• 대한금속재료학회지
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• 제50권9호
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• pp.659-667
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• 2012

Alloy 617 is a Ni-base superalloy and a candidate material for the intermediate heat exchanger (IHX) of a very high temperature gas reactor (VHTR) which is one of the next generation nuclear reactors under development. The high operating temperature of VHTR enables various applications such as mass production of hydrogen with high energy efficiency. Alloy 617 has good creep resistance and phase stability at high temperatures in an air environment. However, it was reported that the mechanical properties decreased at a high temperature in an impure helium environment. In this study, high-temperature corrosion tests were carried out at $850^{\circ}C-950^{\circ}C$ in a helium environment containing the impurity gases $H_2$, CO, and $CH_4$, in order to examine the corrosion behavior of Alloy 617. Until 250 h, Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures. The activation energy for oxidation in helium environment was 154 kJ/mol. The SEM and EDS results elucidated a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbides. The thickness and depths of degraded layers also showed a parabolic relationship with time. A normal grain growth was observed in the Cr-rich surface oxide layer. When corrosion tests were conducted in a pure helium environment, the oxidation was suppressed drastically. It was elucidated that minor impurity gases in the helium would have detrimental effects on the high-temperature corrosion behavior of Alloy 617 for the VHTR application.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.421-428
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• 2012

The Sulfur-Iodine (SI) thermochemical hydrogen production process is one of the most promising thermochemical water splitting technologies. In the integrated operation of the SI process, the $O_2$ produced from a $H_2SO_4$ decomposition section could be supplied directly to the Bunsen reaction section without preliminary separation. A $HI_x$ ($I_2+HI+H_2O$) solution could be also provided as the reactants in a Bunsen reaction section, since the sole separation of $I_2$ in a $HI_x$ solution recycled from a HI decomposition section was very difficult. Therefore, the Bunsen reaction using $SO_2-O_2$ mixture gases in the presence of the $HI_x$ solution was carried out to identify the effect of $O_2$. The amount of $I_2$ unreacted under the feed of $SO_2-O_2$ mixture gases was little higher than that under the feed of $SO_2$ gas only, and the amount of HI produced was relatively decreased. The $O_2$ in $SO_2-O_2$ mixture gases also played a role to decrease the amount of a impurity in $HI_x$ phase by only striping effect, while that in $H_2SO_4$ phase was hardly affected.

• 유기물자원화
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• 제27권2호
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• pp.51-56
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• 2019

황화수소는 매립가스와 바이오가스 사용 전에 제거해야 하는 유해한 불순물이다. 본 연구에서는 공기 산화를 활용한 황화수소 저감 방법을 연구하였다. C시 매립장에서 발생하는 매립가스의 유량 조절이 가능한 실규모 황화수소 저감 장치를 운전하였다. 실험 결과, 세정액 내 용존 철 농도는 황화물 산화 효율에 유의한 영향을 미쳤다. 매립지 발생 침출수 내 철 성분은 매립가스 내 황화수소 제거를 위한 용도로 철킬레이트와 혼용할 수 있었다. 철 농도가 90 mM 이상인 경우 9 초 이내의 접촉 시간에서 83 % 이상의 $H_2S$가 제거되었다. 따라서 촉매 산화 흡착법은 매립가스 및 바이오가스 정제를 위한 용도로서 충분히 가치가 있는 것으로 판단되었다.

• Journal of Radiation Protection and Research
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• 제33권3호
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• pp.113-120
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• 2008

이 연구에서는 국내 개발중인 초고온가스로 (VHTR: Very High Temperature Reactor)를 대상으로, 발생되는 삼중수소 양, 계통간 이송, 제거, 분포 그리고 최종적으로 생산된 수소에 대한 삼중수소에 의한 오염 준위를 예측할 수 있는 해석 모델인 TRITGO 코드를 소개하였고, 수소를 생산하는 IS (Iodine Sulfide) 계통으로의 삼중수소 투과양을 모의할 수 있도록 코드를 개선하였다. 또한 GT-MHR 600MW 열출력을 가정, 최종 수소 생산물의 삼중수소에 의한 오염치를 예측하였다. 예상 오염치는 약 0.055 Bq/$H_2-g$으로 일본 규제치 56 Bq/$H_2-g$에 약 1/1000 수준으로 낮게 예측되었다. 모의 결과 삼중수소 방출을 억제하기 위해서는 피복관의 건전성 유지 및 헬륨 냉각재와 흑연으로 구성된 반사체내 불순물인 $^3He$ 및 Li을 가능한한 낮은 준위로 유지하는 것이 필요함을 보여 주었다. 또한 냉각재내 불순물을 직접 제거할 수 있는 정화계통의 성능이 중요한 설계인자로 판단되었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.215-219
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• 2001

Impurities removal from waste carbon black was carried out to produce high-grade carbon black. A lot of hydrophilic carbon black is produced as a byproduct of the hydrogen production process by flame decomposition of water. Due to its impurity content such as sulphur, iron, ash and etc., it can only be used as low-grade carbon or burnt out. High-grade hydrophilic carbon black is 3-5 times more expensive than oil-based carbon black because of its process difficulties and requires pollutant treatment. Hydrophilic carbon is normally used far conductive materials for batteries, pigment for plastics, electric wire covering, additives for rubber, etc.. In these applications, hydrophilic carbon must maintain its high purity. In this study magnetic separation, froth flotation and ultrasonic treatment were employed to remove impurities from the low-grade hydrophilic carbon black. As results, the ash, iron and sulphur content of product decreased to less than 0.01wt.%, 0.0lwt.% and 0.3wt.% respectively, and the surface area of product was about 930 $m^2$/g.

• Advances in nano research
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• 제2권2호
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• pp.77-88
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• 2014

Solvothermal treatment of late transition metal acetylacetonates in a novel medium composed either of pure acetophenone or acetophenone mixtures with amino alcohols offers a general approach to uniform hydrophilic metal nanoparticles with high crystallinity and low degree of aggregation. Both pure metal and mixed-metal particles can be accesses by this approach. The produced materials have been characterized by SEM-EDS, TEM, FTIR in the solid state and by Nanoparticle Tracking Analysis in solutions. The chemical mechanisms of the reactions producing nanoparticles has been followed by NMR. Carrying out the process in pure acetophenone produces palladium metal, copper metal with minor impurity of $Cu_2O$, and NiO. The synthesis starting from the mixtures of Pd and Ni acetylacetonates with up to 20 mol% of Pd, renders in minor yield the palladium-based metal alloy along with nickel oxide as the major phase. Even the synthesis starting from a mixed solution of $Cu(acac)_2$ and $Ni(acac)_2$ produces oxides as major products. The situation is improved when aminoalcohols such as 2-aminoethanol or 2-dimethylamino propanol are added to the synthesis medium. The particles in this case contain metallic elements and pairs of individual metals (not metal alloys) when produced from mixed precursor solutions in this case.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2959-2962
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• 2013

As the concentration of aqueous $CD_3OH$ solutions was decreased, the OD peaks in $^2H$ NMR spectra grew relative to the $CD_3$ peaks. Isotope impurity for OH groups of $CD_3OH$ and deuterium naturally present in water contributed to the OD peaks. Using these peak area data, the site-specific isotope populations of isotope enriched chemicals were measured. In addition, the method using both $^1H$ and $^2H$ NMR spectroscopy was demonstrated with neat $CD_3OH$ to measure the site-specific isotope populations. The results indicate that although it represents only ~0.015% of hydrogen isotopes, the deuterium naturally present in solvents cannot be ignored, especially when the concentration of deuterium-enriched solutes is varied. Proton/deuteron exchange between methyl and methyl/hydroxyl groups was confirmed to be negligible, while that among hydroxyl groups was detectable.

• Journal of Welding and Joining
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• 제12권2호
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• pp.87-96
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• 1994

Correlation between microstructural features and segregation of elements (Si, Mn, P and S) near the mid of thickness in the base metal and the synthetic HAZ was investigated. Furthermore, the relationship between the degree of center segregation and weld cold cracking susceptibility in the thickness direction was also conducted by evaluating the effect of P concentration on the critical applied stress. The results obtained are as follows: 1) Pearlite band, containing the MnS type inclusion and a locally transformed structure with a higher hardness, was observed in the center segregation region. 2) By the weld thermal cycle, center segregation region was transformed to the white band which had a higher hardness than that of base metal due to a greater hardenability of concentrated Mn, P etc.. 3) Weld cold cracking susceptibility in the thickness direction was mainly dependent on the concentration of impurity elements rather than on the number of the segregated particles near the mid of thickness. 4) During welding, the higher concentrated region was easily changed into white band. Therefore, it could be predicted that the initiation and propagation of a cold crack would be promoted by increasing the restraint stress and hydrogen content.

• 한국표면공학회지
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• 제53권4호
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• pp.169-181
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• 2020

The ferroelectricity in emerging fluorite-structure oxides such as HfO₂ and ZrO₂ has attracted increasing interest since 2011. Different from conventional ferroelectrics, the fluorite-structure ferroelectrics could be reliably scaled down below 10 nm thickness with established atomic layer deposition technique. However, defects such as carbon, hydrogen, and nitrogen atoms in fluorite-structure ferroelectrics are reported to strongly affect the nanoscale polymorphism and resulting ferroelectricity. The characteristic nanoscale polymorphism and resulting ferroelectricity in fluorite-structure oxides have been reported to be influenced by defect concentration. Moreover, the conduction of charge carriers through fluorite-structure ferroelectrics is affected by impurities. In this review, the origin and effects of various kinds of defects are reviewed based on existing literature.

• Archives of Metallurgy and Materials
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• 제66권3호
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• pp.729-733
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• 2021

Ferrotitanium can be produced as a method of recycling Ti scraps. The eutectic composition of ferrotitanium, Fe_29.5Ti_70.5, can be obtained as a nanocrystalline phase due to relatively low melting point. Fe_29.5Ti_70.5 in which FeTi and β-Ti form a lamellar structure have high strength but low strain. To improve this, impurities were removed through hydrogen plasma arc melting (HPAM) and annealed. HPAM can remove substitutional/interstitial solid solutions. As a result, from 6733 ppm to 4573 ppm of initial impurities were removed by HPAM process. In addition, the strain was improved by spheroidizing and coarsening the lamellar structure through annealing. The effect of impurities removed through HPAM on the Young's modulus, yield strength, and strain was observed.