Papers by Author: Yong Ping Zhu

Abstract: 3D-ordered dumbbell-like ZnO microcrystals were prepared under hydrothermal conditions without using any additive, template or surfactant. FE-SEM images show that 3D-ordered dumbbell-like ZnO microcrystals are made of two elements-(Ⅰ) dumbbell-like microrods and (Ⅱ) nanorods that grow on the two ends of microrods. The thermal radiation properties of 3D-ordered dumbbell-like ZnO microcrystals were discussed in detail.

Abstract: La2Ce2O7 nano-powders with cubic fluorite structure have been firstly prepared by Molten Salts method. These nano-powders were prepared at relatively low temperatures(800°C and 900 °C) at different time, using La(NO3)3•6H2O and La(NO3)3•6H2O as raw materials, as well as K2SO4 (anhydrous) and Na2SO4 (anhydrous) as molten salts and dispersant. XRD, SEM were used to characterize the composition, morphology and size of prepared products. The procedure is facile and suitable for the synthesis of the La2Ce2O7 nano-particles and it will be an excellent method for preparation of other pyrochlore type of rare earth zirconate (Re2Zr2O7, Re=rare earth).

Abstract: Isothermal, isobaric chemical vapor infiltration of carbon fiber felts with fiber volume fractions of 7.1% and 14.2% were investigated at infiltration times from 20 to 120 hours, using a constant temperature of 1095 oC and a methane pressure of 22.5 kPa. Bulk densities and the density profiles as well as porosity at various densification stages were determined. Inside–outside densification was obtained in the most infiltrations, the gradients of densification along the infiltration depth decrease with increasing of residence time and infiltration times. Outside–inside densification occurs only in the felt with the lower fiber volume fraction at final infiltration stage and at longer residence times. Microstructure of the obtained matrix carbon was analyzed with a polarized light microscopy. Abruptly change from low/medium textured carbon to medium/high textured carbon are observed in both of the carbon fiber felts, whereas the thickness of the first lower textured layer is about 14 micros in the felt with a fiber volume fraction of 7.1%, whereas it is only 2 micros in the felt with a fiber volume fraction of 14.2%, which is caused by an increasing of initial surface area / volume ratio, [A/V], from 33 to 71 mm-1. Results are completely in agreement with the previous simulations studies on the influence of [A/V] ratios.