纳米TiO_2对Mg_2Ni_(0.75)Cr_(0.25)合金储氢动力学性能的改善

Improvement in hydrogen absorption and desorption kinetics of Mg_2Ni_(0.75)Cr_(0.25) alloy by addition of TiO_2 nanoparticles

采用扩散烧结法制备了Mg2Ni0.75Cr0.25合金,然后与纳米TiO2颗粒混合球磨得到纳米复合材料。X射线衍射分析结果表明,纳米复合材料由Mg2Ni Ni复相合金和纳米TiO2组成,平均晶粒度为24～35nm。纳米TiO2颗粒对Mg2Ni0.75Cr0.25合金储氢动力学性能的提高具有催化作用,降低了Mg2Ni0.75Cr0.25合金的吸、放氢温度,使纳米复合材料氢化生成焓明显降低。对纳米复合材料的储氢性能测试结果表明:添加1.5%(质量分数)TiO2的纳米复合材料在373K、4MPa下5min内完成吸氢,并在463K、0.1MPa下20min内完成放氢,最大放氢量为2.57%。

The nanocomposites were prepared by ball-milling Mg_2Ni_(0.75)Cr_(0.25) alloy fabricated with different mass fractions (0.5%, 1.5%, 2.5%) of TiO_2 nanoparticles. The XRD patterns indicate that the nanocomposites contain Mg_2Ni-Ni alloys and TiO_2 nanoparticles, and the average crystalline sizes are 24～35nm. The TiO_2 nanoparticles can act as catalyst and the nanocomposites show rapid absorption and desorption kinetics, and the absorption and desorption temperatures are greatly decreased. The value of absorption enthalpy for hydride formation of the nanocomposite is decreased as compared with nanocrystalline Mg_2Ni_(0.75)Cr_(0.25) alloy. The absorption of the nanocomposite containing 1.5% TiO_2 nanoparticles is almost finished within 5min at 373K under the hydrogen pressure of 4MPa, and desorption is almost finished within 20min at 463K under the hydrogen pressure of 0.1MPa. The nanocomposite gives the hydrogen content of 2.57% under the condition.