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arXiv · 2506.16249

Nano-silica based Aqueous Colloidal Gels as Eco-friendly Thixotropic Lubricant

Arun Kumar·Vivek Kumar·Yogesh M. Joshi·Manjesh K. Singh
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Abstract

The environmental risks posed by traditional oil and grease-based lubricants can be significantly mitigated by adopting water-based alternatives engineered with superior rheological performance. In this work, we present a fundamentally new and environmentally sustainable aqueous thixotropic colloidal gel of silica nanoparticles formed in the presence of NaCl. We conducted a systematic and detailed investigation of their rheological and tribological characteristics. The tribological performance was evaluated against dry and water-lubricated conditions for steel-steel interface. Our experiments demonstrate that the tribological performance of the formulated nanoparticle gel can be optimized by tuning its rheological properties. A combination of super-low friction and negligible wear was observed. The friction coefficient reduced by up to 97.46% (from 0.63 to 0.016) compared to dry sliding, and by 97.04% (from 0.541 to 0.016) compared to water lubrication. Similarly, the specific wear rate decreased by up to 99.62% and 96.10% under dry conditions and water lubrication respectively. This performance is attributed to a thixotropic, chemically robust gel formed via van der Waals interactions between silica flocs, enabling self-repairing properties, continuous tribo-film formation, and a nano-bearing effect from silica nanoparticles. These attributes enable the gel to maintain and regain its structure during periods of non-shear while also forming a thin film with sufficiently low viscosity to slip into the interfacial contact zone and continuously replenish it with lubricant.

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Arun Kumar, Vivek Kumar, Yogesh M. Joshi, Manjesh K. Singh. 2025-06-19. Nano-silica based Aqueous Colloidal Gels as Eco-friendly Thixotropic Lubricant. https://arxiv.org/abs/2506.16249

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