Layered boron carbide bulletproof ceramic as well as preparation method and application thereof

Abstract

The invention relates to the field of high-performance ceramics and bulletproof, in particular to a high-toughness layered boron carbide bulletproof ceramic and a preparation method thereof. The preparation method of the layered boron carbide bulletproof ceramic comprises the following steps: step 1, adding boron carbide powder and a sintering aid into a mixed solvent, then adding a dispersing agent, a binder and a plasticizer, and carrying out mixing and ball milling to obtain ceramic slurry; step 2, preparing the ceramic slurry into a boron carbide ceramic biscuit sheet by adopting a tape casting process; and laminating the boron carbide ceramic biscuit sheets, pressing, and carrying out hot pressed sintering to obtain the layered boron carbide bulletproof ceramic. Through the layered structure design, the controllable preparation of the layered boron carbide bulletproof ceramic is realized, so that the layered boron carbide bulletproof ceramic shows the characteristics of high strength and high toughness under the action force vertical to the layered direction, and the actual application effect of the layered boron carbide bulletproof ceramic is improved. Meanwhile, the layered structure provided by the invention has designability and operability, and the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the fields of high-performance ceramics and bulletproof applications, and particularly to a high-strength and tough laminated boron carbide bulletproof ceramic and a preparation method thereof. Background Art

[0002] Currently, the types of in-service bulletproof materials are divided into metal bulletproof materials, ceramic bulletproof materials, and high-performance fiber bulletproof materials, etc. Among them, ceramic bulletproof materials represented by boron carbide ceramics have become a research and promotion hotspot in the field of bulletproof materials due to their high strength, high hardness, high elastic modulus, good stability, light weight, etc. The theoretical density of boron carbide is only 2.5 g / cm 3 , and its Mohs hardness is 9.3, which is second only to diamond and cubic boron nitride. As a bulletproof material, it can effectively break projectiles, disperse kinetic energy, and increase the protection ability of equipment. It can be widely used in the protection systems of armored vehicles, tanks, armed helicopters, and warships. In particular, with the continuous improvement of the damage effectiveness of anti-armor weapons, the thickness and weight of traditional armor have been increasing, and the increasing armor weight has significantly deteriorated the tactical mobility of military equipment. This has made protection and lightweight gradually become the basic requirements of modern protective armor. Compared with bulletproof ceramics such as titanium diboride, alumina, and silicon carbide, boron carbide has the highest hardness and the lowest density, meeting the requirements of high strength, high wear resistance, high hardness, and low density for bulletproof materials. It is the best choice for lightweight anti-ballistic ceramics and has currently been applied to the protection systems of high-end equipment.

[0003] Currently, most research mainly focuses on solving the densification problem of boron carbide ceramics by using sintering aids and reinforcing phases in order to improve their mechanical properties. However, the improvement effect on mechanical properties is still insufficient, especially its fracture toughness is still very low, which greatly limits the application of boron carbide ceramics. Therefore, under the development requirement of reducing weight without reducing the protection performance of bulletproof materials, the super improvement of the mechanical properties of boron carbide ceramics is crucial. Summary of the Invention

[0004] Aiming at the technical problem of the low fracture toughness of current boron carbide ceramics, the present invention provides a high-strength and tough laminated boron carbide bulletproof ceramic and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One technical solution of the present invention is a preparation method of a laminated boron carbide bulletproof ceramic, including the following steps:

[0007] Step 1, adding boron carbide powder and a sintering aid into a mixed solvent, and then adding a dispersant, a binder, and a plasticizer and mixing and ball milling to obtain a ceramic slurry;

[0008] Step 2: Prepare a boron carbide ceramic green sheet from the ceramic slurry by using a tape casting process; stack and press the boron carbide ceramic green sheets, and then perform hot pressing sintering to obtain the laminated boron carbide bulletproof ceramic.

[0009] In a preferred embodiment of the present invention, the mass ratio of the boron carbide powder to the sintering aid is 9:1 to 7:3; the sintering aid is a mixture of two of yttrium oxide, cerium oxide, erbium oxide, ytterbium oxide, lanthanum oxide, and samarium oxide mixed in a mass ratio of 1:1.

[0010] In a preferred embodiment of the present invention, the mixed solvent is a mixture of acetone and ethanol with a volume ratio of 1:1; the dispersant is a PEI dispersant; the binder is a PVP binder; the plasticizer is a polyethylene glycol plasticizer.

[0011] In a preferred embodiment of the present invention, the solid content of the ceramic slurry is 50wt% to 80wt%; the addition amount of the dispersant is 0.5wt% to 2wt% of the total mass of the boron carbide powder and the sintering aid; the addition amount of the binder is 1wt% to 5wt% of the total mass of the boron carbide powder and the sintering aid; the addition amount of the plasticizer is 1 to 10wt% of the total mass of the boron carbide powder and the sintering aid.

[0012] In a preferred embodiment of the present invention, the rotation speed of the ball milling is 150 to 300 rpm / min, the time is 12 to 24 h, and the ball milling medium is boron carbide grinding balls with a diameter of 1 to 5 mm.

[0013] In a preferred embodiment of the present invention, the height of the doctor blade in the tape casting process is 0.1 to 2 mm, the casting speed is 1 to 10 mm / s, and the temperature of the casting drying zone is 40 to 70°C; the thickness of the boron carbide ceramic green sheet is 0.1 to 2 mm.

[0014] In a preferred embodiment of the present invention, the number of stacked layers is 50 to 300; the temperature of the pressing is 50 to 90°C, the pressure is 5 to 20 Mpa, and the pressing time is 3 to 10 min; the thickness of the green body obtained by stacking the boron carbide ceramic green sheets is 5 to 60 mm.

[0015] In a preferred embodiment of the present invention, the hot pressing sintering is specifically as follows: the pressure direction is perpendicular to the stacking direction, under the conditions of a pressure of 20 to 40 Mpa and an argon atmosphere, first heat up to 600°C at a heating rate of 1 to 5°C / min and keep it warm for 2 h for degreasing, then continue to heat up to 1850 to 2100°C at a heating rate of 3 to 8°C / min, keep it warm for 1 to 6 h, after the heat preservation ends, cool down to 800°C at a rate of 1 to 5°C / min, and then cool with the furnace.

[0016] Further preferably, first heat up to 600 °C at a heating rate of 1-5 °C / min and keep it warm for 2 h for degreasing, then continue to heat up to 2000 °C at a rate of 3-8 °C / min and keep it warm for 4 h. After the heat preservation is completed, cool it down to 800 °C at a rate of 1-5 °C / min, and then cool it with the furnace.

[0017] The second technical solution of the present invention is a laminated boron carbide bulletproof ceramic prepared according to the above preparation method.

[0018] The third technical solution of the present invention is the application of the above-mentioned laminated boron carbide bulletproof ceramic in an armor protection system.

[0019] The present invention discloses the following technical effects:

[0020] Through the laminated structure design, the present invention realizes the controllable preparation of the laminated boron carbide bulletproof ceramic, so that when it is subjected to the force perpendicular to the laminated direction, it exhibits high strength and high toughness characteristics, improving its application effectiveness. At the same time, the laminated structure proposed by the present invention has designability and operability. The preparation process of the boron carbide ceramic thin sheet is simple, the layer thickness is controllable, and the overall thickness of the boron carbide ceramic is also controllable. When this laminated structure is subjected to force, the force will deflect horizontally between the layers, consuming a large amount of fracture energy. Under the condition of the same thickness of the boron carbide bulletproof ceramic, the more the number of layers, the more fracture energy is consumed, and its strength and toughness can be further improved, promoting the practical application of the boron carbide bulletproof ceramic. Detailed implementation manners

[0021] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation manners of the present invention.

[0022] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded within the range.

[0023] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0024] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0025] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0026] Aiming at the problems of low flexural strength and low fracture toughness of boron carbide ceramics at present, which are prone to large-area cracking and insufficient actual application effects under the action of force impact, the present invention prepares a thin-sheet boron carbide ceramic green body through a tape casting process, and then prepares boron carbide ceramics through laminated hot pressing sintering to realize its layered structure design. This layered structure design enables the cracks to expand along the layer interface when the boron carbide ceramic is subjected to an external force perpendicular to the layer direction, increasing the crack propagation path and consuming more fracture energy, thus realizing the preparation of high-strength and high-toughness boron carbide bulletproof ceramics. The advantages of the present invention are that the preparation process is simple, the layered structure has strong designability, and the obtained boron carbide ceramics have high strength and high toughness.

[0027] The technical solutions described in the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0028] In the examples of the present invention, the average particle size of the boron carbide powder used is 0.5 - 5 μm; the average particle size of the sintering aid used is 1 - 5 μm.

[0029] In the examples of the present invention, the PEI dispersant used is polyetherimide 1000, the PVP binder is polyvinylpyrrolidone 5000, and the molecular weight of the polyethylene glycol plasticizer is 8000.

[0030] The calculation formula for the solid content in this example:

[0031] The detection methods involved in the present invention: The detection of the density, Vickers hardness, room temperature flexural strength and fracture toughness of the laminated boron carbide bulletproof ceramics refers to the national standards GB / T 39688-2020, GB / T 16534-2009, GB / T 4741-1999, GB / T44537-2024.

[0032] The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they cannot be understood as limiting the protection scope of the present invention.

[0033] Example 1

[0034] Step 1: Mix boron carbide powder and sintering aids in a mass ratio of 9:1 and place them in an acetone / ethanol mixed solvent (acetone:ethanol volume ratio is 1:1), where the sintering aids consist of yttrium oxide and cerium oxide in a mass ratio of 1:1; then add 2 wt% of PEI dispersant, 5 wt% of PVP binder, and 10 wt% of polyethylene glycol plasticizer based on the total mass of boron carbide powder and sintering aids. Achieve uniform dispersion of ceramic powder through planetary ball milling. The ball milling speed is 300 rpm / min, the ball milling time is 24 h, and the ball milling medium is boron carbide grinding balls with a diameter of 1 mm to obtain a ceramic slurry with a solid content of 80 wt%.

[0035] Step 2: Adopt the tape casting process, control the doctor blade height to be 0.1 mm, the tape casting speed to be 10 mm / s, and the temperature of the tape casting drying zone to be 70 °C to prepare a boron carbide ceramic green sheet (thickness 0.5 mm) from the ceramic slurry in Step 1; adjust the stacking thickness to be 20 mm, the pressing temperature to be 50 °C, the pressure to be 10 Mpa, and the holding time to be 10 min to prepare a boron carbide green body with 45 layers; conduct hot press sintering on the boron carbide green body. The pressure direction is perpendicular to the stacking direction, the pressure is 30 Mpa, under an argon atmosphere, first heat up to 600 °C at a heating rate of 1 °C / min and hold for 2 h for debinding, then continue to heat up to 2100 °C at a rate of 3 °C / min and hold for 6 h. After the holding ends, cool down to 800 °C at a rate of 5 °C / min, and then cool with the furnace to obtain laminated boron carbide bulletproof ceramics.

[0036] The laminated boron carbide bulletproof ceramics prepared in this example have a density of 99.8%, a Vickers hardness of 45 GPa, a room temperature flexural strength of 610 MPa, and a fracture toughness of 12.15 Mpa·m 1 / 2 。

[0037] Example 2

[0038] Step 1: Mix boron carbide powder and sintering aids in a mass ratio of 8:2 and place them in an acetone / ethanol mixed solvent (acetone:ethanol volume ratio is 1:1), where the sintering aids consist of erbium oxide and ytterbium oxide in a mass ratio of 1:1; then add 0.5 wt% of PEI dispersant, 1 wt% of PVP binder, and 1 wt% of polyethylene glycol plasticizer based on the total mass of boron carbide powder and sintering aids. Achieve uniform dispersion of ceramic powder through planetary ball milling. The ball milling speed is 250 rpm / min, the ball milling time is 24 h, and the ball milling medium is boron carbide grinding balls with a diameter of 3 mm to obtain a ceramic slurry with a solid content of 80 wt%.

[0039] Step 2: Using the tape casting process, control the height of the doctor blade to 0.5 mm, the casting speed to 5 mm / s, and the temperature in the casting drying zone to 60 °C. Prepare the ceramic slurry in Step 1 into a boron carbide ceramic green sheet (with a thickness of 0.6 mm); adjust the stacking thickness to 20 mm, the pressing temperature to 60 °C, the pressure to 35 Mpa, and the holding time to 8 min to prepare a boron carbide green body with 35 layers; perform hot press sintering on the boron carbide green body. The pressure direction is perpendicular to the stacking direction, the pressure is 35 Mpa. Under an argon atmosphere, first heat up to 600 °C at a heating rate of 1 °C / min and hold for 2 h for debinding, then continue to heat up to 2000 °C at a rate of 3 °C / min and hold for 4 h. After the holding is completed, cool down to 800 °C at a rate of 5 °C / min, and then cool with the furnace to obtain the high-strength and tough laminated boron carbide bulletproof ceramic.

[0040] The density of the laminated boron carbide bulletproof ceramic prepared in this example reaches 99.8%, the Vickers hardness is 48 GPa, the room temperature bending strength is 656 MPa, and the fracture toughness is 14.12 Mpa·m 1 / 2 。

[0041] Example 3

[0042] Step 1: Mix boron carbide powder and sintering aids in a mass ratio of 7:3 and place them in an acetone / ethanol mixed solvent (the volume ratio of acetone to ethanol is 1:1). The sintering aids are composed of yttrium oxide and cerium oxide in a mass ratio of 1:1. Then add 1 wt% of PEI dispersant, 2 wt% of PVP binder, and 5 wt% of polyethylene glycol plasticizer based on the total mass of boron carbide powder and sintering aids. Achieve uniform dispersion of ceramic powders through planetary ball milling. The ball milling speed is 250 rpm / min, the ball milling time is 20 h, and the ball milling medium is boron carbide grinding balls with a diameter of 3 mm to obtain a ceramic slurry with a solid content of 80 wt%.

[0043] Step 2: Using the tape casting process, control the height of the doctor blade to 1.5 mm, the casting speed to 8 mm / s, and the temperature in the casting drying zone to 65 °C. Prepare the ceramic slurry in Step 1 into a boron carbide ceramic green sheet (with a thickness of 0.7 mm); adjust the stacking thickness to 20 mm, the pressing temperature to 60 °C, the pressure to 15 Mpa, and the holding time to 5 min to prepare a boron carbide green body with 31 layers; perform hot press sintering on the boron carbide green body. The pressure direction is perpendicular to the stacking direction, the pressure is 28 Mpa. Under an argon atmosphere, first heat up to 600 °C at a heating rate of 1 °C / min and hold for 2 h for debinding, then continue to heat up to 1950 °C at a rate of 3 °C / min and hold for 2 h. After the holding is completed, cool down to 800 °C at a rate of 5 °C / min, and then cool with the furnace to obtain the high-strength and tough laminated boron carbide bulletproof ceramic.

[0044] The density of the laminated boron carbide bulletproof ceramic prepared in this example reaches 99.2%, the Vickers hardness is 40 GPa, the room temperature bending strength is 605 MPa, and the fracture toughness is 12.89 Mpa·m 1 / 2 。

[0045] Example 4

[0046] Step 1: Mix boron carbide powder and sintering aids in a mass ratio of 8.5:1.5, and place them in an acetone / ethanol mixed solvent (acetone:ethanol volume ratio is 1:1). The sintering aids are composed of lanthanum oxide and samarium oxide with a mass ratio of 1:1. Then add 1 wt% of PEI dispersant, 2 wt% of PVP binder, and 5 wt% of polyethylene glycol plasticizer based on the total mass of boron carbide powder and sintering aids. Uniform dispersion of ceramic powder is achieved by planetary ball milling. The ball milling speed is 300 rpm / min, the ball milling time is 22 h, and the ball milling medium is boron carbide grinding balls with a diameter of 5 mm, obtaining a ceramic slurry with a solid content of 80 wt%.

[0047] Step 2: Adopt the tape casting process, control the doctor blade height to be 0.5 mm, the tape casting speed to be 8 mm / s, and the temperature of the tape casting drying zone to be 65°C. Prepare a boron carbide ceramic green sheet (thickness 0.4) from the ceramic slurry in Step 1; adjust the laminated thickness to be 20 mm, the pressing temperature to be 65°C, the pressure to be 18 Mpa, and the holding time to be 6 min to prepare a boron carbide green body with 54 layers; conduct hot pressing sintering on the boron carbide green body. The pressure direction is perpendicular to the laminated direction, the pressure is 38 Mpa, and in an argon atmosphere, first heat up to 600°C at a heating rate of 1°C / min and hold for 2 h for degreasing, then continue to heat up to 2000°C at a rate of 3°C / min and hold for 4 h. After the holding is completed, cool down to 800°C at a rate of 5°C / min, and then cool with the furnace to obtain a high-strength and tough laminated boron carbide bulletproof ceramic.

[0048] The density of the laminated boron carbide bulletproof ceramic prepared in this example reaches 99.6%, the Vickers hardness is 51 GPa, the room temperature bending strength is 678 MPa, and the fracture toughness is 14.89 Mpa·m 1 / 2 。

[0049] Comparative Example 1

[0050] Step 1: Mix boron carbide powder and sintering aids in a mass ratio of 9:1, and place them in an acetone / ethanol mixed solvent (acetone:ethanol volume ratio is 1:1). The sintering aids are composed of yttrium oxide and cerium oxide with a mass ratio of 1:1. Then, add 2 wt% of PEI dispersant, 5 wt% of PVP binder, and 10 wt% of polyethylene glycol plasticizer based on the total mass of boron carbide powder and sintering aids. Achieve uniform dispersion of ceramic powder through planetary ball milling. The ball milling speed is 300 rpm / min, the ball milling time is 24 h, and the ball milling medium is boron carbide grinding balls with a diameter of 1 mm to obtain a ceramic slurry with a solid content of 80 wt%.

[0051] Step 2: Prepare a green body with a thickness of 20 mm from the ceramic powder by a press, and press it for 10 min at a temperature of 50 °C and a pressure of 10 Mpa to obtain a boron carbide green body. Perform hot press sintering on the boron carbide green body. The pressure direction is perpendicular to the lamination direction, the pressure is 30 Mpa, and in an argon atmosphere, first heat it to 600 °C at a heating rate of 1 °C / min and hold for 2 h for degreasing, then continue to heat it to 2100 °C at a heating rate of 3 °C / min and hold for 6 h. After the holding is completed, cool it to 800 °C at a cooling rate of 5 °C / min, and then cool it with the furnace to obtain boron carbide bulletproof ceramics.

[0052] The density of the laminated boron carbide bulletproof ceramics prepared in this comparative example reaches 97.9%, the Vickers hardness is 39 GPa, the room temperature flexural strength is 416 MPa, and the fracture toughness is 4.12 Mpa·m 1 / 2 。

[0053] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a layered boron carbide bulletproof ceramic, characterized in that: The following steps are involved: Step 1, adding boron carbide powder and sintering aid into a mixed solvent, then adding a dispersant, a binder and a plasticizer, mixing and ball milling to obtain a ceramic slurry; Step 2, using a tape casting process to prepare the ceramic slurry into a boron carbide ceramic green sheet; laminating and pressing the boron carbide ceramic green sheets, and then hot pressing and sintering to obtain the layered boron carbide bulletproof ceramic.

2. The method for preparing the layered boron carbide bulletproof ceramic according to claim 1, characterized in that: The mass ratio of the boron carbide powder to the sintering aid is 9:1 to 7:3; the sintering aid is a mixture of two of yttrium oxide, cerium oxide, erbium oxide, ytterbium oxide, lanthanum oxide and samarium oxide in a mass ratio of 1:

1.

3. The method for preparing the layered boron carbide bulletproof ceramic according to claim 1, characterized in that: The mixed solvent is a mixture of acetone and ethanol in a volume ratio of 1:1; the dispersant is a PEI dispersant; the binder is a PVP binder; and the plasticizer is a polyethylene glycol plasticizer.

4. The method for preparing the layered boron carbide bulletproof ceramic according to claim 1, characterized in that: The solid content of the ceramic slurry is 50wt% to 80wt%; the added amount of the dispersant is 0.5wt% to 2wt% of the total mass of the boron carbide powder and the sintering aid; the added amount of the binder is 1wt% to 5wt% of the total mass of the boron carbide powder and the sintering aid; the added amount of the plasticizer is 1 to 10wt% of the total mass of the boron carbide powder and the sintering aid.

5. The method for preparing the layered boron carbide bulletproof ceramic according to claim 1, characterized in that: The scraper height of the tape-casting process is 0.1-2 mm, the tape-casting speed is 1-10 mm / s, and the temperature of the tape-casting drying zone is 40-70° C.; the thickness of the boron carbide ceramic green sheet is 0.1-2 mm.

6. The method for preparing the layered boron carbide bulletproof ceramic according to claim 1, characterized in that: The number of the stacked layers is 50 to 300; the pressing temperature is 50 to 90° C., the pressure is 5 to 20 MPa, and the pressing time is 3 to 10 min; the thickness of the green body obtained by stacking the boron carbide ceramic green sheets is 5 to 60 mm.

7. The method for preparing the layered boron carbide bulletproof ceramic according to claim 1, characterized in that: The hot pressing sintering is specifically as follows: the pressure direction is perpendicular to the stacking direction, under the conditions of 20-40Mpa pressure and argon atmosphere, the temperature is first increased to 600°C at a heating rate of 1-5°C / min and kept for 2 hours for degreasing, and then the temperature is continued to be increased to 1850-2100°C at 3-8°C / min, kept for 1-6 hours, and then the temperature is reduced to 800°C at 1-5°C / min after the end of the keeping, and then cooled with the furnace.

8. The layered boron carbide bulletproof ceramic prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the layered boron carbide bulletproof ceramic as claimed in claim 8 in an armor protection system.