• Macromolecular Research
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• 제13권6호
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• pp.483-490
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• 2005

A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan ($_{k}C$), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for $_{k}C$­g-polymethacrylic acid ($_{k}C$-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were preliminarily investigated. Absorbency in aqueous salt solutions of lithium chloride, sodium chloride, potassium chloride, calcium chloride, and aluminum chloride indicated that the swelling capacity decreased with increased ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. The swelling of super absorbing hydrogels was measured in solutions with pH ranging from 1 to 13. In addition, the pH reversibility and on-off switching behavior, at pH levels of 3.0 and 8.0, give the synthesized hydrogels great potential as an excellent candidate for the controlled delivery of bioactive agents.

• Corrosion Science and Technology
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• 제10권6호
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• pp.199-204
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• 2011

Hot dip metallic coated steels like as galvanized (GI), zinc-aluminium (GL) and aluminium coated steels are mostly used where corrosion resistance is needed. There are two kinds (type 1 and type 2) of aluminium coated steel being commercially used among them. Type 1 aluminium coated steel is coated with an Al-5~11 wt%Si alloy and Type 2 aluminium coated steel consists of commercially pure aluminium. Type 1 Al coated steel is generally used in automotive components and electrical appliances while type 2 aluminium coated steel is mainly used in construction applications such as building cladding panels, air conditioning and ventilation system. In this study, Type 1 aluminium coated steels have tested by accelerated conditions (salt spray or corrosive gas) and outdoor exposure condition in order to understand their corrosion behaviour. Due to the distinct corrosion mechanism of Al which exposes to the severe chloric condition, Salt Spray Test cannot predict the ordinary atmospheric corrosion of Al based coated materials. In addition, the test results and their corrosion feature of Al coated steel sheets will be discussed comparing with other metallic coated steel sheets of GI and GL.

• 전기화학회지
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• 제5권4호
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• pp.178-182
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• 2002

The electrochemical behavior of binder-free carbon anode, comprising of only artificial and natural graphite (AG and NG) particles, for intercalation and deintercalation of lithium ion $(Li^+)$ in aluminum chloride (AICI_3)-I-ethyl­3-methylimidazolium chloride (EMIC)-lithium chloride (LiCl)-thionyl chloride $(SOCI_2)$ room-temperature molten salt (RTMS) was studied. Binder-free carbon electrodes were fabricated using electrophoretic deposition (EPD) method. The binder-free carbon anodes provided a relatively flat charge and discharge potentials $(0\;to\;0.2V\;vs.\;Li/Li^+)$ and current capabilities $(250-340mAh{\cdot}g^{-1})$ for the intercalation and deintercalation of $Li^+$. Stability of the binder-free carbon anodes for intercalation and deintercalation of 50 cycles was confirmed.

• 반도체디스플레이기술학회지
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• 제17권4호
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• pp.11-15
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• 2018

The parts of equipment for semiconductor are protected by anodic aluminum oxide film to prevent corrosion. This study investigated contamination particle and cracking behavior of anodic oxidation in sulfuric acid containing cerium salt. The insulating properties of the sample were evaluated by measuring the breakdown voltage. It was confirmed that the breakdown voltage was about 50% higher when the cerium salt was added, and that the breakdown voltage after the heat treatment was 55% and 35% higher at $300^{\circ}C$ and $400^{\circ}C$, respectively. After heating at $300^{\circ}C$ and $400^{\circ}C$, cracks were observed in non cerium and cerium 3mM, and more cracks occur at $400^{\circ}C$ than at $30^{\circ}C$. The amount of contamination particles generated in the plasma is about 45% less than that of non-cerium specimens.

• 한국세라믹학회지
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• 제41권8호
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• pp.610-617
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• 2004

평균입자크기가 20 ${\mu}$이고, 두께가 0.2∼0.3 ${\mu}m$인 ${\alpha}-Al_2O_3$ 판상체를 제조하기 위하여 전구물질로써 황산알루미늄과 황산나트륨을 사용하여 수산화알루미늄을 제조하였다. 이때 첨가되는 인산나트륨의 양이 ${\alpha}Al_2O_3$ 판상체의 입자크기, 형상, 그리고 두께에 어떠한 영향을 미치는지에 대하여 관찰하였다. 인산나트륨을 첨가하지 않았을 경우, 대부분의 ${\alpha}-Al_2O_3$ 판 상체가 육각판상모양을 띠고 있었으나 그 두께가 1.0 ${\mu}m$ 이상으로 진주안료 기질로는 적합하지 않았다. 반면, 인산나트륨이 첨가되었을 경우, ${\alpha}-Al_2O_3$ 판상체의 두께를 감소시켜 각형비를 증가시키는 현상을 초래하였다.

• 한국표면공학회지
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• 제33권5호
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• pp.381-386
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• 2000

It was found that colloidal silica sprayed to the galvanized steel sheet apparently made the molten zinc layer solidified to be the randomly oriented fine grains. Its spraying effect was also little affected by steel temperature that had been considered as one of the major operating factors in this process. From the results of surface analysis, it is considered that aluminum dissolved in coating layer reduces silica to silicon by the oxidation-reduction reaction, and that the reduced silicon acts as a more effective nucleus in solidification reaction than phosphate salt, siica and alumina.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3952-3965
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• 2021

In this study, volcanic ash was used as raw material to prepare waste forms with different silicon/aluminum (Si/Al) molar ratios to immobilize sodium-salt waste (SSW) containing simulated ¹³⁷Cs. Effects of Si/Al molar ratios (3:1 and 2:1) and sodium salts on sintering behavior of waste forms and immobilization mechanism of Cs⁺ were investigated. Results indicated that the main mineral phase of sintered waste-form matrixes was albite, and the formation of major phases was found to depend on Si/Al molar ratios. Si/Al molar ratio of 2 was favorable for the formation of pollucite, and the formation and crystallization of mineral phases were also decided based on physicochemical characteristics of sodium salts. Furthermore, product consistency test results indicated that the immobilization of Cs⁺ was related to Si/Al molar ratio, types of sodium salts, and glassy phase. Waste forms with Si/Al molar ratio of 2 exhibited better ability to immobilize Cs⁺, whereas the influence of sodium salts and glassy phases on the immobilization of SSW showed more complicated relationship. In waste forms with Si/Al molar ratio of 2, Cs⁺ leaching concentrations of samples containing Na₂B₄O₇·10H₂O and NaOH were low. Na₂B₄O₇·10H₂O easily transformed into liquid phase during sintering to consequently achieve low temperature liquid-phase sintering, which is beneficial to avoid the volatilization of Cs⁺ at high temperature. Results clearly reveal that waste forms with Si/Al molar ratio of 2 and containing Na₂B₄O₇·10H₂O show excellent immobilization of Cs⁺.

• Corrosion Science and Technology
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• 제22권2호
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• pp.99-107
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• 2023

Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.

• 자원리싸이클링
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• 제12권5호
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• pp.10-15
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• 2003

본 연구에서는 세륨연마재 폐슬러리 건조분말로부터 세륨을 포함한 희토류성분과 알루미늄을 분리하고자 하였다. 출발원료인 세륨연마재 폐슬러리 건조분말의 희토류 중에는 산화세륨이 전체 희토류 성분의 약 40% 정도 함유되어 있는데, 산화세륨은 희토류원소들 중에서 가장 안정된 형태로 이에 대한 분해가 용이하지 않다. 그러므로 황산화반응을 이용하여 산화세륨을 분해하므로써 희토류의 분리ㆍ회수율을 향상시키고자 하였으며, 침출용액으로부터 희토류와 알루미늄을 분리하기 위하여, 희토류 원소들은 황산매질에서 황산나트륨과 반응하여 황산나트륨희토류(ReㆍNa($SO_4$)$_2$)를 형성하면서 침전되는 특성을 이용하였으며 쉽게 희토류와 알루미늄을 분리할 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.229-232
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• 2005

인화점이 높은 합성 액체연료인 RJ-4의 제조공정 개선에 관한 연구를 수행하였다. 상용원료인 MCPD(Methylcyclopentadiene dimer)를 이용한 RJ-4 연료제조에서 헤테로폴리 텅스토인산 세슘염 촉매와 2단 열 조절반응기를 사용하여 1차, 2차 수소화 및 이성화반응이 1 단계 연속공정으로 가능함을 알 수 있었다. 또한 $AlCl_3$ 대신에 헤테로폴리산 세슘염을 이성화촉매로 사용시 exe-THDMCPD(Tetrahydrodimethylcyclopentadiene)을 얻는 속도가 더 빠르며, 생성물과의 분리가 용이하고, 폐산 발생이 없으므로 환경친화적인 공정임을 확인하였다.