| Graphite intercalation composite is a new kind of technology material which is prepared with different kinds of inorganic and organic compound and graphite. It is widely used in many fields such as petrochemical industry, metallurgical industry, electric utility industry, mechanical industry, pharmacy industry, auto industry, aerospace industry and nuke industry. Natural squama graphite has layer structure. It can be compounded into graphite intercalation compounds (GIC) after some materials are intercalated into layers because of the weak binder and be produced into a new kind of composite. This kind of material has not only the good properties of natural graphite such as high-temperature, corrosion and radiation resistance, electrical conductivity, but also the characters of flexibility, resilience, self-adhesion, impermeability, adsorption, low density which natural graphite has not.Because of H2SO4 as inset in the old process of expanded graphite, there are remainder sulfur in the product which corrupt metal and affect the result of sealing. Therefore, different kinds of insets had been tried, the product being compounded have different characters.Graphite intercalation composite ——expanded graphite is prepared with HNO3,KMnO4 as oxidant and H3PO4 as intercalation in this paper. The conditions of optimum synthetic processing are discussed, too. The production is compared with the other kinds of productions prepared with different inorganic and organic compound. This series of productions' PH, ash content, anti-oxidation, conductivity of solution, adsorption are studied and compared. The craft process of preparing expanded graphite: HNO3, KMnO4 (oxidant) and inset are added into squama graphite, the mixture is puddle into mash. The materials are kept at certain temperature, washed to PH=5,and dried at maximum of 100℃.Finally, they are exfoliated at 900℃ for 30s.The function of oxidant is to make squama graphite oxygenated, which is the first step of the preparation of GIC. If the quantity of oxidant is too low, the carbon atom is less oxygenated and less GIC are compounded, so the expand volume of product is low; If the quantity of oxidant is too large, the ash content of the product would increase, the quality of the product would decrease. According to the option for HNO3 quantity, first, there are two function in the reaction about HNO3: 1, HNO3 prompt the oxidation ability of oxidant; 2, the quantity of HNO3 is not too large when HNO3 is intercalated into the layers, otherwise, the water content would increase and expand volume would decrease. So, at the beginning, the expand volume increase as the increase of HNO3 quantity, but the expand volume decrease as the increase of HNO3 quantity when the HNO3 quantity increase at certain limit. According to the option for KMnO4 quantity, at the beginning, the mixture react more completely as the increase of KMnO4 quantity, The ash content would increase and the quality would be effected when the KMnO4 quantity increase out of certain limit. According to the option for H3PO4 quantity, the ash content would increase if H3PO4 quantity is too large, so H3PO4 quantity is decreased to the least in order to keep expand volume relatively large. The mixture react more completely and the expand volume is larger when the reaction time and the reaction temperature increase, but the cost would much more. According to different exfoliation time, inset is more fully gasified and expand volume would be larger when the exfoliation time increase, the product will be oxygenated and the quality of the product would decrease if the exfoliation time is too long. Therefore, we take all these factors into account and get the best condition of preparing expanded graphite with H3PO4 is: graphite(g): HNO3(ml): KMnO4(g): H3PO4(ml)= 1:2.4:0.06:0.3.The reaction temperature is 70℃, the reaction time is 1 hour, The exfoliation time is 30s.According to the conductivity of solution of the products, the component of GIC would be presumed. The conductivity of soluti... |
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