Sei-Ki Moon

Preparation of hollow silica microspheres in W/O emulsions with polymers.

Micrometer-sized hollow silica particles were synthesized by sol-gel reaction in water-in-oil emulsion. To obtain hollow structures in silica particles, the viscosity of water droplets in W/O emulsion was controlled with polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP). To stabilize the emulsion structure, hydroxypropyl cellulose (HPC) was added to the oil phase. Without HPC, the particles have an irregular shape and hardly have a particulate form. As the concentration of HPC increased from 0.8 to 1.4 wt%, the size of silica particles decreased from 10 to 1 microm. But above 1.4 wt%, the solution was very viscous, so that it was difficult to handle. Especially, the role of PEG or PVP in the water phase was very important, not only because it stabilized the W/O emulsion structure, but also because it influenced the formation of hollow structure. Interestingly, the hollow silica particles were formed when the molar ratio of water to TEOS (Rw) was 4 and the concentrations of PEG and HPC were 6 and 1.4 wt%, respectively. Also, when PEG was replaced with polyvinylpyrrolidone (PVP), hollow silica particles ranging from 3 to 7 microm were formed.

Preparation of aluminum oxide particles using ammonium acetate as precipitating agent

The effect of ammonium acetate on the preparation of alumina particles as precipitating agent was investigated. Alumina particles were prepared by precipitation of aqueous aluminum chloride solution by using ammonium acetate and ammonium hydroxide. The thermal behaviors, morphologies and surface area were studied for alumina particles formed by ammonium acetate and compared with those of particles formed by ammonium hydroxide. The particles formed by ammonium acetate showed a narrower size distribution, spherical shape, larger surface area and lower crystallinity. These results were explained based on the chelating effects of acetate ions.

Effect of short-chain alcohols as co-surfactants on pseudo-ternary phase diagrams containing lecithin

Lecithin is a natural amphiphilic molecule, the microemulsions of which are often employed as a transdermal delivery medium of drugs and cosmetics. However, it constructs a microemulsion and lamellar phase in a phase diagram without co-surfactant only at a narrow range of composition. In this study, the effect of several short-chain alcohols on pseudo-ternary phase diagrams composed of lecithin, water and dodecane containing 1.0 wt% lidocaine (local anesthetic) was investigated in relation to the application of lecithin-based microemulsion for transdermal drug delivery. The phase diagram for an aqueous solution containing 80.0 wt% ethanol showed a lamellar structure (LC) and bicontinuous isotropic regions. When the mixing ratio of lecithin to alcohols (1-propanol, 1-butanol and n-pentanol) was 2: 1, water-in-oil (L2) and oil-in-water (L1) microemulsions and LC were obtained in a certain range of compositions. The maximum solubilization of water into L2 phase was 38 wt% when the total surfactant was 43 wt% with butanol as cosurfactant.

Isopropyl alcohol decomposition over molybdena-alumina catalyst

The decomposition of isopropyl alcohol was chosen as a probe reaction of acid-base property of molybdena-alumina catalyst. The catalytic kinetics was examined on the oxidized catalyst. The kinetics of the dehydration (yielding propene) and the dehydrogenation (yielding acetone) obeyed the Langmuir-Hinshelwood mechanism in which the rate determining step is the desorption of water for the former and the sur face reaction for the latter, respectively. The effect of varying the extent of reduction of the catalyst was also studied. The trend of variation with the reduction was fairly consistent with the surface chemistry of the catalyst.

RECONSTITUTE TOBACCO PRODUCT DRYING MODEL

Drying is one of the most energy-inrensive and frequently used professes in the tobacco industry. In the present work, heat and mass transfer phenomena in drying sheet materials with impinging air flow are analyzed. A blended leaf (BL) drying model is developed and validated to predict the drying behavior of the reconstitute tobacco product. A numerical method of line technique [Schiesser. 1991] was used to solve the coupled differential equations governing the drying process. This model has been successfully applied to simulate BL drying processes in the pilot plant and the BL. plant. The present model provides a relatively last and efficient way to improve process performance, increase plant productivity, and optimize energy utilisation. With this model, the number of trials necessary to achieve the objectives is reduced, in other words, a large amount of time, money, and manpower is saved. The model results are also helpful in studying the drying behavior of reconstitute tobacco products and understanding the effect of dryer profiles on the sheet strength and subjective results.

Remote RF plasma cleaning for the removal of organic impurity

Summary form only given, as follows. The trends in modern silicon-based microelectronics are pointing in the direction of in-situ processing at low temperature to achieve reliable profiles and to make use of compatible processes. Low energy plasma process, called the plasma cleaning, can be used to clean silicon surfaces from the carbon contaminants and native oxide without any pretreatment of the wafers. In the integrated circuit (IC) fabrication, the photoresist (PR) ashing and PR stripping processes are generally followed the silicon etching process to remove the PR and polymerized residues. However, it was founded no tendency on surface but a benefit of the plasma treatment by means of cleaning the surface. In this work, we investigate the surface reaction of plasma generated in inductively coupled remote plasma with connection of mass spectroscopy.

Formation of hydrophobic thin films on metal surfaces

Summary form only given, as follows. One of the surface properties, water-repellency or hydrophobicity, has been attracted attention in various industrial fields. Hydrophobic surface treatment of materials and preparation of water-repellent films have been performed by using plasma deposition techniques. In this work, the plasma enhanced chemical vapor deposition (PECVD) method has been employed to coat thin fluorocarbon film on metal surface.

Methane activation of plasma and catalytic reaction

Summary form only given, as follows. Conversion of methane to higher hydrocarbon products was investigated through the microwave and RF plasma catalytic reaction. In this study, various experiments have been conducted to find out the effects of parameters on the high frequency region, that was a microwave of 2.45GHz and radio frequency of 13.56 MHz. Manufacturing of C2 products and higher hydrocarbons was carried out by two kinds of discharge equipment and nonoxidative and oxidative coupling of methane. In the microwave plasma catalytic reaction, C2+ products have been obtained much more due to many free radicals produced at low plasma power. Also natural gas containing a little amount of ethane and propane is more active reactant, producing more C2+ products such as ethane, ethylene and acetylene than methane.