• Corrosion Science and Technology
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• v.12 no.1
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• pp.7-11
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• 2013

High velocity oxy-fuel (HVOF) spray coating of WC-metal powder (powder) was carried out to improve the resistances of friction, wear and corrosion of magnetic bearing shaft material Inconel718 (In718) of turbo blower. A micron sized WC-metal powder (86.5% WC, 9.5% Co 4% Cr) was coated onto In718 surface using HVOF thermal spraying. During the spraying, the binder metals and alloy such as Co, Cr and Co-Cr alloy were molten and a small portion of WC particles were partially decomposed to $W_2C$ and free carbon at above its decomposition temperature of $1250^{\circ}C$. The free carbon and excessively sprayed oxygen formed carbon oxide gases, resulting a porous coating of porosity of $2.2{\pm}0.3%$. The surface hardness of substrate increased approximately three times from 400 Hv of In718 to $1260{\pm}30Hv$ of the coating The friction coefficients of the coating were approximately $0.33{\pm}0.03$ at $25^{\circ}C$ and $0.26{\pm}0.03$ at $450^{\circ}C$. These values were smaller than those of In718 substrate at both temperatures due to the lubrication from the free carbon and the cobalt oxide debris. The corrosion resistance of the coating was higher than that of In718 both in salt water of 3.5% NaCl and acid of 1 M HCl solutions, on the contrary, it was lower in base solution of 1 M NaOH. According to this study, the HVOF WC-metal powder coating is recommended for the durability improvement of magnetic bearing shaft of turbo blower.

• Journal of the Korean Applied Science and Technology
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• v.13 no.3
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• pp.25-34
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• 1996

We have synthesized the water-insoluble chitosan derivative, N-dithiocarboxy chitosan sodium salt, through the reaction of chitosan with carbon disulfide in the presence of alkali metal hydroxide, Chitosan itself has been prepared using chitin, one of the most abundant compounds in nature, as a starting material. To elucidate this natural polymer the capacity of adsorbing heavy metal ions, we have performed adsorption experiments using chitosan derivatives of various average molecular weights with different contents of sulfur. The effect of pH, adsorption time and temperature on adsorption efficiency was also studied. The adsorbent derived from chitosan of average molecular weight ranging $5,700{\sim}20,000$ was shown to have the highest capacity of adsorbing heavy metal ions. Adsorbing efficiency was increased as the reaction time was increased and as the reaction temperature range of $25{\sim}45^{\circ}C$. The adsorption capacity at various pH, however, appeared to vary depending on the heavy metal ions studied.

• Journal of the Korean Chemical Society
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• v.41 no.2
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• pp.77-81
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• 1997

The transport rates of transition metal cations were increased in order of Ni(II)$(NtnOenH_4)$and 1,12,15-triaza-3,4;9,10-dibenzo-5,8-dioxacyclo-heptadecane$(NdienOenH_4)$as carriers. The transport rates of transition metal cations was found to be of first order to the salt concentrations. It was also found that the dissociation process in the transport process is rate determining step. From the measurements of the transport rates at various temperatures, the partition free energies of hydration$({\Delta}G_p)$for the transition metal cations were calculated. The results showed that the order of transport rates of transition metal cations was found to be proportional to the magnitudes of negative value of the partition free energies of hydration$({\Delta}G_p)$.

• YAKHAK HOEJI
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• v.10 no.4
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• pp.1-6
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• 1966

Various thiocyanatoammine chromium complex salts are prepared by the known methods and the Rf. value of these complex salts are determined by four developers. These four developers were used in the paper chromatographical work of cobalt complex salts by Yamamoto in 1954. It was also found that the developer A (Ch$_{3}$OH, acetone, NH$_{4}$OH) gave best results of these four developers and the decending development gave better results than ascending development in this experiment. In the case of decending development using developer A, it is found that the Rf. value is increased with the number of thiocyanate radical. The reason of this curious results can be explained that the thiocyanate radical in the complex ion is more active for the organic solvent than ammine radical. Shifting of electrons to the central metal and the charge of the complex ion can also effect ot the Rf. value but much questions are remained for the explanation of the above curious phenomenon. Separation of mixed sample is also studied for various mixture of the above complex salts. In the case of the mixture of hexammine and diammine complex salt, the clear separation is possible but in almost all other mixed sample, the results are not clear. Therefore it can be said that the results of this work can be used in the qualitative analysis of the individual complex salts, except the mixed sample of hexammine and diammine complex salts.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.77-84
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• 2010

Reduction of oxides has been investigated for the volume reduction and recycling of the spent oxide fuel from commercial nuclear power plants. Various oxide reduction methods were proposed and KAERI (Korea Atomic Energy Research Institute) is currently developing an electrochemical reduction process using a LiCl-$Li_2O$ molten salt as a reaction medium. The electrochemical reduction process, the front end of the pyroprocessing, can connect the PWR (Pressurized Water Reactor) oxide fuel cycle to a metal fuel cycle of the sodium cooled fast reactor. This paper summarizes KAERI efforts on the development, improvement, and scale-up of the oxide reduction process.

• Journal of Ginseng Research
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• v.32 no.2
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• pp.114-119
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• 2008

Terpene synthase plays a key role in biosynthesis of triterpene saponins (ginsenosides) and is intermediate in the biosynthesis of a number of secondary metabolites. A terpene synthase (PgTPS) cDNA was isolated and characterized from the root of Panax ginseng c.A. Meyer. The deduced amino acid sequence of PgTPS showed a similarity with A. deliciosa (AAX16121) 61%, V. vinifera (AAS66357) 61%, L. hirsutum (AAG41891) 55%, M. truncatula (AAV36464) 52%. And the segment of a terpene synthase gene was amplified by reverse transcriptase-polymerase chain reaction (RTPCR). We studied expression of terpene synthase under stressful conditions like chilling, salt, UV, and heavy metal stress treatment. Expression of PgTPS was increased gradually after exposure to stresses such as chilling, salt, and UV illumination. But its transcription seems to be reduced by cadmium and copper treatment.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.102-111
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• 1998

This study was concerned with the development of a heavy duty rust-converting agent, the function of which is to form metal complex coatings, containing vinyl halide-acrylic terpolymer emulsion, defoamer, emulsifying agent, glass flakes, chelating agent such as gallotannic acid, gallic acid, and pyrogallic acid, and other additives. The resulted emulsion products(Sample No.1~No.5) were characterized through test either in the forms of emulsions, which include Viscosity, Penetration rate, Acidity and Film drying rate test, or in the forms of coated layer on rusty steel substrates by FT-IR, which include hardness, gloss, salt spray, adhesion and flame retardant test. The test results are as follows ; Penetration rate(0.1~0.4 mm/min), Solid content(70%), Acidity (pH 1.8~2.0), Specific gravity(1.30~1.35), Film drying rate(108min, RH 40% ; 150min, RH 80%), Gloss(83~92, incident angle $60^{\circ}$; 88~97, incident angle $85^{\circ}$), Pencil hardness(4H~5H), Adhesion (100/100), Salt spray test(>720Hr), LOI(%) value(38%), Vertical burning test(UL 94-v-l). According to the various performance of specimens show above, the evaluation of the availability of this heavy duty rust-converting agent can be concluded that all the samples(No.1~No.5) are capable of being used in the field of chemical plant and in the hazard areas of fire and explosion potential. It was observed that the properties of sample No.2, especially gloss and hardness, were much better than that of the other samples.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.369-377
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• 2014

This study was carried out to evaluate the effect of rice husk (RHB) and food waste biochar (FWB) on upland soil with sandy loam texture, in terms of physico-chemical analysis, lettuce seed germination test, and orgainc carbon leaching experiment. RHB and FWB had different physico-chemical properties each other. Carbon to nitrogen ratio (C/N ratio) of RHB was 32, showing two times higher than that of FWB. FWB had high salt and heavy metal content, compared to RHB. This is probably due to different ingredients and production processing between two biochars each other. Results of germination test with Lettuce showed lower germination rate when FWB was applied because of higher salt concentration compared to control and RHB. Organic carbon leaching test using saturated soil column (${\Phi}75{\times}h75mm$) with $10MT\;ha^{-1}$ biochar application rate, showed higher saturated hydraulic conductivity in rice husk biochar treatment column, compared to control and food waste biochar treatment. The highest total organic carbon concentration in column effluent was lower than those in both of rice husk biochar and food waste biochar, whereas the differences was negligible after 9 pore volumes of effluent. Consequently, biochars from byproducts such as rice husk and food waste in sandy loam textured upland soil could enhance a buffer function such as reduction of leaching from soil, but the harmful ingredient to crops such as high salt and heavy metals could limit the agricultural use of biochars.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.662-671
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• 2015

To enrich the genetic resource of microbial xylanases with high activity and stability under alkaline conditions, a xylanase gene (xynSL4) was cloned from Planococcus sp. SL4, an alkaline xylanase-producing strain isolated from the sediment of soda lake Dabusu. Deduced XynSL4 consists of a putative signal peptide of 29 residues and a catalytic domain (30-380 residues) of glycosyl hydrolase family 10, and shares the highest identity of 77% with a hypothetical protein from Planomicrobium glaciei CHR43. Phylogenetic analysis indicated that deduced XynSL4 is closely related with thermophilic and alkaline xylanases from Geobacillus and Bacillus species. The gene xynSL4 was expressed heterologously in Escherichia coli and the recombinant enzyme showed some superior properties. Purified recombinant XynSL4 (rXynSL4) was highly active and stable over the neutral and alkaline pH range from 6 to 11, with maximum activity at pH 7 and more than 60% activity at pH 11. It had an apparent temperature optimum of 70℃ and retained stable at this temperature in the presence of substrate. rXynSL4 was highly halotolerant, retaining more than 55% activity with 0.25-3.0 M NaCl and was stable at the concentration of NaCl up to 4M. The enzyme activity was significantly enhanced by β-mercaptoethanol and Ca²⁺ but strongly inhibited by heavy-metal ions and SDS. This thermophilic and alkaline- and salt-tolerant enzyme has great potential for basic research and industrial applications.

• Textile Coloration and Finishing
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• v.6 no.2
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• pp.10-16
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• 1994

Neutral salts have negative or positive effects on the rates of many chemical reactions and also on the rates of acidic and alkaline hydrolysis of carboxylic esters. The direction of neutral salt effects on the hydrolysis of ester depends on the charge of esters. Neutral salts accelerate alkaline hydrolysis of esters with negative charge, but decelerate alkaline hydrolysis of esters with positive charge, and have little effect on the alkaline hydrolysis of neutral esters. It is expected that the rate of the alkaline hydrolysis of Poly(ethylene terephthalte) (PET), polymeric solid carboxylic polyester with carboxyl end group at the polymer end, is also influenced positively by neutral salts. In the present work, to clarify the mechanism of the neutral salt effect on the alkaline hydrolysis of PET, many salts with different anions like NaF, NACl, NaBr, NaI were added to the aqueous alkaline solutions. Then PET was hydrolyzed with aqueous solutions of many salts in alkali metal hydroxides under various conditions. Some conclusions obtained from the experimental results were summarized as follows. The reaction rate of the alkaline hydrolysis of PET was increased by the addition of neutral salts and In k was increased nearly linearly with the square root of ionic strength of reaction medium. This fact suggested that the ionic strength effect by Debye-Huckel and Bronsted theory was exerted on the reaction. The specific salt effect was also observed. The reaction rate was increased with the decrease in the nucleophilicity of anions of neutral salts, i.e., in the order of $F^-$ <$Cl^-$<$Br^-$<$I^-$. It was thought that the reaction rate was increased in the order of $F^-$ <$Cl^-$<$Br^-$<$I^-$. because the completion of anions with $OH^-$ for carbonyl carbon became weaker with the decrease in the nucleophilicity and with the increase in the size of anions.