A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations

Abstract

The mechanism of nickel sulfide induced rapid crystallization of highly textured tungsten disulfide ( W S 2 ) thin films: An in situ real-time diffraction study J. Appl. Phys. 103, 063501 (2008) A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300°C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite ͑KAlSi 2 O 6 ͒ to analcime ͑NaAlSi 2 O 6 ·H 2 O͒ at 210°C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3Ϯ 1.1 kJ mol −1 . Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

A Flow-Through Reaction Cell for Studying Minerals Leaching by In-Situ Synchrotron Powder X-ray Diffraction

“…There are a number of in-situ techniques, capable of studying the solution phase by X-ray absorption spectroscopy [12] and Raman spectroscopy [13], and solid phase by transmission electron microscopy [14], atomic force microscopy [15], neutron diffraction [16][17][18], and powder X-ray diffraction (PXRD) [19][20][21][22]. In-situ PXRD in the presence of an aqueous solution can reveal the phase evolution of the crystalline materials and has been applied extensively in materials chemistry for elucidating crystallization mechanisms of hydrothermal materials syntheses [23][24][25][26][27][28].…”