Advanced Materials Research Vols. 55-57

Abstract: Zirconia nanofibers were fabricated from alcoholic solution containing zirconatrane and poly(vinyl pyrrolidone) (PVP) using electrospinning and sol-gel process with subsequent calcination process. A low-cost and facile route to synthesize zirconatrane complex, which can be further employed as alkoxide precursor for zirconia or doped zirconia via sol-gel technique, has been developed from the reaction of a very inexpensive and plentiful starting materials via the oxide one-pot synthesis (OOPS) process. Zirconatrane complex was directly synthesized from zirconium hydroxide, triethanolamine and ethylene glycol. The structure of resultant products was fully characterized using FTIR, 1H, 13C-NMR, elemental analysis (EA), and mass spectroscopy (MS). The PVP/zirconia composite nanofibers were electrospun and calcined at different temperatures. The as-electrospun and heat-treated PVP/zirconia composite nanofibers were characterized using TGA, XRD and SEM. After calcination of the as-spun composite fibers at 600oC for 5 h, zirconia nanofibers of about 190 nm in diameter having tetragonal structure were obtained. Increasing the calcination temperature resulted in the formation of zirconia fibers with ribbon-like morphology having an average width of 600 nm and thickness of 140 nm.

Abstract: The characteristics of morphology, friction and nanotribological properties of ZnO thin films were achieved by means of x-ray diffraction, scanning probe microscopy (SPM), and nanoindentation. The ZnO thin films were deposited by a radio frequency magnetron sputtering system. Surface geometry and friction analysis were derived from atomic force microscopy/friction force microscopy (AFM/FFM). The hardness and Young’s modulus of the ZnO thin films were investigated by nanoindentation measurements with a Berkovich indenter. The films exhibited an increase in the hardness with decreasing load i.e. the indentation size effect (ISE) was found. In addition, the nanoscratched mechanical property of the films was discussed.

Abstract: The effects of polyacrylamide (PAM) as a capping agent, and zirconium as a dopant, on the structural and optical properties of ZnO nanoparticles were investigated. All the samples were prepared by microwave irradiation in an aqueous system without a post-annealing step. The crystallite sizes were decreased by the incorporation of Zr and PAM. The photoluminescence efficiency was enhanced for samples with PAM-capped ZnO and PAM-capped ZnO doped with Zr, when compared to the pure ZnO. The broad visible luminescence signified the suitability of these nanoparticles as a white phosphor.

Abstract: A wide variety of toxic metals and organic chemicals are discharged to the environment as industrial or laboratory wastes, causing serious water, air, and soil pollution. One of the interesting materials for using as the adsorbents to adsorb these pollutants in wastewater treatment is porous clay heterostructures (PCHs). These porous materials are obtained by the surfactant-directed assembly of mesostructured silica within clay layers. In the present work, the PCHs were synthesized within the galleries of Na-bentonite clay by the polymerization of tetraethoxysilane (TEOS) in surfactant templates (cetyltrimethylammonium ion and dodecylamine). These PCHs were functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) to obtain the MP-PCH utilizing as heavy metal adsorbent. According to N2 adsorption-desorption data, the results show that PCH has surface areas of 549.7 m2/g, an average pore diameter in the supermicropore to small mesopore range of 3.16 nm, and a pore volume of 0.45 cc/g, while MP-PCH shows pore parameters of 488.7 m2/g, 3.28 nm, and 0.48 cc/g, respectively. Moreover, the MP-PCH was investigated the adsorption properties which concerned with their function as adsorbents for aqueous solution. The results show that the adsorption capacity of MP-PCH was 0.22, 0.24, 0.50 , 0.48 and 0.11 mmol/g for Cd, Cu, Mn, Ni and Pb, respectively. They point out the potential for utilizing as the heavy metal adsorbents in wastewater treatment.

Abstract: Inorganic Mesoporous Membrane is a new alternative to improve high-temperature fuel cell performance in proton exchange membrane fuel cells (PEMFCs) to substitute for Nafion. It possess high porosity and high specific surface areas, resulting in high proton conductivity. In this study, niobium-modified titania and antimony/niobium-modified titania ceramic were prepared via the sol-gel technique. The various contents of antimony, 0 to 3 wt%, and 3% niobium are incorporated into titania to improve the porous surface condition of the ceramic particles. The xerogels were heated at about 500°C. Inorganic membranes were prepared by using the spin-coating technique using epoxy resin as a binder. The physical, chemical, and electrical properties of these membranes were investigated. The XRD and Raman results showed that pure TiO2 and doped TiO2 nanoparticles obtained possess an anatase structure with mesoporosity. The specific surface area of the doped TiO2 was higher than that of pure TiO2 and it is worth pointing out that the doping of antimony affected the surface areas more than the doping of niobium in TiO2. Moreover, these membranes were also tested to evaluate their potential use as an electrolyte in PEMFC by using impedance spectroscopy, TGA, mechanical properties and water uptake.

Abstract: Electrospun fabrics, prepared from 5, 7 and 10%w/v were Poly(vinyl alcohol) (PVA) solutions successfully prepared. The electrospinning condition was 15 kV, distance 15 cm, flow rate of 1 ml/hr and spinning time of 5 hours. Physical properties of electrospun PVA fabrics were analysed by SEM, FE-SEM and contact angle measurement.The contact angle of the electrospun PVA fabrics was 54.5°, characterizing the hydrophilicity of the fabrics. Hydrophobic properties of the electrospun PVA fabrics were improved by plasma treatment using radio frequency inductively coupled plasma (RF-ICP). RF-ICP plasma treatment of the electrospun PVA fabrics were carried out sulphurhexafluorene (SF6) gas with pressure of 0.5 Torr, RF power of 30W and treating time of 30, 60, 90 and 120 seconds. Effects of the PVA solution concentration and plasma treating time on hydrophobicity of the electrospun PVA fabrics were determined by contact angle that result of contact angle of treated fabrics increased when treated time increased and they decreased when concentration of fabrics increased.

Abstract: This research investigated the microstructure and characterization of Portland-bottom ash-silica fume cement pastes. Bottom ash, a by – product from coal-fired thermal power plants, was obtained from Mae Moh power plant, Lampang, Thailand. It currently exists as waste approximately 1.5 MT per year and has not been put to use. Unlike its counterpart, fly ash, which is recognized as an alternative material used to replace part of Portland cement. Silica fume, a nanomaterial from ferrosilicon industry, is nanoparticle and highly amorphous. It is highly pozzolanic reaction and could improve properties of Portland-bottom ash cement pastes. Thus, this research investigated the effect of silica fume on microstructure and characterization of Portland-bottom ash-silica fume cement pastes. The ratios of bottom ash used to replace Portland cement were 0, 10, 20 and 30 percent by weight and silica fume was added at 5 and 10 percent by weight. Compressive strength test was then carried out. SEM and TGA were used to study the microstructure of Portland-bottom ash-silica fume cement pastes. The results show that, the compressive strength of Portland-Bottom ash-silica fume cement pastes increased with added silica fume at 5 and 10 percent. SEM micrographs show C-S-H gel and silica fume around the cement particle in Portland-bottom ash-silica fume cement pastes which gives a highly dense and less porous microstructure. TGA graphs show Ca(OH)2 decreased with silica fume content.

Abstract: ZnO and other nanomaterials were synthesized by thermal evaporation process by carbon assisted method using powder ZnO as a precursors at temperature 1200 oC in one atmosphere of nitrogen for 3 hours. The diameter of nanofibers and nanowires vary from 50 nm to 200 nm and length of several ten micrometers. The size of nanorods vary from 20 nm to 100 nm and length of a few micrometers. The stereo microscope with an image analyzer and scanning electron microscope instruments are used to characterize these nanostructured materials.

Abstract: Nanostructured materials were synthesized by thermal evaporation process using silicon dioxide and carbon from coconut shell charcoal or graphite mixed with GeO2 by the ratio of 5:1:1 at temperature 1200 oC in one atmosphere of nitrogen for 3 hours. The nanostructured materials were characterized by the stereo microscope (image analyzer) and scanning electron microscope. The diameters of nanowires vary from 10 nm to 50 nm and length of several 10 micrometers. Length of nanorods was around 15 micrometers and diameters vary from 10 nm to 100 nm.

Abstract: Zn2TiO4 nanostructures were synthesized by the thermal oxidation method. Zn with 0, 10, 20, and 30 mol% TiO2 mixed powder were blended in polyvinyl alcohol and coated on an alumina substrate to form thick films. The thick films were heated at temperature of 600, 700, and 800°C under normal atmosphere for 24 hrs. FE-SEM images showed belt-liked nanostructures with the length of 0.3-30 µm, the width of 30-1800 µm, and the thickness ranging in the order of nm. Ti was incorporated into the nanostructures with ZnO to form Zinc titanate compound, indicated by EDS. Raman spectra and XRD results suggested that phase of Zinc titanate is cubic Zn2TiO4. The oxidation temperature and TiO2 content are critical to the phase quality of the nanostructures.