Aerogel is a nanoporous solid material, the main component of which is ultrafine particles. The material has the characteristics of large specific surface area, high porosity and small particle size. Aerogel, also known as solid smoke or frozen smoke, is currently regarded as the lightest solid material. Due to the special physical structure of aerogel, it has strong fireproof and heat insulation properties, which can be widely used in the construction field, and has a good development prospect in the field of building energy conservation.
Heat insulation, heat preservation, lightweight, aerogel materials meet the requirements of building energy saving, in line with the development trend of building lightweight.
Since the 1990s, aerogels have received widespread attention worldwide, and countries have invested a lot of money and manpower in their research. Domestic research on aerogel has also accumulated a lot of research and development experience, which has created favorable conditions for the promotion and application of aerogel materials.
Aerogels can be divided into inorganic aerogels, organic aerogels and carbon aerogels. Among them, inorganic aerogels are prepared from organic metal substances by supercritical drying method, and finally form a low-density amorphous solid Material. Inorganic aerogels come in many forms, common ones are ceramic powders, multiple oxide aerogels, ultrafine metals, and unit oxide aerogels. The main materials of organic aerogel are formaldehyde and quinone, and the preparation process is only slightly improved on the preparation process of inorganic aerogel. Carbon aerogel is mainly a kind of nano-carbon material obtained by carbonizing thermosetting organic aerogel. It mainly has the characteristics of amorphous state, light weight, and porous. This material has strong electrical conductivity.
Aerogelmaterials have many properties, and one of the most important properties for building energy-saving applications is thermal insulation. Aerogel materials have high porosity and outstanding heat transfer function. First, the aerogel material has a low density, and the heat propagation path is long in the aerogel structure, which greatly reduces the heat transfer efficiency. Secondly, the particle size of the aerogel material is small, usually below 20nm, which will limit the free movement of air molecules in the aerogel material and reduce the convective thermal conductivity of the air. Aerogels with extremely low thermal conductivity block most infrared radiation, which also has low wavelengths of thermal radiation. Therefore, aerogel has a good thermal insulation effect.
The density of aerogel materials is between 0.16 and 4.0kg/m³, which is much lower than that of other materials, which is in line with the development trend of lightweight construction. In addition, aerogel materials also have the advantages of fire prevention, sound insulation, and corrosion resistance.
Adding aerogel with low thermal conductivity to traditional mortar and concrete can effectively improve material performance.
Aerogel thermal insulation mortar is made of Portland cement as the gelling agent, adding aerogel, SiO2, and glass beads. The size of glass beads is much larger than that of aerogel particles, which can be filled into the mortar matrix, and the smaller aerogel particles further fill the gaps, so that the porosity is reduced as much as possible, and the thermal conductivity of the thermal insulation mortar also decreases. The expected building insulation effect can be obtained. Apply thermal insulation mortar to the surface of the building's exterior wall. The thicker the mortar, the greater the temperature difference between inside and outside. It can be seen that the aerogel thermal insulation mortar can block heat and improve the overall thermal insulation and energy saving effect of the building structure. After adding aerogel to concrete, the weight and thermal conductivity of concrete will be significantly reduced, but it will also damage the mechanical strength of concrete, so aerogel concrete should be avoided in load-bearing walls.
Aerogel powder can be used in interior wall coatings, as a supplement to structural heat insulation measures, not only for the insulation of building interior walls, but also for exterior walls and roof insulation.
Inner wall insulation is an important part of building insulation engineering, but it is often easily overlooked. Internal heat diffuses through the inner wall and is transferred to the outside. The insulation of the inner wall needs to meet the most basic insulation requirements, and it must also have a fireproof function, and non-polluting materials should be selected. The use of aerogel insulation panels can improve thermal insulation and sound insulation effects, and can also meet the fire protection requirements of over 400°C. Aerogel powder can be used in interior wall coatings, as a supplement to structural insulation measures, not only for building interior walls, but also for exterior walls and roof insulation. The main materials of aerogel powder products are aerogel and nano-SiO2, which are made through special processes, and the pore size is extremely small, which can meet the requirements of thermal insulation performance and can be widely used in building thermal insulation layers.
The aerogel material is applied to the water storage tank, heat collector, pipeline and other parts of the water heater, and the heat loss can be reduced by less than 30% compared with the past.
Aerogel materials have been used in roof solar collectors for a long time. They are mainly used in thermal insulation devices of solar water heaters, which can effectively improve the efficiency of solar energy utilization, make them more practical, and meet people's daily needs. The application of aerogel materials in the water storage tanks, heat collectors, pipes and other parts of the water heater can increase the heat collection efficiency by at least 1 times compared with ordinary solar water heaters, and the heat loss can be reduced by less than 30% compared with the past.
Aerogel felt has remarkable hydrophobicity and thermal insulation characteristics, which can improve the insulation effect of pipelines, and is an ideal thermal insulation material. The pipe can be wrapped with aerogel felt as the main insulation layer of the insulation structure, and the metal protection layer is used as the second insulation measure to protect the aerogel insulation layer. When wrapping multi-layer aerogel felt, the staggered overlapping method can be used to enhance the thermal insulation performance. The aerogel felt has better tensile strength, flexibility and compression resistance, and the construction of the insulation layer is relatively simple. In addition, the hydrophobicity of the aerogel blanket keeps the thermal conductivity almost unchanged during use, and the aerogel insulation structure is more energy-saving than the traditional insulation structure.
The use of aerogel glass can improve the thermal insulation effect, reduce the influence of solar radiation, and meet people's needs.
Aerogel glass usually reduces the heat transfer coefficient of glass in the form of hollow, vacuum and interlayer, and can improve the noise reduction ability. The energy-saving effect of aerogel glass is obvious. In hot summer and cold winter regions, aerogel glass can weaken solar radiation in summer and reduce heat loss by about 20%. In winter, aerogel glass can block about 40% of indoor hot air, which has good energy-saving value. Although windows make up only a small portion of the building envelope, energy consumption accounts for about 25% of the total energy consumption. The main reason is that building windows do not play a role in insulating, and internal heat tends to diffuse to the outside through windows. In summer, sunlight shines directly into the room through the windows, causing the indoor temperature to rise. The use of aerogel glass can improve the thermal insulation effect, reduce the impact of solar radiation, and meet people's needs. Compared with ordinary glass, aerogel glass has higher light transmittance, and has little effect on indoor lighting. At this stage, there are two main types of aerogel glass, one is laminated glass and the other is coated glass. Laminated glass consumes more aerogel, and the corresponding cost is higher. In contrast, the price of coated glass is much lower than that of laminated glass, and it has good thermal insulation performance, up to 88% light transmittance, and will not affect indoor lighting.
Aerogel thermal insulation materials are Class A non-combustible materials, which can be used in building fireproof structures.
Aerogel concrete composite wall is a lightweight thermal insulation wall material made of aerogel filling and modified lightweight aggregate. Filling aerogel filling in expanded perlite can prepare aerogel expanded perlite and use it as lightweight aggregate to form a new type of thermal insulation material. Aerogel expanded perlite has a compressive strength of 4.39MPa and a thermal conductivity of 0.062W/(m·K). The aerogel structure is mainly a porous network, which can cover the surface of the steel structure with an aerogel heat-insulating composite material to prolong the burning time without producing toxic substances. At the same time, the aerogel material can hinder the spread of fire, is a class A non-combustible material, and can be used in building fireproof structures.
Aerogel has excellent performance, but the strength of pure aerogel material is low. The research and development of composite aerogel materials should be further strengthened, and the aerogel material should be reasonably combined with other materials to effectively enhance the performance of the material and make up for the aerogel. Insufficient material. At the same time, it is necessary to further reduce the cost of aerogel preparation and use in order to occupy a larger share in the construction market and effectively improve the comprehensive benefits of aerogel materials.