Advanced Materials Research Vol. 620

Abstract: Lead zirconate titanate Pb (Zr_0.52Ti_0.48)O₃, (PZT) ceramic was successfully prepared from the mixture of commercial PbO, TiO₂ and ZrO₂ powders using planetary ball mill at room temperature. The phase formation and microstructure of the milled powders were characterized using X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). XRD results indicated that the perovskite phase of PZT was formed from the mixture of starting materials after milling for 40 h. The grain sizes of the powders have been estimated from the SEM images to be ~200 nm. The compacted PZT samples were then sintered at 950 °C for 1 h. The samples were characterized by XRD and SEM, meanwhile the density was measured by Archimedes principle. XRD analysis on the sintered samples revealed the formation of single phase Pb (Zr_0.52Ti_0.48)O₃ ceramics while the SEM images estimated the grain size to be ~2 µm. The relative density of the obtained sintered PZT ceramics was measured to be approximately 99.93 % of the theoretical density. The results hence indicate that planetary ball mill is an effective preparatory technique to improve the sinterability of PZT ceramics.

Abstract: Activated carbon is produced from high cellulose containing biomass such as filter paper (FP), bamboo waste and palm empty fruit bunches (EFB) by dehydrating agent, concentrated sulfuric acid (H₂SO₄). At room temperature, treatment of H₂SO₄ is removed all the water molecules in the biomass and leaving only porous carbon without emitting any gaseous by-products. After activation by carbon dioxide (CO₂), Brunauer-Emmett-Teller (BET) and X-ray Diffractometer (XRD) analysis showed the bamboo activated carbon (BAC) has good properties with higher surface area (862.76 m²/g), micropore area (463.62 m²/g) and some crystalline (graphite) phase formation. Acid treatment of biomass has shown high carbon content for FP (85.30%), bamboo (77.72%) and EFB (76.55%), and yield obtained was 47.85 wt.% (FP), 62.4 wt.% (bamboo) and 55.4 wt.% (EFB) by using dehydration method.

Abstract: The term microfibril angle (MFA) in wood refers to the angle between the spiralling cellulose fibrils and the long axis of the tracheid cell wall. Diffraction patterns arising from crystal planes of various sample forms of wood trees had attracted scientific research in determining the crystallographic measurements. As such the tropical hard wood in Sabah, Acacia mangium was chosen for experimental data. Age-contributing factors were measured; the angle of reflection (θ), relative intensity, full width at half maximum (FWHM), the nearest between two neighbouring atoms in the crystalline structure (d-spacing) and the peak height, had been taken into account at different ages, pith and bark of tree. Regressions were done in comparing the microfibril angle, MFA at different ages using the least-square method and cubic-spline interpolation. The latter was able to interpolate a polynomial up to the third order. The range of the optimum angle was found to have benefited foresters in deciding the time for tree cropping and harvesting.

Abstract: Gravimetric and elemental analyses were conducted at a site in Kuala Lumpur from 2008 to 2010, representing the local air quality of urban and traffic. Eighteen elements were detected by ED-XRF and was further analysed for enrichment factor and correlation study. About 19.7% elements were identified and detected in PM₁₀, including 8.2% and 11.5% in fine and coarse fractions, respectively. Al was found predominant in coarse fraction. However its composition in PM_2.5 was highly enriched pointed to some anthropogenic emission source. In fine particulates, the total mass was mostly dominated by Al, K, Mg and S. Those elements, probably from biomass burning accounted for more than 90% of total elemental detected in PM_2.5.

Abstract: In the present study, superheating treatment has been applied on A357 reinforced with 0.5 wt.% (Composite 1) and 1.0 wt.% (Composite 2) continuous stainless steel composite. In Composite 1, the microstructure displayed poor bonding between matrix and reinforcement interface. Poor bonding associated with large voids also can be seen in Composite 1. The results also showed that coarser eutectic silicon (Si) particles were less intensified around the matrix-reinforcement interface. From energy dispersive spectrometry (EDS) elemental mapping, it was clearly shown that the distribution of eutectic Si particles were less concentrated at poor bonding regions associated with large voids. Meanwhile in Composite 2, the microstructure displayed good bonding combined with more concentrated finer eutectic Si particles around the matrix-reinforcement interface. From EDS elemental mapping, it was clearly showed more concentrated of eutectic Si particles were distributed at the good bonding area. The superheating treatment prior to casting has influenced the microstructure and tends to produce finer, rounded and preferred oriented α-Al dendritic structures.