Influence of citric acid and calcination temperature on microstructure of the nano precursors of La-Mg hydrogen storage alloy

摘要

The nano precursors of La-Mg hydrogen storage alloy have been prepared using citric acid, lanthanum nitrate and magnesium nitrate by so-gel technology. The effect of citric acid and calcination temperature on microstructure of the nano precursors of La-Mg hydrogen storage alloy have been studied by Infrared Radiation (IR), thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and Transmission electron microscopy (TEM). IR results indicate the molar ratio of citric acid to metal cations increases from 1 to 1.3, the amount of citrate increases correspondingly, when the molar ration increases to 1.6, the amount of citrate goes up to maximum. The most appropriate amount of citric acid is 1.6 times that of the metal cations. In addition, the amount of citric acid have little influence on size of grains. XRD and TG/DTA results show that with increase of calcination temperature the amount of impurity phase, La(OH)_3, decreases markedly. Formation of La_2O_3 and MgO two-phase mixture occurred at 950°C. TEM results reveal that the morphology of the particles is almost flake with the size of ～50nm at 950°C and La, Mg, O three elements are observed in each flake.