Solid State Nitrides

9508522 DiSalvo本研究的目的是探索固态三元氮化物的形成、晶体结构和性能。这项研究是对一类材料的研究的继续，到目前为止，这类材料实际上是尚未开发的相当大的技术用途。其中包括用于机床耐磨涂层的氮化钛，作为高导热陶瓷的氮化铝，以及可通过低温化学工艺沉积硬质防渗膜的许多应用中的氮化硅，以及块体陶瓷。这项研究将讨论开发制备新相小单晶的一般方法，以促进晶体结构的确定，并审查含有一维、二维、特别是三维连续过渡金属氮键网络的材料。这种连续的网络化合物有望表现出更广泛的物理性质，并在机械和化学上更加坚固。将采用的合成方法包括在流动的氨中从氧化物中制备，从金属熔剂中生长晶体，以及在500-1700℃的高压下生长。所制备的化合物的结构将通过X射线衍射来确定，并将确定其电、磁和热性能。在某些情况下，还将检查化学性质，如催化活性或低温下的氧化还原化学(即软化学，如插层)。这些材料的化学和结构行为将与氧化物、硫化物或磷化物等相关化合物进行比较。这个研究小组开创了三元金属氮化物研究的先河，发现了许多新的相。一些氮化物的结构表明，其中一些氮化物的结构特征和性质都相当独特。然而，还有更多的系统需要研究。这些化合物包括由锂以外的碱金属或稀土金属稳定的化合物。在制备单晶和富含过渡金属的化合物方面仍然存在重大挑战。拟议的研究概述了应对这些挑战的方法，并提议继续攻击这一以前被忽视的材料家族。人们的期望是，这些材料中的一些将表现出与一些二元氮化物一样有用的化学或物理性质，甚至更有用。人们希望，一些材料将展示出新的现象，这将导致令人兴奋的科学，甚至可能是新技术。

9508522 DiSalvo The objective of this research is to explore the formation of solid-state ternary nitrides, their crystal structure and properties. This research is a continuation of studies of a class of materials that so far had been virtual y unexplored considerable technological utility. These include titanium nitride for wear resistant coatings on machine tools, aluminum nitride as a high thermal conductivity ceramic, and silicon nitride in numerous applications where hard impervious films are needed and can be deposited by low temperature chemical processes, as well as in bulk ceramics. This research will address the development of general methods for the preparation of small single crystals of the new phases to facilitate crystal structure determination, and the examination of materials that contain continuous networks of transition metal nitrogen bonds in one, two and especially three dimensions. The continuous network compounds are expected to exhibit a wider variety of physical properties and to be mechanically and chemically more robust. The synthetic methods to be used include preparation from oxides in flowing ammonia, growth of crystals from metallic fluxes, and high pressures and at temperatures from 500 to 1700 C. The structures of the compounds prepared will be determined by x-ray diffraction, and the electrical, magnetic and thermal properties will be determined. In some cases chemical properties, such as catalytic activity or redox chemistry at low temperatures (i.e soft chemistry such as intercalation) will also be examined. The chemical and structural behavior of these materials will be compared to related compounds such as oxides, sulfides or phosphides. %%% This research team has pioneered the study of ternary metal nitrides and discovered many new phases. The structure of some nitrides have shown that both the structural features and properties of some of them are rather unique. Yet there are many more systems left to investigate. These include compounds that are stabilized by alkali metals other than lithium, or by rare earth metals. There remain significant challenges in the preparation of single crystals and in compounds that are rich in the transition metal. The proposed research outlines approaches to these challenges and propose to continue the attack on this previously neglected family of materials. The expectation is that some of these materials will exhibit chemical or physical properties that may prove as useful as, or more so than, some of the binary nitrides. The hope is that some materials will exhibit novel phenomena that will lead to exciting science and perhaps even new technology.