A carbon coating was vacuum arc deposited on a smooth surface of a target which was simultaneously ion beam sputtered. The bombarding ions have sufficient energy to create diamond bonds. Spalling occurs as the carbon deposit thickens. The resulting diamond like carbon flakes improve thermal, electrical, mechanical, and tribological properties when used in aerospace structures and components

Banks, B. A.

English

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https://ntrs.nasa.gov/search.jsp?R=19850012957 2020-03-22T18:22:58+00:00Z
United States Patent ~191 [ i l l  Patent Number: 4,495,044 
Banks [45] Date of Patent: Jan. 22, 1985 
[54] DIAMUNDLIKE FLAKES 
[75] Inventor: Bruce- A. Banks, Olmsted Township, 
[73] Assignee: The United States of America as 
Cuyahoga County, Ohio 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
1211 Appf. No.: 591,089 
[22] File& Mar. 19,1984 
Related U.S. Application Data 
1631 Continuation-in-part of Ser. No. 495,381, May 17, 
1983, Pat. No. 4,437,962. 
E511 Int. a . 3  .............................................. C23G w o o  
[52] 
[58] 
€561 References Cited 
U.S. c1. ........................... 204/192 C; 204/192 R; 
204/192 N, 423/445; 423f446; 423/449; 427/39 
Field of Search ....................... 423/446, 445, 449; 
204/192 C, 192 N, 427/39 
U.S. PATENT DOCUMENTS 
3,840,451 10/1974 Golyanov et al. .............. 204/192 C 
3,949,062 4/1976 Vereschagin et al. .............. 423/446 
3,961,103 6/I976 Aisenberg ............................. 427/39 
4,191,735 3/1980 Nelson et al. 423/423 
4,228,142 10/1980 Holcombe et al. ................. 423/445 
4,277,293 7/1981 Nelson et al. ....................... 423/446 
4,288,353 9/1981 Ekkel et al. . 
4,377,565 3/1983 Setaka ......... 
4,409,712 10/1983 Takehara ............................ 423/446 
4,412,980 11/1983 Tsuji- et al. .......................... 403/446 
4,425,315 1/1984 Tsuji et al. ........... 423/446 
4,434,188 2/1984 Kamo et at. ......... 423/446 
4,437,942 3/%984 Banks .............................. 204/192 C 
FOREIGN PATENT DOCUMENTS 
1008618 10/1965 UnitedKingdom . 
OTHER PUBLICATIONS 
Mathine et al., Chem. Abstracts 99, (1983), #148673. 
Primary Examiner-Arthur P. Demers 
Attornes Agent, or Firm-Norman T. Musial; John R. 
Manning 
[57L ABSTRACT 
A carbon coating (36) is vacuum arc deposited on a 
smooth surface of a target (10) which is simultaneausly 
ion beam sputtered. The bombarding ions have suffi- 
cient energy tu create diamond bonds. Spalling occurs 
as the carbon deposit thickens. The resulting diamond- 
like carbon flakes (26) have improved thermal, electri- 
cal, mechanical, and tribological properties when used 
in aerospace structures and components. 
19 €laims, 1 Drawing Figure 
U.S. Patent 
. '  
5 '  . 
16 
4,495,044 
DLAMONDLIKE FLAKES 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured or used by or for the Government with- 
out the payment of any royalties thereon or therefor. 
STATEMENT O F  COPENDENCY 
This application is a continuation-in-part of applica- 
tion Ser. NQ. 495,381 which was filed May 17, 1983 and 
issued as U.S. Pat. No. 4,437,962. 
TECHNICAL FIELD 
This invention is concerned with producing dia- 
mondlike carbon flakes. The properties of the flakes 
produce desirable thermal, electrical, mechanical, and 
tribological properties when used in aerospace struc- 
tures and components. These diamondlike carbon flakes 
are particularly useful as a filler material in a composite. 
Previous composite materials were made from fibers, 
fiber bundles, and woven fiber bundles as the strength 
providing component in a composite material. Fibers of 
graphite, boron, tungsten, and glass have been used 
frequently in conjunction with various organic and 
metallic binders. Oftentimes these materials did not 
have the high tensile strength and other properties re- 
quired of the composite material. 
It is, therefore, an object of the present invention to 
provide carbon flakes having diamondlike properties. 
Another object of the invention is to provide a method 
of making diamondlike carbon flakes. 
BACKGROUND ART 
Aisenberg U.S. Pat. No. 3,961,103 discloses the depo- 
sition of a carbon-diamond film on a substrate by ioniz- 
ing and electrostically accelerating a beam of atomic 
particles of carbon. A plasma ion source produces 
plasma which contains large concentrations of ions of 
the species that is to be deposited on the substrate. 
Eckel et al U.S. Pat. No. 4,288,353 discloses a com- 
posite contact paste produced by mixing solid constitu- 
ents in the form of graphite and metal powder with a 
binder comprising a mixture of epoxy resin and tar. The 
metal powders are selected from a group include iron, 
aluminum, copper and alloys thereof. The resulting 
paste has electrical and thermal conductivity corre- 
sponding to that of carbon blocks. Neither this patent 
nor the Aisenbesg patent is concerned with simulta- 
neously ion beam sputtering and vacuum arc depositing 
to produce diamondlike flakes. 
Nelson et a1 U.S. Pat. No. 4,191,735 discloses a 
method for producing synthetic diamonds utilizing an 
ion source from which ions of carbon and oxygen are 
extracted and passed through a magnetic field. This 
separates the carbon and oxygen beams by virtue of the 
different masses. A flux of carbon ions is thus produced 
having a sufficent energy to penetrate a diamond crystal 
and cause crystal growth which is predominantly inter- 
nal. 
British Pat. No. 1,008,618 is directed to a device for 
producing synthetic diamonds produced by the absorp- 
tion of energies supplied by a laser beam adapted to 
converge upon a glass plate containing graphite inclu- 
sions. These inclusions are situated at the focal point of 
the optical system through which the laser beam passes, 
and a diamond crystal is produced by the absorption of 
energy supplied by the laser beam. 
Both the Nelson et a1 patent and the British patent 
disclose the broad concept of utilizing a carbon ion 
5 beam or laser beam respectively, which is focused on 
the target to prsduce synthetic diamonds. These pa- 
tents, however, do not disclose simultaneously ion beam 
sputtering and vacuum carbon arc depositing to pro- 
duce diamondlike flakes. 
DISCLOSURE: O F  INVENTION 
A unique material is produced in accordance with the 
present iiwention. Carbon flakes are produced whieh 
have certain diamondlike characteristics. 
The diamondlike carbon flakes are produced by the 
vacuum arc deposition of carbon on a smooth surface 
that is simultaneously ion beam sputtered. The bom- 
barding ions have sufficient energy to create diamend 
bonds. As the carbon deposit on the target thickens, 
2o diamondlike carbon flakes spa11 from the target surface. 
BRIEF DESCRIPTION OF THE DRAWING 
The details of the invention will be described in con- 
nection with the accompanying drawing which is a 
25 schematic view showing the apparatus for producing 
diamondlike carbon flakes in accordance with the pres- 
ent invention. 
10 
l5 
BEST MODE FOR CARRYING OUT THE 
30 INVENTION 
Referring now to the drawing, there is shown a target 
10 that is exposed to a beam 12 of 50 eV to 3000 eV 
argon ions at current densities of 0.1 mA/cm2 to 20 
35 mA/cmz. The argon ion beam 12 is furnished by an 
electron bombardment ion source €4 of the type devel- 
oped from electric propulsion technology. 
Argon gas from a suitable source, not shown, is fed 
through a line 16 to a cathode 18 where the gas is ion- 
ized. The argon ions are retained within a chamber 
containing an anode 2CVabout its outer periphery. Sueh 
an ion source is described in “Advances in Electronics 
and Electron Physics” by H. R. Kaufman, vol. 36, pages 
365-373. It will be appreciated that other gasses, in 
45 addition to argon, can be used to form the bombarding 
ions in the beam 12. For example, xenon and hydrogen 
may be used, and even vaporized carbon may be pro- 
vided in the ion source 14. 
Extraction of the beam 12 is accomplished by a two 
50 grid ion optics system 22. Such a system is described in 
AIAA Paper No. 76-1017 entitled “A 30 cm Diameter 
Argon Ion Source”. Such a double grid system includes 
both a screen grid and an accelerator grid. The screen 
grid serves to contain the discharge plasma while form- 
55 ing the necessary ion optics to prevent direct impinge- 
ment of accelerated ions onto the accelerator grid. Ions 
in the near vicinity of the screen grid have a high proba- 
bility of being accelerated through the openings in the 
screen and the accelerator grids because of the high 
Neutralization of the ions is achieved by the interjec- 
tion of electrons into the beam 12. A suitable neutralizer 
24 in the form of a downstream cathode provides these 
electrons. 
The electron bombardment ion source 14 is located in 
a vacuum facility which is sufficiently large to prevent 
back sputtered facility material from contaminating the 
process. The operating pressure within the vacuum 
60 elecfric fields present at the grids. 
65 
3 
4,495,044 
4 
facility during sputtering is about 1 x 10-4 torr OF vacuum chamber toward the deposition target 10, and 
lower. these gasses would condense on this target if active 
Accordihg to the present invention, diamondlike cooling is used to maintain a low temperature. In addi- 
carbon flakes 26 are produced by carbon deposition on tion, a shutter or chopper may be placed between the 
a smooth surface of the target 10 that is simultaneously 5 carbon source and the deposition target to reduce or 
being ion beam sputter bombarded by the beam 12. This regulate the ratio of arrival of carbon atoms to beam 
carbon deposition is produced by a vacuum arc between ions. In certain applications the carbon deposit 36 is 
a carbon rod cathode 28 and an annular carbon anode formed without simultaneously sputter etching the tar- 
30 that are connected to a suitable power supply 32. A get 10. 
striker wand 34 is provided to initiate the arc in a man- 10 It is contemplated that both single and dual ion beams 
ner well known in the art. of argon, carbon, and hydrogen may be used to deposit 
The carbon rod cathode 28 and anode 30 are likewise the diamondlike carbon material 36 on the surface 10. In 
positioned within the vacuum chamber. The target 10 is addition, hydrocarbons may be used in the dual ion 
positioned within 5 0  eentimeters of both the ion source beam technique. 
14 and the arc p~oduced by the electrodes 28 and 30. Plasma deposition and R.F. sputtering may be used to 
The vacuum carbon arc has a low voltage between 20 deposit carbon. from hydrocarbons. Also carbon and 
and 40 volts produced by the power supply 32. This arc argon may be used .with the R.F. sputtering. Other 
also has a high current discharge between 25 and 200 deposition techniques contemplated include using a 
amperes. It is contemplated that automatic feed means carbon-argon ion source, a vacuum arc, or a conical 
may be provided for the carbon rod 28 to maintain the 20 carbon plasma gun. 
arc. While several embodiments of the invention. have 
In operation carbon vapor as well as Carbon ions will been disclosed and described it will be apparent that 
leave the tip of the carbon rod cathode 28, and a portion various modifications may be made to the apparatus 
of these will arrive at the deposition surface of the tar- process. 
get 10 and remain there. The bombarding argon ions in 25 I claim: 
the beam 12 have sufficient energy to create diamond 1. A method of making diamondlike carbon flakes 
sp3 bonds in the carbon coating 36 being deposited by 
the vaccum arc. As the deosited carbon 36 thickens on depositing carbon on a surface 
the deposition target 10, spalling will -occur due to the creating diamond bonds in said carbon by subjecting 
stresses in this deposit. said carbon on said surface to a beam of ions, and 
The spalled flakes 26 are then collected as they fall removing diamondlike carbon flakes from said sur- 
into a receiving container 38. The flakes 26 will vary faces. 
from less than 0.1 microns in thickness to several micron 2. A method of making diamondlike flakes as claimed 
thick. The shapes of the flakes 26 are normally random; in claim 1 wherein the carbon is deposited on the sur- 
however, it is contemplated that a texture patterned or 35 face of a target from an arc between two carbon elec- 
embossed deposition, target 10 may provide some con- trodes. 
trol of the flake-shape and size. 3. A method of making diamondlike flakes as claimed 
The collected flakes may be mixed with or joined by in claim 2 including the step of 
a matrix or binder in a manner described in copending ion beam sputtering the surface of the target while 
patent application Ser. No. 495,381 now U.S. Pat. No. 40 simultaneously depositing said carbon thereon. 
4,437,962. A variety of low viscosity organic binders, 4. A method of making diamondlike flakes as claimed 
such as epoxys, may be used. in claim 3 wherein the surface of the target is sputtered 
It is evident that extremely hard diamondlike carbon’ by ions from a source forming a beam of argon ions. 
flakes 26 are produced by this process, rather than 5. A method of making diamondlike flakes as claimed 
softer and lower strength graphite. The unique proper- 45 in claim 4 wherein the ion beam sputtering and the 
ties of diamondlike carbon flakes are relied on for im- carbon arc depositing are performed in a vacuum envi- 
proved properties in various applications, such as the ronment. 
aforementioned superior composite materials. The table 6. A method of making diamondlike flakes as claimed 
compares certain properties of graphite, diamondlike in claim 5 wherein the depositing and sputtering are 
carbon, and diamond. 
15 
comprising the steps of 
30 
50 performed at a pressure of about 1 X torr. 
DIAMONDLIKE 
PROPERTY GRAPHITE CARBON DIAMOND 
DENSITY, gm/cm3 2.26 1.6-2.8 3.5 
RESISTIVITY, a cm 10- 10-5 io~-iOZO 
RESISTANCE TO 3H2S04-HN03 
BAND GAP, eV 0 0.5-2.8 5 
BREAKDOWN STRENGTH V/M 0 106 t 106 
INDEX OF REFRACTION - 1:8-2.3 2.4 
YES YES 
7. A method of making diamondlike flakes as claimed 
in claim 5 wherein the target is positioned within 50 
ALTERNATE EMBODIMENTS OF THE 
INVENTION 
Other techniques can be employed to produce the 
diamondlike carbon deposit 36 on the deposition target 65 carbon electrodes. 
surface 10. Electron beam evaporation, laser beam 
evaporation, and electro-thermal evaporation may be 
used. Also, organic gasses may be brought into the 
centimeters of both the source of argon ions and the 
8. A method of making diamondlike flakes as claimed 
in claim 5 wherein the vacuum carbon arc has a low 
voltage between about 20 and about 40 volts. 
5 
4,495,044 
6 
9. A method of making diamondlike flakes as claimed 
in claim 5 wherein the vacuum carbon arc has a high 
current discharge between about 25 and about 200 am- 
peres. 
the improvement comprising 
eV and an index of refraction between about 1.8 and 
about 2.3. 
diamondlike flakes as 
claimed in claim 13 wherein the carbon is deposited on 
fib, 5 the surface simultaneously with the ion beam sputter- 
15. A method of making diamondlike flakes as 
claimed in claim L4 wherein the ion beam sputtering and depositing carbon on a surface, 
creating diamond sp3 bonds in said carbon, and carbon depositing are performed in a vacuum environ- 
removing diamondlike carbon flakes from said sur- 10 Dent. 
16. A method of making diamondlike flakes as 
11. A method of making diamondlike flakes as claimed in claim 15 wherein the depositing and sputter- 
claimed in claim 10 wherein the carbon is deposited on ing are performed at a pressure of about 1 X torr or 
the surface of a target from an arc between two carbon less- 
electrodes. 15 17. Diamondlike flakes made in accordance with the 
12. A method of making diamondlike flakes as method 
18. A diamondlike material having improved electri- claimed in claim 10 including the step of cal and mechanical properties comprising ion beam sputtering the carbon on the surface with flakes having diamond sp3 bonds suEcient to 
me- 
13. A method of making diamondlike flakes as 39. A diamondlike as claimed in 18 
wherein the diamondlike carbon flake have a density 
between about 1.6 gm/cm3 and about 2.8 W c m 3 .  
14. A method- Of 
In a method of making diamondlike ing. 
face. 
ions having sufficient energy to create the diamond 2o 
sp3 bonds therein. chanical hardness. 
a hi& chemic, resistance and 
claimed in claim 12 wherein the eneigy in the ions is 
great enough to create diamond sp3 bonds sufficent to 
produce a bandgap between about 0.5 eV and about 2.8 25 * * * * *  
30 
35 
45 
50 
55 
60 
65 


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