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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Measurement of effective Knudsen diffusion coefficients for powder beds used in heterogeneous uptake experiments
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Measurement of effective Knudsen diffusion coefficients for powder beds used in heterogeneous uptake experiments

机译：异质吸收实验中使用的粉床有效Knudsen扩散系数的测量

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摘要

The effective Knudsen diffusion coefficients for characteristic oxide powder beds used in heterogeneous uptake experiments have been measured using countercurrent diffusion and transient pressure drop techniques. Room-temperature thermal-velocity-normalized effective Knudsen diffusion coefficients are found to lie in the 0.15 to 0.35 mu m range for magnesium silicate, aluminum oxide, and iron oxide powder beds. Measured values are compared with theoretical estimates and are consistent with low bed tortuosities ( below 3) expected for media with open porosity above 0.5. The impact of uncertainties in effective diffusion coefficients on corrections of measured uptake coefficients is discussed. The value of careful uptake measurements in both the low and high sample mass limits is reinforced, as this allows uptake corrections independent of explicitly measured or estimated diffusion coefficient values. It is suggested that correction procedures requiring tortuosity values greater than 3 are suspect.
机译：已使用逆流扩散和瞬态压降技术测量了异质吸收实验中使用的特征氧化物粉末床的有效Knudsen扩散系数。对于硅酸镁，氧化铝和氧化铁粉末床，室温热速度归一化的有效Knudsen扩散系数被发现在0.15至0.35μm的范围内。将测量值与理论估计值进行比较，并且与开孔孔隙度大于0.5的介质的低床弯曲度（低于3）一致。讨论了有效扩散系数的不确定性对测得的吸收系数校正的影响。在低和高样品质量极限中仔细摄取测量的值都得到了增强，因为这允许独立于明确测量或估计的扩散系数值进行摄取校正。建议怀疑曲折度值大于3的校正程序。

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