Yen-Pei Fu

CuIn1 − x Ga x Se2 Absorber Layer Fabricated by Pulse-Reverse Electrodeposition Technique for Thin Films Solar Cell

A single phase of CuIn 1-x Ga x Se 2 (CIGS) polycrystalline thin films was successfully fabricated by the pulse-reverse electrodeposition technique. In this study, a multipulse sequence of potentials with varying amplitude and duration time was used to fabricate CIGS thin film, in which the electrolyte was composed of CuCl 2 , InCl 3 , GaCl 3 , SeO 2 , Na-citric, and LiCl. Then these as-deposited films were annealed in argon atmosphere. The crystalline structure of the thin film was characterized by X-ray diffractometer. The results revealed that thin films fabricated by the pulse-reverse electrodeposition technique only produced a chalcopyrite structure, with no occurrence of Cu 2-x Se secondary phases. The identification of Cu 2-x Se secondary microcrystalline phases and vibration modes of chalcopyrite and Cu 2-x Se was used by a micro-Raman spectrum. The morphological features were characterized by scanning electron microscopy, which showed that the films were dense and smooth compared with that fabricated by a one-step electrodeposition technique without a multipulse step. The thickness and roughness of the CIGS thin films were estimated by an Alpha-Step profilometer. Finally, the carrier type of the CIGS thin film is of a p-type nature as confirmed by electrochemical measurement.

Microwave-induced combustion synthesis of Ni0.25Cu0.25Zn0.5 ferrite powders and their characterizations

Abstract Ni–Cu–Zn ferrite powders were successfully synthesized by microwave-induced combustion process. The process takes only a few minutes to obtain as-received Ni–Cu–Zn ferrite powders. The resultant powders were annealed at different temperatures and were investigated by XRD, SEM, VSM, TG/DTA and a surface area measurement. The as-received product shows the formation of cubic ferrite with saturation magnetization (Ms)≈63 emu/g, whereas upon annealing at 700 °C for 2 h, the saturation magnetization (Ms) increases to 75 emu/g.

Strontium hexaferrite powders prepared by a microwave-induced combustion process and some of their properties

Strontium hexaferrite powders were successfully synthesized by a microwave-induced combustion process. The process only took a few minutes to obtain calcined strontium hexaferrite powders. The resultant powders were investigated by XRD, TEM, VSM, TG/DTA, and surface area measurement. The as-received product shows strontium ferrite with a saturation magnetization (Ms) of ≈38 emu/g and an intrinsic coercive force (iHc) of 525 Oe, whereas, upon annealing at 1000 °C for 2 h, the saturation magnetization increases to 62 emu/g and the intrinsic coercive force reaches 1950 Oe.

Preparation of CexZr1−xO2 powders by microwave-induced combustion process

Abstract Ceria–zirconia solid solution powders were successfully synthesized by a microwave-induced combustion process. For the preparation, cerium nitrate, zirconyl nitrate dihydrate, and urea were used for the microwave-induced combustion process. The process took only a few minutes to obtain Ce x Zr 1− x O 2 powders. The resultant powders were investigated by TG/DTA, XRD, TEM, and a surface area measurement. The as-received Ce x Zr 1− x O 2 powders showed that the average particle size ranged from 10 to 20 nm, and the specific surface area was distributed from 40 to 50 m 2 /g.

Fe/Ba Ratio Effect on Magnetic Properties of Barium Ferrite Powders Prepared by Microwave-Induced Combustion

Barium ferrite powders were successfully synthesized by microwave-induced combustion. The magnetic properties of barium ferrite powders with various Fe/Ba ratios varying from 11 to 12 annealed at various temperatures in the range of 850–1050°C were determined. The resultant powders were investigated by X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), differential thermal analyzer/thermogravimeter (DTA/TG), and surface area measurement. Microwave-heated barium ferrite with an Fe/Ba ratio of 11 and annealed at 1000°C for 2 h exhibited optimum magnetic properties for magnetic recording applications, a saturation magnetization of 66 emu/g and an intrinsic coercive force of 2100 Oe. The microwave-heated barium ferrite powders with various Fe/Ba ratios annealed at various temperatures had particles size ranging from 40 to 90 nm. Thus, the fine control of crystal growth by varying the annealing temperature can be exploited for the production of fine magnetic powders of various sizes for a variety of practical applications.

Electrochemical Properties of Solid–Liquid Interface of CuIn1 − x Ga x Se2 Prepared by Electrodeposition with Various Gallium Concentrations

CuIn 1-x Ga x Se 2 (CIGS) thin film has been successfully prepared by the one-step electrodeposition method, in which the faradaic and nonfaradaic processes occurred between the electrode and the electrolyte. Therefore, the investigation of the kinetic behavior of each metal ion is very important. In this study, we used the polarization curves to estimate the reduction potential of each metal ion and the reaction rate of the electrodeposition process. Electrochemical impedance spectroscopy technique has been used to investigate the electrochemical behavior of the interface between the electrode and the electrolyte. In this electrodeposition system, the influence of various deposition times, the concentration of Ga 3+ on the charge transfer, electrical double layer, and charge-transfer resistance was also investigated. Experimental results show that the electrochemical kinetic behavior of the CIGS thin film is strongly influenced by the structure of the electrical double layer existing between the substrate and the electrolyte with different concentrations of Ga 3+ . With an increase in the electrodeposition time, the kinetic behavior of this electrodeposition system was gradually dominated by the diffusion process rather than the charge-transfer process. In this study, the carrier type of the CIGS thin film is of a p-type nature as confirmed by electrochemical measurement.

Oxidation pond for municipal wastewater treatment

This literature review examines process, design, and cost issues related to using oxidation ponds for wastewater treatment. Many of the topics have applications at either full scale or in isolation for laboratory analysis. Oxidation ponds have many advantages. The oxidation pond treatment process is natural, because it uses microorganisms such as bacteria and algae. This makes the method of treatment cost-effective in terms of its construction, maintenance, and energy requirements. Oxidation ponds are also productive, because it generates effluent that can be used for other applications. Finally, oxidation ponds can be considered a sustainable method for treatment of wastewater.

Synthesis and characterization of anatase TiO 2 nanolayer coating on Ni–Cu–Zn ferrite powders for magnetic photocatalyst

In the current research, we successfully prepared TiO 2 /Ni–Cu–Zn ferrite composite powder for magnetic photocatalyst. The core Ni–Cu–Zn ferrite powder was synthesized using the steel pickling liquor and the waste solution of electroplating as the starting materials. The shell TiO 2 nanocrystal was prepared by sol-gel hydrolysis precipitation of titanium isopropoxide [Ti(OC 3 H 7 ) 4 ] on the Ni–Cu–Zn ferrite powder followed by heat treatment. From transmission electron microscopy (TEM) image, the thickness of the titania shell was found to be approximately 5 nm. The core of Ni–Cu–Zn ferrite is spherical or elliptical shape, and the particle size of the core is in the range of 70–110 nm. The magnetic Ni–Cu–Zn ferrite nanopowder is uniformly encapsulated in a titania layer forming core-shell structure of TiO 2 /Ni–Cu–Zn ferrite powder. The degradation efficiency for methylene blue (MB) increases with magnetic photocatalyst (TiO 2 /Ni–Cu–Zn ferrite powder) content. When the magnetic photocatalyst content is 0.40 g in 150 mL of MB, the photocatalytic activity reached the largest value. With a further increase in the content of magnetic photocatalyst, the degradation efficiency slightly decreased. This occurs because the ultraviolet (UV) illumination is covered by catalysts, which were suspended in the methylene blue solution and resulted in the inhibition in the photocatalytic reaction. The photocatalytic degradation result for the relationship between MB concentration and illumination revealed a pseudo first-order kinetic model of the degradation with the limiting rate constant of 1.717 mg/L·min and equilibrium adsorption constant 0.0627 L/mg. Furthermore, the Langmuir–Hinshelwood model can be used to describe the degradation reaction, which suggests that the rate-determining step is surface reaction rather than adsorption is in photocatalytic degradation.

Microwave-induced combustion synthesis of Li0.5Fe2.5−xMgxO4 powder and their characterization

Li0.5Fe2.5−xMgxO4 (0≦x≦1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion using lithium nitrate, ferric nitrate, magnesium nitrate, and carbohydrazide as the starting materials. This process takes only a few minutes to obtain as-received Mg-substituted lithium ferrite powders. The results revealed that the lattice constant increases nonlinearly with increasing Mg content in the Li0.5Fe2.5−xMgxO4 specimens. Moreover, the magnetic properties of Mg-substituted lithium ferrite were also strongly affected by Mg concentration. The saturation magnetization (Ms) of 71.1 emu/g was found at Li0.5Fe2.5O4 specimen. As increased Mg content, the saturation magnetization (Ms) and remanent magnetization (Mr) decreased significantly. This is ascribed to the fact that as Mg content increases, A-O-B (where A represents tetrahedral sites and B represents octahedral sites in ferrite of the spinel type) interactions become weak, and consequently B-O-B interaction...

Synthesis and microwave characterization of 2(MgO, CaO)-2Al2O3-5SiO2 glass ceramics from the sol-gel process

The synthesis and microwave characterization of glass ceramic in the quaternary phase field of the MgO-CaO-Al2O3-SiO2 system synthesized by sol-gel method have been investigated in this paper. The glass powder was obtained by calcining the MgO-CaO-Al2O3-SiO2 xerogel, which was prepared from Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), Aluminum nitrate nonahydrate (Al(NO3)3·9H2O), Calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), and tetraethylortho silicate (TEOS). The powder was characterized by differential thermal analysis, thermogravimety and X-ray diffraction. The calcined powder was pressed, sintered at different temperatures, and then the sintered sample was studied with scanning electron microscope, X-ray diffraction patterns, and microwave properties measurement.