Application of Nanostructured Materials SiO2 Aerogel in Construction
do you know? SiO2 Aerogel is a kind of nanostructured material with high transparency and very low thermal conductivity. These properties make this material has a wide range of applications in the construction field. This paper mainly introduces the performance characteristics of Aerogel materials, the research and application status of this material at home and abroad, and discusses the problems to be solved in the further application of SiO2 Aerogel in building materials.
Aerogel is a new type of amorphous solid material that is aggregated by nano-scale particles and uses air as the dispersion medium. Unlike a wet gel that uses a solvent as a dispersing medium, the Aerogel is a lightweight nanoparticulate porous material made by replacing the solvent in the original matrix with air, unlike the conventional sol-gel method Xerogels, sometimes known as solid or frozen fumes because of their translucent color and ultra-light weight. Due to the super thermal insulation properties of Aerogel nano-pores, it has a wide range of potential applications in the field of building energy efficiency. However, application in the field of construction, the cost of synthesis and application is too high, only to reduce the production cost of these super-materials, can make this new functional material has been widely used.
SiO2 Aerogel material
Aerogels, a porous, lightweight material that was discovered 70 years ago, Kistler S. of the Pacific University of California in 1931 used supercritical drying to remove moisture from the hydrogel and got the first The unconstrained aerogels have developed many potential good properties of the Aerogel during these many years of development and evolution. Now we call the SiO2 aerogels A translucent material composed of a nano-SiO2 skeleton, which has a porosity of up to 99%, a density of 0.05-0.2 g / cm3, a gel size of less than 50 nm, a pore diameter smaller than the mean free path of the molecule, 0.03 to 0.05 W / m · K. Therefore, the best application is its porosity and super thermal insulation properties.
Application of SiO2 Aerogel for Construction at Home and Abroad
The application of SiO2 aerogels in construction is still blank in China. The current research focuses on the development of high value-added application products (Figure 1), such as aerospace and pharmaceutical carriers. In foreign countries, since 2000 for the construction of Aerogel materials have been a certain amount of research and application. Now the main research directions are air-energy-saving windows, Aerogel coatings, Aerogel new panels and roof solar collectors.
1. Aerogel energy-saving window
In 2000, a Russian company first developed a new type of Aerogel glass used in the field of building materials. This kind of glass looks similar to ordinary glass in terms of appearance and transparency, but it has extremely high heat resistance, flame retardant, anti-radioactive radiation, and can also tone and absorb sound.
Filling a double layer of glass with a transparent insulating material is a way to reduce heat transfer through the glass layer. Silicon Aerogel materials have a very small pore structure, much smaller than the wavelength of visible light. In Aerogel, air occupies about 95% to 99% of the volume in pores that are smaller than the mean free path of air. As the Aerogel has sufficient compressive strength, can balance the outside air pressure, vacuum airgel window can be used as a transparent separator. And since the evacuated Aerogel is opaque to most infrared radiation, the net radiative heat loss through the airgel window is minimal. At present, the research on aerogels focuses on the development of thermal insulation products with high transparency, good durability, large blocks and low cost.
Reim M and others at the ISOTEG joint project have developed a new architectural Aerogel for roofing insulation that meets both thermal and optical properties and is starting to be used.
2.Aerogel new plate
The use of Aerogel to produce new insulation panels is one of the focuses of research at home and abroad. Boston Cabet, a chemical materials company, has been developing a new Aerogel insulation panel, the Nanogel sandwich panel, in recent years. It is a completely recyclable material that is moisture-proof, mold-proof, germ-proof and UV- Not flammable and has no damaging effect on the ozone layer during its production. Its granular morphology can be tightly compressed into a composite sandwich panel. Kalwall Building Materials of New Hampshire, using advanced manufacturing techniques, successfully designed a Nanogel composite filled sandwich panel - the Nanogel sandwich panel - . The new sheet has a light transmission of 20% and a heat transfer coefficient of only 0.05 W / (m2 · K). At present, the best thermal insulation properties of Kalwall sandwich panels can only pass 10% of the light, while the heat transfer coefficient of 0.l W / (m2 · K). Currently, Kalwall has completed the installation of windows using this new sheet metal, at a cost comparable to that of Kalwall sandwich panels. This also provides economic feasibility for the new sheet to be introduced into the construction market.
In January 2003, a new roof skylight system from Kalwall was installed on the roof of an indoor hot tub at a small hotel in Manchester. The system achieved good results with the new technology Nanogel sandwich panels instead of the Kalwall sandwich panels that have been used for decades. The new sunroof system at the same time enhance the translucency and did not produce ventilation in its insulation effect, but also does not lose heat in the heavy snow in winter, the hot pool temperature can not melt the snow covered skylight .
3.Roof solar collector
Abroad, Aerogel has been used in roof solar collectors for a long time. In the civilian sector, the efficient insulation of solar water heaters and other heat-collecting devices has become a key factor in further enhancing the energy efficiency of solar installations and further enhancing their practicality. As the production technology of nanoporous super insulation material continues to mature and production costs continue to decline, the material is first applied to solar water heaters in homes and units. The application of nanoporous super thermal insulation to water heaters in water storage tanks, pipelines and collectors will more than double the heat gain of existing solar water heaters and reduce heat loss to less than 30% of existing levels.
The front of the collector is filled with granular Aerogel, opaque amorphous silicon on the back as insulation material. The main feature of this particle-filled Aerogel is the production process and particle collocation. There are pores between the particles, and the thermal conductivity of the obtained Aerogel material is somewhat different from that of the bulk Aerogel. Therefore, to control the particle collocation in the Aerogel manufacturing process, the air gap can be minimized.
After years of research and development, JUDA has produced aerogel composites such as Aerogel Insulation Blanket, Aluminum Foil Aerogel Insulation Blanket, Carbon Fiber Aerogel Insulation Blanket, Aerogel Particles, Aerogel Powder and Aerogel Glass.