Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
1997-01-24
2002-01-29
Hendrickson, Stuart L. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C264S432000, C427S249300
Reexamination Certificate
active
06342195
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to methods for the synthesis of various solids such as diamonds, diamond films, boron nitride and other similar materials. This invention specifically relates to utilizing novel sources of reaction species (e.g., in the case of diamond formation, novel sources of carbon and/or hydrogen and/or seeds) for the manufacture of various materials and the use of such materials for various commercial purposes.
BACKGROUND ART
There are various known methods for producing synthetic diamond. In a first method, diamond grit may be synthesized by precipitating diamond from carbon contained within a metal solution at high temperatures (e.g., 1400° C.,) and high pressures (e.g., 60 Kbar). The resulting diamond which is produced at these high temperatures and high pressures may be free of second phase inclusions, but generally contains significant concentrations of dissolved nitrogen and metal (e.g., nickel, iron, cobalt, etc.).
In a second technique, diamond powder may be produced by shock wave synthesis, wherein an explosive charge is utilized to shock a mixture of carbon and a metal solvent/catalyst. An example of the shock wave synthesis technique can be found in U.S. Pat. No. 3,401,019, which issued on Sep. 10, 1968, in the names of Cowan et al. Drawbacks of the shock wave synthesis procedure are that the diamond which is produced is routinely contaminated with dissolved nitrogen metal (e.g., iron). In addition, the recovery of diamond particles produced requires elaborate chemical processing to separate the diamond particles from the surrounding materials within the reaction chamber (e.g., graphite and metal). Moreover, this method typically produces only submicron diamond powders.
In a third technique, diamond powder can be made by precipitation of diamond within certain amorphous metals which are saturated with carbon. For example, U.S. Pat. No. 4,485,080 to Shingu et al., which issued on Nov. 27, 1984, describes a multi-step process for the rapid solidification of carbon-containing alloys followed by the precipitation of diamond particles within the amorphous metal at temperatures above 100° C. The diamond is thereafter recovered from the metal by acid digestion.
In a more recent development, thin diamond films are synthesized from the vapor phase by an activated chemical vapor deposition (CVD) process. Typically, during such CVD processes, diamond particles nucleate on the surface of an appropriate substrate heterogeneously and thereafter grow in size. The particles thus produced may be widely separated or may be close enough to coalesce into a continuous diamond film. Exemplary techniques showing various aspects of the CVD process can be found in the following patents: U.S. Pat. No. 4,882,138, which issued on Nov. 21, 1989, in the name of John Pinneo, which discloses the use of the combination of diamond particles, atomic hydrogen and a gaseous carbon source, which, when processed, results in diamond being epitaxially deposited on the diamond particles; U.S. Pat. No. 4,958,590, which issued on Sep. 25, 1990, in the name of Robert Goforth, which discloses a specific microwave assisted CVD process and apparatus; U.S. Pat. No. 4,985,227, which issued on Jan. 15, 1991, in the names of Ito et al., which discloses contacting a substrate material with a gaseous source of excited carbon monoxide and excited hydrogen and causing diamond to be deposited onto the substrate; and U.S. Pat. No. 5,112,643, which issued on May 12, 1992, in the names of Ikegaya et al., which discloses the use of a raw material gas which includes a carbon source and hydrogen and activating the raw material gas by a thermoelectron-radiating device and by formation of a DC plasma which results in the deposition of a diamond film on the surface of the substrate. In addition, the CVD process for the formation of diamonds has been reviewed by R. C. DeVries, Annual Review of Materials Sciences 17:161 (1987); A. R. Badzian and R. C. DeVries, Mat. Res. Bull. 23:385 (1988); and J. C. Angus and C. C. Hayman, Science 241:915 (1988). The art further shows that graphite can be a source material for the formation of various gaseous carbon-based species which are capable of depositing on a large, single crystal of diamond, B. V. Spitsyn, L. L. Bouilov and B. V. Derjaguin, Prog. Crystal Growth and Charact. 17:79 (1988). However, no one has to date used the principle of CVD processing to form any object other than a polycrystalline diamond film.
Another technique for the formation of diamond is disclosed in U.S. Pat. No. 4,997,636, which issued on Mar. 5, 1991, in the name of Johan Prins. This patent discloses the use of a non-diamond substrate material having a face-centered cubic crystal structure. The substrate is ion implanted with carbon atoms which are later induced to diffuse out of the substrate and grow epitaxially on a surface of the substrate.
A still further technique for the formation of diamond utilizes a combustion flame. Specifically, U.S. Pat. No. 5,075,096, which issued on Dec. 24, 1991, in the names of Tanabe et al. discloses burning a combustible gas containing carbon in a combustion-supporting gas which contains oxygen to create a reduction atmosphere, and precisely controlling the humidity of the reduction atmosphere, and inserting a substrate into the combustible gas flame to form diamond on a surface of the substrate; and U.S. Pat. No. 5,135,730, which issued on Aug. 4, 1992, in the names of Suzuki et al, discloses forming and burning a mixed gas of a hydrocarbon fuel gas and oxygen to form a flame and contacting the flame with the surface of a substrate to form diamond on said substrate.
All of the above-discussed techniques for the production of diamond suffer from one or more of the following drawbacks: high cost of manufacture, complex production equipment, limited sizes and shapes for diamond production, etc. The present invention overcomes the above described disadvantages inherent in various methods known in the art for the synthesis of diamond and other materials. The invention presents a novel method for the manufacture of various materials including, but not limited to, diamond films, shaped diamond products, boron nitride films, shaped boron nitride products, etc.
SUMMARY OF THE INVENTION
The present invention relates to a novel process for the manufacture of various solids including diamond films, shaped diamond products, boron nitride films, shaped boron nitride products, silicon films, shaped silicon carbide products, etc. With regard to the synthesis of diamond, the process of the invention is a significant improvement over known formation techniques such as high temperature/high pressure reactions, solid precipitation reactions, shock wave synthesis, CVD techniques, combustion flame techniques, etc. The present invention utilizes a novel combination of starting materials and processing conditions to result in novel materials (e.g., diamond). Specifically, with regard to diamond formation, the combination of one or more starting source(s) of carbon in a non-vapor form (e.g., certain solids liquids including, but not limited to, amorphous carbon, carbon black, carbon powder, carbon fibers, graphite, charcoal, polymer materials containing carbon, glassy carbon non-vapor carbon precursor materials, etc.) with one or more appropriate seed material(s) present in addition to the starting source of carbon or inherently present in the starting source of carbon, said seed material(s) having a diamond or diamond-like crystalline structure (e.g., diamond crystals, silicon, silicon carbide, cBN, various face-centered cubic structures which are similar to the crystal lattice of diamond, or other isostructual materials, etc.) and/or one or more seed material precursors which, under the process conditions of the invention, may form one or more seed materials in situ (e.g., Ni, Cu, Mo, Zr, Pt, Pd, etc.) may, when heated to a suitable temperature (e.g., 300° C.-2000° C., and more preferably 300° C.-1600° C. and even more preferably 700° C.-1000° C.) in the
Badzian Andrzej
Dewan Hardial S.
Messier Russell
Ravindranathan Palaniappan
Roy Rustum
Goebel, Jr. Edward W.
Hendrickson Stuart L.
MacDonald, Illig, Jones and Britton LLP
The Penn State Research Foundation
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