Papers by Author: Jian Qi Qi

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Authors: Ji Cheng Zhou, Zhi Jun Liao, Jian Qi Qi, Wei Pang, Ya Wen, Jin Song Wen, Hai Ping Wang, Jun Feng He, Deng Xue Wu, Tie Cheng Lu
Abstract: Transparent AlON ceramics are prepared with single-phase AlON powder synthesized from micron-sized aluminum and nano-sized alumina. The ceramics are prepared through sintering at the temperature of 1880°C for 10, 20 and 40 hours in flowing-nitrogen atmosphere, respectively. The effects of powder and temperature holding-time on transparent ceramic preparation and microstructure and transparency are investigated. The results show that all samples are transparent and of a single-phase AlON and, with increasing holding-time, the average pore size and porosity decreases and consequently, the ceramics are dense and their transparency is improved.
441
Authors: Hai Ping Wang, Deng Xue Wu, Wei Pang, Jian Qi Qi, Ji Cheng Zhou, Jin Song Wen, Zi Meng Cheng, Ya Wen, Zhi Jun Liao, Tie Cheng Lu
Abstract: Aluminum oxynitride powders were synthesized by carbothermal reduction, using nano-sized alpha-alumina, gamma-alumina and carbon as raw materials. Effects of the weight percentages of alpha-alumina in alumina (R) and synthesizing temperatures (T) on the preparation of single-phase AlON powders have been studied. The results showed that proper R can reduce the shrinkage and increase the formation rate of AlON phase, but a high R will reduce the formation rate of AlON phase, because the activity of alpha-alumina was lower than that of gamma-alumina. Single-phase AlON powder with excellent properties can be obtained under the condition of R=0.15, T=1700°C. Moreover, this single-phase AlON powder was well-dispersed with an average size of about 2 μm.
438
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.
2308
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.
549
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.
402
Authors: Jin Song Wen, Tie Cheng Lu, Jian Qi Qi, Ji Cheng Zhou, Wei Pang, Hai Ping Wang, Jun Feng He, Zhi Jun Liao, Deng Xue Wu
Abstract: Single-phase aluminum oxynitride powders were obtained by varying the holding temperature (T) and the weight percentage of α-Al2O3 in Al2O3 (X) with nano-sized Al2O3 and AlN powders as raw materials. Influences of T and X on the phase composition of obtained powders were studied. The results showed that the content of aluminum oxynitride increased with increasing T or X. When X was 50% and T was 1750°C, obtained powders had better properties than those of others.
435
Authors: Jian Qi Qi, Tie Cheng Lu, Xiang Hui Chang, Mu Yun Lei, Cun Xin Huang
Abstract: MgAl2O4 transparent nano-ceramic samples have been successfully prepared by ultrahighpressure- sintering method. The ultrafine MgAl2O4 nano-powder was obtained by high-temperaturecalcination method. The samples were sintered at relatively low temperatures (540, 620 and 700°C) under ultrahigh pressures (3, 3.7 and 5GPa) with a six-pressure-source and hexahedral anvil machine that is customarily used for diamond synthesis. The average grain sizes of the prepared samples range from 50 to 75nm. All of the samples sintered under different conditions are transparent. The sample sintered at 620°C under 3.7GPa has the highest density as well as the highest light transmittance (about 50%) at 1300 ~ 1700 nm. The results showed that the ultrahigh-pressure-sintered samples exhibit unique light transmission properties though their densities are not much higher (<97%), compared to the samples, of which densities are higher (>99.5%), obtained by conventional hot-pressing or hot isotopic pressing sintering methods. The light transmittance, its affecting factors and transparent mechanism of the MgAl2O4 samples have been discussed.
2296
Authors: Jian Qi Qi, Tie Cheng Lu, Ji Cheng Zhou, Wei Pang, Jin Song Wen, Hai Ping Wang, Jun Feng He, Ya Wen, Zi Meng Cheng, Zhi Jun Liao, Deng Xue Wu
Abstract: The single-phase AlON powder used to prepare transparent ceramics was synthesized from solid-state-reaction using nano-sized Al2O3 and AlN powders with high purity. An appropriate amount of the powder was molded into pellets and isostatically pressed using polyvinyl alcohol as the binder. The AlON ceramic samples were obtained by sintering the pellets at 1880°C for 10 h, 20 h and 40 h, respectively. The transparency of the samples increased as the temperature holding time was prolonged. The density, phase compositions and microstructures of the sintered samples were discussed in detail.
447
Authors: Wei Pang, Deng Xue Wu, Hai Ping Wang, Jian Qi Qi, Ji Cheng Zhou, Jin Song Wen, Jun Feng He, Ya Wen, Zhi Jun Liao, Tie Cheng Lu
Abstract: Single-phase AlON powder was prepared by carbothermal reduction in flowing nitrogen atmosphere, using nano-sized alumina and carbon powder as raw materials. Transparent AlON ceramic samples using the single-phase powder were prepared by sintering at the temperature of 1880°C for 10h, 20h and 40h in flowing nitrogen atmosphere, respectively. It showed that the transparency and the density of the ceramic samples increased with increasing temperature holding-time. And the microstructures of the obtained samples were observed.
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