Radiative cooling materials prepared by SiO2 aerogel microspheres@PVDF-HFP nanofilm for building cooling and thermal insulation
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Radiative Cooling
Glass microsphere
Passive cooling
Production of aerogel under bead form at Aspen Aerogels Inc. has made possible utilization of this material in various forms, such as pourable, formable, and sprayable insulation with excellent versatility in a variety of applications with critical low weight requirements. Flowable aerogel insulation showed lower thermal conductivity with decreasing the bead size, increasing the packing density and at lower pressures. Formable bead binder panels showed superior thermal performance compared to the bead foam insulation, while the latter showed superior mechanical strength, outperforming the Sprayed on Foam Insulation (SOFI) used on the External Shuttle Tank. Sprayed aerogel insulation has lower thermal conductivity than the SOFI foam at various temperatures and has good mechanical integrity under high enthalpy at 100°C. Aerogel insulation showed improved thermal and dimensional stability compared to polyurethane foams at cryogenic conditions and after heating at 200°C.
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SiO2 aerogel is a three-dimensional network structure solid materials, with the characteristics of low density, low thermal conductivity, high light transmittance, high porosity, high specific surface area and so on, but also has the excellent performance of fireproof and waterproof. It is a rare light, environmental protection, multifunctional material, which has great application prospects in the broad field of building thermal insulation. With the objective of building energy saving, this paper briefly describes the research on SiO2 aerogels, discusses the possibility of large-scale production from preparation of diverse raw materials, raw materials and drying cost reduction and so on, focuses on the application progress in building insulation of SiO2 aerogel glass and SiO2 aerogel thermal insulation coatings; then, from the point of view of the excellent characteristics, this paper presents the application of a SiO2 aerogel material in building energy saving technology, and from the SiO2 aerogel materials in thermal insulation, waterproof, fireproof and simplifying the construction process and other advantages, constructs the application system that SiO2 aerogel materials replace the current thermal insulation material in building energy saving. At last, it makes a conclusion and expectation of the SiO2 aerogel materials application prospect in building thermal insulation.
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Buildings form a major part of the energy demand in Switzerland. Silica aerogels as high performance insulation materials have the potential to reduce the energy demand for heating and cooling. Silica aerogel insulation materials, can achieve the same thermal insulation performance with only half of the thickness of conventional insulation materials. Translucent, superinsulating silica aerogels exhibit the lowest thermal conductivity of any solid known, typically of the order of 0.015 W· m -1 ·K -1 at ambient temperature, pressure, and relative humidity. The interest in silica aerogels as insulation materials is illustrated by the rapid growth of the aerogel market: in 2004, only about 25 million US$ of aerogel insulation materials were sold, but this had increased to about 500 million US$ by 2013. Still the major drawback for a large scale usage of silica aerogels as standard insulating material in the building sector is their production cost. As a result, most of the current aerogel production is used for industrial applications such as pipeline insulation, rather than building insulation. Silicon alkoxides such as tetramethoxysilane (TMOS), and tetraethoxysilane (TEOS) are the most common precursors for the production of silica aerogel. Although the chemistry of silicon alkoxide gelation is straightforward from a chemical perspective, alkoxides have their drawbacks, for example their high production cost due to a multi-step synthesis procedure. Although less reactive, TEOS is often preferred over TMOS because its price is about four times lower and because it is less hazardous. Still the minimum material cost of the raw materials for silica aerogel production is 700-800 CHF/m 3 of aerogel. Our group developed an alternative route for the silica aerogel production using low cost silica precursors and ambient pressure drying technique. This potentially lowers the material cost by a factor of two or more. With the development of more cost-efficient large-scale production technologies, silica aerogel materials have the potential to gain a significant share of the building insulation market by 2020, particularly for retrofit applications.
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Aerogel is widely recognized as a superinsulating material with great potential for enhancing the thermal insulation performance of building walls. It can be applied in various forms such as aerogel plasters (AP), aerogel fibrous composites (AFC), and aerogel concrete (AC) in practical engineering applications. This study aims to investigate the most efficient application form for maximizing building insulation performance while minimizing the amount of aerogel used. To predict the thermal insulation performance of aerogel-insulated walls, a resistance–capacitance network model integrating the aerogels’ effective thermal conductivity model was developed and was validated by comparing it with Fluent simulation software results in terms of surface temperature. Using the validated models, the thermophysical parameters, transient thermal properties, and transmission load were predicted and compared among AP, AFC, and AC walls. The results indicate that using AFC can result in approximately 50% cost savings to achieve the same thermal resistance. After adding a 20 mm thickness of aerogel to the reference wall without aerogel, the AFC wall exhibited the highest improvement in thermal insulation performance, reaching 46.0–53.5%, followed by the AP wall, and then the AC wall, aligning with considerations of microstructural perspectives, thermal resistance distributions, and thermal non-uniformity factors. Therefore, giving priority to AFC use could reduce the required amount of silica aerogel and enhance economic efficiency. These results provide valuable insights for theoretical models and the application of aerogel-insulated walls in building engineering insulation.
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Aerogels servers as a super thermal insulation material mainly due to its high nano-porosity and low thermal conductivity.In this paper the thermal insulation for aerogel was characterized and the properties of doped aerogel composite materials for thermal insulation in high temperature were explained and concluded.Moreover the current application issues of aerogels served as high temperature thermally insulated material were also studied.
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