Abstract:
Based on the phenomenon of the mechanodynamic diffusion of particles of the external medium in solids, a new in principle method has been proposed for the first time for producing nano-sized powder materials using industrial cement milled in a helium medium as an example. The temperature dependences of the extraction rate and the amount of helium in powders upon their heating in a temperature range of 20–1200$^\circ$C have been obtained using mass spectrometry. It has been shown that milling of the cement powder of the M-400 brand using an MK-1 laboratory mill in helium leads to a considerable shift of its extraction curve towards lower temperatures compared with the air medium. The particle sizes of the powder milled in helium lie in a range of 5–10 nm, which is smaller than the powder size ($\sim$ 500 nm) after milling in the air medium by a factor of 100. The compression strength of cement samples obtained from the powders milled in helium increased by a factor of 2 compared with the strength of the samples from the initial material. The activation energies of helium extraction from the cement powders milled in helium and in air have been analyzed. The obtained results indicate a high efficiency of the method for producing nano-sized powder materials in the helium medium. The method can be used in the industrial scale based on the existing mill equipment with its minimal modernization.
