Papers by Author: Xiang Jie Luo

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Authors: Xiang Hui Chang, Tie Cheng Lu, Jian Qi Qi, Xiang Jie Luo
Abstract: Transparent MgAl2O4 nano-ceramics were prepared by ultrahigh-pressure-sintering method, using improved nano-sized powder synthesized by high-temperature calcination. The synthesis temperatures were exactly measured by nichrome-NiSi thermocouple passing through the samples. The micromorphology of the ceramics was observed by means of dynamic force microscopy (DFM), and the relation between transparency and micro-morphology was investigated. The results show that, the sintering temperatures, now calibrated, of transparent nano-ceramics are just 540~700°C, which are much lower than those of conventional nano-ceramics and transparent ceramics, and the uniformity of grain sizes and orderliness of the grain array are beneficial to the transparency and integrity of the ceramics.
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Authors: Xiang Hui Chang, Tie Cheng Lu, Ying Zhang, Xiang Jie Luo, Qiang Liu, Cun Bing Huang, Jian Qi Qi, Mu Yun Lei, Cun Xin Huang, Li Bin Lin
Abstract: The first experimental work to produce transparent MgAl2O4 nano-ceramics was reported in this paper. The sintering characteristics of transparent nano-ceramics were investigated at relatively low temperature (800 ~ 1100°C) under ultrahigh pressure (2 ~ 5 GPa) using hydrostatic equipment. The morphologies and phases of ceramics were observed by means of SEM and XRD, respectively. The grain sizes of the ceramics are shown to be less than one hundred nanometers, far smaller than the sizes of common transparent ceramics. Furthermore, the higher the sintering temperature and pressure are, the greater the extent of densification is. At the same temperature, the higher the pressure is, the smaller the average grain size is. Under the same pressure, the higher the temperature is, the larger the average grain size is. The optimal sintering condition for preparing transparent nano-ceramics was also determined.
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Authors: Tie Cheng Lu, Xiang Hui Chang, Jie Zhang, Jian Qi Qi, Xiang Jie Luo
Abstract: The transparent nanocrystalline MgAl2O4 spinel ceramics were synthesized at lowtemperature and high-pressure conditions with low-cost nano-sized MgAl2O4 powder. The sintering characteristics of transparent nano-ceramics were investigated at 500~700oC under 2 ~ 5 GPa. The optimal sintering condition for preparing transparent nano-ceramics was determined. The microstructure and phase composition of powder, as well as the microstructures, morphologies, optical properties, densities and mechanical properties of synthetic ceramics were investigated. The grain sizes of the synthetic ceramics are less than 100 nm, far smaller than those of usual transparent micron-ceramics, and the average grain size depends on the pressure and temperature. The transmittance at the saturation plateau can near 80%. The relative densities of all samples are less than 99%, however, they are highly transparent. The toughness, derived from energy dissipation, of the transparent nano-ceramics was investigated and was compared with that of transparent micron-ceramic.
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