Miewon Jung

Synthesis and Structural Analysis of Au-Doped TiO2/SiO2 Mixed Oxide Films Prepared by Sol-Gel Process

The systematic modifications of silica matrix as a function of modified Ti-alkoxide contents (Au nanocrystals doped TiO2/SiO2 mixed oxide thin films) have been investigated by the sol-gel process. A structural analysis on the various steps of the hydrolysis-condensation process as well as solid powder is determined by IR, UV-Visible, and 29Si NMR spectroscopy. 29Si MAS spectra are characterized by broad lines for the three types of sites. Different distributions (Q2, Q3, and Q4 units) observed in the TiO2/SiO2 (1 : 3) sample. Proper control of the process condition, modifying the Ti alkoxide as a less reactive precursor, improves the increase the amount of Ti–O–Si bonding in the silica network of TiO2/SiO2 mixed oxide matrices and the distribution of metal oxides. This method can be used for the preparation of homogeneous metal and metal-metal alloy nanocrystals deposition from mixed oxide thin films.

Characterization of Alumina Doped with Lanthanum and Pluronic P123 via Sol-Gel Process

To direct the evolution of nanostructure and immobilize γ-Al₂O₃ catalyst, nanocrystalline La-doped-Al₂O₃ powder were prepared by the sol-gel process with addition of an amphiphilic block copolymer template (pluronic P123: (poly(ethyleneoxide) 20 -poly(propyleneoxide) 70 -poly(ethyleneoxide) 20 ). The dried gel is amorphous, whereas heating at temperature above 700℃ leads to the formation of nanocrystalline γ and δ-Al₂O₃ and these two phases is kept until 1100℃. α-Al₂O₃ starts to form at 1200℃ with LaAl l1 O 18 . The surface morphology and crystal structure has been observed by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD). Solid state 27 Al MAS NMR indicates two types of local environment, i.e. octahedral and tetrahedral sites. The surface area and pore size was compared among these powders using the BET nitrogen adsorption measurements.

Fabrication and Thermophysical Properties of Al2O3-Based Multicomponent Composites by Sol-Gel Process

has received wide attention with established use as a catalyst and growing application in structural or functional ceramic materials. On the other hand, the boehmite (AlO(OH)) obtained by sol-gel process has exhibited a decrease in surface area during phase transformation due to a decline in surface active site at high temperature. In this work, -CuO/ZnO (ACZ) and -CuO/CeO (ACC) composite materials were synthesized with aluminum isopropoxide, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate or zinc (II) nitrate hexahydrate. Moreover, the Span 80 as the template block copolymer was added to the ACZ/ACC composition to make nano size particles and to keep increasing the surface area. The ACZ/ACC synthesized powders were characterized by Thermogravimetry-Differential Thermal analysis (TG/DTA), X-ray Diffractometer (XRD), Field-Emmision Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller (BET) surface analysis and thermal electrical conductivity (ZEM-2:M8/L). An enhancement of surface area with the addition to Span 80 surfactant was observed in the ACZ powders from 105 /g to 142 /g, and the ACC powders from 103 /g to 140 /g, respectively.

Dip-coating of nano-sized CeO2 on SiC membrane and its effect on thermal diffusivity.

CeO2-SiC mixed composite membrane was fabricated with porous SiC ceramic and cerium oxide powder synthesized by sol-gel process. This CeO2-SiC membrane and SiC membrane which is made by the purified SiC ceramic were pressed and sintered in Ar atmosphere. And then, the SiC membrane was dip-coated by cerium oxide precursor sol solution and heat-treated in air. The surface morphology, particle size, porosity and structure analysis of the mixing and dip-coating SiC membrane were monitored by FE-SEM and X-ray diffraction analysis. Surface area, pore volume and pore diameter were determined by BET instrument. Thermal diffusivity was measured by laser flash method with increasing temperature. The relation between porosity and thermal diffusivity from different preparation process has been discussed on this study.

Hydrogen permeance of Ce0.8Y0.2O1.9/SiC membrane.

SiC is a promising material for various inorganic membranes because there are properties such as high thermal conductivity, thermal shock resistance and high mechanical strength. Due to these advantages, SiC is also suitable for gas and liquid separation filter material. The SiC used as a support membrane and then added Ce0.8Y0.2O1.9 composite powder to effect catalyst and improve porous. The Ce0.8Y0.2O1.9 composite powder was synthesized with yttrium (III) nitrate hexahydrate and cerium(III) nitrate hexahydrate by sol-gel method. The Ce0.8Y0.2O1.9/SiC membrane was prepared from the purified SiC ceramic and the synthesized Ce0.8Y0.2O1.9 composite powder with aid of hydridopolycarbosilane (HPCS) as a binder, followed by heat-treatments. This membrane was characterized by XRD, FE-SEM, EDXS and BET surface analysis. Thermal diffusivity and hydrogen permeance for this membrane will be discussed.

Preparation of SiO 2 -CuO-CeO 2 Composite Powders and Its Thin Film Templated with Oxalic Acid

Silica-based ceramic-matrix composites have shown promise as advanced materials for many applications such as chemical catalysts, ceramics, pharmaceuticals, and electronics. -CuO- multi-component powders and their thin film, using an oxalic acid template as a chelating agent, have larger surface areas and more uniform pore size distribution than those of inorganic acid catalysts. -CuO- composite powders were synthesized using tetraethylorthosilicate, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate with oxalic acid as template or pore-forming agent. The process of thermal evolution, the phase composition, and the surface morphology of these powders were monitored by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDXS). The mesoporous property of the powders was observed by Brunner-Emmett-Teller surface (BET) analysis. The improved surface area of this powder template with oxalic acid was . This multi-component thin film on stainless-steel was prepared by sol-gel dip coating with no cracks.

P123-Templated Co 3 O 4 /Al 2 O 3 Mesoporous Mixed Oxides for Epoxidation of Styrene

, and / mesoporous powders were prepared by a sol-gel method with starting matierals of aluminum isopropoxide and cobalt (II) nitrate. A P123 template is employed as an active organic additive for improving the specific surface area of the mixed oxide by forming surfactant micelles. A transition metal cobalt oxide supported on alumina with and without P123 was tested to find the most active and selective conditions as a heterogeneous catalyst in the reaction of styrene epoxidation. A bBlock copolymer-P123 template was added to the staring materials to control physical and chemical properties. The properties of / powder with and without P123 were characterized using an X-ray diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), a Bruner-Emmertt-Teller (BET) surface analyzer, and MAS NMR spectroscopy. Powders with and without P123 were compared in catalytic tests. The catalytic activity and selectivity were monitored by GC/MS, , and -NMR spectroscopy. The performance for the reaction of epoxidation of styrene was observed to be in the following order: [/ with P123-1173 K > / with P123-973 K > -973 K>/-973 K > / with P123-1473 K > -973 K]. The existence of -alumina and the nature of the surface morphology are related to catalytic activity.

Evaluations of Y 2 O 3 Powder Synthesized Using Oxalic Acid

Nano-sized powders were prepared via a sol-gel method starting with (Yttrium(III) nitrate hexahydrate) and water with ethanol as a cosolvent. is an important rare earth oxide and has been considered for use in nuclear applications, such as ceramic materials, due to its excellent optical and refractory characteristics. It has been used as a chemically stable substrate, a crucible material for melting reactive metals, and a nozzle material for jet casting molten rare earth-iron magnetic alloys. Oxalic acid () has been adopted as a chelating agent in order to control the rate of hydrolysis and polycondensation, and ammonia was added in order to adjust the base condition. The synthesized powder was characterized using TG/DTA, XRD, FE-SEM, BET and Impedance Analyzer analyses. The powder changed its properties in accordance with the pH conditions of the catalyst. As the pH increases according to the FE-SEM, the grain grew and it showed that the pore size decreased while confirming the effect of the grain size. The nano-material powders demonstrated that the surface area was improved with the addition of oxalic acid with ammonium hydroxide.

La이 도핑된 CuO-ZnO-Al2O3 복합 산화물의 합성공정개발

La doped CuO-ZnO-Al2O3 powders are prepared by sol-gel method with aluminum isopropoxide and primarydistilled water as precursor and solvent. In this synthesized process, the obtained metal oxides caused the precursor such ascopper (II) nitrate hydrate and zinc (II) nitrate hexahydrate were added. To improve the surface areas of La doped CuO-ZnO-Al2O3 powder, sorbitan (z)-mono-9-octadecenoate (Span 80) was added. The synthesized powder was calcined at varioustemperatures. The dopant was found to affect the surface area and particle size of the mixed oxide, in conjunction with thecalcined temperature. The structural analysis and textual properties of the synthesized powder were measured with an X-rayDiffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller surface analysis (BET),Thermogravimetry-Differential Thermal analysis (TG/DTA), 27Al solid state Nuclear Magnetic Resonance (NMR) and transforminfrared microspectroscopy (FT-IR). An increase of surface area with Span 80 was observed on La doped CuO-ZnO-Al2O3powders from 25m2/g to 41m2/g.