Wanichaya Mekprasart

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.

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.

Investigation of milling time on particle size reduction and photo-induced activity performance of commercial TiO2 for optical energy harvesting applications

In this research, effect of milling time on crucial physical structures of commercial TiO2 powders in form of anatase phase is investigated. The as-received commercial TiO2 powders were ball-milled with ethanol solvent at room temperature at various operating time ranging from 6-24 hrs. Particle sizes and surface areas of milled powders were characterized by particle analyzer and Brunauer Emmet Teller (BET) method.TiO2 surface morphologies of the powders milled at various times were monitored by scanning electron microscope. The photocatalytic activities of the milled powders were conducted by mean of the photo-induced degradation against RhB aqueous solution. The results reveal that particle size of the commercial TiO2 powders can be effectively minimized to few hundred nanometer range depending on milling time. The drastic reduction in their size results to the increasing active surface area of the particles and the enhanced photo-induced activity that was supported by the photodegradation performance. This enhancement can suggest them to the suitability in optical energy harvesting optoelectronic applications including photovoltaic devices, optical based sensors and related environmental-friendly usage.

Physical, Electrical and Optical Properties of F/Sb Codoped SnO2 Synthesized Via Sonochemical Process

F/Sb-codoped SnO2 nanoparticles were synthesized via sonochemical process using stannic chloride pentahydrate (SnCl4·5H2O) as host precursor while antimony(III) chloride (SbCl3) and ammonium fluoride (NH4F) were chosen as Sb and F dopant precursors, respectively. Their physical properties and morphologies were investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscope while their electrical and optical properties were investigated by Hall measurement and diffuse reflectance spectroscopy. As-synthesized powder of polycrystalline phase SnO2 nanoparticles can be obtained by one-step sonochemical process and its crystallinity can be improved by calcination process. The formation of crystalline phase of SnO2 is assisted by cavitation effect provided by intense ultrasonic radiation via rapid collision. The characterization results disclose that Sb dopant has strong influence on both physical and electrical properties while F dopant provide considerable effect on electrical property of the samples. It is noticed that the codoping of both elements with certain contents can significantly heighten its electrical conductivity.

SnO2 Nanoparticle Synthesized by Ultrasonic-Assisted Process

SnO2 nanoparticles were synthesized by ultrasonic-assisted precipitation process using stannic chloride pentahydrate (SnCl4·5H2O) as a precursor. The stannic chloride aqueous solution was precipitated by ammonia under sonication. The as-synthesized precipitates were dried at 80 oC and then calcined at 400 oC for 2 h. The physical properties of nanoparticles with/without sonication were characterized by thermogravimetic and differential thermal analysis, X-ray diffraction, and transmission electron microscope. The results reveal that ultrasonic radiation has significant influence on phase transformation mechanism from Sn (OH)4 to SnO2, grain size and uniformity of SnO2 nanoparticles.

Photocatalytic Activities under UV Light of Ball-Milled TiO2 Photocatalysts

Anatase TiO2 powders used as photocatalysts were prepared by ball milling process at various milling time and annealed in nitrogen atmosphereat different temperatures. Commercial TiO2 powders were ball-milled with ethanol at room temperature. After ball milling process, the samples were annealed in nitrogen atmosphere. The particle sizes and surface area of milled powders were measured by particle analyzer and Brunauer Emmet Teller method(BET). Effect of milling time and annealing temperature on structural properties of TiO2 powders was investigated by X-ray diffraction(XRD) and scanning electron microscope(SEM). The degradation of aquous RhB dye by ball-milled TiO2 powder photocatalyst was investigated under UV light irradiation. Comparing to P-25, TiO2 powder prepared via ball milling process at 24 hr demonstrated significant enhancement in its photocatalytic activity under UV light due to the increasing active surface area after ball milling process.

Active Ilmenite Surface Structure Influence of Acid Assisted Ball Milling

Active-ilmenite powder derived from natural ilmenite sand was prepared by the ball milling process with acid-solution and Deionized (DI) water. Morphology and particle size of active-ilmenite product in acid/DI-assisted ball milling process were monitored by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Surface atomic component and chemical bonding were investigated by X-ray photoelectron spectroscopy (XPS). Meanwhile, bulk chemical oxidation and fine structure of active-ilmenite were studied by X-ray absorption near edge structure (XANES) and extended X-ray absorption ne-structure spectroscopy (EXAFS) to confirm the oxidation state and local active species structure at surface. Active-ilmenite by acid-assisted ball milling process is a distinctive method for the preparation of active-ilmenite product with high active surface. Moreover, the distortion of TiO6 and FeO6 octahedral cluster on the sample surface was detected in all milled samples with acid-assisted ball milling process. The presence of Fe2+, Fe3+ ions and miniature sulfate was also detected on the sample surface by milled product with acid-assisted method.

Synthesis and characterization of F doped ZnO nanopowders by chemical routes of co-precipitation and sonochemical process

Zinc oxide (ZnO) is an n-type semiconductor material at room temperature which a good absorber in UV region and used in many applications, such as photocatalyst and gas sensor. In this work, ZnO nanopowders were synthesized by chemical routes; co-precipitation and sonochemical method. To improve ZnO nanopowders in optical and electrical properties, fluorine (F) was doped with varied concentration from 0-9 mol%. Zinc nitrate and ammonium fluoride were used as precursor material in both processes. Ammonia solution was dropped in the solution relating to white colloidal solution. Crystalline structure in hexagonal structure of F doped ZnO was identified by X-ray diffraction (XRD). Morphology and chemical element in F doped ZnO were monitored by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). For optical and electrical properties, F doped ZnO particles were analyzed by UV-Visible spectroscopy and four point probe method, respectively. XRD pattern of ZnO structure after F doping with high crystallinity was similar to pure ZnO and obtained by both processes after annealing treatment beyond specific temperature. F doped ZnO morphologies were formed in rod-like structure by co-precipitation method. The increase of rod length was related by adding F doping concentration in ZnO matrix. Meanwhile, F doped ZnO products were formed in spherical structure with same crystallite size and particle size by sonochemical method due to the effect of ultrasound energy in the system. The improvement of optical and electrical properties in F doped ZnO was drastically obtained by co-precipitation method. The decreases of optical bandgap and electrical resistivity by F doped ZnO with co-precipitation method was occurred at 1 and 5 mol% F dopant. The influence of fluorine on ZnO structure was resulted in the defect level in band diagram and rod-like relating to narrow bandgap energy and good conductivity in ZnO.Zinc oxide (ZnO) is an n-type semiconductor material at room temperature which a good absorber in UV region and used in many applications, such as photocatalyst and gas sensor. In this work, ZnO nanopowders were synthesized by chemical routes; co-precipitation and sonochemical method. To improve ZnO nanopowders in optical and electrical properties, fluorine (F) was doped with varied concentration from 0-9 mol%. Zinc nitrate and ammonium fluoride were used as precursor material in both processes. Ammonia solution was dropped in the solution relating to white colloidal solution. Crystalline structure in hexagonal structure of F doped ZnO was identified by X-ray diffraction (XRD). Morphology and chemical element in F doped ZnO were monitored by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). For optical and electrical properties, F doped ZnO particles were analyzed by UV-Visible spectroscopy and four point probe method, respectively. XRD pattern of ZnO structure after F dop...

Extraction and characterization of nanocellulose from sugarcane bagasse by ball-milling-assisted acid hydrolysis

This study is proposed to characterize nanocellulose extracted from sugarcane bagasse (SCB). For extracting cellulose, the bagasse was treated by chemical treatment. The nanocellulose was prepared using ball-milling with acid hydrolysis. Morphology of bagasse, cellulose and nanocellulose were characterized by scanning electron microscopy (SEM). The chemical composition of extracted cellulose and nanocellulose was investigated by Fourier-transformed infrared spectroscopy that verifying the removal of lignin and hemicellulose during cellulose isolation process from sugarcane bagasse. The crystalline structure of cellulose and nanocellulose were characterized by X-ray diffraction (XRD), indicating that the nanocellulose prepared by ball milling with acid hydrolysis has higher crystallinity than nanocellulose prepared only ball milling.This study is proposed to characterize nanocellulose extracted from sugarcane bagasse (SCB). For extracting cellulose, the bagasse was treated by chemical treatment. The nanocellulose was prepared using ball-milling with acid hydrolysis. Morphology of bagasse, cellulose and nanocellulose were characterized by scanning electron microscopy (SEM). The chemical composition of extracted cellulose and nanocellulose was investigated by Fourier-transformed infrared spectroscopy that verifying the removal of lignin and hemicellulose during cellulose isolation process from sugarcane bagasse. The crystalline structure of cellulose and nanocellulose were characterized by X-ray diffraction (XRD), indicating that the nanocellulose prepared by ball milling with acid hydrolysis has higher crystallinity than nanocellulose prepared only ball milling.

Effect of Metal (Mn, Co, Zn, Ni) Doping on Structural, Optical and Photocatalytic Properties of TiO2 Nanoparticles Prepared by Sonochemical Method

Metal-doped TiO2 nanoparticles (Metal = Mn, Co, Zn, Ni) were synthesized by sonochemical method accompanying post calcination process using metallic nitrates of manganese, cobalt, zinc, nickel with various metal contents from 0-5 mol% and titanium isopropoxide as a starting precursors. Sodium hydroxide (NaOH) base was used as a precipitating agent. The influence of ultrasound operated at 750 W 20 kHz on the crystalline structure of metal-doped TiO2 nanoparticles has been characterized by X-ray diffraction (XRD) while morphologies and grain size of the nanoparticles were monitored by field emission scanning electron microscope (FE-SEM). The optical absorptivities and corresponding band gaps were evaluated by diffuse reflectance spectroscopy (DRS). The performance of photocatalytic activities of metal-doped TiO2 nanoparticles against aqueous organic dye Rhodamine B (RhB) under visible light was investigated. The results reveal that their crystallinity of synthesized metal doped TiO2 nanoparticles is in mixed phase between anatase, rutile and brookite with calcination temperature at 500 °C for 3 h and their crystalline of all samples are shown. The incorporation of metal dopant on the photocatalytic performance of TiO2 exhibits a significant enhancement in its photocatalytic activities under visible light due to the decrease in band gap energy of metal doped TiO2 nanoparticles.