• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.332-336
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• 2010

Ionic liquid immobilized on mesoporous amorphous silica was prepared from the coupling of 1-(triethoxysilylpropyl)-3-n-alkyl-imidzolium halides with tetraethyl orthosilicate(TEOS) through template-free condensation under strong acidic conditions. The immobilized 1-n-butyl-3-methyl imidazolium bromide ionic liquid on amorphous silica(BMImBr-AS) was proved to be an effective heterogeneous catalyst for the synthesis of dimethyl carbonate(DMC) from transesterification of ethylene carbonate(EC) with methanol. High temperature, high carbon dioxide pressure and long reaction time were favorable for the reactivity of BMImBr-AS. Kinetic studies based on two step reactions revealed that the proposed reaction model fitted well the experimental data. The apparent activation energy was estimated to be 67.4 kJ/mol.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.128-128
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• 2003

Electrochromism (EC) is defined as a phenomenon in which a change in color takes place in the presence of an applied voltage. Because of their low power consumption, high coloration efficiency, EC devices have a variety of potential applications in smart windows, mirror, and optical switching devices. An EC devices generally consist of a transparent conducting layer, electrochromic cathodic and anodic coloring materials and an ion conducting electrolyte. EC has been widely studied in transition metal oxides(e.g., WO$_3$, NiO, V$_2$O$\sub$5/) Among these materials, WO$_3$ is a most interesting material for cathodic coloration materials due to its lush coloration efficiency (CE), large dynamic range, cyclic reversibility, and low cost material. WO$_3$ films have been prepared by a variety of methods including vacuum evaporation, chemical vapor deposition, electrodeposition process, sol-gel synthesis, sputtering, and laser ablation. Sol-gel process is widely used for oxide film at low temperature in atmosphere and requires lower capital investment to deposit large area coating compared to vacuum deposition process.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.6
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• pp.357-362
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• 2015

A novel $TiO_2$-Coconut Shell Powder Composite (TCSPS), prepared by the controlled sol-gel method with subsequent heat treatment, was evaluated as an innovative photocatalytic absorbent for the removal of methylene blue. Optimal preparation conditions of TCSPC were obtained by a response surface methodology and a central composite design model. As compared with the results obtained from one-factor-at-a-time experiments, the values were approximated to the nearest condition of these values and the following experimental parameters were set as the optimum : $600^{\circ}C$ calcination temperature and 20 g of coconut shell powder loading amount.

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.61-66
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• 2011

In this study, we prepared $TiO_2$ with the sol-gel method and controlled physico-chemical properties by a simple heat treatment. All materials were applied to photocatalytic decomposition of methylene blue and the material treated at 473 K showed the highest photocatalytic efficiency. The high performance resulted from a high adsorption amount of methylene blue due to a high surface area of $229.8m^2/g$. However, the material treated at 873 K, despite of a low surface area of $23.8m^2/g$ and a large particle size of 28.38 nm, exhibits a good photocatalytic performance due to the effect of mixed cyrstalline rutile and anatase phases formed by the high heat treatment temperature.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.100-106
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• 2024

To improve charge transfer and surface contact between NiO and perovskite, sol-gel derived NiO is modified with [2-(9H-car-bazol-9-yl)ethyl] phosphonic acid (2PACz) in p-i-n structured perovskite solar cells (PeSCs). The phosphonic acid head group in the 2PACz can bind to the hydroxyl groups on the surface of NiO by a condensation reaction, which results in a better-matched energy level with the valence band of perovskite layers, reducing nonradiative recombination and energy loss. Furthermore, the formation of pin-hole free perovskite films is observed in the 2PACz modified NiO system. Consequently, the combination of sol-gel processed NiO with optimal 2PACz exhibits a higher efficiency of 17.08% and superior stability under ambient air conditions without any encapsulation, compared to a bare NiO based device showing 13.69%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.257-257
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• 2007

고밀도 FeRAM (Ferroe!ectric Random Access Memory) 소자를 개발하기 위해서는 강유전체 물질을 이용한 안정적인 스텍형의 커패시터 개발이 필수적이다. 특히 $(Bi,La)_4Ti_3O_{12}$ (BLT) 강유전체 물질을 이용하는 경우에는 낮은 열처리 온도에서도 균질하고 높은 값의 잔류 분극 값을 확보하는 것이 가장 중요한 과제 중의 하나이다. 불행히도, BLT 물질은 a-축으로는 약 $50\;{\mu}C/cm^2$ 정도의 높은 잔류 분극 값을 갖지만, c-축 방향으로는 $4\;{\mu}C/cm^2$ 정도의 낮은 잔류 분극 값을 나타내는 동의 강한 비등방성 특성을 보인다. 따라서 BLT 박막에서 각각 입자들의 크기 및 결정 방향성을 세밀하게 제어하는 것은 무엇보다 중요하다. 본 연구에서는 16 Mb의 1T/1C (1-transistor/1-capacitor) 형의 FeRAM 소자를 BLT 박막을 적용하여 제작하였다. 솔-젤 (sol-gel) 용액을 이용하여 스핀코팅법으로 BLT 박막을 증착하고, 후속 열처리 공정을 RTP (rapid thermal process) 공정을 이용하여 수행하였다. 커패시터의 하부 전극 및 상부 전극은 각각 Pt/IrOx/lr 및 Pt을 적용하였다. 반응성 이온 에칭 (RIE: reactive ion etching) 공정을 이용하여 커패시터를 형성시킨 후, 32k-array (unit capacitor: $0.68\;{\mu}m$) 패턴에서 측정한 스위칭 분극 (dP=P*-P^) 값은 약 $16\;{\mu}C/cm^2$ 정도이고, 웨이퍼 내에서의 균일도도 2.8% 정도로 매우 우수한 특성을 보였다. 그러나 단위 셀들의 특성을 평가하기 위하여 bit-line의 전압을 측정한 결과, 약 10% 정도의 커패시터에서 불량이 발생하였다. 그리고 이러한 불량 젤들은 매우 불규칙적으로 분포함을 확인할 수 있었다. 이러한 불량 원인을 파악하기 위하여 양호한 젤과 불량이 발생한 셀에서의 BLT 박막의 미세구조를 분석하였다. 양호한 셀의 BLT 박막 입자들은 불량한 셀에 비하여 작고 비교적 균일한 크기를 갖고 있었다. 이에 비하여 불량한 셀에서의 BLT 박막에는 과대 성장한 입자들이 존재하고 이에 따라서 입자 크기가 매우 불균질한 것으로 확인되었다. 또 이러한 과대 성장한 입자들은 거의 모두 c-축 배향성을 나타내었다. 이상의 실험 결과들로부터, BLT 박막을 이용하여 제작한 FeRAM 소자에서 발생하는 불규칙한 셀 불량의 주된 원인은 c-축 배향성을 갖는 과대 성장한 입자의 생성임을 알 수 있었다. 즉 BLT 박막을 이용하여 FeRAM 소자를 제작하는 경우, 균일한 크기의 입자 및 c-축 배향성의 입자 억제가 매우 중요한 기술적 요소임을 알 수 있었다.