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Preparation of ceria with large particle size and high appearance density。Cerium is one of the most abundant rare earth elements in both bastnasite and monazite. Ceria has been widely used in optical, catalytic, electrolyte, and sensor materials, with unique performances. With the development of functional materials, great interest has been focused on the synthesis and characterization of specific fine/mesoporous ceria powder. In this study, the modified precipitation and recrystallization processes combined with a controlled calcination process for fabricating the ceria with large particle size and high appearance density was reported. Dunng precipitation, a certain amount of mineral acid such as nitric acid served as an additive, to adjust the precipitation and crystallization processes of cerium oxalates. An appropriate acidic condition could lead the process into the Oswald ripening stage and made the particles become bigger. Thus, the appearance density of powder was increased. The optimized conditions, such as the temperature, feeding speed. type and concentration of mineral acids, and the concentration of cerium-contained stock solution, were investigated and evaluated. Rare earth oxalate eluted or immersed with mineral acid could act as a precursor, to obtain an oxide with large particle size and high appearance density, by decomposition in controlled calcinations, in which the moisture must be gradually released first. The treatment of precipitates and the calcination process could affect the particle size distribution and appearance density. The optimized condition approached in this study is: (1) To increase the particle size and appearance density, the solution of nitric acid (5 mol/L) and oxalic acid (1 0 g/L) can be used as an eluent or immersing reagent. (2) The programmed calcination process is necessary, that is, heating the as-elutedhmmersed oxalates mildly from room temperature to 300℃at a heating rate of 5℃/min, and keeping the samples at 300 "C for 1 h; consecutively, heating to 900℃at 10℃/min, and then keeping for 4 h. After the above-mentioned optimization process, the particle size and appearance density of ceria could reach 20 pm and 1.9 g/cm3, respectively. This method could also be applied to prepare praseodymium oxides, however, it was not successful in preparing other light rare earth oxides. Compared with other processes, this study provided a facile strategy with low cost. |
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5楼2009-11-24 08:49:41
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小甲009(金币+85,VIP+0): 11-25 14:43
小甲009(金币+85,VIP+0): 11-25 14:43
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Preparation of ceria with large particle size and high appearance density。 大粒度，高表观比重氧化铈的合成。 Cerium is one of the most abundant rare earth elements in both bastnasite and monazite. 铈元素在氟碳铈矿和独居石矿中天然丰度很高。 Ceria has been widely used in optical, catalytic, electrolyte, and sensor materials, with unique performances. 氧化钵已被广泛应用于光学、催化、电解质、传感器材料中，具有独特的性能。 With the development of functional materials, great interest has been focused on the synthesis and characterization of specific fine/mesoporous ceria powder. 随着功能材料的不断发展，各种特殊物理性能的氧化钵粉体的合成和性能表征研究十分活跃 In this study, the modified precipitation and recrystallization processes combined with a controlled calcination process for fabricating the ceria with large particle size and high appearance density was reported. 本文中，报道了一种对沉淀过程和结晶过程的优化以及对烧结过程的控制来制备大粒度，高表面比重的氧化铈粉体。 Dunng precipitation, a certain amount of mineral acid such as nitric acid served as an additive, to adjust the precipitation and crystallization processes of cerium oxalates. 沉淀过程中，以一定数量的矿物酸如硝酸作为添加剂，来调整草酸铈的沉淀和结晶过程。 An appropriate acidic condition could lead the process into the Oswald ripening stage and made the particles become bigger. Thus, the appearance density of powder was increased. 适当的酸性条件将有助于使反应过程趋向Osward结晶阶段，并使得粒子变大。因此，粉体的表观比重会提高。 The optimized conditions, such as the temperature,feeding speed. type and concentration of mineral acids, and the concentration of cerium-contained stock solution, were investigated and evaluated. 研究和评估了优化的反应条件，比如温度，加酸速度，矿物酸的种类和浓度含铈溶液的浓度等。 Rare earth oxalate eluted or immersed with mineral acid could act as a precursor, to obtain an oxide with large particle size and high appearance density, by decomposition in controlled calcinations, in which the moisture must be gradually released first. 为了获得大粒度和高表观比重的氧化物，稀土草酸盐洗提或浸入矿物酸将可以充当前驱体，在控制烧结条件下分解，这里湿气首先需要逐渐排放。 The treatment of precipitates and the calcination process could affect the particle size distribution and appearance density. 对沉淀物的处理和烧结过程的控制将会影响到粒子的尺度分布和表观比重。 The optimized condition approached in this study is: 本文优化的条件和方法如下： (1) To increase the particle size and appearance density, the solution of nitric acid (5 mol/L) and oxalic acid (1 0 g/L) can be used as an eluent or immersing reagent. 为了提高粒度和表观比重，5mol/L的硝酸和10g/L的草酸混合充当淋洗液或浸泡反应物。 (2) The programmed calcination process is necessary, that is, heating the as-elutedhmmersed oxalates mildly from room temperature to 300℃at a heating rate of 5℃/min, and keeping the samples at 300 "C for 1 h; consecutively, heating to 900℃at 10℃/min, and then keeping for 4 h. After the above-mentioned optimization process, the particle size and appearance density of ceria could reach 20 pm and 1.9 g/cm3, respectively. 程控的烧结过程是必须的，这就是，按5度/分钟逐步加热按这种淋洗制备的草酸盐到300度，保温1小时；接着，按10度/分钟加热到900度，保温4小时。经过上述优化过程以后，氧化铈的粒度和表观比重分布达到20 pm和1.9 g/cm3。 This method could also be applied to prepare praseodymium oxides, however, it was not successful in preparing other light rare earth oxides. Compared with other processes, this study provided a facile strategy with low cost. 这种方法可以应用到制备氧化镨，但是，无法成功应用到制备其他轻稀土氧化物。和其他方法比较，这种方法操作简单，成本低廉。 |
2楼2009-11-22 12:09:37
syh9288
捐助贵宾 (著名写手)
海军上将
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3楼2009-11-22 13:16:56
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小甲009(金币+5,VIP+0): 11-25 14:43
小甲009(金币+5,VIP+0): 11-25 14:43
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沙发好强啊！！但是有些地方可能不太精确 第五句话： In this study, the modified precipitation and recrystallization processes combined with a controlled calcination process for fabricating the ceria with large particle size and high appearance density was reported. modified precipitation ——改性沉淀 recrystallization processes ——再结晶过程 个人觉得这里 是 : 报导了一种 与控制烧结大粒度，高表面比重的氧化铈的过程 相结合的改性沉淀与再结晶过程。 |
4楼2009-11-24 08:45:29
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