A carbon coating is vacuum arc deposited on a smooth surface of a target which is 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 are mixed with a binder or matrix material to form a composite material having improved thermal, electrical, mechanical, and tribological properties when used in aerospace structures and components

Banks, B. A.

English

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(HASA-Oase-LEH-13837-1) DIAMCNDLIKE FIAKE
COMPOSITES Patent (NASA) 6 p CSCL 11D
QO/2U
N84-22695
Unclas
15823
25
25lh Anniversary
1958-1983 APR 9
https://ntrs.nasa.gov/search.jsp?R=19840014627 2020-03-22T08:39:51+00:00Z
United States Patent [19]
Banks
[ii] '" ' - . 4,437,962
[45] Marr20,1984
•T.
[54]
[75]
DIAMONDLIKE FLAKE COMPOSITES
Inventor: Bruce A. Banks, Olmsted Township,
Cuyahoga County, Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
[21] Appl. No.: 495,381
[22] Filed: May 17,1983
[51] Int. C1.3 C23C 15/00
[52] U.S. Q 204/192 C; 204/192 R;
204/192 SP; 423/414; 423/445; 423/446;
;-. 423/449; 423/DIG. 10
[58] Field of Search 204/192 R, 192 C, 192 SP;
423/DIG. 10, 414, 445, 446, 449
[56] References Cited
U.S. PATENT DOCUMENTS
3,809,635 5/1974
3,840,451 10/1974
3,859,422 1/1975
3,949,062 4/1976
3,961,103 6/1976
4,173,522 11/1979
4,191,736 3/1980
Gillot et al 204/192 C
Golynov et al 204/192 C
Home et al 423/445
Vereschagin 423/446
Aisenberg ^427/39
Pulker et al. 204/192 C
Nelson et al. 423/446
4,228,142 10/1980 Holcombe et al 423/445
4,288,353 9/1981 Eckel et al 260/28 R
FOREIGN PATENT DOCUMENTS
1008618 10/1965 Unjted Kingdom : .
 ite,- ..-,t.JW, ,/f
OTHER PUBLICATIONS1*^ -'> t!'' «
Aisenberg et al., J. Appl. Phys. 42(7) 1971, pp.
2953-2958.
Primary Examiner—Arthur P. Demers
Attorney, Agent, or Firm—Norman T. Musial; John R.
Manning; Gene E. Shook
[57] ABSTRACT
A-.carbon coating (36) is vacuum arc deposited on a
smooth surface of a target (10) which is simultaneously
ion beam sputtered. The bombarding ions have suffi-
cient energy to create diamond' bonds. Spalling occurs
as the carbon deposit thickens. The resulting diamond-
like carbon flakes (26) are mixed with a binder or matrix
material (40) to form a composite material (42) having
improved thermal, electrical, mechanical, and tribologi-
cal properties when used in aerospace structures and
components.
18 Claims, 1 Drawing Figure
U.S. Patent Mar. 20, 1984 4,437,962
4,437,962
DIAMONDLIKE FLAKE COMPOSITES
DESCRIPTION
Origin of the Invention
The invention described herein was made by an em-
ployee of the U.S. Government and may be manufac-
tured or used by or for the Government without the
payment of any royalites thereon or therefor. 10
TECHNICAL FIELD
This invention is concerned with producing a unique
composite material that utilizes diamondlike carbon
flakes as the filler material. The properties of the flakes 15
used as a filler in the composite material produce desir-
able thermal, electrical, mechanical, and tribological
properties when used in aerospace structures and com-
ponents.
Previous composite materials were made from fibers, 20
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 25
have the high tensile strength and other properties re-
quired of the composite material.
BACKGROUND ART
Aisenberg U:S. Pat. No. 3,961,103 discloses the depo- 30
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 substrate. 35
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 selected from a group include iron, alu- 40
minum, copper and alloys thereof. The resulting paste
has electrical and thermal conductivity corresponding
to that of carbon blocks. Neither this patent nor the
Aisenberg patent is concerned with simultaneously ion
beam sputtering and vacuum arc depositing to produce 45
diamondlike flakes.
Nelson et al 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 50
separates the carbon and oxygen beams by virtue of the
different masses. A flux of carbon ions is thus produced
having a sufficient energy to penetrate a diamond crys-
tal and cause crystal growth which is predominantly
internal. 55
British U.S. Pat. No. 1,008,618 is directed to a device
for producing synthetic diamonds produced by the
absorption of energies supplied by a laser beam adapted
to converge upon a glass plate containing graphite in-
clusions. These inclusions are situated at the focal point 60
of the optical system through which the laser beam
passes, and a diamond crystal is produced by the ab-
sorption of energy supplied by the laser beam.
Both the Nelson et al patent and the British patent
disclose the broad concept of utilizing a carbon ion 65
beam or laser beam respectively, which is focused on
the target to produce synthetic diamonds. These pa-
tents, however, do not disclose simultaneously ion beam
sputtering and vacuum carbon arc depositing to pro-
duce diamondlike flakes. - • • -
DISCLOSURE OF INVENTION
A unique composite material.is produced in accor-
'dance with the present invention. Diamondlike carbon
flakes are utilized as a filler material with a variety of
organic or metallic binders.
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 diamond
bonds. As the carbon deposit on the target thickens,
spalling occurs and the diamondlike carbon flakes are
collected in a receiving container.
The flakes are mixed with a binder or matrix such as
epoxy or aluminum. The composite material produced
has desirable thermal, electrical, and mechanical prop-
erties.
BRIEF DESCRIPTION OF THE DRAWING
The details of the invention will be described in con-
nection with the accompanying drawing which is a
schematic view showing the apparatus for producing
diamondlike carbon flakes in accordance with the pres-
ent invention.
BEST MODE FOR CARRYING OUT THE
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
mA/cm2. The argon ion beam 12 is furnished by an
electron bombardment ion source 14 of the type devel-
oped for electronic 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 20 about its outer periphery. Such
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
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
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-
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
electric fields present at the grids.
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
facility during sputtering is about 1X 10~4 torr or
lower.
4,437,962
According to the present invention, diamondlike
carbon flakes 26 are produced by carbon deposition on
a smooth surface of the target 10 that is simultaneously
being ion beam sputter bombarded by the beam 12. This
carbon deposition is produced by a vacuum arc between 5
a carbon rod cathode 28 and an annular carbon anode '
30 that are connected to a suitable power supply 32. A
striker wand 34 is provided to initiate the arc in a man-
ner well known in the art.
The carbon rod cathode 28 and anode 30 are likewise 10
positioned within the vacuum chamber. The target 10 is
positioned within 50 centimeters of both the ion source
14 and the arc produced by the electrodes 28 and 30.
The vacuum carbon arc has a low voltage between 20
and 40 volts produced by the power supply 32. This arc 15
also has a high current discharge between 25 and 200
amperes. It is contemplated that automatic feed means
may be provided for the carbon rod 28 to maintain the
arc.
In operation carbon vapor as well as carbon ions will 20
leave the tip of the carbon rod cathode 28, and a portion
of these will arrive at the deposition surface of the tar-
get 10 and remain there. The bombarding argon ions in
the beam 12 have sufficient energy to create diamond
sp3 bonds in the carbon coating 36 being deposited by 25
the vaccum arc. As the deposited carbon 36 thickens on
the deposition target 10, spalling will occur due to the
stresses in this deposit.
The spalled flakes 26 are then collected as they fall
into a receiving container 38. The flakes 26 will vary 30
from less than 0.1 microns in thickness to several mi-
crons thick. The shapes of the flakes 26 are normally
random; however, it is contemplated that a texture
patterned or embossed deposition target 10 may pro-
vide some control of the flake shape and size. 35
The collected flakes are then mixed with or joined by
a matrix or binder from a reservoir 40. A variety of low
viscosity organic binders, such as epoxys, may be used.
The binder is then cured or hardened to form a compos-
ite material 42. It is contemplated that a low melting 40
temperature metallic matrix, such as aluminum, may
likewise be used. The composite material is formed
when the metallic binder cools.
Ideally, the percentage of diamondlike flakes 26 in
the composite material 42 is maximized to fully utilize 45
their unique properties. This is achieved by using bind-
ers that have both low viscosities and low melting tem-
peratures. Such binders not only wet the flakes, but also
accommodate the greatest amount of flakes in a given
volume of composite. 50
Typically, the diamondlike composite material 42
produced by this simultaneous sputter etching and de-
position is insulating, extremely hard, semitransparent,
and resistant to acids that can normally etch graphite. It
is evident that extremely hard diamondlike carbon 55
flakes 26 are produced by this process, rather than
softer and lower strength graphite. The unique proper-
ties of these diamondlike carbon flakes 26 result in the
superior composite material 42. It is contemplated that
the carbon rod 28 may be doped to produce semicon- 60
ducting flakes or other doped flake properties.
While the preferred embodiment of the invention has
been disclosed and described it will be apparent that
various modifications may be made to the apparatus and
process without departing from the spirit of the inven- 65
tion or the scope of the subjoined claims. By way of
example, other techniques can be employed to produce
a carbon deposit 36 on the deposition target surface 10.
Electron beam evaporation, laser beam evaporation,
and electro-thermal evaporation may be used. Also,
organic gasses may be brought into the vacuum cham-
ber toward the deposition target 10, and these gasses
would condense on this target if active cooling is used
to hold the temperature low enough. In addition, a
shutter or chopper may be placed between the carbon
source and the deposition target to reduce or regulate
the ratio of arrival of carbon atoms to beam ions. It is
further contemplated that the carbon deposit 36 could
be formed without simultaneously sputter etching the
target 10 in certain applications.
I claim:
1. A method of making a composite material compris-
ing the steps of
depositing carbon on a surface,
removing flakes of said carbon from said surface, and
mixing said flakes with a matrix material to form the
composite material.
2. A method of making a composite material as
claimed in claim 1 wherein the carbon is deposited on
the surface of a target from an arc between two carbon
electrodes.
3. A method of making a composite material as
claimed in claim 2 including the step of
ion beam sputtering the surface of the target having
the carbon deposited therein.
4. A method of making a composite material as
claimed in claim 3 wherein the carbon arc deposition
and the ion beam sputtering are performed simulta-
neously.
. 5. A method of making a composite material as
claimed in claim 3 wherein the bombarding ions have
sufficient energy to create diamond bonds so that dia-
mondlike carbon flakes spall from the carbon deposit on
the surface of the target.
6. A method of making a composite material as
claimed in claim 3 wherein the surface of the target is
sputtered by ions from a source forming a beam of
argon ions.
7. A method of making a composite material as
claimed in claim 6 wherein the ion beam sputtering and
the carbon arc depositing are performed in a vacuum
environment.
8. A method of making a composite material as
claimed in claim 7 wherein the depositing and sputter-
ing are performed at a pressure of about 1X 10~4 torr.
9. A method of making a composite material as
claimed in claim 7 the target is positioned within 50
centimeters of both the source of argon ions and the
carbon electrodes.
10. A method of making a composite material as
claimed in claim 7 wherein the vacuum carbon arc has
a low voltage between about 20 and 40 volts.
11. A method of making a composite material as
claimed in claim 7 wherein the vacuum carbon arc has
a high current discharge between about 25 and 200
amperes.
12. In a method of making a composite material of the
type where a filler material is mixed with a matrix mate-
rial, the improvement comprising
depositing carbon on a surface,
creating diamond bonds in said carbon, and
removing diamondlike flakes from said surface, said
flakes forming said filler material.
13. A method of making a composite material as
claimed in claim 12 wherein the carbon is deposited on
4,437,962
the surface of a target from an arc between two carbon
electrodes. -
14. A method of making a composite material as
claimed in claim 12 including the step of
ion beam sputtering the carbon on the surface with
ions having sufficient energy to create the diamond
bonds therein.
15. A method of making a composite material as
claimed in claim 14 wherin the carbon is deposited on
the surface simultaneously with the ion beam sputter-
ing.
10
16. A method of making a composite material as
claimed in claim 15 wherein the ion beam sputtering and
carbon depositing are performed in a vacuum environ-
ment.
17. A method of making a composite material as
claimed in claim.16 wherein the depositing and sputter-
ing are performed at a pressure of about 1X 10-4torr or
less.
18. A composite material made in accordance with
the method of claim 1.
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Diamondlike flake composites

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