Novel Low Temperature Routes to Metal Sulfides

技术概述：非氧化物材料越来越引起研究人员的兴趣，因为光电子、催化、能源和其他领域的许多先进应用需要具有氧化物难以或不可能实现的性能。虽然这些材料可能对空气敏感，但性能的提高抵消了处理和保护化合物的困难。金属硫化物因其催化、电子和光学性质而受到人们的关注。许多应用取决于硫化物材料的质量。均匀性，低氧化态，玻璃状结构，或高表面积往往是可取的。传统的固态方法需要高温来克服与扩散相关的动力学障碍，将产物限制在热力学稳定的相中，并且禁止控制晶粒尺寸或表面积。对先进材料日益增长的需求导致了各种替代低温方法的探索。本文将非水解溶胶-凝胶（NHSG）化学扩展到金属硫化物的合成中，提出了一种新的低温合成途径。本研究的具体目标是：1)深入了解选定的二元金属硫化物体系的非水解溶胶-凝胶过程的合成变量空间；2)通过NHSG化学探索相空间以发现新的二元金属硫化物；3)探索三元或四元硫化物的NHSG合成路线。学生将学习新的低温路线，气敏材料的合成，以及一些应用于气敏材料的固态表征方法。自然产生的硫化物矿物晶体将用于外展项目，使公众了解基本的晶体学，以及硫化物的重要性。太阳能电池材料或像三角铁这样的地理标记物将被用作与非科学家联系的例子。这项研究是由美国国家科学基金会固态和材料化学/材料研究部门计划支持的。大多数金属在空气中加热时容易形成氧化物。这使它们成为最广泛探索的固体类别，并导致许多应用。然而，一些应用需要的性能是难以或不可能实现的氧化物，这激发了人们对合成和表征非氧化物材料（如金属硫化物）的兴趣。金属硫化物在石油裂解、固体润滑剂、太阳能电池、电池材料电极、发光二极管和许多其他技术重要领域都有应用。其中一些应用要求材料具有非常高的纯度、可控的氧化态、晶体结构和形态。该提案将探索一种新的合成方法，该方法将允许在低温下制备金属硫化物，并且可以控制氧化态，晶体结构，表面积和材料的最终性能。此外，通过这种方法很可能获得具有未开发性质的新金属硫化物。这些材料将被详细表征，它们的性质可能会导致新的应用。研究生和本科生将学习固态材料的合成和表征，特别强调处理空气敏感材料。将积极招收妇女和少数民族学生。交换学生将在为期6个月的实习期间参与该项目，增加研究小组的多样性。此外，与自然存在的硫化物矿物和技术上重要的硫化物有关的外展计划将被设计，以使公众对晶体学和材料化学有一个欣赏，特别强调不太为人所知的非氧化物材料。这项研究是由美国国家科学基金会固态和材料化学/材料研究部门计划支持的。

TECHNICAL SUMMARY:Non-oxide materials have increasingly attracted the interest of researchers, as many advanced applications in optoelectronics, catalysis, energy and other fields require properties that are difficult or impossible to achieve with oxides. While these materials can be air-sensitive, the improvement in performance offsets the difficulties in handling and protecting the compounds. Metal sulfides have received attention because of their catalytic, electronic and optical properties. Many applications depend on the quality of the sulfide materials. Homogeneity, low oxidation state, glassy structure, or high surface area are often desirable. Traditional solid-state methods require high temperatures to overcome diffusion-related kinetic barriers, restricting products to thermodynamically stable phases, and prohibiting control over grain size or surface area. The growing demand for advanced materials has led to the exploration of a variety of alternative low temperature methods. This proposal introduces a novel low temperature route by extending non-hydrolytic sol-gel (NHSG) chemistry to the synthesis of metal sulfides. The specific objectives of the proposed research are: 1) To gain a thorough understanding of synthetic variable space of non-hydrolytic sol-gel processes for selected binary metal sulfide systems, 2) to explore phase space by NHSG chemistry to discover new binary metal sulfides, and 3) to explore NHSG routes for the synthesis of ternary or quarternary sulfides. Students will be trained in novel low temperature routes, synthesis of air-sensitive materials, and a number of solid-state characterization methods applied to air-sensitive materials. Naturally occurring sulfide mineral crystals will be used in outreach projects to expose the public to basic crystallography, as well as to the importance of sulfides. Solar cell materials or geomarkers like troilite will be used as examples to connect with non-scientists. This research is supported by the NSF Solid-State and Materials Chemistry/Division of Materials Research program.NON-TECHNICAL SUMMARY: Most metals readily form oxides when heated in air. This has made them the most widely explored class of solids, and resulted in many applications. However, some applications require properties that are difficult or impossible to achieve with oxides, which has spurred interest in the synthesis and characterization of non-oxide materials like metal sulfides. Metal sulfides have found use as catalysts in oil cracking, solid lubricants, solar cells, electrodes in battery materials, light emitting diodes, and many other technologically important fields. Some of these applications require materials with very high purity, controlled oxidation state, crystal structure, and morphology. This proposal will explore a novel synthetic method, which will allow the preparation of metal sulfides at low temperatures, and can offer control over oxidation state, crystal structure, surface area, and the resulting properties of the materials. In addition, it is likely that new metal sulfides with unexplored properties will be obtained by this approach. These materials will be characterized in detail, and their properties may lead to novel applications. Graduate and undergraduate students will be trained in synthesis and characterization of solid-state materials, with particular emphasis on handling air-sensitive materials. Women and minority students will be actively recruited. Exchange students will work on the project on six month internships, adding to the diversity of the research group. In addition, outreach programs related to naturally occurring sulfide minerals and technologically important sulfides will be designed to give the general public an appreciation for crystallography and materials chemistry, with particular emphasis on the less well known non-oxide materials. This research is supported by the NSF Solid-State and Materials Chemistry/Division of Materials Research program.