Papers by Author: Othman Mamat

Abstract: The present study aims to develop silica sand nanoparticles using the ball-milling process and to utilize these nanoparticles as reinforcement for iron-based metal matrix composites. Iron-based metal-matrix composites with 5, 10, 15 and 20wt.% of the processed silica sand nanoparticles were developed using powder metallurgy technique and sintered at 900°C, 1000°C and 1100°C. The results showed that the addition of silica sand nanoparticles to iron as reinforcement decreased the green density, albeit with an improvement in sintered densities. It was also observed that the increase in the sintering temperature results in an improvement of microstructure and microhardness of the composites. The maximum hardness of 168HV in iron-based composites was found with the addition of 20wt.% of silica sand nanoparticles at a 1100°C sintering temperature. It is proposed that the mechanism for the occurrence of this observed increment in microhardness is due to diffusion of silica sand nanoparticles into porous sites of the composites, resulting in the formation of FeSi phase.

Abstract: Tronoh silica sand was ground to nanoparticles using a ball mill and it was observed that the milling process increased the percentage purity of silica in silica sand. The size of the nanoparticles of silica sand was verified by using a ZetaSizer nanoparticles analyzer and FESEM analysis. The silica sand nanoparticles were used to develop and study the characterization and properties of metal, ceramic and polymer based composites. The powder metallurgy and powder processing techniques were used to develop MMC and CMC composites. Compression moulding was used to develop polymer matrix (HDPE) composites. An increased hardness in the case of MMC and CMC was observed. The tensile strength and flexural strength exhibited an increasing trend in the case of PMC with up to 15wt.% of silica sand nanoparticles.

Abstract: Copper-based microcomposites fabricated by powder metallurgy with subsequent plastic deformation have received increasing attention over recent years. These microcomposites possess good electrical conductivity in combination with high mechanical properties. The present study aims to explore potential technical merits in developing a prealloyed powder metallurgy copper based composites with silica sand nanoparticles reinforcement. Relevant mechanical properties and electrical conductivity improvements are the main targets. A copper based composite with 5, 10, 15 and 20 wt.% of silica sand nanoparticles were developed through the powder metallurgy process. It was observed that by addition of silica sand nanoparticles with 20% increased the hardness up to 143HV. Optimum electrical conductivity of the composites was achieved in the 15 wt.% silica sand nanoparticles. Advanced particle rearrangement mechanism due to homogeneous and fine distribution of silica sand nanoparticles into pore sites of the composites was also observed. The silica sand nanoparticles composites properties that are much more surface-related seen to be improved convincingly compared with the bulk controlled.

Abstract: Ceramic-ceramic composites are used around the world in demanding thermal, structural and electrical insulating applications. The present study aims to develop Alumina-Silica sand nanoparticles composites through powder processing route. Effect of amount of silica sand nanoparticles on the composite properties at different sintering temperatures was studied. Composites with 5, 10, 15 and 20 wt.% of silica sand nanoparticles were developed and sintered at 1300, 1400 and 1500 oC. It was observed that the incorporation of silica sand nanoparticles enhanced the hardness and sintered density of the composites. FESEM and EDS analysis evidenced the proposed liquid phase sintering, mullite and spinel formation mechanisms are primary cause of the composites mechanical properties improvement.

Abstract: Available information on the composition and methods of production for particulate reinforced metal matrix composites (PRMMCs) for wear resistant applications is reviewed. In general, PRMMCs exhibit better wear resistance compared to its unreinforced counterparts. Nevertheless, under specified conditions, the wear performance of PRMMCs is similar to or lower than its respective alloy. Conflicting results were found among investigators with regards to different tribological parameters used in their investigations. A general framework was developed by identifying three parameters that affect the effectiveness of wear mechanisms model; fabrication method, types and characteristics of reinforcement and wear testing apparatus.

Abstract: Metal matrix-particulate composites fabricated by using powder metallurgy possess a higher dislocation density, a small sub-grain size and limited segregation of particles, which, when combined, result in superior mechanical properties. The present study aims to develop iron based silica sand nanoparticles composites with improved mechanical properties. An iron based silica sand nanoparticles composite with 5, 10, 15 and 20 wt.% of nanoparticles silica sand were developed through powder metallurgy technique. It was observed that by addition of silica sand nanoparticles with 20 wt.% increased the hardness up to 95HRB and tensile strength up to 690MPa. Sintered densities and electrical conductivity of the composites were improved with an optimum value of 15 wt.% silica sand nanoparticles. Proposed mechanism is due to diffusion of silica sand nanoparticles into porous sites of the composites.

Abstract: Diffusion bonding of sialon and 7.5%-Cr Ferritic Steel (FS) in as-received and nitrided condition was studied. Decomposition of sialon and interdiffusion of elements between the sialon and the steel were observed. The interdiffusion of elements produced reaction layers at the joint. The steel moved into the decomposition part of the sialon and replaced the decomposed sialon in this part. Diffusion of silicon into the steel resulted in the silicon-diffusion layer. FeSi2 was formed in the reaction layer when Si in the decomposition part of the sialon reacted with Fe. The use of nitrided steel in the diffusion bonding had suppressed the formation of the FeSi2 in the layer.

Abstract: Silica refractory research and development has taken a down-turn; perhaps due to the problems associated with it, or because of concerns regarding earth conservation, earth being a major source of the raw material - quartz - which is used for silica refractory manufacture. In this review, the authors have pin-pointed the problems associated with silica refractory use from the researches of the early era (1913 to 1990) and have assessed the themes of current research, in order to ascertain how well these current researches have attended to the problems raised in the early research era. The review shows that the gaps identified in the early research era still remain unattended to. It concludes by making a case for nanostructured silica obtained from rice husk ash (RHA), for the production of silica refractory, as a way of solving these problems and making silica refractory production a booming industry once again.