Disturbing phenomena in the measurement of small surface areas by the dynamic desorption method

Determination of low surface areas by the continuous flow method using an interrupted flow technique

“…Problems have arisen previously in the measurement of low surface areas (2)(3)(4). Similar problems occurred in the present case, as shown by Figure la.…”

“…Various methods have been used to overcome anomalous peaks. The most common approach has been to vary the tube geometry (2)(3)(4). In the present work, capillary side arms were used but a bulbous region allowed the use of a reasonable sample size.…”

“…The milled sample gave a similar result whether or not the interrupted flow technique was used. Kourilova and Krejci (3,4) have recognized two distinct thermal gradients which may give rise to anomalous peaks. A radial temperature gradient exists while the sample tube is heating up or cooling down.…”

Powder Surface Area and Porosity

“…Long before these extremely small areas can be measured with nitrogen, the phenomenon of thermal diffusion obscures the signals and imposes a higher lower limit [142]. Thermal diffusion produces a tendency for a gas mixture to separate when exposed to a changing temperature gradient.…”

Adsorption phenomena of a mechanically-alloyed mixture 2Mg+Ni

“…For the adsorption and desorption peaks, small initial peaks appeared. According to Kourilova et al [19] and Lowell et al [20], they result from thermal diffusion. The thermal diffusion makes the adsorption and desorption peak separated when the gas mixture is exposed to changing temperature gradient.…”