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.

对反应途径的理解是合成亚稳态化合物的基础。因此，我们已经开发了用于原位中子衍射的气体压力和气体流动池，其目标是固体与氢（氘）或氨气的反应。对于前者，由于蓝宝石单晶管作为样品容器的适当取向，可达到160 bar气压和400 °C，并具有极低的衍射背景。更高的温度（1000 °C）是使用二氧化硅管实现的，如在气体流动池中。两者都用双面激光系统加热，温度用校准的高温计测量。在法国格勒诺布尔的ILL的高强度衍射仪D20上，现在已经建立了时间分辨率为一分钟的固-气反应的原位中子衍射。研究了各种体系，其中包括钯的氘化物、Zintl相、金属间Li-Al化合物、镧系金属间化合物、VN、V2 N以及经由中间体Fe 3 N的Fe 4 N的形成。对于富钯的金属间相，可以提出一个完整的反应机理，这使得有计划地合成新的亚稳化合物。我们的原位气室的成功概念将根据温度-压力范围（密封和容器材料）、自动压力-温度程序进行优化，并将其安装在FRM-II，Garching的衍射仪SPODI上。利用富钯金属间化合物的已知反应机理，将合成金属M = Tl 1-xPbx、In 1-xSnx、As、Sb、Se、Mn的新亚稳氢化物。同时也将研究混合价镱化合物形成过程中的亚稳中间体以及储氢用轻质金属间化合物的氢化反应。对于氮化物，已经获得的关于钒和铁的知识将被深化并扩展到铬、锰、钴、镍和铜，以产生和结构表征亚稳化合物，例如Fe 16 N2、Fe 8 N或Co 3 N，其中一些化合物鉴于其磁性而非常有趣。亚稳氮化物的其他合成策略包括使用预离解氨、前体材料的分解和金属氮化物的氨解。将研究亚稳氧化物和氮氧化物的形成，以扩大材料的范围并加强SPP内部的合作。原位中子衍射上的氨解Ta 2 O 5将给出一个详细的图片形成的光催化剂Ta 3 N5通过瞬时发生TaON和其亚稳态修改。我们还将跟踪亚稳态方铁锰矿型V2 O3的形成和黑磷的形成。实验研究将得到SPP内外合作的量子力学计算的支持。