In this article, we report the development of a polyacrylonitrile-graphene oxide-silicon dioxide (PAN-GO-SiO2) hybrid membrane for separation of oil and water from their emulsified mixture. The membrane was successfully fabricated using a one-step electrospinning process. GO and SiO2 nanofillers were added in PAN in different concentrations to determine the optimized composition for the PAN-GO-SiO2 hybrid membrane. A scanning electron microscopy (SEM) examination showed that the nanofillers were uniformly embedded in the nanofibrous structure of the electrospun hybrid membrane. The GO was mainly embedded inside the PAN nanofibers, causing knots while SiO2 nanoparticles were found embedded on the nanofiber surface, resulting in the formation of micro-nano protrusions on the fiber surface. The formation of these hierarchical structures, together with enhanced hydrophilicity due to oxygen containing groups on both SiO2 and GO, resulted in a high rejection (>99%) of oil from oil-water emulsion. Membrane performance evaluation under gravity separation tests showed that the separation flux and phase rejection was enhanced with the incorporation of nanofillers. The inclusion of nanofillers also enhanced the mechanical properties of the membrane. The best flux and phase separation performance was obtained for an optimized concentration of 7.5 wt % SiO2 and 1.5 wt % GO in PAN. The flux of separated water was enhanced from 2600 L m−2 h−1 for pristine PAN to 3151 L m−2 h−1 for PAN-GO-SiO2. The hybrid membrane also showed good mechanical and chemical stability, and antifouling propensity.

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Friction stir processing (FSP) technology has received reasonable attention in the past two decades to process a wide range of materials such as aluminum, magnesium, titanium, steel, and superalloys. Due to its thermomechanical processing nature, FSP is used to alter grain structure and enhance mechanical and corrosion behavior in a wide range of steels. The refinement in grains and phase transformations achieved in steel after FSP affects hardness, tensile properties, fracture toughness, fatigue crack propagation rate, wear resistance, and corrosion resistance. A number of review papers are available on friction stir welding (FSW) or FSP of nonferrous alloys. In this article, a comprehensive literature review on the FSP/FSW of different types of steels is summarized. Specifically, the influence of friction stir processing parameters such as advancing speed, rotational speed, tool material, etc., on steels’ performance is discussed along with assessment methodologies and recommendations.

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