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首页> 外文期刊>Journal of Materials Science >THERMAL STABILITY OF ALUMINAS BY HYDROTHERMAL TREATMENT OF AN ALKOXIDE-DERIVED GEL
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THERMAL STABILITY OF ALUMINAS BY HYDROTHERMAL TREATMENT OF AN ALKOXIDE-DERIVED GEL

机译:水热处理烷氧基化物衍生的凝胶对氧化铝的热稳定性

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摘要

Alumina precursors were prepared by hydrothermal treatment of alkoxide-derived alcogels. The crystalline structure of precursor beohmites and their microstructural change during heat treatment were examined and the specific surface area of the alumina precursors after heating was measured. The alu mina prepared by hydrothermal treatment at 270 degrees C retained high specific surface areas at high temperatures; e.g. 35.0, 8.3 and 5.4 m(2) g(-1) at 1200, 1400 and 1500 degrees C, respectively. The thermal stability of the aluminas depended on the hydrothermal temperatures. For excellent thermal stability, the following factors are necessary: (1) grain growth of beohmite as an alumina precursor, and a grain size of more than 20 nm for the (1 20) plane; (2) a crystallite size for the (200) plane exceeding that for the (002) plane; (3) an isotropic growth of the beohmite crystal. In the transition alumina region (less than or equal to 1200 degrees C), the thermal stability of the alumina is caused by raising the a transformation temperature, resulting from decreasing the number of grain boundaries by beohmite growth. In the a-alumina region (>1200 degrees C), inhibiting the three-dimensional grain growth achieves thermal stability, resulting from preservation of the anisotropic structure introduced into the beohmite. [References: 17]
机译:通过对醇盐衍生的醇凝胶进行水热处理来制备氧化铝前体。检查前体重晶石的晶体结构及其在热处理过程中的微观结构变化,并测量加热后的氧化铝前体的比表面积。通过在270摄氏度下进行水热处理而制备的氧化铝在高温下保留了较高的比表面积;例如在1200、1400和1500摄氏度下分别为35.0、8.3和5.4 m(2)g(-1)。氧化铝的热稳定性取决于水热温度。为了获得优异的热稳定性,必须考虑以下因素:(1)作为氧化铝前体的重晶石的晶粒长大,并且(1 20)平面的晶粒尺寸大于20 nm。 (2)(200)平面的微晶尺寸超过(002)平面的微晶尺寸; (3)钠锰矿晶体的各向同性生长。在过渡氧化铝区域(小于或等于1200摄氏度)中,氧化铝的热稳定性是由升高转变温度引起的,这是由于重晶石生长减少了晶界的数量而导致的。在a-氧化铝区域(> 1200摄氏度),抑制三维晶粒生长可实现热稳定性,这是由于保留了引入到钠镁石中的各向异性结构所致。 [参考:17]

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