The Study Of Electrophoresis Preparation Of Exfoliate Graphite

Expandable graphite is a new kind of functional material, which can be applied in seal field, environment protection and medical treatment, and it can be synthesized by chemistry oxidation mainly. The sulfur content of exfoliate graphite is harmful, while synthesized by chemical method with sulfuric acid. So it cannot be used in high-tech domains, such as nuclear power, aerospace and environment protection.In order to find an effective process for fabricating exfoliate graphite without sulfur, the different methods have been investigated in this paper. Based on the theory of chemical process, a novel method of electrophoyesis had been introduced and employed to synthesize expandable graphite successfully. There is operated to investigate the effects of various factors including the proportion of reactants, current intensity, voltage and the reaction time on the intercalated reaction. In addition, the microstructure and morphology of exfoliate graphite have been measured by scanning electron microscope (SEM) and X-ray diffraction (XRD).The electrophoretic intercalation process is an effective process for fabricating exfoliate graphite and employs electric field and oxidizing agent, simultaneously. Electric field is able to drive the charged particles directional movement along the interlayer of graphite. The oxidizing agent has an ability to lead mutual exclusion between carbon atoms and increasing of interlayer distance. They are useful to insert the charged particles, such as CH3COO- and NO3-, into the interlayer of graphite and form graphite intercalation compounds (GIC). Experimental results show that that the best process conditions are following: the weight ratio of nitric acid and acetic anhydride is 5:1, the current intensity is 500 mA, voltage is 150V, the reaction time is 30 min, then, the graphite compounds are cleaned with water till the PH=6-7 and dried at 60℃. Subsequently, the exfoliate graphite with high performance of obtained after heat treatment at 900℃.XRD analysis results of GIC prepared by two different ways show that 1 stage and 2, 3 stage GIC is made by chemical process and electrophoretic intercalationprocess, respectively. After high temperature treatment, the graphite particles that prepared by electrophoretic method have abundance pores observed by SEM. The porous structure is contributed by the effect of electric field and heat treatment. The charged particles can move quickly in the electric field and diffuse deeper into the graphite interlayer. Heat treatment is able to make intercalation material gasify rapidly and lead graphite layers to separate, at last, form "pocket" pores partly. These "pocket" pores are more available to enhance the power of oil storage.Comparing with the traditional process, the electrophoretic intercalation process can be controlled easily. It is a better way to prepare exfoliate graphite with no harmful sulfur and high performance, such as large specific surface area and high sorption capacity.