• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.275-276
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• 2002

아세트알데히드 등 저비점 지방족 알데히드류는 대기 중에 배출된 탄화수소류 등 휘발성 유기화합물의 산화생성물로서 광화학스모그의 원인이며, 또한 악취물질로서도 관심의 대상이 되고 있다. 특히 아세트알데히트의 경우 우리나라의 악취배출허용기준에 명시된 대표적인 악취물질로서 규제의 대상이 되고 있으며 이외에도 프로피온알데히드, 부틸알데히드, 발레르알데히드 등은 일본의 악취방지법에서 규제되고 있어서 장차 우리나라에서도 규제 대상의 가능성이 높은 물질이다. (중략)

• Journal of Power System Engineering
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• v.13 no.6
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• pp.76-81
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• 2009

Thermal desorption systems are designed to remove organic compounds from solid matrices such as soils, sludges and filter cakes without thermally destroying them. It is a separation technology, not a destruction technology. Since it is a thermal process, there is a common belief that temperature is the only significant parameter to be monitored. While it is true that better removal efficiencies are usually achieved at higher temperatures, other factors must be considered. Since the process is governed by mass transfer, heating time and the amount of mixing are also key parameters in optimizing removal efficiency. Thermal desorption have been successfully used for just about every organic contaminant found to date. It has also been used to remove mercury. In the present study, the numerical simulation has been performed to investigate the characteristics of heat transfer of LTTD(low temperature thermal desorption). The commercial software, AMESIM was applied for analyzing the heat transfer process in the LTTD.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.381.1-381.1
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• 2016

분석 방법의 간편함과 용이함의 장점은 물론, 시료 전처리 과정이 적어 시료물질의 임의 파괴나 훼손을 방지한다는 이유에서 최근 10년 간 많은 연구가 이루어지고 있는 대기압 질량분석 기술은 기압차이가 없는 대기압 분위기에서 질량분석이 이루어지기 때문에 시료를 질량분석기 입구 바로 앞에 스테이지를 설치하고서 시료를 이온화하는 경우가 대부분이다. 이 때문에 균질하지 않은 시료의 관심 영역을 모니터링하면서 질량분석을 하기에는 어려움이 있으며, 공간 정보를 추가한 질량분석 이미징에 한계가 있었다. 이에 본 연구팀은 질량분석기 입구에 챔버와 보조 펌프를 장착하여 강제로 기체 흐름 일으켜 시료로부터 발생한 이온을 질량분석기 입구로 유도하여, 원거리에서 시료를 이온화해도 질량분석기 입구까지 이온을 성공적으로 전달시키는 방법을 제안한다. 이를 이용하면 분석하고자 하는 시료를 현미경 스테이지 위에 위치시켜 분석하고자하는 부분을 현미경으로 확인하면서 질량분석을 할 수 있으며, 나아가 대기압 질량 분석 이미징 기술을 구현할 수 있다. 대기압 탈착/이온화원은시료에 열적 손상이 없는 조건으로 시편의 이온화 및 탈착 과정이 이루어지게 하기 위해 저온 대기압 헬륨 플라즈마 젯과 펨토초 레이저를 결합하여 대기압 이온화원을 제작하였다. 이온 전달관은 1/4" (6.35 mm) 외경의 60 cm 길이의 스테인리스 스틸관을 사용하여 질량분석기에서 약 60 cm 떨어진 현미경 위의 시료의 질량분석이 가능하게 했다. 보조 펌프의 계기압과 저온 대기압 헬륨 플라즈마 젯의 헬륨 기체의 유속을 변화시키면서 시료인 PDMS (polydimethylsiloxane) 의 질량 스펙트럼 (m/z 270.314) 세기를 관찰하여 최적의 이온 전달 조건을 찾았다. 추가로 현미경 스테이지에 정밀 2-D 자동 스캐닝 스테이지를 장착하여 질량분석 정보에 공간 정보를 더할 수 있는 질량분석 이미징 기술 방법을 개발하여 생체 시편의 질량분석 이미징을 얻었다.

• Analytical Science and Technology
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• v.19 no.6
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• pp.553-558
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• 2006

In this study, an attempt was made to measure uncertainties involved in the VOC analysis for the VOC working standards prepared by a dilution technique using Tedlar bags. For this purpose, VOC standard gases of benzene, toluene, xylene, and styrene were prepared at four different concentrations (4, 8, 20, and 40 ppb). These standard samples were then loaded on to the GC system equipped with air server/thermal desorption (AS/TD) system. Each of these four standard concentrations was analyzed individually to derive their respective calibration results. These calibration data sets were then compared across four different compounds. According to this comparison, differences in calibration patterns were moderately insignificant within the selected concentration range of 4~40 ppb. It was also observed that the loss of styrene standard was fairly high compared to other VOCs investigated simultaneously. The results of our study suggest that the analytical uncertainty associated with the preparation of VOC starndard gas using a dilution technique can be assessed in a fairly reasonable manner for samples with a narrow concentration range.

• Journal of the Korean Institute of Gas
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• v.9 no.4 s.29
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• pp.17-25
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• 2005

The dealuminated and alkali/alkaline-earth metal exchanged Y-zeolites were prepared as a catalyst. Elemental compositions and structures of the prepared catalysts were analyzed by the various spectroscopic techniques such as inductively coupled plasma-atomic emission spectroscopy(ICP-AES), X-ray fluorescence(XRF) and X-ray diffraction(XRD), and the desorption behaviors of adsorbed species on the catalyst surfaces were investigated via NO-TPD experiment. Comparing with the composition of the starting material of NaY zeolite, the magnitudes of Si/Al ratio in catalytic materials were increased after dealumination. The Si/Al ratio of catalytic materials after dealumination followed by Cs and Ba cation exchange were additionally decreased. Dealumination to catalysts induced a destruction of basic frame due to a detachment of aluminum, which results in reducing framework structure, while increasing non-framework structure. This phenomenon becomes more serious with increasing time of steam treatment and even more significant for the cation exchanged catalysts. In NO-TPD experiments, the desorption peaks of NO which indicates an activity point of catalysts shifted to the low temperature region after dealumination and cation exchange. The desorption peaks of the NO-TPD profiles taken after steam treatment also shifted to the low temperature region as the steam treatment time increased. In dealuminated and cation exchanged Y-zeolites, the catalytic activities were more influenced by exchanged cation and the formation of non-framework structure.

• Analytical Science and Technology
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• v.25 no.6
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• pp.375-381
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• 2012

In this study, we have developed a cryogenic concentration system for the analysis of non-methane hydrocarbons (NMHCs) in air sample. NMHCs with nmol/mol level of concentrations in the atmosphere were quantified by a comparative method with certified reference gas mixture. GC/FID with cryogenic concentration system operated in the range from $-67^{\circ}C$ to $180^{\circ}C$ was adopted. After cryogenic concentration, a fast desorption by heating could achieve a large amount of sample injection into the GC/FID. The linearity of the system was verified with the peak areas of NMHCs of the concentration amount of sample. The reproducibility is less than 10% and the limit of detection (LOD) is 0.1 nmol/mol. For the application of this system, we analyzed NMHCs in gas samples taken from air and soil in Daejeon, Seosan and Goheung.

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.196-201
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• 1995

새로운 증착방법인 UHV-ECRCVD를 이용하여 기판온도 $440^{\circ}C$의 저온에서 격자이온이 일어나지 않고 완벽한 정합상태를 유지하고 있는 무전위 SiGe 에피박막을 성장시켰다. 박막의 두께는 기계적 평형이론(mechanical equilibrium theory)인 Mattews-Blakeslee 임계두께를 초과하였으며, 따라서 본 연구에서 사용하는 낮은 기판온도에 의해 격자이완이 억제되고 있음을 알았다. 한편 성장시에 가해주는 GeH4의 유량이 증가함에 따라 박막내에 GeH4으로부터 생성된 무거운 ion의 기판입사량이 증가하여 격자손상(lattice damage)에 의한 결함이 증가하므로 높은 Ge 함량을 갖는 무전위 SiGe 에피박막을 얻을 수 없었다. 그러나 전체압력을 증가시켜서 에피층을 성장시키면 격자손상에 의한 결함은 생성되지 않았으며, 따라서 전체압력을 증가시키면 높은 Gegkafid을 갖는 무전위 SiGe 에피박막을 성장시킬 수 있을 것이라고 생각된다. 이것은 전체압력 증가로 인해 ECR 플라즈마 안의 전자온도가 감소하여 성장을 주도하는 활성종(reactive species)이 ion에서 radical 로 바뀌기 때문이라고 추정하였다. 본 연구에서는 박막의 Ge 함량이 증가함에 따라 에피층의 성장속도가 증가하는 현상을 관찰하였다. 따라서 ECR 플라즈마를 사용하는 본 연구에서도 표면에서의 수소탈착이 성장속도결정단계임을 알 수 있었다. 한편 인입률(incorporation ratio)은 1에 근접하였으며, 이것은 플라즈마에 의한 원료기체의 분해과정이 thermal CVD와는 달리 무차별적으므로 SiH4과 GeH4의 분해효율이 크게 다르지 않기 때문이라고 추정하였다.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.83-90
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• 2021

In this study, effects of the physical and chemical properties of low temperature heated carbon on electrochemical behavior as a secondary battery anode material were investigated. A heat treatment at 600 ℃ was performed for coking of petroleum based pitch, and the manufactured coke was heat treated with different heat temperatures at 700~1,500 ℃ to prepare low temperature heated anode materials. The physical and chemical properties of carbon anode materials were studied through nitrogen adsorption and desorption, X-ray diffraction (XRD), Raman spectroscopy, elemental analysis. Also the anode properties of low temperature heated carbon were considered through electrochemical properties such as capacity, initial Coulomb efficiency (ICE), rate capability, and cycle performance. The crystal structure of low temperature (≤ 1500 ℃) heated carbon was improved by increasing the crystal size and true density, while the specific surface area decreased. Electrochemical properties of the anode material were changed with respect to the physical and chemical properties of low temperature heated carbon. The capacity and cycle performance were most affected by H/C atomic ratio. Also, the ICE was influenced by the specific surface area, whereas the rate performance was most affected by true density.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.857-864
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• 2005

Dealuminated and alkali/alkaline-earth metal exchanged Y-type and ZSM-5 zeolites were prepared as catalytic materials. Comparing with the composition of starting material, the magnitude of Si/Al ratio was increased after dealumination and cation exchange process. The ratio of Si/Al on surface was appeared to be larger than that in bulk. The destruction of basic frame in catalysts observed was understood to be due to a detachment of aluminum, which results in reducing framework while increasing non-framework. This phenomenon becomes more serious with increasing time of steam treatment and even more significant for the cation exchanged catalysts. The desorption peaks of the NO-TPD profiles taken after dealumination and cation exchanged Y-type and ZSM-5 zeolites shifted to the low temperature region. It was also found that the longer the steam treatment time, the degree of shift toward low temperature region was increased. The catalytic activities are dependent on the nature of cation exchanged, the ratio of Si/Al and the ratio of framework/non-framework by a change in basic frame.

• Clean Technology
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• v.24 no.1
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• pp.55-62
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• 2018

The adsorbent used in water-adsorption cooling system utilizing low-temperature heat of below $90^{\circ}C$ is required to exhibit high water uptake capacity at a relative humidity ($P/P_0$) between 0.1 and 0.3. Mesoporous silica (MCM-41) and MOF(MIL-101) exhibit quite large water adsorption capacity under saturated water vapor at $35^{\circ}C$. However, these adsorbents show small water adsorption capacity ($0.027{g_{water}\;g_{ads}}^{-1}$, $0.074{g_{water}\;g_{ads}}^{-1}$, respectively) in the relative humidity ($P/P_0$) range of 0.1 to 0.3. In this study, the surface properties of mesoporous silica and MOF were modified by simple methods to develop an adsorbent having a higher water uptake than the conventional water adsorbents at a relative humidity ($P/P_0$) of 0.1 ~ 0.3. In the case of mesoporous silica (MCM-41) exhibiting mainly water adsorption at $P/P_0=0.5{\sim}0.7$, aluminum species was functionalized on the mesopore walls and then cations existing near the aluminum were exchanged with various cations (e.g., $Na^+$, ${NH_4}^+$, and $(C_2H_5)_4N^+$). In addition, 20 wt% (to total weight of the composites) of hygroscopic inorganic salt ($CaCl_2$) was impregnated on the MCM-41. In the case of the MIL-101 (MOF), 20 wt% of hygroscopic inorganic salt ($CaCl_2$) was impregnated on the MIL-101. The MCM-41 which was ion-exchanged with various cations has main adsorption branch around 0.5 of $P/P_0$ which was slightly shifted with low-pressure direction in comparison with pristine MCM-41. However, tiny increases were observed on the adsorption in the range of $P/P_0$ between 0.1 and 0.3. After salt impregnation on the MCM-41, the adsorption capacity under $P/P_0=0.1{\sim}0.3$ at $35^{\circ}C$ was increased from $0.027{g_{water}\;g_{ads}}^{-1}$ to $0.152{g_{water}\;g_{ads}}^{-1}$. In the case of MIL-101, the amount of water adsorption at $35^{\circ}C$ under $P/P_0=0.1{\sim}0.3$ was increased from $0.074{g_{water}\;g_{ads}}^{-1}$ to $0.330{g_{water}\;g_{ads}}^{-1}$ after the salt impregnation.