Cool techs: rare earth coating on glass can save energy by 25% and 40%.

SMM: recently, the EASTO.1098 heat-off rare earth glass coating of Baotou rare Earth Research Institute has been identified as the first batch of new materials at the Inner Mongolia Autonomous region level in 2020.

"our material is new because in terms of functionality, it can be applied directly to the glass surface and can quickly cool down within 3 hours, with a maximum adjustable temperature of 715 degrees and an energy saving of 25% and 40%." Said Dr. Yin Jian of Tianjin Branch of Baotou rare Earth Research Institute.

It is reported that the coating is a stable and high-performance rare earth nanocomposite thermal insulation coating product prepared by the rare Earth Research Institute and Chengdu Yitu Jiewei Technology Co., Ltd. through the preparation research and performance screening of ternary rare earth co-doped boride materials.

"We have successfully developed more than ten kinds of industrial preparation technology of rare earth nano-thermal slurry. At present, this technology has published 2 papers and applied for 3 domestic invention patents and 1 design patent." Lu Fei, a senior engineer at Baotou rare Earth Research Institute, said that the coating is ahead of similar products such as glass film, low-E glass and insulating glass in the market in terms of heat breaking effect, convenience and stability.

It is imperative to optimize the thermal insulation performance of glass.

In the 13th five-year Plan for Building Energy Saving and Green Building Development, it is proposed that by 2020, the energy efficiency of new urban buildings in China will be increased by 20%, the proportion of green building area will be more than 50%, and 40% of building energy consumption will be consumed on glass doors and windows. therefore, it is particularly important to improve the thermal insulation performance of glass.

As we all know, the heat energy on the earth's surface mainly comes from sunshine, and the spectrum of sunlight is mainly concentrated in the range of 200-2500nm, in which: 200-400nm is ultraviolet, its energy accounts for about 5% of the total energy of sunlight, and its energy accounts for about 45% of the total energy of sunlight in the range of 400-720nm, while the energy in the range of 720-2500nm is infrared, which accounts for half of the total energy of sunlight.

Infrared is invisible to the human eye, so how to effectively block the infrared and improve the thermal insulation performance of glass without affecting the transmission of visible light is one of the important and difficult points in the research and development of technology at home and abroad. At present, the research and development of thermal insulation films with high quality and high permeability are mainly concentrated in developed countries such as the United States and Japan. "although there are many ways to block sunlight in the existing technology, each of them has many problems." Lu Fei said.

Lu Feina currently the most commonly used building thermal insulation glass is low thermal radiation glass (Low-E) as an example to explain its shortcomings. This kind of glass is coated on the surface of ordinary glass to achieve thermal insulation. However, after this kind of glass is widely used in the building exterior wall, although it has a good thermal insulation and thermal insulation performance to the building itself, it will reflect a lot of sunlight and cause a lot of light pollution problems.

People working in a light-polluted environment for a long time will lead to vision decline, dizziness, insomnia, palpitation, loss of appetite and depression and other symptoms, seriously affecting people's physical and mental health. In addition, Low-E glass can not achieve thermal insulation through post-painting and other methods. In addition, due to the oxidation of the metal layer, the life of the surface layer is much lower than that of the glass itself, which leads to the Low-E glass can not be used as a stock of building glass upgrading.

In addition, colored glass not only absorbs heat, but also absorbs visible light, which greatly sacrifices visible light transmittance and presents obvious color while achieving thermal insulation effect, which greatly limits its application in scenes that require high visible light transmission, such as automobile front screen glass.

"at present, cesium tungsten bronze, which is the most widely used infrared absorption material, has the best infrared absorption effect, but it will appear photochromism under ultraviolet irradiation, and under heating conditions, it will have an irreversible oxidation reaction with water and oxygen to form tungsten trioxide and lose its infrared absorption properties." Yin Jian said.

A new heat-breaking coating came out

From the above analysis, it can be seen that the thermal insulation principle of traditional Low-E glass and glass products is to achieve thermal insulation effect by coating on the surface of ordinary glass. After coating, Low-E glass can reflect the far infrared above the wavelength 2500nm, but it will also cause pollution. Being able to absorb photons may be a better choice.

"We are also inspired by the local surface plasmon resonance ((LSPR)) phenomenon, because the surface electrons of gold nanoribbons with a certain aspect ratio can resonate with incident photons of a certain frequency and strongly absorb incident photons. By adjusting the particle size and morphology of the material, we can achieve selective absorption of infrared photons, which can be used as infrared absorption materials." Lu Fei said.

Lu Fei said that their coating is based on rare earth compounds. on the one hand, because boron atoms have strong electronegativity, they can form a strong force with rare earth elements. the resulting rare earth nano-thermal materials have excellent acid and alkali resistance. On the other hand, in the formed rare earth nano-boride materials, the outer electrons of the rare earth elements provide a large number of free electrons. When the photons of the incident light are excited, the free electrons resonate with the incident photons, which shows the endothermic ability macroscopically.

In addition, the wavelength range of incident photon resonance can be further controlled by adjusting the type of rare earth elements and the amount of doping. Using this method, the R & D team successfully developed a high-performance rare earth nanocomposite heat-breaking material with good weather resistance, which perfectly solved the problem of lack of environmental stability of existing materials and inability to absorb infrared spectrum.

"the red and ultraviolet barrier of the coating we developed is more than 90%, and the visible light transmittance is greater than or equal to 70%. The heat breaking effect, convenience and stability are ahead of similar products such as glass film, Low-E glass and insulating glass." Wen Yongqing said that they also did several experiments, taking the comparison of the effects of LOW-E insulating glass and heat-breaking rare earth adhesive glass as an example, under the same conditions, double silver LOW-E insulating glass and heat-breaking rare earth adhesive glass were put in front of infrared lamp respectively, the infrared calorific value of double silver LOW-E insulating glass was 3417, the UV value of double silver LOW-E insulating glass was 4857, the barrier rate was 50%, and the infrared calorific value of insulating rare earth glass was 320, The UV value of heat-breaking rare earth glue glass is 19.4, and the barrier rate is as high as 99.8%.

It can be seen that even the double-silver LOW-E hollow glass with excellent performance in the market lags behind the single-layer RE glass with heat-off rare earth technology in heat insulation, sun protection and energy saving.

Application of coating promotes the Development of Greening in China

In November 2019, the rare Earth Research Institute and Yi Tu Jiewei Science and Technology established a joint laboratory of heat-breaking rare earths to jointly promote the industrialization process of new rare earth nano-thermal insulation coatings, and the preparation technology of new rare earth nano-thermal insulation materials and coating industry has broken through.

"at present, we have built the first pilot production demonstration line in China with a monthly output of 800 kg of rare earth nano-hot slurry, which can save energy by 25% and 40%." Yang Jie, general manager of Yitu Jiewei Technology, said that the coating index developed is similar to or even better than foreign products, realizing "corner overtaking" at the technical level, filling in the blank of domestic heat-off glass coating materials. at the same time, it can completely replace imported products.

As we all know, solar thermal energy exists mainly through infrared radiation and has the characteristic of transfer from high temperature to low temperature.

Therefore, the outdoor high temperature in summer will rush indoors, resulting in an increase in air conditioning load, and red / ultraviolet can make human skin have a burning sensation; The plasma resonance effect can occur between the coating and the light wave in the range of 200-400nm and 700-2500nm, and the radiant heat energy can not penetrate the coating, so it can achieve good thermal insulation and sun protection performance. at the same time, because of blocking the radiant heat energy, the indoor temperature can not be raised quickly and continuously, so the air conditioning load is reduced, the air conditioning cost is greatly saved, and the purpose of energy saving is achieved.

In winter, the essence of indoor heat source heating is still infrared light, and the electromagnetic wave is transmitted outward by the internal vibration of the particles. therefore, the heating electromagnetic wave can not effectively penetrate the heat-breaking rare earth coating (plasmon resonance), and a large number of heat sources are left indoors. Heating up faster, energy locking, insulation will be better, super energy saving.

The problem of building energy consumption is particularly serious in China. The total building area of our country is huge, more than 90% of which are made of ordinary glass. According to the energy saving target of our country in 2010, the average annual increase of thermal insulation glass is about 1.32 billion square meters, and the market demand of rare earth nano thermal insulation materials is huge.

"after the product is on the market, it can be widely used in energy-saving and environment-friendly vehicles and energy-saving building glass, which can effectively solve the problems of high internal temperature and high energy consumption of air conditioners in cars and buildings, with an output value of more than 100 million yuan, at the same time, to make great contributions to the cause of energy conservation and environmental protection in China." Yang said that 11 branches have been established and product agency agreements have been signed with more than 80 cities in more than 10 provinces across the country, and sales are expected to reach nearly 30 million yuan this year.