Advanced Materials Research Vol. 879

Abstract: The annealing temperature for 250nm PVDF-TrFE (70:30 mol %) spin coated thin films were varied at solvent evaporation (T_s = 79°C), Curies transition (T_c= 113°C) till melting temperature (T_m = 154°C). From the XRD measurement, there was an improvement in the crystallinity of the annealed films, consistent with the increased in the annealing temperatures. Morphological studies of the annealed PVDF-TrFE thin films as observed with Field Emission Scanning Electron Microscope (FESEM) (100k magnification), showed enhanced development of elongated crystallite structures better known as ferroelectric crystal. However, the AN160 thin film showed fibrous-like structure with appearance of nanoscale separations, which suggested to posed high possibility of defects. Ferroelectric characterization indicated an improvement in the remnant polarization of annealed PVDF-TrFE thin films with the exception to AN160 in which leakage of current was inevitable due to the presence of cracks on the film surface.

Abstract: Owing to several steps involved in metal injection moulding (MIM) process, it is important to understand the interactions between metal powder and binder mixture particularly during mixing, injection moulding and debinding. A polar organic compound generally forms hydrogen bonds more readily with metal powder because of acid-base interactions. In this study, the interaction of local binder system comprised of; palm stearin (PS) and thermoplastic natural rubber (TPNR) with conventional binder; polyethylene (PE), polypropylene (PP) and paraffin wax (PW) and mixed with 316L stainless steel powder were investigated. The results showed that all the binder have high interaction with 316L stainless steel that make, the resulting the bonding sufficiently strong and suitable for MIM process. Keywords: Chemical interaction, Injection Moulding, Binder, Rheology

Abstract: The properties of WC-Co are greatly improved with the use of submicron powders. However, grain growth tends to occur during the sintering process which causes the properties to deteriorate to some extent. Free carbon and vanadium carbide are added in this study to serve as grain growth inhibitor. The effect of these two materials is evaluated based on WC-Co properties. In this work, the powders are mixed together via wet mixing process, compacted and undergo cold-isostatic pressing (CIP) before the samples are sintered in the temperature range of 1350-1450°C under nitrogen-based atmosphere. The physical and mechanical properties of the WC-Co sintered powders were analysed. Based on the work done, the WC-Co-C has a better properties compared to WC-Co-VC.

Abstract: The Li₂FeSiO₄ cathode materialwas prepared via a solid state reaction method and subsequently heat treated at around 350°C and 700^O C in Ar₂ atmosphere. High energy ball milling method is applied on the resulting powder with carbon additives to further modify the structure and to enhance the electrochemical performance. The structure and morphology of the prepared Li₂FeSiO₄ powder was characterized by means of X-Ray Diffractometry (XRD) and Field-Emission Scanning Electron Microscope (FESEM). The morphological changes of the Li₂FeSiO₄ resultedfrom different ball milling duration strongly influences the electrochemical performance of this cathode material_. The Li₂FeSiO₄ powder which was ball-milled for 48h delivered in the best electrochemical performance with a discharge capacity of 65.4 mAh/g when cycled between 1.5 and 4.8V vs. Li/Li⁺. Particulate morphology observed from FESEM images showed that samples that were ball-milled for 48h have reduced agglomeration compared to that ball-milled for 24h. The larger surface area for reaction with Li⁺ improves the discharge capacity of the Li₂FeSiO₄ cathode material.

Abstract: In this study, the effect of sintering temperature on the properties of tungsten-copper (W-Cu) composite produced by liquid phase sintering (LPS) process has been investigated. W-20 wt.% Cu composite powders with particle size less than 1 μm was prepared by cold compaction and followed by cold isostatic pressing. The green specimens were then sintered under nitrogen based atmosphere in the temperature range of 1100°C to 1300°C. The sintering studies were conducted to determine the extent of densification and corresponding to microstructure changes. In addition, the properties of the sintered specimens such as physical appearance, microstructure evolution, mechanical and electrical properties were presented and discussed.

Abstract: High-speed machining is one of the modern technologies that enable the increase in efficiency, accuracy and quality of workpieces, as compared to conventional cutting. At the same time, it decreases costs and machining time [.

Abstract: Cobalt-doped ZnO nanorods were successfully synthesized on SiO₂/Si substrate using RF-magnetron sputtering at room temperature. The structural, morphological, and photoluminescence (PL) properties of undoped and Co-doped ZnO nanostructure were characterized using X-ray diffraction, field emission-scanning electron microscopy, and PL analyses. The results showed that Co²⁺ replaces Zn²⁺ in the ZnO lattice without changing the wurtzite structure. As the Co concentration increases, the structure becomes highly crystalline and is gradually converted into nanorods with no extra phases. The as-synthesized nanorod arrays are dense and vertically grow on the SiO₂ substrate. The arrays exhibit diameters of approximately 56.89 nm as well as lengths that range from 247.9 nm to 527.5 nm. PL analysis reveals that the ultraviolet (UV) emission intensity decreases and exhibits a blue shift as the Co doping level is increase.

Abstract: Oxide coatings on AZ91D magnesium alloy were prepared using anodizing technique with 10mA/cm² current density for 5 minutes in electrolyte containing La (NO₃) and Mg (NO₃),with NaVO₃ as an additive. The corrosion behaviors of different coatings condition were evaluated by immersion test in 5.0% NaCl electrolyte for 72 hours. The microstructures were analyzed by Optical Microscope (OM) and Scanning Electron Microscope (SEM). It was found that coatings with the addition of NaVO₃ produced homogeneous primary α-matrix and bigger β-phase (Mg₁₇Al₁₂) compared to untreated AZ91D magnesium alloy. The oxide film formed by anodizing in electrolyte with NaVO₃ enhances the corrosion resistance of the AZ91D magnesium alloy significantly

Abstract: This research is focused on assessing the feasibility of the new and innovative microwave sintering technology for fabricating iron-chromium composites prepared via powder metallurgy route. Accordingly, the microwave sintered iron-chromium compacts was benchmarked against conventional sintered counterparts fabricated in other researches. We also studied the viability of yttria reinforcement to the iron-chromium composites with varying weight fraction from 5 to 20 %. Comparison on the end properties were also being made on the unreinforced iron-chromium matrix (0 wt. % of yttria). The result revealed that the microwave sintered iron-chromium composites possess improved density and micro hardness value. Process evaluation also revealed that microwave assisted sintering can lead to a reduction of 70 % of sintering time when compared to conventional sintering. The micro hardness property of microwave sintered iron-chromium was slightly improved with 5 wt. % addition of yttria, although the density and compressive strength were reduced with increasing content of the ceramic particulates. Most importantly, the study has established the viability of microwave sintering approach used in place of conventional sintering for iron based powder metallurgy composites.