This review focuses on the effect of metal-containing nanomaterials on tribological performance in oil lubrication. The basic data on nanolubricants based on nanoparticles of metals, metal oxides, metal sulfides, nanocomposities, and rare-earth compounds are generalized. The influence of nanoparticle size, morphology, surface functionalization, and concentration on friction and wear is analyzed. The lubrication mechanisms of nanolubricants are discussed. The problems and prospects for the development of metal-containing nanomaterials as lubricant additives are considered. The bibliography includes articles published during the last five years. Friction 7(2): 93-116 (2019) | https://mc03.manuscriptcentral.com/friction Friction 7(2): 93-116 (2019) 97 |www.Springer.com/journal/40544 | Friction http://friction.tsinghuajournals.comFriction 7(2): 93-116 (2019)

Several important synthesis pathways for metal-organic frameworks (MOFs) were applied to determine how the synthesis methods and conditions affect the structure and adsorption capacity of the resulting samples. In the present work, three different synthesis routes were used to obtain copper trimesinate coordination polymer: Slow evaporation (A), solvothermal synthesis using a polyethylene glycol (PEG-1500) modulator (B), and green synthesis in water (C). This MOF was characterized by elemental analysis, infrared spectrometry, X-ray diffraction, scanning electron microscopy, thermogravimetry and volumetric nitrogen adsorption/desorption. The samples have permanent porosity and a microporous structure with a large surface area corresponding to the adsorption type I. The obtained MOF was tested as a sorbent to remove organic dyes methylene blue (МВ), Congo red (CR) and methyl violet (MV) as examples. Dye adsorption followed pseudo-first-order kinetics. The equilibrium data were fitted to the Langmuir and Freundlich isotherm models, and the isotherm constants were determined. Thermodynamic parameters, such as changes in the free energy of adsorption (∆G0), enthalpy (∆H0), and entropy (∆S0), were calculated. Thermolysis of copper trimesinate leads to the formation of carbon materials Cu@C with a high purity.

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Over the last decades, conjugated thermolysis of metal chelate monomers (MCMs) has been widely used to produce various metal and metal oxide nanostructures. In the present study, a detailed analysis of the conjugate thermolysis of MCM based on cobalt(II) acrylate (Acr) complexes with 2,2′‐bipyridine (bpy) and 1,10‐phenanthroline (phen) was carried out. The main stages and kinetics features of conjugated thermolysis of MCMs are estimated. Metal‐polymer nanocomposites containing metal nanoparticles (NPs) uniformly distributed in a stabilizing nitrogen‐containing polymer matrix and Co3O4 NPs are obtained depending on the conditions of conjugated thermolysis. The composition, structure and properties of the nanomaterials obtained were studied using X‐ray diffraction (XRD), IR spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS) and thermal analysis (TA). Analysis of Co3O4 NPs as lubricant additives was carried out in the perspective of their tribological behavior using a pin‐on‐disc tribometer. At an optimum concentration of NPs, the coefficient of friction is the lowest. When the level of NPs increases above the optimum level, the coefficient of friction increases. With an increase in the load to 196 N, the coefficient of friction decreases with increasing concentration.