CaWO_4: Eu³⁺ nanoparticles in acidity (pH = 5) and alkalinity (pH = 10) solutions were prepared by citric acid method, and characterised by SEM and XRD. Tribological behaviour and lubrication performances of nano-CaWO₄:Eu³⁺ as extreme pressure (EP) additives in water-soluble fluid for laminated copper cladding steel sheet during cold rolling were studied. These results suggest that CaWO₄:Eu³⁺ exhibits excellent extreme pressure property, antiwear and antifriction performances in water-soluble fluid, especially when the optimal concentration was 0.3 wt%. The value of WSD reduced from 0.62 to 0.40 mm and the value of COF decreased from 0.078 to 0.068, the surface quality of rolled sheet is improved with the addition of nano-CaWO₄:Eu³⁺ (pH = 5 and pH = 10), because the tribofilm (~20 nm) composed of Fe₂O₃, WO₃, Eu₂O and CaO was formed on the worn surface to avoid direct contact between metal friction pairs in sliding process.

中文翻译：

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纳米 CaWO4:Eu3+ 极压添加剂的制备、摩擦学性能及润滑性能在层压铜包钢冷轧水溶性流体中的应用

采用柠檬酸法制备了酸性(pH=5)和碱性(pH=10)溶液中的CaWO _4: Eu ^{3+纳米粒子，并通过SEM和XRD对其进行了表征。}研究了纳米CaWO ₄ :Eu ³⁺作为极压(EP)添加剂在叠层覆铜钢板冷轧水溶性流体中的摩擦学行为和润滑性能。这些结果表明CaWO ₄ :Eu ³⁺在水溶性流体中表现出优异的极压性能、抗磨和减摩性能，尤其是在最佳浓度为 0.3 wt% 时。WSD值从0.62降低到0.40 mm，COF值从0.078降低到0.068，加入纳米CaWO ₄ :Eu ³⁺ (pH = 5 and pH = 10)提高了轧制板的表面质量，因为在磨损表面形成了由Fe ₂ O ₃、WO ₃、Eu ₂ O和CaO组成的摩擦膜（~20 nm），避免了滑动过程中金属摩擦副之间的直接接触。