Gradient pore sialon-based composite ceramic material as well as preparation method and application thereof

Abstract

The invention provides a gradient pore sialon-based composite ceramic material, which comprises a substrate and a plating layer on the surface of the substrate, the substrate is a sialon ceramic material embedded with boron nitride particles and ceramic fibers, and the interior of the substrate is provided with a gradient pore structure of which the pore diameter is gradually reduced from inside to outside; the plating layer comprises a bottom surface layer and a surface layer, the bottom surface layer comprises an inner layer, a transition layer and an outer layer, and the surface layer is of a multi-layer structure formed by alternately arranging silicon carbonitride and silicon carbide. The invention further provides a preparation method of the gradient pore sialon-based composite ceramic material. The preparation method comprises the steps of raw material treatment, forming, segmented sintering, gradient coating and circulating coating. The invention further provides application of the gradient pore sialon-based composite ceramic material. The gradient pore structure is utilized, stress on an interface is transmitted to other internal pores, the stress is buffered into the whole base body, breakage caused by overlarge local stress is avoided, and the whole film layer has high strength and high abrasion resistance in a high-temperature environment due to the multi-layer film coating structure, is tightly combined with the base body and is difficult to fall off.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-performance ceramics, in particular to a gradient-pore sialon-based composite ceramic material, a preparation method and applications. BACKGROUND

[0002] With the development of science, people's demand for various high-performance materials is getting higher and higher, and high-performance ceramic materials are currently essential important materials in industry, which usually have high chemical stability, high heat resistance, high mechanical strength and other advantages, and are widely used in industrial production. Sialon ceramic is a new type of ceramic material based on silicon nitride as a basic component, and its crystal structure is composed of (Si, Al) (O, N) tetrahedron, which has high chemical stability, high toughness and high temperature mechanical strength. The material has significantly better thermal shock resistance than traditional oxide ceramics, and is suitable for industrial fields such as metal cutting tools and high-temperature thermal machine parts.

[0003] However, the traditional sialon ceramic still has certain performance limitations, such as poor fracture toughness and cracking in high-temperature environment, which cannot meet the demand of high-stress working conditions. In addition, due to its high density, it is difficult to transport and maintain due to its large weight.

[0004] Therefore, in the prior art, there are technical solutions for forming a pore structure in the sialon ceramic to reduce its weight and improve its mechanical properties. For example:

[0005] A pressure-resistant foam ceramic material is disclosed in Chinese patent application CN110183232A. The material includes the following components with the following mass contents: silicon carbide 40-45%, silicon nitride 15-18%, mullite 10-15%, sialon 3-5%, carbon 3-5%, and the balance of aluminum phosphate; the carbon exists in the form of a carbon network. Mullite and sialon are used as a bonding phase to make silicon carbide and silicon nitride better combined with the carbon network, and the strengthening effect of aluminum phosphate is also used to obtain a foam ceramic material with excellent pressure resistance.

[0006] A preparation method of corundum-bonded sialon porous ceramic with a self-coating structure is disclosed in Chinese patent application CN116874312A. Aluminum ash generated during the production of metal aluminum and silicon powder solid waste generated during the cutting process of crystalline silicon are used as aluminum and silicon sources, respectively. On the basis of a pore-forming agent, a self-coating structure of corundum-bonded sialon porous ceramic material is synthesized by solid-phase reaction sintering at high temperature. The aluminum in the raw material melts and diffuses outward at high temperature, and when it diffuses to the surface of the sample, it reacts with oxygen to form a relatively dense aluminum oxide coating layer, thereby improving the mechanical properties of the sialon porous ceramic.

[0007] A Chinese invention patent with publication number CN105727756A proposes a double-gradient pore structure sialon combined with silicon carbide membrane tube and its preparation method. The membrane tube material composition is sialon and silicon carbide, and the membrane tube has a double-gradient filtration structure composed of a support layer and a surface membrane layer. The support body is composed of reaction-generated sialon combined with coarse silicon carbide grains, with an average pore size of 10-50 μm. The surface membrane layer is composed of reaction-generated sialon combined with fine particle silicon carbide grains, with an average pore size of 0.1-5 μm. The overall porosity of the membrane tube is between 40-50%. It has the remarkable characteristics of high porosity, low pressure drop, high strength, good thermal shock resistance, high temperature, and easy backflushing regeneration.

[0008] However, the above technical solutions all have a obvious problem, that is, they are not used in high temperature and high pressure ring conditions, so when facing the problem of internal stress buffer release under high temperature, it is still difficult to achieve sufficient solving effect. For example, the silicon steel continuous annealing work roll, the single crystal silicon production crucible, and the 20-roller mill work roll all require extreme environment resistance, impact resistance and high temperature resistance of the working parts, so as to release the internal stress when subjected to high strength pressure. When facing high strength interfacial pressure, the irregularly distributed pores of the above technical solutions are more likely to cause interfacial cracking, and the pore structure on the surface also reduces the wear resistance of the material. Therefore, a ceramic material that is more suitable for high temperature, high pressure and high wear environment and has a pore structure to release internal stress is needed. SUMMARY

[0009] In view of the deficiencies in the prior art, the present application provides a gradient pore sialon-based composite ceramic material, a preparation method and an application, which solves the problem of the existing pore structure ceramic material in the prior art, that is, it is difficult to release internal stress under high temperature and high pressure environment, and the wear resistance is poor.

[0010] In a first aspect, the present application provides a gradient pore sialon-based composite ceramic material, which comprises a substrate and a plating layer on the surface of the substrate. The substrate is a sialon ceramic material embedded with boron nitride particles and ceramic fibers. The substrate also has a plurality of uniformly distributed pores inside, and the pore size gradually decreases from the inside to the outside, forming a gradient pore structure.

[0011] The plating layer comprises an inner and outer distribution of a bottom layer and a surface layer. The bottom layer comprises an inner layer, a transition layer and an outer layer distributed in turn from the inside to the outside. The inner layer material is silicon carbonitride, the transition layer material is silicon nitride, and the outer layer material is silicon carbide. The surface layer is a multi-layer structure of silicon carbonitride and silicon carbide arranged alternately.

[0012] As a preferred embodiment, the substrate further comprises yttrium oxide nanoparticles with a mass fraction of 1%-2% and titanium boride whiskers with a mass fraction of 3%-5% as modifiers.

[0013] Preferably, the sialon ceramic has an alpha phase content of greater than 60%, the boron nitride particles are hexagonal boron nitride having an aspect ratio of greater than 20, and the boron nitride has a mass content of 30-35% of the mass of the sialon ceramic.

[0014] Preferably, the ceramic fibers have a mass content of 20-25% of the mass of the sialon ceramic, an aspect ratio of 40-50:1, and are silicon carbide-doped alumina ceramic having a mass ratio of silicon carbide to alumina of 0.25-0.3.

[0015] Preferably, in the bottom layer, the inner layer has a thickness of 60-70 μm, the transition layer has a thickness of 2-3 μm, and the outer layer has a thickness of 20-25 μm.

[0016] Preferably, in the surface layer, each layer of silicon carbonitride or silicon carbide has a thickness of 1-1.5 μm, the total number of layers is 30-50, and the number of layers is even.

[0017] In a second aspect, the present application further provides a method for preparing a gradient-pore sialon-based composite ceramic material, comprising the following steps:

[0018] S1, raw material processing: sialon ceramic and boron nitride are ball-mixed for 8-12 h to prepare powder particles having a particle size D50 of 1-2 μm; ceramic fibers are cut to a length of 50-100 μm and then added to the sialon ceramic and boron nitride powder, and a pore-forming agent and a modifier are added and uniformly mixed to form a raw material powder;

[0019] Further, in the step S1, the ceramic fibers are first placed in a 10% polyvinyl alcohol solution for ultrasonic dispersion, the frequency of the ultrasonic dispersion is 40 kHz, and the time is 30-40 min, so that the ceramic fibers are oriented and arranged.

[0020] S2, molding: the raw material powder is subjected to vacuum kneading at a vacuum degree of ≤5 Pa for 2-3 h, and then is molded under a pressure of at least 70 MPa and is kept under pressure for 10-15 min;

[0021] S3, step-by-step sintering:

[0022] In the first stage, the temperature is raised to 600-650 °C at a rate of 2 °C / min under a nitrogen atmosphere, and is kept at this temperature for 2-3 h, at which time the pore-forming agent begins to decompose;

[0023] In the second stage, sintering is performed at 1420-1450 °C under a nitrogen protective environment for 2.5-3.5 h to form a matrix and to form initial pores in the matrix through the pore-forming agent;

[0024] The third stage is to increase the temperature to 1620-1640°C at a rate of 5°C / min under the protection of argon, and keep the temperature for 4-6 hours, so that the boron nitride particles are uniformly distributed and a stable pore structure is formed.

[0025] The fourth stage is to continue sintering for 1-2 hours under the pressure of 200 MPa, so that the surface layer of the substrate is densified.

[0026] After calcination, the surface of the substrate is polished first, and then polished by laser to Ra≤0.1 μm.

[0027] Then, critical CO2 cleaning is performed under the condition of temperature of 31.1°C (near the critical point) and pressure of 8-9 MPa for 1-2 hours to remove phosphorus and iron impurities.

[0028] S4, gradient coating, the specific coating process is as follows:

[0029] S4.1, pore activation: a mixture of NH3 / H2 gas with a volume ratio of 5 / 1 is introduced, and the flow rate is 200 sccm under the condition of pressure of 50 Pa and temperature of 300°C for 30 min, so as to open the pore channel and promote the subsequent gas penetration.

[0030] S4.2, inner layer deposition: a mixture of SiH4 / NH3 / CH4 gas with a volume ratio of 1:3:0.5 is introduced, and the plasma parameters are set as power of 200 W (RF) and duty cycle of 50%, and the carbon nitride silicon is deposited at a speed of 5 μm / h under the condition of pressure of 80 Pa and temperature of 1050°C.

[0031] Among them, the low pressure environment (80 Pa) makes the carbon nitride silicon SiCN preferentially deposited in the pores (penetration depth > 80%) compared with the silicon nitride Si3N4, and the introduction of CH can promote the formation of C-N bond and inhibit the growth of surface SiC and SiN. That is, selective control can be realized to improve the purity of carbon nitride silicon SiCN.

[0032] S4.3, transition layer deposition: a mixture of SiH4 / NH3 gas with a volume ratio of 1:2 is introduced, and Ar gas (total flow rate of 200 sccm) is introduced at the same time, and the plasma parameters are set as power of 300 W (RF) and adjusted to pulse mode (5 ms on / 50 ms off), and the silicon nitride is deposited under the condition of pressure of 150 Pa and temperature of 1100°C.

[0033] S4.4, outer layer deposition: a mixture of SiH4 / CH4 gas with a volume ratio of 1:1.5 is introduced, and the plasma parameters are set as power of 400 W (RF) and duty cycle of 70%, and the silicon carbide is deposited under the condition of pressure of 200 Pa and temperature of 1200°C.

[0034] In the high pressure environment (200 Pa), the surface of the substrate is preferentially deposited with SiC (coverage > 95%), and the high power plasma can activate the decomposition of CH4 to generate high-density SiC grains, thereby improving the selectivity to SiC.

[0035] Preferably, the substrate is continuously rotated at a speed of 5-10 rpm during the deposition process to avoid edge effects. Meanwhile, a multi-channel gas mixing system (accuracy ± 1%) is used inside the deposition chamber to ensure the stability of the concentration gradient of the gas.

[0036] S5, cycle plating: plating is performed by plasma enhanced chemical vapor deposition, the outer surface of the substrate is set to face the moving direction of the deposition gas, the gas composition is controlled, and silicon carbonitride and silicon carbide are alternately deposited to form a multi-layer stacked surface layer structure. The deposition parameters of each are the same as those in step S4 when depositing silicon carbonitride and silicon carbide, and the surface roughness of the plating layer is monitored in real time by AFM detection, and the deposition is terminated when the surface roughness Ra is ≤0.5 nm. Finally, annealing at 550 DEG C for 2h releases the thermal stress of the plating layer.

[0037] In a third aspect, the application also provides an application of the gradient porous zirconium-based composite ceramic material, characterized in that it comprises:

[0038] Silicon steel annealing roller, radiant tube lining, single crystal silicon crucible, rolling mill work roll;

[0039] And the batching roller, melting pool roller, calender roller, tin bath roller, pipe drawing roller, strip plate roller, annealing roller used in glass material production,

[0040] And the nozzle, cooling roller used in amorphous strip production;

[0041] And the digging tooth on the heading machine.

[0042] The technical principle of the application is as follows: a substrate with uniform pore structure is first produced, and then a plating layer is prepared by plasma enhanced chemical vapor deposition. When the gas moves towards the substrate, it first contacts the surface pores and then contacts the internal pores. Obviously, this will result in more complete contact between the surface pores and the gas, and a thicker plating layer. The surface pores of the substrate are thicker, and the internal pores of the substrate are thinner. Finally, the thickness of the plating layer is used to change the pore size, achieving the technical effect of decreasing the pore size from the inside to the outside. At the same time, the surface of the pore also has a multi-layer plating structure, which includes a bottom layer and a surface layer. The bottom layer includes an inner layer, a transition layer and an outer layer distributed from the inside to the outside. The surface layer is a multi-layer structure of silicon carbonitride and silicon carbide arranged alternately. Thus, high connection stability and excellent wear resistance of the film layer are achieved.

[0043] Compared with the prior art, the application has the following beneficial effects:

[0044] 1、The present application has a pore structure with a pore size decreasing from inside to outside, that is, the working surface has the smallest pore size, and the pore size gradually increases away from the working surface direction. Obviously, the region with small pore size and dense accumulation has better compression resistance. In this way, the working interface on the side with small pore size can withstand high pressure impact at high temperature, avoiding damage to the pore structure. At the same time, the stress on the interface is transmitted to other pore structures inside, achieving uniform stress diffusion and buffering the stress to the internal matrix, avoiding local stress and fracture.

[0045] 2、The present application has a multi-layer coating structure on the surface of the matrix pores, with an inner layer of silicon carbonitride, a transition layer of silicon nitride and an outer layer of silicon carbide, forming a tightly bonded coating structure with the pore surface. The inner layer of silicon carbonitride has a similar crystal structure to the matrix, with good bonding stability. The outer layer of silicon carbide has higher hardness and wear resistance. The transition layer of silicon nitride can alleviate the thermal stress difference between the inner and outer layers of silicon carbonitride and silicon carbide, allowing the entire film layer to have high strength, high wear resistance in a high temperature environment, and tightly bond with the matrix without falling off. In addition, the film layer is prepared by plasma enhanced chemical vapor deposition process, which can realize low stress bonding between the coating and the matrix (residual stress < 30MPa), avoiding interface cracking caused by traditional high temperature sintering.

[0046] 3、The present application also has a surface layer coating outside the bottom layer, which forms a stacked alternating layer structure by alternately depositing silicon carbonitride and silicon carbide, additionally improving wear resistance, so that the product only consumes the outermost surface layer under high strength work, without substantially affecting the internal structure. At the same time, the coating layer has multiple different interface layers, so it is not easily corroded by the same acid or alkali substance, and has better corrosion resistance.

[0047] 4、The present application also dopes ceramic fibers in the matrix, thereby increasing the toughness and impact resistance of the matrix, greatly enhancing the internal bonding force of the matrix with pore structure, alleviating the loss of internal structure strength caused by the pore structure, and improving the working life under high working strength.

[0048] 5、When used for silicon steel annealing roller, it can withstand high temperature of 700-1250℃, with anti-nodulation rate > 90%, service life extended to 24 months, replacing traditional imported nickel-chromium alloy roller, rolling capacity increased by 24 times, annual maintenance cost savings over 10 million yuan;

[0049] When used for radiant tube lining, it can withstand 1200-1400℃ sulfur / chlorine corrosion, with corrosion rate < 0.1 μm / h, operating life extended to 12 months (traditional material 6 months);

[0050] For the crucible for single crystal silicon production, the purity of the produced single crystal silicon is >99.9999%, which can be used for solar-grade single crystal silicon production, the thermal shock stability of the crucible is increased by 20 times (no cracking after 2000 cycles at 1400℃), the single furnace cost is reduced by 15%, and the yield is increased by 5%;

[0051] For the work roll of a rolling mill, the impact resistance is increased by 8 times, and the rolling life is extended from 3 months to 2 years;

[0052] For the nozzle for amorphous ribbon production, it can withstand high temperature flushing of 1500℃, the clogging rate of the jet hole is greatly reduced, and the service life is increased to 5 times that of the traditional nozzle. DETAILED DESCRIPTION

[0053] The technical solutions in the present application will be further described below in combination with examples.

[0054] Example 1:

[0055] The gradient porosity zircon-based composite ceramic material in this example is used for a silicon steel annealing roll, and is prepared by the following steps:

[0056] (1) Raw material ratio (mass percentage):

[0057] Zircon ceramic (α phase content >60%): 50%;

[0058] Hexagonal boron nitride (h-BN, diameter-thickness ratio >20): 18.5%;

[0059] Ceramic fiber (mass ratio of silicon carbide to aluminum oxide is 0.25, length-diameter ratio is 40:1): 13%;

[0060] Pore-forming agent (polyacrylonitrile pore-forming fiber, diameter 10μm, length 50μm): 6%;

[0061] Modifier: yttrium oxide nanoparticles 1.5%, titanium boride whiskers 4%;

[0062] Sintering aid (Y2O3+AlN mixture in equal proportions): 7%.

[0063] (2) Raw material treatment: zircon ceramic and boron nitride are ball milled for 8h to prepare powder particles with a particle size D50=1μm; the ceramic fiber is placed in a 10% polyvinyl alcohol solution for ultrasonic dispersion, the ultrasonic dispersion frequency is 40kHz, and the time is 30min, then it is added into the zircon ceramic and boron nitride powder, and the pore-forming agent, modifier and sintering aid are uniformly mixed to form the raw material powder.

[0064] (3) Molding: the raw material powder is vacuum kneaded for 2h at a vacuum degree ≤5Pa, and then molded under a condition of at least 70MPa and pressure holding for 10min.

[0065] (4) Sintering in stages:

[0066] Rise to 600°C at 2°C / min under nitrogen atmosphere, hold for 2h; rise to 1420°C, sinter for 2.5h under nitrogen protection; rise to 1620°C at a rate of 5°C / min under argon protection, hold for 4h; pressurize to 200MPa, continue sintering for 1h to densify the surface layer of the substrate.

[0067] After calcination, polish the surface of the substrate first, polish to Ra≤0.1μm using laser polishing. Then perform critical CO2 cleaning, remove phosphorus and iron impurities under the condition of temperature 31.1°C, pressure 8MPa for 1h.

[0068] (5) Gradient coating (PECVD):

[0069] Pore activation: introduce a mixture of NH3 / H2 gas with a volume ratio of 5 / 1, under the condition of pressure 50Pa, temperature 300°C, at a flow rate of 200sccm for 30min.

[0070] Inner layer deposition: introduce a mixture of SiH4 / NH3 / CH4 gas with a volume ratio of 1:3:0.5, set the plasma parameters as power 200W (RF), duty cycle 50%, deposit 60μm of silicon carbonitride at a rate of 5μm / h under the condition of pressure 80Pa, temperature 1050°C.

[0071] Transition layer deposition: introduce a mixture of SiH4 / NH3 gas with a volume ratio of 1:2, while introducing Ar gas (total flow rate 200sccm), set the plasma parameters as power 300W (RF), adjust to pulse mode (5ms on / 50ms off), deposit 2μm of silicon nitride under the condition of pressure 150Pa, temperature 1100°C.

[0072] Outer layer deposition: introduce a mixture of SiH4 / CH4 gas with a volume ratio of 1:1.5, set the plasma parameters as power 400W (RF), duty cycle 70%, deposit 20μm of silicon carbide under the condition of pressure 200Pa, temperature 1200°C.

[0073] The substrate is continuously rotated at a rate of 5rpm during deposition to avoid edge effects. At the same time, a multi-channel gas mixing system (precision ±1%) is used inside the deposition chamber to ensure stable concentration gradient of the gas.

[0074] (6) Cyclic coating (PECVD): After 1 μm of silicon carbide is deposited, switch to silicon carbonitride deposition for 1 μm, control the cycle for 25 cycles, and the total thickness is 50 μm. The deposition parameters of silicon carbide or silicon carbonitride are the same as those in step S4 for depositing silicon carbonitride and silicon carbide, and the surface roughness of the coating is monitored in real time by AFM, and the deposition is terminated when the surface roughness Ra≤0.5 nm. Finally, anneal at 550°C for 2 h to release the thermal stress of the coating.

[0075] Example 2:

[0076] The gradient porous sialon-based composite ceramic material of this example, used for a nozzle for preparing amorphous materials, is prepared by the following steps:

[0077] (1) Raw material ratio (mass percentage):

[0078] Sialon ceramic (α phase content > 60%): 56.5%;

[0079] Hexagonal boron nitride (h-BN, aspect ratio > 20): 20%;

[0080] Ceramic fiber (mass ratio of silicon carbide to alumina 0.3, aspect ratio 50:1): 14%;

[0081] Pore-forming agent (polyacrylonitrile pore-forming fiber, diameter 10 μm, length 100 μm): 4%;

[0082] Modifier: yttrium oxide nanoparticles 0.5%, titanium boride whiskers 2%;

[0083] Sintering aid (Y2O3+AlN mixture in equal proportions): 3%.

[0084] (2) Raw material processing: mill the sialon ceramic and boron nitride together for 12 h to prepare powder particles with a particle size D50=2 μm; ultrasonically disperse the ceramic fiber in a 10% polyvinyl alcohol solution at a frequency of 40 kHz for 40 min, then add it to the sialon ceramic and boron nitride powder, and then add the pore-forming agent, modifier, and sintering aid, and mix uniformly to form the raw material powder.

[0085] (3) Forming: vacuum knead the raw material powder to a vacuum degree of ≤5 Pa for 3 h, and then mold under a pressure of at least 70 MPa and maintain the pressure for 15 min.

[0086] (4) Subsection sintering:

[0087] Under nitrogen atmosphere, increase to 650℃ at 2℃ / min, keep for 3h; increase to 1440℃, sinter for 3.5h under nitrogen protection; under argon protection, increase to 1640℃ at 5℃ / min, keep for 6h; pressurize to 200MPa, continue to sinter for 2h to densify the surface layer of the substrate.

[0088] After calcination, polish the surface of the substrate first, polish to Ra≤0.1μm by laser polishing. Then perform critical CO2 cleaning, under the environment of temperature 31.1℃, pressure 9MPa, for 2h, to remove phosphorus and iron impurities.

[0089] (5) Gradient coating (PECVD):

[0090] The inner layer is deposited with silicon carbonitride with a thickness of 70μm, the transition layer is deposited with silicon nitride with a thickness of 3μm, and the outer layer is deposited with silicon carbide with a thickness of 25μm. The substrate is continuously rotated at a speed of 10rpm during deposition. The rest is the same as example 1.

[0091] (6) Cyclic coating (PECVD): After depositing 1.5μm of silicon carbide, switch to depositing 1.5μm of silicon carbonitride, control the cycle for 20 cycles, total thickness 60μm. The rest is the same as example 1.

[0092] Example 3:

[0093] The gradient porous zirconium-based composite ceramic material of this example is used for work rolls of rolling mills, and is prepared by the following steps:

[0094] (1) Raw material ratio (mass percentage):

[0095] Zirconium ceramic (α phase proportion > 60%): 58%;

[0096] Hexagonal boron nitride (h-BN, diameter-thickness ratio > 20): 16%;

[0097] Ceramic fiber (mass ratio of silicon carbide to alumina 0.25-0.3, length-diameter ratio 40-50:1): 10%;

[0098] Pore-forming agent (polyacrylonitrile pore-forming fiber, diameter 10μm, length 50-100μm): 5%;

[0099] Modifier: yttrium oxide nanoparticles 1%, titanium boride whiskers 3.5%;

[0100] Sintering aid (Y2O3+AlN mixture in equal proportions): 6.5%.

[0101] (2) Raw material processing: the sialon ceramic and boron nitride were ball-milled for 10 h to prepare powder particles with a particle size D50 = 1.5 μm; the ceramic fibers were placed in a 10% polyvinyl alcohol solution for ultrasonic dispersion, the frequency of ultrasonic dispersion was 40 kHz, and the time was 35 min, then the sialon ceramic and boron nitride powder were added, and pore-forming agents, modifiers and sintering aids were added and uniformly mixed to form a raw material powder.

[0102] (3) Molding: the raw material powder was vacuum kneaded for 2.5 h at a vacuum degree of ≤5 Pa, and then was molded under a pressure of at least 70 MPa and a pressure holding time of 12 min.

[0103] (4) Step sintering:

[0104] Under a nitrogen atmosphere, the temperature was increased to 625 °C at a rate of 2 °C / min, and the temperature was maintained for 2.5 h; the temperature was increased to 1430 °C, and the sintering was performed under a nitrogen protective environment for 3 h; under an argon protective environment, the temperature was increased to 1630 °C at a rate of 5 °C / min, and the temperature was maintained for 5 h; the pressure was increased to 200 MPa, and the sintering was continued for 1.5 h to densify the surface layer of the matrix.

[0105] After calcination, the surface of the matrix was polished first, and laser polishing was performed to Ra≤0.1 μm. Then critical CO2 cleaning was performed, and the phosphorus and iron impurities were removed under a temperature of 31.1 °C and a pressure of 8.5 MPa for 1.5 h.

[0106] (5) Gradient coating (PECVD):

[0107] The inner layer was deposited with silicon carbonitride with a thickness of 65 μm, the transition layer was deposited with silicon nitride with a thickness of 2.5 μm, and the outer layer was deposited with silicon carbide with a thickness of 23 μm. During the deposition process, the substrate was continuously rotated at a rate of 8 rpm. The remaining parts were the same as in Example 1.

[0108] (6) Cyclic coating (PECVD): after depositing 1.2 μm of silicon carbide, the deposition was switched to silicon carbonitride for 1.2 μm, and the cycle was controlled for 15 cycles, and the total thickness was 36 μm. The remaining parts were the same as in Example 1.

[0109] The existing sialon ceramic (purchased from Yongzhou Mingrui Ceramic Technology Co., Ltd.) was used as a comparative example, and the performance of the gradient porous sialon matrix composite ceramic material product prepared in Examples 1-3 was compared, and the results are shown in Table 1.

[0110]

[0111] Table 1

[0112] Wherein, the fracture toughness is detected by indentation method (ISO 12135 standard), the load is 10kg, and the loading time is 10s; the corrosion resistance is tested by 2000 times of molten silicon corrosion at 1400 DEG C, and the average value is taken; the bonding strength is detected by scratch test (ASTM C1624 standard).

[0113] As shown in Table 1, the products in the embodiments 1-3 of the application are superior to the traditional sialon ceramics in various parameters, which fully proves the creativity of the application.

[0114] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the application but not limit the application, although the application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can be modified or replaced equivalently without departing from the purpose and scope of the technical solutions of the application, which should be covered in the scope of the claims of the application.

Claims

1. A gradient-pore ceronyl composite ceramic material, characterized in that: The material includes a substrate and a coating on the surface of the substrate. The substrate is a silane ceramic material embedded with boron nitride particles and ceramic fibers. The substrate also has a number of uniformly distributed pores inside, and the pore size gradually decreases from the inside to the outside to form a gradient pore structure. The coating includes a bottom layer and a surface layer distributed inside and outside. The bottom layer includes an inner layer, a transition layer and an outer layer distributed from the inside to the outside. The inner layer is made of silicon carbonitride, the transition layer is made of silicon nitride and the outer layer is made of silicon carbide. The surface layer is a multilayer structure with alternating silicon carbonitride and silicon carbide.

2. The gradient porosity seronyl composite ceramic material as described in claim 1, characterized in that: The matrix also includes 1%-2% by mass of yttrium oxide nanoparticles and 3%-5% by mass of titanium boride whiskers as modifiers.

3. The gradient porosity seronyl composite ceramic material as described in claim 1, characterized in that: The α phase of the silon ceramic accounts for more than 60%, and the boron nitride particles are hexagonal boron nitride with an aspect ratio > 20, and the mass of boron nitride is 30%-35% of the mass of the silon ceramic.

4. The gradient porosity seronyl composite ceramic material as described in claim 1, characterized in that: The ceramic fiber has a mass of 20%-25% of the mass of the silane ceramic and an aspect ratio of 40-50:

1. The ceramic fiber is silicon carbide-doped alumina ceramic, wherein the mass ratio of silicon carbide to alumina is 0.25-0.

3.

5. The gradient porosity seronyl composite ceramic material as described in claim 1, characterized in that: In the bottom layer, the inner layer has a thickness of 60-70 μm, the transition layer has a thickness of 2-3 μm, and the outer layer has a thickness of 20-25 μm.

6. The gradient porosity seronyl composite ceramic material as described in claim 1, characterized in that: In the surface layer, each layer of silicon carbonitride or silicon carbide has a thickness of 1-1.5 μm, and the total number of layers is 30-50, with the number of layers being an even number.

7. A method for preparing the gradient porosity seronyl composite ceramic material as described in claim 1, characterized in that, Includes the following steps: S1. Raw material processing: Sion ceramics and boron nitride are ball-milled and mixed for 8-12 hours to prepare powder particles with a particle size D50 of 1-2 μm; ceramic fibers are cut to a length of 50-100 μm and then added to the Sion ceramics and boron nitride powder, followed by the addition of pore-forming agent and modifier, and uniformly mixed to form raw material powder; S2. Molding: Vacuum refining of raw material powder is carried out at a vacuum degree ≤5Pa for 2-3 hours, followed by molding under a pressure of at least 70MPa and holding pressure for 10-15 minutes. S3, Segmented sintering: In the first stage, the temperature was increased to 600-650℃ at a rate of 2℃ / min under a nitrogen atmosphere. In the second stage, sintering is carried out continuously at 1420-1450℃ under nitrogen protection to form a matrix and to form preliminary pores inside the matrix through a pore-forming agent. In the third stage, under argon protection, the temperature is increased to 1620-1640℃ at a rate of 5℃ / min, and then held for sintering to ensure that the boron nitride particles are evenly distributed and form a stable porous structure. In the fourth stage, the pressure is increased to 200MPa and sintering continues, which densifies the surface layer of the matrix. S4. Gradient Coating: Coating is performed using plasma-enhanced chemical vapor deposition. The outer surface of the substrate is positioned so that it faces the direction of the depositing gas movement, allowing the outer surface of the substrate to contact the depositing gas first. The coating thickness is higher in the pores on the outside of the substrate, resulting in smaller pore sizes and thus forming a pore structure with pore sizes decreasing from the inside to the outside. The gas composition is set to sequentially deposit a bottom layer structure with an inner layer, a transition layer, and an outer layer. S5. Cyclic Coating: Coating is performed by plasma-enhanced chemical vapor deposition. The outer surface of the substrate is positioned facing the direction of the deposition gas movement. The gas composition is controlled, and silicon carbonitride and silicon carbide are deposited alternately to form a multi-layer stacked surface layer structure.

8. The preparation method according to claim 7, characterized in that: In step S1, the ceramic fibers are first placed in a 10% polyvinyl alcohol solution for ultrasonic dispersion at a frequency of 40 kHz for 30-40 min, so that the ceramic fibers are oriented.

9. The preparation method according to claim 7, characterized in that: In step S4, a pore activation treatment is performed before gradient coating by introducing an NH3 / H2 gas mixture with a volume ratio of 5 / 1 at a flow rate of 200 sccm for 30 minutes under an environment of 50 Pa pressure and 300 °C, thereby opening the pore channels and promoting subsequent gas permeation.

10. An application of the gradient porosity ceronyl composite ceramic material as described in claim 1, characterized in that, include: Silicon steel annealing rolls, radiant tube liners, single-crystal silicon crucibles, rolling mill work rolls; And the feeding rollers, melting pool rollers, rolling rollers, tin bath rollers, tube drawing rollers, stencil rollers, and annealing rollers used in glass material production. In addition, sprue bases, crucibles, nozzles, and cooling rollers are used for the production of amorphous ribbons; And the tunneling teeth on the tunneling machine.

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