Advanced Materials Research Vol. 879

Abstract: Tendency of injection moulded parts to necessitate a long debinding time which consequently leads to an increase of defects formation has been a major obstacle for the economic process of Metal Injection Moulding (MIM). In the present study, a novel binder system based on waste rubber has been formulated in injection moulding of Molybdenum High Speed Steel (M2 HSS). The feedstock consisted of M2 HSS powder with mean diameter particle size of 16μm and binder which comprised of palm stearin, polyethylene, waste rubber and stearic acid. The moulded part was immersed into n-heptane at 60°C in order to remove the palm stearin and stearic acid, followed by sintering in a controlled vacuum atmosphere. Results showed that solvent extraction debinding technique allowed complete removal of palm stearin and stearic acid from the injection moulded part within 3 hours without swelling or distortion of the debound part. In addition, this study has demonstrated that, the novel binder system has successfully shorten the debinding time through a single stage debinding process whilst the sintered part possessed approximate density of 8.1 g/cm³ and hardness of 76.9 HRC.

Abstract: Polyurethane (PU) adhesives were prepared from three different polyols based on polycaprolactone (PCL)/palm kernel oil (PKO) with an aromatic and cycloaliphatic diisocyanate. The adhesives were characterized through Fourier Transformer Infrared (FTIR) spectroscopy in order to ensure the formation of urethane and the completeness of polymer reaction. The effects of NCO/OH ratios and types of diisocyanate on PU adhesive strength were investigated. The adhesive strength of metal to metal bonding was determined by single lap shear joint testing. The correlation between crosslinking of PU network and adhesive strength was also studied by performing swelling tests.

Abstract: Magneticmesoporousɣ-Fe2O3/SiO2 synthesized using an evaporation-induced self-assembly (EISA) approach. The non-ionictriblock copolymer P123 was used as surfactant template with various amounts of iron oxide (1.8g-2.4g) and varied during the synthesis. Characterizations of the surface area and magnetic properties for prepared materials were done using N₂-sorption analyses, and a superconducting quantum interference device interfaced with a vibrating sample magnetometer (SQUID-VSM) respectively. From this study, N₂-sorption analysis indicated that most of the ɣ-Fe₂O₃ domains of several nanometres were embedded in the silica matrix. In addition, the obtained magneticmesoporouscomposite which contains 2.3g amount ofiron oxide has revealedhigher magnetism saturation value of (4.564 emu/g) compared to other prepared samples which been evaluated by VSM analysis.

Abstract: The tribological properties of sintered 316L stainless steel fabricated via injection molding were investigated. Tests were carried out at room temperature comparing metal injection molded dog bone tensile samples at different sintering temperatures. The parameter used for the pin on disk test is a 10kN load, 500m sliding distance and a chromium steel ball as a sliding partner. The morphologies and compositions of the worn surfaces were analyzed by SEM, Raman and XPS. The results showed that the wear mechanism and friction coefficient of SS316L depended strongly on the microstructure which was influenced by the sintering temperature.

Abstract: The most demanding high temperature application requires nickel-based super alloys, named Inconel 718 (IN718) is a precipitation hardenable nickel chromium alloy containing significant amount of iron, niobium and molybdenum along with lesser amounts of aluminium and titanium. The development of IN718 for metal injection molding was already proposed to provide increased resistance to distortion during and prior to debinding. This paper reports on the effects of sintering temperature on physical and mechanical properties of IN718 alloy. IN718 powder (60 vol%) with binder formulation (40 vol%) consists of polyethylene (PE) and palm stearin (PS) were mixed homogeneously and injected to produce green compacts. The binders then was removed and sintered at 1100 °C and 1200 °C for 8 h respectively. During sintering, the debound part is heated, which is allowing densification of the powder into a dense solid followed by elimination of pores. The sample sintered in vacuum condition at atmosphere 10^-5 mbar whereby samples sintered at 1100 °C, show the density of 6.806 g/cm³ compared to samples sintered at 1200 °C is 8.186 g/cm³. Super alloy sintered at 1200 °C exhibited better densification rate with lower porosity. The preliminary results indicate that super alloy can be used in the MIM fabrication of nickel based super alloys to produce high-density sintered parts.

Abstract: This paper reports effect of modification thin film surface morphology using thermal annealing process in order to enhance organic photovoltaic solar cell performance. The organic photovoltaic solar cell (OPV) were fabricated using bulk heterojunction structure, consist of p-type semiconductor of polythiophene (PT) derivative and an n-type of fullerene, C-61 derivative. The devices structure can be named as Al/LiF/polymer composite film/PEDOT-PSS/ITO. For comparison, the devices were varies; as cast and annealed at 125°C for half an hour to modify the thin film surface structure. The performances of the devices were studied by observing the current-voltage characteristics of the device in dark at ambient temperature and under standard A.M 1.5 illumination. The light conversion efficiency of the resulting photovoltaic devices increases from 0.04% (as cast) to 2.3% after thermal annealing process. As a result, the annealed organic photovoltaic devices, show enhanced efficiencies compared with as cast device due to the enhancement in transport properties of polymer base photovoltaic device.

Abstract: Ionic liquids are new alternative solvents that can be used to separate carbon dioxide in the gas separation process. However, the high viscosity of ionic liquids limits the mass transfer of solutes into ionic liquids. In this work, 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([hmi [Tf₂) was impregnated onto porous Al₂O₃ and SiO₂ and tested for CO₂ adsorption at pressure up to 40 bar at 25 °C. The screening process showed that [hmi [Tf₂-Si gave higher CO₂ adsorption capacity compared to [hmi [Tf₂-Al and pure [hmi [Tf₂. The experimental work was further investigated by varying the composition of [hmi [Tf₂ inside SiO₂ pores. The composition of [hmi [Tf₂ was varied from 10 wt% to 40 wt%. The result showed the 10 wt% composition gave the highest CO₂ adsorption compared to 20 wt%, 30 wt% and 40 wt%. The lower CO₂ adsorption by 20 wt%, 30 wt% and 40 wt% might be due to the blockage of SiO₂ pores by excess [hmi [Tf₂. From this research, it proved that porous solid support can provide high surface area that is necessary to accommodate intimate contact between CO₂ and solid supported ionic liquid and increases the CO₂ adsorption capacity.

Abstract: Nanoparticles of Zn_1-xFe_xS ( x=0.0,0.1,0.2 and 0.3) were prepared by chemical co-precipitation method from homogenous solution of zinc and ferum salt at room temperature with controlled parameter. These nanoparticles were sterically stabilized using Sodium Hexamethaphospate (SHMP). Here, a study of the effect of Fe doping on structure, morphological and optical properties of nanoparticles was undertaken. Elemental analysis, morphological and optical properties have been investigated by Fourier-Transform-Infrared spectroscopy (FT-IR), X-Ray Fluorescence (XRF), Field Emmision Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and UV-Visible Spectroscopy. FTIR measurement confirmed the presence of SHMP in the nanoparticles structure with the FESEM images depicting considerable less agglomeration of particles with the presence of SHMP. While XRF results confirm the presence of Fe²⁺ ion as prepared in the experiment. The particles sizes of the nanoparticles lay in the range of 2-10 nm obtained from the TEM image were in agreement with the XRD results. The absorption edge shifted to lower wavelengths with an increase in Fe concentration shown in the UV-Vis spectroscopy. The band gap energy value was in the range of 4.95 5.15 eV. The blueshift is attributed to the quantum confinement effect.

Abstract: Inconel 718 has been widely used as a super alloy in aerospace application due to the high strength at elevated temperatures, satisfactory oxidation resistance and heat corrosion resistance. In this study, the Inconel 718 with different solid loading (System A - 50/50 vol.% and System B - 60/40 vol.%) has been fabricated using high technology of Metal Injection Moulding (MIM) process due to the cost effective technique for producing small, complex and precision parts in high volume compared with conventional method through machining. Through MIM, the binder system is one of the most important criteria in order to successfully fabricate the Inconel 718. Even though, the binder system is a temporary, but failure in the selection and removal of the binder system will affect on the final properties of the sintered parts. Therefore, the binder system based on palm oil derivative which is palm stearin has been formulated and developed. The rheological studies of the mixture between the powder and binders system have been determined properly in order to be successful during injection into injection moulding machine. After moulding, the binder holds the particles in place. The binder system has to be removed completely through debinding step. During debinding step, solvent debinding and thermal pyrolysis has been used to remove completely of the binder system. The debound part is then sintered to give the required physical properties.

Abstract: This paper reports on the compatibility of waste rubber as binder for M2 High Speed Steel injection moulding. The feedstock was prepared at a powder loading of 65 vol.% using 22μm M2 High Speed Steel powder and the binders consisting of 55wt.% paraffin wax, 21wt.% polyethylene, 14wt.% waste rubber and 10wt.% stearic acid. The specimens were then sintered in vacuum and 95%N₂/5%H₂ atmosphere. The sintering in vacuum atmosphere occurred within a temperature range from1200°C to 1260°C, whilst the 95%N₂/5%H₂ atmosphere was carried out within a temperature range from 1220°C to 1300°C. The effects of the sintering atmosphere and temperature on the physical properties, mechanical properties and microstructure were investigated.