Materials with a grain size in the nanometer (10-9 m) range have been the focus of considerable research interest, since such materials have been shown to possess useful properties not obtained with larger grain sizes. However, the preparation of these materials has required at least two processing steps, usually involving the preparation of nanometer-sized grains in powder form (either from rapid solidification from vapor phase or mechanical milling of larger-sized grains) followed by the consolidation of such powders into denser materials by rapid sintering. A University of California scientist, in collaboration with an international research team, has invented a one-step method for synthesizing and consolidating dense nanophase materials. In the UC process, the activation of the synthetic reaction and its short duration ensure that grain growth is totally avoided or markedly minimized, while generating a highly consolidated product that does not require sintering. So far, this process has been successfully employed with ceramics, intermetallics, and composite materials ( e.g. MoSi2, FeAl, TiB2-TiN), and appears to be readily extensible to numerous other materials of varying complexity. Thus, commercial applications of this invention may extend to the production of a wide variety of ceramic materials and devices. (more...)

Transition metal carbides, nitrides and carbonitrides hold considerable commercial interest because of their properties of hardness, corrosion resistance and thermal stability. The manufacture of the whole class of materials has, however, remained cumbersome and costly up to now. The conventional synthesis of Titanium carbonitride involves three steps: Formation of a carbide phase, a nitride phase, and an homogenization of the two conducted at high temperatures over the course of several hours. Materials scientists at the University of California have recently developed a technique for the direct synthesis of titanium carbonitride. Their procedure takes place in a single, rapid step. Under the conditions of the procedure, a 2000 degree Celsius, self-sustaining combustion wave passes through and converts reactants at a velocity of 9 mm per second. Following propagation of the initial wave, the reaction is complete after approximately 1.7 seconds. The synthesis technique has all the attractive features of combustion syntheses in general, including straight-forwardness, high purity of products, and easy applicability to the manufacture of large items. UC investigators have submitted their products to X-ray analysis, and have found that the synthesis converts reactants completely to a single, cubic, NaCl-type crystal phase with lattice parameters of 0.4269-0.4309 nm. No other phases, by-products, or regions of nonhomogeneity appear in the reacted mixtures. The high temperature at which conversion to titanium carbonitride takes place indicates the high thermal stability of this material. A quality that has attracted additional attention to this particular transition-metal carbonitride is the affinity with which it conjugates with nickel. Titanium carbonitride/nickel cermets have the advantages of tungsten carbide/cobalt cermets but are considerably less costly to produce, given the low cost of nickel relative to cobalt. The development of a direct synthesis by UC researchers makes titanium carbonitride the most desirable material of its type. (more...)