Deep eutectic solvents (DESs) serve as functionalized solvents with superior lubricating properties. However, limited research has been conducted on their application for modifying and treating nanomaterials as nonpolar lubricant additives. Consequently, this paper presents the synthesis of a menthol/thymol/tetradecylphosphonic acid oil-soluble ternary DES, which was employed to modify and treat MXene. The DES facilitates the expansion of MXene's interlayer spacing, while the grafting of long carbon chains in the DES enhances the dispersion stability of MXene in nonpolar lubricants. Furthermore, the tribological properties of DES complexed MXene lubricant additives were examined, revealing a reduction in the coefficient of friction and wear rate by 46.6 and 56.8% for both 0.1 wt % DES/MXene and 2 wt % DES base oil at 25 degrees C, and by 40.3 and 48.1% at 100 degrees C, respectively. The superior lubrication performance is attributed to optimal dispersion stability, exceptional wettability, and the synergistic impact of the dual lubrication film created by DES and the interlayer shear mechanism of MXene.

In this paper, we review recent research developments regarding the tribological performances of a series of inorganic nano-additives in lubricating fluids. First, we examine several basic types of inorganic nanomaterials, including metallic nanoparticles, metal oxides, carbon nanomaterials, and "other" nanomaterials. More specifically, the metallic nanoparticles we examine include silver, copper, nickel, molybdenum, and tungsten nanoparticles; the metal oxides include CuO, ZnO, Fe3O4, TiO2, ZrO2, Al2O3, and several double-metal oxides; the carbon nanomaterials include fullerene, carbon quantum dots, carbon nanotubes, graphene, graphene oxides, graphite, and diamond; and the "other" nanomaterials include metal sulfides, rare-earth compounds, layered double hydroxides, clay minerals, hexagonal boron nitride, black phosphorus, and nanocomposites. Second, we summarize the lubrication mechanisms of these nano-additives and identify the factors affecting their tribological performance. Finally, we briefly discuss the challenges faced by inorganic nanoparticles in lubrication applications and discuss future research directions. This review offers new perspectives to improve our understanding of inorganic nano-additives in tribology, as well as several new approaches to expand their practical applications.

In this study, polydopamine-modified graphene oxide (PGO) nanomaterials were prepared based on the self-polymerization of dopamine in a weakly alkaline environment. In the friction experiment, the lubricants with 0.15 wt% PGO nanomaterials have optimal friction properties. Subsequently, X-ray photoelectron spectroscopy (XPS), X-ray energy spectroscopy (EDS), and laser Raman spectroscopy were performed on the wear scar. Compared to pure oil, the friction coefficient was reduced by 31%, and the trace width was reduced by 47.69%. In addition, molecular dynamics simulations showed that PGO has the lowest diffusion coefficient among n-hexadecane and the interaction energy between PGO and n-hexadecane molecules was the largest, and oil droplets containing PGO exhibited the best adsorption performance on the surface of the Si3N4/GCr15. The results showed that compared with other additives, PGO as a lubricant additive can play a significant role in reducing friction and anti-wear.

In this study, we successfully synthesized CD@CuCo-MOF composites, which are composed of ultrathin twodimensional (2D) nanosheets of metal-organic framework (MOF) doped with carbon dots (CDs). The synthesis process involved hydrothermal and ultrasonically assisted self-assembly with a proper solvent ratio. The composites were then dispersed into pentaerythritol ester (PETE) with the aid of ultrasonic treatment. We thoroughly evaluated the physicochemical features and tribological properties of the CD@CuCo-MOF composites using advanced testing and characterization techniques including XRD, Raman, FTIR, TG, XPS, FIB-TEM and so on. The results demonstrated that the addition of CD@CuCo-MOF resulted in a 61.1 % reduction in the coefficient of friction (COF) at a concentration of 0.1 wt% when compared to the base oil at room temperature. With the rise in temperature, CD@CuCo-MOF exhibited excellent lubricating properties due to its hybrid inorganic-organic structure and interlayer sliding effect. This led to a reduction of 59.2 % and 42.9 % in the mean COF compared to PETE oil at temperatures of 100 degrees C and 200 degrees C. This enhancement in the tribological performance of CD@CuCo-MOF could be attributed to several factors, including its superior dispersion stability, excellent lubricating properties, and involvement in the formation of a tribofilm. The tribofilm formed from a combination of CDs, CuCo-MOF, metal oxides, carbides, and nitrides promoted the rearrangement of the contact surface, thereby minimizing the friction and wear between the rubbing surfaces. These findings hold significant guiding implications for advancing the development of potential-controlled lubrication using MOFs doped with CDs across a wide temperature range.

As an efficient, safe, and environmentally friendly technology, semiconductor photocatalysis has been widely used in the removal of antibiotics from wastewater. In this work, a novel Ag/BiOI/g-C3N4 composite photocatalytic material, BiOI/g-C3N4, g-C3N4, and BiOI are prepared as the photocatalysts. The morphologies, chemical properties, and photocatalytic performances of the photocatalysts are characterized using scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectrometer, ultraviolet-visible spectroscopy (UV-Vis) diffuse reflectance spectra, and photoluminescence spectra. In addition, tetracycline hydrochloride (TC) and ceftiofur sodium aqueous solutions are used to simulate wastewater and the photocatalytic degradation performances of the photocatalysts are investigated and compared under visible light. Compared to g-C3N4, BiOI, and BiOI/g-C3N4, the Ag/BiOI/g-C3N4 demonstrates superior performance, increasing the removal rates of TC and ceftiofur sodium to 85.6% and 90.2%, respectively. The photocatalytic mechanism of the Ag/BiOI/g-C3N4 may involve the promotion of the visible light-harvesting ability and inhibition of the recombination of photogenerated electron/hole pairs. Furthermore, the primary active groups in the system are identified as superoxide radicals (& BULL;O-2(-)) and hydroxyl radicals (& BULL;OH). Herein, some valuable insights into the development of innovative photocatalytic materials are offered for the effective removal of antibiotics from water.

Purpose - The purpose of this study is to prepare ZnFe2O4 nanospheres, sheet MoS2 and three ZnFe2O4@MoS2 core-shell composites with various shell thicknesses, and add them to the base oil for friction and wear tests to simulate the wear conditions of hybrid bearings.Design/methodology/approach - Through the characterization and analysis of the morphology of wear scars and the elemental composition of friction films, the tribological behavior and wear mechanism of sample materials as lubricant additives were investigated and the effects of shell thickness and sample concentration on the tribological properties of core-shell composite lubricant additives were discussed.Findings - The findings demonstrate that each of the five sample materials can, to varying degrees, enhance the lubricating qualities of the base oil and that the core-shell nanocomposite sample lubricant additive has superior lubricating properties to those of ZnFe2O4 and MoS2 alone, among them ZnFe2O4@MoS2-2 core-shell composites with moderate shell thickness performed most ideally. In addition, the optimal concentration of the ZnFe2O4@MoS2 lubricant additive was 0.5 Wt.%, and a concentration that was too high led to particle deposition and affected the friction effect. Originality/value - In this work, ZnFe2O4@MoS2 core-shell composites were synthesized for the first time using ZnFe2O4 as the carrier and the lubrication mechanism of core-shell composites and single materials were compared and studied, which illustrated the advantages of core-shell composite lubricant additives. At the same time, the influence of different shell thicknesses on the lubricant additives of core-shell composites was studied.Peer review - The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2022-0367/

电主轴在工作时,因其转速较高会导致轴承产生振动噪声。轴承的振动噪声是评价其性能的核心指标。轴承噪声不仅直接影响主机的性能,其过大的噪声还会对人体造成噪声疲劳。滚动轴承的振动与其结构型式、表面效应、摩擦与润滑及工况条件有直接关系。其中因润滑不良而导致的摩擦噪声甚至会引起尖锐噪声。改善润滑油的润滑效果,能有效减少轴承运转时因摩擦振动而辐射的噪声。石墨烯纳米颗粒具有减摩抗磨性能,将其作为润滑油添加剂减少摩擦副的摩擦系数已经得到证实,研究石墨烯润滑油润滑条件下的轴承噪声特性,对提高主机的性能具有重要意义。本文选取GCr15/GCr15、Si3N4/GCr15、Si3N4/Si3N4三种轴承材料摩擦副模拟轴承,以表面粗糙度、相对运动速度、载荷、润滑油中石墨烯质量分数为变量,探究其对摩擦系数及摩擦噪声的影响。建立了石墨烯润滑条件下的轴承辐射噪声模型,并对石墨烯润滑油的作用机理进行讨论。最后以电主轴为实验平台,对石墨烯润滑条件下轴承的运转噪声进行测量与分析。结果表明,摩擦副的表面粗糙度越小,摩擦系数越小,摩擦噪声越小;相对运动速度提升时,摩擦副接触面处压力变低,油膜厚度增加,摩擦系数减少,但微凸体之间的冲击力变强,摩擦噪声提升;载荷提升时,摩擦副接触面处的微凸体产生塑性变形,在油膜的保护下摩擦系数降低,摩擦噪声也随之降低;使用石墨烯润滑油首先会对摩擦副间的摩擦系数产生影响,其次会在摩擦副接触面间形成一层边界润滑膜,起到缓冲物质的作用,减少了微凸体间的冲击力,进而有效降低摩擦噪声;通过对轴承辐射噪声模型的研究发现,石墨烯润滑油通过影响摩擦系数、接触刚度系数、阻尼系数、切入深度等因素,极大的影响了轴承部件间的接触力,进而降低轴承的运转噪声;从对轴承噪声的仿真结果来看,随着石墨烯质量分数的提高,轴承部件的辐射噪声整体呈现降低趋势;对石墨烯润滑条件下的电主轴运转噪声进行测量,从实验结果可以看出,添加石墨烯的润滑油能有效降低轴承的辐射噪声,质量分数为0.1%的石墨烯润滑油降噪效果最好。随着转速的提升,轴承部件接触点处的压力降低,油膜厚度增加。使摩擦副之间的石墨烯润滑膜变厚,提升了润滑效果,石墨烯润滑油的降噪效果也逐渐提升。

近年来,纳米材料作为润滑油添加剂得到广泛应用,石墨烯及氧化石墨烯因其独特的抗磨减摩特性也成为广大摩擦学学者的研究热点。然而作为润滑油添加剂,要想发挥良好的润滑性能,其在润滑油中的分散稳定性好坏至关重要。超声分散方法作为分散石墨烯润滑油的有效途径,其分散性能对于石墨烯润滑油的润滑效应具有重要意义。本文基于LAMMPS分子动力学模拟石墨烯及氧化石墨烯润滑油在超声环境中的分子运动轨迹,通过均方根位移方程,计算石墨烯及氧化石墨烯分子扩散系数,从微观角度揭示超声分散机理的同时,对比二者在不同超声条件下的分散效果。仿真结果表明:超声功率与环境温度的改变会影响石墨烯分子及氧化石墨烯分子在正十六烷烃分子中的运动状态。当超声功率为500W、环境温度为323K时,石墨烯分子的均方根位移曲线斜率最高。当超声功率与超声时间持续升高后,曲线斜率减小,扩散行为减弱;当超声功率为600W、环境温度为333K时,氧化石墨烯分子的均方根位移曲线斜率最高,当超声功率与超声时间持续升高后,曲线斜率减小,扩散行为减弱。实验通过ZOLLO-1000Y型号的超声波细胞粉碎机对石墨烯及氧化石墨烯润滑油进行不同超声功率与不同超声时间的超声分散。将超声试验后的石墨烯及氧化石墨烯润滑油进行Zeta电位测量,通过电位强度表征不同超声条件下的石墨烯及氧化石墨烯润滑油的分散稳定效果。并使用摩擦磨损试验机球面接触式旋转模块考察不同超声条件下的石墨烯及氧化石墨烯润滑油对GCr15/Si3N4摩擦副润滑及冷却性能的影响。通过扫描电镜对摩擦磨损试验后的试件磨痕表面进行表征。当石墨烯作为润滑油添加剂时,超声分散试验、Zeta电位测量试验、摩擦磨损试验及扫描电镜试验结果表明:石墨烯润滑油的分散稳定性与超声功率及超声时间在一定程度上呈正相关曲线。最佳超声条件为:超声时间为90min,超声功率为500W。且当超声时间超过90min,超声功率超过500W后,石墨烯润滑油的分散稳定性反而有所下降。该特性也正面影响石墨烯润滑油的润滑效果。当氧化石墨烯作为润滑油添加剂时,超声分散试验、Zeta电位测量试验、摩擦磨损试验及扫描电镜试验结果表明:氧化石墨烯润滑油在不同超声条件下获得的分散体系的分散稳定性与润滑效果均有所差异。最佳超声条件为:超声时间为105min,超声分散功率为600W。此时分散体系的分散效果最好,且润滑效果也最佳。本文研究表明,超声分散方法不但可以改善石墨烯及氧化石墨烯润滑油的分散稳定效果,而且不同超声条件下的超声分散可以不同程度的影响分散体系的分散效应。主要是因为石墨烯及氧化石墨烯分子比表面积大,且易团聚沉淀。一定程度的超声分散,可以减弱石墨烯及氧化石墨烯分子表面能,从而使其扩散开。但长时间且大功率的超声分散,又会破坏石墨烯及氧化石墨烯的表面形态,使其发生弯曲、折叠等现象,反而会导致石墨烯及氧化石墨烯分子发生重新团聚沉淀的行为。

摩擦在日常生活及工业生产中不可避免,近年来新型纳米物质由于具有优异的摩擦学特性在摩擦学领域有着广泛的应用。如果用石墨烯润滑油代替传统润滑油对机床进行润滑,会明显降低机床由于摩擦导致的磨损以及产热量,进一步减小设备的热变形,提高机床加工精度和工作效率。但石墨烯由于独特的六元苯环结构,原子之间有很强的范德华力,使其难以被打断极易团聚,造成石墨烯在基础油中的溶解性很差,不仅难以发挥石墨烯自身的优异性能,而且会造成机床的损害和环境污染。本研究采用离子液体作为石墨烯润滑油改性剂,构建离子液体/石墨烯润滑油体系,解决石墨烯分散性差的问题,并研究其分散稳定性及摩擦学行为。主要研究内容如下:（1）利用MS仿真软件,通过分子动力学与量子化学结合的方法计算不同离子液体下的石墨烯润滑油中石墨烯和正十六烷烃(C16H34)之间的范德华力、均方根位移、分散度以及离子液体与石墨烯相互作用体系的电子特性,揭示离子液体对石墨烯润滑油的微观分散机理。结果表明,咪唑类离子液体由于其本身的环状结构容易与石墨烯片层表面形成Π-Π相互作用,将电荷转移到石墨烯上,从而产生静电排斥力。（2）通过实验验证仿真,将离子液体加入石墨烯润滑油中,通过考察离子液体浓度、种类、超声条件等因素,结果发现,超声时间60min、超声功率600w的咪唑类离子液体/石墨烯润滑油的分散稳定性较石墨烯润滑油均有显著提高。（3）利用MS仿真软件通过分析润滑油与摩擦副之间的范德华能、剪切应力、类固膜厚度以及膜厚上的温度分布等几个方面来探究不同种类的离子液体/石墨烯润滑油在Si3N4-GCr15摩擦副上的吸附作用。结果表明加入离子液体之后,润滑体在氮化硅及轴承钢表面的吸附能增加。且咪唑类的离子液体/石墨烯润滑油形成的类固膜厚度与摩擦副之间的范德华力均高于季磷盐类离子液体。咪唑类离子液体与上下壁面有较低的剪切应力。（4）为验证仿真中得到的结论,本文通过对不同条件下的离子液体/石墨烯润滑油摩擦磨损试验。并利用摩擦系数表征各超声条件的离子液体/石墨烯润滑油的润滑效果。结果显示,由于离子液体的分散作用,导致石墨烯在润滑油中分散的较为均匀,离子液体与石墨烯一起作用,会在摩擦副之间形成混合油膜,避免了由于摩擦副直接接触而造成表面磨损。且咪唑类离子液体/石墨烯润滑油润滑效果更好,与石墨烯润滑油相比摩擦系数减小30%左右。向石墨烯润滑油中加入离子液体不但改善了石墨烯容易团聚的问题,而且离子液体由于其本身的自润滑特性有效的提高了石墨烯润滑油的润滑特性。在摩擦学领域虽然对离子液体的研究还位于起步的阶段,但离子液体一定会凭借着自身优异的属性与石墨烯一起成为最具前景的新型复合润滑材料。

Carbon quantum dots (CQDs) doped with silver (Ag-CQDs) was prepared using a facile hydrothermal method. With the combination of ultrasound vibration and ionic liquid (IL), the dispersion stability of the Ag-CQDs additive in poly alpha olefin (PAO) was improved. The tribological performance of the CQDs and Ag-CQDs as additives over a wide temperature range were evaluated through four-ball tests and a ball-on-disk reciprocating configuration. The four-ball test results revealed that the CQDs and Ag-CQDs additives could effectively reduce the coefficient of friction (COF) of the base oil and wear scar diameter (WSD) of lower balls. When the concentration was 0.05 wt%, the Ag-CQDs additive could lead to 42.2% lower COF and 35.3% lower WSD than the base oil. Meanwhile, the tribological performance at elevated temperatures results revealed that the CQDs and Ag-CQDs additives could substantially decrease friction and wear when the ambient temperature was above 200 degrees C. The Ag-CQDs exhibited better lubricating performance than the CQDs. The lubricating mechanism was attributed to the formation of a tribofilm composed of Ag-CQDs, multicomponent oxides, carbonates and nitrides induced by tribochemical reactions, which provided effective protection for the rubbing pair and maintained low friction and wear.