High-strength silicon nitride ceramic material and preparation method thereof

Abstract

The invention discloses a high-strength silicon nitride ceramic material and a preparation method thereof, and relates to the technical field of ceramic materials and preparation thereof.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; according to the ceramic material, through carbon fiber reinforced phase interface modification, gradient TiCN transition layer design and diamond coating laser microstructuring, the comprehensive performance of light weight, high toughness, superhardness, wear resistance, efficient heat dissipation and corrosion resistance is achieved, the mechanical property and interface bonding stability of the material are improved, meanwhile, multi-color customization is supported, such as black, bronze and yellow, and the ceramic material has the advantages of being high in heat dissipation efficiency and good in heat dissipation performance. In addition, due to the introduction of polishing equipment and a laser microstructuring technology in the preparation process, the surface quality and the wear resistance are further optimized, and the ceramic material has the advantages of high toughness, corrosion resistance and process controllability.

Description

Technical Field

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

[0002] Currently, the backplane materials of consumer electronic products such as smart phones and smart watches mainly use zirconia ceramics, but they have defects such as high density and poor thermal conductivity, and it is difficult to meet the requirements of lightweight and high heat dissipation.

[0003] At present, Chinese Patent Application No.: CN201811057057.X discloses a silicon nitride ceramic material for mobile phone backplane and a preparation method thereof. This method uses a mixture containing a silicon source, a colorant, and a sintering aid as raw materials, mixes, shapes, and sinters each raw material component to obtain the silicon nitride ceramic material.

[0004] However, the surface coating of the existing silicon nitride ceramic material is prone to peeling due to the difference in thermal expansion coefficient, resulting in a decrease in wear resistance. Moreover, the existing process is inconvenient to balance the decorative properties of multiple color systems and super-hard protection, and the hardness of the coloring layer is generally low. And the carbon fiber reinforcing phase is prone to react with the matrix during sintering, resulting in a decrease in interface strength. Also, during the process of grinding and polishing the sintered body, linear pressing and polishing are usually used, which is inconvenient to process into a curved surface and is prone to edge chipping caused by sudden pressure changes, affecting the processing efficiency. Summary of the Invention

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

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: 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. The material layer is prepared from the following raw materials:

[0007] Silicon nitride powder;

[0008] Carbon fiber reinforcing phase, accounting for 3 - 8% of the total weight of the mixed materials, with a fiber length of 50 - 200 μm, and a titanium nitride interface layer with a thickness of 50 - 200 nm is coated on the surface, 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 mixed materials;

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

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

[0012] A plasticizer, accounting for 1-3% of the total weight of the mixed materials;

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

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

[0015] Preferably, the coloring 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. The atomic ratio of Al to Ti in the AlTiN black coating is (1.5-2.5):1.

[0016] Preferably, before the carbon fiber reinforcing phase is coated with a titanium nitride interface layer, it is subjected to pickling activation treatment and high-temperature degumming treatment, which specifically includes the following steps:

[0017] Placing the carbon fiber in a nitric acid solution with a mass concentration of 5-8% and performing ultrasonic treatment for 10-20 minutes;

[0018] Performing heat treatment at 800-1000 °C for 0.5-1 hour in an argon atmosphere to remove the surface colloid.

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

[0020] S1. Adding a rare earth oxide sintering aid, a dispersant, silicon nitride powder and a carbon fiber reinforcing phase to a solvent for the first ball milling and mixing. 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 h;

[0021] S2. Adding a binder and a plasticizer to the mixture in step S1 for the second ball milling. The ball milling rotation speed is 100-200 rpm, the time is 1-2 h, and then defoaming and aging for 12-24 h;

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

[0023] S4. Sequentially drying, peeling and cutting, and slicing the green tape to obtain a blank sheet layer, and powdering and boxing on the surface of the blank sheet layer;

[0024] S5. Degrease the box-shaped green body at a degreasing temperature of 300 - 500 °C, a heating rate of 1 - 3 °C / min, and a holding time of 2 - 12 h;

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

[0026] S7. Polish the surface of the sintered body through a polishing device to form a material layer;

[0027] S8. Perform glow discharge cleaning using a mixed gas of argon and hydrogen with a gas volume ratio of (3 - 5):1, a power of 300 - 500 W, and a treatment time of 10 - 30 min;

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

[0029] S10. Deposit a transition layer on the surface of the coloring layer. Use the 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 increases from 10 at% to 50 at% in a gradient manner. The deposition temperature is 350 - 500 °C, the bias voltage is -50 to -150 V, and the deposition time is 30 - 90 minutes;

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

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

[0032] Preferably, after the treatment in the S11 step, use a picosecond laser to form a micron-level 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 device includes a base, a top cover fastened to the top side of the base, an arc grinding mechanism installed in the middle side of the interior of the top cover, a first conveying main body and a second conveying main body respectively arranged on the left and right sides of the interior of the top cover, a support fixed to the middle side of the top of the base, and a lower grinding head main body arranged on the middle side of the top of the support. The support and the lower grinding head main body are located in the middle of the inner sides of the first conveying main body and the second conveying main body. The first conveying main body and the second conveying main body have the same structure and are both composed of a driving member and arranged guide rollers. Oblique plates are arranged on both the left and right sides of the lower grinding head main body, and the bottoms of the two oblique plates are fixed to the support. The grinding mechanism includes a cover seat fastened to the top side of the top cover. First adjustment structures and second adjustment structures are respectively arranged on the left and right sides of the interior of the cover seat. The first adjustment structure and the second adjustment structure have the same structure and size and are symmetrically arranged in the middle of the cover seat. The bottoms of the first adjustment structure and the second adjustment structure are both connected to a bracket. The bracket is divided into three parts from left to right, and a conveying belt, a grinding roller structure, and an arc pressing block are respectively installed on the three parts from left to right. The height position of the bottom end of the arc pressing block is lower than the height position of the bottom end of the conveying belt.

[0034] Preferably, the first adjustment structure includes a vertical plate fixed to the top side of the cover seat, a first motor fastened to the left side of the vertical plate, a first screw rod connected to the bottom end of the first motor, a support block wrapped around the outer top side of the first screw rod, an internal thread block threadedly connected to the outer surface of the first screw rod, a sliding plate fixedly connected to the outside of the internal thread block, a displacement plate fastened to the left side of the sliding plate, a support column fixedly connected to the bottom end of the displacement plate, and upper and lower springs respectively arranged on the upper and lower sides of the outer surface of the support column. The right side of the support block is fixed to the vertical plate. The right side of the sliding plate is slidably connected to the vertical plate. Sliding grooves are opened on both the left and right sides of the interior of the cover seat, and the displacement plate is longitudinally slidably connected to the inside of the sliding groove. The support column penetrates and slides inside the top of the bracket, and the bottom side of the upper spring and the top side of the lower spring are both abutted against the bracket.

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

[0036] Preferably, the orbit adjustment assembly includes a connection seat fixed to the right side of the mounting frame, a second motor fastened to the right side of the bottom of the connection seat, a second screw rod connected to the left output end of the second motor, an internally threaded moving block threadedly connected to the outer surface of the second screw rod, a sliding seat fixedly connected to the right side of the internally threaded moving block, and two push rods rotatably connected to the middle parts of the front and rear sides of the internally threaded moving block. A groove is formed in the middle of the bottom of the connection seat, and the second screw rod is arranged inside the groove. The internally threaded moving block and the sliding seat are both slidably connected inside the groove. The left ends of the two push rods are rotatably connected to the gantry frame.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The high-strength silicon nitride ceramic material prepared by the present invention realizes comprehensive properties of light weight, high strength and toughness, super hardness and wear resistance, high-efficiency heat dissipation and corrosion resistance through carbon fiber reinforced phase interface modification, gradient TiCN transition layer design and diamond coating laser microstructuring. Moreover, the mechanical properties and interface bonding stability of the material are improved. At the same time, multi-color customization is supported, 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, making the ceramic material have both high strength and toughness, corrosion resistance and process controllability.

[0039] In the preparation process of the present invention, a polishing equipment is optimized for use. Under the action of the first position adjustment structure and the second position adjustment structure, the height position of the bracket is adjusted and changed. The bracket is divided into three parts from left to right, and a conveyor belt, a grinding roller structure and an arc-shaped pressing block are respectively installed on the three parts from left to right. After the longitudinal orientation of the bracket is changed, the conveyor belt and the arc-shaped pressing block are respectively close to above the first conveying main body and the second conveying main body to tightly position the sintered body on both sides. The height position of the bottom end of the arc-shaped pressing block is lower than the height position of the bottom end of the conveyor belt, improving 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 track, gradually decreasing towards both sides to form a pressure gradient, avoiding edge chipping caused by sudden pressure change in traditional linear polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic structural diagram of the high-strength silicon nitride ceramic material of the present invention;

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

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

[0043] Figure 4Schematic diagram of the connection between the bearing of the present invention and the main body of the lower grinding head;

[0044] Figure 5 Schematic diagram of the arc grinding mechanism of the present invention;

[0045] Figure 6 Schematic diagram of the structure of the grinding roller of the present invention;

[0046] Figure 7 Schematic diagram of the track adjustment assembly of the present invention.

[0047] In the figure: material layer - 1, coloring layer - 2, transition layer - 3, diamond coating - 4, base - 5, top cover - 6, arc grinding mechanism - 7, first conveying main body - 8, second conveying main body - 9, bearing - 10, main body of the lower grinding head - 11, inclined plate - 101, cover seat - 71, first position adjustment structure - 72, second position adjustment structure - 73, bracket - 74, conveyor belt - 75, grinding roller structure - 76, arc pressing block - 77, chute - 711, vertical plate - 721, first motor - 722, first screw - 723, supporting block - 724, internally threaded block - 725, sliding plate - 726, shifting plate - 727, pillar - 728, upper spring - 729, lower spring - 7210, mounting frame - 761, track adjustment assembly - 762, portal frame - 763, mounting seat - 764, main body of the upper grinding head - 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, internally threaded moving block - 7624, sliding seat - 7625, push rod - 7626. Detailed implementation manners

[0048] In order to further explain the technical solution of the present invention, the following will be elaborated in detail through specific embodiments.

[0049] Please refer to Figure 1, the present invention provides a high-strength silicon nitride ceramic material, whose structure is sequentially arranged from bottom to top as material layer 1, coloring layer 2, transition layer 3 and diamond coating 4. The multi-layer composite structure realizes a gradient transition of mechanical properties, taking into account the matrix strength, decoration and super-hard protection. Material layer 1 is prepared from the following raw materials: silicon nitride powder; carbon fiber reinforcing phase, accounting for 3-8% of the total weight of the mixed materials, with a fiber length of 50-200 μm and a titanium nitride interface layer with a thickness of 50-200 nm coated on the surface, formed by chemical vapor deposition. The titanium nitride interface layer inhibits the high-temperature reaction between carbon fiber and silicon nitride matrix, improves the interface bonding strength, and enhances the continuity of the heat conduction path at the same time; 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 mixed materials. The composite aid reduces the sintering temperature, promotes the formation of grain boundary glass phase, and improves the material density; dispersant, accounting for 0.5-1.2% of the total weight of the mixed materials; binder, accounting for 3-8% of the total weight of the mixed materials; plasticizer, accounting for 1-3% of the total weight of the mixed materials; the total weight of the mixed materials is the sum of silicon nitride powder, carbon fiber reinforcing phase, rare earth oxide sintering aid, dispersant, binder and plasticizer; the thickness of coloring layer 2 is 0.5-3 μm, transition layer 3 is a gradient-structured TiCN layer, and the carbon content increases from 10 at% to 50 at% along the thickness direction. The composition gradient design gradually reduces the coefficient of thermal expansion, improves the matching degree with diamond coating 4, and reduces thermal stress cracks. The thickness of diamond coating 4 is 0.1-0.5 μm. Coloring layer 2 is composed of at least one of the following coatings: AlTiN black coating formed by magnetron sputtering, TiSiN bronze coating formed by arc ion plating, 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, before coating the carbon fiber reinforcing phase with the titanium nitride interface layer, it undergoes pickling activation treatment and high-temperature degumming treatment, which specifically includes the following steps:

[0051] Place the carbon fiber in a nitric acid solution with a mass concentration of 5-8% and perform ultrasonic treatment for 10-20 minutes;

[0052] Under an argon atmosphere, heat-treat at 800-1000 °C for 0.5-1 hour to remove the surface colloid.

[0053] Please refer to Figure 1 and Figure 2 , the present invention provides a preparation method of a high-strength silicon nitride ceramic material, which includes the following steps:

[0054] S1. Add the rare earth oxide sintering aid, dispersant, silicon nitride powder and carbon fiber reinforcing phase into a solvent for the first ball milling and mixing. 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 h;

[0055] S2. Add a binder and a plasticizer to the mixture in step S1 and perform secondary ball milling at a ball milling speed of 100 - 200 rpm for 1 - 2 h, and then defoam and age for 12 - 24 h;

[0056] S3. Make a green tape from the aged slurry through a tape casting process, with a casting thickness of 0.5 - 2 mm and a casting speed of 5 - 20 cm / min;

[0057] S4. Dry, peel, cut, and slice the green tape in sequence to obtain a blank sheet layer, and apply powder and load it into a box on the surface of the blank sheet layer;

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

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

[0060] S7. Polish the surface of the sintered body through a polishing device to form a material layer 1;

[0061] S8. Perform glow discharge cleaning using a mixed gas of argon and hydrogen, with a gas volume ratio of (3 - 5):1, a power of 300 - 500 W, and a treatment time of 10 - 30 min;

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

[0063] S10. Deposit a transition layer 3 on the surface of the coloring layer 2, and adjust the flow ratio of C2H2 to N2 in stages using a multi - arc ion plating process to make the carbon content of the TiCN layer increase from 10 at% to 50 at% in a gradient manner, with a deposition temperature of 350 - 500 °C, a bias voltage of - 50 to - 150 V, and a deposition time of 30 - 90 minutes;

[0064] S11. Deposit 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, the solvent is a mixed solution of ethanol and xylene with a volume ratio of 1:(0.8 - 1.5); in step S2, the binder is polyvinyl butyral, the plasticizer is dibutyl phthalate. After the treatment in step S11, a microgroove array is formed on the surface of the diamond coating 4 by a picosecond laser, with a groove depth of 0.5 - 2 μm, a width of 10 - 30 μm, and a spacing of 50 - 100 μm. The groove structure reduces the residual stress of the diamond coating 4 and simultaneously increases the heat dissipation area.

[0066] Please refer to Figures 2 - 7 , the present invention provides a preparation method of a 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 in the middle side inside the top cover 6, a first conveying main body 8 and a second conveying main body 9 respectively arranged on the left and right sides inside 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 main 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 main body 11 by the first conveying main body 8 for polishing treatment. While polishing, the arc-shaped grinding mechanism 7 plays a role of pressing and positioning the sintered body to prevent the workpiece from displacing. The support 10 and the lower grinding head main body 11 are located in the middle inside the first conveying main body 8 and the second conveying main body 9. The first conveying main body 8 and the second conveying main body 9 have the same structure and are both composed of a driving member and arranged guide rollers. Oblique plates 101 are arranged on both the left and right sides of the lower grinding head main body 11, and the bottoms of the two oblique plates 101 are both fixed to the support 10 to guide the polished and ground materials downward for discharge. The grinding mechanism 7 includes a cover seat 71 fastened to the top side of the top cover 6. The left and right sides inside the cover seat 71 are respectively provided with a first position adjustment structure 72 and a second position adjustment structure 73. The first position adjustment structure 72 and the second position 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 position adjustment structure 72 and the second position adjustment structure 73 are both connected to a bracket 74 to drive the height position of the bracket 74 to change under the action of the first position adjustment structure 72 and the second position adjustment structure 73. The bracket 74 is divided into three parts from left to right, and a conveyor belt 75, a grinding roller structure 76, and an arc-shaped pressing block 77 are respectively installed on the three parts from left to right. After the longitudinal position of the bracket 74 changes, the conveyor belt 75 and the arc-shaped pressing block 77 are respectively close to above the first conveying main body 8 and the second conveying main 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 height position of the bottom end of the conveyor belt 75 to improve the fitting and pressing effect after polishing.

[0067] Among them, the first displacement structure 72 includes a vertical plate 721 with its top side fixed to the cover base 71, a first motor 722 fastened to the left side of the vertical plate 721, a first screw rod 723 connected to the bottom end of the first motor 722, a support block 724 wrapped around the outer top side of the first screw rod 723, an internal thread block 725 threadedly connected to the outer surface of the first screw rod 723, a sliding plate 726 fixedly connected to the outside of the internal thread block 725, a displacement plate 727 fastened to the left side of the sliding plate 726, a support column 728 fixedly connected to the bottom end of the displacement plate 727, and an upper spring 729 and a lower spring 7210 respectively arranged on the upper and lower sides of the outer surface of the support column 728. The right side of the support block 724 is fixed to the vertical plate 721, and the right side of the sliding plate 726 is slidably connected to the vertical plate 721. Taking the first motor 722 as the power source, the first screw rod 723 rotates, and through the cooperation of the first screw rod 723 and the internal thread block 725, the sliding plate 726 drives the displacement plate 727 to make a longitudinal displacement movement inside the cover base 71. Chutes 711 are provided on both the left and right sides inside the cover base 71, and the displacement plate 727 is longitudinally slidably connected to the inner side of the chutes 711 to ensure the stability of the moving position of the displacement plate 727. The support column 728 passes through and slides inside the top side of the bracket 74, and the bottom side of the upper spring 729 and the top side of the lower spring 7210 are both abutted against the bracket 74, so as to make a slight up and down position change of the bracket 74 through the upper spring 729 and the lower spring 7210, thereby ensuring the pressing effect on the sintered body.

[0068] Among them, the grinding roll structure 76 includes a mounting frame 761, an orbit adjusting component 762 arranged on the right side of the mounting frame 761, a gantry frame 763 rotatably connected to the left end of the orbit adjusting component 762, a mounting seat 764 fastened to the bottom side of the gantry frame 763, an upper grinding head main body 765 arranged in the middle of the bottom of the mounting seat 764, a first sliding sleeve 766 and a second sliding sleeve 767 respectively rotatably connected to the left and right sides of the top of the gantry frame 763, a first support rod 768 slidably penetrating inside the first sliding sleeve 766, a second support rod 769 slidably penetrating inside the second sliding sleeve 767, and a positioning frame 7610 mounted on the top sides of the first support rod 768 and the second support rod 769. Under the action of the orbit adjusting component 762, the gantry frame 763 and the upper grinding head main body 765 are respectively driven to change their positions inside the first support rod 768 and the second support rod 769 through the first sliding sleeve 766 and the second sliding sleeve 767, so that the upper grinding head main body 765 makes a position movement along an arc trajectory, thereby enabling curved surface machining of the sintered body, and generating the maximum normal pressure at the lowest point of the arc trajectory, gradually decreasing towards both sides, forming a pressure gradient, and avoiding edge chipping caused by sudden pressure changes in traditional linear polishing. The bottom of the mounting frame 761 is fastened to the positioning frame 7610, the orbit adjusting component 762 is fixed to the middle 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 inside the positioning frame 7610. The orbit adjusting component 762 includes a connecting seat 7621 fixed to the right side of the mounting frame 761, a second motor 7622 fastened to the bottom right side of the connecting seat 7621, a second screw rod 7623 connected to the left output end of the second motor 7622, an internally 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 internally threaded moving block 7624, and two push rods 7626 rotatably connected to the middle parts of the front and rear sides of the internally threaded moving block 7624. A groove is formed in the middle of the bottom of the connecting seat 7621, and the second screw rod 7623 is arranged inside the groove. The internally threaded moving block 7624 and the sliding seat 7625 are both slidably connected inside the groove. The left ends of the two push rods 7626 are rotatably connected to the gantry frame 763. Under the action of the second motor 7622, the second screw rod 7623 drives the push rods 7626 to move horizontally through cooperation with the internally threaded moving block 7624, and the push rods 7626 push the gantry frame 763 to move on the surfaces of the first support rod 768 and the second support rod 769, so that the gantry frame 763 makes a displacement movement along an arc trajectory.

[0069] Example 1

[0070] I. Raw material pretreatment

[0071] Carbon fiber treatment

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

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

[0074] Titanium nitride coating: Adopt chemical vapor deposition, introduce TiCl4 with a flow rate of 50 sccm and NH3 with a flow rate of 150 sccm, and deposit a 100-nm-thick TiN layer at 800 °C.

[0075] 2. Preparation of silicon nitride powder

[0076] Select β-Si3N4 powder with a purity of 99.9% and an average particle size of 0.5 μm, add 4 wt% rare earth oxide sintering aids, Y2O3:La2O3 = 3:1, and premix by high-energy ball milling.

[0077] II. Tape casting process

[0078] 1. Ball milling and mixing

[0079] First ball milling: Mix silicon nitride powder, a carbon fiber reinforcing phase accounting for 5 wt% of the total weight of the mixed material, a rare earth oxide sintering aid (Y2O3:La2O3 = 3:1) accounting for 4 wt% of the total weight of the mixed material, and an ammonium polyacrylate dispersant accounting for 1.0 wt% of the total weight of the mixed material. Use an ethanol-xylene mixed solution with a volume ratio of 1:1 as the solvent, with a ball milling speed of 300 rpm and a time of 6 h;

[0080] Second ball milling: Add a polyvinyl butyral binder accounting for 5 wt% of the total weight of the mixed material and a dibutyl phthalate plasticizer accounting for 2 wt% of the total weight of the mixed material. The ball milling speed is 150 rpm and the time is 1.5 h;

[0081] Defoaming and aging: Let it stand and age for 18 h.

[0082] 2. Tape casting

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

[0084] III. Debinding and sintering

[0085] 1. Debinding treatment: Heat up to 400 °C at a rate of 2 °C / min in a nitrogen atmosphere, hold for 3 h to remove the organic additives;

[0086] 2. Sintering process: Sinter at 1700 °C for 3 h in a nitrogen atmosphere, apply a pressure of 3 MPa during the holding stage to obtain a dense sintered body with a density of 3.22 g / cm 3 ³.

[0087] IV. Surface polishing

[0088] Equipment: Polishing equipment;

[0089] Parameters: Grind and polish the sintered body on both the upper and lower sides by the lower grinding head body 11 and the upper grinding head body 765. The polishing time is 30 minutes, and the surface roughness Ra is controlled to be 0.05 μm.

[0090] V. Glow Discharge Cleaning

[0091] Gas ratio: The volume ratio of argon to hydrogen is 4:1, and the total flow rate is 200 sccm.

[0092] Process parameters: The power is 400 W, the processing time is 20 minutes, and the surface oxygen content is reduced.

[0093] VI. Deposition of Coloring Layer and Transition Layer

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

[0095] Process: Chemical vapor deposition, the substrate temperature is 350 °C, the working pressure is 0.5 Pa, TiCl4 with a flow rate of 50 sccm reacts with CH4 with a flow rate of 25 sccm, and the deposition thickness is 1.5 μm.

[0096] 2. Transition layer (gradient TiCN)

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

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

[0099] VII. Diamond Coating Deposition

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

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

[0102] VIII. Laser Microstructuring

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

[0104] Processing mode: Scanning speed is 200 mm / s, groove depth is 1.2 μm, width is 20 μm, spacing is 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 ; flexural strength 1050 MPa, fracture toughness 7.2 MPa·m¹ / ²; surface hardness 100 GPa; the carbon content of its gradient TiCN transition layer is 10 at% → 50 at%, which synergistically acts with the diamond coating, the matrix thermal conductivity reaches 30 W / m·K, and the coating thermal conductivity reaches 1000 W / m·K; the thermal expansion coefficient shows a gradient change of 3.2 - 3.8×10 -6 / K, no cracking occurs under the thermal cycle from -50°C to 500°C. At the same time, by laser microstructuring grooves with a depth of 1.2 μm, the wear resistance is increased by 3 - 5 times, and the surface can remain undamaged in the corrosion environment with pH 3 - 11.

[0106] The above are only the preferred examples of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-strength silicon nitride ceramic material, characterized in that, Its structure 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). The material layer (1) is prepared from the following raw materials: Silicon nitride powder; Carbon fiber reinforcing phase, accounting for 3 - 8% of the total weight of the mixed materials, with a fiber length of 50 - 200 μm and a titanium nitride interface layer with a thickness of 50 - 200 nm coated on the surface, 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 mixed materials; Dispersant, accounting for 0.5 - 1.2% of the total weight of the mixed materials; Binder, accounting for 3 - 8% of the total weight of the mixed materials; Plasticizer, accounting for 1 - 3% of the total weight of the mixed materials; The total weight of the mixed materials is the sum of the silicon nitride powder, carbon fiber reinforcing phase, rare earth oxide sintering aid, dispersant, binder, and plasticizer; The thickness of the coloring layer (2) is 0.5 - 3 μm, the transition layer (3) is a gradient structure TiCN layer, and the carbon content increases from 10 at% to 50 at% along the thickness direction. The thickness of the diamond coating (4) is 0.1 - 0.5 μm.

2. The high-strength silicon nitride ceramic material according to claim 1, characterized in that 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.

3. The high-strength silicon nitride ceramic material according to claim 1, wherein, Before coating the carbon fiber reinforcing phase with the titanium nitride interface layer, it undergoes pickling activation treatment and high-temperature degumming treatment, specifically including the following steps: Placing the carbon fiber in a nitric acid solution with a mass concentration of 5 - 8% and performing ultrasonic treatment for 10 - 20 minutes; Performing heat treatment at 800 - 1000 °C for 0.5 - 1 hour in an argon atmosphere to remove the surface colloid.

4. The preparation method of the high-strength silicon nitride ceramic material according to any one of claims 1-3, characterized in that, It includes the following steps: S1. Adding the rare earth oxide sintering aid, dispersant, silicon nitride powder, and carbon fiber reinforcing phase to a solvent for the first ball milling and mixing. 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 h; S2. Adding the binder and plasticizer to the mixture in step S1 for the second ball milling. The ball milling rotation speed is 100 - 200 rpm, the time is 1 - 2 h, and then defoaming and aging for 12 - 24 h; S3. Making a green tape from the aged slurry through a casting forming process. The casting thickness is 0.5 - 2 mm, and the casting speed is 5 - 20 cm / min; S4. Sequentially drying, peeling, cutting, and slicing the green tape to obtain a blank sheet layer, and applying powder and packing it in a box on the surface of the blank sheet layer; S5. Performing degreasing treatment on the boxed blank. The degreasing temperature is 300 - 500 °C, the heating rate is 1 - 3 °C / min, and the holding time is 2 - 12 h; S6. Sintering the degreased blank in a nitrogen atmosphere. The sintering temperature is 1700 - 1900 °C, and the holding time is 3 - 6 h to form a sintered body; S7. Performing surface grinding and polishing treatment on the sintered body through a polishing device to form the material layer (1); S8. Glow discharge cleaning is carried out using a mixed gas of argon and hydrogen, with a gas volume ratio of (3 - 5):1, a power of 300 - 500 W, and a treatment time of 10 - 30 min; S9. A coloring layer (2) is deposited by PVD or CVD process, with a working pressure of 0.3 - 1.0 Pa and a substrate temperature of 200 - 400 °C; S10. A transition layer (3) is deposited on the surface of the coloring layer (2). The flow ratio of C2H2 to N2 is adjusted in stages using the multi - arc ion plating process, so that the carbon content of the TiCN layer increases gradually from 10 at% to 50 at%. The deposition temperature is 350 - 500 °C, the bias voltage is - 50 to - 150 V, and the deposition time is 30 - 90 minutes; S11. A diamond coating (4) is deposited on the surface of the transition layer (3), with a deposition temperature of 500 - 800 °C, using the microwave plasma - assisted chemical vapor deposition method.

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

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

7. The preparation method of a high-strength silicon nitride ceramic material according to claim 4, characterized in that: 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 in the middle of the interior of the top cover (6), a first conveying main body (8) and a second conveying main body (9) respectively arranged on the left and right sides of the interior of the top cover (6), a support (10) fixedly connected to the middle of the top of the base (5), and a lower grinding head main body (11) arranged in the middle of the top of the support (10). The support (10) and the lower grinding head main body (11) are located in the middle of the inner sides of the first conveying main body (8) and the second conveying main body (9). The first conveying main body (8) and the second conveying main body (9) have the same structure and are both composed of a driving part and arranged guide rollers. Oblique plates (101) are arranged on both the left and right sides of the lower grinding head main body (11), and the bottoms of the two oblique plates (101) are fixed to the support (10). The grinding mechanism (7) includes a cover base (71) whose top side is fastened to the top cover (6). First adjustment structures (72) and second adjustment structures (73) are respectively arranged on the left and right sides of the interior of the cover base (71). The first adjustment structures (72) and the second adjustment structures (73) have the same structure and size and are symmetrically arranged in the middle of the cover base (71). The bottoms of the first adjustment structures (72) and the second adjustment structures (73) are both connected to a bracket (74). The bracket (74) is divided into three parts from left to right, and a conveyor belt (75), a grinding roller structure (76), and an arc - shaped pressing block (77) are respectively installed on the three parts from left to right. The height position of the bottom end of the arc - shaped pressing block (77) is lower than the height position of the bottom end of the conveyor belt (75).

8. The preparation method of a high-strength silicon nitride ceramic material according to claim 7, characterized in that: The first position adjustment structure (72) includes a vertical plate (721) with its top side fixed to the cover base (71), a first motor (722) fastened to the left side of the vertical plate (721), a first screw rod (723) connected to the bottom end of the first motor (722), a support block (724) wrapped around the outer top side of the first screw rod (723), an internal thread block (725) threadedly connected to the outer surface of the first screw rod (723), a sliding plate (726) fixedly connected to the outside of the internal thread block (725), a displacement plate (727) fastened to the left side of the sliding plate (726), a support column (728) fixedly connected to the bottom end of the displacement plate (727), and an upper spring (729) and a lower spring (7210) respectively arranged on the upper and lower sides of the outer surface of the support column (728). The right side of the support block (724) is fixed to the vertical plate (721), the right side of the sliding plate (726) is slidably connected to the vertical plate (721). Chute grooves (711) are provided on both the left and right sides inside the cover base (71), and the displacement plate (727) is longitudinally slidably connected to the inside of the chute grooves (711). The support column (728) passes through and slides inside the top side of the bracket (74), and the bottom side of the upper spring (729) and the top side of the lower spring (7210) are both abutted against the bracket (74).

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

10. The preparation method of a high-strength silicon nitride ceramic material according to claim 9, characterized in that: The orbit adjustment assembly (762) includes a connection seat (7621) fixed to the right side of the mounting frame (761), a second motor (7622) fastened to the right bottom side of the connection seat (7621), a second screw rod (7623) connected to the left output end of the second motor (7622), an internally 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 internally threaded moving block (7624), and two push rods (7626) rotatably connected to the middle parts of the front and rear sides of the internally threaded moving block (7624). A groove is formed in the middle side of the bottom of the connection seat (7621), and the second screw rod (7623) is arranged inside the groove. Both the internally threaded moving block (7624) and the sliding seat (7625) are slidably connected inside the groove. The left ends of the two push rods (7626) are rotatably connected to the gantry (763).

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