NOUFERROUS METALLURGICAL EQUIPMENT

In this paper, the effect of Ti/Cr ratio on the microstructures as well as the hydrogen ab/desorption properties of V₄₀(TiCrFe)₆₀ alloy was systematically investigated. It was found that the alloy s lattice constant decreases with the declining of Ti/Cr ratio, from 3.05? for Ti/Cr=1.0 down to 3.023? for Ti/Cr=0.7. Thus, the hydrogen uptake decreases from 3.81 wt% for Ti/Cr=1.0 down to 3.56 wt% for Ti/Cr=0.7, and the hydrogen release plateau increases from 0.135 MPa for Ti/Cr=1.0 up to 1.73 MPa for Ti/Cr=0.7. The decrease in Ti/Cr ratio slows down the hydrogen uptake kinetics of the alloys, and the time to reach the saturation uptake decreases from 2.1 min for Ti/Cr=1.0 down to 3.9 min for Ti/Cr=0.7, which is 85.71% longer, but all of them can reach the saturation hydrogen absorption within 5 min. Additionally, lowering the Ti/Cr ratio increases the hydrogen absorption enthalpy of the V₄₀(TiCrFe)₆₀ alloy from -40.47 kJ/mol at Ti/Cr=1.0 to -26.64 kJ/mol at Ti/Cr=0.7, while the hydrogen desorption enthalpy decreases from 42.82 kJ/mol at Ti/Cr=1.0 to 32.5 kJ/mol at Ti/Cr=0.7, which reduces the stability of the hydrides. The amount of hydrogen desorbed increases from 2.20 wt% at Ti/Cr=1.0 up to 2.37 wt% at Ti/Cr=0.7, which enhances the hydrogen desorption rate of the alloy while reducing the residual hydrogen content. Finally, the V₄₀(TiCrFe)₆₀ alloy with a smaller Ti/Cr ratio shows less capacity decay during the cycling process and a higher cycling retention rate. The alloy with a Ti/Cr ratio of 0.7 has an effective hydrogen storage capacity of 2.22 wt% and a capacity retention rate of 92.12% after 30 cycles. This is attributed to the fact that the alloys with smaller Ti/Cr ratios have smaller particle sizes after pulverization in the initial cycling stage, and the degree of particle size refinement during subsequent cycles is also smaller.