Diamond carbon nitrides

Tessier, P. Y., Pichon, L., VUlechaise, P, Linez, P., Angleraud, B., MubumbUa, N., Fouquet, V, Straboni, A., Milhet, X., and Hildebrand, H. F., Carbon Nitride Thin Films as Protective Coatings for Biomaterials Synthesis, Mechanical and Biocompatibility Characterizations, Diamond Relat. Mater, Vol. 12,2003,pp. 1066-1069. 

The work on carbon nitride solids is strongly related to research on diamondlike carbon (DLC) materials [5, 6]. DLC materials are thin film amorphous metastable carbon-based solids, pure or alloyed with hydrogen, which have properties similar to that of crystalline diamond (high hardness, low friction coefficient, high resistance to wear and chemical attack). This resemblance to diamond is due to the DLC structure, which is characterized by a high fraction of highly cross-linked sp -hybridized carbon atoms. To obtain this diamond-like structure... 

Ling, H. Wu, J.D. Sun, J. Shi, W. Ying, Z.F. Li, F.M. Electron cyclotron resonance plasma-assisted pulsed laser deposition of boron carbon nitride films. Diamond Relat. Mater. 2002, 11, 1623-1628. 

Straboni a, Milhet X and Hildebrand HE (2003) Carbon nitride thin films as protective coating for biomaterials synthesis mechanical and bio-compatibility characterizations. Diamond ... 

Since the publication of theoretical studies predicting that carbon nitride might be harder than diamond, a considerable amount of research has been directed toward the preparation of pure C3N4 <1989SCI841>. In contrast, carbon nitride molecules with the C3N4 formula have seldom been studied <2003AGE5206>. 

There is understandably some pessimism regarding a commercial synthesis of superhard carbon nitride especially in view of the intense effort that has been put into its synthesis by many laboratories in the last few years with no firm result to date. Yet the wisdom of the computational arguments upon which the various structures of the material have been predicted seems firm and they have been shown to be capable of giving us valuable insight in many other areas of materials science. Experiences gained regarding the commercial synthesis of diamond and cubic BN could probably lead ways that carbon nitride can be synthesized, yet other more novel routes also cannot be excluded. 

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... 

Although superhard materials other than diamond and CBN have been synthesized in recent years - including boron carbon nitride, cubic... 

Carbon nitride (C3N4) should exist according to expectations based on pseudopotential calculations. The solid should be approximately as hard as diamond and have the structure of Si3N4. There have been many attempts to make it but so far its extreme inertness has only permitted the synthesis of a hard glassy form from ion beam deposition that comes close to the expected stoichiometry. 

Diamond is the hardest material known, with a value of 10 on the Mohs scale, which is a scratch hardness test or, on the Knoop scale, which is an indentation test dependent on the load, indenter shape and the crystal face, giving a value of 5,700-10,400 kgmm . The hardness is attributed to the strength of bonding of the atoms in conjunction with the uniformity. There is, however, a possibility that there are new materials, sueh as carbon nitride (C3N4) and compressed Ceo that may eventually be shown to be harder than diamond. 

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