Method for preparing interlayer stress buffer structure gradient boron carbide
By preparing rare earth-boron carbide composite powder and encapsulating it with MXene dispersion to form a core-shell powder, and combining it with three-dimensional carbon nanotubes and metal powder, a 5-layer gradient composite intermediate layer powder was prepared, which solved the fracture problem of boron carbide armor under impact load and achieved high bonding strength and stability of the interlayer stress buffer structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI FINE NEW MATERIAL CO LTD
- Filing Date
- 2025-12-05
- Publication Date
- 2026-05-19
AI Technical Summary
Existing boron carbide armor is prone to fracture under impact loads and suffers from interlayer stress mismatch, leading to interface cracking and failure. Traditional transition layers have insufficient bonding strength and discontinuous performance gradient changes, making it difficult to effectively buffer impact energy.
Rare earth-boron carbide composite powder is encapsulated with MXene dispersion to form a core-shell powder, which is combined with three-dimensional carbon nanotubes and metal powder. A five-layer gradient composite intermediate layer powder is prepared by ball milling. After casting, it is stacked with a pre-sintered ceramic layer and hot-pressed to form an interlayer stress buffer structure.
It significantly improves the interfacial bonding strength and overall stability, and forms a continuous transition layer through gradient distribution and chemical reaction, effectively buffering interlayer stress and extending the failure time of the armor.
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Figure CN121653498B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of boron carbide preparation technology, and in particular to a method for preparing gradient boron carbide with interlayer stress buffer structure. Background Technology
[0002] In the field of armor protection materials, boron carbide (B4C) has become a core material for lightweight armor due to its ultra-high hardness, low density, and excellent ballistic performance. However, its inherent brittleness makes it prone to sudden fracture under impact loads, limiting its application potential. To overcome this deficiency, ceramic-metal composite armor technology has emerged, which combines boron carbide ceramics with a metal backing plate, utilizing the ductility of the metal to absorb energy and improve overall toughness. However, the "ceramic-metal" binary structure has drawbacks: the physical properties of the two components differ greatly (poor matching of thermal expansion coefficients, elastic moduli, etc.), and severe thermal and mechanical stresses are easily generated between the layers during sintering and service impacts, leading to interface cracking, delamination, and other failures, thus weakening protective effectiveness.
[0003] Traditional solutions alleviate stress by introducing a transition layer, but this approach has limitations: First, transition layers often use a single material or a simple mixture, resulting in insufficient interfacial bonding strength with the ceramic and metal layers, making them prone to stress concentration points. Second, the performance gradient is discontinuous, failing to achieve a smooth transition from the high hardness of ceramics to the high toughness of metals. Third, the transition layer itself has weak impact resistance, making it difficult to effectively transfer and absorb impact energy. Furthermore, boron carbide sintering requires the addition of additives and high-temperature processes, further exacerbating thermal mismatch with the metal layer. Traditional powder mixing and molding processes also struggle to precisely control the compositional gradient of the transition layer, leading to poor consistency and reliability of the armor structure.
[0004] Therefore, two core issues urgently need to be addressed: first, how to construct a strong and tough interface that effectively buffers interlaminar stress while ensuring high bonding strength and preventing interface debonding; and second, how to achieve continuous gradient matching of material properties so that the armor can absorb energy step by step during impact and extend the failure time. Developing an interlaminar stress buffer structure with smooth performance transition, strong interlaminar bonding, and excellent impact resistance has become the key to improving the overall protective effectiveness of boron carbide gradient armor. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this application provides a method for preparing a gradient boron carbide interlayer stress buffer structure. The main steps include: firstly, preparing rare earth-boron carbide composite powder, then encapsulating it with MXene dispersion via electrostatic adsorption to form a core-shell powder; mixing the core-shell powder, three-dimensional carbon nanotubes, and titanium and aluminum metal powders in a specific ratio, and ball-milling each mixture to obtain a 5-layer gradient composite intermediate layer powder; simultaneously, preparing a boron carbide mixed powder containing sintering aids and pre-sintering it; casting the gradient composite intermediate layer powder to obtain a gradient layer; then stacking the pre-sintered ceramic layer with the gradient layer, performing hot-pressing sintering for interface strengthening; finally, cooling, processing, and surface polishing the sintered structure to obtain an interlayer stress buffer structure, improving the interfacial performance and overall stability of the entire interlayer stress buffer structure.
[0006] To achieve the above objectives, this application adopts the following technical solution:
[0007] This application provides a method for preparing a gradient boron carbide interlayer stress buffer structure, comprising: preparing rare earth-boron carbide composite powder, encapsulating it with MXene dispersion through electrostatic adsorption to form a core-shell powder, mixing the core-shell powder, three-dimensional carbon nanotubes, and titanium and aluminum metal powders in proportion, ball milling them to obtain 5 layers of gradient composite intermediate layer powder, casting the gradient composite intermediate layer powder to obtain a gradient layer, pre-sintering the boron carbide mixed powder containing sintering aid to obtain a pre-sintered ceramic layer, stacking the pre-sintered ceramic layer and the gradient layer together and then hot-pressing and sintering them, and cooling, processing and surface polishing the sintered structure to obtain an interlayer stress buffer structure.
[0008] Preferably, the preparation process of the boron carbide mixed powder containing sintering aid is as follows: weigh boron carbide powder and titanium boride sintering aid, with a mass ratio of boron carbide powder to titanium boride sintering aid of (12-20):1, use anhydrous ethanol as medium, mix in a boron carbide ball mill jar at a ball-to-material ratio of 5:1 and a rotation speed of 250-300 rpm for 3-4 hours, dry at 80-90℃ and pass through a 200-mesh sieve to obtain the boron carbide mixed powder containing sintering aid.
[0009] Preferably, the preparation process of the rare earth-boron carbide composite powder is as follows: lanthanum trioxide and boron carbide powder are weighed at a mass ratio of 1:5, and ball-milled for 4-6 hours under argon protection at a rotation speed of 400-600 rpm and a ball-to-material ratio of 15:1.
[0010] Preferably, the preparation process of the core-shell powder is as follows: etching the Ti2AlC MAX phase with hydrofluoric acid, ultrasonically peeling and centrifuging, taking the supernatant to obtain MXene dispersion; adding rare earth-boron carbide composite powder to MXene dispersion at a mass ratio of 10:1, adjusting the pH to 6.0-7.0, magnetically stirring for 1-2 hours, and then centrifuging, washing and freeze-drying to obtain the powder.
[0011] Preferably, the mass ratio of the core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:(9-15):700. The content of three-dimensional carbon nanotubes in the five-layer gradient composite intermediate layer powder decreases from the ceramic side to the metal side. Each layer of gradient composite intermediate layer powder is ball-milled for 3-4 hours under argon protection at a speed of 300-500 rpm and a ball-to-material ratio of 10:1.
[0012] Preferably, the five-layer gradient layer is prepared by a five-layer gradient composite intermediate layer powder, wherein the first layer is ceramic-side and the fifth layer is metal-side, wherein:
[0013] In the first layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:15:700;
[0014] In the second layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:13:700;
[0015] In the third layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:11:700;
[0016] In the fourth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:10:700;
[0017] In the fifth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:9:700.
[0018] Preferably, the pre-sintering of the boron carbide mixed powder containing sintering aids includes: cold isostatic pressing the boron carbide mixed powder containing sintering aids at 200 MPa to obtain a green body, and then performing spark plasma sintering at 1850°C and 50 MPa for 10-15 minutes in a vacuum environment.
[0019] Preferably, the process of casting the gradient composite intermediate layer powder involves adding 8-10% polyvinyl alcohol and 2-4% polyethylene glycol plasticizer by mass to the gradient composite intermediate layer powder, mixing and ball milling, casting the mixture onto a polyethylene terephthalate film using a gradient scraper, drying the film, and then cutting it into preforms.
[0020] Preferably, the layers are stacked on a graphite mold, and ethanol is sprayed between the layers.
[0021] Preferably, the hot pressing sintering is performed as follows: in an environment with an argon flow rate of 50-60 mL / min, the temperature is increased to 1000℃ at 10℃ / min, and then increased to 1750℃±20℃ at 5℃ / min, and held at that temperature for 2-3 days.
[0022] Beneficial technical effects:
[0023] In the preparation of rare earth-boron carbide composite powder, the introduced lanthanum trioxide reacts with the metal phase (aluminum) and the surface of boron carbide in the subsequent gradient layer. The reaction of lanthanum trioxide with the boron carbide surface generates rare earth aluminate phases such as LaAlO3. LaAlO3 fills the micropores at the boron carbide-metal interface, reducing interfacial porosity. LaAlO3 also strengthens interfacial bonding through ionic bonding, significantly enhancing interfacial adhesion. During the preparation of the gradient composite intermediate layer powder and subsequent hot-pressing sintering, titanium in the metal powder reacts with boron carbide. The TiB2 and TiC phases generated by the reaction of titanium and boron carbide are both high-hardness ceramic phases with high lattice matching with boron carbide, forming a continuous reinforcing transition layer at the interface. LaAlO3 eliminates interfacial defects through chemical filling, while TiB2 / TiC enhances interfacial bonding strength through structural matching, jointly improving interfacial adhesion and preventing interlayer delamination. Simultaneously, in the gradient composite intermediate layer powder, the three-dimensional carbon nanotubes exhibit a gradient distribution decreasing from the ceramic side to the metal side. Three-dimensional carbon nanotubes on the ceramic side can bind to the boron carbide and TiB2 / TiC surfaces through van der Waals forces, further suppressing the initiation of interfacial cracks. As the transition towards the metal side occurs, the content of three-dimensional carbon nanotubes decreases, and their interfacial reaction with the metal phases (Al, Ti) gradually weakens, avoiding the decrease in toughness on the metal side due to excessive brittle phases. This gradient distribution, combined with the interfacial strengthening effect of rare earth aluminate phases and TiB2 / TiC, forms a spatial complement, enabling a smooth transition of interfacial bonding strength from the ceramic side to the metal side, reducing stress abrupt changes. This, along with the hot-pressing sintering interfacial strengthening step after the pre-sintered ceramic layer and gradient layer stack assembly, ultimately significantly improves the interfacial performance and overall stability of the entire interlayer stress buffer structure. Attached Figure Description
[0024] Figure 1 This is a process flow diagram of a method for preparing a gradient boron carbide structure with interlayer stress buffer. Detailed Implementation
[0025] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. However, this should not be construed as limiting the scope of this application to the following embodiments. All other embodiments obtained by those skilled in the art without creative effort, without departing from the above-described methodological spirit, are within the scope of protection of this application.
[0026] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.
[0027] The singular forms “for,” “a,” “any one,” and “as described” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.
[0028] Furthermore, the terms "first" and "second" appearing in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0029] The following describes in detail, with reference to different embodiments, a method for preparing an interlayer stress buffer structure gradient boron carbide provided in this application.
[0030] Example 1
[0031] like Figure 1 As shown, a method for preparing an interlayer stress buffer structure gradient boron carbide includes the following steps:
[0032] S1. Weigh lanthanum trioxide and boron carbide powders at a mass ratio of 1:5, and ball mill them for 5 hours under argon protection at a speed of 500 rpm and a ball-to-particle ratio of 15:1, so that rare earth ions are adsorbed on the surface of boron carbide particles to obtain rare earth-boron carbide composite powder.
[0033] S2. Etch the Ti2AlC MAX phase with hydrofluoric acid, ultrasonically peel it off, and centrifuge at 5000 rpm for 10 min. Take the supernatant to obtain a monolayer MXene dispersion with a concentration of 2 mg / mL.
[0034] Rare earth-boron carbide composite powder was added to MXene dispersion at a mass ratio of 10:1, the pH was adjusted to 6.5, the mixture was magnetically stirred for 1.5 h, centrifuged, washed, and freeze-dried to obtain core-shell powder.
[0035] S3. Weigh the core-shell powder and mix it with three-dimensional carbon nanotubes (CNTs) and metal powders (Ti and Al powders) to obtain a mixed powder. Divide the mixed powder into 5 portions, and ball mill each portion separately under argon protection at a speed of 400 rpm, a ball-to-powder ratio of 10:1, and a time of 3.5 h to obtain a 5-layer gradient composite intermediate layer powder.
[0036] S4. Weigh boron carbide powder, add titanium boride sintering aid, put it into a boron carbide ball mill jar, use anhydrous ethanol as medium, ball-to-powder ratio 5:1, speed 300 rpm, mix for 3 hours, dry at 85℃ and pass through a 200-mesh sieve to obtain boron carbide mixed powder containing sintering aid; the mass ratio of boron carbide powder to titanium boride sintering aid is 15:1.
[0037] S5. The boron carbide mixed powder containing sintering aid is loaded into a rubber mold, held at 200MPa for 10min to obtain a green body, and then subjected to discharge plasma sintering at 1850℃ and 50MPa for 10min in a vacuum environment.
[0038] Add 9% polyvinyl alcohol and 3% polyethylene glycol plasticizer by mass to the gradient composite intermediate layer powder, mix and ball mill, then cast on a polyethylene terephthalate film using a gradient scraper, dry and cut into preforms to obtain the gradient layer. The first layer is the ceramic side and the fifth layer is the metal side, wherein the content of three-dimensional carbon nanotubes decreases from the ceramic side to the metal side.
[0039] In the first layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:15:700;
[0040] In the second layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:13:700;
[0041] In the third layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:11:700;
[0042] In the fourth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:10:700;
[0043] In the fifth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:9:700.
[0044] After stacking the boron carbide ceramic layer and the first to fifth layers in sequence, the layers are placed in a graphite mold, and ethanol is sprayed between the layers to enhance temporary adhesion.
[0045] In an environment with an argon flow rate of 55 mL / min, the temperature was increased to 1000℃ at 10℃ / min, then increased to 1750℃ at 5℃ / min, and held for 2.5 h. At 1000℃, 10 MPa was applied, and at 1400℃, the pressure was increased to 35 MPa.
[0046] S6. After cooling to 200℃ in the furnace, the material is removed, wire-cut to the target size, rough-ground with a diamond wheel, and fine-polished with 1μm diamond polishing fluid to obtain an interlayer stress buffer structure.
[0047] Example 2
[0048] like Figure 1 As shown, a method for preparing an interlayer stress buffer structure gradient boron carbide includes the following steps:
[0049] S1. Weigh lanthanum trioxide and boron carbide powders at a mass ratio of 1:5, and ball mill them for 6 hours under argon protection at a speed of 400 rpm and a ball-to-particle ratio of 15:1, so that rare earth ions are adsorbed on the surface of boron carbide particles to obtain rare earth-boron carbide composite powder.
[0050] S2. Etch the Ti2AlC MAX phase with hydrofluoric acid, ultrasonically peel it off, and centrifuge at 8000 rpm for 10 min. Take the supernatant to obtain a monolayer MXene dispersion with a concentration of 2 mg / mL.
[0051] Rare earth-boron carbide composite powder was added to MXene dispersion at a mass ratio of 10:1, pH was adjusted to 6.0, magnetic stirring was performed for 1 hour, and the powder was then centrifuged, washed, and freeze-dried to obtain core-shell powder.
[0052] S3. Weigh the core-shell powder and mix it with three-dimensional carbon nanotubes (CNTs) and metal powders (Ti and Al powders) to obtain a mixed powder. Divide the mixed powder into 5 parts, and ball mill each layer of powder separately under argon protection at a speed of 300 rpm, a ball-to-powder ratio of 10:1, and a time of 3 hours to obtain a 5-layer gradient composite intermediate layer powder.
[0053] S4. Weigh boron carbide powder, add titanium boride sintering aid, place in a boron carbide ball mill jar, use anhydrous ethanol as the medium, a ball-to-powder ratio of 5:1, a rotation speed of 250 rpm, mix for 4 hours, then dry at 80℃ and pass through a 200-mesh sieve to obtain a mixed boron carbide powder containing the sintering aid. The mass ratio of boron carbide powder to titanium boride sintering aid is 12:1.
[0054] S5. The boron carbide mixed powder containing sintering aids is loaded into a rubber mold and held at 200 MPa for 15 min to obtain a green body. Then, it is subjected to discharge plasma sintering at 1850℃ and 50 MPa for 10 min in a vacuum environment.
[0055] Add 8% polyvinyl alcohol and 2% polyethylene glycol plasticizer by mass to the gradient composite intermediate layer powder, mix and ball mill, then cast on a polyethylene terephthalate film using a gradient scraper, dry and cut into preforms to obtain the gradient layer. The first layer is the ceramic side and the fifth layer is the metal side, wherein the content of three-dimensional carbon nanotubes decreases from the ceramic side to the metal side.
[0056] In the first layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:15:700;
[0057] In the second layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:13:700;
[0058] In the third layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:11:700;
[0059] In the fourth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:10:700;
[0060] In the fifth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:9:700.
[0061] After stacking the boron carbide ceramic layer and the first to fifth layers in sequence, the layers are placed in a graphite mold, and ethanol is sprayed between the layers to enhance temporary adhesion.
[0062] In an environment with an argon flow rate of 55 mL / min, the temperature was increased to 1000℃ at 10℃ / min, then increased to 1750℃ at 5℃ / min, and held for 2.5 h. At 1000℃, 10 MPa was applied, and at 1400℃, the pressure was increased to 35 MPa.
[0063] S6. After cooling to 250°C in the furnace, the material is removed, wire-cut to the target size, rough-ground with a diamond wheel, and fine-polished with 1μm diamond polishing fluid to obtain an interlayer stress buffer structure.
[0064] Example 3
[0065] like Figure 1 As shown, a method for preparing an interlayer stress buffer structure gradient boron carbide includes the following steps:
[0066] S1. Weigh lanthanum trioxide and boron carbide powder at a mass ratio of 1:5, and ball mill for 4 hours under argon protection at a speed of 600 rpm and a ball-to-particle ratio of 15:1, so that rare earth ions are adsorbed on the surface of boron carbide particles to obtain rare earth-boron carbide composite powder.
[0067] S2. Etch the Ti2AlC MAX phase with hydrofluoric acid, ultrasonically peel it off, and centrifuge at 5000 rpm for 10 min. Take the supernatant to obtain a monolayer MXene dispersion with a concentration of 2 mg / mL.
[0068] Rare earth-boron carbide composite powder was added to MXene dispersion at a mass ratio of 10:1, pH was adjusted to 7.0, magnetic stirring was carried out for 2 hours, and after centrifugation, washing and freeze drying were performed to obtain core-shell powder.
[0069] S3. Weigh the core-shell powder and mix it with three-dimensional carbon nanotubes (CNTs) and metal powders (Ti and Al powders) to obtain a mixed powder. Divide the mixed powder into 5 portions, and ball mill each portion separately under argon protection at a speed of 500 rpm, a ball-to-powder ratio of 10:1, and a time of 4 hours to obtain a 5-layer gradient composite intermediate layer powder.
[0070] S4. Weigh boron carbide powder, add titanium boride sintering aid, place in a boron carbide ball mill jar, use anhydrous ethanol as the medium, a ball-to-powder ratio of 5:1, a rotation speed of 300 rpm, mix for 4 hours, then dry at 90℃ and pass through a 200-mesh sieve to obtain a mixed boron carbide powder containing the sintering aid. The mass ratio of boron carbide powder to titanium boride sintering aid is 20:1.
[0071] S5. The boron carbide mixed powder containing sintering aids is loaded into a rubber mold and held at 200 MPa for 15 min to obtain a green body. Then, it is subjected to discharge plasma sintering at 1850℃ and 50 MPa for 15 min in a vacuum environment.
[0072] 10% polyvinyl alcohol and 4% polyethylene glycol plasticizer by mass were added to the gradient composite intermediate layer powder. After mixing and ball milling, the mixture was cast onto a polyethylene terephthalate film using a gradient scraper. After drying, it was cut into preforms to obtain the gradient layer. The first layer was the ceramic side and the fifth layer was the metal side. The content of three-dimensional carbon nanotubes decreased from the ceramic side to the metal side.
[0073] In the first layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:15:700;
[0074] In the second layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:13:700;
[0075] In the third layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:11:700;
[0076] In the fourth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:10:700;
[0077] In the fifth layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder is 300:9:700.
[0078] After stacking the boron carbide ceramic layer and the first to fifth layers in sequence, the layers are placed in a graphite mold, and ethanol is sprayed between the layers to enhance temporary adhesion.
[0079] In an environment with an argon flow rate of 55 mL / min, the temperature was increased to 1000℃ at 10℃ / min, then increased to 1750℃ at 5℃ / min, and held for 2.5 h. At 1000℃, 10 MPa was applied, and at 1400℃, the pressure was increased to 35 MPa.
[0080] S6. After cooling to 300℃ in the furnace, the material is removed, wire-cut to the target size, rough-ground with a diamond wheel, and fine-polished with 1μm diamond polishing fluid to obtain an interlayer stress buffer structure.
[0081] Comparative Example 1
[0082] A method for preparing an interlayer stress buffer structure gradient boron carbide, which differs from Example 1 in that it does not include rare earth-boron carbide composite powder.
[0083] Comparative Example 2
[0084] A method for preparing an interlayer stress buffer structure gradient boron carbide, which differs from Example 1 in that core-shell powder is not added.
[0085] The performance of the interlayer stress buffer structure gradient boron carbide prepared in Examples 1-3 and Comparative Examples 1-2 was tested, and the test results are shown in Table 1.
[0086] Test the interfacial bonding strength: The prepared interfacial stress buffer structure is made into a three-point bending specimen. The fracture load is measured by loading, and the interfacial bonding strength is calculated based on the specimen size.
[0087] Interlayer stress distribution testing: The stress distribution is obtained by recording minute interlayer deformations through laser interferometry and combining the results with finite element model inversion.
[0088] Measuring ballistic maximum velocity: A 12.7mm caliber ballistic gun was used to fire a hard alloy projectile at a velocity of 1200m / s, and the projectile's penetration process was recorded by a high-speed camera;
[0089] Impact wear volume test: A sample containing the complete gradient layer, measuring 50mm×50mm×10mm, was taken. The test surface was the impact-bearing surface of the armor. After 5000 impacts with 20J, the wear volume of the sample was measured.
[0090] Table 1. Test results of interlaminar stress buffer structures prepared in the examples and comparative examples.
[0091]
[0092] As shown in Table 1, the interfacial bonding strength, interlayer stress distribution, ballistic limiting velocity, and impact wear volume of Examples 1-3 are all superior to those of Comparative Examples 1-2. This is because the MXene surface in the examples has functional groups such as -OH and -F, which result in stronger electrostatic adsorption with the rare earth-boron carbide composite powder, forming a more uniform core-shell structure. Its layered structure combines high toughness and conductivity, and can act as a stress buffer layer to absorb impact energy and inhibit crack propagation from the ceramic side to the metal side. Comparative Example 1 lacks rare earth-boron carbide composite powder, and Comparative Example 2 lacks core-shell powder, so it cannot effectively transfer stress. The CNTs in Examples 1-3 capture cracks through the bridging effect, and their conductivity can disperse impact loads through electron tunneling, reducing local stress concentration. TiB2, generated by the in-situ reaction of Ti with B4C at high temperature, is both a reinforcing phase and a transition phase at the ceramic-metal interface, improving the interfacial bonding strength. In the embodiments, Al exhibits high plasticity and undergoes plastic deformation under impact loads, absorbing impact energy through energy dissipation effects. In contrast, Cr / Fe readily forms brittle intermetallic compounds, which exacerbates interfacial cracking.
[0093] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.
[0094] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.
Claims
1. A method for preparing a gradient boron carbide interlayer stress buffer structure, characterized in that, Includes the following steps: After preparing rare earth-boron carbide composite powder, a core-shell powder was formed by electrostatic adsorption and encapsulation with MXene dispersion. The core-shell powder, three-dimensional carbon nanotubes, and titanium and aluminum metal powders were mixed in a specific ratio and ball-milled to obtain a five-layer gradient composite intermediate layer powder. The gradient composite intermediate layer powder was then cast to form a gradient layer. A pre-sintered boron carbide mixed powder containing sintering aids was pre-sintered to obtain a pre-sintered ceramic layer. The pre-sintered ceramic layer and the gradient layer were stacked and assembled, followed by hot-pressing sintering. The sintered structure was then cooled, processed, and surface-polished to obtain an interlayer stress buffer structure. The preparation process of the rare earth-boron carbide composite powder was as follows: lanthanum trioxide and boron carbide powders were weighed at a mass ratio of 1:5 and ball-milled for 4-6 hours under argon protection at a speed of 400-600 rpm and a ball-to-material ratio of 15:
1. The preparation process of the core-shell powder was as follows: Ti2AlC was etched with hydrofluoric acid. The MAX phase was ultrasonically exfoliated and centrifuged to obtain an MXene dispersion from the supernatant. Rare earth-boron carbide composite powder was added to the MXene dispersion at a mass ratio of 10:1, the pH was adjusted to 6.0-7.0, and the mixture was magnetically stirred for 1-2 hours. After centrifugation, washing, and freeze-drying, the 5-layer gradient composite intermediate layer powder was obtained. The first layer was ceramic-side, and the fifth layer was metal-side. The mass ratio of the core-shell powder, three-dimensional carbon nanotubes, titanium and aluminum metal powder was 300:(9-15):
700. The content of three-dimensional carbon nanotubes in the 5-layer gradient composite intermediate layer powder decreased from the ceramic side to the metal side.
2. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, The preparation process of the boron carbide mixed powder containing sintering aid is as follows: weigh boron carbide powder and titanium boride sintering aid, with a mass ratio of boron carbide powder to titanium boride sintering aid of (12-20):
1. Using anhydrous ethanol as the medium, mix in a boron carbide ball mill jar at a ball-to-material ratio of 5:1 and a rotation speed of 250-300 rpm for 3-4 hours. Dry at 80-90℃ and pass through a 200-mesh sieve to obtain the boron carbide mixed powder containing sintering aid.
3. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, Each layer of gradient composite intermediate powder was ball-milled for 3-4 hours under argon protection at a speed of 300-500 rpm and a ball-to-material ratio of 10:
1.
4. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, In the first layer, the mass ratio of core-shell powder, three-dimensional carbon nanotubes, titanium, and aluminum powder is 300:15:700; in the second layer, the mass ratio is 300:13:700; in the third layer, the mass ratio is 300:11:700; in the fourth layer, the mass ratio is 300:10:700; and in the fifth layer, the mass ratio is 300:9:
700.
5. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, The pre-sintering of the boron carbide mixed powder containing sintering aids includes: cold isostatic pressing the boron carbide mixed powder containing sintering aids at 200 MPa to obtain a green body, and then performing spark plasma sintering at 1850℃ and 50 MPa for 10-15 minutes in a vacuum environment.
6. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, The process of casting the gradient composite intermediate layer powder involves adding 8-10% polyvinyl alcohol and 2-4% polyethylene glycol plasticizer by mass to the gradient composite intermediate layer powder, mixing and ball milling, casting the mixture onto a polyethylene terephthalate film using a gradient scraper, drying the film, and then cutting it into preforms.
7. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, The stack assembly is as follows: pre-sintered ceramic layers and gradient layers are stacked sequentially on a graphite mold, and ethanol is sprayed between the layers.
8. The method for preparing an interlayer stress buffer structure gradient boron carbide according to claim 1, characterized in that, The hot pressing sintering process is as follows: in an environment with an argon flow rate of 50-60 mL / min, the temperature is increased to 1000℃ at a rate of 10℃ / min, and then increased to 1750℃±20℃ at a rate of 5℃ / min, and held at that temperature for 2-3 hours.