A high-strength diamond boron carbide composite ceramic material and its preparation method

Abstract

The present invention discloses a high-strength diamond-boron carbide composite ceramic material and a preparation method thereof. The preparation method comprises the following steps: preparing a powder raw material, molding, degreasing, and siliconizing and sintering. The powder raw material preparation comprises: using diamond powder and B4C powder as raw materials, adding a binder, mixing the raw materials, and drying to obtain a mixed material. The diamond powder comprises diamond micropowder and diamond nanopowder. The particle size of the diamond micropowder is 5 to 100 μm, the particle size of the diamond nanopowder is 5 to 500 nm, and the particle size of the B4C powder is 50 to 300 μm. The particle size ratio of the diamond micropowder, diamond nanopowder, and B4C powder is 1:(0.001 to 0.02):(3 to 10). By controlling the particle size range and particle size ratio of the diamond powder and the boron carbide powder and adopting a specific method for preparing the powder raw material, the present invention can effectively improve the powder fluidity and reduce friction, and also reduce the impact of the siliconizing reaction on the performance of the ceramic material.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic material processing, and in particular relates to a high-strength diamond boron carbide composite ceramic material and a preparation method thereof. Background Art

[0002] Diamond is the hardest natural material known to mankind. It also possesses exceptional properties such as extremely high thermal conductivity, low thermal expansion coefficient, high strength, and high wear resistance. However, its oxidation and corrosion resistance are relatively low. Boron carbide ceramics offer the advantages of high hardness, good wear resistance, and low density. Compared to diamond, boron carbide ceramics are relatively inexpensive. Due to their lightweight, high hardness, and high elastic modulus, boron carbide ceramics are currently one of the most important protective materials. Therefore, combining these two materials creates lightweight diamond / boron carbide composite ceramics with excellent mechanical properties such as high hardness, high strength, and high toughness, suitable for use in protective armor applications. Common methods for preparing diamond-boron carbide ceramics include high-temperature and high-pressure sintering, spark plasma sintering, hot isostatic pressing, precursor conversion, and chemical vapor deposition. However, these methods are relatively complex and require high equipment, making them unsuitable for large-scale industrial production.

[0003] Currently, the manufacturing process for ceramic materials generally includes powder preparation, mixing, granulation, molding, sintering, and post-processing of the sintered body. Ceramic fine powders are typically granulated before molding and sintering to improve the packing density and fluidity of the ceramic powder. However, the granulation process is relatively complex, and when using powders with large size variations to prepare ceramics, uneven granulation distribution can occur. Furthermore, granulation requires a balanced approach to agglomeration strength. Too low a strength can lead to pulverization and poor fluidity, while too high a strength can make the powder difficult to break during subsequent molding, affecting sintering performance. When dry pressing or isostatic pressing is used in the subsequent molding process, the powder formed after the granulated material is crushed is still prone to agglomeration, and the high friction of the powder can easily cause internal unevenness in the resulting green body. To simplify the process and improve ceramic performance, a ceramic material preparation process that does not require granulation and can improve powder fluidity is urgently needed. While existing methods of adding dispersants can improve the fluidity of ceramic powders to a certain extent, the improvement is significantly affected by the powder structure, and these dispersants can easily affect other properties of the powder, making performance uncontrollable.

[0004] In addition, the interfacial bonding strength between diamond and boron carbide is relatively poor. To solve this problem, the most commonly used method is to siliconize the blank made of diamond and boron carbide. Silicon reacts with part of the diamond to produce silicon carbide, thereby forming a composite of diamond and silicon carbide. Silicon carbide can improve the interfacial bonding strength between it and boron carbide, thereby avoiding the impact of poor interfacial bonding strength on the performance of the composite ceramic material. However, this method has the following two problems: (1) Part of the diamond is consumed in the siliconization reaction, affecting the strength and hardness of the composite ceramic material; (2) The reaction activity of silicon and diamond in the siliconization reaction is insufficient, which easily produces free silicon in the gaps of the blank, affecting the strength, toughness and thermal conductivity of the ceramic material.

[0005] In summary, how to provide a high-strength diamond boron carbide composite ceramic material and its preparation method, which can improve powder fluidity and reduce friction without granulating the ceramic powder, and also reduce the impact of siliconization reaction on the performance of the ceramic material, is an urgent problem to be solved. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide a high-strength diamond-boron carbide composite ceramic material and a preparation method thereof. By controlling the particle size range and particle size ratio of diamond powder and boron carbide powder and adopting a specific method to prepare the powder raw materials, the powder fluidity can be effectively improved and the friction can be reduced. Then, through carburization treatment and a specific degreasing process, the influence of siliconization reaction on the performance of the ceramic material can be reduced, thereby producing a high-strength diamond-boron carbide composite ceramic material with excellent comprehensive performance. The process is highly operable, the finished product has few defects, and is suitable for industrial promotion.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a high-strength diamond boron carbide composite ceramic material comprises the following steps: powder raw material preparation, molding, degreasing, and siliconization and sintering.

[0009] The powder raw material preparation comprises: taking diamond powder and B4C powder as raw materials, adding a binder to mix the raw materials, and drying them to a moisture content of 1.2-1.5% to obtain a mixed material.

[0010] The diamond powder includes diamond micropowder and diamond nanopowder. The D50 particle size of the diamond micropowder is 5 to 100 μm, preferably 10 to 50 μm. The D50 particle size of the diamond nanopowder is 5 to 500 nm, preferably 50 to 200 nm. The D50 particle size of the B4C powder is 50 to 300 μm, preferably 100 to 200 μm. The particle size ratio of the diamond micropowder, diamond nanopowder, and B4C powder is 1:(0.001 to 0.02):(3 to 10), preferably 1:(0.003 to 0.005):(4 to 10).

[0011] Preferably, the mass ratio of the diamond powder to the B4C powder is (1-7):(3-9), and the mass ratio of the diamond micropowder to the diamond nanopowder is 1:(0.1-0.3). The amount of the binder added is 0.5-5% of the total mass of the diamond powder and B4C powder, and more preferably 1-3%.

[0012] The binder is selected from one or more of polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), and polyvinyl pyrrolidone (PVP).

[0013] Preferably, the binder includes a thermoplastic binder A and a water-soluble binder B, and the raw material mixing includes the following steps: evenly mixing the molten binder A with the diamond nanopowder, evenly spraying it onto the surface of the diamond micropowder and B4C powder, cooling it, and then adding the binder B and water and mixing them evenly.

[0014] Preferably, the binder A is polyvinyl butyral (PVB) or polymethyl methacrylate (PMMA), the binder B is polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP), and the mass ratio of binder A to binder B is (0.1-0.4):1.

[0015] Preferably, the amount of water added is 10 to 20 times the mass of the binder B.

[0016] Preferably, the forming is one or both of dry pressing and isostatic pressing. The pressure of dry pressing is 15-100 MPa, and the pressure of isostatic pressing is 150-210 MPa.

[0017] Preferably, the siliconizing sintering temperature is 1450-1600°C and the time is 60-120 minutes. The specific siliconizing sintering steps are as follows: place the degreased green body in a graphite crucible, spread elemental silicon particles on the green body, heat it to 1450-1600°C, keep it at this temperature for 60-120 minutes, and then cool it in the furnace to remove excess elemental silicon on the surface.

[0018] The present invention further comprises performing a carbon increasing treatment on the ceramic blank after forming, wherein the carbon increasing treatment is a high carbon residue solution immersion treatment, a high carbon residue compound synthesis treatment or a chemical vapor infiltration treatment.

[0019] Preferably, prior to impregnation with a high-carbon-residue solution or chemical vapor infiltration, the ceramic blank is degreased (at 900-1100°C for 24-60 hours). This primarily removes the binder and creates pores within the blank to facilitate carbonization. Degreasing is not required prior to the synthesis of high-carbon-residue compounds.

[0020] Preferably, the high carbon residue solution is prepared by mixing one or more of phenolic resin, sucrose, and asphalt resin with a corresponding solvent, wherein the solvent is one or more of water, methanol, ethanol, acetone, chloroform, and carbon disulfide, and the mass concentration of the high carbon residue solution is 5-50%. The carburizing medium used in the chemical vapor infiltration is a hydrocarbon gas.

[0021] Preferably, the high carbon residue solution immersion treatment is specifically as follows: placing the ceramic green body in a high carbon residue solution with a mass concentration of 5-50% at 30-80° C. and immersing it for 1-4 hours, and then evaporating the solvent; the amount of high carbon residue solution added is 2-12 times the volume of the ceramic green body.

[0022] Preferably, when the high carbon residue compound synthesis process is adopted, the binder B is polyvinyl alcohol (PVA), and the high carbon residue compound synthesis process comprises the following steps:

[0023] Place the ceramic body in a polyol aqueous solution (5 to 20 times), then add acid (hydrochloric acid) to adjust the pH value to 1.5, then add furfural solution (mass concentration is 6 to 12 g / L) dropwise, react at 80 to 90 ° C for 2 to 4 hours, finally add alkali (organic base, triethylamine or urea) to adjust the reaction solution to neutrality, and then evaporate to dryness.

[0024] The polyol is selected from one or more of agarwood tetraol, sugars (such as glucose, fructose, lactose, etc.), sugar alcohols (such as erythritol, xylitol, sorbitol, etc.), glycerol, pentanetriol, and pentaerythritol. Preferably, the polyol is agarwood tetraol.

[0025] Preferably, the mass ratio of the polyol, furfural and binder B polyvinyl alcohol is (10-50): (5-20):1.

[0026] The degreasing process parameters of the present invention are: degreasing temperature is 1000-1200 DEG C, and degreasing time is 12-48 hours.

[0027] The degreasing temperature rise curve includes:

[0028] Raise the temperature to 100-160°C at a rate of 1-3°C / min and keep warm for 20-40 minutes;

[0029] Then heat to 170-200°C at a rate of 2-4°C / min and keep warm for 30-60 minutes;

[0030] Then, the temperature is raised to 300-400°C at a rate of 3-5°C / min and kept at this temperature for 60-120 minutes;

[0031] Then, heat to 500-700°C at a rate of 3-5°C / min and keep at this temperature for 50-80min;

[0032] Finally, the temperature is raised to 1000-1200°C at a rate of 4-7°C / min and kept at this temperature for 12-48 hours.

[0033] The present invention also provides a high-strength diamond boron carbide composite ceramic material, which is prepared by the above preparation method.

[0034] Technical effects of the present invention:

[0035] 1. The present invention prepares a high-strength diamond-boron carbide composite ceramic material by compounding smaller-particle diamond powder with larger-particle boron carbide powder. By controlling the particle size range and particle size ratio of diamond powder and boron carbide powder, the following effects are achieved: (1) There is no need to grind boron carbide, and larger-particle boron carbide can be used directly, which saves cost and improves the hardness of the ceramic material; (2) Boron carbide powder and diamond micropowder or diamond nanopowder with a specific particle size ratio are used to improve the fluidity of each other without granulation; (3) Large-particle boron carbide powder (50-200 um) is used as a skeleton support, and diamond micropowder (10-50 um) is used as a support for the core. um) and diamond nanopowder (50-500nm) fill the gaps, so that the bulk density of the mixed powder reaches a larger value, which promotes the densification of the sintering process and improves the strength and thermal conductivity of the ceramic; (4) The thermal expansion difference between diamond and boron carbide will cause interfacial stress, and the use of large-particle boron carbide powder can form a stress buffer zone, reduce the generation of microcracks, and reduce shrinkage.

[0036] 2. In the powder raw material preparation process of the present invention, after molten thermoplastic binder A is mixed with diamond nanopowder, other powders (boron carbide powder + diamond micropowder) are coated, and a ball structure of diamond nanopowder is formed on the surface of the boron carbide powder and diamond micropowder, forming a relatively smooth surface. The powder is then dispersed in a low-viscosity water-soluble binder B solution to form a material with good fluidity, low friction between the materials, and no change in fluidity during the subsequent molding process. The friction with the molding mold is low, and the molded blank has a high density (low porosity).

[0037] 3. The present invention also performs a carbon enrichment treatment on the ceramic blank after forming to increase the carbon content of the blank and form amorphous carbon in the pores of the ceramic blank. The amorphous carbon can fill the pores and has a high reaction activity. It can react with silicon in the subsequent siliconization reaction to produce silicon carbide, thereby improving the interface bonding strength between the ceramic blank and the boron carbide. While improving the toughness, it will not consume diamonds, thereby ensuring that the strength of the ceramic is not affected.

[0038] The carbon increase treatment of the present invention can be selected from high carbon residue solution impregnation treatment, high carbon residue compound synthesis treatment or chemical vapor infiltration treatment, preferably high carbon residue compound synthesis treatment, which directly uses the binder B (polyvinyl alcohol) in the ceramic green body as a raw material for condensation reaction, and synthesizes a high carbon residue compound (modified furfural resin) in the green body pores, so that no unnecessary degreasing step is required before the carbon increase treatment, which saves the process and avoids the performance impact of multiple degreasing processes on the ceramic body.

[0039] 4. When the present invention performs a high carbon residue compound synthesis treatment on a ceramic blank, the ceramic blank is added with a polyol solution and a furfural solution to carry out a condensation reaction, which can generate a high carbon residue compound (modified furfural resin) in the pores of the blank. Compared with direct impregnation with a high carbon residue solution (with a larger molecular weight), the high carbon residue compound synthesis treatment of the present invention uses a smaller molecular weight compound for impregnation, which is easier to enter the ceramic pores and directly generate a high molecular weight high carbon residue compound in the ceramic pores, which can promote the high carbon residue compound to enter the pores and be evenly distributed. In addition, the introduction of a polyvinyl alcohol structure into the high carbon residue compound can promote the surface activity of the high carbon residue compound and improve its dispersion in the pores of the blank.

[0040] The polyol used in the synthesis treatment of the high residual carbon compound of the present invention is preferably agarwood tetraol, which can introduce heterocyclic structure branches and can be cracked during the high-temperature degreasing process to form a carbon skeleton with many branches, thereby increasing the reactivity of carbon and silicon in the subsequent siliconization reaction and reducing the generation of free silicon.

[0041] 5. The degreasing process of the present invention mainly targets the binder A (PVB or PMMA) and high carbon residue compounds (modified furfural resin) in the ceramic body. The types of these substances determine that the degreasing process of the present invention needs to be carried out under a specific degreasing temperature curve to avoid uneven pyrolysis causing deformation or cracking of the ceramic body.

[0042] The present invention first uses a low temperature (100-160°C) for preheating, then heats at the melting temperature of the binder A (170-200°C) to melt and discharge it, and then degreases the binder A and the high carbon residue compound in stages at 300-400°C, 500-700°C, and 900-1100°C, which can effectively prevent cracking and deformation of the green body and reduce the degreasing cycle (the conventional degreasing process generally takes 7-10 days).

[0043] 6. The process of preparing ceramic materials by compounding diamond and boron carbide in the present invention can achieve good performance within different boron carbide dosage ranges. DETAILED DESCRIPTION

[0044] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0045] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art. Example 1

[0046] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, comprising the following steps:

[0047] (1) Preparation of powder raw materials: Diamond powder and B4C powder with a mass ratio of 5:5 are used as raw materials, and a polyvinyl alcohol aqueous solution (polyvinyl alcohol is mixed with 15 times the mass of water) (polymerization degree 500-2000) is added to mix the raw materials, and dried to a moisture content of 1.2-1.5% to obtain a mixed material; the amount of polyvinyl alcohol added is 2% of the total mass of diamond powder and B4C powder.

[0048] The diamond powder includes diamond micropowder and diamond nanopowder in a mass ratio of 1:0.2. The D50 of the diamond micropowder is 30um, the D50 of the diamond nanopowder is 100nm, and the D50 of the B4C powder is 150um. The particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.003:5.

[0049] (2) Molding: The mixed material is placed in a mold and dry pressed (40 MPa), followed by isostatic pressing (200 MPa) to obtain a ceramic blank.

[0050] (3) Degreasing: The ceramic blank is degreased at a temperature of 1100°C and a degreasing time of 24 hours to obtain a degreased blank.

[0051] (4) Siliconization sintering: Place the degreased blank in a graphite crucible, spread elemental silicon particles on the top of the blank, heat it to 1550℃, keep it warm for 90 minutes, cool it in the furnace and remove the excess elemental silicon on the surface to obtain diamond boron carbide composite ceramic material. Example 2

[0052] Based on Example 1, this example adopts a specific method for mixing raw materials to provide a method for preparing a high-strength diamond boron carbide composite ceramic material, including the following steps:

[0053] (1) Preparation of powder raw materials: Diamond powder and B4C powder with a mass ratio of 5:5 are used as raw materials, a binder is added to mix the raw materials, and the raw materials are dried to a moisture content of 1.2-1.5% to obtain a mixed material; the amount of binder added is 2% of the total mass of diamond powder and B4C powder.

[0054] The diamond powder includes diamond micropowder and diamond nanopowder in a mass ratio of 1:0.2. The D50 of the diamond micropowder is 30um, the D50 of the diamond nanopowder is 100nm, and the D50 of the B4C powder is 150um. The particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.003:5.

[0055] The binder includes polyvinyl butyral and polyvinyl alcohol in a mass ratio of 0.2:1. The raw material mixing includes the following steps: evenly mixing the molten polyvinyl butyral with diamond nanopowder, evenly spraying it onto the surface of the diamond micropowder and B4C powder, cooling it, then mixing the polyvinyl alcohol with 15 times the mass of water and adding it, and then mixing evenly.

[0056] (2) Molding: The mixed material is placed in a mold and dry pressed (40 MPa), followed by isostatic pressing (200 MPa) to obtain a ceramic blank.

[0057] (3) Degreasing: The ceramic blank is degreased at a temperature of 1100°C and a degreasing time of 24 hours to obtain a degreased blank.

[0058] (4) Siliconization sintering: Place the degreased blank in a graphite crucible, spread elemental silicon particles on the top of the blank, heat it to 1550℃, keep it warm for 90 minutes, cool it in the furnace and remove the excess elemental silicon on the surface to obtain diamond boron carbide composite ceramic material. Example 3

[0059] Based on Example 1, this example further adds a carburizing treatment, and provides a method for preparing a high-strength diamond boron carbide composite ceramic material, comprising the following steps:

[0060] (1) Preparation of powder raw materials: Diamond powder and B4C powder with a mass ratio of 5:5 are used as raw materials, a binder is added to mix the raw materials, and the raw materials are dried to a moisture content of 1.2-1.5% to obtain a mixed material; the amount of binder added is 2% of the total mass of diamond powder and B4C powder.

[0061] The diamond powder includes diamond micropowder and diamond nanopowder in a mass ratio of 1:0.2. The D50 of the diamond micropowder is 30um, the D50 of the diamond nanopowder is 100nm, and the D50 of the B4C powder is 150um. The particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.003:5.

[0062] The binder includes polyvinyl butyral and polyvinyl alcohol in a mass ratio of 0.2:1. The raw material mixing includes the following steps: evenly mixing the molten polyvinyl butyral with diamond nanopowder, evenly spraying it onto the surface of diamond micropowder and B4C powder, cooling it, and then adding polyvinyl alcohol and 15 times the mass of water and mixing them evenly.

[0063] (2) Molding: The mixed material is placed in a mold and dry pressed (40 MPa), followed by isostatic pressing (200 MPa) to obtain a ceramic blank.

[0064] (3) Carbon enrichment treatment: A high residual carbon compound synthesis treatment was used. The ceramic blank was placed in a 10-fold volume of agarwood tetraol aqueous solution. Hydrochloric acid was then added to adjust the pH to 1.5. Furfural solution (mass concentration: 8 g / L) was then added dropwise. The reaction was allowed to proceed at 85°C for 3 h. Finally, triethylamine was added to adjust the reaction solution to neutrality. The water was then evaporated to obtain the carbon enriched blank. The mass ratio of agarwood tetraol, furfural, and polyvinyl alcohol was 15:5:1.

[0065] (4) Degreasing: The carbonized blank is degreased at a temperature of 1100°C and a degreasing time of 24 hours to obtain a degreased blank.

[0066] (5) Siliconization sintering: Place the degreased blank in a graphite crucible, spread elemental silicon particles on the top of the blank, heat it to 1550℃, keep it warm for 90 minutes, cool it in the furnace and remove the excess elemental silicon on the surface to obtain diamond boron carbide composite ceramic material. Example 4

[0067] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, which differs from Example 3 in that, during the carbonization treatment in step (3), agarwood tetraol is replaced with erythritol. Example 5

[0068] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, which differs from Example 3 in that, during the carbonization treatment in step (3), agarwood tetraol is replaced with glycerol. Example 6

[0069] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, which differs from Example 3 in that, during the carbonization treatment in step (3), the ceramic blank is first degreased (temperature 1000°C, time 48h), and then immersed in a high carbon residue solution: at 60°C, the ceramic blank is immersed in a phenolic resin ethanol solution with a mass concentration of 10% for 3h, and then the ethanol is evaporated to obtain a carbonized blank; the amount of high carbon residue solution added is 5 times the volume of the ceramic blank. Example 7

[0070] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, which differs from Example 6 in that, during the carbonization treatment in step (3), the phenolic resin ethanol solution is replaced with a sucrose aqueous solution. Example 8

[0071] On the basis of Example 3, this example designs a heating curve for the degreasing process in step (4), and provides a method for preparing a high-strength diamond boron carbide composite ceramic material, comprising the following steps:

[0072] (1) Preparation of powder raw materials: Diamond powder and B4C powder with a mass ratio of 5:5 are used as raw materials, a binder is added to mix the raw materials, and the raw materials are dried to a moisture content of 1.2-1.5% to obtain a mixed material; the amount of binder added is 2% of the total mass of diamond powder and B4C powder.

[0073] The diamond powder includes diamond micropowder and diamond nanopowder in a mass ratio of 1:0.2. The D50 of the diamond micropowder is 30um, the D50 of the diamond nanopowder is 100nm, and the D50 of the B4C powder is 150um. The particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.003:5.

[0074] The binder includes polyvinyl butyral and polyvinyl alcohol in a mass ratio of 0.2:1. The raw material mixing includes the following steps: evenly mixing the molten polyvinyl butyral with diamond nanopowder, evenly spraying it onto the surface of diamond micropowder and B4C powder, cooling it, and then adding polyvinyl alcohol and 15 times the mass of water and mixing them evenly.

[0075] (2) Molding: The mixed material is placed in a mold and dry pressed (40 MPa), followed by isostatic pressing (200 MPa) to obtain a ceramic blank.

[0076] (3) Carbon enrichment treatment: A high residual carbon compound synthesis treatment was used. The ceramic blank was placed in a 10-fold volume of agarwood tetraol aqueous solution. Hydrochloric acid was then added to adjust the pH to 1.5. Furfural solution (mass concentration: 8 g / L) was then added dropwise. The reaction was allowed to proceed at 85°C for 3 h. Finally, triethylamine was added to adjust the reaction solution to neutrality. The solution was then evaporated to dryness to obtain a carbon enriched blank. The mass ratio of agarwood tetraol, furfural, and polyvinyl alcohol was 15:5:1.

[0077] (4) Degreasing: The carbonized blank is degreased at a temperature of 1100°C for 24 hours to obtain a degreased blank.

[0078] The degreasing temperature rise curve includes:

[0079] Raise the temperature to 130°C at a rate of 2°C / min and keep warm for 30 min;

[0080] Then, the temperature was raised to 180°C at a rate of 3°C / min and kept at this temperature for 45 min;

[0081] Then the temperature was raised to 350°C at a rate of 4°C / min and kept at this temperature for 90 min;

[0082] Then the temperature was raised to 600°C at a rate of 4°C / min and kept at this temperature for 60 min;

[0083] Finally, the temperature was raised to 1100°C at a rate of 5°C / min and kept at this temperature for 24 h.

[0084] (5) Siliconization sintering: Place the degreased blank in a graphite crucible, spread elemental silicon particles on the top of the blank, heat it to 1550℃, keep it warm for 90 minutes, cool it in the furnace and remove the excess elemental silicon on the surface to obtain diamond boron carbide composite ceramic material. Example 9

[0085] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, comprising the following steps:

[0086] (1) Preparation of powder raw materials: Diamond powder and B4C powder with a mass ratio of 2:8 are used as raw materials, a binder is added to mix the raw materials, and the raw materials are dried to a moisture content of 1.2-1.5% to obtain a mixed material; the amount of binder added is 1% of the total mass of diamond powder and B4C powder.

[0087] The diamond powder includes diamond micropowder and diamond nanopowder in a mass ratio of 1:0.1. The D50 of the diamond micropowder is 10um, the D50 of the diamond nanopowder is 50nm, the D50 of the B4C powder is 100um, and the particle size ratio of the diamond micropowder, diamond nanopowder and B4C powder is 1:0.005:10.

[0088] The binder includes polyvinyl butyral and polyvinyl alcohol in a mass ratio of 0.1:1. The raw material mixing includes the following steps: evenly mixing the molten polyvinyl butyral with diamond nanopowder, evenly spraying it onto the surface of the diamond micropowder and B4C powder, cooling it, then evenly mixing the polyvinyl alcohol and 10 times the mass of water, adding it, and then mixing evenly.

[0089] (2) Molding: Place the mixed material into a mold and dry press it (100MPa) to obtain a ceramic blank.

[0090] (3) Carbon enhancement treatment: A high residual carbon compound synthesis treatment was used. The ceramic blank was placed in a 5-fold volume of agarwood tetraol aqueous solution. Hydrochloric acid was then added to adjust the pH to 1.5. Furfural solution (mass concentration: 6 g / L) was then added dropwise. The reaction was allowed to proceed at 80°C for 4 h. Finally, triethylamine was added to adjust the reaction solution to neutrality. The solution was then evaporated to dryness to obtain a carbon enhanced blank. The mass ratio of agarwood tetraol, furfural, and polyvinyl alcohol was 10:5:1.

[0091] (4) Degreasing: The carbonized blank is degreased at a temperature of 1000°C and a degreasing time of 48 hours to obtain a degreased blank.

[0092] The degreasing temperature rise curve includes:

[0093] Raise the temperature to 100°C at a rate of 1°C / min and keep warm for 40 minutes;

[0094] Then, the temperature was raised to 170°C at a rate of 2°C / min and kept at this temperature for 60 min;

[0095] Then, the temperature was raised to 300°C at a rate of 3°C / min and kept at this temperature for 120 min;

[0096] Then the temperature was raised to 500°C at a rate of 3°C / min and kept at this temperature for 80 min;

[0097] Finally, the temperature was raised to 1000°C at a rate of 4°C / min and kept at this temperature for 48 h.

[0098] (5) Siliconization sintering: Place the degreased blank in a graphite crucible, spread elemental silicon particles on the top of the blank, heat it to 1450℃, keep it warm for 120 minutes, cool it in the furnace, and remove the excess elemental silicon on the surface to obtain diamond boron carbide composite ceramic material. Example 10

[0099] This embodiment provides a method for preparing a high-strength diamond boron carbide composite ceramic material, comprising the following steps:

[0100] (1) Preparation of powder raw materials: Diamond powder and B4C powder with a mass ratio of 7:3 are used as raw materials, a binder is added to mix the raw materials, and the raw materials are dried to a moisture content of 1.2-1.5% to obtain a mixed material; the amount of binder added is 5% of the total mass of diamond powder and B4C powder.

[0101] The diamond powder includes diamond micropowder and diamond nanopowder in a mass ratio of 1:0.3. The D50 of the diamond micropowder is 50um, the D50 of the diamond nanopowder is 200nm, and the D50 of the B4C powder is 200um. The particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.004:4.

[0102] The binder includes polymethyl methacrylate and polyvinyl alcohol in a mass ratio of 0.4:1. The raw material mixing includes the following steps: evenly mixing the molten polymethyl methacrylate with diamond nanopowder, evenly spraying it onto the surface of the diamond micropowder and B4C powder, cooling it, then evenly mixing the polyvinyl alcohol and 20 times the mass of water, adding the mixture, and then mixing evenly.

[0103] (2) Molding: The mixed material is placed in a mold and dry pressed (40 MPa), followed by isostatic pressing (150 MPa) to obtain a ceramic blank.

[0104] (3) Carbon enhancement treatment: Using a high residual carbon compound synthesis treatment, the ceramic blank is placed in a 20-fold volume of agarwood tetraol aqueous solution and stirred evenly. Hydrochloric acid is then added to adjust the pH to 1.5. Furfural solution (mass concentration: 12 g / L) is then added dropwise. The reaction is carried out at 90°C for 2 h. Urea is then added to adjust the reaction solution to neutrality. The solution is then evaporated to dryness to obtain a carbon enhanced blank. The mass ratio of agarwood tetraol, furfural, and binder B (polyvinyl alcohol) is 50:20:1.

[0105] (4) Degreasing: The carbonized blank is degreased at a temperature of 1200°C and a degreasing time of 12 hours to obtain a degreased blank.

[0106] The degreasing temperature rise curve includes:

[0107] Raise the temperature to 160°C at a rate of 3°C / min and keep warm for 20 min;

[0108] Then, the temperature was raised to 200°C at a rate of 4°C / min and kept at this temperature for 30 min;

[0109] Then, the temperature was raised to 400°C at a rate of 5°C / min and kept at this temperature for 60 min;

[0110] Then the temperature was raised to 700°C at a rate of 5°C / min and kept at this temperature for 50 min;

[0111] Finally, the temperature was raised to 1200°C at a rate of 7°C / min and kept at this temperature for 12 h.

[0112] (5) Siliconization sintering: Place the degreased blank in a graphite crucible, spread elemental silicon particles on the top of the blank, heat it to 1600℃, keep it warm for 60 minutes, cool it in the furnace, and remove the excess elemental silicon on the surface to obtain diamond boron carbide composite ceramic material.

[0113] Comparative Example 1

[0114] The difference between this comparative example and Example 1 is that the particle size of B4C powder is smaller, the particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.003:2, the D50 of diamond micropowder is 30um, the D50 of diamond nanopowder is 100nm, and the D50 of B4C powder is 60um.

[0115] Comparative Example 2

[0116] The difference between this comparative example and Example 1 is that the particle size of B4C powder is larger, the particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.003:11, the D50 of diamond micropowder is 30um, the D50 of diamond nanopowder is 100nm, and the D50 of B4C powder is 330um.

[0117] Comparative Example 3

[0118] The difference between this comparative example and Example 1 is that the particle size of the diamond nanopowder is smaller, the particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.00005:5, the D50 of the diamond micropowder is 30um, the D50 of the diamond nanopowder is 15nm, and the D50 of the B4C powder is 150um.

[0119] Comparative Example 4

[0120] The difference between this comparative example and Example 1 is that the particle size of the diamond nanopowder is larger, the particle size ratio of diamond micropowder, diamond nanopowder and B4C powder is 1:0.03:5, the D50 of the diamond micropowder is 30um, the D50 of the diamond nanopowder is 900nm, and the D50 of the B4C powder is 150um.

[0121] Comparative Example 5

[0122] The difference between this comparative example and Example 2 is that the binder only includes polyvinyl butyral, and the raw material mixing includes the following steps: uniformly mixing the molten polyvinyl butyral with the diamond nanopowder, uniformly spraying it onto the surface of the diamond micropowder and B4C powder, and cooling.

[0123] Comparative Example 6

[0124] The difference between this comparative example and Example 2 is that the raw material mixing includes the following steps: uniformly mixing polyvinyl butyral with 15 times the amount of ethanol, adding diamond nanopowder and mixing uniformly, then adding diamond micropowder and B4C powder, then mixing polyvinyl alcohol with 15 times the amount of water and adding, and then mixing uniformly.

[0125] Comparative Example 7

[0126] The difference between this comparative example and Example 8 is that no agarwood tetraol is added during the carbonization treatment.

[0127] Comparative Example 8

[0128] The difference between this comparative example and Example 8 is that the carbon increase treatment adopts a high residual carbon compound for impregnation treatment, the ceramic blank is placed in 10 times the volume of water and soaked for 0.5h, then the ceramic blank is taken out, agarwood tetraol is added to the remaining water and stirred evenly, then hydrochloric acid is added to adjust the pH value to 1.5, and then furfural solution (mass concentration is 8g / L) is added dropwise, and the reaction is carried out at 85°C for 4h, and finally triethylamine is added to adjust the reaction solution to neutrality, and the ceramic blank is added to the obtained reaction solution for impregnation, and after impregnation for 3h, it is evaporated to dryness to obtain a carbon increase blank.

[0129] Comparative Example 9

[0130] The difference between this comparative example and Example 8 is that the degreasing temperature rise curve includes:

[0131] Raise the temperature to 180°C at a rate of 3°C / min and keep warm for 45 min;

[0132] Then the temperature was raised to 350°C at a rate of 4°C / min and kept at this temperature for 90 min;

[0133] Then the temperature was raised to 600°C at a rate of 4°C / min and kept at this temperature for 60 min;

[0134] Finally, the temperature was raised to 1100°C at a rate of 5°C / min and kept at this temperature for 24 h.

[0135] Comparative Example 10

[0136] The difference between this comparative example and Example 8 is that the degreasing temperature rise curve includes:

[0137] Raise the temperature to 130°C at a rate of 2°C / min and keep warm for 30 min;

[0138] Then the temperature was raised to 350°C at a rate of 4°C / min and kept at this temperature for 90 min;

[0139] Then the temperature was raised to 600°C at a rate of 4°C / min and kept at this temperature for 60 min;

[0140] Finally, the temperature was raised to 1100°C at a rate of 5°C / min and kept at this temperature for 24 h.

[0141] Comparative Example 11

[0142] The difference between this comparative example and Example 8 is that the degreasing temperature rise curve includes:

[0143] Raise the temperature to 130°C at a rate of 2°C / min and keep warm for 30 min;

[0144] Then, the temperature was raised to 180°C at a rate of 3°C / min and kept at this temperature for 45 min;

[0145] Then the temperature was raised to 600°C at a rate of 4°C / min and kept at this temperature for 60 min;

[0146] Finally, the temperature was raised to 1100°C at a rate of 5°C / min and kept at this temperature for 24 h.

[0147] Comparative Example 12

[0148] The difference between this comparative example and Example 8 is that the degreasing temperature rise curve includes:

[0149] Raise the temperature to 130°C at a rate of 2°C / min and keep warm for 30 min;

[0150] Then, the temperature was raised to 180°C at a rate of 3°C / min and kept at this temperature for 45 min;

[0151] Then the temperature was raised to 350°C at a rate of 4°C / min and kept at this temperature for 90 min;

[0152] Finally, the temperature was raised to 1100°C at a rate of 5°C / min and kept at this temperature for 24 h.

[0153] 1. Influence of the powder raw material preparation step in the ceramic material preparation process of the present invention

[0154] 1. Fluidity and friction coefficient of the mixture

[0155] The powder raw material preparation step of step (1) was carried out according to the methods of Examples 1 to 3, 8 to 10 of the present invention and Comparative Examples 1 to 6. The fluidity (angle of repose) and friction coefficient of the obtained mixed material were measured. The results are shown in Table 1.

[0156] Table 1

[0157]

[0158] As shown in Table 1, Examples 1-3 and 8-10 of the present invention utilize powders with specific particle size ratios to prepare the powder raw materials. The resulting mixed materials exhibit excellent fluidity, with angles of repose ranging from 20° to 35°. Compared to Example 1, Examples 2, 3, and 8-10 utilize a specific method for raw material mixing, significantly reducing the friction coefficient of the mixed materials to 0.17-0.20, reducing inter-powder friction, and significantly lowering the angle of repose to 20° to 22°, demonstrating excellent powder fluidity.

[0159] Compared with Example 1, Comparative Examples 1 to 4 changed the particle size ratio of each powder, resulting in a significant decrease in the angle of repose of the mixed material and an increase in the friction coefficient. Compared with Example 2, Comparative Examples 5 and 6 changed the raw material mixing method, resulting in a significant decrease in the angle of repose and an increase in the friction coefficient.

[0160] 2. Porosity of ceramic green body

[0161] The forming step of step (2) was carried out according to the methods of Examples 1 to 3, 8 to 10 of the present invention and Comparative Examples 1 to 6, and the porosity of the obtained ceramic blanks was measured. The results are shown in Table 2.

[0162] Table 2

[0163]

[0164] As shown in Table 2, the ceramic green bodies produced in Examples 1-3 and 8-10 of the present invention exhibit relatively low porosity, ranging from 24% to 37% (commonly found in the 40% to 60% range), and exhibit good green body density. In particular, Examples 2, 3, and 8-10, after employing a specific method for raw material mixing, exhibited an excellent porosity of 24% to 25%.

[0165] Compared with Example 1 and Example 2, Comparative Examples 1 to 6 respectively changed the powder particle size ratio and the raw material mixing method, resulting in a significant increase in the porosity of the ceramic green body and a deterioration in the molding effect.

[0166] 3. Properties of ceramic materials

[0167] The properties of the ceramic materials prepared in Examples 1 to 10 of the present invention and Comparative Examples 1 to 6 were measured. The results are shown in Table 3.

[0168] Table 3

[0169]

[0170] As shown in Table 3, the ceramic materials prepared in Examples 1-10 and Comparative Examples 1-6 of the present invention exhibit excellent properties, including thermal conductivity of 120-149 W / (m·K), hardness of 38-58 GPa, flexural strength of 400-570 MPa, and porosity of 0.02-0.70%. Examples 8-10 exhibit particularly excellent properties.

[0171] Compared with Example 1 and Example 2, Comparative Examples 1 to 6 respectively changed the powder particle size ratio and the raw material mixing method, resulting in reduced performance of the ceramic materials.

[0172] 2. Influence of Carbonization Treatment in the Preparation Process of Ceramic Materials of the Present Invention

[0173] 1.Carbonization effect

[0174] Carbonization treatment was performed according to the methods of Examples 3 to 8 of the present invention and Comparative Examples 7 and 8 to obtain carbonized blanks. The mass difference between the carbonized blanks and the defatted blanks obtained by degreasing after the carbonization treatment was compared, and the weight gain rate was calculated to characterize the carbonization effect. The results are shown in Table 4.

[0175] Table 4

[0176]

[0177] As shown in Table 4, the carbonization treatment of ceramic green bodies in Examples 3 to 8 of the present invention achieved weight gains ranging from 5.0% to 10.1%, demonstrating good carbonization effects. In particular, Examples 3 and 8 (using agarwood tetraol) achieved excellent carbonization effects of approximately 10.0%.

[0178] Compared with Example 8, the carbonization treatment method was changed in Comparative Examples 7 and 8, resulting in a poor carbonization effect.

[0179] 2. Strength and toughness of ceramic materials

[0180] Ceramic materials were prepared according to the methods of Examples 2 to 8 of the present invention and Comparative Examples 7 and 8, and their properties such as strength and toughness were measured. The results are shown in Table 5.

[0181] Table 5

[0182]

[0183] As shown in Table 5, compared with Example 2, the flexural strength of the ceramic materials prepared in Examples 3 to 8 of the present invention after carburization treatment is significantly improved, and the fracture toughness is also improved to varying degrees. In particular, the performance improvement effect of Examples 3 and 8 is more obvious.

[0184] Compared with Example 8, Comparative Examples 7 and 8 changed the carburizing treatment method, resulting in poor strength and toughness.

[0185] 3. Free silicon content of ceramic materials

[0186] Ceramic materials were prepared according to the methods of Examples 2 to 8 of the present invention and Comparative Examples 7 and 8, and the free silicon content was measured. The results are shown in Table 6.

[0187] Table 6

[0188]

[0189] The results in Table 6 show that, compared with Example 2, the free silicon content in the ceramic materials obtained in Examples 3 to 8 of the present invention after carburization treatment is significantly reduced, especially in Examples 3 and 8.

[0190] Compared with Example 8, the carbon addition treatment methods were changed in Comparative Examples 7 and 8, resulting in an increase in the free silicon content.

[0191] Influence of degreasing process in the preparation process of ceramic materials of the present invention

[0192] 1. Properties of defatted blank.

[0193] The degreasing step of step (4) was carried out according to the methods of the present invention 3, 8 and comparative examples 9 to 12, and the porosity of the obtained degreased blank was measured. The results are shown in Table 7.

[0194] Table 7

[0195]

[0196] It can be seen from the results in Table 7 that, compared with Example 3, after Example 8 of the present invention adopts a specific degreasing heating curve, the porosity of the degreased blank obtained is significantly reduced to 10%.

[0197] Compared with Example 8, Comparative Examples 9 to 12 changed the degreasing temperature rise curve, resulting in an increase in the porosity of the degreased green blank.

[0198] 2. Product defect rate of ceramic materials

[0199] Ceramic materials were prepared according to the methods of the present invention 3, 8 and comparative examples 9 to 12. The number of products with cracks, deformations, etc. was counted, and the product defect rate was calculated. The results are shown in Table 8.

[0200] Table 8

[0201]

[0202] It can be seen from the results in Table 8 that, compared with Example 3, after Example 8 of the present invention adopts a specific degreasing heating curve, the product defect rate of the ceramic material obtained is significantly reduced to 0.3%.

[0203] Compared with Example 8, Comparative Examples 9 to 12 changed the degreasing temperature rise curve, resulting in an increase in the product defect rate of the ceramic material.

[0204] 3. Strength of ceramic materials

[0205] Ceramic materials were prepared according to the methods of the present invention 3, 8 and comparative examples 9 to 12, and their strengths were measured. The results are shown in Table 9.

[0206] Table 9

[0207]

[0208] It can be seen from the results in Table 9 that, compared with Example 3, after Example 8 of the present invention adopts a specific degreasing heating curve, the flexural strength of the ceramic material obtained is further improved to 563 MPa.

[0209] Compared with Example 8, Comparative Examples 9 to 12 changed the degreasing temperature rise curves, resulting in reduced flexural strength of the ceramic materials.

[0210] Finally, it should be noted that 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, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements 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 method for preparing a high-strength diamond boron carbide composite ceramic material, characterized by: The method comprises the following steps: powder raw material preparation, molding, degreasing and siliconizing sintering; The powder raw material preparation includes: using diamond powder and B4C powder as raw materials, adding a binder to mix the raw materials, and drying to obtain a mixed material; The diamond powder includes diamond micropowder and diamond nanopowder, the particle size of the diamond micropowder is 5-100 μm, the particle size of the diamond nanopowder is 5-500 nm, the particle size of the B4C powder is 50-300 μm, and the particle size ratio of the diamond micropowder, diamond nanopowder and B4C powder is 1: (0.001-0.02): (3-10); The binder includes a thermoplastic binder A and a water-soluble binder B. The raw material mixing includes the following steps: uniformly mixing the molten binder A with the diamond nanopowder, spraying the mixture evenly onto the surface of the diamond micropowder and the B4C powder, cooling the mixture, and then adding the binder B and water and mixing the mixture evenly. The binder A is polyvinyl butyral or polymethyl methacrylate, the binder B is polyvinyl alcohol or polyvinyl pyrrolidone, and the mass ratio of the binder A to the binder B is (0.1-0.4):

1.

2. The preparation method according to claim 1, wherein: The mass ratio of the diamond powder to the B4C powder is (1-7): (3-9), the mass ratio of the diamond micropowder to the diamond nanopowder is 1: (0.1-0.3), and the amount of the binder added is 0.5-5% of the total mass of the diamond powder and the B4C powder.

3. The preparation method according to claim 1, wherein: After forming, the ceramic green body is also subjected to a carbon increasing treatment, which includes a high carbon residual solution impregnation treatment, a high carbon residual compound synthesis treatment or a chemical vapor infiltration treatment.

4. The preparation method according to claim 1, wherein: The degreasing temperature is 1000-1200℃ and the degreasing time is 12-48 hours; The degreasing temperature rise curve includes: Raise the temperature to 100-160°C at a rate of 1-3°C / min and keep warm for 20-40 minutes; Then heat to 170-200°C at a rate of 2-4°C / min and keep warm for 30-60 minutes; Then, the temperature is raised to 300-400°C at a rate of 3-5°C / min and kept at this temperature for 60-120 minutes; Then, heat to 500-700°C at a rate of 3-5°C / min and keep at this temperature for 50-80min; Finally, the temperature is raised to 1000-1200°C at a rate of 4-7°C / min and kept at this temperature for 12-48 hours.

5. The preparation method according to claim 3, wherein: Before the high carbon residue solution impregnation treatment or chemical vapor infiltration treatment is used, the ceramic blank needs to be degreased. The high carbon residue solution is prepared by using one or more of phenolic resin, sucrose, asphalt resin and corresponding solvents.

6. The preparation method according to claim 3, wherein: When the high carbon residue compound synthesis process is adopted, the binder B is polyvinyl alcohol, and the high carbon residue compound synthesis process includes the following steps: Place the ceramic blank in a polyol solution, then add acid to adjust the pH to 1.5, then dropwise add furfural solution, react at 80-90°C for 2-4 hours, finally add alkali to adjust the reaction solution to neutrality, and then evaporate to dryness; The polyol is selected from one or more of agarwood tetraol, sugars, sugar alcohol glycerol, pentanetriol, and pentaerythritol.

7. The preparation method according to claim 6, characterized in that: The mass ratio of the polyol, furfural and binder B polyvinyl alcohol is (10-50): (5-20): 1, and the polyol is agarwood tetraol.

8. A high-strength diamond boron carbide composite ceramic material, characterized by: The invention is prepared by the preparation method according to any one of claims 1 to 2.

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