Advanced Materials Research Vol. 701

Abstract: Functionalization of Santa Barbara Amorphous-15 (SBA-15) with vinyltriethoxysilane (VTES) via post-grafting method has been synthesized with the effect of calcination time span and temperature range. X-ray powder diffraction has been a means to evident the incorporation of VTES functional groups and to characterize the peak diffraction pattern. The samples of parent SBA-15 have been treated in different calcination temperature and time, ranging from 400°C to 800°C and 2 hr to 8 hr, respectively. The XRD results show that two dimensional p6mm of high order hexagonal mesoscopic structure of VTES/SBA-15 could not be retained at higher temperature of calcination than 700°C. However, the higher time spans of calcination up to 8 hrs preserve the long-range order of functionalized SBA-15.

Abstract: Single crystal of LiNbO₃ has been successfully grown by the Czochralski method in an air atmosphere with a r.f heating crystal growth system namely Automatic Diameter Control Crystal Growth System (ADC-CGS). This paper reports on the effect of new thermal insulation on the growth process of LiNbO₃ single crystal. The effect of hot zone thermal insulation design was investigated. The conditions required to grow high quality LiNbO₃ single crystals are described. A set of crystal growth processes were conducted with the rotation rate of the seed at 15 rpm and the pulling rate at 2.0 mm/hr kept constant. All of the runs were grown along <104> orientation. To control the diameter of the crystal, we have to alter the thermal environment inside the hot zone. In other words, during the crystal growth we have to increase the control power to get smaller diameter and decrease the control power to get larger diameter.

Abstract: onic conductivity and dielectric properties of starch based polymer electrolytes doped with silver nitrate (AgNO₃) at elevated temperatures were studied. The solid polymer electrolytes were prepared using the solution cast method. X-ray diffraction (XRD) analysis implied that the incorporation of 6 wt.% AgNO₃ increased the amorphous phase of the electrolyte. Temperature dependence conductivity plots showed that electrolyte containing 6 wt.% AgNO₃ obeyed Arrhenius rule with activation energy, E_a of 0.71 eV. The effect of temperature on the dielectric properties of the electrolyte was also studied in relation to the conductivity properties. The variation of dielectric loss with frequency was obtained from the power law exponent. Temperature dependence of the power law exponent concluded that the conduction mechanism of the 94 wt.% starch-6 wt.% AgNO₃ electrolyte followed the correlated barrier hopping (CBH) model.

Abstract: In the present study, the electrical and dielectric properties of a solid biopolymer electrolyte system based on starch doped with different amounts of silver nitrate (AgNO₃) were analyzed. The electrolyte system was prepared via solution cast technique. Electrical impedance spectroscopy (EIS) measurement for the system was conducted over a frequency range of 50 Hz - 1 MHz at room temperature. It was found that the sample containing 6 wt.% AgNO₃ obtained the highest conductivity value of 1.03 × 10^-9 S cm^-1. The effect of salt concentration on the dielectric properties of the electrolytes was also studied in relation to the conductivity properties. The dielectric studies indicated that the electrolytes in the present study obeyed non-Debye behavior.

Abstract: My ab initio electronic structure calculations in RSn_2n-1Te_2n, n=16, R = a vacancy, Cd, and In show that when Sn atom is substituted by R, the Density of State (DOS) of the valence and conduction bands get strongly perturbed. There are significant changes near the band gap region. Sn vacancy causes very little change near the bottom of the conduction band DOS whereas there is an increase in the DOS near the top of the valence band. Results for In impurity shows that, unlike PbTe, the deep defect states in SnTe are resonant states near the top of the valence band. In PbTe these deep defect states lie in the band-gap region (act as n-type). This fundamental difference in the position of the deep defect states in SnTe and PbTe explains the experimental anomalies seen in the case of In impurities (act as n-type in PbTe and p-type in SnTe).

Abstract: A potential candidate for intermediate temperature solid oxide fuel cell (IT-SOFC) cathode material which is strontium-doped lanthanum cobaltite, La_0.6Sr_0.4CoO_3-α (LSCO) has been synthesized by a complexing method. Citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) were used as a combined chelating agent and ethylene glycol (EG) was employed as surfactant. The obtained powder was characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). TGA results showed the thermal decomposition of the precursor gel was completed at 700 °C. A single perovskite phase of LSCO with cubic structure was obtained at calcination temperature of 1000 °C with heating/cooling rate of 10 °C min^-1 as confirmed by XRD analysis. SEM result revealed that the morphology of the powder was spherical in shape with diameter ranging from 250 to 650 nm. Apparently, the bulk sample consists of almost homogeneous and identical particles.

Abstract: Dielectric materials are one of the major parameters of RLSA antenna. Although so many studies have been conducted on optimization of RLSA antenna but little have been done on examining the effect of slow wave factor in the design. This paper examines the possible pitfall on the antenna performance due to dielectric materials.

Abstract: Malaysian low grade iron ore is unsuitable as raw material for domestic iron making due to high energy consumption which correspond to low iron content. The present agricultural residues from domestic palm oil industry are attractive proposition as energy source for iron making. This work describes the use of ash produced from pyrolysis of palm oil Empty Fruit Bunch (EFB) to magnetize the low grade iron ore. A briquette composite of iron ore and ash is subjected to reduction process using an electric tube furnace under argon atmosphere at 873K and 1073K. The ore was successfully magnetized through reduction process as carbon in EFB ash act as reductant. The results showed that the reduction degree was greatly enhanced with increasing of temperature and time. The significant phase changes of iron ore from a non-magnetic material of goethite to a strong magnetic material of magnetite was detected in XRD patterns. The process indicated that substitution of coal with EFB ash as an energy source has a potential in replacing fossil fuel by magnetizining the iron ore as well as encourage waste management control.

Abstract: Silver nanoparticles were deposited on glass slides and surgical suture as antibacterial agent. The silver nanoparticles were prepared by chemical reduction with sodium borohydride and using a synthetic polyelectrolyte as capping agent. Poly (4-styrenesulfonic acid-co-maleic acid) sodium salt PSSMA was used to stabilize the silver nanoparticles and provide an anionic surface charge which then allowed the layer-by-layer deposition method with poly (dially dimethyl ammonium chloride) PDADMAC. Various concentration of capping agent were used to prepare the silver nanoparticles which were then deposited on glass slide and surgical suture. The layer-by-layer deposition of the nanoparticles was studied using UV-Vis spectroscopy by monitoring the intensity of the characteristic Plasmon band of the nanoparticles at 400nm. The leaching of the silver nanoparticles in buffered solutions of pH 3,7 and 9 was monitored by recording the decrease in absorbance of silver nanoparticles film as a function of time for each pH solutions and each capping concentrations. Finally, suture material coated with silver nanoparticles were tested for their antibacterial activity against Staphylococcus aureus and results showed that all coated sutures had more than 99% bacterial reduction. So these suture material could be applied to use in medical products for promoted wound healing and decreased bacterial colony leading to relieve inflammation of patient.

Abstract: The effect of filler to the binary compound of Magnesium Iodide ( MgI₂) and Magnesium Phosphate (Mg₃ (PO₄)₂ is investigated. A small amount Alumina (Al₂O₃) filler in the range of 2-10 weight percent is added to the optimum composition with maximum conductivity of binary compound 0.7 Mg₃(PO₄)₂ and 0.3 MgI_2.The electrical conductivity of theMgI₂- Mg₃ (PO₄)₂ - Al₂O₃measured using the impedance spectroscopy (IS) method and result shows that the electrical conductivity of the compound has improved up to 9.84x10^-4Scm^-1. Field Emission Scanning Electron Microscopy (FESEM) images show some changes in the morphology after introduce the filler. The samples with filler showsnano flakes like structure with some space createdallowing the Mg²⁺cations to migrate that lead to enhanced conductivity.