Wisanu Pecharapa

Microwave-assisted synthesis of ZnO/MWCNT hybrid nanocomposites and their alcohol-sensing properties

Zinc oxide and multi-walled carbon nanotube (ZnO/MWCNT) hybrid nanocomposites were synthesised by microwave-assisted method using the mixed solution of zinc acetate dehydrate (Zn(CH3COO)2·2H2O) and treated MWCNTs. The syntheses were carried out at various microwave irradiation powers. The characterisation of the as-synthesised nanocomposites was conducted by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results revealed that the composites were composed of two phases of MWCNTs and hexagonal wurzite ZnO. The SEM results showed that the ZnO nanoparticles were well decorated on the surface of MWCNTs. The amount of ZnO nanoparticles and their size increased with increasing irradiation power. Thick-film sensors were fabricated onto interdigitated conducting electrodes using as-synthesised hybrid composites as sensing materials. The alcohol-sensing behaviour of the hybrid composite films was investigated. The results indicated that the irradiation power had significant influence on the sensing response of the sensors toward alcohol. The sensor fabricated from the composite synthesised at higher irradiation power exhibited an enhanced alcohol-sensing performance.

Structural, optical and photo catalytic properties of Cu-doped ZnO nanoparticles synthesised by co-precipitation method

In this work, co-precipitation method was utilised to synthesise Cu-doped ZnO nanoparticles using zinc nitrate (Zn(NO 3 ) 2 ·6H 2 O), and copper(II) nitrate trihydrate (Cu(NO 3 ) 2 ·3H 2 O) as starting precursors for Zn and Cu sources, respectively. Structural and physical properties of as-prepared powders were examined by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES). The XRD results reveal that Cu-doped ZnO nanopowders are in hexagonal wurtzite structure and their crystallinity deteriorates with increasing Cu doping content. FTIR results additionally show the existence of relevant chemical bonding in the samples. Meanwhile, XPS and XANES results indicate the existence of Cu ion with relevant electronic state in ZOptical properties of the samples were investigated and the corresponding results suggest that Cu additive plays a crucial ro...

Synthesis and characterization of carbon nanotube/zinc oxide composites

ZnO/CNT composites were successfully prepared by sol-gel method based on zinc acetate 2-hydrate (Zn(CH3COO)2·2H2O), absolute ethanol (C2H5OH) and diethanolamine (HN(CH2CH2OH)2, DEA) as a solvent and sol stabilizer. Carbon nanotube with 0.1, 0.3 and 0.5 %w/v were loaded into the prepared sol. Then the mixed sols were dried at 100 °C and annealed at 300, 350 and 400 °C in ambient air. The crystalline structure and surface morphology ZnO/CNT composites were characterized by XRD and SEM. The preliminary results shown that the ZnO/CNT composites with CNT-doped 0.1 %w/v exhibited hexagonal wurtzite structure with (100), (002), (101), (102) and (110) peak orientation plane for all annealed temperatures. In addition, ZnO grain sizes increased with annealed temperatures. SEM results shown that ZnO covered the CNT surface.

Optical, dielectric and photocatalytic properties of perovskite ZnTiO 3 nanoparticle synthesized by sonochemical process

The sonochemical method was employed for synthesizing perovskite zinc titanate nanopowders. The yield powders were calcined at 600-900°C for 2 h. High crystallinity phase of cubic ZnTiO3 was obtained at calcination temperature of 600°C while mixing phase of cubic and hexagonal was observed in the sample calcined at 700°C. For the samples calcined at 800 and 900°C, the hexagonal structure was dominant phase with a trace of rutile TiO2 and spinel Zn2TiO4 phase. X-ray absorption near edge spectroscopy technique (XANES) was used to probe crystal and local structure of the synthesized powders. The samples calcined at 700°C exhibited the superior photocatalytic performance in decolorization of Rhodamine B dye under ultraviolet irradiation within 75 min. The dielectric permittivity and loss tangent of ZnTiO3 calcined at 700°C was found to be 20 and <;10-2. Effect of calcination temperature on structural, morphology, optical, dielectric properties and photocatalytic activity were also investigated and discussed.

Characterization and Phase Formation Study of ZnO:Sn Nanoparticles Synthesized by Co-precipitation Method

ZnO:Sn were successfully prepared by co-precipitation method using zinc acetate dihydrate and tin (IV) chloride hexahydrate as host and dopant precursor sources, respectively. The ratio of Sn doping content in ZnO was designated at 0, 5, 10 and 20 wt.% and calcined at different temperatures at 200, 300, 400 and 500°C. Physical properties and composition of Sn-doped ZnO powder were monitored by X-ray diffraction and scanning electron microscope. Chemical bonding of as-synthesized powders were investigated by Fourier transform spectroscopy. The preliminary results indicate that the crystallinity and morphologies of ZnO nanoparticle are significantly affected by Sn dopant. The phase formation of Zn-Sn-O was observed depending on the Sn-doping composition and calcination temperature. Meanwhile, FTIR results indicate the existence of mixture phases of ZnO:Sn in the compounds which were obtained via precipitation process.

A Comparison of Cation Distribution and Valence State in Spinel Crystal Structure of Zinc and Nickel Ferrites Using the Synchrotron X-ray Absorption Spectroscopy (XAS) Analysis

In this work, the physical structure, magnetism and local structure of zinc and nickel ferrites (ZnFe2O4 and NiFe2O4) synthesized by typical sol-gel combustion method, were investigated by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The formation of the single phase cubic spinel crystal structure and the different values of crystallite size (D), interplanar distance (d) and lattice constant (a) for all ferrite samples were evaluated by the XRD data. The VSM measurement provides the characteristic magnetic hysteresis loop (M-H) for each sample which was found to be significantly different from each other. The chemical shifts in Zn, Ni and Fe K-edges XANES spectra indicate the existence of Zn2+, Ni2+ and Fe3+ ions in these ferrites. The EXAFS spectra analyses applied to track Zn, Ni and Fe cation distribution indicate the distinct character of spinel crystal structure of both ferrites. The results exhibit that zinc ferrite is a normal spinel, while the nickel ferrite is an inverse spinel. Moreover, these EXAFS spectra analyses reveal that the distances between metal ion (Zn2+ or Ni2+) to central oxygen ion and to Fe3+ ions in the opposite lattice site for each ferrite sample are unequal which highly affect its magnetism. The overall simulated results are one of the important evidence encouraging the explanation on the paramagnetism for ZnFe2O4 and the ferrimagnetism for NiFe2O4.

CaCu3Ti4O12 Ceramic Synthesized by Sonochemical-Assisted Process

CaCu3Ti4O12 powders were synthesized by sonochemical-assisted process via a precursor solution of calcium nitrate trihydrate, titanium isopropoxide and copper nitrate trihydrate. The reaction process was conducted with the assistance of intense sonication using Sonics Model VCX 750 until the completely precipitated product was reached, followed by calcinations process. The physical microstructures, morphologies of as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. From XRD observation, it is evident that CaCu3Ti4O12 ceramic could be obtained by this synthesis process. It was additionally revealed that its crystallization and particle size was strongly dependent on the reaction time and calcinations temperature.

Effect of PVP concentration on microstructure and physical properties of electrospun SnO2 nanofibers

ABSTRACT The various exceptional crystalline morphologies of tin oxide (SnO2) nanofibers were fabricated using conventional electrospinning and calcination process. Polyvinylpyrrolidone (PVP) was used as polymer template and tin (IV) chloride (SnCl4·5H2O) was chosen as starting material for electrospun SnO2 nanofibers. The concentration of PVP was varied from 6%w/w to 12%w/w while the concentration of SnCl4·5H2O was kept constantly. The diameter of the as-spun SnO2 nanofiber was ranging from 154 to 464 nm. After calcination at 600°C for 3 h, the crystal structure can be identified to the tetragonal structure of SnO2 with various morphologies. The EDX analysis confirmed the existence of major elements and formation of SnO2 from starting precursor. SEM results revealed that low PVP concentration led to the formation of porous SnO2 nanofibers comprising long chain of SnO2 nanobeads. When the PVP concentration was reached to 12%w/w, the arrangement of crystalline of SnO2 became the cluster of SnO2 plates.

Synthesis and Characterization of Zn-Doped TiO2 Nanoparticles via Sonochemical Method

Zn-doped TiO2 nanoparticles were successfully fabricated using sonochemical method accompanying post calcination process. Titanium isopropoxide (Ti[OC3H7]4) and Zinc chloride (ZnCl2) were used as starting precursors for Ti and Zn sources, respectively. The homogeneous mixing solution of different Zn (0–1 mol%) and Ti ratio were irradiated in high intensity ultrasound sonometer (750 W 20 kHz) for 30 min at room temperature to obtain as-synthesized Zn-doped TiO2 nanoparticles followed by calcination at 400–700°C. To evaluate the structure and phase identification of prepared powders, the X-ray diffraction (XRD) and Raman spectroscopy were employed. The results reveal that the as-synthesized Zn-doped TiO2 nanoparticles are in anatase phase and their crystallinity increases with increasing calcined temperature. The morphology of as-synthesized powders was investigated by transmission electron microscope (TEM). The effect of Zn content and calcinations temperature on TiO2 properties was also discussed.

Effect of Precursor Concentration on Physical Properties of Cube-Like Zn2SnO4 Powders Synthesized by Co-Precipitation Method

Cube-like Zinc stannate (Zn2SnO4) spinel powders were synthesized by co-precipitation method using chloride starting precursors of zinc and tin. The influence concentration of precursors on relevant physical properties of Zn2SnO4 was investigated by increasing concentration of precursor material at 0.1 to 0.4 M (Zn:Sn at ratio 1:1). Structural properties of as-synthesized and Zn2SnO4 crystal were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray absorption spectroscopy (XAS). The results indicate that as-prepared material without calcination process is in cubic symmetry of zinc hydroxy stannate (ZnSn(OH)6) affirmed by SEM and XRD results. Meanwhile, spinel phase of Zn2SnO4 with strong crystalline and eminent cubic structure can be achieved after calcination at 1000°C. Homogenous dispersion, high crystallinity and good cubic structure of Zn2SnO4 powders are occurred at higher concentration of precursors. Moreover, the oxidation state of these samples were investigated by the Zn K-edge and Sn L3-edge X-ray absorption near edge structure (XANES) using the synchrotron radiation light source. The analyses of XANES spectra revealed that the oxidation state of Zn was +2 and Sn valence was +4 in all Zn2SnO4 samples, which well corresponds to the theoretical values.