SiO 2/SiC material with core-shell structure and preparation method and application thereof
阅读说明：本技术 一种核壳结构SiO2/SiC材料及其制备方法与用途 (SiO 2/SiC material with core-shell structure and preparation method and application thereof ) 是由 曹宏 王丹 汪晗 薛俊 郑雨佳 于 2019-08-01 设计创作，主要内容包括：本发明涉及一种核壳结构SiO_2/SiC材料及其制备方法与用途,包括SiO_2核以及包裹于所述SiO_2核外表面的SiC。该核壳结构的制备方法包括如下步骤：以二氧化硅颗粒为硅源,以有机聚合物粘结剂为碳源制备得到二氧化硅和有机聚合物粘结剂的混合分散液；对所述混合分散液进行加热处理得到二氧化硅/有机聚合物粘结剂前驱体；将所述前驱体干燥处理后进行碳化处理得到包覆有碳的二氧化硅颗粒；将所述包覆有碳的二氧化硅颗粒在1200-1400℃、真空条件下煅烧2-5h,得到初产物；将所述初产物煅烧除碳处理得到核壳结构SiO_2/SiC。根据本发明的方法以有机粘结剂为碳源,以二氧化硅颗粒为硅源,原位合成核壳结构SiO_2/SiC材料,所用原料廉价易得,合成工艺简单,有利于工业化生产,具有很大的潜在应用前景。(The invention relates to a SiO 2 /SiC material with a core-shell structure and a preparation method and application thereof, wherein the material comprises a SiO 2 core and SiC coated on the outer surface of the SiO 2 core, the preparation method of the core-shell structure comprises the following steps of preparing a mixed dispersion liquid of silicon dioxide and an organic polymer binder by using silicon dioxide particles as a silicon source and an organic polymer binder as a carbon source, heating the mixed dispersion liquid to obtain a precursor of the silicon dioxide/organic polymer binder, drying the precursor and then carbonizing the precursor to obtain silicon dioxide particles coated with carbon, calcining the silicon dioxide particles coated with carbon at 1200-1400 ℃ for 2-5h under a vacuum condition to obtain an initial product, and calcining the initial product to remove the carbon to obtain the SiO 2 /SiC material with the core-shell structure.)
1. The SiO 2/SiC material with the core-shell structure is characterized by comprising a SiO 2 core and a SiC shell layer wrapping the outer surface of the SiO 2 core.
2. The SiO 2/SiC material with the core-shell structure of claim 1, wherein the particle size of the SiO 2 core is 50nm-2 μm.
3. A preparation method of a SiO 2/SiC material with a core-shell structure is characterized by comprising the following steps:
1) Preparing a mixed dispersion liquid of silicon dioxide and an organic polymer binder by taking silicon dioxide particles as a silicon source and an organic polymer binder as a carbon source;
2) Heating the mixed dispersion liquid to obtain a silicon dioxide/organic polymer binder precursor;
3) Drying the precursor, and then carbonizing to obtain silicon dioxide particles with surfaces coated with carbon;
4) Calcining the silicon dioxide particles coated with carbon for 2-5h at 1200-1400 ℃ under a vacuum condition to obtain an initial product;
5) And calcining the primary product to remove carbon to obtain the SiO 2/SiC with the core-shell structure.
4. The preparation method of the SiO 2/SiC material with the core-shell structure of claim 1, wherein the silica particles in step 1) are amorphous silica, and the particle size of the silica particles is 50nm-2 μm.
5. The preparation method of the SiO 2/SiC material with the core-shell structure according to claim 1, wherein the dispersion solvent in the mixed dispersion liquid of step 1) is ethanol and water, the organic polymer binder is selected from one or more of PVP, PAM or PVA, and the molar ratio of carbon atoms to silicon atoms in the mixed dispersion liquid is (3-5): 1.
6. The preparation method of the SiO 2/SiC material with the core-shell structure according to claim 1, wherein in the step 2), the mixed dispersion liquid is heated and stirred for 0.5-2h at 80-100 ℃ to obtain a precursor of the silica/organic polymer binder.
7. The method for preparing SiO 2/SiC material with core-shell structure as claimed in claim 1, wherein the precursor in step 3) is dried at 80-110 ℃ and carbonized at 450-600 ℃ in nitrogen atmosphere for 0.5-3 h.
8. The method for preparing SiO 2/SiC material with core-shell structure as claimed in any one of claims 1 to 7, wherein in step 5), the primary product is calcined at 600-700 ℃ for 2-5h to remove unreacted carbon, so as to obtain SiO 2/SiC with core-shell structure.
9. A core-shell structure SiO 2/SiC material, which is characterized by being prepared according to the preparation method of the core-shell structure SiO 2/SiC material of any one of claims 3-8.
10. use of the core-shell structure SiO 2/SiC material according to any of claims 1 or 2 or the core-shell structure SiO 2/SiC material according to claim 10, characterized in that the core-shell structure SiO 2/SiC is used as a wave-absorbing stealth material or a photocatalyst.
Technical Field
The invention belongs to the technical field of composite material preparation, and particularly relates to a SiO 2/SiC material with a core-shell structure, and a preparation method and application thereof.
Background
Silicon carbide as a third-generation semiconductor material has the advantages of ideal band gap, high physicochemical stability, acid and alkali resistance, no toxicity, high electronic drift saturation speed and the like, and the silicon carbide nano material has special optical and electrical characteristics due to the change of an energy band under the restraint of nano diameter, and has wide application prospects in the fields of photocatalytic reduction of carbon dioxide, water decomposition, pollutant degradation and the like.particularly, in the process of photocatalytic reaction, in order to make up for the defects of easy recombination of a photo-generated electron hole pair and low visible light responsiveness of silicon carbide, and simultaneously improve the catalytic efficiency under visible light, domestic and foreign scholars modify silicon carbide by compounding silicon carbide with non-metal oxides, metal oxides or metals, wherein the silicon carbide nano material is an important advanced core-shell material, and has application values in the fields of super-hydrophobic surfaces, coating materials, solar cells, nano reactors and catalysts and the like due to the unique structure and properties of a core/void/shell, so that the silicon carbide is a potential core-shell material prepared by SiC (SiC/nano nanowire 2, SiO) and a coaxial shell coating process of SiC, SiO 27, 2.
Disclosure of Invention
The invention solves the problems that the SiO 2/SiC material with the core-shell structure and the preparation method and the application thereof are provided, the SiO 2/SiC takes SiO 2 particles as the core and takes SiC as the shell, and has great potential application prospect.
The invention provides a SiO 2/SiC material with a core-shell structure, which comprises a SiO 2 core and a SiC shell layer wrapped on the outer surface of the SiO 2 core.
The SiO 2/SiC takes SiO 2 particles as a core and takes SiC as a shell, has a unique core-shell structure and has great potential application prospect.
Further, the particle size of the SiO 2 core is 50nm-2 μm.
Therefore, a series of SiO 2/SiC materials with core-shell structures and different SiO 2 core particle sizes can meet different application requirements.
The invention also provides a preparation method of the SiO 2/SiC material with the core-shell structure, which comprises the following steps:
1) Preparing a mixed dispersion liquid of silicon dioxide and an organic polymer binder by taking silicon dioxide particles as a silicon source and an organic polymer binder as a carbon source;
2) heating the mixed dispersion liquid to obtain a silicon dioxide/organic polymer binder precursor;
3) drying the precursor, and then carbonizing to obtain silicon dioxide particles with surfaces coated with carbon;
4) Calcining the silicon dioxide particles coated with carbon for 2-5h under the vacuum condition of 1200-1400 ℃ to obtain an initial product;
5) And calcining the primary product to remove carbon to obtain the SiO 2/SiC with the core-shell structure.
During the calcination process, SiO 2 reacts with carbon particles attached to the surface of the SiO 2 (formula 1), the generated SiO gas reacts with CO gas, the SiO gas which has not yet diffused reacts with the carbon particles attached to the surface of SiO 2 in situ (formula 2), the gas which has not yet diffused reacts with SiO 2 attached to the surface of SiO 2 (formula 3) to generate SiO gas (g) which is used as a raw material of the reaction formula (2), and after the full reaction, a SiC thin layer is generated on the surface of SiO 2.
The main chemical reactions involved in the preparation process are:
C(s)+SiO2＝SiO(g)+CO(g) (1)
C(s)+SiO(g)＝SiC(s)+CO(g) (2)
CO(g)+SiO2＝SiO(g)+CO2(g) (3)
The beneficial effect who adopts above-mentioned scheme is:
(1) The organic binder is used as a carbon source, and the organic binder has viscosity, so that SiO 2 can be bonded and coated and is fully mixed and contacted with SiO 2, carbon in the silicon dioxide and carbon mixture after carbonization is coated on the surface of silicon dioxide particles, the silicon dioxide and the carbon are tightly bonded, and finally the reaction is carried out to generate the SiO 2/SiC material with a firm core-shell structure.
(2) According to the technical scheme, the organic binder is used as a carbon source, the silicon dioxide particles are used as a silicon source, SiC is synthesized in situ and finally SiO 2/SiC with a core-shell structure is formed, and in practical application, SiO 2/SiC with core-shell structures of different SiO 2 core particle sizes and different SiC shell thicknesses can be synthesized by controlling the size of SiO 2 particles and the carbon-silicon ratio.
(3) the raw materials are cheap and easy to obtain, the preparation process is simple and easy to implement, and the method is favorable for industrial production.
on the basis of the scheme, the invention can be further improved as follows:
Further, the silicon dioxide particles in the step 1) are amorphous silicon dioxide, and the particle size of the silicon dioxide particles is 50nm-2 μm.
the amorphous silicon dioxide has high activity, is softened by heating, has certain viscosity, is tightly combined with the carbon source, and is convenient for subsequent full reaction to generate a firm core-shell structure.
Further, the dispersing solvent in the mixed dispersion liquid in the step 1) is ethanol and water, the organic polymer binder is selected from one or more of PVP, PAM or PVA, and the molar ratio of carbon atoms to silicon atoms in the mixed dispersion liquid is (3-5): 1.
The organic binder PVP, PAM or PVA plays a role in dispersion and bonding, and can be tightly bonded with the silica particles after heat treatment.
Specifically, the silica is dispersed with absolute ethanol, an organic binder (PVP, PAM, or PVA) is dissolved in distilled water to obtain an aqueous solution of the organic binder, and after the two are mixed, the mixture is ultrasonically dispersed to obtain a uniform mixed dispersion.
Preferably, the particle size of the silicon dioxide is 50nm-2 μm, and the organic binder is PVP-K30.
Under the condition, the dispersibility of the silicon dioxide is good, the PVP-K30 and the silicon dioxide particles are tightly bonded, and the subsequent reaction is convenient to generate a firm core-shell structure.
Further, in the step 2), the mixed dispersion liquid is heated and stirred for 0.5-2h at the temperature of 80-100 ℃, and a precursor of the silicon dioxide/organic polymer binder is obtained.
therefore, the organic adhesive has viscosity, the silicon dioxide in the mixed dispersion liquid has better viscosity after being heated and softened, and the organic adhesive can be fully adhered to the surface of the silicon dioxide particles after a period of heating treatment.
Further, the precursor in the step 3) is dried at the temperature of 80-110 ℃ and carbonized at the temperature of 400-600 ℃ for 0.5-3 h.
therefore, the drying treatment removes the excessive water, the sample begins to be carbonized at 450 ℃, and the organic polymer binder can be completely carbonized within 0.5-3 h.
preferably, the carbon-coated silica particles are calcined under a vacuum condition of 1350 ℃ for 3 hours to obtain a calcined product.
Under the condition, the crystallinity of the calcined product is better, the granularity is uniform, and the SiC layer on the surface of the silicon oxide is compact and firm.
Further, in the step 5), the primary product is calcined at 600-700 ℃ for 2-5h to remove unreacted carbon, so as to obtain SiO 2/SiC with the core-shell structure.
thus, the carbon which is not completely reacted reacts with oxygen in the air to generate CO 2 gas, and the CO 2 gas is removed, so that the SiO 2/SiC with a high-purity core-shell structure is obtained.
The invention also provides a SiO 2/SiC material with a core-shell structure, which is prepared according to the preparation method of the SiO 2/SiC material with the core-shell structure.
The invention also provides application of the SiO 2/SiC material with the core-shell structure, and the SiO 2/SiC material with the core-shell structure is used as a wave-absorbing stealth material or a photocatalyst.
the SiO 2/SiC nano particles with the core-shell structure are used as photocatalysts, the inner core of the SiO 2/SiC nano particles is made of non-conductor material silicon dioxide, and photo-generated electrons can be promoted to diffuse to a silicon carbide shell layer of a semiconductor material in a direction away from the silicon dioxide in the process of photocatalytic reaction, so that the number of effective electrons which can participate in the photocatalytic reaction on the surface of the SiC is increased, and the photocatalytic activity of the SiC semiconductor material is improved.
Drawings
FIG. 1 is a flow chart of preparation of SiO 2/SiC material with core-shell structure based on the method of the invention.
FIG. 2 is an XRD spectrum of the SiO 2/SiC material with core-shell structure prepared in example 1 of the present invention.
FIG. 3 is an optical micrograph of a SiO 2/SiC material with a core-shell structure prepared in example 1 of the present invention.
FIG. 4 is an XRD spectrum of the SiO 2/SiC material with core-shell structure prepared in example 2 of the present invention.
FIG. 5 is an SEM image of the SiO 2/SiC material with the core-shell structure prepared in example 2 of the invention.
FIG. 6 shows TEM and HRTEM spectra of SiO 2/SiC material with core-shell structure prepared in example 2 of the present invention.
FIG. 7 is a TEM image of the disintegrated SiO 2/SiC core-shell structure obtained in example 14 of the present invention.
Detailed Description
For a better understanding of the present invention, the following further illustrates the present invention with reference to the accompanying fig. 1-7 and the specific embodiments, but the present invention is not limited to the following embodiments.
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