Dear Andre Duevel,

We have worked in a vacuum with powders and porous materials. Experiments were conducted with materials such as Fe, Cu, SiO2, SiC, Al2O3, ZrO2, MoS2, WS2 and a number of other porous materials and powders. At the same time we are constantly observed the phenomenon of temperature increase, samples of materials by 1.5 - 2.0 degrees when removing the pressure and flow of air in the system. We attributed this phenomenon to a gas friction upon penetration into the pores of the material, and into the space between powder particles. Of course, the adsorption effects also cannot be ruled out.

With best regards

Professor Pavel Kudryavtsev

Dear Andre Duevel,

we have a similar experience for "this paradox",  when we treat porous material (paper, etc.), following this work flow.  Yes, the adsorption of (nominally pure ~99%) Ar seems to be a possible reason.

Yes, exotherm adsorption means endotherm desorption, thus, a considerable warming should not occur... So probably it is really the gas that is warmed up somewhere and the small volumes of the materials allow a fast warming of them (a glass or similar object does not warm up due to the procedure). 

Dear Andre Duevel,

We have worked in a vacuum with powders and porous materials. Experiments were conducted with materials such as Fe, Cu, SiO2, SiC, Al2O3, ZrO2, MoS2, WS2 and a number of other porous materials and powders. At the same time we are constantly observed the phenomenon of temperature increase, samples of materials by 1.5 - 2.0 degrees when removing the pressure and flow of air in the system. We attributed this phenomenon to a gas friction upon penetration into the pores of the material, and into the space between powder particles. Of course, the adsorption effects also cannot be ruled out.

With best regards

Professor Pavel Kudryavtsev

mass-rates of Ar upon adsorption / desorption in porous material (paper, etc.),  are not the same, following common work flow in a GB.