Advanced Materials Research Vol. 545

Abstract: Pure and lithium-doped zirconia fibres have been produced using the electrospinning process. These fibres are seen to be mesoporous in nature and possess a dense outer skin that correlates with the existance of tetragonal structure. This tetragonal form exists in materials below a certain average grain size and also correlates well with capacitance retention, CV measurements and impedance response. During electrical performance, an initial irreversible solid electrolyte interface is believed to form and average grain size has a significant effect. This study suggests that in this mesoporous/skin form, electrospun zirconia fibres are promising energy storage materials.

Abstract: We have studied the effects of deposition conditions on the crystal structure of InN films deposited on Si substrate. InN thin films have been deposited on Si(100) substrates by reactive radio frequency (RF) magnetron sputtering method with pure In target at room temperature. The nitrogen gas pressure, applied RF power and the distance between target and substrate were 2×10^-2 Torr, 60 W and 8 cm, respectively. The effects of the Ar–N2 sputtering gas mixture on the structural properties of the films were investigated by using scanning electron microscope, energy-dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction techniques.

Abstract: We report the deposition of aluminium doped zinc nitride film (Al-Zn₃N₂) on glass substrates by RF sputtering. Thermal oxidation of the film under different annealing temperature (500°C to 600°C) was carried out. Structural and electrical properties of the annealed films were investigated. XRD analysis showed that Al-Zn₃N₂ film was successfully converted into Al-N zinc oxide (ANZO) at 500°C. I-V characteristics of the films were measured and the lowest estimated resistivity of the films of 4kΩ.cm can be achieved at 600°C.

Abstract: In this work, electrolyte films based on epoxidized natural rubber-50 (ENR-50) and lithium imide (LiN(SO₂CF₃)₂) salt were prepared using solution casting method. X-ray diffraction pattern for undoped ENR-50 shows a broad peak which indicated amorphous nature of the film. The intensity of ENR-50 peak decreases with increase in salt concentration. Thermal property study was carried out using Differential Scanning Calorimetry (DSC) to determine glass transition temperature, Tg. The DSC result displays an increasing trend of Tg with increase in salt concentration and opposite to the trend of variation of conductivity with salt concentration. This indicates that the increase in Tg dose not give adverse effect on ionic conductivity. The increase in Tg with concentration of salt may be due to formation of transient cross-linking between ENR-50 chains via the coordinated interaction between ENR-50 chains and LiN(SO₂CF₃)₂. The highest room temperature ionic conductivity obtained is in the order of 10^-5 S cm^-1 for the film containing 50 wt.% of LiN(SO₂CF₃)₂. The ionic conductivity of this electrolyte system increases with increase in temperature and obeys the Vogel-Tammam-Fulcher (VTF) relation in the temperature range of 303–373 K. The increase in ionic conductivity of the electrolyte system could be correlated to increase in number of charge carriers and the migration rate of charge carriers.

Abstract: Poly [2-methoxy, 5-(2-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) is a conjugated polymer that exhibit excellent luminescence properties in the visible spectrum. The fundamental absorption edge in the film is formed by the direct allowed transitions. In this work, free-standing films of MEH-PPV and MEH-PPV/MCMB were obtained by a solvent casting method. Mesocarbon Microbead (MCMB), a type of carbon, is added to the polymer producing composite films. The films were characterized by using the UV-Vis-NIR spectrophotometer. The film samples exhibited an absorption band in the red visible region. This is due to the electron transition between the non-localized bands. However, when MCMB is doped into the polymer matrix, the band absorption edge is red-shifted compared to that of the MEH-PPV pure film. Therefore, the optical band gaps of the composite films have decreased due to the presence of MCMB.

Abstract: Poly(vinyl) chloride (PVC)-NH₄I-EC films have been prepared by solution cast technique. The sample containing 30 wt. % NH₄I exhibited highest room temperature conductivity of 4.60 × 10^-7 S cm^-1. The conductivity increased to 1.08 × 10^-6 Scm^-1 when 15 wt. % of ethylene carbonate (EC) was added to 70 wt. % PVC - 30 wt. % NH₄I. Fourier Transform Infrared (FTIR) showed evidence of polymer–salt complexation while DSC showed increase in glass transition temperature (T_g ) of PVC -NH₄I - EC polymer electrolytes. The conductivity behavior of the studied system could be accounted by the changes in T_g values.

Abstract: Films of hexanoyl chitosan containing lithium perchlorate (LiClO₄) or lithium triflouromethanesulfonate (LiCF₃SO₃) were prepared by solution casting technique. The effect of anion size on the conductivity behaviour of hexanoyl chitosan has been investigated. The conductivity of 4.15 × 10^-7 S/cm and 4.07 × 10^-6 S/cm were achieved for the hexanoyl chitosan-LiClO₄ and hexanoyl chitosan-LiCF₃SO₃ electrolyte system at 50wt.% of salt concentration, respectively. The Rice and Roth model was used to analysis quantitatively the obtained conductivity trends for the prepared electrolyte systems. The diffusion coefficients of cations and anions were calculated from the conductivity and transference number measurements. This is followed by the discussion on the diffusion coefficients of ClO₄^- and CF₃SO₃^- anion.

Abstract: Ni_0.4Zn_0.6Fe₂O₄-polypropylene (PP) composites were investigated for their dielectric property which constitutes the dielectric constant , and dielectric loss factor . Nickel zinc ferrites (NZF) were prepared via the conventional solid state method and sintered at 1250 °C for 10 hours. Ni_0.4Zn_0.6Fe₂O₄ acts as filler while PP is the matrix. 5% and 25% NZF were added into the PP and blended to form NZF-PP composites. Dielectric measurements were made from room temperature to 120 °C at 20 °C intervals using the HP 4284A Precision LCR Meter at frequencies 240 Hz to 1 MHz. is almost constant and independent of frequency and temperature below 100 KHz before decreasing showing dispersion probably due to space charge or interfacial polarization. Distinct relaxation loss peaks can be seen emerging at about 100 KHz shifting towards the higher frequency with increasing temperature. Generally, increasing the content of filler improve the dielectric strength of the composite. Thus, addition of NZF enhances the dielectric properties of NZF-PP composite.

Abstract: In this study, composite lumber from a combination of bamboo strips and oil palm trunk veneers was produced and physically tested. The bamboo strips and oil palm trunk veneers were laid-up together alternately with two different types of layer orientation, such as parallel and cross orientations to each other. The composite lumber was pressed using hydraulic hot pressing machine at two different pressing times, such as 12 and 15 minutes. Phenol formaldehyde (PF) adhesive was used in the lamination process. Physical performance tests such as cold water delamination (CWD), hot water delamination (HWD), flexural and compression were conducted based on Japanese Agricultural Standard for LVL JAS: SE-10 [1]. Results showed that longer pressing time has increased the physical performance, except for flexural and compression performance of parallel orientation composite lumber. Cross orientation has increased the bonding strength behaviour between bamboo strips and oil palm trunk veneers, thus influenced the low delamination percentage and good modulus of elasticity value of composite lumber. Generally, this study has increased the understanding on physical performance of bamboo strips-oil palm trunk veneers composite lumber at different layer orientations and hot pressing times.

Abstract: This article investigated the effects of particle size of zinc oxide (ZnO) and polystyrene-co-maleic anhydride (SMA) compatibilizer on impact strength and morphology of polystyrene (PS)/ZnO71 (71 nm) and PS/ZnO250 (250 nm) nanocomposites. PS/ZnO nanocomposites with varying concentration of ZnO and SMA were prepared by a melt mixing technique in a twin screw extruder. It was found that the impact strength of PS nanocomposites increased up to a ZnO content of 1.0 wt%. Moreover, PS/ZnO250 nanocomposites had higher impact strength than PS/ZnO71 nanocomposites. The addition of SMA increased the impact strength of PS/ZnO nanocomposites with increasing SMA content. The result showed that SMA could improve impact strength of nanocomposites. The dispersion of ZnO particles on PS/ZnO nanocomposites was studied by scanning electron microscope (SEM). It was observed that the dispersion of ZnO particles of PS/ZnO nanocomposites without SMA was non-uniform and the agglomeration of ZnO particles in the polymer matrix increased with increasing ZnO content. The dispersion of ZnO particles of PS/ZnO nanocomposites after adding SMA was relatively good and only few aggregations exist. These observations support the results of the impact test where the PS/ZnO nanocomposites with SMA displayed higher impact strength than the PS/ZnO nanocomposites without SMA. The study showed that SMA was used as a compatibilizer to improve the dispersability and compatibility of ZnO particles in PS matrix.