Status and Applications of Diamond and Diamond-Like Materials An Emerging Technology (1990) / Chapter Skim
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1 Introduction
1 Introduction
Pages 5-18
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From page 5... ...
The related diamond-like materials show great potential for tribological surfaces, corrosion protection, passivating layers, and diffusion barriers as well as in photolithography. By way of background, annual world production of natural rough diamonds is about 94 million carats (18.7 tons)
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The types of materials considered may be categorized by their elemental composition. Most of the materials considered fall in the "composition tetrahedron" shown in Figure 1-2 and are compounds or solid solutions involving the elements boron, carbon, nitrogen, and silicon.
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A summary of the principal terms used to describe the diamond-like materials is given in Table 1-1. TABLE 1-1 Nomenclature for Diamond-Like Materials Nonhydrogenated Hydrogenated Used in This Report Diamond-like carbons a-C DLC Not Used in This Report Dense carbons a-D i-C Hard carbons Diamond-like hydrocarbons a-C:H DLHC Dense hydrocarbons
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and bulk modulus versus some function of interatomic spacing (Cohen, 1985~. Similarly, hardness correlates strongly with atomic number density and with bond energy density.
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on the diagram. These curves define the minimum P-T conditions for high- pressure diamond synthesis by the solvent-catalyst method.
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Although cubic BN abrasive grain has been available since 1957, the first optically and electrically useful crystals were synthesized in 1987 (Mishima et al., 1987~. Metastable Diamond Growth Metastable phases can form from precursors with high chemical potential if the activation barriers to more stable phases are sufficiently high.
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The diamond-like carbons may, in fact, include several different types of structures ranging from microcrystalline diamond to complex, amorphous materials containing significant amounts of both sp2 and Sp3 carbon sites. The diamond-like materials are made by energetically assisted deposition processes -- for ~ ~ ..
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Crystallume for example, has announced the commercial availability of 6-mm diameter x-ray windows. The high thermal conductivity has led to the use of diamond as a heat sink material in electronic applications.
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Hermetic coatings to protect optical fibers and hightemperature superconductors are other potential applications. These materials have been used as antireflection coatings on germanium optics because of their hardness and the ability to control their refractive indexes by varying the carbon/hydrogen ratio.
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Statistics from industry sources provide a comparison: in the past 5 years, of 573 patents granted in the new diamond technology, 488 were awarded to Japanese companies and only 28 were awarded in the United States. Soviet workers, particularly Deryagin's group, have a long history in lowpressure diamond research (Badzian and DeVries, 1988~.
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Fundamental theoretical studies of the types of molecular structures that lead to "hardness and basic studies of the atomic-scale processes during inelastic deformation are appropriate. This research could lead to new superhard materials and to designed modifications of existing superhard materials.
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1988. High rate synthesis of diamond by dc plasma jet chemical vapor deposition.
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1987. Characterization of diamondlike carbon films and their application as overcoats on thin-film media for magnetic recording.
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