Vegetable oils exhibit excellent lubrication properties owing to their polar functional groups, which are liable to adsorb on the metal surfaces to form adsorption film and tribofilm. Additionally, nanoparticles play significant roles in enhancing the tribological performances of base oils by means of forming a tribofilm between friction parts. However, little work has been done on clarifying the interaction of nanoparticles and vegetable oils in the film-forming process. In this paper, two varieties of lanthanum borate nanospheres with average diameters of 50 nm (named LBN-1) and 105 nm (named LBN-2) were synthesized. The morphologies, size distribution, and chemical compositions of the nanospheres were characterized using a scanning electron microscopy, dynamic light scattering, Fourier transform infrared, and X-ray diffraction. The tribological characteristics of soybean oils with lanthanum borate nanospheres were evaluated by a four-ball tribo-tester. The tribological performances of soybean oils were obviously improved by lanthanum borate nanospheres. The focused-ion beam/transmission electron microscope analyses results revealed a uniform tribofilm containing LBN-1 was formed, contributing to excellent friction-reducing and anti-wear performances. Whereas the tribofilm of soybean oil/LBN-2 was uneven in thickness and contained more wear debris. The outcome of this work provides significant insights into the tribofilm formation for metal surfaces lubricated with vegetable oils containing different sizes of lanthanum borate nanoparticles.

植物油由于其极性官能团而表现出优异的润滑性能，该极性官能团易于吸附在金属表面上以形成吸附膜和摩擦膜。另外，纳米颗粒通过在摩擦部件之间形成摩擦膜而在增强基础油的摩擦学性能中起重要作用。但是，在阐明纳米颗粒和植物油在成膜过程中的相互作用方面所做的工作很少。本文合成了两种平均直径分别为50 nm（命名为LBN-1）和105 nm（命名为LBN-2）的硼酸镧纳米球。使用扫描电子显微镜，动态光散射，傅立叶变换红外光谱和X射线衍射对纳米球的形貌，尺寸分布和化学成分进行了表征。用四球摩擦测试仪评估了硼酸镧纳米球与大豆油的摩擦学特性。硼酸镧纳米球明显改善了大豆油的摩擦学性能。聚焦离子束/透射电子显微镜的分析结果表明，形成了均匀的含LBN-1的摩擦膜，有助于降低摩擦和抗磨性能。大豆油/ LBN-2的摩擦膜厚度不均且含有更多的磨损碎屑。这项工作的结果为使用含有不同尺寸硼酸镧纳米粒子的植物油润滑的金属表面的摩擦膜形成提供了重要的见识。硼酸镧纳米球明显改善了大豆油的摩擦学性能。聚焦离子束/透射电子显微镜的分析结果表明，形成了含有LBN-1的均匀摩擦膜，有助于降低摩擦和抗磨性能。大豆油/ LBN-2的摩擦膜厚度不均且含有更多的磨损碎屑。这项工作的结果为使用含有不同尺寸硼酸镧纳米粒子的植物油润滑的金属表面的摩擦膜形成提供了重要的见识。硼酸镧纳米球明显改善了大豆油的摩擦学性能。聚焦离子束/透射电子显微镜的分析结果表明，形成了含有LBN-1的均匀摩擦膜，有助于降低摩擦和抗磨性能。大豆油/ LBN-2的摩擦膜厚度不均且含有更多的磨损碎屑。这项工作的结果为使用含有不同尺寸硼酸镧纳米粒子的植物油润滑的金属表面的摩擦膜形成提供了重要的见识。有助于实现出色的减摩和抗磨性能。大豆油/ LBN-2的摩擦膜厚度不均且含有更多的磨损碎屑。这项工作的结果为使用含有不同尺寸硼酸镧纳米粒子的植物油润滑的金属表面的摩擦膜形成提供了重要的见识。有助于实现出色的减摩和抗磨性能。大豆油/ LBN-2的摩擦膜厚度不均且含有更多的磨损碎屑。这项工作的结果为使用含有不同尺寸硼酸镧纳米粒子的植物油润滑的金属表面的摩擦膜形成提供了重要的见识。