• Journal of Hydrogen and New Energy
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• v.9 no.4
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• pp.161-167
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• 1998

It has been investigated the effects of alloying elements and binders on the corrosion behavior of metal hydride electrodes for anode of Ni/MH secondary battery. The $AB_5$-type alloys, $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ and $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$, were used for the experiments. The electrodes were prepared by mixing and cold-pressing of alloy powders with Si sealent or PTFE powders, or cold-pressing the electroless copper coated alloy powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.

• Journal of the Korean Chemical Society
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• v.40 no.7
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• pp.492-500
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• 1996

The solvent extraction of trace Bi, Cd and In in seawater samples using ammonium pyrrolidine dithiocarbamate(APDC) as a complexing agent was studied. The pH of sample solution, the amount of APDC, the type of solvent and the shaking time were investigated together with back-extraction conditions. After the pH of 200 mL seawater was adjusted to 4.0 and 5.0 mL of 1% APDC was added, analytes were extracted with 10.0 mL of MIBK by shaking for 35 minutes. The organic phase seperated was washed with a 0.05 M NaOH 10.0 mL to remove HPDC. The analytes were stripped by the back-extraction of 5 minute shaking with 5 mL of 4 M HNO3 containing 150 ㎍/mL Pd(Ⅱ). Detection limits of Bi, Cd and In were 0.038, 0.0057 and 0.023 ng/mL, respectively. Both of Bi(Ⅲ) and In(Ⅲ) were not detected in two kinds of water samples of the East Sea and the contents of Cd(Ⅱ) were 0.018 and 0.016 ng/mL. The recoveries of over 90% showed that this procedure was applicable to the determination of such trace elements in seawater samples.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.233-242
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• 1988

The uranium(VI) complexes with new unsaturated macrocyclic ligands of cryptand types and the neodymium(III) complexes with cryptand 222 and DBC ligands have been investigated polarographically in dimethylsulfoxide solvent. The reduction states, electron numbers involved in the reduction process, effects of the added acid on the polarograms of complexes, and the mechanisms of the reduction electrode reactions have been examined. The stability constants and mole-ratio of new complexes were also obtained by polarographic method. The reaction of ligands was controlled by the diffusion in the reduction with four electrons at a step, whereas the redox reaction with six electrons at three steps in $UO_2\;^{2+}$ complexes with macrocyclic ligands and the redox reaction with one electron at a step in $Nd^{3+}$ complexes with cryptand 222 and DBC have been observed. The imine ligands formed stable complexes with uranium(VI) above pH 7.0, and the neodymium(III) complexes with cryptand 222 and DBC ligands were stable above pH 4.0.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.294-301
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• 1993

${\pi}$-A isotherms of the Palmitic acid(PA) with increasing pH shifted to the low area/molecule due to the dissociation of PA at the air-water interface. More condensation of PA monolayers occurred by the addition of Mg$^{2+}$, Ca$^{2+}$ and Ba$^{2+}$ ion in subphase. This condensing effect was increased with increasing the concentration of these ions. Due to the interaction with each ion, PA were formed Mg, Ca, Ba-Palmitate complex. The binding structure between alkaline earth ion and carboxylate ligand in PA has been identified by IR spectrometry. The order of condensing effect of alkaline earth ions at pH 8 was Ca$^{2+}$ > Ba$^{2+}$+ > Mg$^{2+}$. The condensing effect except for Mg$^{2+}$ decreased with increasing atomic number. Whereas, the condensing effect in pure water system decreased with decreasing atomic number in the sequence: Ba$^{2+}$ > Ca$^{2+}$ > Mg$^{2+}$. The miscibility of binary system of PA and hexadecanol in monolayer showed that the miscibility was good for the pure water system. But, in the buffered pH 8 system, bad miscibility was found.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.377-384
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• 2009

Among 27 Bacillus sp. isolated from Meju, a traditional Korean soybean fermented food, a strain MJ-226 was selected due to its strong fibrinolytic activity, and it was identified to be Bacillus subtilis MJ-226 according to morphological and biochemical characterization and sugar utilization. The fibrinolytic enzyme of B. subtilis MJ-226 was maximally produced by cultivating in the Tryptic Soy Broth (TSB) for 24~26 h at $37^{\circ}C$, and the enzymes activity was promoted with adding glucose, fructose, peptone or yeast extract to TSB. The fibrinolytic enzyme was stable at the range of pH from 6.0 to 8.0, and between 35 and $40^{\circ}C$. Also, when the crude enzyme was exposed to various metal ions and chemical inhibitors for 12 h, the enzyme stability was maintained by $MnSO_4$, $CaCl_2$, KCl, and NaCl. However, the stability was destroyed by treatment with $CuSO_4$, $MgSO_4$, $ZnSO_4$, $FeSO_4$, and $BaCl_2$, and the enzyme was unstable in the presence of chemical inhibitors such as iodoacetic acid, leupeptin, phenylmethanesulphonyl fluoride (PMSF), sodium dodecyl sulfate (SDS), thiourea, trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA) and ethylenediaminetetraacetic acid (EDTA).

• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1196-1204
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• 1999

We have carried out copper MOCVD(metalorganic chemical vapor deposition) onto the reactive sputtered PVD-TiN and rapid thermal converted RTP-TiN substrates using direct liquid injection for effective delivery of the (hfac)Cu(vtmos) [$C_{10}H_{13}O_{5}CuF_{6}$Si: 1,1,1,5,5,5-hexafluoro-2,4- pentadionato (vinyltrimethoxysilane) copper (I)] precursor. Especially, the influences of deposition conditions and the substrate type on growth rate, crystal structure, microstructure, and electrical resistivity of copper deposits have been discussed. It is found that the film growth with 0.2ccm precursor flow rate become mass-transfer controlled up to Ar flow rate of 200sccm and pick-up rate controlled at a vaporizer above 1.0Torr reactor pressure. The surface-reaction controlled region from 155 to 225$^{\circ}C$ at 0.6Torr reactor pressure results in the apparent activation energies of 12.7~14.1kcal/mol, and above 224$^{\circ}C$ the growth rate with $H_2$ addition could be improved compared to the pure Ar carrier. The Cu/RTP-TiN structures which have high copper nucleation density in initial stage of growth show more pronounced (111) preferred orientations and lower electrical resistivities than those on PVD-TiN. The variation of electrical resistivity with substrate temperature reflects the three types of film microstructure changes, showing the lowest value for the deposit at 165$^{\circ}C$ with small grains of good contacts.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.315-321
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• 1999

Metal matrix composites have been extensively studied because of their excellent characteristics for structural application. $Al_2O_3$ and SiC have been used as a common reinforcement owing to their good mechanical properties. However the manufacturing cost of these ceramic reinforcement is expensive, so the use of the composites has been restricted to special purposes. In this study, we tested the application possibility as a reinforcement of $Al_2O_3$-TiC powder synthesized by SHS(Self-propagating High-temperature Synthesis) process to Al alloy matrix composite. Also, $Al_2O_3$ short fibers were added with the synthesized powders in order to apply to the Al matrix hybrid composites. Squeeze infiltration casting process was used to make the composite with 25vol% of reinforcement. Microstructure and crystal structure were examined by SEM, OM and XRD, also the mechanical properties were studied by the compressive test and wear test.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.3
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• pp.180-188
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• 1999

The dynamic elastic properties of metal matrix composites were investigated by resonant ultrasound spectroscopy(RUS). The composites used in this study consisted of 2124 aluminum alloy reinforced with different concentrations of SiC particles. RUS can determine the nine independent elastic stiffness($C_{ij}$) for the orthorhombic symmetry on a small specimen simultaneously. The elastic constants were determined as a function of the volume fraction. A concept of effective aspect ratio. which combine the aspect ratio and the orientation of reinforcement. was used to calculate the initial moduli from Mori-Tanaka theory for the input of RUS minimization code. Young's moduli can be obtained from the measured stiffnesses. The results show that the elastic stiffness increases with increment of the particle content. The behavior of elastic stiffness indicates that the particle redistribution induced by the extrusion process enlarges the transversely isotropic symmetry as the fraction of reinforced particles increase. This relationship could be used for determination of the volume fractions of reinforcement as a potential tool of nondestructive material characterization.

• Resources Recycling
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• v.29 no.5
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• pp.55-63
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• 2020

In order to investigate the separation of Co(II) and Ni(II) by ionic liquids from weak hydrochloric acid solutions, extraction experiments were performed by changing the type and concentration of ionic liquids and the initial pH of the aqueous phase. Two kinds of ionic liquids based on Aliquat 336 were employed in this work; one was synthesized by reacting organophosphorus acids(D2EHPA, PC88A, Cyanex 272, Cyanex 301) with Aliquat 336 and the other was prepared by exchanging the chloride ion of Aliquat 336 with SCN^-. The three types of ionic liquids (ALi-D2, ALi-PC, and ALi-CY272) showed better extraction of Co(II) than Ni(II), and the equilibrium pH was higher than the initial pH. In the case of ALi-CY301, the selectivity of Co(II) and Ni(II) depended on the extraction conditions. In addition, the effect of the addition of TBP to the ionic liquid on the extraction of two metals was also investigated. Employment of ALi-SCN as an extractant resulted in selective extraction of Co(II) and complete separation of the two metal ions was possible.