Tahir Ahmad

Studying the Effects of Adding Silica Sand Nanoparticles on Epoxy Based Composites

The research about the preparation of submicron inorganic particles, once conducted in the past decade, is now leading to prepare polymer matrix composite (PMC) reinforced with nanofillers. The objective of present research is to study the modified effects of reinforcement dispersion of nanoparticle silica in epoxy resin on the physical properties, mechanical and thermal behaviour, and the microstructure of resultant composites. Stirrer mixing associated with manual mixing of silica sand nanoparticles (developed in our earlier research) (Ahmad and Mamat, 2012) into epoxy was followed by curing being the adopted technique to develop the subject nanocomposites. Experimental values showed that 15 wt.% addition of silica sand nanoparticles improves Young’s modulus of the composites; however, a reduction in tensile strength was also observed. Number of holes and cavities produced due to improper mixing turn out to be the main cause of effected mechanical properties. Addition of silica sand nanoparticles causes a reduction in degree of crystallinity of the nanocomposites as being observed in differential scanning calorimetry (DSC) analysis.

Characterization and Properties of Iron/Silica-Sand-Nanoparticle Composites

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.

Improvement in mechanical and thermal properties of unsaturated polyester- based hybrid composites

Polymer matrix composites are used in automobile, structure and aerospace industries due to their light weight and high strength. The present research has an aim to reinforce locally developed silica nanoparticles and glass fibers in unsaturated polyester to produce polymer-based hybrid composites. Composites were synthesized by hand lay-up method with 1, 2, 3 and 4 wt% of silica sand nanoparticles and glass fiber. Mechanical tests like tensile, impact and micro-hardness were performed on the obtained polymer hybrid composites. The results of mechanical properties of the hybrid polymer matrix composites revealed an increasing trend. The SEM analysis was performed on the developed and fractured tensile testing samples. The SEM analysis showed the presence of silica nanoparticles in the samples and pulling action of fibers were seen under fractured tensile tests. The pulling actions of fibers from polymer matrix delayed the fractured mechanism and enhanced the mechanical properties. Silica nanoparticles filled the cavities generated during tensile test and extensive enhancement was revealed in tensile as well as impact energy. Toughness of the hybrid composite was also enhanced as a result. The thermal properties of the hybrid polymer composites were analyzed using thermogravimetric analysis. Thermal stability of the composite has been marginally increased with increasing wt% of reinforcement.

Evaluation of Surface Preparation Techniques for Steel Substrates Prior to Coating Application

The performance of organic coatings on steel substrates is strongly affected by substrate cleanliness and anchor patterns. During present research work, Surface pre-treatments were applied to remove contaminants from steel surfaces. Electrochemical Impedance Spectroscopy (EIS) was used to characterize such surfaces in terms of electrochemical parameters to find out the extent of activeness of prepared surfaces, and electrochemical processes are modeled into corresponding electrical equivalent circuits (EECs). Surface roughness parameters were evaluated to find out the extent of mechanical interlocking between prepared surface and the coating to be applied over it. The optimum surface preparation technique prior to application of organic coating was characterized.

Tronoh Silica Sand Nanoparticle Production and Applications Design for Composites

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.

Studying the Effect of Different Combinations of Salt Modifier on the Mechanical Properties and Microstructure of A356 Al-Si Alloy

The present study aims to develop A356 Al-Si alloy using high purity aluminium and various master alloy in gas fired pit furnace. Three different ratio of salt modifier (1:1, 1:2 & 1:3) was used to prepare the casting. Sand casting and permanent mould casting techniques were used to prepare the alloys. Optical microscope and universal tensile testing machine were used for the metallurgical evaluation of the prepared alloy. It was observed that the addition of modifier improved the mechanical properties and microstructure of the alloy. It was also observed that modifying agent NaF with CaCl2 in 1:1 ratio has shown the best results in terms of microstructure and the mechanical properties.

Effect of Different Modifiers on Microstructure and Strength of Locally Developed A356 Al-Si Alloy

The present research aims to study the effect of various combination of salt and metal modifiers (SrCl2, KCl and NaCl salts with NaF including Sb & Sr ) on the locally developed A356 Al-Si alloy. A series of different heats with these modifiers were prepared using a pit type furnace. Casting of the molten metal was carried out using sand casting technique and fluxes at various stages followed by degassing. Sr modifier was used as Al-Sr master alloy, while Sb metal was used in high purity form. However salt modifiers were thoroughly dried before plunging at the bottom of the crucible containing the molten metal. It was observed that the samples containing Sr as modifier showed the best results in terms of microstructure & tensile properties as compared to Sb modifier. A combination of SrCl2, KCl with NaF showed almost the similar and well modified microstructure with better tensile properties as compared to the samples containing NaCl with NaF salt modifier.

Studying the Formation of Fe2SiO4 and Pearlite Phasesin Iron-Silica Sand Nanoparticle Composites

Metal matrix composites have grown rapidly with their usefulness in many applications for industries. The present research aims to study the formation of Fe2SiO4 and pearlite phases, the reaction product of iron-silica sand nanoparticles composites. In this study iron based silica sand nanoparticles composite with 5, 10, 15 and 20wt.% of silica sand nanoparticles were developed using powder metallurgy technique being sintered at 1100°C. It was observed during the X-Ray Diffraction (XRD) and XPS analysis that the reaction between iron and silica sand nanoparticles forms the Fe2SiO4 phase. Field Emission Scanning Electron Microscopy (FESEM) analysis at higher magnification also reveals the formation of pearlite phase. The presence of liquid phase sintering is also observed with frozen liquid spots at microstructure of iron-silica sand nanoparticles reaction.

Investigating the Pitting Resistance of 316 Stainless Steel in Ringer's Solution Using the Cyclic Polarization Technique

Corrosion rate, corrosion potential and susceptibility to pitting corrosion of a metal are measured using cyclic polarization Direct Current (DC) electrochemical technique. The aim of the present research is to investigate the pit nucleation resistance of polished, ground and passivated surfaces of 316 stainless steels in Ringers solution. The electrochemical cyclic polarization results showed that polished surface gave better pitting resistance as compared to ground surface. It was also observed that passivation treatment gave better pitting resistance to both polished and ground surface of 316 stainless steels in Ringers solution.

Physico-Mechanical Properties of Sintered Iron-Silica Sand Nanoparticle Composites: A Preliminary Study

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.