• Economic and Environmental Geology
• /
• v.26 no.3
• /
• pp.421-429
• /
• 1993

Dissolution reactions of chemical grade zinc sulfide and natural sphalerite were studied in ferric chloride solution as an oxidant. To enhance the leaching reaction, ultrasonic technique was employed in this investigation. For the reaction with pure zinc sulfide, chemical reaction was the rate limiting step in the range of low conversion irrespective of applying ultrasonic wave. And the diffusion through liquid film instead of diffusion through product layer of free sulfur was the rate determining step because ultrasonic vibration removes the product from reaction zone. In the case of sphalerite with the ultrasonic vibrator, it was found that inert mineral layer diffusion was the rate determining step, in which the elemental sulfurs formed were removed by the ultrasonic action. Experimental results showed that the ultrasonic technique proved to be the methods which can significants improve the leaching performance.

• Journal of the Korean Applied Science and Technology
• /
• v.11 no.1
• /
• pp.53-60
• /
• 1994

The Synthesis of azobenzene containing long chain fatty acid and poly vinyl alcohol by esterification reaction($C_{n}-Azo-PVA$) was optimized, starting from P-(P'-hydroxy phenyl azo)-benzoic acid and the product of reaction containing azobenzene chromophores was investigated by ultraviolet spectrophotometery in toluene solvent at room temperature. In addition, UV absorption spectra of Langmmuir Blodggett (LB) film deposited on quartz plate have been measured and the structure of these compounds were ascertained by means of Ultraviolet and FT-IR. Recrystallization of reaction product in the solvent results the experimental yield obtained about 22.27% P-(P'-octadecyloxy phenyl azo)-benzoic acid-poly vinyl alcohol. Long chain azobenzene derivative-poly vinyl alcohols are induced phtoisomerization by u, v, and visible light irradiation. The LB film of azobenzene containing long chain fatty acids($C_{18}-Azo-PVA$) are possible of being applied to functional molecular devices such as photomemory and light switching.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.624-628
• /
• 2003

Lanthanum oxyfluoride can be synthesized by mechanochemical (MC) reaction between lanthanum oxide ($La_2O_3$) and polytetrafluoroethylene (PTFE, ($({CF_2CF_2}_n)$) in air using a planetary mill. MC reaction between the two materials induced from intensive grinding operation. The MC reaction is almost finished by 240min, and the products ground for 240min or more are composed of LaOF, amorphous $La(CO_3)F$ and amorphous carbon (C). Heating this MC reaction products at $600^{\circ}C$ enables us to eliminate amorphous C and decompose $La(CO_3)F$ into LaOF, so that pure LaOF material can be obtained as the final product. The average particle size of the final product (purified LaOF) is around few ten nanometers.

• Journal of Power System Engineering
• /
• v.5 no.4
• /
• pp.74-81
• /
• 2001

The infiltration behavior of molten Al-alloy, microstructures, hardness, and the interfacial reactions of $SiC_p/Al$ composites fabricated by the pressureless infiltration technique were investigated. It was made clear that both the weight fraction of SiC reinforcement and additive Mg content considerably influenced on the infiltration behavior of the molten Al-alloy matrix. Complete infiltration of molten Al-alloy achieved under the conditions that weight fraction of SiC content is more than 30wt%, and additive Mg content is more than 9wt%. Interfacial region of Al-alloy matrix and SiC reinforcement phase, $Mg_2Si$ was formed by the reaction between Mg and SiC. Another reaction product AlN was also formed by the reaction between Al-alloy matrix and gas atmosphere nitrogen.

• Journal of Microbiology
• /
• v.35 no.1
• /
• pp.15-20
• /
• 1997

Kinetic studies were done to elucidate the reaction mechanism of purine nucleoside phosphorylase (PNP) in Micrococcus Luteus. PNP catalyzes the reversible phosphorolysis of ribonucleosides to their respective base. The effect of alternative competing substrates suggested that a single enzyme was involved in binding to the active site for all purine nucleosides, inosine, deoxyiosine, guanosine, deoxyguanosine, adenosine and deoxyadenosine. Affinity studies showed that pentose moiety reduced the binding capacity and methylation of ring N-1 of inosine and guanosine had little effect on binding to bacterial enzyme, whereas these compounds did not bind to the mammalian enzymes. The initial velocity and product inhibition studies demonstrated that the predominant mechanism of reaction was an ordered bi, bi reaction. The nucleoside bound to the enzyme first, followed by phosphate. Ribose 1-phosphate was the first product to leave, followed by base.

• Journal of the Korean Ceramic Society
• /
• v.27 no.8
• /
• pp.965-970
• /
• 1990

A nitrogenation of coal ash in the presence of carbon was carried out to examine the effects of reaction temperature, reaction time and carbon composition on the formation of AlN, SiC and Si3N4. Decreasing the particle size increased the formation of AlN and its maximum composition in the product was obtaiend under 1450~150$0^{\circ}C$, 2 hours of reaction time and about 30% of carbon addition(on the basis of sample weight). Compositions of SiC and Si3N4 were distributed to the opposite so that SiC showed a higher composition compared with Si3N4 at a lower temperature, a shorter reaction time and a greater carbon addition.

• Bulletin of the Korean Chemical Society
• /
• v.14 no.2
• /
• pp.287-291
• /
• 1993

Catalytic iminohydroacylation has been achieved by the reaction of aldimine 1 and 1,5-hexadiene (2a) with Wilkinson's complex as catalyst. Compounds 7a, 8a and 9a were obtained as final product after hydrolysis of the resulting iminohydroacylation products 4a, 5a and 6a. Depending on the reactant ratio (2/1), the ratio of products were changed dramatically : As the 2/1 ratio was increased, 7a is the major product after hydrolysis while 8a is the major with an 1/1 ratio of 2/1. The mechanism of the formation of 5a is determined by the reaction of 1 and 2b under the identical reaction conditions. Considering that 5a may not be formed from the hydroiminoacylation of 14a since 5b cannot be formed from that of conjugate diene 14b generated from isomerization of 2b, 5a must be formed from the reaction of 4a and 10 by addition-elimination mechanism.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.2
• /
• pp.153-158
• /
• 1996

The synthesis of common skeleton of podosporin A and aureol was studied through cationic olefin cyclization as a key step. The generation of thermodynamic silyl enol ether or enol acetate under known conditions gave regioselectivity of 88:12. The enolate alkylation of 2,3-dimethylcyclohexanone with 2,5-dimethoxybenzyl bromide at the more substituted site via lithium enolate gave poor yield. In this case an organozincate or an ammonium enolate also proved to be ineffective or not practical in terms of yield. Side chain elongation of the substituted cyclohexanone 13 through Grignard reaction, Wittig reaction, or Shappiro reaction did not proceed because of steric hindrance and side reactions. However, Stille coupling reaction via enol triflate produced the desired product 18 in high yield. The advanced intermediate 22, which was efficiently synthesized from 18, produced 24 instead of the desired product under a cationic olefin cyclization condition, indicating that the cyclization occurred in a stepwise mannervia the organomercury intermediate 23.

• Journal of Surface Science and Engineering
• /
• v.13 no.1
• /
• pp.3-7
• /
• 1980

The crystalline structure and leveling action on the deposit of zinc from the cyanide zinc electroplating bath containing organic additives, such as aldehydes, polymers, amines and condensed product, have been studied by microscope and X-ray diffraction methods. The crystalline structure of the deposit from the bath containing no-additive, polymers and aldehydes appeared very strong orientation on (101) plane and the surface was rough, while from condensed product having remarkable effects in brightness appeared very strong orientation on (110) and the crystallinity was very fine. In the leveling action, the effect of any additives except reaction product was not appreciable, whereas the effect of the reaction product obtained remarkably excellent result.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.178-179
• /
• 2019

The purpose of this study was to investigate the possibility as mineral admixture of agriculture by-product. XRD and XRF analysis were performed on rice straw ashes at various combustion temperatures to identify chemical compositions. Also to evaluate properties of pozzolanic reaction, pH change method was tested.