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In this work, a facile two-step method for the synthesis of highly thermal conductive expanded graphite (EG) was proposed. A binary component system of ammonium persulfate and concentrated sulfuric acid was prepared for the synthesis of EG from natural graphite flakes in which the former one acted as an oxidizing agent and the latter one used as an intercalating agent. Further, the silane functionalization of EG (mEG) was purposefully completed, as confirmed from the X-ray diffraction and Fourier transform infrared spectroscopy analysis. Epoxy-based thermal interface materials (TIMs) were fabricated with reinforcing EG and mEG by stir-casting method at different filler fraction. The guarded heat flow meter method indicated that the enhancement in thermal conductivity (TC) was 12.12-fold at 10 wt% loading of mEG (mEG10-Ep) than neat epoxy. The binding strength of mEG10-Ep composite tuned to 6.18 ± 0.8 MPa and determined by a single lap shear test, which confirms better reinforcing effect of silane functionalized EG than neat EG counterpart. The same was also corroborated from porosity evaluation of the composite system. At 50% weight loss in nitrogen atmosphere, thermogravimetric analysis revealed that the composite was stable up to 430°C. Dynamic mechanical analysis was engaged to estimate the glass transition temperature (T g) of the epoxy composite system, which validates its prospective application as preferred TIMs in the electroactive device. The electrical conductivity of composite was deteriorated due to the encapsulation of EG with nonconductive silane functional groups. The uniform dispersion was achieved by mEG-filled composite as compared to its EG counterpart, which was visualized from fracture surface through scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membranes (PEMs) of sulfonated polysulfone (SPSf) and sulfonated montmorillonite (SMMT) have been developed. Sodium montmorillonite (NaMMT) has been sulfonated with 4-sulfophthalic acid and incorporated into the SPSf matrix for further enhancement of proton conductivity. Sulfonation of NaMMT has been confirmed using Fourier transform infrared spectroscopy and X-ray diffraction (XRD) analysis. The XRD patterns proved that the SMMT layers were completely exfoliated within the SPSf matrix. The performances of the PEM in terms of their liquid uptake, oxidative stability, and proton conductivity were investigated. The morphological characterizations have been carried out using scanning electron microscopy and atomic force microscopy. SPSf/SMMT membrane with 5 wt% of SMMT loading showed adequate thermal stability and an improved proton conductivity. The reduction in methanol permeability from 8.9 ×10−5 cm2 s−1 to 2.4 × 10−5 cm2 s−1 has been observed when SMMT loading content increased from 1 wt% to 5 wt%. Direct methanol fuel cell (DMFC) performance showed a power density value of 49 mW cm−2for SPSf/SMMT membrane, indicating its candidature for DMFC applications. [ABSTRACT FROM AUTHOR]