Preparation And Tribological Performance Of Crystalline Carbon Based Nanocomposites

Graphene oxide and carbon nanotubes are newly emerged crystalline carbon lubricating nanomaterials.Due to their excellent friction-reducing and anti-wear performance,stable thermal oxidation properties and anti-erosion performance,GO and CNTs are widely used in tribological erea.In this paper,initially,we investigated the tribological performance of different dimensional carbon materials comparatively.Then,an environmental-friendly material polydopamine which was full of abundant phenolic hydroxyl groups and amino groups was utilized to modify the GO,CNTs and GO-CNTs hybrids,due to the electrostatic force,a great many Cu2+ ions were adsorbed on the PDA functionalized carbon nanomaterials.Ultimately,the crystalline carbon based nanocomposites were prepared through facile hydrothermal reduction.The tribological performance of the as-prepared nanocomposites were investigated.This study start a new pathway for the preparation of carbon based nanocomposites with superior lubricating performance.The primary research contents and results are listed as follows:1)GO was prepared via oxidation method with potassium ferrate and CSs were made from hydrothermal method using glucose.The GO and CSs were dispersed in the base oil to investigate their tribological performance.Test results showed that lamellar GO can reduce the friction coefficient of the base oil,however,the improvement efficiency of the CSs was limited.2)The Cu/PDA/GO nanocomposites were fabricated using a facile hydrothermal reduction method,of which,GO was used as supporters,PDA as modifier agent,Cu(CH3COO)2·H2O as copper resource and NaH2PO2·H2O as reducing agent.Cu NPs were uniformly immoblized on the PDA modified GO nanosheet.Compared with the pure base oil,Cu/PDA/GO filled base oil reduced friction and wear effectively,outperformed the tribological properties of GO,Cu NPs and Cu/GO additives.The excellent lubricating mechanisms ascribe to the remaining phenolic hydroxyl groups and amino groups in PDA which benefit for the long term dispersion stability of Cu/PDA/GO in the base oil,and the well dispersed Cu NPs on GO nanosheets canprevent the agglomeration of GO,all these help the formation of stable Cu/PDA/GO tribofilms on the rubbing surface,which help to reduce the friction and wear of the tribo-pairs.3)The Cu/PDA/CNTs nanocomposites were successfully prepared using a hydrothermal method after the CNTs were functionalized by PDA nanolayer,of which,the CNTs were acted as supporters,Cu(CH3COO)2·H2O as copper resource and NaH2PO2·H2O as reducing agent.The anchored Cu NPs with diameters of 4-7 nm were well dispersed on PDA modified CNTs.Tribological test results show that friction-reduction and anti-wear performance of the base oil was enhanced with the addition of Cu/PDA/CNTs nanocomposites,outperformed the tribological performance of Cu NPs,CNTs and Cu/CNTs additives.The superior lubricating performance can be ascribed to the synergistic lubricating effect of CNTs and Cu NPs which act as nano-bearing in different directions.4)The Cu/PDA/GO-CNTs hybrid nanocomposites were fabricated by a facile hydrothermal reduction strategy after GO-CNTs hybrids were modified by PDA,of which,Cu(CH3COO)2·H2O was used as copper resource and NaH2PO2·H2O was used as reducing agent.The decorated Cu NPs with diameters about 5-10 nm were scatteredly distributed on GO-CNTs hybrids surfaces,a stable hybrid structure was constructed from the composition of GO,CNTs and Cu NPs.When used as lubricant additives,Cu/PDA/GO-CNTs play a vital role to improve the lubricating efficiency of the base oil,additionally,it outperformed the single additives such as GO,CNTs and Cu NPs.The excellent lubricating performance was attributed to the perfect combination of the laminated GO nanosheets and the ball-bearing Cu NPs and CNTs.