石墨粉末润湿特性及其表面自由能的研究

On humid and surface free energy properties of powder-graphite

利用毛细上升法测定了去离子水对石墨粉末的接触角，分析温度对石墨粉末润湿性的影响，并测算了石墨粉末的表面自由能，对将石墨用作净水滤料有指导作用。在20～40℃温度范围内接触角变化不大，平均为84．11°。其主要原因是表面张力σ和黏度η随温度变化对接触角的影响相反，综合作用结果导致接触角随温度变化不大。石墨粉末表面色散自由能为21．8mJ·m^-2，极性自由能为I．8mJ·m^-2，总的表面自由能约为23．6mJ·m^-2，以色散自由能为主。这是去离子水能够湿润石墨粉末，但湿润性相对较差的一个原因。可知极性流体对石墨粉末的润湿性比较差。

This paper is concerned with the authors＇ study on the humid and surface free energy properties of powder-graphite. For the sake of the author＇s research interest, the paper has made a careful analysis of the effect of temperature on its wetability and a detailed calculation of its surface free energy. In addition, we have also measured the contact angle that stilled water contact with powder-graphlte with the capillary rise method based on Washburn＇s equation. The results of our study indicate that the contact angle is not quite different within the temperature range of 20 - 40 ℃ on the average of 84.11°. The reason why there is no noticeable difference between the contact angles at different temperatures is that the comprehensive results that surface tension and viscosity affects the contact angle reversely along with the change of temperature. We have also found that its dispersion free energy is 21.8 mJ·m^-2 with its polar free energy being 1.8 mJ·m^-2 and the total energy - 23.6 mJ·m^-2. Though the dispersion free energy is the dominant part of its surface free energy source, the distilled energy can also help to moisten the powdergraphite in spite of the moistening effect being weak. Thus, it can be concluded that the wetability of polar fluid to powder- graphite is weak of its force.