化学计量学
氢化物
结晶学
三元运算
六方晶系
空间组
三角晶系
群(周期表)
相(物质)
氢
镁
材料科学
类型(生物学)
晶体结构
化学
无机化学
X射线晶体学
衍射
物理化学
冶金
有机化学
物理
程序设计语言
生物
光学
计算机科学
生态学
作者
Lucille Lemort,Michel Latroche,B. Knosp,Patrick Bernard
摘要
New pseudobinary phases have been synthesized in the ternary system Pr–Mg–Ni. The Pr1.5Mg0.5Ni7 compound is obtained as a pure phase, but it exists under two polymorphic structures: hexagonal Ce2Ni7-type (2H; space group P63/mmc) and rhombohedral Gd2Co7-type (3R; space group R3̅m). The Pr3.75Mg1.25Ni19 compound is found in equilibrium with the PrNi5-type secondary phase, and it adopts also two polymorphic structures: hexagonal Sm5Co19-type (2H; space group P63/mmc) and rhombohedral Ce5Co19-type (3R; space group R3̅m). The crystallographic structures as well as the thermodynamic properties of these hydrogen-absorbing compounds have been determined and are compared to those of the binary compounds Pr2Ni7 and Pr5Ni19. The two compounds are able to form hydrides at room temperature, in the pressure range of 0–10 MPa. The replacement of 25 at. % of the rare earth by magnesium for both stoichiometries leads to an increase of the weight capacity and a decrease of the equilibrium pressures with the formation of well-defined plateaus.
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