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메조기공의 실리카-티타니아 코겔의 제조와 자율적 조습 및 광촉매 특성
이상화,곽중협,서태수,김효중,김동표 한국공업화학회 2003 공업화학 Vol.14 No.3
수용액상의 졸겔반응에 의해 메조기공의 실리카-티타니아 코겔을 제조하고 이들의 자율적 조습력과 광촉매 특성에 대해 검토하였다. 실리카-티타니아 코겔에 있어 조습력과 관계되는 세공크기와 용적은 본 연구에서 고안된역적정법에 의해 Ph 7부근 및 SiO_2/TiO_2 비가 상대적으로 큰 9/1인 경우에 가장 큰 생성물이 얻어졌다. 폐놀 분해율에 의한 광촉매 특성은 동일조건에서 SiO_2/TiO_2 비가 감소함에 따라 증가하였고, SiO_2/TiO_2 비가 9/1에서 세공크기 4.0~6.0 nm 및 세공용적 0.6~0.8 mL/g 범위로 제어된 코겔의 경우 환경습도 40~70% 범위에서 흡습량 25%, 방습량 45%로서 종래 조습재료 보다 자율조습력이 큰 것을 볼 수 있었고, 같은 조성의 실리카-티타니아 혼합 산화물과의 폐놀 분해율에 의한 광촉매 특성 비교에서도 우수한 물성을 보이고 있었는데 이것은 Ti-O-Si 결합형성으로 인해 코겔 구조내에 음전하 과잉으로 인한 활성점(브렌스테드 산점) 발현에 기인된 것으로 고찰된다. Silica-titania cogel materials have been prepared by aqueous sol-gel process using a back titration technique designed for this study. The humidity self-control and photocatalytic properties of the materials have been also investigated. In these silica-titania cogel materials, relatively large pore size and pore volume than can give a good humidity control ability are desired, and they were synthesized under the reaction condition at pH of 7 and SiO_2/TiO_2 ratio of 9/1. The photocatalytic property, which was measured by the decomposition ratio of phenol, increased with the decrease of SiO_2/TiO_2 ratio in the composition. The cogel at the SiO_2/TiO_2 ratio of 9/1, resulted in the pore size of 4.0~6.0 nm and the pore volume of 0.6~0.8mL/g. At the relative humidity range of 40~70%, the amounts of moisture absorption and desorption were 25% 45%, respectively, and these had a better humidity control ability than conventional ones. In addition, the cogel showed a superior photocatalytic property compared to that of silica and titania mixture with the same composition. This enhancement is probably due to the revelation of active sites by the excess negative charges that were induced by Ti-O-Si bond formation in the cogel structure.
분체공학 , 유동층 고분자 , 재료 ( 무기 , 유기 ) : 주형을 이용한 티타니아 나노구조체 합성
김효중(Hyo Joong Kim),곽중협(Chung Heop Kwak),서태수(Tae Soo Suh),서동수(Dong Soo Suhr) 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.3
A novel technique for synthesis of titania nanostructures with needle-like template, hydroxyapatite, having particle size of nanometer diameter was investigated in this study. The synthetic routes involve the preparation of nanoprecursor(silica-coated templates), calcination of nanoprecursor and removal of templates. The analysis of nanoprecursor by means of scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) showed that titania particles were successfully deposited onto the surface of templates. Considering the chemical shift of binding energy of Ti 2p_(3/2) on the titania-coated template, it was inferred that TiO_2 in the coating thin-film is combined onto template surface through chemical bond. TEM images of tiatnia nanostructures showed that the formation of uniform titania nanostuuctures was dependent on the addition amount of water. The diameters of the synthesized nanostructures, mainly in the range of 50-200㎚, correspond with the diameters of the templates. The results confirm that the proposed technique in this study can be utilized as a new method to fabricate the nanostructures.
분체공학 , 유동층 고분자 , 재료 ( 무기 , 유기 ) : 주형을 이용한 실리카 나노구조체 합성
김효중(Hyo Joong Kim),곽중협(Chung Heop Kwak),서태수(Tae Soo Suh),서동수(Dong Soo Suhr) 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.3
A novel technique for the synthesis of silica nanostructures with needle-like template, hydroxyapatite, having nanometer diameter was investigated in this study. The synthetic method consisted of the following main steps: the preparation of nanoprecursor(silica-coated templates), the calcination of nanoprecursor and the removal of templates. The analysis results of scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photo-electron spectroscopy(XPS) for nanoprecursor revealed that silica particles were deposited onto the surface of templates. Further examinations(curve-fitting processing) of the asymmetrical broadening of O 1s peaks in the XPS spectra indicate the presence of multiple oxygen species on the surface. Energy dispersive X-ray spectroscopy(EDS) result confirmed that nanostructures were composed of silicon and oxygen. The diameters of the synthesized nanostructures, mainly in the range of 50-200㎚, correspond to the diameters of the templates. The results confirm that the proposed technique in this study can be utilized as a new method to fabricate the nanostructures.
김효중(Hyo Joong Kim),곽중협(Chung Heop Kwak),서태수(Tae Soo Suh),서동수(Dong Soo Suhr) 한국공업화학회 2002 공업화학 Vol.13 No.3
주형법과 biomimetic process를 혼합한 새로운 방법으로 균일한 티타니아 나노튜브를 합성하였다. 본 합성법은 주형표면에 슬폰기를 갖는 유기자기조립박막의 형성, 티탄 락테이트에 의한 티타니아 피복 및 주형제거 과정으로 구성되어 있다. 광전자 분석을 통해 주형인 나노다공성 알루미나 멤브레인(alumina membrane) 표면애 유기 자기조립 박막과 티타니아 피복이 원활히 형성되었음 확인할 수 있었다. 합성된 티타니아 나노튜브는 티탄과 산소의 조성으로 되어 있었으며 전자현미경으로 관찰된 나노튜브의 직경은 대부분 약 200nm 정도의 크기로 주형의 동공경과 동일한 양상을 보임이 관찰되었는데, 이는 합성 티나니아 나노튜브의 직경을 주형의 동공크기로 원활히 제어할 수 있음을 나타내며 이러한 결과들을 통해 본 연구에서 시도한 새로운 합성법이 나노구조체 합성에 적용 가능함을 확인할 수 있었다. Uniform titania nanotubes were prepared by means of combining biomimetic process and template method Synthetic method consisted of the following main steps; The formation of organic self-assembled mono-layers(SAMs) bearing sulfonate functional group onto template surface, the deposition of titania with titanium lactate and the removal of template. XPS results showed that self-assembled monolayers and titania films were successfully prepared on the surface of nanoporous alumina membrane, and it was found that nanostructures were composed of titanium and oxygen. Transmission electron microscopy images confirmed that the diameter of nanotubes, mainly in the range of about 200 nm, correspond to that of the templates, which provides a promising way to control the diameters of the titania nanotubes. The above results confirmed that the proposed technique in this study can be used as a new method to fabricate nanostructures.
가수분해법에 의한 TiO<sub>2</sub> 피복 운모의 제조(I)
박윤창,김효중,곽중협,서태수,Park, Yoon-Chang,Kim, Hyo-Joong,Kwak, Chung-Heop,Suh, Tae-Soo 한국공업화학회 1997 공업화학 Vol.8 No.5
암모니아수를 이용한 가수분해법에 의해 운모의 이산화티타늄 피복을 시행하여 합성조건의 영향을 조사했다. 운모표면에 균일한 $TiO_2$ 피막을 얻기 위해서는 운모의 입자경이 작고 비표면적이 넓은 쪽이 유리하다. 또한 반응용액상에서 생선된 입자는 운모표면에 유리상태로 부착하여 피막을 불균일화시키므로, 용액상에서의 수화 $TiO_2$ 콜로이드 입자 생성속도를 느리게 제어할 필요가 있다. 본 실험에서 운모의 크기는 $14.7{\mu}m$, 운모 슬러리 용액의 pH는 2.5, $TiOSO_4$ 용액의 F.A.는 291, 반응온도는 $80{\sim}100^{\circ}C$ 정도가 적당하였다. 이상의 결과로부터 균일한 피복을 실현하기 위해서는, 반응온도를 변화시켜 입자의 석출율을 제어하는 일이 필요하다. 이 경우 석출율이 큰 쪽이 균일하고 치밀한 피막을 얻을 수 있었다. 이렇게 하여 얻어진 $TiO_2$ 피복 운모는 $900^{\circ}C$의 소성전후에서 형태에 큰 변화는 없었다. $TiO_2$ hydrate coating on mica in an aqueous solution of $TiOSO_4$ by the hydrolysis using ammonia water studied with emphasis on coating conditions for a uniform coating. For the uniform coating of $TiO_2$ film on mica surface, it was found that smaller mica particles were coated more uniformly compared to larger particles. It was necessary to suppress the rate of formation of hydrated $TiO_2$ particles in solution, which were deposited on mica and generate irregular coating. It was also necessary to control precipitation yield by varying the reaction temperature to obtain uniform coating. More uniform coating was obtained with higher precipitation yield. A uniform dense film was formed when mica particles of average size of $14.7{\mu}m$ is used for mica slurry solution, of which pH is 2.5, and the factor of acidity of $TiOSO_4$ solution is 291, and the solution was kept at $80^{\circ}C$ for 3 hours. The morphology of $TiO_2$ film formed on mica was little affected by firing at $900^{\circ}C$.