Effect of cationic and non-ionic surfactants on the microstructure of ambient pressure dried zirconia aerogel

Jung, Hae-Noo-Ree,Han, Wooje,Cho, Hyung Hee,Park, Hyung-Ho American Scientific Publishers 2017 Materials express Vol.7 No.4

Characterization of Mechanical Property Change in Polymer Aerogels Depending on the Ligand Structure of Acrylate Monomer

Lee, Kyu-Yeon,Jung, Hae-Noo-Ree,Mahadik, D.B.,Park, Hyung-Ho The Korean Microelectronics and Packaging Society 2016 마이크로전자 및 패키징학회지 Vol.23 No.3

In an effort to overcome the weakness of aerogel, polymer aerogels have been prepared by copolymerizing the different types of monomers through sol-gel process. Polymerizing the successive phase of a high internal phase emulsion, which has interconnected porous structure, porous polymer aerogel can be manufactured. In this paper, we use the styrene/divinylbenzene chain as a basic monomer structure, and additionally use 2-ethylhexyl methacrylate (2-EHMA) or 2-ethylhexyl acrylate (2-EHA) as monomers for distinguishing the visible mechanical properties of synthesized polymer aerogel. We can observe the different tendency of polymer aerogels by kinds of monomer or ratio. Flexibility and microstructure can be changed by the types of monomer. EHA polymer aerogel shows high flexibility and thin microstructure, and EHMA polymer aerogel shows high hardness and thick microstructure. EHA/EHMA polymer aerogel shows the intermediate nature between them. By utilizing the mechanical properties of three types of polymer aerogels to adequate situation or environment, polymer aerogels could be used as drug agent, ion exchange resin, oil filter and insulator, and so on.

Improvement in the high temperature thermal insulation performance of Y₂O₃ opacified silica aerogels

Parale, Vinayak G.,Jung, Hae-Noo-Ree,Han, Wooje,Lee, Kyu-Yeon,Mahadik, Dinesh B.,Cho, Hyung Hee,Park, Hyung-Ho Elsevier 2017 Journal of Alloys and Compounds Vol.727 No.-

<P><B>Abstract</B></P> <P>To improve the high-temperature thermal insulation characteristics of silica aerogels, it is important to reduce the radiative heat transfer. This can be achieved by Y<SUB>2</SUB>O<SUB>3</SUB> doping in the silica sol to opacify the infrared radiation of silica aerogels. The purpose of the present work was to study the effect of Y<SUB>2</SUB>O<SUB>3</SUB> incorporation on the structural and physicochemical properties of opacified silica aerogels prepared by a simple ambient pressure drying method. The influence of Y<SUB>2</SUB>O<SUB>3</SUB> addition on specific extinction coefficient and high temperature thermal insulation of prepared aerogels were investigated. The synthesized aerogels were lightweight and crack-free, with a granular, nanoporous morphology. The specific surface area, pore diameter, and bulk density of the prepared samples were 917.5–937.6 m<SUP>2</SUP>/g, 5.64–6.58 nm, and 0.047–0.076 g/cm<SUP>3</SUP>, respectively. The thermal conductivity of opacified silica aerogel at 1000 K was 0.080 W/(m.K), which was lower than the unopacified silica aerogel and it was around 0.104 W/(m.K) at same temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Low density Y<SUB>2</SUB>O<SUB>3</SUB> opacified SiO<SUB>2</SUB> aerogels by APD for HT thermal insulation. </LI> <LI> Y<SUB>2</SUB>O<SUB>3</SUB> effect on structural, physicochemical and morphological properties of aerogels. </LI> <LI> Aerogels: 917.5 m<SUP>2</SUP>/g surface area, 3.422 cm<SUP>3</SUP>/g pore volume, 6.58 nm pore diameter. </LI> <LI> 0.080 W/(m.K) of thermal conductivity of Y<SUB>2</SUB>O<SUB>3</SUB> opacified aerogels at 1000 K. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Elastic and Superhydrophobic Monolithic Methyltrimethoxysilane-based Silica Aerogels by Two-step Sol-gel Process

Mahadik, D.B.,Jung, Hae-Noo-Ree,Lee, Yoon Kwang,Lee, Kyu-Yeon,Park, Hyung-Ho The Korean Microelectronics and Packaging Society 2016 마이크로전자 및 패키징학회지 Vol.23 No.1

The flexible and superhydrophobic properties of silica aerogels are extremely important material for thermal insulation and oil spill cleanup applications for their long-term use. Flexible silica aerogels were synthesized by using a two-step sol-gel process with precursors, methyltrimethoxysilane (MTMS) followed by supercritical drying. Silica aerogels were prepared at different molar ratio of methanol to MTMS (M). It was observed that the silica aerogels prepared at M=28 were monolithic but inelastic in nature, however, for M=35, the obtained aerogels were monolithic, elastic in nature with less shrinkage. The microstructural studies were carried out using scanning electron microscopy and surface area measurements. The hydrophobicity was confirmed by Fourier transform Infrared spectroscopy and water contact angle measurements. The detailed insight mechanism for flexible nature of silica aerogels and hydrophobic behavior were studied.

Ambient pressure dried tetrapropoxysilane-based silica aerogels with high specific surface area

Parale, Vinayak G.,Han, Wooje,Jung, Hae-Noo-Ree,Lee, Kyu-Yeon,Park, Hyung-Ho Elsevier 2018 Solid state sciences Vol.75 No.-

<P><B>Abstract</B></P> <P>In the present paper, we report the synthesis of tetrapropoxysilane (TPOS)-based silica aerogels with high surface area and large pore volume. The silica aerogels were prepared by a two-step sol-gel process followed by surface modification via a simple ambient pressure drying approach. In order to minimize drying shrinkage and obtain hydrophobic aerogels, the surface of the alcogels was modified using trichloromethylsilane as a silylating agent. The effect of the sol-gel compositional parameters on the polymerization of aerogels prepared by TPOS, one of the precursors belonging to the Si(OR)<SUB>4</SUB> family, was reported for the first time. The oxalic acid and NH<SUB>4</SUB>OH concentrations were adjusted to achieve good-quality aerogels with high surface area, low density, and high transparency. Controlling the hydrolysis and condensation reactions of the TPOS precursor turned out to be the most important factor to determine the pore characteristics of the aerogel. Highly transparent aerogels with high specific surface area (938 m<SUP>2</SUP>/g) and low density (0.047 g/cm<SUP>3</SUP>) could be obtained using an optimized TPOS/MeOH molar ratio with appropriate concentrations of oxalic acid and NH<SUB>4</SUB>OH.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optically transparent and hydrophobic silica aerogel using TPOS was successfully synthesized. </LI> <LI> Sol-gel compositional effect using TPOS on the polymerization of aerogels was firstly reported. </LI> <LI> MeOH/TPOS and acid/base concentrations strongly influenced on the physical and textural properties. </LI> <LI> High surface area (938 m<SUP>2</SUP>/g) and low density (0.047 g/cm<SUP>3</SUP>) are obtained using TPOS as precursor. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Role of oxalic acid in structural formation of sodium silicate-based silica aerogel by ambient pressure drying

Nah, Ha-Yoon,Parale, Vinayak G.,Jung, Hae-Noo-Ree,Lee, Kyu-Yeon,Lim, Chang-Hyun,Ku, Yang Seo,Park, Hyung-Ho Springer-Verlag 2018 Journal of sol-gel science and technology Vol.85 No.2

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Facile synthesis of hydrophobic, thermally stable, and insulative organically modified silica aerogels using co-precursor method

Parale, Vinayak G.,Lee, Kyu-Yeon,Jung, Hae-Noo-Ree,Nah, Ha-Yoon,Choi, Haryeong,Kim, Tae-Hee,Phadtare, Varsha D.,Park, Hyung-Ho Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.4

<P><B>Abstract</B></P> <P>Silica aerogels have low density and high specific surface area, but there are restrictions regarding their durability and commercialization owing to their fragile nature and the strong moisture absorbing behavior of the siloxane network. To overcome these restrictions, this study evaluated hybrid organically modified silica (ORMOSIL) aerogels by employing 3-(trimethoxysilylpropyl) methacrylate (TMSPM) in tetraethyl orthosilicate (TEOS) through a two-step sol-gel co-precursor method. The methacrylate organic groups were incorporated into the silica networks via reactions between the Si-OH moieties in silica aerogels, resulting in ORMOSIL aerogels. The properties of the ORMOSIL aerogels were strongly affected by the amount of TMSPM co-precursor. The highest concentration of TMSPM (30wt%) resulted in ORMOSIL aerogels with improved characteristics when compared with the pristine TEOS-based silica aerogels, such as hardness (0.15GPa), Young's modulus (1.26GPa), low thermal conductivity (0.038W/mK), high water contact angle (140°), and high thermal stability (350°C).</P>

산 촉매가 물유리 기반 실리카 에어로겔의 기공구조에 미치는 영향

나하윤,정해누리,이규연,구양서,박형호,Nah, Ha-Yoon,Jung, Hae-Noo-Ree,Lee, Kyu-Yeon,Ku, Yang Seo,Park, Hyung-Ho 한국마이크로전자및패키징학회 2017 마이크로전자 및 패키징학회지 Vol.24 No.3

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. Water glass is much cheaper than silicon alkoxide, so it has advantage for commercialization. A condensation by acid catalyst makes considerable effect about the properties of water glass based silica aerogel among many factors in silica aerogel process. The pore structural properties of water glass based silica aerogel such as specific surface area and pore size distribution have been investigated through the changes in the amount and the kinds of acid catalyst. It has been confirmed that water glass based silica aerogel is affected by various conditions of catalyst in the condensation reaction such as the kind, concentration, and the amount of mole of acid catalyst on the properties of final products. Especially, it is checked that the effect of mole of acid is more prominent than that of concentration. In the case for conventional method with introducing 4M HCl in condensation step, the silica aerogel could be synthesized which has $394m^2/g$ of specific surface area, 2.20 cc/g of pore volume, 22.3 nm of average pore size, and 92.53% of porosity. On the other hand, when 4M sulfuric acid was used with 73 mmol at the condensation step of water glass based silica aerogel, the pore structural characteristics of water based silica aerogel showed better properties than the case of using HCl, for example, specific surface area was measured as $516m^2/g$, and pore volume, average pore diameter, and porosity were obtained as 3.10 cc/g, 24.1 nm, and 96.1%, respectively.