International
Tables for
Crystallography
Volume H
Powder diffraction
Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk

International Tables for Crystallography (2018). Vol. H, ch. 2.9, pp. 196-197

Section 2.9.3.4.4. Hydrothermal reaction cells

W. van Beeka* and P. Pattisona,b

aSwiss–Norwegian Beamlines at ESRF, CS 40220, 38043 Grenoble CEDEX 9, France, and bLaboratory for Quantum Magnetism, Institute of Physics, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland
Correspondence e-mail:  wouter@esrf.fr

2.9.3.4.4. Hydrothermal reaction cells

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Many materials with potential applications in technologically important fields can only be prepared by the supercritical hydrothermal synthesis method. A detailed knowledge of the reaction mechanisms is lacking, mainly because the processes take place within sealed and thick-walled reaction vessels. A technique is required that can penetrate the walls of the vessel during the reaction, and can reveal the kinetics and mechanism of bulk sample synthesis. Neutron diffraction is the ideal tool for this task. For example, Ok et al. (2010[link]) constructed a relatively simple chemical-reaction cell for investigating syntheses, even under extreme supercritical conditions, using of time-of-flight techniques. The cell itself was machined from a single ingot of Inconel, and had a maximum wall thickness of 4.0 mm. Thinner sections of 2.7 mm thickness were used in parts of the cell to reduce attenuation of the incident and scattered neutron beams. The vessel had a normal working pressure and temperature of 40 MPa at 723 K. The experiments were carried out on the POLARIS diffractometer at the ISIS pulsed spallation neutron source.

Another example of a hydrothermal reaction cell of somewhat different design is that used by Xia et al. (2010[link]). In this case, a large sample volume was chosen (320 ml internal volume) to allow bulk properties to be investigated. The cell had a dumbbell configuration, assembled from commercial stainless-steel components, that held most of the hydrothermal liquid, and a zero-scattering Ti–Zr alloy sample compartment with a 0.4 mm wall thickness. This choice of material and wall thickness for the sample cell dramatically reduced the background scattering from the container, but limited the operational range to temperatures up to 573 K and pressures up to 9 MPa. The cell was commissioned at the Wombat neutron powder diffractometer at ANSTO, using the in situ kinetic study of the hydrothermal phase transformations from leucite (KAlSi2O4) to analcime (NaAlSi2O6·H2O) as a demonstration of the capabilities of the equipment.

References

Ok, K. M., O'Hare, D., Smith, R. I., Chowdhury, M. & Fikremariam, H. (2010). New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction. Rev. Sci. Instrum. 81, 125107.Google Scholar
Xia, F., Qian, G., Brugger, J., Studer, A., Olsen, S. & Pring, A. (2010). A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations. Rev. Sci. Instrum. 81, 105107.Google Scholar








































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