Materials Science Forum Vol. 981

Abstract: There are three objectives to be achieved in this research which include to synthesis high purity ZnO pellets with different sintering time and green body pressure by using powder metallurgy process, the growth of ZnO crystal on ceramic bar by applying different current when conducting electric current heating (ECH) method and the characterization of ZnO crystal growth. In this research, high purity of ZnO powder is grinded and compressed at 3.5 tons, 4.5 tons and 5.5 tons to fabricate ZnO green pellets. Then, the ZnO green pellets are sintered for 3 hours and 5 hours. Next, the pellets are cut into bars and apply ECH method. The amount of current applied for the crystal growth are 2A and 3A. Finally, the crystal grown on the ZnO ceramic bar is characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Ultraviolet-visible Spectroscopy (UV-Vis) and Photoluminescence Spectroscopy (PL). High purity ceramic pellets are successfully synthesis by powder metallurgy process. By conducting ECH method, crystal are grown on the surface of ceramic bar. Most crystal structure found in ZnO ceramic bar is needle-liked rod structure which is hexagonally formed by many nanorod. The crystal grown in (100) orientation with the crystalline size of from 57.80 nm to 100.31 nm. The band gap energy obtained from UV-Vis were found between 3.2 eV to 3.4 eV which is nearly similar to the theoretical value of 3.37 eV. Lastly, PL emission measurement give the peak that range between 579 nm to 587 nm which indicate that the sample exhibit yellow colour. Among three different pressure applied, 4.5 tons gives the lowest emission energy. It is considered as the critical pressure in the synthesis of ZnO crystal. The intensity of PL is considered inversely proportional to intensity of XRD in [100] direction. Pressing pressure doesn’t show significant effect on the crystal growth of ZnO but current applied during ECH method and sintering time do give effect on UV-Vis absorption spectra and XRD result respectively.

Abstract: The optimization of magnetic uses of magnetic garnet type ferrites is largely known depending on their microstructure, synthesis process and chemical composition of the materials. This research investigates the effect of dopants substitution on microstructure and magnetic properties of Yttrium Iron Garnet (YIG). The oxide-mixture route was employed in synthesizing the YIG powders using Aluminium and Lanthanum as dopants with concentration of 0.5 prior to sintering at 1400 °C. The samples were characterized in several testing applications in order to study the structural, microstructural, magnetic properties and density effects toward the samples workability as ferromagnetic materials. Characterization of the samples were carried out by using Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Impedance/Materials Analyzer and density measurement. The results showed that La-doped YIG shows an incredible achievement as a new ferromagnetic material, meanwhile with the substitution of Aluminum ion would increase the magnetic response of YIG.

Abstract: Metal-organic frameworks (MOFs) composed by coordination bonds between metal ion with organic linker has a uniform combination of micro and mesoporous structures has been used for several application including battery supercapacitor hybrid. (BSH). In BSH, MOF offer several advantages including high surface area, porous, and structure tunability. This paper reports the synthesis of ternary MOF of copper (Cu), nickel (Ni) and cobalt (Co) with 1,4-benzenedicarboxylic acid. The Co/Cu/Ni-MOF is synthesized using hydrothermal method at 160 °C for 12h and further develop as a BSH electrode. The physicochemical properties of MOF were characterized using FESEM, FTIR, XRD, BET and the electrochemical properties were evaluated using cyclic voltammetry (CV), charge-discharge cycling (CDC) and electrochemical impedance spectroscopy (EIS). Electrochemical analysis indicated that the MOF has high specific capacitance (C_S) of 591 F g^-1 at a current density of 1 A g^-1 and 519 F g^-1 at scan rate of 2 mV s^-1, and possess low series resistance (R_S) of 0.44 Ω and equivalent distributed resistance (R_d) of 1.07 Ω.

Abstract: Graphene oxide (GO) is a promising material that currently a common precursor in the synthesis of graphene material. GO has emerged as a rapidly developed material due to its remarkable application in electronics, energy storage, biomedical and chemistry. However, controlling the oxygen content in the GO is one of the significant factors for tailoring GO that able to fulfil various applications. In this paper, diluted sulfuric acid was employed during the oxidation. Based on the characterization results from Fourier Transform Infrared Spectrometer (FTIR), Ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD) and Thermogravimetric analysis (TGA) it found that the partially oxidized graphene oxide (PGO) was fabricated. The PGO synthesis show an insignificant absorption of C=O peak in FTIR and weak peak intensity at 300 nm for UV-Vis analysis that found in fully oxidized graphene oxide. Therefore, the PGO synthesis claimed to be partially oxidized.

Abstract: Corrosion performance of graphene oxide (GO) coatings from different sheets sizes in 3.5 wt% NaCl solution was investigated. The GO dispersion was subjected to 5 and 10 hours of ultrasonication before electrophoretically deposited (EPD) onto the copper substrate. It was found that the EPD-GO coating from smaller sheets (10h ultrasonication) possess hydrophobic, thinner film and smooth surfaces. It is suggested that the corrosion performance of the coating from smaller GO sheets is improved due to the surface texture and compactness of the coating as compared to the larger GO sheets.

Abstract: This present work focuses on the conduction properties investigation on solid biopolymer electrolytes (SBEs) based alginate doped with various composition of glycolic acid (GA). The film was successfully prepared via solution casting technique and was characterized for conduction properties by using impedance spectroscopy. Based on ionic conductivity study, sample containing with 20 wt. % of GA possessed an optimum ionic conductivity of 5.32 × 10^-5 Scm⁻¹ at ambient temperature (303 K). The dielectric analysis revealed the highest ionic conductivity sample based alginate-GA SBEs has the highest dielectric constant and loss and increased significantly when temperature increases at ambient temperature. The dielectric properties shows that the entire alginate-GA SBEs are non-Debye behavior where there is no single relaxation occurred in the present system.

Abstract: Dielectric elastomer (DE) technology are used in several applications for example generator, sensor and actuator. One of the major factors that limits the DE performance is premature electrical breakdown. Compositing is the example that have been reported to increase the breakdown strength. In this study polydimethylsiloxane (PDMS) film will be incorporated with two different fillers which are titanium dioxide (TiO₂) and zinc oxide (ZnO). Both metal oxides will be calcined up to 300°C before they are added to the PDMS elastomer as fillers. The results show that the calcined TiO₂ and ZnO that incorporated in PDMS films show significant increase of breakdown strengths. Meanwhile, the calcined TiO₂ PDMS film give higher breakdown strength as comparison to the calcined ZnO counterpart.

Abstract: The fabrication technique applied in this research to grow ZnO crystal is known as ECH method. It is a preferred method due to its low cost, simplicity in operating and low growth temperature. However the condition of ECH method to produce the optimum crystal growth has not been studied further. The objectives of this research are to synthesize ZnO ceramic pellets, to produce ZnO micro/nanostrcutures on ZnO ceramics bar by ECH method, as well as to characterize and analyze structural, morphological, and optical properties of ZnO crystals grown. ZnO pellets were formed by pressed at 3, 4, 5 tons and sintered at 1,100 °C in air for 4 and 72 hours. ZnO ceramic bar was joule heated by direct current of 2 A and 3 A. The result is the grain size of ZnO pellets increased with increasing sintering time and pressing pressure. XRD results indicated mostly crystal prefer to grow along (100) orientation. SEM images showed crystals grown was in a variety of shapes and sizes. PL measurements at room temperature revealed high intensity peak of in visible region in which yellow-level emission was observed from ZnO crystals grown.

Abstract: This research deals with ambient energy harvesting by using zinc oxide thin film. The objectives of this thesis are to prove the ZnO film as a piezoelectric material can produce electric when vibration is applied and determine its optimal voltage. The thesis describes the sol gel spin coating technique to fabricate zinc oxide thin film. Zinc acetate dehydrate, absolute ethanol and diethanolamine were used in this thesis to act as sol gel precursor. Sol gel was coated on glass slide which wrapped by aluminum foil. The thin film was formed after preheating and annealing. The thin film was characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Photoluminescence spectroscopy (PL) and Ultraviolet-visible spectroscopy (UV-Vis) as well as analyzed using vibration technique. From XRD results, the films were preferentially diffracted at around 65° which corresponding to (1 1 2) diffraction phase. From FESEM results, it was observed that when the spin speed was increased at same annealing temperature, the thickness was also decreased. When the annealing temperature was increased at same spin speed, both grain size and thickness were increased. From the PL results, there was only film with spin speed of 2000 rpm and annealing temperature of 300 °C had slightly left wavelength which was 380 nm. Annealing temperature would affect only the intensity of PL wavelength. From the results of UV-Vis, it was observed that when the spin speed was increased at same annealing temperature, the band gap was decreased. When the annealing temperature was increased at same spin speed, the band gap was decreased. Piezoelectric test had proven the ZnO film could produce electricity. The maximum voltage (20.7 mV) was produced by the ZnO film with spin speed of 2000 rpm and annealing temperature of 300 °C.