Thermal transport in organic and opacified silica monolithic aerogels

Lu, X.; Wang, P.; Arduini-Schuster, M.; Kühn, Joachim; Büttner, D.; Nilsson, Ove; Heinemann, Ulrich; Fricke, J.

doi:10.1016/s0022-3093(05)80457-0

Cited by 81 publications

(33 citation statements)

References 5 publications

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“…The changes in the thermal conductivities followed the same rule as did the changes in the densities. In general, the thermal conductivity of aerogel in the air is contributed by solid heat, gas heat, and radiation transfers . The contributions of radiation transfer can be neglected at ambient temperatures .…”

Section: Resultsmentioning

confidence: 99%

Thermal Insulation Characteristics of Polybenzoxazine Aerogels

Xiao

Zhang

et al. 2019

Macro Materials & Eng

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Polybenzoxazine (PBO) aerogels with low densities and low thermal conductivities are prepared from Bisphenol A (BPA) benzoxazine monomers by ring‐opened polymerisation using HCl as a catalyser at 10 °C. The obtained PBO aerogels have cross‐linked and 3D network structures with the densities ranging from 0.084 to 0.526 g cm−3. The thermal conductivities under different pressures (3–105 Pa, air) and different atmospheres (N2, Ar, and CO2, 105 Pa) are investigated. The thermal conductivities are in the range of 0.0335–0.0652 W m K−1 under ambient pressure and 0.0098–0.0571 W m K−1 at 3 Pa. The thermal transfer mechanism under different gas pressures is analyzed with increasing pressure. Under different atmospheres, the thermal conductivities decrease as the molecular weight of the gas increases. Compared with the traditional organic foam insulating materials of phenolic foam, polyurethane and polystyrene, which have similar apparent densities, PBO aerogels exhibit lower thermal conductivity of 0.0335 W m K−1 than that of traditional organic foam at room temperature.

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Section: Resultsmentioning

confidence: 99%

Thermal Insulation Characteristics of Polybenzoxazine Aerogels

Xiao

Zhang

et al. 2019

Macro Materials & Eng

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“…Moreover, different oxide‐based aerogels have their own unique properties. SiO 2 aerogel with ultralow thermal conductivity and excellent nonflammability was used in 2003 Mars Exploration Rovers for thermal insulation . The gradient aerogel which combines the SiO 2 aerogel with the gradient density structure was used to capture the high‐velocity particles in outer‐space in 2006 Stardust Mission .…”

Section: Preparation and Classification Of Aerogelsmentioning

confidence: 99%

Versatile Aerogels for Sensors

Yang

Zheng

et al. 2019

Small

118

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Aerogels are unique solid‐state materials composed of interconnected 3D solid networks and a large number of air‐filled pores. They extend the structural characteristics as well as physicochemical properties of nanoscale building blocks to macroscale, and integrate typical characteristics of aerogels, such as high porosity, large surface area, and low density, with specific properties of the various constituents. These features endow aerogels with high sensitivity, high selectivity, and fast response and recovery for sensing materials in sensors such as gas sensors, biosensors and strain and pressure sensors, among others. Considerable research efforts in recent years have been devoted to the development of aerogel‐based sensors and encouraging accomplishments have been achieved. Herein, groundbreaking advances in the preparation, classification, and physicochemical properties of aerogels and their sensing applications are presented. Moreover, the current challenges and some perspectives for the development of high‐performance aerogel‐based sensors are summarized.

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“…One method consists in aging the aerogels in liquid media, particularly in alkoxides [66]. Inorganic powders or organic binders can also be added, although they make the silica aerogels more opaque [67] (Chaps. 13 and 15).…”

Section: Technical Characterization Of Aerogels and Development Of Thmentioning

confidence: 99%

History of Aerogels

Pierre¹

2011

Aerogels Handbook

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This chapter presents a historical account of the progressive development of the solid materials known as aerogels. The founding work of Kistler is first summarized. His precursory work attracted the attention of scientists who focused on the physics and chemistry of aerogels, reviewed in the second section. The latter studies allowed for the understanding of how a very high open porosity solid could be maintained when drying a gel and how some specific properties such as transparency or a hydrophobic character could be granted to these materials. In turn, a better knowledge of the scientific basis behind aerogels led to determining their technical characteristics and developing their applications, as addressed in the third section. The most recent developments summarized in the last section aim at a progressive transfer of these applications toward the industry. The Founding Studies by KistlerThe term aerogel was first introduced by Kistler in 1932 to designate gels in which the liquid was replaced with a gas, without collapsing the gel solid network [1]. While wet gels were previously dried by evaporation, Kistler applied a new supercritical drying technique, according to which the liquid that impregnated the gels was evacuated after being transformed to a supercritical fluid. In practice, supercritical drying consisted in heating a gel in an autoclave, until the pressure and temperature exceeded the critical temperature T c and pressure P c of the liquid entrapped in the gel pores.This procedure prevented the formation of liquid-vapor meniscuses at the exit of the gel pores, responsible for a mechanical tension in the liquid and a pressure on the pore walls, which induced gel shrinkage. Besides, a supercritical fluid can be evacuated as gas, which in the end lets the "dry solid skeleton" of the initial wet material. The dry samples that were obtained had a very open porous texture, similar to the one they had in their wet stage.Overall, aerogels designate dry gels with a very high relative or specific pore volume, although the value of these characteristics depends on the nature of the solid and no official convention really exists (Chap. 21). Typically, the relative pore volume is of the order of 90% in the most frequently studied silica aerogels [2]

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Thermal transport in organic and opacified silica monolithic aerogels

Cited by 81 publications

References 5 publications

Thermal Insulation Characteristics of Polybenzoxazine Aerogels

Thermal Insulation Characteristics of Polybenzoxazine Aerogels

Versatile Aerogels for Sensors

History of Aerogels

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