A gradient self-healing basalt fiber composite ceramic armor plate and a preparation method thereof

Abstract

This invention belongs to the field of high-performance composite materials and individual / light armor protection technology, specifically involving a gradient self-healing basalt fiber composite ceramic armor plate and its preparation method. It employs a three-dimensional woven structure to physically eliminate the layering interface, utilizing an integrally continuous fiber skeleton to achieve continuous load transfer, transforming the armor from "interlayer physical stacking" to "structural integration," effectively improving the problem of interlayer delamination. The invention uses slurry impregnation combined with multi-dimensional gradient zoning to effectively balance "deep damage repair" and "damage resistance." Preliminary layered impregnation of components is achieved through "sidewall graded interface directional flow," and is immediately combined with "stepwise in-situ gelation" to construct a temporary physical barrier layer, realizing the construction of a precise gradient structure within the interconnected pores.

Description

Technical Field

[0001] This invention belongs to the field of high-performance composite materials and individual / light armor protection technology, specifically relating to a gradient self-healing basalt fiber composite ceramic armor plate and its preparation method. Background Technology

[0002] With the escalating threats on modern battlefields, stringent requirements have been placed on protective armor, demanding that it be lightweight, resistant to multiple attacks, and possess both penetration resistance and energy absorption capabilities. Existing technologies suffer from the following significant shortcomings: 1. Weak interlayer bonding and poor resistance to multiple hits: Traditional ceramic composite armor mostly adopts a physical lamination structure of "ceramic faceplate + fiber backplate". Under the action of ballistic shock wave, the interface of heterogeneous materials is very prone to reflected tensile wave damage, causing the faceplate and backplate to separate prematurely, making the armor's protection capability almost zero when hit by a second bullet.

[0003] 2. The ceramic matrix is ​​brittle and has poor deep damage repair efficiency: Although high-hardness ceramics (such as silicon carbide and boron carbide) have strong penetration resistance, their fracture toughness is low, making them highly susceptible to cracking due to impact. While existing technologies attempt to introduce self-healing microcapsules to endow ceramics with repair capabilities (such as mixing microcapsules into ceramic coatings or filling pores), the following bottlenecks remain for armor protection scenarios: (1) Limitations of repair dimensions: Existing technologies mostly employ surface spraying or macroscopic filling, with repair factors remaining only on the material surface. Faced with penetrating damage caused by ballistic strikes, the repair components cannot reach the core of the deep damage; (2) Imbalance between penetration resistance hardness and self-healing efficacy: In the existing technology, the introduction of self-healing components often leads to a decrease in the overall hardness of ceramics, making it difficult to balance the requirements of "high hardness on the impact-facing surface" and "high healing on the back impact-facing surface".

[0004] 3. Difficulty in controlling the gradient manufacturing process: Theoretical studies have shown that functionally graded materials can effectively alleviate stress concentration. However, in monolithic fiber preforms, liquid ceramic slurry is prone to disordered flow and mixing under capillary action and gravity. Existing vacuum infusion or RTM processes struggle to achieve gradient construction with "clear boundaries between layers and precise component partitioning," often resulting in the designed "hard on the outside and tough on the inside" structure becoming a "homogeneous mixture" during fabrication, thus losing its gradient advantage. CN120667978A discloses a method for preparing a recrystallized silicon carbide matrix, wherein steps (1) and (2) both involve vacuum impregnation at a vacuum level of -0.0095 MPa to 0.1 MPa. In its process logic, the slurry is integrally filled into the pores of the matrix. Due to the lack of spatial partition control and real-time blocking mechanism for the impregnation process, when this conventional vacuum infusion process is applied to a fiber preform with three-dimensional interconnected pores, the slurry will flow disorderly throughout the entire skeleton due to strong capillary action and pressure difference. This inevitably leads to severe diffusion and mixing of different slurry components at the interface, causing the expected gradient structure to degenerate into a homogeneous mixture, affecting the elastic performance and self-healing efficiency.

[0005] 4. Gradient manufacturing control is difficult and lacks multidimensional damage pattern matching: Existing conventional solutions fail to meet the asymmetric damage physical characteristics of armor when hit by projectiles, which involve "shattering on the front and tearing on the back." Due to the lack of targeted multidimensional damage mode matching design, the distribution of self-healing factors is disconnected from the ballistic stress field, making it difficult to meet the dual requirements of high hardness of the outer layer and high healing efficiency of the inner layer, thus limiting the damage tolerance and full life protection cycle of the armor plates. Summary of the Invention

[0006] To address the technical problems of existing laminated armor, such as easy delamination under ballistic impact, weak resistance to multiple strikes, and the inability of existing self-healing methods to repair deep penetrating damage and the disconnect between the distribution of self-healing factors and the ballistic stress field, this invention provides a gradient self-healing basalt fiber composite ceramic armor plate and its preparation method. This armor plate utilizes an integral three-dimensional woven structure to bridge macroscopic layers, employs interfacial chemical "molecular bridges" to enhance bonding, and utilizes gradient-distributed self-healing microcapsules to achieve damage repair. Furthermore, it incorporates a unique visual flow guidance and stepwise gelation process to achieve precise gradient construction of components within a fully connected fiber skeleton. The present invention addresses the above problems through the following technical means: (1) For the peeling problem: a continuous reinforcing skeleton is constructed using an overall three-dimensional woven structure, which effectively bridges the physical boundaries between layers; (2) For the repair depth bottleneck: a gradient impregnation process is adopted after slurrying with microcapsules and ceramic powder, so that the repair factors are deeply embedded in the micro gaps of the fiber skeleton, achieving damage self-healing in the full thickness dimension; (3) For the performance balance problem: with the sidewall graded interface directional flow and step-by-step in-situ gelation process, a component gradient is precisely constructed in the overall connected skeleton, achieving an asymmetric match between high hardness of the impact surface and high repair capability of the back surface.

[0007] This invention employs a three-dimensional woven structure to physically eliminate the layered interface, utilizing an integrally continuous fiber skeleton to achieve continuous load transfer, transforming the armor from "physical stacking between layers" to "structural integration," effectively improving the problem of interlayer delamination; it adopts slurry impregnation + multi-dimensional gradient zoning to effectively balance "deep damage repair" and "damage resistance," achieving initial layered impregnation of components through "sidewall graded interface directional flow," and immediately cooperating with "stepwise in-situ gelation" to construct a temporary physical barrier layer, realizing the construction of a precise gradient structure within the connected pores.

[0008] This invention addresses the requirement of the outer layer of the projectile-facing surface to withstand extremely high-pressure stress fragmentation in warheads by combining low-content microcapsules with high-hardness ceramics to maintain the integrity of the matrix. Conversely, it addresses the vulnerability of the inner layer to tearing damage caused by reflected tensile waves by combining high-content microcapsules with high-toughness ceramics, along with a high-density fiber support layer to absorb residual momentum. Through "sidewall guidance" and "stepwise gelation" processes, this invention achieves accurate multi-dimensional gradient partitioning of fibers, ceramics, and microcapsules in three-dimensional space within interconnected pores, overcoming the challenge of performance imbalance among components under complex protection requirements.

[0009] This invention prepares three gradient slurries by combining microcapsules with ceramic powder of varying contents, and then impregnates them using a stepwise vacuum flow process. This allows the repair factors to be deeply embedded in the microscopic gaps of the three-dimensional woven fibers, achieving self-healing capability implanted throughout the entire thickness direction. The actively designed gradient slurries with low A-phase, medium B-phase, and high C-phase content, combined with the physical constraints created by the stepwise in-situ gelation process, effectively ensure that the outer layer maintains high hardness to break up projectiles, while the inner layer is enriched with repair factors to cope with tearing damage. This combination of "component gradient control" and "three-dimensional fiber skeleton" significantly alleviates the problem of concentration mixing of self-healing factors in interconnected pores, improving the damage tolerance of the armor.

[0010] The main innovation of this invention lies in: 1. Material selection for SPS sintering process The innovative use of basalt fiber to replace carbon fiber (which is easily oxidized) and glass fiber (which has low temperature resistance) solves the problem of fiber damage or performance degradation in ceramic matrix composites during rapid sintering.

[0011] 2. Structure-oriented functional gradient integration Employing a holistic three-dimensional woven structure with a "sparse outer layer and dense inner layer," the Z-direction bonding yarns effectively bridge the interlayer boundaries, achieving a leap from "interfacial physical bonding" to "continuous cross-layer structure." By inducing a gradient distribution of matrix components through fiber density gradients, a smooth functional transition is constructed from the "high hardness and penetration resistance" of the outer layer to the "high toughness and energy absorption" of the inner layer. This effectively solves the problem of easy interface peeling caused by abrupt changes in mechanical properties in traditional laminated armor, improving its resistance to multiple attacks.

[0012] 3. Dual-bonding interface "molecular bridge" A two-way chemical anchoring structure of "fiber-covalent bond-coupling agent-ether bond / Si-N bond-matrix" was constructed. A silane coupling agent was used to establish a stable chemical connection between inorganic basalt fibers and the organic-inorganic composite matrix, thereby improving the interfacial bonding strength.

[0013] 4. Damage pattern matching gradient self-healing Based on the physical characteristics of armor plate damage—"surface crushing and back tearing"—a gradient distribution of self-healing microcapsules with "lower outer layer and higher inner layer" was designed. This maximizes the crack repair and structural restoration capabilities of the inner layer while ensuring the hardness of the outer layer, thereby extending equipment lifespan.

[0014] 5. Visualized flow guidance and step-by-step gel molding (process support) The pioneering "sidewall vacuum diversion + stepwise in-situ gelation" process overcomes the manufacturing challenge of achieving precise partitioning of multi-component slurry in a connected fiber skeleton by utilizing physical flow field confinement and temporary curing blocking technology.

[0015] The specific technical solution of this invention is as follows: The preparation method of gradient self-healing basalt fiber composite ceramic armor plate mainly consists of the following interconnected stage modules: Phase 1: Preparation of basalt fiber three-layer gradient structure preform and construction of surface molecular bridges; Phase 2: Synthesis of polyurea-formaldehyde (UF)-coated dicyclopentadiene (DCPD) self-healing microcapsules; Phase 3: Preparation of ceramic slurry with rheological gradient; Phase 4: Gradient impregnation molding based on visual flow guidance and stepwise in-situ gelation; Phase 5: Gradient degreasing and spark plasma sintering (SPS).

[0016] More specifically, the preparation method of the gradient self-healing basalt fiber composite ceramic armor plate includes the following specific steps.

[0017] Phase 1: Preparation of basalt fiber three-layer gradient structure preform and construction of surface molecular bridges; (1) Gradient weaving (thickness and weft density control): Using continuous basalt fiber with a linear density of 1200-2400 tex as raw material, a three-layer gradient structure prefabricated body is constructed along the thickness direction of the prefabricated body by a computer-controlled three-dimensional braiding machine. The three-layer gradient structure prefabricated body is divided into an outer layer, a middle layer and an inner layer. The weft density gradually increases and the braiding angle gradually decreases from the outer layer to the inner layer.

[0018] In the three-layer gradient structure prefabricated body, the three layers are physically interlocked throughout the thickness through Z-direction knotting yarns. During the weaving process, the Z-direction yarns shuttle along the thickness direction, tightly binding the warp and weft yarns of the outer, middle and inner layers. This structure enhances the interlayer bonding stability under elasticity and effectively suppresses interface peeling.

[0019] The outer layer (the surface facing the spring) with a looser weave density can reduce the resistance of slurry injection in subsequent steps, and promote the slurry to evenly and fully wet the fiber skeleton. The inner layer (the surface facing the spring) with a denser weave density can build a high-strength support layer, improve the tensile modulus, and the small weave angle can maximize the high tensile strength of basalt fiber, effectively intercept and absorb residual kinetic energy, and suppress the bulging deformation of the surface facing the spring.

[0020] More specifically, with the total thickness of the precast body as H, the parameters for each layer are designed as follows: Outer layer (A layer): The thickness range is set to 30-40% of the total thickness H, the weft density is 5-8 threads / cm, and the weft angle is 45-60°, forming a loose energy-absorbing layer with a low fiber volume fraction; Middle layer (B layer): The thickness range is set to 30-35% of the total thickness H, the weft density is 8-12 threads / cm, the weft angle is 30-45°, forming a modulus transition layer; Inner layer (C layer): The thickness range is set to 30-35% of the total thickness H, the weft density is 12-18 wefts / cm, and the weaving angle is 15-30°, forming a dense support layer with a high fiber volume fraction.

[0021] (2) Preparation of coupling agent solution (construction of a two-system hydrolysis environment): A mixture of anhydrous ethanol and deionized water is used as a mixed solvent, wherein the volume fraction of anhydrous ethanol is 80%-95% and the volume fraction of deionized water is 5%-20%. KH-560 or KH-550 is selected as a coupling agent and dissolved in the mixed solvent to prepare a coupling agent solution. The mass concentration of the coupling agent in the coupling agent solution is 1.0-3.0 wt%.

[0022] Specifically, when KH-560 is used, γ-glycidoxypropyltrimethoxysilane (KH-560) is added to the mixed solvent, and the pH value is adjusted to 4.0-5.0 using pure glacial acetic acid (preferably with a purity ≥99.5%) or an aqueous solution of glacial acetic acid with a mass concentration of 10-30%. The mixture is stirred at room temperature for 30-90 minutes. The acidic environment helps to stabilize the hydrolysis of epoxy silane. When KH-550 is selected, γ-aminopropyltriethoxysilane (KH-550) is added to the mixed solvent. Although the solution is naturally alkaline, in order to suppress premature self-condensation of silanol groups and improve the pot life of the solution, it is preferable to use pure glacial acetic acid (preferably with a purity ≥99.5%) or a 10-30% aqueous solution of glacial acetic acid to adjust the pH to 4.0-5.0. Under these slightly acidic conditions, the amino groups undergo protonation (-NH4+). 3+ This process promotes the solubility and stability of silanes in the aqueous phase, and the product can be used after stirring at room temperature for 30-60 minutes.

[0023] The KH-550 and KH-560 can be selected according to the interface design requirements.

[0024] (3) Vacuum impregnation (deep penetration): The woven three-layer gradient structure preform is completely immersed in the prepared coupling agent solution and placed in a vacuum chamber. Under negative pressure (e.g., -0.08~-0.098 MPa), a vacuum is drawn for 10-30 minutes to force out the air between the dense fiber bundles. Then, it is immersed at normal pressure for 0.5-2 hours (no need to change the immersion solution, and there is no specific temperature requirement) to ensure that the coupling agent solution is fully impregnated.

[0025] (4) Cleaning and thermosetting (grafting reaction): Take out the three-layer gradient structure preform obtained in step (3), rinse it with deionized water to remove unreacted monomers and physical adsorbents on the surface, put it into a forced-air drying oven, and dry and solidify it at 70-90℃ for 3-6 hours to initiate a condensation reaction and complete the surface grafting.

[0026] In stage one, molecular bridges were constructed, and the chemical reaction mechanisms and equations involved are as follows: Scenario 1: Using KH-560 (epoxy type) (1) Hydrolysis activation reaction: Mechanism explanation: The three methoxy groups (-OCH3) at one end of the KH-560 molecule are subjected to nucleophilic attack in acidic aqueous solution, lose methanol (CH3OH), and are converted into highly reactive silanol groups (-Si-OH). Reaction equation: G-Si(OCH3)3+3H2O→G-Si(OH)3+3CH3OH; Where G represents: CH2(O)CH-CH2-O-(CH2)3-; (2) Dehydration condensation reaction: Mechanism explanation: During the heating and curing stage, the silanol groups generated by the coupling agent undergo dehydration condensation with the silanol groups (Fiber-Si-OH) on the surface of the basalt fiber to form a stable siloxane covalent bond (Si-O-Si), which anchors the epoxy functional groups on the fiber. Fiber-Si-OH+(HO)3-Si-G→Fiber-Si-O-Si(OH)2-G+H2O.

[0027] Scenario 2: Using KH-550 (amino type) (1) Hydrolysis activation reaction: Mechanism explanation: KH-550 stock solution is strongly alkaline. Direct use can easily cause silane molecules to undergo rapid self-condensation in the solution, forming a white flocculent precipitate that is difficult to penetrate into the dense basalt fiber bundles. This invention uses glacial acetic acid to adjust the system to a slightly acidic state (pH 4.0-5.0), under which two key reactions occur: 1. Amine protonation: The amino group (-NH2) captures protons (H+) in solution. + ) is converted into positively charged ammonium ions (-NH4+) 3 + This significantly improves the solubility and stability of silanes in the aqueous phase, inhibits the early self-condensation of silanol groups, and extends the pot life of the slurry; 2. Acid-catalyzed hydrolysis: The three ethoxy groups (-OC2H5) on the silicon atom undergo rapid hydrolysis under acid catalysis, removing ethanol and generating active silanol groups (-Si-OH).

[0028] Reaction equation: (1) Amine protonation reaction: H2N-(CH2)3-Si(OC2H5)3+H + (Provided by acetic acid) → + H3N-(CH2)3-Si(OC2H5)3; (2) Hydrolysis reaction: + H3N-(CH2)3-Si(OC2H5)3+ЗH2О→ + H3N-(CH2)3-Si(OH)3+3C2H5ОH; (3) Dehydration condensation Covalent bond construction: The silanol groups undergo dehydration condensation with the hydroxyl groups on the surface of basalt fibers to form Si-O-Si covalent bonds, completing the anchoring of one end of the molecular bridge. Chemical reaction equation: Fiber-Si-OH+(HO)3-Si-(CH2)3-NH 3+ →Fiber-Si-O-Si(OH)2-(CH2)3-NH 3+ +H2O.

[0029] In Phase One, using holistic three-dimensional weaving technology, a fiber skeleton with a macroscopic "sparse on the outside and dense on the inside" structural gradient is constructed by dynamically adjusting weaving parameters. Z-direction through-yarns penetrate each layer, bridging the macroscopic physical layering interfaces. Utilizing the sol-gel chemical properties of silane coupling agents, KH-560 (containing epoxy groups) or KH-550 (containing amino groups) are selected. Through hydrolysis, active silanol groups are generated, which then undergo dehydration condensation with hydroxyl groups on the inorganic fiber surface. This "grafts" a layer of reactive organic functional groups onto the fiber surface, constructing a chemical "molecular bridge" connecting the inorganic fiber and the organic-inorganic composite matrix.

[0030] Phase 2, Synthesis of polyurea-formaldehyde (UF)-coated dicyclopentadiene (DCPD) self-healing microcapsules: (1) Raw material preparation and quality proportioning: Prepare the raw materials of each component according to the following mass proportions. (a) Continuous phase (aqueous phase): 100-300 parts solvent, 1.0-5.0 parts emulsifier; (b) Dispersed phase (core material / oil phase): 15.0-50.0 parts of repair agent; (c) Wall material precursor: 2.0-10.0 parts of skeleton agent, 5.0-25.0 parts of crosslinking agent, and 0.1-1.0 parts of modifier.

[0031] Specifically, the solvent is deionized water, the emulsifier is styrene-maleic anhydride copolymer (SMA) with a molecular weight of 10,000-100,000 g / mol, the repair agent is liquid (e.g., preheated to a liquid state) dicyclopentadiene (DCPD), the skeleton agent is urea, the crosslinking agent is a 37 wt% formaldehyde aqueous solution, and the modifier is resorcinol.

[0032] The mass ratio of the continuous phase to the dispersed phase was controlled at 3:1 to 8:1 to ensure emulsion stability; the mass ratio of the dispersed phase to the total mass of the wall material precursor was controlled at 1:1 to 5:1 to balance the drug loading and mechanical strength of the microcapsules.

[0033] (2) Core material emulsification (particle size control): Dissolve the emulsifier in the solvent and stir at 60°C until clear to obtain a continuous phase. Slowly add the repair agent to the continuous phase, start the high-shear emulsifier, adjust the speed to 800-1500 rpm, and shear and stir for 10-20 minutes. Use shear force to overcome interfacial tension to form a stable O / W (oil-in-water) emulsion. Under the above conditions, droplets with an average particle size of 20-80 μm can be obtained.

[0034] (3) Wall material prepolymer synthesis: In a separate reaction vessel, mix the skeleton agent, crosslinking agent, and modifier in the above proportions. Adjust the pH value to 8.0-9.0 (weakly alkaline environment) using a 10%-30% triethanolamine aqueous solution. Stir the reaction at 65-75℃ for 0.5-1.5 hours to generate a transparent urea-formaldehyde prepolymer solution with a certain degree of polymerization.

[0035] (4) In situ encapsulation (capsulation reaction): Slowly add the urea-formaldehyde prepolymer solution from step (3) to the emulsion from step (2), and slowly adjust the pH of the system to 2.0-3.0 using an acidic regulator (such as ammonium chloride solution or dilute hydrochloric acid) (to initiate acidic catalysis). Control the reaction temperature at 50-60℃, reduce the stirring speed to 300-600 rpm (to prevent damage to the capsule wall), and continue the reaction for 2-4 hours to allow the prepolymer to further condense and crosslink at the oil-water interface to form a solid capsule wall.

[0036] (5) Post-treatment (purification and drying): After the reaction was completed, the mixture was cooled to room temperature, the product was separated by filtration, and the microcapsules were obtained by washing with water, washing with alcohol and drying.

[0037] Specifically, in step (5) of stage two, the water washing, alcohol washing, and drying are as follows: Washing: Wash three times with deionized water, each time using enough water to completely cover the surface of the filter cake or until the effluent is neutral, to remove residual acidic catalyst and unreacted formaldehyde. Alcohol washing: Rinse once quickly with a small amount of anhydrous ethanol. There is no particular limit to the amount of anhydrous ethanol used for rinsing. Usually, it is 2-3 times the mass of the product after water washing to remove excess oily core material adsorbed on the surface. Drying: Vacuum drying at 40-50℃ and -0.08~-0.095 MPa for 12-36 hours yields well-dispersible microcapsule powder.

[0038] Phase two involved the synthesis of the wall material for the microcapsules, and the chemical reaction equations involved are as follows: (1) Nucleophilic addition reaction (to form hydroxymethylurea): Under alkaline conditions, the amino group (-NH2) of urea undergoes nucleophilic addition with the carbonyl group (C=O) of formaldehyde; H2N-CO-NH2+HCHO→H2N-CO-NH-CH2OH (It generates monohydroxymethylurea, and dihydroxymethylurea can be generated as the formaldehyde ratio increases); (2) Condensation reaction (crosslinking to form a network): Under acidic conditions, the hydroxymethyl group (-CH2OH) undergoes dehydration condensation with an amino group or another hydroxymethyl group to form a methylene bridge (-CH2-) or an ether bond (-CH2-O-CH2-), constructing a three-dimensional network polymer structure. ①Methylene bridge (-CH2-) formation reaction: R-NH-CH2OH + H2N-R' → R-NH-CH2-NH-R'+ H2O, where R and R' represent urea residues (i.e., NH2-CO- or -NH-CO-NH-). ② Reaction for the formation of ether bonds (-CH2-O-CH2-): R-CH2OH + HOCH2-R' → R-CH2-O-CH2-R' + H2O, where R represents the molecular chain segment containing the urea skeleton (NH2CONH-CH2-) and R' represents the molecular chain segment containing the hydroxymethyl group (-CH2-NHCONH2).

[0039] In stage two, in-situ polymerization is used. Under acidic catalytic conditions, urea and formaldehyde undergo nucleophilic addition and condensation reactions. The resulting polyurea-formaldehyde (UF) prepolymer is enriched under the surface tension of the interface between the oily core material (repair agent) and the aqueous phase, and further cross-linked and deposited, eventually forming a tough and dense polymer capsule wall that encapsulates the liquid repair agent.

[0040] Phase 3, Preparation of ceramic slurry with rheological gradient: (1) Component weighing and formulation design (establishing a component gradient): According to the design requirements, raw material powders were prepared for the outer, middle, and inner layers. Phase A raw material corresponds to the outer layer (projectile-facing surface), primarily providing high hardness to break the projectile core; Phase B raw material corresponds to the middle layer (transition layer), responsible for wave impedance matching and mitigating shock wave stress gradients; Phase C raw material corresponds to the inner layer (backplate surface), primarily providing high toughness and backplate energy absorption to prevent ceramic chipping. Based on the total mass of the main phase (ceramic powder) in each layer, the mass percentage (wt%) of each component is calculated as follows: Phase A raw material (high hardness, penetration resistance): Main phase: High-hardness ceramic powder; Functional phase: 3.0-7.0 wt% self-healing microcapsules (low content to maintain rigidity); Phase B material (transition / wave impedance matching): Main phase: a mixture of SiC or B4C and Al2O3 powder; Functional phase: 5.0-10.0 wt% self-healing microcapsules added; C-phase material (high toughness / backplate energy absorption): Main phase: High-toughness ceramic powder; Functional phase: 7.0-12.0 wt% self-healing microcapsules (high content to maximize repair capacity); The functional phase content in phase A raw material is less than that in phase B raw material, which in turn is less than that in phase C raw material.

[0041] Preferably, the main phase of the A-phase raw material is selected from SiC or B4C, with a particle size of 0.5-1.5 μm; In the main phase of the B-phase raw material, the mass ratio of SiC or B4C to Al2O3 is 1:1 to 2:1, and the particle size is preferably 1.5-3.0 μm; The main phase of the C-phase raw material is selected from Al2O3 or Si3N4, and the particle size is preferably 3.0-5.0 μm.

[0042] (2) Ball milling dispersion and slurry preparation: The A-phase raw materials, B-phase raw materials, and C-phase raw materials were each placed in three separate ball mill jars. Then, additives and deionized water were added as solvents. The mixtures were then ball milled in a planetary ball mill at a speed of 200-400 rpm for 24-48 hours to ensure uniform mixing and no agglomeration. The additives were organic binders and dispersants. The deionized water solvent was used to adjust the solid content of the slurry to 40-55 vol%. The amount of organic binder added was 1.0-3.0 wt% of the total mass of the powders of each phase (referring to the sum of the main phase powders and functional phase microcapsules) (to provide green strength).

[0043] In some embodiments of the present invention, the organic binder is selected from polyvinyl alcohol (PVA) with an average molecular weight range of 20,000-70,000 g / mol, and the dispersant is selected from ammonium polyacrylate (PAA) with an average molecular weight range of 3,000-8,000 g / mol. In actual operation, the dispersant is preferably added in the form of an aqueous solution with a mass concentration of 10-20%, but the initial addition amount of the dispersant, based on the effective solid mass, is 0.2-1.5 wt% of the total mass of the mixed powder of each phase (i.e., the sum of the main phase powder and the functional phase microcapsules).

[0044] (3) Fine-tuning of rheological properties (establishing a viscosity gradient): After ball milling, each phase slurry was placed in a vacuum degassing machine and treated for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove air bubbles. Then, the A-phase, B-phase, and C-phase slurries were taken out for rheological testing. The viscosities of the A-phase, B-phase, and C-phase slurries were adjusted to the following specific ranges by adding trace amounts of dispersant (PAA), organic binder, water, or extending the vacuum degassing time (test standard: rotational viscometer, shear rate 100 s). -1 ): C-phase slurry (high-penetration type): viscosity controlled at 0.5-1.5 Pa·s; Principle: Extremely low viscosity ensures penetration deep into dense fiber bundles with high volume fraction; B-phase slurry (equilibrium type): viscosity controlled at 2.0-5.0 Pa·s; Principle: Medium viscosity, balancing the permeation rate and the stability of the interlayer interface; Phase A slurry (anti-sagging / thixotropic): viscosity controlled at 6.0-12.0 Pa·s; Principle: High viscosity and significant thixotropy (shear thinning) prevent the slurry from being lost due to gravity in the loose fiber layer (large pores).

[0045] (4) Stability determination criteria: After the above rheological modification, the A, B, and C three-phase slurry exhibits excellent colloidal stability due to the precise anchoring of the dispersant and the physical constraint of the continuous phase. Its quality indicators are as follows: the absolute value of the Zeta potential |ζ| remains above 30mV, effectively generating electrostatic repulsion to prevent particle flocculation; simultaneously, after standing in the dark for 24 hours at room temperature and pressure, the volume ratio of the supernatant is less than 5%, and no hard precipitate forms at the bottom, ensuring that the components of the slurry will not segregate or separate during the subsequent gradient impregnation molding operation.

[0046] In stage three, the ceramic powder and microcapsules are uniformly dispersed through ball milling. The key technology lies in using dispersants (such as ammonium polyacrylate, PAA) to adjust the zeta potential and double-layer thickness of the particles, thereby precisely controlling the viscosity gradient of the slurry. This viscosity gradient must be strictly matched to the weaving density of the different layers of the preform; the inner layer requires low viscosity for penetration, while the outer layer requires high viscosity to utilize thixotropy to prevent sagging and aid in subsequent physical isolation.

[0047] Phase Four: Gradient Impregnation Molding Based on Visual Flow Guidance and Stepwise In-situ Gelification (1) Mold preparation and assembly: The three-layer gradient structure preform obtained in Stage 1 is loaded into a corresponding dedicated mold. The dedicated mold is made of transparent acrylic resin, and its inner cavity shape is consistent with the size of the three-layer gradient structure preform. The dedicated mold has three independent interfaces on its side wall along the thickness direction. From bottom to top, the dedicated mold is divided into layer C (corresponding to the dense layer back surface of the three-layer gradient structure preform, i.e., the inner layer), layer B (corresponding to the middle layer of the three-layer gradient structure preform, i.e., the transition layer), and layer A (corresponding to the loose layer front surface of the three-layer gradient structure preform, i.e., the outer layer). The independent interfaces include the corresponding C layer group, B layer group, and A layer group. The C layer group includes a C layer inlet located at the bottom of the mold, and a C / B interface vacuum port located at the bottom edge height of layer B (i.e., the upper area of ​​layer C). The B layer group includes a B layer inlet located at the bottom edge height of layer B, and a B / A interface vacuum port located at the bottom edge height of layer A (i.e., the upper area of ​​layer B). The A layer group includes a C layer inlet located at the bottom edge height of layer B, and a B / A interface vacuum port located at the bottom edge height of layer A (i.e., the upper area of ​​layer B). The design logic for the interface positions of the A-layer feed port at the bottom edge height of the layer and the top vacuum port set at the top of the mold is "feeding at the bottom of each layer and venting / vacuuming at the top of each layer". The height position of the special mold interface can be calculated and set according to the actual thickness parameters of the A, B and C layers of the three-layer gradient structure preform. The inner diameter of the interface can be adjusted according to the actual situation, generally 1-2 mm.

[0048] Heating modules are arranged in close contact with the outer periphery of the sidewall of the special mold. The heating modules are arranged in three independent zones: A, B, and C, with each zone having its own independent temperature control. Specifically, the heating module corresponding to zone C is located at the bottom of the mold at the scale 0 to h. C Between these points, the corresponding zone heating module for layer B is located at scale h on the bottom of the mold. C to h B +h C Between these points, the zone heating module corresponding to layer A is located at scale h on the bottom of the mold. B +h C to h A +h B +h C Between (where h) A h B h C (These are the thicknesses of each layer of the preform); the heating module is connected to an external intelligent temperature control box via a temperature sensor to form a closed-loop control system, which is used to provide the thermal field required for stepwise in-situ gelation after each layer is impregnated; the heating module is preferably an electric heating element or a flexible silicone heating strip.

[0049] The principle behind using specialized molds to achieve zoned impregnation and layered barrier is based on the thermal sensitivity of the binder in each phase of the slurry, employing a "stepwise injection-in-situ gelation" strategy. After the current layer of slurry is injected, an external thermal field induces in-situ gelation of that layer, thereby forming a high-viscosity gel barrier band with physical sealing at the interface between adjacent layers. This barrier band forms a solid barrier at the interlayer interface, effectively resisting interface disturbances caused by the subsequent injection of the next layer of slurry under the feeding pressure, and preventing the diffusion and mixing of heterogeneous slurries at the interface. This macroscopically ensures that the final product has a clear component gradient interface in the thickness direction.

[0050] C-layer group: C-layer feed port and C / B interface vacuum port at the C / B interface height. The bottom edge scale of the C-layer feed port is 0 (close to the bottom surface of the mold), and the top edge scale is D (interface aperture), ensuring that the material is smoothly cut in from the bottom layer. The bottom edge scale of the C / B interface vacuum port is h. C -D(h C (C layer thickness), top edge scale is h C (Align the boundary line between layer C and layer B), connect the vacuum port of the C / B interface to the transparent flexible tube; B-layer group: The B-layer feed inlet and the B / A interface vacuum port at the B / A interface height, wherein the bottom edge scale of the B-layer feed inlet is h. C (Close to the C / B interface line), the top scale is h. C +D (D is the interface aperture), the B-phase inlet is located at the bottom of the middle layer (B-phase), ensuring that the B-phase slurry can be inserted tightly against the top surface of the C-phase, achieving seamless interlayer grouting; the bottom edge scale of the vacuum port at the B / A interface is h. C +h B -D(h B (This refers to the thickness of layer B), with the top edge scale marked h. C +h B (Align the boundary line between layer B and layer A), the vacuum port of the B / A interface is set at the top of the middle layer (layer B). Its function is to use negative pressure to guide the B phase slurry to fill the middle layer space from bottom to top, and to overflow in time through the port when the slurry reaches the interface of layer A. The vacuum port of the B / A interface is connected to a transparent hose. Layer A: Layer A inlet and top vacuum port, where the bottom edge of the Layer A inlet is marked with h. C +h B (Close to the B / A interface line), the top scale is h. C +h B+D (D is the interface aperture), the A-layer inlet is located at the bottom of the outermost layer to ensure that the A-phase slurry can cut into the top surface of the B-layer and complete the filling of the last layer; the top vacuum port is directly located at the top of the mold and is set through the top cover of the mold. It serves as the end exhaust and vacuum outlet of the entire gradient injection system. When the A-layer slurry enters from its bottom inlet, under the action of the top negative pressure, the slurry will penetrate vertically upward and fill all the loose pores of the A-layer, and finally reach the top of the mold. The top vacuum port is connected to a transparent hose. The A-layer, B-layer, and C-layer inlet ports are each connected to their respective slurry storage tanks via pressure-resistant hoses. The slurry storage tanks are connected to compressed air pumps (feed pumps) to provide a constant feed pressure, with feed valves (such as ball valves) installed in between, corresponding to the C-layer, B-layer, and A-layer feed valves. The C / B interface vacuum port, B / A interface vacuum port, and top vacuum port are each connected to a vacuum collection tank (buffer tank) via transparent hoses, and then connected to a vacuum pump system, with vacuum valves (such as shut-off valves) installed in between, corresponding to the C / B interface vacuum valve, B / A interface vacuum valve, and top vacuum valve. Heating modules are arranged in close contact with the outer periphery of the special mold sidewall. These heating modules are independently zoned according to the A, B, and C layers, with each zone having independent temperature control. For example, the heating module corresponding to the C-layer is located at the bottom of the mold at the 0 to h mark. C Between these points, the corresponding zone heating module for layer B is located at scale h on the bottom of the mold. C to h B +h C Between these points, the zone heating module corresponding to layer A is located at scale h on the bottom of the mold. B +h C to h A +h B +h C Between them, the heating module is connected to an external intelligent temperature control box through a temperature sensor to form a closed-loop control system. The heating module is an electric heating element or a flexible silicone heating strip. There are no proportional requirements for the feed flow rate of each layer. The interface observation is used as the judgment standard.

[0051] (2) C-layer (inner layer) impregnation and in-situ gelation: Directional impregnation: Open only the C-layer feed valve and the C / B interface vacuum valve, close all other valves, and start the vacuum pump and feed pump. Under the combined guidance of a constant feed pressure (provided by a compressed air pump) and a negative pressure at the front end, the highly permeable C-layer slurry fills the dense fiber layer of the inner layer from the bottom up in the slurry storage tank. The negative pressure can be adjusted according to the actual situation, preferably from -0.08 MPa to -0.095 MPa. Visual endpoint determination: Observe the transparent hose connected to the vacuum port of the C / B interface. When continuous slurry flow (overflow) appears in the hose, it indicates that the C layer has been completely filled. Immediately close the C layer feed valve and the C / B interface vacuum valve. Physical blocking (gelation): Immediately turn on the heating module of the C layer area of ​​the mold, set the temperature to 60-80℃, and keep it at that temperature for 15-30 minutes. This will cause the organic binder in the C layer slurry to undergo partial cross-linking and transform into a semi-solid gel that is not sticky to the touch, forming the base plate for subsequent steps.

[0052] (3) Impregnation and in-situ gelation of layer B (middle layer): Directional impregnation: Open only the B-layer feed valve and the B / A interface vacuum valve, close all other valves, and start the vacuum pump and feed pump. Under the combined guidance of a constant feed pressure (provided by a compressed air pump) and a negative pressure at the front end, the slurry in the slurry storage tank causes the B-layer slurry to flow directionally above the C-layer gel interface (the lower layer is blocked by gel and cannot penetrate, while the upper layer is attracted by vacuum), filling the pores of the B-layer. The negative pressure can be adjusted according to the actual situation, preferably from -0.08 MPa to -0.095 MPa. Visual endpoint determination: When slurry overflow is observed in the transparent hose of the vacuum port of the B / A interface, the B layer feed valve and the B / A interface vacuum valve must be closed immediately. Physical blocking (gelation): Immediately turn on the heating module in the B layer area and keep it at 60-80℃ for 15-30 minutes to transform it into a gel state.

[0053] (4) Impregnation and overall drying of layer A (outer layer): Directional impregnation: Open only the A-layer feed valve and the top vacuum valve, close all other valves, and start the vacuum pump and feed pump. Under the combined guidance of a constant feed pressure (provided by a compressed air pump) and a negative pressure at the front end, the slurry in the slurry storage tank fills the pores of the A-layer with the A-phase slurry. The negative pressure can be adjusted according to the actual situation, preferably from -0.08 MPa to -0.095 MPa. Visual endpoint determination: When slurry overflow is observed in the transparent hose of the top vacuum port, the A-layer feed valve and the top vacuum valve must be closed immediately; Physical blocking (gelation): Immediately turn on the heating module in the A layer area and keep it at 60-80℃ for 15-30 minutes to transform it into a gel state.

[0054] Overall drying: Place the mold after grouting into an oven and dry it at 40-60℃ for 24-72 hours until the green body is dehydrated and shaped. The dehydration and shaping of the green body can be monitored by the oven drying method (mass method). By comparing the change in the overall weight of the mold, when the mass difference between two weighings (with an interval of 4 hours) is less than 0.1%, it can be determined that the shaping is complete. Then demolding is performed to obtain the gradient green body.

[0055] In stage four, a special mold with multiple independent interfaces on the sidewalls is used to establish a pressure gradient field pointing to a specific interface inside the preform by opening the air extraction valve at a specific height, guiding the slurry to flow in a specific direction. The transparent pipe connected to the air extraction port is used to achieve a visual and accurate determination of the impregnation endpoint. By utilizing the thermal cross-linking properties of organic binders (such as PVA), the slurry is transformed into a non-flowing semi-solid gel through stepwise in-situ low-temperature semi-curing, thereby constructing a temporary physical barrier layer in the interconnected porous medium and achieving precise zoning of the multi-component slurry.

[0056] Phase 5, Gradient debinding and spark plasma sintering (SPS): (1) Gradient degreasing (gel removal): The gradient green body obtained in stage four is placed in a tube furnace or atmosphere furnace, and a flowing inert atmosphere (N2 or Ar, flow rate 200-500 mL / min) is introduced. The following gradient heating program is then executed: Low temperature section: Heat to 300℃ at a rate of 0.5-1.0℃ / min and hold for 1-2 hours (to remove moisture and low molecular weight organic matter). High temperature section: Continue to increase the temperature to 500-600℃ at a rate of 1.0-2.0℃ / min, and hold for 2-4 hours (to decompose polymers such as PVA and SMA). Cooling: The furnace cools naturally.

[0057] (2) Mold filling: Carefully place the degreased porous preform into a high-strength graphite mold. Spray or coat a layer of boron nitride (BN) or graphite paper (physical fixation, generally through its own tension or compression) between the preform and the inner wall of the mold as a release agent to prevent adhesion during high-temperature reaction.

[0058] (3) SPS rapid sintering: Place the mold in an SPS sintering furnace and evacuate it to <10 Pa or introduce a protective atmosphere, which may be argon or nitrogen. Heating: Rapidly increase the temperature at a rate of 50-150℃ / min; Sintering temperature: set at 1500-1750℃, depending on the melting point of the ceramic matrix. For example, the SiC / Al2O3 system is usually 1600℃. A protective atmosphere, wherein the protective atmosphere may be argon or nitrogen; Pressure: Apply a base pressure of 5-10 MPa before heating to the first temperature of 1000-1200℃. After heating above the first temperature, simultaneously change the pressure to the target pressure of 30-80 MPa. After holding at the sintering temperature, unload the pressure to below the base pressure of 5 MPa or completely remove the pressure, and then begin cooling. By eliminating high-pressure constraints during the cooling stage, residual stress or microcracks can be effectively prevented from forming in the green compact during cooling shrinkage. Heat preservation: Hold at the sintering temperature for 3-15 minutes (a very short time to inhibit grain growth and capsule failure). Cooling: Allow the furnace to cool naturally to room temperature.

[0059] In stage five, the interfacial chemical reaction mechanism (final curing and reinforcement) is as follows: During the heating and high-temperature stages of sintering, the silane coupling agent grafted onto the fiber surface in stage one undergoes a chemical reaction with the matrix, permanently locking the interface. Depending on the selected coupling agent, the reaction mechanism is as follows: Scenario 1: If KH-560 (epoxy type) is used Mechanism: The epoxy groups at the end of the coupling agent undergo ring-opening addition reactions with the hydroxyl groups or residual carbon on the surface of the ceramic matrix to form thermodynamically stable COC ether bonds; at higher temperatures (>1000℃), this organic interface layer is transformed in situ into a Si-OC amorphous ceramic interface layer, achieving chemical metallurgical bonding. Reaction equation (ether bond formation): R-CH(O)CH2+Matrix-OH→R-CH(OH)-CH2-O-Matrix; Scenario 2: If KH-550 (amino type) is used Mechanism: The amino group (-NH2) at the end of the coupling agent exhibits extremely strong reactivity at high temperatures. It undergoes a dehydration condensation reaction with the hydroxyl groups or oxide layer on the ceramic matrix surface to form Si-N bonds. This nitrogen-doped interface layer has extremely high bond energy, which can effectively prevent crack propagation along the fiber surface; Reaction equation (amide-like bond / nitrogen bridge formation, during slurry preparation, protonated -NH3) + (Deprotonation to active amino group -NH2) Fiber-···-(CH2)3-NH2+HO-Matrix→Fiber-···-(CH2)3-NH-Matrix+H2O↑.

[0060] In stage five, the organic components (organic binders and dispersants) are slowly removed in an inert atmosphere by precisely controlling the heating rate, preventing microcapsule bursting or green body cracking due to rapid gas release. Subsequently, using spark plasma sintering (SPS) technology, the ceramic matrix is ​​rapidly densified at a lower temperature and in a very short time through the Joule heating effect and field-assisted effect generated by pulsed high current, thereby maximizing the preservation of the chemical activity of the self-healing microcapsules and the mechanical strength of the basalt fibers.

[0061] Using the above method, a gradient self-healing basalt fiber composite ceramic armor plate was finally obtained. The composite ceramic armor plate exhibits a significant density gradient and performance asymmetry: its outer layer possesses extremely high hardness, capable of effectively crushing high-hardness projectile cores; the inner layer maintains excellent fracture toughness, and the enriched microcapsules endow it with high deep-layer damage repair capabilities. Experimental tests show that after undergoing penetrating damage from ballistic impacts, the flexural strength recovery rate of its inner ceramic matrix can reach over 76% through induced repair, while the overall structure remains intact without macroscopic interlaminar delamination.

[0062] Through the above technical solutions, the present invention effectively solves several problems in the prior art and achieves the following significant and beneficial technical effects: 1. Effectively overcomes the risk of delamination between layers in traditional laminated armor plates, significantly improving resistance to multiple attacks. This invention employs an integral three-dimensional woven structure, utilizing Z-direction interlocking yarns to physically bridge the macroscopic layer interfaces, achieving mechanical interlocking between layers. Compared to traditional laminates, the interlayer shear strength is significantly improved, effectively suppressing reflective tensile damage caused by shock waves, maximizing the structural integrity of the armor plate under continuous impact, and avoiding the risk of catastrophic spalling.

[0063] 2. Breakthrough in the technical bottleneck of precise manufacturing of component gradients in connected media. This pioneering "sidewall visible flow guidance + step-by-step in-situ gelation" process overcomes the challenge of easy mixing of liquid slurry in connected fiber skeletons by physically defining the flow field endpoint through the vacuum port location, combined with visual judgment through a transparent tube and in-situ low-temperature curing blocking, thus achieving precise zoning and gradient design of multi-component slurry.

[0064] 3. A robust "inorganic-organic-inorganic" dual chemical interface was constructed. A chemical "molecular bridge" was constructed using a silane coupling agent. One end of the bridge is anchored to basalt fibers via Si-O-Si covalent bonds, while the other end is anchored to the matrix network via COC (ether bonds) or Si-N bonds. This bidirectional chemical bonding significantly reduces interfacial thermal resistance, greatly enhances interfacial bonding strength, and effectively inhibits crack propagation along the interface.

[0065] 4. Achieved intelligent full-lifecycle protection with damage mode matching. Based on the damage characteristics of "external fragmentation and internal cracking," a gradient distribution of "low outer layer and high inner layer" was designed for self-healing microcapsules. While ensuring the high hardness and penetration resistance of the outer layer, it endows the inner layer with extremely high crack repair capabilities. After heat treatment, it can recover more than 76% of its mechanical properties, which is beneficial to extending the service life of equipment.

[0066] 5. Achieving efficient synergy between ceramic densification and the activity of functional components. The high viscosity and yield stress of the slurry (rheological control) effectively counteract the buoyancy of the microcapsules, uniformly suspending them in a specific layer of slurry. Subsequently, a stepwise in-situ gelation process is used to physically fix the microcapsules in the matrix network before macroscopic migration. This locking mechanism, combined with SPS low-temperature rapid sintering, enables the chemical activity retention rate of the microcapsules to exceed 85%, significantly reducing the failure risk caused by capsule floating or high-temperature decomposition in traditional processes. Attached Figure Description

[0067] Figure 1 This is a schematic diagram illustrating the module composition and interaction relationships of the various stages of the gradient self-healing basalt fiber composite ceramic armor plate preparation method of the present invention. Figure 2 This is a schematic diagram of a mold for a gradient dip molding process (heating modules A, B, and C on the mold are all in close contact with the outer periphery of the mold sidewall). Figure 3 This is a schematic diagram of the cross-sectional technical principle of the gradient self-healing basalt fiber composite ceramic armor plate of the present invention. Detailed Implementation

[0068] The technical solution of the present invention will be further described below with reference to specific embodiments. These embodiments are only used to illustrate the technical solution of the present invention in more detail and should not be construed as limiting the scope of protection of the present invention.

[0069] Three-dimensional braiding machines are conventional textile / composite material processing equipment in this field, and conventional three-dimensional four-dimensional or three-dimensional five-dimensional braiding machines can be selected. For high-shear emulsifiers, conventional laboratory-grade or industrial-grade high-shear dispersion equipment in this field should be selected, with a rotation speed capable of reaching 1000-3000 rpm; The maximum temperature of the spark plasma sintering system (SPS) is no less than 2000℃, the maximum uniaxial pressure is no less than 100kN, and the vacuum degree can reach below 10 Pa. Commercially available models can meet the requirements, such as Sumitomo of Japan or major domestic brands.

[0070] Particle size was determined using a laser particle size analyzer (such as the Malvern Mastersizer 3000) to measure the median diameter (D) of the powder. 50The testing standard refers to GB / T 19077-2016 "Particle Size Analysis by Laser Diffraction"; Viscosity was measured using a rotational viscometer (such as the Brookfield DV2T from the USA) at 25°C and a shear rate of 100 s⁻¹. -1 The viscosity was measured at 60 rpm (or at a rotation speed of 60 rpm), referring to GB / T 10247-2008 "Methods for Viscosity Measurement"; Solid content was determined by constant weight weighing method. The sampled slurry was dried at 105℃ to constant weight, and the percentage of solids was calculated based on the mass difference before and after drying, referring to GB / T 1725-2007 "Determination of nonvolatile matter content in paints, varnishes and plastics"; Zeta potential was determined using a Zeta potential analyzer (such as the Malvern Zetasizer Nano) and the principle of electrophoretic light scattering to detect the surface potential of the slurry at the current pH value, referring to GB / T 32668-2016 "Zeta Potential Analysis of Colloidal Particles by Electrophoresis". Settling stability was tested using the natural settling ratio method. 100 mL of the slurry to be tested was poured into a graduated stoppered cylinder, sealed, and placed in a constant temperature environment at 25±2℃. The height (Hs) of the supernatant precipitated at the top of the cylinder was recorded at 24h, 48h, and 72h. The settling rate (S) was calculated using the formula: S = (Hs / Hs) s / H0)×100% (where H0 is the initial total height of the slurry). Judgment criteria: If the 24-hour settling rate S < 3% and no hard sediment forms at the bottom (it can be easily stirred with a glass rod), then the slurry is judged to have good stability.

[0071] Density testing is based on Archimedes' principle (GB / T 1033.1-2008). The ballistic resistance performance is based on the "Test Method for Ballistic Resistance Performance of Military Armor Plates" (GJB 4300A-2012). The three-point bending strength test is performed according to the "Test Method for Room Temperature Bending Strength of Fine Ceramics" (GB / T 6569-2006). The calculation of the "flexural strength recovery rate (self-healing efficiency η)" adopts the standard formula commonly used in the international field of self-healing materials. It was proposed by SR White et al., the founders of self-healing microcapsule technology, in the top journal *Nature*. Reference: White, SR, et al. "Autonomic healing of polymer composites." *Nature* 409.6822 (2001): 794-797; Self-healing efficiency η= ×100%. Among them, The standard bending strength of the original undestructed specimen. The bending strength is the value of the sample after it has been damaged and induced to be repaired at 130°C.

[0072] The styrene-maleic anhydride copolymer (SMA) used has a molecular weight of 10,000-100,000 g / mol.

[0073] Unless otherwise specified, the equipment, materials, and reagents used in the following examples and comparative examples are all commercially available products.

[0074] Example 1: A standard SiC / Al2O3 gradient self-healing armor plate, which is a three-layer gradient armor plate with dimensions of 100 mm × 100 mm × 12 mm, such as... Figure 1 As shown, it is prepared by the following method.

[0075] Step 1: Preparation of basalt fiber three-layer gradient structure preform and construction of surface molecular bridges Gradient weaving: 1200 tex basalt continuous fiber is selected. A three-layer gradient structure prefabricated body with a total thickness of 12 mm is prepared using a computer-controlled three-dimensional weaving machine. The three-layer gradient structure prefabricated body consists of an outer layer, a middle layer, and an inner layer (each layer is 100 mm in length and width). Outer layer (Layer A, 4mm thickness): weft density 6 threads / cm, braid angle 55° (loose energy-absorbing layer); Middle layer (B layer, 4mm thick): weft density 10 threads / cm, weave angle 35° (modulus transition layer). Inner layer (C layer, 4mm thick): weft density 16 threads / cm, weave angle 20° (dense support layer).

[0076] Molecular bridge construction (using the KH-560 scheme): Solution preparation: Measure 900 mL of anhydrous ethanol and 100 mL of deionized water, add 20 g of KH-560, and adjust the pH to 4.5 by adding pure glacial acetic acid (99.5% purity). Stir at room temperature for 60 minutes.

[0077] Impregnation and curing: The three-layer gradient structure preform is completely immersed in the prepared coupling agent solution and placed in a vacuum chamber. Under negative pressure (-0.08~-0.095 MPa), it is impregnated at room temperature for 20 minutes, followed by soaking at room temperature and pressure for 1 hour. After removal, it is rinsed with deionized water until the effluent is neutral, and then placed in a forced-air drying oven for drying and curing at 80℃ for 4 hours.

[0078] Step 2: Synthesis of UF / DCPD self-healing microcapsules Emulsification: Dissolve 3.0 g SMA in 200 g deionized water and stir at 60°C until clear. Add 30.0 g of high-purity dicyclopentadiene (DCPD) preheated to 40°C and in liquid state. Shear emulsify in a high-shear emulsifier at 1000 rpm for 15 minutes to obtain an emulsion with an average particle size of about 50 μm. Encapsulation: In a separate reaction vessel, 5.0 g of urea, 12.5 g of formaldehyde aqueous solution (37 wt%), and 0.5 g of resorcinol were mixed. The pH was adjusted to 8.5 using a 15% triethanolamine aqueous solution. The mixture was stirred at 70°C for 1 hour to obtain a urea-formaldehyde prepolymer solution. The urea-formaldehyde prepolymer solution was slowly added dropwise to the emulsion obtained in the aforementioned emulsification step. The pH was adjusted to 2.5 using a 10% ammonium chloride aqueous solution. The mixture was then reacted at 55°C for 3 hours at a speed of 500 rpm.

[0079] Post-processing: After the reaction was completed, the mixture was cooled to room temperature, and the product was separated by filtration. After washing with water and alcohol, the product was dried under vacuum at 45°C and -0.08 to -0.095 MPa for 24 hours to obtain microcapsules. The water washing consisted of washing three times with deionized water, each time with enough water to completely cover the surface of the filter cake or until the effluent was neutral. The alcohol washing consisted of a rapid rinse once with anhydrous ethanol.

[0080] Step 3: Preparation of ceramic slurry with rheological gradient Three groups of slurries (each with a solid content of 50 vol%) were prepared. In the preparation of the three groups of slurries, a planetary ball mill was used for dispersion and mixing. Grinding ball material: High-purity zirconium oxide (ZrO2) grinding balls are selected (to avoid introducing impurities, and the high density results in high grinding efficiency); Grinding ball gradation: A mixture of Φ5mm and Φ10mm grinding balls (mass ratio 1:1). Ball-to-material ratio: set to 5:1 (by mass); Ball mill speed: 300 rpm; Ball milling time: 24 hours.

[0081] Specific ingredients and preparation: According to the design requirements, solid powder materials were prepared for the outer, middle, and inner layers respectively: Phase A slurry (high hardness / high viscosity): Weigh 300 g of Phase A raw material SiC (particle size 0.5-1.5 μm) and 9 g of microcapsules (3 wt%). Place the above raw material into a ball mill jar, then add 5 g of PVA (molecular weight 40000-70000 g / mol) (organic binder), and add 1.0 g of PAA (dry weight) (molecular weight 3000-5000 g / mol) (dispersant) in the form of a 15% aqueous solution. Finally, add deionized water until the solid content of the system is 50 vol%. Ball mill according to the above general parameters to obtain the Phase A slurry. Rheological control: After ball milling, the slurry is poured out and placed in a vacuum degassing machine for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove the large number of microbubbles introduced during ball milling. The slurry viscosity is then measured. If the viscosity is too high, it is adjusted by adding a small amount of 15% PAA aqueous solution or deionized water; if the viscosity is too low, it is adjusted by adding a small amount of 5% PVA aqueous solution or appropriately extending the vacuum degassing time. Finally, the viscosity of the A-phase slurry is adjusted to 9.0 Pa·s (high viscosity to prevent sagging).

[0082] B-phase slurry (transitional / medium viscosity): Weigh 150 g of B-phase raw materials SiC, 150 g of Al2O3 (both powders have a particle size of 1.5-3.0 μm), and 18 g of microcapsules (6 wt%). Place the above raw materials into a ball mill jar, then add 5 g of PVA (molecular weight 40000-70000 g / mol) (organic binder) and a 15% (w / w) aqueous solution of PAA (molecular weight 3000-5000 g / mol) (based on a PAA dry weight of 2.0 g). Finally, add deionized water until the solid content of the system is 50 vol%. Ball mill according to the above general parameters to obtain the B-phase slurry. Rheological control: After ball milling, the slurry was poured out and placed in a vacuum degassing machine for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove the large number of microbubbles introduced during ball milling. The slurry viscosity was then measured. If the viscosity was too high, it was adjusted by adding a small amount of 15% PAA aqueous solution or deionized water; if the viscosity was too low, it was adjusted by adding a small amount of 5% PVA aqueous solution or appropriately extending the vacuum degassing time. The final viscosity of the B-phase slurry was adjusted to 3.5 Pa·s.

[0083] C-phase slurry (high toughness / low viscosity): Weigh 300 g of C-phase raw material Al2O3 (particle size 3.0-5.0 μm) and 27 g of microcapsules (9 wt%). Place the above raw material into a ball mill jar, then add 5 g of PVA (molecular weight 40000-70000 g / mol) (organic binder) and a 15% (w / w) aqueous solution of PAA (molecular weight 3000-5000 g / mol) (equivalent to 3.5 g of PAA dry weight). Finally, add deionized water until the solid content of the system is 50 vol%. Ball mill according to the above general parameters to obtain C-phase slurry. Rheological control: After ball milling, the slurry is poured out and placed in a vacuum degassing machine for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove the large number of microbubbles introduced during ball milling. The slurry viscosity is then measured. If the viscosity is too high, it is adjusted by adding a small amount of 15% PAA aqueous solution or deionized water; if the viscosity is too low, it is adjusted by adding a small amount of 5% PVA aqueous solution or appropriately extending the vacuum degassing time. Finally, the viscosity of the C-phase slurry is precisely adjusted to 1.0 Pa·s (low viscosity for high penetration).

[0084] Stability testing: The absolute value of the Zeta potential of all three groups of slurries was >35 mV, the sedimentation (i.e. the volume ratio of the supernatant) was <3% after 24 h, and no hard sediment was formed at the bottom.

[0085] Parameter control instructions (closed-loop correction): Rheological regulation and performance locking: After ball milling, the slurry was placed in a vacuum degassing machine and treated under a negative pressure of -0.08 to -0.098 MPa for 15-30 minutes to remove microbubbles. The viscosity and Zeta potential of the slurry were then measured, and fine-tuned according to the aforementioned parameter targets to ensure the slurry reached its optimal physical state. Viscosity target achieved: Based on the measurement results, the viscosity of the three-phase slurry A, B, and C was locked within the aforementioned range by means of micro-dropping of PAA aqueous solution with a mass concentration of 15%, deionized water, or supplementing with 5% PVA aqueous solution and extending the vacuum degassing time; among them, the addition of PAA helps to reduce viscosity through electrostatic repulsion while maintaining solid content.

[0086] Stability Co-locking: During viscosity adjustment, if the absolute value of the Zeta potential deviates from the target, the pH value of the slurry is adjusted to 9.0-10.0 by adding ammonia. By changing the charge distribution of the double layer, it has been verified that adjusting the pH to this range can ensure that the absolute value of the Zeta potential reaches above 35mV, thereby locking the long-term colloidal stability of the slurry.

[0087] After the above adjustments, the final A, B, and C slurries not only met the viscosity requirements of the gradient design, but also had an absolute Zeta potential value of >35mV. After standing in the dark for 24 hours, the volume ratio of the upper clear liquid was <3%, and no hard sediment was formed at the bottom, thus meeting the technical requirements for slurry stability.

[0088] Step 4: Gradient impregnation molding based on visual flow guidance and stepwise in-situ gelation like Figure 2 As shown, the three-layer gradient structure preform obtained in step 1 is loaded into the corresponding special mold. The special mold is square in shape and made of transparent acrylic resin. The inner cavity shape is consistent with the size of the three-layer gradient structure preform. The special mold has three independent interfaces on its side wall along the thickness direction. From bottom to top, the special mold is divided into layer C (corresponding to the dense layer back surface of the three-layer gradient structure preform, i.e., the inner layer), layer B (corresponding to the middle layer of the three-layer gradient structure preform, i.e., the transition layer), and layer A (corresponding to the loose layer front surface of the three-layer gradient structure preform, i.e., the outer layer). The independent interfaces include the corresponding C layer group, B layer group, and A layer group. The C layer group includes the C layer inlet at the bottom of the mold and the C / B interface vacuum port at the bottom edge of layer B (i.e., the upper area of ​​layer C). The B layer group includes the B layer inlet at the bottom edge of layer B and the B / A interface vacuum port at the bottom edge of layer A (i.e., the upper area of ​​layer B). The A layer group includes the C layer inlet at the bottom edge of layer B and the B / A interface vacuum port at the bottom edge of layer A (i.e., the upper area of ​​layer B). The design logic for the A-layer feed port at the bottom edge height of the layer and the top vacuum port set at the top of the mold is "feeding at the bottom of each layer and venting / vacuuming at the top of each layer". The height position of the special mold interface is calculated and set according to the actual thickness parameters of the A, B and C layers of the three-layer gradient structure preform, and the inner diameter of the interface is 1.5 mm.

[0089] C-layer group: C-layer feed port and C / B interface vacuum port at the C / B interface height. The bottom edge scale of the C-layer feed port is 0 (close to the bottom surface of the mold), and the top edge scale is D (interface aperture). The bottom edge scale of the C / B interface vacuum port is h. C -D(h C (C layer thickness), top edge scale is h C (Align the boundary line between layer C and layer B), connect the vacuum port of the C / B interface to the transparent flexible tube; B-layer group: The B-layer feed inlet and the B / A interface vacuum port at the B / A interface height, wherein the bottom edge scale of the B-layer feed inlet is h. C (Close to the C / B interface line), the top scale is h. C +D (D is the interface aperture), the bottom edge scale of the vacuum port at the B / A interface is h. C +h B -D(hB (This refers to the thickness of layer B), with the top edge scale marked h. C +h B (Align the boundary line between layer B and layer A), connect the vacuum port of the B / A interface to the transparent flexible tube; Layer A: Layer A inlet and top vacuum port, where the bottom edge of the Layer A inlet is marked with h. C +h B (Close to the B / A interface line), the top scale is h. C +h B +D (D is the interface aperture), the top vacuum port is directly set at the top of the mold, passing through the top cover of the mold, and the top vacuum port is connected to a transparent hose; The A-layer, B-layer, and C-layer inlet ports are each connected to their respective slurry storage tanks via pressure-resistant hoses. The slurry storage tanks are connected to compressed air pumps to provide a constant feed pressure. Feed valves (such as ball valves) are installed in the middle, including C-layer, B-layer, and A-layer feed valves. The C / B interface vacuum port, B / A interface vacuum port, and top vacuum port are each connected to a vacuum collection tank (buffer tank) via transparent hoses, and then connected to a vacuum pump system. Vacuum valves (such as shut-off valves) are installed in the middle, including C / B interface vacuum valves, B / A interface vacuum valves, and top vacuum valves. Heating modules are arranged in close contact with the outer periphery of the special mold sidewall. The heating modules are independently zoned according to the A, B, and C layers, with each zone having independent temperature control. For example, the heating module corresponding to layer C is located at the bottom of the mold at the scale 0 to h. C Between these points, the corresponding zone heating module for layer B is located at scale h on the bottom of the mold. C to h B +h C Between these points, the zone heating module corresponding to layer A is located at scale h on the bottom of the mold. B +h C to h A +h B +h C Between them, the heating module is connected to the external intelligent temperature control box through a temperature sensor to form a closed-loop control system. The heating module is an electric heating element or a flexible silicone heating strip, and the inner diameter of all interfaces is uniformly 1.5 mm.

[0090] The characteristics of layers A, B, and C and their corresponding spatial positions in the special mold are shown in Table 1: Table 1. Characteristics of Layers A, B, and C and their corresponding spatial positions in the special mold. Impregnation and gelation: Before impregnation, it is necessary to ensure that the preform and the mold are in strict correspondence: the C layer group corresponds to the inner layer of the preform (the bottom dense support layer, with a thickness of 0-4mm); the B layer group corresponds to the middle layer (the transition layer, with a thickness of 4-8mm); and the A layer group corresponds to the outer layer (the top loose energy-absorbing layer / projectile-facing surface, with a thickness of 8-12mm). C-layer impregnation and gelation: Open only the C-layer feed valve and the C / B interface vacuum valve, close all other valves, and start the vacuum pump and feed pump. Under the combined guidance of constant feed pressure (provided by the compressed air pump) and front-end negative pressure, the slurry storage tank maintains a negative pressure environment of -0.085 MPa to -0.095 MPa within the system. Under the guidance of negative pressure, the C-layer slurry fills the dense fiber layer of the inner layer (C-layer) from bottom to top. When overflow is observed from the transparent hose connected to the C / B interface vacuum port, it is determined that the C-layer space is saturated. Immediately close all valves, turn on the heating module of the C-layer area of ​​the mold, and heat at 75°C for 20 minutes to transform the C-layer slurry into a gel state in situ, completing the impregnation and locking of the C-layer.

[0091] B-layer impregnation and gelation: Open only the B-layer feed valve and the B / A interface vacuum valve, close all other valves, and start the vacuum pump and feed pump. Under the combined guidance of constant feed pressure (provided by the compressed air pump) and front-end negative pressure, the slurry storage tank maintains a negative pressure environment of -0.085 MPa to -0.095 MPa within the system. Under the guidance of negative pressure, the B-layer slurry flows directionally above the C-layer gel interface (the lower part is blocked by gel and cannot penetrate, while the upper part is attracted by vacuum), filling the pores of the B-layer. When overflow is observed from the transparent hose connected to the vacuum port of the B / A interface, it is determined that the B-layer space is saturated. Immediately close all valves, turn on the heating module of the B-layer area of ​​the mold, and heat at 75°C for 20 minutes to transform the B-layer slurry into a gel state in situ, completing the impregnation and locking of the B-layer.

[0092] Layer A Impregnation and Gelation: Open only the Layer A feed valve and the top vacuum valve, close all other valves, and start the vacuum pump and feed pump. Under the combined guidance of a constant feed pressure (provided by a compressed air pump) and front-end negative pressure, the slurry storage tank maintains a negative pressure environment of -0.085 MPa to -0.095 MPa within the system. Under the guidance of negative pressure, the Phase A slurry fills the pores of Layer A. When overflow is observed from the transparent hose connected to the top vacuum port, it is determined that the Layer A space is saturated. Immediately close all valves, turn on the heating module of the Layer A area of ​​the mold, and heat at 75°C for 20 minutes to transform the Layer A slurry into a gel state in situ, completing the impregnation and locking of Layer A.

[0093] Overall drying: Place the mold after grouting into an oven and dry at 50°C for 48 hours until the green body is dehydrated and shaped (using the oven drying method (mass method) for monitoring; by comparing the change in the overall weight of the mold, when the mass difference between two weighings (with an interval of 4 hours) is less than 0.1%, it can be determined that the shaping is complete), and obtain the gradient green body.

[0094] Step 5: Gradient degreasing and spark plasma sintering Gradient degreasing (binder removal): Place the gradient green body obtained in step 4 into a tube furnace, introduce a flowing inert atmosphere, and execute a gradient heating program.

[0095] Equipment: The dried gradient green body is placed in a tube furnace to perform a gradient heating program; Atmosphere: High-purity nitrogen (N2) is introduced as a protective gas at a flow rate of 300 mL / min to prevent oxidation and product accumulation during the decomposition of organic matter; The gradient heating program is as follows: Low temperature section: The temperature is slowly increased to 300℃ at a rate of 0.5℃ / min and held for 2 hours to remove moisture and low molecular weight organic matter; High temperature section: Continue to heat up to 500℃ at a rate of 1.0℃ / min and hold for 3 hours to decompose high molecular polymers such as PVA binder and PAA dispersant; Cooling: After degreasing, allow the furnace to cool naturally to room temperature.

[0096] Objective: To slowly remove PVA binder and PAA dispersant to prevent cracking of the preform or bursting of microcapsules due to rapid gas release.

[0097] Mold filling: Remove the degreased blank and place it into a high-strength graphite mold; Isolation treatment: Spray a layer of boron nitride (BN) aerosol (using commercially available industrial-grade high-temperature boron nitride release agent, such as ZYP Coatings, Inc.; model: BN AerosolLubricoat, or 3M Corporation; model: 3M™ Boron Nitride Spray WS) between the blank and the inner wall of the mold, or wrap a layer of graphite paper (cut the graphite paper into a cylindrical shape and place it tightly against the inner wall of the graphite mold to isolate the sides of the blank; at the same time, cut the graphite paper into circular pieces that match the inner diameter of the mold and place them between the upper surface of the blank and the upper pressure head, and between the lower surface of the blank and the lower pressure head, respectively, to isolate the upper and lower end faces) to prevent carbon diffusion and adhesion at high temperatures.

[0098] SPS rapid sintering: Equipment: Place the assembled mold into the furnace chamber of the spark plasma sintering system (SPS); Environment: Evacuate the furnace cavity until the vacuum level reaches <10 Pa; Sintering process: Heating: Under the action of pulsed current, the temperature is rapidly increased at a rate of 100℃ / min; Parameters: The target sintering temperature is set to 1600℃; Insulation: Keep warm at 1600℃ for 5 minutes; Cooling: After sintering, the power is turned off, and the furnace is allowed to cool naturally to room temperature. Pressure: Apply a basic uniaxial pressure of 10 MPa at a rate of 100℃ / min before heating to 1000℃ to ensure good electrical contact between the pressure head, graphite paper and green body, maintain the conductivity of the current circuit, and avoid crushing the brittle green body; after heating to above 1000℃ (the material gradually enters the plastic deformation zone), gradually increase the pressure to the target uniaxial pressure of 50 MPa at a steady rate; after heating to the target sintering temperature of 1600℃, hold at a constant temperature of 50 MPa for 5 minutes to promote the full densification of the gradient layers; immediately disconnect the power after the holding period, and gradually and slowly remove the uniaxial pressure during the natural cooling process to room temperature with the furnace to fully release the residual thermal stress inside the ceramic and prevent cracking of the sintered body; Ultimately, a high-performance gradient self-healing basalt fiber composite ceramic armor plate was obtained.

[0099] Performance test results: Internal structure: The cross-section clearly shows a three-layer gradient structure with no mixed layers and tight interface bonding; Density gradient: 3.12 g / cm³ for layer A, 3.58 g / cm³ for layer B, and 3.86 g / cm³ for layer C.

[0100] Ballistic performance: Fired with a 7.62 mm armor-piercing round, it did not penetrate; the backplate protrusion is 10.5 mm.

[0101] Self-healing efficiency: Standard three-point bending specimens (3 mm × 4 mm × 30 mm) were cut from the back of the inner layer (C layer, Al2O3-based) of the shot-damaged area. The specimens were placed at 130℃ for 30 minutes to induce DCPD polymerization repair. The bending strength recovery rate was measured to be 82%.

[0102] Example 2: A gradient self-healing armor plate (lightweight B4C / Si3N4 system + KH-550 coupling agent) was prepared by the following method to verify the applicability of different ceramic matrices and coupling agent systems.

[0103] Steps 1 and 2 are basically the same as in Example 1, except that in Example 2, a KH-550 coupling agent solution is used. 900 mL of anhydrous ethanol and 100 mL of deionized water are measured, and 20 g of KH-550 is added. Pure glacial acetic acid (99.5% purity) is added dropwise to adjust the pH to 4.5, and the mixture is stirred at room temperature for 40 minutes. The impregnation process is the same as in Example 1.

[0104] Step 3: Preparation of ceramic slurry with rheological gradient The setup of the planetary ball mill is the same as in Example 1.

[0105] Specific ingredients and preparation: According to the design requirements, solid powder materials were prepared for the outer, middle, and inner layers respectively: Phase A slurry (B4C based, high hardness / high viscosity): Weigh 300g of Phase A raw material, B4C powder (particle size 0.5-1.5μm), and 15g of microcapsules (5 wt%). Place the above raw materials in a ball mill jar, then add 5g of PVA (molecular weight 40000-70000g / mol) (organic binder), and add 0.8g of PAA (dry weight) (molecular weight 3000-5000 g / mol) (dispersant) in the form of a 15% aqueous solution. Finally, add deionized water until the solid content of the system is 50 vol%. Ball mill according to the above general parameters to obtain the Phase A slurry. Rheological control: After ball milling, the slurry was poured out and placed in a vacuum degassing machine for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove the large number of microbubbles introduced during ball milling. The slurry viscosity was then measured. If the viscosity was too high, it was adjusted by adding a small amount of 15% PAA aqueous solution or deionized water; if the viscosity was too low, it was adjusted by adding a small amount of 5% PVA aqueous solution or appropriately extending the vacuum degassing time. The final viscosity of the A-phase slurry was adjusted to 11.0 Pa·s.

[0106] B-phase slurry (transitional / medium viscosity): Weigh 150 g of B4C, 150 g of Al2O3 (both powders have a particle size of 1.5-3.0 μm), and 24 g of microcapsules (8 wt%). Place the above raw materials into a ball mill jar, then add 5 g of PVA (molecular weight 40000-70000 g / mol) (organic binder) and a 15% (w / w) aqueous solution of PAA (molecular weight 3000-5000 g / mol) (based on a PAA dry weight of 2.0 g). Finally, add deionized water to a system solid content of 50 vol%. Ball mill according to the above general parameters to obtain the B-phase slurry. Rheological control: After ball milling, the slurry was poured out and placed in a vacuum degassing machine for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove the large number of microbubbles introduced during ball milling. The slurry viscosity was then measured. If the viscosity was too high, it was adjusted by adding a small amount of 15% PAA aqueous solution or deionized water; if the viscosity was too low, it was adjusted by adding a small amount of 5% PVA aqueous solution or extending the vacuum degassing time. The final viscosity of the B-phase slurry was adjusted to 4.0 Pa·s.

[0107] C-phase slurry (Si3N4 based, high toughness / low viscosity): Weigh 300 g of C-phase raw material Si3N4 (particle size 3.0-5.0 μm) and 30 g of microcapsules (10 wt%). Place the above raw material in a ball mill jar, then add 5 g of PVA (molecular weight 40000-70000 g / mol) (organic binder) and a 15% (w / w) aqueous solution of PAA (molecular weight 3000-5000 g / mol) (based on PAA dry weight of 4.5 g). Finally, add deionized water to a solid content of 50 vol%. Ball mill according to the above general parameters to obtain C-phase slurry. Rheological control: After ball milling, the slurry is poured out and placed in a vacuum degassing machine for 15-30 minutes under a negative pressure of -0.08 to -0.098 MPa to remove the large number of microbubbles introduced during ball milling. The slurry viscosity is then measured. If the viscosity is too high, it is adjusted by adding a small amount of 15% PAA aqueous solution or deionized water; if the viscosity is too low, it is adjusted by adding a small amount of 5% PVA aqueous solution or extending the vacuum degassing time. Finally, the viscosity of the C-phase slurry is adjusted to 0.8 Pa·s (low viscosity for high penetration).

[0108] Stability testing: The absolute value of the Zeta potential of all three groups of slurries was >35 mV, the sedimentation (i.e. the volume ratio of the supernatant) was <3% after 24 h, and no hard sediment was formed at the bottom.

[0109] The parameter adjustment method is the same as in Example 1.

[0110] Step 4 is the same as in Example 1.

[0111] Step 5 is basically the same as in Example 1, except that in SPS sintering, the sintering temperature is adjusted to 1550℃ (to prevent B4C reaction), the target uniaxial pressure is increased to 60 MPa, and the temperature is held for 8 minutes.

[0112] Performance test results: Internal structure: Cross-sectional morphology examination revealed a clear three-layer gradient structure with no layer mixing. Thanks to the color difference between B4C and Si3N4, the interlayer boundaries were clearly visible; no delamination, peeling, or macroscopic crack defects were observed in the sample cross-section.

[0113] Lightweighting: Thanks to the intrinsically low density of the selected matrix materials B4C (theoretical density approximately 2.52 g / cm³) and Si3N4 (theoretical density approximately 3.18 g / cm³), this embodiment achieves excellent macroscopic weight reduction. Overall Comparison: At the same armor plate thickness (taking 12 mm as an example), the measured overall areal density of Example 1 (SiC / Al2O3 system) is approximately 41.5 kg / m², while the measured overall areal density of Example 2 is reduced to approximately 34.0 kg / m². Compared to Example 1, the absolute value of the overall areal density is reduced by 18%, significantly reducing the carrying weight of individual soldiers or equipment. Ballistic performance: A vertical firing test using a 7.62mm high-velocity armor-piercing round resulted in no penetration. The measured backplate protrusion is 12.5 mm. Self-healing efficiency: A standard specimen was cut from the inner layer (C layer, Si3N4 base) of the shot-damaged area. The specimen was placed at 130℃ for 30 minutes, and the flexural strength recovery rate was measured to be 76%.

[0114] Example 3: A gradient self-healing armor plate, which is an armor plate with optimized thickness ratio, such as... Figure 3 As shown, the thickness ratio of the preform was adjusted compared to Example 1 to cope with higher energy level impacts, and it was prepared by the following method.

[0115] Steps 1, 2, and 3 are basically the same as in Example 1, except that: Parameter adjustment: The total thickness of the precast body is increased to 15 mm.

[0116] Layer A (outer layer): 40% thickness (6 mm), weft density 8 threads / cm.

[0117] Layer B (middle layer): 30% of the thickness (4.5 mm), weft density 12 threads / cm.

[0118] C layer (inner layer): 30% of the thickness (4.5 mm), weft density 18 threads / cm.

[0119] Microcapsule content: The amount of microcapsules added in the C phase raw material was increased to 12 wt%.

[0120] Steps 4 and 5 are the same as in Example 1.

[0121] Performance test results: Internal structure and overall areal density: The cross-section clearly shows a three-layer gradient structure, with the thickness of each layer conforming to the design ratio (A:B:C = 4:3:3). Due to the increase in total thickness to 15 mm, the measured value of the overall areal density increases accordingly to approximately 52.0 kg / m², in order to match the higher energy level of physical protection requirements.

[0122] Ballistic performance: Test 1 (Single-shot heavy fire): Vertical firing using a 12.7mm armor-piercing incendiary round. Result: No penetration. The measured backplate protrusion is 18.5 mm, indicating that the thickened preform effectively dispersed the impact energy.

[0123] Test 2 (Multiple Consecutive Shots): Three shots were fired in quick succession using 7.62mm armor-piercing rounds (50mm interval between impact points). The result was that none of the rounds penetrated. The maximum backplate protrusion was measured at 15.8 mm (at the point of impact of the third shot).

[0124] Structural integrity (anti-delamination verification): After withstanding the above three consecutive impacts, the target plate underwent ultrasonic non-destructive testing. The results showed that the delamination area was limited to a range of less than 20 mm around the impact point, and no macroscopic delamination occurred across the entire plate surface. This confirms the excellent shear resistance under the synergistic effect of Z-direction bonding yarns and cross-linked molecular bridges.

[0125] Self-healing efficiency: The sampling location was a standard sample cut from the inner layer (C layer, Al2O3-based, with a capsule content as high as 12%) of the damaged area. The sample was placed in an environment of 130°C for 30 minutes, and the bending strength recovery rate was measured to be as high as 88% (Note: This recovery rate is better than that of Examples 1 and 2, which is attributed to the highest content (12 wt%) of self-healing microcapsules enriched in the C layer, which released a sufficient amount of DCPD repair agent after damage, achieving efficient filling and bridging of matrix cracks, and significantly improving the secondary protection potential after armor plate repair).

[0126] Comparative Example 1 (homogeneous, gradient-free three-dimensional woven fiber skeleton) This comparative example aims to verify the necessity and technical effect of the "sparse on the outside and dense on the inside" fiber weaving physical gradient in this invention. The preparation method of this comparative example is basically the same as that of Example 1, the only difference being the fiber structure in step 1: Instead of using a three-layer gradient weaving method, a homogeneous three-dimensional woven preform with a total thickness of 12 mm was prepared using the same 1200 tex basalt continuous fiber through a three-dimensional weaving machine. The preform exhibits no density or angle variation in the thickness direction and adopts uniform medium weaving parameters (weft density of 10 threads / cm and weaving angle of 35°).

[0127] The processing techniques, slurry formulations, and sintering parameters for steps 2 to 5 are consistent with those in Example 1.

[0128] Performance test results: Internal structure: Cross-sectional observation shows that due to the homogenization of the fiber skeleton (uniform porosity), the high viscosity A-phase slurry (SiC-based) in Comparative Example 1 has increased permeation resistance during impregnation, resulting in a small number of micropore defects on the surface of the impact-resistant surface; while for the inner layer, due to the reduction in weft density, the pores become wider, and the low viscosity C-phase slurry, which was originally designed for dense pores, lacks sufficient capillary binding force, resulting in uneven distribution of high-concentration microcapsules and failure to form an ideal dense matrix support network.

[0129] Ballistic performance: Vertical firing was performed using a 7.62 mm armor-piercing round. The result was no penetration, but the measured backplate protrusion increased to 17.2 mm.

[0130] Self-healing efficiency: A standard specimen was cut from the inner layer of the shot-damaged area and kept at 130°C for 30 minutes. The measured flexural strength recovery rate was only 38%.

[0131] Conclusion and Analysis: The comparative results show that the homogeneous skeleton loses the structural advantage of "sparse on the outside and dense on the inside". Mechanically, the sparser inner fiber leads to a weakening of the tensile modulus of the back elastic surface and a sharp reduction in the ability to resist out-of-plane deformation (increased protrusions); rheologically, the large pores cannot form in-situ locking of the slurry, resulting in uneven distribution of repair factors, lack of uniform repair agent coverage along the crack propagation path, and a significant decrease in macroscopic self-healing efficiency.

[0132] Comparative Example 2 (microcapsules did not use a gradient and showed a uniform distribution) This comparative example aims to verify the necessity and technical effectiveness of the "specific gradient distribution design of self-healing microcapsules" in this invention. The preparation method is the same as in Example 1, and the gradient of the ceramic matrix (SiC → SiC / Al2O3 → Al2O3), the viscosity control target of each layer, and the stepwise gelation impregnation process remain unchanged. The only difference is the amount of microcapsules added in step 3: instead of the "low outside, high inside (3 wt% → 6 wt% → 9 wt%)" gradient in Example 1, the amount of microcapsules added in the three-phase slurry A, B, and C is uniformly set to 6 wt% (average).

[0133] Performance test results: Internal structure: The cross-section clearly shows a three-layer gradient structure with no mixed layers.

[0134] Ballistic performance: 7.62 mm armor-piercing projectiles were fired vertically. The result was no penetration, but the measured backplate protrusion increased to 13.8 mm.

[0135] Self-healing efficiency: A specimen cut from the inner layer of the shot-damaged area was placed at 130°C to induce repair. The measured flexural strength recovery rate was only 45%.

[0136] Conclusion Analysis: Test data shows that even with a perfect physical structure, the uniform distribution of microcapsules leads to performance compromises. This is because: firstly, increasing the microcapsule content on the projectile-facing surface (layer A, SiC-based) from 3 wt% to 6 wt% results in excessive flexible organic components weakening the absolute hardness of the outer ceramic layer, leading to a decrease in projectile fragmentation efficiency (i.e., core fragmentation capability), and the projectile's penetration kinetic energy cannot be effectively dissipated at the surface (increased backplate protrusion); secondly, on the back surface (layer C), as the core area of ​​tearing damage, the uniform 6 wt% microcapsule content cannot provide sufficient repair agent for deep macroscopic cracks, resulting in a significant decrease in self-healing efficiency. This demonstrates that a uniform distribution without gradients cannot simultaneously meet the dual core requirements of "external hardness and internal toughness" and "deep repair."

[0137] Comparative Example 3 (using the opposite microcapsule concentration gradient) This comparative example aims to verify the necessity of the "low on the outside, high on the inside" specific gradient distribution of the self-healing microcapsules of the present invention (precisely matching the physical damage pattern of armor).

[0138] The preparation method was exactly the same as in Example 1, with the ceramic matrix gradient, rheological control, and impregnation molding process remaining unchanged. The only difference was that the concentration gradient of the microcapsules in step 3 was completely reversed (higher on the outside and lower on the inside): A-phase slurry (outer layer, SiC-based): the microcapsule addition amount was increased to 9 wt%. B-phase slurry (middle layer, mixed matrix): the microcapsule addition amount remained at 6 wt%. C-phase slurry (inner layer, Al2O3-based): the microcapsule addition amount was reduced to 3 wt%.

[0139] Performance test results: Internal structure: The cross-section shows a clear three-layer gradient structure with no mixed layers.

[0140] Ballistic performance: Vertical firing with a 7.62 mm armor-piercing round resulted in penetration.

[0141] Self-healing efficiency: Samples were prepared by collecting residual fragments in the middle layer of the damaged area and inducing repair at 130℃. The measured flexural strength recovery rate was 15%.

[0142] Conclusion and Analysis: Using a microcapsule concentration gradient completely opposite to that of this invention (high concentration on the outside, low concentration on the inside) leads to armor performance degradation. The reasons are as follows: First, the introduction of up to 9 wt% flexible microcapsules into the projectile-facing surface (layer A) severely disrupts the continuous rigidity and macroscopic hardness required by the SiC ceramic matrix to resist ballistic penetration, causing the armor to lose its primary ability to fragment and penetrate the projectile core, thus allowing it to be penetrated. Second, the inner layer microcapsule concentration is too low (only 3 wt%), failing to release sufficient repair agent for structural bridging when a fatal tear occurs in the backplate. This demonstrates that the specific gradient design of this invention—"low content in the outer layer to maintain hardness, high content in the inner layer to enhance healing"—is the key to achieving a perfect match between ballistic protection and deep repair.

[0143] Comparative Example 4 (using conventional continuous vacuum perfusion without stepwise gelation blockade) This comparative example aims to verify the necessity of the "stepwise in-situ gelation" process, which is the first of its kind in this invention, to achieve precise partitioning of multiple components in the connected fiber skeleton (to prevent layer mixing), and the synergistic supporting role of this process and rheological gradient control.

[0144] The preparation method is exactly the same as in Example 1, including the fiber gradient skeleton, the A / B / C three-phase slurry formulation, and the rheological viscosity. The only difference is in the impregnation molding process in step 4: the "stepwise in-situ gelation (heat curing)" step of this invention is omitted. Specifically, after injecting the C-phase slurry and filling the inner layer, the heating module is not activated to block gelation; instead, the B-phase and A-phase slurries are continuously injected in a liquid state. This employs the "continuous vacuum infusion" process commonly used in traditional resin-based composite materials. Performance test results: Internal structure: Cross-sectional observation revealed severe layering and interface blurring. Due to the complete interconnection of pores within the fiber skeleton and the lack of physical blocking by the gel layer, under the pressure difference of subsequent vacuuming and the capillary force of the fibers, the liquid C, B, and A phase slurries underwent disordered penetration and cross-diffusion at the interface, causing the expected three-layer gradient structure to degenerate into a disordered mixture with blurred boundaries.

[0145] Ballistic performance: Vertical firing was performed using a 7.62 mm armor-piercing round. The result was no penetration, but the measured backplate protrusion increased significantly to 16.5 mm.

[0146] Self-healing efficiency: The bending strength recovery rate was measured to be 52% when the inner layer of the specimen was cut from the shot-damaged area.

[0147] Conclusion and analysis: Due to severe intercalation, the impact-facing surface was mixed with too much low-viscosity Al2O3 and high-concentration microcapsules, resulting in a decrease in surface penetration resistance (larger protrusions); while the repair factors originally enriched in the back impact-facing surface also diffused backward to the middle and outer layers, resulting in a decrease in the true self-healing ability of the inner layer.

[0148] Conclusion and Analysis: Even with a perfect rheological gradient in interconnected porous media, the precise fabrication of functionally graded materials is difficult to achieve without the core process of "stepwise in-situ gelation." This process and material formulation form a strong technological synergy, representing a key strategy for constructing structure-guided functional armor.

[0149] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any equivalent substitutions or modifications made by those skilled in the art within the spirit and principle of the present invention without any creative effort should be included within the protection scope of the present invention.

Claims

1. A method for preparing a gradient self-healing basalt fiber composite ceramic armor plate, characterized in that, It consists of the following interconnected phase modules: Phase 1: Preparation of basalt fiber three-layer gradient structure preform and construction of surface molecular bridges; Phase 2: Synthesis of polyurea-formaldehyde-coated dicyclopentadiene self-healing microcapsules; Phase 3: Preparation of ceramic slurry with rheological gradient; Phase 4: Gradient impregnation molding based on visual flow guidance and stepwise in-situ gelation; Phase 5: Gradient degreasing and discharge plasma sintering.

2. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 1, characterized in that, The specific steps of Phase One are as follows: (1) Gradient weaving: Using continuous basalt fiber with a linear density of 1200-2400 tex as raw material, a three-layer gradient structure prefabricated body is constructed along the thickness direction of the prefabricated body by a computer-controlled three-dimensional braiding machine. The three-layer gradient structure prefabricated body is divided into an outer layer, a middle layer and an inner layer. The weft density gradually increases and the braiding angle gradually decreases from the outer layer to the inner layer. (2) Preparation of coupling agent solution: A mixture of anhydrous ethanol and deionized water is used as the mixed solvent, wherein the volume fraction of anhydrous ethanol is 80%-95% and the volume fraction of deionized water is 5%-20%. KH-560 or KH-550 is selected as the coupling agent and dissolved in the mixed solvent to prepare a coupling agent solution. The mass concentration of the coupling agent in the coupling agent solution is 1.0-3.0 wt%. (3) Vacuum impregnation: The woven three-layer gradient structure preform is completely immersed in the above-prepared coupling agent solution, placed in a vacuum chamber, and vacuumed for 10-30 minutes under negative pressure to force out the air between the dense fiber bundles. Then, it is restored to normal pressure and soaked for 0.5-2 hours. (4) Cleaning and heat curing: Take out the three-layer gradient structure preform obtained in step (3), rinse it with deionized water to remove unreacted monomers and physical adsorbents on the surface, put it into a forced-air drying oven, and dry and solidify it at 70-90℃ for 3-6 hours to initiate a condensation reaction and complete the surface grafting.

3. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 2, characterized in that: With the total thickness of the precast body as H, the parameters for each layer are designed as follows: Outer layer: The thickness range is set to 30-40% of the total thickness H, the weft density is 5-8 threads / cm, and the weft angle is 45-60° to form a loose energy-absorbing layer; Middle layer: The thickness range is set to 30-35% of the total thickness H, the weft density is 8-12 threads / cm, the weft angle is 30-45°, forming a modulus transition layer; Inner layer: The thickness range is set to 30-35% of the total thickness H, the weft density is 12-18 threads / cm, and the weft angle is 15-30° to form a dense support layer; When KH-560 is selected, add KH-560 to the mixed solvent, adjust the pH value to 4.0-5.0, and stir at room temperature for 30-90 minutes; When KH-550 is selected, add KH-550 to the mixed solvent, adjust the pH value to 4.0-5.0, and stir at room temperature for 30-60 minutes.

4. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 1, characterized in that, The second stage specifically refers to: (1) Raw material preparation and mass proportioning: Prepare the raw materials of each component according to the following mass proportions: (a) Continuous phase: 100-300 parts solvent, 1.0-5.0 parts emulsifier; (b) Dispersed phase: 15.0-50.0 parts of repair agent; (c) Wall material precursor: 2.0-10.0 parts of skeleton agent, 5.0-25.0 parts of crosslinking agent, and 0.1-1.0 parts of modifier; The solvent is deionized water, the emulsifier is a styrene-maleic anhydride copolymer with a molecular weight of 10,000-100,000 g / mol, the repair agent is liquid dicyclopentadiene, the skeleton agent is urea, the crosslinking agent is a 37 wt% formaldehyde aqueous solution, and the modifier is resorcinol. The mass ratio of continuous phase to dispersed phase is controlled at 3:1 to 8:1; the mass ratio of dispersed phase to total mass of wall material precursor is controlled at 1:1 to 5:

1. (2) Core material emulsification: Dissolve the emulsifier in the solvent and stir at 60°C until clear to obtain a continuous phase. Slowly add the repair agent to the continuous phase, start the high-shear emulsifier, adjust the speed to 800-1500 rpm, and shear and stir for 10-20 minutes to form a stable O / W emulsion with an average droplet size of 20-80 μm. (3) Wall material prepolymer synthesis: In a separate reaction vessel, mix the skeleton agent, crosslinking agent, and modifier in the above proportions, adjust the pH value to 8.0-9.0, and stir the reaction at 65-75℃ for 0.5-1.5 hours to generate a urea-formaldehyde prepolymer solution. (4) In-situ covering: Slowly add the urea-formaldehyde prepolymer solution from step (3) to the emulsion from step (2), slowly adjust the pH of the system to 2.0-3.0, control the reaction temperature at 50-60℃, reduce the stirring speed to 300-600 rpm, and continue the reaction for 2-4 hours. (5) Post-processing: After the reaction was completed, the mixture was cooled to room temperature, the product was separated by filtration, and the microcapsules were obtained by washing with water, washing with alcohol and drying.

5. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 4, characterized in that, In step (5) of stage two, the water washing, alcohol washing, and drying are specifically as follows: Wash with water: Wash 3 times with deionized water, each time using enough water to completely cover the surface of the filter cake or wash until the effluent is neutral; Alcohol wash: Rinse once quickly with a small amount of anhydrous ethanol; Drying: Vacuum drying at 40-50℃ and -0.08~-0.095 MPa for 12-36 hours yields well-dispersible microcapsule powder.

6. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 1, characterized in that, The third stage specifically refers to: (1) Component weighing and formulation design: According to the design requirements, raw material powders were prepared for three layers: outer, middle, and inner. Phase A raw material corresponds to the outer layer; Phase B raw material corresponds to the middle layer; and Phase C raw material corresponds to the inner layer. Based on the total mass of the main phase in each layer, the mass percentage of each component was calculated as follows: Phase A raw material: Main phase: High-hardness ceramic powder; Functional phase: 3.0-7.0 wt% self-healing microcapsules added; Phase B raw materials: Main phase: a mixture of SiC or B4C and Al2O3 powder; Functional phase: 5.0-10.0 wt% self-healing microcapsules added; C-phase raw material: Main phase: High-toughness ceramic powder; Functional phase: 7.0-12.0 wt% self-healing microcapsules added; The functional phase content in phase A raw material is less than that in phase B raw material, which in turn is less than that in phase C raw material. The main phase of the A-phase raw material is selected from SiC or B4C, with a particle size of 0.5-1.5 μm; In the main phase of the B-phase raw material, the mass ratio of SiC or B4C to Al2O3 is 1:1 to 2:1, and the particle size is 1.5-3.0 μm; The main phase of the C-phase raw material is selected from Al2O3 or Si3N4, with a particle size of 3.0-5.0 μm; (2) Ball milling dispersion and slurry preparation: The A-phase, B-phase, and C-phase raw materials were each placed in three separate ball mill jars. Additives and deionized water were then added, and the mixtures were ball-milled in a planetary ball mill at 200-400 rpm for 24-48 hours. The additives were organic binders and dispersants. The solvent, deionized water, was used to adjust the slurry solid content to 40-55 vol%. The amount of organic binder added was 1.0-3.0 wt% of the total mass of each phase powder. The organic binder is selected from polyvinyl alcohol with an average molecular weight range of 20,000-70,000 g / mol, and the dispersant is selected from ammonium polyacrylate with an average molecular weight range of 3,000-8,000 g / mol. (3) Fine-tuning of rheological properties: After ball milling, each phase slurry was placed in a vacuum degassing machine and treated under a negative pressure of -0.08 to -0.098 MPa for 15-30 minutes. Then, the A-phase, B-phase, and C-phase slurries were taken out for rheological testing. The viscosities of the A-phase, B-phase, and C-phase slurries were adjusted to the following specific ranges by adding dispersants, organic binders, water, or extending the vacuum degassing time: C-phase slurry: viscosity controlled at 0.5-1.5 Pa·s; B-phase slurry: viscosity controlled at 2.0-5.0 Pa·s; Phase A slurry: viscosity controlled at 6.0-12.0 Pa·s; After the above rheological regulation, the absolute value of the zeta potential of the slurry remained above 30 mV, and after standing in the dark for 24 hours at normal temperature and pressure, the volume ratio of the supernatant was less than 5%.

7. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 1, characterized in that, The fourth stage specifically refers to: (1) Mold preparation and assembly: The three-layer gradient structure preform obtained in Stage 1 is installed into a corresponding special mold. The special mold is made of transparent acrylic resin, and its inner cavity shape is consistent with the size of the three-layer gradient structure preform. The special mold has three sets of independent interfaces on its side wall along the thickness direction. The special mold is divided into C layer, B layer and A layer from bottom to top. The independent interfaces include the corresponding C layer group, B layer group and A layer group. The C layer group includes the C layer inlet at the bottom of the mold and the C / B interface vacuum port at the bottom edge of the B layer. The B layer group includes the B layer inlet at the bottom edge of the B layer and the B / A interface vacuum port at the bottom edge of the A layer. The A layer group includes the A layer inlet at the bottom edge of the A layer and the top vacuum port at the top of the mold. The inner diameter of the interface is 1-2 mm. C / B interface vacuum port connected to transparent flexible tube; B / A interface vacuum port connected to transparent flexible tube; A transparent flexible tube is connected to the top vacuum port; The A-layer inlet, B-layer inlet, and C-layer inlet are each connected to the corresponding slurry storage tank via pressure-resistant hoses. The slurry storage tank is connected to a feed pump to provide a constant feed pressure, and feed valves are installed in the middle, corresponding to the C-layer feed valve, B-layer feed valve, and A-layer feed valve. The C / B interface vacuum port, B / A interface vacuum port, and top vacuum port are each connected to a vacuum collection tank via transparent hoses, and then connected to a vacuum pump system, with vacuum valves installed in the middle, corresponding to the C / B interface vacuum valve, B / A interface vacuum valve, and top vacuum valve. Heating modules are arranged closely around the outer periphery of the sidewall of the special mold. The heating modules are arranged in three independent zones: A, B, and C. Each zone is independently temperature controlled. The heating modules are connected to an external intelligent temperature control box through temperature sensors. The heating modules are electric heating elements or flexible silicone heating strips. (2) C-layer impregnation and in-situ gelation: Directional impregnation: Open only the C-layer feed valve and the C / B interface vacuum valve, close all other valves, start the vacuum pump and feed pump, and apply a negative pressure of -0.08 MPa to -0.095 MPa; Visual endpoint determination: Observe the transparent hose connected to the vacuum port at the C / B interface. When continuous slurry flow appears in the hose, immediately close the C-layer feed valve and the C / B interface vacuum valve. Physical blocking: Activate the heating module in the C layer area of ​​the mold, set the temperature to 60-80℃, and keep it warm for 15-30 minutes; (3) Layer B impregnation and in-situ gelation: Directional impregnation: Open only the B-layer feed valve and the B / A interface vacuum valve, close all other valves, start the vacuum pump and feed pump, and apply a negative pressure of -0.08 MPa to -0.095 MPa; Visual endpoint determination: When slurry overflow is observed in the transparent hose of the vacuum port of the B / A interface, immediately close the B layer feed valve and the B / A interface vacuum valve; Physical barrier: Activate the heating module in the B layer area and maintain the temperature at 60-80℃ for 15-30 minutes; (4) Layer A impregnation and overall drying: Directional impregnation: Open only the A-layer feed valve and the top vacuum valve, close all other valves, start the vacuum pump and feed pump, and apply a negative pressure of -0.08 MPa to -0.095 MPa; Visual endpoint determination: When slurry overflow is observed in the transparent hose of the top vacuum port, immediately close the A-layer feed valve and the top vacuum valve; Physical barrier: Activate the heating module in area A and maintain the temperature at 60-80℃ for 15-30 minutes; Overall drying: Place the mold after grouting into an oven and dry it at 40-60℃ for 24-72 hours until the green body is dehydrated and shaped. Then demold to obtain a gradient green body.

8. The method for preparing the gradient self-healing basalt fiber composite ceramic armor plate according to claim 1, characterized in that, The fifth stage specifically includes: (1) Gradient defatting: The gradient green body obtained in stage four is placed in a tube furnace or atmosphere furnace, and a flowing inert atmosphere, namely N2 or Ar at a flow rate of 200-500 mL / min, is introduced. The following gradient heating program is then executed: Low temperature section: Heat to 300℃ at a rate of 0.5-1.0℃ / min and hold for 1-2 hours; High temperature section: Continue to raise the temperature to 500-600℃ at a rate of 1.0-2.0℃ / min, and hold for 2-4 hours; Cooling: Natural cooling with the furnace; (2) Mold filling: Carefully place the degreased porous preform into a high-strength graphite mold, and spray or coat a layer of boron nitride or graphite paper between the preform and the inner wall of the mold as a separating agent. (3) SPS rapid sintering: Place the mold in an SPS sintering furnace and evacuate it to <10 Pa or introduce a protective atmosphere, which may be argon or nitrogen. Heating: Rapidly increase the temperature at a rate of 50-150℃ / min; Sintering temperature: set at 1500-1750℃; A protective atmosphere, wherein the protective atmosphere is argon or nitrogen; Pressure: Apply a base pressure of 5-10 MPa before heating to the first temperature of 1000-1200℃. After heating to above the first temperature, simultaneously change the pressure to the target pressure of 30-80 MPa. After holding at the sintering temperature, unload the pressure to the base pressure below 5 MPa or completely remove the pressure, and then start cooling. Heat preservation: Hold at the sintering temperature for 3-15 minutes; Cooling: Allow the furnace to cool naturally to room temperature.

9. A gradient self-healing basalt fiber composite ceramic armor plate, prepared by the method described in any one of claims 1-8.

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