• Applied Chemistry for Engineering
• /
• v.7 no.5
• /
• pp.861-868
• /
• 1996

Skeletal isomerization reaction known as exothermic reaction shows possible maximum yield of i-butene from n-butene at $110^{\circ}C$ over $Pt/MoO_3/SiO_2$. Compared with conventional catalyst such as silica, zeolite, alumina etc., $Pt/MoO_3/SiO_2$ demonstrates higher yield while by-products except 2-butene do not form. Faster H spillover rate over $Pt/MoO_3/SiO_2$ is demonstrated via isothermal reduction experiment at $110^{\circ}C$ compared to the rate over $Pt/MoO_3/Al_2O_3$. Overall isomerization rates are proportional to higher spillover rates from Pt onto $MoO_3$ surface. The skeletal isomerization reaction is composed of two elementary steps. First, carbonium ion formation over Pt crystallites by H spillover. Second, carbenium ion formation over $MoO_3$ followed by formation of i-butene. Moreover, it is suggested that H spillover step from Pt surface onto $MoO_3$ is assumed to be the rate determining step and control the overall isomerization rate.

• The Journal of Engineering Research
• /
• v.5 no.1
• /
• pp.73-87
• /
• 2004

The synthesis and crystallization of amorphous calcium carbonate($CaCO_3$.$nH_2 O$) obtained from gas-liquid reaction between aqueous solution of calcium hydroxide and carbon dioxide at 15~$50^{\circ}C$ are investigated by electrical conductometry, XRD and TEM. The results are as follows: The initial reaction products prior to the formation of precipitated calcium carbonate is amorphous calcium carbonate. The electrical conductivity values in the slurry are decreased during the formation of amorphous calcium carbonate which covers particle surface of calcium hydroxide and retard the dissolution of calcium hydroxide into the solution. that amorphous calcium carbonate is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. While amorphous calcium carbonate crystallizes into chain-like calcite, the conductivity values are recovered rapidly and the apparent viscosity of slurry containing higher concentration of calcium hydroxide increase. At below pH 9.5, chain-like calcite separates into individual particles to form precipitated calcium carbonate. The formation and synthetic temperature range of amorphous calcium carbonate is most suitable a primary decreasing step(a-step) at $15^{\circ}C$ in the electrical conductometry.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.132-139
• /
• 2017

A huge amount of de-icing agent is sprayed during winter to promote traffic safety in cold regions, and the quantity of de-icing agent sprayed has increased each year. The main ingredients in commonly used de-icing agents are chlorides, such as calcium chloride($CaCl_2$) and sodium chloride(NaCl). While calcium chloride is mostly used in Korea and sodium chloride is usually used in the U.S. and Japan, all de-icing agents include chloride ions. The chlorides included in sprayed calcium chloride-based de-icing agents have severe adverse effects, including the corrosion of reinforcing steels through salt damage by infiltrating into road structures, reduced structural performance of pavement or damage to bridge structures, and surface scaling, in combination with freezing damage in winter, as well as water pollution. In addition, the deterioration of paved concrete road surface that occurs after the use of calcium chloride-based de-icing agent accelerates the development of visual problems with traffic structures. Therefore, the present study was performed to prepare an environment-friendly liquid de-icing agent through a reaction between waste organic acids and calcium-based by-products, which are industrial by-products, and to analyze the properties of the de-icing agent in order to evaluate its applicability to road facilities.

• Clean Technology
• /
• v.8 no.4
• /
• pp.173-180
• /
• 2002

As a primary material for MLCC, $BaTiO_3$ particles coated with two additives in a core-shell structure were prepared in this study. This composite powder can not only reduce the VOC emission during MLCC manufacture but also increase the density and reliability of electronic products. The additives were $Y_2O_3$ and $MnCO_3$, whose composition information was obtained from domestic companies. It was observed that the surface of $BaTiO_3$ particles was uniformly as well as simultaneously coated by those two materials via urea-decomposition reaction over $70^{\circ}C$ as the reaction temperature. Elemental analysis indicated that the measured content of each additve was quite close to the designated value. The effect of polymeric dispersant such as PVP, on the coating characteristics was not as significant as expected.

• Applied Chemistry for Engineering
• /
• v.4 no.2
• /
• pp.381-392
• /
• 1993

Anionic oligomer surfactants, dodecyl polyoxyethylene ${\alpha}-sulfa$ alkanoates, had been synthesized through the esterification of dodecyl polyoxyethylene glycol and ${\alpha}-sulfa$ alkanoic acid with straight chain alkyl group having from 10 to 18 carbon atoms to good yield. ${\alpha}-sulfa$ alkanoic acids were obtained by reaction with long chain alkanoic acids and sulfur trioxide-dioxane complex, and dodecyl polyoxyethylene glycols, by addition reaction with dodecyl alcohol and ethylene oxide(addition, 5, 10, 20mol) respectively. All the synthetic products could be separated by means of the thin layer and column chromatography, and their structure has characterized with IR, $^1HNMR$ and elemental analysis, respectively.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.6
• /
• pp.917-930
• /
• 2018

Intracellular synthesis of silver/silver chloride nanoparticles (Ag/AgCl-NPs) using Meyerozyma guilliermondii KX008616 is reported under aerobic and anaerobic conditions for the first time. The biogenic synthesis of Ag-NP types has been proposed as an easy and cost-effective alternative for various biomedical applications. The interaction of nanoparticles with ethanol production was mentioned. The purified biogenic Ag/AgCl-nanoparticles were characterized by different spectroscopic and microscopic approaches. The purified nanoparticles exhibited a surface plasmon resonance band at 419 and 415 nm, confirming the formation of Ag/AgCl-NPs under aerobic and anaerobic conditions, respectively. The planes of the cubic crystalline phase of the Ag/AgCl-NPs were confirmed by X-ray diffraction. Fourier-transform infrared spectra showed the interactions between the yeast cell constituents and silver ions to form the biogenic Ag/AgCl-NPs. The intracellular Ag/AgCl-NPs synthesized under aerobic condition were homogenous and spherical in shape, with an approximate particle size of 2.5-30nm as denoted by the transmission electron microscopy (TEM). The reaction mixture was optimized by varying reaction parameters, including temperature and pH. Analysis of ultrathin sections of yeast cells by TEM indicated that the biogenic nanoparticles were formed as clusters, known as nanoaggregates, in the cytoplasm or in the inner and outer regions of the cell wall. The study recommends using the biomass of yeast that is used in industrial or fermentation purposes to produce Ag/AgCl-NPs as associated by-products to maximize benefit and to reduce the production cost.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.11
• /
• pp.826-830
• /
• 2013

In this paper, we carried out the investigations of both etch characteristics and mechanisms for the $SnO_2$ thin films in $O_2/BCl_3/Ar$ plasma. The dry etching characteristics of the $SnO_2$ thin films was studied by varying the $O_2/BCl_3/Ar$ gas mixing ratio. We determined the optimized process conditions that were as follows: a RF power of 700 W, a DC-bias voltage of - 150 V, and a process pressure of 2 Pa. The maximum etch rate was 509.9 nm/min in $O_2/BCl_3/Ar$=(3:4:16 sccm) plasma. From XPS analysis, the etch mechanism of the $SnO_2$ thin films in the $O_2/BCl_3/Ar$ plasma can be identified as the ion-assisted chemical reaction while the role of ion bombardment includes the destruction of the metal-oxide bonds as well as the cleaning of the etched surface form the reaction products.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.8
• /
• pp.2408-2412
• /
• 2013

We demonstrate herein the synthesis and modification of magnetic nanoparticles and its use in the immobilization of the lipase. Magnetic $Fe_3O_4$ nanoparticles (MNPs) were prepared by simple co-precipitation method in aqueous medium and then subsequently modified with tetraethyl orthosilicate (TEOS) and 3-aminopropyl triethylenesilane (APTES). Silanization magnetic nanoparticles (SMNP) and amino magnetic nanomicrosphere (AMNP) were synthesized successfully. The morphology, structure, magnetic property and chemical composition of the synthetic MNP and its derivatives were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) analysis, X-ray diffraction, superconducting quantum interference device (SQUID) and thermogravimetric analyses (TGA). All of these three nanoparticles exhibited good crystallization performance, apparent superparamagnetism, and the saturation magnetization of MNP, SMNP, AMNP were 47.9 emu/g, 33.0 emu/g and 19.5 emu/g, respectively. The amino content was 5.66%. The AMNP was used to immobilize lipase, and the maximum adsorption capacity of the protein was 26.3 mg/g. The maximum maintained activity (88 percent) was achieved while the amount of immobilized lipase was 23.7 mg $g^{-1}$. Immobilization of enzyme on the magnetic nanoparticles can facilitate the isolation of reaction products from reaction mixture and thus lowers the cost of enzyme application.

• Journal of the Semiconductor & Display Technology
• /
• v.18 no.1
• /
• pp.15-20
• /
• 2019

Inspection and measurement of surface quality is one of the most critical processes for manufacturing products such as semiconductor wafers, sapphire substrates, and display panels. The vibrations of the inspection and measurement devices are supposed to be the most dominant factors for severe measurement errors and longer measuring time. In this study, dynamic characteristics of an inspection and measurement device are analyzed through frequency response experiment and computer simulation to obtain parameters such as frequencies, magnitudes, mode shapes, and periods of vibrations. And then an active damper which consists of sensor, interface board, and actuator is designed based on the parameters to formulate the most effective reaction signal to suppress the vibrations which is generated by an interface board, and provided by an actuator. If the vibrations are measured by the sensor, the active damper immediately generates and provides the corresponding reaction signal to inspection and measurement device. The result shows that the active damper can suppress structural vibrations effectively and reduce measuring time of the device and enhance the productivity.

• 한국연소학회:학술대회논문집
• /
• 2006.10a
• /
• pp.86-94
• /
• 2006

This paper investigates the effects of acoustic forcing on NOx emissions and mixing process in the near field region of turbulent hydrogen nonpremixed flames. The resonance frequency was selected to force the coaxial air jet acoustically, because the resonance frequency is effective to amplify the forcing amplitude and reduce NOx emissions. When the resonance frequency is acoustically excited, a streamwise vortex is formed in the mixing layer between the coaxial air jet and coflowing air. As the vortex develops downstream, it entrains both ambient air and combustion products into the coaxial air jet to mix well. In addition, the strong vortex pulls the flame surface toward the coaxial air jet, causing intense chemical reaction. Acoustic excitation also causes velocity fluctuations of coaxial air jet as well as fuel jet but, the maximum value of centerline fuel velocity fluctuation occurs at the different phases of $\Phi$=$180^{\circ}$ for nonreacting case and $\Phi$=$0^{\circ}$ for reacting case. Since acoustic excitation enhances the mixing rate of fuel and air, the line of the stoichiometric mixture fraction becomes narrow. Finally, acoustic forcing at the resonance frequency reduces the normalized flame length by 15 % and EINOx by 25 %, compared to the flame without acoustic excitation.