Development of a 'pressure composition temperature' (PCT) apparatus for in-situ neutron diffraction studies of hydrides

'Full text:' Unlike x-ray diffraction, neutron diffraction unambiguously enables the study of atomic position of hydrogen in hydrides, structural phase transitions between hydride structures, and the ability to discern whether the hydrogen is in solid solution, or in distinct hydrides phases. In-situ neutron diffraction is therefore a critical tool for a fundamental understanding of the mechanism of hydrogen storage, facilitating therefore the development of advanced hydrogen storage materials. NRC-CNBC has designed and built an in-situ neutron apparatus to enable the measurement of the structural state of hydride systems (during hydrogenation or dehydrogenation) with a neutron diffractometer under controlled pressure-temperature conditions. This equipment is designed to be used for up to 9 bar gas pressure and is fully controlled by a computer using Labview software. The temperature range for in-situ neutron diffraction measurements is between 80 and 673K. Three types of gas (hydrogen, deuterium and helium) can be used for experiments with helium being used as a purge gas. The amount of sample for experiments is set to be around 0.8 cc. The apparatus is to be used on the high resolution C2 diffractometer (Chalk River), which is open to Canadian and international research communities. (author)