Changes in the Surface Properties of Powder Titanium under Mechanoactivation

The adsorption properties of titanium powders with an effective particle size of 18–32 μm mechanoactivated in a planetary ball mill in a protective atmosphere of n-hexane have been studied at different activation times. It has been established that indicators of the specific surface area, Henry’s constant, monolayer capacity, and particle size for activated titanium powders pass through the zones of extreme (min–max) activation values. In this case, the heat of adsorption and the energy of the surface during the adsorption of standard benzene vapor depend on the amount of surface coverage with adsorbed benzene molecules and on the degree of mechanoactivation of the titanium powder. It was found that, at all times of mechanoactivation, the filling of the surface adsorption monolayer has an endothermic sign of the differential molar isosteric heat of adsorption. The reversal of the sign of the heat of adsorption from endothermic to exothermic for all powders corresponds to the completion of the filling of the monolayer and surface nanopores. The observed effect of negativity of the heat of adsorption in the initial region of fillings of the surface of activated titanium powders is explained by the endothermic contribution of the adsorption deformation of the expansion of powder particles with surface nanocracks.