A high-strength silicon nitride ceramic material and preparation method thereof

Abstract

The present invention discloses a high-strength silicon nitride ceramic material and a preparation method thereof, relating to the technical field of ceramic materials and their preparation. The high-strength silicon nitride ceramic material comprises a material layer, a coloring layer, a transition layer and a diamond coating from bottom to top. The ceramic material of the present invention achieves the comprehensive properties of lightweight, high strength and toughness, superhard wear resistance, efficient heat dissipation and corrosion resistance through carbon fiber reinforced phase interface modification, gradient TiCN transition layer design and diamond coating laser microstructuring, and improves the mechanical properties and interface bonding stability of the material. At the same time, it supports multi-color customization, such as black, bronze and yellow. The diversified selection expands the decorative and functional application scenarios of the material. In addition, the introduction of polishing equipment and laser microstructuring technology in the preparation process further optimizes the surface quality and wear resistance, so that the ceramic material has high strength and toughness, corrosion resistance and process controllability.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials and preparation thereof, in particular to a high-strength silicon nitride ceramic material and a preparation method thereof. Background Art

[0002] Currently, the back panel materials of consumer electronic products such as smartphones and smart watches are mainly made of zirconia ceramics, but it has defects such as high density and poor thermal conductivity, which makes it difficult to meet the needs of lightweight and high heat dissipation.

[0003] At present, Chinese patent application number: CN201811057057.X discloses a silicon nitride ceramic material for mobile phone back panels and its preparation method. The method uses a mixture containing a silicon source, a colorant and a sintering aid as raw material, mixes, shapes and sinters the raw material components to obtain the silicon nitride ceramic material.

[0004] However, the surface coating of silicon nitride ceramic materials in the existing technology is prone to peeling due to differences in thermal expansion coefficients, resulting in reduced wear resistance. In addition, the existing process is not convenient for taking into account both multi-color decorativeness and ultra-hard protection, and the hardness of the colored layer is generally low. In addition, the carbon fiber reinforcement phase is easy to react with the matrix during sintering, resulting in reduced interface strength. In the process of grinding and polishing the sintered body, linear compression polishing is usually used, which is inconvenient to process to form curved surfaces and is prone to edge chipping due to sudden pressure changes, affecting processing efficiency. Summary of the Invention

[0005] The object of the present invention is to provide a high-strength silicon nitride ceramic material and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a high-strength silicon nitride ceramic material, whose structure is sequentially arranged from bottom to top as a material layer, a coloring layer, a transition layer, and a diamond coating, wherein the material layer is prepared from the following raw materials:

[0007] Silicon nitride powder;

[0008] The carbon fiber reinforcement phase accounts for 3-8% of the total weight of the mixture, has a fiber length of 50-200 μm, and is coated with a titanium nitride interface layer with a thickness of 50-200 nm, formed by chemical vapor deposition;

[0009] Rare earth oxide sintering aid, which is a composite of yttrium oxide and lanthanum oxide, accounting for 1.5-4% of the total weight of the mixture;

[0010] Dispersant, accounting for 0.5-1.2% of the total weight of the mixture;

[0011] Binder, accounting for 3-8% of the total weight of the mixture;

[0012] Plasticizer, accounting for 1-3% of the total weight of the mixture;

[0013] The total weight of the mixed material is the sum of silicon nitride powder, carbon fiber reinforcement phase, rare earth oxide sintering aid, dispersant, binder and plasticizer;

[0014] The coloring layer has a thickness of 0.5-3 μm, the transition layer is a TiCN layer with a gradient structure, the carbon content of which increases from 10 at % to 50 at % along the thickness direction, and the diamond coating has a thickness of 0.1-0.5 μm.

[0015] Preferably, the colored layer is composed of at least one of the following coatings: an AlTiN black coating formed by magnetron sputtering, a TiSiN bronze coating formed by arc ion plating, and a TiN / TiC yellow coating formed by chemical vapor deposition, wherein the atomic ratio of Al to Ti in the AlTiN black coating is (1.5-2.5):1.

[0016] Preferably, the carbon fiber reinforced phase is subjected to an acid washing activation treatment and a high-temperature debonding treatment before being coated with the titanium nitride interface layer, specifically comprising the following steps:

[0017] The carbon fiber is placed in a nitric acid solution with a mass concentration of 5-8% and ultrasonically treated for 10-20 minutes;

[0018] Heat treatment at 800-1000°C for 0.5-1 hour in an argon atmosphere was performed to remove surface colloids.

[0019] In addition, the present invention also provides a method for preparing a high-strength silicon nitride ceramic material, comprising the following steps:

[0020] S1. Add rare earth oxide sintering aid, dispersant, silicon nitride powder and carbon fiber reinforcement into solvent and perform first ball milling. The ball milling medium is anhydrous ethanol, the ball-to-material ratio is 3:1, the rotation speed is 200-400 rpm, and the time is 4-8 hours.

[0021] S2. Add a binder and a plasticizer to the mixture of step S1 and perform a second ball milling at a speed of 100-200 rpm for 1-2 hours, followed by degassing and aging for 12-24 hours;

[0022] S3, the aged slurry is formed into a green tape by a tape casting process, with a thickness of 0.5-2 mm and a casting speed of 5-20 cm / min;

[0023] S4, drying, peeling, cutting, and slicing the green tape in sequence to obtain green sheets, and applying powder on the surface of the green sheets and packing them into a box;

[0024] S5. Degreasing the boxed blank at a temperature of 300-500°C, a heating rate of 1-3°C / min, and a holding time of 2-12h.

[0025] S6. Sintering the degreased green body in a nitrogen atmosphere at a sintering temperature of 1700-1900° C. for a holding time of 3-6 hours to form a sintered body;

[0026] S7, performing surface grinding and polishing treatment on the sintered body by a polishing device to form a material layer;

[0027] S8. Glow discharge cleaning is performed using a mixture of argon and hydrogen, with a gas volume ratio of (3-5):1, a power of 300-500W, and a processing time of 10-30min;

[0028] S9. Depositing a coloring layer by PVD or CVD process, with a working pressure of 0.3-1.0 Pa and a substrate temperature of 200-400°C;

[0029] S10, depositing a transition layer on the surface of the colored layer, using a multi-arc ion plating process to adjust the flow ratio of C2H2 and N2 in stages, so that the carbon content of the TiCN layer is gradually increased from 10at% to 50at%, with a deposition temperature of 350-500°C, a bias voltage of -50 to -150V, and a deposition time of 30-90 minutes;

[0030] S11. Depositing a diamond coating on the surface of the transition layer at a deposition temperature of 500-800° C. using microwave plasma assisted chemical vapor deposition.

[0031] Preferably, in step S1, the dispersant is ammonium polyacrylate, and the solvent is a mixture of ethanol and xylene in a volume ratio of 1:(0.8-1.5); in step S2, the binder is polyvinyl butyral, and the plasticizer is dibutyl phthalate.

[0032] Preferably, after the treatment in step S11, a picosecond laser is used to form a micron-scale groove array on the surface of the diamond coating, with a groove depth of 0.5-2 μm, a width of 10-30 μm, and a spacing of 50-100 μm.

[0033] Preferably, the polishing equipment includes a base, a top cover fastened to the top side of the base, an arc-shaped grinding mechanism installed on the middle side of the top cover, a first conveying body and a second conveying body respectively arranged on the left and right sides of the top cover, a support fixedly connected to the middle side of the top of the base, and a lower grinding head body arranged on the middle side of the top of the support, the support and the lower grinding head body are located in the middle of the inner side of the first conveying body and the second conveying body, the first conveying body and the second conveying body have the same structure, and are both composed of a driving member and arranged guide rollers, and the left and right sides of the lower grinding head body are provided with inclined plates, and the two inclined plates The bottoms are fixed to the support, and the grinding mechanism includes a cover seat whose top side is fastened to the top cover, and a first positioning structure and a second positioning structure are respectively provided on the left and right sides of the cover seat, and the first positioning structure and the second positioning structure are of the same structure and size, and are symmetrically arranged in the middle of the cover seat, and the bottoms of the first positioning structure and the second positioning structure are both connected to the bracket, and the bracket is divided into three parts from left to right, and a conveyor belt, a grinding roller structure and an arc-shaped pressure block are respectively installed on the three parts from left to right, and the height position of the bottom end of the arc-shaped pressure block is lower than the bottom end position of the conveyor belt.

[0034] The cam is fixed to the left side of the sliding plate, and the sliding plate is fixed to the bottom end of the sliding plate, and the cam is connected to the bottom end of the sliding plate.

[0035] Preferably, the grinding roller structure includes a mounting frame, a track adjusting assembly arranged on the right side of the mounting frame, a portal frame rotatably connected to the left end of the track adjusting assembly, a mounting seat fastened to the bottom side of the portal frame, an upper grinding head body arranged on the middle side of the bottom of the mounting seat, a first sliding sleeve and a second sliding sleeve rotatably connected to the left and right sides of the top of the portal frame, a first support rod sliding through the inside of the first sliding sleeve, a second support rod sliding through the inside of the second sliding sleeve, and a positioning frame installed on the top side of the first support rod and the second support rod, the bottom of the mounting frame is fastened to the positioning frame, the track adjusting assembly is fixed to the middle right side of the inside of the bracket, the first support rod and the second support rod are arranged in an inclined shape, and are fastened to the left and right sides of the inside of the positioning frame, respectively.

[0036] Preferably, the track adjusting assembly includes a connecting seat fixed to the right side of the mounting frame, a second motor fastened to the right side of the bottom of the connecting seat, a second screw connected to the left output end of the second motor, an internal threaded moving block threadedly connected to the outer surface of the second screw, a sliding seat fixedly connected to the right side of the internal threaded moving block, and two push rods rotatably connected to the middle parts of the front and rear sides of the internal threaded moving block, a groove is opened on the middle side of the bottom of the connecting seat, and the second screw is arranged inside the groove, the internal threaded moving block and the sliding seat are both slidably connected to the inside of the groove, and the left ends of the two push rods are rotatably connected to the portal frame.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The high-strength silicon nitride ceramic material prepared by the present invention achieves the comprehensive performance of lightweight, high strength and toughness, ultra-hard wear resistance, efficient heat dissipation and corrosion resistance through carbon fiber reinforced phase interface modification, gradient TiCN transition layer design and diamond coating laser microstructuring, and improves the mechanical properties and interface bonding stability of the material. At the same time, it supports multi-color customization, such as black, bronze and yellow. The diversified choices expand the decorative and functional application scenarios of the material. In addition, the introduction of polishing equipment and laser microstructuring technology in the preparation process further optimizes the surface quality and wear resistance, so that the ceramic material has high strength and toughness, corrosion resistance and process controllability.

[0039] The present invention optimizes the use of polishing equipment during the preparation process, and drives the height position of the bracket to be adjusted and changed under the action of the first positioning structure and the second positioning structure. The bracket is divided into three parts from left to right, and the three parts from left to right are respectively installed with a conveyor belt, a grinding roller structure and an arc-shaped pressing block. After the longitudinal orientation of the bracket is changed, the conveyor belt and the arc-shaped pressing block are respectively close to the top of the first conveying body and the second conveying body to press and position the sintered body on both sides. The height position of the bottom end of the arc-shaped pressing block is lower than the bottom end position of the conveyor belt, which improves the fitting and pressing effect with the sintered body after grinding and polishing. The sintered body can be processed into a curved surface through the grinding roller structure, and the maximum normal pressure is generated at the lowest point of the arc trajectory, which gradually decreases to both sides to form a pressure gradient, thereby avoiding edge collapse caused by sudden pressure changes in traditional linear polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of the high-strength silicon nitride ceramic material of the present invention;

[0041] Figure 2 This is a flowchart of the preparation method of the high-strength silicon nitride ceramic material of the present invention;

[0042] Figure 3 It is a structural schematic diagram of the polishing equipment of the present invention;

[0043] Figure 4This is a schematic structural diagram of the connection between the support and the lower grinding head body of the present invention;

[0044] Figure 5 It is a structural schematic diagram of the arc-shaped grinding mechanism of the present invention;

[0045] Figure 6 It is a structural schematic diagram of the grinding roller structure of the present invention;

[0046] Figure 7 It is a structural schematic diagram of the track adjustment assembly of the present invention.

[0047] Figure: Material layer 1, coloring layer 2, transition layer 3, diamond coating 4, base 5, top cover 6, arc-shaped grinding mechanism 7, first conveying body 8, second conveying body 9, support 10, lower grinding head body 11, inclined plate 101, cover seat 71, first adjustment structure 72, second adjustment structure 73, bracket 74, conveyor belt 75, grinding roller structure 76, arc-shaped pressure block 77, slide 711, vertical plate 721, first motor 722, first screw 723, support block 724, internal thread block -725, slide plate -726, shift plate -727, pillar -728, upper spring -729, lower spring -7210, mounting frame -761, track adjustment assembly -762, portal frame -763, mounting seat -764, upper grinding head body -765, first sliding sleeve -766, second sliding sleeve -767, first support rod -768, second support rod -769, positioning frame -7610, connecting seat -7621, second motor -7622, ​​second screw -7623, internal thread shift block -7624, slide seat -7625, push rod -7626. DETAILED DESCRIPTION

[0048] In order to further explain the technical solution of the present invention, specific embodiments are described in detail below.

[0049] See also Figure 1The present invention provides a high-strength silicon nitride ceramic material, which has a structure consisting of a material layer 1, a coloring layer 2, a transition layer 3, and a diamond coating 4 from bottom to top. The multi-layer composite structure achieves a gradient transition in mechanical properties, taking into account matrix strength, decorative properties, and ultra-hard protection. The material layer 1 is prepared from the following raw materials: silicon nitride powder; a carbon fiber reinforcement phase, which accounts for 3-8% of the total weight of the mixture, has a fiber length of 50-200 μm, and is coated with a titanium nitride interface layer with a thickness of 50-200 nm, formed by chemical vapor deposition. The titanium nitride interface layer inhibits the high-temperature reaction between the carbon fiber and the silicon nitride matrix, improves the interface bonding strength, and enhances the continuity of the thermal conductivity path; a rare earth oxide sintering aid, which is a composite of yttrium oxide and lanthanum oxide, which accounts for 1.5-4% of the total weight of the mixture. The composite aid reduces the sintering temperature, promotes the formation of a grain boundary glass phase, and improves the material density; and a dispersant, which accounts for 0.5-1% of the total weight of the mixture. 2%; binder, accounting for 3-8% of the total weight of the mixture; plasticizer, accounting for 1-3% of the total weight of the mixture; the total weight of the mixture is the sum of silicon nitride powder, carbon fiber reinforcement, rare earth oxide sintering aid, dispersant, binder and plasticizer; the coloring layer 2 has a thickness of 0.5-3 μm, the transition layer 3 is a TiCN layer with a gradient structure, and the carbon content increases from 10 at% to 50 at% along the thickness direction. The composition gradient design gradually reduces the thermal expansion coefficient, improves the matching degree with the diamond coating 4, and reduces thermal stress cracks. The thickness of the diamond coating 4 is 0.1-0.5 μm, and the coloring layer 2 is composed of at least one of the following coatings: an AlTiN black coating formed by magnetron sputtering, a TiSiN bronze coating formed by arc ion plating, and a TiN / TiC yellow coating formed by chemical vapor deposition. The atomic ratio of Al to Ti in the AlTiN black coating is (1.5-2.5):1.

[0050] Among them, the carbon fiber reinforcement phase undergoes acid washing activation treatment and high-temperature debonding treatment before being coated with the titanium nitride interface layer, which specifically includes the following steps:

[0051] The carbon fiber is placed in a nitric acid solution with a mass concentration of 5-8% and ultrasonically treated for 10-20 minutes;

[0052] Heat treatment at 800-1000°C for 0.5-1 hour in an argon atmosphere was performed to remove surface colloids.

[0053] See also Figure 1 and Figure 2 The present invention provides a method for preparing a high-strength silicon nitride ceramic material, comprising the following steps:

[0054] S1. Add rare earth oxide sintering aid, dispersant, silicon nitride powder and carbon fiber reinforcement into solvent and perform first ball milling. The ball milling medium is anhydrous ethanol, the ball-to-material ratio is 3:1, the rotation speed is 200-400 rpm, and the time is 4-8 hours.

[0055] S2. Add a binder and a plasticizer to the mixture of step S1 and perform a second ball milling at a speed of 100-200 rpm for 1-2 hours, followed by degassing and aging for 12-24 hours;

[0056] S3, the aged slurry is formed into a green tape by a tape casting process, with a thickness of 0.5-2 mm and a casting speed of 5-20 cm / min;

[0057] S4, drying, peeling, cutting, and slicing the green tape in sequence to obtain green sheets, and applying powder on the surface of the green sheets and packing them into a box;

[0058] S5. Degreasing the boxed blank at a temperature of 300-500°C, a heating rate of 1-3°C / min, and a holding time of 2-12h.

[0059] S6. Sintering the degreased green body in a nitrogen atmosphere at a sintering temperature of 1700-1900° C. for a holding time of 3-6 hours to form a sintered body;

[0060] S7, performing surface grinding and polishing treatment on the sintered body by a polishing device to form a material layer 1;

[0061] S8. Glow discharge cleaning is performed using a mixture of argon and hydrogen, with a gas volume ratio of (3-5):1, a power of 300-500W, and a processing time of 10-30min;

[0062] S9. Depositing a coloring layer 2 by PVD or CVD process, with a working pressure of 0.3-1.0 Pa and a substrate temperature of 200-400° C.;

[0063] S10, depositing a transition layer 3 on the surface of the colored layer 2, using a multi-arc ion plating process to adjust the flow ratio of C2H2 and N2 in stages, so that the carbon content of the TiCN layer is gradually increased from 10at% to 50at%, with a deposition temperature of 350-500°C, a bias voltage of -50 to -150V, and a deposition time of 30-90 minutes;

[0064] S11. Depositing a diamond coating 4 on the surface of the transition layer 3 at a deposition temperature of 500-800° C. using a microwave plasma assisted chemical vapor deposition method.

[0065] Among them, in step S1, the dispersant is ammonium polyacrylate, and the solvent is a mixture of ethanol and xylene, with a volume ratio of 1:(0.8-1.5); in step S2, the binder is polyvinyl butyral, and the plasticizer is dibutyl phthalate. After processing in step S11, a picosecond laser is used to form a micron-scale groove array on the surface of the diamond coating 4, with a groove depth of 0.5-2μm, a width of 10-30μm, and a spacing of 50-100μm. The groove structure reduces the residual stress of the diamond coating 4 and increases the heat dissipation area.

[0066] See also Figure 2-Figure 7 The present invention provides a preparation method of high-strength silicon nitride ceramic material. A polishing device is used in the preparation process. The polishing device includes a base 5, a top cover 6 fastened to the top side of the base 5, an arc-shaped grinding mechanism 7 installed on the middle side of the inside of the top cover 6, a first conveying body 8 and a second conveying body 9 respectively arranged on the left and right sides of the inside of the top cover 6, a support 10 fixedly connected to the middle side of the top of the base 5, and a lower grinding head body 11 arranged on the middle side of the top of the support 10. The sintered body is moved and conveyed between the arc-shaped grinding mechanism 7 and the lower grinding head body 11 by the first conveying body 8 for grinding and polishing. During polishing, the arc-shaped grinding mechanism 7 plays a role of pressing and positioning the sintered body to prevent the workpiece from displacement. The support 10 and the lower grinding head body 11 are located in the middle of the inner sides of the first conveying body 8 and the second conveying body 9. The first conveying body 8 and the second conveying body 9 have the same structure and are composed of a driving member and arranged guide rollers. Inclined plates 101 are provided on the left and right sides of the lower grinding head body 11, and the bottoms of the two inclined plates 101 are fixed to the support 10. The polished material is guided downward for discharge. The polishing mechanism 7 includes a cover seat 71 fastened to the top cover 6 on the top side. The left and right sides of the cover seat 71 are respectively provided with a first adjustment structure 72 and a second adjustment structure 73. The first adjustment structure 72 and the second adjustment structure 73 have the same structure and size and are symmetrically arranged in the middle of the cover seat 71. The bottoms of the first adjustment structure 72 and the second adjustment structure 73 are both connected to the bracket 74 to drive the bracket 74 under the action of the first adjustment structure 72 and the second adjustment structure 73. The height position is adjusted and changed. The bracket 74 is divided into three parts from left to right, and the three parts from left to right are respectively installed with a conveyor belt 75, a grinding roller structure 76 and an arc-shaped pressing block 77. After the longitudinal orientation of the bracket 74 is changed, the conveyor belt 75 and the arc-shaped pressing block 77 are respectively close to the first conveyor body 8 and the second conveyor body 9 to press and position the sintered body on both sides. The height position of the bottom end of the arc-shaped pressing block 77 is lower than the bottom end position of the conveyor belt 75, so as to improve the fitting and pressing effect with the sintered body after grinding and polishing.

[0067] The first adjustment structure 72 includes a vertical plate 721 fixed to the cover seat 71 on the top side, a first motor 722 fastened to the left side of the vertical plate 721, a first screw 723 connected to the bottom end of the first motor 722, a support block 724 wrapped around the top side of the first screw 723, an internal thread block 725 threadedly connected to the outer surface of the first screw 723, a slide 726 fixedly connected to the outside of the internal thread block 725, a shift plate 727 fastened to the left side of the slide 726, a pillar 728 fixedly connected to the bottom end of the shift plate 727, and an upper spring 729 and a lower spring 7210 respectively provided on the upper and lower sides of the outer surface of the pillar 728. The right side of the support block 724 is fixed to the vertical plate 721, and the right side of the slide 726 is fixed to the vertical plate The plate 721 is slidably connected, and the first motor 722 is used as the power source to rotate the first screw 723. The first screw 723 cooperates with the internal thread block 725 to enable the slide plate 726 to drive the shift plate 727 to perform longitudinal shifting action inside the cover seat 71. Slide grooves 711 are provided on the left and right sides of the cover seat 71, and the shift plate 727 is longitudinally slidably connected to the inner side of the slide groove 711 to ensure the stability of the moving position of the shift plate 727. The pillar 728 slides through the top side of the bracket 74. The bottom side of the upper spring 729 and the top side of the lower spring 7210 are both in contact with the bracket 74, so that the bracket 74 can be slightly changed in position up and down through the upper spring 729 and the lower spring 7210, thereby ensuring the pressing effect on the sintered body.

[0068] The grinding roller structure 76 includes a mounting frame 761, a rail adjustment assembly 762 arranged on the right side of the mounting frame 761, a door frame 763 rotatably connected to the left end of the rail adjustment assembly 762, a mounting seat 764 fastened to the bottom side of the door frame 763, an upper grinding head body 765 arranged on the middle side of the bottom of the mounting seat 764, a first sliding sleeve 766 and a second sliding sleeve 767 rotatably connected to the left and right sides of the top of the door frame 763, a first support rod 768 sliding through the inside of the first sliding sleeve 766, a second support rod 769 sliding through the inside of the second sliding sleeve 767, and a support rod 768 and a second support rod 769 installed on the first support rod 768 and the second support rod 769. The positioning frame 7610 on the top side, under the action of the track adjustment assembly 762, drives the portal frame 763 and the upper grinding head body 765 to change their positions inside the first support rod 768 and the second support rod 769 respectively through the first sliding sleeve 766 and the second sliding sleeve 767, so that the upper grinding head body 765 moves in an arc trajectory, thereby being able to perform curved surface processing on the sintered body, and generating the maximum normal pressure at the lowest point of the arc trajectory, which gradually decreases to both sides, forming a pressure gradient, thereby avoiding edge chipping caused by sudden pressure changes in traditional straight line polishing. The bottom of the mounting frame 761 is fastened to the positioning frame 7610, and the track adjustment assembly 762 is fixed to the mounting frame 7610. Fixed to the right side inside the bracket 74, the first support rod 768 and the second support rod 769 are arranged in an inclined shape and are respectively fastened to the left and right sides of the positioning frame 7610. The track adjustment assembly 762 includes a connecting seat 7621 fixed to the right side of the mounting frame 761, a second motor 7622 fastened to the right side of the bottom of the connecting seat 7621, a second screw rod 7623 connected to the left output end of the second motor 7622, ​​an internal threaded moving block 7624 threadedly connected to the outer surface of the second screw rod 7623, a sliding seat 7625 fixedly connected to the right side of the internal threaded moving block 7624, and a sliding seat 7625 rotatably connected to the front and rear sides of the internal threaded moving block 7624. The two push rods 7626 in the middle part, a groove is opened on the middle side of the bottom of the connecting seat 7621, and the second screw rod 7623 is arranged inside the groove, the internal thread moving block 7624 and the sliding seat 7625 are both slidably connected inside the groove, and the left ends of the two push rods 7626 are rotatably connected to the door frame 763. Under the action of the second motor 7622, ​​the second screw rod 7623 drives the push rod 7626 to shift laterally through cooperation with the internal thread moving block 7624, and the push rod 7626 pushes the door frame 763 to move its position on the surface of the first support rod 768 and the second support rod 769, so that the door frame 763 performs an arc-shaped displacement action.

[0069] Example 1

[0070] 1. Raw material pretreatment

[0071] Carbon fiber processing

[0072] 1. Pickling activation: Immerse the T300 grade carbon fiber in 6% nitric acid solution and ultrasonically clean it for 15 minutes to remove surface impurities;

[0073] High temperature degumming: Under argon protection, heat treatment at 900℃ for 45 minutes to completely remove the surface colloid;

[0074] Titanium nitride coating: Chemical vapor deposition was used to deposit a 100 nm thick TiN layer at 800°C by introducing TiCl4 at a flow rate of 50 sccm and NH3 at a flow rate of 150 sccm.

[0075] 2. Silicon Nitride Powder Preparation

[0076] β-Si3N4 powder with a purity of 99.9% and an average particle size of 0.5 μm was selected, 4 wt% of rare earth oxide sintering aid was added, Y2O3:La2O3=3:1, and pre-mixed by high-energy ball milling.

[0077] 2. Tape Casting Process

[0078] 1. Ball milling

[0079] First ball milling: Silicon nitride powder, 5 wt% of the total weight of the mixture, carbon fiber reinforcement, 4 wt% of the total weight of the mixture (Y2O3:La2O3 = 3:1) rare earth oxide sintering aid, and 1.0 wt% of the total weight of the mixture as ammonium polyacrylate dispersant were mixed in a 1:1 ethanol-xylene mixture as the solvent at a ball milling speed of 300 rpm for 6 h.

[0080] Second ball milling: add 5 wt% of the total weight of the mixture as polyvinyl butyral binder and 2 wt% of the total weight of the mixture as dibutyl phthalate plasticizer, ball milling speed 150 rpm, time 1.5 h;

[0081] Degassing and aging: Let it stand for 18 hours.

[0082] 2. Tape casting

[0083] The casting thickness is 1.0 mm, the base tape is polyester film, the casting speed is 10 cm / min, and the temperature is 30°C.

[0084] 3. Degreasing and sintering

[0085] 1. Degreasing treatment: In a nitrogen atmosphere, heat up to 400℃ at 2℃ / min and keep warm for 3 hours to remove organic additives;

[0086] 2. Sintering process: sintering at 1700℃ for 3h in nitrogen atmosphere, applying 3MPa pressure during the holding period, and obtaining a density of 3.22g / cm 3 dense sintered body.

[0087] 4. Surface polishing

[0088] Equipment: polishing equipment;

[0089] Parameters: The lower grinding head body 11 and the upper grinding head body 765 are used to grind and polish the upper and lower sides of the sintered body for 30 minutes, and the surface roughness is controlled to Ra = 0.05 μm.

[0090] 5. Glow discharge cleaning

[0091] Gas ratio: Argon: Hydrogen volume ratio is 4:1, total flow rate is 200 sccm;

[0092] Process parameters: power 400W, processing time 20 minutes, reducing surface oxygen content.

[0093] 6. Deposition of coloring layer and transition layer

[0094] 1. Coloring layer (TiN / TiC yellow coating)

[0095] Process: Chemical vapor deposition, substrate temperature 350°C, working gas pressure 0.5Pa, TiCl4 flow rate 50sccm and CH4 flow rate 25sccm reaction, deposition thickness 1.5μm;

[0096] 2. Transition layer (gradient TiCN)

[0097] Magnetron sputtering parameters: using a target material Ti with a purity of 99.99%, the CH4 / N2 flow ratio was gradually adjusted from 1:5 to 1:1, the deposition rate was 5 nm / s, and the total thickness was 2 μm.

[0098] Argon ion bombardment: After every 100nm of deposition, 150eV argon ions were used for bombardment for 45 seconds, and the surface roughness Ra = 0.2μm.

[0099] 7. Diamond coating deposition

[0100] Equipment: Microwave plasma CVD system, frequency 2.45 GHz;

[0101] Parameters: methane concentration 1.5%, hydrogen flow rate 500 sccm, deposition temperature 650°C, power 3 kW, time 2 hours, coating thickness 0.3 μm, grain size 50-100 nm.

[0102] 8. Laser Microstructuring

[0103] Laser parameters: picosecond laser, wavelength 1064 nm, pulse width 10 ps, ​​energy 0.5 mJ / pulse;

[0104] Processing mode: scanning speed 200 mm / s, groove depth 1.2 μm, width 20 μm, spacing 80 μm, forming a regular array.

[0105] The prepared high-strength silicon nitride ceramic material has the following characteristics: density 3.22 g / cm 3 The flexural strength is 1050 MPa, the fracture toughness is 7.2 MPa·m¹ / ², and the surface hardness is 100 GPa. The carbon content of the gradient TiCN transition layer is 10at%→50at%, which works synergistically with the diamond coating. The thermal conductivity of the substrate reaches 30 W / m·K, and the thermal conductivity of the coating reaches 1000 W / m·K. The thermal expansion coefficient is 3.2-3.8×10 -6 / K gradient changes, no cracking under -50℃ to 500℃ thermal cycling, while laser microstructuring of 1.2μm deep grooves improves wear resistance by 3-5 times, and the surface can remain intact in a pH3-11 corrosive environment.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-strength silicon nitride ceramic material, characterized in that: The structure thereof is sequentially arranged from bottom to top as a material layer (1), a coloring layer (2), a transition layer (3) and a diamond coating (4), wherein the material layer (1) is prepared from the following raw materials: Silicon nitride powder; The carbon fiber reinforcement phase accounts for 3-8% of the total weight of the mixture, has a fiber length of 50-200 μm, and is coated with a titanium nitride interface layer with a thickness of 50-200 nm, formed by chemical vapor deposition; Rare earth oxide sintering aid, which is a composite of yttrium oxide and lanthanum oxide, accounting for 1.5-4% of the total weight of the mixture; Dispersant, accounting for 0.5-1.2% of the total weight of the mixture; Binder, accounting for 3-8% of the total weight of the mixture; Plasticizer, accounting for 1-3% of the total weight of the mixture; The total weight of the mixed material is the sum of silicon nitride powder, carbon fiber reinforcement phase, rare earth oxide sintering aid, dispersant, binder and plasticizer; The coloring layer (2) has a thickness of 0.5-3 μm, the transition layer (3) is a TiCN layer with a gradient structure, the carbon content of which increases from 10 at% to 50 at% along the thickness direction, and the diamond coating (4) has a thickness of 0.1-0.5 μm.

2. A high-strength silicon nitride ceramic material according to claim 1, characterized in that: The colored layer (2) is composed of at least one of the following coatings: an AlTiN black coating formed by magnetron sputtering, a TiSiN bronze coating formed by arc ion plating, and a TiN / TiC yellow coating formed by chemical vapor deposition, wherein the atomic ratio of Al to Ti in the AlTiN black coating is (1.5-2.5):

1.

3. The high-strength silicon nitride ceramic material according to claim 1, characterized in that: The carbon fiber reinforced phase is subjected to an acid washing activation treatment and a high-temperature debonding treatment before being coated with the titanium nitride interface layer, specifically comprising the following steps: The carbon fiber is placed in a nitric acid solution with a mass concentration of 5-8% and ultrasonically treated for 10-20 minutes; Heat treatment at 800-1000°C for 0.5-1 hour in an argon atmosphere was performed to remove surface colloids.

4. The method for preparing a high-strength silicon nitride ceramic material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Add rare earth oxide sintering aid, dispersant, silicon nitride powder and carbon fiber reinforcement into solvent and perform first ball milling. The ball milling medium is anhydrous ethanol, the ball-to-material ratio is 3:1, the rotation speed is 200-400 rpm, and the time is 4-8 hours. S2. Add a binder and a plasticizer to the mixture of step S1 and perform a second ball milling at a speed of 100-200 rpm for 1-2 hours, followed by degassing and aging for 12-24 hours; S3, the aged slurry is formed into a green tape by a tape casting process, with a thickness of 0.5-2 mm and a casting speed of 5-20 cm / min; S4, drying, peeling, cutting, and slicing the green tape in sequence to obtain green sheets, and applying powder on the surface of the green sheets and packing them into a box; S5. Degreasing the boxed blank at a temperature of 300-500°C, a heating rate of 1-3°C / min, and a holding time of 2-12h. S6. Sintering the degreased green body in a nitrogen atmosphere at a sintering temperature of 1700-1900° C. for a holding time of 3-6 hours to form a sintered body; S7, performing surface grinding and polishing treatment on the sintered body by a polishing device to form a material layer (1); S8. Glow discharge cleaning is performed using a mixture of argon and hydrogen, with a gas volume ratio of (3-5):1, a power of 300-500W, and a processing time of 10-30min; S9, depositing the coloring layer (2) by PVD or CVD process, with a working pressure of 0.3-1.0 Pa and a substrate temperature of 200-400° C.; S10, depositing a transition layer (3) on the surface of the coloring layer (2), using a multi-arc ion plating process to adjust the flow ratio of C2H2 and N2 in stages, so that the carbon content of the TiCN layer is gradually increased from 10at% to 50at%, the deposition temperature is 350-500°C, the bias voltage is -50 to -150V, and the deposition time is 30-90 minutes; S11. Depositing a diamond coating (4) on the surface of the transition layer (3) at a deposition temperature of 500-800° C. using a microwave plasma assisted chemical vapor deposition method.

5. The method for preparing a high-strength silicon nitride ceramic material according to claim 4, characterized in that: In the step S1, the dispersant is ammonium polyacrylate, and the solvent is a mixture of ethanol and xylene, with a volume ratio of 1:(0.8-1.5); in the step S2, the binder is polyvinyl butyral, and the plasticizer is dibutyl phthalate.

6. The method for preparing a high-strength silicon nitride ceramic material according to claim 4, characterized in that: After the S11 step, a picosecond laser is used to form a micron-scale groove array on the surface of the diamond coating (4), with a groove depth of 0.5-2 μm, a width of 10-30 μm, and a spacing of 50-100 μm.

7. The method for preparing a high-strength silicon nitride ceramic material according to claim 4, characterized in that: The polishing device comprises a base (5), a top cover (6) fastened to the top side of the base (5), an arc-shaped grinding mechanism (7) installed on the inner middle side of the top cover (6), a first conveying body (8) and a second conveying body (9) respectively arranged on the left and right sides of the inner side of the top cover (6), a support (10) fixedly connected to the top middle side of the base (5), and a lower grinding head body (11) arranged on the top middle side of the support (10), wherein the support (10) and the lower grinding head body (11) are located in the middle of the inner sides of the first conveying body (8) and the second conveying body (9), the first conveying body (8) and the second conveying body (9) have the same structure and are both composed of a driving member and arranged guide rollers, and the lower grinding head body (11) is provided with inclined plates (101) on the left and right sides, and the bottoms of the two inclined plates (101) are provided with inclined plates (101). The grinding mechanism (7) includes a cover seat (71) whose top side is fastened to the top cover (6), and a first positioning structure (72) and a second positioning structure (73) are respectively provided on the left and right sides of the cover seat (71). The first positioning structure (72) and the second positioning structure (73) have the same structure and size and are symmetrically arranged in the middle of the cover seat (71). The bottoms of the first positioning structure (72) and the second positioning structure (73) are both connected to the bracket (74). The bracket (74) is divided into three parts from left to right, and the three parts from left to right are respectively installed with a conveying belt (75), a grinding roller structure (76) and an arc-shaped pressing block (77). The bottom end of the arc-shaped pressing block (77) is lower than the bottom end of the conveying belt (75).

8. The method for preparing a high-strength silicon nitride ceramic material according to claim 7, characterized in that: The first positioning structure (72) includes a vertical plate (721) fixed to the cover seat (71) on the top side, a first motor (722) fastened to the left side of the vertical plate (721), a first screw (723) connected to the bottom end of the first motor (722), a support block (724) wrapped around the top side of the first screw (723), an internal thread block (725) threadedly connected to the outer surface of the first screw (723), a slide plate (726) fixedly connected to the outside of the internal thread block (725), a shift plate (727) fastened to the left side of the slide plate (726), and a support (728) fixedly connected to the bottom end of the shift plate (727). 728) and an upper spring (729) and a lower spring (7210) respectively arranged on the upper and lower sides of the outer surface of the pillar (728), the right side of the support block (724) is fixed to the vertical plate (721), the right side of the slide plate (726) is slidably connected to the vertical plate (721), the left and right sides of the interior of the cover seat (71) are provided with a slide groove (711), and the shift plate (727) is longitudinally slidably connected to the inner side of the slide groove (711), the pillar (728) penetrates and slides on the top side of the interior of the bracket (74), and the bottom side of the upper spring (729) and the top side of the lower spring (7210) are both in contact with the bracket (74).

9. The method for preparing a high-strength silicon nitride ceramic material according to claim 7, characterized in that: The grinding roller structure (76) includes a mounting frame (761), a rail adjustment assembly (762) arranged on the right side of the mounting frame (761), a door frame (763) rotatably connected to the left end of the rail adjustment assembly (762), a mounting seat (764) fastened to the bottom side of the door frame (763), an upper grinding head body (765) arranged on the middle side of the bottom of the mounting seat (764), a first sliding sleeve (766) and a second sliding sleeve (767) rotatably connected to the left and right sides of the top of the door frame (763), and a sliding sleeve (767) sliding through the first sliding sleeve (766). The first support rod (768) inside, the second support rod (769) sliding through the second sliding sleeve (767), and the positioning frame (7610) installed on the top side of the first support rod (768) and the second support rod (769), the bottom of the mounting frame (761) is fastened to the positioning frame (7610), the track adjustment assembly (762) is fixed to the right side inside the bracket (74), the first support rod (768) and the second support rod (769) are arranged in an inclined shape, and are fastened to the left and right sides of the positioning frame (7610) respectively.

10. The method for preparing a high-strength silicon nitride ceramic material according to claim 9, characterized in that: The track adjustment assembly (762) includes a connecting seat (7621) fixed to the right side of the mounting frame (761), a second motor (7622) fastened to the right side of the bottom of the connecting seat (7621), a second screw (7623) connected to the left output end of the second motor (7622), an internal threaded moving block (7624) threadedly connected to the outer surface of the second screw (7623), a slide (7625) fixedly connected to the right side of the internal threaded moving block (7624), and two push rods (7626) rotatably connected to the middle of the front and rear sides of the internal threaded moving block (7624), a groove is opened in the middle side of the bottom of the connecting seat (7621), and the second screw (7623) is arranged inside the groove, the internal threaded moving block (7624) and the slide (7625) are both slidably connected to the inside of the groove, and the left ends of the two push rods (7626) are both rotatably connected to the door frame (763).

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