• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.349-352
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• 2014

Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i.e., meshed pore, was produced.

• 한국세라믹학회지
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• 제46권5호
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• pp.528-533
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• 2009

High purity $\beta$-SiC powders were synthesized using sol-gel processing. TEOS and phenol resin were used as the starting material for the silicon source and carbon source, respectively. The process turned out to be capable of producing high purity SiC powder purity degree with 99.98 %. However, it was difficult to control the shape and size of $\beta$-SiC powders synthesized by sol-gel process. In this study, $\beta$-SiC powder with size of $1{\sim}5$ um an 30 nm were used as the seeds for $\beta$-SiC to control the $\beta$-SiC powder morphology. It was found that $\beta$-SiC powder seeds was effective to increase the powder average size of synthesized $\beta$-SiC using sol-gel process by acting as the preferred growing sites for $\beta$-SiC.

• 열처리공학회지
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• 제25권1호
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• pp.22-26
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• 2012

An influence of the addition of copper (0.5, 1.0 and 1.5 mass% Cu) on the microstructure and mechanical properties of high purity iron (99.998 mass%) was characterized. The microstructure and microhardness of high-purity iron based samples, which were rolled at room temperature and subsequently annealed, were investigated in this work. The microstructure of the samples has been observed by electron back scattering diffraction (EBSD) and the mechanical properties have been studied by using micro-Vickers hardness test. The results of microstructural observation showed that deformation band was formed in high purity iron by rolling at room temperature, and it was recovered by annealing up to about 900 K. The microhardness results showed that the softening of high-purity iron occurred by annealing up to about 900 K, while the hardness of iron added with about 0.5-1.5 mass% copper was kept over 100 Hv and at the early time of annealing reached a maximum. The hardness of iron added with a small amount of copper may be attributed to precipitation hardening as well as solution hardening. The orientation of crystal in recrystallized grain was almost same as that of deformed grain.

• 한국기계가공학회지
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• 제13권4호
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• pp.13-20
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• 2014

In this paper, the effects of a nonionic surfactant on the etch uniformity and the etch profile during the wet-etching process of high-purity aluminum were investigated for the fabrication of uniform micropattern arrays. To improve the surface roughness of a high-purity aluminum plate, a mechanical lapping process and an electrolytic polishing process were used. After electrolytic polishing process, the surface roughness, Ra, of the high-purity aluminum plate was improved from $1.25{\mu}m$ to $0.02{\mu}m$. A photoresist was used as an etching mask during the aluminum etching process, where the mixture of phosphoric acid, acetic acid, nitric acid, a nonionic surfactant and water was used as the aluminum etchant. Different amounts of the Triton X-100 nonionic surfactant were added to the aluminum etchant to investigate the effect of a nonionic surfactant during the wet-etching process of high-purity aluminum. The etch rate and the etch profile were measured by an optical interferometer and a scanning electron microscope.

• Journal of Ceramic Processing Research
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• 제20권4호
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• pp.388-394
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• 2019

In this study, high-purity single-walled carbon nanotubes (SWCNTs) were prepared by removing the unreacted metal constituents and amorphous carbon impurities using a post-annealing process. Unlike conventional thermal processing techniques, this technique involved different gas atmospheres for efficient removal of impurities. A heat treatment was conducted in the presence of chlorine, oxygen, and chlorine + oxygen gases. The nanotubes demonstrated the best characteristics, when the heat treatment was conducted in the presence of a mixture of chlorine and oxygen gases. The scanning electron microscopy, transmission electron microscopy, ultraviolet absorbance, and sheet resistance measurements showed that the heat treatment process efficiently removed the unreacted metal and amorphous carbon impurities from the as-synthesized SWCNTs. The high-purity SWCNTs exhibited improved electrical conductivities. Such high-purity SWCNTs can be used in various carbon composites for improving the sensitivity of gas sensors.

• 설비공학논문집
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• 제23권4호
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• pp.281-286
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• 2011

The objective of this study is to optimize the four-bed six-step pressure swing adsorption(PSA) process for high purity $CH_4$ recovery from the biogas. The effects of P/F(purge to feed) ratio and cycle time on the process performance were evaluated. The cyclic steady-states of PSA process were reached after 12 cycles. The purity and recovery rate of product gas, pressure and temperature changes were constant as the cycle repeated. It was shown that the P/F ratio gave significant effect on the product recovery rate by increasing the amount of purge gas in purge and regeneration step. The optimal P/F ratio was found to be 0.08. As the cycle time increased, the product purity decreased by increasing the feed gas flow rate. It was found that the optimal operating conditions were P/F ratio of 0.08 and total cycle time of 1,440 seconds with the purity of 97%.

• 한국식품영양과학회지
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• 제45권11호
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• pp.1564-1570
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• 2016

본 연구에서는 고순도 ${\beta}$-1.3/1.6-glucan이 선천면역계에 중요한 역할을 하는 대식세포와 자연살해세포의 활성화와 적응면역계에서 중요한 역할을 하는 T 세포 면역계에 대한 면역조절 효과를 살펴보고자 대식세포의 활성능, 자연살해 세포의 활성능, 그리고 T 세포 면역계에 조절작용을 하는 사이토카인, CD4+/CD8+ T 세포에 미치는 영향을 관찰하였다. 마우스 복강에서 불리한 대식세포를 이용하여 세포독성을 확인한 결과 고순도 ${\beta}$-1.3/1.6-glucan $10{\sim}200{\mu}g/mL$의 농도에서 독성이 나타나지 않았다. 또한, 고순도 ${\beta}$-1.3/1.6-glucan은 대식세포의 활성능, 자연살해세포의 활성능에 도움을 주어 활성능을 증가시켜 외부로부터 침입한 미생물, 감염된 세포나 종양세포 등을 효과적으로 제거할 수 있을 것이라 예상할 수 있었다. 마지막으로 T 세포 면역계에 조절작용을 하는 사이토카인과 CD4+/CD8+를 확인한 결과 고순도 ${\beta}$-1.3/1.6-glucan이 사이토카인들의 분비량 및 CD4+/CD8+를 증가시켜 T 세포 면역계에 조절뿐아니라 B 세포 면역계의 조절에 도움을 줄 것이라 예상할 수 있었다. 결론적으로 고순도 ${\beta}$-1.3/1.6-glucan은 선천면역뿐 아니라 적응면역에서 영향을 미칠 것이라 생각하며 면역조절에 긍정적인 변화를 보였으므로 추후 면역 조절제로서 기능성 식품의 상업화에 기초 자료가 되어 국내 기능성 소재로서의 개발 가능성을 기대할 수 있다.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.557-566
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• 2011

A cold spray coating (CSC) of copper was studied for its application to a high-level radioactive waste (HLW) disposal canister. Several copper coatings of 10 mm thick were fabricated using two kinds of copper powders with different oxygen contents, and SS 304 and nodular cast iron were used as their base metal substrates. The fabricated CSC coppers showed a high tensile strength but were brittle in comparison with conventional non-coating copper, hereinafter defined to as "commercial copper". The corrosion behavior of CSC coppers was evaluated by comparison with commercial coppers, such as extruded and forged coppers. The polarization test results showed that the corrosion potential of the CSC coppers was closely related to its purity; low-purity (i.e., high oxygen content) copper exhibited a lower corrosion potential, and high-purity copper exhibited a relatively high corrosion potential. The corrosion rate converted from the measured corrosion current was not, however, dependent on its purity: CSC copper showed a little higher rate than that of commercial copper. Immersion tests in aqueous HCl solution showed that CSC coppers were more susceptible to corrosion, i.e., they had a higher corrosion rate. However, the difference was not significant between commercial copper and high-purity CSC copper. The decrease of corrosion was observed in a humid air test presumably due to the formation of a protective passive film. In conclusion, the results of this study indicate that CSC application of copper could be a useful option for fabricating a copper HLW disposal canister.

• E2M - 전기 전자와 첨단 소재
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• 제11권11호
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• pp.46-52
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• 1998

Barium titanate owes its great importance to the fact that its dielectric constant is about 100 times higher than that of conventional dielectric materials provided its compositional and structural purity is extremely high. The value of crystalline BaTiO3 bodies as used, for instance, in computer elements, magnetic amplifiers, memory device, ets., depend on boththe compositional and the structural purity of the BaTiO3 crystals. This purity will, in turn, depend on the purity of the raw materials used in manufacturing the BaTiO3 compound and on the particularmethods of manufacture which determine the size, homogeneity, and the structural purity of the crystals. This paper reviews the important theoretical considerations, processing techniques and applications related to sol-gel derived thin films.

• 한국항공운항학회지
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• 제14권3호
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• pp.51-59
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• 2006

The air purity-sterilizer was developed and the CFD and experimental studies were carried out in order to investigate the performance of a air purity-sterilizer. Overhaul and exchange efficiency were increased by the modularization of the air purity-sterilizer. The good performance was validated by the hot-wire measurements and flow simulations in the room. Mean velocities at the exit of the air purity-sterilizer were 0.91, 1.62, 1.99, and 6.14 m/sec according to the fan mode. And the flow visualization of pured air was shown by using CFD flow simulation in the room of 24, 50 pyeong. The results show that the air purity-sterilizer has a high performance enough to produce air purity-sterilizer on a commercial scale.