Advanced Materials Research Vol. 545

Abstract: Great interests in metallic oxides have emerged because of the possibility to modify the properties of these materials for different applications such as catalysis or sensors. In this work, CuO, ZnO and CuO-ZnO nanoparticles were prepared by a novel sol-gel route under ultrasonic condition using triethanolamine as an emulsifying surfactant. Fine powders were obtained when the pH of the sols were increased to 13 using NaOH. Particle sizes of the produced oxide materials were in the range of 3-4 nm, 40-50 x 100-150 nm (diameter x length) and 100-200 nm for CuO, ZnO and CuO-ZnO, respectively. The molar ratio of triethanolamine to metal nitrate precursors was set at 2:3. TEM micrographs of these particles were obtained to elucidate the morphology of the nanoparticles. Experimental results show that the band gap energies (E_g) for CuO, ZnO and CuO-ZnO were found to be 2.71, 3.35 and 2.82 eV, respectively.

Abstract: The effects of reactant concentration on the growth of ZnO nanostructures and the photovoltaic performance of inverted organic solar cells based on a blend of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV) as donor and (6,6)-phenyl-C61 butyric acid methyl ester (PCBM) as acceptor with a structure of FTO/ZnO nanostructures/MEHPPV:PCBM/Ag utilizing ZnO nanostructures as electron collecting layer and silver as a hole collecting electrode were investigated. The ZnO preparation consisted of ZnO nanoparticles seed layer coating and followed by ZnO nanostructures growth in equimolar aqueous solution of zinc nitrate hexahydrate (0.02-0.08 M) and hexamethylenetetramine (0.02-0.08 M). ZnO nanorods having diameter of 50-70 nm and with length up to 120 nm were obtained at reactant concentration of 0.04 M. The ZnO nanorods started to merge with each other and formed irregular nanostructures vertically on the substrates at higher reactant concentrations of 0.06 M and 0.08 M. The solar cell with ZnO nanorods prepared at reactant concentration of 0.04 M provided the largest interface area between polymer active layer and ZnO, resulting in the highest power conversion efficiency of 0.053 % with short circuit current density of 0.43 mA/cm², open circuit voltage of 0.42 V and fill factor of 29 %.

Abstract: The morphology and physical properties of ZnO nanoparticles are greatly influenced by the way it is synthesized. In this work, we study the influence of iodine ion in Zn- Ethanol reaction as this ion is believes to have the ability to control the nucleation and growth of ZnO particles [1]. The morphology of ZnO particles in the presence of iodine shows nearly spherical in shape (size ~ 110 nm) whereas ZnO particles without the presence of iodine exhibit hollow microsphere with feeler like structure growth outward of the sphere . Photoluminescence (PL) spectra shows a broad UV emission peak for both of the sample where sample with the absence of iodine possess lower intensity of UV emission centered at 380 nm compared to samples with iodine which demonstrates stronger intensity at 390 nm despite of having very weak visible secondary emission peak at 530 nm. Iodine contribution to ZnO morphology, structural and optical properties was discussed where iodine has shown to have more controlled on the formation and nucleation of ZnO particles.

Abstract: The retention of nanometric microstructures is a challenge in any presureless sintering process. Grain size influences mechanical properties and grain coarsening retards densification upon sintering, thus resulting in the poor overall product properties. Hence, it is important to select, among others a suitable sintering regime which promotes densification and retards microstructure coarsening. In this work, Y-TZP ceramic bodies were fabricated under four different sintering regimes to investigate the governance of conventional Single-Stage Sintering (SSS) with 1 min and 2 h dwell time, and comparing their performance with bodies produced by Two-Stage Sintering (TSS). It was revealed that TSS sintered samples, yielded better properties than the SSS samples sintered at 1400°C with a dwell time of 2 hours. In the hydrothermal ageing test, TSS samples did not undergo the low-temperature degradation via the martensitic phase transformation of tetragonal to monoclinic symmetry. Nevertheless, it was found by XRD analysis that Y-TZP ceramics sintered by the SSS method using a short dwell time of 1 minute was effective in maintaining the tetragonal phase stability after 50 hours of exposure in superheated steam conditions.

Abstract: Abstract. Gallium Nitride (GaN) nano and micro structures were grown on different substrates, such as ceramic boat and alumina plate using thermal evaporation method with commercial GaN powder under the flow of Argon (Ar) gas atmosphere. Micro structural studies by scanning electron microscopy (SEM) revealed the role of different substrates in the nucleation of the GaN nano and micro wires and ribbons. Additional structural and optical characterizations were performed using energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. Results indicated that the nanowires and nanoribbons are of single-crystal hexagonal GaN and are more and less orderly in their growth with different substrates. The quality of growth of the GaN nanowires and nanoribbons for different substrates is highly dependent on the lattice mismatch between the nanowires and their substrates and it also depends on the conditions of the growth.

Abstract: Titanium dioxide (titania) nanomaterials have been extensively studied for various applications including gas sensor [1], dye-sensitized solar cell [2] and photocatalyst [3]. Titania nanomaterials can be produced using various methods depending on the desired surface morphology. As such the optimization of methods is the key to produce nanomaterials with desired properties where the study here focuses on the effect of autoclaving temperature for the hydrothermal growth. Titania P25 (Degussa, Germany) in 5 M sodium hydroxide solution (NaOH) was treated hydrothermally for 24 hours at 100 °C, 120 °C, 150 °C and 170 °C. Hydrothermal treatment for 24 hours at 150 °C produced nanotubes and treatment at 170 °C produces nanowires. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX) and X-ray Diffraction (XRD) were performed to study the surface and internal morphology of nanomaterials formed. Nanowires produced are of average width of 20 nm and length of 200 nm to 1 µm. Nanotubes produced are average width of 25 nm consisting of multiple walls. Varying the autoclaving temperature will affect the surface morphology of nanomaterials; forming nanotubes at 150 °C and nanowires at 170 °C. Understanding the effect of the process temperature would allow for optimization of the process in order to produce titania nanomaterial with specific characteristics that exhibit enhanced functionality for the development of their applications.

Abstract: ZnO and Zn_1-xCd_xO thin films have been deposited onto glass substrate using spray pyrolysis at 200°C. Cadmium-zinc alloy thin films have been prepared by taking different concentrations of cadmium (Cd). The elemental analysis and the surface morphology of the films were carried by the energy dispersive X-ray (EDX) and scanning electron microscopy (SEM). The EDX data show that the films are highly stoichiometric. The SEM images show that the film changes from nano fiber to grain with the increase of Cd concentrations. The X-ray diffraction pattern shows that the films are polycrystalline in nature. The crystal structure of the films changes from hexagonal-ZnO to cubic-CdO depending on the concentration of Zn and Cd in the Zn_1-xCd_xO films. The optical properties of these films were studied by UV-VIS spectroscopy. The optical band gap of the films was changed from 3.2 to 2.4 with the variation of cadmium.

Abstract: This paper describes the development of colloidal Au-SiO₂ with core-shell structure nanoparticle radioactive tracers by neutron activation in nuclear reactor that produce Au-198 (T1/2=2.7 d) emitting gamma ray of 412 keV. Using conventional citrate-reduction method, gold nanoparticles were prepared from its corresponding metal salts in aqueous solution then coated with uniform shells of amorphous silica via a sol-gel reaction. The citrate-reduction-based method provides gold nanoparticles with higher concentration and narrow size distribution. By using transmission electron microscopy (TEM), the resultant of particle size and silica coatings could be varied from tens to several hundred of nanometers by controlling the catalyzer and precipitation time. Au-SiO2 core-shell nanostructure is good to prevent the particles from getting agglomerated resulting in a big mass. In addition, silica surface offer very good chances that make the hydrophobic and hydrophilic behavior on the gold nanoparticles. EDXRF spectrum has proven that Au-SiO2 core-shell nanoparticles sample consists purely of a gold and silica particles. This target material of radiotracer application used to investigate multiphase system in process industries without disturbing the system operation.

Abstract: The mechanical properties of adhesive materials change over time, especially when they are subjected to long-term loading regimes. The significance of this is often overlooked at the design stage. When adhesives are subjected to a constant load, they may deform continuously, depending on temperature, humidity and cross-link density. This progressive deformation is called creep and will continue until rupture or yielding causes failure. It is imperative that reliable accelerated tests be developed to determine the long-term time-dependent performance of adhesives under different environmental conditions. The long-term creep behaviors of thixotropic and room temperature cure epoxy based adhesives reinforced with nano-particles specially formulated for in-situ bonding of pultruded rod into timber for repair and strengthening of timber structures were investigated. In this study two epoxy-based adhesives with nano-particles (silica fume and rubber) addition were subjected to bending creep tests, in accelerated environments. Experimental data showed that the adhesives reinforced with nano-rubber particles showed less creep deformation than the unreinforced adhesives.

Abstract: Nanocellulose was isolated from mengkuang leaves (Pandanus tectorius) by using concentrated sulphuric acid. The structural analysis of the leaves at different stages of treatments was performed by fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Transmission electron microscope (TEM) was used to investigate the dimensions of the isolated nanocellulose. The FTIR and XRD results indicated that the hemicelluloses and lignin were removed extensively in the extracted cellulose and nanocellulose, and the crystallinity were increased after removing these components. The TEM image showed that the diameter of isolated nanocellulose between 5-25 nm. The isolated nanocellulose may have applications in the fields of nanocomposites.