Jiankang Wang

Investigation of absorptance and emissivity of thermal control coatings on Mg-Li alloys and OES analysis during PEO process.

Thermal control ceramic coatings on Mg–Li alloys have been successfully prepared in silicate electrolyte system by plasma electrolytic oxidation (PEO) method. The PEO coatings are mainly composed of crystallized Mg2SiO4 and MgO, which have typical porous structure with some bulges on the surface; OES analysis shows that the plasma temperature, which is influenced by the technique parameters, determines the formation of the coatings with different crystalline phases and morphologies, combined with “quick cooling effect” by the electrolyte; and the electron concentration is constant, which is related to the electric spark breakdown, determined by the nature of the coating and the interface of coating/electrolyte. Technique parameters influence the coating thickness, roughness and surface morphology, but do not change the coating composition in the specific PEO regime, and therefore the absorptance (αS) and emissivity (ε) of the coatings can be adjusted by the technique parameters through changing thickness and roughness in a certain degree. The coating prepared at 10 A/dm2, 50 Hz, 30 min and 14 g/L Na2SiO3 has the minimum value of αS (0.35) and the maximum value of ε (0.82), with the balance temperature of 320 K.

Co/Cu2O assisted growth of graphene oxide on carbon nanotubes and its water splitting activities

A hybrid nanomaterial of Co/Cu2O based on carbon nanotubes (CNTs) is proposed as a highly promising photocatalyst for solar hydrogen production. Cu2O nanoparticles are active catalysts for hydrogen evolution from copper acetate by polyol process, but Cu0 nanoparticles are easily formed in this process, resulting in Cu associated Cu2O. To suppress the formation of metallic copper, metallic cobalt loaded CNT is used as a substitute for the non-loaded CNT for Cu2O formation. The metallic cobalt nanoparticles are not only effective in preventing the reduction of Cu2+ to Cu0, but they also enhance the efficiency of the CNT-substrated hybrid material preparation. Furthermore, graphene oxide (GO) is formed in the fabrication process of CNT/Co materials, and the GO is obtained from the exfoliated tube wall of CNT, which is evidenced by the uneven distribution of Co and Co/Cu2O on the GO flakes. The hybrid materials of CNT/Co/Cu2O and [CNT + GO]/Co/Cu2O are investigated as photocatalysts for water splitting. The results reveal that CNT/Co/Cu2O and [CNT + GO]/Co/Cu2O can be used to split water, thus enabling the economic production of hydrogen.