In this research, polyethylene terephthalate (PET), as a high-density thermoplastic sheet, and Aluminum A5052, as a metal with seven distinct surface roughnesses, were joined by friction spot welding (FSW). The effect of A5052’s various surface states on the welding joining mechanism and mechanical properties were investigated. Friction spot welding was successfully applied for the dissimilar joining of PET thermoplastics and aluminum alloy A5052. During FSW, the PET near the joining interface softened, partially melted and adhered to the A5052 joining surface. The melted PET evaporated to form bubbles near the joining interface and cooled, forming hollows. The bubbles have two opposite effects: its presence at the joining interface prevent PET from contacting with A5052, while bubbles or hollows are crack origins that induce crack paths which degrade the joining strength. On the other hand, the bubbles’ flow pushed the softened PET into irregularities on the roughened surface to form mechanical interlocking, which significantly improved the strength. The tensile-shear failure load for an as-received surface (0.31 μ $\mathrm{m}$ R_a) specimen was about 0.4–0.8 kN while that for the treated surface (>0.31 μ $\mathrm{m}$ R_a) specimen was about 4.8–5.2 kN.

Ultrafiltration membrane technology holds promise for wastewater treatment, but its widespread application is hindered by fouling and flux reduction issues. One effective strategy for enhancing ultrafiltration membranes involves incorporating activated carbon powder. In this study, composite polyethersulfone (PES) ultrafiltration membranes were fabricated to include activated carbon powder concentrations between 0 and 1.5 wt.%, with carbon size fixed at 200 mesh. The ultrafiltration membranes were evaluated in terms of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, protein separation, and E-coli bacteria removal. It was found that the addition of activated carbon to PES membranes resulted in improvements in some key properties. By incorporating activated carbon powder, the hydrophilicity of PES membranes was enhanced, lowering the contact angle from 60° to 47.3° for composite membranes (1.0 wt.% of activated carbon) compared to the pristine PES membrane. Water flux tests showed that the 1.0 wt.% composite membrane yielded the highest flux, with an improvement of nearly double the initial value at 2 bar, without compromising bovine serum albumin rejection or bacterial removal capabilities. This study also found that the inclusion of activated carbon had a minor impact on the membrane’s porosity and equilibrium water content. Overall, these insights will be beneficial in determining the optimal concentration of activated carbon powder for PES ultrafiltration membranes.

Dissimilar materials joining between AZ31 magnesium alloy and SPHC mild steel with Al–Mg powder additives were successfully produced by the friction stir welding process. Al–Mg powder additives were set in a gap between AZ31 and SPHC specimen’s butt prior to welding. The experiments were performed for different weight percentages of Al–Mg powder additives at welding speeds of 25 mm/min, 50 mm/min, and 100 mm/min with a constant tool rotational speed of 500 rpm. The effect of powder additives and welding speed on tensile strength, microhardness, characterization across welding interface, and fracture morphology was investigated. Tensile test results showed a significant enhancement of tensile strength of 150 MPa for 10% Al and Mg (balance) powder additives welded joint as compared to the tensile strength of 125 MPa obtained for the welded joint without powder additives. The loss of aluminum in the alloy is compensated by the addition of the Al–Mg powder during welding under a suitable heat input condition identified by varying welding speeds. Microstructural analysis revealed that the Al–Mg powder was well mixed and dispersed at the interface of the joint at a welding speed of 50 mm/min. The intermetallic compound detected in the welding interface contributed to the welding strength.