Research On Graphene Preparation And Its Tribological Properties

In this paper, the preparation methods of graphene were discussed. Then made it into nickel based composite coatings and added it into lubricating oil to value its tribological properties.Using chemical method and solution plasma discharge method to prepare the graphene sheets, then observe the morphologies of graphene by SEM and TEM, analyse the phase and composition by XRD, FT-IR and Raman spectra. Comparing the influence of different preparation methods and process parameters on the quality of graphene, and then achieve the best method and parameters for graphene preparation.Using double pulse electrodeposition process to prepare the graphene/nickel based composite coatings with different graphene addition on45#steel surface. Evaluate the mechanical properties of composite coating by micro hardness tester and scratch instrument. Observe the morphologies of composite coatings by optical metallographic microscope and SEM. Analyse the phase and composition by XRD and EDS. Then test its tribological properties by pin on disk friction machine under dry friction condition using GCr15pin. The tribological performance graphene as lubricating oil additive was tested by self-made reciprocating friction machine in oil lubrication condition using piston ring wear against cylinder liner. SEM and EDS were used to anlyse the morphology and composition of grinding crack.The results show that:through improved hummers method for graphite oxide, then use the hydrazine reduction method and high temperature treatment can obtain a better quality of graphene. In the process of preparation of graphite oxide, the best volume ratio for H3PO4and H2SO4is2:8. In hydrazine reduction, the best mass ratio of oxidation graphene and reducing agent is1:1. The temperature of high temperature treatment should be higher than350℃.Different forms of carbon nano particles can be obtained by solution plasma processing (SPP) with different electrolyte and different parameters. In certain conditions, graphene is detected in the discharge product using NaCO3as electrolyte.The thickness of graphene/nickel based composite coating is about20-30um. The composite coatings are well attached to the substrate and the hardness is greatly raised by graphene addition. Composite coatings can reduce the friction coefficient and wear rate concurrently. The friction coefficient reduce20～30%compared with Cr coatings and the wear rate reduced50%compared with matrix45#steel. Graphene can be in relatively stable dispersion in lubricating oil and can significantly the friction coefficient and wear rate. The friction coefficient reach minimum which is about0.043when adding content is0.3%wt.