2P-157 Fabrication of Nano Porous Silica Aerogel-Polydimethylsiloxane (PDMS) Insulation Film

노영아,김희택,송시내,박성수,심호형,김진이,( Tran Xuan Tin ) 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

The silica aerogel is a suitable material to apply for insulation material with lower thermal conductivity than that of air to save energy. However expensive precursor and drying process were the main issues of the silica aerogel synthesis. Therefore, we demonstrate an ecofriendly route toward silica-PDMS insulation film with low thermal conductivity under ambient pressure. Silica aerogel was synthesized from rice husk ash, which was an agricultural waste to be able to recycle. The silica aerogel is prepared by sol-gel processing and obtained by modification of silica hydrogel surface and dry at ambient pressure. Finally, aerogel film was respectively fabricated by the different content with aerogel in PDMS. Silica aerogel particle size was analyzed by Scanning electron microscope and silica aerogel with high surface area (832.26 m²/g) was characterized by Brunauer Emmett Teller. Then thermal conductivity of silica Aerogel-PDMS insulation film was analyzed by thermal wave system.

Effect of fiber surface-treatment on the properties of ceramic fiber reinforced silica aerogel blanket

송봉관,홍창국 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Silica aerogel is a porous-structured material with low thermal conductivity. Due to this thermal property, silica aerogel has attracted attention for their wide range of applications such as thermal insulator, wave adsorption. However, from the point of view of applications, aerogel has poor mechanical property and it makes they cannot be easily handled. Therefore, fiber-reinforced aerogel blanket has been prepared as an alternative to improve mechanical property. In this study, ceramic fiber reinforced silica aerogel blankets for insulation were prepared under ambient drying using sodium silicate as a source of silica and TMCS as a surface modification agent. The ceramic fiber as a supporting skeleton. To increase thermal insulation property of silica aerogel blanket, its surface treated with acid to enhance compatibility between fiber and aerogel. The silica aerogel blanket is characterized by scanning electron microscope, Fourier transform infrared spectroscopy.

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>

Synthesis of Hydrophobic Silica Aerogel from Rice Husk Biomass

반가람,김희택,박성수 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Silica aerogel has received attention in various fields due to its properties such as large specific surface area, high porosity, low density, and low thermal conductivity. However, general procedure for the synthesis of silica aerogel, which includes expensive precursors and supercritical drying, limits mass production of the aerogel. One way to solve these issues that uses inexpensive starting materials has been developed. For this reason, this study proposes the method for synthesis of silica aerogel from rice husk. Rice husk, which contains high content of silica, is considered as a cheap natural source of silica-based materials. Rice husk ash (RHA) was obtained after thermal decomposition of organic matter in rice husk. Silica was extracted from RHA with sodium hydroxide. The prepared solution was converted into hydrogel via sol-gel process, then the silica gel was experienced solvent exchange and surface modification. After drying at ambient pressure, silica aerogel was attained.

Synthesis of Monolithic Titania-Silica Composite Aerogels with Supercritical Drying Process

Kim, Won-Il,Hong, In-Kwon 한국공업화학회 2003 Journal of Industrial and Engineering Chemistry Vol.9 No.6

Monolithic titania-silica composite aerogels have been prepared by complexation and impregnation methods. In the case of complexation method, monolithic titania-silica composite aerogels had good transparency and homogeneity. Particularly, the sol-gel reaction rate was successfully controlled by modifying tetrabutyl orthotitanate (TBOT) with acetylacetone, and the resulting titania-silica composite aerogel bad very high specific surface area. From W-vis diffuse reflectance spectra and FT-IR spectra, it was evident that the resulting titania-silica composite aerogels had homogeneous Si-0-Ti bonds. However, they had more crack and shrinkage than those prepared by impregnation method after supercritical drying and calcination. It was possible to produce crack-free titania-silica composite aerogels hy impregnation method, hut those composite aerogels showed some drawbacks of low Ti contents and non-uniformly distributed Ti phase. We have investigated the influence of addition of various polymers on the synthesis of monolithic aerogel. As a result, it was possible to enhance the hardness of gel network and consequently get a crack-free titania-silica composite aerogel.

Biomedical applications of silica-based aerogels: a comprehensive review

Fatemeh Soghra Jahed,Samin Hamidi,Monireh Zamani‑Kalajahi,Mohammadreza Siahi‑Shadbad 한국고분자학회 2023 Macromolecular Research Vol.31 No.6

Silica-based aerogels are the appropriate and well-known porous materials that have become interesting in science and technology, especially in the biomedical community. Silica-based aerogels are prepared from silica gels where the liquid is drawn out of the network structure so that its three-dimensional structure is not disturbed. From a nanotechnologist's perspective, silica aerogels will have a special place in nanotechnology because they have low density, large surface area and nanometer pores, and the size of their pores can be adjusted in different ways. In addition to their prominent features, these materials are very attractive despite the possibility of changing their chemical composition according to the desired applications. Recent advances in silica-based aerogels as well-known porous materials have had a great impact on extensive application in various fields mostly in high-tech science and engineering, and biomedical usages, including environmental control, tissue engineering, cancer diagnosis, cancer therapy, biomarking, and drug delivery. Many vital and key issues in the field of (nano) material applications, especially their usages in biomedicine, should be investigated before clinical applications. Some of these important issues include toxicity, bioactivity, compatibility, and so on. Minimal toxicity and maximum biodegradability are two important future challenging issues related to the interaction of (nano) materials and biological systems. So, it is essential to know how to design and synthesize nanoscale structures for medical and biological applications. Engaging with materials whose characteristics can be customized is very important in the medical field. In this review, we intend to provide up-to-date information on silica-based aerogels and applications in biomedicine. Hence, this review summarizes biomedical applications of silica-based aerogels and discusses the potential toxicity induced by them. The present study focuses on the basic concepts and recent advances in silica-based aerogels in the biomedical field.

순수/불투명화 실리카 에어로겔의 기계적 강도 및 열전도도

현상훈,이찬호,김동준,성대진 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.9

The properties of microstructure, hydrophobicity/hydrophilicity, mechanical strength, and thermal conduction of pure/opacified silica aerogels synthesized by the sol-gel supercritical drying technique were investigated. The hydrophobic surface of opacified silica aerogels doped with carbon (0.13 g/cm3 density, 94% porosity, 580 m2/g specific surface area) transformed to hydrophilic surface after heat-treated above 30$0^{\circ}C$. The values of compressive modulus (1.85 MPa) and strength (0.5 MPa) of opacfied silica aerogels were about 20 times higher than those of pure silica aerogels. The mechanical properties of pure silica aerogels heat-treated at $700^{\circ}C$ were also considerably improved without changing their porosity and density. Particularly, compressive modulus and compressive strength of pure silica aerogels GPSed under 100$0^{\circ}C$ and 80 bar were improved 140 and 37 times, respectively. Thermal conductivities of pure/opacified silica aerogels measured at room temperature and 227$^{\circ}C$ were about 0.013 and 0.019 W/m.K, respectively, and were to be found very low value of 0.004 W/m.K below 10 torr pressure at room temperature.

Thermal Insulation Performance of Cotton and PET-based Hybrid Fabrics Impregnated with Silica Aerogel via a Facile Dip-dry Process

Jing Yan,최형열,홍영기,정영규 한국섬유공학회 2018 Fibers and polymers Vol.19 No.4

We report the morphological features and thermal insulation properties of a series of cotton- and PET-based hybrid fabrics impregnated with silica aerogel. For the purpose, commercially available cotton and PET knitted fabrics were dipped into aqueous dispersions including different silica aerogel contents, dried, and stacked to 1, 3, and 5 layers. The SEM images revealed that the silica aerogel particles were well incorporated into cotton or PET knitted fabrics. The thermal insulating performance of the hybrid fabrics as functions of the silica aerogel content and the number of layers of stacked fabrics were characterized by monitoring the surface temperatures of the fabrics on a plate with a wide temperature range of ~50-80 oC using an infrared camera. The higher thermal insulation performance was attained for both cotton- and PET-based hybrid fabrics with higher silica aerogel contents. In addition, 3-layered hybrid fabrics exhibited noticeably improved thermal insulation performance, compared to 1- or 5-layered fabrics. The thermal insulation property of the cotton-based hybrid fabrics was dominantly influenced by silica aerogel than that of PET-based hybrid fabrics. The overall results demonstrated that the cotton- and PET-based hybrid fabrics with silica aerogel manufactured by a facile dip-dry process could be utilized as protective garments, heat-sensitive devices, pipes, automotive, aircrafts, and buildings for thermal insulation applications.

실리카 에어로젤을 이용한 단열 · 내화재 개발에 관한 연구

조명호(Cho, Myung Ho),홍성철(Hong, Sung-Chul) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.10

본 연구에서는 기존의 글라스울의 흡습에 의한 변형을 해결하고 단열성능향상을 위해 실리카 에어로젤을 이용한 단열재를 개발하였다. 글라스울 단열재에 액상의 혼합 바인더를 이용하여 실리카에어로젤이 함침된 글라스울 복합체를 제조 하였다. 액상의 혼합 바인더는 수용성바인더(CMC, carboxymethyl cellulose)와 물에 분산시킨 실리카 에어로젤을 이용하여 준비하였다. 초기 0.048 g/㎤의 밀도를 갖는 글라스울 보드를 준비하고 실리카 에어로젤을 함침시켜 0.065 g/㎤의 밀도를 갖 는 단열보드를 제작할 수 있었다. 이렇게 제조된 실리카 에어로젤 함침 글라스울 보드 복합체는 단일 글라스울 보드의 단열 성능보다 7.4% 향상된 0.0315 W/mK의 열전도율(thermal conductivity)을 나타내었다. 제조된 실리카 에어로젤-글라스울 복합 체는 불꽃 관통시험에서 362초간 내화 저항성을 나타내어 단일 글라스울 보드에 비하여 2.7배나 높은 내화성능을 보였다. 또한 일반 글라스울 보드는 흡습에 의하여 수직방향으로 처짐현상을 나타내는 단점이 있었으나, 실리카 에어로젤이 함침된 보드에서는 실리카 에어로젤의 발수특성으로 인하여 높은 내수성능을 나타내는 것을 확인하였다. In this study, silica aerogel-glass wool composites were developed for improvement of thermal conductivity and overcoming the water adsorption of glass wool boards. Silica aerogel-glass wool composites were prepared by glass wool and silica aerogel with liquid binder. Mixtures with binder were composed of CMC (carboxymethyl cellulose) and silica aerogel for glass wool board. Silica aerogel-glass wool composite boards were had 0.065 g/㎤ density by impregnation silica aerogel where from origin glass wool board at 0.048 g/㎤ density. Thermal conductivity of silica aerogel-glass wool composites were 0.0315 W/mK (up to 7.4% thermal resistance) and fire penetration time came to 362 seconds (up to 2.7 times stronger than origin glass wool board). In addition, hydrophobic aerogel characteristics prevented the adsorption of water onto silica aerogel-glass wool composite boards that was good for lightweight.

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>