Jiang Zhengwu

Porous ZnO Sheets Transformed from Zinc Sulfate Hydroxide Hydrate and Their Photoluminescence Performance

Highly crystalline, porous ZnO sheets were prepared from chemically-deposited zinc sulfate hydroxide hydrate (ZSH) sheets by sintering at 1000 °C. The formation mechanism of ZSH in Zn 2+ - hexamethyltetramine (HMT) precursor system, the transformation process of ZSH to ZnO, and the crystalline, microstructural and optical properties of the ZnO sheets were investigated. The porous ZnO sheets possessed a well-defined hexagonal shape with controllable size (10-50 μm) and thickness (200-500 nm), high crystallinity, and strong ultraviolet photoluminescence without detectable defect- related visible emission. Submicron-sized pores (100-500 nm) and polygonal or irregular ZnO particles resulting from the limited mass transport during high temperature sintering were observed in the ZnO sheets. Analysis of the formation mechanism indicated that the high affinity of SO 2-

Self-desiccation effect of high performance concrete

Effects of water to binder ratio (mW/mB), types and addition content of mineral admixtures on the autogenous relative humidity (ARH) change of concrete resulting from self-desiccation were studied. The parameters of coefficient of mineral self-desiccation-effect k and efficient water to binder ratio re were proposed, and experimental results were fitted non-linearly and analyzed using these proposed parameters. The experimental results indicate that ARH reduction of concrete at different ages increases with the decrease of mW/mB. The ARH change laws of concrete with mW/mB lower than 0.4 can be expressed with a non-linear equation. The extent of the effect of types and addition content of mineral admixtures on ARH reduction of concrete resulting from self-desiccation can be reflected by the non-linear equation with the parameter of efficient water to binder ratio re effectively.