9705237 Barsoum The proposed research will study the physical properties of two new classes of ceramic material. The two classes are the `312' and the `H-phase' (M3BC2 and M2BX, respectively, where M is a transition metal, B is a group B-element such as Si, Al, Ge, Sn, Pb, In, Ga, and X is either carbon or nitrogen). Both classes have layered hexagonal structures, with alternating close-packed layers of the B-group elements and transition metal carbides (or nitrides). These materials were first identified in the late sixties, but then were ignored until recent preliminary work by the PI and his group showed that they had unusual properties. They have high thermal and electrical conductivity, are not susceptible to thermal shock, and are machinable like metals. Like ceramics, they are refractory and oxidation resistant. Fully dense, single phase, bulk samples of a variety of compositions will be fabricated and characterized to determine the elastic, thermal, and electrical properties of these compounds as a function to temperature and anisotropy. The objective of the research is to better understand the nature of the bonding in these compounds, especially that between the B-group elements and the transition metal carbide or nitride layers. %%% These two new classes of ceramics will be examined for their physical properties. These materials were first identified in the late sixties, but then were ignored until recent preliminary work by the PI and his group showed that they had unusual properties. They have high thermal and electrical conductivity, are not susceptible to thermal shock, and are machinable like metals. Like ceramics, they are refractory and oxidation resistant. These materials have a variety of potential structural and functional applications. ***
