A thermal spraying composite ceramic powder material, its preparation method and application

Abstract

The present invention relates to a thermal spraying composite ceramic powder material, its preparation method and application, belonging to the technical field of high-temperature electromagnetic functional ceramic materials, and solves the problems of narrow absorption bandwidth, low absorption loss, poor temperature resistance, and poor cohesive bonding strength of existing electromagnetic functional materials, resulting in poor bonding force with the substrate and easy detachment. The composite ceramic material includes a matrix material and a functional material. The matrix material is mullite, etc., and the functional material includes SiBCNFe, Ti3SiC2, CNTs, MoSi2, ZnO and YSZ. The multiple functional materials of the present invention have multiple loss mechanisms, broaden the electromagnetic wave absorption bandwidth, improve the absorption loss, and undertake the controllability of electromagnetic functions; by controlling the material size, density and sphericity, the cohesive bonding strength and fluidity of the material are improved, which is beneficial to reducing the porosity of the prepared coating and improving the coating density and mechanical properties; in addition, the multiple electromagnetic functional materials are all temperature-resistant materials, which is beneficial to the expansion of the preparation process and application environment of the composite ceramic material of the present invention.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature electromagnetic functional ceramic materials, and particularly to a thermal spraying composite ceramic powder material, a preparation method thereof, and an application thereof. Background Art

[0002] With the progress of technology, electromagnetic waves are increasingly widely used. They not only harm human health and interfere with the normal use of equipment, but also the detection means are becoming increasingly diverse. Correspondingly, higher requirements are put forward for materials that interfere with and shield electromagnetic waves. The application environment of electromagnetic functional materials is becoming more and more demanding. In practical applications, electromagnetic functional adjustable performance is required to adapt to environmental changes.

[0003] At present, single electromagnetic functional materials and loss mechanisms limit their electromagnetic wave absorption performance. They often have a narrow absorption band and limited absorption loss, unable to meet the usage requirements. To address this problem, people are committed to researching composite electromagnetic absorption materials composed of multiple electromagnetic functional materials to increase the loss mechanism of the materials for electromagnetic waves and broaden the absorption band.

[0004] However, in practical applications, the mechanical properties of electromagnetic functional coatings composed of composite electromagnetic absorption materials are poor, and the bonding strength is low (~6 MPa). When the environment changes, including factors such as environmental temperature and medium, the coating is prone to cohesive fracture. Especially under harsh usage conditions, problems such as coating peeling and failure are likely to occur, affecting the electromagnetic wave absorption efficiency and service life.

[0005] Therefore, it is necessary to find an electromagnetic functional material with excellent performance in various aspects, including temperature resistance, electromagnetic wave absorption bandwidth, and bonding force with the substrate, to meet the higher requirements for electromagnetic wave absorption materials under increasingly complex application conditions. Summary of the Invention

[0006] In view of the above analysis, an embodiment of the present invention aims to provide a thermal spraying composite ceramic powder material, a preparation method thereof, and an application thereof, so as to solve at least one of the problems of narrow absorption band, poor temperature resistance, and poor cohesive bonding strength of existing electromagnetic functional materials, resulting in poor bonding force with the substrate and easy peeling.

[0007] In a first aspect, an embodiment of the present invention provides a thermal spraying composite ceramic material. The composite ceramic material includes a matrix material and a functional material. Among them, the matrix material is at least one of mullite, zirconia, cordierite, silicon dioxide, silicon nitride, and boron nitride, and the functional material includes SiBCNFe or / and SiCuCN, Ti3SiC2 or / and TiC, CNTs or / and carbon fiber, MoSi2 or / and Si3N4, ZnO or / and MnO2, and YSZ. The functional material is uniformly dispersed in the matrix material.

[0008] Further, by mass percentage, the contents of the components in the composite ceramic material are as follows: SiBCNFe 8%-10%, Ti3SiC2 15%-18%, CNTs 2%-5%, MoSi2 5%-8%, ZnO 4%-6%, YSZ 22%-27%, and the balance is mullite.

[0009] Further, the composite ceramic material is spherical powder with a particle size of 25-110 μm.

[0010] Further, the bulk density of the spherical powder is 0.4-2.2 g / cm 3 , and the fluidity is 30-50 s / 50 g.

[0011] In a second aspect, an embodiment of the present invention provides a method for preparing the composite ceramic material, and the method includes:

[0012] (1) According to the composition of the composite ceramic material, mix matrix raw materials, functional raw materials with deionized water and a binder to obtain a mixed slurry;

[0013] (2) Spray granulate the mixed slurry to obtain agglomerated powder;

[0014] (3) Sinter the agglomerated powder;

[0015] (4) Perform plasma spheroidization treatment on the powder sintered in step (3), and screen it.

[0016] Further, in step (1), the mass of deionized water is 1-1.2 times the mass of the raw materials.

[0017] Further, the mass of the binder is 0.5-1% of the mass of the raw materials.

[0018] Further, in step (2), the process parameters of the spray granulation are as follows: inlet temperature 340-350 °C, outlet temperature 100-110 °C, spray disc rotation speed 30-40 Hz, and feeding speed 35-45 rpm.

[0019] Further, in step (3), the process parameters of the sintering are as follows: under a protective atmosphere, sinter at a temperature of 550-950 °C for 2-4 h; sinter at a temperature of 1100-1500 °C for 2-5 h.

[0020] Further, in step (4), the process parameters of the plasma spheroidization treatment are as follows: current 600-650 A, main gas Ar 100-110 SCFH, auxiliary gas H2 7-9 SCFH, carrier gas Ar 8-10 SCFH, and powder feeding rate 2.0-3.0 r / min.

[0021] In a third aspect, an embodiment of the present invention provides a high-temperature electromagnetic functional coating. The high-temperature electromagnetic functional coating includes a functional layer, and the material of the functional layer contains the thermal spraying composite ceramic material described in the first aspect or the thermal spraying composite ceramic material obtained by the preparation method described in the second aspect.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] 1. The present invention uniformly disperses a variety of electromagnetic functional materials into the matrix material. The various electromagnetic functional materials have multiple loss mechanisms, which broaden the electromagnetic wave absorption frequency band, improve the absorption loss, and undertake the controllability of electromagnetic functions. For example, SiBCNFe and SiCuCN have magnetic loss and dielectric loss mechanisms, CNTs and carbon fibers have resistance loss mechanisms, and Ti3SiC2, MoSi2, ZnO, TiC, Si3N4, AlN, and MnO2 have dielectric loss mechanisms.

[0024] In addition, the various electromagnetic functional materials are all temperature-resistant materials, which is beneficial to the expansion of the preparation process and application environment of the composite ceramic material of the present invention.

[0025] 2. The various electromagnetic functional materials adopted in the present invention cooperate with each other and coordinate with each other to play a role in broadening the electromagnetic wave absorption frequency band. In addition to limiting the composition of the composite ceramic material, the present invention also limits the content of each component; the composite ceramic material not only broadens the electromagnetic wave absorption frequency band by increasing the loss mechanism, but also considers that the different physical and chemical properties of different electromagnetic functional materials may affect the morphology structure and properties of the composite ceramic material obtained after combination, and further affect its electromagnetic function and service life in actual applications. Therefore, the present invention needs to limit the component content.

[0026] 3. The present invention defines that the composite ceramic material is spherical powder, which has good fluidity and compactness. Among them, the loose bulk density of the composite ceramic powder is 0.4 - 2.2 g / cm 3 , and the fluidity is 30 - 50 s / 50 g, which is beneficial to reducing the porosity of the prepared coating and improving the mechanical properties of the coating; in addition, the particle size and uniformity of the spherical powder will affect the compactness and bonding strength of the prepared coating. The particle size of the composite ceramic powder of the present invention is 25 - 110 μm. The ceramic powder with this range of particle size makes the coating have better bonding strength and lower porosity, and during the thermal spraying process, it will also reduce the element evaporation loss, improve the protective performance and service life of the coating.

[0027] 4. The spray granulation process adopted in the method of the present invention not only has high production efficiency, but also can realize the regulation of the morphology and particle size of the composite ceramic powder by controlling the solid content of the slurry and the process parameters of the granulation process, etc. In addition, the method of the present invention sinters and spheroidizes the agglomerated powder obtained by spray granulation, improves the bonding strength between small particles inside the agglomerated powder, improves the fluidity of the powder, improves the density of the coating made of the thermal spraying composite ceramic material, reduces the porosity of the coating, and improves the mechanical properties, thereby solving the problem that the high-temperature electromagnetic functional coating is prone to peeling and failure in the actual use environment.

[0028] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be made obvious from the description, or understood by implementing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the content specifically pointed out in the description and the drawings. Description of the Drawings

[0029] The drawings are only for the purpose of showing specific embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference signs represent the same components;

[0030] FIG. 1 is a SEM image of the composite ceramic powder 1 prepared in Example 1, (a) overall appearance of the particles (b) partial enlarged view of the particle appearance;

[0031] Figure 2 is a SEM image of the composite ceramic powder 2 prepared in Example 2;

[0032] Figure 3 is a SEM image of the composite ceramic powder 3 prepared in Example 3;

[0033] Figure 4 is a SEM image of the composite ceramic powder 4 prepared in Comparative Example 1;

[0034] Figure 5 is a SEM image of the composite ceramic powder 5 prepared in Comparative Example 2;

[0035] Figure 6 is a SEM image of the composite ceramic powder 6 prepared in Comparative Example 3;

[0036] Figure 7 is a SEM image of the composite ceramic powder 7 prepared in Comparative Example 4;

[0037] Figure 8 is a test chart of the environmental resistance of the electromagnetic functional composite coating 1 prepared from the composite ceramic powder 1, (a) salt spray resistance, (b) solvent oil resistance;

[0038] Figure 9Test diagrams of the environmental resistance of the electromagnetic functional composite coating 2 prepared from the composite ceramic powder 2, (a) salt spray resistance, (b) solvent oil resistance;

[0039] Figure 10 Test diagrams of the environmental resistance of the electromagnetic functional composite coating 3 prepared from the composite ceramic powder 3, (a) salt spray resistance, (b) solvent oil resistance;

[0040] Figure 11 Test diagrams of the environmental resistance of the electromagnetic functional composite coating 4 prepared from the composite ceramic powder 4, (a) salt spray resistance, (b) solvent oil resistance;

[0041] Figure 12 Test diagrams of the environmental resistance of the electromagnetic functional composite coating 5 prepared from the composite ceramic powder 5, (a) salt spray resistance, (b) solvent oil resistance;

[0042] Figure 13 Test diagrams of the environmental resistance of the electromagnetic functional composite coating 6 prepared from the composite ceramic powder 6, (a) salt spray resistance, (b) solvent oil resistance;

[0043] Figure 14 Test diagrams of the environmental resistance of the electromagnetic functional composite coating 7 prepared from the composite ceramic powder 7, (a) salt spray resistance, (b) solvent oil resistance. Detailed implementation manners

[0044] The preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings, in which the accompanying drawings form a part of the present invention and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not used to limit the scope of the present invention.

[0045] With the increasingly wide application of electromagnetic waves, higher requirements are also put forward for materials that interfere with, shield, and absorb electromagnetic waves. The application environment of electromagnetic functional materials is becoming more and more demanding. Due to the limitations of single electromagnetic functional materials and loss mechanisms on their electromagnetic wave absorption performance, people are committed to researching composite electromagnetic absorption materials composed of multiple electromagnetic functional materials to broaden the absorption frequency band.

[0046] However, in practical applications, the mechanical properties of the electromagnetic functional coating composed of the composite electromagnetic absorption material are poor, and the bonding strength is low (~6 MPa). When the environment changes, including factors such as environmental temperature and medium, the coating is prone to cohesive fracture, especially under harsh usage conditions, problems such as coating peeling and failure are likely to occur, affecting the electromagnetic wave absorption efficiency and service life.

[0047] Therefore, the present invention provides a thermal spray composite ceramic material, which comprises a matrix material and a functional material. Among them, the matrix material is one or more of mullite, zirconia, cordierite, silicon dioxide, silicon nitride, and boron nitride, and the functional material includes SiBCNFe or / and SiCuCN, Ti3SiC2 or / and TiC, CNTs or / and carbon fiber, MoSi2 or / and Si3N4, ZnO or / and MnO2, and YSZ.

[0048] According to some preferred embodiments of the present invention, the matrix material is mullite, and the functional material includes SiBCNFe, Ti3SiC2, CNTs, MoSi2, ZnO, and YSZ.

[0049] The present invention uniformly disperses a variety of electromagnetic functional materials into the matrix material. The various electromagnetic functional materials have multiple loss mechanisms, which broaden the electromagnetic wave absorption frequency band, improve the absorption loss, and undertake the controllability of electromagnetic functions, as shown in Table 2.

[0050] Specifically, SiBCNFe and SiCuCN have magnetic loss and dielectric loss mechanisms, CNTs and carbon fiber have resistance loss mechanisms, and Ti3SiC2, MoSi2, ZnO, TiC, Si3N4, AlN, and MnO2 have dielectric loss mechanisms.

[0051] The various electromagnetic functional materials of the present invention are all temperature-resistant materials, which are beneficial to the expansion of the preparation process and application environment of the composite ceramic material of the present invention. The composite ceramic powder material can be prepared by a spray granulation process, and the size, morphology, and structure of the powder material can be controlled by adjusting process parameters; the composite ceramic powder material can be sprayed and deposited on the surface of the matrix at a certain speed by a thermal spray process to improve the bonding strength with the matrix, achieve controllable coating thickness, simplify the coating preparation process, and reduce the influence on the matrix material.

[0052] Furthermore, the various electromagnetic functional materials used in the present invention cooperate with each other and coordinate with each other to play a role in broadening the electromagnetic wave absorption frequency band. In addition to limiting the composition of the composite ceramic material, the present invention also limits the content of each component.

[0053] According to some preferred embodiments of the present invention, by mass percentage, the content of each component in the composite ceramic material is: SiBCNFe 8%-10%, Ti3SiC2 15%-18%, CNTs 2%-5%, MoSi2 5%-8%, ZnO 4%-6%, YSZ 22%-27%, and the balance is mullite.

[0054] The composite ceramic material not only broadens the electromagnetic wave absorption frequency band by increasing loss mechanisms, but also takes into account that the different physical and chemical properties of different electromagnetic functional materials may affect the morphology, structure and properties of the obtained composite ceramic material, and further affect its electromagnetic function and service life in practical applications.

[0055] It should be noted that for an electromagnetic wave absorbing material to absorb electromagnetic waves, it must meet the impedance matching condition and the attenuation condition. The impedance matching requires that within the entire frequency range, the dielectric constant of the coating matches the magnetic permeability to reduce the reflection of electromagnetic waves at the incident interface. When the absorbents with multiple loss mechanisms constitute the composite absorbent system of the present invention, a large number of interfaces and defects cause the electromagnetic waves to be reflected and transmitted multiple times, so that as much as possible enters the material body, improving the impedance matching and being conducive to the absorption of electromagnetic waves.

[0056] It should be noted that the composite ceramic material of the present invention contains electromagnetic wave absorbing materials with different loss mechanisms. Among them, the magnetic loss absorbent mainly absorbs electromagnetic waves through an appropriate magnetic permeability to generate magnetic loss; the dielectric loss absorbent utilizes an appropriate dielectric constant to absorb electromagnetic waves to generate dielectric loss; the resistance loss absorbent converts the electromagnetic wave energy into heat loss through mechanisms such as electron clouds and lattice vibrations in the material. Magnetic loss, dielectric loss and resistance loss do not exist in isolation, but cooperate and act together. The absorbents with different loss mechanisms form a complex electromagnetic field distribution in the coating, and the electromagnetic waves will be simultaneously affected by multiple loss mechanisms when propagating therein. This synergistic effect can significantly improve the electromagnetic wave absorption performance of the coating, enabling it to achieve high absorption rate in a wider frequency band. The proportions of the magnetic loss, dielectric loss and resistance loss materials are precisely controlled to balance the contributions of dielectric loss, magnetic loss and resistance loss. Generally, through experiments and simulation, the optimal composition ratio combination is found to achieve the best synergistic effect.

[0057] Specifically, the composite ceramic material of the present invention is spherical powder, which has good fluidity and compactness, is conducive to reducing the porosity of the coating prepared by thermal spraying, improving the coating density, improving the mechanical properties of the coating and the bonding strength with the substrate; the loose bulk density of the composite ceramic powder of the present invention is 0.4 - 2.2 g / cm 3 , and the fluidity is 30 - 50 s / 50 g.

[0058] The present invention also limits the particle size of the spherical powder. The size and uniformity of the particle size will affect the density and bonding strength of the prepared coating. Among them, during the thermal spraying process of the material, the particle size will also affect the evaporation loss of elements, thereby affecting the protective performance and service life of the coating.

[0059] Specifically, the particle size of the composite ceramic powder in the present invention is defined as 25 - 110 μm. If the particle size is too small, the fluidity of the powder is poor, and the evaporation loss of elements will also increase, affecting the coating composition and density; if the particle size is too large, it is likely to cause insufficient melting of the powder in the high-temperature heat flow, affecting the deposition efficiency; in addition, the powder particle size distribution should not be too wide to avoid uneven heating of the powder during the thermal spraying process.

[0060] In the present invention, test techniques such as EDS, XRD, laser particle size analyzer, Hall flowmeter, SEM, etc. can be used to characterize the composition, content, structure and properties of the thermal spraying composite ceramic material.

[0061] The present invention provides a preparation method of a thermal spraying composite ceramic material, and the method includes:

[0062] (1) According to the composition of the composite ceramic material, mix the matrix raw material, functional raw material with deionized water and binder to obtain a mixed slurry;

[0063] (2) Spray granulate the mixed slurry to obtain agglomerated powder;

[0064] (3) Sinter the agglomerated powder;

[0065] (4) Perform plasma spheroidization treatment on the powder sintered in step (3) and screen it.

[0066] Specifically, in step (1), the specific mixing steps are as follows: at room temperature, accurately weigh the raw materials according to the mass ratio and place them in a stirring container, and then add deionized water and binder to the stirring container and stir to obtain a uniformly mixed slurry.

[0067] Furthermore, the stirring speed is 100 - 150 rpm and the time is 5 - 7 h.

[0068] Furthermore, in order to control the morphology, density and forming and sintering properties of the particles obtained by subsequent spray granulation, it is necessary to limit the amount of deionized water and the amount of binder in the mixed slurry. Among them, the proportion of the binder should be appropriate to ensure that the viscosity of the slurry is moderate, so as to be beneficial to the spheroidization and densification of the powder after granulation.

[0069] Specifically, in the mixed slurry of the present invention, the mass of deionized water is 1 - 1.2 times the mass of the raw materials; the mass of the binder is 0.5 - 1% of the mass of the raw materials.

[0070] Furthermore, the binder of the present invention is compatible with the materials, ensuring a high powder yield and not affecting the spray granulation process performance. It can be selected from one or more of polyvinyl alcohol, phenolic resin, polyacrylamide, and polyacrylate. In view of the fact that polyvinyl alcohol also functions as a dispersant during the raw material mixing process, in some preferred embodiments of the present invention, the binder is polyvinyl alcohol.

[0071] The spray granulation process used in the method of the present invention not only has high production efficiency, but also can realize the regulation of the morphology and particle size of the composite ceramic powder by controlling the solid content of the slurry and the process parameters during the granulation process.

[0072] Specifically, in step (2), the process parameters of the spray granulation of the present invention are an inlet temperature of 340 - 350 °C, an outlet temperature of 100 - 110 °C, a spray disk rotation speed of 30 - 40 Hz, and a feeding speed of 35 - 45 rpm.

[0073] Among them, the inlet and outlet temperatures of the spray granulation affect the drying efficiency of the droplets and the performance of the separated material after drying. Too high a temperature will reduce the effect of the binder, affect the cohesive bonding strength of the agglomerated powder, and at the same time easily cause the particles to be too fine; too low a temperature is likely to cause wall sticking and result in insufficient strength of the powder particles, making them easy to break.

[0074] In addition, the spray disk rotation speed affects the atomization effect of the slurry and the particle size of the obtained powder. The faster the rotation speed, the smaller the atomized droplets and the higher the drying efficiency; the feeding speed affects the size and uniformity of the droplets. For example, too fast a feeding speed may lead to too large or irregularly shaped particles; while too slow a feeding speed may lead to too small or agglomerated particles and reduce the production efficiency.

[0075] According to some preferred embodiments of the present invention, among the process parameters of the spray granulation, the inlet temperature is 340 °C, 345 °C, or 350 °C respectively, the outlet temperature is 100 °C, 105 °C, or 110 °C respectively, the spray disk rotation speed is 30 Hz, 35 Hz, or 40 Hz respectively, and the feeding speed is 35 rpm, 40 rpm, or 45 rpm respectively.

[0076] Furthermore, in order to improve the cohesive bonding strength between the small particles inside the agglomerated powder obtained by spray granulation, the present invention performs a sintering treatment on the agglomerated powder.

[0077] Specifically, in step (3), the specific steps of the sintering treatment are as follows: Place the crucible containing the agglomerated powder in a sintering furnace and perform sintering under a protective atmosphere: sinter at a temperature of 550 - 950°C for 2 - 4 hours; sinter at a temperature of 1100 - 1500°C for 2 - 5 hours. The present invention uses sintering of the agglomerated powder at different high and low temperatures, which is beneficial to removing the binder and homogenizing the particles, better promoting the densification of the particles and the improvement of mechanical properties, and avoiding the generation of defects.

[0078] According to some preferred embodiments of the present invention, the conditions for sintering are sintering at a temperature of 950°C for 2 hours + sintering at a temperature of 1100°C for 2 hours, or sintering at a temperature of 950°C for 2 hours + sintering at a temperature of 1150°C for 2 hours; or sintering at a temperature of 950°C for 2 hours + sintering at a temperature of 1200°C for 2 hours.

[0079] Furthermore, the present invention also performs plasma spheroidization treatment on the sintered agglomerated powder to improve the fluidity of the powder, further improve the bonding strength between small particles inside the thermal spraying powder, improve the density of the coating prepared from the thermal spraying composite ceramic material, reduce the coating porosity, and improve the mechanical properties of the coating.

[0080] Specifically, in step (4), the process parameters for plasma spheroidization are: current 600 - 650 A, main gas (Ar) 100 - 110 SCFH, auxiliary gas (H2) 7 - 9 SCFH, carrier gas (Ar) 8 - 10 SCFH, powder feeding rate 2.0 - 3.0 r / min.

[0081] According to some preferred embodiments of the present invention, the conditions for plasma spheroidization are: current 600 A, main gas (Ar) 100 SCFH, auxiliary gas (H2) 7 SCFH, carrier gas (Ar) 8 SCFH, powder feeding rate 2.0 r / min; or: current 625 A, main gas (Ar) 105 SCFH, auxiliary gas (H2) 8 SCFH, carrier gas (Ar) 9 SCFH, powder feeding rate 2.5 r / min; or: current 650 A, main gas (Ar) 110 SCFH, auxiliary gas (H2) 9 SCFH, carrier gas (Ar) 10 SCFH, powder feeding rate 3.0 r / min.

[0082] Furthermore, the method of the present invention also includes screening the spheroidized agglomerated powder to obtain a powder with a particle size and range meeting the requirements.

[0083] Specifically, place the agglomerated powder in an oscillating screen analyzer, and the screening parameters are: amplitude 2 - 3 mm, screening time 3 - 5 minutes, intermittent time 10 s, to obtain a thermal spraying composite ceramic powder with a particle size range of 25 - 110 μm.

[0084] The present invention also provides a high-temperature electromagnetic functional coating, which includes a functional layer, and the material of the functional layer contains the above-mentioned thermal spraying composite ceramic material. Specifically, the composite ceramic material is deposited on the surface of the substrate by thermal spraying process as the functional layer of the electromagnetic functional coating. The prepared electromagnetic functional coating not only has a relatively wide electromagnetic wave absorption bandwidth and large absorption loss, but also has a low porosity of the coating, a high bonding strength with the substrate, improves the mechanical properties of the coating, and avoids the problems that the existing electromagnetic functional coating is prone to cohesive fracture due to changes in the external environment, including environmental temperature, medium and other factors, especially under harsh use conditions, the coating is prone to peeling and failure, affecting the electromagnetic wave absorption efficiency and service life.

[0085] Furthermore, the high-temperature electromagnetic functional coating further includes a bonding layer, a protective layer, and a surface layer.

[0086] Specifically, from the inside to the outside of the substrate surface, the composite coating specifically includes: a bonding layer, a protective layer, a functional layer, and a surface layer, with thicknesses of 0.1-0.2 mm, 0.03-0.05 mm, 1.25-1.4 mm, and 0.05-0.1 mm respectively. The material of the functional layer contains the thermal spraying composite ceramic material; wherein, the composite ceramic material includes a matrix material and a variety of electromagnetic functional materials dispersed in the matrix material.

[0087] The present invention defines the thickness of the bonding layer as 0.1-0.2 mm. If the bonding layer is too thin, it cannot play the role of thermal expansion coefficient transition, and the temperature resistance and thermal shock performance of the coating system will decline; if the bonding layer is too thick, it will cause a relatively large increase in the weight of the coating system and an increase in the surface density of the coating.

[0088] The present invention defines the thickness of the protective layer as 0.03-0.05 mm. If the protective layer is too thin, it cannot completely cover the bonding layer and cannot play the role of protecting the bonding layer, and the environmental resistance performance such as salt spray resistance and solvent oil resistance of the coating will decline; because the thermal expansion coefficient of the protective layer is relatively low, if the protective layer is too thick, it will cause a mismatch in the thermal expansion coefficient of the coating system, and the temperature resistance and thermal shock performance of the coating system will decline.

[0089] The present invention defines the thickness of the functional layer as 1.25-1.4 mm. If the functional layer is too thin, the electromagnetic function of the coating will be poor and the wave absorption performance will be poor; if the functional layer is too thick, although the maximum absorption loss will increase, the wave absorption bandwidth will decrease, and at the same time, it will also cause a relatively large increase in the weight of the coating system and an increase in the surface density of the coating.

[0090] The present invention defines the thickness of the surface layer as 0.05-0.1 mm. If the surface layer is too thin, it cannot completely cover the functional layer and cannot play the role of protecting the functional layer, and the environmental resistance performance such as salt spray resistance and solvent oil resistance of the coating will decline; if the surface layer is too thick, it will cause a relatively large increase in the weight of the coating system and an increase in the surface density of the coating.

[0091] The substrate material of the present invention is one of superalloy and stainless steel.

[0092] Furthermore, from the inside to the outside of the substrate surface, the functional layer includes three layers: a first wave-absorbing layer, a wave-transmitting layer, and a second wave-absorbing layer. Among them, the materials of the first wave-absorbing layer and the second wave-absorbing layer are thermal spraying composite ceramic materials.

[0093] The functional layer of the present invention has a trap structure. Electromagnetic waves undergo multiple reflections and interferences inside the multi-layer structure, increasing the interaction time and number of times between the electromagnetic waves and the material, thereby improving the absorption efficiency of the electromagnetic waves and realizing multiple absorptions of the electromagnetic waves entering the coating inside the material.

[0094] The functional layer in the electromagnetic functional composite coating of the present invention has a three-layer trap structure. A wave-transmitting layer is provided in the middle of the two wave-absorbing layers composed of composite ceramic materials. The wave-transmitting layer can guide the electromagnetic waves that have been preliminarily attenuated by the second wave-absorbing layer deep into the coating. The first wave-absorbing layer further absorbs and attenuates the transmitted electromagnetic waves, increasing the contact opportunity between the electromagnetic waves and the subsequent wave-absorbing layers, realizing multiple absorptions of the electromagnetic waves entering the coating, and enhancing the wave-absorbing effect; through the combination of the multi-layer structure of the functional layer, the width of the absorption frequency band of the coating is further broadened, better solving the problem of the relatively narrow absorption frequency band of the high-temperature electromagnetic functional coating; in addition, the design of the wave-transmitting layer can also optimize the impedance matching between materials, further reducing the reflection loss of electromagnetic waves at the interface. And the thickness of each layer is limited to reduce the coating weight, improve the bonding strength, facilitate carrying and installation, and broaden the application.

[0095] Furthermore, the material of the wave-transmitting layer should have high temperature resistance and appropriate electromagnetic parameters, and can transmit the electromagnetic waves to be absorbed. It can be one of alumina, mullite, zirconia, cordierite, silica, silicon nitride, and boron nitride.

[0096] According to some preferred embodiments of the present invention, the material of the wave-transmitting layer is alumina.

[0097] Test the electromagnetic parameters of the thermal spraying composite ceramic powder material, and use CST software to calculate the simulated reflectivity of the three-layer structure of the electromagnetic functional layer. In the frequency range of 4-18 GHz, the optimal thickness of the alumina layer is calculated to be 0.35-0.4 mm.

[0098] Furthermore, in order to realize the effective combination of the electromagnetic functional coating and the substrate material, the present invention uses a material with good temperature resistance, good oxidation resistance, and appropriate thermal expansion coefficient as the bonding layer, not only realizing the firm combination between the substrate and the electromagnetic functional coating, but also reducing the difference in thermal expansion coefficient between the wave-absorbing electromagnetic functional coating and the substrate in practical applications, improving the bonding strength, and preventing the coating from peeling off.

[0099] Specifically, the raw material forming the bonding layer is metal alloy powder, selected from one or more of NiCrAlYSi, NiCrAlY, NiCrCoAlY, nickel-chromium alloy, and cobalt-chromium alloy.

[0100] According to a preferred embodiment of the present invention, the binder is NiCrAlYSi.

[0101] Furthermore, in order to prevent corrosive substances from entering the interior of the bonding layer, the bonding layer obtained by spraying is heat-treated to form a dense metal oxide layer on the surface of the bonding layer, preventing corrosive substances from entering the interior of the bonding layer through pores and causing corrosion failure of the bonding layer.

[0102] Furthermore, in order to make the connection between the bonding layer and the electromagnetic functional coating more uniform and densified, and further prevent corrosive substances from entering the electromagnetic functional composite coating, the present invention uses a heat-resistant resin to spray and cure and coat the bonding layer to form a protective layer to fill the pores and improve the coating density and mechanical properties.

[0103] Specifically, the heat-resistant resin forming the protective layer has good densification and excellent environmental resistance after curing, and can be selected from one or more of modified polysilazane resin, modified polysiloxane, modified siloxane, and modified silicone resin.

[0104] Furthermore, in order to isolate the electromagnetic functional layer from the external environment, prevent oxidation of the electromagnetic functional material under high-temperature conditions, and improve the temperature resistance of the coating, the present invention sprays a heat-resistant wave-transparent material on the surface of the electromagnetic functional coating to form a surface layer located on the outermost layer of the composite coating; in addition, the surface layer can also play a role in further preventing corrosive substances from entering the electromagnetic functional composite coating.

[0105] Specifically, the material constituting the surface layer is an inert material with low oxygen permeability, good matching of the thermal expansion coefficient with the rest of the coating, and good phase structure stability, and no phase transformation occurs in the working environment; it can be selected from one or more of high-entropy rare-earth disilicate (La 1 / 6 Hf 1 / 6 Ta 1 / 6 Yb 1 / 6 Er 1 / 6 Gd 1 / 6 )2Si2O7, mullite, BSAS (BaO-SrO-Al2O3-SiO2), alumina, and YSZ.

[0106] According to a preferred embodiment of the present invention, the material of the surface layer is high-entropy rare-earth disilicate (La 1 / 6 Hf 1 / 6Ta 1 / 6 Yb 1 / 6 Er1 / 6 Gd 1 / 6 )2Si2O7。

[0107] The electromagnetic functions (absorption bandwidth, maximum absorption loss, etc.), heat resistance, bonding strength, porosity and other properties of the electromagnetic functional composite coating are tested by using GJB 2038A-2011 standard, GB / T 5210 standard, GB / T 15749-1995 standard, GB / T 1771 standard, and GB / T 9274 standard respectively in this invention.

[0108] The technical solution of the present invention will be further explained and illustrated with specific embodiments below.

[0109] Example 1

[0110] A method for preparing thermal spraying composite ceramic powder 1 includes:

[0111] (1) Weigh 160 g of SiBCNFe, 300 g of Ti3SiC2, 40 g of CNTs, 100 g of MoSi2, 80 g of ZnO, 440 g of YSZ, 880 g of mullite, 2000 g of deionized water, and 10 g of polyvinyl alcohol and place them in a stirring container. Stir at a stirring speed of 100 r / min for 5 h to obtain a mixed slurry;

[0112] (2) Use a spray dryer to spray granulate the mixed slurry prepared in step (1). The spray granulation process parameters are: inlet temperature 340 °C, outlet temperature 100 °C, spray disc rotation speed 30 Hz, feed rate 35 rpm to obtain spherical agglomerated powder;

[0113] (3) Place the spherical agglomerated powder in a crucible, and place the crucible in an atmosphere sintering furnace for sintering. The sintering process is: sinter at 950 °C for 2 h and at 1100 °C for 2 h under Ar protective atmosphere, and cool with the furnace;

[0114] (4) Feed the sintered agglomerated powder into a plasma spheroidizing device. The plasma spheroidizing process parameters are: current 600 A, main gas (Ar) 100 SCFH, auxiliary gas (H2) 7 SCFH, carrier gas (Ar) 8 SCFH, powder feeding rate 2.0 r / min;

[0115] (5) Screen the spheroidized powder in an oscillating sieve shaker. The screening parameters are: amplitude 2 mm, screening time 3 min, intermittent time 10 s to obtain thermal spraying composite ceramic powder 1.

[0116] The SEM photograph of the thermal spraying composite ceramic powder 1 is shown in Figure 1. As can be seen from Figure 1, the ceramic powder particles have good sphericity, with a uniform and dense surface. There is no aggregation phenomenon among the raw material particles inside the spherical powder, and the original particles with different particle sizes are evenly distributed in the spherical powder, indicating that the functional materials are evenly distributed in the matrix. After testing, the average particle size of the composite ceramic powder 1 is 80 μm, and the loose bulk density is 1.2 g / cm 3 , and the flowability is 32 s / 50 g.

[0117] Example 2

[0118] A method for preparing the thermal spraying composite ceramic powder 2 includes:

[0119] (1) Weigh 180 g of SiBCNFe, 330 g of Ti3SiC2, 70 g of CNTs, 130 g of MoSi2, 100 g of ZnO, 490 g of YSZ, 700 g of mullite, 2200 g of deionized water, and 15 g of polyvinyl alcohol and place them in a stirring container. Stir at a stirring speed of 120 r / min for 6 h to obtain a mixed slurry;

[0120] (2) Use a spray dryer to perform spray granulation on the mixed slurry prepared in step (1). The spray granulation process parameters are: inlet temperature 345 °C, outlet temperature 105 °C, spray disc rotation speed 35 Hz, feed rate 40 rpm, to obtain spherical agglomerated powder;

[0121] (3) Place the spherical agglomerated powder in a crucible, and place the crucible in an atmosphere sintering furnace for sintering. The sintering process is: sinter at a temperature of 950 °C for 2 h and at a temperature of 1150 °C for 2 h under an Ar protective atmosphere, and cool with the furnace;

[0122] (4) Feed the sintered agglomerated powder into a plasma spheroidizing device. The plasma spheroidizing process parameters are: current 625 A, main gas (Ar) 105 SCFH, auxiliary gas (H2) 8 SCFH, carrier gas (Ar) 9 SCFH, powder feeding rate 2.5 r / min;

[0123] (5) Screen the spheroidized powder in an oscillating sieve shaker. The screening parameters are: amplitude 2.5 mm, screening time 4 min, intermittent time 10 s, to obtain the thermal spraying composite ceramic powder 2.

[0124] The SEM photograph of the thermal spraying composite ceramic powder 2 is as Figure 2 shown. As can be seen from Figure 1, the ceramic powder particles have good sphericity, with a uniform and dense surface. After testing, the average particle size of the composite ceramic powder 2 is 82 μm, and the loose bulk density is 1.5 g / cm 3 , and the flowability is 38 s / 50 g.

[0125] Example 3

[0126] A method for preparing thermal spraying composite ceramic powder 3, comprising:

[0127] (1) Weigh 200 g of SiBCNFe, 360 g of Ti3SiC2, 100 g of CNTs, 160 g of MoSi2, 120 g of ZnO, 540 g of YSZ, 520 g of mullite, 2400 g of deionized water, and 20 g of polyvinyl alcohol and place them in a stirring container. Stir at a stirring speed of 150 r / min for 7 h to obtain a mixed slurry;

[0128] (2) Use a spray dryer to spray granulate the mixed slurry prepared in step (1). The spray granulation process parameters are: inlet temperature 350 °C, outlet temperature 110 °C, spray disc rotation speed 40 Hz, feeding speed 45 rpm, to obtain spherical agglomerated powder;

[0129] (3) Place the spherical agglomerated powder in a crucible, and place the crucible in an atmosphere sintering furnace for sintering. The sintering process is: sinter at 950 °C for 2 h under an Ar protective atmosphere, sinter at 1200 °C for 2 h, and cool with the furnace;

[0130] (4) Feed the sintered agglomerated powder into a plasma spheroidizing device. The plasma spheroidizing process parameters are: current 650 A, main gas (Ar) 110 SCFH, auxiliary gas (H2) 9 SCFH, carrier gas (Ar) 10 SCFH, powder feeding rate 3.0 r / min;

[0131] (5) Screen the spheroidized powder in an oscillating sieve shaker. The screening parameters are: amplitude 3 mm, screening time 5 min, intermittent time 10 s, to obtain thermal spraying composite ceramic powder 3.

[0132] The SEM photograph of the thermal spraying composite ceramic powder 3 is as Figure 3 shown. As can be seen from Figure 1, the ceramic powder particles have good sphericity, and the surface is uniform and densified; after testing, the average particle size of the composite ceramic powder 3 is 78 μm, and the loose bulk density is 2.0 g / cm 3 , and the fluidity is 42 s / 50 g.

[0133] Comparative Example 1

[0134] The thermal spraying composite ceramic powder 4 was prepared by the same method as in Example 2, except that: in step (1), 180 g of SiBCNFe, 400 g of Ti3SiC2, 130 g of MoSi2, 100 g of ZnO, 490 g of YSZ, 700 g of mullite, 2200 g of deionized water, and 15 g of polyvinyl alcohol were placed in a stirring container and stirred at a stirring speed of 120 r / min for 6 h to obtain a mixed slurry; and then through steps (2)-(5), the thermal spraying composite ceramic powder 4 was finally obtained.

[0135] The SEM photograph of the thermal spraying composite ceramic powder 4 is as Figure 4 shown. After testing, the average particle size of the composite ceramic powder 4 was 68 μm, the apparent density was 3.0 g / cm 3 , and the flowability was 60 s / 50 g.

[0136] Comparative Example 2

[0137] The thermal spraying composite ceramic powder 5 was prepared by the same method as in Example 2, except that: the spheroidizing process in step (4) was not included in the preparation process, and finally the thermal spraying composite ceramic powder 5 was obtained.

[0138] The SEM photograph of the thermal spraying composite ceramic powder 5 is shown in Figure 5. After testing, the average particle size of the composite ceramic powder 5 was 65 μm, the apparent density was 1.1 g / cm 3 , the flowability was 88 s / 50 g, and the powder surface was relatively rough.

[0139] Comparative Example 3

[0140] The thermal spraying composite ceramic powder 6 was prepared by the same method as in Example 2, except that:

[0141] The sintering process in step (3) was: sintering at 450 °C for 1 h and at 1000 °C for 1 h in an Ar protective atmosphere, and cooling with the furnace;

[0142] The process of plasma spheroidization in step (4) was: current 550 A, main gas (Ar) 85 SCFH, auxiliary gas (H2) 5 SCFH, carrier gas (Ar) 4 SCFH, powder feeding rate 6 r / min; and finally the thermal spraying composite ceramic powder 6 was obtained.

[0143] The SEM photograph of the thermal spraying composite ceramic powder 6 is shown in Figure 6. After testing, the average particle size of the composite ceramic powder 6 was 66 μm, the apparent density was 3.1 g / cm 3 , the flowability was 66 s / 50 g, and partial regions of the powder surface were densified while partial regions were not densified.

[0144] Comparative Example 4

[0145] The thermal spray composite ceramic powder 7 was prepared by the same method as in Example 2, except that the spray granulation process parameters in step (2) were as follows: the inlet temperature was 245 °C, the outlet temperature was 115 °C, the rotation speed of the spray disk was 50 Hz, and the feeding speed was 60 rpm, to obtain spherical agglomerated powder; finally, the thermal spray composite ceramic powder 7 was obtained.

[0146] The SEM photograph of the thermal spray composite ceramic powder 7 is shown in Figure 7. After testing, the average particle size of the composite ceramic powder 7 was 60 μm, and the loose bulk density was 3.4 g / cm 3 , and the fluidity could not be tested. The poor sphericity of the powder led to poor fluidity, and further unstable powder feeding during the spheroidization process, incomplete densification on the surface of the powder after spheroidization, and low powder strength.

[0147] Application Example 1

[0148] The functional layers in the high-temperature electromagnetic functional coatings 1-7 were prepared by thermal spraying the composite ceramic powders 1-7 prepared in Examples 1-3 and Comparative Examples 1-4. The substrate material was a superalloy. From the inner to the outer surface of the substrate, the high-temperature electromagnetic functional coating included a NiCrAlYSi bonding layer, a modified polysilazane resin protective layer, a functional layer, and a (La 1 / 6 Hf 1 / 6 Ta 1 / 6 Yb 1 / 6 Er 1 / 6Gd 1 / 6 )2Si2O7 surface layer, and the thickness of each layer was shown in Table 1; from the inner to the outer surface of the substrate, the functional layer included a first wave-absorbing layer, an alumina wave-transmitting layer, and a second wave-absorbing layer, and the thickness of each layer was shown in Table 1. Among them, the materials of the first wave-absorbing layer and the second wave-absorbing layer were the above-mentioned composite ceramic powders respectively.

[0149] Table 1

[0150]

[0151] The electromagnetic function, bonding strength, porosity, temperature resistance performance, and environmental resistance performance of the high-temperature electromagnetic functional coatings 1-7 were tested. Under the same other conditions, the test results were shown in Table 2, Figures 8-14 as shown. Among them, the test methods and standards for each performance were as follows:

[0152] Coating electromagnetic function test: According to the standard of GJB 2038A-2011, the bow-tie method was used for testing. Based on the principle of reflection and absorption of electromagnetic waves on the material surface, the electromagnetic function of the material was measured.

[0153] Pull-off adhesion: According to the standard of GB / T 5210, the test column is bonded to the coating surface with an adhesive, and then tensile stress is applied on a tensile testing machine to measure the tensile force required to break the adhesion per unit area between the coating and the substrate, so as to evaluate the adhesion of the coating.

[0154] Coating porosity test: According to the standard of GB / T 15749-1995, the line intercept method in the quantitative metallographic manual measurement method is used to measure the porosity of the coating, that is, the pores in the coating are regarded as one phase, and the coating entity is regarded as one phase, and the two-dimensional parameters measured from the metallographic polished surface are used to calculate the pore content in the three-dimensional space.

[0155] Salt spray resistance: According to the standard of GB / T 1771, a salt spray test is carried out for 192 hours in an environment of (35±1)°C and 5% NaCl. After the test is completed, the specimen is taken out, wiped dry with absorbent cotton or soft paper to remove water stains / salt particles, placed in a standard test environment for 30 minutes, and the appearance is observed within 30 minutes.

[0156] Solvent oil resistance: According to the standard of GB / T 9274, the coating is immersed in solvent oil, and a medium resistance test is carried out for 7 days at (23±2)°C. After the test is completed, the specimen is taken out, wiped dry with absorbent cotton or soft paper to remove oil stains (it is allowed to dip 120# solvent gasoline to remove the residual solvent oil), placed in a standard test environment for 30 minutes, and the appearance is observed within 30 minutes.

[0157] Table 2

[0158]

[0159] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A thermal spraying composite ceramic material for electromagnetic wave absorption on a superalloy or stainless steel substrate, characterized in that, The composite ceramic material includes a matrix material and a functional material. Among them, the matrix material is mullite, and the functional material includes SiBCNFe, Ti3SiC2, CNTs, MoSi2, ZnO, and YSZ; the functional material is uniformly dispersed in the matrix material; by mass percentage, the contents of the components in the composite ceramic material are: SiBCNFe 8%-10%, Ti3SiC2 15%-18%, CNTs 2%-5%, MoSi2 5%-8%, ZnO 4%-6%, YSZ 22%-27%, and the balance is mullite; the composite ceramic material is spherical powder with a particle size of 25-110 μm; the loose bulk density of the spherical powder is 0.4-2.2 g / cm 3 , and the fluidity is 30-50 s / 50 g; Method for preparing the composite ceramic material, comprising: (1) According to the composition of the composite ceramic material, mixing matrix raw materials, functional raw materials with deionized water and a binder to obtain a mixed slurry; (2) Spray granulating the mixed slurry to obtain agglomerated powder; (3) Sintering the agglomerated powder; (4) Performing plasma spheroidization treatment on the powder sintered in step (3) and screening; wherein, the process parameters of the spray granulation are: inlet temperature 340 - 350 °C, outlet temperature 100 - 110 °C, spray disc rotation speed 30 - 40 Hz, feeding speed 35 - 45 rpm; the process parameters of the sintering are: sintering at a temperature of 550 - 950 °C for 2 - 4 h under a protective atmosphere; sintering at a temperature of 1100 - 1500 °C for 2 - 5 h; the process parameters of the plasma spheroidization treatment are: current 600 - 650 A, main gas Ar 100 - 110 SCFH, auxiliary gas H2 7 - 9 SCFH, carrier gas Ar 8 - 10 SCFH, powder feeding rate 2.0 - 3.0 r / min.

2. A method for preparing the composite ceramic material according to claim 1, characterized in that, The method comprises: (1) According to the composition of the composite ceramic material, mixing matrix raw materials, functional raw materials with deionized water and a binder to obtain a mixed slurry; (2) Spray granulating the mixed slurry to obtain agglomerated powder; (3) Sintering the agglomerated powder; (4) Performing plasma spheroidization treatment on the powder sintered in step (3) and screening; In step (2), the process parameters of the spray granulation are: inlet temperature 340 - 350 °C, outlet temperature 100 - 110 °C, spray disc rotation speed 30 - 40 Hz, feeding speed 35 - 45 rpm; In step (3), the process parameters of the sintering are: sintering at a temperature of 550 - 950 °C for 2 - 4 h under a protective atmosphere; sintering at a temperature of 1100 - 1500 °C for 2 - 5 h; In step (4), the process parameters of the plasma spheroidization treatment are: current 600 - 650 A, main gas Ar 100 - 110 SCFH, auxiliary gas H2 7 - 9 SCFH, carrier gas Ar 8 - 10 SCFH, powder feeding rate 2.0 - 3.0 r / min.

3. A high-temperature electromagnetic functional coating, characterized in that, The high-temperature electromagnetic functional coating includes a functional layer, and the material of the functional layer comprises the thermal spraying composite ceramic material as claimed in claim 1 or the thermal spraying composite ceramic material obtained by the preparation method as claimed in claim 2.

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