| Taking natural black tourmaline produced from a certain place in Mongolia as an sample, this paper reported the effect rule and mechanism of heat treatment on surface free energy of tourmaline powders, which belonged to the category of Ecomaterials science in the fields of inorganic metalloid material technology.Tourmaline fine powders were baked at 400-900℃with different time. The contact angle of tourmaline powders were measured with water, alcohol and 30% ethylene glycol respectively. Surface free energy of tourmaline powders was calculated by means of Wu formula. The mechanism of heat treatment on surface free energy and polarity component of tourmaline powders were studied with X-Ray diffraction, scanning electron, infrared absorption spectrum and so on.The results indicated that the surface free energy of tourmaline powders increased as temperature increasing, and the maximum was at 800℃before phase transformations occurred. The value of surface free energy of tourmaline powders changed regularly and was low after 2 h heat treatment at the same temperature. Polarity component played a major role in the composition of surface free energy of tourmaline powder, which increased from 76% to 86% as temperature increasing. Because of the influence of heat expansion, the value decreased after 2 h heat treatment at 500℃.The effect rule of heat treatment on surface free energy and composition of tourmaline powder was connected closely to the cell volume of tourmaline. The cell volume of tourmaline decreased as temperature increasing. With the time of heat treatment increased, the cell volume of tourmaline changed regularly. The reduction of the cell volume and the increase of surface free energy of tourmaline powder were approximately inversely proportional to the changes of the cell volume.
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