Nanocomposite sheet based on ball-milled oil fly ash/SWCNT as an efficient, scalable, and low-cost thermoelectric material for power generation near room temperature

Nanocomposites based on carbon nanomaterials and polymers are promising candidates for low-cost, scalable thermoelectric (TE) materials. Nevertheless, their widespread adoption is still hindered by relatively low TE performance, high raw-material costs, and lengthy processing times. In this work, ball-milled nanoparticles (BMN) derived from oil fly ash are introduced as a new class of TE materials. Small amounts of poly(methyl methacrylate) (PMMA) were used as a binder, while single-walled carbon nanotubes (SWCNTs) were incorporated to enhance electrical conductivity through network formation, resulting in a free-standing nanocomposite sheet. The optimum composition for maximum TE performance was found to be BMN:PMMA:SWCNT = 15:1:0.5 (by weight). The optimized nanocomposite sheet exhibited an electrical conductivity of 18,000 S/m at 293 K and a Seebeck coefficient of approximately 28 μV/K, yielding a power factor of 14 μW/m·K 2 . Notably, the thermal conductivity was reduced from 0.314 W/m·K for pure BMN pellet to 0.140 W/m·K for the optimized sheet. Overall, this nanocomposite demonstrates superior TE performance compared with similar systems reported in the literature. The TE power output of both single-leg and π-type modules (0.5 × 12 × 14 mm) was evaluated. The single-leg module delivered 24 nW at a temperature difference (Δ T ) of 20 K and approximately 80 nW at Δ T = 40 K, while the π-type module generated nearly twice the power of the single-leg configuration. Owing to these attractive characteristics, the developed nanocomposite shows strong potential for TE device applications. • Nanocomposite sheet based on ball-milled oil fly ash/SWCNT has been produced. • This low-cost, scalable nanocomposite is found to be highly efficient TE material. • Poly (methyl methacrylate) was added as a binder to form a free-standing sheet. • At room temperature the power factor reached 14 μW/mK 2 . • The generated power from a small single module at ΔT = 40 K recorded ∼ 80 nW.