UniMAP Conference and Proceedings
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PublicationLa-Doped CaCu₃Ti₄O₁₂ ceramics synthesized under argon environment(Universiti Malaysia Perlis (UniMAP), 2010-06-09)The properties of undoped and La-doped CaCu₃Ti₄O₁₂ (CCTO) ceramics synthesized via solid state reaction under argon environment had been studied. La-doped CCTOs found to have higher dielectric constant than undoped CCTO. X-ray Diffraction (XRD) analysis indicated that all of the samples have single-phase cubic structure (space group) with no trace of other impurity phases. However, compared with undoped CCTO, minor shifts are observed in the peak positions for La-doped specimens, which are attributed to the lattice expansion caused by ionic size effects (as La3+ is bigger than Ca2+). The lattice parameter estimated from XRD patterns of undoped CCTO were found to be 7.348 Å and the increases in lattice parameter of La-doped CCTO from 7.348 – 7.377 Å, suggesting that La ions have effectively substituted into the Ca site of CCTO
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PublicationEffect of Al₂O₃/ZrO₂ reinforcement on the mechanical properties of PMMA denture base(Universiti Malaysia Perlis (UniMAP), 2010-06-09)Study on the properties of denture base materials made from PMMA filled with Al₂O₃/ZrO₂ was carried out. The amount of Al₂O₃/ZrO₂ filler was fixed at 5 wt%. However, the ratio of Al₂O₃ to ZrO₂ added was from 0 to 100. Samples were prepared for fracture toughness, flexural strength and tensile tests. The fracture surface was analyzed using SEM and EDS. It was found that for Al₂O₃/ZrO₂ of 80:20 ratio shows the highest fracture toughness and flexural properties. SEM micrographs indicate that distribution of Al₂O₃ and ZrO₂ in the PMMA matrix is fairly homogeneous. The interface between the reinforcement particles and matrix is good. Therefore, addition of Al₂O₃/ZrO₂ in PMMA is able to improve the mechanical properties of this denture base material.
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PublicationHeating rate effects on properties of powder metallurgy Fe-Cr-Al₂O₃ composites(Universiti Malaysia Perlis (UniMAP), 2010-06-09)The aim of this study is to determine the optimum heating rate in fabricating Fe-Cr-Al₂O₃ composites by powder metallurgy methods. The Fe-based composites reinforced with ceramics are widely used due to their high strength, hardness and wear resistance. Among steps in powder metallurgy methods are mixing, compaction and sintering. Sintering is a very important step due to its ability to evolve microstructural features that govern the end properties. Sintering of green compacts made of iron powder mixture must be performed in vacuum or in a reducing atmosphere because water-atomised iron powder particles are oxidized on the surface and in this way some deoxidation reaction can occur during sintering. The heating process up to sintering temperature, plays a major role, the major proportion of densification occurs during the heating process. The composites produced were subjected to the following tests: densification, Vickers micro hardness, microstructure using SEM and X-ray diffraction analysis. From this investigation, to achieve higher densification and hardness the optimal heating rate is 10°C/minute. X-Ray Diffraction study showed that the fabrication of the composites does not lead to any compositional changes of the matrix phase and the reinforcing phase.
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PublicationEffect of La₂O₃ addition on microstructure, morphology and pressure sensing behaviour of PZT based ceramics sintered in Al₂O₃ environment(Universiti Malaysia Perlis (UniMAP), 2010-06-09)Effect of La₂O₃ addition on microstructure, morphology and pressure sensing behaviour of (Pb1-x, Lax)(Zr₀.₅₂, Ti₀.₄₈)O₃ based ceramics was studied in three different compositions of La₂O₃, namely x = 0.10, 0.12 and 0.15. The samples were prepared through a conventional solid-state reaction method using high purity metal oxides powders. In order to control the PbO losses due to high sintering temperature, a novel approach was explored whereby the samples were sintered in Al₂O₃ environment. Structural investigation using XRD revealed that all samples exhibited a tetragonal crystal structure. However the c/a ratios exhibited a decreasing trend as the La₂O₃ content increased, indicating that (Pb1-x, Lax)(Zr₀.₅₂, Ti₀.₄₈)O₃ crystals gradually evolved towards pseudocubic structure. SEM micrographs showed that in all samples the grains have uniform pebble stone morphology. The average grain size reduced from ~ 4.5 μm to ~ 3.0 μm with the increment of La₂O₃ content. The performance of pressure sensing behaviour which was investigated using custom-made pressure chamber showed that sample with composition of x = 0.10 exhibited the best piezoelectric properties with high pressure sensitivity, good stability and repeatability.
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PublicationGrowth of Cu-Zn₅ and Cu₅Zn₈ intermetallic compounds in the Sn-9Zn/Cu joint during liquid state aging(Universiti Malaysia Perlis (UniMAP), 2010-06-09)The phase and intermetallic thickness of Cu-Zn₅ and Cu₅Zn₈ has been investigated under liquid state aging using reflow method. Both the intermetallic was formed by reacting Sn-9Zn lead free solder with copper substrate. Scanning electron microscope (SEM) was used to see the morphology of the phases and energy dispersive x-ray (EDX) was used to estimate the elemental compositions of the phases. The morphology of the Cu₅Zn₈ phase was rather flat but when the soldering temperature and tine increases, the morphology becomes scallop. Intermetallic thickness measurements show that the thickness of the Cu-Zn₅ decreases with increasing soldering time and temperature. Whereas, the thickness of the Cu₅Zn₈ intermetallic increases with soldering time and temperature.