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Effects of air flow rate on the oxidation of NBG-18 and NBG-25 nuclear graphite

机译:空气流速对NBG-18和NBG-25核石墨氧化的影响

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The effects of air flow rate (FR) (FR range: 1-10 L/min) on the oxidation of NBG-18 and NBG-25 nuclear graphite grades at temperatures between 600 and 1100 degrees C were studied, in reference to the standard test procedure for measuring oxidation rates of nuclear graphite in air (ASTM D 7542-09). The results showed that the FR effects on oxidation rate (OR) increase with increasing temperature with negligible FR effects at 600 degrees C for both materials. At high temperatures (>800 degrees C) there appears to be a two-stage relationship between FR and OR, which corresponds to the transition between reaction rates dominated by chemical kinetics and those dominated by diffusion. The material-specific microstructure appeared strongly influences this transition. The overall OR-FR behaviours of NBG-18 were higher than NBG-25 at 600 800 degrees C while negligible differences in the OR-FR behaviours between the two grades were observed at 900-1100 degrees C. The mercury porosimetry data showed that the higher OR-FR behaviours observed in NBG18 may partly be attributed to the differences in the pore size distribution (open porosity and cumulative pore area) between the grades, especially for the large size pores (diameter 5 x 10(3) nm). (C) 2017 Published by Elsevier B.V.
机译:空气流量的(FR)的影响(FR范围:1-10升/分钟)上NBG-18和NBG-25核石墨等级的在600个1100℃的温度之间的氧化进行了研究,在参照标准测量空气中核石墨氧化速率的试验方法(ASTM D 7542-09)。结果表明,对氧化速率(或)的氧化率(或)的影响随着较高的温度而增加,对于两种材料,可忽略的FR效应忽略于600℃。在高温下(> 800℃)似乎似乎是FR和或者之间的两级关系,或者,这对应于由化学动力学主导的反应速率与由扩散主导的反应速率之间的过渡。材料特异性微观结构显得强烈影响这种转变。 NBG-18的总体或-Fr行为在600 800℃下高于NBG-25,而在900-1100摄氏度下观察到两种等级之间的或-FR行为的差异。汞孔隙率数据显示在NBG18中观察到的更高或-FR行为可能部分地归因于等级之间的孔径分布(开放孔隙率和累积孔面积)的差异,特别是对于大尺寸孔(直径 5×10(3)Nm) 。 (c)2017年由Elsevier B.V发布。

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