Preparation And Properties Of Graphite Intercalation Composite

Graphite intercalation composite is a new kind of technology materialwhich is prepared with different kinds of inorganic and organic compound andgraphite. It is widely used in many fields such as petrochemical industry,metallurgical industry, electric utility industry, mechanical industry, pharmacyindustry, auto industry, aerospace industry and nuke industry.Natural squama graphite has layer structure. It can be compounded intographite intercalation compounds(GIC) after some materials are intercalatedinto layers because of the weak binder and be produced into a new kind ofcomposite. This kind of material has not only the good properties of naturalgraphite 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 graphitehas not.Because of H₂SO₄ as inset in the old process of expanded graphite, thereare remainder sulfur in the product which corrupt metal and affect the result ofsealing. Therefore, different kinds of insets had been tried, the product beingcompounded have different characters.Graphite intercalation composite — expansible graphite is prepared withHNO₃, KMnO₄ as oxidant and P₂O₅, HAc as multiplex intercalation in thispaper. The conditions of optimum synthetic processing are discussed , too. Theproduction is compared with the other kinds of productions pretared withsingle intercalation: P2O5 and HAc. This series of productions' expandvolume , ash content, volatile fraction are studied and compared.The craft process of preparing expansible graphite: HNO3, KMnO4(oxidant), P2O5 and HAc (inset) are added into squama graphite the mixture ispuddle into mash. The materials are kept at 25℃ for an hour, washed to ph=5,and dried at 50-60℃. Finally, they are exfoliated at 900℃ for 30s.The materials are kept at 25℃, because it is near room temperature. Iftemperature is lower, the reaction will need too much time, and expandvolume will be small. On the other hand, if temperature is higher, it goesagainst the reaction. Because the reaction is exothermic reaction, and that HAcis volatile. 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 istoo low, the carbon atom is less oxygenated and less GIC are compounded, sothe expand volume of product is low;If the quantity of oxidant is too large, theash content of the product would increase, the quality of the product wouledecrease. According to the option for HNO3 quantity, first, there are twofunction in the reaction about HNO3 : 1. HNO3 prompt the oxidation ability ofoxidant;2. the quantity of HNO3 is not too large when HNO3 is intercalatedinto the layers, otherwise, the water content would increase and expandvolume woule decrease. So, at the beginning, the expand volume increase asthe increase of HNO3 quantity, but the expand volume decrease as the increaseof HNO3 quantity when the HNO3 quantity increase at certain limit. Accordingto the option for KMnO4 quantity, at the beginning, the mixture react morecompletely as the increase of KMnO4 quantity. The ash content woule increaseand the quality woule be effected when the KMnO4 quantity increase out ofcertent limit. According to the option for P2O5 quantity, the ash content wouldincrease if P2O5 quantity is too large, so P2O5 quantity is decreased to the leastin order to keep expand volume large. As another inset, the expand volumewoule increase as the increase of HAc quantity. But if the quantity of HAc istoo large, the water content would increase and expand volume woule decrease.Therefore, we take all these factors into account and get the best condition ofpreparing expansible graphite with multiplex intercalation is: graphite(g):HNO3(g): KMnO4 (g): P2O5(g): HAc(g)= 1:3.4:0.08:0.4:0.6.Through element analyse, we get that in the sulfur-free expansiblegraphite prepared with multiplex intercalation, the content of P2O5 is 0.060﹪,which of HAc is 0.075﹪. Therefore, P2O5 and HAc both have beeninserted into graphite layer. The reaction formula is:n graphite+ nHNO3+ n[B] + n2 [O] ==[graphite+·NO 3? ·HAc?H3PO4]n + n2 H2OB is multiplex intercalationThrough XRD, we also find that the peaks of expansible graphiteprepared with P2O5 . HAc and multiplex intercalation are entirely different,which prove the method is feasible again.When HAc are used as inset, the product has low ash content and smallexpand volume. Because organic compound is volatile.When P2O5 are used asinset, the product has large expand volume, low sulfur content and high ashcontent. The sulfur-free expansible graphite prepared in this paper integrate thestrongpoint of the two expansible graphite. The product with multiplexintercalation has large expand volume, low volatile fraction and ash content.The structure of expanded graphite is loosen and porous and expandedgraphite has relatively large specific surface area(50-200m2/g). The apertureis mainly middle or large. So non-polarity organic macromolecule(especiallyoil substance)is easily absorbed by expanded graphite. According to theresearch of the adsorption of the products, the absorption of expanded graphiteis better than active carbon. The absorption of expanded graphite is better thanthe other absorbent. Expanded graphite has the properties of low density, light,high chemical stability, innocuous, porous and special flexibility. It willbecome a new kind of absorption material comparison to active carbon. It willwidely used in many fields such as petrochemical industry, environmentprotection industry. The application of expanded graphite as absorption isfar-reaching significant in the period of environment protection becomingmore important.