La_2Zr_2O_7 ultrafine powders were prepared by sol-gel method.SEM indicated that La_2Zr_2O_7 particles aremosily spherical in shape and average particle sizes are smaller than 0. 5 pe XRD patterns showed that no in-to...La_2Zr_2O_7 ultrafine powders were prepared by sol-gel method.SEM indicated that La_2Zr_2O_7 particles aremosily spherical in shape and average particle sizes are smaller than 0. 5 pe XRD patterns showed that no in-tormediare phase was observed in the course of La_2Zr_2O_7 formation. The crystal structure of La_2Zr_2O_7 wasfound to be of the fluorite type when calcination temperature was 800～900℃ and of the pyrochlore type at1000℃ . The latter is cubic, its space group is Fd3m. Cxlculation of crystallite size indicated that the averagecrystallite size increased with the increasing calculation temperature. The average crystal lattice distortion ratedecreaed with the increase of particle sizes. IR spectra showed that the smaller the particles are , the higher surface activity the particles have.展开更多
The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic pro...The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic properties of powders were respectively studied by means of X-ray diffractometer (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG) and vibrating sample magnetometer (VSM). The powders before and after combustion and calcination at 450–850 °C with different mole ratio of Nd to Ba (0.1–1.0) were compared in terms of XRD. In addition, the effects of different synthesis conditions on magnetic properties of powders were also discussed. The results show that at pH 7.0 or so, mole ratio of citrate to nitrate (1–3) and calcination temperature of 850 °C for 1 h, M-type BaNd x Fe12?x O19(x=0.1?1.0) fine powders can be obtained, and the coercive force reaches 436880 A·m?1 at x=1, which is far greater than that of barium permanent ferrite (BaFe12O19).展开更多
利用阴离子交换膜为隔膜将电解槽分为两室,控制阴极室电极的恒定电流密度,在电解过程中消耗阴极室溶液中的H+浓度,促使TiO2+与电解产生的OH-中和水解反应,形成TiO2·xH2O均匀沉淀,在不同温度的热处理后,得到不同晶型的纳米TiO2微粒...利用阴离子交换膜为隔膜将电解槽分为两室,控制阴极室电极的恒定电流密度,在电解过程中消耗阴极室溶液中的H+浓度,促使TiO2+与电解产生的OH-中和水解反应,形成TiO2·xH2O均匀沉淀,在不同温度的热处理后,得到不同晶型的纳米TiO2微粒． TEM 和XRD分析表明:在773K焙烧2h后,TiO2微粒呈锐钛矿型结构,粒径约为30-50nm;在 873K热处理后可得到金红石相约占3．85％的锐钛矿型和金红石型混晶结构的TiO2粉体．本文对其形成的机理进行了初步的探讨．展开更多
文摘La_2Zr_2O_7 ultrafine powders were prepared by sol-gel method.SEM indicated that La_2Zr_2O_7 particles aremosily spherical in shape and average particle sizes are smaller than 0. 5 pe XRD patterns showed that no in-tormediare phase was observed in the course of La_2Zr_2O_7 formation. The crystal structure of La_2Zr_2O_7 wasfound to be of the fluorite type when calcination temperature was 800～900℃ and of the pyrochlore type at1000℃ . The latter is cubic, its space group is Fd3m. Cxlculation of crystallite size indicated that the averagecrystallite size increased with the increasing calculation temperature. The average crystal lattice distortion ratedecreaed with the increase of particle sizes. IR spectra showed that the smaller the particles are , the higher surface activity the particles have.
文摘The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic properties of powders were respectively studied by means of X-ray diffractometer (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG) and vibrating sample magnetometer (VSM). The powders before and after combustion and calcination at 450–850 °C with different mole ratio of Nd to Ba (0.1–1.0) were compared in terms of XRD. In addition, the effects of different synthesis conditions on magnetic properties of powders were also discussed. The results show that at pH 7.0 or so, mole ratio of citrate to nitrate (1–3) and calcination temperature of 850 °C for 1 h, M-type BaNd x Fe12?x O19(x=0.1?1.0) fine powders can be obtained, and the coercive force reaches 436880 A·m?1 at x=1, which is far greater than that of barium permanent ferrite (BaFe12O19).
文摘利用阴离子交换膜为隔膜将电解槽分为两室,控制阴极室电极的恒定电流密度,在电解过程中消耗阴极室溶液中的H+浓度,促使TiO2+与电解产生的OH-中和水解反应,形成TiO2·xH2O均匀沉淀,在不同温度的热处理后,得到不同晶型的纳米TiO2微粒． TEM 和XRD分析表明:在773K焙烧2h后,TiO2微粒呈锐钛矿型结构,粒径约为30-50nm;在 873K热处理后可得到金红石相约占3．85％的锐钛矿型和金红石型混晶结构的TiO2粉体．本文对其形成的机理进行了初步的探讨．
