El-Eskandarany Mohamed Sherif, Banyan Mohammad, Al-Ajmi Fahad
Nanotechnology and Advanced Materials Program, Energy and Building Research Center, Kuwait Institute for Scientific Research Safat 13109 Kuwait
RSC Adv. 2018 Sep 14;8(56):32003-32008. doi: 10.1039/c8ra07068g. eCollection 2018 Sep 12.
Formation of a new metastable fcc-MgH nanocrystalline phase upon mechanically-induced plastic deformation of MgH powders is reported. Our results have shown that cold rolling of mechanically reacted MgH powders for 200 passes introduced severe plastic deformation of the powders and led to formation of micro-lathes consisting of γ- and β-MgH phases. The cold rolled powders were subjected to different types of defects, exemplified by dislocations, stacking faults, and twinning upon high-energy ball milling. Long term ball milling (50 hours) destabilized β-MgH (the most stable phase) and γ-MgH (the metastable phase), leading to the formation of a new phase of face centered cubic structure (fcc). The lattice parameter of fcc-MgH phase was calculated and found to be 0.4436 nm. This discovered phase possessed high hydrogen storage capacity (6.6 wt%) and revealed excellent desorption kinetics (7 min) at 275 °C. We also demonstrated a cyclic-phase-transformation conducted between these three phases upon changing the ball milling time to 200 hours.
据报道，在MgH粉末的机械诱导塑性变形过程中形成了一种新的亚稳fcc-MgH纳米晶相。我们的结果表明，对机械反应后的MgH粉末进行200次冷轧会使粉末产生严重的塑性变形，并导致形成由γ-MgH相和β-MgH相组成的微片层。冷轧后的粉末存在不同类型的缺陷，如位错、堆垛层错以及高能球磨时产生的孪晶。长时间球磨（50小时）使β-MgH（最稳定相）和γ-MgH（亚稳相）失稳，从而导致形成面心立方结构（fcc）的新相。计算得出fcc-MgH相的晶格参数为0.4436纳米。这一发现的相具有高储氢容量（6.6 wt%），并在275°C下显示出优异的解吸动力学（7分钟）。我们还证明了在将球磨时间改为200小时时，这三个相之间会发生循环相变。
