Ceramics carbon nitride

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. 

Volume 1 starts with an introduction into novel ultra hard ceramics including diamond and diamond-like carbon, carbon nitrides and silicon nitrides as well as boron containing carbides, nitrides and carbonitrides. Here we wish to recognize the great fundamental and technological challenge of developing new superhard... 

Electrochemical applications of a-BN include its use as carrier material for catalysts in fuel cells [297], as a constituent of electrodes in molten salt fuel cells [298, 299], as anticracking particles in the electrolyte for molten carbonate fuel cells [300, 301], and in seals for insulating terminals of Li/FeS batteries from the structural case [302], A BN-coated membrane is used in an electrolysis cell for the manufacture of high-purity rare earth metals from salt melts [381]. A porous boron nitride layer is applied to the upper outer surface of the electrolyte tube in sodium-sulfur batteries [303], and ceramic boron nitride separators are used in liquid fuel cells and batteries [304, 305]. Boron nitride powder may be included in the electrolyte of electrolytic capacitors for high-frequency utilization [306]. 

Boron-carbon-nitride ceramic is deposited on iron-based sliding parts by chemical vapor deposition (CVD) it is used as rotary compressor shafts, in order to improve the wear resistance [1 to 5]. Such B-C-N coatings have also been applied to dynamic pressure air bearings [6]. In gas-cooled nuclear reactors, °B-enriched B-C-N can be deposited by CVD in the fluid channels of the fuel elements for permanent deactivation in case of an emergency [7]. Radiofrequency or microwave-enhanced CVD is employed in order to deposit a diamond carbon and (3-BN superlattice structure [8]. 

Slow crack is also observed for systems free of alkali. Results similar to those found for silicate glasses at room temperature are also found for a variety of other ceramic materials, such as porcelains, glassy carbon, Portland cement, high-alumina ceramics, silicon nitride, lead zirconite, and barium titanate [12]. 

J. D. Buckley, ed.. Advanced Materials, Composite Carbon, Preparation Symposium, American Ceramics Society, Inc., Columbus, Ohio, 1972. Papers on composite materials including carbon and graphite or nitride composites. 

Nonoxide fibers, such as carbides, nitrides, and carbons, are produced by high temperature chemical processes that often result in fiber lengths shorter than those of oxide fibers. Mechanical properties such as high elastic modulus and tensile strength of these materials make them excellent as reinforcements for plastics, glass, metals, and ceramics. Because these products oxidize at high temperatures, they are primarily suited for use in vacuum or inert atmospheres, but may also be used for relatively short exposures in oxidizing atmospheres above 1000°C. 

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... 

Development of practical and low cost separators has been an active area of ceU development. CeU separators must be compatible with molten lithium, restricting the choice to ceramic materials. Early work employed boron nitride [10043-11-5] BN, but a more desirable separator has been developed using magnesium oxide [1309-48-4], MgO, or a composite ofMgO powder—BN fibers. Corrosion studies have shown that low carbon steel or... 

Vapor—sohd reactions (13—17) are also commonly used ia the synthesis of specialty ceramic powders. Carbothermic reduction of oxides, ia which carbon (qv) black mixed with the appropriate reactant oxide is heated ia nitrogen or an iaert atmosphere, is a popular means of produciag commercial SiC, Si N, aluminum nitride [24304-00-3], AIN, and sialon, ie, siUcon aluminum oxynitride, powders. 

Jiang, L. and L. Gao, Fabrication and characterization of carbon nanotube-titanium nitride composites with enhanced electrical and electrochemical properties. Journal of the American Ceramic Society, 2006. 89(1) p. 156-161. 

The hard layers are represented with a wide range of coating based on carbon, metals, ceramics, various oxides (Ti02, Si02) and nitrides (ZrN) and their combinations [14,16,24,47,136-143]. These layers can streghten the material surface, especially in materials designed for hard tissue surgery, such as... 

One further finding with the —lIRNMeR — pyrolysis studies comes from Raman studies of the ceramic product. The NMR data show no traces of Si—C bonds, nor does the Raman spectrum. However, the Raman spectrum does show the presence of C—N bonds up to 1200 °C (the highest temperature studied). This suggests that the silicon nitride nanoparticles interact with the carbon matrix through C—N bonds. One might speculate that the interface looks somewhat like C3N4. 

In the following sections some examples are given of the ways in which these principles have been utilized. The first example is the use of these techniques for the low temperature preparation of oxide ceramics such as silica. This process can also be used to produce alumina, titanium oxide, or other metal oxides. The second example describes the conversion of organic polymers to carbon fiber, a process that was probably the inspiration for the later development of routes to a range of non-oxide ceramics. Following this are brief reviews of processes that lead to the formation of silicon carbide, silicon nitride, boron nitride, and aluminum nitride, plus an introduction to the synthesis of other ceramics such as phosphorus nitride, nitrogen-phosphorus-boron materials, and an example of a transition metal-containing ceramic material. 

Recent research has explored a wide variety of filler-matrix combinations for ceramic composites. For example, scientists at the Japan Atomic Energy Research Institute have been studying a composite made of silicon carbide fibers embedded in a silicon carbide matrix for use in high-temperature applications, such as spacecraft components and nuclear fusion facilities. Other composites that have been tested include silicon nitride reinforcements embedded in silicon carbide matrix, carbon fibers in boron nitride matrix, silicon nitride in boron nitride, and silicon nitride in titanium nitride. Researchers are also testing other, less common filler and matrix materials in the development of new composites. These include titanium carbide (TiC), titanium boride (TiB2), chromium boride (CrB), zirconium oxide (Zr02), and lanthanum phosphate (LaP04). 

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