CN107778015B

CN107778015B - Infrared opacifier with SiCN as core layer and preparation method and application thereof

Info

Publication number: CN107778015B
Application number: CN201610739551.9A
Authority: CN
Inventors: 刘洪丽; 魏宁; 李洪彦; 李婧; 李亚静
Original assignee: Tianjin Chengjian University
Current assignee: Tianjin Chengjian University
Priority date: 2016-08-26
Filing date: 2016-08-26
Publication date: 2020-08-21
Anticipated expiration: 2036-08-26
Also published as: CN107778015A

Abstract

The invention provides an infrared opacifier taking SiCN as a nuclear layer and a preparation method and application thereof, and the infrared opacifier taking SiCN as the nuclear layer is SiCN @ ZrO with controllable size₂Core-shell ceramic microspheres, the core-shell structure being ZrO₂Coating SiCN with size of 0.75-0.85 μm, wherein the thickness of core layer SiCN is 0.55-0.75 μm, and shell layer ZrO₂The thickness of the ceramic is 0.1-0.2 μm, and the ceramic is prepared by adopting tetrabutyl Zirconate (ZBT), acetonitrile, alkylphenol polyoxyethylene ether (OP-10), polysilazane ceramic Precursor (PVSZ) and toluene as raw materials. The core-shell structure ceramic microspheres have controllable sizes and high temperature resistance, and can effectively improve SiO₂The infrared resistance of (1).

Description

Infrared opacifier with SiCN as core layer and preparation method and application thereof

Technical Field

The invention relates to a size-controllable SiCN-based core-shell structure ceramic microsphere and a preparation method thereof, belonging to the field of high-temperature heat insulation materials.

Background

The rapid development of social economy causes the global energy consumption to be too fast, and the shortage of energy becomes a worldwide problem. One of the most effective measures for saving energy is to research and apply environment-friendly heat-insulating materials. The fields of modern industry, building industry, aerospace and the like require that the heat-insulating material has a series of performances of high temperature resistance, light weight, high strength, high stability and the like. The existing traditional heat insulation materials are increasingly difficult to meet the higher requirements of various industries on heat insulation materials. Nano SiO₂The aerogel used as a nano porous transparent heat insulation material has extremely high porosity (85-99 percent), smaller average pore diameter (2-50nm), and large specific surface area (500- & gt 1300 m)²In g) and very low density (30-150 kg/m)³)。SiO₂The aerogel has ultralow heat conductivity, and the effective heat conductivity of the aerogel at normal temperature and normal pressureThe thermal conductivity of the coating is only 0.013-0.020W/(m.k), which is lower than that of room-temperature static air. However, when the use temperature rises above 300 ℃, pure SiO₂The thermal insulation performance of the aerogel becomes poor. SiO 2₂The aerogel is almost transparent to near infrared radiation with the wavelength of 2.5-7 mu m, however, the radiation is mainly concentrated in the wave band at the high temperature of 300-1300K, and the radiation heat transfer is the main energy transfer mode at the high temperature, thereby greatly limiting the application of the aerogel in the high-temperature environment. Currently, to address this problem, a common effective approach is to enhance the SiO by introducing infrared opacifiers₂Aerogel thermal insulation performance.

In the existing domestic and foreign research, carbon black and inorganic compounds SiC and Fe are mainly adopted₃O₄、TiO₂、ZnO、ZrO₂Etc. as SiO₂Aerogel infrared sunscreens. Numerous studies have shown that the shape, type, size and addition of infrared opacifiers can all significantly affect SiO₂Aerogel composites have thermal insulation properties. In SiO₂Inorganic ceramic fibers or rod-shaped fillers are added into the aerogel, so that the shielding capability of the material on infrared rays is improved to a certain degree, but the shading effect is general. In contrast, the effect of the spherical sunscreen is better.

Compared with single-component microspheres, the core-shell composite microspheres containing two or more than two different performance substances have more excellent physical and chemical properties, so that the core-shell microspheres become indispensable nano materials in the fields of optics, catalysis and the like in the last decades. In recent years, with further research on core-shell structure microspheres, the microspheres have great application prospects in the field of infrared shading.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for preparing SiO₂An infrared high-shielding core-shell structure opacifier of aerogel and a preparation method thereof. The emulsion method and the ceramic precursor conversion method are combined to prepare the ceramic microsphere opacifier with the core-shell structure with controllable size, and the optimal SiCN @ ZrO is obtained by changing the size and the interface state of the core-shell structure₂An anti-infrared opacifier.

The purpose of the invention is realized by the following technical scheme.

SiCN@ZrO₂The core-shell ceramic microspheres are prepared by adopting tetrabutyl Zirconate (ZBT), acetonitrile, alkylphenol ethoxylates (OP-10), a polysilazane ceramic Precursor (PVSZ) and toluene as raw materials; SiCN @ ZrO with SiCN as core layer and infrared opacifier with controllable size₂Core-shell ceramic microspheres, the core-shell structure being ZrO₂Coating SiCN with size of 0.75-0.85 μm, wherein the thickness of core layer SiCN is 0.55-0.75 μm, and shell layer ZrO₂The thickness of (A) is 0.1 to 0.2 μm.

The ceramic microsphere with SiCN as the core layer and the preparation method thereof are carried out according to the following steps:

step 1, adding 1000 parts by weight of mixed solution of acetonitrile and deionized water into a beaker, wherein the volume ratio of water to acetonitrile is (2-4) - (6-8), then adding 10 parts by weight of emulsifier alkylphenol polyoxyethylene ether (OP-10) into the mixed solution of acetonitrile and water, carrying out ultrasonic stirring until the mixture is uniformly mixed to form a water phase, sequentially adding 100 parts by weight of toluene, 100 parts by weight of polysilazane ceramic precursor and 6-15 parts by weight of tetrabutyl zirconate into another beaker, carrying out ultrasonic stirring until the mixture is uniformly mixed to form an oil phase, slowly dripping the oil phase into the water phase under the condition of magnetic high-speed stirring to form a uniform emulsion system, putting the formed emulsion into a polytetrafluoroethylene lining of a high-pressure reaction kettle, and carrying out curing reaction in a constant-temperature oven to obtain a cured product;

step 2, centrifugally cleaning the cured product obtained in the step 1 by using an organic solvent and water, and then drying the cured product in an oven;

and 3, putting the product obtained in the step 2 into an atmosphere furnace for sintering to obtain the powdered infrared opacifier taking SiCN as a nuclear layer.

In the step 1, in the mixed solution of acetonitrile and deionized water, the volume ratio of water to acetonitrile is 3: 7; conditions of the curing reaction: the curing reaction temperature is 180 ℃ and 260 ℃, and the curing reaction time is 4-8 h; in the preparation of the water phase and the oil phase, ultrasonic stirring conditions are as follows: the ultrasonic stirring speed is 30-50KHz, and the ultrasonic stirring time is 10-20 min; when the oil phase is dripped into the water phase, uniform dripping is adopted, the dripping time is controlled to be 0.5-3 hours, preferably 2-3 hours, and magnetic high-speed stirring is kept during the dripping process at the speed of 200-500 r/min per minute.

In the step 2, the organic solvent is one of normal hexane, carbon tetrachloride, chloroform, benzene, paraffin ether and carbon disulfide, centrifugal cleaning is carried out for 1-3 times, the speed of centrifugal cleaning is 9000-10000r/min, the time of centrifugal cleaning is 4-6min, and the temperature of an oven is 70-90 ℃.

In step 3, the material is pyrolyzed for 1 to 3 hours from room temperature (20 to 25 ℃) to 800-1400 ℃ at the heating rate of 3 to 6 ℃/min, and is naturally cooled to room temperature (20 to 25 ℃) after being cooled to 400 ℃ at the cooling rate of 4 to 6 ℃/min, wherein the sintering atmosphere is inert gas, such as nitrogen, helium or argon.

When in use, 100 parts by weight of SiCN as a nuclear layer of the infrared opacifier and 1000 parts by weight of nano-silica are uniformly mixed and then are subjected to compression molding, steam curing and heat treatment to obtain the doped modified silica aerogel, the average effective extinction coefficient of which is 20-45m²Kg (i.e. the use of infrared sunscreens with a core layer of SiCN for improving the properties of nanosilica).

Wherein, the mixed raw materials are put into a 50mm cylindrical die and are pressed and molded, and the pressure of the pressing and molding is 1-3 MPa; adopting a steam curing method to carry out anti-rebound pretreatment on the mixed raw materials; the temperature of the heat treatment is 140-160 ℃, and the time of the heat treatment is 1-3 h.

As shown in figure 1, the ceramic microspheres obtained by high-temperature pyrolysis at 1400 ℃ can still maintain complete spherical morphology and rough surface, the particle size of the microspheres is about 0.75-0.85 μm, and the size shrinkage rate of the microspheres converted from polymer microspheres to ceramic microspheres is 14.2-15%; as shown in FIG. 2, it can be seen that SiCN @ ZrO₂The core-shell structure ceramic microspheres show an obvious core-shell structure; as shown in FIG. 3, SiCN @ ZrO₂The TEM picture of the local part of the core-shell structure ceramic microsphere obviously shows that the ceramic microsphere has an uneven shell layer, so that a rough surface is observed in an SEM picture, the thickness of the shell layer is 0.1-0.2 mu m, and the thickness of the core layer is 0.55-0.75 mu m. FIG. 4 is a partial magnification at high resolutionSiNC@ZrO₂Part of the shell of the core-shell ceramic microsphere, and FIG. 5 is a photograph of the width of nano-lattice stripe of the ceramic microsphere with high resolution and local magnification, the width of the nano-lattice stripe is 0.318nm and ZrO₂The crystal structure has a (101) lattice d of 0.31 nm. EDS characterization is carried out on the ceramic microspheres, as shown in the following table, the core-shell ceramic microsphere shell layer part after 1400 ℃ pyrolysis contains elements such as C, O, Si, N, Zr and the like, wherein the Zr content is about 12.21%, and the composite microsphere shell layer is preliminarily proved to be composed of Si-C-N and ZrO₂。

Element(s)	Percentage of
		Si	27.21
Zr	12.21
		C	6.03
N	0.83
		O	53.72

As shown in FIG. 6, it can be seen from the graph that the weight loss of the microspheres increases with increasing temperature, and the final cracking yield of the microspheres is about 76.4%, indicating PVSZ @ ZrO₂The core-shell microspheres have good thermodynamic stability, and the weight loss of a sample is about 3.78% below 180 ℃, mainly composed of water, residual solvent anddue to the volatilization of low molecular weight substances. The temperature rise was at 180 ℃ and 400 ℃, the thermogravimetric curve showed a minor mass loss of about 2.08%, while the DTA curve showed an endothermic peak in this section, where the thermal crosslinking reaction mainly occurred, and between 400 ℃ and 800 ℃, the weight loss was about 17.58%, mainly due to the degradation of the side chain organic groups, and no significant mass loss was detected in the region above 800 ℃, indicating that the ceramization of the microspheres was substantially complete and the pyrolysis yield was about 76.4%.

As shown in FIG. 7, when compared with a standard PDF card, ZrO appeared at a pyrolysis temperature of 800 deg.C₂(ICDDPDF: No.49-1642) diffraction peaks at 30.12 ° (111) and 50.22 ° (220). With increasing pyrolysis temperature, it was observed that ZrO is responsible for₂The intensity of the diffraction peak of (A) is gradually increased at 1100 ℃, a characteristic diffraction peak belonging to β -SiC (ICDD PDF: No.48-0708) is observed at 36.22 DEG 2 theta, and ZrO is formed after pyrolysis at 1400 DEG C₂The diffraction peak intensity of (A) became significantly stronger, while the pattern showed relatively sharp β -SiC (JCPDS #48-0708) diffraction peaks at 36.22 ° (103), 60.05 ° (110) and 72.08 ° (311), with α -Si appearing at the 26.5 ° and 45 ° positions₃N₄(JCPDS # 09-0250). In the range of 1100-1400 ℃, along with the increase of temperature, the inorganic structure of the microsphere pyrolysis product is further perfected, the amorphous state is converted into the crystalline state, and ZrO appears₂β -SiC and α -Si₃N₄A crystalline phase. Therefore, the precursor conversion method can be used for converting the PVSZ @ ZrO₂The core-shell microspheres can be pyrolyzed at 1400 ℃ in an inert atmosphere to obtain SiCN @ ZrO₂Core-shell ceramic microspheres.

As shown in FIG. 8, it can be seen from the spectrum that PVSZ @ ZrO was prepared at 220 deg.C₂The core-shell microspheres show characteristic absorption peaks as follows: at 3400cm^-1And 1170cm^-1At 2970cm of N-H stretching vibration peak^-1And 2902cm^-1Unsaturated C-H (-CH ═ CH)₂) Telescopic vibration peak, 2350cm^-1Si-H stretching vibration peak at 1260cm^-1At the peak of Si-C stretching vibration, 1406cm^-1C ═ C stretching vibration peak, and 540cm^-1The peak belongs to the vibration absorption peak of Zr-O-Zr. With heatThe decomposition temperature was raised to 800 ℃, and the characteristic absorption peaks of the organic functional groups N-H, C-H, Si-H, Si-C and C ═ C were observed to gradually decrease or even disappear. The breaking of the C-H, Si-C and N-H bonds indicates that the microspheres begin to transition from the organic to the inorganic state, yielding Si-C-N amorphous products. At a pyrolysis temperature of 1100 ℃, the characteristic absorption peak of the organic functional group almost completely disappears, and only the absorption peak at 900-1100cm can be observed^-1A relatively broad absorption peak of Si-C and Si-N-Si, etc. superposed, and 540cm^-1The Zr-O-Zr absorption peak indicates that the process of converting the polymer to ceramic is basically finished. The absorption peak position in the infrared spectrum of the microspheres pyrolyzed at 1400 ℃ is basically the same as that at 1100 ℃, and the inorganic transition is complete.

As shown in FIG. 9, in the wavelength range of 2.5 to 7 μm, the temperature is PVSZ @ ZrO at different temperatures₂And (3) an infrared transmittance change rule curve of core-shell microsphere pyrolysis. Generally, a higher infrared transmittance over a certain wavelength band indicates a weaker light-shielding ability of the microsphere. It can be observed from the figure that the PVSZ @ ZrO obtained by crosslinking and curing at 220 ℃ is₂The core-shell microspheres have high infrared transmittance, which is about 65.1-77.8%, and this indicates that the product has low infrared radiation shielding capability. When the sample is subjected to pyrolysis treatment at 800 ℃, the obtained infrared transmittance is reduced to 32.1%, and according to thermogravimetry and XRD analysis, the microspheres are converted from organic to inorganic at the moment, the product is in an amorphous state, and the extinction performance of the product is obviously enhanced. The infrared transmittance of the sample after pyrolysis treatment at 1100 ℃ was 26.8%. When the pyrolysis temperature is further increased to 1400 ℃, the infrared transmittance reaches the minimum value of about 12.5 percent, and at the moment, the core-shell ceramic microspheres mainly contain crystalline ZrO₂SiC crystal phase and Si₃N₄A crystalline phase. The results show that the infrared transmittance of the product is gradually reduced along with the increase of the pyrolysis temperature, which shows that the pyrolysis temperature has great influence on the infrared shielding performance of the product, and crystalline SiCN @ ZrO₂The core-shell ceramic microspheres have more effective shading performance and stronger infrared radiation scattering capability.

As shown in FIG. 10, different amounts of SiCN @ ZrO were added₂An infrared transmittance curve diagram of the composite material obtained by the core-shell ceramic microspheres in a range of 2.5-7 mu m. As can be seen from the figures, it is,SiCN@ZrO₂the doping amounts of the core-shell ceramic microspheres are respectively 0 wt%, 10 wt%, 20 wt% and 30 wt%, and the obtained corresponding infrared transmittances are 65.8-89.7%, 28.5%, 11.8% and 19.4% in sequence, namely with SiCN @ ZrO₂The infrared transmittance of the core-shell ceramic microspheres tends to decrease and then increase when the addition amount of the core-shell ceramic microspheres is increased, and the IR transmittance of the core-shell ceramic microspheres reaches the minimum value when the addition amount is 20 wt%. When the addition amount is increased to 30 wt%, the IR transmittance becomes large on the contrary. This indicates SiCN @ ZrO₂The addition amount of the core-shell ceramic microspheres is 20 wt%, and the shielding effect on infrared radiation is better and is obviously stronger than 10 wt% and 30 wt%.

The invention has the beneficial effects that:

1. the ceramic microsphere of the invention is a core layer of SiCN and ZrO₂Is a core-shell structure of a shell layer. SiCN has good high-temperature stability, creep resistance and low processing temperature. At the same time, because of ZrO₂The material has the advantages of inactive chemical property, high refractive index and excellent high temperature resistance, so that the material becomes an important functional material in the existing infrared scattering heat insulation material. The intensity of infrared ray passing through the coating interface of the core-shell microsphere is continuously reduced, so that the SiO is improved₂The radiation resistance properties of aerogel materials in high temperature environments;

2. the preparation method is simple, the method does not need to add any complexing agent and catalyst, adopts the combination of an emulsion method and a precursor conversion method, and has the characteristics of molecular designability, simple forming process, low sintering temperature and the like;

the size is controllable, and the average grain diameter of the opacifier core-shell structure can be controlled by adjusting the process parameters such as the content of each component, the curing reaction time, the curing reaction temperature and the like.

Drawings

FIG. 1 is SiCN @ ZrO₂SEM photograph of core-shell structure ceramic microsphere.

FIG. 2 is SiCN @ ZrO₂TEM photograph of core-shell structure ceramic microsphere.

FIG. 3 is SiCN @ ZrO₂Local TEM photo of the core-shell structure ceramic microsphere.

FIG. 4 is a partial magnification of SiNC @ ZrO at high resolution₂TEM photograph of partial shell layer of the core-shell ceramic microsphere.

Fig. 5 is a photograph of the width of the nano-lattice fringes of the ceramic microspheres at high resolution with local magnification.

FIG. 6 is PVSZ @ ZrO₂TG/DTA curve graph of core-shell microspheres.

FIG. 7 shows SiCN @ ZrO obtained by pyrolysis at pyrolysis temperatures of 800 deg.C, 1100 deg.C and 1400 deg.C₂XRD pattern of the ceramic microsphere with core-shell structure.

FIG. 8 shows SiCN @ ZrO obtained by pyrolysis at pyrolysis temperatures of 800 deg.C, 1100 deg.C and 1400 deg.C₂FT-IR spectrogram of the ceramic microsphere with the core-shell structure.

FIG. 9 is a graph showing PVSZ @ ZrO pyrolyzed at pyrolysis temperatures of 800 deg.C, 1100 deg.C and 1400 deg.C₂And (3) an infrared transmittance change rule curve of core-shell microsphere pyrolysis.

FIG. 10 is SiCN @ ZrO₂The infrared transmittance curve diagram of the doped modified silicon dioxide aerogel obtained by adding 0 wt%, 10 wt%, 20 wt% and 30 wt% of the core-shell structure ceramic microspheres in the range of 2.5-7 mu m.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples.

Wherein the parameters of the used raw materials are shown in the following table, and an inert gas nitrogen atmosphere is used as a calcining atmosphere; uniformly mixing by using magnetic stirring, wherein the ultrasonic stirring speed is 30-50KHz, and the ultrasonic stirring time is 20 min; when the oil phase is dripped into the water phase, uniform dripping is adopted, the dripping time is controlled to be 2-3 hours, and magnetic high-speed stirring is kept in the dripping process at the speed of 200-500 revolutions per minute/min.

Example 1

1) A mixed solution of 10g of acetonitrile and deionized water was added to the beaker, wherein the ratio of water to acetonitrile was 3: 7. Then 0.1g of emulsifier OP-10 is added into the mixed solution of acetonitrile and water, and the mixture is stirred by ultrasonic wave until the mixture is mixed evenly to form a water phase; adding 1g of toluene, 1g of polysilazane ceramic precursor and 0.15g of tetrabutyl zirconate into another beaker, and ultrasonically stirring until the mixture is uniformly mixed, wherein the ultrasonic stirring speed is 30kHz, and the ultrasonic stirring time is 20min to form an oil phase; slowly dripping the oil phase into the water phase under the condition of magnetic high-speed stirring to form a uniform emulsion system; putting the formed emulsion into a polytetrafluoroethylene lining of a high-pressure reaction kettle, and carrying out curing reaction for 8 hours at 260 ℃ in a constant-temperature oven;

2) centrifugally cleaning the product obtained in the step 1 with an organic solvent and water for 2 times, 5min each time, wherein the cleaning speed is 9000r/min, and drying in an oven at the temperature of 80 ℃;

3) putting the product obtained in the step 2 into an atmosphere furnace, and sintering for 1h at 1400 ℃;

4) and (3) uniformly mixing 3g of the powder obtained in the step (3) with 10g of nano silicon dioxide, pretreating the mixed raw materials by adopting a steam curing method, performing compression molding under the molding pressure of 1MPa, and performing heat treatment on the molded block and the film product at the temperature of 150 ℃ for 2 hours to prepare the doped modified silicon dioxide aerogel.

The average size of the core-shell structure ceramic microspheres is 0.75 μm. The effective extinction coefficient of the nano silicon dioxide material is 2.9-9.7m²Per kg, the effective extinction coefficient of the doped nano silicon dioxide composite material is 34.9-38.9m²/kg。

Example 2

1) A mixed solution of 10g of acetonitrile and deionized water was added to the beaker, wherein the ratio of water to acetonitrile was 3: 8. Then 0.1g of emulsifier OP-10 is added into the mixed solution of acetonitrile and water, and the mixture is stirred by ultrasonic wave until the mixture is mixed evenly to form a water phase; adding 1g of toluene, 1g of polysilazane ceramic precursor and 0.10g of tetrabutyl zirconate into another beaker, and ultrasonically stirring until the materials are uniformly mixed, wherein the ultrasonic stirring speed is 40kHz, and the ultrasonic stirring time is 15min, so as to form an oil phase; slowly dripping the oil phase into the water phase under the condition of magnetic high-speed stirring to form a uniform emulsion system; putting the formed emulsion into a polytetrafluoroethylene lining of a high-pressure reaction kettle, and carrying out curing reaction for 6 hours in a constant-temperature oven at 220 ℃;

2) respectively centrifugally cleaning the product obtained in the step 1 by using an organic solvent and water for 3 times, wherein each time is 4min, the cleaning speed is 9600r/min, and drying the product in a 70 ℃ drying oven;

3) putting the product obtained in the step 2 into an atmosphere furnace, and sintering for 2h at 1100 ℃;

4) and (3) uniformly mixing 2g of the powder obtained in the step (3) with 10g of nano silicon dioxide, pretreating the mixed raw materials by adopting a steam curing method, performing compression molding under the molding pressure of 2MPa, and performing heat treatment on the molded block and the film product at the temperature of 140 ℃ for 3 hours to prepare the doped modified silicon dioxide aerogel.

The average size of the core-shell structure ceramic microspheres is 0.80 μm. The effective extinction coefficient of the nano silicon dioxide material is 2.9-9.7m²Per kg, the effective extinction coefficient of the doped nano silicon dioxide composite material is 39.1-43.7m²/kg。

Example 3

1) A mixed solution of 10g of acetonitrile and deionized water was added to the beaker, wherein the ratio of water to acetonitrile was 2: 7. Then 0.1g of emulsifier OP-10 is added into the mixed solution of acetonitrile and water, and the mixture is stirred by ultrasonic wave until the mixture is mixed evenly to form a water phase; adding 1g of toluene, 1g of polysilazane ceramic precursor and 0.06g of tetrabutyl zirconate into another beaker, and ultrasonically stirring until the mixture is uniformly mixed, wherein the ultrasonic stirring speed is 60kHz, and the ultrasonic stirring time is 10min to form an oil phase; slowly dripping the oil phase into the water phase under the condition of magnetic high-speed stirring to form a uniform emulsion system; putting the formed emulsion into a polytetrafluoroethylene lining of a high-pressure reaction kettle, and carrying out curing reaction for 4 hours at 180 ℃ in a constant-temperature oven;

2) respectively centrifugally cleaning the product obtained in the step 1 by using an organic solvent and water for 1 time, wherein the cleaning speed is 10000r/min each time for 6min, and drying the product in a 90 ℃ drying oven;

3) putting the product obtained in the step 2 into an atmosphere furnace, and sintering for 3h at 800 ℃;

4) and (3) uniformly mixing 1g of the powder obtained in the step (3) with 10g of nano silicon dioxide, pretreating the mixed raw materials by adopting a steam curing method, performing compression molding under the molding pressure of 3MPa, and performing heat treatment on the molded block and the film product at the temperature of 160 ℃ for 1h to prepare the doped modified silicon dioxide aerogel.

The average size of the core-shell structure ceramic microspheres is 0.84 μm. The effective extinction coefficient of the nano silicon dioxide material is 2.9-9.7m²Per kg, the effective extinction coefficient of the doped nano silicon dioxide composite material is 24.7-28.8m²/kg。

Comparative example

The method comprises the following steps of pretreating 10g of nano silicon dioxide by adopting a steam curing method, carrying out compression molding under the molding pressure of 2MPa, and carrying out heat treatment on a molded block and a film product at the temperature of 150 ℃ for 2 hours to obtain the silicon dioxide aerogel.

The ceramic microsphere powder can be prepared by adopting the content adjustment process recorded in the content of the invention, and the ceramic microsphere powder shows the property basically consistent with the property of the application after being mixed with the nano silicon dioxide.

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims

1. The infrared opacifier taking SiCN as a core layer is characterized in that the infrared opacifier taking SiCN as the core layer is SiCN @ ZrO₂Core-shell ceramic microspheres, the core-shell structure being ZrO₂Coating SiCN with size of 0.75-0.85 μm, wherein the thickness of core layer SiCN is 0.55-0.75 μm, and shell layer ZrO₂Is 0.1 to 0.2 μm, according to the following steps:

step 1, adding 1000 parts by weight of a mixed solution of acetonitrile and deionized water into a beaker, wherein the volume ratio of water to acetonitrile is (2-4) - (6-8), then adding 10 parts by weight of emulsifier alkylphenol polyoxyethylene ether into the mixed solution of acetonitrile and water, carrying out ultrasonic stirring until the mixture is uniformly mixed to form a water phase, sequentially adding 100 parts by weight of toluene, 100 parts by weight of polysilazane ceramic precursor and 6-15 parts by weight of tetrabutyl zirconate into another beaker, carrying out ultrasonic stirring until the mixture is uniformly mixed to form an oil phase, slowly dripping the oil phase into the water phase under the condition of magnetic high-speed stirring to form a uniform emulsion system, putting the formed emulsion into a polytetrafluoroethylene lining of a high-pressure reaction kettle, and carrying out curing reaction in a constant-temperature oven to obtain a cured product; the curing reaction temperature is 180 ℃ and 260 ℃, and the curing reaction time is 4-8 h;

step 3, putting the product obtained in the step 2 into an atmosphere furnace for sintering, heating the product from 20-25 ℃ to 800-1400 ℃ at a heating rate of 3-6 ℃/min for pyrolysis for 1-3h, cooling the product to 400 ℃ at a cooling rate of 4-6 ℃/min, and then naturally cooling the product to 20-25 ℃ under the inert gas atmosphere; thus, a powdery SiCN-based infrared sunscreen agent was obtained.

2. An infrared sunscreen having a core layer of SiCN as claimed in claim 1 characterized in that in step 1, the volume ratio of water to acetonitrile in the mixed solution of acetonitrile and deionized water is 3: 7.

3. An infrared sunscreen having a core layer of SiCN as claimed in claim 1 characterized in that in step 1, in the preparation of the aqueous phase and the oil phase, the conditions of ultrasonic agitation are: the ultrasonic stirring speed is 30-50KHz, and the ultrasonic stirring time is 10-20 min.

4. The infrared sunscreen agent with SiCN as core layer as claimed in claim 1, wherein in step 2, the organic solvent is one of n-hexane, carbon tetrachloride, chloroform, benzene, paraffin ether, carbon disulfide, centrifugal cleaning is performed for 1-3 times, the speed of centrifugal cleaning is 9000-10000r/min, the time of centrifugal cleaning is 4-6min, and the temperature of the oven is 70-90 ℃.

5. The infrared sunscreen agent with SiCN as core layer as claimed in claim 1, wherein in step 1, when the oil phase is dropped into the water phase, the dropping is performed at a constant speed, the dropping time is controlled to be 0.5-3 hours, and the magnetic stirring is maintained at a high speed during the dropping at a speed of 200 revolutions per minute and 500 revolutions per minute.

6. An infrared screening agent having a SiCN core layer according to claim 5, wherein in step 1, when the oil phase is dropped into the aqueous phase, the dropping time is controlled to be 2 to 3 hours.

7. An infrared sunscreen having a SiCN core layer as claimed in claim 1 wherein in step 3, said inert gas is nitrogen, helium or argon.

8. The preparation method of the infrared opacifier taking SiCN as a core layer is characterized by comprising the following steps:

9. A method of preparing an infrared sunscreen having a core layer of SiCN as claimed in claim 8 wherein in step 1, in the mixed solution of acetonitrile and deionized water, the volume ratio of water to acetonitrile is 3: 7; in the preparation of the water phase and the oil phase, ultrasonic stirring conditions are as follows: the ultrasonic stirring speed is 30-50KHz, and the ultrasonic stirring time is 10-20 min.

10. A method for preparing an infrared screening agent with SiCN as core layer as claimed in claim 8, wherein in step 1, when the oil phase is dropped into the water phase, the dropping is carried out at a constant speed, the dropping time is controlled to be 0.5-3 hours, and the magnetic stirring is kept at a high speed during the dropping process, the speed is 200-500 rpm.

11. A method for preparing an infrared sunscreen having SiCN as a core layer as claimed in claim 10, wherein in step 1, when the oil phase is dropped into the aqueous phase, the dropping time is controlled to be 2 to 3 hours.

12. The method for preparing an infrared opacifier with SiCN as a core layer according to claim 8, wherein in the step 2, the organic solvent is one of n-hexane, carbon tetrachloride, chloroform, benzene, paraffin ether and carbon disulfide, the centrifugal cleaning is performed for 1-3 times, the speed of the centrifugal cleaning is 9000-10000r/min, the time of the centrifugal cleaning is 4-6min, and the temperature of the oven is 70-90 ℃.

13. A method of preparing an infrared sunscreen having a core layer of SiCN as claimed in claim 8 wherein in step 3, said inert gas is nitrogen, helium or argon.

14. The use of an infrared opacifier with SiCN as a core layer for improving the performance of nano-silica as claimed in claim 1, wherein 100-300 parts by weight of the infrared opacifier with SiCN as the core layer and 1000 parts by weight of the nano-silica are uniformly mixed and then subjected to compression molding, steam curing and heat treatment to obtain the doped modified silica aerogel, wherein the average effective extinction coefficient is20-45m²The mixed raw materials are put into a 50mm cylindrical die and are pressed and molded, and the pressure of the pressing and molding is 1-3 MPa; adopting a steam curing method to carry out anti-rebound pretreatment on the mixed raw materials; the temperature of the heat treatment is 140-160 ℃, and the time of the heat treatment is 1-3 h.