Effect of microstructure on ~3He migration in TiT_(1.9) films

Two kinds of films were prepared to study the effect of microstructure on helium migration in Ti tritides. Both films showed different release behaviors and helium bubble distributions. In the film consisting of columnar grains, a twolayered structure was observed. Inclusions with a strip feature were found at the grain boundary, and no helium bubbles were distributed in these inclusions. However, helium preferred to migrate to the boundaries of these inclusions. Bubble linkage as a ribbon-like feature developed parallel to the film surface in the film consisting of columnar grains. More cracks were developed at the grain boundaries of the film consisting of columnar grains, although the helium content in the film consisting of columnar grains was less than that in the film consisting of equiaxed grains. A surface region with a small number of bubbles, or ＂depleted zone＂, was observed near the surface. The cracks extending to the film surface were the pathways of the critical helium released from the film. The helium migration was strongly influenced by the grain microstructure.

3D carbon network supported porous SiOC ceramics with enhanced microwave absorption properties

Porous SiOC ceramic was successfully prepared by pyrolysis of dimethylsilicone oil,silane coupling agent and melamine foam.The microwave absorbing properties of porous SiOC were studied for the first time.At the matching layer thickness of 3.0 mm,the paraffin-based composite with porous SiOC displays a minimum reflection coefficient(RC)of-39.13 d B(11.76 GHz)and an effective absorption bandwidth(EAB)of 4.64 GHz which are much larger than that of paraffin-based composite with ordinary SiOC.It is found that the porous structure of SiOC is crucial to achieve its high microwave absorption performance by improving both the polarization loss and conduction loss.The enhanced polarization loss is originated from the dipole polarization and interfacial polarization,while the improvement of conduction loss is attributed to the carbon skeleton of porous SiOC.These results indicate that porous SiOC ceramic is a promising candidate for high-performance ceramic-based microwave absorbing materials.

Compositional dependence of hydrogenation performance of Ti-Zr-Hf-Mo-Nb high-entropy alloys for hydrogen/tritium storage

A series of Ti-Zr-Hf-Mo-Nb high-entropy alloys with different Mo concentrations were developed as candidate materials for hydrogen/tritium storage in solid phase.The crystal structures and hydrogenation properties of the Ti-Zr-Hf-Mo-Nb alloys were investigated by X-ray diffraction and differential scanning calorimetry techniques.All the alloys have a body-centred cubic single phase structure.The results demonstrate that the cell volume of the Ti-Zr-Hf-Mo-Nb hydride decreases with increasing Mo concentration,which reduces their thermal stability.The theoretical calculation proposes that the lower binding energy of the Ti-Zr-Hf-Mo-Nb hydride decreases the thermal stability of Ti-Zr-Hf-Mo-Nb alloys with higher Mo content.The great hydrogenation performance for all the Ti-Zr-Hf-Mo-Nb alloys is owing to their reversible single-phase transformation during the hydrogen absorption-desorption cycle,which would be bene ficial to improving the hydrogen recycling rate and preventing the disproportionation.The compositional dependence of the hydrogenation performance of the Ti-Zr-Hf-Mo-Nb alloys was established and will be useful in designing novel hydrogen/tritium storage materials to satisfy the requirements of diffe rent application fields in hydrogen,solar thermal and nuclear energy.

FeNi@CNS nanocomposite as an efficient electrochemical catalyst for N_(2)-to-NH_(3) conversion under ambient conditions

The electrocatalytic nitrogen reduction reaction(NRR)has emerged as a promising renewable energy source and a feasible strategy as an alternative to Haber-Bosch ammonia(NH_(3))synthesis.However,finding an efficient and cost-effective robust catalyst to activate and cleave the extremely strong triple bond in nitrogen(N_(2))for electrocatalytic NRR is still a challenge.Herein,a FeNi@CNS nanocomposite as an efficient catalyst for N_(2) fixation under ambient conditions is designed.This FeNi@CNS nanocomposite was prepared by a simple water bath process and post-calcination.The FeNi@CNS is demonstrated to be a highly efficient NRR catalyst,which exhibits better NRR performance with exceptional Faradaic efficiency of 9.83%and an NH_(3) yield of 16.52μg h^(−1) cm^(−2) in 0.1 M Na_(2)SO_(4) aqueous solution.Besides,high stability and reproducibility with consecutive 6 cycles for two hours are also demonstrated throughout the NRR electrocatalytic process for 12 h.Meanwhile,the FeNi@CNS catalyst encourages N_(2) adsorption and activation as well as effectively suppressing competitive HER.Therefore,this earth-abundant FeNi@CNS catalyst with a subtle balance of activity and stability has excellent potential in NRR industrial applications.