| Graphene is a monolayer carbon material with two-dimensional honeycomb structure tightly arranged from sp2 hybrid bonded carbon atoms.Due to the excellent physical and chemical properties,graphene has a good prospect in many diverse applications.The research of the large-scale green preparation method is an important exploration target of the graphene industry production.Graphene nanoplatelets(GNPs)have been prepared using the leonardite based humic acid(HA)as carbon source through low-temperature reduction of arylation and high-temperature vacuum.The influence factors of heating temperature,holding time,accelerant and its dosage on the structure of GNPs precursor have been investigated by infrared spectroscopy(FT-IR),Raman spectroscopy(Raman),X ray diffraction(XRD),scanning electron microscopy(SEM)analysis method,and then the optimum process conditions have been determined.The GNPs precursor has been stripped and analyzed.Finally,the pyrolysis behavior of humic acid in the reaction process and action mechanism of accelerator have been discussed.Results show that the optimal condition for preparing GNPs precursor is mass ratio HA:calcium acetate=1:2,nitrogen atmosphere,2?/min,450?,4 h,and high-temperature(700?)vacuum carbonization is helpful for the delamination of the film.Humic acid based graphene is made up of multilayer graphite sheets which has high crystalline structure,but it contains a small amount of hydroxyl groups.The pyrolysis behavior of humic acid under the action of calcium acetate has been studied by TG-DSC.The research shows that calcium may be linked to carboxyl groups in humic acid by ion exchange to form the cross linked calcium humate.With the increase of pyrolysis temperature,the release of the oxygen containing groups and heteroatom produces a large number of aromatic clusters,and Ca precipitates in the form of calcium carbonate.The large area of aromatic ring network structure is synthesized by free radical,and then the GNSs precursor is obtained. |
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