脉冲热导法测定铝中氢的探讨

Discussion on determination of hydrogen in aluminium by impulse heating thermal conductivity

探讨了样品前处理方法、空白和分析功率对脉冲热导法测定铝中氢的影响,并探索了实验中遇到的表面氢问题、热抽取氢失败的问题及二次样仍能测出氢的问题。实验表明：铝中氢分析要求现车新鲜表面样品,最好在气体分析实验室备有车床现车现分析,且增加超声波清洗程序,以有效清除样品制备过程中可能存在的微量污染,确保样品足够清洁;坩埚空白差值为0.01~0.04μg/g,对于0.10μg/g附近的超低含量氢的分析,需要单个扣除空白,对于0.19μg/g以上较高含量氢的分析,用平均值扣空白亦可;为使每单个样品的分析功率落在最佳微小区域,每次取出坩埚时,均需使样品熔融后为亮球状态最佳,一般分析功率控制在1 100~1 300kW之间。按照实验方法对铝合金标准样品进行测定,8次平行测定结果的相对标准偏差（RSD）为4.1%,测定值为（0.19±0.029）μg/g,比该标样证书给出的（0.19±0.04）μg/g更好,且每个点均不超差。方法可以准确测定低至0.09μg/g铝中总氢或全氢。

The influence of sample pretreatment method,blank and analytical power on determination of hydrogen in aluminum was investigated by impulse heating thermal conductivity.Some problems in experiments were explored,including surface hydrogen,failed heat-extraction for hydrogen,and detectability of hydrogen in secondary sample.The results showed that the fresh lathing sample surface was required for analysis of hydrogen in aluminum.It was better to prepare lathe in gas analysis laboratory to lathe immediately sample before analysis.In addition,the ultrasonic cleaning procedure should be added to effectively eliminate the possible micro pollution existing in sample preparation process to ensure that the sample was cleaned enough.The blank difference of crucible was in range of 0.01-0.04μg/g.As a result,the blank should be conducted from individual deduction for the analysis of hydrogen with ultra low content about0.10μg/g.For the analysis of hydrogen with relatively high content more than 0.19μg/g,the blank could be conducted from average.In order to make the analytical power of every sample in optimal small range,the sample in crucible should be fused to bright ball state.Generally,the analytical power was controlled between 1 100 kW and 1 300 kW.The certified reference material of aluminum alloy was determined according to the experimental method.The relative standard deviation（RSD,n=8）was 4.1%.The result was（0.19±0.029）μg/g,which was better than the value of（0.19±0.04）μg/g in certificate.Moreover,all of the results were not out of tolerance.The proposed method was applicable for the accurate determination of total or whole hydrogen in aluminum with the lowest content of 0.09μg/g.