Composite silicon carbide material and method of making the same

Abstract

The application provides a composite silicon carbide material and a preparation method thereof. The composite silicon carbide material comprises N functional layers and N-1 interface layers, the N-1 interface layer is located between the N functional layer and the N-1 functional layer, wherein N is a positive integer of 3-5, the functional layer comprises a silicon carbide material and a functional sintering aid, the particle size Dv90 of the silicon carbide material in the N functional layer is 2-4 times the particle size Dv90 of the silicon carbide material in the N-1 functional layer, the interface layer comprises nano silicon carbide with a particle size of 50-200 nm, a toughening agent and an interface sintering aid, and the particle size Dv90 of the nano silicon carbide in the N-1 interface layer is 2-4 times the particle size Dv90 of the nano silicon carbide in the N-2 interface layer. The composite silicon carbide material has strong structural integrity, and can reduce or even avoid defects such as high-temperature delamination and cracks. The composite silicon carbide material is prepared by the preparation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon carbide materials, and particularly relates to a composite silicon carbide material and a preparation method thereof. BACKGROUND

[0002] Silicon carbide materials are widely used in aerospace, nuclear energy, chemical industry and other fields due to their high hardness, high temperature resistance, corrosion resistance and excellent thermal conductivity. Traditional single-layer silicon carbide materials are prone to cracking due to thermal stress concentration in extreme environments, while the multi-layer composite structure can improve the overall performance of the silicon carbide material through flexible and differentiated design of each layer of material. However, in the prior art, the preparation of multi-layer silicon carbide materials is mostly by bonding or mechanical assembly after separate forming, and the multi-layer composite silicon carbide material prepared in this way has problems such as low interfacial bonding strength, mismatch of interlayer thermal expansion coefficient, easy delamination at high temperature, etc. At the same time, during the preparation of the composite silicon carbide material, when high-temperature sintering is carried out, there will be a difference in shrinkage rate between the multi-layer composite silicon carbide layers, resulting in deformation or cracking of the product and reducing the yield of finished products. SUMMARY

[0003] In order to overcome the problems of mismatch of interlayer thermal expansion coefficient, low interfacial bonding strength, easy delamination at high temperature and low sintering yield of the multi-layer composite silicon carbide material in the prior art, the composite silicon carbide material of the present application is designed by differentiating each layer of material, which meets the requirements of different performances of the composite silicon carbide material in high-end fields, reduces the difference in thermal expansion coefficient of each layer of silicon carbide layer, reduces the difference in thermal shrinkage rate of each layer at high temperature, and at the same time, the silicon carbide layers have strong interfacial bonding force, so that the multi-layer composite silicon carbide material is not easy to delaminate at high temperature, enhances the structural integrity of the multi-layer composite silicon carbide material, improves its high temperature performance, at the same time, the preparation method of the multi-layer silicon carbide material is integrated forming, which improves the overall performance of the multi-layer composite silicon carbide material, effectively reduces the sintering defect rate and simplifies the production process.

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a composite silicon carbide material, which comprises N functional layers and N-1 interfacial layers, the N-1 interfacial layer is located between the N functional layer and the N-1 functional layer, wherein N is a positive integer of 3-5;

[0005] The functional layer comprises silicon carbide material and functional sintering aid, the particle size Dv90 of the silicon carbide material in the N functional layer is 2-4 times the particle size Dv90 of the silicon carbide material in the N-1 functional layer;

[0006] The interfacial layer comprises nano-silicon carbide, toughening agent and interfacial sintering aid, the particle size of the nano-silicon carbide is 50-200 nm, the particle size Dv90 of the nano-silicon carbide in the N-1 interfacial layer is 2-4 times the particle size Dv90 of the nano-silicon carbide in the N-2 interfacial layer.

[0007] The second aspect of the present application provides a method for preparing the composite silicon carbide material.

[0008] The present application has the following advantages by adopting the above technical solutions:

[0009] In the composite silicon carbide material, the particle size Dv90 of the silicon carbide material in the Nth functional layer is 2-4 times the particle size Dv90 of the silicon carbide material in the (N-1)th functional layer, so that the particle size Dv90 of the silicon carbide material increases from the first functional layer to the Nth functional layer, the thermal expansion coefficients of the functional layers are matched, the shrinkage rate difference of the functional layers at high temperature is effectively reduced, and the delamination and defects of the composite silicon carbide material at high temperature are reduced; and the particle size of the nano silicon carbide in the interface layer matches the particle size of the adjacent functional layer, which can effectively fill the gap of the functional layer, reduce the porosity, and improve the density of the composite silicon carbide material; the functional sintering aid in the functional layer and the interface sintering aid in the interface layer are chemically bonded, and the interface layer also includes a toughening agent, which can play a bridging role, thereby improving the interface bonding strength between the functional layers; therefore, the multi-layer composite silicon carbide material has good structural integrity and use performance, and is not easy to delaminate or fail at high temperature, and can meet the use under different working conditions.

[0010] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The endpoints of the ranges of values and the values thereof can be combined with other endpoints to form new ranges and new values within the scope of the current disclosure. Unless otherwise specified, all ranges include endpoints. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A schematic view of a cylindrical mold is shown. DETAILED DESCRIPTION

[0012] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0013] Unless otherwise defined, all scientific and technical terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0014] The first aspect of the present application provides a composite silicon carbide material, which comprises N functional layers and N-1 interface layers, the N-1 interface layer is located between the N functional layer and the N-1 functional layer, wherein N is a positive integer of 3-5 (for example, 3, 4 or 5);

[0015] The functional layer comprises silicon carbide material and functional sintering aid, the particle size Dv90 of the silicon carbide material in the N functional layer is 2-4 times (for example, 2 times, 3 times, 4 times or within the range of any two of the above values) of the particle size Dv90 of the silicon carbide material in the N-1 functional layer;

[0016] The interface layer comprises nano-silicon carbide, toughening agent and interface sintering aid, the particle size of the nano-silicon carbide is 50-200 nm, the particle size Dv90 of the nano-silicon carbide in the N-1 interface layer is 2-4 times (for example, 2 times, 3 times, 4 times or within the range of any two of the above values) of the particle size Dv90 of the nano-silicon carbide in the N-2 interface layer.

[0017] The particle size of the silicon carbide material of the present application has a significant influence on the thermal expansion coefficient of the functional layer, the particle size Dv90 of the silicon carbide material in the N functional layer is 2-4 times of the particle size Dv90 of the silicon carbide material in the N-1 functional layer, it can be seen that from the first functional layer to the N functional layer, the particle size distribution of the silicon carbide material shows an overall increasing trend, and the thermal expansion coefficient of the first functional layer to the N functional layer gradually increases, so that the thermal expansion coefficient distribution of the multi-layer composite silicon carbide material continuously changes from the first functional layer to the N functional layer, the thermal expansion coefficients of each functional layer are matched, effectively reducing the difference in shrinkage rate of each functional layer at high temperature, improving the structural integrity of the multi-layer composite silicon carbide material, and effectively reducing the delamination and failure of the multi-layer composite silicon carbide material at high temperature; at the same time, the particle size Dv90 of the nano-silicon carbide in the N-1 interface layer is 2-4 times of the particle size Dv90 of the nano-silicon carbide in the N-2 interface layer, it can be seen that from the first interface layer to the N-1 interface layer, the particle size of the nano-silicon carbide increases, when the particle size of the silicon carbide material increases from the first layer functional layer to the N layer functional layer, the particle size gap of the functional layer will increase accordingly, the particle size of the nano-silicon carbide in the interface layer increases from the first layer to the N-1 layer, which can match the gap between adjacent functional layers, effectively fill the micropores in the functional layer, and improve the density of the composite silicon carbide material; in addition, the functional layer comprises a functional sintering aid, and the interface layer comprises an interface sintering aid, so that the adjacent functional layers and interface layers can be chemically bonded, and the interface layer also comprises a toughening agent, which can play a bridging role, improve the toughness of the interface layer, and enhance the interfacial bonding force of the functional layer, thereby effectively reducing or even avoiding the delamination failure of the composite silicon carbide material at high temperature, enhancing its high temperature resistance, so that the composite silicon carbide material has good structural integrity and can maintain good performance at different temperatures.

[0018] It can be understood that, in the present application, the main body of the multi-layer composite silicon carbide material is composed of functional layers, the thermal expansion coefficients of each layer of the functional layers are kept matched, which can reduce the difference in thermal shrinkage of the whole multi-layer composite silicon carbide material, and the interface layer only plays a bonding role and does not affect the thermal shrinkage of the whole multi-layer composite silicon carbide material.

[0019] In the present application, the particle size Dv90 of the silicon carbide material in the functional layer refers to the particle size corresponding to the cumulative volume particle size distribution percentage of 90% of the silicon carbide material in the functional layer arranged in order of particle size from small to large. The particle size Dv90 of the silicon carbide material in the functional layer can be obtained by a laser particle size analyzer. Before preparation, the raw material of the silicon carbide material for preparing the corresponding functional layer is placed in the laser particle size analyzer to obtain the volume particle size distribution curve of the silicon carbide material. The particle size corresponding to the cumulative volume particle size distribution percentage of 90% of the silicon carbide material is the particle size Dv90.

[0020] By controlling the particle size Dv90 of the silicon carbide material in the Nth functional layer to be 2-4 times the particle size Dv90 of the silicon carbide material in the (N-1)th functional layer, and the particle size Dv90 of the nano silicon carbide in the (N-1)th interface layer to be 2-4 times the particle size Dv90 of the nano silicon carbide in the (N-2)th interface layer, and adding sintering aids and toughening agents, compared with the prior art, the comprehensive performance of the composite silicon carbide material can be enhanced, the thermal expansion coefficients of each functional layer of the multi-layer composite silicon carbide material can be kept matched, the difference in thermal shrinkage at high temperature can be reduced, and the interfacial bonding force between the functional layers can be enhanced. In order to further improve the effect, one or more technical features can be further optimized.

[0021] In some embodiments, the composite silicon carbide material is a silicon carbide cylinder, which comprises, from the outer layer to the inner layer, a first functional layer, a second functional layer to an Nth functional layer, i.e. the particle size of the silicon carbide material in the functional layer increases from the outer layer to the inner layer, a multi-layer silicon carbide cylinder with a complex shape, which has uniform stress distribution between layers, strong interlayer bonding force, is not easy to delaminate or fail at high temperature, and can maintain good performance at different temperatures, and the overall comprehensive performance is effectively improved, realizing long-term stable operation under complex working conditions (such as nuclear reactors and spacecraft thermal protection). When the silicon carbide cylinder comprises, from the outer layer to the inner layer, an Nth functional layer, an (N-1)th functional layer to a first functional layer, i.e. the particle size of the silicon carbide material in the functional layer decreases from the outer layer to the inner layer, when heated, the huge expansion trend of the outer layer functional layer will be constrained by the inner layer functional layer, resulting in extremely high stress of the outer layer functional layer, thereby causing cracks and delamination.

[0022] In some embodiments, the diameter of the silicon carbide cylinder is 150mm-500mm (e.g., 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, or within a range between any two of the aforementioned values).

[0023] In some embodiments, the length of the silicon carbide cylinder is less than or equal to 800mm (e.g., 100mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, or within a range between any two of the aforementioned values). The length of the silicon carbide cylinder within the aforementioned range can avoid the bending deformation of the silicon carbide cylinder and ensure that the coefficients of thermal expansion of the functions of the silicon carbide cylinder match.

[0024] In some embodiments, the shape of the composite silicon carbide material is a cuboid, and from one end face to the other end face of the cuboid, the first functional layer, the second functional layer, and the Nth functional layer are sequentially arranged.

[0025] In some embodiments, the particle size of the silicon carbide material in any functional layer is 0.5μm-8μm (e.g., 0.5μm, 1μm, 2μm, 2.5μm, 3μm, 4.5μm, 6μm, 8μm, or within a range between any two of the aforementioned values).

[0026] In some embodiments, the weight ratio of the functional sintering aid and the silicon carbide material in any functional layer is 1:(8-47.5) (e.g., 1:8, 1:12, 1:18, 1:25, 1:32, 1:40, 1:45, 1:47.5, or within a range between any two of the aforementioned values).

[0027] In some embodiments, the weight ratio of the functional sintering aid and the silicon carbide material in any functional layer is 1:(15-30).

[0028] In some embodiments, any functional layer includes 80wt%-95wt% (e.g., 80wt%, 82wt%, 84wt%, 86wt%, 88wt%, 90wt%, 92wt%, 95wt%, or within a range between any two of the aforementioned values) silicon carbide material and 2wt%-20wt% (e.g., 82wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, or within a range between any two of the aforementioned values) functional sintering aid.

[0029] In some embodiments, the functional sintering aid includes Al2O3, Y2O3, MgO, CeO2, La2O3, B4C, SiC-B, AlN, Y3Al5O12 at least one of Al2O3-Y2O3, silicon powder, carbon powder, nano-SiC-C composite, graphene sheet.

[0030] In some embodiments, the weight ratio of toughening agent, interface sintering aid and nano silicon carbide in any interface layer is 1:(2.5-13.3):(25-100) (e.g., 1:2.5:25, 1:4:40, 1:6:55, 1:8:70, 1:10:85, 1:12:95, 1:13.3:100 or within a range between any two of the above values).

[0031] In some embodiments, any interface layer includes 60wt%-90wt% (e.g., 60wt%, 63wt%, 67wt%, 70wt%, 74wt%, 78wt%, 82wt%, 86wt%, 90wt% or within a range between any two of the above values) nano silicon carbide, 0.9wt%-24wt% (e.g., 0.9wt%, 2wt%, 5wt%, 8wt%, 12wt%, 16wt%, 20wt%, 24wt% or within a range between any two of the above values) toughening agent, 6wt%-20wt% (e.g., 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt% or within a range between any two of the above values) interface sintering aid.

[0032] In some embodiments, the toughening agent in any interface layer includes at least one of chopped carbon fiber, organic nanoparticle, inorganic nanoparticle, thermoplastic plastic particle, core-shell structure particle, micro-nano hybrid particle, toughening film and ex situ toughening.

[0033] In some embodiments, the toughening agent is chopped carbon fiber, and the length of the chopped carbon fiber is 50μm-200μm (e.g., 50μm, 70μm, 90μm, 120μm, 150μm, 180μm, 200μm or within a range between any two of the above values).

[0034] In some embodiments, the interface sintering aid includes Al2O3, Y2O3, MgO, CeO2, La2O3, B4C, SiC-B, AlN, Y3Al5O 12 at least one of Al2O3-Y2O3, silicon powder, carbon powder, nano-SiC-C composite, graphene sheet.

[0035] In the present application, the functional sintering aid between the functional layers can be the same or different, and the interface sintering aid and the toughening agent between the interface layers can be the same or different.

[0036] In some embodiments, the composite silicon carbide material comprises three functional layers and two interface layers, the three functional layers are respectively a first functional layer, a second functional layer and a third functional layer, and the two interface layers are respectively a first interface layer and a second interface layer. In the first functional layer, the particle size Dv90 of the silicon carbide material is 0.5-1.5 μm (for example, 0.5 μm, 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm, 1.5 μm or within a range between any two of the above values). The particle size Dv90 of the silicon carbide material in the first functional layer is small, and the hardness is high.

[0037] In some embodiments, in the second functional layer, the particle size Dv90 of the silicon carbide material is 2-4 μm (for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or within a range between any two of the above values). When the particle size Dv90 of the silicon carbide material in the second functional layer is moderate, the thermal shock resistance is good.

[0038] In some embodiments, in the third functional layer, the particle size Dv90 of the silicon carbide material is 5-8 μm (for example, 5 μm, 6 μm, 7 μm, 8 μm or within a range between any two of the above values). The particle size Dv90 of the silicon carbide material in the third functional layer is large, and the thermal conductivity is strong.

[0039] In some embodiments, in the first interface layer, the particle size Dv90 of the nano-silicon carbide is 50-120 nm (for example, 50 nm, 65 nm, 80 nm, 95 nm, 110 nm, 120 nm or within a range between any two of the above values). In some embodiments, in the second interface layer, the particle size Dv90 of the nano-silicon carbide is 160-200 nm (for example, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm or within a range between any two of the above values).

[0040] In some embodiments, the first functional layer comprises 90-95 wt% (for example, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt% or within a range between any two of the above values) silicon carbide material and 2-10 wt% (for example, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt% or within a range between any two of the above values) functional sintering aid.

[0041] In some embodiments, the second functional layer comprises 85wt% - 90wt% (e.g., 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, or a range between any two of the foregoing) second silicon carbide material, 2wt% - 10wt% (e.g., 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or a range between any two of the foregoing) functional sintering aid.

[0042] In some embodiments, the third functional layer comprises 80wt% - 88wt% (e.g., 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt%, 86wt%, 87wt%, 88wt%, or a range between any two of the foregoing) silicon carbide material, 2wt% - 10wt% (e.g., 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or a range between any two of the foregoing) functional sintering aid.

[0043] In some embodiments, the first interface layer comprises 60wt% - 90wt% (e.g., 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 88wt%, 90wt%, or a range between any two of the foregoing) nanosized silicon carbide, 0.9wt% - 24wt% (e.g., 0.9wt%, 4wt%, 7wt%, 10wt%, 13wt%, 16wt%, 20wt%, 24wt%, or a range between any two of the foregoing) toughening agent, 6wt% - 20wt% (e.g., 6wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, 20wt%, or a range between any two of the foregoing) interface sintering aid;

[0044] In some embodiments, the second interface layer comprises 60wt% - 90wt% (e.g., 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 88wt%, 90wt%, or a range between any two of the foregoing) nanosized silicon carbide, 0.9wt% - 24wt% (e.g., 0.9wt%, 4wt%, 7wt%, 10wt%, 13wt%, 16wt%, 20wt%, 24wt%, or a range between any two of the foregoing) toughening agent, 6wt% - 20wt% (e.g., 6wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, 20wt%, or a range between any two of the foregoing) interface sintering aid.

[0045] In some embodiments, the first functional layer has a thickness of 1-5 mm (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4.5 mm, 5 mm, or a range between any two of the above).

[0046] In some embodiments, the second functional layer has a thickness of 1-5 mm (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4.5 mm, 5 mm, or a range between any two of the above).

[0047] In some embodiments, the third functional layer has a thickness of 1-5 mm (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4.5 mm, 5 mm, or a range between any two of the above).

[0048] In some embodiments, the first interface layer has a thickness of 10-50 μm (e.g., 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 45 μm, 50 μm, or a range between any two of the above).

[0049] In some embodiments, the second interface layer has a thickness of 10-50 μm (e.g., 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 45 μm, 50 μm, or a range between any two of the above).

[0050] In some embodiments, the difference between the thermal expansion coefficient of the Nth functional layer and the (N-1)th functional layer is less than 0.3 x 10 -6 / °C (e.g., 0.05 x 10 -6 / °C, 0.10 x 10 -6 / °C, 0.15 x 10 -6 / °C, 0.20 x 10 -6 / °C, 0.25 x 10 -6 / °C, 0.29 x 10 -6 / °C, or a range between any two of the above).

[0051] In the present application, the particle size Dv90 of the silicon carbide material in the Nth functional layer is 2-4 times the particle size Dv90 of the silicon carbide material in the (N-1)th functional layer, the particle size of the silicon carbide material in the Nth functional layer is larger than the particle size of the silicon carbide material in the (N-1)th functional layer, the degree of disorder of the silicon carbide material in the Nth functional layer is higher, the constraint on thermal expansion is relatively weakened, and therefore the thermal expansion coefficient of the Nth functional layer is larger than that of the (N-1)th functional layer. The difference between the thermal expansion coefficients of the Nth functional layer and the (N-1)th functional layer is obtained by subtracting the thermal expansion coefficient of the (N-1)th functional layer from the thermal expansion coefficient of the Nth functional layer.

[0052] The difference between the thermal expansion coefficients of the Nth functional layer and the (N-1)th functional layer is less than 0.3*10 -6 / ℃, the thermal shrinkage rates of the functional layers remain consistent in a high-temperature state, the risk of delamination failure is reduced, and the heat resistance is improved.

[0053] In the present application, the difference between the thermal expansion coefficients of the Nth functional layer and the (N-1)th functional layer is measured by high-temperature diffraction. Specifically, the composite silicon carbide material sample is placed on a controllable temperature high-temperature diffraction sample stage, and the Nth functional layer and the (N-1)th functional layer of the sample are irradiated with monochromatic X-rays. The diffraction signals generated by the crystal lattices are converted into diffraction patterns by a detector. The crystal lattice constants at different temperatures are analyzed according to the Bragg equation, the changes in the crystal lattice constants with temperature are calculated, the thermal expansion coefficients of the crystal lattice planes of the two functional layers are obtained, and the difference between the two is obtained.

[0054] In some embodiments, the porosity of the composite silicon carbide material is less than 5% (for example, 1%, 2%, 3%, 4%, 4.5%, or within a range defined by any two of the above values). The porosity of the composite silicon carbide is less than 5%, the degree of densification is high, the heat resistance of the composite silicon carbide material is strong, the performance of the composite silicon carbide material under complex working conditions is guaranteed, and the effective application of the composite silicon carbide material in high-end fields such as aerospace, nuclear energy, and chemical industry is facilitated.

[0055] In the present application, the porosity of the composite silicon carbide material is measured by the following method. Specifically, the sample is completely dried before testing and the dry weight is measured; the sample is completely dried before testing and the dry weight (m1) is measured; then the sample is immersed in distilled water, and the pores are fully saturated by boiling for several hours or vacuumizing; after the surface water is wiped off, the wet weight (m2) is measured; and then the saturated water sample is suspended in water and the suspended weight (m3) is measured. The apparent bulk density is calculated using the formula pv=m1 / (m2-m3)*pw (pw is the density of water), and the theoretical density (pt) is calculated according to the material composition and proportion. The total porosity can be obtained according to the formula porosity=[1-(pv / pt)]*100%.

[0056] In some embodiments, the shear strength between the Nth functional layer and the (N-1)th functional layer is greater than or equal to 40 MPa (e.g., 40 MPa, 42 MPa, 44 MPa, 46 MPa, 48 MPa, 50 MPa, 52 MPa, 54 MPa, 56 MPa, or within a range between any two of the above).

[0057] In the present application, the shear strength between the Nth functional layer and the (N-1)th functional layer is measured by the following method: the sample of the composite silicon carbide material is clamped on a universal testing machine, a shear load is applied between the Nth functional layer and the (N-1)th functional layer until fracture, and the load data at the time of fracture is recorded, which is the shear strength between the Nth functional layer and the (N-1)th functional layer. After the shear strength test, the fracture surface is observed microscopically by scanning electron microscopy, and it is found that the fracture presents a mixed fracture mode, which indicates that the outer layer and the intermediate layer have good interfacial bonding performance.

[0058] The second aspect of the present application provides a preparation method of the composite silicon carbide material provided in the first aspect of the present application, which comprises the following steps:

[0059] (1) preparing functional layer slurries: the functional layer slurries comprise N kinds of functional layer slurries, which are respectively a first functional layer slurry, a second functional layer slurry,..., and an Nth functional layer slurry, wherein N is a positive integer of 3-5 (e.g., 3, 4, or 5), any one of the functional layer slurries comprises silicon carbide material and functional sintering aids, and the particle size Dv90 of the silicon carbide material in the Nth functional layer slurry is 2-4 times (e.g., 2 times, 3 times, 4 times, or within a range between any two of the above) that of the silicon carbide material in the (N-1)th functional layer slurry.

[0060] (2) preparing interface layer slurries: the interface layer slurries comprise N-1 kinds of interface layer slurries, which are respectively a first interface layer slurry, a second interface layer slurry,..., and an (N-1)th interface layer slurry, wherein N is a positive integer of 3-5, any one of the interface layer slurries comprises nano-silicon carbide, a toughening agent, and an interface sintering aid, and the particle size Dv90 of the nano-silicon carbide in the (N-1)th interface layer slurry is 2-4 times (e.g., 2 times, 3 times, 4 times, or within a range between any two of the above) that of the nano-silicon carbide in the (N-2)th interface layer slurry.

[0061] (3) layer-by-layer slurry injection: the first functional layer slurry, the second functional layer slurry, and the Nth functional layer slurry are sequentially injected in a mold to form a first functional layer, a second functional layer, and an Nth functional layer, respectively; before the second functional layer slurry is injected, the first interface layer slurry is sprayed on the surface of the first functional layer;..., and before the Nth functional layer slurry is injected, the (N-1)th interface layer slurry is sprayed on the surface of the (N-1)th functional layer to obtain a green body.

[0062] (4) sequentially performing cold isostatic pressing, debinding, pressure sintering and gradient cooling on the green body.

[0063] The preparation method of the composite silicon carbide material provided by the application adopts an integrated forming technology of layer-by-layer slip casting-forming, cold isostatic pressing, debinding and sintering to integrally form the multilayer composite silicon carbide material at one time, thereby reducing the complex process of assembling after separate forming in the traditional process, simplifying the production process, and effectively reducing or even avoiding defects such as delamination, cracks and weak interfacial bonding force of the multilayer composite silicon carbide material, reducing the sintering defect rate, improving the yield and product performance, and at the same time, the integrated forming technology is used to prepare a multilayer silicon carbide cylinder with a complex shape, solves the problem of uneven interlayer stress distribution, makes it not easy to delaminate at high temperature, and the integrated forming technology not only can improve the production efficiency and ensure the consistency of product quality, but also can meet the quality requirements of composite silicon carbide materials in high-end application fields.

[0064] In some embodiments, the viscosity of any functional layer slurry is 1000-1500 mPa·s, for example, 1000 mPa·s, 1100 mPa·s, 1200 mPa·s, 1300 mPa·s, 1400 mPa·s, 1500 mPa·s or within a range between any two of the above values.

[0065] Controlling the viscosity of the functional layer slurry in the above range makes the flowability of the functional layer slurry moderate, avoids delamination or sedimentation during slip casting, ensures uniform distribution of the silicon carbide material in the slurry, reduces the difference in expansion coefficient between the functional layers, and at the same time, is beneficial to the removal of air bubbles in the slurry, avoiding defects such as pores during sintering.

[0066] In the application, the viscosity of the functional layer slurry is measured by a rotary viscometer.

[0067] In some embodiments, any functional layer slurry further comprises an organic binder, a dispersant and water.

[0068] In some embodiments, in any functional layer slurry, the weight percentage of the silicon carbide material is 80-95% (e.g., 80%, 82%, 85%, 87%, 90%, 92%, 94%, 95%, or within a range between any two of the aforementioned values), the weight percentage of the functional sintering aid is 2-10% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 9%, 10%, or within a range between any two of the aforementioned values), the weight percentage of the organic binder is 1-5% (e.g., 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4.5%, 5%, or within a range between any two of the aforementioned values), the weight percentage of the dispersant is 0.5-2% (e.g., 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.7%, 1.9%, 2%, or within a range between any two of the aforementioned values), and the weight percentage of the water is 0-3% (e.g., 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 2.8%, 3%, or within a range between any two of the aforementioned values).

[0069] In some embodiments, the dispersant comprises ammonium polyacrylate.

[0070] In some embodiments, the viscosity of any interface layer slurry is 200-500 mPa-s (e.g., 200 mPa-s, 250 mPa-s, 300 mPa-s, 350 mPa-s, 400 mPa-s, 450 mPa-s, 500 mPa-s, or within a range between any two of the aforementioned values). Controlling the viscosity of the interface layer slurry within the aforementioned range facilitates uniform spraying of the interface layer, improves the adhesion of the interface layer, ensures the consistency of the bonding force of the functional layers at the interface, and improves the bonding force between the functional layers.

[0071] In the present application, the viscosity of the functional layer slurry is measured by a rotational viscometer.

[0072] In some embodiments, any interface layer slurry further comprises an organic binder and a solvent (e.g., ethanol), which can provide temporary adhesion to facilitate the coating and molding of the interface layer slurry.

[0073] In some embodiments, in any of the interface layer slurries, the toughening agent has a weight percentage of 0.3%-0.8% (e.g., 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or within a range between any two of the aforementioned values), the nano-silicon carbide has a weight percentage of 20%-30% (e.g., 20%, 22%, 24%, 26%, 28%, 30%, or within a range between any two of the aforementioned values), the interface sintering aid has a weight percentage of 2%-4% (e.g., 2%, 2.5%, 3.0%, 3.5%, 4%, or within a range between any two of the aforementioned values), the organic binder has a weight percentage of 4%-6% (e.g., 4%, 4.5%, 5%, 5.5%, 6%, or within a range between any two of the aforementioned values), and the solvent has a weight percentage of 60%-70% (e.g., 60%, 62%, 64%, 66%, 68%, 70%, or within a range between any two of the aforementioned values).

[0074] In some embodiments, the organic binder comprises polyvinyl alcohol and / or phenolic resin.

[0075] In some embodiments, the mold is made of metal (e.g., stainless steel) or high-temperature-resistant resin, and the inner wall of the mold is polished to a mirror surface to effectively prevent the slurry from sticking.

[0076] In some embodiments, in step (3), the mold is preheated to a temperature of 50°C-80°C (e.g., 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 78°C, 80°C, or within a range between any two of the aforementioned values). Preheating the mold to the aforementioned temperature can reduce the temperature difference between the slurry and the mold, reduce the generation of bubbles, and accelerate the initial solidification speed of the slurry.

[0077] In some embodiments, in step (3), a low-speed constant-flow pump is used to inject the slurry at a flow rate of 5 mL / min-20 mL / min (e.g., 5 mL / min, 7.5 mL / min, 10 mL / min, 12.5 mL / min, 15 mL / min, 17.5 mL / min, 20 mL / min, or within a range between any two of the aforementioned values), which can effectively prevent the impact of the injected slurry on the solidified functional layer from causing deformation.

[0078] In some embodiments, in step (3), after the functional layer slurry is injected into the mold, homogenization, vacuum debubbling, and drying are performed in sequence, and the surface is polished (e.g., using 600-mesh sandpaper) after drying to increase the roughness between the layers.

[0079] In some embodiments, the homogenization includes centrifugation, ultrasonic, etc., the centrifugation conditions include: a rotation speed of 300 rpm-800 rpm (for example, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, or within a range between any two of the above values), and a centrifugation time of 3 minutes-5 minutes (for example, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, or within a range between any two of the above values). The homogenization treatment can expel air bubbles and improve the density.

[0080] In some embodiments, the vacuum debubbling conditions include: a vacuum degree of ≤0.1 MPa, and a holding time of 5-10 minutes (for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, or within a range between any two of the above values), and elimination of micropores.

[0081] In some embodiments, the drying is performed in a hot air circulating drying box at 40°C-60°C (for example, 40°C, 45°C, 50°C, 55°C, 60°C, or within a range between any two of the above values) to surface solidification (moisture content <5%) for 1 hour-2 hours (for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, or within a range between any two of the above values).

[0082] In some embodiments, the cold isostatic pressing conditions include: a pressure of 100 MPa-200 MPa, for example, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, or within a range between any two of the above values, and a duration of 1 h-2 h (for example, 1 h, 1.2 h, 1.5 h, 2 h, or within a range between any two of the above values). The cold isostatic pressing treatment under the above conditions can eliminate the interlayer gap, enhance the bonding between the functional layers, improve the green body density, and simultaneously uniformly compress each layer and reduce the difference in sintering shrinkage rate between the functional layers.

[0083] In some embodiments, after the cold isostatic pressing treatment of the green body, demolding is performed, and then precision machining is performed using a numerical control machine tool.

[0084] In some embodiments, the debinding conditions include: heating to 600℃ at a heating rate of 1℃ / min-3℃ / min (e.g., 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, or within a range between any two of the aforementioned values) under an inert atmosphere, and holding for 1h-4h (e.g., 1h, 2h, 3h, 4h, or within a range between any two of the aforementioned values). The debinding under the above conditions can effectively remove the organic binder in the green body, avoid residual carbide or pores, and further reduce the sintering defect rate.

[0085] In some embodiments, the gas pressure sintering conditions include: heating to a temperature of 1950℃-2100℃ (e.g., 1950℃, 1975℃, 2000℃, 2025℃, 2050℃, 2075℃, 2100℃, or within a range between any two of the aforementioned values) at a heating rate of 10℃ / min-15℃ / min (e.g., 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, or within a range between any two of the aforementioned values) under an argon and / or vacuum environment at a pressure of 5MPa-20MPa, and holding for 1h-4h (e.g., 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, or within a range between any two of the aforementioned values). The sintering under the above temperature can further improve the densification of the composite silicon carbide material through atomic diffusion, while maintaining the above gas pressure, which can effectively inhibit the decomposition of silicon carbide and ensure good performance of the composite silicon carbide material.

[0086] In some embodiments, the gradient cooling conditions include: slow cooling to 800℃ at a rate of 2℃ / min-5℃ / min (e.g., 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, or within a range between any two of the aforementioned values).

[0087] In some embodiments, in step (3), the functional layer slurry is sequentially injected into the cylindrical mold in the order of the first functional layer slurry, the second functional layer slurry, and the Nth functional layer slurry, and the cylindrical mold is located in a centrifuge to obtain a cylindrical green body through centrifugation.

[0088] As Figure 1As shown, the cylindrical mold 2 comprises a slip casting gate 1 and a centrifugal rotating table 3, and the functional layer slurries are sequentially injected into the mold in the order of the first functional layer slurry, the second functional layer slurry and the Nth functional layer slurry, to obtain a cylindrical green body, which comprises the first functional layer slurry, the second functional layer slurry and the Nth functional layer slurry in turn from the outer layer to the inner layer.

[0089] Unless otherwise specified, the raw materials and methods for preparing the lithium ion battery described in the present application are conventional choices in the art.

[0090] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0091] The materials and reagents used in the following examples can be obtained from commercial channels unless otherwise specified.

[0092] The present application will be described in detail below with reference to specific examples, which are used for understanding rather than limiting the present application.

[0093] Preparation Example 1

[0094] (1) Preparation of functional layer slurry

[0095] The first functional layer slurry was prepared by sequentially adding 92wt% of silicon carbide material (particle size Dv90 of 1 μm), 5wt% of Al2O3-Y2O3 (functional sintering aid), 5wt% of polyvinyl alcohol (organic binder) into water, and finally adding 0.5wt% of ammonium polyacrylate (dispersant) to adjust the slurry viscosity to 1200 mPa·s;

[0096] The second functional layer slurry was prepared by sequentially adding 88wt% of silicon carbide material (particle size Dv90 of 4 μm), 5wt% of Al2O3-Y2O3 and B4C (mass ratio of 3:2) (functional sintering aid), 4wt% of polyvinyl alcohol (organic binder) into water, and finally adding 1wt% of ammonium polyacrylate (dispersant) to adjust the slurry viscosity to 1200 mPa·s;

[0097] The third functional layer slurry was prepared by sequentially adding 85wt% of silicon carbide material (particle size Dv90 of 8 μm), 10wt% of B4C and AlN (mass ratio of 8:2) (functional sintering aid), 10wt% of polyvinyl alcohol (organic binder) into water, and finally adding 2wt% of ammonium polyacrylate (dispersant) to adjust the slurry viscosity to 1200 mPa·s.

[0098] The particle size Dv90 of the silicon carbide material in the second functional layer slurry is 4 times the particle size Dv90 of the silicon carbide material in the first functional layer slurry, and the particle size Dv90 of the silicon carbide material in the third functional layer slurry is 2 times the particle size Dv90 of the silicon carbide material in the second functional layer slurry.

[0099] (2) Preparing the interface layer slurry

[0100] The first interface layer slurry: 25wt% of nano-silicon carbide (particle size Dv90 is 90nm), 3wt% of Al2O3-Y2O3 (interface sintering aid), and 0.5wt% of short carbon fiber are added to ethanol and ultrasonically dispersed, and then 5wt% of phenolic resin (organic binder) is added and mechanically stirred until the fiber is uniformly dispersed, and finally the slurry viscosity is adjusted to 300mPa·s to obtain the first interface layer slurry.

[0101] The second interface layer slurry: 25wt% of nano-silicon carbide (particle size Dv90 is 180nm), 3wt% of Al2O3-Y2O3 (interface sintering aid), and 0.5wt% of short carbon fiber are added to ethanol and ultrasonically dispersed, and then 5wt% of phenolic resin (organic binder) is added and mechanically stirred until the fiber is uniformly dispersed, and finally the slurry viscosity is adjusted to 300mPa·s to obtain the second interface layer slurry.

[0102] The particle size Dv90 of the nano-silicon carbide in the second interface layer slurry is 2 times the particle size Dv90 of the nano-silicon carbide in the first interface layer slurry.

[0103] (3) Layer-by-layer slurry injection

[0104] The mold is preheated to 60℃ to reduce the temperature difference between the slurry and the mold, reduce the generation of bubbles, and accelerate the initial solidification speed of the slurry;

[0105] A low-speed constant-flow pump is used to inject the first functional layer slurry, the second functional layer slurry, and the third functional layer slurry into the cylindrical mold in the centrifuge at a flow rate of 15mL / min. After injecting any functional layer slurry, centrifugation is performed at a speed of 500rpm for 5h, followed by vacuum degassing (vacuum degree ≤0.1MPa), and drying in a 50℃ hot air circulation drying oven until the surface is solidified (moisture content <5%). After drying, the surface is lightly polished using 600-mesh sandpaper to increase the interlayer roughness. From the outside to the inside, the first functional layer, the second functional layer, and the third functional layer are formed. Before injecting the second functional layer slurry, the first interface layer slurry is sprayed on the surface of the first functional layer to form the first interface layer. Before injecting the third functional layer slurry, the second interface layer slurry is sprayed on the surface of the second functional layer to form the second interface layer, and finally the cylindrical green body is obtained.

[0106] (4) Cold isostatic pressing, debinding, gas pressure sintering

[0107] Cold isostatic pressing: the green body was packaged in a rubber mold and cold isostatic pressing was performed at a pressure of 150 MPa for 2 hours;

[0108] Debinding: under a nitrogen atmosphere, the temperature was raised to 600°C at a rate of 2°C / min and held for 3 h;

[0109] Gas pressure sintering: in an argon environment, the temperature was raised to 2000°C at a rate of 10°C / min, a gas pressure of 15 MPa was applied, and held for 3 h.

[0110] Preparation Example 2

[0111] (1) Prepare the functional layer slurry: refer to Preparation Example 1;

[0112] (2) Inject the slurry to obtain the first functional layer, the second functional layer and the third functional layer, respectively:

[0113] Preheat the mold to 60°C to reduce the temperature difference between the slurry and the mold, reduce the generation of bubbles, and speed up the initial solidification speed of the slurry;

[0114] A low-speed constant-flow pump was used to inject the first functional layer slurry into the cylindrical mold in the centrifuge at a flow rate of 15 mL / min, and the centrifuge was operated at a speed of 500 rpm for 5 h. Then vacuum degassing (vacuum degree ≤0.1 MPa) was performed, and drying was carried out in a 50°C hot air circulation drying box until the surface was solidified (moisture content <5%). Then cold isostatic pressing, debinding and gas pressure sintering were performed to obtain the first functional layer, wherein the cold isostatic pressing, debinding and gas pressure sintering were performed according to Preparation Example 1;

[0115] The preparation of the second functional layer and the third functional layer refers to the first functional layer;

[0116] (3) Assemble to obtain a silicon carbide cylinder

[0117] The first functional layer, the second functional layer and the third functional layer were assembled by adhesion to form a silicon carbide cylinder, wherein the first functional layer was located at the outermost side, the third functional layer was located at the innermost side, and the second functional layer was located between the first functional layer and the third functional layer.

[0118] Example 1

[0119] The composite silicon carbide material prepared by Preparation Example 1 was a silicon carbide cylinder, wherein the composite silicon carbide material included three functional layers and two interface layers, from the outer layer to the inner layer, the three functional layers were the first functional layer, the second functional layer and the third functional layer, respectively, and the two interface layers were the first interface layer and the second interface layer, respectively. The first interface layer was located between the second functional layer and the first functional layer, and the second interface layer was located between the third functional layer and the second functional layer.

[0120] The particle size Dv90 of the silicon carbide material in the first functional layer is 1 μm; the particle size Dv90 of the silicon carbide material in the second functional layer is 4 μm; the particle size Dv90 of the silicon carbide material in the third functional layer is 8 μm; the particle size Dv90 of the silicon carbide material in the second functional layer is 4 times the particle size Dv90 of the silicon carbide material in the first functional layer; the particle size Dv90 of the silicon carbide material in the third functional layer is 2 times the particle size Dv90 of the silicon carbide material in the second functional layer.

[0121] The particle size Dv90 of the nano-silicon carbide in the first interface layer is 90 nm; the particle size Dv90 of the nano-silicon carbide in the second interface layer is 180 nm; the particle size Dv90 of the nano-silicon carbide in the second interface layer is 2 times the particle size Dv90 of the nano-silicon carbide in the first interface layer.

[0122] The first functional layer comprises 94.8 wt% silicon carbide material, 5.2 wt% Al2O3-Y2O3 (functional sintering aid); the second functional layer comprises 94.6 wt% silicon carbide material, 5.4 wt% Al2O3-Y2O3 and B4C (mass ratio of 3:2, functional sintering aid); the third functional layer comprises 89.5 wt% silicon carbide material, 10.5 wt% B4C and AlN (mass ratio of 8:2, functional sintering aid);

[0123] The thickness of the first functional layer, the second functional layer and the third functional layer is 2 mm.

[0124] The first interface layer comprises 87.7 wt% nano-silicon carbide, 1.8 wt% short carbon fiber, 10.5 wt% Al2O3-Y2O3 (interface sintering aid); the second interface layer comprises 87.7 wt% nano-silicon carbide, 1.8 wt% short carbon fiber, 10.5 wt% Al2O3-Y2O3 (interface sintering aid).

[0125] The thickness of the first interface layer, the second interface layer and the third interface layer is 30 μm.

[0126] Example 2

[0127] This example is implemented with reference to Example 1, except that the first interface layer and the second interface layer do not comprise short carbon fiber.

[0128] Example 3

[0129] This example is implemented with reference to Example 1, except that the first interface layer and the second interface layer do not comprise interface sintering aid.

[0130] Example 4

[0131] This example was performed according to Example 1, except that the first functional layer, the second functional layer and the third functional layer each comprised 11 wt% functional sintering aid and 77 wt% silicon carbide material.

[0132] Example 5

[0133] This example was performed according to Example 1, except that the silicon carbide cylinder comprised, from the outer layer to the inner layer, the third functional layer, the second functional layer and the first functional layer.

[0134] Example 6

[0135] This example was performed according to Example 1, except that the composite silicon carbide material was not a silicon carbide cylinder.

[0136] Comparative Example 1

[0137] This example was performed according to Example 1, except that in the first functional layer, the particle size Dv90 of the silicon carbide material was 1 μm; in the second functional layer, the particle size Dv90 of the silicon carbide material was 5 μm; in the third functional layer, the particle size Dv90 was 25 μm; the particle size Dv90 of the silicon carbide material in the third functional layer was 5 times the particle size Dv90 of the silicon carbide material in the second functional layer; and the particle size Dv90 of the silicon carbide material in the second functional layer was 5 times the particle size Dv90 of the silicon carbide material in the first functional layer.

[0138] Comparative Example 2

[0139] This example was performed according to Example 1, except that in the first functional layer, the particle size Dv90 of the silicon carbide material was 2 μm; in the second functional layer, the particle size Dv90 of the silicon carbide material was 2 μm; in the third functional layer, the particle size Dv90 was 2 μm; the particle size Dv90 of the silicon carbide material in the third functional layer was 1 times the particle size Dv90 of the silicon carbide material in the second functional layer; and the particle size Dv90 of the silicon carbide material in the second functional layer was 1 times the particle size Dv90 of the silicon carbide material in the first functional layer.

[0140] Comparative Example 3

[0141] This example was performed according to Example 1, except that in the first interface layer, the particle size Dv90 of the nanoscale silicon carbide was 90 nm; in the second interface layer, the particle size Dv90 of the nanoscale silicon carbide was 90 nm; and the particle size Dv90 of the nanoscale silicon carbide in the second interface layer was 1 times the particle size Dv90 of the nanoscale silicon carbide in the first interface layer.

[0142] Comparative Example 4

[0143] The silicon carbide cylinder was prepared according to Preparation Example 2.

[0144] Test Example

[0145] The carbonized silicon composite materials prepared in the examples and comparative examples were subjected to performance tests, and the specific test methods were as follows, and the test results are shown in Table 1.

[0146] (1) Sintering defect rate

[0147] The delamination and crack of the composite silicon carbide material obtained by the preparation example of the present application was tested by ultrasonic flaw detection, and the total detection pieces were 20, the delamination or crack was recorded as a defective piece, and the defect rate calculation formula was: (defective piece number / 20) x 100%.

[0148] (2) Difference in thermal expansion coefficient between the Nth functional layer and the N-1th functional layer

[0149] The composite silicon carbide material sample was placed on a temperature controllable high temperature diffraction sample stage, and the Nth functional layer and the N-1th functional layer of the sample were irradiated by monochromatic X-rays, and the diffraction signals generated by the crystal lattices were converted into diffraction patterns by a detector. According to the Bragg equation, the lattice constants at different temperatures were analyzed, and the change of the lattice constants with temperature was calculated, and the lattice layer thermal expansion coefficients of the two functional layers were obtained, and then the difference between them was obtained.

[0150] (3) Porosity of the composite silicon carbide material

[0151] During the test, the sample was completely dried and weighed; the sample was completely dried and weighed (m1) during the test; then the sample was immersed in distilled water, and the open pores were fully soaked by boiling for several hours or vacuumizing, and the wet weight (m2) was weighed after the surface water was wiped off; the saturated water sample was suspended in water and weighed (m3). The apparent volume density was calculated by the formula pv=m1 / (m2-m3) x pw (pw is the density of water), and the theoretical density (pt) was calculated by the material composition in proportion, and the total porosity was calculated by the formula porosity=[1-(pv / pt)]x100%.

[0152] (4) Shear strength between the Nth functional layer and the N-1th functional layer

[0153] The composite silicon carbide material sample was clamped on a universal testing machine, and a shear load was applied between the Nth functional layer and the N-1th functional layer until fracture, and the load data at fracture was recorded, which was the shear strength between the Nth functional layer and the N-1th functional layer.

[0154] Table 1

[0155]

[0156] " / " indicates that the data does not exist here.

[0157] As can be seen from the test results of the comparative examples and the examples in Table 1, the composite silicon carbide material in the examples has a reduced difference in the coefficient of thermal expansion between the third functional layer and the second functional layer and between the second functional layer and the first functional layer, and a reduced porosity, so that the shear strength between the third functional layer and the second functional layer and between the second functional layer and the first functional layer is significantly improved, and the bonding strength between the functional layers is enhanced, which indicates that by controlling the particle size Dv90 of the silicon carbide material in the Nth functional layer to be 2-4 times the particle size Dv90 of the silicon carbide material in the (N-1)th functional layer, and the particle size Dv90 of the nano silicon carbide in the (N-1)th interface layer to be 2-4 times the particle size Dv90 of the nano silicon carbide in the (N-2)th interface layer, and adding the sintering aid and the toughening agent, the coefficient of thermal expansion of each functional layer of the multilayer composite silicon carbide material can be kept matched, the difference in thermal shrinkage at high temperature can be reduced, the porosity can be reduced, and thus the shear strength and the bonding force between the functional layers can be enhanced, and the delamination and failure of the silicon carbide material at high temperature can be reduced.

[0158] As can be seen from the comparison between Preparation Example 1 and Preparation Example 2 in Table 1, the sintering defect rate of Preparation Example 1 is lower than that of Preparation Example 2, and the integrated forming preparation method of the composite silicon carbide material provided by the application can effectively reduce or even avoid the defects such as delamination, cracks, and weak interface bonding force of the multilayer composite silicon carbide material, and reduce the sintering defect rate.

[0159] It should be noted that in this document, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusions, so that processes, methods, articles, or devices that include a series of elements not only include those elements, but also include other elements not explicitly listed, or include elements inherent to such processes, methods, articles, or devices. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the process, method, article, or device that includes the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, but can also include performing functions in a substantially simultaneous manner or in a reverse order, for example, the described method can be performed in an order different from that described, and various steps can also be added, omitted, or combined. In addition, the features described with reference to certain examples can be combined in other examples.

[0160] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A composite silicon carbide material, characterized by, The composite silicon carbide material includes N functional layers and N-1 interface layers, wherein the N-1th interface layer is located between the Nth functional layer and the N-1th functional layer, and N is a positive integer from 3 to 5. The functional layer includes silicon carbide material and functional sintering aid. The particle size Dv90 of the silicon carbide material in the Nth functional layer is 2 to 4 times that of the silicon carbide material in the N-1th functional layer. The interface layer includes nano-silicon carbide, toughening agent and interface sintering aid. The particle size of the nano-silicon carbide is 50nm-200nm. The particle size Dv90 of the nano-silicon carbide in the N-1th interface layer is 2 to 4 times that of the particle size Dv90 of the nano-silicon carbide in the N-2th interface layer. In any functional layer, the particle size Dv90 of the silicon carbide material is 0.5μm-8μm; and the weight ratio of the functional sintering aid and the silicon carbide material in any of the functional layers is 1:(8-47.5); the weight ratio of the toughening agent, the interface sintering aid and the nano silicon carbide in any of the interface layers is 1:(2.5-13.3):(25-100); the functional sintering aid comprises at least one of Al2O3, Y2O3, MgO, CeO2, La2O3, B4C, SiC-B, AlN, Y3Al5O 12 , Al2O3-Y2O3, silicon powder, carbon powder, nano SiC-C composite, graphene sheet; the toughening agent comprises at least one of chopped carbon fiber, organic nanoparticle, inorganic nanoparticle, thermoplastic plastic particle, core-shell structure particle, micro-nano hybrid particle, toughening film and ex situ toughening; the interface sintering aid comprises at least one of Al2O3, Y2O3, MgO, CeO2, La2O3, B4C, SiC-B, AlN, Y3Al5O 12 , Al2O3-Y2O3, silicon powder, carbon powder, nano SiC-C composite, graphene sheet.

2. The composite silicon carbide material of claim 1, wherein, The composite silicon carbide material is a silicon carbide cylinder, which includes a first functional layer, a second functional layer, and an Nth functional layer from the outer layer to the inner layer; the diameter of the silicon carbide cylinder is 150mm-500mm; and the length of the silicon carbide cylinder is less than or equal to 800mm.

3. The composite silicon carbide material of claim 1, wherein, The composite silicon carbide material comprises three functional layers and two interface layers. The three functional layers are a first functional layer, a second functional layer, and a third functional layer. The two interface layers are a first interface layer and a second interface layer. In the first functional layer, the particle size Dv90 of the silicon carbide material is 0.5 μm-1.5 μm; in the second functional layer, the particle size Dv90 of the silicon carbide material is 2 μm-4 μm; in the third functional layer, the particle size Dv90 of the silicon carbide material is 5 μm-8 μm. In the first interface layer, the particle size Dv90 of the nano-silicon carbide is 50 nm-120 nm; in the second interface layer, the particle size Dv90 of the nano-silicon carbide is 160 nm-200 nm.

4. The composite silicon carbide material of claim 3, wherein, The first functional layer comprises 90wt%-95wt% silicon carbide material and 2wt%-10wt% functional sintering aid; the thickness of the first functional layer is 1mm-5mm; And / or, the second functional layer comprises 85wt%-90wt% of a second silicon carbide material and 2wt%-15wt% of a functional sintering aid; the thickness of the second functional layer is 1mm-5mm; And / or, the third functional layer comprises 80wt%-88wt% silicon carbide material and 2wt%-20wt% functional sintering aid; the thickness of the third functional layer is 1mm-5mm.

5. The composite silicon carbide material according to claim 3, characterized in that, The first interface layer comprises 60wt%-90wt% nano-silicon carbide, 0.9wt%-24wt% toughening agent, and 6wt%-20wt% interface sintering aid; the thickness of the first interface layer is 10μm-50μm. And / or, the second interface layer comprises 60wt%-90wt% nano-silicon carbide, 0.9wt%-24wt% toughening agent, and 6wt%-20wt% interface sintering aid; the thickness of the second interface layer is 10μm-50μm.

6. The composite silicon carbide material according to claim 1 or 2, characterized in that, The absolute value of the difference of the thermal expansion coefficients between the Nth functional layer and the N-1th functional layer is less than 0.3x10 -6 / ℃; And / or, the porosity of the composite silicon carbide material is less than 5%; And / or, the shear strength between the Nth functional layer and the (N-1)th functional layer is greater than or equal to 40 MPa.

7. A method for preparing the composite silicon carbide material according to any one of claims 1-6, characterized in that, The method includes the following steps: (1) Preparation of functional layer slurry: The functional layer slurry includes N kinds of functional layer slurry, namely the first functional layer slurry, the second functional layer slurry and the Nth functional layer slurry, where N is a positive integer from 3 to 5. Any kind of functional layer slurry includes silicon carbide material and functional sintering aid. The particle size Dv90 of silicon carbide material in the Nth functional layer slurry is 2 to 4 times that of silicon carbide material in the N-1th functional layer slurry. (2) Preparation of interface layer slurry: The interface layer slurry includes N-1 types of interface layer slurry, namely the first interface layer slurry, the second interface layer slurry and the N-1th interface layer slurry, where N is a positive integer from 3 to 5. Any one of the interface layer slurries includes nano-silicon carbide, toughening agent and interface sintering aid. The particle size Dv90 of nano-silicon carbide in the N-1th interface layer slurry is 2 to 4 times that of nano-silicon carbide in the N-2th interface layer slurry. (3) Layer-by-layer grouting: The first functional layer grout, the second functional layer grout and the Nth functional layer grout are sequentially injected into the mold to form the first functional layer, the second functional layer and the Nth functional layer respectively. Before injecting the second functional layer grout, the first interface layer grout is sprayed on the surface of the first functional layer. Until the Nth functional layer grout is injected, the N-1th interface layer grout is sprayed on the surface of the N-1th functional layer to obtain the green body. (4) The blank is subjected to cold isostatic pressing, degreasing, gas pressure sintering and gradient cooling in sequence.

8. The method for preparing the composite silicon carbide material according to claim 7, characterized in that, The conditions for cold isostatic pressing include: a pressure of 100MPa-200MPa and a duration of 1h-2h; the conditions for degreasing include: heating to 600℃ at a heating rate of 1℃ / min-3℃ / min under an inert atmosphere and holding for 1h-4h; the conditions for gas pressure sintering include: heating to 1950℃-2100℃ at a heating rate of 10℃ / min-15℃ / min under an argon and / or vacuum environment and a pressure of 5MPa-20MPa and a holding time of 1h-4h. And / or, the viscosity of any functional layer slurry is 1000 mPa·s-1500 mPa·s; the viscosity of any interface layer slurry is 200 mPa·s-500 mPa·s.

9. The method for preparing the composite silicon carbide material according to claim 7 or 8, characterized in that, In step (3), the functional layer slurry is injected into the cylindrical mold in the order of the first functional layer slurry, the second functional layer slurry to the Nth functional layer slurry. The cylindrical mold is located in a centrifuge, and a cylindrical blank is obtained by centrifugation.

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