US3432330A

US3432330A - Pyrolytic vacuum deposition from gases

Info

Publication number: US3432330A
Application number: US105507A
Authority: US
Inventors: Russell J Diefendorf
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1961-04-25
Filing date: 1961-04-25
Publication date: 1969-03-11
Anticipated expiration: 1986-03-11

Description

March 11, 1969 R. J. DIEFENDORF' 3,432,330

PYROLYTIC VACUUM DEPOSITION FROM GASES Filed April 25, 1961 /-//'s Attorney.

United States Patent 3,432 330 PYROLYTIC VACUUM DEPOSITION FROM GASES Russell J. Diefendorf, Schenectady, N.Y., assignor to This invention relates to methods of forming articles and coatings and more particularly to methods of forming pyrolytic articles and coatings.

Pyrolytic articles and coatings are defined as materials made from gases by thermal decomposition or from materials by evaporation and deposition on a surface. In pyrolytic materials, planar crystallites are arranged so that their layer structures are parallel to the deposition surface. These materials are useful in high temperature environments. Development of missile and space propulsion systems has created an additional requirement for pyrolytic components in these systems.

carbonaceous gases have been thermally decomposed and deposited on a surface to produce pyrolytic graphite. As a result of the decomposition, carbon is removed from the gas and deposits on the surface so that planar graphite crystallites are aligned into a layer structure. It would be desirable to provide other pyrolytic articles and coatings for high temperature application. It would also be advantageous to provide pyrolytic articles and coatings with high electrical resistance.

It is an object of my invention to provide a deposition method of forming pyrolytic articles.

It is another object of my invention to provide a deposition method of forming pyrolytic coatings.

It is a further object of my invention to provide a deposition method of forming pyrolytic articles and coatings having high electrical resistance.

In carrying out my invention in one form, a deposition method comprises providing a chamber, providing a deposition surface in the chamber, heating the chamber to a temperature in the range of 1,400 C. to 2,000 C., and flowing a mixture of boron, carbon, and nitrogen through the chamber whereby pyrolytic material is formed on the surface.

These and various other objects, features and advantages of the invention will be better understood from the following description taken in connection with the accompanying drawing in which:

FIGURE 1 is a sectional view of a deposition apparatus for forming pyrolytic articles and coatings in accordance with my invention;

FIGURE 2 is a sectional view of a modified deposition apparatus; and

FIGURE 3 is a sectional view of another modified deposition apparatus.

In FIGURE 1 of the drawing, a deposition apparatus shown generally at comprises a brass chamber 11 including a cylindrical body portion 12 and end closure plates 13. A flange 14 is located at each end of body portion 12 to which an associated plate 13 is fastened by means of bolts 15 extending through apertures in both the flange and plate. In one end plate 13, an aperture 16 is located in which a tube 17 is positioned and extended to a pump 18 for evacuating chamber 11. A window 19 is located in body portion 12 to view the operation. A pair of spaced water-cooled, brass electrodes 20 are positioned within chamber 11. An electrical lead 21 is secured to each electrode 20 and to a suitable alternating current power source (not shown) to heat the electrodes to a temperature in the range of 1,400" C. to 2,000 C. Each electrode 20 has a supporting fin 22 attached thereto, which fins support a graphite member 23 therebetween. A deposit 24 of Patented Mar. 11, 1969 "ice pyrolytic material is shown on member 23. A water chamber 25 surrounds each end of chamber 11 and is provided with a water inlet line 26 and water outline line 27. An air nozzle 28 cools the central portion of chamber 11. A container 29 is positioned within chamber 11 to hold materials containing boron and nitrogen, boron and carbon, or nitrogen and carbon components. An inlet line 30, which is connected to chamber 11, supplies a material containing a boron, carbon or nitrogen component which is not provided in container 29.

In FIGURE 2 of the drawing, a modified deposition apparatus is shown which is identical to the apparatus of FIGURE 1 except that an additional inlet line 31 is connected to chamber 11. In the apparatus of FIGURE 2, one material containing a boron, carbon or nitrogen component is held in container 29 while inlet lines 30 and 31 supply the remaining materials containing the additional components to provide a mixture of boron, carbon and nitrogen.

In FIGURE 3 of the drawing, another modified deposition apparatus is shown which comprises a chamber 11 having a cylindrical body portion 12 with end closure plates 13. A flange 14 is located on each end of body portion 12 to which an associated plate 13 is fastened by means of bolts 15 extending through apertures in both the flange and plate. A water-cooled electrode 32 is positioned adjacent each end plate and fastened by means of bolts 15 around its outer periphery between flange 14 and plate 13. Electrodes 32 support an inner chamber 33 in the form of a raphite tube concentrically within chamber 11. In one end plate 13, an aperture 16 is located in alignment with the outlet end of inner chamber 33. Tube 17 is positioned in aperture 16 and connected to pump 18 for evacuating chamber 11. An aperture 34 is located in the opposite end plate in alignment with the inlet end of inner chamber 33. A closure 35 covers aperture 34 and is provided with two apertures through which

inlet lines

36 and 37 extend to connect with inner chamber 33.

Inlet lines

36 and 37 furnish materials containing boron, carbon and nitrogen components to the inner chamber. Electrodes 32 heat chamber 33 to a temperature in the range of 1,400" C. to 2,000 C. Water-cooling coils 38 surround the outer surface of chamber 11.

I discovered unexpectedly that pyrolytic articles and coatings were formed with high electrical resistance by providing a deposition surface in a chamber, heating the chamber to a temperature in the range of 1,400 C. to 2,000 C., and flowing a mixture of boron, carbon and nitrogen through the chamber. The preferred chamber pressure is in the range of 0.05 millimeter of mercury to 3 centimeters of mercury. I found that materials containing boron, carbon and nitrogen components which can be employed in my deposition method include trimethylborate, boron trichloride, nitrogen, ammonia, methane, B- trichlorborazole, and diethylamine. Trimethylborate, methane and diethylamine provide the carbon component. Boron trichloride, B-trichlorborazole, and trimethylborate produce the boron component. Nitrogen and ammonia provide the nitrogen component.

In the operation of the deposition apparatus in FIG- URE 1, a material containing boron and carbon, boron and nitrogen, or nitrogen and carbon components, isplaced in container 29 and the chamber is evacuated to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury. Power is supplied to leads 21 to heat watercooled electrodes 20 to a temperature in the range of 1,4-00 C. to 2,000 C. Member 23 of graphite is heated by electrodes 20 and associated fins 22 to this temperature range. The material in container 29 contains two components of the required three components of boron, carbon and nitrogen while inlet line 30 supplies the third component. For example, trimethylborate, a liquid, is placed in container 29 to provide the carbon and boron components while ammonia is supplied through inlet line 30 to provide the nitrogen component. When member 23 is heated to a temperature in the range of 1,400 C. to 2,000 O, a mixture of boron, carbon and nitrogen forms which flows through the chamber and deposits on this member as a pyrolytic material. Pump 18 maintains a low pressure in chamber 11 while it removes the products of the reaction therefrom.

The operation of the deposition apparatus in FIGURE 2 is identical with the operation of the apparatus in FIG- URE 1 except that three materials are provided in container 29, and through inlet line 30 and 31, respectively, to provide the mixture of boron, carbon and nitrogen. For example, diethylamine is placed in container 29, ammonia is fed through line 30 and boron trichloride is fed through line 31. When member 23 is heated to a temperature in the range of 1,400 C. to 2,000 C., a mixture of boron, carbon and nitrogen forms which flows through the chamber and deposits on this member as a pyrolytic material.

In the operation of the deposition chamber in FIGURE 3, power is supplied through leads (not shown) to heat water-cooled electrodes 32 and inner chamber 33 to a temperature in the range of 1,400 C. to 2,000 C. Chamber 33 is evacuated to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury. A material containing boron and carbon, boron and nitrogen, or nitrogen and carbon components is supplied through inlet line 36 to chamber 33. A material containing the third component is supplied through inlet line 37 to chamber 33. For example, B-trichlorborazole is heated to 80 C. and supplied through inlet line 36 to provide the boron and nitrogen components while methane is supplied through inlet line 37 to provide the carbon component. A mixture of boron, carbon and nitrogen forms which flows through chamber 33 and deposits on the interior surface thereof as a pyrolytic material. Pump 18 maintains a low pressure in the chamber while it removes the reaction products.

It will be understood that the interior surface of the chamber or a portion thereof can be employed as a deposition surface. Furthermore, three inlets can be employed to feed the materials containing boron, carbon and nitrogen components to chamber 11. If it is desired, all the materials can be placed within one or more containers within chamber 11.

Several examples of pyrolytic material which were made in accordance with the methods of the present invention are as follows:

EXAMPLE I A deposition apparatus was set up in accordance with FIGURE 1 of the drawing wherein a 4% inch diameter cylindrical brass chamber having a length of 8 inches was provided with end closure plates. A pair of watercooled brass electrodes with fins supported a graphite member having end diameters of %32 inch and a one-inch reduced center portion having a diameter of 6 inch. The ends of the chamber were water-cooled while the center portion was air-cooled. Trimethylborate was placed in a container which was positioned in chamber 11 to provide the carbon and boron components. The chamber was closed and evacuated. Power was supplied through the electrodes and heated the member to a temperature of 1,650 C. at its reduced center portion. Ammonia was fed to the chamber through an inlet line to provide the nitrogen component. The member was heated for one minute, during which time the pressure rose to about centimeters of mercury. A mixture of boron, carbon and nitrogen was formed which flowed through the chamber and deposited as pyrolytic material on the center portion of the graphite member. The pyrolytic material exhibited a resistance of 0.008 ohm centimeter along the surface of the deposit.

4 EXAMPLE II A deposition apparatus was set up in accordance with FIGURE 2 of the drawing wherein a 4% inch diameter cylindrical brass chamber having a length of 8 inches was provided with end closure plates. A pair of water-cooled brass electrodes with fins supported a graphite member having an end diameter of inch and a one-inch reduced center portion having a diameter of inch. The ends of the chamber were water-cooled while the center portion was air-cooled. Diethylamine was placed in a container which was positioned in chamber 11 to provide the carbon component. The chamber was closed and evacuted. Power was supplied through the electrodes and heated the member to a temperature of l,650 C. at its reduced center portion. Ammonia was fed to the chamber through an inlet line to provide the nitrogen component. Boron trichloride was fed to the chamber through a second inlet line to provide the boron component. The member was heated for about one minute. A mixture of boron, carbon and nitrogen was formed which flowed through the chamber and deposited as pyrolytic material on the center portion of the graphite member. The pyrolytic material exhibited a resistance of 40.0 megohm centimeters along the surface of the deposit.

EXAMPLE III A deposition apparatus was set up generally in accordance with FIGURE 3 of the drawing. The inner chamber in the form of a graphite tube furnace had a diameter of 1 inch and a length of 7 inches. The exterior surface of the outer chamber was provided with coils to water-cool the tube furnace. Power was supplied through leads to heat the water-cooled electrodes and inner chamber to a temperature of 1,500 C. along the tube. The chamber was evacuated to a pressure of 0.05 mm. of mercury. B-trichlorborazole was heated to a temperature of C. and supplied to an inlet line to the inner chamber to provide the boron and nitrogen components. Methane was supplied at a rate of 1 cubic foot per hour to the inlet line to the inner chamber to provide the carbon component. The inner chamber was heated for about four hours. A mixture of boron, carbon, and nitrogen was formed which flowed through the inner chamber and deposited as pyrolytic material on the inner surface of the chamber tube. The pyrolytic material exhibited a resistance of 2.0 ohm centimeters along the surface of the deposit.

While other modifications of this invention and variations of method which may be employed within the scope of the invention have not been described, the invention is intended to include such that may be embraced within the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A deposition method which comprises providing a chamber, providing a deposition surface in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, heating said chamber to a temperature in the range of l,400 C. to 2,000 0, providing a mixture of boron, carbon and nitrogen from materials containing boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said surface.

2. A deposition method which comprises providing a chamber, providing a deposition surface in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, heating said surface to a temperature in the range of l,400 C. to 2,000 C., providing a mixture of boron, carbon and nitrogen from materials containing boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said surface.

3. A deposition method which comprises providing a chamber, positioning at least one member in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, heating said chamber to a temperature in the range of l,400 C. to 2,000 C., providing a mixture of boron, carbon and nitrogen from materials containing boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said member.

4. A deposition method which comprises providing a chamber, positioning at least one member in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, heating said member to a temperature in the range of "l,400 C. to 2,000 O, providing a mixture of boron, carbon and nitrogen from materials containing boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said member.

5. A deposition method which comprises providing a chamber, positioning at least one member in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, feeding materials containing boron, carbon and nitrogen components to said chamber, heating said chamber to a temperature in the range of 1,400" C. to 2,000 C. to provide a mixture of boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said member.

6. A deposition method which comprises providing a chamber, positioning at least one member in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, feeding materials containing boron, carbon and nitrogen components to said chamber, heating said member to a temperature in the range of 1,400 C. to 2,000 C. to provide a mixture of boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said member.

7. A deposition method which comprises providing a chamber, positioning at least one member in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, providing materials containing boron, carbon and nitrogen components within said chamber, heating said chamber to a temperature in the range of 1,400 C. to 2,000 C. to provide a mixture of boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said member.

8. A deposition rnethod which comprises providing a chamber, positioning at least one member in said chamber, evacuating said chamber to a pressure in the range of 0.05 millimeter of mercury to 3 centimeters of mercury, providing materials containing boron, carbon and nitrogen components within said chamber, heating said member to a temperature in the range of 1,400 C. to 2,000 C. to provide a mixture of boron, carbon and nitrogen, and flowing said mixture through said chamber whereby pyrolytic material is deposited on said member.

9. The process of producing an alloy comprising pyrolytic graphite and boron which comprises cont-acting a gaseous hydrocarbon and boron trichloride at a temperature between about 1,500 C. and 2,000 C. and a pressure below about 20 mm. of mercury.

10. The process of producing an alloy comprising pyrolytic graphite and boron which comprises contacting methane and boron trichloride at a temperature between about 1,500 C. and 2,000 C. and a pressure below about 20 mm. of mercury.

References Cited UNITED STATES PATENTS 2,405,449 8/1946 Robinson et a1. 117226 X 2,853,969 9/1958 Drewett 117--46 2,200,521 5/ 1940 Siegel 117-46 2,764,510 9/1956 Ziegler 117-216 2,810,365 10/1957 Keser 11847 2,810,664 10/ 1957 Gentner 1l7--226 RALPH S. KENDALL, Primary Examiner.

A. GOLIAN, Assistant Examiner.

US. Cl. X.R. 117-106, 121

Claims

1. A DEPOSITION METHOD WHICH COMPRISES PROVIDING A CHAMBER, PROVIDING A DEPOSITIONSURFACE IN SAID CHAMBER, EVACUATING SAID CHAMBER TO A PRESSURE IN THE RANGE OF 0.05 MILLIMETER OF MERCURY TO 3 CENTIMETERS OF MERCURY, HEATING SAID CHAMBER TO A TEMPERATURE IN THE RANGE OF 1,400*C. TO 2,000*C., PROVIDING A MIXTURE OF BORON, CARBONAND NITROGEN FROM MATERIALS CONTAINING BORON, CARBONAND NITROGEN, AND FLOWING SAID MIXTURE THROUGH SAID CHAMBER WHEREBY PYROLYTIC MATERIAL IS DEPOSITED ON THE SURFACE.