Papers by Author: A.K. Arof

Abstract: Crystalline thin of zinc selenide have been electrochemically deposited on conducting substrates of indium tin oxide, ITO glass. Initial investigation with voltammetry was done and shows that the zinc selenide films were stable towards oxidation. The best deposition potential obtained was at -0.95 V vs. Ag /AgCl while at lower deposition potentials, the films do not form well. Energy Dispersive Analysis and X-Ray spectrum indicate that the films deposited at 65oC and -0.95 V vs. Ag/AgCl have nearly stoichiometric Zn: Se ratio.

Abstract: Electrodeposition of ZnTe thin films by controlled potential method from aqueous solutions on ITO were done to investigate characteristics suitable as a window material in solar cells technology. The influence deposition of potential towards the Zn:Te ratio and the crystallinity are discussed. The electrodeposited films were investigated by using X-Ray Diffraction and Energy Dispersive Analysis of X-Ray. The Te content decreases at higher deposition potentials.

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.

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.

Abstract: Corrosion protection is one of the important performance properties of organic coatings. In this study, an attempt has been made to develop a high temperature coating. Different compositions of silicone and polyester resins are taken and mixed well with the addition of a hardener. The binder system is applied on the pre-treated cold rolled steel panels. Physical and mechanical properties are evaluated. Thermal resistance of the coating system is done according to specification of ASTM D2485 standards. DSC and TGA analyses are carried out to study the glass transition temperature and temperature dependence of the sample prepared respectively. Corrosion protection ability of the system is evaluated by electrochemical impedance spectroscopy (EIS) and immersion studies. From the thermal studies, the coating containing 40% silicone and 60% polyester has withstood up to 498 K.

Abstract: Measurement of the ionic conductivity for the CA-NH4CF3SO3-DMC system was carried out at frequencies of 50 Hz to1 MHz and also at temperatures of 298 K to 313 K. The plot of log σ versus 1000/T shows a linear behavior suggesting that the samples obey the Arrhenius relationship. The electrical relaxation of the system was analyzed using the complex electric modulus M* of the sample with the highest ionic conductivity at various temperatures. The analysis of electrical modulus and dissipation factor (tan δ) shows that charge transport occurs through a hopping mechanism.

Abstract: The corrosion protection property of the coating consisting of acrylic resin mixed with curcumin and dammar was investigated by immersing in 3% NaCl solution using potential - time measurement. The investigation was performed until corrosion occurred at the coating and substrate interface. As the coating degraded the penetration of electrolyte, the potential value of the coated sample decreases to a value of – 0.65 V. In this study the coating with pigment volume concentration of KC30% can withstand against corrosion by 3% NaCl solution.

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.

Abstract: A gel electrolyte system was prepared by dissolving poly(methyl methacrylate) (PMMA) in ethylene carbonate (EC) and propylene carbonate (PC) doped with salicylic acid (SA) and plasticized with dibutyl phthalate (DBP). The composition of the electrolyte was 35 wt% EC-30 wt% PC-5 wt% SA-5wt% DBP-25 wt% PMMA. The presence of a hump at ~760 cm-1 and a shoulder at 1155 cm-1 in the spectrum of SA-DBP indicate the protonation of DBP. The effect of these bands can also be observed in the spectrum of the gel. Hence, SA has dissociated producing H+ which then interacts datively at the oxygen sites of DBP.

Abstract: In this work, lawsonia pigment obtained from Henna leaves was mixed with acrylic resin and a mixture of acrylic and dammar resins (RD50%) to form two paint systems BC30% and BDP30%. The two paint systems were characterized by potential-time measurements, impact resistance, glass transition temperature (Tg) and cross hatch tests.