Key Engineering Materials Vols. 675-676

Abstract: Nanocomposite filters were prepared by sintering of hydroxyapatite (HA) and Lampang clay composite nanopowder. 50 wt% amount of Lampang clay nanopowder are incorporated into HA nanopowder. The mixing powders are uniaxially compact and then sintering at 900°C-1050°C in air. The bending strength tests were performed and microstructure characterizations were carried out by scanning electron microscopy and mercury porosimetry analysis in order to determine the optimum sintering conditions. Filtration studies using optimized filter were performed for rubber wastewater. The results from this work clearly show that nanocomposite filter is an efficient and ecologically suited environmental technology for decontamination of the wastewater generated from rubber processing.

Abstract: SnO₂/CNT nanocomposites were synthesized via microwave-assisted process using SnCl₄·5H₂O as a starting precursor and UV-treated multi-wall carbon nanotubes (MWCNTs) as scaffolds. The concentration of SnCl₄ was varied in the range of 0.01-0.05 M. Effect of precursor concentration on their physical properties and micro structural morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD results indicate that the as-synthesized composites are the mixture of two separated phases including SnO₂ and MWCNT. SEM images indicate that the surfaces of MWCNT are thoroughly covered with SnO₂ nanoparticles. Comparative gas sensing result reveals that the prepared hybrid SnO₂/MWCNT composites exhibit much higher sensing sensitivity and recovery property in detecting alcohol gas at room temperature than the bare SnO₂.

Abstract: In this research, the self-striking red glass coloration from gold nanoparticles (AuNPs) doped in glasses has been developed. The glass samples were prepared in formula (63.995-x)SiO₂ : 15Na₂O : 10CaO : 10K₂O : 0.5Sb₂O₃ : 0.005SeO₂ : 0.5SnO₂ : xAuNPs (where x is 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 % by weight). The glasses were melted by normal melt-quench technique at 1,500 °C in normal atmosphere. The red color was obtained immediately when take the glass out of furnace. The red color of glasses were confirmed by UV-visible spectrophotometer in the wavelength range 200-1100 nm and color coordinate in CIE L*a*b* system.

Abstract: In this study, the NaCu₃Ti₃NbO₁₂ ceramics + (0-0.5 vol%)MgO nanopowder were prepared by solid state reaction. The precursors were ball milled for 24 hours and calcined at 700-1000°C. Selected the calcinations temperature with calculate pure phase from XRD results. The powders on selected temperature were various dwell time for 2-24 hours. The optimum calcination condition for NaCu₃Ti₃NbO₁₂ powder is 950°C for 24 hours. The calcined powders were doped with small amounts of MgO nanopowder and pressed into a disc shape. Sinter the green body at 975-1025°C for 10 hours. Microstructure and density were examined by scanning electron microscope (SEM) and Archimedes method with distilled water as the fluid, respectively. The rectangular grain and normal grain growth are observed. The highest relative density of NaCu₃Ti₃NbO₁₂ ceramics + (0-0.5 vol%)MgO nanopowder sintered at 1000°C are close to 90%. An impedance analyzer was also used to measure the dielectric constant (ε_r) of 1000°C sintered sample at room temperature. The doping of small amounts of MgO nanopowder to make improved NaCu₃Ti₃NbO₁₂ ceramic dielectric constants and the optimum condition for doping MgO nanopowder is 0.1 vol%.

Abstract: The effects of cobalt (Co) addition on structural and optical properties of TiO₂ nanopowders have been investigated. A co-precipitation method was employed to synthesize TiO₂ nanoparticles with various Co additives from 0-10 mol% using tetrabutyl titanate and Cobalt (II) nitrate hexahydrate as starting precursors for Ti and Co source, respectively. The crystallinity of Co-doped TiO₂ nanopowders is heightened by calcination process. The crystal structure, phase formation and the corresponding functional groups of Co-doped TiO₂ were analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The scanning electron microscope (SEM) was taken to observe their morphologies. The chemical compositions of Co additive into TiO₂ matrix are confirmed by EDAX. Their optical properties were investigated by diffuse reflectance spectroscopy. Diffuse reflectance spectra of samples exhibit the increasing absorption in visible region with an increasing Co content. The overall characterization results indicated that the crystallinity and optical properties of TiO₂ nanoparticles are significantly affected by Co dopant.

Abstract: The efficiency of dye-sensitized solar cell (DSSC) has been improved by various ways. In this work, The CdS nanoparticles were added in the TiO₂ working electrode for improving the efficiency of DSSC. The DSSC structure comprises of TiO₂ working electrode with and without CdS powder, Pt counter electrode, rutherium (II) (N719) dye and lithium iodide electrolyte. Normally, the TiO₂ paste was screened for five layers. In this work, the TiO₂ paste with CdS nanoparticles was screened for various numbers of layers on the layers of pure TiO₂ to get the total of five layers. Then TiO₂ mixed and unmixed CdS nanoparticles and Pt films were annealed at the temperature of 500°C for 50 min. Impedance spectroscopy (IS) was used to study charge transport in each interface of DSSC. For illumination condition, the measured IS can be divided into three regions that were charge transport at Pt layer, charge transport at working electrode/dye/electrolyte interface and ion contribution at electrolyte layer. The carrier transport parameters extracted from fitting IS spectra were chemical capacitance, charge transfer resistance and time constant.

Abstract: In the present work, the effects of sintering temperature on physical and mechanical properties of HA/YSZ nanocomposites were investigated. The obtained results have been proved that the sintering temperature contributed greatly to densification and the compressive strength with the highest at 4.80 g/cm³ and 74.20 MPa for 80 wt.% of YSZ content in nanocomposites, respectively. The densification increased with increasing sintering temperature, where the compressive strength value was related with densification for the same ratio amount of YSZ. The higher the YSZ contents also significantly produced the ascendant of densification and the compressive strength.

Abstract: In this paper we report the study of the change in electrical properties of semiconducting carbon nanotubes (CNTs) under uniaxial compressive deformations using the “Vienna ab initio simulation package” (VASP). We present an extension of density functional theory calculations to the electronic properties of the tubes, namely the density of states obtained for the optimized geometries of the tubes. There is an energy gap of 0.772 eV between occupied and unoccupied region in the optimized structure calculation. The band gap for the semi-conducting zigzag (10,0) CNTs decreases as the strain increases. It suggests that the semiconducting CNTs may become semimetal or metal upon deformation.

Abstract: Gold nanoparticles (Au NPs) decorated on zinc oxide nanorods (ZnO NRs) arrays by combining hydrothermal method toward ZnO nanorods template and subsequent decoration on Au NPs on the ZnO surfaces by DC magnetron sputtering. The hybrids Au NPs-ZnO NRs were characterized using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The average diameter and length of ZnO NRs template were estimate at 80 and 430 nm, respectively. In addition, antibacterial tests confirmed that adding Au NPs enhances antibacterial effect.

Abstract: Abstract. Zinc oxide nanorods (ZnO-NRs) as a photoelectrochemical water splitting electrode have been fabricated by the seed-assisted hydrothermal process. Initially, ZnO-seed thin film was deposited on indium doped tin oxide (ITO) via DC magnetron sputtering system. Period to fabricate ZnO-NRs, the precursor concentration of zinc nitrate (Zn(NO₃)₂) and hexamethylenetetramine (HMTA) were precisely controlled during 10 – 50 mM, meanwhile the ratio was constantly kept at 1:1. The crystallography and surface morphology of the fabricated ZnO-NRs were investigated by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). The XRD patterns perform wurtzite ZnO crystal structure of with the prefered orientation in (002) and (101) plane. According to FE-SEM photograph, growth rate, density and diameter of the fabricated ZnO-NRs electrode significantly increase, with the increasing of the precursor concentration. This precursor concentration provides a crucial role on the feature of ZnO-NRs for photoelectrochemical water splitting electrode. Finally, the photoelectrochemical water splitting performance was examined and provided that the precursor concentration became close to 30 mM in 1 M Na₂SO₄ exhibited the highest photocurrent.