• 한국전기전자재료학회논문지
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• 제16권12호
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• pp.1150-1154
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• 2003

The voltage profile during discharge of the zinc air battery has very flat pattern until reach to end of discharge voltage. But, when zinc air battery is discharged by high current, the discharge voltage and energy becomes low. Therefore, we focused on effects of catalyst size to solve this problems by increasing active sites of oxygen reduction reaction. The size of catalyst was reduced from 27 to l${\mu}{\textrm}{m}$ and we examined average discharge voltage, capacity, energy, resistance and characteristics during GSM pulse discharge of zinc air battery with change of current density. And we also measured porosity of the cathode according to the ASTM. So we have got improvement of average discharge voltage and energy when catalyst was minimized and we have got optimum size of catalyst at 5${\mu}{\textrm}{m}$.

• 에너지공학
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• 제2권1호
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• pp.114-122
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• 1993

A model describing the reaction rate and catalyst deactivation in a simplified reaction system was developed to investigate the significance of catalyst pore structure in terms of porosities, porosity ratios, and size ratios of reactants to pores. The model showed that the unimodal catalyst could give a better performance than the bimodal in certain circumstances and the crossover found in the reactivity curves resulted from a trade-off between surface area and diffusivity. Under the assumption of uniform coke buildup, the bimodal catalyst appeared to provide better resistance to deactation than unimodal catalyst.

• 한국항공우주학회지
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• 제34권9호
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• pp.89-96
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• 2006

본 연구에서는 소형 위성용 하이브리드 로켓 점화장치에 적용되는 N2O 촉매 베드의 유동 및 열적 현상에 대한 이론적인 고찰을 하였다. 허니콤 형상을 가지는 촉매 베드 내의 열적 현상을 분석하기 위해서 다공성 매질 접근법을 사용하였다. 유동장은 Brinkman- extended Darcy 모델을 사용하였고, 온도장은 One-equation 모델을 사용하여 촉매 베드 내에서 유동장 및 온도장에 대한 해석해들을 구하였다. 다공성 매질 접근법을 적용한 모델의 해석해와 기존 실험결과를 비교하여 본 모델의 정확성을 검증하였다. 해석해에 근거하여 N2O 촉매 베드에 영향을 미치는 중요한 변수들이 촉매 베드의 기공률, 유효 체적비, 촉매 베드와 기공의 직경비, 공급열, 그리고 펌핑파워임을 확인하였으며 촉매 베드 내에서의 열적현상에 대한 중요 변수들의 효과를 연구하였다.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.21-30
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• 2015

Ceramic foams are prepared as positive images corresponding to a plastic foam structure which exhibits high porosities (85-90%). This structure makes the ceramic foams attractive as a catalyst in a dry reforming process, because it could reduce a high pressure drop problem. This problem causes low mass and heat transfers in the process. Furthermore, the reactants would shortly contact to catalyst surface, thus low conversion could occur. Therefore, this research addressed the preparation of dry reforming catalysts using a sol-gel catalyst preparation via a polymeric sponge method. The specific objectives of this work are to investigate the effects of polymer foam structure (such as porosity, pore sizes, and cell characteristics) on a catalyst performance and to observe the influences of catalyst preparation parameters to yield a replica of the original structure of polymeric foam. To accomplish these objectives industrial waste foams, polyurethane (PU) and polyvinyl alcohol (PVA) foams, were used as a polymeric template. Results indicated that the porosity of the polyurethane and polyvinyl alcohol foams were about 99% and 97%. Their average cell sizes were approximate 200 and 50 micrometres, respectively. The cell characteristics of polymer foams exhibited the character of a high permeability material that can be able to dip with ceramic slurry, which was synthesized with various viscosities, during a catalyst preparation step. Next, morphology of ceramic foams was explored using scanning electron microscopy (SEM), and catalyst properties, such as; temperature profile of catalyst reduction, metal dispersion, and surface area, were also characterized by $H_2-TPR$ and $H_2-TPD$ techniques, and BET, respectively. From the results, it was found that metal-particle dispersion was relatively high about 5.89%, whereas the surface area of ceramic foam catalysts was $64.52m^2/g$. Finally, the catalytic behaviour toward hydrogen production through the dry reforming of methane using a fixed-bed reactor was evaluated under certain operating conditions. The approaches from this research provide a direction for further improvement of marketable environmental friendly catalyst production.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.60-67
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• 2008

The catalytic filter of Cu-ZSM5/alumina beads was considered to reduce NOx in the urea SCR system. Catalytic support of porous alumina beads with mean pore size $130{\mu}m$ and porosity $75{\sim}83%$ were prepared using foaming and gel-casting method. The Cu-ZSM5 catalysts were coated on the supporting alumina beads using $Cu(NO_3)_2$ by ion exchange method. After a washcoating process was applied to coat 10w% Cu-ZSM5 on porous alumina bead, coating layer was estimated $20{\mu}m$ in thickness. The characterization and the feasibility as a catalytic supports were investigated. And the NOx conversion test in Cu-ZSM5/Alumina Beads filter system was conducted by using Urea as reductants under laboratory test. The NOx conversion was increased as size and porosity of beads and observed more than 95% excellent NOx conversion above $300^{\circ}C$.

• 분석과학
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• 제15권3호
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• pp.263-269
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• 2002

평균입경이 200 ${\mu}m$인 코디어라이트 분말로 다공성 필터를 제조한 후, 진공함침법으로 Pt, Pd, Cu, Co, La, $V_2O_5$ 촉매를 담지시켰다. VOC의 일종인 톨루엔을 촉매담지 세라믹필터에 통과시키며 촉매산화시킴으로서 톨루엔에 대한 촉매들의 활성에 대하여 고찰하였다. 제조된 다공성 필터의 겉보기 기공률은 62%였고, 압축강도는 약 10 MPa이었으며, 5 cm/sec 유속에서의 차압은 15 mmHg였다. 촉매를 필터에 담지시키면 기공률은 감소하고, 차압과 압축강도는 증가하였다. 필터에 담지된 촉매들 중에서 Pt 촉매의 활성이 가장 높았고, 250 $^{\circ}C$의 온도에서 90% 이상의 톨루엔을 제거시킬 수 있었다. 250 $^{\circ}C$ 이하의 온도에서는 Pt 촉매 담지량이 톨루엔의 전환율에 영향을 미쳤지만, 그 이상의 온도에서는 Pt 촉매 담지량의 차이에 의한 영향은 나타나지 않았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.669-669
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• 2013

Hierarchical N doped TiO2 nanostructured catalyst with micro, meso and macro porosity have been synthesized by a facile self-formation route using ammonia and titanium isopropoxide precursor. The samples were calcined in different calcination temperature ranging from $300^{\circ}C$ to $800^{\circ}C$ at slow heating rate ($5^{\circ}C$/min) and designated as NHPT-300 to NHPT-800. $TiO_2$ nanostructured catalyst have been characterized by physico-chemical and spectroscopy methods to explore the structural, electronic and optical properties. UV-Vis diffuse reflectance spectra confirmed the red shift and band gap narrowing due to the doping of N species in TiO2 nanoporous catalyst. Hierarchical macro porosity with fibrous channel patterning was observed (confirmed from FESEM) and well preserved even after calcination at $800^{\circ}C$, indicating the thermal stability. BET results showed that micro and mesoporosity was lost after $500^{\circ}C$ calcination. The photocatalytic activity has been evaluated for methanol oxidation to formaldehyde in visible light. The enhanced photocatalytic activity is attributed to combined synergetic effect of N doping for visible light absorption, micro and mesoporosity for increase of effective surface area and light harvestation, and hierarchical macroporous fibrous structure for multiple reflection and effective charge transfer.

• 마이크로전자및패키징학회지
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• 제24권3호
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• pp.13-18
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• 2017

물유리는 기존의 silicon alkoxide보다 훨씬 단가가 저렴하여 상업화에 유리하다는 장점을 나타낸다. 물유리 기반 실리카 에어로겔의 제조에서 산 촉매에 의한 중합 과정이 최종 미세 기공구조 특성에 상당한 영향을 끼치는데, 본 연구에서는 이러한 산 촉매의 종류와 양에 대한 물유리 기반 실리카 에어로겔의 비표면적, 기공 크기 분포 등 각 경우에 해당하는 물성 및 그에 따른 차이를 연구하였다. 최종 생성물의 물성을 통해 물유리 기반 실리카 에어로겔은 중합 반응에 관여하는 산 촉매의 종류와 농도, 몰수에 의해 영향을 받고, 특히 산 촉매의 몰수에 의한 영향이 몰 농도에 의한 영향보다 크게 작용함을 확인하였다. 기존 방식으로 4M 염산 촉매를 첨가할 경우 비표면적이 $394m^2/g$, 기공의 부피가 2.20 cc/g, 평균 기공 지름이 22.3 nm이며 기공률이 92.53%인 실리카 에어로겔을 합성할 수 있었다. 반면 4M의 황산 촉매를 적정량의 몰수인 73 mmol로 투입하여 최종 물유리 기반 실리카 에어로겔을 제조할 경우 비표면적은 $516m^2/g$, 기공의 부피는 3.10 cc/g, 평균 기공 지름은 24.1 nm, 기공률은 96.1%로, 기존의 산 촉매를 투입하여 만든 물유리 기반 실리카 에어로겔보다 전반적으로 기공구조의 특성이 향상됨을 확인하였다.

• 한국분말재료학회지
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• 제21권6호
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• pp.454-459
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• 2014

In this study, the porous ceramic filter was developed to be able to remove both dust and hazardous gas contained in fuel gas at high temperature. The porous ceramic filters were fabricated and used as a catalyst support. And the effects have been investigated such as the mean particle size, organic content and addition of foaming agent on the porosity, compressive strength and pressure drop of ceramic filters. With the increase of mean powder size and the organic content for the cordierite filter, the porosity was increased, but the compressive strength and pressure drop were decreased. From the results of the research, the optimum condition for the fabrication of ceramic filters could be acquired and they had the porosity of 58%, the compressive strength of 13.4 MPa and the pressure drop of 250 Pa. It was expected that this ceramic filter was able to be applied to the glass melting furnace, combustor, and dust/toxic gas removal filter.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.99-102
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• 1998

Cordierite ceramics with low dielectric constants were obtained through sol-gel techniques using as metal alkoxides. The powders for the sintered cordierite ceramics were prepared by hydrolysis of metal alkoxides with ethanol and distilled water. In the hydrolysis, the mole ratio of HCI/TEOS was controlled by changing the amount of HCI as a catalyst. The sol-gel derived powders were dried, pressed, and fired at $1300^{\circ}C$. The dried powders were calcined at $800{\circ}C$ for 3hours to remove residual organics. The fired bodies with different dielectric constants were obtained by using HCI adjusted to various mole ratios of HCI/TEOS in the process. The variation of the amount of HCI catalyst led to a significant influence on dielectric contant, which was attributed to the formation of pores in the sintered body. Especially, the porosity of the sintered body influenced the dielectric constants.