at -65?C +2?C. The bath consisted of
1500 cc of methyl alcohol in a Dewar flask. The bath was cooled to the
desired temperature with dry ice and had sufficient heat capacity to make
adjustments about -65?C an easy task when the test samples were dissipating
several watts. The magnetic samples were sealed in the brass tube (to
avoid air circulation) about 4 inches below the bath liquid surface. A
thermocouple was attached to the outside of the brass tube adjacent to the
sample. The bath was stirred manually. In this arrangement, the tempera-
ture of the ferrite was permitted to rise until its heat loss to the walls
reached steady state. At least one minute was allowed for this, although
the observable 'changes were accomplished in 30 seconds.
Core loss measurements. Hysteresis energy loss per unit volume
per cycle is defined by
e"
D?dli
with H varying from -Hmax to -fflmax around the closed
for computing the loss in watts per cubic centimeter
p= (1/4n)fABH x 10-7
where
f . frequency of operation in cps
A = area of hysteresis loop in cm2
B = scale factor, gauss/cm
11 . scale factor, oersted/cm
p . loss in watts/cm3
Via*,
-
20
loop. The formula
is
(1)
Figure 14 shows the loss in watts/cm3 for toroid 704 F 158-1SB
as a function of Bmax and frequency. The data for Figure 14 were obtained
with the sample immersed in water at 30?C. It is seen that the core
losses reach the maximum power output capacity of the hysteresigraph driver.
It is also of interest to express the losses in ergs/cm3 per cycle.
This representation As shown in Figure 1.1. The dependence of loss on B
ranges from (Bmax)1.? at 50 kc to (Bmax) at 400 kc.
To obtain the frequency dependence of loss, data from Figure 15
are replotted in Figure 16. Figure 16 shows loss in ergs/cm3 per cycle as
a function of frequency with Bmax as parameter. The frequency dependence
is geen to be approximately 0.35 at 100 gauss, f0'55 at 300 gauss, and
f?'' at 1000 gauss, considerably below an fl'? eddy current dependence.
Figure 17 is a graphic representation of several scattered experi-
mental measurements made in air. The object of obtaining this information
was to determine the range of permeabilities obtainable in selected frequency
and flux density intervals. The data for Figure 17 were obtained with the
core in air at 25?C ambient for a given frequency and flux level; the core
was allowed to attain an equilibrium operating temperature. At 200 kc and
a peak flux of 600 gauss, the resulting equilibrium core temperature lay be-
tween 8o?c and 93?C. At the same frequency and a peak flux of 1055 gauss,
a temperature between 149?C and 163?C was attained. Still at 200 kc but
1460 gauss, the temperature rose to the interval 288?C to 316?C.
It was further observed that at 100 kc and below, the core can be
saturated without charring the magnet wire but, of course, the saturation
value is lower than that observed under DC conditions at 25?C. The break
even point with respect to charring and saturation occurs at about 200 kc.
It may be further mentioned that the Formex wire used in these experiments
begins to char at 200?C. Flux levels at 1000 kc above those shown resulted
in charring of the formex wire.
Compositional Control
It was pointed out above that one objective to the approach govern-
ing the development of high power ferrites was the incorporation of magnetite
in solid solution with the nickel-zinc ferrite. The amount of magnetite
present is reflected by the Fe2+ content of a given sample, which is con-
trolled by the oxygen concentration of the firing atmosphere.
A series of experiments was carried out for two purposes. These
were: (1) to determine the effects of atmospheres of different oxygen con-
centration on the Fe2+ content; and (2) to produce a series of nickel-zinc-
ferrous ferrite samples containing a wide range of Fe2+ contents. Composi-
tions 690, 7041 737, 730A, and 731 were used in these experiments.
21
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05 CIA-RDP81-01043R002800240003-8
LOSS WATTS / CM3
100
1
LIMIT FIXED BY POWER AVAILABLE FROM DRIVER
1.s. am= alm dm. a. am. ems dm. ammo ??mm
10 100 0 KC/ 400KC 200 KC
100 KC
1.0
0.1
.01
WO
Figure 14.
LOSS ERGS/ CM3/ CYCLE
Figure 15.
CORE LOSS
704F 158? ISB
IN WATER 30' C
300 1000
limax GAUSS
50KC
3000
Core Loss in Watts/cm3 for Toroid 704 F 158-1SB
as Function of Bmax with Frequency as Parameter
1000
100
10
1000 /
KC /
/
400 KC '
50 KC
100 KC
200 KC
100
CORE LOSS
704 FI58? ISB
IN WATER AT 30' C
300 1000
8 max GAUSS
3000
Core Loss in Ergs/cm per Cycle for Toroid
704 F 158-1SB as Function of Bmax with
Frequency as Parameter
22
LOSS ERGS /CM 3/ CYCLE
1000
100
10
1
2000
GAUSS
1000
GAUSS
300
CORE
704 F158-ISB
IN WATER
GAUSS
LOSS
30?C
100 GAUSS
50 100 200 400
FREQUENCY (KILIOCYCLES /SEC.)
1000
Figure 16. Core Loss in Ergs/cm3 per Cycle for Toroid
704 F 158-13B as Function of Frequency with
Bmax as Parameter
44 2000
co
cc
ta
0
1500
1000
500
2
Lu
CC
a.
II,
2000 GAUSS
1'
704FI58 - I SB
IN AIR AT 25?C
,
I
1000 GAUSS
_
CORE TEMPERATURE
AT STEADY
STATE
NO0
GAUSS
250
GAUSS
N
50 100 200 400
FREQUENCY (KILOCYCLES/SEC.)
Figure 17. Permeability of Toroid 704 F 158-1SB as
Function of Frequency with Bmax as Parameter
1000
23
STAT
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
Experiment 690 F 144. Five 1/4 x 1/4 x 1/2 inch slugs of Composi-
tion 690 were fired in a tube furnace. The rate of rise was 46?C/hr in
flowing oxygen. The samples were held at 1507?C for 1 hour in flowing oxygen.
At the end of 1 hour, sample number I was quenched into water. With the temp-
erature still at 1507?C, the atmosphere was changed to flowing air for 1 hour '
at which time sample number 2 was quenched into water. The atmosphere
was then changed to a 97.4% argon - 2.6% oxygen mixture for one hour at
which time sample number 3 was quenched into water. Sample number 4 had
an additional hour in 0.24% oxygen. Sample number 5, besides all that had
gone before, had an additional hour in 0.042% oxygen. Analysis for Pea+
yielded the following results:
Sample
%02
Fe2+
No. 1
100
1.26
No. 2
20
1.08
No. 3
2.6
1.73
No. 4
0.24
1.97
No. 5
0.024
1.82
The expected result in this experiment is to have the weight %
+
Fe2 increase steadily from sample number 1 through sample number 5. There
Is a trend toward such behavior and on a plot of weight % Fe2+ vs. percent
oxygen a line of positive slope could be fitted to these points. Actually,
the Fe2+ content overshot the mark. The weight % Fe2+ for all the excess
iron converted to magnetite is 1.68% for this composition. Three of the
five samples exceed this value. In ferrite systems with which we are
familiar the presence of Fe2+ in excess of the stoichiometric amount is
accompanied by a second solid phase. The surface appearance of these
samples did not arouse any suspicion of a second phase so were not examined
under the microscope. Whether or not another phase was present is not known.
The deviation of values from the expected increase probably arises
in parts from the heating cycle. The heating rate was slow and the firing
temperature high. It is possible that even before the samples reached the
high temperature soak, their density was near maximum and their porosity
very small. At the end of the high temperature soak, their Fe2+ content
was about 1.2%. There probably was a scatter of a few tenths of a percent
in the Fe2+ content of the five samples at this point, presumably due to
variations in density and porosity. In the course of the experiment, each
successive decrease in the oxygen content of the furnace atmosphere increased
the net rate of escape of oxygen from the samples. However, this rate of
escape may also have been determined largely by variations in density and
porosity. This same condition is encountered in all the experiments which
will be described below.
24
Experiment 690 F 143. Five slugs of Composition 690 were fired
in oxygen with a rise rate of 79?C/hr, soaked at 1415?C for 3 hours. Sample
number 1 was quenched into water. Then a schedule of gas changes, similar
to those of the experiment described above but with 2 hour treatments at each
change of gas was carried out with the following results:
Sample
$02
Wt % Fe2+
No. 1
100
1.22
No. 2
20
1.39
No. 3
2.8
1.47
No. 4
0.28
1.35
No. 5
0.028
1.81
The Fe2+ values encountered here are subject to the same varia-
bility as those of the previous experiment. Except for the number 3 sample,
they show the expected trend.
Experiment 690 F 145. Four slugs of Composition 690 were fired
in air at 96?C/hr rate of rise, soaked at 1405?C for 4 hours, then cooled
in about 30 minutes to 1205?C at which temperature they were held for 3
hours. Sample number I was quenched into water then a schedule of gas
changes was begun. The amount of time for each gas was much longer than
in the experiments above since it was anticipated that a much longer time
would be required for diffusion processes to achieve equilibrium at this
lower temperature. The times used are indicated below:
Sample
No. 1
No. 2
No. 3
No. 4
%02
Duration Wt % Fe2+
20 3 hours 1.05
1.06
2.0
0.20
0.02
3
2 1/2 0.73
4 1.04
In this experiment, there is less scatter of results than in the
previous one, but one is forced to conclude that the different treatments
made negligible difference in 1e2+ content. The fact seems to be that for
samples which have been fired to 1400?C and above the response to different
values of oxygen content in the furnace atmosphere are sluggish and erratic
Experiments 704 F 143 and 704 F 144. Similar sluggish and erratic
response was found using slugs of Composition 704. The gas changes were
identical to those used in the 690 experiments.
25
STAT
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i
f:
Sample *02
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Wt% Fe2+
at 1507?C at 1405?C
No. 1
100
1.41
No. 2
20
1.45
1.48
No. 3
2.0
1.03
1.60
No. 4
0.20
1.55
1.44
No. 5
0.02
1.71
1.94
The weight percent Fe2+ for all the excess iron converted to
magnetite is 2.81%. This was not exceeded in these experiments. A possible
explanation is that temperatures higher than were used here are required to
drive off enough oxygen to convert all the excess iron to magnetite. If
this is the case, for this composition, the densification process can take
place at a temperature further removed from the temperature at which sub-
stantial amounts of oxygen are driven off. This, in turn, makes the forma-
tion of Fe2+ an even slower process than in Composition 690. Keeping in
mind that there will be a scatter of values due to variations in density
from sample to sample, we must conclude that in this series of treatments,
Composition 704 has failed to respond to different values of oxygen content
in the furnace atmosphere out to 0.20% 02.
Permeability and Fe2+ content. Although the sluggish response of
the Fe2+ content of these ferrites has thus far prevented the preparation
of magnetic test samples by a method that will give an accurately predicted
value of Fe2+ content, some data relating magnetic properties and Fe2+
content have been collected. Seven samples of Composition 704 were selected
(because of their high B values at A = 1 oersted with direct current) from
seven separate firings. The differences between firings were trivial, con-
sisting of small differences in soak temperature or soak time. The samples
were analyzed for Fe2+ content for the purpose of determining whether or
not this collection of superior samples occurred at any particular content
of Fe2+. Thus, results of these analyses are plotted against B values in
Figure 18. They occupy a relatively narrow band of Peal' contents. The
lowest B of the set lies at the low Fe2+ edge of the series. If there is
a trend, it seems to be that the higher B values go with the higher Fe2+
values.
Domain Wall Relaxation and Dispersion
From Figures 2 through 13 above, it is seen that the effective
large signal permeability for a given ferrite decreases with increasing
frequency. This dispersion in the large signal permeability is due to
domain wall relaxation.
26
- Caniti7Pri r.npv Approved for Release ? 50-Yr
03.1.83ANO0 204e.A SS30X3 11V 240A z CO.A 7.8?Z
? e
ese
a31S830 I 3. H 80d 9
A RDP81 01043R002800240003-8
27
0
0
0
V.
Campos it ion 704.
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The domain wall relaxation
phenomenon can be described as follows.
When a core is being driven around a
hysteresis loop and a condition of
dynamic equilibrium has been achieved,
the same pattern of domain wall creation
and motion takes place during each
cycle. Wall motion in a given direction
must be accomplished during the time
occupied by half of the cycle. At very
low frequencies, the progress of a
domain wall in sweeping out its as-
signed volume depends upon the magni-
tude of the magnetizing field effec-
tive in the volume occupied by the wall,
and upon the "height" of the barriers
currently impeding the motion of the
wall. A wall once over a barrier moves
to the next barrier in a time short
compared with the time for half a
cycle. In this situation, B reaches
its maximum at the same time as H
reaches its maximum.
At sufficiently high fre-
quencies a different situation obtains.
A wall once freed from a barrier may not
advance to the next barrier in a time
small compared with the time required
for half a cycle. A wall may continue
to move in the same direction after the
value of H has passed through its maxi-
mum value. In this case, B reaches its
maximum value after H has reached its
maximum value and the hysteresis loop
assumes an elliptical shape. When the
frequency is so high that many walls
fail to reach barriers for lack of
time, the maximum value of B associated
with a driving field of a given maxi-
mum value begins to decline. At suf-
ficiently high frequencies, the walls
may move practically not at all.
Rotation of the magnetization of
whole domains may in comparison with
domain wall motion be the easier pro-
cess for changing the direction of
magnetization.
4.74,
28
(a) LOW FREQUENCY
B MAX
HMAX
(b.) INTERMEDIATE FREQUENCY
( c.) HIGH FREQUENCY
The situation is schematically represented in the accompanying set
of diagrams. Diagram (a) corresponds to the low frequency case with Bmax
and Hmax occurring at the same time.
In diagram (b) the frequency is intermediate, Bmax occurs at a
later time in comparison with Hmax and some ellipticity in the loop has been
introduced. At sufficiently high frequencies, diagram (c), the loop is
essentially elliptical and the permeability is considerably reduced.
Additional experiments were performed to determine the dispersion
of the large signal permeability in high temperature transformer ferrites.
In these experiments, Compositions 704, 737, 730A, and 731 were used.
The test specimens were toroids of OD = 0.75 inch, ID = 0.50 inch,
ht = 0.20 inch before firing.
In order to have the critical parts of the firing take place
during the working day so that they could be observed, the following firing
procedure was used: The samples were loaded in a tube furnace at the end
of the day and the furnace temperature was programmed to arrive at 982?C
at 8 a.m. During this rise, the samples were in flowing air. The gas or
gas mixture to be used was then set flowing through the tube containing the
samples. Since these compositions will precipitate a hematite second phase
if cooled in oxygen or gases containing appreciable oxygen) it was necessary
to switch to argon for atmosphere protection during the fall. However, if
argon is admitted too soon, the ferrite is damaged. To minimize the danger,
0.01% oxygen mixture was used from 1100?C to 982?C and argon from 982?C to
roam temperature.
The rate of rise from 982?C to the soak was 123?C/hr, our maximum
controlled rate, and the rate of fall after soak, 371?C/hr. These rates al-
lowed the process to fit into a working day.
The magnetic evaluation had to be kept as brief as possible be-
cause of the large number of samples involved, nearly 100. For a first
screening, measurements of B were made for two values of HI 0.7 oersteds and
1.4 oersteds. The B values were obtained at D.C. (ballistic galvanometer),
50 kc, and 1000 kc. Based on these data, ten samples were chosen which
represented a wide variety of dispersion behavior. These were then measured
in more detail between 50 kc and 1000 kc to determine the shapes of the
dispersion curves.
Magnetic evaluation. An introduction to the dispersion of large
signal permeability can best be obtained from the curves for the ten selec-
ted samples shown in Figure 19. These samples were measured carefully to
determine the shapes of the curves between 50 kc and 1000 kc. The dashed
29
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kr;
4000
3000
2
2000
co
1000
H CONSTANT
1
0.7oe
A
B ?
C
D
E
....---
?11.?
1
104
105
fCPS
106
COMP FIRED
A 704 2730F I HR.
B 704 2530F 3 HR.
C 704 2730F I HR.
D 704 2430F 2 1/2 HR.
E 704 2430F 21/2 HR.
ATMOSPHERE
100% 02
0.2% 02
0.2%02
0.2% 02
4.0%02
4000
3000
2000
co
0.7
1000
H CONSTANT O.7 o.
0103
104 105icf
fCPS
Declassified in Part - Sanitized Copy Approved for Release @ 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
4000
3000
< 2000
co
1000
0310
74-1
...-- ........
....--
.....
'H CONSTANT
I.4oe
...,--"
..
....? ?
---7...
E
104
105
fCPS
106
COMP FIRED
ATMOSPHERE
F
731
2730 IHR.
100%
G
731
2610 IHR.
100%
02
H
730A
2530 3HR.
0.2%
02
J
731
2530 3HR.
0.2%
02
K
730
2610 2HR.
0.01%
02
4000
3000
? 2000
CD
a)
1000
0
1.4
I
H CONSTANT
..
FGH
i
1.40.
? ....?
----
--.
JK
-------
,
104 105
fCPS
106
Figure 19. Typical Dispersion Curves at Two Values of H
30
part of each curve connects the 50 kc value to the D.C. value which has
arbitrarily been placed at 1 kc. This is a way of indicating where the
curve ultimaterly should terminate.
Composition numbers and firing conditions are shown on the figure.
There are some general features to be noted. When H = 0.7 oersteds,
the curves are concave upward if B is greater than 1000 gauss at 50 kc. The
curves have an inflection point after which they are concave downward if B
is less than 1000 gauss at 50 kc.
When H = 1.4 oersteds, nine of the ten curves are concave downward
at 50 kc, two curves, A and F) have inflection points. Curves A and F are
examples in which a large part of the dispersion takes place between 50 kc
and 1000 kc. The shapes of the other curves can be understood when it is
realized that only portions of curves are seen the shapes of which are simi-
lar to those of A and F.
Examined from this point of view) the concave upward curves ob-
tained at H = 0.7 oersteds are the "high frequency" part of dispersion
curves. The concave downward curves obtained at H = 1.4 oersteds are the
"low frequency" part of dispersion curves. The curves which have inflection
points are exhibiting the middle frequencies of their dispersion curves.
These curves illustrate how the relaxation is shifted to higher
frequencies when the driving field is increased. The steep part of the
dispersion curve occurs at those frequencies which are beginning to allow
insufficient time for a domain wall to sweep through the same volume that
was traversed at lower frequencies. Within certain limits, increasing the
? driving field will increase the domain wall velocity and consequently.move
the steep part of the dispersion curve to higher frequencies.
Figures 20, 21, 22, 23 show additional results. Each figure pre-
sents data for samples fired in one atmosphere beginning with 100% oxygen
in Figure 20, through 0.01% oxygen in Figure 23. The shapes of the disper-
sion curves have been assumed to be similar to those shown in Figure 19
and were obtained by joining the 50 kc and 1000 kc points with an approp-
riate curve chosen from Figure 19.
Consider the 50 kc properties first. The highest permeabilities
are obtained by firing at the highest temperature, 1500?C in 100% oxygen.
The individual compositions rate in the order of the amount of extra Fe203
they contain. Composition 704 contains the most excess Fe203. The peak
in low frequency permeability shifts to lower firing temperatures as the
oxygen content of the gas is decreased. ?
at the
oxygen
High permeability at 1000 kc is obtained most reliably by firing
lower temperatures and low percent oxygen such as 1390?C in 0.2%
or 1330?C in 0.01% oxygen.
31
STAT
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
6-1
-
Dispersion curves were extended to lower frequencies for samples
of Compositions 704 and 730A. The entire set of characteristic curves for
these specimens are shown in Figures 24 and 25. From these results, it is
seen that the relaxation frequency associated with Composition 730A is
greater than that for Composition 702. The high relaxation frequency of
Composition 730A accounts for the superior behavior at 1000 kc of this
material over Composition 704 with respect to permeability.
32
F247
4000
3000
0
A B
-... -
a. N.
% %
%
N
N \
\\
FIRED
2730F
IHR
io 3
104
f C.P.S.
o 5
106
A= COMP 704
B = COMP 737
C= COMP 730A
D= COMP 731
F249
400
3000
(nu) 2000
CD
CO
1000
0
1
FIRED
_
2530F
......
2/1 HR
2
.at...,
4....
....
0.. ...
....
A BC
.......
..
D
.....z....
....-
? .........
io3
104
f C.F?S.
io 5
106
F240
4000
3
(1') 2000
co
CD
ca
1000
I I
FIRED 2610F
2HR
ABC D
r:
_
10 3
104
fC.PS.
10 5
106
ALL SAMPLES FIRED IN 100%02
MEASURED IN WATER 25?C
F251
4000
3000
cn
co 2000
CD
CD
1000
0
I
FIRED
1
2430 F24HR
1
........
..?
OM ....
'
ABC
D
N
,
103 104 105
f C.PS.
iocS
Fiaure 20, Dispersion Curves at H 0.7 Oersteds And H = 1.h Oersteds
33
TAT
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?
?
Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
F-242
4000
3000
co
2000
CD
1000
FIRED 2610F 2HR.
?
1111V".?
???..
?
%ft
0
1133 104 105
I CPS
106
A= COMP 704
B= COMP 737 '
C* COMP 730A
D= COMP 731
F-253
ALL SAMPLE FIRED IN 4%02
AT TEMPERATURES INDICATED
MEASURED IN WATER 25?C
F-249
Figure 21. Dispersion Curves at H 0.7 Oersteds and H 1.1 Oersteds
31t
F-248
4000
3000
(J) 2000
CD
1000
I
FIRED
I
2730F
IHR
..... ?
C D
.111 IL.
..?
fCPS
lo.
A= COMP 704
B = COMP 737
C = COMP 730A
= COMP 731
F-245
4000
3000
u) 2000
4
CD
CO
1000
I
FIRED
...?....4.1.
I
2530F
.....
3HR.
---
,
ABCD
.......4. on. .1..
.%?...
?????
.??,.
.II, ?
1??
Ion ma flo ei on .un
ihillih
MED WED INN
_
i03 IO 4 I05
fCPS
F-241
4000
3000
V, 2000
1000
...
FIRED
I I
2610F
...
2 HR.
? -5-
- --
,
1.?.-
.......
7-1-
AB
?
CD
.......
--?
.0.10
?
OW
4111 1111116\
io 4
fCPS
106
ALL SAMPLES FIRED IN 0.2%0
MEASURED IN WATER 25?C
F-250
4000
3000
2 2000
CD
1000
I
FIRED
I
2430F
21/2 HR
...
0/.
???
.....
?
.....-
?0
....
?
ABC'
\
\
OM
,Ilr
OM
.?
,I=I?
an&
=10
11116"4"14.4
a?mb am
4MID OM
il.
i?3
RY4 105
fCPS
106
figure 22. Dispersion Curves at H = 0.7 Oersteds and H = 1.4 Oersteds
35
STAT
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
iff.i ?
A= COMP 704
B= COMP. 737
C= COMP. 730A
D= COMP 731
F-254
F-243
4000
3000
D 2000
1000
FIRED
1
2610F
2 HR.
0-
.-- ?
waINIM?
0.2M.0
..-
im. owe
IMO ....t
?--.-....
, a.. ?
C D
A
,-i-
MID MIEN00.?
B
104 105
fCPS
106
4000
3000
Cl)
D 2000
100
?
I
FIRED 2545F
'-..1-----=.*:
A. B
I
21/2
HR.
CD
.../.-.,1
....,,..
.....
_............
......_
,
103 104 105
fCPS
106
ALL SAMPLES FIRED IN 0.01% 02
MEASURED IN WATER 25?C
F-252
4000
3000
2000
CD
1000
0
1
I, FIRED
1
2430F 2
4I. ..... '''
1/2HR.
lo 4IM.
A B
0.
C D
.... - ? ?
, ,
..... .... ....
- - -
?
...Vs
????? ....
WED Ewa aim WPM .?=1
....
.21i.
3 I04 105
fCPS
106
Figure 23. Dispersion Curves at H = 0.7 Oersteris and H = 1.4 Oersteds
36
4000
3500
3000
2500
0
I; 2000
0
1500
1000
50Q
FREQUENCY KC/SEC
4.0 10 25 50 100 250 630 1000
2.5 I 6.3 16 I 40165 160 I 400
H=3.0 oe
H=1.4oe
H=1.0 oe
H=0.78
oe
H'0.68
.,
Hz0.48oe
H=0.22oe
104 105
FREQUENCY CPS
Figure 24. Dispersion Curves for Toroi0 70/4 F 158-1SB
in Water at 250C
37
106
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10
? k*
4000
3500
3000
2500
2000
cp
1500
1000
500
40
FREQUENCY K /C SEC
10 25 50 100 250 630 1000
2.5
6.3
16
MR1111111111111114%
4*
GO
160
1
1 400
1 1
:??
H3.0 Oe
H=1.4 oe
IL
H= 0.7oe
1E
1
H=0.52 oe
116.
Hz0,46oe 1II
-4.11.1
Hz0;3 oe
H= 0.15 oe
-
104
105
FREQUENCY CPS
106
Figure 25. Dispersion Curves for Toroid 730k F 21..-1 in
Water at 25?0
38
Y.4
Conclusions and Recommendations
The utility of a high temperature transformer ferrite depends
upon its intended application. The magnetization curves given in the body
of the text may be considered as characteristics for design use. However,
from the point of view of large signal permeability definite recommendations
can be made as a result of the investigations carried out during the period
covered by this report.
For operation at frequencies up to 200 kc in an ambient tempera-
ture range -65?C to +250?C, Composition 704 is recommended for high large
signal permeability. The proper firing schedule is 1480?C for 2 hours in
100% oxygen. This material must be cooled in a protective atmosphere such
as argon.
For operation at frequencies between 200 kc and 1000 kc in an
ambient temperature range -65?C to +250?C, Composition 731 is recommended
for high large signal permeability. The characteristics of Composition 731
are similar to those of Composition 730A but are more reproducible. The
proper firing schedule is 1370?C for 3 hours in 0.2% oxygen, and cooled in
the same atmosphere.
A measure of the large signal permeability can be obtained by
considering the flux in the core when the driving field is 1.0 oersted.
Thus, below 200 kc the permeability of Composition 704 lies between 3000
and 1500, the decrease occurring monotonically with frequency. For frequen-
cies between 200 kc and 1000 kc, the large signal permeability of Composition
731 varies between 1500 and 600.
It is also recommended that work in this area'of ferrite materials
development be terminated until the present materials are evaluated in a
specific application. After this evaluation, further effort may be fruitful
in tailoring specific properties to the needs of a given device.
39
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ti
71'
SECTION III
MATERIALS FOR LOW SIGNAL APPLICATIONS
Objective
The objective of this work is to produce ferrite materials having
a high ?Q product and low temperature coefficient of permeability. It is
desired that the characteristics of developmental samples be relatively
unaffected by prolonged exposure to high humidity, and suitable for opera-
tion over the temperature range -65?C to +250?C.
Approach
The approach taken in this effort is to determine the processing
conditions and compositions necessary to yield the above combination of
properties. It is well known that for a given composition, specimens fired
at low temperature and for short times (low heat work) generally exhibit
lower loss than samples fired at high temperature for long times (high heat
work). Typical data showing this trend are given in Table III. All aspects
of the preparation and treatment of the samples listed in Table III were
equivalent except the final firing. It should be stressed that the aspect
of preparation concerned with here is that of firing temperature and time.
The comparison in Table III is given only to illustrate that particular pro-
cessing parameter. It should not be inferred that this is the only para-
meter which controls the low loss characteristics in low signal materials.
Pressing pressure, particle size, heating and cooling rates, and specific
composition, as well as the effects of impurities and additives strongly
influence the ultimate low loss characteristics.
TABLE III
EFFECT OF FIRING TIME AND TEMPERATURE ON MAGNETIC Q.
COMPOSITION: 48 MOL% Fe2031 25 MOL% ZnO) 26.5 MOL%
NiO, 0.5 MOI % V205.
Sintering
Temp.
Sintering
Time
Q at 1 mc
Q at 4 mc
1139?C
1266
30 min.
240 min.
60
21
47
5
The firing cycle should be such as to discourage the formation of ferrous
iron as this is known to reduce the resistivity in ferrites giving rise to
appreciable eddy current losses at high frequencies.
The nickel zinc ferrites with small additions of vanadium pent-
oxide present a promising system in which to work. Nickel zinc ferrites
have been studied extensively and processing variations permit a wide lati-
tude of properties.
110
Compositions of interest to this study must contain less than
18 moPS ZnO in order that the Curie temperature be sufficiently high (above
350?C). The temperature coefficient of initial permeability then can be
expected to remain low up to 250?C. The temperature coefficient generally
increases strongly in the neighborhood of the Curie temperature.
Ferrite Compositions
The range of compositions investigated during the phase covered
by this report is given in Table IV.
TABLE IV
DESCRIPTION OF FERRITE COMPOSITIONS
FOR LOW SIGNAL APPLICATIONS
Comp.
No.
Mol%
Fe203
Mol%
NiO
Mol%
ZnO
Mol%
V205
NiO/ZnO
67
50.0
34.5
15.0
0.5
2.30
59
56.o
28.5
15.0
0.5
1.90
73
48.o
36.5
15.0
0.7
2.43
75
50.0
32.4
17.1
0.5
1.90
76
48.0
33.7
17.8
0.5
1.90
77
49.9
34.4
15.0
0.7
2.30
78
49.9
32.3
17.1
0.7
1.90
79
47.9
33.6
17.8
0.7
1.90
8o
55.9
28.4
15.0
0.7
1.90
81
50.1
32.5
17.1
0.3
1.90
82
48.1
33.8
17.8
0.3
1.90
83
56.1
28.6
15.0
0.3
1.90
84
49.7
32.6
17.1
0.5
1.90
85
49.5
32.8
17.2
0.5
1.90
86
50.1
34.6
15.0
0.3
2.30
285
50.0
42.0
7.5
0.5
5.60
141
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;1
Of the compositions listed in Table IV, three were shown to be
of particular interest, Compositions 67, 841 and 285. The low signal
properties of these materials are such to cover a range of initial permea-
bility from 12 to 120, exhibit low loss, and possess a low temperature co-
efficient of permeability over the temperature interval -65?C to +250?C.
Also, these low signal properties are not affected by prolonged exposure
to high humidity.
Standard ceramic fabrication procedures have been followed in
the processing of these compositions. Usual practice has been to weigh
out approximately 1 kg total batch on a large (2 kg) analytical balance.
The resultant mixture is ball milled overnight for about 16 hours in a
one gallon iron mill with steel balls, in the presence of about 1 1/2 liter
deionized water. This process both mixes and grinds. The slurry is then
placed in glass drying pans and brought to dryness in standard ovens. The
next step in the process is to run the dried powder through a pulverizer
for sizing.
Binder is added as & by weight Hyform emulsion containing 30%
wax. The resulting slurry is again ball-milled for 15 hours, after which
it is dried at a low temperature (less than 60?C). The cake is then broken
and pelletized through a 60 mesh sieve.
Some initial experiments included the preparation of Composition
285 in pellet sizes: (a) -20, material retained on No. 20 sieve; (b)
,20-401 material passing No. 20 sieve retained on No. 4o sieve; (c) +20,
all material passing No. 20 sieve; (d) +801 all material passing No. 8o
sieve. The results of these early evaluations indicated that small pellets
yield a greater densification and better quality ceramic when fired at low
temperature and short time. Thus, the procedure was standardized using the
60 mesh sieve. (60 mesh pellets are easier to handle than 80 mesh and this
sorting is preferred from a manufacturing point of view.)
Results of Magnetic Evaluation
The primary results of magnetic evaluation of the various composi-
tions of interest are given below.
Humidity effects. Under proper conditions a saturated solution
of lead nitrate will maintain a relative humidity of 98% at 20?C in a closed
chamber. Wound toroids of Composition 67, 84, and 285 were placed in this
environment for 350 hours (approximately 15 days) and measurements of permea-
bility and Q were made at intervals at a frequency of 1.5 mc.
Data for Compositions 67 and 84 are given in Table V . For Compo-
sition 285 the sample used had a permeability of 14 which remained constant
over the entire time interval. The intrinsic loss in the 285 sample was so
low that after the correction for wire loss was made the associated Q values
were infinite within the limits of experimental error. This was the case
for measurements made over the entire time interval of 350 hours. As a re-
sult, the data for composition 285 are not given in Table V.
1.2
Although Q values appear somewhat erratic, it is safe to con-
clude that if loss increases with exposure to high humidity, (2 decreases
no more than 10t over the period considered here. It is seen from Table
V that permeabilities remain constant.
TABLE V
EFFECT OF HIGH HUMIDITY ON go AND Q
FOR COMPOSITIONS 67 AND 84
(RELATIVE HUMIDITY - 98%)
Comp.
Firing
57
84
1100'C-10 min.
Pereny furnace
1150C-11 min.
Pereny furnace
Time
4o
9
0 hrs.
Y5
240
25
75
255
75
75
208
170
75
211.0
350
75
223
o
125
221
25
125
278
75
125
178
170
125
212
350
125
205
In addition to the results presented in Table VI further measure-
ments were made on a selected toroid of Composition 84 (toroid 84.11). De-
termination of permeability And Q were made over a period of 215 hours. The
lata are presented in Table VI.
The results obtained here are essentially the same as observed pre-
viously. The permeability is unaffected by prolonged exposure and a slight
increase in loss is observed with increasing time of exposure. .Apparently,
the entire decrease in Q, about 10%, takes place during the first 120 hours.
)43
????
STAT
STAT
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TABLE VI
EFFECT OF HIGH HUMIDITY ON
PERMEABILITY AND Q OF TOROID 84.11
Time
P.?
Q
Temp.
0 hours
110
235
2?C
1
110
235
24
20
110
223
24
45
110
225
24
120
110
220
25
140
110
218
24
170
110
218
26
190
110
223
26
215
110
220
23
Permeability, Q, and ?Q product. In Figures 26 through 30 permea-
bility, magnetic Q and the ?Q product as functions of temperature are shown
for several samples. The measurements were made at a frequency of 1.5 mc.
Table VIIbelow lists the toroids for which the data in Figures 26
through 30 were obtained.
TABLE VII
DESCRIPTION OF comrosiTioNs
Comp.
No.
Toroid
No.
Eeat Treatment
67
57.24
uncalcined
Fired 1100?C - 20 min.
67
67.52
calcined (750?C - 3 hrs.)
Fired 1100?C - 15 min.
67
57.54
uncalcined
Fired 1100?C - 15 min.
84
84.7
uncalcined
Fired 1050?C - 10 min.
84
84.11
uncalcined
Fired 1152?C - 11 min.
From Figure 26, it can be seen that the major effect of calcina-
tion is to increase significantly the temperature coefficient of initial
permeability.
Figures 27 and 28 give the results for selected samples of Compo-
sition 67 which has a larger Ni0nn0 ratio than Composition 84. The data
for Composition 84 are given in Figures 29 and 30.
44
x d
03
MOM
a) 0

a
V
c
C
a
C,
I
I
a
a
.
\
i
_
0
rti
0
0
03
0
8
0
45
0
0
T
STAT
STA
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a n.
50 100
240 90
230 80
220 70
a,
210 60
200 50
-150 -100 -50 0 50
TEMPERATURE IN ? C
. ???-? ?-;.-147 7r_e, 1.4".""
- .
Po
?momimlion
if
?
a 3,
230 100
220 90
80
210
200
70
190
60
180
50
100
'7
0
o
31
28
25
22
19
16
150 200 250
-Figure 27. Temperature Variation of p, and Q. for Toroid 67.24 f = 1.5 me
?Siki
)
????????
25
22
Pc)
19
1-
-150 - Km -50 0 50 100 150 200 250
TEMPERATURE IN ?C
'Figure 28. Temperature Variation of p and Q, for Toroid 67.5Z
0)f = 1.5 mc
?0")
'H
:?
H
16
13
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. .2?.7,-
a
=.
230
120
220
110
210
100
200 90
co
190 80
180 70
-150
_
? ? s- ';;;;;;;;:47,4-..;1.4;
I
I
\
I
'1111
?
-100 -50 0 50
TEMPERATURE IN ?C
Vjure 29.
42121:44:4S.V1,1-- ?
250 140
130
235 120
110
220 100
-150
100
150
Temperature Variation of n and Q. for Toroid 84.7 f 2r- 1.5 me
larst,Viaiaf 4,741A.t' 411:
200
a
8
5
2
19
16
13
250
...z.v41?;;; qr.;;VAtilia.,145:,i14-kia,i14v,kr,V111,4ji." 4,7'A .7, 7"."
/
0
I
FA
A
PQ
I
diaiMMIW
IIIM?l?
_
?
?
?
-100 50 0 50
TEMPERATURE IN ?C
100
150
Figure 30. Temperature Variation of p and Q for Toroid 814.11 f 1.5-me
200
30
27
24
21
18
250
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It is well known that the measured values of permeability and Q
depend upon the amplitude of the driving signal. The true low signal values
of these parameters are obtained by extrapolating the measured values to
zero field. Figure 31 shows the results obtained for a selected sample of
Composition 84. In Figure 31, ?. and Q are shown as functions of driving
field, and it is clear that these parameters are essentially independent
of drive over the range considered. The constancy of Q indicates a very
low value of hysteresis coefficient for this material.
A General Radio Twin-T bridge was used to obtain the spectrum of
the low signal parameters over the frequency range 1 to 30 mc. Seven test
bodies were examined, six of Composition 84 and one of Composition 285.
Table VIII gives the data on the firing of these samples.
Figure 32 shows Q as a function of frequency for the seven samples
referred to above. From Figure 32, it is seen that the Q of Composition 285
(Sample 7) is considerably higher than that for Composition 84 (Samples 1-6)
at frequencies above 10 mc. Of course, the initial permeability of Sample 7
is only about 1/2 to 1/3 that of the Composition 84 bodies.
Figure 33 shows the frequency response of ?o for Sample 3. In this
material, ?0 is approximately independent of frequency over the investigated
range. For Composition 285, ?. increases slightly with increasing frequency
to 30 mc.
Figure 34 shmis the ?Q product as a function of frequency for Compo-
sition 84 and 285. Again, it is seen that Composition 285 holds up better
at high frequencies, but this material has a lower j.LQ product than Composition
84 below 7 mc.
TABLE VIII
PROCESSING OF TEST BODIES FOR LOW SIGNAL APPLICATIONS
Sample
No.
Comp.
Brand of
iron oxide
Soak
temp.
Soak
time
Rise
rate
Ramming
pressure
1
84
Baker
_
1105?C
20 min.
575?C/hr.
14,700 psi
2
84
Map. 110-2
1105
20
5.75
18,800
3
84
Baker
1056
20
1300
14,700
4
84
Baker
1100
20
slow
14,700
5
84
Map. 110-2
1100
20
200
4,200
6
84
Map. 477
1055
20
1300
14,700
7
285
r Baker
1154
20
580
14,700
So
t
0 0
2
0
0
S2
OW 0
0
0
a.
X
COMPOSITION 84
0
0
CI.
0
X
0
X
X
0
0
0
X
0
A1.1118Y31`013d ii
51
8
0
0
0
STATT
-
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I
SAMPLE
3
4
I
COMPOSITION
I
+
.
04
_
_
?
Figure 33. Frequency Spectrum of Initial Permeability
Frequency Spectrum of Qmat for Selected Samples
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COMPOSITION 84
COMPOSITION 285
ti 3000
2000
Processing of Low Loss, Low Signal Ferrites
Below the results are given for a series of investigations de-
signed to determine the effects of various processing techniques on the
low signal properties of the ferrites of interest in the present develop-
ment. These include the effects of calcine, the addition of V205, the
effects observed when compositions are prepared using different sources
of Fe201, the effects of rise rate, the effects of ramming pressure, and
the effgcts of oxygen firing.
Effect of calcine. In the preparation of ferrites for low sig-
nal applications) the general practice is to press samples for firing
using raw oxides rather than calcined material. It is known that bodies
prepared from pre-reacted powder of a given composition will generally
exhibit higher loss and permeability than bodies fired from raw oxides,
particularly for low heat work. However, an optimum may exist for the
?Q product in considering the competition between the increase in ? and
the decrease in Q. Composition 67 was chosen for the calcination experi-
ments.
Composition 67 was calcined for three hours in oxygen at various
temperatures in a tube furnace. Toroids were then pressed in the usual
manner with the exception that no binder was used. After firing for 10
minutes at 1100?C, permeability, Q and shrinkage were measured. Data are
given in Figure 35 and Table IX. It is evident that calcination at 650?C
gives the highest ?Q product among the temperatures tried. A temperature
of about 900?C appears to be a critical one for this composition. The
data given in Table IX for the 900?C calcine include measurements made on
samples prepared from powder located at different positions in the furnace
during calcine.
TABLE IX
EFFECT OF CALCINATION TEMPERATURE ON SHRINKAGE, ?., AND Q
TOROIDS FIRED AT 1100?C FOR 10 MINUTES
Calcine Temp.
% Shrinkage
go
Q at 1.5 mc
RA
Uncalcined
14.5
84.o
256.
_
21,500
650?c
18.7
lo6.
240.
25,400
750?C
17.4
107.
225.
24,100
870?c
16.9
113.
200.
22)600
"900?C"-front portion
14.7
108.
131.
14,200
"900?C"-center portion
5.7
81.7
162.
13,300
""900?C"-end portion
3.6
88.8
138.
12,200
4 5 10 20 30 40 50
FREQUENCY IN MC/SEC.
Figure 34. Frequency Spectrum of pogmat for Two Selected 3arples
54
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7 -
........ 01--"'"''''
_
1
\
\
COMP. 67
CALCINE -3HRS. IN 02
FIRED - 1100 ?C, 10 MIN.
\
\
\
-PERMEABILITY
?
%
\
\
\
I L_
O cb
A11119V311183d 1VIIINI
0
0
0
01
0
0
cv
0
0
cv
C.)
?
TEMPERATURE
UI
0
0
it
'&-
4
C.)
.
Is)
Cr)
I I 10
O 0 0 C5.j k
0 0 0 ?i-i6
O 0r 0 cr-4
CC u?
a
CsJ
56
oil
OA-
Even though the expected optimum was observei for the ?Q product
(650?C calcine), further measurements, Figure 26, showed that the tempera-
ture coefficient of permeability was increased significantly as a result
of the calcine. Thus, no calcination was included in subsequent body prep-
aration.
Addition of v205. The primary effect of introducing vanadium
pentoxide in small quantities, less than 1.0 molep, is to increase shrinkage
during firing. Thus for a given low heat work cycle the presence of V205
allows an increase in ceramic curing over that which would be experienced
when this additive is omitted. Though: conclusive evidence is lacking, it
is felt that the favorable results obtained under exposure to high humidity
for materials prepared using V205 is attributable to the inclusion of this
additive.
Illustrative data which indicate the primary effect of V205 ad-
dition are shown in Table X.
TABLE X
EFFECT OF 0.5 MOL% VANADIUM PENTOXIDE
FOR 10 MINUTE FIRING AT 1100?C
Comp.
Description
%
Shrinkale
110
Q at
1.5 mc
67
50 Moll% Fe203 with V205
14.4
76.
250.
68
50 mol% Fe203; v205 omitted
4.7
15.
High
69
Excess Fe203 with V205
17.1
125.
go.
70
Excess Fe203; V205 omitted
8.1
23.
160.
Comparison of different brands of iron oxide. It has been pointed
out that low signal ferrite materials are fabricated using a heat treatment
cycle that includes short time firing at relatively low temperature. Thus
the impurity content of the various commercial iron oxides can alter the
ceramic curing rate for bodies which are only partially sintered. As a re-
sult, sample preparation and evaluation has been carried out utilizing
several brands of iron oxide.
Only Composition 84 was used to evaluate the effects arising from
the use of different sources of iron oxide. Results are given in Tables XI,
XII, and XIII. Close study of Table XI shows2 first, that the brand of ferric
oxide consistently makes a great difference in permeability and Q. The
highest Q is consistently obtained using the C.P. ferric oxide of the J. T.
Baker Co. In general, Columbian Carbon Co. High Purity produces the highest
?; however, for this work, we are primarily interested in a high ?Q product,
and this brand does not give as high a product as the others..
57
STAT
STAT
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It is also clear from Table XI that the rise rate upon heating
is of more importance than the actual soak temperature. Note that the
sets in Table XI are arranged according to increasing rise rates toward
the bottom, and the Q for a particular brand follows the trend of increas-
ing rates. No such agreement with sintering temperature is found.
TableXIIpresents somewhat similar results for a repeat study.
All firings were made at the same temperature for 20 minutes. Table XII
also shows the effect of cooling rate.
As before, J. T. Baker iron oxide is the preferred one for high
Q properties) although Mapico 110-2 is also very good, and available in
commercial quantities. Columbian Carbon Co. H.P. and C.K. Williams 5098
are somewhat equivalent showing higher permeability and lower Q. But, for
this type of firing the Columbian Carbon Co. H.P. iron oxide shows consis-
tently higher initial permeability than any of the others.
This study (Table XII) also shows the same increase in Q at higher
rise rates) the sintering temperature being held constant. No clear trend
in permeability is evident.
TableXII also presents the results of a simple experiment to de-
termine the effect of cooling rate. Although this suffers from insufficient
data due to broken cores, the data show a general increase in permeability
for the slower furnace cooled samples. Q does not show a clear trend.
In Table XIII, the effects of pressure on go and Q are given. All
samples were fired for 20 minutes at the soak temperature, but the tempera
tures measured with an optical pyrometer did not turn out exactly the same.
Results are inconclusive. The ?Q product does appear to peak at 12,500 psi,
but the effect is not large. The effect upon Q is even less clear although
one is tempted to see a trend toward higher Q at lower pressure.
Effects of rise rate. Some information on the effects of rise
rate on the low signal properties were reported above. This work was ex-
tended to cover a wider range of rise rate variable. The results are shown
in Figure 36 and Table XIV. Here again, an increase in ?Q product is rea-
lized as the rise rate increases) but only up to a point -- about 700?C/hr.
The improvement is realized almost entirely through increase in Q. This
can readily be seen by inspection of Table XIV.
Pressure studies. Table XIII gives the results obtained from ram-
ming pressure exi)eriments made on bodies prepared from Mapico 110-2 and
J.T. Bakerl.ferric oxides. These experiments were extended and the results
shown in Figures 37 and 38.
In Figure 37, initial permeabilities and the ?Q products are pre-
sented for samples made with J.T. Baker and Mapico 110-2 ferric oxide. The
effect of increasing pressure shows up differently for samples made with the
different iron oxides. Samples made with Mapico 110-2 iron oxide increase
in permeability and ?Q product with increasing pressure, while those made
with J.T. Baker do exactly the opposite. Thus, no generalization can be made
on the effect of pressure except that a series of experiments may be required
to find the optimum.
58
TABLE XI
MAGNETIC PROPERTIES OF COMPOSITION NO. 84
PREPARED WITH DIFFERENT IRON OXIDES
(3/4 IN. TOROIDS PRESSED 8000 PSI,
ALL FIRING TIMES 20 MINUTES)
Brand of Fe.,1
Sint.
Temp.
,
Rise P.
Rate (1.5mc)
4
(1.5mc)
?Q
.
Columbian Carbon Co. H.P.
Mapico 110-2
J. T. Baker C.P.
1150?C
It
It
200?C191
152
120
48
47
120
9200
7200
14400
..
Hr.
it
It
Columbian Carbon Co. H.P.
Mapico 110-2
J. T. Baker) C.P.
1090?C
II
it
?
300c- 18o
Hr.
It 133 '
it 92
57
72
214
10300
9600
19700
,
Columbian Carbon Co. H.P.
Mapico 110-2
J. T. Baker, C.P.
1050?C
it
11
.
ilor?c 18o
3-
it 123
11 96
75
115
266
13500
14100
25400
Columbian Carbon Co. H.P.
Mapico 110-2
J. T. Baker) C.P.
1115?C
it
11
400%198
114
93
73
125
215
114.500
114.200
20000
,
Hr.
it
II'
Columbian Carbon Co. H.P.
Mapico 110-2
J. T. Baker, C.P.
,
1100?C
it
II
625?c
160 160
115
112
75
337
347
12000
39000
39000
Hr.
ti
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59
c-rn-ri
STATi
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TABLE XII
TABLE XIII
COMPARISON OF BRANDS AND EFFECTS OF HEATING AND
COOLING RATES ON COMPOSITION NO. 84
TOROIDS PRESSED AT 14.200 PSI AND FIRED 1100?C - 20 MIN.
IRON RISE
OXIDE RATE
COOLING
RATE
100?C/Hr.
Quench 3 min.
ti it SI
158
122
79
150
11900
7900
26800
6200
Col. Carbb N.P.
Mapico 110-2
Baker C.P.
CKW No. 5098
100?C/Hr.
It
165
176
log
63
92
262
lo400
16200
26600
Cracked
200?C/Hr.
Quench 3 min.
178
110
86
173
14loo
lo800
28000
6900
Pres
lb/in
Sint.
Temp.
Sint.
Time
Rise
Rate
,
g
1.5 me
.q
1.5 me
g(2
Mapico 110-2 Ferric Oxide
4700
1059?C
20 min.
350?C/Hr.
4o
253
10100
6300
1059
20 min.
350?C/Hr.
39
261
10200
9400
1074
20 min.
350?C/Hr.
51
292
114.900
.12500
1074
20 min.
350?C/Hr.
50
286
14300
J. T. Baker Ferric Oxide
14.700
1053?C
20 min.
350?C/Hr.
73
317
23000
6300
1053
20 min.
350?C/Hr.
79
315
24900
9400
1068
20 min.
350?C/Hr.
71
378
26800
12500
1069
. 20 min.
350?C/Hr.
77
305
23500
114.700
1069
20 min.
350?C/Hr.
81
300
24300
TABLE XIV
Col. Carb. H.P.
Mapico 110-2
Baker CP
CKW No. 5098
Col. Carb. H.P.
Mapico 110-2
Baker CP
CKW No. 5098
200?C/Hr.
Furnace Cool 178
15500
40500
Broken
Broken
EFFECT OF RISE RATES ON go AND Q
ALL SAMPLES PREPARED WITH MAPICO 477 IRON OXIDE
1 1/8 IN TOROIDS PRESSED AT 114.700 PSI
ALL MEASURED AT 1.5 MC - G.R. TWIN-T BRIDGE
350?C/Hr.
Quench 3 min.
144
82
74
111
194
455
436
148
ze000
37300
32200
1611.00
Col. Carb. H.P.
Mapico 110-2
Baker CP
CKW No. 5098
Furnace Cool 113
ft tl
152
97
8
18
230
172
22300
Rd.se
?C/Hr.
(Opt. Pyr.)
110
Qmat
I-LQ
100
1C48?C
204
26
5300
200
1051
139
88
12200
300
1049
111
107
11900
400
- - Cracked - -
500
1057
144
183
26300
600
1057
138
189
26100
700
1056
149
211
31400
1000
1054
154
207
30000
1300
1055
132
255
33600
1700
1057
147
205
30200
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.1'
i;
1 I!
' 111
'
t I
_
I
0
COMPOSITION 84
fz1.5mc TWIN-T BRIDGE
0
MAPICO 477 F6203
SOAK 1050?C-20 MIN
0
.
0
_
t
e
.
10?
eN us r1
0
Irm007/
62
0
0
0
800 1000
RISE RATE IN ? C/HR
Rise Rate
25000
MOO
19000
17000
15000
0 5 10 15 20 25 30 35
RAMMING PRESSURE IN PSI
Mo Qmo VS RAMMING PRESSURE FOR COMPOSITION 84
.,
MAPICO
110-2
- 20 MIN.
COOL
I
Fe2 03
,
0
.
105?C
575?C/HR
?
T. BAKER
-20 MIN.
COOL
X
J.
i(1135?C
x 800?C/HR
Fit2 03 ---'
.
f z LO mc
TWIN -7
I
BRIDGE
,
40,000
Ito INITIAL PERMEABILITY
130
120
II 0
100
90
90
0 5 10 15 20 25 SO
RAMMING PRESSURE IN PSI
INITIAL PERMEABILITY VS RAMMING PRESSURE
J. T. BAKER
I
X
,
,
X
-..,
-..
A
0
0
0
MAPCO
110-'2
f z 1.0XiC
1
TWIN -1.
I
BRIDGE
35
Figure 37. pg and p vs. Ramming Pressure for Composition 84
63
STAT
STAT,
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3500
340
3300
320
it
z
a
31000
30000
29000
28000
)
J. t
1105?C-20
MEASURED
1
BAKER Fe2-03
MIN 574?C/HR
ON G. R. TWIN
i
COOL
-T BRIDGE
1
C)
10 mc
0
X
X
6
-
K
,
1.5 mc
,
5000 10000 15000
RAMMING PRESSURE IN PSI
20000
Figure 38. pi; vs. Ramming Pressure for Composition 84
25000
Somewhat more interesting results are presented in Figure 38 where
the ?Q products at different pressures are given, but at two different fre-
quencies. These curves indicate that higher A products at higher frequen-
cies should be obtained by lower ramming pressures.
Atmosphere firings. As part of the development program on Composi-
tion 84; a comparison series of samples was fired, two toroids at a time in
a double tube furnace, one sample in air, the other in pure oxygen. Hence,
rise rates and soak times were identical, and soak temperatures also were
very nearly the same. The air and oxygen were supplied as. a steady stream
to each tube at 2 liters/min throughout rise, soak and fall.
In all, twenty-four comparison firings were made and the test toroids
(1 1/8 inches O.D.) were measured on a G. R. Twin-T bridge. The values, are
reported in Table XV. Oxygen treatment during firing consistently improved
the permeability although not uniformly. Greatest improvement was gained at
lowest rise rates. Q also was generally increased slightly by oxygen treat-
ment although there are a few exceptions. As a result of this study, it is
clear that oxygen firing is desirable in order to develop the optimum permea-
bility and Q. A moderate rise rate is also indicated.
Low Temperature Evaluation
For the development of low signal level ferrite materials, applicable
properties of these materials must be studied throughout the temperature range
-65?C to 250?C. For the low end of this temperature range, it was decided to
study these properties under the best and most reproducible conditions - namely
with a vacuum cryostat.
Using such equipment, residual water which might be trapped on the
surface or in the interior of highly porous samples can largely be eliminated
and hence icing which has been a problem is no longer troublesome here.
Description of equipment. While the vacuum cryostat used in this
study is not of a new design, it will be worth while to point out its salient
features. Figure 39 shows a block diagram of the cryostat.
The cryostat consists essentially of a liquid nitrogen container
placed in the vacuum chamber. At the base of this, and inside the vacuum, is
connected a copper rod around which heater windings have been applied. At
the extremity of the end of this heater rod is screwed a copper chamber in-
side of which the sample is contained. Hence, the basic operation of this
system is clear. Good thermal contact between sample and liquid nitrogen
container allows temperatures of -170?C at the sample to be readily obtained.
Upon the application of power to the heater windings temperatures up to near
0?C can be achieved. For temperatures from that of room to about 100?C, just
the heater windings are used without any coolant such as liquid N2.
The sample chamber which screws on tightly to the heater rod to main-
tain good thermal contact is made of copper and is large enough so that there
windings. STAT
is essentially no thermal gradient along it when no power is applied to the
65
STAT
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CERAMIC
ELECTRICAL
SEALS
Rise
?C /Hr.
Firing
Temp.
Hapico 110-2 Iron Oxide
lo94?C
1?87
19500
19400
30400
19004
24600
TO VACUUM
I SYSTEM
26100
27700
23500
27100
17700
29200
LIQUID NITROGEN
CONTAINER
J. T. Baker Iron Oxide
-0?COPPER
ROD
23900
02
600 Air
02
1200 Air
02
SAMPLE
SAMPLE
CHAMBER
(COPPER)
Figure 39. Block Disarm of Cryostat
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
?
Several Cu - Cons tantan thermocouples are provided to measure
temperatures in various locations within the cryostat. These thermocouples
as yell as sample leads and the power leads of the heater windings are
soldered to ceramic vacuum-tight lead through insulators.
It has been possible by proper thermal design to minimize loss of
liquid N2 after the liquid N2 chamber has been sufficiently cooled. The
coolant will remain in the chamber for over 2 hours if no power is supplied
to the heater ,windings; if the heater is used, as during a run, this storage
time for liquid N2 is somewhat reduced.
The entire liquid nitrogen container-heater rod-sample chamber
assembly is soldered to the top flange of the cryostat with an "0" ring pro-
viding the vacuum seal between the top flange and the flange of the body of
the cryostat. This type of demountable design has worked exceedingly well.
The cryostat is evacuated by means of a side port connected
directly to the main glass vacuum line through a "Sylphon" bellows and a
Kovar-glass seal.
? The vacuum system used is a conventional one. A Welch 1405-B
DuoSeal mechanical forepump is used in conjunction with a low vacuum ballast,
an H.I.T. mercury diffusion pump and a liquid nitrogen condensing trap. An
NRC 501 thermocouple gauge reads the pressure between the forepump and bal-
last while a Philips-type cold cathode ionization gauge reads the pressure
on the high vacuum side, i.e. on the main line to the cryostat. For conven-
ience of operation there is a roughing line to the high vacuum side of the
line. Under good operation ofethe cryostat, it has been possible to obtain
vacuum of the order of 6 x 10-0 mm lig as measured with the Philips gauge.
Figure 40 shows an external view of the cryostat connected to the
main vacuum line. The potentiometer pictured is a Leeds and Northrup Model
8657-C and is used to measure the thermal emf's.
:!!
To measure ? and Q of the samples, a radio frequency bridge is used.
The signal is supplied from a Marconi Instruments Ltd. Standard Signal Genera-
tor Model TF 867. This particular generator is rated from 15 kc to 44o mc.
A National HRO-50T1 receiver is used as the detector. An internal modulator
allows an audio output to be displayed on an oscilloscope.
Figure 41 shows the general setup of the equipment used in conjunc-
tion with the cryostat.
Method of measurement. A block diagram of the circuit used to
measure ?01 the initial permeability, and Qmag, the material quality factor
of the toroidal cores is shown in Figure 42.
A typical toroid is prepared for measurement by winding it with 30
turns of number 31 wire (about 20 inches). After placing the sample in the
cryostat, its inductance and resistance are measured on .a radio frequency
bridge. Generally it is necessary to correct the results because of lead
capacitance, inductance and resistance. The bridge measures the equivalent
68
69
Photograph of Cryostat
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STAT
STAT
',..t".-WLIL`,,,ta,14=P?ra, ta:XL..*--...t..."?=MWV;414.-1...X.4.,,r...
?
Photograph of Equipment Used in Conjunction with, Cryostat
RADIO NULL
SIGNAL ??--?.0FREOUENCY....????? ....--....
RECEIVER DETECTOR
GENERATOR 0.?----.4, BRIDGE 6"-'41 ip..---...
(OSCILLOSCOPE)
Figure h2. Block Diagram of Circuit Used to Determine Initial Permeability and
Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
71.
parallel inductance and resistance between its terminals which is easily
converted to the actual series inductance and resistance of the toroid and
leads provided lead capacitance does not have to be considered. See
Figure 43.
Some initial measurements of 11. as a function of temperature are
presented in Figure 44 for a sample of Composition 67, toroid .75HQ67.23.
Composition 67 is described in Section III. Toroid .75HQ67.23 was sintered
at 1100?C for 20 minutes. Figure 44 shows that the initial permeability
increases .07% per degree Centigrade over the temperature range -170?C to
25?C. Snag did not vary appreciably over this range.
One additional remark should be made regarding the low temperature
behavior of the nickel-zinc ferrites investigated during this program. In
the course of permeability measurements in the temperature range -50?C to
-25?C, an indication of a "thermal arrest" was observed in the heating
curve, which may be indicative of an ionic ordering taking place somewhere
in this temperature interval. Time did not permit a detailed investigation
of this effect so no significant data are available. However) close
scrutiny of the behavior of properties in this temperature range should be
made in any future work on this ferrite system.
72
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'Series and Parallel Equivalent Circuits of Coil
STAT
STAT
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ft
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0
klA :300
f = 1.5 Mc/SEC
h .127 INCHES
= .641 INCHES
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Differential Thermal Analysis
Fabricating high quality ferrite pieces is beset by many diffi-
culties for which no good evaluation procedure is available. A finished
test piece of ferrite material is no better than the weakest link in the
chain of steps leading to the finished specimen. But the situation may
be even worse. Failure to produce a high performance specimen is fre-
quently a matter of severe failure of one operation or process rather
than a summation of partial failures in many steps. And without good
evaluation procedures for individual unit processes, it is difficult, in
fact almost impossible, to exert the vigilance required to produce fer-
rites of the highest quality.
One of these difficult processes is "binder burnoff". Although
in small pieces it does not cause much trouble, it becomes more and more
serious as the size of the pressed piece increases. The difficulties
also mount with increasing binder content particularly for large pieces
heavily loaded with binders and lubricants.
For extrusion, large concentrations of binder are used to
achieve uniformity during ejection. But during the subsequent drying
and binder elimination strains and even cracks can be introduced.
Careful and complete binder elimination before high temperature
firing is also important for developing maximum permeability and satura-
tion as in the nickel zinc ferrites for large signal use. Binder burnoff
is also a problem of some consequence in preparation of the low loss
materials for low signal applications.
For best pressing or extrusion characteristics ferrite powders
are mixed with binders, powder lubricants and other conditioning agents.
The elimination of these materials proceeds by several different processes,
such as (a) volatilization, (b) cracking followed by vaporization and,
(c) combustion of carbonaceous materials.
Practice varies considerably on kind of binder, some favoring
polyvinyl alcohol (PVA) types with others preferring wax base emulsions.
This makes considerable difference in the processes by which they are
eliminated. PVA can be eliminated largely by depolymerization at lower
temperatures to volatile products, while wax types must be largely burned
off. Actually on rising temperature the hydrocarbon waxes first give off
volatiles, an endothermic process, then they start to crack, also endo-
thermic; then the new volatile components start to burn, and finally the
tarry residue begins to burn, the latter both exothermic processes. In
addition starchy materials also break down in a somewhat similar manner
leaving hard carbon residues which must be removed by oxidation at fairly
high temperatures.
Since some of these processes are endothermic while others are
exothermic, their study can be profitably pursued by differential thermal
analysis (DTA). Methods of approach other than DTA have been applied to
this problem, e.g. use of a recording thermobalance, but it is difficult
to interpret the data. Since the DTA will give a different type information
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75
t'
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1,4
STATI;'
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we hope to get a better understanding of the mechanism of the physical
and chemical processes in binder elimination. For this purpose a special
small furnqce was constructed which was adapted from the design of
Borschardt'. A somewhat schematic diagram of the furnace is given in
Figure 45. Test material and reference material are supplied as powder
(0.1 g) into the tubes marked Sample in Figure 45. Both loosely piled
powders as well as tamped specimens have been tried. Packed samples
were generally preferred.
After early troubles with the aluminum block furnace described
above, it was redesigned to reduce heat loss by removing some of the
aluminum in the flange and then rewound and again placed in service.
With these improvements, we were able to pursue the differential thermal
analyses to 500?C many times. At this temperature the aluminum blocks
had a tendency to weld together, making it extremely difficult to sepa-
rate the parts of the furnace.
However, sufficient data were obtained to indicate that still
higher temperatures would be desirable. A special fire brick door
(Figure 46) was designed to fit into a small standard muffle furnace
(Tempco 1400 watts). The furnace is controlled by the same Leeds Northrup
cam program control, amplifier and X-Y recorder used on the previous fur-
nace. This apparatus with this second furnace was proved out to 800?c
several times and was adequate for use in binder studies.
The special fire brick door carrying the sample holders shown
in Figure 46 was made up by cementing fire brick together after channels
(tubes) for the thermocouples were provided. Thermocouples (Pt - 13% Rh)
are cemented in the protection tubing which projects 1/4 inch above the
brick. Three thermocouple junctions are shown, two differential junctions
and 6T2, and a third T3, which measures the sample temperature.
This latter tube can also be supplied with a metal tube and unknown powder
to measure the temperature of the sample by substitution.
The bosses carrying the thermocouple junctions provide the seats
for the thin walled metal tubes which are pushed down upon them making
easily demountable crucibles. We use stainless steel tubes 1/4 inch in
diameter by 1/2 inch high with 6 mil wall. These tubes have withstood
temperatures up to 1000?C without severe oxidation and are quite satis-
factory, but platinum tubes would be more suitable for higher temperatures.
To clean the setup, the tubes are removed and the powdered sample brushed
off from the thermocouples and bosses, after which it is ready for a re-
peat analysis.
Although this furnace setup is satisfactory for binder-burnoff
studies, it is limited to about 800?C because it does not have sufficient
electrical power capacity to maintain the constant rise rate above this
temperature. For studies of calcination phenomenala higher temperature
and higher power furnace has been provided and is described later.
1. H. J. Borschardt, J. Chem. Educ. 31 103 (1956)
76
cs,-lciFir in Prt - Sanitized CODY ADrrov
it\
4A'
47.
TO
VAR IAC'
SAMPLE
READ T.C.
CONTROL T.C.
TRANSITE
?
?
?
?
?o/
1k 34
MATERIAL : ALUMINUM
DIFFERENTIAL THERMOCOUPLE
5*
Figure 45. D.T.A. Furnace
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77
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Results of burnoff studies in furnaces No. 1 and No. 2. None
of the nickel ferrites under study in this contract was available with a
wax binder already mixed in. And since several magnesium manganese fer-
rites were immediately available with Hyform binder (wax), several dif-
ferential thermal analyses were made on these materials. However, thermo-
grams of the materials with polyvinyl alcohol (PVA) and methylmethacrylate
(MMA) were made on nickel zinc ferrites.
Many different experimental procedures have been tried but no
completely standard procedure evolved. In general, it was found that
0.1 g. samples accurately weighed give very satisfactory sensitivity. In-
stead of using powdered A1203as the standard material,as is common in
DTA, our practice was to use powdered ferrite with binder in one tube and
the same ferrite without binder in the other. This discounts most effects
except that of the binder. A powder at least as fine as minus 60 mesh is
used and lightly tamped. Before we began to tamp the samples, the result-
ing differential thermograms were quite variable. Mostly, a heating rate
of 3?C per minute has been used, primarily because it was not easy to alter.
Although nearly two dozen differential thermograms have been made,
only a few representative examples are shown in Figure 47. Sample tempera-
ture is plotted on the x-axis and the difference temperature (4T) on the
y axis. Exothermic reactions show a positive deviation (+4T) and endo-
thermic negative (-AT). The largest AT shown is about 15?C, and all dif-
ferential thermograms given are plotted on the same scale.
In order to prove that the apparatus was working properly and was
capable of resolution of fine detail a differential thermogram of copper
sulfate decahydrate was prepared and appears at the top of the group. It
agrees quite well with that published by Borschardt1 except that it shows
detail beyond his high temperature limit. Presumably these peaks are due
to decomposition of the anhydrous sulfate.
The next four curves are all of calained ferrite material incor-
porating a wax type binder (Hyform). The top one contains 16% by weight of
Hyform emulsion ()-i..8% by weight, wax), 3/4% by weight of Flocgel (starch)
and 3/4% by weight of magnesium stearate. The other three have 8% of Hyform
emulsion only (2.4% wax).
All of the thermograms of samples containing wax cover about the
same range of temperature and show large differential heat effects in the
range from about 200?C to 11-50?C. The maximum varies somewhat but generally
occurs from 300? - 340?C. However, as a generalization, one might say that
exothermic reaction begins very early on heating, accelerates very rapidly
around 200? - 250?C and starts to fall off at 350?C and is practically over
at 420?C. But the final stages of combustion of the carbonaceous matter
are not complete until 500?C.
In spite of the general agreement among the thermograms of the
samples containing wax there are differences among them that seem under-
standable. All three of the samples containing 8% Hyform emulsion (2.4%
wax in sample) show structure in the combustion peak. Note that the finer
powder (-140 mesh) shows substantially the same behavior as the others.
STAT
.,r'lciFir in Prt - Sanitized CODY ADrDrOv
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Declassified in Part - Sanitized Co .y Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
CuSO4 ? 10H20
4.8% HYFORM
0.75% FLOCGEL
0.75% MAGNESIUM STEARATE
?60 MESH
2.4% HYFORM ?60 MESH
2.4% HYFORM ?60 MESH
2.4% HYFORM ?140 MESH
I% MMA
PVA
0 100 200 300 400 500 600
TEMPERATURE ( ?C)
?
700 800 900
Figure 47, Differential Thermograms
80
fl-Iiifir1 in Part - Sanitized Coov A
On the other hand, the one containing 16% Hyform, 3/4% Flocgel and 3/4%
magnesium stearate (top) shows a larger and smoother peak. With twice
as much binder more heat would be expected. And with several combustible
binder components one would expect better packing and smearing of the
combustion curve, just what is found.
Polyvinyl alcohol and methyl methacrylate are also eliminated
by exothermic reaction. Methyl methacrylate begins to leave the sample
at 100?C and is entirely gone before 300?C is reached. On the other hand,
polyvinyl alcohol begins to go at about 300?C and is all gone by 440?C.
The total net heat evolved in the process is much less than with the wax.
However, it should be pointed out that the total weight of binder is less
in these two cases, 10% by weight.
Although the present work is by no means conclusive, it does
point to need for great care in the "binder burn-off heating cycle". With
temperature differences as large as 15?C between the unknown and standard
specimens in a small 1/4 in. x 1/8 in. lightly packed sample, one would
expect large temperature differences in a large densely rammed production
piece. On the basis of these differential thermograms, it appears that
the most sensitive temperature zone for wax (Hyform) burnoff is 200? 325?C.
From the peak at 325?C an increasing rate could be used up to 450?C.
High temperature DTA in sintering range. A new furnace was pro-
vided to pursue the differential thermal analysis up in temperature to in-
clude the sintering range, 1100?C to 1200?C. For a variety of reasons, a
wire wound furnace was preferred to one using Globars. None of the commer-
cially available furnaces seemed appropriate, so one was built to suit the
needs of the present program.
Furnace No. 3 is a tube type, 12 inches long by 12 inches overall
outside diameter, and is shown in Figure 48. The tube muffle is 2 inches
inside diameter and grooved outside to carry the wire, Kanthal A-1 which
allows operating temperatures to 1350?C. The winding consists of twenty-
three feet of B and S Gage No. 20 wire (0.85 ohms/ft) giving a cold resis-
tance of 10 ohms for the furnace; a center tap allows the net magnetic
field due to current in the winding to be reduced to zero at the sample
position. Before assembly, the heating element was cemented to the muffle
with a cement specifically designed for use with Kanthal wire.
K-30 high temperature insulating fire brick was cut to shape to
fill the space between the wire wound muffle and the stainless steel can
making up the shell of the furnace. The ends of the shell are also stain-
less steel and fitted with handles so that the furnace can be carried easily
or used in the vertical position. The furnace is used in the vertical posi-
tion, mounted on an angle iron stand which holds the furnace 9 inches above
the bench top.
The furnace has been tested to 1300?C and has sufficient reserve
power to maintain a rise rate of 6?C/min or greater up to that temperature.
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FURNACE CONTROL
THERMOCOUPLE
ALUNDUM
MUFFLE
CEMENT IMBEDDED WINDINGS
OF KANTHAL Al WIRE
STAINLESS STEEL
CAN
K-3I INSULATING
BRICK
In the previous DTA furnaces, the samples were contained in
stainless steel tubing, slipped onto the thermocouple protection tubing
to make demountable crucibles. That system worked well and has been in-
corporated in the third design. However, there is always some possibility
of reaction with the metal container. Therefore, pressed pellets of
material were substituted as shown in Figure 49 rather than powdered
samples.
A special small die was constructed to press the pellet sample
(3/16 inch 0.D.) with a small hole to allow the sample to sit upon the
thermocouple junction. Mechanically, this works fine. It also gives a
sufficient T for measurement. As yet, it is not clear that use of
pellets is superior to powder in crucibles, but the pellet technique is
much cleaner and simpler.
Unfortunately, even before this furnace (No. 3) was built,
trouble was encountered with noise in the electronic circuits of the measur-
ing equipment, i.e. the X-Y recorder. This has been continually getting
worse. Since the third furnace has been in use, noise and erratic behavior
of the control and measuring equipment have hampered progress considerably.
Shielding of the thermocouple lines and grounding of amplifier cheeses did
not remove the trouble. A complete metal tubular shield inside of the fur-
nace surrounding the samples and thermocouple leads was tried and showed
promise.
In order to obtain measurements at high temperature, independent
of the difficulties encountered in the electronic circuitry, the X-Y re-
corder was replaced by two thermocouple potentiometers and a firing was
carried out to 1300?C. No erratic behavior was apparent in this setup.
The results are shown in Figure 50. From Figure 50, it appears that the
binder burnoff accounts for the major part of the response but that the
heat effects in the sintering range are very small, only two or three micro-
volts as recorded by the differential potentiometer. If desired, the de-
flection could be magnified through the use of a sensitive galvanometer but
it appears that the X-Y recorder would not be sufficiently sensitive to
make fnvestigations in the sintering range fruitful.
Figures 51 and 52 are photographs showing the DTA furnace and the
temperature and differential temperature recorders. Further work in dif-
ferential thermal analysis should be extended to calcination studies with
and without additives and sintering studies with and without additives.
However, it appears that the best method should include exploratory measure-
ments using point by point potentiometric methods. After this initial work,
an indication will have been obtained of the required sensitivity. The
final analysis would then be made using a galvanometer with the appropriate
sensitivity. These recommendations are based upon the results shown in
Figure 50.
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Conclusions and Recommendations
The effort expended on the development of low loss, low signal
ferrites during the period covered by this report has yielded a series of
high Q materials with permeabilities in the range 12 to 120. The Curie
temperatures of these materials lie between 385?C and 500?C and high Q
behavior persists over the temperature interval -65'C to +250?C. In ad-
dition, the low signal properties of these materials have been shown to
be relatively unaffected by prolonged exposure to high humidity. Of
particular importance is the low temperature coefficient of permeability
exhibited in the range -65?C to +25?C. In this critical temperature inter-
val, the variation in Compositions 84 and 67 is less than 0.1% per degree
C.
The variation of the gQ product with frequency is an important
design characteristic. Composition 84 bodies have been prephred which ex-
hibit ?Q products greater than 10)000 at 7 mc. For applications which re-
quire operation above 7 mc, Composition 285 bodies are available with ?Q
products in the range 10,000 to 7,000 between 7 mc and 20 mc; at 30 mc,
the gQ product is still as large as 1500.
Much useful information was gained from the investigation of
the effects of processing techniques, the investigation of the effects of
different brands of iron oxide, and the results of differential thermal
analysis. Knowledge of this type is necessary to assure reproducibility
of developmental samples for future large quantity use.
Thus, the broad objectives of the low signal materials program
have been achieved. Future work in the development of low signal ferrites
should include further study of sintering control in these partially cured
materials in the hope that the ?Q product can be increased in the fre-
quency range 10 to 30 mc and that better control can be exercised over the
temperature coefficient of permeability, particularly at low temperatures.
Also, broad objectives, which applied in the phase of effort currently com-
pleted, should be narrowed to stipulate specific low signal parameter
values.
-
88
171,
SECTION IV
HIGH FREQUENCY NARROW BAND MODULATED DELAY LIVES
Introduction
The use of delay lines has become an integral part of a large
variety of electronic systems. Radar, color television, correlators, and
computers are but a few of the many applications utilizing delay lines.
The specifications for a particular line are of course a function of the
needs of the specific application. However, one can classify delay lines
in terms of the range of delay times that are required. Very short delays
of the order of 0.1 of a microsecond are conveniently achieved with lumped
constant elements. Delay times of the order of one microsecond to several
microseconds are usually accomplished with lumped constant or distributed
parameter systems. Finally, delays of the order of tens or hundreds of
microseconds are usually obtained by some form of sonic element. However,
in each of these groups the objectives are very similar.
An adequate delay line must be capable of passing a band of fre-
quencies with a constant time delay and constant attenuation for each fre-
quency component in the pass band. Though there may be many solutions to
these two problems, one is usually compelled to compromise with other
factors such as overall size, ease of fabrication, costjaccuracy of time
delay adjustment, temperature stability, and the impedance level that is
desired.
The present report is concerned with the development of a narrow
band, high frequency ferrite delay line, the delay of which can be varied
by a biasing magnetic field, thus yielding a component which can be used
for phase modulation.
Of the many ways by which one can produce phase modulation, the
use of a controllable delay line appears most attractive. The usual pro-
cedure for the production of a phase modulated carrier is to generate a
low frequency carrier to which the modulation is applied and the final
carrier is generated through a series of multiplications. The modulation
itself is usually produced by some form of reactance tube. In order to
decrease the overall size and power consumption during the modulation pro-
cess, it would be more desirable to perform the modulation function at the
actual transmitted frequency or at a stage which reduces the number of
multiplications required. A delay line whose time delay could be varied
with an electrical signal would meet such requirements.
Objective
The objective of this phase is to produce a ferrite delay line whose
delay can be adjusted by the application of a biasing magnetic field. The
present goal is to achieve a total delay of approximately 0.5 microseconds and
a variable delay of 0.1 microsecond at 30 mc.
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89
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S TAT:
Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05 CIA-RDP81-01043R002800240003-8
General Considerations
A phase modulation element operating at 30 mc with a modulation
of 30 - 3000 cps is desired. However, it was decided to work in the 10 mo
region at the start of the project' and progress toward the 30 mc region in
determining the feasibility of the device. Since the delay of a distri-
buted constant line is equal to ALC), where L is a function of the permea-
bility of the medium, the delay can be modulated by changing the permea-
bility. In a ferrite, the permeability is a function of the applied magnetic
field. A ferrite delay line can therefore be modulated by establishing a
magnetic field in the line with the modulation signal. The delay line must
also have reasonable attenuation and a fairly high order of time delay, with
respect to the change in delay desired. Moreover, it must be fairly small
if the input modulation power is to be minimized. While the line must
operate at the carrier frequency, it need not have a flat time delay
characteristic, since it will operate about a fixed carrier frequency. A
line having a total time delay of 0.5 microseconds at 10 mc in three inches
length would be acceptable, if a variation of +0.1 microseconds can be ef-
fected. The delay line output could be peaked at 10 mc to obtain lower
attenuation, if desired.
The design of the lines discussed below, including choice of di-
mensions, was governed by the analytical development presented in WADC
Technical Report TR 56-2740 Part V. In this analysis, the time delay vs.
frequency characteristic for a given permeability of rod and sleeve was pre-
sented. The important feature of this curve is a flat portion which persists
until a critical frequency is reached. At this critical frequency the delay
decreases sharply with frequency. In the present development, this is of no
real concern except that sufficient magnitude of delay must be available so
that the appropriate changes in delay can be effected by application of a
biasing field.
Materials Prepar4tion and Initial Evaluation
The initial phase entailed the measurement of fern tea in order to
determine the variations of permeability with bias obtainable at high fre-
quencies. The circuit arrangement shown in Figure 53 was used for the
measurement of ? vs. bias. A National Electronics Laboratories Radio Fre-
quency Permeameter was modified slightly by drilling two small hole* through
the main body. This permitted the insertion of a wound toroid whose leads
could be brought through the permeameter to a d.c. supply. The tuned cir-
cuit was inserted so that the power supply would not load down the perme-
ameter. The use of a Q-meter in conjunction with the permeameter allowed
for a rapid determination of ? vs. bias field. The number of turns, n,
that are wound on the core is determined by two factors. It is desirable
that n be as large as possible in order to reduce the amount of current re-
quired. On the other hand, n must be reduced far enough so that the self-
resonant frequency is sufficiently far above the test frequency. In most
cases, this required about 15 turns on a half-inch toroid.
A sample of Composition 84 (toroid .75HQ84.10) was evaluated
using the modified National Electronics Laboratories Radio Frequency
'41w
90
:
rs,m/ Annrnved for Release
?
Er,
Permeameter by the technique outlined above. The results are shown in
54. In Figure 54, the low signal permeability decreased by a factor
Figure
f817fram zero field to a field of 19 oersteds for the initially unmagne-
tized sample. The change in permeability observed from remanence to satu-
ration is shown by dotted line and the return solid line.
Other materials, Compositions 67 and 285, were similarly evaluated
at 10 mc but it was immediately obvious that the necessary change in permea-
bility could not be obtained in these materials.
Figure 53. Permeameter Schematic for y. vs. Bias
50-Yr 2014/02/05 CIA-RDP81-01043R002800240003-8
91
STATT't
Declassified in Part - Sanitized Copy Ap roved for Release ? 50-Yr 2014/02/05 CIA-RDP81-01043R002800240003-8
Having established that sufficient permeability variation can
be obtained using Composition 84, rods and tubes were extruded for the
fabrication of dell4i44:sio.;; zitlillibil7):771114.turazitloCoarzli..tri70:44.4115.
con-
sists of 66.96 wt%
Standard ceramic fabrication procedures were followed in the
processing of this composition. Usual practice is to weigh out approxi-
mately 1 kg total batch on a large (2 kg) analytical balance. The re-
sultant mixture is ball milled overnight for about 16 hours in a one
gallon iron mill with steel balls, in the presence of about 1 1/2 liter
deionized water. This process both mixes and grinds. The slurry is then
placed in glass drying pans and brought to dryness in standard ovens.
The next step in the process is to run the dried powder through a pulver-
izer for sizing.
DuPont No. 7005 polyvinyl alcohol (PVA) is used as a binder for
the extrusion in the extent of about 4 1/2 wt%. The PVA is made up fresh
each time in a 17% water solution. Homogenizing and mixing were done in
a Lancaster mixer.
Rods and tubes of Composition 84 were extruded. One set of ex-
trusion samples consisted of rods 0.250" in diameter, tubes with an O.D.
of 0.375" and an I.D. of 0.255", and tubes with an 0.D. of 0.500" and an
I.D. of 0.255". Another extrusion yielded rods 0.094" in diameter and
tubes with an O.D. of 0.157". The dimensions given are for samples in
thetreen state".
Five different firings were made. These firings consisted of a
20 minute soak with a fast rise rate of the order of 600?C/hr after the
binder had been burned off. Soak temperatures of 1175?C, 1160?C, 1140?C,
1125?C and 1100?C were used with an optimum, as determined by desirable
end results in the finished delay line, occurring at about 1140?C to
1150?C.
More specifically, for the firings of 1175?C for 20 minutes, the
permeability of the material as measured on the prototype line was excel-
lent while the Q or attenuation was rated good. Firing at 1160?C for 20
minutes still maintained an excellent ? while the Q or attenuation improved.
Essentially, the same thing was true for the firing at 1140?C for 20 min-
utes. The firing at 1125?C for 20 minutes resulted in a good permeability
but only fair Q while the firing at 1100?C produced lines which had both
a low g and poor attenuation. The exact values of permeability and Q were
not directly obtainable) but were inferred from the resulting delay line
performance.
In order to establish modulation techniques and testing procedures,
initial experiments were performed on lines constructed using rods and tubes
of ferrite composition 205. Composition 205 was developed under Contract No.
AF 33(616)-2009 for application in a video delay line. The oxidic constitu-
ents are 48 mol% Fe2031 26.5 mol% NiO, 25.0 mol% ZnO, and 0.5 mo4 V205.
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+M.
ROD
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TUBE
WINDING
SILVER
PATCHES SILVER
PAINT
Figure 55. Ferrite relay Line
The processing of this material and the subsequent video delay line fabri-
cation is described in full in NADC TR 56-274, Part V. The particular
Composition 205 ferrite used here is of no significant interest. However,
it was a simple matter to test evaluation methods with materials immediately
at hand. The prior development showed that the rods and tubes of Composition
205 were of sufficient attenuation that usable delay lines could be produced.
However, Composition 205 cannot be operated at frequencies above 8 mc so
that this material does not satisfy the needs of the present program.
9!.
in Dar+ - arIIfI7d Cony Aooroved for Release
?
v.47:
4c:
5
A rod of Composition 205 5.1 cm long having one continuous silver
stripe and three notched ones was wound with No. 42 HF FORMEX wire.
(Figure 55). The tube had a silver coating which was of the same material
as that used on the rod (DuPont 4916 lacquer). Two unsilvered stripes were
left on the tube to reduce any possible eddy current losses. The silvered
areas were grounded at the output and the entire line placed in a ferrite
"C" core magnetic yoke wound with 1000 turns of number 38 OF wire. Silver
paint was used to isolate the line from the yoke structure (Figure 56).
The line was left open circuited and an R.F. signal applied while
the magnet windings of the yoke were excited with a direct current (Figure
57). The time delay, Td, could then be measured by noting the current maxi-
ma on the vacuum tube voltmeter, Vi. Since the admittance of an open cir-
cuited transmission line will be a maximum when the line length is an odd
number of quarter wavelengths, and since the total delay, Td, is the ratio
of length to velocity of propagation, then Td = n/(4f) where f is the fre-
quency in cps and n an odd integer. Therefore, by noting those frequencies
at which V1 peaks we may find the time delay of the line. By applying D.C.
signals to the yoke the family of curves of Figure 53 may be obtained.
At one megacycle Td . 0.65 microseconds with a variation of 0.35
microseconds with the application of 200 ampere turns and an attenuation of
9db.
A further experiment in modulation techniques used a similar fer-
rite yoke having 5000 turns of number 38 QF wire. A line was constructed
and wound with number 42 H.F. formex wire on a rod having eight silver
patches arranged in three stripes. The line was terminated in its character-
istic impedance of 6.5K. The input and output wave-forms were viewed simul-
taneously on a Tektronix type 535 oscilloscope with a type 53C dual trace
preamp triggered by the input waveform (Figure 59). The change in delay
without a ferrite tube as noted on the oscilloscope = 0.08 microseconds with
an applied field of 1250 ampere-turns. With the tube, which was unsilvered,
the change in delay . 0.6 microseconds. Clearly, the ferrite tube extended
the usable time delay in this region.
Before proceeding to lines constructed using Composition 84, Compo-
sitions 67 and 75 were used in further establishing proper fabrication tech-
niques. (Compositions 67 and 75 are described in Section III of this report.)
Tables XVI and XVII indicate the physical characteristics and magnetic evalua-
tion of various lines constructed from a variety of materials, including
Compositions 205, 67, 75 and 84.
The data given in Tables XVI and XVII for lines I and II are self-
explanatory. ;,ines III and IV were fabricated to investigate the use of
indium-amalgam? in place of DuPont type 14.916 silver bearing lacquer as a
conducting coating for capacitive patching on rods and ground planes on
tubes. It is evident from the information of Tables VI and VII, and Figures
60 and 61 that the indium-amalgam is a better conductor on a ferrite surface.
4/02/05 CIA RDP81-01043R002800240003-8
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STAT
Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
SILVER PAI NT
FERRITE
YOKE
RF SIGNAL
INPUT
0
FERRITE
DELAY
LINE
R F SIGNAL
OUTPUT
SILVER PAINT
MAGNETIC MODULATION
WINDING
Figure 56. Ferrite Deley Line Mounted in Ferrite Yoke
96
R. F.
GENERATOR
ion
POWER
SUPPLY
INPUT
DELAY
LINE
OUTPUT
0
V.T.V.M
VI
1111111111111111r
MAGNETIC
-N
YOKE
? ? '1
1L
?..
Figure 57, Block Diagram for Modulated Delay Evaluation
97
STAT
1
STAT
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
RF
0
GENERATOR
R.F. SIGNAL
IN
POWER
SUPPLY
YOKE?a
DELAY LINE
RE SIGNAL
OUT
0 a 6.5K
NJ V' 1...7
INPUT A
INPUT B
r?co
00-
SYNCH
TEKTRONIX
TYPE 535
OSCILLOSCOPE
WITH DIAL
TRACE PREAMP
Figure 59. Block Diagram for Visual Presentation
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99
S T ?7-IA T
Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
Line
No.
Material
Length
inches
Diam.*
Wire
Size
Modulation
Structure**
_
Description
of Line
I
205
2
L
42HF
Y
Rod and tube silvered with DuPont
14.916 lacquer.
_
ha
IIb
67.8
67.8
2
2
L
L
42HF
42HF
Y
Y
Patched rod, 3 patches in 3
stripes; without tube.
Patched rod, 3 patches in 3
stripes; unsilvered tube.
Ina
IIIb
75
75 1
2
2
S
S
42HF
4211F
Y
Y
Rod and tube patched with 8
patches; DuPont 4916 lacquer.
Tube had 2 nonconducting stripes;
indium-amalgam.
IV
75
2
L
42HF
Y
Rod and tube patched with 10
patches; indium-amalgam. Tube
had 2 nonconducting stripes.
V
84
2
1
S
42F
Y and C
Tube patched with indium-amalgam
with one nonconducting stripe.
Rod not patched.
When the number of nonconducting
stripes on the tube was increased
to six progressively, no change
in output characteristics could
be noted.
VI
84
2
L
42F
Y
Rod and tube patched with indium-
amalgam.
VII
84
3.85
s
42F
C
Tube patched with indium-amalgam
in one nonconducting stripe. Rod
not patched.
VIII /
I
84
2
_
S
42F
C
Temperature check) line operated
at ambient temperatures of -44?c
to +110?C.
* Diameter refers to large (L) tube or rod diameters
Large: Tube 0.D. = 0.29 inches Small: Tube
Rod O.D. = 0.193 inches Rod
** Refers to ferrite yoke (Y) or concentric coil (C)
or small (S)
= 0.122 inches
= 0.078 inches
MAGNETIC AND ELECTRICAL EVALUATION OF DELAY LINES
a)
g,-)
IA
(at 1 kc)
..?..
0
0
2
o 4' co
N 0la
"O
.- E-4
I
0 .0
.--.
0 o -0
0
0 0
...... 4.. 0
44 0 .1-1
..--.
0
0
u)
=
......
E-I
44 -
00
a)
0 to
?. =
0 ......,
0
71
OE-4
clo
0
...1 0
4.).?1
o
i-4'
r-1
.0 0
0-r4 TJ
Z 4-1 E-4
Comments
I
2.2
0.54
1 9
.6
.35
200 a.t.
his
rib
7.1
.56
1 6
1 10
.o8
.60
1250 a.t.
Ferrite tube necessary
for large change in
delay at high freq.
Illa
b
6.5
6.5
.34
.47
see Figure
Line with indium-
amalgam patching ex-
hibited peaking, other
did not..
IV
5.1
.56
see Figure
Peaking shifted up in
frequency as patching
and diameter increased.
V
7.5
.43
10 10
20 20
see Figure
.12
.06
4
300 Oe.
Modulation power so low
that yoke dispensed with.
Feed-through at 10 mc
occurred when the rod
was patched.
VI
10 20
.01
600 Oe.
Large cross section
line not as effective.
VII
8.5
,
.70
10 20*
see Figures
.1
and
60 gadss
0.35 watts
driving
power
* Can be peaked to 5 db.
(see discussion)
VIII
see Figure
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Declassified in Part - Sanitized Copy Approved for Release @ 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
.t.,
- - -
1.3
12
1.1
10
.9
.8
.7
.6
5
4
,
o
LINES
?
o
....0.
0
_
.
0
o
..
.
o
o
o
o
.-
-
o
d/C)NN.............%....a.
3
LINER
2
.
I
,
100kc 2
3
4
5
6
7
a 9 Irn.c.
2
3
4
5 6
7
a
910
FREQUENCY
Figure 60. Time De1=4y vs. Frequency for Ealay Lines Patched with Indium-Amalo.am. Lines III and IV
ATd
.14
.13
.12
.10
.09
t
7t,
10 mc.
.06
.05
.04
.03
.02
.01
0
5 10
20 30
D.C. MODULATION CURRENT --a- ma.
Figure 61. Change in Delay vs. D. C. Modulation Current. Line V
40
50
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Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05 : CIA-RDP81-01043R002800240003-8
The amalgam undoubtedly adheres better to the ferrite surface. The peak-
ing displayed in Figure 60 could not be observed with the silver lacquer.
In line IV the peaking has been extended to a higher frequency by using a
large cross section line which has less distributed capacitance.
When line V was first constructed, the rod was not patched since
only a cross-check on the permeameter reading on Composition 84 was desired.
The line exhibited excellent characteristics and was operable at 20 mega-
cycles (Figure 61). Its modulation requirements were so moderate that the
ferrite yoke structure was replaced by a simple solenoidal winding. This
procedure eliminated some feed-through problems, since the yoke structure
had represented an alternate low resistance path to the incoming f,ignal.
However, when the rod was patched, feed-through of the input waveform be-
came the dominant factor at the output. It was found that this feedthrough
was due to the capacitive link formed by these patches. The patches could
not be reduced in size to the point where the effect would be .tolerable,
and had to be abandoned. At 10 mc the impedance presented by the stray
capacitance was considerably less than that offered by the ferrite to the
solenoidal wave. Peaking could be accomplished only through the geometry
of the line and the output load.
Line VI established that a larger cross sectional area was not as
effective as the smaller cross section. The product of the frequency, f,
time delay, Td, and diameter of the line D is equal to the line inductance,
Ll. That is, fTdD = Ll. A given delay will occur at a higher frequency
if D is kept small. Also, less flux will be necessary to saturate a line
of smaller cross section. This, of course, will result in smaller modu-
lating power requirements.
Line VII clearly established the feasibility of the modulated
delay line. Although its attenuation is somewhat high it can be peaked
with a proper resonant load. At 10 megacycles, with a 10 microhenry in-
ductor shunting an 8 ??f Textronix oscilloscope probe, the attenuation was
reduced to 5db, and a comparatively linear time delay-modulating current
characteristic resulted to 0.1 microseconds change in delay (Figure 62).
The hysteresis effect noted in Figure 62is of the order of 5% which is
within the distortion limits of the best reactance tube methods. The time
delay vs. modulation current relation, of course, becomes nonlinear if
operation is pursued into the saturation region. Longer lines would tend
to avoid this problem as would materials of still higher permeability, by
presenting a greater initial delay.
It will be noted from Figure 63 that the point at which the time
delay-modulation current relation becomes nonlinear coincides with the
point at which the output amplitude increases drastically. This evidently
occurs because the line is approaching saturation and behaves like an air
core line with low loss. This region is not valuable, however, because
of the large nonlinearity.
The modulation winding of line VII was a solenoid wound upon a
form concentric with the rod and tube. No attempt was made to get a close
fit as the isolation afforded by the separation precluded any coupling be-
tween the carrier RF signal and the audio or DC modulation current. Although
10)4
npniassified in Part - Sanitized COPY Approved for Release
50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
17;
Declassified in Part - Sanitized Copy Approved for Release ? 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
et
C-C4
co
Allikik.-111111
0 0) a) I"- co in I. N
4F-----
4P 3anindriv NI NOI1V11:11/A
106
C',
the modulation signal could have been applied to the same winding as the
RF carrier, the additional winding afforded a means of isolating the two
signals and gave a flexible four terminal network where the impedance of
the modulation circuit could be adjusted to that of its drive circuitry.
The DC modulation characteristics noted demonstrate the practi-
cality of the delay line phase modulator. The impedance of line VII at
10 megacycles was found to have a magnitude of about 750 ohms. The delay
line cannot be loaded, however, since it still has a rather high series
impedance. The unpeaked attenuation of line VII was 20 db. The attenua-
tion may, however, be reduced to 6 db, if the line is matched into a
class Al amplifier and its output peaked: In a typical communications
transmitter, at least three stages could be eliminated by the 10 megacycle
delay line. Line VIII was the basis of a determination of the effects of
temperature on the variation in time delay with DC modulation current.
The results are shown in Figure 64. It is evident that the device is
stable through the range of -44?c to 110?c.
Additional lines were fabricated and the change in delay avail-
able determined as a function of D.C. modulation current. Table XIX is a
summary of the firing and winding conditions for each line. The corres-
ponding curves of change in time delay vs. bias are shown in Figures 65
and 66. It is apparent that line No. 10A is the superior one of this
group.
Further tests were made with line No. 10A in a commercial fre-
quency modulating equipment. A summary of the results are shown in Table
XVIII.
TABLE XVIII
TEST INFORMATION FOR LINE NO. 10A
Modulation freq. 1000 cps
Carrier freq. 10 mc
Final freq. 00 mc
Freq. deviation at 30 mc + 7.5 kc (+ .1 'Is)
Audio power required 0.3 watt
RETMA distortion
5.2j
Similar tests taken at 30 mc on line No. 10C, indicated a change
in time delay of + .01 ?s, in the linear range. Systematic testing at 30
mc has not been possible until very recently. With the acquisition of a
calibrated 30 mc receiver, it now is possible to determine whether the
basic limitations are produced by the line geometry or the material charac=
teristics. The tentative conclusion at present is that the original goal
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107
I
STAT
1
STAT
Declassified in Part - Sanitized Copy Approved for Release a 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
-
.12 110 ?C
Figure 64. Change in Delay vs. D.C. Modulation Current with Temperature as
Parameter Line VIII
I . 4
-OAT ?ri."3.4*AV-11146-9"*. 104 T,
0
\0
w
H w
> H
H >
H
7..01r.M5PMEMT
TABLE XIX
DELAY LIVE FABRICATION DATA
,?.?%
.:)t ?
'Fir4
*(i
7.`.?
,?!"
Line
No.
Line
Length
Soak Temp.
?C
Soak Time
(min.)
Rise Rate
?C/hr.
Fall
Rate
(ohms)
Resistance of
Modulation
. Winding ,
%
,
4A
2'
1140
'20
500
Furnace Cool
800
5
2'
1125
20
500
it
750
5
2"
1100
20
boo
it it
950
7A
3 7/8"
1150
20
400
t I It
1850
7B
3 3/4"
1150
20
400
ii ii
2250
9
2 3/4"
1135
20
800
ii ii
1650
10A
4 3/4"
1160
20
600
Slow Cool
1850
( 100?C/hr.)
10B
3 1/2"
1160
20
boo
Slow Cool
2000
( 100?C/hr.)
10C
2 1/4"
llbo
20
boo
slow Cool
800
( 100?C/hr.)
A, B, and CI for a given designation, refer to different lines fabricated from a
particular firing.
A
.01'16?.6=46=1WANAM:=PRIMNIStage4tAlseilFOCIPAroxsPreftwanowee,....*-...
F4th:*. ?
Wirg=MMIWARMerWPWW~KaMMIIIR-wmr.swer.
Declassified in Part - Sanitized Copy Approved for Release a 50-Yr 2014/02/05: CIA-RDP81-01043R002800240003-8
LINE NO.7A
LINE NO.
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44
D.C.MODULAT1ON CURRENT IN MILLIAMPS
Figure 65. Change in relv vs. D.C. Modulation Current
"
W-1
.32
.30
28
.26
.24
.22
20
-
(.)
?J
4.0 59.5
2.0 59.4
fr
MO Am
am ase ????
..
."..
.....
%
?
.?
?
%
%
4,6 ?? %
...1
fa......
e
/
e /?
?? .........
.....
No
-,
/
/
/
/
/
/
k i
/
/
/
I
/
......
I
_
0.2 0.4 0.6
BIAS CURRENT IN AMPERES
0.8
Figure 75. Variation of frs fa and k with Bias Current for
Toroid 285.52
127
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66.5 67
FREQUENCY IN KILOCYCLES
Figare 76. Voltage-Frequency Characteristic for Toroid
285.56
The values of temperature coefficient of resonant frequency and
coupling coefficient obtained for toroid 285.56 at low temperatures are
very nearly equal to those reported for toroid 285.52. The values obtained
for toroid 285.52 were determined from measurements taken between 25?C and
250?C. These two samples were prepared under similar conditions.
Conclusions and Recommendations
Of the various areas of effort investigated during the contract
period covered by this report, the development of magnetostrictive materials
was the least extensive. As a result, it is difficult to arrive at signifi-
cant and detailed conclusions. However, the present work has indicated
that the temperature interval -65?C to +250?C is too broad to expect a uni-
formly small temperature coefficient of resonant frequency over the entire
interval. The goal of 10 parts per million per degree centigrade was not
attained. As a result, no attempt was made to fabricate geometries to
give rise to oscillations in the frequency region 455 kc to 1000 kc.
Further effort in this field should be more properly directed
toward obtaining specific materials for specified filter application. The
temperature coefficient requirement should be stipulated over the smallest
temperature interval reasonable.
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SECTION VI
CONCLUSIONS
In the body of the text, conclusions and recommendations have
been given covering a given phase of effort. In this Section, the per-
tinent results are summarized and in some respects extended. ?
Perhaps the most significant accomplishment of the effort
covered by this report is the development of a usable modulated ferrite
delay line for application at 10 mc. Even though the ultimate goal of a
30 mc carrier line was not achieved, the utility of the device in hand is
unquestionable. Operation in a commercial frequency modulating equipment
Indicated that the present line gives rise to low distortion and that the
audio power required for operation is nominal. The necessary total delay
and change in delay with field has been obtained using Composition 84
ferrite which was developed under the low signal materials program. Ex-
trusion of this material in rods and tubes of the requisite strength and
straightness has been accomplished without the sacrifice of the desirable
magnetic properties.
Until the utility of the 10 mc carrier line has been shown to
be inadequate, it is recommended that no further effort be expended in de-
veloping a 30 mc carrier line giving +0.1 microsecond change in delay. It
has been shown, however, that the present materials and configuration can
be used for operation as high as 15 mc and with a small amount of additional
work, be extended to 20 mc. For phase modulation systCms which require a
constant phase shift in radians, independent of carrier frequency, the pre-
sent line possibly could be extended to give +0.05 microsecond change in
delay at 30 mc.
In the development of high power ferrite materials, two Composi-
tions, 704 and 731, are recommended for application to cover the frequency
range 20 kc to 1000 kc. These materials exhibit usable permeabilities over
the temperature interval -65?C .to +250?C. (Characteristic curves are given
in the body of the text.)
It is recommended that work in the area of high power ferrite
materials development be terminated until the present materials are evalu-
ated in a specific application. After this evaluation, further effort may
be fruitful in tailoring specific properties to the needs of a given device.
During the course of the present development, high power materials were sup-
plied to the American Research and Manufacturing Corporation for possible
application in a rapid response magnetic amplifier being developed under
Contract No. AF 33(615)-3377. However, no results have been received to
date in connection with the evaluation of these materials.
The broad objectives of the program dealing with the development.
of low loss, low signal materials were achieved. A series of high Q materi-
als have been made available with permeabilities in the range 12 to 120.
The Curie temperatures of these materials lie between 385?C and 500?C and
high Q behavior persists over the temperature interval -65?C to +250?C.
17 4
130
In addition, the low signal properties of these materials have been shown
to be relatively unaffected by prolonged exposure to high humidity. Of
particular importance is the low temperature coefficient of permeability
exhibited in the range -o5?C to +25?C. In future work, the broad objec-
tives, which applied in the phase of effort currently completed, should
be narrowed to stipulate specific low signal parameter values.
Materials developed under the low signal ferrites program have
been supplied to the Federal Telecommunications Laboratories for possible
application in developments being carried out under Contract AF 33(500)-32050,
and to the Emerson Radio and Phonograph Company for possible application
in developments being pursued under Contract No. AF 33(600)-31464.
In the development of ferrite materials for magnetostrictive
applications, the goal of a temperature coefficient of resonant frequency
less than 10 ppm per ?C was not achieved. It is recommended that further
effort in this field be directed toward obtaining specific materials for
specified filter application. The temperature coefficient of resonant fre-
quency requirement should be stipulated over the smallest temperature inter-
val possible.
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