CN106928994A - A kind of photochromic composite nano powder and preparation method thereof, application - Google Patents

Abstract

The present invention relates to a kind of photochromic composite nano powder and preparation method thereof, application, the photochromic composite nano powder particle is core shell structure, and shell is molybdenum trioxide, and kernel is titanium dioxide, wherein described titanium dioxide is anatase titanium dioxide nano particle, is shaped as graininess.The preparation of the powder employs simple and quick one step hydro thermal method, will molybdenum source and titanium source mixing, through hydro-thermal reaction obtain molybdenum oxide cladding Titanium dioxide nanoparticle；The photochromic composite nano powder can apply to energy-conservation pad pasting, energy-saving glass or energy-saving wall field.The photochromic composite nano powder of foregoing invention, has been capable of achieving the small-sized of molybdenum oxide, with excellent dispersiveness, stability, with efficient photochromic properties.

Description

A kind of photochromic composite nano-powder and its preparation method and application

technical field

The invention relates to the field of inorganic nano-materials, in particular to a photochromic composite nano-powder and a preparation method thereof.

Background technique

It is estimated that building energy consumption generally accounts for one-third of the total energy consumption in society. At the same time, building energy contributes as much as 25% to the world's greenhouse gas emissions, so energy conservation and emission reduction is the top priority of world energy conservation, and energy conservation and emission reduction must give priority to building energy conservation. Data show that 50% of building energy consumption is carried out through glass windows, which are the main channel for light and heat exchange between buildings and the outside world. Therefore, building energy saving is mainly achieved through the development of new intelligent energy-saving windows to reduce energy consumption and greenhouse gas emissions. Ultimately achieve the purpose of energy saving and environmental protection.

The current energy-saving windows or energy-saving films (referred to as energy-saving windows) are roughly divided into two categories. One is energy-saving windows with fixed optical properties, represented by low-emissivity (Low-E) glass currently on the market. It is cheap, has excellent thermal insulation performance, and is the most widely used, but the disadvantage is that it cannot realize real-time adjustment in winter and summer due to seasonal changes, and it is difficult to adapt to the needs of most cold winter and hot summer regions in my country. The other type is called "intelligent energy-saving glass", which uses a variety of chromogenic materials to produce corresponding optical changes in response to various physical stimuli, and is suitable for most regions with warm winter and hot summer, saving energy and making the indoor environment more comfortable . Smart energy-saving glass is divided into four types: electrochromic, aerochromic, thermochromic and photochromic. Electrochromic materials need to apply voltage, complex structure, high preparation process requirements, resulting in high price; aerochromic needs to be fed with hydrogen to achieve two-way adjustment; thermochromic glass lacks aesthetic feeling; The photochromic energy-saving window that can be developed, because it can automatically adjust the light transmittance according to the change of light intensity in the four seasons, has a simple structure and does not require artificial energy, it is expected to become one of the next low-carbon and environmentally friendly energy-saving glass materials.

The so-called photochromic material refers to the phenomenon that compound A can generate product B with different structures and spectral properties through a specific chemical reaction when it is illuminated by wavelength h1, and reversibly forms a compound under the action of light or heat with wavelength h2 . There are many kinds of photochromic materials, which can be generally divided into organic photochromic and inorganic photochromic. One of the most popular inorganic photochromic materials is molybdenum oxide.

There are two ways to prepare photochromic smart glass, that is, the physical preparation method of preparing molybdenum trioxide coated glass by large-scale magnetron sputtering, and the preparation of molybdenum trioxide nanopowder by chemical means in advance by using nanotechnology, and then the nanopowder The body is prepared by chemical coating and other methods to become a chemical preparation method of film-attached energy-saving glass. Compared with the former method, the latter method is easier to be accepted by the market due to its obvious advantages of simple equipment, strong universality, low price, easy large-scale production, and wide application.

There are many ways to prepare molybdenum oxide, and there are many shapes, but there is a common problem: the prepared particles have a large size. In Chinese patents (CN103288138A, CN102603005A, CN102153142A), the particles are as large as hundreds of nanometers, and the smallest is also larger than 50 nanometers. However, this patent relies on the fineness of titanium oxide particles and coats it with a layer of molybdenum oxide, which reduces the size of the particles as a whole.

At the same time, due to the limitation of the energy band (in the ultraviolet range) of the molybdenum trioxide semiconductor itself, the dimming range and discoloration efficiency of the material are far worse than ideal applications. In order to solve this problem, amorphous molybdenum trioxide can be coated on a semiconductor metal oxide that matches molybdenum trioxide. The fundamental reason is that two semiconductors with matching energy bands can form a heterojunction structure, which reduces the Bandwidth, expand the dimming range, avoid the recombination of photogenerated electrons and holes, and improve the photochromic efficiency.

There are many choices of semiconductor oxides that match the energy band of molybdenum oxide, and titanium dioxide has outstanding performance. There are more materials, which is absolutely helpful to improve the photochromic efficiency of molybdenum trioxide; 2) Titanium dioxide has stable performance and good repeatability; 3) Molybdenum trioxide and titanium dioxide are coated to form a new optical structural unit, similar to the design The multilayer film obtains the same anti-reflection effect. A greater optical effect can be obtained by using the complex optical effect of the core-shell structure.

The preparation of the above-mentioned core-shell structure is also a difficulty in this patent. Some existing methods have synthesized titanium oxide and molybdenum oxide composites (Sensors and Actuators B (2011) 270, J.Am.Chem.Soc. (2000) 5138). However, the above method is complicated to operate, time-consuming and energy-consuming. Moreover, the composite coating of these morphologies has not studied the photochromic performance.

To sum up, the main reasons for the current lack of research on molybdenum oxide are: 1) After comparing organic and inorganic photochromic materials, many researchers have shifted to organic photochromic materials, while ignoring the use of chemical means to improve three-dimensional photochromic materials. Research on properties of molybdenum oxide. 2) There is a lack of simple and mature technology for compounding molybdenum oxide and titanium oxide. 3) There is a lack of technology for coating this coating into an energy-saving film. Due to the above reasons, there is currently no nanoparticle and energy-saving film with better performance and structure in photochromism.

Contents of the invention

The technical problem to be solved by the present invention is to provide a photochromic composite nano powder and a preparation method thereof. The photochromic composite nano powder has efficient photochromic performance.

In the present invention, the photochromic composite nanopowder has a core-shell structure, the outer shell is molybdenum trioxide, and the inner core is titanium dioxide. Wherein the titanium dioxide is anatase titanium dioxide nanoparticles, the shape is small particles, the particle size is different, the distribution range is 4-20nm, the preferred particle size is 5-10nm, and the molybdenum trioxide is amorphous Molybdenum nanoparticles, coating thickness 2-10nm.

The invention provides a method for preparing photochromic composite nanopowder, comprising selecting a molybdic acid solution or dissolving other molybdates in an acid solution to obtain a molybdic acid solution as a molybdenum source, and adding a titanium source to the molybdic acid solution , to obtain a precursor solution; adding an alkali and a redox agent to the precursor solution, and obtaining the composite nanoparticles of molybdenum trioxide-coated titanium dioxide through hydrothermal reaction.

Preferably, the molar ratio of the amount of titanium ions added to the molybdenum acid solution relative to the amount of molybdenum ions is 19:1-1:1.

Preferably, the molybdate is ammonium molybdate or sodium molybdate. The titanium source is preferably titanium tetrachloride or titanium sulfate.

Preferably, the acid solution has the same acid radical as the titanium source. The acid solution concentration is preferably 2-3ml/L. The acid solution is preferably a hydrochloric acid solution or a sulfuric acid solution. The concentration of the molybdic acid solution is preferably 0.0083-1.588 g/ml.

Preferably, the molar ratio of titanium ions to hydrogen ions in the acid solution is 6:(15-20).

Preferably, the alkaline solution is ammonia water, sodium hydroxide or potassium hydroxide, more preferably ammonia water.

Preferably, the redox agent is 35% hydrogen peroxide, and the amount of hydrogen peroxide added is 0.1-1 g per 1 mL of titanium source.

The photochromic composite nano-powder of the present invention is composed of molybdenum oxide-coated titanium oxide nanoparticles; the preparation of the powder adopts a simple and rapid one-step hydrothermal method, that is, mixing molybdenum source and titanium source, and obtaining oxidation by hydrothermal reaction. Molybdenum-coated titanium oxide nanoparticles; the photochromic composite nano-powder can be applied to the fields of energy-saving film, energy-saving glass or energy-saving wall. The photochromic composite nanopowder of the above invention can realize the miniaturization of molybdenum oxide, has excellent dispersibility and stability, and has efficient photochromic performance.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) collection of patterns of the molybdenum trioxide coated titanium dioxide nanoparticles prepared in embodiment 1;

Fig. 2 is the XRD figure of pure titanium oxide among the present invention;

Fig. 3 is the transmission electron microscope (TEM) photo of molybdenum trioxide coating titanium dioxide nanoparticle of the present invention, X-ray energy spectrum (EDS) and select electron diffraction pattern;

Fig. 4 is the XRD figure and the SEM figure of pure molybdenum oxide among the present invention;

Fig. 5 is a photochromic performance comparison diagram between molybdenum trioxide-coated titanium dioxide nanoparticles and pure phase molybdenum oxide in the present invention;

Figure 6 is a TEM comparison diagram of different molybdenum sources/titanium sources;

Fig. 7 is a graph of dimming efficiency of different molybdenum sources/titanium sources.

detailed description

In the present invention, the photochromic composite nanopowder is composed of titanium oxide nanoparticles coated with molybdenum oxide. The molybdenum oxide-coated titanium oxide nanoparticles have a core-shell structure, with anatase titanium dioxide nanoparticles as the core and amorphous molybdenum trioxide nanoparticles as the shell. The titanium dioxide nanoparticles are spherical, the molybdenum trioxide nanoparticles evenly coat the titanium dioxide nanoparticles, and the size distribution of the coated particles prepared by different proportions is uneven, ranging from 4-20nm. The coating thickness of the molybdenum trioxide is 2-10nm. According to its dimming efficiency, preferably, the particle diameter of the coating particles is 5-10 nm.

The photochromic composite nano-powder of the present invention is composed of molybdenum oxide-coated titanium oxide nanoparticles; the preparation of the powder adopts a simple and fast one-step hydrothermal method, specifically adding molybdenum source and titanium source to acid solution to prepare the precursor solution, and then add an alkali and a redox agent to obtain the molybdenum oxide-coated titanium oxide nanoparticles through hydrothermal reaction. The molybdenum salt can be ammonium molybdate, sodium molybdate. The titanium source may be titanium tetrachloride or titanium sulfate.

Regarding the preparation of the precursor solution, specifically, molybdates such as ammonium molybdate or sodium molybdate can be dissolved in an acid solution with a concentration greater than 2mol/L to obtain a molybdic acid solution with a concentration of 0.0083-1.588g/ml. At room temperature, stir The obtained molybdic acid solution is added with a titanium source having the same acid radical as the acid solution, such as titanium tetrachloride or titanium sulfate, to obtain a precursor solution. It is also possible to directly select a molybdenum acid solution with a concentration of 0.0083-1.588g/ml as the molybdenum source. At room temperature, stir the obtained molybdenum acid solution and add a titanium source with the same acid radical as the acid solution, such as titanium tetrachloride or titanium sulfate. Obtain the precursor solution. Regarding the concentration of the acid solution, it is preferably greater than 2 mol/L and less than 3 mol/L, so as to fully dissolve the titanium source and reduce its volatilization.

An alkali solution is added to the precursor solution, and after alkalization, a molybdenum-titanium sol is obtained. At this time, the sol is neutral or alkaline. Then add a redox agent to the molybdenum-titanium sol, put it into a reaction kettle, and then undergo a hydrothermal reaction to obtain a dispersion liquid. The alkaline solution added can be ammonia water, sodium hydroxide or potassium hydroxide, preferably ammonia water. In order to neutralize the acid solution to form a titanic acid structure without too fast neutralization affecting the formation of the coating structure, the mass fraction of the added alkali solution is preferably 28%. The amount of the added alkali solution is monitored with a pH meter, and when the solution is neutral or slightly alkaline, all the titanium sources are complexed into titanic acid and the molybdenum source is adsorbed. The selected redox agent is hydrogen peroxide with a concentration of 35%, and the amount added is 0.1-1 g per 1 mL of titanium source, which is used to desorb the hydroxide in the precipitation reaction. The reaction temperature of hydrothermal reaction should be controlled at 150 degrees Celsius, and the reaction time is 6 hours. The dispersion liquid was cooled to room temperature, filtered, washed with deionized water and absolute ethanol in sequence, and dried to obtain molybdenum oxide-coated titanium oxide nanoparticles. The drying temperature can be 70-90 degrees Celsius.

As an example, further specifically describe the preparation method of the photochromic composite nanopowder of the present invention, which includes the following steps: 1) molybdenum source is dissolved in the acid solution to obtain molybdic acid solution, the molybdic acid solution of stirring; 2 ) at room temperature, stirring the molybdenum acid solution and adding a titanium source to obtain a precursor solution; 3) adding an alkali solution to the precursor solution and basifying to obtain a molybdenum-titanium sol; 4) adding a molybdenum-titanium sol in the molybdenum-titanium A redox agent is added to the sol, and a dispersion is obtained through hydrothermal reaction; 5) the dispersion is cooled to room temperature, filtered and washed to obtain molybdenum oxide-coated titanium oxide nanoparticles. Optionally, the molybdenum source is ammonium molybdate, sodium molybdate or molybdic acid, the titanium source is titanium tetrachloride or titanium sulfate, and the acid radical of the acid solution is the same as that of the titanium source; The concentration of the acid solution is greater than 2ml/L, and the concentration of the molybdic acid solution is 0.0083-1.588g/ml. Preferably, the acid solution is hydrochloric acid or sulfuric acid, the titanium source is titanium tetrachloride, and the volume ratio of the titanium source to the acid solution is 6:(15-20). Optionally, the alkaline solution is ammonia water, sodium hydroxide or potassium hydroxide, preferably, the alkaline solution is ammonia water, and the sol is neutral or alkaline. Optionally, the redox agent is hydrogen peroxide, preferably, the hydrogen peroxide concentration is 35%, and the added amount is 0.1-1 g per 1 mL of titanium source.

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

This example describes a method for preparing molybdenum trioxide-coated titanium dioxide nanoparticles, including:

S1: Add 0.1576g ammonium paramolybdate into 10ml, 2mol/L hydrochloric acid solution to obtain soluble molybdic acid solution;

S2: Add 1ml of titanium tetrachloride to the soluble molybdic acid solution under stirring at room temperature to obtain a precursor solution;

S3: adding an appropriate amount of ammonia water dropwise to the precursor solution to make the solution pH>7, and alkalization to obtain a molybdenum-titanium sol;

S4: In the molybdenum-titanium sol, add 0.5g of hydrogen peroxide for every 1mL of titanium source, put it into a reaction kettle, react at a temperature of 150°C for 6 hours, and obtain a dispersion after the reaction is completed;

S5: Cool the dispersion to room temperature, wash with deionized water and absolute ethanol in turn, and dry to obtain molybdenum trioxide-coated titanium dioxide (TiO ₂ -MoO ₃ coated) core-shell nanopowder, named TM -10.

Example 2

Preparation of pure titanium oxide: refer to the preparation steps of molybdenum trioxide-coated titanium dioxide nanoparticles described in Example 1, step S1 hydrochloric acid solution in Example 1 does not add ammonium paramolybdate, and all the other steps are the same as in Example 1. Prepare pure titanium oxide.

FIG. 1 is an X-ray diffraction (XRD) pattern of molybdenum trioxide-coated titanium dioxide nanoparticles prepared in Example 1, and FIG. 2 is an XRD pattern of pure titanium oxide prepared in Example 2. Comparing Figure 1 and Figure 2, it can be seen that the characteristic peak of the molybdenum trioxide-coated titanium dioxide nanoparticles prepared in Example 1 is TiO ₂ , and no other impurity peaks appear in Figure 1, indicating that the TiO in the molybdenum trioxide-coated titanium dioxide nanoparticles ₂ is crystalline and MoO ₃ is amorphous.

Please refer to FIG. 3: FIG. 3 is a transmission electron microscope (TEM) photo, an X-ray energy spectrum (EDS) and a selected electron diffraction diagram of the molybdenum trioxide-coated titanium dioxide nanoparticles prepared in Example 1. Combining the TEM image and the EDS image, it can be seen that the middle of the sample prepared in Example 1 is granular crystalline TiO ₂ , surrounded by amorphous MoO ₃ . In addition, the selected electron diffraction photo has a diffraction ring, which further illustrates the crystallization TiO ₂ is polycrystalline, therefore, in the molybdenum oxide-coated titanium oxide nanoparticles prepared in Example 1, TiO ₂ is polycrystalline, and MoO ₃ is amorphous.

Example 3

In order to study the improvement of photochromic performance of TiO ₂ -MoO ₃ coated nanospheres, comparative samples were prepared. About the preparation of pure-phase molybdenum oxide: refer to the preparation steps of molybdenum trioxide-coated titanium dioxide nanoparticles described in Example 1. Step S2 is omitted in Example 1, and the remaining steps are the same as in Example 1, so that pure Titanium oxide.

Fig. 4 is an XRD pattern and an SEM pattern of pure molybdenum oxide in the present invention, and the pure phase molybdenum oxide prepared in this embodiment is molybdenum oxide nanorods. Analysis of the XRD pattern in Figure 4 shows that the structure of molybdenum oxide is α-MoO ₃ .

Example 4

The molybdenum trioxide-coated titanium dioxide nanopowder prepared in Example 1 and the pure-phase molybdenum oxide powder prepared in Example 3 were uniformly dispersed in the ethanol solution respectively to obtain a 0.3wt% sample solution to test their photochromic properties .

Please refer to FIG. 5 . FIG. 5 is a comparison chart of the photochromic properties of molybdenum trioxide-coated titanium dioxide nanoparticles and pure phase molybdenum oxide in the present invention. As can be seen from Figure 5, the photochromic efficiency of the molybdenum trioxide-coated titanium dioxide nanoparticles prepared in Example 1 is 20 times that of the pure-phase molybdenum oxide prepared in Example 3, thus it can be seen that three Molybdenum oxide-coated titanium dioxide nanoparticles have high photochromic properties.

Examples 5, 6, 7 and 8 are single-variable comparative examples. Referring to the preparation process of Example 1, the only thing changed is the molar ratio of molybdenum ions and titanium ions. The molar ratios of molybdenum ions and titanium ions correspond to: 5:95, 15:85, 25:75, 50:50. And accordingly named TM-5, TM-15, TM-25, TM-50. Other variables are no longer explained in detail in the patent, but can not be used to limit the scope of rights of the present invention.

Please refer to Figure 6, Figure 6 is a TEM comparison image of different molybdenum sources/titanium sources. With the increase of molybdenum source, the average particle size becomes smaller, the particle dispersibility becomes better, and the particle distribution range becomes smaller and smaller. The distribution of TM-5 is 4-20nm, and that of TM-25 is reduced to 5-8nm. When there are too many molybdenum sources, the particles grow again, and different types of particles appear. Therefore TM-25 is the smallest size coating.

Please refer to FIG. 7 . FIG. 7 is a graph of the dimming efficiency of different molybdenum sources/titanium sources. The solution preparation follows Example 4, and the concentration of the sample solution is prepared to be 0.05wt%. It can be seen that the best size TM-25 has the highest dimming efficiency. This is the reason for particle size optimization in the preceding claims.

What is disclosed above is only a preferred embodiment of the present invention, and of course it cannot limit the scope of rights of the present invention. Those of ordinary skill in the art can understand all or part of the process for realizing the above embodiments, and according to the rights of the present invention The equivalent changes required still belong to the scope covered by the invention.

Claims (8)

1. a kind of photochromic composite nano powder, it is characterized in that, the photochromic composite nano powder particle is core shell structure, and shell is molybdenum trioxide, and kernel is titanium dioxide, wherein described titanium dioxide is anatase titanium dioxide nano particle, graininess is shaped as, clad structure particle diameter of nanometer powder is distributed as 4-20nm, and the molybdenum trioxide is unbodied molybdenum trioxide nano particle, cladding thickness distribution is uneven, and distribution is 2-10nm.

2. it is a kind of as claimed in claim 1 photochromic composite nano powder preparation method, it is characterised in that including：Choose molybdenum acid solution or be dissolved in other molybdates and molybdenum acid solution as molybdenum source is obtained in acid solution, and titanium source is added in the molybdenum acid solution, obtain precursor solution；Alkali and reductant-oxidant are added in the precursor solution, the composite nanometer particle of the molybdenum trioxide cladding titanium dioxide is obtained through hydro-thermal reaction.

3. photochromic composite nano powder preparation according to claim 2, it is characterised in that the molybdenum salt is ammonium molybdate, sodium molybdate, the titanium source is titanium tetrachloride or titanium sulfate.

4. the photochromic composite nano powder preparation according to Claims 2 or 3, it is characterised in that the acid solutions 2-3ml/L.

5., according to one of any described photochromic composite nano powder preparations of claim 2-4, it is characterised in that the molybdenum acid solution concentration is 0.0083-1.588g/ml, titanium ion and the mol ratio of molybdenum ion are 19 in reaction solution:1-1:1.

6. according to one of any described photochromic composite nano powder preparations of claim 2-5, it is characterised in that titanium ion is 6 with the hydrionic mol ratio of the acid solution:（15-20）.

7. according to one of any described photochromic composite nano powder preparations of claim 2-6, it is characterised in that the aqueous slkali is the alkaline solutions such as ammoniacal liquor, NaOH, potassium hydroxide.

8., according to one of any described photochromic composite nano powder preparations of claim 2-7, it is characterised in that the reductant-oxidant is the hydrogen peroxide of concentration 35%, the amount of addition is to add 0.1~1g hydrogen peroxide per 1mL titanium sources relatively.