• Journal of Powder Materials
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• v.11 no.2
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• pp.137-142
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• 2004

In this study, chemical solution mixing and hydrogen reduction method was used to fabricate nanostructured $Fe_xCo_{1-x}$ alloy powders. Fe-Co chloride mixture, FeCl$_2$ and COCI$_2$ with 99.9％ purity, were reduced in hydrogen atmosphere. Nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated. Magnetic properties of fabricated $Fe_xCo_{1-x}$(x=0, 10, 30, 50, 70, 100) alloy powders with the same grain size were measured because size factor can affect magnetic properties. Coercivity of Fe-Co alloy powders were increased with increasing Co contents. Maximum value of coercivity in various Co contented Fe-Co alloy powders with similar grain size was 125 Oe at Fe$_{100}$. Saturation magnetization value at Fe$_{70}$Co$_{30}$ composition showed maximum value of 219 emu/g and saturation magnetization value decreased with increasing Co contents and minimum value of 155 emu/g was observed at Co$_{100}$.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.286-294
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• 2018

Hot-press forming(HPF) steel can be applied successfully to auto parts because of its superior mechanical properties. However, its resistances to aqueous corrosion and the subsequent hydrogen embrittlement(HE) decrease significantly when the steel is exposed to corrosive environments. Considering that the resistances are greatly dependent on the properties of coating materials formed on the steel surface, the characteristics of the corrosion and hydrogen diffusion behaviors regarding the types of coating material should be clearly understood. Electrochemical polarization and impedance measurements reveal a higher corrosion potential and polarization resistance and a lower corrosion current of the Al-coating compared with Zn-coating. Furthermore, it was expected that the diffusion kinetics of the hydrogen atoms would be much slower in the Al-coating, and this would be due mainly to the much lower diffusion coefficient of hydrogen in the Al-coating with a face-centered cubic structure. The superior surface inhibiting effect of the Al-coating, however, is degraded by the formation of local cracks in the coated layer under severe stress conditions, and therefore further study will be necessary to gain a clearer understanding of the effect of cracks formed on the coated layer on the subsequent corrosion and hydrogen diffusion behaviors.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.21-26
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• 2022

Zinc is emerging as a environment-friendly plating material to replace cadmium, which is harmful to the human body, to prevent hydrogen gas penetration or release from metal materials. Electroplating of Zn and Zn alloys, which is usually performed in an aqueous acidic atmosphere, has disadvantages such as low coulombic efficiency, corrosion, and hydrogen release, resulting in industrial use difficult. In this study, a deep-eutectic solvent was synthesized using choline chloride and ethylene glycol. Using this as a solvent, an electrolyte for Zn plating was prepared, and then zinc was plated on the STS 304 substrate. The surface microstructure and roughness were observed using SEM and AFM. The crystal structure of the electro-plated film was analyzed using XRD. Finally, the preventing effects of hydrogen release through Zn-based deep-eutectic plating on the STS 304 substrate were compared with the uncoated substrate.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1997-2002
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• 2011

The nucleophilic substitution reactions of dicyclohexyl phosphinic chloride [3; $cHex_2$P(=O)Cl] with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at 60.0 $^{\circ}C$. The anilinolysis rate is too slow to be rationalized by the stereoelectronic effects. The rate is contrary to expectations for the electronic influence of the two ligands and exhibits exceptionally great negative deviation from the Taft's eq. The deuterium kinetic isotope effects (DKIEs) involving deuterated anilines invariably change from primary normal ($k_H/k_D$ > 1; max $k_H/k_D$ = 1.10 with X = 4-MeO) with the strongly basic anilines (X = 4-MeO, 4-Me, 3-Me) to secondary inverse ($k_H/k_D$ < 1; min $k_H/k_D$ = 0.673 with X = 3-Cl) with the weakly basic anilines (X = H, 4-F, 4-Cl, 3-Cl). A concerted $S_N2$ mechanism is proposed on the basis of both secondary inverse and primary normal DKIEs. The obtained DKIEs imply that the fraction of a frontside attack increases as the aniline becomes more basic. A hydrogen-bonded, four-center-type transition state is suggested for a frontside attack, while the trigonal bipyramidal pentacoordinate transition state is suggested for a backside attack.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.98-105
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• 2020

By the gravimetric method at atmospheric pressure, the solubility of two α-amino acids was resolved over temperatures from (293.15 to 323.15) K. The α-amino acids studied were L-arginine and L-histidine. Results showed a salting-out effect on the solubility of the tested amino compounds. It is obvious that there was an increase in the solubility, in aqueous chloride solutions, with the increasing temperature. Results were translated regarding the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The solubility data was precisely associated with a semi-empirical equation. The standard molar Gibbs free energies of transfer of selected α-amino compounds (Δ_trG^o) from pure water to aqueous solutions of the chloride salts have been calculated from the solubility data. The decrease in solubility is correlated to the positive (Δ_trG^o) value which is most part of the enthalpic origin.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.2003-2008
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• 2007

The aminolysis of diphenyl thiophosphinic chloride (2) with substituted anilines in acetonitrile at 55.0 oC is investigated kinetically. Kinetic results yield large Hammett ρX (ρnuc = ?3.97) and Bronsted βX (βnuc = 1.40) values. A concerted mechanism involving a partial frontside nucleophilic attack through a hydrogen-bonded, four-center type transition state is proposed on the basis of the primary normal kinetic isotope effects (kH/kD = 1.0-1.1) with deuterated aniline (XC6H4ND2) nucleophiles. The natural bond order charges on P and the degrees of distortion of 42 compounds: chlorophosphates [(R1O)(R2O)P(=O)Cl], chlorothiophosphates [(R1O)(R2O)P(=S)Cl], phosphonochloridates [(R1O)R2P(=O)Cl], phosphonochlorothioates [(R1O)R2P(=S)Cl], chlorophosphinates [R1R2P(=O)Cl], and chlorothiophosphinates [R1R2P(=S)Cl] are calculated at the B3LYP/ 6-311+G(d,p) level in the gas phase.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.126-136
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• 1996

Synthesis of perfluoromethanesulfonyl fluoride(PFMSF) which is a valuable precursor of perfluoro-chemicals such as surface modifier and fine chemicals was studied by electrochemical fluorination (ECF). In order to determine the termination of preelectrolysis, it was carried to monitor the variation of current during preelectrolysis by means of constant cell voltage operation. In a batch cell, chronopotentiometric electrolysis and various chemical analysis such as GC, GC/MS and If were used to understand the potential change of electrode and synthesis and control of hazardous gases products. Termination of preelectrolysis was determinated by measurement the current and/or detection of $F_2$ gas generation. And during the preelectrolysis, an amount of generated $OF_2$ was shown that a lot of moisture was absorbed from air when a cell was filled with anhydrous hydrogen fluoride( AHF ). Above 4V cell voltage, $F_2$ gas was generated and acted on any form of fluorinating agents. In the ECF of MSC (methane sulfonyl chloride) by constant current operation, the potential of anode was intimately relation with generation of $SO_2F_2$. Exchange of Cl to F was dominatly occured in a initial stage. There were various gaseous products including PFMSF as main product and $C_4$ compounds.

• Journal of Electrochemical Science and Technology
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• v.14 no.1
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• pp.15-20
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• 2023

Ionic liquids are considered as a promising, alternative solvent for the electrochemical synthesis of metals because of their high thermal and chemical stability, relatively high ionic conductivity, and wide electrochemical window. In particular, their wide electrochemical window enables the electrodeposition of metals without any side reaction of electrolytes such as hydrogen evolution. The electrodeposition of silver is conducted in 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) ionic liquid system with a silver source of AgCl. This study is the first attempt to electrodeposit silver nanoparticles without using co-solvents other than [C4mim]Cl. Pulse electrolysis is employed for the synthesis of silver nanoparticles by varying applied potentials from -3.0 V to -4.5 V (vs. Pt-quasi reference electrode) and pulse duration from 0.1 s to 0.7 s. Accordingly, the silver nanoparticles whose size ranges from 15 nm to ~100 nm are obtained. The successful preparation of silver nanoparticles is demonstrated regardless of the kinds of substrate including aluminum, stainless steel, and carbon paper in the pulse electrolysis. Finally, the antimicrobial property of electrodeposited silver nanoparticles is confirmed by an antimicrobial test using Staphylococcus aureus.

• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.111-116
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• 1978

The kinetics of phenylmethanesulfonyl chloride in methanol-water, ethanol-water, acetone-water and acetonitrile-water has been investigated. The rate was faster in protic solvents than in aprotic solvents while susceptibility of rate to the ionizing power, i. e., m of the Winstein plot and solvation number of the transition state were much smaller in protic solvents. This was considered in the light of initial state stabilization by hydrogen-bonding solvation of the protic solvents. It was concluded that the reaction proceeds by an $S_N2$ mechanism in which bond-formation precedes bond-breaking at the transition state in all solvent systems.

• YAKHAK HOEJI
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• v.29 no.4
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• pp.183-187
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• 1985

During investigation of the anthelmintic substances against Clonorchis sinensis which are based on the structure of meso-dihydroguairaretic acid, some non-mesoic diaryl butanes were synthesized by Grignard reaction and their anthelmintic activities were determined. In this reaction, an aryl butanone was reacted with benzylmagnesium chloride to produce the corresponding diaryl hydroxybutane which was converted to the corresponding diaryl butane by zinc and hydrogen chloride. The substituents in benzene ring of the diaryl butanes were changed by methylation or demethylation. Among the synthesized substances, 4-phenyl-1-(3, 4-dihydroxyphenyl)-2, 3-dimethylbutane(VII), 4-phenyl-1-(3-hydroxy-4-methoxyphenyl)-2, 3-dimethylbutane(IX) and 4-phenyl-1-(4-hydroxy-3-methoxyphenyl)-2, 3-dimethylbutane(VI) showed strong wormicidal effects against Clonorchis si-nensis in that order. Phenolic hydroxyl group seemed to play a certain role for the wormicidal activity of the diaryl butanes.