In-Tak Nam

New Synthetic Route of Z-Type (Ba

Z-type barium hexaferrite particles were synthesized by a one-step mixing-calcination process (MCP) and its magnetic properties were characterized and compared to the sol-gel (SGP) and the conventional ceramic (CCP) processed Z-type Ba hexaferrite with two-step calcination. We have used 71.2% pure M-type (BaFe12O19) and 83.8% pure Y-type (Ba2Co2Fe12O22) precursors to synthesize Z-type by the MCP. As a result, 77.8% pure Co2Z hexaferrite particles were obtained. The purities of Co2Z hexaferrite particles processed by SGP and CCP were 75.1% and 70.7%, respectively. It was found that purity of Z-phase was controllable by purity of M- and Y-type precursor particles in the MCP. Loss tan delta of sintered MCP Co2Z decreased from 0.17 at 50 MHz to 0.068 at 300 MHz, while loss tan delta of sintered SGP and CCP Co2Z were 0.12 and 0.09 at 300 MHz. It is found that this loss tan delta is controllable by the purity of Z-phase and sintering process. These results imply that our new process is potentially applicable to synthesis of any other hexaferrites and also cost-effective.

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A combination of energetic shake-milling and a subsequent double sintering process was employed to synthesize Co_0.8Zn_1.2Z (Ba₃Co_0.8Zn_1.2Fe₂₄O ₄₁) hexaferrite nanoparticles with a high-saturation magnetization and a low coercivity. A homogeneous mixture of BaCO₃, CoO, ZnO, 40-nm sized alpha-Fe₂O₃, and heat-treating in an oxygen environment were important factors for synthesizing single-phase Co₂Z-type ferrite nanoparticles. In addition to an X-ray diffraction pattern, Mossbauer spectra confirmed that only Fe³⁺ cations are present in the synthesized Co_0.8Zn_1.2Z particles, implying single phase of the particles. Low-temperature sintering processing, 900degC, was then successfully applied to the single-phase Co_0.8Zn_1.2Z particles. The coercivities of the Co _0.8Zn_1.2Z powder and the low-temperature sintered disk were 9 and 20 Oe, respectively, while maintaining the saturation magnetization of 50 emu/g

Co

The presence of nondegradable organic compounds and xenobiotic chemicals in water is a great concern for the general public because of their polar properties and toxicity. For instance, trichloroethylene (TCE) is a widely used solvent in the chemical industry, and it is also a contaminant of soil, surface water, and groundwater. Recent studies on new treatment technologies have shown that photocatalyst-based advanced oxidation processes are appropriate for removing these polar and toxic compounds from water. The objective of this study was to remove TCE from water using novel nano-ZnO-laponite porous balls prepared from photocatalyst ZnO with nanoscale laponite. These nano-ZnO-laponite porous balls have a porosity of approximately 20%. A lower initial concentration of TCE resulted in high removal efficiency. Moreover, the removal efficiency increased with increasing pH in the photocatalytic degradation experiments employing UVC light with nano-ZnO-laponite. The optimal dosage of nano-ZnO-laponite was 30 g and the use of UVC light resulted in a higher removal efficiency than that achieved with UVA light. In addition, the removal efficiency of TCE significantly increased with increasing light intensity. We think that TCEs removal in water by using porous ball of nano-ZnO and nanoclay composite is a result of degradation from hydroxide by photons of nano-ZnO and physical absorption in nanoclay.

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ZrO2-SiO2 coatings deposited on 316 L stainless steel were prepared to protect chemically the substrates by sol-gel process using Zr(OC3H7 n)4/Si(OC2H5)4 as precursors. The influence of the ZrO2-SiO2 coatings on the corrosion resistance of the 316 L stainless steel was evaluated with the potentiodynamic polarization curves in deareated 15% H2SO4 solutions at 25, 40 and 50 °C . Comparative test was performed on uncoated one. The values of the electrochemical parameters explain how. ZrO2-SiO2 films increase the resistance of stainless steel against corrosion.

Fe

Summary form only given. Hexagonal barium ferrite (BaM) thin film is considered to be an attractive magnetic recording medium because of its large coercivity, corrosion resistance, high anisotropy field, mechanical hardness, and chemical stability. It has been shown that the structure and magnetic properties of thin films can be improved using an underlayer. The purpose of this research was to study microstructure and magnetic properties of the BaM thin films with various underlayers.

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The solid-state amorphization by the interdiffusion reaction in sputter-deposited Ni-Zr multilayer films with oxygen contamination has been investigated by differential scanning calorimetry and X-ray diffractometry. Through X-ray photoelectron spectroscopy analysis, it was found that the multilayer films were contaminated with oxygen during deposition in a low-vacuum system (10−5 torr), and the concentration was modulated having the maximum in zirconium-rich regions. The kinetics of amorphization reactions has been examined by non-isothermal and isothermal annealing. Oxygen introduced into the sample during sample preparation and annealing treatments appears to affect the kinetics of the amorphization reaction associated with variation of the activation energy for interdiffusion in the amorphous layer and a critical thickness of the amorphous layer. The origins of abnormal behaviour in forming intermetallic compound as well as amorphous phase, are discussed in the context of the oxygen incorporation.