• 분석과학
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• 제35권6호
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• pp.249-255
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• 2022

본 연구에서는 기체 크로마토그래피-불꽃이온화검출기(GC-FID)를 이용한 고순도 질소의 새로운 순도분석법을 개발하였다. 고순도 질소에 존재할 수 있는 불순물인 일산화탄소(CO), 이산화탄소(CO₂), 및 메탄(CH₄)에 대한 3 µmol/mol 수준의 인증표준물질(Certified reference material, CRM)을 중량법을 이용하여 제조하였고, 이를 순도분석에 활용하였다. 개발된 순도분석법에서는 운반가스로 초고순도 질소와 순도분석 대상 질소를 사용하여, 제조된 인증표준물질의 기체 크로마토그래피에서 얻어지는 크로마토그램의 면적 값 차이를 비교함으로써 순도분석 대상 질소의 불순물을 정량 분석하였다. 순도분석 대상 질소로는 액체질소 및 제조사가 각기 다른 3곳의 고순도 질소를 사용하였다. 또한, 개발된 순도분석법의 유효성을 평가하기 위하여 순도분석 대상 질소 내 불순물의 물질량 분율을 기존 순도분석법과 비교하였다. 두 가지 순도분석법을 이용하였을 때 대상 질소 내 불순물의 물질량 분율이 불확도 (k = 2) 내에서 서로 일치함을 확인함으로써, 개발된 순도분석법이 유효함을 확인하였다.

• 한국재료학회지
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• 제15권4호
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• pp.217-223
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• 2005

Thermal, electrical and mechanical properties of high purity niobium and tantalum refractory rare metals were investigated tn evaluate the physical purity. Higher purity niobium and tantalum metals showed lower hardness due to smaller solution hardening effect. Temperature dependence of electrical resistivity showed a typical metallic behavior. Remarkable decrease in electrical resistivity was observed for a high purity specimen at low temperature. However, thermal conductivity increased for a high purity specimen, and abrupt increase in thermal conductivity was observed at very low temperature, indicating typical temperature dependence of thermal conductivity for high purity metals. It can be known that reduction of electron-phonon scattering leads to increase in thermal conductivity of high purity niobium and tantalum metals at low temperature.

• Elastomers and Composites
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• 제32권5호
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• pp.318-324
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• 1997

Since the rigid and continuous networks of high-purity silica(white carbon) were relatively transparent to microwaves, high purity silica coupled with microwaves using a zirconia susceptor at room temperature and it was then heated to its melting temperature. The low-purity silica, contained small amount of impurities, yielded greater microwave absorption owing to easy motion of the interstitial alkali ions and it was then heated to its melting temperature. X-ray diffraction patterns of the low-purity silica were broader than those of the high-purity silica due to higher concentration of non-bridging bond and more deformed random network structure. In the vulcanization process of whitened or coloured rubber compound which is employing low-purity silica(white carbon) as a reinforcing filler, vulcanizate could be obtained effectively by microwave heating energy.

• 한국결정성장학회지
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• 제27권1호
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• pp.57-63
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• 2017

High-purity ${\beta}-SiC$ powders for SiC single-crystal growth were synthesized by direct carbonization. The use of high-purity raw materials to improve the quality of a SiC single crystal is important. To grow SiC single crystals by the PVT method, both the particle size and the packing density of the SiC powder are crucial factors that determine the sublimation rate. In this study, we tried to produce high-purity ${\beta}-SiC$ powder with large particle sizes and containing low silicon by introducing a milling step during the direct carbonization process. Controlled heating improved the purity of the ${\beta}-SiC$ powders to more than 99 % and increased the particle size to as much as ${\sim}100{\mu}m$. The ${\beta}-SiC$ powders were characterized by SEM, XRD, PSA, and chemical analysis to assess their purity. Then, we conducted single-crystal growth experiments, and the grown 4H-SiC crystals showed high structural perfection with a FWHM of about 25-48 arcsec.

• Journal of Microbiology
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• 제38권2호
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• pp.99-104
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• 2000

Hydrogen peroxide has been used in cleaning the piping of an advanced high-purity water system that supplies ultra-high purity water (UHPW) for 16 megabyte DRAM semiconductor manufacturing. The level of hydrogen peroxide-resistant bacteria in UHPW water was monitored prior to and after disinfecting the piping with hydrogen peroxide. Most of the bacteria isolated after hydrogen peroxide disinfection were highly resistant to hydrogen peroxide. However, the percentage of resistant bacteria decreased with time. The hydrogen peroxide-resistant bacteria were identified as Micrococcus luteus, Bacillus cereus, Alcaligenes latus, Xanthomonas sp. and Flavobacterium indologenes. The susceptibility of the bacteria to hydrogen peroxide was tested as either planktonic cells or attached cells on glass. Attached bacteria as the biofilm on glass exhibited increased hydrogen peroxide resistnace, with the resistance increasing with respect to the age of the biofilm regrowth on piping after hydrogen peroxide treatment. In order to optimize the cleaning strategy for piping of the high-purity water system, the disinfecting effect of hydrogen preoxide and peracetic acid on the bacteria was evaluated. The combined use of hydrogen peroxide and peracetic acid was very effective in killing attached bacteria as well as planktonic bacteria.

• 대한금속재료학회지
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• 제47권6호
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• pp.331-337
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• 2009

To lower the annealing temperature and the deviation of the mechanical properties of bake hardening steels, high purity steels were investigated. The steels were characterized by treating at low recrystallization temperature. It was confirmed that the strengthening originated from the solid solution of carbon and the ferrite grain refinement by fine MnS precipitates as carbon and sulfur contents increased in high purity steels. However, it was observed that there was no more increase of strength in steels containing over 40 ppm of carbon. It was considered that the excess carbon formed either the carbon cluster or the low temperature unstable carbides which had the negligible effect on the strengthening because they were reported to be highly coherent with the matrix. The carbon cluster and unstable carbides could be transformed to the stable cementite during bake hardening treatment. MnS was not observed in the high purity steel containing 5 ppm S, resulting in very coarse recrystallized grains and good ductility. As sulfur content increased, the recrystallized grain size decreased due to the formation of the fine MnS precipitates.

• 한국세라믹학회지
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• 제55권6호
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• pp.608-617
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• 2018

The effects of the purity and monoclinic phase of feedstock powder on the thermal durability of thermal barrier coatings (TBC) were investigated through cyclic thermal exposure. Bond and top coats were deposited by high velocity oxygen fuel method using Ni-Co based feedstock powder and air plasma spray method using three kinds of yttria-stabilized zirconia with different purity and monoclinic phase content, respectively. Furnace cyclic thermal fatigue test was performed to investigate the thermal fatigue behavior and thermal durability of TBCs. TBCs with high purity powder showed better sintering resistance and less thickness in the thermally grown oxide layer. The thermal durability was found to strongly depend on the content of monoclinic phase and the porosity in the top coat; the best thermal fatigue behavior and thermal durability were in the TBC prepared with high purity powder without monoclinic phase.

• Journal of Microbiology and Biotechnology
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• 제10권4호
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• pp.554-558
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• 2000

Bacteria were isolated and identified from an advanced high-purity water system that supplies ultra-high purity water (UHPW) for 16-megabyte DRAM semiconductor manufacturing. Scanning electron microscopic and microbiological observations revealed that the primary source of the bacteria isolated from the UHPW was detached cells from biofilms developed on the pipe wall through which the UHPW, a man-made and extremely nutrient poor environment, was passing. About 63-65% of the bacteria isolated from the UHPW and the pipe wall were Gram-positive, whereas only 10% of the bacteria isolated from the feed water were Gram-positive. The of Gram-positive bacteria and seven genera of Gram-negative bacteria. Strains of the UHPW bacteria effectively adhered to and formed a biofilm on the surface of polyvinyl chloride (PVC) pipe.

• 한국결정성장학회지
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• 제23권6호
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• pp.309-313
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• 2013

실리콘카바이드(SiC)는 높은융점과 내마모성 및 열전도 특성으로 산업적으로 널리 활용되고 있다. 특히 고순도 SiC는 고효율 전력 변환용 SiC 반도체 및 LED 공정에 적용되는 미래소재로 각광받고 있다. 본 연구에서는 고순도 SiC를 합성하기 위한 원료인 고순도 카본(C)을 유도 열플라즈마(RF Inductively thermal plasma)를 이용하여 합성하였으며, 출발원료로서 탄화수소계 액상물질인 도데칸이 사용되었다. 유도 열플라즈마 합성된 고순도 카본은 반응관과 필터에서 포집되며, 필터에서 포집된 카본 분말은 반응관에서 포집된 카본 분말보다 작은 입도(10~20 nm)와 낮은 결정성을 갖는 것으로 확인하였다. 반응관과 필터부에서 포집된 카본 분말의 순도는 각각 99.9997 %(5N7)와 99.9993 %(5N3)로 측정되었으며, 카본 분말에서 검출되는 불순물은 열플라즈마 합성장비에서 기인한 것으로 확인되었다.

• Journal of Microbiology and Biotechnology
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• 제20권11호
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• pp.1534-1538
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• 2010

Fed-batch cultures of Hansenula polymorpha were studied to develop an efficient biosystem to produce recombinant human serum albumin (HSA). To comply with this purpose, we used a high-purity oxygen-supplying strategy to increase the viable cell density in a bioreactor and enhance the production of target protein. A mutant strain, H. polymorpha GOT7, was utilized in this study as a host strain in both 5-l and 30-l scale fermentors. To supply high-purity oxygen into a bioreactor, nearly 100% high-purity oxygen from a commercial bomb or higher than 93% oxygen available in situ from a pressure swing adsorption (PSA) oxygen generator was employed. Under the optimal fermentation of H. polymorpha with highpurity oxygen, the final cell densities and produced HSA concentrations were 24.6 g/l and 5.1 g/l in the 5-l fermentor, and 24.8 g/l and 4.5 g/l in the 30-l fermentor, respectively. These were about 2-10 times higher than those obtained in air-based fed-batch fermentations. The discrepancies between the 5-l and 30-l fermentors with air supply were presumably due to the higher contribution of surface aeration over submerged aeration in the 5-l fermentor. This study, therefore, proved the positive effect of high-purity oxygen in enhancing viable cell density as well as target recombinant protein production in microbial fermentations.