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We report on the first in situ synchrotron radiation powder X-ray diffraction study (SR-PXD) of the ammonolysis reaction of selected alkaline and alkaline earth metal hydrides (i.e., LiH, NaH, KH, MgH 2 , and CaH 2 ). The investigation was performed using an in situ SR-PXD pressure cell at an initial NH 3 pressure of 6.5 bar in a range of temperature between room temperature (RT) and 350 °C. The results of this work give new important insights into the formation of metal amides and imides starting from the corresponding metal hydrides. LiH was observed to react with NH 3 to form LiNH 2 already at RT, and then it decomposes into Li 2 NH at 310 °C through the formation of nonstoichiometric intermediates of the Li 1+x NH 2−x form. The formation of NaNH 2 takes place nearly at RT (28 °C), and it melts at 180 °C. As for LiH, KH reacts with NH 3 at RT to surprisingly form, what it seems to be, cubic KNH 2 . However, we believe this phase to be a solid solution of KH in KNH 2 . At high temperature, the possible formation of several solid solutions of K(NH 2 ) 1−y H y with defined composition is also observed. The formation of Mg(NH 2 ) 2 was observed to starts at around 220 °C, from the interaction γ-MgH 2 and NH 3 . At 350 °C, when all γ-MgH 2 is consumed, the formation of Mg(NH 2 ) 2 stops and MgNH is formed by the reaction between β-MgH 2 and NH 3. Our results indicate that the formation of the γ-MgH 2 is a key step in the synthesis of Mg(NH 2 ) 2 at low temperature (e.g., via ball milling technique). CaH 2 was observed to react with NH 3 at around 140 °C to form CaNH. At higher temperature the appearance of new reflections of possible Ca 1+x NH phases, with the same crystalline structure of CaNH but with a smaller cell parameter was observed.

Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality He and the associated tremendous increase of its price, the supply of large neutron detection systems with 3 He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid 10 B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area 10 B 4 C coatings of up to 2 lm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system. The 10 B 4 C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and RutherfordBack-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical 10 B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black 3 He-monitor. Thus, these converter coatings contribute to the development of 3 He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative 3 He-free converter elements available for large area neutron detection systems.

In this work the effect of a partial replacement of CaH 2 with CaF 2 on the sorption properties of the system CaH 2 + MgB 2 has been studied. The first five hydrogen absorption and four desorption reactions of the CaH 2 + MgB 2 and 3CaH 2 + CaF 2 + 4MgB 2 systems were investigated by means of volumetric measurements, high-pressure differential scanning calorimetric technique (HP-DSC), 11 B and 19 F MAS NMR spectroscopy, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD). It was observed that already during the mixing of the reactants formation of a nonstoichiometric CaF 2−x H x solid solution takes place. Formation of the CaF 2−x H x solid solution sensibly affects the overall hydrogen sorption reactions of the system CaH 2 + MgB 2 .