阅读说明：本技术 透明遮热微粒子、微粒子分散体、其制法及用途 (Transparent heat-shielding fine particles, fine particle dispersion, process for producing the same, and use thereof ) 是由 金平实 纪士东 孙光耀 李�荣 于 2019-07-17 设计创作，主要内容包括：本发明提供透明遮热微粒子、微粒子分散体、其制法及用途。所述微粒子包括核和包覆所述核的壳,所述核的材料是通过在化学式为M<Sub>x</Sub>WO<Sub>3-δ</Sub>的钨青铜结构中掺杂氮而得的透明遮热材料,其中M为碱金属、碱土金属及稀土元素中的任一种以上元素,0.1≦x≦1,W为钨,O为氧,0≦δ≦0.5,所述壳为碳,壳的厚度为1nm～10nm。(The invention provides transparent heat shielding microparticles, microparticle dispersions, and their preparation methods and uses. The micro-particle comprises a core and a shell coating the core, wherein the core is made of a material with a chemical formula of M x WO 3‑ The transparent heat shielding material obtained by doping nitrogen into a tungsten bronze structure, wherein M is at least one element selected from alkali metals, alkaline earth metals and rare earth elements, x is at least 0.1 and at most 1, W is tungsten, O is oxygen, 0 is at most 0.5, the shell is carbon, and the thickness of the shell is 1nm to 10 nm.)

1. The transparent heat shielding microparticle with the core-shell structure is characterized by comprising a core and a shell coating the core, wherein the core is made of a material with a chemical formula of M_xWO_3-The transparent heat shielding material obtained by doping nitrogen into a tungsten bronze structure, wherein M is at least one element selected from alkali metals, alkaline earth metals and rare earth elements, x is at least 0.1 and at most 1, W is tungsten, O is oxygen, 0 is at most 0.5, the shell is carbon, and the thickness of the shell is 1nm to 10 nm.

2. The core-shell structure transparent heat shielding microparticles as claimed in claim 1, wherein the composition of the transparent heat shielding material is represented by formula M_xWO_yN_zN is nitrogen, 2.5 ≦ y + z ≦ 3, and the ratio of z to y is 1/4 or less, preferably 1/10 or less, and more preferably 1/20 or less.

3. The core-shell structure transparent heat shielding microparticles according to claim 1 or 2, wherein the particle size of the core is 1nm to 100 nm.

4. A method for preparing the core-shell structure transparent heat shielding microparticles according to any one of claims 1 to 3, comprising the following steps:

(1) keeping the temperature of a mixture of a tungsten source and an M metal source at 450-750 ℃ for 2-8 hours in a vacuum state with a nitrogen-containing atmosphere to obtain a transparent heat shielding material, and crushing the transparent heat shielding material into transparent heat shielding particles; or

Stirring and drying a solution in which nano tungsten oxide powder and an M metal source are uniformly dispersed to obtain a precursor, and preserving the temperature of the precursor at 400-700 ℃ for 1-8 hours in a vacuum state with a nitrogen-containing atmosphere to obtain transparent heat shielding microparticles;

(2) the transparent heat-shielding particles and a carbon source are subjected to hydrothermal reaction at a temperature of 120-180 ℃ for 1-24 hours.

5. The production method according to claim 4, wherein the tungsten source is selected from at least one of tungsten oxide, tungstic acid, ammonium tungstate, preferably ammonium tungstate;

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

6. The method according to claim 4 or 5, wherein the nitrogen-containing atmosphere is ammonia gas, nitrogen gas or a mixed gas thereof, or a mixed gas of the above gas and hydrogen gas.

7. The production method according to any one of claims 4 to 6, wherein the carbon source is at least one selected from sucrose, glucose, glycogen, and vitamin C.

8. The method according to any one of claims 4 to 7, wherein in the step (2), the mass ratio of the carbon source to the transparent heat shielding fine particles is (1-20): 100.

9. a transparent heat-shielding fine particle dispersion, which is obtained by dispersing the transparent heat-shielding fine particles according to claim 8 in a medium.

10. 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 sheet, a glass substrate, a chemical fiber, and a woven fabric.

Technical Field

The invention belongs to the field of functional new nano materials, and particularly relates to transparent heat-shielding inorganic nano powder and microparticles with a core-shell structure, a transparent heat-shielding transparent resin composite microparticle dispersion, a preparation method and application thereof.

Background

The wavelength range of sunlight is about 300-2500 nm, wherein the wavelength range of visible light is 380-780 nm, and the wavelength of near infrared is 780-2500 nm. In building and vehicle glass components, the near infrared part of sunlight is greatly shielded while the high visible light transmittance is kept, so that the energy conservation and emission reduction are facilitated, and the comfort of living space is improved.

In the agricultural field, with the increasing warming of the climate, crops in the form of greenhouses or mulch films stop growing and even die in hot seasons due to excessive temperatures. Meanwhile, the lack of manpower and the aging of the population of the agriculture also put higher demands on the working environment.

In the field of a plurality of heat storage and heat preservation materials, such as heat storage fibers or fabric products, the heat storage and heat preservation of human bodies and organisms can be realized efficiently by absorbing sunlight and converting the sunlight into far infrared heat radiation.

Thus, there is a great potential need in the marketplace for transparent heat shielding materials and products. Among them, a novel transparent infrared heat-shielding coating, film, sheet, fiber product, which is formed by combining an inorganic nano heat-shielding material with a resin, has been gradually expanding the market size and application field.

Conventional inorganic nano-grade heat-shielding materials include transparent conductive materials (such as ITO, ATO, etc.), or lanthanum hexaboride (LaB)₆) Meanwhile, recently discovered series of transparent heat shielding materials with a tungsten bronze structure (doped tungsten bronze) are widely concerned due to their high visible light transmittance and excellent heat shielding, heat storage and heat preservation properties.

For example, patent document 1 discloses a method for producing a tungsten oxide-based transparent heat shielding material having excellent properties, which is represented by the general formula MxWyOz, wherein M is at least one selected from the group consisting of alkali metals, alkaline earth metals, rare earth elements, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, and Re.

Also, patent document 2 discloses a tungsten bronze structure heat shielding nanopowder doped with a metal element, the doping element being one or a mixture of several elements selected from Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Ti, Mn, Fe, Co, Ni, Cu or Zn.

However, in a heat-shielding product formed of a heat-shielding material of tungsten bronze structure and a resin, such as a heat-shielding laminated film or laminated glass, a problem of insufficient stability of optical properties is found during use, as manifested by various degrees of change or deterioration of optical properties with the increase of use time, specifically as manifested by local discoloration under ultraviolet irradiation and discoloration originating from the edges of the product in a moist heat environment.

Detailed research results (see non-patent documents 1 to 4) show that the mechanism of performance deterioration is due to reversible photochromism (coloration) caused by cesium deficiency generated on the surface of CWO particles and reaction with hydrogen elements, or performance failure (discoloration) caused by oxidation of the surface of CWO particles in a hot and humid environment, in a composite material (e.g., PET heat shielding film) formed with a resin by fine particles of a metal-doped tungsten bronze structure (e.g., cesium tungsten bronze CWO).

Disclosure of Invention

Therefore, an object of the present invention is to provide a novel tungsten-doped bronze heat shielding material having stable properties, which solves the problem of unstable optical properties of the material and the resin product.

The inventor finds that for the tungsten bronze structure doped with the same metal, such as cesium tungsten bronze, the size ratio of cesium ions to a network lattice constant is improved by reducing the lattice constant of a tungsten-oxygen network crystal structure containing cesium, so that the escape of the cesium ions can be effectively limited, and the stability of the material is improved.

In addition, the forbidden band width of the traditional doped tungsten bronze structure is larger, namely the ultraviolet shielding capability is lower. Excessive UV irradiation is detrimental to the shielding ability and life of the heat-shielding resin product, and excessive UV-shielding additives are added, or cause an increase in cost and a decrease in optical and mechanical properties.

Therefore, the forbidden bandwidth of the doped tungsten bronze structure is reduced, the red shift of the absorption end is realized, the ultraviolet absorption rate of the structure can be increased, and the color change caused by the photo-induced coloring in the heat shielding resin is effectively inhibited while the ultraviolet shielding efficiency is increased.

Therefore, the inventor designs a novel nitrogen-doped tungsten bronze structure, and can simultaneously realize the reduction of the lattice constant and the red shift of the absorption end.

In order to improve the oxidation resistance of the nitrogen-doped tungsten bronze nanoparticles to the maximum extent, the inventor further designs a core-shell structure, and the invention is completed.

In a first aspect, the present invention provides a transparent heat shielding microparticle with a core-shell structure, wherein the microparticle comprises a core and a shell covering the core, and the core is made of a material represented by a chemical formula M_xWO_3-The transparent heat shielding material obtained by doping nitrogen into a tungsten bronze structure, wherein M is at least one element selected from alkali metals, alkaline earth metals and rare earth elements, x is at least 0.1 and at most 1, W is tungsten, O is oxygen, 0 is at most 0.5, the shell is carbon, and the thickness of the shell is 1nm to 10 nm.

According to the invention, the nitrogen doping is firstly carried out on the traditional metal doped tungsten bronze structure to obtain a new nitrogen doped metal tungsten bronze structure. Doping nitrogen into tungsten-oxygen skeleton and replacing part of oxygen in tungsten-oxygen skeleton results in distortion of crystal lattice, makes lattice constant small, and makes doped metal ion (such as cesium) not easy to escape from ligand gap, so as to raise stability of structure.

Meanwhile, nitrogen doping and partial replacement of oxygen change the forbidden bandwidth of the original crystal structure, so that the absorption end is red-shifted, the ultraviolet shielding performance is improved, and the shielding of solar radiation is facilitated.

Further carrying out carbon coating on the nitrogen-doped metal tungsten bronze particles (transparent heat shielding material particles) to form a core-shell structure, wherein the thickness of the C shell is 1 nm-10 nm. By coating the C shell with the thickness, the chemical stability of the nitrogen-doped metal tungsten bronze material can be further improved, and excessive influence on the transparency of the micro-particles is avoided.

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

Preferably, the composition of the transparent heat shielding material is represented by the general formula MxWOyNz, N is nitrogen, and 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 core-shell structure transparent heat shielding microparticles, including the following steps:

(1) keeping the temperature of a mixture of a tungsten source and an M metal source at 450-750 ℃ for 2-8 hours in a vacuum state with a nitrogen-containing atmosphere to obtain a transparent heat shielding material, and crushing the transparent heat shielding material into transparent heat shielding particles; or

Stirring and drying a solution in which nano tungsten oxide powder and an M metal source are uniformly dispersed to obtain a precursor, and preserving the temperature of the precursor at 400-700 ℃ for 1-8 hours in a vacuum state with a nitrogen-containing atmosphere to obtain transparent heat shielding microparticles;

(2) the transparent heat-shielding particles and a carbon source are subjected to hydrothermal reaction at a temperature of 120-180 ℃ for 1-24 hours.

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

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

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

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

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

in a third aspect, the present invention provides a transparent heat shielding fine particle dispersion in which the transparent heat shielding fine particles are dispersed in a medium.

Preferably, the medium is selected from any one of a liquid containing a resin, a transparent resin film sheet, a glass substrate, a chemical fiber, and a woven fabric.

The medium can be selected from a variety of transparencies, such as resin, glass, aerogel, and the like. Among them, the resin-based media are high in transparency, various in form and easy to process, and the media are preferably various resin-based media, and preferably resin media with high transparency, such as PET (polyethylene terephthalate), PE (polyethylene), EVA (ethylene-vinyl acetate copolymer), PVB (polyvinyl butyral), PI (polyimide), PC (polycarbonate) and the like.

According to the present invention, transparent heat shielding fine particles and a transparent heat shielding fine particle dispersion having stable properties can be provided.

Drawings

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

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

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

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

Fig. 7 is a spectral transmittance curve of the PET heat-shielding film according to the embodiment of the present invention.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

The core-shell structure transparent heat shielding microparticle comprises a core and a carbon shell coating the core, wherein the core is made of a material with a chemical formula of M_xWO_3-The tungsten bronze structure is doped with nitrogen to obtain the transparent heat shielding material.

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

In some embodiments, the transparent heat shielding material is of the formula M_xWO_yN_zN is nitrogen, and 2.5. ltoreq. y + z. ltoreq.3. The core-shell structure transparent heat-shielding microparticle can be represented by the general formula M_xWO_yN_z@ C denotes. M in core-shell structure_xWO_yN_zIs core and C is shell.

The stability of the doped tungsten bronze structure is related to the ionic radius of the doping element, such as in an alkali metal doped tungsten bronze structure, the larger the ionic radius of the alkali metal, the more stable the structure. Thus, where M comprises an alkali metal, the alkali metal is preferably cesium.

The tungsten bronze structure before being doped with N may be in an oxygen deficient state. After N is doped, N can replace the position of O and can also occupy oxygen vacancy. In some embodiments, y + z ≧ 3-.

Although the performance of tungsten bronze is improved by proper amount of nitrogen doping, the difficulty of large amount of doping exists in the process, and the stability can be influenced by excessive distortion of the crystal structure due to excessive doping amount. Therefore, the nitrogen to oxygen ratio (i.e., z/y) after doping should not exceed 1/4, preferably does not exceed 1/10, and more preferably does not exceed 1/20. On the other hand, the nitrogen to oxygen ratio (i.e., z/y) after doping is preferably 1/100 or more, which ensures improved tungsten bronze performance.

In some embodiments, 0.001 ≦ z ≦ 0.5.

The diameter of the core may be 1nm to 100 nm. Within the particle size range, the optical glass does not scatter visible light, which contributes to reduction of haze of the product and improvement of transparency.

The thickness of the C shell can be 1 nm-10 nm. In the thickness range, the shell C is transparent, and the carbon coating can increase the chemical stability of the microparticles and cannot generate excessive influence on the transparency of the microparticles.

The transparent heat shielding microparticle dispersion can be formed by dispersing the transparent heat shielding microparticle with the core-shell structure in a medium. The medium may be a transparent body.

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

The transparent heat-shielding coating is coated on a substrate, and a transparent heat-shielding coating film can be obtained.

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

In some embodiments, the transparent heat-shielding microparticles are uniformly dispersed in a transparent resin film (e.g., PET, PE, PI, PVB, or EVA), or a resin sheet (PC), to obtain a transparent heat-shielding film or sheet article.

In some embodiments, the transparent heat-shielding particles are uniformly dispersed in chemical fibers (such as terylene, chinlon, acrylon, clolon, vinylon, spandex, polyolefin stretch yarn, and the like) to obtain heat-storage and heat-preservation fibers and textile (clothing, quilt, filler, and the like) products.

Hereinafter, a method for producing the core-shell structure transparent heat shielding fine particles according to the embodiment of the present invention will be described as an example.

First, transparent heat-shielding fine particles are prepared.

In some embodiments, a mixture of a tungsten source and an M source (M is any one or more of an alkali metal, an alkaline earth metal, and a rare earth element) 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 pulverized 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, and for example, may be selected from at least one of tungsten oxide, tungstic acid, ammonium tungstate, and the like, and more preferably a substance further containing nitrogen element, such as ammonium tungstate. The tungsten element is combined with oxygen to form a crystal skeleton with a tungsten bronze structure in the synthesis process, and a doped metal element is introduced into a polyhedral vacancy of the skeleton to generate infrared absorption. Because ammonium tungstate contains ammonium groups, namely nitrogen elements, the nitrogen elements existing in the starting raw materials are beneficial to doping of nitrogen. And the solubility of the ammonium tungstate in water is high, which is beneficial to the uniform mixing and chemical reaction of the raw materials.

The M source (raw material containing M element) may be selected from salts containing no metal other than M, such as carbonate, chloride, sulfate, and organic acid salt of M element. 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 ionic dispersion liquid, and promotes the raw materials to realize uniform mixing and chemical reaction. In a more preferred embodiment, the M source is cesium carbonate, which has high stability due to the large ionic radius of cesium in cesium tungstate.

And uniformly mixing the tungsten source and the M source to obtain a mixture. The method can be that the tungsten source and the M source are directly mixed evenly; or preparing the tungsten source and the M source into solutions respectively, uniformly mixing the solutions, and drying the mixed solution.

The resulting mixture was placed in a reaction apparatus. The reaction apparatus is preferably a dynamic reaction apparatus such as a rotary kiln, which allows the reaction to be more complete and uniform. Vacuumizing the reaction device, and introducing gas containing nitrogen element, such as ammonia gas, nitrogen gas or mixed gas thereof; alternatively, hydrogen gas may be added to the above gas as necessary to form a reducing mixed gas. The total gas flow rate 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). Keeping the reaction device in a vacuum state, heating the reaction device from room temperature to 450-750 ℃, and preserving heat for 2-8 hours. In this process, the rotary kiln is preferably started.

After the heating process is finished, the furnace is kept in a rotation state and is cooled to be near the room temperature, and reaction products are taken out to obtain the transparent heat shielding material.

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

The pulverization may be carried out, for example, by mixing the transparent heat-shielding material with water and then pulverizing the mixture in a sand mill.

In some embodiments, tungsten source nanopowder is used as a raw material, so that transparent heat shielding microparticles with nanometer size can be directly obtained without pulverization.

The tungsten source nanopowder is preferably a nano tungsten oxide powder having a particle size of preferably less than 100nm, more preferably less than 50 nm.

The M source may be as described above and will not be described further herein.

Dissolving the M source in a solvent to prepare a solution. The solvent used can be at least one selected from water, alcohol and ether, preferably methanol or ethanol, and is easy to volatilize, thereby being beneficial to improving the drying efficiency; the volatilized alcohol can be reused through a recovery system, reducing environmental load.

And dispersing the tungsten source nano powder into the M source solution, uniformly mixing, stirring for a period of time such as 5-120 minutes, and then drying to obtain the nano precursor.

And placing the obtained nano precursor in a reaction device. The reaction apparatus is preferably a dynamic reaction apparatus such as a rotary kiln, which allows the reaction to be more complete and uniform. Vacuumizing the reaction device, and introducing gas containing nitrogen element, such as ammonia gas, nitrogen gas or mixed gas thereof; alternatively, hydrogen gas may be added to the above gas as necessary to form a reducing mixed gas. The total gas flow rate 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). Keeping the reaction device in a vacuum state, heating the reaction device to 400-700 ℃ from room temperature, and preserving heat for 1-8 hours. In this process, the rotary kiln is preferably started.

After the heating process is finished, the furnace is kept in a rotation state and is cooled to be near the room temperature, and reaction products are taken out to obtain the transparent heat shielding particles with nanometer sizes.

Then, the transparent heat shielding fine particles are coated with carbon. In one embodiment, the transparent heat-shielding particles and a carbon source are placed in a hydrothermal reaction kettle, and the temperature is maintained at 120-180 ℃ for 1-24 hours, so that carbon coatings are formed on the surfaces of the transparent heat-shielding particles.

The carbon source is preferably a water-soluble carbon source, and may be selected from one or more of sucrose, glucose, glycogen, and vitamin C, for example. 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 shell thickness is related to the addition amount and the reaction time. Under the reaction proportion, the thickness of the shell layer can be 1-10 nm, and under the condition of the thickness, the optical performance of the structure is not influenced, and meanwhile, the stability of the obtained structure is improved.

In the embodiment of the invention, before the formation of the tungsten bronze crystal, the heating is carried out in the vacuum state of the nitrogen element-containing atmosphere, the heating is started from room temperature to the highest temperature and is kept for a certain time, and the nitrogen element-containing atmosphere and the vacuum state are always kept in the cooling process, so that the sufficient nitrogen doping is easily realized. Once the tungsten bronze crystal is formed, for example, the tungsten bronze crystal is subjected to a heat treatment in a nitrogen-containing atmosphere, sufficient nitrogen doping, if any, is difficult to achieve, and the doping amount is far smaller than that of the present invention under the same heat treatment conditions.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.