• Journal of the Korean Chemical Society
• /
• v.36 no.4
• /
• pp.558-564
• /
• 1992

Product yields were determined for the reaction of styrene with sodium hypochlorite (NaOCl) in CH$_2$Cl$_2$ with various substituted manganese porphyrin complexes as catalysts. In the presence of the electron withdrawing group and ortho-substituted manganese porphyrin complexes, reaction rate and epoxide selectivity are increased. Also reaction rate and epoxide selectivity are largely increased by the presence of imidazole which behaves as axial ligand of the manganese porphyrin complexes. By the kinetic study with Michealis-Menten equation, the factor significantly affected to catalytic ability is $K_m$ value. A large binding affinity consists with the low $K_m$. With theoretical analysis by EHMO calculation, the results are in good agreement with experimental data.

• Bulletin of the Korean Chemical Society
• /
• v.10 no.6
• /
• pp.485-488
• /
• 1989

A carbon paste coated-wire ion-selective electrode for chloride (carbon chloride-CWE) was constructed using epoxy resin, ion-exchanger and carbon powder as a polymer membrane. Its utility, the composition of a polymer membrane, the response characteristics, and the selectivity were examined and applied to the environmental water analysis. The carbon chloride-CWE was prepared using a silver wire, which was covered with silver chloride and then coated with epoxy resin into which chloride ion-exchanger and carbon powder were previously incorporated in advance. The response of the carbon chloride-CWE was Nernstian for $1.0{\times}10^{-2}-2{\times}10^{-5}$ M chloride and the useful pH range from $10^{-2} M Cl- to 10^{-4} M Cl^-$ was 3.0-9.0. Furthermore, the selectivity of chloride over iodide, bromide, and cyanide was much improved compared with those for a solid state epoxy body chloride electrode and a liquid membrane chloride electrode. The carbon chloride-CWE was applied to determine Cl^-$ in tap and ground water. The obtained results were in good agreement with those by the established methods such as spectrophotometric or other chloride-selective electrode methods.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2018.11a
• /
• pp.379-379
• /
• 2018

MXenes are a new family of 2D transition metal carbide nanosheets analogous to graphene (Lv et al., 2017; Sun et al., 2018). Due to the easy availability, hydrophilic behavior, and tunable chemistry of MXenes, their use in applications for environmental pollution remediation such as heavy metal adsorption has recently been explored (Li et al., 2017). In this study, three-dimensional (3D) MXene ($Ti_3C_2T_x$) films with high adsorption capacity, good mechanical strength, and high selectivity for specific radionuclide from aquose solution were successfully fabricated by a polymeric precursor method using vacuum-assisted filtration. The highest removal efficiency on the films was 99.54%, 95.61%, and 82.79% for $Sr^{2+}$, $Co^{2+}$, and $Cs^+$, respectively, using a film dosage of 0.06 g/ L in the initial radionuclide solution (each radionuclide concentration = 1 mg/L and pH = 7.0). Especially, the adsorption process reached an equilibrium within 30 min. The expanded interlayer spacing of $Ti_3C_2T_x$ sheets in MXene films showed excellent radionuclide selectivity ($Cs^+$ and/or $Sr^{2+}/Co^{2+}$) (Simon, 2017). Besides, the MXene films was not only able to be easily retrieved from an aqueous solution by filtration after decontamination processes, but also to selectively separate desired target radionuclides in the solutions. Therefore, the newly developed MXene ($Ti_3C_2T_x$) films has a great potential for radionuclide removal from aqueous solution.

• Korean Membrane Journal
• /
• v.1 no.1
• /
• pp.1-7
• /
• 1999

Pd-ceramic composite membranes and catalytic membrane reactors(CMR) have been studied for hydrogen and its isotopes (deuterium and tritium) purification and recovery in the fusion reactor fuel cycle. Particularly a closed-loop process has been studied for recovering tritium from tritiated water by means of a CMR in which the water gas shift reaction takes place. The development of the techniques for coating micro-porous ceramic tubes with Pd and Pd/Ag thin layers is described : P composite membranes have been produced by electroless deposition (Pd/Ag film of 10-20 $\mu$m) and rolling of thin metal sheets (Pd and Pd/Ag membranes of 50-70 $\mu$m). Experimental results of the electroless membranes have shown a not complete hydrogen selectivity because of the presence of some defects(micro-holes) in the metallic thin layer. Conversely the rolled thin Pd and Pd/ag membranes have separated hydrogen from the other gases with a complete selectivity giving rise to a slightly larger (about a factor 1.7) mass transfer resistance with respect to the electroless membranes. Experimental tests have confirmed the good performances of the rolled membranes in terms of chemical stability over several weeks of operation. Therefore these rolled membranes and CMR are adequate for applications in the fusion reactor fuel cycle as well as in the industrial processes where high pure hydrogen is required (i.e. hydrocarbon reforming for fuel cell)

• Journal of Sensor Science and Technology
• /
• v.13 no.6
• /
• pp.424-429
• /
• 2004

$Cr_{2}O_{3}$ thick films were fabricated by screen printing method on alumina substrates and annealed at $700^{\circ}C$, $800^{\circ}C$, and $900^{\circ}C$ in air, respectively. Structural properties examined by XRD and SEM showed (116) dominant $Cr_{2}O_{3}$ peak and increased grain sizes with the annealing. The resistance of the films decreased with increasing the annealing temperature. Gas sensing characteristics to $NH_{3}$, CO, $C_{4}H_{10}$, and NO gases showed sensitivity only to $NH_{3}$ gas. $Cr_{2}O_{3}$ thick films annealed at $700^{\circ}C$ had the sensitivity of about 15 % for 100 ppm $NH_{3}$ gas at the working temperature of $300^{\circ}C$. The thick films had good selectivity to the $NH_{3}$ gas. The response time to $NH_{3}$ gas was about 10 seconds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.67-67
• /
• 2009

Due to the scaling down of the dielectrics thickness, the leakage currents arising from electron tunneling through the dielectrics has become the major technical barrier. Thus, much works has focused on the development of high k dielectrics in both cases of memories and CMOS fields. Among the high-k materials, $Al_2O_3$ considered as good candidate has been attracting much attentions, which own some good properties as high dielectric constant k value (~9), a high bandgap (~2eV) and elevated crystallization temperature, etc. Due to the easy control of ion energy and flux, low ownership and simple structure of the inductively coupled plasma (ICP), we chose it for high-density plasma in our study. And the $BCl_3$ was included in the gas due to the effective extraction of oxygen in the form of BClxOy compound. In this study, the etch characteristic of ALD deposited $Al_2O_3$ thin film was investigated in $BCl_3/N_2$ plasma. The experiment were performed by comparing etch rates and selectivity of $Al_2O_3$ over $SiO_2$ as functions of the input plasma parameters such as gas mixing ratio, DC-bias voltage and RF power and process pressure. The maximum etch rate was obtained under 15 mTorr process perssure, 700 W RF power, $BCl_3$(6 sccm)/$N_2$(14 sccm) plasma, and the highest etch selectivity was 1.9. We used the x-ray photoelectron spectroscopy (XPS) to investigate the chemical reactions on the etched surface. The Auger electron spectroscopy (AES) was used for elemental analysis of etched surface.

• The Korean Journal of Pesticide Science
• /
• v.3 no.1
• /
• pp.96-101
• /
• 1999

3-Trifluoromethylpyrazoles and 4-benzenecarbinolpyrazoles were prepared by the new synthetic methodologies, and their herbicidal effects were tested (in vivo) in the upland conditions and in the flooded paddy conditions for the purpose of the development of new herbicides. In upland conditions, most of the pyrazoles showed weak herbicidal effects at 4 kg/ha dosage in the post-emergence test, while no herbicidal effects in the pre-emergence test. In the flooded paddy conditions, some of the pyrazoles showed good herbicidal effects at a rate of 4 kg/ha, especially, 3-trifluoromethyl-4-(4-methoxybenzoyl)pyrazole showed the best herbicidal activity with good selectivity between rice and weeds. But other derivatives substituted with electron-donating groups such as dior trimethoxy and sulfides, and 4-benzenecarbinolpyrazoles showed weak herbicidal effects.

• Membrane Journal
• /
• v.29 no.1
• /
• pp.1-10
• /
• 2019

Poly(ether block amide) (PEBA) is one of the commercially important class of block copolymer very much suitable specifically for $CO_2$ separation. Gas separation membrane need to have good mechanical strength as well as high gas permeability. The crystalline polyamide (PA) block provides the mechanical strength while the rubbery polyether (PE) group being $CO_2$-philic facilitate $CO_2$ permeation though the membrane. Composition of thermoplastic and rubbery phase in the polymer are changed to fit into suitable gas separation application. Although PEBA has good permeability, the selectivity of the membrane can be enhanced by incorporating molecular sieve without affection much the gas permeability. Mixed matrix membrane (MMM), a class of composite membrane combine the advantage of polymer matrix with the inorganic fillers. However, there are some disadvantages based on the compatibility of the inorganic fillers and polymeric phase. This review covers both the advantage and limitations of PEBA block copolymer based composite membrane.

• Korean Journal of Optics and Photonics
• /
• v.8 no.3
• /
• pp.241-244
• /
• 1997

A speckle pattern from an optical fiber is used for a reference beam in writing and reading a volume hologram. The photorefractive volume hologram with this scheme shows good spatial selectivity for spatial(shift) multiplexing because the speckle pattern in writing and reading a hologram looses correlation with a small spatial shift. This scheme has the insensitivity to axial movement. The data storage system with this scheme will have a high storage density and a good stability in operation. We theoretically analyze the diffracted beam from a volume hologram recorded with the speckle pattern from the optical fiber. Experimental results are presented and compared with numerical analysis.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.12
• /
• pp.1380-1384
• /
• 2001

The chemoselective reactions of 1,n-dicarbonyl compounds with allyl halides using indium metal were investigated. $\alpha-Ketoesters$ such as ethyl pyruvate, ethyl 3-methyl-2-oxobutyrate and ethyl benzoylformate reacted with a variety of allyl halides i n the presence of indium to afford hydroxy unsaturated carbonyl compounds in good to excellent yields in MeOH/HCl at $25^{\circ}C.$ For the allyl bromide, the presence of various substituents at the $\alpha$ or $\gamma$ position exhibited little effects on both the reaction rates and yields. Ethyl acetoacetate or ethyl levulinate was treated with allylindium reagent to give hydroxy unsaturated carbonyl compounds in good yield. These results mean that both reactivity and selectivity are independent of the distance between carbonyl groups. 2,3-Butanedione or 1-phenyl-1,2-propanedione reacted with allylindium to produce monoallylation product as major compound.