No abstract

No abstract

TiC as a novel catalyst was used in preparing TiC-doped sodium aluminum hydride by ball-milling NaH/Al mixture or NaAlH4 with TiC powder under a hydrogen atmosphere. It is found that TiC-doped NaH/Al composite absorbs 4.77 wt % hydrogen at 120 °C, desorbs more than 80% hydrogen of its initial hydrogen capacity at 155 °C with a stable cycling dehydriding rate and capacity, and exhibits better reversible hydrogen storage properties than those of TiC-doped NaAlH4 composite or Ti-doped NaH/Al composite. The catalytic mechanism of TiC for reversible hydrogen storage behavior of TiC-doped sodium aluminum has been studied through XRD and SEM-EDS analyses. The experiment led us believe that the refined TiC particles inlaid on the surface of a larger hydride matrix act not only as the catalytic active sites for the redox reaction of hydrogen, and act as the hydrogen spillover for hydrogen diffusion, but also prevent the growth in size of small spherical alanate, resulting in the improvement of hydriding/dehydriding properties of the sodium alanate system.

No abstract

The structure and magnetic properties of the compounds (x = 0 - 1.0) have been investigated. All the compounds crystallize in -type structure. Substitution of Y for Pr led to a monotonic decrease in the lattice constants and the unit-cell volume. Samples in this alloy system exhibit a crossover from ferromagnetic ordering for to antiferromagnetic ordering for as a function of concentration. The low-temperature behaviours of samples in the range were studied using magnetic measurements. Based on the magnetic measurements the tentative magnetic phase diagram showing three concentration regions of qualitatively different magnetic behaviour has been determined. Increasing substitution of Y for Pr in shows a depression of ferromagnetic ordering and the gradual development of antiferromagnetic ordering. For compounds with the magnetization first shows a clear ferromagnetic transition at , followed by a gradual drop at lower temperature, and then increases again. For compounds with x < 0.4 or , only ferromagnetic ordering or antiferromagnetic ordering occurs respectively.