• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.51-57
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• 2018

The objective of the present study is to examine the feasibility on the development of high-insulation concrete using aerogels with hydrophilic surface treatment. To prevent the segregation and enhance the dispersibility of agerogels in the cement pastes, the substrate of aerogels was modified to be hydrophobic property using surfactant. The modified aerogels were added from 0% to 100% of the cement volume at the interval of 25% under the constant cement content. Some cement pastes showed segregation phenomenon and flocculation of aerogels during mixing phase. The addition of aerogels decreased the compressive strength of cement pastes but enhanced the thermal conductivity. The thermal conductivity of pastes with 100% aerogels was lower by 43% when compared with that measured in the conventional paste. To improve the compressive strength and insulation capacity of concrete containing aerogels, a reliable surface treatment method of aerogels needs to be further investigated.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.829-834
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• 1999

The silica aerogels opacified via adding oxides were prepared by the sol-gel supercritical drying technique and their characteristics of mechanical strength and thermal conduction were investigated. The compressive strength of SiO2-10 mol% TiO2 and SiO2-10mol% Fe2O3 aerogels were 0.11 and 0.047 MP a respectively much higher than 0.025 MPa of pure silica aerogels. The thermal conductivity of silica aerogels opacified by TiO2 was as low as 0.02505 W/m${\cdot}$K at $400^{\circ}C$ It was found that the TiO2 -opacifier for improving mechanical strength and suppressing high temperature conduction of pure silica aerogels was more effective than the Fe2O3 -opacifier

• Composites Research
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• v.33 no.6
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• pp.336-340
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• 2020

In this study, carbon aerogels (CA) were prepared by sol-gel polycondensation of resorcinol and furfural in isopropanol using hexamethylenetetramine as a catalyst, and then directly drying the organic gels under isopropanol freeze-drying conditions, followed by carbonization under a nitrogen atmosphere. The preparation conditions of the CA were explored by changing the mole ratio of resorcinol to furfural. The effect of the preparation conditions on the pore structure of the CA was studied by nitrogen adsorption isotherms. The characteristics of the CA were studied by scanning and transition electron microscopy, and infrared spectrometry. The accessibility of pores and performance of the CA as an electrode in electric double layer capacitors were also electrochemically investigated. As a result, BET surface area and specific capacitance increased with the molar ratio of resorcinol to catalyst (R/C) ratio; the maximum values of 765 ㎡/g and 132 F/g were achieved at the R/C ratio of 200, respectively. Consequently, it was confirmed that increasing the R/C ratio increased the average pore size of the CA electrode, which improved the rate capability of the system.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.963-968
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• 1999

The global environmental problems have been caused by the release of CFCs. Therefore, methods for safe destruction of recoverd CFCs will be eventually needed. The objective of this study was to develop and test a catalyst operating at a mild condition for the decomposition of CFC-113. In this work, catalytic oxidative decomposition of CFC-113 was carried out over aerosol $TiO_2/SiO_2(ATS)$ catalysts prepared by the sol-gel method. All ATS catalysts(Ti/Si mol ratio=1, 2, 2.33, 4) showed high initial activity. However, the deactivation of ATS catalysts was found that more remarkable due to an attack of fluorine and the destruction of ATS structure(Si-F reaction) from analyses of SEM-EDX, XRD than $TiO_2/SiO_2(ATS)$ catalyst prepared by the precipitation method. ATS catalysts prepared by more acidic prehydrolysis condition were found to have still more activity and longer life-time by increasing of acidity. The activity of ATS catalyst also depend on the content of $TiO_2$. There was reason that the acidity of the ATS catalyst was increased with the increased content of $TiO_2$ from 50 to 80 mol %. Solid superacid catalyst ($ATX/SO_4{^{2-}}$) modified with $H_2SO_4$ solution was prepared for high activity and lower deactivation. The reaction of $ATS/SO_4{^{2-}}$ catalyst also exhibited even higher activity and lower deactivation than the original ATS catalyst. It is suggested that the addition of the sulphate species clearly inhibit the deactivation.

• Fire Science and Engineering
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• v.32 no.1
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• pp.81-88
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• 2018

Air and ultra lightweight aerogels were used to lighten the weight of the firefighters' protective clothing. In order to lighten the firefighters' protective clothing composed of 3 layers (outer shell, mid-layer, lining), it was most effective to replace the lining which occupied the largest weight in the total weight with the new materials. Thermal protective performance tests were carried out on flame (ASTM D 4108), radiant heat (KS K ISO 6942) and mixing heat (KS K ISO 17492) of flame and radiation. When the lining felt was replaced with an air layer, the air layer must be at least 3 mm to meet the KFI and ISO standards for the thermal protective performance. However, even if the thickness of the air layer increased to 10 mm, the thermal protective performance was lower than that of the existing products. When the felt was replaced with aerogels, the TPP rating (ASTM D 4108) satisfied the KFI standard at the 2 mm thickness of the aerogels. When the thickness of the aerogels was 3 mm, the TPP rating was improved about 140% compared to the existing products. It was confirmed that not only weight reduction but also thermal protective performance was improved by use of aerogels. However, due to the fragile nature of aerogels, a method of fixing them to a constant thickness between layers constituting a firefighters' protective clothing should be considered in the future.