Study On Synthesis And Properties Of Modified Graphene Oxide Composites

Graphene oxide,as a derivative of graphene materials,has good dispersibility in aqueous system due to its oxygen-containing functional groups on its surface,which has also attracted interest in the field of cement-based materials.Relevant research results show that graphene oxide has a positive effect on compressive strength and flexural strength of cement-based materials.However,the addition of graphene oxide has obvious"Thickening and Viscosity increasing"effect on cement paste,which will seriously reduce the performance of the paste,thus limiting its application in cement-based materials.Therefore,surface modification of graphene oxide to improve its negative impact on cement-based materials has become the focus of relevant research.In this paper,Polycarboxylic acid-silane-modified graphene oxide complex were prepared by surface modification of graphene oxide with vinyltriethoxysilane,TPEG macromonomer and acrylic acid.The effect of the composites on the performance and hydration process of cement paste was studied,and the mechanism of the results was analyzed.Firstly,the surface of graphene oxide was modified by vinyltriethoxysilane.Silane modified graphene oxide with active carbon-carbon double bond on the surface of the sheet was prepared.Under the action of initiator,free radical polymerization of graphene oxide with TPEG macromonomer and acrylic acid monomer occurred,which made polycarboxylic acid molecules link to the surface of graphene oxide sheet.FTIR,XRD,TG-DTA and TEM were used to characterize the modification and grafting products.It was proved that the successful modification of graphene oxide lamellae by silane and the successful grafting of polycarboxylic acid chains on the surface of graphene oxide lamellae.It was suggested that the molar ratio of TPEG macromonomer to double bond was 10,and the acid-ether ratio was 4.5,which could be used as a better ratio for the synthesis of the composite.The cement paste doped with graphene oxide and Polycarboxylic acid-silane-modified graphene oxide complex are tested by fluidity test and rheological parameters measurement.The influence mechanism was analyzed by optical microscope observation,ion concentration test and Zeta potential test.The results show that graphene oxide forms flocculation structure under the combined action of Ca²⁺and OH^-ion in cement paste.By encapsulating mixed water,adsorbing water reducing agent and forming"recombinant flocculation structure"with cement particles,the paste fluidity decreases greatly,the yield stress and plastic viscosity increase greatly,and the"Thickening and Viscosity increasing"effect is obvious.Polycarboxylic acid-silane-modified graphene oxide complex coiled in the liquid phase of the paste through the polycarboxylic acid molecule chain complexing Ca²⁺ions,resulting in anti-agglomeration and electrostatic mutual exclusion,so that it would not form a flocculation structure,so the fluidity and rheological properties of the paste as a whole did not change significantly.The effects of graphene oxide and Polycarboxylic acid-silane-modified graphene oxide complex on the hydration process of cement are studied by means of mechanical properties,hydration heat,TG-DTA,XRD and SEM.The results show that the flexural strength and compressive strength of cement-based materials can be improved by adding graphene oxide and Polycarboxylic acid-silane-modified graphene oxide complex.Graphene oxide has no obvious influence on the hydration process of cement.The strength of cement paste can be improved by refinement of hydrated product crystals and reduction of interfacial defects.The addition of Polycarboxylic acid-silane-modified graphene oxide complex obviously delayed the hydration of cement in the early stage,but in the later stage,it promoted the hydration degree of cement and promoted the crystal growth.The strength of cement paste can be improved by overlapping the fiber network structure。...