Inelastic neutron scattering (INS) is increasingly being used for the characterization of heterogeneous catalysts. As the technique is uniquely sensitive to hydrogen atoms, vibrational spectra can be obtained that emphasize a hydrogenous component or hydrogen-containing moieties adsorbed on to an inorganic support. However, due to sensitivity constraints, the technique typically requires large sample masses (∼10 g catalyst). A reaction system is hereby described that enables suitable quantities of heterogeneous catalysts to be appropriately activated and operated under steady-state conditions for extended periods of time prior to acquisition of the INS spectrum. In addition to ex situ studies, a cell is described which negates the need for a sample transfer stage between reaction testing and INS measurement. This cell can operate up to temperatures of 823 K and pressures up to 20 bar. The apparatus is also amenable to adsorption experiments at the gas-solid interface.
Accessing the intrinsic hydrogen content within ammonia, NH 3 , has the potential to play a very significant role in the future of a CO 2-free sustainable energy supply. Inexpensive light metal imides and amides are effective at decomposing ammonia to hydrogen and nitrogen (2NH 3 3H 2 + N 2), at modest temperatures, and thus represent a low-cost approach to on-demand hydrogen production. Building upon this discovery, this paper describes the integration of an ammonia cracking unit with a post-reactor gas purification system and a small-scale PEM fuel cell to create a first bench-top demonstrator for the production of hydrogen using light metal imides.
The counterintuitive phenomenon of pressure-induced softening in materials is likely to be caused by the same dynamical behavior that produces negative thermal expansion. Through a combination of molecular dynamics simulation on an idealized model and neutron diffraction at variable temperature and pressure, we show the existence of extraordinary and unprecedented pressure-induced softening in the negative thermal expansion material scandium fluoride ScF 3. The pressure derivative of the bulk modulus B, B 0 ¼ ð∂B=∂PÞ P¼0 , reaches values as low as −220 AE 30 at 50 K, and is constant at −50 between 150 and 250 K.
The signal-to-noise ratio is the ultimate limiting factor for high pressure neutron scattering experiments where sample environment equipment could create significant background signal which in many cases may significantly exceed the signal from the sample itself. This is the particularly serious issue in case of high-pressure sample environment for inelastic neutron scattering. Here we review materials which could be used for development of new generation of high-pressure cells for inelastic and quasi-elastic neutron scattering experiments. We also present results of modelling of the background of high-pressure vessels made out of different materials. This approach will allow designing and producing high pressure vessels with parameters desired for particular neutron scattering experiment.
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