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N-doped graphene oxide quantum dots (NGOQDs) with MoS2 and Al2O3 nanocomposites were prepared by solvothermal method. The morphology and the composition and structure of the prepared composites were characterized by TEM, XRD, Raman, ATR-FTIR, and XPS. Tribological behavior of NGOQDs-MoS2 and NGOQDs-Al2O3 nanocomposites as lubricant additive in aqueous glycerol were studied. Through experiments and MD simulations, the tribochemistry-induced lubrication mechanism was disclosed. The results shows that the combination of NGOQDs and hydrated glycerol can significantly improve lubrication performance, and the addition of NGOQDs-MoS2 and NGOQDs-Al2O3 nanoparticles can further improve tribological properties. The formation of a tribofilm through tribochemical induced lubrication mechanism improves the wear resistance of metal surfaces. [ABSTRACT FROM AUTHOR]

Nano-BN/Si and BN/Al2O3 composite lubricants was prepared by a hydrothermal stirring synthesis method. Orthogonal experiments were conducted by changing the mass fraction of Si and Al2O3. The extreme pressure and wear resistance performance of nano-BN lubricants were investigated using the four-ball machine method. The effect of nano-BN on the friction and wear performance of AlN plates was studied using multifunctional friction and wear tests. SEM, EDS, and XPS were used to characterize the wear morphology and element distribution on the wear surface of the steel balls and the sliding AlN plates. The wear and friction mechanism of nano-BN/Si and BN/Al2O3 as anti-wear additives contained in the nano-composite lubricants between the metal friction pairs were proposed. The excellent tribological performance of the BN composite lubricants is attributed to the synergistic effect between nano-Si particles or Al2O3 particles and layered nano-BN particles. This accelerates the formation of solid lubrication film composed of BN, Si, Al2O3, and Fe2O3 on the surface of the AlN plate, thus reducing the wear between friction pairs. [ABSTRACT FROM AUTHOR]

The powders of hBN, SiC, and B4C were employed as the raw ingredients to prepare the B4C–SiC–hBN composite ceramics by a vacuum high-pressure sintering method with hBN and SiC contents in the range of 0, 10, and 20 wt.%, respectively. A pin-on-disc testing equipment was used to assess the tribological properties of B4C–SiC–hBN composite ceramics with various hBN and SiC content when sliding against AISI 347 steel immersed in the emulsion. The experiment's findings indicate that the sliding COF of the B4C/AISI 347 steel pair marginally drops as the sliding distance increases. Besides, the sliding COF of the B4C–10 wt.% SiC–20 wt.% hBN/AISI 347 steel pair rapidly declines. By tribopairs of B4C–SiC–hBN composite ceramics against AISI 347 steel under the condition of lubrication by water-based emulsion, the steady-state friction may move into a state of mix lubrication as the hBN concentration rises, improving the tribological performance. The steady-state COF considerably decreases to 0.01 from 0.386 as the hBN and SiC concentration is increased to 20 wt.% and 10 wt.% from zero, showing a decreasing trend for both the B4C–SiC–hBN pin and AISI 347 steel disc samples' COWs. The steady-state friction of tribopairs of B4C–SiC–hBN composite ceramics against AISI 347 steel may enter a state of mixed lubrication in the emulsion. The wear resistance of composite ceramics was improved by the addition of hBN and SiC particles because of their lubricating and reinforcing effects. These findings offer valuable insights into the design and development of advanced composite ceramics for various industrial applications that require improved tribological properties. [ABSTRACT FROM AUTHOR]

WO3:Eu3+ powder was prepared by microemulsion method with cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The prepared WO3:Eu3+ samples were wrapped with SiO2 by a coating method. The WO3:Eu3+@ SiO2 nanocomposites with the core-shell structure were prepared by controlling tetraethyl orthosilicate (TEOS) content (1, 3, 5 and 7%) and water–alcohol ratio (1:3, 1:1.5, 1:1 and 2:1). The structure, morphology and luminescence properties of the prepared WO3:Eu3+@ SiO2 samples were characterized by XRD, SEM, TEM and fluorescence spectra. The results show that the prepared WO3:Eu3+@SiO2 nanocomposites are spherical and granular, and the average particle size is below 100 nm. Under the condition of different TEOS contents, the strongest characteristic peak is located at 554 nm in the green light band at the excitation wavelength of 328 nm. Among the different water–alcohol ratio conditions, the prepared WO3:Eu3+@SiO2 nanocomposite has the strongest luminescence intensity at the water–alcohol ratio of 1:3, and the excitation wavelength is 328 nm. The excitation spectra measured at 612 nm have prominent characteristic peaks at 362, 394, 422, 465 and 499 nm, which correspond to the transition of 7F0→5D4, 7F0→5L6, 7F0→5D3, 7F0→5D2 and 7F0→5D1, respectively. [ABSTRACT FROM AUTHOR]

Tungsten trioxide (WO3) nanoparticles were prepared by the citric acid method, using ammonium paratungstate as the tungsten source, and doped with rare earth europium (Eu) under various pH values and Eu content. The microstructure, morphology, and luminescence properties of the prepared samples were characterized by XRD, SEM, and a fluorescence spectrometer. The results show that Eu3+ doped WO3 nanoparticles were successfully obtained by the citric acid method, the prepared nanoparticles were spherical and rhomboidal, and the average particle size of the prepared samples reached 56 nm. The excitation spectrum consisted of a series of linear excitation peaks in the range of 250–550 nm. The strongest excitation peak was located at 543 nm, which belongs to the 7F0 → 5D1 transition of Eu3+. [ABSTRACT FROM AUTHOR]

Purpose: WO3 particles were prepared by the sol-gel method. Tetraethyl silicate (TEOS) was used to obtain a SiO2-coated WO3 nanoparticle. Quantum chemical parameters of oleic acid, triethanolamine, glycerol and methyl pentane as dispersants were theoretically calculated. Tribological properties of SiO2/WO3 nanocomposite lubricant were carried out on an MRS-10A four-ball friction and wear tester. Design/methodology/approach: The purpose of this study is to investigate the preparation and tribological properties of SiO2/WO3 nanocomposite lubricant. Findings: The obtained SiO2-coated WO3 nanoparticle (nano-SiO2/WO3) with a particle size of about 70 nm. The calculated adsorption energy of triethanolamine on the surface of the steel ball is 554.6 eV, and triethanolamine is selected as the dispersant. The dispersion effect of SiO2/WO3 nanocomposite lubricant is good, which shows that triethanolamine oleate plays a good dispersion role in the preparation of lubricant, which is consistent with the calculation results of the adsorption capacity of dispersant. As a good auxiliary lubricant, SiO2 can improve the tribological properties and wear resistance of WO3. Originality/value: Nanocomposite lubricants have been the focus of research in recent years, which could greatly reduce energy consumption. And the SiO2/WO3 exhibited excellent lubrication performance as a lubricant additive. The lubrication mechanism of SiO2/WO3 nanocomposite lubricant is the synergistic lubrication mechanism of friction film lubrication and antifriction bearing. This study could provide a certain reference for the practical application of nanocomposite lubricants. [ABSTRACT FROM AUTHOR]

Eu-doped WO3 (WO3:Eu3+) nanoparticles were prepared by the Pechini method. Tetrabutyl titanate (TBOT) was used to prepare TiO2-encapsulated WO3:Eu3+ nanoparticles (TiO2@WO3:Eu3+). Microstructure and morphology of the prepared nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results show that the mean diameter of the TiO2@WO3: Eu3+ nano powder prepared at pH = 10 is the smallest, up to 50 nm. The tribological properties of the TiO2@WO3:Eu3+ as extreme pressure and wear resistance agents in water-based lubricant were investigated by a four-ball machine. The results showed that TiO2@WO3:Eu3+ exhibits excellent load-carrying capacity, anti-wear, and anti-friction properties in water-based lubricant, especially when the concentration of TiO2@WO3:Eu3+ was 0.4 wt%. The average wear scar diameter (WSD) was decreased from 0.62 to 0.34 mm and the coefficient of friction (COF) was reduced from 0.0721 to 0.053. This is mainly because of the formation of tens of nanometers thick tribofilm, the actual contact between metals is prevented. [ABSTRACT FROM AUTHOR]

Nano-WO3:EU3+ powder was prepared by Pechini method under acidic and alkaline condition, and the prepared acidic nano-WO3:Eu3+ mixed with the silver nanowires (AgNWs) in ethanol and acetone solution. The solution was mixed with PMMA and EP, respectively. Then, drops of the solutions were added to the indium tin oxide (ITO) conductive glass as the substrate; a AgNWs/WO3:Eu3+ composite film was obtained with spin coating by spin coater and solidification process. Microstructure, morphology, optical properties, preparation process and UV transmittance of the prepared nano-WO3:Eu3+ and AgNWs/WO3:Eu3+ composite films were investigated by XRD, SEM, fluorescence spectroscopy and UV spectrophotometer. The results show that the prepared acidic nano-WO3 is triclinic, and the average particle size is 71.63 nm. The prepared alkaline nano-WO3 is monoclinic, with an average particle size of 95.66 nm. Both of them have good luminescence properties. Under different monitoring wavelengths, in the emission range of 450–500 nm, it belongs to the green light region, and its excitation peak is the largest, indicating that green light is the best excitation light source for WO3:Eu3+ powder. The transmittance of EP/AgNWs/WO3:Eu3+ composite film is the highest when the spin coating time is more than 30 s and above 3000 rpm, no more than three layers spin coating and the content of curing agent is between 0.1 and 0.2 g. [ABSTRACT FROM AUTHOR]

Chambersite (Mn3B7O13Cl) precursor was prepared by the citric acid method, sodium borate dehydrate was used as a boron source, modified by cetyl trimethyl ammonium bromide (CTAB) as a surfactant, and its pH value was adjusted to 5 by ammonia. Mn3B7O13Cl nanoparticles were prepared by sintering at 500, 560, 600, and 650°C, respectively, and then ground by mortar. The microstructure, surface morphology, and luminescent properties of the prepared nano-Mn3B7O13Cl samples were analyzed by XRD, SEM, and fluorescence spectrometer. The effect of sintering temperature on the synthesis of manganese nano-Mn3B7O13Cl powder was studied. The prepared nano-Mn3B7O13Cl samples are spherical particles with irregular edges. When the sintering temperature is 650°C, the size of nanoparticles is the smallest, with an average size of 35 nm. When the excitation wavelength is 450 and 460 nm, the emission spectra of the nano-Mn3B7O13Cl samples prepared at different sintering temperatures have two emission peaks. There is a green emission peak at 550 nm and a red emission peak at 652 nm. When the excitation wavelength is 470, 480, and 490 nm, the emission spectra of the nano-Mn3B7O13Cl samples at different sintering temperatures have an emission peak in the range of green light band at 567, 589, and 601 nm, which is different from that at 450 nm and 460 nm. Under different excitation wavelengths, the emission peak intensity of the prepared nano-Mn3B7O13Cl samples sintered at 560°C is the highest, and the luminescence performance is better. The lowest emission peak and luminescence properties of the nano-Mn3B7O13Cl samples sintered at 500°C were studied. The excitation peak in the green band shifts to the orange band with increased excitation wavelength. The luminescence of the nano-Mn3B7O13Cl samples prepared at different sintering temperatures is the 4T1–6A1 transition of Mn2+ ion. [ABSTRACT FROM AUTHOR]

Genetic function approximation (GFA) algorithm was used to model the quantitative structure–activity relationship (QSAR) among corrosion inhibition efficiency, friction coefficient and oil film strength of the thiadiazole derivatives as corrosion inhibitor and antiwear and friction-reducing agent. Corrosion inhibition efficiency, friction coefficient and oil film strength of these compounds on the steel surface contained in the emulsion were studied by weight loss test and a fourball friction and wear test. The results show that quantum descriptors are a better choice for predicting the corrosion inhibition efficiency, friction coefficient and oil film strength of lubricants. For the thiadiazole derivatives, friction coefficient of the lubricants is inversely proportional to their inhibition efficiency and oil film strength. [ABSTRACT FROM AUTHOR]