Nano-capsuled thermal interface materials filler using defective multilayered graphene-coated silver nanoparticles

To increase the thermal conductivity of thermal interface materials (TIM), the selection of thermally conductive filler is crucial. In this study, defective graphene-coated silver nanoparticles (Ag NPs) were selected as TIM fillers with low electrical resistivity. Poly-vinylpyrrolidone (PVP) coated Ag NPs were fabricated by polyol process to be used as a precursor, while a multi-layer graphene (MLG) coated layer about 3–4 nm in thickness was formed on the surface of Ag NPs which is 95 nm through a chemical vapor deposition (CVD) process. For application as a metal TIM filler for MLG-coated Ag NPs, the thermal properties of MLG-coated Ag NPs with varying ratios of PVP solution added to the PVP-coated Ag NPs during CVD, were evaluated. Moreover, the peak for crystalline carbon was confirmed through XRD analysis at 26.207°, while the d-spacing was measured to be 3.40 Å. Through Raman analysis, the presence of D peak (1350 cm⁻¹), G peak (1590 cm⁻¹), and 2D peak (2850 cm⁻¹) proved the successful formation of defective MLG on the surface of Ag NPs. Finally, high thermal conductivity of 71 W/(m∙K) with electrical resistivity of 6.0 × 10⁻⁸ Ω∙m was obtained when adding 60 wt% PVP solution to PVP-coated Ag NPs during CVD, showing complete isolation among MLG-coated Ag NPs while PVP solution added less than 60 wt% did not prevent Ag NPs from coarsening, increasing its electrical resistivity. Therefore, nano-capsuled TIM fillers composed of defective MLG-coated Ag NPs with high thermal conductivities were obtained to demonstrate their potential for high-performance computing devices in thermal management.