Functional Materials and Devices

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Authors: Baktiar Musa, Ahmad K. Yahya, Faizah Md. Salleh, R. Abd-Shukor
Abstract: This paper reports on the effects of Ag addition on physical properties of high temperature superconductors DyBa2Cu3O7-δ (Dy123). A series of the Dy123 - Agx composite was prepared by solid state reaction method with varying amount of metallic silver (x = 0 – 0.3). Resistance versus temperature measurement was done using the four-point-probe method in the temperature range of 79 K to 300 K. Pure DyBa2Cu3O7-δ was found to superconduct with Tc onset of 91 K and Tc zero of 78 K. Addition of Ag at x = 0.05 caused both Tc onset and Tc zero to increase to 93 K and 84 K, respectively. However, Tc onset and Tc zero dropped for higher silver contents. We found that the optimum silver content in DyBa2Cu3O7-δ for best superconducting behavior and hardness is between x = 0.05 and 0.10. Microstructure analysis using SEM and EDAX showed that most of the silver is uniformly distributed along the grain boundaries filling the pores and hence increasing the hardness of the samples.
Authors: A. Huda, S.A. Halim, K.P. Lim, O.J. Lee, S. Elias, A.A. Sidek, Z. Hishamuddin
Abstract: Polycrystalline samples of La0.67Ba0.33(Mn1-xRux)O3 with x = 0, 0.05, 0.1, 0.15 and 0.2 have been prepared using solid state reaction. The effects of doping of Ru at Mn site on La-Ba-Mn- O ceramics, the characteristics and magnetotransport properties of CMR materials are investigated. The magnetoresistance (MR) effect is measured using the four point probe technique. The magnetoresistance defined as MR% = (Ro – RH)/RH x 100% was measured at a magnetic field of H ≤ 1T at 90K, 100K, 150K, 200K, 250K, 270K and 300K for the sample of doping x = 0, 0.05, 0.1, 0.15 and 0.2. Overall, MR drops slowly when temperature rises. All doping concentration gives small variation range (~2.7% to ~26.78%). The electrical property has determined by using standard four-point probe resistivity measurement in a temperature range of 30 K to 300 K. Metalinsulator transition temperature (Tp) shifted to lower temperatures as Ru doping is increased. In this paper the structural pattern and microstructure property have investigated via XRD. XRD patterns show that these systems are in orthorhombic distorted perovskite structures.
Authors: K. Ramesh, Z.H.Z Abidin, Zurina Osman, Wan Jeffrey Basirun, A.K. Arof
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.
Authors: Hyoun Woo Kim
Abstract: We have studied on the use of a GaN powders for growing gallium oxide (Ga2O3) nanoribbons and nanosheets by the thermal evaporation technique. We used x-ray diffraction, scanning electron microscopy, and transmission electron microscopy to characterize the samples. The results showed that the produced Ga2O3 nanomaterials had single crystalline monoclinic structures. The proportion of wider nanoribbons or nanosheets to nanoribbons increased by increasing the growth temperature and by employing the mixture of GaN and ZnO powders.
Authors: H.T. Ooi, Kamarulazizi Ibrahim
Abstract: This paper presents an analysis of diamond-like carbon thin film deposited using homebuilt microwave chemical vapor deposition. Two different deposition conditions were investigated, namely, with and without microwave power. Post deposition analysis included Raman spectroscopy, scanning electron microscope (SEM), energy dispersed X-ray (EDX), four-pointprobe resistivity measurements and refractive spectroscopy. Substrate with pretreatment was observed to have thin film formation. Samples with diamond paste pretreatment show better quality compared to SiC treated samples as suggested by Raman spectral. The presences of sp3 and sp2 peaks were identified in the Raman spectral. The overall resistivity is low due to the graphite content.
Authors: A.Y. Hudeish, C.K. Tan, Azlan Abdul Aziz, Hassan Zainuriah
Abstract: In this paper we report on the characteristics of Pd/GaN and Pd/Si Schottky barriers exposed to different gases at various temperature range from 25°C to 500°C. The characteristics of Pd/GaN and Pd/Si Schottky barriers as gas sensors were measured as a function of temperature and ambient. Both types of sensor show changes in forward current upon introduction of different gases (N2, air, H2) into the ambient. The devices can be operated at large forward current, leading to large signal size for current at short response time for switching from one gas ambient to another such as N2 to H2 (2%) in N2. The signal size increases with the increase in measurement temperature due to more efficient cracking of the gas molecules. Both types of devices appear well suited to combustion control and leak detection.
Authors: Khaulah Sulaiman, Wan Haliza Abd Majid, Muhamad Rasat Muhamad
Abstract: The molecular organization of the phospholipids Langmuir-Blodgett (LB) films on solid substrates has been studied via Fourier Transform Infra Red (FTIR) spectroscopy. In this study, the formation of well organized ultra thin LB films of phospholipid molecules has been performed by depositing the monolayer onto the solid substrates of silicon wafer. The space filling molecular models of two types of phospholipids have been proposed on the basis of the FTIR spectra.
Authors: Sha Shiong Ng, Hassan Zainuriah, Abu Hassan Haslan, M.E. Kordesch
Abstract: In this paper, we report on the characterization of a set of MOCVD grown GaN samples with a variety of structural or crystalline quality. X-ray diffraction (XRD) was used to observe the change of the crystalline structure with deposition temperature. All results show that the structure type of the GaN deposited films is sensitive to the growth temperature. Our results also revealed that a good crystalline structure of GaN films could be grown at temperatures higher than 600°C. Finally, a general picture on the correlations between the growth temperature and the GaN deposited films crystalline is reported.
Authors: Iis Sopyan
Abstract: SiO2 -TiO2 glass fibers have been prepared via dry spinning of the viscous solutions of polytitanosiloxanes followed by steam treatment and pyrolysis at 500, 700, and 900 °C for 1 h under ambient condition. The polymer was prepared via polycondensation of partially hydrolyzed tetraethoxysilane (TEOS) and an acetylacetone-chelated titan compound at various H2O/TEOS and Si/Ti ratios. Gel fibers formed shown tensile strength as low as 200 MPa and increased around 3 times after pyrolysis. The higher degree of TEOS hydrolysis the higher tensile strength of the fibers. The polymer with higher Si/Ti ratio also provided stronger fibers due to more extensive siloxane network. Fibers with the highest tensile strength, 610 MPa, was obtained from the polymer synthesized with SiO2/TiO2 mol ratio 20 and pyrolysis temperature 700 °C.
Authors: Hyoun Woo Kim, Ju Hyun Myung, Chong Mu Lee
Abstract: We have synthesized the film-like and rod-like structures of indium oxide (In2O3) by metalorganic chemical vapor deposition (MOCVD) method. The structural morphology of the deposits changed from the film to the arrays of 1-dimensional (1-D) materials with increasing the deposition temperature. The 1-D materials with the serrated surfaces prepared at 350°C possessed a crystalline cubic structure and had preferentially grown along the [111] direction.

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