Automotive and Tractors Engineering Department, Faculty of Engineering, Minia University, El-Minia 61519, Egypt; Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China; Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan 430070, China.
Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China; Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan 430070, China.
J Colloid Interface Sci. 2020 Oct 15;578:24-36. doi: 10.1016/j.jcis.2020.05.092. Epub 2020 May 30.
Nanomaterials stabilization in lube oils poses an acute challenge in nanolubricants/nanofluids formulation. This study aims to improve the dispersion stability of copper (Cu) nanomaterials in polyalphaolefin-6 (PAO6) oil to overcome the agglomeration/sedimentation problem. Here, we modified the surface of Cu nanomaterials using bis(2-ethylhexyl) phosphate (IL) to enhance the electrostatic repulsion force in Cu nanomaterials. We evaluated the dispersion behavior of Cu nanolubricants by visual observation, ultraviolet-visible spectroscopy, dynamic light scattering, and zeta potential measurements. Furthermore, we determined the rheological and thermo-oxidation behavior of Cu nanolubricants using Brookfield viscometer, thermogravimetric, and Fourier transform infrared. Our experiments showed that dispersion stability depends on Cu concentration and settling time. IL demonstrated effective miscibility when blended with PAO6 oil and displayed non-Newtonian behavior. The results suggest that Cu modified by IL provides superior dispersion in PAO6 oil without sedimentation for 60 days, compared to unmodified Cu. Moreover, the hydrodynamic diameter of the modified Cu did not exceed 240 nm even after 60 days of preparation. The excellent dispersion behavior can be ascribed to the domination of the electrostatic repulsion forces over the inter-nanomaterials van der Waals interactions, which is related to the formation of the electrical adsorption layer on the Cu surface. The obtained colloidal dispersions have the potential to be utilized as green nanolubricants for lubricating tribological systems.
纳米材料在润滑油中的稳定存在是纳米润滑剂/纳米流体配方中一个亟待解决的问题。本研究旨在提高铜（Cu）纳米材料在聚α烯烃-6（PAO6）油中的分散稳定性，以克服团聚/沉降问题。在这里，我们使用双（2-乙基己基）磷酸酯（IL）对 Cu 纳米材料的表面进行改性，以增强 Cu 纳米材料中的静电排斥力。我们通过目视观察、紫外-可见光谱、动态光散射和zeta 电位测量来评估 Cu 纳米润滑剂的分散行为。此外，我们还使用 Brookfield 粘度计、热重分析仪和傅里叶变换红外光谱仪来测定 Cu 纳米润滑剂的流变和热氧化行为。我们的实验表明，分散稳定性取决于 Cu 浓度和沉降时间。IL 与 PAO6 油混合时表现出有效的混溶性，并表现出非牛顿行为。结果表明，与未改性的 Cu 相比，用 IL 改性的 Cu 在 PAO6 油中具有更好的分散性，在 60 天内没有沉降。此外，即使在制备 60 天后，改性 Cu 的水动力学直径也没有超过 240nm。优异的分散行为可归因于静电排斥力对纳米材料间范德华相互作用的主导作用，这与 Cu 表面形成的电吸附层有关。所得胶体分散体有望用作润滑摩擦系统的绿色纳米润滑剂。
