Improvement in hydriding property of LaNi_4.8Al_0.2 alloy encapsulated by SiO₂ sol

Highlights: • LaNi_4.8Al_0.2 powder can be enwrapped in the SiO₂ network effectively. • Fine pores can restrict impurities entering into matrix avoiding metal poisoning. • Anti-pulverization property of LaNi_4.8Al_0.2 is enhanced after being encapsulated. • Anti-poisoning property of LaNi_4.8Al_0.2 is enhanced after being encapsulated. - Abstract: LaNi_4.8Al_0.2 alloy particles encapsulated by SiO₂ matrix were prepared by the sol gel method. Scanning electron microscope (SEM) imaging was applied to determine the silica network outside the encapsulated alloy. The hydriding kinetics, pulverization and poisoning characteristics of LaNi_4.8Al_0.2 alloy were investigated before and after being encapsulated by silica. The results reveal that the hydriding properties of encapsulated alloy are excellent. The hydrogenation rate of encapsulated alloy is faster than that of the original alloy. The quantities of hydrogen stored by the encapsulated and original alloy are 169.3 Nml/g and 147.1 Nml/g, respectively. The LaNi_4.8Al_0.2 alloy particles are broken up into powder after 10 times hydrogen absorption/desorption cycles, while the encapsulated alloy do not show any breakdown after 30 times hydrogen adsorption/desorption cycles. The quantities of hydrogen absorbed by original alloy particles are less than 8.2 Nml/g in H₂-14.4% CO and 18.6 Nml/g in H₂-12.8% CO₂, while the quantities of hydrogen absorbed by encapsulated alloy agglomerations are 84.5 Nml/g in H₂-14.4% CO and 168.9 Nml/g in H₂-12.8% CO₂. These results clearly indicate that the pulverization and poisoning resistance properties of LaNi_4.8Al_0.2 alloy are evidently enhanced after being encapsulated by silica network