Wicharn Techitdheera

DYNAMIC POTENTIAL WELL GENERATION AND CONTROL USING DOUBLE RESONATORS INCORPORATING AN ADD/DROP FILTER

We propose a novel system of the dynamic potential well generation and control using light pulse control within an add/drop optical filter. The multiplexing signals of the dark solition with bright/Gaussian pulses are controlled, tuned and amplified within the system. The optical storage rings are embedded within the add/drop optical filter system, whereas the generated optical signals can be stored and amplified within the design system. In application, the storage signals can be configured to be an optical trapping tool which is known as optical tweezers, where the high field peak or well can be formed. The advantages are that the dynamic well can be stored and the array of well can be generated for multiple well applications. The difference in time of the first two dynamic wells of 1 ns is noted.

Dark soliton array generation using fiber loop and ring resonators

We propose a system that can be used to generate a dark soliton pulse array by using multidark soliton sources in the microring resonators and an optical multiplexer, where the different dark soliton center wavelengths can be generated. To verify the simulation results, the experimental setup was employed by using the Brillouin enhanced fiber laser in the fiber ring resonator (loop) system, where two different systems, called forward and backward schemes, were used to generate the dark soliton arrays. Three different center wavelengths of dark solitons were generated and seen to be in good agreement with the theoretical results.

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.

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.

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.

Alcohol Sensing Properties of SnO2/CNT Nanocomposites Synthesized by Microwave-Assisted Process

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.

Indium Tin Oxide conductive nanoparticles synthesized by sonochemical method

ABSTRACT This work reports the synthesis of Indium Tin Oxide (ITO) nanoparticles via sonochemical process at various calcination temperature using InCl3 and SnCl4·5H2O as starting precursors for In and Sn sources, respectively. The crystal structure properties of the samples were investigated by X-ray diffraction. Meanwhile, the size, shape and microstructure of the particles were observed by field emission scanning electron microscope and chemical composition was investigated by energy dispersive X-ray Spectrophotometer. The corresponding optical band gap was determined by diffuse reflectance spectra. The XRD results showed that the as-prepared powders were initially formed in amorphous phase and the crystalline structure of powders were obtained after calcination beyond specific temperature. The correlated reactions and mechanisms during sonochemical process responsible for ITO formation are suggested. The comparison between ITO powders prepared by sonochemical process and co-precipitation process is additionally carried out and the results show significant differences in their morphology and crystallite sizes of the particles.

Physical and Optical Properties of Indium Oxide: Tin Nanoparticles Synthesized by Co-Precipitation Method

Indium oxide:tin nanoparticles were synthesized by co-precipitation method using InCl3 and SnCl4·5H2O as starting precursor with different molar ratios of Sn:In. The crystalline structure, optical properties, chemical bonding and morphologies of all samples were characterized by X-ray diffraction (XRD), UV–vis spectrometer, Raman spectroscopy and field emission scanning electron microscope, respectively. The XRD results show that the crystallinity of as-synthesized powders was initially amorphous phase. After calcination at 400 °C for 2 h, a single phase ITO powder with 10% (mol%) SnO2 was obtained. The particle size of each sample is approximately 20-25 nm. The color of indium oxide:tin nanopowders after heat treatment changed from white to yellow due to the substitution of oxygen vacancies in the sample. After calcination, the intensity of Raman peak significantly decreased with increasing amount of Sn loading. This phenomenon indicates that ion substitution may occur during the synthesis process. Moreover, it is noticed that the optical absorbance of obviously changed with increasing Sn loading.

Physical properties of Ti-doped ITO nanoparticles synthesized by co-precipitation method

Ti-doped indium tin oxide (ITO) nanoparticles (TITO) with different molar ratios of Ti:ITO were synthesized by co-precipitation method using Ti(OCH2CH2CH2CH3)4, InCl3 and SnCl4·5H2O as starting precursors. Deionized (DI) water was selected as the solvent in this process. The as-precipitated powders were calcined at different temperature in range of 700 °C for 2 h. For all samples, their crystal structures, Optical property and morphologies were investigated by X-ray diffraction (XRD), UV-Vis absorption spectroscopy and Scanning electron microscope (SEM), respectively. XRD results reveal that the purity of as-synthesized sample is increased by the increase of calcination temperatures. Moreover, it is noticed that the incorporation of Ti into ITO matrix significantly affects to their relevant physical properties especially optical properties. In addition, SEM micrographs show that the sample agglomeration is noticeably influenced by Ti doping content.

Synthesis and Characterization of Thermochromic La0.75Ca0.25MnO3 Perovskite Manganites Nano-powders by Microwave-assisted Solution Combustion Synthesis

The microwave-assisted solution combustion synthesis was developed for application with initially synthesized thermochromic perovskite manganese oxide La0.75Ca0.25MnO3 nano-powders. Dry and very fine powders were obtained after one-step combustion reaction for less than 10 min in a modified domestic microwave oven. The thermal behavior, phase formation and purity of the precursor, and as-synthesized and calcined powders, were investigated by TGA/DTA, X-ray diffraction (XRD) and FT-IR techniques. The morphology of the powder obtained was characterized using a scanning electron microscope (SEM). The XRD pattern and FT-IR results showed that as-synthesized La0.75Ca0.25MnO3 powders were crystalline, and the monophasic perovskite phase occurred with an average crystallite size of 30.46 ± 5.54 nm for 6 h at a relatively low calcination temperature of 900°C. The small particle size obtained by SEM suggested a high specific surface area and high sinterability. This method was found to be simple, rapid and cheap, and an effective way to prepare nano-size perovskite powders.