LaMn1-xCuxO3±δ perovskite oxides (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscop...LaMn1-xCuxO3±δ perovskite oxides (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray fluorescence spectroscopy, N2 adsorption, and temperature-programmed reduction. Their catalytic activity in the oxidation of methane and CO was evaluated. EDS and SEM results showed that the Pechini samples had more homogeneity and smaller particles (higher specific surface area). The catalytic activity for methane combustion was highest for x = 0.2. In CO oxidation, the oxides with x = 0.2 and x = 0.4 were the most active. The Pechini samples had higher activity and stability than the sol-gel samples.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
目前,对五声音阶的命名有以下几种:五音音阶(chelle de cing notes)、五调音阶(gamme de cingtons)、五声(pentaphone)、五音的(pentaphoni-que)、五音(pentaphonie),以及五声音阶(pentatonique)。 对于一个普通的西方创作人员来说,一...目前,对五声音阶的命名有以下几种:五音音阶(chelle de cing notes)、五调音阶(gamme de cingtons)、五声(pentaphone)、五音的(pentaphoni-que)、五音(pentaphonie),以及五声音阶(pentatonique)。 对于一个普通的西方创作人员来说,一段五声音阶结构的旋律,即使不是“中国的”,至少也是“异国情调的”。创作人员们认为,五声音阶就是中国、蒙古或盖耳人音乐中的音阶。新近去世的罗马尼亚音乐学家C.Brailoiu,在其著名的《论一首俄罗斯乐曲》一文中指出:五声音阶——不仅在中国有。展开更多
A novel sol-gel process for preparing oxides and mixed oxides sols from precipitation and peptization process is reported in this article. Inorganic salts are used as raw materials in this study. It is found that the ...A novel sol-gel process for preparing oxides and mixed oxides sols from precipitation and peptization process is reported in this article. Inorganic salts are used as raw materials in this study. It is found that the amount of acid has great influence on the stability and particle diameter distribution of the precursor sols. Ultrasonic treatment is used to prepare alumina sol at room temperature. The result of27Al NMR shows that there exist Al13 7+ species in the sol. By controlling the sol particles with narrow particle diameter distribution, alumina, titania and silica-alumina (SA) materials with narrow mesoporous distribution are formed by regular packing of sol particles during gelation without using any templates. The results also show that the structure and particle diameter distribution of precursor sol determine the final materials’ texture.展开更多
文摘LaMn1-xCuxO3±δ perovskite oxides (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray fluorescence spectroscopy, N2 adsorption, and temperature-programmed reduction. Their catalytic activity in the oxidation of methane and CO was evaluated. EDS and SEM results showed that the Pechini samples had more homogeneity and smaller particles (higher specific surface area). The catalytic activity for methane combustion was highest for x = 0.2. In CO oxidation, the oxides with x = 0.2 and x = 0.4 were the most active. The Pechini samples had higher activity and stability than the sol-gel samples.
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).
文摘目前,对五声音阶的命名有以下几种:五音音阶(chelle de cing notes)、五调音阶(gamme de cingtons)、五声(pentaphone)、五音的(pentaphoni-que)、五音(pentaphonie),以及五声音阶(pentatonique)。 对于一个普通的西方创作人员来说,一段五声音阶结构的旋律,即使不是“中国的”,至少也是“异国情调的”。创作人员们认为,五声音阶就是中国、蒙古或盖耳人音乐中的音阶。新近去世的罗马尼亚音乐学家C.Brailoiu,在其著名的《论一首俄罗斯乐曲》一文中指出:五声音阶——不仅在中国有。
基金Acknowledgements This work was supported by the Chinese Academy of Sciences, the Research Institute of Petroleum Processing SINOPEC and the National Natural Science Foundation of China (Grant Nos. 20073043 and 29873050).
文摘A novel sol-gel process for preparing oxides and mixed oxides sols from precipitation and peptization process is reported in this article. Inorganic salts are used as raw materials in this study. It is found that the amount of acid has great influence on the stability and particle diameter distribution of the precursor sols. Ultrasonic treatment is used to prepare alumina sol at room temperature. The result of27Al NMR shows that there exist Al13 7+ species in the sol. By controlling the sol particles with narrow particle diameter distribution, alumina, titania and silica-alumina (SA) materials with narrow mesoporous distribution are formed by regular packing of sol particles during gelation without using any templates. The results also show that the structure and particle diameter distribution of precursor sol determine the final materials’ texture.
