Advanced Materials Research Vol. 802

Abstract: The ferroelectric ceramic, Barium Strontium Tinanate (Ba_0.7Sr_0.3TiO₃), was prepared by the sol-gel combustion method using citric acid, urea, and glycine as the fuel for reduce the calcination temperature. The molar ratio of sol powderto fuel was 1:1. All of the samples were calcined at 450, 550, 650, 750, 850 and 950°C for 2 h. Then,Ba_0.7Sr_0.3TiO₃ powders were applied with acid treatment process. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM) analysis were used to characterize the crystal structure and microstructure. The perovskite phases of BST and the pyrochlore (BaCO₃,SrCO₃) were obtained after the calcinations temperature of 550°C. BST powders were applied with acid treatment process.The XRD result showed the pure perovskite phase without the phase of pyrochlore in all of the samples. Ba_0.7Sr_0.3TiO₃was in cubic structure, corresponding to JCPDS 34-0411. SEM analysis of BST powders calcined at 750°C.The particles were spherical morphology and had agglomerates while the particles sizes were larger corresponding with the increase of calcinations temperature.The results for TEM analysis of the BST powders prepared by using urea as the fuel had a smaller particles,and the average of particle size was about 47 nm.

Abstract: A sol-gel combustion method has been effectively used to prepare SrTiO₃ nanopowders. The effect of chitosan solution content addition in sol-gel combustion method on microstructure and morphology of SrTiO₃ powders was investigated by XRD and SEM. It was demonstrated that the addition of chitosan solution is beneficial to the homogenously distributed in powder products. The particle sizes of powders were found that they were a large amount of agglomerated with the structure feature of nearly spherical in shape and consisted of nano-sized crystallites, which indicated by SEM.

Abstract: The objective of this paper was to study the influence of aluminium on the color, microstructure and hardness of the as-cast nickel-free white alloys. In order to specify the suitable aluminium content, aluminium in each composition varied from 0, 1, 2, 3, 4 and 5 wt% were investigated. The CIE LAB color system was selected to describe the color of alloys. The results indicated that the increase in the aluminium contents, red-green values (a*) were gradually increased, but yellow-blue values (b*) were slightly decreased. No correlation had been found between the aluminium content and lightness (L*). The microstructures of alloys consisted of the alpha, beta phases and small particles. The hardness of alloys was increased with increasing in the aluminium contents. It was distinct that the hardness of aluminium-free alloy (117 HV) was the lowest value in comparison with other alloys. The obtained results suggested that the variation in the aluminium contents of had a pronounced effect on the increasing hardness and the development of structures. However, the aluminium addition in the ranges of 1.3-5.1wt% resulted in a gradual changing the color.

Abstract: Epitaxial lateral overgrowth (ELO) was performed to grow cubic GaN layers on stripe-patterned GaAs (001) substrates via metalorganic vapor phase epitaxy. Growth time was varied from 10 to 120 minutes to investigate an evolution of growth morphologies and crystal structures of GaN, which were respectively analyzed by scanning electron microscopy and micro-Raman scattering spectroscopy. Growth features of ELO cubic GaN for [1-10] oriented mask stripe-pattern showed the {113} side-wall facets. On the other hand, the {111} side-wall facets were observed for ELO cubic GaN grown on the [110] oriented mask stripe-pattern. In case of [100] oriented mask stripe-pattern, growth feature with top rough surface and unclear side-wall facets was obtained. Micro-Raman spectroscopy was used as a tool to identify both cubic and hexagonal GaN structures performed on surface of the top and side-wall facets of the GaN stripes. ELO cubic GaN layer with growth time of 60 min along the [1-10] oriented mask stripe-pattern exhibited the highest ratio of cubic to hexagonal GaN, which was examined from an integrated intensity of LO phonon mode at 738 cm^-1 for cubic GaN comparing with that of hexagonal GaN, appearing at A₁ (TO) 538 cm^-1, E₁ (TO) 558 cm^-1 and E₂ (high) 568 cm^-1.

Abstract: In this work, lead-free silicon brass (Cu-Si-Zn) with tin addition was studied to investigate on the comparative influence of the adding and non-adding tin on the microstructures and microhardness. In order to produce new alloy compositions, varied amount of silicon (0.5, 1.0, 2.0, 3.0 wt%) were incorporated. The ranges of chemical compositions were copper contents between 58.7 and 60.3 wt%, tin content 0.6 wt% and zinc remaining. The silicon brasses were prepared by melting pure elements with a graphite crucible using an induction furnace. The chemical composition of each alloy has been determined by X-ray fluorescence spectrometry (XRF). Microstructures of the as-cast silicon brass ingots have been observed by optical microscopy and scanning electron microscopy. The respective chemical analysis of the phases was determined by energy dispersive X-ray spectroscopy (EDS) and the hardness was measured by Vickers hardness test. The results revealed that the hardness of 60Cu-0.5Si-39.5Zn brass was 123.4 HV. The higher silicon content improved the higher hardness of samples. Moreover, the addition of tin together with silicon increased amount of beta (β) phase and more uniform dispersive gamma (γ) phase than those of the silicon addition alone. It could be concluded that the tin addition enhanced the hardness of lead-free Cu-Si-Zn brass and trended to be helpful for machining.

Abstract: The aim of this work is to investigate the effect of injection parameters on morphology in stainless steel 316L metal injection moulding. In the experiment, samples were prepared by injection moulding process with varies parameters such as gate locations, pressures and speeds. The physical appearance of green parts was examined. After that, the cross sections of samples were investigated by scanning electron microscope including chemical analysis of the phase determined by x-ray energy dispersive spectroscopy. The experimental results showed that a perpendicular gate injection caused a separate section between outer skin and core at the cross section of specimens. The high pressure and speed for both injection directions caused crack. In conclusion, a parallel gate injection of feedstock with low pressure and speed was successful to mould the homogeneous samples without black streak, crack and phase separation. Therefore, the observed results could be useful to establish guideline for moulding in order to receive the complete green parts without defects

Abstract: The objective of this work is to study the effect of antimony on as-cast microstructures and hardness of dual phase brassed. The studied compositions consisted of 56Cu-(42-X)Zn-1Si-0.5Al-0.5Sn-(X)Sb with varied antimony content in the range of 0.5-2.0 wt%. The alloys were prepared by melting pure elements using an induction furnace in graphite crucible at the temperature about 1,200 °C. The chemical composition of each alloy has been analyzed by X-ray fluorescence (XRF). Microstructures of the as-cast ingots were investigated by optical microscopy and scanning electron microscopy including the chemical analysis of the phase determined by X-ray energy dispersive spectroscopy (EDS). The obtained results suggested that the microstructures of as-cast ingots exhibited the beta-gamma dual phases. The beta phase was the matrix and the gamma phase extended along the grain boundary. The increase in antimony content increased the gamma phase and enhanced the hardness. Moreover, the antimony addition 2 wt% created the intermetallic compound (IMC) phase like a needle shape. The EDS analysis of IMC displayed 12.35 wt% antimony.

Abstract: Carboxyl methylcellulose (CMC) doped with oleic acid (OA) and plasticized with propylene carbonate (PC) was successfully manufactured into thin film using solution cast technique. Impedance study shows the ionic conductivity falls into two region. With the addition of 5wt% of PC the ionic conductivity falls from 2.11x10^-5S/cm to 2.00x10^-7 S/cm. The highest conductivity gained at ambient temperature is 2.52x10^-7 S/cm for sample CMC-OA-PC 10 wt. %. The system obeys the non-Debye dependence based on the dielectric and modulus study.

Abstract: To improve writing capability of high magnetic anisotropy medium - L1₀-FePt, graded medium multilayer is one key candidate. Therefore, investigation of magnetic material properties of graded media multilayer is essential. In this work, we focus on magnetic properties of L1₀-FePt/Fe graded media multilayer such as hysteresis loop, magnetic energy and magnetic domain by the micromagnetic simulation the object oriented micromagnetic framework software based on the Landau - Lifshitz - Gilbert equation. The graded media multilayer can achieve reducing the switching field, H_sw, below available writing head field with high thermal stability. The anisotropy energy in graded media is higher than single layer and bilayer media that results in unstable magnetization in preferred direction. The proposed graded (f) and (g) structures are high grading magnetocrystalline anisotropy constant, K_u, that can reduce H_sw below single layer, bilayer and available writing head field. The hysteresis loop of low grading K_u structures has different steps; however, it disappear with high grading K_u structures of graded (e) - (g) structures. They have narrow loop compared with single layer. The results from this work lead to improve magnetic trilemma issue and increase data density.

Abstract: The present work deals with the findings on the ionic conduction behavior based on ethylene carbonate (EC) as plasticizer in carboxymethyl cellulose (CMC) – dodecyltrimethyl ammonium bromide (DTAB) for green polymer electrolytes (GPEs) that were prepared via solution casting technique. The highest ionic conductivity obtained for CMC-DTAB film was 7.72 x 10^-4 S/cm and enhanced to 2.37 x 10^-3 S/cm with addition 10wt. % of EC. The conductivity-temperature of GPEs system obeys the Arrhenius relation where the ionic conductivity increases with temperature. The temperature dependence of the power law exponent for plasticized CMC-DTAB based GPEs system follows the quantum mechanical tunneling (QMT) model for conduction mechanism.