On humid and surface free energy properties of powder-graphite
Hui Shi · Applied Mechanics and Materials · 2007
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-graphite 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 powder-graphite 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.