CN112279683A

CN112279683A - Preparation method of vertically-arranged boron nitride nanosheet film and material with film arranged on surface

Info

Publication number: CN112279683A
Application number: CN202011183152.1A
Authority: CN
Inventors: 李艳娇; 刘彬; 郭剑锋; 王鑫峰; 候立安
Original assignee: Rocket Force University of Engineering of PLA
Current assignee: Rocket Force University of Engineering of PLA
Priority date: 2020-10-29
Filing date: 2020-10-29
Publication date: 2021-01-29
Anticipated expiration: 2040-10-29
Also published as: CN112279683B

Abstract

The invention discloses a preparation method of a vertically-arranged boron nitride nanosheet film and a material with the film arranged on the surface. According to the method, cheap boron oxide powder is used as a boron source, the boron oxide powder is mixed with metal iron powder and magnesium powder and then subjected to ball milling for more than 0.5 hour to prepare a reaction precursor, then metal, ceramic, silk screen, porous ceramic and the like are used as deposition substrates, a tubular atmosphere protection annealing furnace is used for heating to 1200-1300 ℃ in a high-purity ammonia atmosphere and preserving heat for 1-8 hours, a layer of grey BN nanosheet film is deposited on the surface of a substrate, the contact angle of the film to water is 144-146 degrees, and the grey BN nanosheet film has good hydrophobic property. Can be applied to the fields of self-cleaning surfaces, self-lubricating surfaces, metal protection, oil-water separation and the like, in particular to high-temperature corrosive environments. The preparation method has the advantages of simple preparation process and mild reaction conditions, and the used raw materials are boron oxide powder, iron powder, magnesium powder and ammonia gas, are cheap and easily available, are non-toxic and harmless, and are suitable for large-scale industrial production.

Description

Preparation method of vertically-arranged boron nitride nanosheet film and material with film arranged on surface

Technical Field

The invention belongs to the field of nano materials, and relates to a preparation method of a vertically-arranged boron nitride nanosheet film and a material with the film arranged on the surface.

Background

Boron nitride has the molecular formula BN, and is a graphite-like layered structure material composed of nitrogen (N) atoms and boron (B) atoms. The BN nano material refers to a BN material with at least one dimension in a nano scale range in a three-dimensional space. The BN nano-sheet film is a BN nano-sheet film with thick BN nano-sheets vertically grown on the surface of a ceramic or metal substrate, a silk screen or a porous material. Because of the existence of a large number of BN nano-sheets on the surface of the substrate, dense nano-scale small protrusions are formed on the surface of the substrate, and the specific surface area and the surface roughness of the substrate are improved, so that the substrate has good adsorption performance and hydrophobic performance. Meanwhile, the BN material has the characteristics of good lubricity, high temperature resistance, corrosion resistance and the like, so that the base material for growing the BN nanosheet film also has the excellent characteristics, and is particularly suitable for being applied to complex environments with high temperature corrosivity and the like.

Wettability is one of the important properties of solid surfaces and is also one of the most common interfacial phenomena. Typically, the wettability of a solid surface is characterized by the water contact angle. Surfaces with contact angles <90 ° are referred to as hydrophilic surfaces, surfaces with contact angles >90 ° are referred to as hydrophobic surfaces, while surfaces with contact angles above 150 ° and contact angle lags <3 ° are referred to as superhydrophobic surfaces. Due to the special wettability of the super-hydrophobic surface, the super-hydrophobic surface has wide application prospects in the fields of self-cleaning, corrosion prevention, fog prevention, ice coating prevention, oil-water separation, fluid drag reduction and the like. However, the preparation process is complicated, the conditions are harsh, the weather resistance of the product is poor, and certain limitations exist in the practical production application.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation method of a vertically-arranged boron nitride nanosheet film and a material with the film arranged on the surface, the preparation method is simple, the cost is low, and the finally prepared boron nitride nanosheet film has good weather resistance.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a preparation method of a vertically-arranged boron nitride nanosheet film comprises the following steps;

firstly, carrying out ball milling and mixing on boron oxide powder and iron powder or mixed powder of iron and magnesium according to a molar ratio of 1: 0.5-2, and placing a substrate on the mixed powder, wherein the substrate is a metal, a ceramic substrate, a wire mesh or a porous material without a catalyst;

and secondly, heating from the normal temperature under the condition of introducing inert protective atmosphere, wherein the heating rate is 5-10 ℃/min, stopping introducing the inert protective atmosphere when the temperature is increased to 300-500 ℃, then introducing high-purity ammonia gas, preserving the heat for 1-8 hours after the temperature of the furnace is increased to 1200-1300 ℃, then stopping introducing the high-purity ammonia gas, introducing the inert protective atmosphere, and naturally cooling to the room temperature to obtain the boron nitride nanosheet film on the substrate.

Preferably, the powder obtained in the first step is subjected to ball milling for 2-12 hours in an inert protective atmosphere by using a planetary ball mill, so as to obtain solid powder with the particle size of 2-10 microns.

Preferably, the flow rate of introducing the inert protective atmosphere in the second step is 20-100 ml/min.

Preferably, the inert protective atmosphere in step two is argon.

Preferably, the flow rate of the high-purity ammonia gas introduced in the step two is 20-200 ml/min.

Preferably, a catalyst is added to the boron oxide in the first step, and the catalyst is metal powder with a catalytic effect.

The material with the vertically-arranged boron nitride nanosheet film arranged on the surface, which is prepared based on any one of the methods, comprises a base body, wherein a plurality of boron nitride nanosheets grow vertically upwards on the base body, and the free ends of the boron nitride nanosheets are curled.

Preferably, the substrate is a metal, ceramic substrate, wire mesh or porous material that does not contain a catalyst.

Preferably, the length of the boron nitride nanosheet is 300-400 nm, the width of the boron nitride nanosheet is 100-200 nm, and the thickness of the curled part is 10-20 nm.

Compared with the prior art, the invention has the following beneficial effects:

according to the method, a partially gasified boron oxide precursor and ammonia gas react at high temperature under the catalytic action of metallic iron or iron and magnesium, and a large number of vertically-grown boron nitride nanosheets are deposited on the surface of an aluminum oxide ceramic substrate. Preparing a reaction precursor through a ball milling activation process, and then heating through a tubular atmosphere protection annealing furnace to obtain a final product. The preparation method is simple. The preparation equipment is a ball mill and an annealing furnace which are common equipment and have low price. And the ball milling activation reduces the reaction temperature, thereby reducing the energy consumption and the production cost of the whole preparation process. The raw materials used are boron oxide powder, metal iron powder and metal magnesium powder, which belong to common chemical raw materials in industrial production, and have the advantages of wide sources, low price, easy obtainment, no toxicity and no harm. The finally prepared boron nitride nanosheet film not only has excellent hydrophobic property, but also has good weather resistance such as high temperature resistance and corrosion resistance.

The BN nano film with the dense BN nano sheets vertically grows on the substrate. As a large number of BN nano sheets vertically grow on the surface of the composite material, dense nano-scale small protrusions are formed on the surface of the base material, and the specific surface area and the surface roughness of the composite material are improved, so that the composite material has good adsorption performance and hydrophobic performance. Therefore, the surface of the metal or ceramic material growing with the BN nanosheet film has good self-cleaning capability. The metal or ceramic material can be used for manufacturing instruments and equipment with self-cleaning capability or building outer walls. The BN material has good lubricating property, so that the lubricating property of the base material can be improved, and meanwhile, the BN material has high temperature resistance and corrosion resistance, so that the base material on which the BN nanosheet film grows can also keep good lubricating property in a high-temperature corrosive environment. Therefore, the BN nanosheet film growing on the surface of the metal and ceramic material can reduce the surface friction coefficient and improve the lubricating property, thereby achieving the purpose of protecting the metal and ceramic material.

Furthermore, the BN nanosheet film growing on the surface of the pores of the silk screen or the porous ceramic not only can reduce the pore size, improve the specific surface area of the porous ceramic and enhance the adsorption capacity of the porous ceramic, but also can enable the porous ceramic to have excellent hydrophobic performance. When the silk screen or porous ceramic growing with the BN nanosheet film is applied to the field of sewage treatment, the impurity adsorption is realized, and simultaneously, the high-efficiency separation of oil and water can be realized; when being applied to the field of flue gas treatment, the adsorption capacity of the flue gas treatment agent can be enhanced. Due to the characteristics of high temperature resistance and corrosion resistance of the BN nanosheet, the silk screen or porous ceramic growing with the BN nanosheet film can also be applied to sewage treatment and flue gas filtration in a high-temperature corrosive environment, and the problems of impurity adsorption and oil-water separation in a complex environment are solved.

Drawings

FIG. 1 is an SEM photograph of a surface film of a ceramic substrate after annealing in example 1 of the present invention;

FIG. 2 is an EDS energy spectrum of a surface film after annealing of a ceramic substrate in example 1 of the present invention;

FIG. 3 is a high magnification SEM photograph of a BN nanosheet film of the present invention;

FIG. 4 is a SEM photograph of a cross section of a BN nanosheet thin film of the present invention;

FIG. 5 is a transmission electron micrograph of a BN nanoplate of the invention;

FIG. 6 is a selected area diffraction pattern of a BN nanoplate of the invention;

FIG. 7 is a high resolution TEM image of a single BN nanoplate of the invention;

FIG. 8 is a photograph showing the contact angle of the surface of a ceramic substrate of the present invention to a water droplet before annealing;

FIG. 9 is a photograph showing the contact angle of the surface of the ceramic substrate of the present invention to water drops after annealing.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

and (1) ball-milling and mixing boron oxide and metal iron powder or mixed powder of iron and magnesium according to a molar ratio of 1: 0.5-2, putting the mixture into a ball-milling tank, vacuumizing the ball-milling tank, introducing nitrogen, and performing ball-milling for 4 hours in a positive and negative rotation alternate operation mode to obtain uniformly mixed solid powder with the particle size of about 2-10 microns.

Step (2), placing the solid powder obtained in the step (1) in a square porcelain boat, and placing a substrate on the porcelain boat, wherein the substrate is metal without a catalyst, a ceramic substrate, a silk screen or a porous material; and placing the ceramic boat in a tubular atmosphere protection annealing furnace, heating up from normal temperature under the protection of 20-100 ml/min argon at the heating rate of 5-10 ℃/min, closing an argon valve when the temperature is raised to 300 ℃, introducing high-purity ammonia gas at the flow rate of 20-200 ml/min, preserving the temperature for 1-8 hours when the temperature is further raised to 1200-1300 ℃, stopping introducing the ammonia gas, naturally cooling to room temperature under the protection atmosphere, and depositing an off-white substance on the ceramic substrate, wherein the off-white substance is the boron nitride nanosheet film.

The inert protective atmosphere in the step (2) is helium, neon, argon, krypton, xenon, radon and other inert gases. The inert atmosphere is preferably argon.

Example 1

And (1) mixing boron oxide and metal iron powder according to a molar ratio of 1:1, placing the mixture in a ball milling tank, vacuumizing the ball milling tank, introducing nitrogen, and performing ball milling for 4 hours in a positive and negative rotation alternate operation mode to obtain uniformly mixed solid powder with the particle size of about 2-10 microns.

Step (2), the solid powder obtained in the step (1) is placed in a square porcelain boat, and a piece of Al with the thickness of 30mm multiplied by 30mm is placed on the porcelain boat₂O₃And placing the ceramic substrate in a middle position, placing the ceramic boat in a tubular atmosphere protection annealing furnace, heating from normal temperature under the protection of 100ml/min argon, wherein the heating rate is 10 ℃/min, closing an argon valve when the temperature is raised to 300 ℃, introducing high-purity ammonia gas, keeping the flow rate at 200ml/min, keeping the temperature for 2 hours when the temperature is further raised to 1250 ℃, stopping introducing the ammonia gas, naturally cooling to room temperature under the protection atmosphere, and depositing an off-white substance on the ceramic substrate, wherein the off-white substance is the boron nitride nanosheet film.

FIG. 1 shows Al in example 1₂O₃Ceramic materialSEM photos of the surface film after the substrate is annealed show that even, dense and vertically-grown petal-shaped nanosheets are prepared on the surface of the ceramic substrate.

FIG. 2 shows Al in example 1₂O₃EDS energy spectrum of the surface film after the ceramic substrate is annealed. FIG. 2 shows Al of FIG. 1 with BN nanoplates grown₂O₃EDS energy spectrum of ceramic substrates. The EDS energy spectrum chart shows that Al with BN nano-sheets grows₂O₃The ceramic substrate mainly contains elements such as B, N, O, Al, Si, etc. Wherein, the peaks of O, Al and Si are from the alumina ceramic substrate, and the O can also be from the surface of the BN nano-sheet to adsorb oxygen atoms in air. The other elements are B and N, the atomic ratio of the B to the N is approximate to 1:1, and the BN nano-film conforms to the chemical equivalent characteristic of a BN material, so that the BN nano-film can be proved to be a BN component, namely the nano-sheets are BN nano-sheets.

Fig. 3 is a high-magnification SEM photograph of the prepared BN nanosheet film, and as can be seen from fig. 3, the BN nanosheets are petal-shaped and uniform in size. The length of the film is about 300-400 nm, and the width of the film is about 100-200 nm. The thickness of the curled end is about 10 nm-20 nm, which shows that the actual thickness of the nano sheet is about 2 nm-5 nm or even thinner.

FIG. 4 is an SEM photograph of a vertically grown upper tile section of a BNNSs film. It can be seen from this figure that BNNSs grow vertically upward perpendicular to the substrate surface, and it is this upward growth of BN nanosheets that roughens the tile surface, creating a near superhydrophobic surface. Meanwhile, it can be seen that the height of the BNNSs film is about 2-2.5 μm. SEM photographs in FIG. 3 and FIG. 4 show that the uniform, dense and vertically grown nanosheets are prepared on the surface of the ceramic substrate according to the present invention.

FIG. 5 is a transmission electron micrograph and a selected diffraction pattern of a BN nanosheet on the surface of a ceramic substrate. Many edge black, nearly transparent sheet structures in the middle can be seen. Because the thickness of the boron nitride nanosheet is very thin, the image under an electron gun is nearly transparent, and the black part is formed by multilayer superposition of the curled boron nitride nanosheets.

Fig. 6 is a selected area diffraction pattern of the nanosheet of fig. 5, showing the nanosheet being polycrystalline hexagonal boron nitride.

Fig. 7 is a high-resolution transmission electron micrograph of the BN nanosheets. Regularly arranged lattice stripes can be seen, and the interplanar spacing is about 0.334nm and is consistent with the interplanar spacing of the boron nitride crystal structure (002). The product was indeed demonstrated to be hexagonal boron nitride nanoplates.

FIG. 8 is a photograph showing the contact angle of the surface of the ceramic substrate to a water droplet before annealing. As can be seen from the photographs, the ceramic substrate before annealing exhibited hydrophilicity due to its smooth surface and small contact angle of 59 deg..

Fig. 9 is a photograph of a contact angle of the surface of the ceramic substrate to a water droplet after annealing, a large number of BN nanosheets vertically grow on the surface of the ceramic substrate, the surface is rough and uneven, and a large number of small protrusions with nanometer sizes are formed, so that the surface of the ceramic substrate has strong hydrophobic property, the contact angle reaches 145 degrees, and the super-hydrophobic level is almost reached.

The spectra show that the boron nitride nanosheet film prepared by the method has excellent super-hydrophobic performance.

Example 2

The reaction temperature in the step (2) of example 1 was changed to 1225 ℃ and the other operations were the same as in example 1, except that Al was added₂O₃And a large number of dense BN nano sheets grow on the surface of the ceramic substrate. The SEM photograph shows that the morphology is the same as in example 1. The test shows that the obtained Al is covered with BN nano-sheet₂O₃The ceramic substrate has a contact angle of 144 degrees and excellent hydrophobic property.

Example 3

The reaction temperature in the step (2) of example 1 was changed to 1275 ℃ and the other operations were the same as in example 1, except that Al was added₂O₃A large number of dense BN nano-sheets vertically grow on the surface of the ceramic substrate. The SEM photograph shows that the morphology is the same as in example 1. Tests show that the obtained Al with BN nanosheets growing on the surfaces₂O₃The ceramic substrate has a contact angle of 146 degrees and excellent hydrophobic property.

Example 4

The molar ratio of boron oxide and metallic iron powder in the step (1) in the example 1 is changed to 1:0.5, and the other operations are the same as the example 1, so that the product is obtained as in the example 1.

Example 5

The mixture ratio of the boron oxide and the metallic iron powder in the step (1) in the example 1 is changed to 1:2, and other operations are the same as the example 1, so that the product is obtained as in the example 1.

Example 6

The iron powder used as the catalyst in the step (1) in the example 1 is changed into a mixture of iron powder and magnesium powder, and the molar ratio of the mixture to the raw material boron oxide is B₂O₃Fe, Mg 2:1:1, substrate Al₂O₃The porous ceramic was prepared in the same manner as in example 1 except that the operation was changed to the above-mentioned example 1.

Example 7 to example 11

The ball milling time of the step (1) in the example 1 is respectively changed into 2 hours, 6 hours, 8 hours, 10 hours and 12 hours, the temperature rise rate in the step (2) is 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min and 9 ℃/min, the temperature rise is started from the normal temperature in the step (2) under the protection of argon gas of 20ml/min, 40ml/min, 50ml/min, 70ml/min and 90ml/min, the flow rate of introducing high-purity ammonia gas is 20ml/min, 50ml/min, 100ml/min, 130ml/min and 180ml/min, and other operations are the same as the example 1, so that the product is obtained as the product in the example 1.

Examples 12 to 15

The annealing reaction time in the step (2) in example 1 was changed to 1 hour, 4 hours, 6 hours, and 8 hours, and the other operations were the same as in example 1, to obtain the same product as in example 1.

Examples 16 to 20

Mixing Al₂O₃The operation of changing the ceramic substrate into a silicon substrate, a silicon oxide substrate, a porous ceramic substrate, a molybdenum mesh substrate and a titanium mesh, and the other operations are the same as those in example 1, and the product is obtained in the same way as in example 1.

The inert protective atmosphere of the invention is helium, neon, argon, krypton, xenon or radon and other inert gases. The substrate is any metal, ceramic substrate, porous material or filter screen which does not contain iron, chromium, nickel, copper, magnesium and other catalysts.

The implementation of the comparative example shows that the method adopts the boron oxide, the iron powder and the magnesium powder which are cheap and easy to obtain to prepare the boron nitride nanosheet film, has low preparation cost and stable process, is nontoxic and reliable, and is suitable for large-scale production.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a vertically-arranged boron nitride nanosheet film is characterized by comprising the following steps;

and secondly, heating from the normal temperature under the condition of introducing inert protective atmosphere, wherein the heating rate is 5-10 ℃/min, stopping introducing the inert protective atmosphere when the temperature is increased to 300-500 ℃, then introducing high-purity ammonia gas, preserving the temperature for 1-8 hours after the temperature is increased to 1200-1300 ℃, then stopping introducing the high-purity ammonia gas, introducing the inert protective atmosphere, and naturally cooling to the room temperature to obtain the boron nitride nanosheet film on the substrate.

2. The preparation method of the vertically arranged boron nitride nanosheet film according to claim 1, wherein the powder obtained in the first step is ball-milled for 2-12 hours in an inert protective atmosphere by using a planetary ball mill to obtain solid powder with a particle size of 2-10 microns.

3. The method for preparing a vertically-arranged boron nitride nanosheet film according to claim 1, wherein the flow rate of the inert protective atmosphere introduced in step two is 20-100 ml/min.

4. The method for preparing a vertically aligned boron nitride nanosheet film of claim 1, wherein the inert protective atmosphere in step two is argon.

5. The method for preparing a vertically aligned boron nitride nanosheet film according to claim 1, wherein the flow rate of high purity ammonia gas introduced in step two is 20-200 ml/min.

6. The method for preparing a vertically aligned boron nitride nanosheet film according to claim 1, wherein a catalyst is added to the boron oxide in step one, the catalyst being a catalytic metal powder.

7. A material with a vertically-arranged boron nitride nanosheet thin film on the surface, prepared by the method of any one of claims 1-6, is characterized by comprising a substrate, wherein a plurality of boron nitride nanosheets grow vertically upwards on the substrate, and the free ends of the boron nitride nanosheets are curled.

8. The material with the surface provided with the vertically-arranged boron nitride nanosheet thin film according to claim 7, wherein the substrate is a metal, a ceramic substrate, a wire mesh or a porous material which does not contain a catalyst.

9. The material with the surface provided with the vertically-arranged boron nitride nanosheet film according to claim 7, wherein the boron nitride nanosheet has a length of 300-400 nm, a width of 100-200 nm, and a thickness of a curled portion of 10-20 nm.