• Advances in materials Research
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• v.13 no.3
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• pp.161-171
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• 2024

This study aimed to investigate the effect of physicochemical properties and mix ratios of iron ore (oxide feed): coke (reductant) on the carbothermic reductions of iron ore. Coke size was fixed at ≤63 ㎛ while iron ore size varied between 150-63 ㎛ and ≤63 ㎛ respectively. Mix ratios were changed from 100:0 (reference) to 80:20 and 60:40 while the temperature, heating rate and soaking duration in muffle furnace were fixed at 1100 ℃, 10 ℃/min and 1 hour. Particle size analyzer, XRF, CHNS and XRD analyses were used for determination of raw feed characteristics. The occurrence of phase transformations from various forms of iron oxides to iron during the carbothermal reductions were identified through XRD profiles and supported with weight loss (%). XRF analysis proved that iron ore is of high grade with 93.4% of Fe₂O₃ content. Other oxides present in minor amounts are 2% Al₂O₃ and 1.8% SiO₂ with negligible amounts of other compounds such as MnO, K₂O and CuO. Composite pellet with finer size iron particles (≤63 ㎛) and higher carbon content of 60:40 exhibited 45.13% weight lost compared to 32.30% and 3.88% respectively for 80:20 and 100:0 ratios. It is evident that reduction reactions can only occur with the presence of coke, the carbon supply. The small weight loss of 3.88% at 100:0 ratio occurs due to the removal of moisture and volatiles and oxidations of iron ore. Higher carbon supply at 60:40 leads into better heat and mass transfer and diffusivity during carbothermic reductions. Overall, finer particle size and higher carbon supply improves reactivity and gas-solid interactions resulting in increased reductions and phase transformations.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.121-122
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• 2003

Deposition to the sea surface is one of ozone's principal loss mechanisms (Galbally and Roy, 1980; Levy et al., 1985; Kramm, 1995). However, since complicated physical and chemical processes are involved, large uncertainties remain in evaluating this loss mechanism that need to be better characterized. In this study we attempted to explore possible causes that give rise to large variability of ozone deposition velocity in terms of wind speed and chemical reactivity in the aqueous-phase film. (omitted)

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2299-2303
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• 2010

A new approach to the use of potassium peroxodisulphate as an oxidizing reagent is proposed and applied to the case of oxidative aromatization of 1, 4-dihydropyridines with cetyltrimethylammonium peroxodisulfate, a phase transfer oxidant. We demonstrate how it is possible to increase the reactivity of potassium peroxodisulphate in the presence of phase transfer catalyst. Dealkylation in case of 4-n-alkyl/n-alkenyl was not obtained.

• Journal of the Korean Chemical Society
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• v.15 no.6
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• pp.359-366
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• 1971

The extended Huckel calculations on five organic accelerators of vulcanization have been carried out. Various MO quantities e.g., electron populations and AO coefficients, are used to explain accelerator reactivity of the compounds. Results of these analyses lead us to support free radical mechanism of acceleration in vulcanization.

• Journal of the Korean Chemical Society
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• v.37 no.11
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• pp.982-984
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• 1993

• Journal of the Korean Chemical Society
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• v.13 no.4
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• pp.387-393
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• 1969

Gamma-ray induced copolymerization of phenyl acetylene with styrene is compared with that of the Ziegler catalyzed. The reactivity of styrene is greater than that of phenyl acetylene in the gamma-ray induced polymerization but much less than that of phenyl acetylene in the Ziegler catalyzed. The resulting copolymer is identified by means of DTA and spectrophotometry. Further, the liquid scintillation counting of styrene-${\alpha}-C^{14}$clarified the relative composition of the copolymers.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1948-1950
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• 2004

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.641-644
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• 2003

• Elastomers and Composites
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• v.28 no.1
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• pp.13-21
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• 1993

Polyurethane resin was especially mixed with polybutadiene rubbers which had each other different molecular structures and functional groups. Liquid and cure properties were tested experimentally for mixtures. Viscosity of mixtures and drying time were influenced by solubility of thinner and reactivity of rubber. Adhesive strength represented maxium at rubber content $15{\times}22%$ (Wt. % ), and rapidly decreased over 25%. DBTDL(di-n-butyltindilaurate) showed the longest stroage stability.

• Bulletin of the Korean Chemical Society
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• v.7 no.2
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• pp.111-113
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• 1986

The axial alcohol in trans-3,3,5-trimethylcyclohexanol was oxidized more readily than the equatorial alcohol in cis-3,3,5-trimethylcyclohexanol by NBS in aqueous dioxane. On the contrary, the equatorial alcohol was preferentially oxidized to the axial one by 10% aqueous sodium hypochlorite in the presence of tetrabutylammonium hydrogen sulfate (TBHS). The specificity indicates the presence of two different mechanism. In acidic medium, the cleavage of C-H bond is rate determining step while the reactivity of the alcohol is important in the presence of TBHS. The mechanism in basic medium without TBHS will be discussed.