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流动吸附法测定比表面是近年来发展起来的快速、准确而又方便的比表面测定方法,但此法在测定小表面时会出现反常峯,使准确测定带来困难。本文分析研究了反常峯出现的原因,主要是由于温度梯度的存在引起He—N_2气体的热扩散分离所造成的。文中对热扩散分径向和纵向进行了分析,从而得出了径向扩散造成的反常峯是正反峰面积相等的,纵向扩散造成的N_2在样品管中的积累量很小,计算时可以忽略,从而对小表面测定出现的反常峯进行正反峯面积代数和的方法计算吸(脱)附峯面积,再求比表面,测定的结果与实际情况符合,实现了对小至0.01M~2的小表面的准确测定。
Flow-adsorption method to determine the specific surface is developed in recent years, rapid, accurate and convenient method for the determination of specific surface, but this method in the determination of small surface anomalous peaks appear to make accurate determination of the difficulties. The reason for the appearance of anomalous peaks is analyzed in this paper, mainly due to the thermal diffusion separation of He-N 2 gas due to the temperature gradient. In this paper, the radial and longitudinal distributions of thermal diffusivities are analyzed. It is concluded that the anomalous peaks caused by radial diffusion have the same area of positive and negative peaks. The accumulation of N2 in the longitudinal tubes caused by longitudinal diffusion is very small. Ignore, and thus small surface determination of peak anomalies peak area of the pros and cons of the peak area and calculate the absorption (off) peak area, and then find the specific surface, the measured results in line with the actual situation, as small as 0.01M ~ 2 small surface accurate determination.