R Velmurugan

The current study focuses on reusing spent catalysts and fly ash, presenting an interesting and intriguing topic for the researchers. The waste catalyst and fly ash from the petroleum and coal industries were initially considered hazardous. One of the most common approaches to recycling spent catalyst and fly ash involves incorporating them into the aluminum matrix to improve the mechanical behaviour for specific applications. This study uses pure aluminum as the matrix material for synthesizing a hybrid composite using an ultrasonic-aided squeeze casting technique. The spent catalyst and fly ah particles were ball-milled before being utilized as reinforcing particles with varying concentrations (2 wt% and 4 wt%) and mean particle sizes of 221.75 nm and 201.25 nm, respectively. The microstructure and mechanical behaviour of the aluminum composites produced using both reinforcements were investigated and compared. The scanning electron microscope (SEM) analysis shows that using ultrasonic treatment in squeeze casting improves the uniform dispersion of the reinforcement nanoparticle. The optical microscope shows that incorporating nanoparticles, coupled with intensive ultrasonic treatment, reduces the grain size of α-Al dendrites. Energy dispersive X-ray analysis (EDAX) and X-ray diffraction (XRD) indicate that the fabricated nanocomposite is free from impurities, contaminants, and oxide formations. The hardness, compressive, and tensile tests were conducted on the prepared aluminum composites. The overall results show that Al+2 wt% spent catalyst+2 wt% fly ash composite improves hardness, tensile, and compressive strength by 98.55 %, 43.24 %, and 29.24 %, respectively, compared to the base pure aluminum. The strength of the aluminum composites has been evaluated using various strengthening mechanism techniques. The strengthening contributions are primarily due to the temperature mismatch between the waste reinforcement nanoparticles and the aluminum matrix. It is well known that metal-based composites strengthen dispersion, in which the dispersed particles hinder dislocation motion and significantly increase the composite strength.

The primary concerns in the adhesive bonding of metal substrate surfaces include inadequate wettability, compatibility, and insufficient mechanical interaction at the bonding interface. These factors are significant barriers to developing and manufacturing high-strength bonded materials. This study utilized three different anodising techniques, such as H3PO4, H2SO4, and NaOH, to produce micro-rough surfaces that improve the adhesive bond between aluminium alloy and mild steel. A novel and a simple method known as resin pre-coating (RPC) were used to increase the wetting and effectively seal the micro-cavities of mild steel and aluminium surfaces. RPC solution comprises 10 wt% resin (Absence of hardener) and 90 wt% acetone, which facilitated the penetration of resin into the microcavities surface, thereby increasing the bonding surfaces. Subsequently, the normal adhesive mixed with hardener is placed onto the metal surfaces. The adhesive bonding strength was evaluated by conducting the single lap shear test under various surface conditions. The surface topography of anodised samples were examined by X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), and Contact Angle Goniometer. Experimental results of a lap shear test revealed that the adhesive bond strength of H3PO4 anodised samples is greater than those of H2SO4 and NaOH anodised samples. Furthermore, the RPC treatment increased the bond strength of all H3PO4 anodised samples by 46.91–47.26 %, for H2SO4 samples by 39.71–42.22 %, and NaOH samples by 37.89–48.51 %, compared to the readings obtained without RPC treatment. The combined use of H3PO4 and RPC treatment results in the greatest bonding strength of 16.765 MPa, which is 9.17 % and 20.10 % greater than the bonding strength of H2SO4 and NaOH anodised samples. Thus, the H3PO4 anodised method improved the wetting ability of the metal surface and maximized the use of contact area on the rough substrate surfaces. The anodising treatment details in this study are inexpensive and simple for creating strong adhesive joints in aviation, automobile, and aerospace applications.