Volume 48, No 2, 2026, Pages 366-378
Download full text in PDFComposition-Dependent Stability and Tribological Performance of Biodiesel-Derived Hybrid TiO2/MoS2 Tribofluids Based on a Peltophorum pterocarpum and Waste Cooking Oil Methyl Ester Blend
Authors:
T. Dayananda Murthy 
,
H. Yogish ,
N.S. Kumaraswam ,
R. Pavankumar
DOI: 10.24874/ti.2190.04.26.06
Received: 23 April 2026
Revised: 15 May 2026
Accepted: 1 June 2026
Published: 15 June 2026
Abstract:
This study evaluates TiO₂-, MoS₂-, and hybrid TiO₂/MoS₂ nanoparticles as additives for a characterized 50:50 Peltophorum pterocarpum methyl ester:waste cooking oil methyl ester base fluid. The base fluid was dominated by methyl oleate, methyl linoleate, and methyl palmitate and had an acid number of 0.27 mg KOH/g, water content of 318 mg/kg, and oxidation stability of 4.7 h. A two-stage design screened additives at 0.05 wt.% and then optimized the 25:75 TiO₂:MoS₂ hybrid from 0.025 to 0.10 wt.%. Tribofluids with 0.20 wt.% Span 80 were assessed by density, viscosity, apparent zeta potential, sedimentation, four-ball testing, and SEM/EDS. The 0.05 wt.% 25:75 hybrid gave the best batch-specific response, with apparent zeta potential of -45.7 ± 1.1 mV, 60 d sedimentation index of 2.5 ± 0.2%, coefficient of friction of 0.049 ± 0.001, wear scar diameter of 0.51 ± 0.01 mm, and comparative wear-rate index of 3.10 ± 0.08 × 10⁻⁶ mm³/N·m. Friction, wear scar diameter, and wear-rate index decreased by 43.0%, 28.2%, and 40.4% relative to the base fluid. SEM/EDS indicated smoother tracks and more uniform Ti/Mo/S-associated signals than the overloaded 0.10 wt.% formulation. The optimum applies to this batch and preparation route.
Keywords:
Biodiesel tribofluid, TiO2/MoS2 hybrid nanoparticles, Peltophorum pterocarpum, Waste cooking oil, Dispersion stability, Four-ball tribology, Wear reduction
