Cubic boron nitride properties

A wide range of cutting-tool materials is available. Properties, performance capabilities, and cost vary widely (2,7). Various steels (see Steel) cast cobalt alloys (see Cobalt and cobalt alloys) cemented, cast, and coated carbides (qv) ceramics (qv), sintered polycrystalline cubic boron nitride (cBN) (see Boron compounds) and sintered polycrystalline diamond tbin diamond coatings on cemented carbides and ceramics and single-crystal natural diamond (see Carbon) are all used as tool materials. Most tool materials used in the 1990s were developed during the twentieth century. The tool materials of the 1990s... 

Cubic boron nitride (c-BN) is a different material altogether from h-BN, with a structure similar to that of diamond, which is characterized by extremely high hardness (second to diamond) and high thermal conductivity.As such, it is a material of great interest and a potential competitor to diamond, particularly for cutting and grinding applications. Its characteristics and properties are shown in Table 10.3... 

Summary of Characteristics and Properties of Cubic Boron Nitride... 

Cubed compound, in PVC siding manufacture, 25 685 Cube lattice, 8 114t Cubic boron nitride, 1 8 4 654 grinding wheels, 1 21 hardness in various scales, l 3t physical properties of, 4 653t Cubic close-packed (CCP) structure, of spinel ferrites, 11 60 Cubic ferrites, 11 55-57 Cubic geometry, for metal coordination numbers, 7 574, 575t. See also Cubic structure Cubic symmetry Cubic silsesquioxanes (CSS), 13 539 Cubic structure, of ferroelectric crystals, 11 94-95, 96 Cubic symmetry, 8 114t Cubitron sol-gel abrasives, 1 7 Cucurbituril inclusion compounds,... 

Table 3 summarizes the properties of the so-called nonmetallic hard materials, including diamond and the diamondlike carbides B4C, SiC, and Be2C. Also included in this category are comndum, A1203, cubic boron nitride, BN, aluminum nitride, AIN, silicon nitride, S N and silicon boride, SiB6 (12). 

DeVries RC (1972) Cubic boron nitride handbook of properties. General Electric... 

Despite the excellent properties of cubic boron nitride, it is a very difficult crystal to grow. Thus far the crystal size has been limited to micrometer-type size. Little is known about the ultimate potential of cubic boron nitride in electronics. Potential donors include Si with activation energy of 0.24 eV, C with activation energy of 0.28 eV, and sulfur with activation energy of... 

Grinding and polishing is one of the oldest applications for wide band-gap materials primarily owing to the property of hardness that some of these materials possess (e.g., diamond). SiC and cubic boron nitride, in addition to diamond, have found a commercial market in grinding and polishing, primarily for ferromagnetic materials with high carbon solubility. 

The synthesis of diamond and cubic boron nitride has strongly motivated improvements in the development of high-pressure equipment and increased the interest in these materials, which have exceptional properties. Single crystals are required for optical and electronic applications. Consequently, specific crystal-growth processes have been set up under very high-pressure conditions. The principle is similar to that described, at lower pressures, for the preparation of single crystals of a-Si02. 

Until recently, there were no tool materials that would stand up to the high stresses and temperatures necessary for FSW of materials with higher melting points, such as steels, stainless steels, and nickel-base alloys. In 1998, tungsten alloys and polycrystalline cubic boron nitride (PCBN) were developed to create FSW tools for use in steel, stainless steel, titanium alloys, and nickel-base alloys. Properties of the resultant welds have been shown to be outstanding. Although some issues remain (primarily limited tool life with tungsten-base tools), FSW has been demonstrated as a technically and eco-... 

A. A. Shulzhenko, S. A. Bozhko, A. N. Sokolov, A. Petrusha, N. P. Bezhenar, A. I. Ignatusha, Cubic Boron Nitride Synthesis, Sintering and Properties, The Ukrainian Academy of Sciences, Institute for Superhard Materials, Kiev Naukova Dumka, 1993, 254. 

Silicon carbide is noted for its extreme hardness [182-184], its high abrasive power, high modulus of elasticity (450 GPa), high temperature resistance up to above 1500°C, as well as high resistance to abrasion. The industrial importance of silicon carbide is mainly due to its extreme hardness of 9.5-9.75 on the Mohs scale. Only diamond, cubic boron nitride, and boron carbide are harder. The Knoop microhardness number HK-0.1, that is the hardness measured with a load of 0.1 kp (w0.98N), is 2600 (2000 for aAl203, 3000 for B4C, 4700 for cubic BN, and 7000-8000 for diamond). Silicon carbide is very brittle, and can therefore be crushed comparatively easily in spite of its great hardness. Table 8 summarizes some typical physical properties of the SiC ceramics. 

There is presently much effort in basic science and applied research to work on novel ceramic hard materials denoted as super- or ultra-hard materials that can compete with the hardness of conventional diamond. Aim and scope of the research in this field is to develop hard materials with superior mechanical and chemical properties and with similar hardness. Moreover, calculations of properties of hypothetical carbon nitrides like C3N4 indicated that there might be compounds exhibiting even higher hardness values than that of diamond. The low-temperature synthesis of diamond and cubic boron nitride on the one hand as well as the successful research on new carbon nitrides on the other hand have caused an enormous impact around the world on both the basic science and the technological development of these novel ultra-hard materials. 

Superhard compounds are obviously formed by a combination of the low atomic number elements boron, carbon, silicon, and nitrogen. Carbon-carbon as diamond, boron-nitrogen as cubic boron nitride, boron-carbon as boron carbide, and silicon-carbon as silicon carbide, belong to the hardest materials hitherto known. Because of their extreme properties and the variety of present and potential commercial applications, silicon carbide (SiC) and boron carbide (B4C) are, besides tungsten carbide-based hard metals, considered by many as the most important carbide materials. 

The field of transformation of other BN phases (i.e., a-BN Including rhombohedral and turbostratic BN, y-BN) into cubic boron nitride (P-BN) has been the subject of numerous reviews within the past four years. Perhaps the most comprehensive review of p-BN formation, structure, and properties was compiled by Rapoport [1]. Another review is given in English [2], and there are reviews in French [3], Japanese [4 to 8], Russian [9 to 12], and German [13]. In... 

The structural analogy with the carbon allotropes can be extended to the properties of the two borrm-nitride allotropes. For instance, hexagonal boron nitride (h-BN) is soft and lubricious like grsqihite, and cubic boron nitride (c-BN), like diamond, is extremely hard. 

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