Preparation And Tribological Properties Of Oxidized Carbon Nitride-based Nanocomposites

The new oxynitride（O-g-C₃N₄）has a few-layer flake structure similar to graphene oxide.Because of its unique two-dimensional layered nanostructure and abundant oxygen-containing functional groups on the surface,it is widely used in the field of friction and lubrication.At the same time,it is also an ideal material in the current nano friction field.However,a single O-g-C₃N₄still has many drawbacks in practical applications.In order to further improve the tribological properties of O-g-C₃N₄,the development and design of high-performance O-g-C₃N₄composite lubricants has important theoretical and practical significance.In this paper,the study combines nanomaterials such as oxidized carbon nitride and copper nanoparticles（CuNPs）,flake molybdenum disulfide（MoS₂）,graphene oxide（GO）to improve the tribological properties of oxidized carbon nitride.This research provides a new thinking for preparing O-g-C₃N₄nanocomposites with excellent lubricating properties.The main research contents are as follows:（1）O-g-C₃N₄was prepared by calcining melamine in a muffle furnace three times by thermal oxidation method.O-g-C₃N₄was modified with polydopamine（PDA）,andcupricacetate（Cu（CH₃COO）₂·H₂O）andSodium hypophosphite（Na H₂PO₂·H₂O）were used as raw materials.The effective construction of zero-dimensional and two-dimensional nanostructures is realized by hydrothermal reduction method and copper nanoparticles with a size of about 5-10 nm were uniformly attached to the PDA-modified O-g-C₃N₄by the hydrothermal reduction method,then Cu/PDA/O-g-C₃N₄nanocomposites with 0D/2D structure were prepared.The tribological properties test shows that the PDA provides a large amount of phenolic hydroxyl groups to form hydrogen bonds with amino groups and carboxyl groups in rapeseed oil,so Cu/PDA/O-g-C₃N₄can be stably dispersed in the base oil for a long time and can greatly improve the lubricity of the base oil.CuNPs can act as ball in flake nanomaterials during friction,so Cu/PDA/O-g-C₃N4 wear resistance is better than CuNPs,O-g-C₃N4 and Cu/O-g-C₃N₄additives.（2）Using carbon oxynitride,sodium molybdate and cysteine as raw materials,MoS₂/O-g-C₃N₄nanocomposites with 2D/2D structure prepared by one-step hydrothermal method,and a series of characterizations were carried out.The microscopic morphology of MoS₂/O-g-C₃N₄shows that the flake molybdenum disulfide covers the surface of carbon oxide nitride,and the surface of the nanosheet remains flat.Tribological performance tests show that MoS₂/Og-C₃N₄nanocomposites can be stably dispersed in the base oil for a long time and can improve the friction properties of the base oil.This composite of two-dimensional layered materials further hinders the direct contact between the two metal surfaces,so it has better anti-friction and anti-wear performance than single O-g-C₃N₄nano-materials and sheet-shaped MoS₂nano-materials.（3）Modified MoS₂/O-g-C₃N₄with PDA,using Cu（CH₃COO）₂·H2O and Na H₂PO₂·H₂O as raw materials.Cu/MoS₂/O-g-C₃N₄（PDA is omitted for writing convenience）with 0D/2D/2D structure was prepared by uniformly attaching CuNPs on the surface of MoS₂/O-g-C₃N₄by hydrothermal reduction method.The size of CuNPs is about 5-10 nm.Tribological performance tests show that because CuNPs can act as balls in the flake nanomaterials during the friction process,Cu/MoS2/Og-C₃N₄nanocomposites can significantly improve the friction performance of the base oil as an additive,which is better than MoS2/Og-C₃N₄nano material has better anti-friction and anti-wear performance.（4）Hybridize GO and O-g-C₃N₄under van der Waals force to obtain GO/O-g-C₃N₄.Modified GO/O-g-C₃N₄with PDA,using Cu（CH₃COO）₂·H₂O and Na H₂PO₂·H₂O as raw materials.Cu/GO/O-g-C₃N₄（PDA is omitted for writing convenience）with 0D/2D/2D structure was prepared by uniformly attaching CuNPs on the surface of GO/O-g-C₃N₄by hydrothermal reduction method,and the size of CuNPs is about 5-10 nm.Tribological performance tests show that Cu/GO/O-g-C₃N₄can be stably dispersed in the base oil for a long time and can greatly improve the lubricity of the base oil.During the friction process,the collaboration between the three of CuNPs,GO and Og-C₃N₄makes the Cu/GO/O-g-C₃N₄nanocomposite exhibit better anti-friction and anti-wear performance.