• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.198-198
• /
• 2013

Metal-Oxide-Semiconductor (MOS)에서 사용되는 다양한 channel materials로 high electron mobility을 가지는 III-V compound semiconductor가 대두되고 있다 [1,2]. 하지만 이러한 III-V compound semiconductor는 Si에 비해 안정적인 native oxide가 부족하기 때문에 Si, Ge, Al2O3과 BeO 등과 같은 다양한 물질들의 interface passivation layers (IPLs)에 대한 연구가 많이 되고 있다. 이러한 IPLs 물질은 0.5~1.0 nm의 매우 얇은 physical thickness를 가지고 있고 또한 chemical inert하기 때문에 플라즈마 식각에 대한 연구가 되고 있지만 IPLs 식각 후 기판인 III-V compound semiconductor에 physical damage과 substrate recess를 줄이기 위해서 높은 선택비가 필요하다. 이러한 식각의 대안으로 원자층 식각이 연구되고 있으며 이러한 원자층 식각은 반응성 있는 BCl3의 adsorption과 low energy의 Ar bombardment로 desorption으로 self-limited한 one monolayer 식각을 가능하게 한다. 그러므로 본 연구에서는, III-V compound semiconductor 위에 IPLs의 adsorption과 desorption의 cyclic process를 이용한 원자층식각으로 다양한 물질인 SiO2, Al2O3 (self-limited one monolayer etch rate=about 1 ${\AA}$/cycle), BeO (self-limited one monolayer etch rate=about 0.75 ${\AA}$/cycle)를 얻었으며 그 결과 precise한 etch depth control로 minimal substrate recess 식각을 할 수 있었다.

• 한국미생물·생명공학회지
• /
• 제41권4호
• /
• pp.456-461
• /
• 2013

단일가닥 DNA와 이중가닥 DNA의 흡착 율의 차이를 이용하여, 본 연구는 산화 그래핀에 흡착된 단일 가닥 DNA을 사용하여 Klenow fragment의 효소 활성을 검출하기 위하여 실시간 형광에세이 방법을 사용했다. 실험 결과에 의하면, 산화그래핀에 흡착된 형광표지 ssDNA는 형광이 ��칭(quenching) 되지만, cDNA 첨가에 의해서 흡착된 단일가닥 DNA가 유리되었다. Klenow fragment의 활성을 측정하기 위해서 형광표지 틀(template) DNA, 산화그래핀과 시발체(primer)가 존재할 때, 고분자 반응이 진행됨에 따라 ��칭된 형광세기가 증가하였다. 그리고 겔 전기영동 실험은 산화 그래핀에서 DNA 합성과 hybridization 반응을 확인하였다.

• 한국의류학회지
• /
• 제24권7호
• /
• pp.1065-1072
• /
• 2000

The molecular areas and the interfacial tension behavior of ten nonionic surfactants, i.e., Span 20 and Tween 20, 40, 60. 80, 21, 61, 81, 65, & 85 are tested to assay their effects on the wetting and liquid retention properties of hydrophilic and hydrophobic fibrous materials. The molecular areas at water/air interface are derived from Gibbs’adsorption equations. The following conclusions are drawn from the results: 1) Span 20 is efficient in lowering the interfacial tension and effective in adsorption at the water/air interface, resulting in the low interfacial tension at critical micelle concentration (${\gamma}$$_{CMC}$) and a small molecular area($\omega$), 2) when the hydrophiles of the surfactants are constant, $\omega$’s increase as hydrophobe carbon numbers of the surfactants increase, 3) when the hydrophobes are constant, ${\gamma}$$_{CMC}$’s and $\omega$’s increase as the hydrophile ethylene oxide units increase, indicating effectiveness and efficiency is parallel in this case, 4) the ethylene oxide unit length as a hydrophile has greater influence on u than the hydrophobe chain length.han the hydrophobe chain length.gth.

• Composites Research
• /
• 제35권6호
• /
• pp.402-411
• /
• 2022

In this study, the channels-contained hybrid membranes have been fabricated through the incorporation of glass fibers and GO sheets (GO/glass fibers, GG), or a mixture of chitosan/GO (CS/GO/glass fibers, CGG), as hybrid membranes using in organic dye removal. The material properties are well investigated the terms in the morphological, chemical, crystal, and thermal characterizations for verifying interactions in their formed structure. These hybrid membranes have been fitted well in pseudo-second order and Langmuir models that are associated with chemical adsorption and a monolayer approach, respectively. The highest adsorption ability of methylene blue and methyl orange reached 59.40 mg/g and 229.07 mg/g (GG); and 287.47 mg/g and 252.91 mg/g (CGG), which is more enhanced than that of previous GO-based other adsorbents. Moreover, the dye separation on these membranes could be favorable to superb sealing and trapping dye molecules from water instead of only the dye connection occurring on their surface, regarding the physically sieving effect. The membranes can also be reused within two and three adsorbing-desorbing cycles on the GG and CGG ones, respectively. These membranes can become future adsorbents to be applied for wastewater treatment due to their structural features.

• 공업화학
• /
• 제33권4호
• /
• pp.352-366
• /
• 2022

Nuclear power plant operations for electricity generation, rare-earth mining, nuclear medical research, and nuclear weapons reprocessing considerably increase radioactive waste, necessitating massive efforts to eradicate radioactive waste from aquatic environments. Cobalt (⁵⁸Co) and strontium (⁹⁰Sr) radioactive elements have been extensively employed in energy generation, nuclear weapon testing, and the manufacture of healthcare products. The erroneous discharge of these elements as pollutants into the aquatic system, radiation emissions, and long-term disposal is extremely detrimental to humans and aquatic biota. Numerous methods for treating radioactive waste-contaminated water have emerged, among which the adsorption process has been promoted for its efficacy in eliminating radioactive waste from aquatic habitats. The current review discusses the adsorptive removal of radioactive waste from aqueous solutions using low-cost adsorbents, such as graphene oxide, metal-organic frameworks, and inorganic metal oxides, as well as their composites. The chemical modification of adsorbents to increase their removal efficiency is also discussed. Finally, the current state of ⁵⁸Co and ⁹⁰Sr removal performances is summarized and the efficiencies of various adsorbents are compared.

• Journal of Electrochemical Science and Technology
• /
• 제14권3호
• /
• pp.222-230
• /
• 2023

Capacitive deionization of saline water is one of the most promising water purification technologies due to its high energy efficiency and cost-effectiveness. This study synthesizes porous carbon composites composed of reduced graphene oxide (rGO) and activated carbon (AC) with various rGO/AC ratios using a facile chemical method. Surface characterization of the rGO/AC composites shows a successful chemical reduction of GO to rGO and incorporation of AC into rGO. The optimized rGO/AC composite electrode exhibits a specific capacitance of ~243 F g^-1 in a 1 M NaCl solution. The galvanostatic charging-discharging test shows excellent reversible cycles, with a slight shortening in the cycle time from the ~260^th to the 530^th cycle. Various monovalent sodium salts (NaF, NaCl, NaBr, and NaI) and chloride salts (LiCl, NaCl, KCl, and CsCl) are deionized with the rGO/AC electrode pairs at a cell voltage of 1.3 V. Among them, NaI shows the highest specific adsorption capacity of ~22.2 mg g^-1. Detailed surface characterization and electrochemical analyses are conducted.

• 공업화학
• /
• 제9권2호
• /
• pp.278-285
• /
• 1998

배출가스중의 $SO_2$ 제거를 위하여 다양한 금속산화물로 구성된 천연망간광석, 철광석, $CuO/{\gamma}-A1_2O_3$ 등을 흡착제로 사용하여 고정층반응기에서 흡착용량실험을 하였다. 또한 흡착제중 흡착용량이 떨어지는 철광석을 제외한 두 가지 흡착제를 이용하여 유동층반응기에서 유속, 온도, 입자크기 등의 조업조건에 따른 $SO_2$ 흡착실험을 수행하였다. 모든 흡착제에서 온도가 증가할수록 흡착량이 증가하는 화학흡착반응을 보였고 유동층반응기에서 $U_o/U_{mf}$ 및 $U_o-U_{mf}$와 같은 유속조건에 따라 입자 크기에 따른 흡착량의 변화가 다르게 나타났으며 유동층반응기 성능식으로부터 반응속도상수를 얻었다. 이 실험을 통하여 천연망간광석이 유동층반응기에서 $SO_2$ 흡착제로의 사용가능성을 확인할 수 있었다.

• 농업과학연구
• /
• 제48권3호
• /
• pp.589-596
• /
• 2021

Nitrogen applied to soil is highly prone to leaching and volatilization leading to gaseous emissions of nitrous oxide (N₂O) and ammonia (NH₃) which are of great environmental concern. Usage of biochar to reduce the discharge of nitrogen to the environment has attracted much interest in the recent past. Biochar is produced by pyrolyzing various biomasses under oxygen-limited conditions. Biochar is a carbonized material with high adsorptive powers for not only plant nutrients but also heavy metals. The objective of this study was to investigate the adsorption characteristics of NH₄-N onto biochar made from pine needles. The biochar was produced at various pyrolysis temperatures including 300, 400 and 500℃ and holding times of 30 and 120 minutes. The Langmuir isotherm was used to evaluate the adsorption test results. The chemical properties of the biochar varied with the pyrolysis conditions. In particular, the pH, EC and total carbon content increased with the increasing pyrolysis conditions. The rate of adsorption of NH₄-N by the biochar decreased with the increasing pyrolysis conditions. Of these conditions, biochar that was pyrolyzed at 300℃ for 30 minutes showed the highest adsorption rate of approximately 0.071 mg·g^-1. Thus, the use of biochar pyrolyzed at low temperatures with a short holding time can most efficiently reduce ammonia emissions from agricultural land.

• Bulletin of the Korean Chemical Society
• /
• 제33권10호
• /
• pp.3213-3217
• /
• 2012

Reactive adsorption desulfurization (RADS) experiments were conducted over a series of commercial metal oxide supports ($Al_2O_{3-}$, $SiO_{2-}$, $TiO_{2-}$ and $ZrO_{2-}$) supported Ni/ZnO adsorbents. The adsorbents were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), and Fourier transform infrared spectroscopy (FTIR) in order to find out the influence of specific types of surface chemistry and structural characteristics on the sulfur adsorptive capacity. The desulfurization performance of all the studied adsorbents decreased in the following order: Ni/ZnO-$TiO_2$ > Ni/ZnO-$ZrO_2$ > Ni/ZnO-$SiO_2$ > Ni/ZnO-$Al_2O_3$. Ni/ZnO-$TiO_2$ shows the best performance and the three hour sulfur capacity can achieve 12.34 mg S/g adsorbent with a WHSV of $4h^{-1}$. Various characterization techniques suggest that weak interaction between active component and support component, high dispersion of NiO and ZnO, high reducibility and large total Lewis acidity of the adsorbents are important factors in achieving better RADS performance.

• Environmental Engineering Research
• /
• 제14권3호
• /
• pp.164-169
• /
• 2009

A powder form of aluminum (hydr)oxides is not suitable in wastewater treatment/filtration systems because of low hydraulic conductivity and large sludge production. In this study, aluminum (hydr)oxide-coated sand (AOCS) was used to remove phosphate from aqueous solution. The properties of AOCS were analyzed using a scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectrometer (EDS) and an X-ray diffractometer (XRD). Kinetic batch, equilibrium batch, and closed-loop column experiments were performed to examine the adsorption of phosphate to AOCS. The XRD pattern indicated that the powder form of aluminum (hydr)oxides coated on AOCS was similar to a low crystalline boehmite. Kinetic batch experiments demonstrated that P adsorption to AOCS reached equilibrium after 24 h of reaction time. The kinetic sorption data were described well by the pseudo second-order kinetic sorption model, which determined the amount of P adsorbed at equilibrium ($q_e$ = 0.118 mg/g) and the pseudo second-order velocity constant (k = 0.0036 g/mg/h) at initial P concentration of 25 mg/L. The equilibrium batch data were fitted well to the Freundlich isotherm model, which quantified the distribution coefficient ($K_F$ = 0.083 L/g), and the Freundlich constant (1/n = 0.339). The closed-loop column experiments showed that the phosphate removal percent decreased from 89.1 to 41.9% with increasing initial pH from 4.82 to 9.53. The adsorption capacity determined from the closed-loop experiment was 0.239 mg/g at initial pH 7.0, which is about two times greater than that ($q_e$ = 0.118 mg/g) from the kinetic batch experiment at the same condition.