Solid State Nitrides

本研究的目的是探讨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研究的延续，迄今为止，这些材料实际上尚未被开发出相当大的技术效用。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，以及用于需要坚硬不透水薄膜的众多应用的氮化硅，这些应用可以通过低温化学工艺沉积，也可以用于大块陶瓷。本研究将致力于发展制备新相小单晶的一般方法，以促进晶体结构的确定，并检查包含一维，二维，特别是三维过渡金属氮键连续网络的材料。连续网络化合物有望表现出更广泛的物理性质，并且在机械和化学上更加坚固。将使用的合成方法包括在流动的氨中从氧化物中制备，从金属助熔剂中生长晶体，以及在500至1700摄氏度的高压下，所制备的化合物的结构将通过x射线衍射确定，并将确定其电、磁和热性能。在某些情况下，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）也将被检查。这些材料的化学和结构行为将与相关化合物如氧化物、硫化物或磷化物进行比较。这个研究小组率先研究了三元金属氮化物，并发现了许多新相。一些氮化物的结构表明，其中一些氮化物的结构特征和性能都是相当独特的。然而，还有更多的系统有待研究。这些化合物包括由除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，并建议继续对这一以前被忽视的材料家族进行攻击。我们的期望是，这些材料中的一些将表现出化学或物理性质，可能被证明与某些二元氮化物一样有用，甚至比它们更有用。人们希望一些材料能表现出新奇的现象，从而带来令人兴奋的科学，甚至是新技术。

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.