A gas-tight Cu Kα x-ray transparent reaction chamber for high-temperature x-ray diffraction analyses of halide gas/solid reactions

Abstract

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 [TiF4 (g) / SiO2 (s)] reaction involving a halide gas reactant formed at elevated temperatures (up to 350 °C) from a condensed source (TiF4 powder) sealed within the chamber. The reaction chamber possessed x-ray transparent windows comprised of a thin (13 μm) internal layer of Al foil and a thicker (125 μm) external Kapton film. After sealing the SiO2 specimens (diatom frustules or Stöber spheres) above TiF4 powder within the reaction chamber, the chamber was heated to a temperature in the range of 160-350 °C to allow for internal generation of TiF4 (g). The TiF4 (g) underwent a metathetic reaction with the SiO2 specimen to yield a TiOF 2 (s) product. HTXRD analysis, using Cu Kα x rays passed through the Kapton/Al windows of the chamber, was used to track the extent of SiO2 consumption and/or TiOF2 formation with time. The Al foil inner layer of the windows protected the Kapton film from chemical attack by TiF4 (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. © 2009 American Institute of Physics.