Si3n4 / sio2 core-shell structure powder material and preparation method and application thereof

Abstract

The application discloses a Si3N4 / SiO2 core-shell structure powder material and a preparation method and application thereof, and belongs to the technical field of wave-transparent ceramics. Si3N4 particles are used as a base, KH550 and silicon oil are mixed in a certain mass ratio, and then added into an acetone solution of the Si3N4 particles; the obtained mixture is heated and stirred, and a lubricant is added dropwise to obtain a composite solution system; KH550 and silicon oil are coated on the surface of the base; centrifugation is carried out; the obtained composite is subjected to air treatment to obtain an intermediate product; coating and air treatment are repeated to obtain the Si3N4 / SiO2 core-shell structure powder material. The Si3N4 / SiO2 core-shell structure powder material provided by the application has a tangent loss of 2.25-4.77*10 ‑3 , and the dielectric constant of graphene can be adjusted in the range of 2.74-6.55.

Description

Technical Field

[0001] This invention belongs to the field of microwave-transparent ceramics technology, and in particular relates to a Si3N4 / SiO2 core-shell structure powder material, its preparation method and application. Background Technology

[0002] In the military field, with the rapid development of radar technology, weapons and military targets have nowhere to hide. To improve the combat performance of weapons and equipment, they need to be made stealthy to evade radar detection. In modern military industry, the stealth capability of military equipment has become an important indicator for measuring its mechanical performance, and stealth coatings have, to a certain extent, become crucial materials determining its survivability. Stealth technology can greatly improve the penetration capability, survivability, and combat effectiveness of combat platforms and weapon systems, and can achieve proactive advantages in many aspects such as strategy, tactics, and technology. It has become a key technology researched in the modern defense field.

[0003] Among numerous materials, graphene is widely used in the field of electromagnetic wave absorption due to its excellent properties. Graphene is a material with excellent electrical, thermal, and mechanical properties, as well as a high specific surface area. Graphene oxide (GO) is a single-layer material exfoliated from graphite, while reduced graphene oxide (rGO) is prepared from graphene oxide through photocatalysis, heat treatment, and other methods. Its high dielectric constant, large porosity, and high specific surface area make it suitable as an electromagnetic wave absorbing material. Furthermore, graphene's unusual band structure allows for the existence of individual holes and electrons. This unique structure not only improves graphene's impedance matching performance, providing energy for transitions from adjacent energy levels to the Fermi level, but also introduces defect polarization relaxation and dipole relaxation, which are beneficial for electromagnetic wave absorption. However, the high complex dielectric constant and low complex permeability constant lead to poor impedance matching, significantly deviating from the zero reflection condition. This also prevents graphene's wave absorption performance from meeting the requirements for practical applications.

[0004] Currently, the main problem with using graphene as a microwave absorbing material lies in its less-than-ideal impedance matching. This problem can be solved by preparing graphene-based microwave absorbing composites. By introducing appropriate dopants, the electromagnetic parameters of the composite material can be tuned, synergistically optimizing impedance matching and thus achieving better microwave absorption performance. However, existing magnetic loss-type graphene microwave absorbing composites constructed by doping with ferrites, magnetic nanoparticles, etc., generally suffer from high density, narrow effective absorption bandwidth, and poor corrosion resistance, failing to meet the requirements of next-generation microwave absorbing materials that are "lightweight, high-strength, wide-bandwidth, and thin-layered." Therefore, there is an urgent need for a new material with high strength, low density, and the ability to adjust the dielectric constant of graphene while solving the impedance mismatch problem. Summary of the Invention

[0005] The purpose of this invention is to provide a Si3N4 / SiO2 core-shell structured powder material, its preparation method, and its application, so as to solve the problems existing in the prior art.

[0006] One of the technical solutions provided by this invention:

[0007] A method for preparing Si3N4 / SiO2 core-shell structured powder material involves using Si3N4 particles as a matrix, mixing equal masses of KH550 (γ-aminopropyltriethoxysilane) and silicone oil, and then adding the mixture to an acetone solution of Si3N4 particles. The mixture is heated and stirred, and a lubricant is added dropwise to obtain a composite solution system. KH550 and silicone oil are coated on the surface of the matrix. The mixture is centrifuged, and the resulting composite is air-treated to obtain an intermediate product. The coating and air-treatment processes are repeated to obtain the Si3N4 / SiO2 core-shell structured powder material.

[0008] This invention utilizes the inherent film-forming properties of organic materials. By dispersing and solidifying organic materials within powder, a film is deposited and shaped on the particle surface, preventing adhesion between particles. The film's framework structure consists of continuous silicon-oxygen chain groups, with some oxygen-bridged and nitrogen-bridged bonds, as well as carbon-core small groups such as methyl groups. Through simultaneous pyrolysis and oxidation, carbon-containing groups are removed. The inorganicization process of the film also includes the reconstruction of Si-O chains, forming silica nano-sintered clusters and a continuous phase. The resulting microwave-transparent ceramic powder can effectively improve the impedance matching problem of graphene, thus enabling the preparation of high-performance microwave absorbing materials.

[0009] Preferably, the Si3N4 particles are α-Si3N4 nanoparticles.

[0010] Preferably, in the composite solution system, the mass concentration of Si3N4 particles is 10%-15%, the mass concentration of KH550 is 1%-2%, the mass concentration of silicone oil is 1%-2%, and the mass concentration of lubricant is 0.5%-0.8%.

[0011] More preferably, the mass concentration of Si3N4 particles in the composite solution system is 12%-13%, the mass concentration of KH550 is 1.2%-1.4%, the mass concentration of silicone oil is 1.2%-1.4%, and the mass concentration of lubricant is 0.55%-0.65%.

[0012] In this invention, the mass of KH550 accounts for 0.1%-10% of the mass of Si3N4 particles. When it is less than 0.1%, the final product will have poor film formation effect, and the particles will stick together, affecting the final performance. When it is greater than 10%, it will reduce the product reaction rate and reduce the final yield.

[0013] Preferably, the heating and stirring temperature is 50-90℃ and the time is 60-120 min; more preferably, the temperature is 60-80℃ and the time is 80-100 min.

[0014] Preferably, the centrifugation speed is 15000 r / min-18000 r / min and the time is 0.6 h-1.5 h; more preferably, the speed is 15000 r / min and the time is 1 h.

[0015] Preferably, the conditions for the air-passing treatment are: the air temperature is controlled at 220-335℃ and the air-passing time is 10-55s; more preferably, the air temperature is controlled at 260-320℃ and the air-passing time is 15-50s.

[0016] Preferably, the repeated wrapping and air-conditioning are performed 1-4 times, more preferably 2-3 times.

[0017] The second technical solution provided by this invention:

[0018] A Si3N4 / SiO2 core-shell structured powder material prepared by the above preparation method.

[0019] The third technical solution provided by this invention:

[0020] Application of the above-mentioned Si3N4 / SiO2 core-shell structure powder material in adjusting the dielectric constant of graphene.

[0021] The beneficial effects of this invention are:

[0022] This invention uses Si3N4 particles as a matrix, coats the surface with KH550 and lubricant, then air-processes to obtain an intermediate product, and finally repeats the coating and air-processing to obtain Si3N4 / SiO2 core-shell structured powder material.

[0023] This invention utilizes Si3N4 particles as a matrix, coating the surface with KH550 and silicone oil, followed by air treatment to obtain an intermediate product. Finally, the coating and air-treatment processes are repeated to obtain a Si3N4 / SiO2 core-shell structured powder material. Taking advantage of the inherent film-forming properties of organic materials, KH550 and silicone oil are used to form and solidify a film on the surface of Si3N4 particles. The film is then inorganicated, forming silica nano-sintered clusters and a continuous phase on the surface. This invention provides a Si3N4 / SiO2 core-shell structured powder material with a loss tangent of 2.25–4.77 × 10⁻⁶. -3 The dielectric constant of graphene can be adjusted within the range of 2.74 to 6.55.

[0024] This invention involves saturating and curing KH550 and silicone oil onto the surface of Si3N4, while simultaneously adding a lubricant to reduce friction and shear between the shell layers of the organosilicon particles, thus lowering the probability of agglomeration. This results in a continuous silicon-oxygen chain structure in the film framework, containing partially oxygen-bridged and nitrogen-bridged bonds, as well as carbon-core small groups such as methyl groups. After air treatment, the film framework is pyrolyzed and oxidized simultaneously, removing carbon-containing groups. The inorganicization process of the film also includes the reconstruction of Si-O chains, leading to the formation of silica nano-sintered clusters and a continuous phase on the Si3N4 surface.

[0025] The preparation method of this invention is simple, green and efficient, and does not have high requirements for related equipment. It can achieve the mass production of Si3N4 / SiO2 core-shell structure powder in a short time, which meets the needs of industrial production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The image shows a transmission electron microscope (TEM) image of the Si3N4 / SiO2 core-shell structured powder material prepared in Example 1.

[0028] Figure 2 This is a photograph of the Si3N4 / SiO2 core-shell structured powder material prepared in Example 1.

[0029] Figure 3 The dielectric parameters of the real part of the graphene in the experimental example are shown in the diagram.

[0030] Figure 4 The dielectric parameters of the real part of the Si3N4 / SiO2@graphene composite powder prepared for the experimental example are shown in the figure.

[0031] Figure 5 The dielectric parameters of the imaginary part of graphene in the experimental example are shown.

[0032] Figure 6 The dielectric parameters of the imaginary part of the Si3N4 / SiO2@graphene composite powder prepared for the experimental example are shown in the figure.

[0033] Figure 7 Transmission electron microscopy (TEM) image of Si3N4 / SiO2@graphene composite powder prepared for the experimental example. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] Traditional preparation processes typically involve hydrolyzing SiO2-mH2O (hydrate) with KH-550 followed by dehydration. The problem is that the SiO2 film ultimately consists of SiO2 nanoparticle clusters. This invention utilizes the inherent film-forming properties of organic materials, employing KH550 and silicone oil to saturate and disperse organic materials on the particle surface, dispersing them into a film. After curing, the film is fixed on the particle surface. The organic material prevents adhesion between particles, resulting in a continuous silicon-oxygen chain structure with oxygen-bridged, nitrogen-bridged, and carbon-core small groups such as methyl groups. Through air drying, simultaneous pyrolysis and oxidation are achieved, removing the carbon-containing groups. The inorganicization process also includes the reconstruction of Si-O chains, forming sintered silica nanoparticle clusters and a continuous phase.

[0040] All raw materials used in the following examples were obtained through conventional commercial channels.

[0041] Example 1: A method for preparing Si3N4 / SiO2 core-shell structured powder material

[0042] S1. Dissolve 10g of α-Si3N4 nanoparticles in 250g of acetone solution;

[0043] S2. Mix 1g of KH550 with 1g of silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0044] S3. Stir the mixture at 80°C for 60 minutes, adding 1g of oleic acid dropwise during the stirring process;

[0045] S4. Centrifuge the stirred mixture (5000 r / min, 1 h), and then pass the centrifuged complex 1 in air at 340 ℃ for 20 s to obtain intermediate product 1.

[0046] S5. Dissolve 15g of intermediate product 1 obtained from S4 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 2.

[0047] S6. Dissolve 10g of intermediate product 2 obtained from S5 in 250g of acetone, and repeat S2-S4 to obtain Si3N4 / SiO2 core-shell structured powder material.

[0048] Figure 1 The image shown is a transmission electron microscope (TEM) image of the Si3N4 / SiO2 core-shell structured powder material prepared in Example 1. Figure 1 It can be seen that the material successfully possesses a core-shell structure, proving that the method can effectively synthesize this material;

[0049] Figure 2 The image shown is a photograph of the Si3N4 / SiO2 core-shell structured powder material prepared in Example 1. Figure 2 It can be seen that the synthesized powder has good dispersion, and the particle size can be further improved by grinding to meet the particle size requirements under different conditions.

[0050] Example 2: A method for preparing a Si3N4 / SiO2 core-shell structured powder material

[0051] S1. Dissolve 15g of α-Si3N4 nanoparticles in 450g of acetone solution;

[0052] S2. Mix 1.5g KH550 with 1.5g silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0053] S3. Stir the mixture at 60°C for 60 minutes, adding 1g of petroleum jelly dropwise during the stirring process;

[0054] S4. Centrifuge the stirred mixture (5000 r / min, 1.5 h), and then pass the centrifuged complex 1 in air at 340 ℃ for 60 s to obtain intermediate product 1.

[0055] S5. Dissolve 20g of intermediate product 1 obtained from S4 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 2.

[0056] S6. Dissolve 15g of intermediate product 2 prepared in S5 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 3.

[0057] S7. Dissolve 10g of intermediate product 3 obtained from S6 in 250g of acetone, and repeat S2-S4 to obtain Si3N4 / SiO2 core-shell structured powder material.

[0058] Example 3: A method for preparing Si3N4 / SiO2 core-shell structured powder material

[0059] S1. Dissolve 10g of α-Si3N4 nanoparticles in 250g of acetone solution;

[0060] S2. Mix 0.5g KH550 and 0.5g silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0061] S3. Stir the mixture at 80℃ for 90 minutes, adding 1g of glycerol dropwise during the stirring process;

[0062] S4. Centrifuge the stirred mixture (5000 r / min, 1 h), and then pass the centrifuged complex 1 in air at 340 ℃ for 60 s to obtain intermediate product 1.

[0063] S5. Dissolve 20g of intermediate product 1 obtained from S4 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 2.

[0064] S6. Dissolve 15g of intermediate product 2 prepared in S5 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 3.

[0065] S7. Dissolve 10g of intermediate product 3 obtained from S6 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 4.

[0066] S8. Dissolve 10g of intermediate product 4 prepared in S7 in 250g of acetone, and repeat S2-S4 to obtain Si3N4 / SiO2 core-shell structured powder material.

[0067] Example 4: A method for preparing a Si3N4 / SiO2 core-shell structured powder material

[0068] S1. Dissolve 10g of α-Si3N4 nanoparticles in 250g of acetone solution;

[0069] S2. Mix 1g KH550 with 1g silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0070] S3. Stir the mixture at 80°C for 60 minutes, adding 1g of octadecanoic acid dropwise during the stirring process;

[0071] S4. Centrifuge the stirred mixture (5000 r / min, 1.5 h), and then pass the centrifuged composite under air atmosphere at 340 ℃ for 60 s to obtain Si3N4 / SiO2 core-shell structure powder material.

[0072] Comparative Example 1

[0073] Same as Example 1, except that KH550 is not added in S2.

[0074] Comparative Example 2

[0075] Same as Example 1, except that no oleic acid was added in S3.

[0076] Comparative Example 3

[0077] Same as Example 1, except that in S4, the air treatment is performed at room temperature.

[0078] Comparative Example 4

[0079] Same as Example 1, except that it was not air-dried. The specific preparation method is as follows:

[0080] S1. Dissolve 10g of α-Si3N4 nanoparticles in 250g of acetone solution;

[0081] S2. Mix 1g of KH550 with 1g of silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0082] S3. Stir the mixture at 80°C for 60 minutes, adding 1g of oleic acid dropwise during the stirring process;

[0083] S4. Centrifuge the stirred mixture (5000 r / min, 1 h) to obtain centrifuged product 1;

[0084] S5. Dissolve 15g of the centrifuged product obtained in S4 in 250g of acetone, and repeat S2-S4 to obtain centrifuged product 2.

[0085] S6. Dissolve 10g of the centrifuged product 2 obtained in S5 in 250g of acetone, and repeat S2-S4 to obtain Si3N4 / SiO2 core-shell structured powder material.

[0086] Comparative Example 5

[0087] S1. Dissolve 10g of α-Si3N4 nanoparticles in 250g of acetone solution;

[0088] S2. Mix 1g of KH550 with 1g of silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0089] S3. Stir the mixture at 80°C for 1 hour, adding 1g of oleic acid dropwise during the stirring process;

[0090] S4. Centrifuge the stirred mixture (5000 r / min, 1.5 h), and then pass the centrifuged composite 1 in air at 80 ℃ for 60 s to obtain Si3N4 / SiO2 core-shell structure powder material.

[0091] Comparative Example 6

[0092] S1, Same as Example 1;

[0093] S2. Mix 1g KH550 with 2g silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0094] S3. Stir the mixture at 80°C for 60 minutes, adding 1g of oleic acid dropwise during the stirring process;

[0095] S4-S6 are the same as in Example 1.

[0096] Comparative Example 7

[0097] S1, Same as Example 1;

[0098] S2. Mix 1.5g KH550 with 1.5g silicone oil and add the mixture to the above acetone solution to obtain a mixture;

[0099] S3. Stir the mixture at 80℃ for 60 minutes, adding 1.5g of oleic acid dropwise during the stirring process;

[0100] S4-S6 are the same as in Example 1.

[0101] Performance testing

[0102] The Si3N4 / SiO2 core-shell structured powder materials prepared in Examples 1-4 and Comparative Examples 1-7 were mixed with graphene at a ratio of 1:4 and then composited using a hydrothermal method. After drying, the powder was pressed into an absorbing ring with paraffin at a filling ratio of 20%. The microwave absorption performance of the obtained product was measured as follows.

[0103] 1. The loss tangent is used to measure the damping capacity of a material. The loss tangent represents the ratio between the electric field energy and the magnetic field energy in the medium, that is, the fraction of energy consumed in the medium. The smaller the dielectric loss tangent, the smaller the dielectric loss, and the magnetic loss increases accordingly. The absorption performance is improved within a certain range. However, the greater the dielectric loss, the worse the absorption performance.

[0104] The loss tangent of the above products was measured using a vector network analyzer, and the results are shown in Table 1.

[0105] Table 1

[0106]

[0107] Test case

[0108] To verify the ability of the Si3N4 / SiO2 core-shell structure powder material prepared in this invention to adjust the dielectric parameters of graphene, Si3N4 / SiO2@graphene composite powder was prepared by hydrothermal method, and its dielectric parameter adjustment was tested. The preparation steps are as follows:

[0109] 1. 0.1 g of Si3N4 / SiO2 core-shell structured powder material prepared in Example 1 and 0.4 g of graphene were placed in deionized water, heated at 180°C for 2 h, and centrifuged and stirred (1000 rpm) to obtain mixture A;

[0110] 2. The mixture A obtained above is dried at 100°C;

[0111] 3. Grind the dried solid to obtain Si3N4 / SiO2@graphene composite powder.

[0112] The properties of the Si3N4 / SiO2@graphene composite powder were characterized, and the results are shown in the figure. Figure 3-6 ,in Figure 3 The dielectric parameters of the real part of the graphene in the experimental example are shown in the diagram. Figure 4 The dielectric parameters of the real part of the Si3N4 / SiO2@graphene composite powder prepared for the experimental example are shown in the figure. Figure 5 The dielectric parameters of the imaginary part of graphene in the experimental example are shown. Figure 6 Table 2 shows the dielectric parameters of the imaginary part of the Si3N4 / SiO2@graphene composite powder prepared for the experimental example. Table 2 also shows the dielectric parameters of the real and imaginary parts of the Si3N4 / SiO2@graphene composite powder and graphene prepared for the experimental example.

[0113] Table 2

[0114]

[0115] pass Figure 3 , Figure 4 As shown in Table 2, the real part of the prepared Si3N4 / SiO2@graphene composite powder increases by about 6 in the S and C bands compared to graphene, and there are corresponding increases in other bands.

[0116] pass Figure 5 , Figure 6 As shown in Table 2, the imaginary part of the prepared Si3N4 / SiO2@graphene composite powder is reduced by about 8 in the S and C bands compared with graphene, which proves the regulating effect of the Si3N4 / SiO2 core-shell structure powder material prepared in this invention on the dielectric parameters of graphene.

[0117] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a Si3N4 / SiO2 core-shell structured powder material in adjusting the dielectric constant of graphene, characterized in that, The preparation method of the Si3N4 / SiO2 core-shell structured powder material includes the following steps: S1. Dissolve 10g of α-Si3N4 nanoparticles in 250g of acetone solution; S2. Mix 1g KH550 with 1g silicone oil and add the mixture to the acetone solution to obtain a mixture; S3. Stir the mixture prepared in S2 at 80°C for 60 minutes, adding 1g of oleic acid dropwise during the stirring process; S4. Centrifuge the mixture obtained by adding oleic acid in S3, and then expel the resulting complex 1 in air at 340°C for 20 seconds to obtain intermediate product 1. S5. Dissolve 15g of intermediate product 1 obtained from S4 in 250g of acetone, and repeat S2-S4 to obtain intermediate product 2. S6. Dissolve 10g of intermediate product 2 obtained from S5 in 250g of acetone, and repeat S2-S4 to obtain Si3N4 / SiO2 core-shell structured powder material.

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