La-Mg-Ni-Cu系Mg2Ni型合金氣態(tài)貯氫動力學

La-Mg-Ni-Cu系Mg2Ni型合金氣態(tài)貯氫動力學Gaseous storage hydrogen kinetics of La-Mg-Ni-Cu system Mg2Ni type alloys

為了改善Mg2Ni型合金的氣態(tài)貯氫動力學性能，在合金中添加少量La，并用快淬工藝制備La-Mg-Ni-Cu系Mg2Ni型(Mg24Ni10Cu2)100-xLax (x=0, 5, 10, 15, 20) (摩爾分數(shù)，x %)合金。采用XRD、SEM及HRTEM分析鑄態(tài)及快淬態(tài)合金的微觀結(jié)構(gòu)；采用全自動Sieverts測試儀測試合金的氣態(tài)吸放氫動力學；采用差熱分析儀測試不同加熱速率下合金的放氫DSC曲線，并用Kissinger方程計算合金的放氫激活能。建立動力學與La含量及淬速的關系。結(jié)果表明：添加La不改變合金的主相Mg2Ni相，但導致第二相La2Mg17和LaMg3相出現(xiàn)，第二相的量隨La含量的增加而增加。添加La和快淬有助于合金形成納米晶-非晶結(jié)構(gòu)，降低放氫激活能，從而改善放氫動力學。當La含量x從0增加到20時，鑄態(tài)合金的放氫激活能 從73.18 kJ/mol下降到60.41 kJ/mol，而30m/s的快淬態(tài)合金的 值從66.16 kJ/mol下降到50.50 kJ/mol。

In order to improve the gaseous hydrogen storage kinetics of Mg2Ni type alloys, a small quantity of La was added to alloys, and the La-Mg-Ni-Cu system Mg2Ni type (Mg24Ni10Cu2)100-xLax (x=0, 5, 10, 15, 20) (mole fraction, x %) alloys were prepared by rapid quenching. The structures of the as-cast and quenched alloys were analyzed by XRD, SEM and HRTEM. The gaseous hydrogen absorption and desorption kinetics of alloys were tested by a fully automatic Sieverts equipment. Hydrogen desorption DSC curves of alloys were tested at different heating rates by a differential thermal analyzer, and the activation energy of alloys was calculated by using the equation of Kissinger. The relationship between the kinetics and La content and quenching rate was established. The results show that adding La doesn’t change the Mg2Ni major phase, however, leads to the formation of the second phases including La2Mg17 and LaMg3 phases. The phase abundance of the second phases increases with increasing the La content. Increasing La content and quenching rate are helpful to form the nanocrystalline and amorphous structure, and reducing the hydrogen desorption activate energy, thus improving the hydrogen desorption kinetics for Mg2Ni type alloys. The hydrogen desorption activation energy reduces from 73.18 kJ/mol to 60.41 kJ/mol and 66.16 kJ/mol to 50.50 kJ/mol for the as-cast alloy and as-spun alloy (30 m/s), respectively.

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