Study On Preparation And Conductive Properties Of Doped Graphite-based Geopolymers

In winter,snowfall often occurs in northern China,and it has a large coverage area and a long time snow days,which seriously hinders traffic travel,poses a great threat to the travel safety of pedestrians,and brings great inconvenience to transportation.The traditional mechanical cleaning method is not clean,and the equipment costs a lot of money.What’s more the traditional method of snow removal by salt melting method will have a bad impact on the environment.At the same time,the use of collective heating in the north not only consumes a lot of resources,but also pollutes the environment,which is also one of the main reasons for the production of haze.In spring,"rainy season" will appear in the south of our country,which affects people’s health,the traditional treatment method is inefficient,consumes a lot of energy,and causes a serious waste of resources.By using the Joule effect of conductive geopolymer,the role of snow melting and dehumidification can be achieved on the premise of avoiding excessive waste of resources and polluting the environment.In order to solve the above problems,this experiment refers to the process of graphite conductive concrete and phosphoric acid base polymer,using metakaolin and graphite as raw materials and phosphoric acid as activator to prepare doped graphitebased conductive geopolymers.Firstly,taking the compressive strength as the index,the effects of different temperature,H₂O,phosphoric acid and graphite content on the doped graphite-based conductive geopolymers were investigated.Taking the resistivity as the index,the effects of different temperature,H₂O,phosphoric acid addition,graphite addition and graphite particle size on the electrical conductivity of doped graphite-based conductive geopolymers were investigated.The main results are as follows:（1）The curing system with better compressive strength of doped graphite-based conductive geopolymers is to demoulding at 60℃ for 1 day,then curing in sealed bags for 2 days,and then open for 2 days.When the mass ratio of phosphoric acid to metakaolin is 0.8,the mass ratio of H₂O / metakaolin is 1.4,the mass ratio of graphite to metakaolin is 0.9,and the number of graphite mesh is 8000,the maximum compressive strength is 6.91 MPa.（2）The curing system with the lowest resistivity of doped graphite-based conductive geopolymers is demoulding at 60℃ for 1 day,then curing in sealed bags for 2 days,and then open curing for 2 days;When the mass ratio of phosphoric acid to metakaolin is 0.8,the mass ratio of H₂O to metakaolin is 1.4,the mass ratio of graphite to metakaolin is 0.8,and the number of graphite mesh is 8000,the resistivity is the lowest 0.039Ω·m.（3）The doped graphite-based conductive geopolymers were characterized by XRD.It was found that the doped graphite-based conductive geopolymers had dispersion peaks in the range of 20°³0°,and the graphite still maintained the original characteristic peaks in the geological polymers.There is no new characteristic peak,indicating that the doped graphite-based conductive geopolymers are similar to phosphoric acid base polymers and are amorphous,and the phase of graphite does not change in the reaction.（4）From the infrared spectrum analysis,the infrared spectrum of the geological polymer with graphite is basically the same as that of the geological polymer without graphite,and there is no new chemical bond.Moreover,the infrared spectra of different graphite additions are basically the same,indicating that the amount of graphite does not participate in the geological polymerization,and the amount of graphite does not affect the formation of phosphoric acid base polymer,which is consistent with the results of XRD.However,with the increase of the amount of graphite,the compressive strength of graphite-based conductive geopolymers will decrease.（5）From the SEM analysis,it is found that the graphite particles are wrapped by the gel formed by geological polymerization.When the amount of graphite is less,the graphite particles are dispersed and the contact area between the particles is smaller.At this time,the conductive geopolymer conducts electricity mainly through tunneling effect and field emission effect,and the resistivity is high.With the increase of graphite powder,the contact area between graphite particles increases,which mainly depends on the conductive path effect,and the resistivity of geological polymer decreases greatly.