Functional Materials and Devices

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Authors: Rozidawati Awang, Goh Boon Tong, Siti Meriam Ab. Gani, Richard Ritikos, Saadah Abdul Rahman
Abstract: A direct-current plasma enhanced chemical vapour deposition (PECVD) system was designed and built in-house for the deposition of hydrogenated amorphous carbon(a-C:H) thin films. In this work, a-C:H thin films prepared using this system at different deposition pressures were studied. The influence of deposition pressure on the deposition rate, energy gap, bonded hydrogen content and structure of the film has been investigated. The characterization techniques were determined from optical transmission spectroscopy, Fourier transform infrared spectroscopy and Xray diffraction measurements. The results demonstrated that the deposition pressure had strong influence on the deposition rate, optical energy gap and the bonded H content in the film. Evidence of crystallinity was observed in films prepared at low deposition pressure.
Authors: Tan Winie, S.R. Majid, M.F. Hassan, A.K. Arof
Abstract: Hexanoyl chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. The effect of plasticizers on the electrical properties of hexanoyl chitosan: LiCF3SO3 electrolytes have been investigated. The plasticizers used were EC, PC and a mixture of EC and PC. The highest room temperature conductivity of about 1.1 x 10-4 S cm-1 was achieved for electrolyte with composition of 50:50 (wt.%) mixture of PC: EC. The variations in conductivity have been explained using the Rice and Roth model from which the numbers of free ions per unit volume, mobility and diffusion coefficient of free ions were obtained. Electrochemical cells based on LiCoO2/MCMB couple were assembled using the electrolyte that exhibited the highest ionic conductivity. The performance of the cells have been studied and discussed in this paper.
Authors: M.F. Hassan, N.H. Idris, S.R. Majid, Tan Winie, A.S.A. Khiar, A.K. Arof
Abstract: The plasticized PEO-KOH films have been investigated using the electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The conductivity of films increased by about 2 orders of magnitude from 10-5 to 10-3 S cm-1 at r.t. on addition of 0.5 wt.% of ethylene sulphite (ES). The degree of crystallinity was calculated from the XRD patterns. SEM micrographs show that the plasticized films were porous. The highest conductivity of plasticized films at r.t. was (1.3 ± 0.2) x 10-3 S cm-1 for the film with 0.5 wt.% of ES content. The number density of mobile ions was shown to increase indicating that ES has dissociated more salts into ions and thereby increasing the conductivity.
Authors: O.J. Lee, S.A. Halim, K.P. Lim, Z.A. Talib, A. Huda, I. Priscilla
Abstract: The significant influences of substituting low concentration Dy at La- site for La0.667Sr0.333MnO3 perovskites compounds in structural, electrical and magnetoresistance properties have been studied. The polycrystalline samples (La1-xDyx)0.667Sr0.333MnO3 with x= 0.00, 0.02 and 0.10 were synthesized via conventional solid-state reaction in bulk. This work measured their resistivity properties with (below 1 Tesla) and without the presence of magnetic field (0 Tesla) as a function of temperature, microstructure and particle distribution and structural distortion using four point probe resistivity technique, X- ray diffractometer (XRD) and Atomic Force Microscope (AFM). The resistivity in applied magnetic field or so-called magnetoresistance ratio is defined as MR% = (Ro – RH)/RH x 100 was measured at 90K, 100K, 150K, 200K, 250K, 270K and 300K. The highest MR% values for x=0.00, 0.02 and 0.10 are 15.3%, 15.5% and 20.6% at 1 Tesla respectively. The metal- insulator transition temperature, TMIT correspond to >300K, 298K and 230K of sample with x= 0.00, 0.02 and 0.10 respectively were observed from resistivitytemperature (R-T) curve.
Authors: M.I.N. Isa, S.R. Majid, A.K. Arof
Abstract: A gel electrolyte system was prepared by dissolving poly(methyl methacrylate) in ethylene carbonate and propylene carbonate doped with salicylic acid and plasticized with dibutylphthalate (DBP). The gel was heated to 70 0C before it was cast into glass dishes. The composition of the electrolytes was 35 wt% EC, 30 wt% PC, 5 wt% SA, 5wt% DBP and 25 wt% PMMA. The gel electrolyte was sandwiched between two stainless-steel blocking electrodes and impedance measurements were conducted. The conductivity of the gel electrolyte was 2.03 x 10-4 S cm-1 at room temperature. The conductivity activation energy was obtained from the log σ versus 103/T graph. Loss tangent was calculated at every frequency for all temperatures. From the tan δ versus frequency plot, the activation energy of relaxation of the ion was calculated and plotted as ln τ versus 103/T. The conductivity activation energy value was (0.21 ± 0.04) eV and the activation energy of relaxation was (0.24±0.07) eV. The similarity between these activation energies imply that the protons ‘hop’ from one electronegative oxygen site in DBP to another.
Authors: Siti Aishah Hashim Ali
Abstract: A mathematical model for the transport in cathode of a lithium-ion cell is developed and analytical solutions to the model equations are obtained. The derived equation is tested by fitting it to published experimental discharge characteristics. Wherever possible, the values of the relevant parameters are obtained from the same literature from which the discharge characteristics were obtained. The agreement between the predicted and the experimental discharge curves are measured statistically using t-test. Since the discharge characteristics are usually plotted as voltage versus time or capacity or even state-of-discharge, hence the expression for the cell voltage has been derived.
Authors: Abdul Hadi, Iskandar Idris Yaacob, Cheah Seok Gaik
Abstract: Nanocrystalline cerium dioxide (CeO2) has been successfully synthesized by mechanochemical technique at 12, 24, 36, 48 and 60 hours milling times. The starting materials, hydrated cerium carbonate and sodium hydroxide, were mixed in a weight ratio of 4:1 and were milled in a planetary ball mill with ball to powder ratio of 10:1. The high energy impact forces provided by the milling media caused collision of starting materials and allowed the chemical reaction to occur thus produced nanocrystalline cerium dioxide. The products were characterized using a battery of characterization methods, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and gas adsorption-desorption measurement. The nanocrystalline CeO2 with 6.7 nm of crystallite size and specific surface area of 66.66 m2/g was obtained when the sample was milled for 60 hrs and they annealed in air at 350 oC. The result showed that the crystallinity of nanocrystalline CeO2 decreased with increasing milling time.
Authors: B. Vengadaesvaran, R. Puteh, A.K. Arof
Abstract: Silicone modified acrylic polymer dispersion was prepared by blending methoxy functional silicone intermediate resin with acrylic polyol resin in different ratios. The physical, mechanical and thermal properties were investigated. The physical property of the blend has been carried out by using Kruss G40 contact angle measuring system, mechanical property of the blend evaluated by using impact resistance tester and adhesion tester (Cross Hatch- Cutter) and thermal analysis has been carried out by using Metler Toledo thermal analysis system DSC821. It is found that the incorporation of 50% silicone resin with 50% acrylic resin gives good adhesion on metal substrate (mild steel substrate) and optimal cross-linking is achieved.
Authors: Mohd Ambar Yarmo, Raja Saadiah Raja Shariff, Siti Rohaya Omar, Juan Joon Ching, Roziana Haron
Abstract: This paper will review on the latest development on solid acid catalysts used in industries as well in research activities. Application of heterogeneous acid catalysis becomes current trend for many industries due to world wide environmental concern. Conventional synthetic or natural zeolites widely used for petrochemical processing, has some limitation because its pore size is normally smaller than reactant molecules. To overcome this challenge new delaminated zeolite process was introduced. In this process specific synthetic zeolite (i.e. ferrierite) was swelled up using specific surfactant followed by sonification to produce the delaminated zeolite. Further modification of this material such as sulfonification reaction to its surface has been found to improve the catalytic activity and selectivity for esterification reaction. Other acid catalyst systems based on mesoporous molecular sieves and Keggin heteropolyacids (HPA) are also discussed in this paper.
Authors: Shahrul Nizam Shahdan, Azman Jalar, Muhammad Azmi Abd Hamid
Abstract: A tin-lead solder is generally used to mount an electronic package on to a printed circuit board (PCB) of an electronic devices. In this study, we investigated the microstructure of the solder joint from a four years old used mobile phone. Microstructure and morphology of the joint was obtained using optical and scanning electron microscopy (OM and SEM) respectively. Cracks and voids can clearly be seen in the solder area for the most of the sample observed. Crack up to 10 μm wide appeared to be propagating along the solder line between Cu lead and Cu substrate. Energy dispersive X-ray (EDX) analysis revealed that cracks occurred at the richer tin content. It was not clear the exact mechanism that leads to the existence of the crack. However we believe that thermomechanical cause such as thermal fatigue, void formation and the thicker layer of intermetallic compound contributed to the failure of the solder joint.

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