边界润滑状态下水合阴离子的宏观超润滑性,ACS Applied Materials & Interfaces

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边界润滑状态下水合阴离子的宏观超润滑性
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2023-08-25 , DOI: 10.1021/acsami.3c09277
Tianyi Han ₁ , Mingbo Zhao ₁ , Chuan Sun ₁ , Ruiqi Zhao ₁ , Wanxing Xu ₁ , Shumin Zhang ₂ , Sudesh Singh _{1,

3} , Jianbin Luo ₁ , Chenhui Zhang ₁

Affiliation

由于电荷周围有水化壳组成的边界层，阳离子在微观和宏观条件下都可以在光滑界面上实现优异的水化润滑，但阴离子呢？常用的摩擦副在固/溶液界面处带负电。通过构建带正电的表面实现阴离子吸附是研究阴离子水化润滑的先决条件。在这里，我们报道了在pH低于等电点的酸性电解质溶液中，由吸附在带正电的聚合物/蓝宝石界面上的阴离子组成的水化层，这有助于阴离子的水化润滑。_{强水合阴离子（对于 SO 4}^2–的情况）表现出与阳离子相当的稳定超润滑性，在接触压力高于 15 MPa 且无需磨合期的情况下，边界摩擦系数极低，为 0.003-0.007。阴离子的水化润滑性能由基于表面电位和摩擦学实验的离子水化强度和离子吸附密度决定。研究结果揭示了阴离子在超润滑和水化润滑中的作用，这可能有助于理解酸性环境中的润滑机制和改善润滑性能，例如在酸性泵、处理酸性介质的压缩机密封环和加工中核废料装置。

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Macroscale Superlubricity of Hydrated Anions in the Boundary Lubrication Regime

Cations can achieve excellent hydration lubrication at smooth interfaces under both microscale and macroscale conditions due to the boundary layer composed of hydration shells surrounding charges, but what about anions? Commonly used friction pairs are negatively charged at the solid/solution interface. Achieving anionic adsorption through constructing positively charged surfaces is a prerequisite for studying the hydration lubrication of anions. Here we report the hydration layer composed of anions adsorbed on the positively charged polymer/sapphire interface at acidic electrolyte solutions with pH below the isoelectric point, which contributes to the hydration lubrication of anions. Strongly hydrated anions (for the case of SO₄^2–) exhibit stable superlubricity comparable to cations, with strikingly low boundary friction coefficient of 0.003–0.007 under contact pressures above 15 MPa without a running-in period. The hydration lubrication performance of anions is determined by both the ionic hydration strength and ion adsorption density based on the surface potential and tribological experiments. The results shed light on the role of anions in superlubricity and hydration lubrication, which may be relevant for understanding the lubrication mechanism and improving lubrication performance in acidic environments, for example, in acid pumps, sealing rings of compressors for handling acidic media, and processing devices of nuclear waste.

更新日期：2023-08-25

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