Advanced Materials Research Vols. 55-57

Abstract: BaFe0.5Nb0.5O3 (BFN) exhibits very high dielectric constant over a wide temperature range. However, these materials normally require high-temperature sintering to achieve a maximum densification. The aim of this study is to determine the effect of potassium fluoride salt on the sintering and dielectric properties of BFN ceramics. The results show that KF additive lower the sintering temperature by 100-200°C without affecting the formation of BFN phase. Ceramics doped with 1% KF show optimum densities of about 95% of the theoretical value when sintered at 1300°C. The addition of fluoride salt in the BFN ceramics causes very broad dielectric constant curves over a wide temperature range indicating the diffuse phase transition characteristic. Furthermore, this addition also reduces in the dielectric loss when compared with pure BFN ceramics

Abstract: In this work, preparation conditions and effect of ZrO2 doped BaFe0.5Nb0.5O3 ceramics were studied. Relationship between structure and dielectric properties was investigated. Single-phase cubic BFN powder was synthesized by solid-state reaction at 1200°C for 4 hours with heating and cooling rate of 5°C/min. Various amount of ZrO2 doped from 0.1 to 0.5 %weight were used for doping. After that BFN ceramics were formed via uniaxial pressing and sintered at 1300°C for 4 hours with heating and cooling rate of 5°C/min. Physical properties, microstructure, phase evolution and dielectric properties were studied to find out the optimum conditions for high voltage capacitor applications.

Abstract: Polyhydroxyalkanoate (PHA) is biodegradable polyester, which can be synthesized by many microorganisms through catabolic pathway, without producing any toxic byproduct. Owing to it special and versatile properties, this polymer has attracted much attention as a possible replacement for traditional plastics in the future. Feasibility of PHA production from inexpensive substrates was investigated by using Alcaligenes latus, gram negative bacteria, which can be grown in various types of wastewater. Four substrates were employed, i.e., wastewater from palm oil industry (oil-lean palm oil and oil-rich palm oil), wastewater from soymilk industry, and a control synthetic wastewater. The results show that PHA copolymer, poly(hydroxybutyrate-co-hydroxyvalerate) P(HB-co-HV), is produced from the metabolic pathways of A. latus. Soxhlet extractor was then employed in extraction process of the PHA copolymer. The resulting copolymer was characterized by Fourier Transform Infrared (FTIR) spectroscopy, and Nuclear Magnetic Resonance (NMR) Spectroscopy.

Abstract: Urea fertilizer is a major source of nitrogen, which is one of the essential nutrients for plant growth. Due to its uncontrollable release, this chemical can be wasted easily by leaching and volatilization that can adversely cause the contamination to the environment. In this work, a controlled-release material for urea fertilizer has been prepared by using degradable polylactic acid. Unlike other conventional controlled-release system, the resulting material is able to provide an efficient supply of urea fertilizer, without causing further contamination to the environment from residue material, as polylactic acid can be degraded in the environment. Micron-size particles of polylactic acid coated urea were prepared by employing atomizing technique. Effect of the preparation conditions; urea/PLA composition, PLA concentration, and pressure of atomizing gun on the particle size of material are investigated. The urea release rate of these samples is then studied by employing UV-Visible spectrophotometer. In addition, the effect of preparation conditions on shape and morphology of sample is determined by using Scanning Electron Microscope (SEM).

Abstract: Ferromagnetic materials are now interested by researchers as they have applications in various industries. Due to the complexity of the materials, an important contribution to enhance the technological development has come from the theoretical and simulation studies especially from the Monte Carlo simulation. Nevertheless, the Monte Carlo is often limited in its performance because the computational limitations, such as the simulated system sizes and simulation times. These limitations also put a constraint on the simulation time which caps the numerical accuracy. The artificial neural network is used in this study in cooperating with the Monte Carlo simulation. The aim is to investigate the possibility in obtaining the Curie temperature of ferromagnetic Ising spin in a fine scale without an intense computational required. From the results, the extracted Curie temperature is found to agree well with those from the exact theoretical analysis which verifies the artificial neural network to be a very useful technique.

Abstract: ontrolled-release materials for urea are prepared by spray coating urea granulates with lactic acid based homo- and co-polymers solutions. Percent coating as a function of polymer types, molecular weight, polymer concentration, and dose applications are examined by gravimetric analysis. Percentage of urea dissolution in water of the coated fertilizer is measured by monitoring refractive index of the solutions. Morphology of the polymer coating surfaces is revealed by Scanning Electron Microscopy (SEM). It was found that an amount of cracks and pin-holes, which is dependent on polymer types and molecular weight, plays a significant role in controlling the rate of urea release. Results from urea dissolution test also suggests that the synthesized poly(lactic acid-co-ethylene terephthalate) show urea-holding efficiency comparable to that of commercial PLA, despite its much lower molecular weight, indicating that the copolymer is potentially suitable for this specific application.

Abstract: The goal of the current research is the development of an approach that anchors b-cyclodextrin (b-CD) and vanillin fragrance to cotton fabrics simultaneously using traditional pad-dry-cure and pad-dry-batch processes. 2-hydroxypropyl-b-cyclodextrin (HP-b-CD) was mixed with vanillin in water at room temperature and the resultant complex was then applied on the fabric with the use of two crosslinking agents, i.e. glyoxal and a commercial CIBA Knittex® FA CONC. The effects of the amount of HP-b-CD and the type of crosslinking agents on the amount of vanillin deposited on the fabric and its release rate were investigated using UV spectrophotometry.

Abstract: To recover residual rubber from skim natural rubber (SNR) latex, the effective and environmentally friendly methodology developed based on using hydroxypropylmethylcellulose (HPMC) as a thermo-responsive flocculant. The SNR particles could be completely separated to form high concentrated latex as cream phase within only 5 hours. Almost 100% of SNR was recovered when using HPMC 0.7%w/w. Quality of SNR obtained from this technique was higher and color of it was lighter than SNR obtained from the conventional method. HPMC could be easily precipitated from the serum phase by heating the serum phase at about 70 °C. The cloud point and the precipitation point of HPMC were affected by the additions of α-D-glucose, sn-phosphatidyl chloride and inorganic salts. It was found that reduction of the cloud point and the precipitation point of HPMC also depended on both concentration and type of cations and anions of inorganic salts.

Abstract: The microstructure and interface quality of chemical solution deposited barium titanate thin films on Ni foil were studied. Cross-sectional transmission electron microscopy shows that a ~200 nm thick barium titanate film annealed in a controlled oxygen partial pressure consists of equiaxed grains with grain size range of 24-75 nm (~ 42 nm average). NiO was detected after re-oxidation by X-ray diffraction, but not by transmission electron microscopy, suggesting that the oxide is not a continuous barrier layer, but is spatially distributed in the films. Oxygen non-stoichiometry and the existence of C in barium titanate films were observed by electron energy loss spectrometry. In addition, it was found that there is a 5-8 nm thick Ni-Ba alloy developed at the interface between the barium titanate film and Ni foil.

Abstract: Indium tin oxide (ITO) films had been deposited on glass substrate without substrate heating and then tungsten oxide (WO3) films were deposited on ITO films by DC magnetron sputtering. In this work, we present the annealing ambient effect of ITO substrate on electrochromic properties of WO3 films. The ITO films were annealing in air and in vacuum at 350°C before coating with WO3 films. The structural, optical, and electrical properties of ITO films for as-deposited, annealing in air and in vacuum were investigated by X-ray diffraction, UV-VIS-NIR spectroscope and four point probe. The ITO films had a better crystallinity and lager grain size after annealing in air and in vacuum. The resistivity of ITO films increase with annealing in air, but decrease with annealing in vacuum. The WO3 films show difference surface morphology with higher grain size and surface roughness when coating on annealed ITO films in both cases. The electrochemical properties of film systems were characterized by cyclic voltammetry. The film systems of ITO plus WO3 showed that the charge capacity of ITO substrate annealing in vacuum was higher than the as-deposited ITO substrate and the ITO substrate annealing in air, respectively. This result corresponded to electrical conductivity of each ITO substrate.