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采用自行搭建的热重实验平台对798~973K温度范围内温度对A3-3基体石墨的氧化行为进行研究,氧化剂为100 mL/min的空气。不同温度下石墨试样均被氧化至失重10%~15%。结果表明,基体石墨的氧化速率(OR)随着温度的升高显著提升,温度为973K时基体石墨的OR约为798K时的70倍。虽然973K时氧气供给速率与平均碳消耗速率的比值仅为4.3,但石墨OR的Arrhenius曲线依然保持了很好的线性关系,表明该温度下基体石墨的氧化机理没有发生改变。在798-973K温度范围内,A3-3基体石墨在空气中的氧化均处于化学区,其活化能为176 kJ/mol,Arrhenius氧化方程可描述为:OR=2.9673×10~8·exp(-21 124.8/T),单位为wt%/min。与堆内的核级结构石墨相比,基体石墨的活化能相对较低,说明基体石墨在空气中更易被氧化,这主要跟基体石墨中含有未完全石墨化的树脂炭有关。
The oxidation behavior of A3-3 matrix graphite at 798 ~ 973K temperature was studied by using self-built thermogravimetry experiment platform. The oxidant was 100 mL / min air. Graphite samples at different temperatures were oxidized to 10% ~ 15% weight loss. The results showed that the oxidation rate (OR) of matrix graphite significantly increased with the increase of temperature, and the OR of matrix graphite was 70 times higher than that of 798K at 973K. Although the ratio of oxygen supply rate to average carbon consumption rate at 973K was only 4.3, the Arrhenius curve of graphite OR still maintained a good linear relationship, indicating that the oxidation mechanism of the matrix graphite did not change at this temperature. In the temperature range of 798-973K, the oxidation of A3-3 matrix graphite in the air is in the chemical zone with an activation energy of 176 kJ / mol. The Arrhenius oxidation equation can be described as OR = 2.9673 × 10 ~ 8 · exp (- 21 124.8 / T) in wt% / min. Compared with the nuclear-grade graphite in the reactor, the activation energy of the matrix graphite is relatively low, indicating that the matrix graphite is more easily oxidized in the air, which is mainly related to the incomplete graphitization of the resin carbon in the matrix graphite.