• 한국분말재료학회지
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• 제18권4호
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• pp.347-358
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• 2011

Two different schemes were adopted to fabricate ordered macroporous structures with face centered cubic lattice of air spheres. Monodisperse polymeric latex suspension, which was synthesized by emulsifier-free emulsion polymerization, was mixed with metal oxide ceramic nanoparticles, followed by evaporation-induced self-assembly of the mixed hetero-colloidal particles. After calcination, inverse opal was generated during burning out the organic nanospheres. Inverse opals made of silica or iron oxide were fabricated according to this procedure. Other approach, which utilizes ceramic precursors instead of nanoparticles was adopted successfully to prepare ordered macroporous structure of titania with skeleton structures as well as lithium niobate inverted structures. Similarly, two different schemes were utilized to obtain disordered macroporous structures with random arrays of macropores. Disordered macroporous structure made of indium tin oxide (ITO) was obtained by fabricating colloidal glass of polystyrene microspheres with low monodispersity and subsequent infiltration of the ITO nanoparticles followed by heat treatment at high temperature for burning out the organic microspheres. Similar random structure of titania was also fabricated by mixing polystyrene building block particles with titania nanoparticles having large particle size followed by the calcinations of the samples.

• Korean Chemical Engineering Research
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• 제57권2호
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• pp.185-197
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• 2019

Deactivation of porous photocatalytic materials was studied using three types of microstructured particles: macroporous titania particles, titania microspheres, and porous silica microspheres containing CNTs and $TiO_2$ nanoparticles. All particles were synthesized by emulsion-assisted self-assembly using micron-sized droplets as micro-reactors. During repeated cycles of the photocatalytic decomposition reaction, the non-dimensionalized initial rate constants (a) were estimated as a function of UV irradiation time (t) from experimental kinetics data, and the results were plotted for a regression according to the exponentially decaying equation, $a=a_0\;{\exp}(-k_dt)$. The retardation constant ($k_d$) was then compared for macroporous titania microparticles with different pore diameters to examine the effect of pore size on photocatalytic deactivation. Nonporous or larger macropores resulted in smaller values of the deactivation constant, indicating that the adsorption of organic materials during the photocatalytic decomposition reaction hinders the generation of active radicals from the titania surface. A similar approach was adopted to evaluate the activation constant of porous silica particles containing CNT and $TiO_2$ nanoparticles to compare the deactivation during recycling of the photocatalyst. As the amount of CNTs increased, the deactivation constant decreased, indicating that the conductive CNTs enhanced the generation of active radicals in the aqueous medium during photocatalytic oxidation.

• Korean Chemical Engineering Research
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• 제56권4호
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• pp.524-535
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• 2018

본 연구에서는 에멀젼 자기조립틀을 활용하여 거대기공을 갖는 타이타니아 분말을 합성하였으며, 자외선 조사를 활용한 광촉매 실험을 통해 상용화된 타이타니아 나노입자와 다공질 타이타니아 분말을 이용한 고초균의 살균 효과를 비교하였다. 다공질 분말의 기공 크기를 달리하여 자외선 조사 시간에 따른 고초균 수의 감소를 측정하였으며, 살균 실험의 최적 조건을 도출하기 위하여 기공 크기에 따른 다공질 타이타니아 분말의 살균력을 비교하였다. 기공 크기가 작아질수록 살균 효과는 증대됨을 관찰하였으며, 광촉매의 활용 및 자외선 조사에 의해 1시간 동안 50% 이상의 고초균이 제거되는 효과를 확인하였다. 또한 활성 화학종의 발생을 촉진하기 위하여 과산화수소의 희석 용액을 광촉매 살균 방식과 결합하였으며, 1시간 동안의 자외선 조사에 의해 균주의 거의 대부분이 사멸되는 등 고초균에 대한 살균 효과를 증진시킬 수 있었다.