Capacitor fabrication by solidifying mixture of ferromagnetic metal particles, nonferromagnetic particles, and dielectric materia

Hrach, F. J.

Papell, S. S.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE ADMlNlSrrRATlON 
W ~ ~ ~ n o T o m .  D.C 20W 
REPLY TO 
ATTMOfr G p  
FROM8 
 office of Ass i~ tap t  General Counsel for  
Patent Matters 
SUBJECTS Annouxicement oE NASA-owned U. 8. Patents i n  STAR 
In accordance 
and Code USI,  
forwarded for  
with the procedures agreed upon by Cod? GP 
the attached NASA-owned U. So ,. Patent i s  be&ng 
abstracting and announcement i n  NASA STAR0 ' 
U. S . Patent No. 
Government or 
Corporate Employee 
Supplementary Corporate 
Source (if applicable) r HA. 
NASA Patenti Case No, 
NOTE - If th is  patent covers an invention made by a corporate 
employee of a NASA Contractor, the following is applicable: 
yes NO €3 
Pursuant t o  Section 305(a) of the National Aeronautics and 
Space Acto the name of the Administrator of NASA appears on 
the f i r s t  page of the patent8 however, the name of the actual 
inventor (author) appears a* the heading of Colusan Noe 1 sf . 
the Specificationo following the wordo .e w i t h  ~teapect to 
- ----- 
- 
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. 
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Enclosure 
https://ntrs.nasa.gov/search.jsp?R=19710004047 2020-03-17T02:32:46+00:00Z
BY 
ATTORNEYS 
United States Patent 06 3,535,602 
'@ Patented Oct. 20, 1070 
1 2 
3,535,602 DESf RIPTION OF THE PREFERRED 
CAPACITOR AND ME'PINOD OF MAKING SAME ElilE031TdENT 
Frank J. Hsach, Parma, and Solomon 8. Papell, Berea, Referring now to FIG. 1, there is shown a container O&o, assignors to the United States of America as pg which, if desired, may serve as a casing for a finished 
represented by the Administrator of the National Aero- capacitor made in accordance the invention. In 
nautics and Space Administration 
Filed May 7, 1969, Ser. No. 822,518 accordance with the invention, a pair of ferromagnetic 
In(. CI. HOlg 3/06 metal foils II and 12 having respective electrical leads 
U.S. CI. 317-258 14 Claims 13 and 14 attached thereto are disposed at respective op- 
posite ends of the container 1Q against the inside surfaces. 
10 In a like manner, a pair of nonferromagnetic metal foils 
ABSTRACT OF THE DISCLOSUJXE 15 and 16 are respectively disposed against the inner sur- 
A method of making a capacitor by solidifying a mix- faces of opposite sides of the container 10. The foils 15 
ture of ferromagnetic metal particles, nonferromagnetic and 16 are provided with electrical leads 17 and 18, re- 
particles and a dielectric material in the presence of mu- 15 spectively, and serve as electrodes for capacitor 9. 
tual perpendicular magnetic and electric fields. A capacitive body 19 of the inventive capacitor is formed 
by mixing ferromagnetic metal particles and nonferro- 
magnetic metal particles in a molten or liquid dielectric 
A capacitor is disclosed wherein ferromagnetic par- material within the container 10 and then solidifying the 
titles and nonferromagnetic particles are retained in a 20 dielectric material in the presence of magnetic and elec- 
predetermined orientation by a dielectric matrix to form trical fields as will be described presently. To  the end that 
a capacitive body. ~ l ~ ~ ~ ~ ~ d ~ ~  are provided on the body the capacitor will have maximum capacity with a reason- 
for electrical connections. able voltage rating the mixture which forms the capacitive 
body 19 should preferably contain from about 10% to 
ORIGIN O F  THE INVENTION 25 about 20% by volunle of dielectric material, the remainder 
The invention described herein was made by employees being approximately equally divided between ferromag- 
of the United States Government and may be manufac- netic and nonferromagnetic particles. However, it will be 
tured and used by or for the Government of the United clear to those skilled in the art that the voltage rating 
States of America for governmental purposes without may be increased by increasing the percentage of dielec- 
the payment of any royalties thereon or therefor. 30 tric material in the capacitive body 19. 
BACKGROUND OF THE INVENTION To the end that the ferromagnetic particles and the 
nonferromagnetic particles mixed into the dielectric ma- 
Capacitors of the prior art basically comprise a layer terial will assume respective orientations which will pro- 
of dielectric material sandwiched between two metal vide maximum capacity in the capacitive body 19, a 
plates. Capacitors are made in a wide variety of shapes 35 magnetic field is applied perpendicular to the ferromag- 
and sizes. For example, one common form of capacitor netic foils P I  and 12 by suitable magnet poles 20 and 21. 
comprises several layers of plastic and metal foil which At the same time, the electrical leads 17 and 18 are con- 
are rolled into a cylindrical shape. Many electrolytic nected across a series combination of electrical eleme~~ts 
capacitors are formed by stacking a plurality of foils conlprising an AC generator 22, an ammeter 23 and a 
each of which is coated with a dielectric paste. Some early 40 variable current limiting resistor 24. The voltage of the 
capacitors comprised metal plates disposed in a dielec- AC generator 22 is increased from zero to impress an 
tric liquid. alternating electric field between the foils 15 and 16 
All of these prior art capacitors are similar in con- perpendicular to the magnetic field. This causes the non- 
struction. Additionally, they are relatively heavy. ferromagnetic particles to form conductive chains o r  
OBJECTS AND SUMMARY OF THE INVENTION g5 filan~ents between the plates 15 and 16. When no further 
current increase is indicated by ammeter 23 as the voltage 
It is an of the invention to provide a new and of generator 22 increases the desired electric field has been 
novel capacitor. reached. 
It is another object of the invention to provide a capaci- While the magnetic field and the alternating electric 
tor having a high capacitance to weight ratio. field are inlpressed across the capacitive body 19, the mix- 
It is a further object of the invention to provide a tllre of ferromagnetic pal.ticles, nonferro~nagnetic par- 
method for making a high capacitance to weight ratio ticles, and dielectric material is caused to solidify when 
capacitor. ammeter 23 indicates a stable curent condition. As a re- 
1t is yet another object of the invention to provide a salt, the dielectric material freezes the ferromagnetic and 
capacitor in which magnetic and nonmagnetic metal par- S j  rronferromagnetic particles in the positions which they 
ticles are restrained in respective predetermined orienta- assun,ecl as a result of the impl.essed electrical and mag- 
tions by a suitable matrix to form a capactive body. netic fields. The fields are then removed and the dielectric 
Still another object of the invention is to provide a serves as a matrix for the particles. 
method of making a capacitor by solidifying a dielectric As described above, an alternating electric field is im- 
matrix material while metal particles in the dielectric are pressed betLveen the foils 45 and 16. The alternating field 
maintained in respective predetermined orientations. prevcnts drift of the nonferromagnetic particles toward 
In surnmary, i t  is an object of the invention to provide one r?onferrornagrnetic foil and away from the other 21s 
a riew and novel capacitor which has high capacitance in would occur if a unidirectiorral electric field were nseci, 
relation lo its weight and lo provide ;I inethod lor rilakirry ~ h ,  frequency of the AC generator niust be 
such a capacitor. (jj enoi~gh to prevent substantial drift of the nonferromag- 
BRIEF DESCRIPTION OF THE DRAWINGS netic particles toward either foil 15 or 16. This frequency is dependent on the size of the nonferromagiletic par- 
FIG. 1 is an illustration showing the apparatus and ma- ticles as well as on the solidification time of the dielectric 
terials used to make a capacitor embodying the invention; material. 
and T o  Where the dielectric material is one which solidifies 
FIG. 2 is a schematic drawing of a capacitor embody- rapidly or where means is provided to quickly chiil the 
ing the invention. dielectric material, the AC generator may be replaced 
3,535,602 
3 4 
by a sriitable direct. current source and a switch. With What is c?:iimetl is: 
this arrangement, a unidii.ectiona1 electric field can be 1. A method of innking a capacitor comprisiog the steps 
impressed briefiy between the foi!s 15 and I6 witl~out of: 
causing significant drift of the nonferromagnetic particles. mixing ferromagnetic particles, rionferromagnetic par- 
With regard to  the dielectric material, it may he a iicli-s :in<! a clielectric material; 
substance such as halo wax or a similar material iviiich " subjecting the mixiure to mutually perpendicular mag- 
must be heated above ambient temperature to melt it. netic and electric fields; 
With such materials for use as dielectrics, heat may be solidifying the dielectric material thereby providing a 
applied to the container 10 from a suitable heat source matrix for the particles; and, 
25. Solidification is achieved by removing the heat source lo removing said magnetic and electric fields. 
25 and, additionally, cooling the contniner if desired. 2. The method of claim 1 wherein a pair of ferroniag- 
Where speed is not an  important consideration, melt- netic foils with leads attached thereto are placed against 
ing of the dielectric material may be achieved by heat respective inner surfaces of opposite ends of a container 
generated by the alternating electric field. Of course, as for the mixture substantially perpendicular to the mag- 
the nonferromagnetic particles form filaments between netic field, and a pair of nonferromagnetic foils with Ieads 
the foils 15 and 16 the heating effect will decrease be- attached thereto are placed against respective inner SUr- 
cause of the increasing conductivity thus allowing the faces of opposite sides of the container substantially 
dielectric material to solidify automatically. perpendicular to the electric field before the particles and 
For  convenience and to achieve high uniformity of the dielectric are mixed. 
distribution of the metal particles in the dielectric ma- 20 3. The method of claim 1 wherein the dielectric mate- 
terial, a powdered dielectric material can be advantage- rial of said mixture is a powder and including the step of 
ously used. The metal particles may be first thoroughly heating said dielectric material to melt same after mix- 
mixed with the powdered dielectric material before or  ing step. 
after being placed in the container 10. Heat is then ap- 4. The method of claim 1 wherein the mixture com- 
plied to  the mixture to melt the dielectric material in 25 prises from about 10% to about 20% b~ volume of di- 
the presence of the magnetic and electric fields, after electric material. 
which the dielectric is solidified to form the capacitive 5. The method of claim 1 wherein said ferromagnetic 
body 19. and said nonferromagnetic particles range in  size from 
In order to obtain maximum capacity in the capacitive about 0.2 micron to about 1.0 micron. 
body 19, maximum paclting of the ferromagnetic and 30 G. The method of claim 1 wherein said ferronlagnetic 
nonferrolnagnetic is desire(]. ~~~~~di~~,~, the particles are iron and said nonferromagnetic particles are 
size of the particles must be as small as possible. In  ac- aluminum. 
cordance with the invention, the ferromagnetic and non- 4 .  The method of claim 1 wherein substantially all of 
ferromagnetic particles preferably range in size from 0.2 said ferromagnetic and nonferromagnetic particles are ap- 
nlici-ons up to 1 micron. Because this is the general 35 proximately eqllal in size. 
colloidal range, particles of this size may be used with a 8. The method of claim 1 wherein the electric field is of 
relatively low viscosity dielectric without settling-out the alternating type. 
problems. Larger size ferromagnetic and nonferromag- 9. A capacitor comprising: 
netic particles may be used at  the expense of reduced a plurality of ferromagnetic particles; 
capacity and decreased voltage rating of the capacitor in '$0 a plurality of nonferromagnetic particles; and 
order to achieve economy. For particles above about 30 a dielectric matrix, said particles being distributed 
microns, n o  special manufacturing process is reqcired and, throughout said matrix, said ferromagnetic particles 
consequently, they are very inexpensive. However, they forming a plurality of filaments disposed in a first di- 
must be used with a high viscosity dielectric material and, rection, said nonferromagnetic particles forming a 
as indicated previously, will reduce the capacity and volt- 45 plurality of filaments in  a second direction which is 
age ratings of the capacitor. substantially perpendicular to said first direction. 
In a preferred embodiment of the invention, the ferro- 10. The capacitive body set forth in claim 9 and includ- 
magnetic foils 11 and 12, and the ferromagnetic particles ing a pair of spaced apart ferromagnetic electrode foils dis- 
are iron. The ncnferronlagnetic foils 15 and 16, and the posed substantially perpendicular to the filaments formed 
nonferromagnetic particles are aluminum. Preferably, all 50 by the ferromagnetic particles and a pair of spaced apart 
of the ferromagnetic and nonferromagnetic particles are "onferromagnetic electrode foils disposed substantially 
of approximately equal size. perpendicular to the filaments formed by said nonferro- 
Referring now to FIG. 2 there is shown in schematic magnetic particles. 
form the capacitor 3 of FIG. 1, like parts being identified 11. The structure of claim 9 wherein substantially all of 
by like numerals. Filaments 26 forined of ferromagnetic 55 said ferronlagnetic and nonferromagnetic  articles are a p  
particles 24 which are shown in grossly exaggerated size, proximately in size. 
provide direct metallic connections between the ferro- 12. The structure of claim 9 wherein said ferromagnetic 
magnetic foils 11 and 12. A filament 28 formed of non- ~"ticles are iron and said nonferromagnetic particles are 
ferromagnetic particles 29, which are shown in grossly al"'"i"um. 
exaggerated s i x ,  is shown connecting the nonferromag- 13. The capacitive body of claim 9 wherein said ferro- 
foils 15 and 16. while only filaments 26 and 29 are magnetic particles and said nonferromagnetic particles 
shonin for clarity, it be understood that a plLlra]ity of range in size froin about 0.2 micron to about I micron. 
nllit~lal perpendicular filan~ents of both ferromagnetic and 14. The capacitive body of claim 9 wherein said ferro- 
nonfei.romagiletic t~~~~~ exist in the body 19. magnetic particles said nonferromagr~etic particles 
there will be a substantial rrilmber of partial fils- (j5 '"S in size fronl about 1.0 micron to about 30 microns, 
menls. RccortiingIy, io obtain maximum cnpacitance, 
partial filaments which extend inmarcfly Ei-om the foils 11, References Cited 
21,! d h n c l  16 are uti!ized by connecting lead.; 13 and 17 to UNITED STATES PATENTS 
Ieads 14 and 18, respectively. This connects like pairs of 2,992,139 6/1$59 Safzberg 317-258 
foils together and esiablisEles two output coni~ection Ieads 
for  the capacitor. ELLIOT A. GOLDBERG, Priinary Examiner 
TI will be understood that cI~anges and mociilications may 
be made in the iibove-described capacitor and mzthod U.S. 61. X.R. 
without departing from the spirit and scope of the in\.clr- 29-25.42; 252-63.5 
tion as set forth in the claims appended hereto. 75 


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