• 한국태양에너지학회 논문집
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• 제21권3호
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• pp.1-8
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• 2001

고온의 태양열을 저장하기 위한 한 방편으로 화학반응을 이용한 태양에너지의 화학에너지로의 변환공정을 고려하였다. 태양에너지의 저장은 메탄의 수증기 개질반응으로 선정하였으며, 이 흡열반응에서 메탄의 전화율 특성을 살펴보았다. 반응기는 직경, 6.25 mm, 그리고 길이 30 cm 인 stainless steel을 코일형태로 제작하였다. 반응온도 범위내에서 메탄의 전화율은 반응온도에 따라서 선형적으로 증가하였으며 반응온도 $500^{\circ}C{\sim}900^{\circ}C$ 범위에서 메탄의 전화율은 약 $60%{\sim}90%$ 로 측정되었다. 이 실험을 통하여 태양열 저장을 위한 메탄의 수증기 개질반응의 타당성을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제20권12호
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• pp.1653-1663
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• 2010

The first gene (${\alpha}$-gal1) encoding an extracellular ${\alpha}$-Dgalactosidase from the thermophilic fungus Talaromyces emersonii was cloned and characterized. The ${\alpha}$-gal1 gene consisted of an open reading frame of 1,792 base pairs interrupted by six introns that encoded a mature protein of 452 amino acids, including a 24 amino acid secretory signal sequence. The translated protein had highest identity with other fungal ${\alpha}$-galactosidases belonging to glycosyl hydrolase family 27. The ${\alpha}$-gal1 gene was overexpressed as a secretory protein with an N-terminal histidine tag in the methylotrophic yeast Pichia pastoris. Recombinant ${\alpha}$-Gal1 was secreted into the culture medium as a monomeric glycoprotein with a maximal yield of 10.75 mg/l and purified to homogeneity using Hisbinding nickel-agarose affinity chromatography. The purified enzyme was maximally active at $70^{\circ}C$, pH 4.5, and lost no activity over 10 days at $50^{\circ}C$. ${\alpha}$-Gal1 followed Michaelis-Menten kinetics ($V_{max}\;of\;240.3{\mu}M/min/mg,\;K_m\;of\;0.294 mM$) and was inhibited competitively by galactose ($K_m{^{obs}}$ of 0.57 mM, $K_i$ of 2.77 mM). The recombinant T. emersonii ${\alpha}$-galactosidase displayed broad substrate preference, being active on both oligo- and polymeric substrates, yet had strict specificity for the ${\alpha}$-galactosidic linkage. Owing to its substrate preference and noteworthy stability, ${\alpha}$-Gal1 is of particular interest for possible biotechnological applications involving the processing of plant materials.

• 전기화학회지
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• 제6권3호
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• pp.178-182
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• 2003

용융탄산염형 연료전지의 특성을 결정짓는 탄산염 전해질에 있어, 기존의 Li-K와 Li-Na 탄산염과는 다른 Li-Na-K 삼원계 탄산염의 특성을 산소환원 및 산화니켈 용해거동을 통해 검토하였다. 대상 삼원계 전해질은 Li-Na-K=47.4-32.6-20, 60-20-20, 50-40-10, $40-40-20mo1\%$이었으며, $650^{\circ}C$, 1기압 조건에서 산소환원 거동은 전기화학적 방법을 통해, NiO용해거동은 화학적 방법을 통해 검토하였다 삼원계 조성에 따라 산소환원 전류치의 차이가 관찰되어, 산소용해도가 조성에 의존함을 나타내었다. 또한 $Li-Na-K = 50-40-10 mol\%$ 조성에서는 다른 형태의 산소환원 피크가 관찰되어 조성에 따라 산소환원 메카니즘의 차이가 존재할 수 있음을 시사하였다. 그러나 산화니켈 용해도는 조성에 크게 의존하지 않는 특성을 보여주었다.

• 한국세라믹학회지
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• 제38권12호
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• pp.1162-1166
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• 2001

석유화학 공정 중 Styrene(SM) 공정에서 발생되는 산화철 폐촉매는 산업 폐기물로서 전량 매립되고 있는데, 이를 출발 원료로 사용하여 NiZn-페라이트를 합성하였고 그 자기적 특성을 조사하였다. 산화철 폐축매 펠렛을 분쇄한 후 NiO 및 ZnO를 혼합하여 90$0^{\circ}C$에서 하소하고 123$0^{\circ}C$에서 5시간 소결하여 스핀넬형 페라이트 소결체를 얻었다. N $i_{x}$ Z $n_{1-x}$F $e_2$ $O_4$(x=0.36, 0.50, 0.66)조성에 대하여 초투자율을 측정하였고, S-parameter를 측정하여 반사 감쇄량을 계산하였다. 산화철 폐촉매를 이용하여 X-band 주파수 영역에서 높은 전자파 흡수능을 갖는 전파흡수체를 제조할 수 있음을 확인하였다.다.

• 한국결정성장학회지
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• 제16권6호
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• pp.256-259
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• 2006

Vapor phase epitaxy(VPE)법을 사용하여 amorphous $SiO_x$. nanowires를 성장시켰다. Ni thin film을 촉매로 사용하여 Si 기판위에 $800{\sim}1100^{\circ}C$ 범위의 온도에서 성장시켰으며, $SiO_x$ nanowires의 성장 메커니즘은 Vapor-liquid-solid(VLS)으로 확인되었다. $SiO_x$ nanowires의 shape와 morphology는 scanning electron microscope(SEM)으로 분석하였으며, cotton-like형태이고 길이는 $10{\mu}m$정도였다. 그리고 구조적 특징은 transmission electron microscope(TEM)으로 관찰하였고, $SiO_x$ nanowires의 성분 분석은 energy dispersed X-ray spectroscopy(EDS)로 하였다. EDX spectrum으로 nanowires가 Si와 O로 구성되어졌음을 확인하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.216-227
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• 2005

The head penetrations for control rod drive mechanism and instrumentation systems are installed at the reactor pressure vessel head of PWRs. Primary coolant water and the operating conditions of PWR plants can cause cracking of these nickel-based alloy through a process called primary water stress corrosion cracking (PWSCC). Inspection of the head penetrations to ensure the integrity of the head penetrations has been interested since reactor coolant leakages were found at U. S. reactors in 2000 and 2001. The complex geometry of the head penetrations and the very low echo amplitude from the fine, multiple flaws due to the nature of the see made it difficult to detect and size the flaws using conventional pulse-echo UT methods. Time-of-flight-diffraction technique, which utilizes the time difference between the flaw tips while pulse-echo does the flaw response amplitude from the flaw, has been selected for this inspection for it's best performance of the detection and sizing of the head penetration see flaws. This study defines the limits of the detectable and accurately sizable minimum flaw size which can be detected by the General TOFD and the Delta TOFD techniques for circumferentially and axially oriented flaws respectively. These results assures the reliability of the inspection techniques to detect and accurately size for various kind of flaws, and will also be utilized for the future development and qualifications of the TOFD techniques to enhance the detecting sensitivity and sizing accuracy of the flaws of the reactor head penetrations in nuclear power plants.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1995년도 제9회 학술발표회 논문개요집
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• pp.154-154
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• 1995

The Xu-Tec process is also called the double glow surface alloying technology and is a new method of surface metallurgy which can produce an alloy layers with sp ecial phisical and chemical properties on the surface of common and inexpensive mater ials. Many super alloys and alloy steels, sueh as nickel base alloys, high speed steels and staiinless steels, have been produced by Xu-Tee Process on the surfaces of carbon steels. The depth of the alloy lasyers may vary from several microns up to 300 micr ons with alloying elements in a concentration of few percentage to 100%. World wide patents for Xu-Tec process have been granted in the United states, Canada, United Ki ngdom, Australia and Japan. High performance saw blades have been successfully produced by the Xu-Tee process with much simper processing steps and less cost than bimetal high speed saw blades. A comparison of the cutting times and wear rates of the Xu-Tee blades with the conventional bimetal blades has been made. The Xu-Tee bIases demonstrates sim ilar or better performance than bimetal blades. A Xu-Tec Unit for the commercial pr oduction of Xu-Tec saw blades has been designed and manufactured. This Unit can t reat 10,000 haek saw blades at one time. Three Xu-Tec hack saw blades production I ines have been set up in China. China.

• KSBB Journal
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• 제18권4호
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• pp.306-311
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• 2003

융합단백질의 절단을 위해 EK를 고정화하여 액상 절단반응과 같은 80％의 절단수율을 얻을 수 있었다. 그리고 니켈 친화칼럼을 이용하여 간단한 정제공정을 구축하였다. 공유결합한 EK의 경우 니켈친화 결합한 EK보다 높은 재접힘 수율을 나타내었고 풀림과 재접힘을 이용하여 효소의 초기 활성을 회복함에 따라서 반복사용을 통한 경제적인 절단공정을 구축할 수 있게 되었다. 그러나 고정화 과정에서 효소의 활성이 감소하는 문제점과 고정화 수율을 높이기 위한 연구가 필요하다.

• 한국재료학회지
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• 제26권2호
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• pp.79-83
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• 2016

A commercial NiO (green nickel oxide, 86 wt% Ni) powder was reduced using a batch-type fluidized-bed reactor in a temperature range of 500 to $600^{\circ}C$ and in a residence time range of 5 to 90 min. The reduction rate increased with increases in temperature; however, agglomeration and sintering (sticking) of Ni particles noticeably took place at high temperatures above $600^{\circ}C$. An increasing tendency toward sticking was also observed at long residence times. In order to reduce the oxygen content in the powder to a level below 1% without any sticking problems, which can lead to defluidization, proper temperature and residence time for a stable fluidized-bed operation should be established. In this study, these values were found to be $550^{\circ}C$ and 60 min, respectively. Another important condition is the specific gas consumption rate, i.e. the volume amount ($Nm^3$) of hydrogen gas used to reduce 1 ton of Green NiO ore. The optimum gas consumption rate was found to be $5,000Nm^3/ton$-NiO for the complete reduction. The Avrami model was applied to this study; experimental data are most closely fitted with an exponent (m) of $0.6{\pm}0.01$ and with an overall rate constant (k) in the range of 0.35~0.45, depending on the temperature.

• Journal of Electrochemical Science and Technology
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• 제13권4호
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• pp.497-503
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• 2022

Spinel ferrites (Ni_xFe_3-xO₄; x = 0.25, 0.5, 0.75 and 1.0) have been prepared at 550℃ by egg white auto-combustion route using egg white at 550℃ and characterized by physicochemical (TGA, IR, XRD, and SEM) and electrochemical (CV and Tafel polarization) techniques. The presence of characteristic vibration peaks in FT-IR and reflection planes in XRD spectra confirmed the formation of spinel ferrites. The prepared oxides were transformed into oxide film on glassy carbon electrodes by coating oxide powder ink using the nafion solution and investigated their electrocatalytic performance for OER in an alkaline solution. The cyclic voltammograms of the oxide electrode did not show any redox peaks in oxygen overpotential regions. The iR-free Tafel polarization curves exhibited two Tafel slopes (b₁ = 59-90 mV decade^-1 and b₂ = 92-124 mV decade^-1) in lower and higher over potential regions, respectively. Ni-substitution in oxide matrix significantly improved the electrocatalytic activity for oxygen evolution reaction. Based on the current density for OER, the 0.75 mol Ni-substituted oxide electrode was found to be the most active electrode among the prepared oxides and showed the highest value of apparent current density (~9 mA cm^-2 at 0.85 V) and lowest Tafel slope (59 mV decade^-1). The OER on oxide electrodes occurred via the formation of chemisorbed intermediate on the active sites of the oxide electrode and follow the second-order mechanism.