Tribochemical Transformation of Nano TiO₂ to Ilmenite on the Surface of Wearing Steel Parts: Antiwear Action of Nano TiO₂ as an Additive in Engine Oil

ABSTRACT

TiO₂ nanoparticles of average size about 20–30 nm were hydrothermally synthesized from TiCl₄ under mild acidic conditions. The nanoparticles were mixed with dispersant and base oil to give a partially transparent concentrate with 1.5 wt% of Ti content. The concentrate was dispersed in hexane and base oil to characterize, respectively, by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The concentrate was diluted with base oil to a parts per million level of Ti containing dispersion blends that were evaluated for wear and friction control performance. Nano TiO₂ containing fully formulated oil blend showed excellent load-bearing capability in Swingung, Reibung, Verschleiβ (SRV; oscillation, friction, wear) tests. Four-ball test results show that the wear scar diameter was considerably reduced to 0.30 mm for TiO₂-added blend compared to neat base oil (0.60 mm). The performance of TiO₂-added blend was comparable to secondary zinc dialkyl dithiophospate (ZDDP)-added blend under identical condition. Raman spectra of the worn surface on the tested ball revealed the presence of ilmenite (FeTiO₃) and no deposits of pure TiO₂.

KEYWORDS:

• Nano TiO₂
• antiwear additive
• greener additive
• illmenite
• Raman
• wear scar diameter
• SRV

Acknowledgements

The authors are thankful to the Indian Oil R&D Centre for the support and kind approval of our work. M.V. thanks the reviewers for their constructive and critical suggestions that led to the present form of this article.