High-content graphene nanoplatelet reinforced aluminum composites produced by ball milling and hot extrusion

Due to the high specific surface area of graphene, the effective incorporation of high-content graphene in metals is challenging.Here, aluminum composites with graphene nanoplatelet(GNP) content up to 5.0 vol% were prepared by spark plasma sintering(SPS) of blended powders with various ball milling regimes and subsequent hot extrusion. The effects of GNP distribution state on the properties of GNP/Al composite were investigated. 5.0 vol% GNPs were uniformly dispersed in aluminum matrix by high-speed ball milling(HSBM) process, but with damage GNPs due to the too high energy input. By contrast, the wellstructured and dispersed GNPs in aluminum powders were obtained via shift-speed ball milling(SSBM). The clear GNP-Al interface in extruded SSBM composite was attributed to well-structured GNPs. As a result, the yield strength(YS) and ultimate tensile strength(UTS) of composite produced by SSBM reached 279 and 303 MPa, which are 166% and 116% higher than those of monolithic Al. This demonstrated that it may be promising to introduce high-content GNPs with tailorable interface in Al alloys via modified ball milling technique and hot extrusion.     

湿法磷酸的工艺研究进展

介绍了以磷矿为生产原料的硝酸法、盐酸法、硫酸法等湿法磷酸生产工艺，并对其工艺进行了说明和比较。突出了湿法磷酸生产中的除氟问题。指出了湿法磷酸产生磷石膏废物将是制约湿法磷酸生产的主要环节。     

Effect of atmospheric aerosol on surface ozone variation over the Pearl River Delta region

Our analysis of the surface aerosol and ultraviolet(UV) measurements in Pearl River Delta(PRD) region shows that the sur-face UV radiation is reduced by more than 50% due to high aerosol concentrations.This has important impacts on urban eco-system and photochemistry,especially on ozone photochemical production over the region.The quantitative effect of aerosols on surface ozone is evaluated by analyzing surface observations(including ozone,ultraviolet radiation,aerosol radiative pa-rameters) and by using r...