Methodological Features of Determination the Specific Surface Energy of Mineral Quartz-Containing Powders

Abstract

Methods for sample preparation of prototypes for the subsequent determination of the specific surface energy by the Owens, Wendt, Rabel and Kaelble (OWRK) method are worked out on the example of highly dispersed powders of quartz sand, characterized by a SiO2 content of 98.3%. For this purpose, dry grinding in a planetary ball mill disperses the raw material, the mechanical activation time is varied in the range of 15÷45 min. Five fractions of highly dispersed powders are obtained. They are characterized by the specific surface area. This parameter is changed in the following range: 1200÷3000 kg/m2. Prototypes for subsequent research by the OWRK method are made by pressing with a pressing force of 2 to 16 tons. As a criterion for optimizing sample preparation conditions, the coefficient of determination of the functional dependence of the cosine of the wetting angle of the surface of test samples with working fluids (decane, glycerin, water) on the dispersion component of their surface tension is proposed. It has been established that for the quartz sand used, the maximum value of the coefficient of determination (0.94) is noted at a pressing force of fine fractions equal to two tons. An increase in the specific surface area of powder materials over 2370 kg/m2, obtained by mechanical dispersion and an increase in pressing force up to 12÷16 tons, leads to additional errors in determining the surface tension of compacted prototypes by the OWRK method.