用XRD、SEM等方法与手段,研究TiMn_(2-5x)(V_4Fe)_x(x＝0.30,0.35)贮氢合金的相结构及电化学性能.结果表明:主相为体心立方(bcc)结构的合金,其晶胞参数随x的增加而增大;SEM显示在基体中存在岛状结构,随着x的增加,岛状结构较基体的比率减少;电化学测试表明,x=0.35合金在常温下难以活化,加热到327 K才能活化;而x=0.30合金常温下即可活化,该合金在充电过程中出现钝化,327 K温度下钝化消除.比较合金在298 K的PCT曲线,发现x=0.30合金的平台氢压约为0.2 MPa,平台宽度较大,更有开发价值;同时计算x=0.30合金放氢过程的焓和熵,分别为-36.1 kJ/mol,-126.9 J/(mol·K).
Structures and electrochemical properties of TiMn_(2-5x)(V_4Fe)_x(x＝0.30,0.35)alloys were investigated. The results of XRD analysis show that the alloys are mainly composed of body centered cubic (bcc) phase, whose lattice parameters are enhanced with the increase of V and Fe content. The SEM images of the alloys show that there are some colonies in the matrix phase. The proportion of colony to the matrix decreases with increasing of V and Fe content. The electrochemical measurements show that TiMn_(0.25)(V_4Fe)_(0.35) alloy has unfavorable activation performance until temperature reaches 327 K, while TiMn_(0.50)(V_4Fe)_(0.30) alloy shows better activation performance, but passivation phenomenon was found in the process of charging at low temperature, which can be eliminated by heating to high temperature. The PCT curves of alloys show that the TiMn_(0.50)(V_4Fe)_(0.30) alloy has a good comprehensive performance, with a favorable plateau pressure at room temperature and wide plateau. The enthalpy and entropy in hydrogen desorption of TiMn_(0.50)(V_4Fe)_(0..30) alloy were also calculated and they are -36.1 kJ/mol, -126.9 J/(mol·K), respectively.
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