Shian Samuel, Sandhage Kenneth H
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Rev Sci Instrum. 2009 Nov;80(11):115108. doi: 10.1063/1.3257973.
An externally heated, x-ray transparent reaction chamber has been developed to enable the dynamic high temperature x-ray diffraction (HTXRD) analysis of a gas/solid [TiF(4)(g)/SiO(2)(s)] reaction involving a halide gas reactant formed at elevated temperatures (up to 350 degrees C) from a condensed source (TiF(4) powder) sealed within the chamber. The reaction chamber possessed x-ray transparent windows comprised of a thin (13 microm) internal layer of Al foil and a thicker (125 microm) external Kapton film. After sealing the SiO(2) specimens (diatom frustules or Stober spheres) above TiF(4) powder within the reaction chamber, the chamber was heated to a temperature in the range of 160-350 degrees C to allow for internal generation of TiF(4)(g). The TiF(4)(g) underwent a metathetic reaction with the SiO(2) specimen to yield a TiOF(2)(s) product. HTXRD analysis, using Cu K alpha x rays passed through the Kapton/Al windows of the chamber, was used to track the extent of SiO(2) consumption and/or TiOF(2) formation with time. The Al foil inner layer of the windows protected the Kapton film from chemical attack by TiF(4)(g), whereas the thicker, more transparent Kapton film provided the mechanical strength needed to contain this gas. By selecting an appropriate combination of x-ray transparent materials to endow such composite windows with the required thermal, chemical, and mechanical performance, this inexpensive reaction chamber design may be applied to the HTXRD analyses of a variety of gas/solid reactions.
已开发出一种外部加热的、X射线透明的反应室，以实现对气/固[TiF₄(g)/SiO₂(s)]反应的动态高温X射线衍射（HTXRD）分析，该反应涉及一种卤化物气体反应物，它是由密封在反应室内的冷凝源（TiF₄粉末）在高温（高达350℃）下形成的。反应室具有由薄（13微米）的铝箔内层和较厚（125微米）的外部聚酰亚胺薄膜组成的X射线透明窗口。在将SiO₂样品（硅藻壳或斯托伯球）密封在反应室内TiF₄粉末上方后，将反应室加热到160 - 350℃的温度范围，以允许内部生成TiF₄(g)。TiF₄(g)与SiO₂样品发生复分解反应，生成TiOF₂(s)产物。使用穿过反应室聚酰亚胺/铝窗口的Cu Kα X射线进行HTXRD分析，以跟踪SiO₂消耗和/或TiOF₂形成随时间的程度。窗口的铝箔内层保护聚酰亚胺薄膜免受TiF₄(g)的化学侵蚀，而较厚、更透明的聚酰亚胺薄膜提供了容纳这种气体所需的机械强度。通过选择合适的X射线透明材料组合，使这种复合窗口具备所需的热、化学和机械性能，这种低成本的反应室设计可应用于各种气/固反应的HTXRD分析。
