• Nuclear Engineering and Technology
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• 제48권2호
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• pp.448-456
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• 2016

Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies themass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The $H_2O$ content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of $CO_2$ necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core-concrete interaction analysis.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1355-1360
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• 2004

The oxidative decomposition of trichloroethylene (TCE) was investigated using palladium catalysts supported on pure and sulfated zirconia. The reactions were performed under dry and wet conditions in the temperature between 200 and $550^{\circ}C$ keeping GHSV of 14,000 $h^{-1}.$ The products such as $C_2Cl_4,\;C_2HCl_5,\;CO\;and\;CO_2$ were observed in the reaction. The addition of water in the feed affected the distribution of reaction product with dramatically improved catalytic activity. The spectroscopic investigations gave an evidence that the strong acid sites play an important role on controlling the catalytic activity. Among the catalysts investigated, the Pd-loaded sulfated zirconia catalyst with 1 wt% Pd was found to exhibit the highest catalytic activity in the presence of water vapor having the stability for 30 h of the reaction at $500^{\circ}C$. The successful performance of the catalyst might be attributed to promotional effect of Pd active sites and strong acid sites induced from surface sulfate species on zirconia.

• Biomaterials and Biomechanics in Bioengineering
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• 제3권1호
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• pp.59-69
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• 2016

A surface resisting protein adsorption and cell adhesion is highly desirable for many biomedical applications such as diagnostic devices, biosensors and blood-contacting devices. In this study, a surface conjugated with sulfobetaine molecules was fabricated via the click reaction for the anti-fouling purpose. An alkyne-containing substrate (Alkyne-PPX) was generated by chemical vapor deposition of 4-ethynyl-[2,2]paracyclophane. Azide-ended mono-sulfobetaine molecules were synthesized and then conjugated on Alkyne-PPX via the click reaction. The protein adsorption from 10% serum was reduced by 57%, while the attachment of L929 cells was reduced by 83% onto the sulfobetaine-PPX surface compared to the protein adsorption and cell adhesion on Alkyne-PPX. In conclusion, we demonstrate that conjugation of mono-sulfobetaine molecules via the click chemistry is an effective way for reduction of non-specific protein adsorption and cell attachment.

• Korean Chemical Engineering Research
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• 제50권3호
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• pp.398-402
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• 2012

본 연구는 암모니아와 물이 함께 존재하는 황화수소를 선택적 산화 반응을 통해 원소 황의 형태로 제거하는 기상 촉매 공정의 개발에 관한 것이다. 최적의 촉매를 개발하기 위해 여러 가지 금속산화물에 대한 반응성 실험 결과 $Fe_2O_3/SiO_2$ 촉매가 $240{\sim}280^{\circ}C$의 온도 범위에서 90% 이상의 $H_2S$ 전화율과 아주 낮은 $SO_2$ 방출을 나타내어 실제 공정에 적용하기에 가장 적합하였다. $Fe_2O_3/SiO_2$ 촉매 상에서 황화수소의 선택적 산화 반응에 대한 메커니즘 규명을 위하여 반응 온도, $O_2/H_2S$ 몰 비, 암모니아와 수증기의 분압이 촉매 활성에 미치는 영향에 관하여 고찰하였다. 전화율은 반응 온도가 $260^{\circ}C$에서 최대값을 보였고, $280^{\circ}C$ 이상에서는 전화율과 원소 황의 선택도가 모두 감소하는 경향을 나타내었다. $O_2/H_2S$ 비가 0.5에서 4로 증가하면 전화율이 증가하였으나 선택도는 크게 감소하였다. 암모니아 분압이 증가하면 전화율이 증가하고 $SO_2$ 발생은 감소하였으며 원소 황의 선택도가 증가하였다. 수증기가 함께 존재하면 전화율과 원소 황의 선택도는 감소하고, ATS의 선택도가 증가하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.264.2-264.2
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• 2013

Molecular layer deposition (MLD) is sequential, self-limiting surface reaction to form conformal and ultrathin polymer film. This technique generally uses bifunctional precursors for stepwise sequential surface reaction and entirely organic polymer films. Also, in comparison with solution-based technique, because MLD is vapor-phase deposition based on ALD, it allows epitaxial growth of molecular layer on substrate and is especially good for surface reaction or coating of nanostructure such as nanopore, nanochannel, nanwire array and so on. In this study, polyurea film that consisted of phenylenediisocyanate and phenylenediamine was formed by MLD technique. In situ Fourier Transform Infrared (FTIR) measurement on high surface area SiO2 substrate was used to monitor the growth of polyurethane and polyurea film. Also, to investigate orientation of chemical bonding formed polymer film, plan-polarized grazing angle FTIR spectroscopy was used and it showed epitaxial growth and uniform orientation of chemical bones of polyurea films.

• 한국세라믹학회지
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• 제32권4호
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• pp.419-428
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• 1995

Polycrystalline silicon carbide (SiC) thick films were depostied by low pressure chemical vapor deposition (LPCVD) using CH3SiCl3 (MTS) and H2 gaseous mixture onto isotropic graphite substrate. Effects of deposition variables on the SiC film were investigated. Deposition rate had been found to be surface-reaction controlled below reactor temperature of 120$0^{\circ}C$ and mass-transport controlled over 125$0^{\circ}C$. Apparent activation energy value decreased below 120$0^{\circ}C$ and deposition rate decreased above 125$0^{\circ}C$ by depletion effect of the reactant gas in the direction of flow in a horizontal hot wall reactor. Microstructure of the as-deposited SiC films was strongly influenced by deposition temperature and position. Microstructural change occurred greater in the mass transport controlled region than surface reaction controlled region. The as-deposited SiC layers in this experiment showed stoichiometric composition and there were no polytype except for $\beta$-SiC. The preferred orientation plane of the polycrystalline SiC layers was (220) plane at a high reactant gas concentration in the mass transfer controlled region. As depletion effect of reactant concentration was increased, SiC films preferentially grow as (111) plane.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.253-253
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• 2012

Low temperature SiOx film process has being required for both silicon and oxide (IGZO) based low temperature thin film transistor (TFT) for application of flexible display. In recent decades, from low density and high pressure such as capacitively coupled plasma (CCP) type plasma enhanced chemical vapor deposition (PECVD) to the high density plasma and low pressure such as inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) have been used to researching to obtain high quality silicon oxide (SiOx) thin film at low temperature. However, these plasma deposition devices have limitation of controllability of process condition because process parameters of plasma deposition such as RF power, working pressure and gas ratio influence each other on plasma conditions which non-leanly influence depositing thin film. In compared to these plasma deposition devices, neutral beam assisted chemical vapor deposition (NBaCVD) has advantage of independence of control parameters. The energy of neutral beam (NB) can be controlled independently of other process conditions. In this manner, we obtained NB dependent high crystallized intrinsic and doped silicon thin film at low temperature in our another papers. We examine the properties of the low temperature processed silicon oxide thin films which are fabricated by the NBaCVD. NBaCVD deposition system consists of the internal inductively coupled plasma (ICP) antenna and the reflector. Internal ICP antenna generates high density plasma and reflector generates NB by auger recombination of ions at the surface of metal reflector. During deposition of silicon oxide thin film by using the NBaCVD process with a tungsten reflector, the energetic Neutral Beam (NB) that controlled by the reflector bias believed to help surface reaction. Electrical and structural properties of the silicon oxide are changed by the reflector bias, effectively. We measured the breakdown field and structure property of the Si oxide thin film by analysis of I-V, C-V and FTIR measurement.

• 한국재료학회지
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• 제24권12호
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• pp.694-699
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• 2014

We report the chemical vapor deposition growth characteristics of graphene on various catalytic metal substrates such as Ni, Fe, Ag, Au, and Pt. 50-nm-thick metal films were deposited on $SiO_2/Si$ substrates using dc magnetron sputtering. Graphene was synthesized on the metal/$SiO_2$/Si substrates with $CH_4$ gas (1 SCCM) diluted in mixed gases of 10% $H_2$ and 90 % Ar (99 SCCM) using inductively-coupled plasma chemical vapor deposition (ICP-CVD). The highest quality of graphene film was achieved on Ni and Fe substrates at $900^{\circ}C$ and 500 W of ICP power. Ni substrate seemed to be the best catalytic material among the tested materials for graphene growth because it required the lowest growth temperature ($600^{\circ}C$) as well as showing a low ICP power of 200W. Graphene films were successfully grown on Ag, Au, and Pt substrates as well. Graphene was formed on Pt substrate within 2 sec, while graphene film was achieved on Ni substrate over a period of 5 min of growth. These results can be understood as showing the direct CVD growth of graphene with a highly efficient catalytic reaction on the Pt surface.

• 한국분말재료학회지
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• 제14권5호
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• pp.281-286
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• 2007

Ordered $L1_0$ to FePt nanoparticles are strong candidates for high density magnetic data storage media because the $L1_0$ phase FePt has a very high magnetocrystalline anisotropy $(K_u{\sim}6.6-10{\times}10^7erg/cm^3)$, high coercivity and chemical stability. In this study, the ordered $L1_0$ FePt nanoparticles were successfully fabricated by chemical vapor condensation process without a post-annealing process which causes severe particle growth and agglomeration. The $Fe_{50}Pt_{50}$ nanopowder was obtained when the mixing ratio of Fe(acac) and Pt(arac) was 2.5 : 1. And the synthesized FePt nanoparticles were very fine and spherical shape with a narrow size distribution. The average particle size of the powder tended to increase from 5 nm to 10 nm with increasing reaction temperature from $800^{\circ}C$ to $1000^{\circ}C$. Characterisitcs of FePt nanopowder were investigated in terms of process parameters and microstructures.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E2호
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• pp.35-42
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• 2001

Recent development of photocatalytic degradation method that is mediated by TiO$_2$ is of interest in the treatment of volatile organic compounds(VOCs). In this study, trichloroethylene(TCE) and acetone were closely examined in a batch scale of photo-reactor as a function of water vapor, oxygen, and temperature. Water vapor inhibited the photocatalytic degradation of acetone, while there was an optimum concentration in TCE. A lower efficiency was found in nitrogen atmosphere than air, and the effect of oxygen on photocatalytic degradation of acetone was greater than on that of TCE. The optimum reaction temperature on photocatalytic degradation was about 45$^{\circ}C$ for both compounds. NO organic byproducts were detected for both compounds under the present experimental conditions. It was ascertained that the photocatalytic reaction in a batch scale of photo-reactor was very effective in removing VOCs such as TCE and acetone in the gaseous phase.