Realizing the efficiency benefits of low viscosity lubricants requires novel strategies to avoid failures resulting from increased boundary contact. Zirconium dioxide (ZrO₂) nanoparticles (NPs) form protective tribofilms through tribosintering at lubricated contacts in pure hydrocarbon base oils, suggesting they hold promise for reducing boundary contact-induced failures. However, their tribological behavior alongside co-additives found in fully formulated oils has not been examined in depth. Here, the macroscopic tribological performance of dispersed ZrO₂ NPs (1 wt% loading; 5 nm diameter nearly spherical ZrO₂ tetragonal phase NPs with organic capping ligands for oil solubility) with and without the presence of co-additives found in fully formulated commercial gear oils was studied using a mini-traction machine (MTM). The results show that ZrO₂ NPs reproducibly develop surface-bound ~ 100 nm thick tribofilms on both contacting surfaces under a wide range of rolling-sliding contact conditions, from 0 to 100% slide-to-roll ratio. Steady-state traction coefficient values of ZrO₂ tribofilms formed alongside co-additives (0.10–0.11) do not substantially differ from ZrO₂ tribofilms formed in neat polyalphaolefin base oils (0.10–0.13). However, there is improvement in the tribological performance of the contact, with at least a twofold reduction of wear of the steel. This behavior is proposed to be a result of cooperating mechanisms, where the extreme pressure additives adsorbed on the steel surfaces protect them against early adhesive wear, during the time that a protective ZrO₂ tribofilm incorporating the co-additives forms on the steel surfaces, preventing further wear.

Graphic Abstract

中文翻译：

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二氧化锆纳米粒子和极压添加剂在形成保护性摩擦膜之间的协同作用：致力于实现低粘度润滑剂

要实现低粘度润滑剂的效率优势，就需要采取新颖的策略来避免因边界接触增加而导致的故障。二氧化锆（ZrO ₂）纳米颗粒（NPs）在纯烃基础油中的润滑接触处通过摩擦烧结形成保护性摩擦膜，表明它们有望减少边界接触引起的失效。但是，尚未对它们在全配方油中发现的与助剂一起的摩擦学行为进行深入研究。在这里，分散的ZrO ₂ NP的宏观摩擦学性能（1 wt％的负载；直径为5 nm的近似球形ZrO ₂使用微型牵引机（MTM）研究了在有机配方中发现和不存在共添加剂的有机封端配体的四方相NPs。结果表明，ZrO ₂ NPs可在宽范围的滑动滑动接触条件下（滑动比为0至100％）在两个接触表面上可重复形成约100 nm厚的表面结合的摩擦膜。的ZrO稳态牵引系数的值₂一起共添加剂（0.10-0.11）形成摩擦膜基本上不从不同的ZrO ₂纯聚α-烯烃基础油（0.10–0.13）中形成的摩擦膜。但是，接触件的摩擦性能得到了改善，钢的磨损至少减少了两倍。提议这种行为是由于协作机制的结果，在这种机制下，吸附在钢表面的极压添加剂可保护它们免受早期粘合剂的磨损，而在此过程中，在钢表面上形成了掺有共添加剂的ZrO ₂摩擦保护膜，可防止进一步磨损。

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