Thermal conductivity of silica aerogel powders at temperatures from 10 to 275 K

AbstractThe aim of the study was to develop a simple and cost-effective method to improve thermal insulation and hydrophobicity of wood. Herein, we attempted to use commercially available silica aerogel powders suspended in ethanol to treat the wood by a simple vacuum impregnation process. The effects of particle size (20 µm and 40 nm) of silica aerogels and the number of impregnation cycles (1, 3, and 5 cycles) were examined on the thermal conductivity and the surface hydrophobicity. The results showed that the thermal conductivity of silica aerogel-impregnated wood decreased by approximately 38%. The water contact angle of the impregnated wood increased up to the maximum values 153° with a comparison with 80° of the untreated wood, indicating effective hydrophobization after silica aerogel impregnation. The tensile properties of the impregnated wood were found slightly improved. The results indicate that the impregnation of silica aerogel powders in wood can be a facile and efficient approach to prepare wood with thermal insulation and hydrophobicity, which may hold great promise to be employed in manufacturing wood-based materials used in interior decoration and buildings.

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Studies on Thermal Property of Silica Aerogel/Epoxy Composite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.1581 ◽

2007 ◽

Vol 546-549 ◽

pp. 1581-1584 ◽

Cited By ~ 14

Author(s):

Jiu Peng Zhao ◽

Deng Teng Ge ◽

Sai Lei Zhang ◽

Xi Long Wei

Keyword(s):

Thermal Conductivity ◽

Thermal Property ◽

Epoxy Resin ◽

Silica Aerogel ◽

Epoxy Composite ◽

Transfer Model ◽

Insulation Material ◽

Thermal Transfer ◽

Heat Distortion Temperature ◽

Ft Ir

Silica aerogel/epoxy composite, a kind of efficient thermal insulation material, was prepared by doping silica aerogel of different sizes into epoxy resin through thermocuring process. The results of thermal experiments showed that silica aerogel/epoxy composite had a lower thermal conductivity (0.105W/(m·k) at 60 wt% silica aerogel) and higher serviceability temperature (Martens heat distortion temperature: 160°C at 20 wt% silica aerogel). In addition, the composite doping larger size (0.2-2mm) of silica aerogel particle had lower thermal conductivity and higher Martens heat distortion temperature. Based on the results of SEM and FT-IR, the thermal transfer model was established. Thermal transfer mechanism and the reasons of higher Martens heat distortion temperature have been discussed respectively.

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Thermal Conductivity of Silica Aërogel

Industrial & Engineering Chemistry ◽

10.1021/ie50294a016 ◽

1934 ◽

Vol 26 (6) ◽

pp. 658-662 ◽

Cited By ~ 65

Author(s):

S. S. Kistler ◽

A. G. Caldwell

Keyword(s):

Thermal Conductivity ◽

Silica Aerogel

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Silica Aerogel Monoliths Derived from Silica Hydrosol with Various Surfactants

Molecules ◽

10.3390/molecules23123192 ◽

2018 ◽

Vol 23 (12) ◽

pp. 3192 ◽

Cited By ~ 3

Author(s):

Dong Chen ◽

Xiaodong Wang ◽

Wenhui Ding ◽

Wenbing Zou ◽

Qiong Zhu ◽

...

Keyword(s):

Thermal Conductivity ◽

Thermal Stability ◽

Silica Aerogel ◽

Low Cost ◽

Ambient Pressure ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Low Thermal Conductivity ◽

Silica Hydrosol ◽

High Production Cost

Owing to their ultra-low thermal conductivity, silica aerogels are promising thermal insulators; however, their extensive application is limited by their high production cost. Thus, scientists have started to explore low-cost and easy preparation processes of silica aerogels. In this work, a low-cost method was proposed to prepare silica aerogels with industrial silica hydrosol and a subsequent ambient pressure drying (APD) process. Various surfactants (cationic, amphoteric, or anionic) were added to avoid solvent exchange and surface modification during the APD process. The effects of various surfactants on the microstructure, thermal conductivity, and thermal stability of the silica aerogels were studied. The results showed that the silica aerogels prepared with a cationic or anionic surfactant have better thermal stability than that prepared with an amphoteric surfactant. After being heated at 600 °C, the silica aerogel prepared with a cationic surfactant showed the highest specific surface area of 131 m2∙g−1 and the lowest thermal conductivity of 0.038 W∙m−1∙K−1. The obtained low-cost silica aerogel with low thermal conductivity could be widely applied as a thermal insulator for building and industrial energy-saving applications.

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Research on Heat Transfer Characteristics of Nano-Porous Silica Aerogel Material and its Application on Mars Surface Mission

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.924.329 ◽

2014 ◽

Vol 924 ◽

pp. 329-335 ◽

Cited By ~ 5

Author(s):

Cong Hang Li ◽

Shi Chen Jiang ◽

Zheng Ping Yao ◽

Song Sheng ◽

Xin Jian Jiang ◽

...

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Silica Aerogel ◽

Thermal Environment ◽

Porous Silica ◽

Heat Transfer Model ◽

Heat Radiation ◽

Transfer Model ◽

Ambient Conditions ◽

Coupled Heat Transfer

Based on the nanoporous network structure features of silica aerogel, the gas-solid coupled heat transfer model of silica aerogel is analyzed, and the calculation formulas of the gas-solid coupled, the gas thermal conductivity and the heat radiation within the aerogel are derived. The thermal conductivity of pure silica aerogel is calculated according to the derived heat transfer model and is also experimentally measured. Moreover, measurements on the thermal conductivities of silica aerogel composites with different densities at ambient conditions are performed. And finally, a novel design of silica aerogel based integrated structure and thermal insulation used for withstanding the harsh thermal environment on the Martin surface is presented.

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Analysis of the Transient Hot-Wire Method to Measure Thermal Conductivity of Silica Aerogel: Influence of Wire Length, and Radiation Properties

Journal of Heat Transfer ◽

10.1115/1.4025921 ◽

2014 ◽

Vol 136 (4) ◽

Cited By ~ 11

Author(s):

Ellann Cohen ◽

Leon Glicksman

Keyword(s):

Thermal Conductivity ◽

Silica Aerogel ◽

Test Method ◽

Wire Radius ◽

Wire Length ◽

Transient Hot Wire ◽

Hot Wire ◽

End Effects ◽

Transient Hot Wire Method ◽

Wire Method

When the transient hot-wire method is used to measure the thermal conductivity of very low thermal conductivity silica aerogel (in the range of 10 mW/m·K at 1 atm) end effects due to the finite wire size and radiation corrections must be considered. An approximate method is presented to account for end effects with realistic boundary conditions. The method was applied to small experimental samples of the aerogel using different wire lengths. Initial conductivity results varied with wire length. This variation was eliminated by the use of the end effect correction. The test method was validated with the NIST (National Institute of Standards and Technology) Standard Reference Material 1459, fumed silica board to within 1 mW/m·K. The aerogel is semitransparent. Due to the small wire radius and short transient, radiation heat transfer may not be fully accounted for. In a full size aerogel panel radiation will augment the phonon conduction by a larger amount.

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Thermographic Studies of Aerogel Composites

Chemical Product and Process Modeling ◽

10.1515/cppm-2019-0074 ◽

2020 ◽

Vol 15 (2) ◽

Author(s):

K. Keerthi Sanghamitra ◽

A. Yamini ◽

A. Venu Vinod ◽

Neha Hebalkar

Keyword(s):

Thermal Conductivity ◽

Silica Aerogel ◽

Cold Water ◽

High Porosity ◽

Fiber Mats ◽

Aerospace Applications ◽

Thermal Insulating ◽

Wide Range ◽

Composite Form ◽

Insulation Performance

AbstractAerogels are regarded as the superior thermal insulating materials for wide range of temperatures, from cryogenic insulation, cold water diving garments to high temperature applications and even to defense and aerospace applications. For most of such applications, the aerogels are used in composite form rather than monolithic form as aerogels are fragile in nature due to its high porosity of up to 98%. These composites constitute aerogel infiltrated fiber mats to give flexibility, on the other hand, compromises on the insulation performance due to reinforcing aerogel with fibers that have comparatively higher thermal conductivity than silica aerogel. To increase the efficiency, density of the fiber mat needs to be reduced to incorporate higher loading of silica aerogel. Many techniques are being used to study the insulation performance of these composites. This paper presents about the study of insulation performance of fibre mats with different aerogel content and composition using a well-known thermography technique. The morphological, compositional, thermal and physical studies of the fiber mats and its composites using FESEM, EDAX, BET, thermal conductivity etc., are discussed.

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