Correlation between microstructural and mechanical behavior of nanostructured MgH2 upon hydrogen cycling

Mechanical behavior of highly reactive nanostructured MgH2

“…It is composed of a SS316L cylindrical sample holder and 2 Linear Variable Differential Transformers (LVDT) as displacement transducers. Contrarily to the previous study [22], the sample holders we used here are thin wall tubes with 20.1 mm internal diameter and 0.5 mm thick. The use of thin-walled sample holders permits a better mechanical sensitivity upon increasing the deformation amplitude and can reveal more accurately the different stages of materials behavior.…”

“…% of TieVeCr alloy were also tested by dilatometry measurements. Correlations were established between the irreversible swelling of the composites and microstructure changes occurring during hydriding cycles: the expansion is due to the evolution of granulometry from a dense bi-modal distribution where the small particles fill the space between the large ones to a mono-disperse powder whose porosity is higher [22]. The purpose of the present paper was to go further in the analyses of the recrystallization mechanisms and to focus on the characterization of mechanical properties such as Young modulus and nanohardness, and to correlate their behavior and the swelling effect associated to the microstructure changes of the composites upon cycling.…”

Importance of thermal conductivity and stress level during a phase (hydride) transformation in magnesium

“…Еще одним примером фактического уменьшения размера частиц в процессе первых циклов гидрирования может служить результат, полученный в [29,30]. Авторы работы [29] проводили гранулометрические исследования эволюции размеров порошков до начала циклирования (после размола в шаровой мельнице) и после первых 10 циклов.…”

“…Еще одним примером фактического уменьшения размера частиц в процессе первых циклов гидрирования может служить результат, полученный в [29,30]. Авторы работы [29] проводили гранулометрические исследования эволюции размеров порошков до начала циклирования (после размола в шаровой мельнице) и после первых 10 циклов. До начала экспериментов максимум распределения размеров порошка соответствовал 50 мкм, после циклирования обнаружено бимодальное распределение размеров порошка.…”

On the degradation mechanisms of Mg hydride pellets for hydrogen storage in tanks

“…In this phase the hydrogen uptake and release is slowed down, probably owing to a reduction in the thermal conductivity inside the pellets caused by the internal porosity. The degradation process has been studied by some authors who reported about the pellet swelling during cycling simulating tank exercise behavior [13,14], revealing how this process can be quite complex and how several factors contribute to it. In particular, besides the expansion/contraction effects caused by the hydrogen uptake and release, the compacted powders show a complex morphological and structural evolution which effect on the pellet properties has to be clearly ascertained in order to design materials and devices with a reduced degradation and a minimized swelling effect with cycling.…”