Diamond reinforced boron carbide bulletproof ceramic and preparation method thereof

Abstract

The invention provides a diamond-reinforced boron carbide bulletproof ceramic and a preparation method thereof, and the preparation method comprises the following steps: preparing a diamond dispersion liquid and boron carbide powder slurry; adding the diamond dispersion liquid into the boron carbide powder slurry, and continuously carrying out ball milling for 6-12 hours to obtain mixed slurry; carrying out spray granulation on the mixed slurry to obtain diamond / boron carbide mixed powder; the preparation method comprises the following steps: filling a forming die cavity with diamond / boron carbide mixed powder, forming a green body under pressure, coating a powder coating on the surface of diamond / boron carbide, carrying out degumming treatment, and finally, carrying out reactive sintering to obtain a compact ceramic block. A human body bulletproof flashboard obtained by compounding the diamond-reinforced boron carbide bulletproof ceramic and a conventional ultra-high molecular weight polyethylene fiber back plate can stably resist effective hit of three 53 type 7.62 mm armor-piercing incendiary bombs without penetrating damage under the condition that the surface density does not exceed 37 kg / m < 2 >.

Description

Technical Field

[0001] The invention relates to a diamond-reinforced boron carbide bulletproof ceramic and a preparation method thereof, and relates to the technical field of bulletproof ceramic preparation. Background Art

[0002] Bulletproof ceramics are the core components of lightweight ceramic composite armor. When a bullet impacts the composite armor, the ceramics utilize their exceptional hardness and strength to shatter the bullet, dissipating a significant portion of the bullet's energy. Elastic modulus, hardness, and strength are crucial performance indicators for bullet-breaking performance. Furthermore, the density of the ceramics determines the degree of lightweighting achieved in ceramic composite armor, which undoubtedly impacts the tactical mobility of both the wearer and the weaponry.

[0003] At present, the bulletproof ceramics that have been widely used include alumina, silicon carbide, boron carbide, etc. Among them, boron carbide with the highest hardness and lowest density has become the best choice for the new generation of lightweight and high-performance protective armor.

[0004] Boron carbide is a strongly covalently bonded compound that is extremely difficult to sinter to a high density under conventional conditions. Currently, three sintering processes for dense boron carbide ceramics are available: pressureless sintering, hot pressing, and reaction sintering. Pressureless sintering utilizes ultrafine, high-purity powders in the nanometer or submicron range, sintering at temperatures above 2200°C. This process leverages the diffusion properties of ultrafine, high-purity powders at temperatures close to the melting point of boron carbide to achieve sintering densification. Hot pressing applies high pressure to the green body once it reaches the sintering temperature, promoting diffusion and creep of the boron carbide ceramic at high temperatures. However, this sintering temperature typically requires temperatures above 1950°C. Reaction sintering involves reacting molten silicon with pre-disposed carbon in the ceramic green body to form silicon carbide. This secondary silicon carbide is then used to sinter the boron carbide particles into a dense, integrated structure. Since silicon has a melting point of only 1410°C, reaction sintering typically requires temperatures below 1650°C.

[0005] Over the past decade, boron carbide ballistic ceramics have become a mainstream material for lightweight protective armor, finding widespread use in weight-sensitive applications such as helicopter armor and body armor plates. After years of research and development, the ballistic performance of boron carbide ceramics has reached its limits. To meet the demands of even higher-performance protective equipment, materials with even higher mechanical properties than single-phase boron carbide ceramics are needed.

[0006] Diamond is the hardest material known and a natural choice for strengthening boron carbide ceramics. However, the preparation of diamond / boron carbide composite ceramics faces several technical difficulties.

[0007] First of all, diamond is an extremely hydrophobic material and is difficult to disperse in ceramic aqueous slurry. It needs to be modified to ensure uniform dispersion of diamond in ceramics.

[0008] Secondly, similar to the sintering process of single-phase boron carbide, the sintering and densification of diamond and boron carbide composite ceramics also requires extremely high temperatures. Hot pressing sintering temperatures are usually above 1950°C, and pressureless sintering temperatures need to be above 2050°C to achieve a certain degree of sintering density of diamond and boron carbide composite ceramics. The sintering temperatures of these two processes far exceed the graphitization transition temperature of diamond (1700°C). During the sintering process, a considerable portion of the diamond in the composite ceramic will inevitably transform into the graphite phase. Therefore, the preparation of diamond / boron carbide composite ceramics can only be achieved by reaction sintering (the sintering temperature of which can be below 1650°C).

[0009] However, during the reaction sintering process of diamond / boron carbide composite ceramics, the infiltrated liquid silicon will also react with part of the diamond to produce silicon carbide, thereby consuming part of the diamond and reducing the strengthening effect of the diamond. On the other hand, during the reaction sintering process, the liquid silicon reacts with the original carbon in the green body to form silicon carbide, resulting in volume expansion. While achieving sintering densification, it will also generate large internal stress in the body. The carbon source in conventional reaction sintered boron carbide is carbon black or phenolic resin pre-added to the mixed powder. The latter will be cracked at high temperature before sintering to obtain amorphous carbon. The density of these carbon sources is mostly between 1.9 and 2.1 g / cm 3 However, the density of diamond is as high as 3.52g / cm 3 This means that compared to conventional reaction sintering carbon sources, the same volume of diamond reacting with silicon to form silicon carbide will experience a volume expansion of more than 1.7 times, generating greater internal stress within the green body. Consequently, cracking is a common phenomenon during the reaction sintering of diamond / boron carbide composite ceramics. Improving the uniformity of diamond dispersion within the green body and optimizing and adjusting the composite ceramic forming and sintering process are key solutions to this problem.

[0010] Invention patent CN202410004208 discloses a method for preparing a boron carbide-bonded diamond composite super-hard bulletproof ceramic, which comprises mixing 2050 parts by weight of boron carbide, 2070 parts by weight of diamond powder, 36 parts by weight of carbon powder, 1020 parts by weight of phenolic resin, and 1030 parts by weight of glycerin, followed by granulation, pressing, drying and debinding, silicon plate pressing, and sintering. However, the above method does not solve the problem of uniform dispersion of diamond in the powder, nor does it mention the problem of cracking caused by the reaction between diamond and silicon during the sintering process.

[0011] Invention patent CN202410591689 discloses a boron carbide / diamond composite bulletproof ceramic and its preparation method. The process consists of preparing composite diamond micropowder, preparing coated diamond, mixing, granulating, preparing a green body, preparing a silicon plate, sintering, and post-processing. The mixing comprises, by weight, mixing large-particle boron carbide micropowder, medium-particle boron carbide micropowder, small-particle boron carbide micropowder, composite diamond micropowder, coated diamond, carbon powder, phenolic resin, glycerin, and water, and stirring uniformly to obtain a mixed slurry. The process is extremely complex, and the method of directly mixing diamond powder with boron carbide powder will result in uneven distribution of diamond in the powder, making it difficult to avoid cracking of the green body during sintering.

[0012] Invention patent CN115010496B discloses a method for preparing a B4C-diamond composite with controllable properties. The method involves wet-mixing three raw powders (boron carbide powder, diamond, and phenolic resin) in a ratio of 0.8:(0.1-0.2):(0-0.1) to obtain a mixture. The mixture is then dried, ground, and sieved. After compression molding, the mixture is dried and carbonized, and then infiltrated with silicon at low temperatures (1450°C) or high temperatures (1650°C). This yields a high-hardness, high-wear-resistant B4C-diamond composite (low-temperature infiltration) or a high-flexural-strength B4C-diamond composite (high-temperature infiltration). However, this method still fails to address the problem of uniform diamond dispersion in the mixed powder during large-scale production, nor does it propose a method for suppressing the reaction strength between diamond and silicon. Furthermore, it fails to address the problem of cracking during reactive sintering of diamond / boron carbide composite ceramics.

[0013] On the other hand, the high diamond mass fraction in the ceramic formula of the aforementioned patent will inevitably lead to high ceramic costs, making it difficult to promote and apply. For the specific application scenario of ballistic ceramics using reaction-sintered boron carbide as protective armor, it is necessary to explore new ceramic structures. The core function of ballistic ceramics is to use high-hardness ceramics to crush projectiles. This process requires the ceramic's projectile-facing surface to have ultra-high hardness and strong support to prolong the projectile's residence time, thereby maximizing the consumption of the bullet's kinetic energy. Summary of the Invention

[0014] In response to the shortcomings of the existing technology, the present invention provides a diamond-reinforced boron carbide bulletproof ceramic and a preparation method thereof. The prepared bullet-proof ceramic has a gradient structure, taking into account the ceramic's bullet-breaking efficiency and self-supporting performance. The ceramic has a high protection factor and low cost.

[0015] In order to solve the above technical problems, the present invention provides a method for preparing diamond-reinforced boron carbide bulletproof ceramics, which comprises the following steps: Prepare diamond dispersion: weigh 10-20 parts, 80-90 parts, and 0.1-0.4 parts by mass of diamond powder, water, and dispersant, respectively, to prepare diamond dispersion; Prepare boron carbide powder slurry: weigh boron carbide powder, carbon powder, sucrose, polyvinyl alcohol, and water in 100 parts by mass, 6-10 parts by mass, 20-40 parts by mass, 20-30 parts by mass, and 120-154 parts by mass, respectively. After ball milling, mix and stir to prepare boron carbide powder slurry; Prepare a mixed slurry: add the diamond dispersion to the boron carbide powder slurry, and continue ball milling for 6 to 12 hours to obtain a mixed slurry, wherein the mixed slurry includes a high-content slurry and a low-content slurry, and the mass ratio of diamond to boron carbide in the high-content slurry is (25 to 35): (65 to 75); the mass ratio of diamond to boron carbide in the low-content slurry is (5 to 10): (90 to 95); Preparing powder: spraying and granulating the high-content slurry and the low-content slurry to obtain high-content diamond / boron carbide mixed powder and low-content diamond / boron carbide mixed powder; Ceramic body molding: Filling a high-content diamond / boron carbide mixed powder and a low-content diamond / boron carbide mixed powder into a molding cavity to obtain a ceramic body with a gradient distribution of diamond content; Applying powder coating: Apply powder coating to the surface of the ceramic body, degumming treatment, evenly covering the silicon powder cake and then reacting and sintering to obtain a dense ceramic block.

[0016] Preferably, the diamond dispersion is prepared by first stirring and mixing a dispersant with water, then adding diamond micropowder and continuing to stir to obtain a diamond dispersion; the dispersant is one or more of polyvinyl pyrrolidone, polyacrylic acid, and sodium dodecylbenzene sulfonate, and the particle size of the diamond micropowder is 35-50 μm.

[0017] Preferably, the gradient distribution is to fill the high-content diamond / boron carbide mixed powder as the front-rebound surface, the thickness of which accounts for 45-65% of the overall thickness of the ceramic, and to fill the low-content diamond / boron carbide mixed powder as the back-rebound surface.

[0018] Preferably, the ceramic body is formed at a molding pressure of 20-25 MPa to ensure a molding density of the ceramic green body of 2.0-2.2 g / cm 3 .

[0019] Preferably, the air inlet temperature of the spray granulation is 195-205°C, and the air outlet temperature is 85-100°C.

[0020] Preferably, the powder coating is a powder coating obtained by ball-milling a mixture of zirconium carbide, polyethylene glycol, polyvinyl alcohol and water, and the thickness of the powder coating is 0.6-1 mm.

[0021] After applying powder coating to the surface of the diamond / boron carbide blank, a degumming treatment was performed in a mesh belt sintering furnace. The powder coating is a high-melting-point, inert carbide from CN114853479A. Its specific composition is: zirconium carbide powder with an average particle size of 2.5 microns, polyethylene glycol with an average molecular weight of 200, polyvinyl alcohol with an average molecular weight of 20,000, and deionized water, in a mass ratio of 46:4:6:44. The powder coating is approximately 0.8 mm thick, and the degumming treatment temperature is 900°C for 1-3 hours.

[0022] Preferably, the reaction sintering has a sintering temperature of 1600-1700°C, a holding time of 2-3 hours, and a vacuum degree of not less than 10 -2 Pa.

[0023] Preferably, after the reaction sintering, post-treatment is performed to remove residual silicon on the ceramic surface.

[0024] As one aspect of the present invention, the present invention provides a diamond-reinforced boron carbide bullet-proof ceramic prepared by the above method, which includes a diamond / boron carbide layer with a gradient distribution.

[0025] Preferably, the diamond-reinforced boron carbide bulletproof ceramic includes a first diamond / boron carbide layer and a second diamond / boron carbide layer, the diamond to boron carbide mass ratio of the first diamond boron carbide layer is greater than that of the second diamond boron carbide layer, and the thickness of the first diamond boron carbide layer is greater than that of the second diamond boron carbide layer.

[0026] Compared with the prior art, the present invention has the following beneficial effects: The diamond-reinforced boron carbide bulletproof ceramic prepared by the present invention has a significantly improved overall protection factor according to the standard experimental conditions of GJB 5119-2002 "Method for Determining the Protection Factor of Armor Materials", and its cost is relatively low, with great application prospects. The human body bulletproof insert obtained by combining the diamond-reinforced boron carbide bulletproof ceramic of the present invention with a conventional ultra-high molecular weight polyethylene fiber backing has a surface density of no more than 37kg / m 2 Under the conditions of GJB4300A-2012 "Technical Performance Requirements for Safety of Military Body Armor", it can stably withstand the effective hits of three Type 53 7.62mm armor-piercing incendiary bullets without causing penetrating damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a morphology image of the ceramic powder prepared in Example 1; Figure 2 This is a morphology diagram of the ceramic powder prepared in Comparative Example 1; Figure 3 This is the cracking state of the diamond / boron carbide ceramic in Comparative Example 1; Figure 4 This is the metallographic structure diagram of the diamond / boron carbide ceramic prepared in Example 1; Figure 5 This is the metallographic structure diagram of the diamond / boron carbide ceramic prepared in Comparative Example 1; Figure 6 Schematic diagram of the test structure for the protection factor of ceramic plates; Figure 7 This is a picture of the bullet hole morphology of the bulletproof insert made of the ceramic plate in Example 1 after being hit by a bullet. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described.

[0029] Example 1 A method for preparing diamond-reinforced boron carbide bulletproof ceramics, specifically comprising: Step 1: Prepare diamond dispersion: Disperse 0.2 parts of polyvinyl pyrrolidone (PVP) in 90 parts of deionized water by mass, stir evenly, add 10 parts of diamond micropowder (D50 particle size of 40 μm), stir vigorously at 500-800 rpm for 4 hours to form diamond dispersion. Step 2: Prepare boron carbide powder slurry: Mix 100 parts of boron carbide powder (D50 particle size is 20 μm), 8 parts of carbon powder (D50 particle size is 3 μm), 30 parts of sucrose, 25 parts of polyvinyl alcohol, and 137 parts of water, and stir and ball mill at a speed of 100 rpm for 6 hours; Step 3: Prepare high / low content diamond / boron carbide mixed slurries: Add the required diamond dispersion to the boron carbide powder slurry according to the high content slurry and low content slurry, and continue stirring and ball milling for 10 hours according to the ball milling process conditions of step 2 to prepare high / low content diamond / boron carbide mixed slurries. The ratio of the high content diamond / boron carbide mixed slurry is 300 parts diamond dispersion: 210 parts boron carbide powder slurry; the ratio of the low content diamond / boron carbide mixed slurry is 100 parts diamond dispersion: 270 parts boron carbide powder slurry. Step 4: Preparation of high / low content diamond / boron carbide mixed powder: The high / low content diamond / boron carbide mixed slurry obtained in step 3 is sprayed and granulated in a centrifugal atomizer with an air inlet temperature of 195°C and an air outlet temperature of 90°C. The granulated powder is passed through a 50-mesh sieve to obtain a high / low content diamond / boron carbide mixed powder. The powder dispersion state is as follows: Figure 1 As shown, it can be seen that the powder particle size is relatively uniform and the dispersion state is good; Step 5: Diamond / boron carbide ceramic green body molding: 40 parts by mass of low-content diamond / boron carbide mixed powder were spread on the bottom of the female mold, and then 60 parts of high-content diamond / boron carbide mixed powder were spread on the low-content diamond / boron carbide powder. The powders were pressed and molded on a hydraulic press to obtain a density of 2.1 g / cm 3 green body; Step 6: Powder coating: Mix 46 parts zirconium carbide powder (average particle size 2.5 microns), 4 parts polyethylene glycol (average molecular weight 200), 6 parts polyvinyl alcohol (average molecular weight 20,000), and 44 parts deionized water and ball mill for 3 hours to obtain a powder coating. The powder coating is applied to the diamond / boron carbide ceramic surface to a thickness of approximately 0.8 mm. The ceramic is then debonded in a mesh belt sintering furnace at 900°C for 1.5 hours. Step 7, reaction sintering of diamond / boron carbide ceramics: Place silicon powder cake on the surface and surrounding of the green body coated with powder coating, and then sinter them together in a vacuum furnace at a sintering temperature of 1650°C, a holding time of 3 hours, and a vacuum degree of 10 -2 Pa; Step 8. Post-processing of ceramic reaction sintering: After reaction sintering, the ceramic is taken out and residual silicon on the surface of the ceramic is removed with a shovel or other tool to obtain diamond-reinforced boron carbide bullet-resistant ceramic.

[0030] Example 2 Steps 1 and 2 are the same as those in Example 1.

[0031] Step 3: Prepare high / low content diamond / boron carbide mixed slurries: Add the diamond dispersion to the boron carbide powder slurry, and continue ball milling for 10 hours according to the ball milling process conditions of Step 2 to obtain a diamond / boron carbide mixed slurry. The ratio of the high-content diamond / boron carbide mixed slurry is 300 parts diamond dispersion: 170 parts boron carbide powder slurry; the ratio of the low-content diamond / boron carbide mixed slurry is 100 parts diamond dispersion: 270 parts boron carbide powder slurry.

[0032] Steps 4 to 8 are the same as those in Example 1.

[0033] Comparative Example 1 Step 1: Mix 30 parts of diamond powder (D50 particle size 40 μm), 100 parts of boron carbide powder (D50 particle size 20 μm), 8 parts of carbon powder (D50 particle size 3 μm), 30 parts of sucrose, 25 parts of polyvinyl alcohol, and 237 parts of water, and stir and ball mill for 10 hours.

[0034] Step 2: Preparation of diamond / boron carbide mixed powder: The diamond / boron carbide mixed slurry obtained in step 1 is sprayed and granulated in a centrifugal atomizer with an air inlet temperature of 195°C and an air outlet temperature of 90°C. The granulated powder is passed through a 50-mesh sieve to obtain a diamond / boron carbide mixed powder. The morphology of the mixed powder is shown in FIG. Figure 2 .

[0035] Step 3: Diamond / boron carbide ceramic green body molding: Spread the diamond / boron carbide mixed powder obtained in step 2 on a hydraulic press and press the powder to obtain a density of 1.9 g / cm 3 of the green body.

[0036] Step 4: Applying powder coating: the same as step 6 of Example 1.

[0037] Step 5: Reaction sintering of diamond / boron carbide ceramics: the same as step 7 in Example 1.

[0038] Step 6: Post-processing of ceramic reaction sintering: the same as step 8 in Example 1.

[0039] In Comparative Example 1, some of the green bodies cracked during sintering. Figure 3 The cracking is caused by the uneven distribution of diamonds and silicon during the sintering process, which generates large internal stress.

[0040] Comparative Example 2 Steps 1 and 2 are the same as those in Example 1.

[0041] Step 3 is the same as step 3 of Example 1 for preparing high-content diamond / boron carbide mixed powder, that is, the ratio of diamond / boron carbide mixed slurry is 300 parts of diamond dispersion: 210 parts of boron carbide powder slurry.

[0042] Step 4: Prepare diamond / boron carbide mixed powder: The diamond / boron carbide mixed slurry obtained in step 3 is sprayed and granulated in a centrifugal atomizer with an air inlet temperature of 195°C and an air outlet temperature of 90°C. The granulated powder is passed through a 50-mesh sieve to obtain a diamond / boron carbide mixed powder.

[0043] Step 5: Diamond / boron carbide ceramic green body molding: The diamond / boron carbide mixed powder obtained in step 4 is pressed on a hydraulic press to obtain a density of 2.1 g / cm 3 of the green body.

[0044] Steps 6 to 8 are the same as steps 6 to 8 of Example 1, respectively.

[0045] To illustrate the superiority of the two-step dispersion method used in the present invention, the metallographic structures of the diamond-reinforced boron carbide ceramics obtained in Example 1 and Comparative Example 1 are compared. Figure 4 and Figure 5 As shown, it can be seen that the diamonds (black dots) of Example 1 are more evenly distributed in the ceramic.

[0046] To demonstrate the superior overall ballistic performance of the diamond-reinforced boron carbide ceramics produced by the present invention, the protection factor of the ceramics was tested according to the test method for brittle armor materials specified in GJB 5119-2002, "Method for Determining the Protection Factor of Armor Materials." The test results for the examples and comparative examples are listed in Table 1. The specific test parameters are as follows: The overall thickness of the ceramic plate was fixed at 9.5 mm. The thicknesses of the homogeneous armor steel front and back plates were 7 mm and 30 mm, respectively, with the ceramic plate between them. Bolts were used to connect the three components into a solid whole. The structural diagram is shown in Figure 1. Figure 6 As shown in the figure, a simulated armor-piercing projectile with a penetration power of 70mm was used as the test projectile.

[0047] Table 1 Ceramic quality protection factors of examples and comparative examples .

[0048] Both Examples 1 and 2 utilize a two-step dispersion method to obtain diamond-reinforced boron carbide bulletproof ceramic plates. The protection factor results show that increasing the diamond content does not significantly improve the overall protection factor, with Example 1 achieving the best diamond-reinforced boron carbide bulletproof ceramic plate with the diamond content. Comparative Example 1 and Example 1 contain the same diamond content in the overall ceramic, but the ceramic prepared using a one-step dispersion method has a much lower protection factor than the ceramic prepared using the two-step dispersion method. Comparative Example 2, also using a two-step dispersion method, produces a boron carbide bulletproof ceramic plate uniformly reinforced with diamond, lacking the gradient composition structure of Example 1. Despite a higher diamond content than Example 1, its protection factor does not significantly improve, which is related to the bullet-breaking mechanism of the bullet-proof ceramic. When a high-speed projectile strikes the bullet-proof ceramic, the high-hardness ceramic first shatters the bullet, and the resulting projectile fragments continue to pass through the subsequent ceramic plates. The hardness of the ceramic is crucial for projectile fragmentation efficiency: higher hardness results in greater fragmentation efficiency. After the projectile breaks, the mass of the projectile fragments has become much smaller, and the impact force of the bullet is also much smaller. Therefore, the diamond content in the ceramic does not need to be too high to play the role of grinding the bullet and preventing it from continuing to penetrate. Therefore, the protection factor of the ceramic in Comparative Example 2 is not more significantly superior to that of Example 1.

[0049] The diamond reinforced boron carbide bulletproof ceramic plate with a thickness of 9.5 mm to 10 mm prepared by the present invention is composited with an ultra-high molecular weight polyethylene fiber laminate to produce a surface density of 37 kg / m 2The bulletproof insert plate, tested according to the GJB4300A-2012 "Technical Performance Requirements for Safety of Military Body Armor", can stably withstand three effective hits of Type 53 7.62mm armor-piercing incendiary bullets (speed greater than 868m / s) without penetrating damage. The morphology of the insert plate after the bullet impact is shown in the figure below. Figure 7 As shown in the figure, it can be seen that the three bullet holes are all relatively regular circles and are basically the same in size, indicating that the properties of the ceramic are uniform and consistent, and its ability to resist bullet impact is good.

[0050] In order to solve the technical problem of easy cracking in large-scale production of diamond / boron carbide ceramics, the preparation method of the present invention comprises the following steps: preparing a diamond dispersion; adding diamond slurry with different contents to boron carbide slurry and continuing ball milling; spray granulating the obtained mixed slurry to obtain a diamond / boron carbide mixed powder; filling the diamond / boron carbide mixed powder with different components into a forming cavity in sequence according to a certain proportion, and forming a blank under pressure; applying a pre-prepared powder coating to the surface of the diamond / boron carbide and then degumming it, then evenly spreading silicon powder cake on the surface and around the blank, and using a reaction sintering process to obtain a dense ceramic block; and polishing the surface of the sintered block to remove residual silicon on the surface. The present invention adopts a method of first preparing a diamond dispersion and then mixing it with a boron carbide slurry, thereby effectively improving the dispersion uniformity of the diamond. A method of using a relatively high molding pressure, simultaneously using sucrose instead of phenolic resin as a carbon source, and adding polyvinyl alcohol to improve the formability of the green body, thereby obtaining a green body with a relatively high density and a relatively low carbon content after degumming, reducing the reaction intensity between silicon and carbon during the reaction sintering process and lowering the particle size of the residual silicon. Diamond-reinforced boron carbide ballistic-resistant ceramics with gradient composition and performance are used to improve the ballistic-resistant function of the ceramics and significantly reduce the ceramic manufacturing cost, laying a good foundation for expanding the application field of diamond / boron carbide ballistic-resistant ceramics.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing diamond-reinforced boron carbide bulletproof ceramics, characterized in that: The following steps are included: Prepare diamond dispersion: weigh 10-20 parts, 80-90 parts, and 0.1-0.4 parts by mass of diamond powder, water, and dispersant, respectively, to prepare diamond dispersion; Prepare boron carbide powder slurry: weigh boron carbide powder, carbon powder, sucrose, polyvinyl alcohol, and water in 100 parts by mass, 6-10 parts by mass, 20-40 parts by mass, 20-30 parts by mass, and 120-154 parts by mass, respectively. After ball milling, mix and stir to prepare boron carbide powder slurry; Prepare a mixed slurry: add the diamond dispersion to the boron carbide powder slurry, and continue ball milling for 6 to 12 hours to obtain a mixed slurry, wherein the mixed slurry includes a high-content slurry and a low-content slurry, and the mass ratio of diamond to boron carbide in the high-content slurry is (25 to 35): (65 to 75); the mass ratio of diamond to boron carbide in the low-content slurry is (5 to 10): (90 to 95); Preparing powder: spraying and granulating the high-content slurry and the low-content slurry to obtain high-content diamond / boron carbide mixed powder and low-content diamond / boron carbide mixed powder; Ceramic body molding: Filling a high-content diamond / boron carbide mixed powder and a low-content diamond / boron carbide mixed powder into a molding cavity to obtain a ceramic body with a gradient distribution of diamond content; Applying powder coating: Apply powder coating to the surface of the ceramic body, degumming treatment, evenly covering the silicon powder cake and then reacting and sintering to obtain a dense ceramic block.

2. The method for preparing the diamond-reinforced boron carbide bulletproof ceramic according to claim 1, wherein: The diamond dispersion is prepared by first stirring and mixing a dispersant with water, then adding diamond micropowder and continuing to stir to obtain the diamond dispersion; the dispersant is one or more of polyvinyl pyrrolidone, polyacrylic acid, and sodium dodecylbenzene sulfonate, and the particle size of the diamond micropowder is 35-50 μm.

3. The method for preparing the diamond-reinforced boron carbide bulletproof ceramic according to claim 1, wherein: The gradient distribution is that the high-content diamond / boron carbide mixed powder is filled as the elastic surface, and its thickness accounts for 45-65% of the overall thickness of the ceramic, and the low-content diamond / boron carbide mixed powder is filled as the anti-elastic surface.

4. The method for preparing the diamond-reinforced boron carbide bulletproof ceramic according to claim 1, wherein: The ceramic body is formed by selecting a forming pressure of 20-25 MPa to ensure that the forming density of the ceramic green body is 2.0-2.2 g / cm 3 .

5. The method for preparing diamond-reinforced boron carbide bulletproof ceramic according to claim 1, wherein: The spray granulation has an air inlet temperature of 195-205°C and an air outlet temperature of 85-100°C.

6. The method for preparing the diamond-reinforced boron carbide bulletproof ceramic according to claim 1, wherein: The powder coating is obtained by mixing zirconium carbide, polyethylene glycol, polyvinyl alcohol and water through ball milling, and the thickness of the powder coating is 0.6-1 mm.

7. The method for preparing diamond-reinforced boron carbide bulletproof ceramics according to claim 1, wherein: The reaction sintering has a sintering temperature of 1600-1700°C, a holding time of 2-3 hours, and a vacuum degree of not less than 10 -2 Pa.

8. The method for preparing diamond-reinforced boron carbide bulletproof ceramics according to claim 1, characterized in that: After the reaction sintering, post-treatment is performed to remove residual silicon on the ceramic surface.

9. A diamond-reinforced boron carbide bulletproof ceramic, characterized by: It includes a diamond / boron carbide layer with a gradient distribution of diamond content.

10. The diamond-reinforced boron carbide bulletproof ceramic according to claim 9, characterized in that: The diamond-reinforced boron carbide bulletproof ceramic includes a first diamond / boron carbide layer and a second diamond / boron carbide layer. The first diamond boron carbide layer has a greater diamond to boron carbide mass ratio than the second diamond boron carbide layer, and the first diamond boron carbide layer is thicker than the first and second diamond boron carbide layers.

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