Papers by Author: Abu Bakar Sulong

Abstract: Optimization of molding parameter on the flexural strength of carbon black/graphite/epoxy (CB/G/EP) nanocomposites using Taguchi method was studied. Three molding parameters was chosen in this study which are molding temperature, molding pressure and molding time. Experimental trials were carried out based orthogonal array design using those three parameters. The results were analyses using the signal to noise (S/N) and analysis ofvariance (ANOVA). Flexural strength of the CB/G/EP nanocomposites increases from 56.23 MPa to 65.11 MPa usingoptimize parameter obtained from the analysis method. These results shown that the Taguchi method is successfully to get optimum parameters of molding parameters to produce CB/G/EP nanocomposites.

Abstract: Recycling is a process that involves the three Rs (reduce, reuse, and recycling) of managing recyclable items such as paper, metal, glass, and plastic. An index system has been established to calibrate the level of processing reliability or cycle reliability with a specific metric that uses reprocessability index (RPI). The subject of this study is a unit of a co-axial compressor automotive air conditioning system that affects the shape, area, and volume of other units of the same system. The main objective of this study is to determine the component life cycle and to formulate recommendations for design changes with a controlled RPI level for the new automotive air conditioning compressor unit based on the original product. Analysis in this study is based on the value of R1, R2, R3, R4, R5, R6, and RPI for each component such as C01 (front cover), C02 (valve plates), C03 (front cylinder body), C04 (rear cylinder body), C05 (piston), C06 (shaft power), C07 (swash plate), C08 (back cover), C09 (inlet valve), and C10 (discharge valve). The RPI values for these components are 7.249, 12.480, 10.869, 10.869, 9.567, 9.578, 7.346, 7.002, 7.532, and 8.239, respectively. All components have an RPI value between 7 and 13, which indicates that they still have a limit on the reprocess ability. Appropriate redesign of a component can alter these RPI values. In this study, two improvements are proposed for the design of the C04. The first redesign shifts the RPI of this component to 23, which indicates thatC04 cannot be reprocessed. The second design reduces the RPI to 8, which improves the reprocessability. Then, the consideration of the research and development engineer for the same or other functions makes the product throughout its life cycle. These approaches can prevent wastage of energy and mineral resources as well as control industrial pollution.

Abstract: Metal Injection Molding (MIM) is widely known as net shape process to mass production for complex shape. In this study polyethylene and palm stearin was used as binder system for composite HA and Ti6Al4V. Ti6Al4V has spherical shape with particle size 25 μm and Hydroxyapatite has particle size 5 μm. Brabender^® was used to mix HA and Ti6Al4V powder and binder for making feedstock, rheological properties of feedstock was examined by capillary rheometer. Effects of temperature, viscosity, shear rate and activation energy were discussed in this paper. Binder was removed by thermal debinding. Rheological test showed feedstock of composite HA and Ti6Al4V shows pseudoplastic behavior. Sintering was conducted on 1200°C by argon with holding time 2 hour.

Abstract: The rheological behavior of feedstock needs to be examined for manufacturing parts without defects by micro powder injection molding (μPIM). In this study, submicron tungsten carbide (WC) and cobalt (Co) were milled for several hours. The distribution and morphology of the powder mixture were analyzed by laser diffraction and scanning electron microscopy. After measurement of critical powder loading, cemented tungsten carbide (WCCo) powder was mixed with a thermoplastic/paraffin wax binder with a powder loading volume from 50% to 52% to obtain feedstock. The flow properties of the WCCo feedstock were evaluated using a capillary rheometer at different temperatures. It was found that feedstock exhibit a pseudoplastic flow behavior, which is one of the main requirements for μPIM. Feedstock is also shown to be highly sensitive to temperature at high powder loading. Low powder loading led to low viscosity at a high shear rate that cannot be used in μPIM because it results in powder and binder separation.

Abstract: Micro metal injection molding has become the promising method in powder metallurgy research in order to fabricate small-scale intricate parts in an influential process and competitive cost of mass production. Stainless steel 316 L powders with powder size of 150 nm and 5 μm were mixed with a binder with a water soluble component which consisted of a major fraction of water soluble Polyethylene Glycol (PEG), a minor fraction of polymethyl-methacrylate (PMMA) and some stearic acid has been used as a surfactant. This work aims to investigate the rheological properties of a feedstock which are efficiently characterised by capillary Rheometry to measure apparent viscosities at different temperatures and shear rates. Results obtained by the varying feedstock characteristics, when viscosity decreases by increasing of shear rate at certain temperature feedstock should have a pseudoplastic behaviour. Melt viscosity of the feedstock was decreased by adding nanoscale powders. The reduced (n) values at high temperature with addition of nanoparticles indicated a possible increase in the shear-thinning behavior.

Abstract: Polymer composite has attracted many researchers from various field of application due to its unique features and properties including light weight, low cost, ease to process and shaping and corrosion resistant [1-3]. Fillers is typically added to enhance the chemical and physical properties of polymers [4, 5]. One of the properties is the electrical conductivity. Carbon based filler such as graphite (G), carbon black (CB), carbon fibers (CF) and carbon nanotubes (CNT) has been extensively used to improve electrical properties of polymer composite [6-8]. Electrical properties of the composite can be explained from percolation theory which means electrical percolation in mixtures of electrically conducting and non-conducting materials [9]. The concentration of conducting phase must above the critical value called percolation threshold, in order for the material become electrically conductive [10].

Abstract: Micro metal injection molding has become the promising method in powder metallurgy research in order to fabricate small-scale intricate parts in an influential process and competitive cost of mass production. Stainless steel 316 L powders with powder size of 150 nm and 5 μm were mixed with a binder with a water soluble component which consisted of a major fraction of water soluble Polyethylene Glycol (PEG), a minor fraction of polymethyl-methacrylate (PMMA) and some stearic acid has been used as a surfactant. This work aims to investigate the rheological properties of a feedstock which are efficiently characterised by capillary Rheometry to measure apparent viscosities at different temperatures and shear rates. Results obtained by the varying feedstock characteristics, when viscosity decreases by increasing of shear rate at certain temperature feedstock should have a pseudoplastic behaviour. Melt viscosity of the feedstock was decreased by adding nanoscale powders. The reduced (n) values at high temperature with addition of nanoparticles indicated a possible increase in the shear-thinning behavior.

Abstract: This study investigates the effect of carbon nanotubes (CNTs) as conductive fillers and epoxy resin as matrix on the electrical conductivity and hardness property. The different CNTs weight percentage (0 ~ 10 wt.%) were added into the epoxy resin. The dispersion of CNTs in epoxy resin was conducted by high speed mixer through mechanical shearing mechanism. The mixture of CNTs/epoxy was poured into the mold and compression molding was conducted for fabrication of CNTs/epoxy nanocomposites. The electrical conductivity and hardness of CNTs/epoxy nanocomposites by several of CNTs loading concentration were measured by the four point probe and dynamic ultra micro hardness tester. Agglomeration of CNTs in epoxy matrix was observed on fractured surface by scanning electron microscopic. Non conductive epoxy polymer becomes conductor as addition of CNTs. Electrical conductivity of CNTs/epoxy nanocomposites were increased with increasing of CNTs loading concentration. Hardness property of CNTs/epoxy nanocomposites ware reached the highest value at 5 wt.%, and then it was decreased.

Abstract: As an environmentally friendly technology, the fuel cell is one of the alternative technologies that can replace fossil fuels. Various types of fuel cells are available in the market, including the solid oxide fuel cell (SOFC). The planar and tubular designs of SOFC are the leading designs mentioned in the literature. Several factors such as manufacturing cost, manufacturing process and production scale differentiate between the two main designs. Each cell component can be produced using a number of methods, two of which are the most common, namely dry pressing and screen printing techniques for the making of planar SOFC. This paper thus reviews several works that have utilized each of the fabricating methods mentioned. The processing steps, technical parameters, and results, such as the maximum power density of each method are discussed.

Abstract: La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ–samarium-doped ceria (SDC) carbonate thin films are produced on SDC carbonate substrates by the electrophoretic deposition (EPD) method. EPD is performed by fixing the voltage and suspension pH while varying the deposition time to obtain a >20 μm-thick layer. The deposition time of 30 min yields more particle deposits than 10, 15, 20, and 25 min. Thin films with an average thickness of 22.9050 μm are obtained from the EPD technique when the voltage is 20 V and the suspension pH is 5.