Mechanismen der Bildung metastabiler Hydride und Nitride mittels in situ-Neutronenbeugung von Fest-Gas-Reaktionen

利用固-气反应的原位中子衍射研究亚稳态氢化物和氮化物的形成机制

• 批准号: 142461806
• 负责人: Professor Dr. Holger Kohlmann
• 金额: --
• 依托单位: Max-Planck-Institut für Chemische Physik fester Stoffe (MPI CPfS)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2009
• 资助国家: 德国
• 起止时间: 2008-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/142461806?language=en
• 关键词: Mechanismen; der; Bildung; metastabiler; Hydride

Understanding of reaction pathways is a fundamental basis in the synthesis of metastable compounds. Therefore, we have developed gas-pressure and gas-flow cells for in situ neutron diffraction aiming on the reaction of solids with hydrogen (deuterium) or ammonia gas. With the former 160 bar gas pressure and 400 °C are accessible in combination with extremely low diffraction background due to proper orientation of a sapphire single crystal tube as a sample container. Higher temperatures (1000 °C) are achieved using silica tubes like in the gas-flow cell. Both are heated with a two-sided laser system and the temperature is measured with a calibrated pyrometer. In situ neutron diffraction on solid-gas reactions with hydrogen or ammonia gas with a time resolution of one minute is now well established with both cells on the high-intensity diffractometer D20 at the ILL in Grenoble, France. A variety of systems was studied, amongst them the formation of deuterides of palladium, Zintl phases, intermetallic Li-Al compounds, lanthanide intermetallics, VN, V2N, and of Fe4N via intermediate Fe3N. For palladium rich intermetallic phases a complete reaction mechanism could be proposed, which allowed the planned synthesis of new metastable compounds. The successful concept of our in situ gas cells will be optimized in view of the temperature-pressure range (seal and container materials), automated pressure-temperature programs and installing them on the diffractometer SPODI at the FRM-II, Garching. Using the known reaction mechanism for palladium rich intermetallics, new metastable hydrides will be synthesized for metals M = Tl1-xPbx, In1-xSnx, As, Sb, Se, Mn. Metastable intermediates in the formation of mixed-valent ytterbium hydrides and the hydrogenation of light-weight intermetallics of interest for hydrogen storage will be studied as well. For nitrides the knowledge already acquired on vanadium and iron will be deepened and extended to chromium, manganese, cobalt, nickel and copper, in order to yield and structurally characterize metastable compounds, such as Fe16N2, Fe8N or Co3N, some of them are highly interesting in view of their magnetic properties. Other synthetic strategies to metastable nitrides include the use of predissociated ammonia, decomposition of precursor materials and the ammonolysis of metal hydrides.The formation of metastable oxides and oxide nitrides will be studied, in order to widen the range of materials and to strengthen collaboration within the SPP. In situ neutron diffraction on the ammonolysis of Ta2O5 will give a detailed picture of the formation of the photocatalyst Ta3N5 via transiently occurring TaON and its metastable modification. We will also follow the formation of metastable bixbyite type V2O3 and the formation of black phosphorous. Experimental studies will be backed up by quantum mechanical calculations in cooperation within and outside the SPP.

对反应的理解是亚稳态化合物的基础。由于在固体中，使用硅管，因此由于适当的温度（1000°C），因此较低的衍射背景是较高的温度现在，在法国格勒诺布尔（Grenoble）的高强度衍射仪D20上，两个细胞在法国的高强度衍射仪D20上都建立了一分钟的氢气或氨气。 ，通过富含媒介的金属间阶段的Fe4n可以提出完整的反应机制，鉴于温度压力范围（密封材料和容器材料），将优化新的亚稳态化合物的ESI。自动压力温度程序和FRM-II处的衍射仪SPODI。还将研究混合价值的氢化物的中间人和氢储存的氢化物的氢化。 NDS，例如FE16N2，FE8N或CO3N，鉴于其磁性的策略，其中一些高度交织。研究属于TA2O5的氨解会的原位中子衍射将通过瞬时地对TA3N5进行详细的图像，我还将按照可口的Bixbyite typo3进行量子。 SPP内外的合作。