WO2021008563A1

WO2021008563A1 - Transparent heat-shielding particulate, particulate dispersoid, and preparation method and use thereof

Info

Publication number: WO2021008563A1
Application number: PCT/CN2020/102162
Authority: WO
Inventors: 金平实; 曹逊
Original assignee: 中国科学院上海硅酸盐研究所
Priority date: 2019-07-17
Filing date: 2020-07-15
Publication date: 2021-01-21
Also published as: CN111547771B; CN111547771A; JP7323828B2; JP2022537755A

Abstract

A transparent heat-shielding particulate, a particulate dispersoid, and a preparation method and use thereof. The particulate comprises a core and a shell enclosing the core. The core is made of a transparent heat-shielding material obtained by doping, with nitrogen, a tungsten bronze structure expressed in a chemical formula of M _xWO _3- _δ, where M is any one of an alkali metal element, an alkaline earth metal element and a rare earth element, 0.1 ≤ x ≤1, W is tungsten, O is oxygen, 0 ≤ δ ≤ 0.5, the shell is carbon, and the thickness of the shell is 1 nm-10 nm.

Description

Transparent heat-shielding microparticles, microparticle dispersions, preparation methods and uses thereof

Technical field

The invention belongs to the field of functional nano new materials, and specifically relates to a transparent heat-shielding inorganic nano powder and microparticles with a core-shell structure, a transparent heat-shielding transparent resin composite microparticle dispersion, its preparation method and use, and its high stability , Easy to prepare, can be widely used in transparent heat-shielding coatings, heat-shielding films, heat-shielding glass, and various light-to-heat conversion materials.

Background technique

The wavelength range of sunlight is about 300-2500nm, of which the wavelength range of visible light is 380-780nm, and the wavelength of near-infrared is 780-2500nm. In the glass parts of buildings and vehicles, while maintaining high visible light transmittance, the near-infrared part of sunlight is largely shielded, which helps to save energy and reduce emissions and improve the comfort of living spaces.

In the agricultural field, with the continuous intensification of climate warming, crops in the form of greenhouses or mulching films stop growing or even die due to high temperatures in the hot season. At the same time, the shortage of manpower in agriculture and the aging of the population also put forward higher requirements for the working environment.

In the fields of heat storage and heat preservation materials, such as heat storage fibers or fabric products, through the absorption of sunlight and conversion into far-infrared heat radiation, high-efficiency heat storage and heat preservation for the human body and organisms can be realized.

Therefore, the market has a huge potential demand for transparent heat shielding materials and products. Among them, the new type of transparent infrared heat-shielding coatings, films, plates, and fiber products made by combining inorganic nano heat-shielding materials and resins have gradually expanded the market scale and application fields.

Traditional inorganic nano heat shielding materials include transparent conductive materials (such as ITO, ATO, etc.), or lanthanum hexaboride (LaB ₆ ), and recently discovered series of transparent heat shielding materials with tungsten bronze structure (doped tungsten bronze) , Because of its high visible light transmittance and excellent heat-shielding, heat-storage and heat preservation performance, it is widely concerned.

For example, Patent Document 1 discloses a method for preparing a tungsten oxide-based transparent heat shielding material with excellent performance. This material can be represented by the general formula MxWyOz, where the M element is an alkali metal, alkaline earth metal, rare earth element, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Choose one or more of Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re.

Similarly, Patent Document 2 discloses a metal element doped tungsten bronze structure heat shielding nanopowder, the doping element is Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, One or several mixed elements of Te, Ti, Mn, Fe, Co, Ni, Cu or Zn.

However, in the heat-shielding products formed by the heat-shielding material of the tungsten bronze structure and the resin, such as the heat-shielding laminated film or laminated glass, the problem of insufficient optical performance stability has been found during use, which manifests itself as the use time increases. Different degrees of optical performance change or deterioration, specifically manifested as local discoloration under ultraviolet radiation and fading originating from the edge of the product in a humid and hot environment.

Detailed research results show (see Non-Patent Documents 1-4) that the performance degradation mechanism is due to the metal-doped tungsten bronze structure fine particles (such as cesium tungsten bronze CWO) in the composite material (such as PET heat shielding film) formed with resin , Due to the lack of cesium on the surface of CWO particles and the reaction with hydrogen to cause reversible photochromism (coloring), or the performance failure (fading) caused by the oxidation of the surface of CWO particles in a humid and hot environment.

Existing technical literature:

Patent Literature:

Patent Document 1: Japanese Patent JP2005-187323A;

Patent Document 2: Chinese Patent CN107200357A;

Non-patent literature:

Non-Patent Document 1: K. Adachi, Y. Ota, H. Tanaka, M. Okada, N. Oshimura, A. Tofuku, Chromatic instabilities in cesium-doped tungsten bronze nanoparticles, J. Appl. Phys. 114 (19) (2013) 11.

Non-Patent Document 2: Yunxiang Chena,b,1, Xianzhe Zeng, Yijie Zhou, Rong Li, Heliang Yao, Xun Cao, Ping Jin, Core-shell structured CsxWO3@ZnO with excellent stability and high performance on near-infrared shielding, Ceramics International 44 (2018) 2738-2744,

Non-Patent Document 3: Yijie Zhou, ab Ning Li, ab Yunchuan Xin, a Xun Cao, Shidong Ji and Ping Jin, CsxWO3 nanoparticle-based organic polymer transparent foils: low haze, high near infraredshielding ability and excellent photochromic stability, J. Mater. Chem. C, 2017, 5, 6251-6258.

Non-Patent Document 4: Xianzhe Zeng, Yijie Zhou, Shidong Ji, Hongjie Luo, Heliang Yao, Xiao Huang and Ping Jin, The preparation of a high performance nearinfrared shielding Cs xWO3/SiO2 composite resin coating and research on its optical stability under ultraviolet Illumination, J. Mater. Chem. C, 2015, 3, 8050-8060.

technical problem

Therefore, the purpose of the present invention is to provide a new type of doped tungsten bronze heat shielding material with stable performance to solve the problem of unstable optical performance of materials and resin products.

Technical solutions

The inventor found that for the same metal doped tungsten bronze structure, such as cesium tungsten bronze, by reducing the lattice constant of the tungsten oxide network crystal structure containing cesium element, the size ratio of the cesium ion to the network lattice constant can be increased. Effectively limit the escape of cesium ions and improve the stability of the material.

In addition, the traditional doped tungsten bronze structure has a larger band gap, that is, its ability to shield ultraviolet rays is low. Excessive ultraviolet irradiation is not conducive to the shielding ability and life of the heat shielding resin product, and adding too much ultraviolet shielding additives may cause an increase in cost and a decrease in optical and mechanical properties.

Therefore, by reducing the forbidden band width of the doped tungsten bronze structure, the red shift of the absorption end can be realized, and the ultraviolet absorption rate of the structure can be increased. While increasing the ultraviolet shielding efficiency, it also effectively suppresses the photochromic caused by the heat shielding resin. The color changes.

Therefore, the inventors designed a new nitrogen-doped tungsten bronze structure that can simultaneously reduce the lattice constant and the red shift of the absorption end.

In order to maximize the oxidation resistance of nitrogen-doped tungsten bronze nanoparticles, the inventor further designed a core-shell structure and completed the present invention.

In the first aspect, the present invention provides a core-shell structure transparent heat-shielding microparticles. The microparticles include a core and a shell covering the core. The core material is made of tungsten bronze with a chemical formula of M _x WO _3- _δ . Transparent heat shielding material doped with nitrogen in the structure, where M is any one or more of alkali metals, alkaline earth metals and rare earth elements, 0.1≦x≦1, W is tungsten, O is oxygen, 0≦δ≦ 0.5, the shell is carbon, and the thickness of the shell is 1 nm-10 nm.

According to the present invention, firstly, the traditional metal-doped tungsten bronze structure is doped with nitrogen to obtain a new structure of nitrogen-doped metal tungsten bronze. The doped nitrogen enters the tungsten-oxygen skeleton and replaces part of the oxygen in it, resulting in distortion of the lattice, making the lattice constant smaller, and doping metal ions (such as cesium) difficult to escape from the ligand gap, thereby increasing the structure stability.

At the same time, nitrogen doping and its partial replacement of oxygen change the band gap of the original crystal structure, make the absorption end redshift, and increase the ultraviolet shielding performance, which is beneficial to shielding from the sun.

Further, the nitrogen-doped metal tungsten bronze particles (transparent heat-shielding material particles) are coated with carbon to form a core-shell structure, and the thickness of the C shell is 1 nm-10 nm. By covering the C shell with this thickness, the chemical stability of the nitrogen-doped metal tungsten bronze material can be further improved without excessively affecting the transparency of the particles.

Preferably, the particle size of the core is 1 nm to 100 nm.

Preferably, the composition of the transparent heat shielding material is represented by the general formula M _x WO _y N _z , where N is nitrogen, 2.5≦y+z≦3.

Preferably, 0.001≦z≦0.5.

Preferably, the ratio of z to y is 1/4 or less, preferably 1/10 or less, more preferably 1/20 or less.

In a second aspect, the present invention provides a method for preparing any of the above-mentioned core-shell transparent heat-shielding microparticles, which includes the following steps:

(1) The mixture of the tungsten source and the M metal source is kept at 450-750°C for 2-8 hours in a vacuum with a nitrogen-containing atmosphere to obtain a transparent heat-shielding material, which is crushed into transparent heat-shielding particles ;or

The solution uniformly dispersed with nano-tungsten oxide powder and M metal source is stirred and dried to obtain a precursor. The obtained precursor is kept at 400-700°C for 1-8 hours in a vacuum with a nitrogen-containing atmosphere to obtain a transparent mask. Thermal particles

(2) Hydrothermally react the transparent heat-shielding fine particles and the carbon source at a temperature of 120-180°C for 1-24 hours.

Preferably, the tungsten source is selected from at least one of tungsten oxide, tungstic acid, and ammonium tungstate, preferably ammonium tungstate.

Preferably, the M metal source is a carbonate of element M, preferably cesium carbonate.

Preferably, the nitrogen-containing atmosphere is ammonia, nitrogen or a mixed gas thereof, or a mixed gas of the foregoing gas and hydrogen.

Preferably, the carbon source is selected from at least one of sucrose, glucose, glycogen, and vitamin C.

Preferably, in step (2), the mass ratio of the carbon source to the transparent heat shielding particles is (1-20):100.

In a third aspect, the present invention provides a transparent heat-shielding fine particle dispersion, which is formed by dispersing the above-mentioned transparent heat-shielding fine particles in a medium.

Preferably, the medium is selected from any one of resin-containing liquids, transparent resin films, transparent resin film plates, glass substrates, chemical fibers, and fabrics.

The medium can be selected from a variety of transparent bodies, such as resin, glass, aerogel and the like. Among them, resin-based media have high transparency, various forms, and easy processing. The media is preferably various resin-based media, preferably resin media with higher transparency, such as PET (polyethylene terephthalate), PE (polyethylene ), EVA (ethylene-vinyl acetate copolymer), PVB (polyvinyl butyral), PI (polyimide), PC (polycarbonate), etc.

Beneficial effect

According to the present invention, it is possible to provide a transparent heat-shielding microparticle and a dispersion of transparent heat-shielding microparticles with stable performance.

Description of the drawings

FIG. 1 is an XRD diffraction spectrum of nitrogen-doped cesium tungsten bronze powder according to an embodiment of the present invention.

2 is a transmission electron micrograph of nitrogen-doped cesium tungsten bronze powder according to an embodiment of the present invention.

3 is a transmission electron micrograph of a carbon-coated nitrogen-doped cesium tungsten bronze powder according to an embodiment of the present invention.

4 is a scanning electron micrograph of a nitrogen-doped cesium tungsten bronze powder according to an embodiment of the present invention.

Fig. 5 is a transmittance spectrum of a heat shielding laminated glass according to an embodiment of the present invention.

Fig. 6 is a transmission electron microscope photograph of a PET heat shielding film according to an embodiment of the present invention.

Fig. 7 is a graph showing the spectral transmittance of a PET heat shielding film according to an embodiment of the present invention.

The best mode of the invention

The present invention will be further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

The core-shell structure transparent heat-shielding microparticles in one embodiment of the present invention include a core and a carbon shell covering the core, and the core material is obtained by doping nitrogen in a tungsten bronze structure with a chemical formula of M _x WO _3- _δ The transparent heat shielding material.

Wherein M is any one or more of alkali metals, alkaline earth metals and rare earth elements, 0.1≦x≦1, W is tungsten, O is oxygen, and 0≦δ≦0.5.

In some embodiments, the composition of the transparent heat shielding material is represented by the general formula M _x WO _y N _z , where N is nitrogen, 2.5≦y+z≦3. The composition of the core-shell structure transparent heat-shielding fine particles can be expressed by the general formula M _x WO _y N _z @C. In the core-shell structure, M _x WO _y N _z is the core and C is the shell.

The stability of the doped tungsten bronze structure is related to the ion radius of the doping element. For example, in the alkali metal doped tungsten bronze structure, the larger the alkali metal ion radius, the more stable the structure. Therefore, when M contains an alkali metal, the alkali metal is preferably cesium.

The tungsten bronze structure before undoped N can be in an oxygen-deficient state. After N doping, N can replace the position of O and can also occupy oxygen vacancies. In some embodiments, y+z≥3-δ.

Although an appropriate amount of nitrogen doping improves the performance of tungsten bronze, a large amount of doping is difficult in the process. Too much doping may affect the stability due to excessive distortion of the crystal structure. Therefore, the nitrogen-oxygen ratio (ie z/y) after doping should not exceed 1/4, preferably not more than 1/10, and more preferably not more than 1/20. On the other hand, the nitrogen-oxygen ratio (ie z/y) after doping is preferably 1/100 or more, which can ensure that the performance of tungsten bronze is improved.

In some embodiments, 0.001≦z≦0.5.

The diameter of the core can be 1 nm to 100 nm. Within this particle size range, visible light will not be scattered, which will help reduce product haze and improve transparency.

The thickness of the C shell can be 1 nm to 10 nm. Within the above thickness range, the C shell is transparent, and the carbon coating can increase the chemical stability of the microparticles without excessively affecting the transparency of the microparticles.

Dispersing the above-mentioned core-shell structure transparent heat-shielding fine particles in a medium can form a transparent heat-shielding fine particle dispersion. The medium may be a transparent body.

In some embodiments, the transparent heat-shielding fine particles are uniformly dispersed in the resin-containing liquid to obtain an aqueous or solvent-based transparent heat-shielding coating.

The transparent heat-shielding paint is coated on the substrate to obtain a transparent heat-shielding coating film.

In some embodiments, transparent heat-shielding fine particles are uniformly dispersed or coated on a glass substrate to obtain transparent heat-shielding glass.

In some embodiments, the transparent heat-shielding fine particles are uniformly dispersed in a transparent resin film (for example, PET, PE, PI, PVB, or EVA) or resin sheet (PC) to obtain a transparent heat-shielding film or sheet product.

In some embodiments, the transparent heat-shielding particles are uniformly dispersed in chemical fibers (such as polyester, nylon, acrylic, chlorinated, vinylon, spandex, polyolefin stretch yarn, etc.) to obtain heat storage and thermal insulation fibers, which are combined with fabrics (clothes, quilts, quilts, etc.). Filling, etc.) products.

Hereinafter, the preparation method of the core-shell structure transparent heat-shielding microparticles according to the embodiment of the present invention will be exemplified.

First, prepare transparent heat shielding fine particles.

In some embodiments, a mixture of a tungsten source and a M source (M is any one or more of alkali metals, alkaline earth metals, and rare earth elements) is heat-treated in a vacuum state with a nitrogen-containing atmosphere to obtain a transparent heat shielding material, and then The obtained transparent heat shielding material is crushed into transparent heat shielding fine particles.

The tungsten source (raw material containing tungsten element) is preferably a substance containing both tungsten element and oxygen element. For example, it may be selected from at least one of tungsten oxide, tungstic acid, ammonium tungstate, etc., and is more preferably a substance that also contains nitrogen. For example, ammonium tungstate. The tungsten element combines with oxygen to form a tungsten bronze structure crystalline bone during the synthesis process, and doped metal elements are introduced into the polyhedral vacancies of the bone to produce infrared absorption. Since ammonium tungstate contains ammonium root, which is nitrogen element, the nitrogen element existing in the starting material is beneficial to nitrogen doping. Moreover, ammonium tungstate has high solubility in water, which is conducive to the uniform mixing and chemical reaction of raw materials.

The M source (raw material containing the M element) can be selected from salts of carbonates, chlorides, sulfates, and organic acid salts of the M elements that do not contain other metals other than M. When the M element is an alkali metal, the M source is preferably an alkali metal carbonate, because the carbonate is cheap and good, has high solubility in water, can form a high-concentration ion dispersion, and promote the uniform mixing and chemical reaction of the raw materials. In a more preferred embodiment, the M source is cesium carbonate, because cesium tungstate has a large ion radius and high stability.

The tungsten source and the M source are mixed uniformly to obtain a mixture. The method can be to directly mix the tungsten source and the M source uniformly; or to separately prepare the tungsten source and the M source into solutions and mix the solutions uniformly, and then dry the mixed solution.

The resulting mixture was placed in a reaction device. The reaction device is preferably a dynamic reaction device such as a rotary kiln, so that the reaction is more sufficient and uniform. After the reaction device is evacuated, a gas containing nitrogen, such as ammonia, nitrogen or a mixed gas thereof, is passed; or hydrogen can be added to the above gas to form a reducing mixed gas as required. The total gas flow can be 10-1000 standard milliliters per minute. The volume ratio of the nitrogen-containing gas to the hydrogen gas can be (1～99): (99～1). Keep the reaction device in a vacuum state and heat it from room temperature to 450-750°C for 2-8 hours. In this process, the rotary kiln is preferably turned on.

After the heating process is over, keep the furnace in a rotating state and cool to near room temperature, take out the reaction product, and obtain a transparent heat shielding material.

The obtained transparent heat-shielding material is pulverized, for example, pulverized to below 100 nm to obtain transparent heat-shielding fine particles.

The pulverization method may be, for example, mixing the transparent heat shielding material with water and putting it in a sand mill for pulverization.

In some embodiments, the tungsten source nano-powder is used as a raw material to directly obtain nano-sized transparent heat-shielding particles without pulverization.

The tungsten source nano powder is preferably a nano tungsten oxide powder, and its particle size is preferably less than 100 nanometers, more preferably less than 50 nanometers.

The source of M can be as described above and will not be repeated here.

The M source is dissolved in the solvent to prepare a solution. The solvent used can be selected from at least one of water, alcohol, and ether, preferably methanol or ethanol, because it is easy to volatilize, which is beneficial to improve the drying efficiency; the volatilized alcohol can be reused through the recovery system to reduce environmental load.

Disperse the tungsten source nano powder in the M source solution, mix uniformly, stir for a period of time, for example, 5 to 120 minutes, and then dry to obtain a nano precursor.

The obtained nano precursor is placed in a reaction device. The reaction device is preferably a dynamic reaction device such as a rotary kiln, so that the reaction is more sufficient and uniform. After the reaction device is evacuated, a gas containing nitrogen, such as ammonia, nitrogen or a mixed gas thereof, is passed; or hydrogen can be added to the above gas to form a reducing mixed gas as required. The total gas flow can be 10-1000 standard milliliters per minute. The volume ratio of the nitrogen-containing gas to the hydrogen gas can be (1～99): (99～1). Keep the reaction device in a vacuum state and heat it from room temperature to 400-700°C for 1-8 hours. In this process, the rotary kiln is preferably turned on.

After the heating process is completed, keep the furnace in a rotating state and cool to near room temperature, take out the reaction product, and obtain nano-sized transparent heat shielding particles.

Then, the transparent heat shielding fine particles are coated with carbon. In one embodiment, the transparent heat-shielding fine particles and the carbon source are placed in a hydrothermal reaction kettle and kept at a temperature of 120-180° C. for 1-24 hours to form a carbon coating on the surface of the transparent heat-shielding fine particles.

The carbon source is preferably a water-soluble carbon source, for example, one or more selected from sucrose, glucose, glycogen, and vitamin C. Thus, a uniform coating structure can be formed on the surface of the transparent heat shielding particles.

The mass ratio of the carbon source to the transparent heat shielding fine particles can be (1-20):100. The thickness of the shell is related to the amount of addition and the reaction time. Under this reaction ratio, the thickness of the shell layer can be 1-10 nm. Under this thickness condition, the optical performance of the structure is not affected, and the stability of the obtained structure is improved.

In the embodiment of the present invention, the tungsten bronze crystals are heated in the vacuum state of the nitrogen-containing atmosphere before the formation of the tungsten bronze crystals, and the heating is started from room temperature to the highest temperature and kept for a certain period of time, and the nitrogen-containing atmosphere is always maintained during the cooling process. With the vacuum state, it is easy to achieve sufficient nitrogen doping. Once the tungsten bronze crystal is formed, for example, the tungsten bronze crystal is subjected to a nitrogen-containing atmosphere heat treatment, it is difficult to achieve sufficient nitrogen doping. Even if there is a certain amount of doping, under the same heat treatment conditions, the doping amount is much smaller than the present invention.

Embodiments of the invention

The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the present invention. The scope of protection. The specific process parameters in the following examples are only an example in the appropriate range, that is, those skilled in the art can make selections within the appropriate range through the description herein, and are not limited to the specific values illustrated below.

Example 1

Mix 0.652kg of cesium carbonate and 3.132kg of ammonium paratungstate and put them into a 50L rotary heating furnace, close the furnace door, use a vacuum unit to evacuate and then pass in ammonia gas to maintain its flow rate at 100SCCM (standard milliliters per minute), and Keep a certain vacuum state during the whole synthesis process; turn on the furnace rotary device, heat up from room temperature to 750°C within 2 hours, and keep it at this temperature for 4 hours; stop heating, and the furnace temperature is naturally cooled to around room temperature; open the rotary furnace door to exit Material to obtain the specified cesium tungsten bronze powder.

Through powder XRD measurement, the obtained powder has a single-phase cesium tungsten bronze crystal structure (Figure 1). Through a more detailed comparison and analysis of the XRD diffraction peaks, compared with the theoretical ratio of the hexagonal cesium tungsten bronze (Cs0.33WO3) diffraction peak, the diffraction peak position is slightly shifted to a higher angle (for example, at 27.8° The nearby (200) lattice diffraction position shifts to a high angle by about 0.2°), which can be considered to be caused by the distortion of the lattice constant caused by nitrogen doping.

The above reaction process can be expressed by the following reaction formula:

(NH ₄ ) ₁₀ (H ₂ W ₁₂ O ₄₂ ) 4H ₂ O + Cs ₂ CO ₃ + NH ₃ → Cs _0.33 WO ₃ : N + NH ₃ + H ₂ O

The moisture and the like that are gradually generated during the reaction are gradually exhausted from the vacuum during the initial heating process. The nitrogen-containing raw materials and the nitrogen element in the ammonia atmosphere are added to the cesium tungsten bronze crystal lattice formation reaction process from room temperature, and the nitrogen-doped cesium tungsten bronze crystal structure is finally formed after gradually heating and treating.

The main reasons for achieving nitrogen doping through the above preparation process are: 1) Using nitrogen-containing tungsten source, such as ammonium tungstate, 2) heating in a nitrogen-containing atmosphere before forming cesium tungsten bronze crystals, so that nitrogen is formed in cesium tungsten bronze In the process, it always exists as a reactant and participates in the formation of tungsten bronze lattice. 3) Always keep the reactant in a nitrogen-containing atmosphere under a certain vacuum state during heating, heat preservation and cooling to prevent the overflow of nitrogen. If once the cesium tungsten bronze crystal is formed, nitrogen doping is attempted, such as heat treatment of the cesium tungsten bronze crystal powder in a nitrogen-containing atmosphere, it is difficult to achieve sufficient nitrogen doping.

Figure 2 is a TEM photograph of the nitrogen-doped cesium tungsten bronze powder obtained. The powder is in the form of particles with a particle size of ~ hundreds of nanometers.

Weigh 200 grams of the above nitrogen-doped cesium tungsten bronze powder, together with 6000ml of deionized water, 25 grams of sucrose (Sinoma Pharmaceutical Analytical Pure), and place them in a horizontal rod-pin structure sand mill for 24 hours. Take out the dispersion and put it in It is sealed in a stainless steel magnetically stirred hydrothermal reaction vessel with a volume of 10 liters, and heated at 180°C for 12 hours for hydrothermal reaction. After cooling, the reaction precipitate is filtered, washed and dried to obtain the predetermined carbon-coated nitrogen-doped cesium tungsten bronze Nano powder.

(A) in Figure 3 is a TEM picture of carbon-coated nitrogen-doped cesium tungsten bronze nanopowder, with an average particle size of about 20 nm. (B) in Figure 3 is a TEM image of one of the carbon-coated nitrogen-doped cesium tungsten bronze nanoparticles, where the thickness of the carbon coating layer is about 3 nm.

Example 2

Dissolve 0.325 kg of cesium carbonate in methanol completely to obtain a cesium carbonate methanol solution; put 1.391 kg of nano tungsten oxide (commercially available WO ₃ , average particle size 50nm) into the solution, stir and dry, to obtain a cesium tungsten bronze precursor; The obtained cesium-tungsten bronze precursor is added to a 50L rotary furnace, the furnace door is closed, and a mixture of nitrogen and hydrogen (7:3) is evacuated by a vacuum unit, and the total flow rate is maintained at 100SCCM. The furnace is kept at a certain degree of vacuum; the furnace rotary device is turned on, the temperature is raised from room temperature to 500°C within 2 hours, and the temperature is kept at this temperature for 8 hours; the heating is stopped and the furnace temperature is naturally cooled to near room temperature; the rotary furnace door is opened to discharge, Obtain the determined nitrogen-doped cesium tungsten bronze powder.

The powder XRD analysis showed that the obtained powder had a single-phase cesium tungsten bronze crystal structure, and its XRD spectrum was similar to Figure 1. The above reaction process can be expressed by the following reaction formula:

Cs ₂ CO ₃ + CH ₃ OH + WO ₃ + N ₂ + H ₂ → Cs _0.33 WO ₃ : N + N ₂ + H ₂ + CO ₂

Figure 4 is a scanning electron micrograph of the obtained powder. The powder is composed of nitrogen-doped cesium tungsten bronze nanocrystals with an average particle size of about 60nm. Its morphology and particle size distribution are similar to those of nano-tungsten oxide containing tungsten raw materials. Due to the use of nano-tungsten oxide as the raw material, the uniform dispersion of cesium ion alcohol solution, and the heat treatment at a lower temperature, the obtained nitrogen-doped cesium tungsten bronze nano-powder basically maintains the original nanometer size. In this preparation method, the pulverization process is not required, and the nano powder is directly used to obtain the nano heat shielding product.

Weigh 200 grams of the above-mentioned nitrogen-doped cesium tungsten bronze nanopowder, together with 6000ml deionized water and 20 grams of vitamin C (Sinopec Analytical Pure), put them into a 10-liter stainless steel magnetically stirred hydrothermal reaction vessel and seal it. After heating at 160°C for 6 hours, the reaction precipitate is filtered, washed and dried to obtain the predetermined carbon-coated nitrogen-doped cesium tungsten bronze nanopowder.

Example 3

Mix 200g of nitrogen-doped cesium tungsten bronze nanopowder obtained in Example 2 with 15kg of plasticizer (3G8) uniformly with a mixer, and gradually add the mixed liquid to 35kg of PVB powder through a funnel and fully perform it in a horizontal mixer. After mixing, it is plasticized by a twin-screw extruder at a temperature of 160°C, and a PVB heat-shielding intermediate film (0.38mm×1m×100m) containing nitrogen-doped cesium tungsten bronze nanoparticles is obtained by extrusion molding.

Example 4

Cut an appropriate amount of the PVB heat-shielding intermediate film obtained in Example 3, place it between two pieces of glass (3mm×30mm×30mm), place it on a heating table, and keep it under pressure at 95℃ for a certain period of time. After cooling down, PVB is obtained Cover the heat with laminated glass.

The optical transmittance of the heat-shielding laminated glass (N-CWO) obtained in Example 4 was measured with a spectrophotometer, and compared with the use of cesium tungsten bronze nanopowders without nitrogen doping (except during heating Except that only hydrogen is used to avoid nitrogen doping, the preparation method is the same as that in Example 2), and the cesium tungsten bronze heat-shielding laminated glass (CWO) obtained by the same method in Examples 3 and 4 is compared. The results are shown in Figure 5. Shown.

As shown in Figure 5, the heat-shielding laminated glass using nitrogen-doped cesium tungsten bronze has a higher infrared blocking rate and also achieves a partial red shift of the absorption end.

Example 5

Place the two heat-shielding laminated glasses shown in Figure 5 in a high-temperature and high-humidity (90°C/90% relative humidity) laboratory cabinet, take them out every 24 hours and measure their transmittance spectra, which are compared with the original spectra in Figure 5 Compare.

The comparison results show that the transmittance of CWO laminated glass increased by about 2% after 24 hours of storage, while the transmittance of N-CWO laminated glass only increased by 0.5% after 72 hours of storage. As mentioned earlier, the increase in transmittance is caused by the escape of cesium atoms caused by the oxidation of the cesium tungsten bronze particles. Obviously, nitrogen doping increases the oxidation resistance of cesium tungsten bronze particles.

Comparative example 1

Weigh 100 grams of cesium carbonate and tungstic acid at a molar ratio of Cs to W of 0.33. After they are fully mixed in an automatic mortar, they are heated at 600°C for 120 minutes in a reducing atmosphere (Ar:H ₂ =97:3 volume ratio). After the reactant is cooled to room temperature, the temperature is raised to 800°C again in pure Ar atmosphere and kept for 60 minutes to obtain a cesium tungsten bronze product, which is determined by XRD and has a hexagonal structure of Cs0.33WO3, which is located near 27.8° (200) The diffraction position of the lattice is consistent with the theoretical value.

The above reaction can be described by the following reaction formula:

Cs ₂ CO ₃ + H ₂ WO ₄ + H ₂ → Cs _0.33 WO ₃ + H ₂ O + CO ₂

The powder obtained above was heated in an NH3 atmosphere with a flow rate of 500 ml/min at 450°C for 60 minutes to obtain a cesium tungsten bronze powder product, which was measured by XRD and was located in the (200) lattice near 27.8° The diffraction position is slightly shifted to the high angle, and the shift is about 0.05°, which indicates that the cesium tungsten bronze after the subsequent heat treatment has nitrogen doping. The reaction formula can be expressed by the following formula:

Cs _0.33 WO ₃ + NH ₃ → Cs _0.33 WO ₃ :N + NH ₃ (heating temperature 450℃)

However, compared with the case where the reactant precursor was heated in a nitrogen-containing vacuum from room temperature in Examples 1 and 2, the XRD diffraction peak shift was much smaller, which means that the nitrogen in Comparative Example 1 The doping amount is far less than the nitrogen doping amount in Examples 1 and 2.

The cesium tungsten bronze product obtained in Comparative Example 1 was prepared according to the same method as in Example 4 to prepare heat-shielding laminated glass, and tested according to the same method as in Example 5. The results show that the transmittance of the heat-shielding laminated glass increased by about 1.2% after being placed for 72 hours.

Example 6

The carbon-coated nitrogen-doped cesium tungsten bronze powder, dispersant and masterbatch polymer carrier obtained in Example 1 were thoroughly mixed with a high-speed mixer, and then passed through a twin-screw extruder at a temperature of 250°C to 280°C The well-mixed mixture is blended, melted and extruded to obtain PET nano heat shielding masterbatch.

The dispersant is 3-aminopropyltriethoxysilane (APTES), the carrier polymer used is polyethylene terephthalate (PET), in which carbon-coated nitrogen-doped cesium tungsten bronze powder, The mass ratio of dispersant to carrier polymer PET is 1:0.1:8.9.

The obtained PET nano heat-shielding masterbatch is matched with PET raw materials in an appropriate ratio, and the heat-shielding PET film is formed by biaxial stretching. The transmission electron microscope photo is shown in Figure 6. The nano powder forms a nano-dispersed state in the PET.

The transmittance of the heat shielding film was measured by a spectrophotometer, and the result is shown in Figure 7. The transmittance of the film in the visible light band is greater than 75%, and the blocking rate of infrared rays is close to 90%.

Put the heat shielding film into a commercially available radiation resistance testing machine, take it out after 1000 hours of UV irradiation under the conditions specified by the national standard, test the spectral transmittance and compare it with the unirradiated sample. The result is shown in Figure 7.

After 1000 hours of ultraviolet intensification test, the performance of the heat shielding film prepared by using carbon-coated nitrogen-doped cesium tungsten bronze powder has almost no deterioration.

Example 7

Take 100g of carbon-coated nitrogen-doped cesium tungsten bronze nanopowder obtained in Example 2, add 2g of dispersant and 200g of toluene into a sand mill, keep it at a rotation speed of 2600r/min for 5 hours, take it out and obtain carbon-coated nitrogen-doped Cesium tungsten bronze nano dispersion.

Measure 25 g of the above dispersion, mix it with 75 g of silicone resin, 4 g of polymerization inhibitor, and 1 g of BYK-385N to obtain dispersion A.

Weigh 50 g of toluene, add 10 g of ultraviolet absorber and 5 g of stabilizer, and after uniformly dissolving, dispersion B is obtained.

Mix material A and material B uniformly to obtain a transparent heat-shielding paint. It is applied to transparent substrates (glass or polymer) by spraying, knife coating, etc., after curing, transparent heat-shielding glass or transparent heat-shielding coated sheet is obtained.

Example 8

Take 100g of carbon-coated nitrogen-doped cesium tungsten bronze nanopowder obtained in Example 2, dispersant (3-aminopropyltriethoxysilane (APTES), carrier polymer polyamide 6 resin (PA6), according to mass The ratio is 1:0.1:8.9, after being fully mixed by a high-speed mixer, blended and extruded with a twin-screw extruder at a temperature of 220°C to 250°C to obtain a heat storage and heat preservation masterbatch.

The prepared heat storage and heat preservation masterbatch is mixed with the fiber matrix polymer in a mass ratio of 2:8, and extruded with an extruder at a temperature of 240 ℃ to obtain filaments. The filament is wound at a winding speed of m/min to obtain a 110D/48F partially aligned yarn. Finally, the partially aligned yarn is made into a 70D/48F conventional heat storage and warmth-keeping nylon fiber by a friction type extension false twister.

Claims

A core-shell structure transparent heat-shielding microparticles, characterized in that the microparticles comprise a core and a shell covering the core, and the material of the core is made by mixing a tungsten bronze structure with a chemical formula of M x WO 3- δ A transparent heat shielding material derived from nitrogen, where M is any one or more of alkali metals, alkaline earth metals and rare earth elements, 0.1≦x≦1, W is tungsten, O is oxygen, 0≦δ≦0.5, so The shell is carbon, and the thickness of the shell is 1 nm to 10 nm.
The core-shell structure transparent heat-shielding fine particles according to claim 1, wherein the composition of the transparent heat-shielding material is represented by the general formula M x WO y N z , where N is nitrogen, 2.5≦y+z≦3, The ratio of z to y is 1/4 or less, preferably 1/10 or less, and more preferably 1/20 or less.
The core-shell structure transparent heat-shielding fine particles according to claim 1 or 2, wherein the particle size of the core is 1 nm-100 nm.
A preparation method of core-shell structure transparent heat-shielding microparticles according to any one of claims 1 to 3, characterized in that it comprises the following steps:

(1) The mixture of the tungsten source and the M metal source is kept at 450-750°C for 2-8 hours in a vacuum with a nitrogen-containing atmosphere to obtain a transparent heat-shielding material, which is crushed into transparent heat-shielding particles ;or

The solution uniformly dispersed with nano-tungsten oxide powder and M metal source is stirred and dried to obtain a precursor. The obtained precursor is kept at 400-700°C for 1-8 hours in a vacuum with a nitrogen-containing atmosphere to obtain a transparent mask. Thermal particles

(2) Hydrothermally react the transparent heat-shielding fine particles and the carbon source at a temperature of 120-180°C for 1-24 hours.
The preparation method according to claim 4, wherein the tungsten source is selected from at least one of tungsten oxide, tungstic acid and ammonium tungstate, preferably ammonium tungstate;

The M metal source is a carbonate of element M, preferably cesium carbonate.
The preparation method according to claim 4 or 5, wherein the nitrogen-containing atmosphere is ammonia, nitrogen or a mixed gas thereof, or a mixed gas of the above gas and hydrogen.
The preparation method according to any one of claims 4 to 6, wherein the carbon source is selected from at least one of sucrose, glucose, glycogen, and vitamin C.
The preparation method according to any one of claims 4 to 7, characterized in that, in step (2), the mass ratio of the carbon source to the transparent heat shielding fine particles is (1-20):100.
A transparent heat-shielding microparticle dispersion, characterized in that it is formed by dispersing the transparent heat-shielding microparticles according to claim 8 in a medium.
The transparent heat shielding fine particle dispersion according to claim 9, wherein the medium is selected from any one of a resin-containing liquid, a transparent resin film, a transparent resin film sheet, a glass substrate, a chemical fiber, and a fabric .