• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.6
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• pp.529-537
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• 1993

Several methods were examined for purification of docosahexaenoic acid (DHA, 22:6n-3) from skipjack Euthynnus pelamis orbital tissue oil, a marine by-product, and a modified method for isolation of a high purity DHA was proposed. Skipjack orbital tissue contained $55.4\%$ of total lipid(TL), and DHA accounted for $23.7\%$ of the TL. Application of low-temperature crystallization and urea inclusion compound methods to the orbital fatty acid mixture resulted in increases of DHA concentrations to approximately $46\%\;and\;61\%$, respectively. These methods were suitable for large production of DHA with relative low purity because of the simple purification procedure. DHA of approximately $74\%$ in purity was obtained by silver nitrate aqueous solution method, but the method gave a very low recovery($<10\%$). Silver nitrate-impregnated silica column chromatography was suitable for purification of a high purity DHA(purity, $>98\%$ and recovery, $>90\%$) A modified method, silver nitrate-impregnated silica column chromatography combined with low-temperature crystallization(two step purication method) was proposed as the most effective method to obtain DHA with high purity($99.9\%$) from the skipjack orbital oil.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.4
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• pp.757-768
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• 1997

The purpose of this study was to identify the effect of religious habits and hair styles on korean catholic sister's impression. The subject consisted of 256 female high school students and 256 female undergraduated students The experimental materials developed for this study were 16 color photographs stimuli of drawing and 7-point semantic differential scale composed of 30 bipolar adjectives representing personal traits. The major findings drawn from this study were as follows: 1) Four factors emerged to account for the dimentional structure of the impression of the Korean catholic sister's in religious habits. Four factors involved purity, formality, potency, appearance. 2) The clothing types and hair styles had significant effect on purity, formality, potency, appearance. The clothing types had an effect on purity, formality and potency while the hair styles affected formality. 3) Perceiver's age influenced impressions formed by clothing and hair styles. Female high school students were affected by clothing and hair styles in formality, potency, appearance while female undergraduate students in purity, formality, potency. Therefore the religious habits and hair styles had significant effect on korean catholic women's impression of purity, formality, potency, appearance and impression formation was varied according to perceiver's age.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1309-1310
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• 2006

High-purity and super-hard nano-polycrystalline diamond has been successfully synthesized by direct conversion from high-purity graphite under static pressures above 15 GPa and temperatures above $2300^{\circ}C$. This paper describes research findings on the formation mechanism of nano-structure and on the contributing factor leading to high hardness.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.99-104
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• 2016

High purity Si-C (99.999%) powder prepared by mechanical alloying was added to a commercial SiC powder as a sintering additive. Reaction bonded silicon carbide balls and jars with high purity (99.98%) were used for the mechanical alloying. As a result, the purity of the sintered Si-C was higher than 99.99%. When sintered at $2200^{\circ}C$ under 50 MPa pressure for 1 h, SiC containing 10 wt% of high purity Si-C showed a relative density of 95.3%, similar to the relative density of commercial SiC (95%). However, the relative density of SiC decreased to 90.6% without the additive when the applied pressure decreased to 40 MPa. In contrast, the relative density was nearly unaffected by the decrease of the pressure when using the Si-C additive. Therefore, the addition of Si-C powder promoted the densification of SiC above $2000^{\circ}C$ under 40 MPa pressure.

• Transactions on Electrical and Electronic Materials
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• v.9 no.5
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• pp.209-212
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• 2008

We developed a simple and effective purification method to obtain high-purity single-walled carbon nanotubes (SWCNTs) with low surface damage. The purification process consists of oxidization at $430^{\circ}C$ for 1 h in a furnace system of air atmosphere and homogenization in dilute hydrochloric acid solution for extremely short time. The role of homogenizer was examined during purification process in terms of purity and quality of purified SWCNTs. High-purity and low surface damage of SWCNT products was obtained using homogenizer which was operated at 8500 rpm for 10 min in the environment of 7 % HCI solution. From XRD spectra, we observed that metal catalysts were thoroughly removed. Raman spectra showed that the intensity values of crystallization ($I_{G}/I_{D}$) of purified SWCNTs were very similar with that of pristine SWCNTs. Moreover, the structure damage of purified SWCNTs was hard to find from electron microscopy. Consequently, homogenizing, which is a quick and simple manner, can be promising method for obtaining final SWCNTs with clearly high purity and crystallinity.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.271-276
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• 2014

Silica nano-powder (SNP) is an inorganic material able to provide high-performance in various fields because of its multiple functions. Methods used to synthesize high purity SNP, include crushing silica minerals, vapor reaction of silica chloride, and a sol-gel process using TEOS and sodium silicate solution. The sol-gel process is the cheapest method for synthesis of SNP, and was used in this study. First, we investigated the shape and the size of the silica-powder particles in relation to the variation of HCl and sodium silicate concentrations. After drying, the shape of nano-silica powder differed in relation to variations in the HCl concentration. As the pH of the solution increased, so did the density of crosslinking. Initially, there was NaCl in the SNP. To increase its purity, we adopted a washing process that included centrifugation and filtration. After washing, the last of the NaCl was removed using DI water, leaving only amorphous silica powder. The purity of nano-silica powder synthesized using sodium silicate was over 99.6%.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.409-412
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• 2001

The high purity manganese oxides were made from the dust, generated in AOD process that produces a medium-low carbon ferromanganese and collected in the bag filter. Manganese oxide content in the dust was about 90%, and its phase was confirmed as Mn₃O₄. In the extraction of manganese, because of remaining amorphous MnO₂, the dust was reduced to MnO by roasting with charcoal. The pulp density of the reduced dust can control pH of the solution more than 4 and then Fe ion is precipitated to a ferric hydroxide. Because a ferric hydroxide co precipitates with Si ion etc, Fe, Si ion was removed f개m the solution. Heating made water to be volatized and nitrates was left in reactor Then nitrates were a liquid state and stirring was possible. Among the nitrates in reactor, only the manganese nitrate which have the lowest pyrolysis temperature pyrolyzed into β-MnO₂powder and NO₂(g) at the temperature less than 200℃. When the pyrolysis of manganese nitrate has been completed about 90%, injection of water stopped the pyrolysis. Nitrates of impurity dissolved and the spherical high purity β-MnO₂powders were obtained by filtering and washing. Mn₂O₃or Mn₃O₄ powder could be manufactured from β-MnO₂powder by controlling the heating temperature. Lastly, a manufactured manganese oxide particle has 99.97% purity.

• Analytical Science and Technology
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• v.35 no.5
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• pp.205-211
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• 2022

Deuterium (D) is an isotope with one more neutron number than hydrogen (H). Heavy elements rarely change their chemical properties with little effect even if the number of neutrons increases, but low-mass elements change their vibration energy, diffusion rate, and reaction rate because the effect cannot be ignored, which is called an isotope effect. Recently, in the semiconductor and display industries, there is a trend to replace hydrogen gas (H₂) with deuterium gas (D₂) in order to improve process stability and product quality by using the isotope effect. In addition, as the demand for D₂ in industries increases, domestic gas producers are making efforts to produce and supply D₂ on their own. In the case of high purity D₂, most of them are produced by electrolysis of heavy water (D₂O), and among D₂, hydrogen deuteride (HD) molecules are present as isotope impurities. Therefore, in order to maximize the isotope effect of hydrogen in the electronic industry, HD, which is an isotope impurity of D₂ used in the process, should be small amount. To this end, purity analysis of D₂ for industrial processing is essential. In this study, HD quantitative analysis of D₂ for high purity D₂ purity analysis was established and hydrogen isotope RM (Reference material) was developed. Since hydrogen isotopes are difficult to analyze with general gas analysis instrument, they were analyzed using a high-precision mass spectrometer (Gas/MS, Finnigan MAT271). High purity HD gas was injected into Gas/MS, sensitivity was determined by a signal according to pressure, and HD concentrations in two bottles of D₂ were quantified using the corresponding sensitivity. The amount fraction of HD in each D₂ was (4518 ± 275) μmol/mol, (2282 ± 144) μmol/mol. D₂, which quantifies HD amount using the developed quantitative analysis method, will be manufactured with hydrogen isotope RM and distributed for quality management and maintenance of electronic industries and gas producers in the future.

• Journal of Korea Foundry Society
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• v.11 no.3
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• pp.236-244
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• 1991

This paper describes a study of the nucleation and growth of graphite crystal of levitation melted high purity Fe-C-Si alloys with emphasis on hypereutectic composition. Spherulitic graphite was observed to form at high purity alloy and converted to compacted by changing the starting iron from ultra-pure zone refined iron to 99.95 pct electrolitic iron. Residual C-C clusters might be acting as an effective nucleation site for graphite, and sulphur was the element to prevent graphite from nucleating. The graphite morphology changed from compacted to spherulitic as the sulphur content decreased.

• Journal of the Korean Ceramic Society
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• v.44 no.2 s.297
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• pp.93-97
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• 2007

High purity Si powder was prepared in the system of $SiO_2-Mg$ combustion reaction. Various conditions of combustion reaction and leaching were investigated. As the particle size of Mg decreased and the compaction pressure increased the quantity of the unreacted power was decreased. In the acid leaching of MgO, increasing particle size, reaction temperature, rotating speed and reaction time made leaching effect low. Final Si powder produced by combustion and leaching reaction, has a high purity of 99.9% with irregular shape.