Preparation method of bulletproof ceramic

Abstract

The invention discloses a bulletproof ceramic preparation method, which comprises: S1, mixing 60-75 parts by mass of alumina powder, 15-25 parts by mass of talc powder, 5-12 parts by mass of glass powder, and 1-3 parts by mass of CaF2 to prepare ceramic powder; s2, mixing the ceramic powder with a pore-forming agent, wherein the pore-forming agent comprises a starch-based pore-forming agent, a cellulose ether thickening agent and a surfactant; s3, adding a polyvinyl alcohol binding agent and a paraffin lubricant, and mixing and granulating; s4, the mixture is subjected to compression molding under the pressure of 120-180 MPa, and a ceramic green body is obtained; s5, degreasing the ceramic body for 2-4 hours, wherein the heating rate is 1-3 DEG C / min; s6, presintering at 860-900 DEG C for 1-2 hours, and continuously heating to 1350-1450 DEG C for sintering to obtain a ceramic matrix; and S7, coating the surface of the ceramic with a polyimide coating. Compared with the prior art, the prepared bulletproof ceramic is remarkably improved in strength, toughness and light weight, and is suitable for the field of military and civil protection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramics, and particularly relates to a bulletproof ceramic and a preparation method thereof. BACKGROUND

[0002] Bulletproof ceramics are widely used in the fields of military armor, police protection equipment and civil safety protection as important protection materials. Currently, the commonly used bulletproof ceramics mainly include alumina ceramics, silicon carbide ceramics and boron nitride ceramics, among which the alumina ceramics are widely used due to relatively low cost and relatively mature preparation process.

[0003] The traditional alumina bulletproof ceramic is usually prepared by a high-temperature sintering process at 1600-1700 DEG C. Although a high density and hardness can be obtained, the following problems exist: firstly, the high-temperature sintering leads to high energy consumption, which limits the industrial application; secondly, the single alumina phase structure is prone to brittle fracture and has insufficient toughness under high-speed impact; and thirdly, the ceramic prepared by the traditional process has a high density, which increases the overall weight of the protection equipment.

[0004] In order to improve the toughness of the alumina ceramic, the existing technology mainly adopts the addition of zirconium oxide, silicon carbide and other second phase particles for toughening. It is found that talc (3MgO·4SiO2·H2O) has a layered silicate structure and a low thermal expansion coefficient, and can form periclase (MgO) and quartz (SiO2) phases in situ during the ceramic sintering process. The in-situ reaction can form fine second phase dispersion in the matrix, which is beneficial to improving the thermal shock stability and toughness of the ceramic. At the same time, the addition of talc can effectively reduce the sintering temperature as a sintering aid.

[0005] However, the talc is mainly used in daily ceramics and building ceramics in the existing technology, and the application research in the field of bulletproof ceramics is less, especially how to realize the bulletproof ceramic with sufficient strength and good energy absorption capacity by combining the composite of talc and alumina and the pore forming process, which needs further research. SUMMARY

[0006] The technical problem to be solved by the present application is that the existing bulletproof ceramic has the technical defects of low impact strength, uncontrollable pore structure and poor environmental stability. In order to solve the above technical problems, the present application provides a preparation method of a bulletproof ceramic, which comprises the following steps: S1: mixing alumina powder 60-75 parts, talc powder 15-25 parts, glass powder 5-12 parts and CaF2 1-3 parts by mass fraction to obtain ceramic powder; S2: mixing the ceramic powder with a pore forming agent, the pore forming agent comprising starch-based pore forming agent 2-5 parts, cellulose ether thickening agent 0.5-1.5 parts and surfactant 1-2 parts by mass fraction; S3: adding 3-6 parts of polyvinyl alcohol binder and 0.5-1.5 parts of paraffin lubricant by mass fraction, mixing and granulating; S4: pressing the mixture into a ceramic body under a pressure of 120-180 MPa; S5: degreasing the ceramic body at 500-600℃ for 2-4 hours, with a heating rate of 1-3℃ / min; S6: after pre-sintering at 860-900℃ for 1-2 hours, continuing to heat to 1350-1450℃ to sinter the ceramic matrix; S7: coating a polyimide coating on the ceramic surface.

[0007] Preferably, the starch-based pore-forming agent comprises a mixture of corn starch and potato starch in a weight ratio of (2.0-4.5):1, with a particle size controlled at 20-80μm. The combination of corn starch and potato starch can be decomposed step by step at different temperature ranges, forming a gradient pore-forming effect and achieving precise control of the pore structure.

[0008] The average particle size of the alumina powder is 1-5μm, and the average particle size of the talc powder is 10-30μm; the glass powder is borosilicate glass powder. This particle size grading design can achieve dense packing while ensuring sintering activity, and the softening point of the glass powder matches the degreasing temperature, avoiding premature softening that affects the degreasing effect.

[0009] The technical features of the degreasing treatment in step S5 are: Slow heating, with a heating rate controlled at 1-3℃ / min, to avoid the rapid decomposition of organic matter caused by rapid heating, which causes the gas to be discharged too quickly, resulting in cracking or deformation of the body.

[0010] Sufficient heat preservation: heat preservation at the set temperature for 2-4 hours to ensure complete decomposition of the organic matter inside the body, especially the starch-based pore-forming agent which needs to be fully burned to form the pore structure.

[0011] Temperature selection: a temperature of 500-600℃ can ensure complete decomposition of organic matter without adversely affecting the inorganic components of the ceramic body.

[0012] Specifically, the cellulose ether thickening agent is hydroxypropyl methylcellulose or sodium carboxymethylcellulose. This precise compounding ratio ensures the best dispersion effect and stability of the pore-forming agent system.

[0013] Hydroxypropyl methyl cellulose has good water retention and film forming property, sodium carboxymethyl cellulose has excellent thickening effect, and the two can realize synergistic effect by compounding in a specific ratio. Polyoxyethylene sorbitan monostearate is a non-ionic surfactant, and sodium dodecyl sulfate is an anionic surfactant, and the two can reduce interfacial tension and improve the dispersion uniformity of the pore forming agent.

[0014] Specifically, the surfactant is prepared by compounding polyoxyethylene sorbitan monostearate and sodium dodecyl sulfate at a weight ratio of (1-2.6):1.

[0015] Specifically, the particle size of CaF2 is 5-15 mu m; and the ceramic body is placed for 12-24 hours after pressing.

[0016] CaF2 is a special fluxing agent, which has better thermal stability than traditional alkali metal oxides, and can effectively reduce the sintering temperature without volatilization.

[0017] Specifically, in the step S6, the sintering process comprises: pre-sintering at 860-900 DEG C for 1-2 hours, then heating to 1350-1450 DEG C at 2-5 DEG C / min and keeping for 2-4 hours.

[0018] Specifically, in the step S7, the preparation method of the polyimide coating comprises: applying the polyamide acid solution to the ceramic surface by spraying or dipping, then pre-curing at 150-200 DEG C for 30-60 minutes, and finally completely curing at 280-350 DEG C for 1-3 hours.

[0019] Specifically, in the step S3, the granulation process adopts spray granulation or extrusion granulation, and the particle size of the granules after granulation is controlled to be 100-500 mu m, and the water content is controlled to be 8-12%.

[0020] The appropriate forming density and standing time ensure the full release of internal stress of the body, and avoid cracking in the sintering process.

[0021] Specifically, the impact strength is 240-350 MPa, the density is 2.9-3.3 g / cm³, and the porosity is 10-16%.

[0022] The core innovation of the application lies in the following aspects of synergistic design: 1. Multi-element synergistic ceramic matrix system: alumina provides a high hardness skeleton, talc powder decomposes to form a toughness phase at high temperature, glass powder acts as a bonding phase to enhance the interface bonding, and CaF2 acts as a clean fluxing agent to reduce the sintering temperature, and the four components synergistically realize the best balance of strength, toughness and process performance.

[0023] 2、Controllable pore-forming technology system: a composite system of starch-based pore-forming agent and additive is adopted, the particle size distribution and decomposition characteristics of the pore-forming agent are controlled, and the porosity in the range is accurately controlled, so as to provide a structural basis for energy absorption.

[0024] 3、Precise sintering process control: through segmented heating and protective atmosphere sintering, the controllability of the ceramic densification process is ensured, and the defects of overburning and underburning are avoided.

[0025] 4、Surface functionalization modification: the polyimide coating provides environmental protection and stress relief function, and significantly improves the service life of the material.

[0026] Compared with the prior art, the present application has the following beneficial effects: 1、Functional layer, realizes the unity of high strength and light weight.

[0027] 2、Mechanism level: the magnesium silicate phase produced by the decomposition of talc powder at high temperature acts as a tough phase, effectively preventing crack propagation; the controllable pore structure provides multiple energy absorption mechanisms, including pore wall plastic deformation, pore collapse and crack deflection; the CaF2 flux forms a dense grain boundary phase without volatilization, enhancing the overall strength of the ceramic.

[0028] 3、Process advantage: the sintering temperature is lower than that of the traditional process, and the energy consumption is reduced; the introduction of the pore-forming agent system makes the pore structure controllable, and the product consistency is significantly improved; the surface coating process is simple and suitable for industrial production.

[0029] In summary, through systematic material composition optimization, process innovation and surface modification, the present application successfully solves the key technical problems of existing bulletproof ceramics, and provides a new technical path for the development of protective material technology. DETAILED DESCRIPTION

[0030] The present application will be further described below in conjunction with specific embodiments, but the present application is not limited to these embodiments. Those skilled in the art should realize that the present application encompasses all possible alternatives, improvements and equivalents within the scope of the claims.

[0031] Example 1: S1: take 65 parts of alumina powder (average particle size 3 μm), 20 parts of talc powder (average particle size 20 μm), 8 parts of borosilicate glass powder and 2 parts of CaF2 (particle size 10 μm) by mass fraction, dry mix in a ball mill for 4 hours, and prepare ceramic powder.

[0032] S2: Mix the ceramic powder with the pore-forming agent, which includes 3.5 parts of starch-based pore-forming agent (50μm particle size) compounded with corn starch and potato starch in a weight ratio of 3:1, 1 part of hydroxypropyl methylcellulose, and 1.5 parts of surfactant compounded with polyoxyethylene sorbitan monostearate and sodium dodecyl sulfate in a weight ratio of 1.8:1. Mix in a V-type mixer for 30 minutes.

[0033] S3: Add 4 parts of polyvinyl alcohol binder and 1 part of paraffin lubricant, granulate in a spray granulator, control the particle size to be 300μm, and the moisture content to be 10%.

[0034] S4: Press the mixture under a pressure of 150MPa to obtain a ceramic green body, and let it stand for 18 hours.

[0035] S5: Heat the ceramic blank to 550℃ at a heating rate of 2℃ / min and degrease it for 3 hours.

[0036] S6: Heat to 880℃ at a heating rate of 3℃ / min, pre-sinter for 1.5 hours, then heat to 1400℃ at a heating rate of 3℃ / min and hold for 3 hours to obtain a ceramic matrix.

[0037] S7: Apply the polyamic acid solution to the ceramic surface by spraying, pre-cur at 180°C for 45 minutes, and then fully cure at 320°C for 2 hours to obtain a bulletproof ceramic with a dry film thickness of 35μm.

[0038] Example 2: S1: By mass, take 60 parts of alumina powder (average particle size 1μm), 25 parts of talc powder (average particle size 15μm), 5 parts of borosilicate glass powder, and 1 part of CaF2 (particle size 5μm), and dry mix them in a ball mill for 5 hours to obtain ceramic powder.

[0039] S2: Mix the ceramic powder with the pore-forming agent, which includes 2 parts of starch-based pore-forming agent (30μm particle size) compounded with corn starch and potato starch in a weight ratio of 2:1, 0.5 parts of sodium carboxymethyl cellulose, and 1 part of surfactant compounded with polyoxyethylene sorbitan monostearate and sodium dodecyl sulfate in a weight ratio of 1:1. Mix in a high-speed mixer for 40 minutes.

[0040] S3: Add 3 parts of polyvinyl alcohol binder and 0.5 parts of paraffin lubricant, granulate in an extrusion granulator, control the particle size to be 150μm, and the moisture content to be 8%.

[0041] S4: Press the mixture under 120MPa pressure to obtain a ceramic green body, and let it stand for 12 hours.

[0042] S5: Heat the ceramic blank to 500℃ at a heating rate of 1℃ / min and degrease it for 2 hours.

[0043] S6: Heat to 860℃ at a heating rate of 2℃ / min, pre-sinter for 1 hour, then heat to 1350℃ at a heating rate of 2℃ / min and hold for 2 hours to obtain a ceramic matrix.

[0044] S7: Apply the polyamic acid solution to the ceramic surface by impregnation, pre-cur at 150°C for 30 minutes, and then fully cure at 280°C for 1 hour to obtain a bulletproof ceramic with a dry film thickness of 20μm.

[0045] Example 3: S1: By mass, take 75 parts of alumina powder (average particle size 5μm), 15 parts of talc powder (average particle size 30μm), 12 parts of borosilicate glass powder, and 3 parts of CaF2 (particle size 15μm), and dry mix them in a planetary ball mill for 6 hours to obtain ceramic powder.

[0046] S2: Mix the ceramic powder with the pore-forming agent, which includes 5 parts of starch-based pore-forming agent (80μm particle size) compounded with corn starch and potato starch in a weight ratio of 4.5:1, 1.5 parts of hydroxypropyl methylcellulose, and 2 parts of surfactant compounded with polyoxyethylene sorbitan monostearate and sodium dodecyl sulfate in a weight ratio of 2.6:1. Mix in a three-dimensional mixer for 50 minutes.

[0047] S3: Add 6 parts of polyvinyl alcohol binder and 1.5 parts of paraffin lubricant, granulate in a spray granulator, control the particle size to be 450μm, and the moisture content to be 12%.

[0048] S4: Press the mixture under 180MPa pressure to obtain a ceramic blank, and let it stand for 24 hours.

[0049] S5: Heat the ceramic blank to 600℃ at a heating rate of 3℃ / min and degrease it for 4 hours.

[0050] S6: Heat to 900℃ at a heating rate of 5℃ / min, pre-sinter for 2 hours, then heat to 1450℃ at a heating rate of 4℃ / min and hold for 4 hours to obtain the ceramic matrix.

[0051] S7: Apply the polyamic acid solution to the ceramic surface by spraying, pre-cur it at 200°C for 60 minutes, and then fully cure it at 350°C for 3 hours to obtain a bulletproof ceramic with a dry film thickness of 50μm.

[0052] Comparative Example 1 The method of Example 1 was followed, but borosilicate glass powder was not added in step S1, and the content of alumina powder was increased accordingly.

[0053] Comparative Example 2 The procedure was carried out according to the method of Example 1, but without adding a starch-based pore-forming agent in step S2.

[0054] Comparative Example 3 The method of Example 1 was followed, but the defatting heating rate in step S5 was increased to 5°C / min.

[0055] Comparative Example 4 The procedure was carried out according to the method of Example 1, but in step S6, pre-sintering was not performed; the temperature was directly raised to 1400°C for sintering.

[0056] Comparative Example 5 Basic properties: impact strength 336MPa, density 3.1g / cm³, porosity 13% (consistent with the matrix of Example 1).

[0057] Environmental testing (performed according to GJB150.9A-2009 standard): Temperature cycling (-55℃~125℃, 10 cycles): Surface microcracks with a depth >10μm appeared (no cracks in Example 1). Damp heat test (240 hours, 40℃ / 95%RH): mass loss rate 1.8% (0.2% in Example 1), surface corrosion area ratio 22% (≤3% in Example 1); Conclusion: Comparative Example 5 failed the GJB150.9A-2009 environmental adaptability certification, proving that the polyimide coating plays an irreplaceable role in the long-term service stability of bulletproof ceramics by blocking water vapor penetration (contact angle >110°) and inhibiting electrochemical corrosion.

[0058] The performance of the bulletproof ceramics prepared in Examples 1-3 and Comparative Examples 1-5 was tested, and the test results are shown in the table below. The impact strength of the bulletproof ceramics prepared in each example and comparative example was determined according to JC / T1057-2007 "Ceramic Tiles - Impact Test Method". The density of the ceramic material was determined according to GB / T1966-2024 "Porous Ceramics - Determination of Apparent Porosity and Bulk Density", and the porosity was determined using the Archimedes' displacement method. The bulletproof ceramics prepared in each example and comparative example were placed in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 24 hours before testing. For the surface coating test, the bonding strength between the coating and the substrate was evaluated according to GB / T5210-2018 "Paints and Varnishes - Pull-Off Adhesion Test". The test results are shown in Table 1.

[0059]

[0060] Table 1. Test results of bulletproof ceramic performance

[0061] The test results show that the bulletproof ceramics prepared in Examples 1-3 have excellent performance, with impact strength, density, and porosity all meeting the requirements. Comparative Example 1, lacking borosilicate glass powder, resulted in a significant decrease in the ceramic's impact strength; Comparative Example 2, lacking a pore-forming agent, had excessively low porosity, which, although theoretically increasing strength, failed to absorb impact energy due to the lack of a gradient pore structure; Comparative Example 3, with its excessively rapid degreasing and heating rate, led to the formation of internal microcracks; Comparative Example 4, omitting the pre-sintering step, resulted in uneven grain growth, leading to a decrease in impact strength; and Comparative Example 5, lacking a polyimide coating, failed to meet military requirements.

[0062] Ballistics performance assessment: Tests were conducted according to GJB 4300-2002 requirements (using 7.62mm standard bullets with an initial velocity of 710±10m / s). The results showed that the ceramics prepared in Examples 1-3 maintained structural integrity after testing, with back-side deformation ≤10mm, meeting the energy absorption requirements of the protection standard. In contrast, the ceramics in Comparative Examples 1-4 showed penetrating damage after the first impact. These results confirm that the ceramics prepared in this invention possess the impact resistance required for practical ballistic protection applications.

[0063] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing bulletproof ceramic, characterized in that, Includes the following steps: S1: Ceramic powder is prepared by mixing 60-75 parts of alumina powder, 15-25 parts of talc powder, 5-12 parts of glass powder, and 1-3 parts of CaF2 by weight. S2: Mix the ceramic powder with a pore-forming agent, wherein the pore-forming agent comprises, by weight, 2-5 parts of starch-based pore-forming agent, 0.5-1.5 parts of cellulose ether thickener, and 1-2 parts of surfactant; S3: Add 3-6 parts of polyvinyl alcohol binder and 0.5-1.5 parts of paraffin lubricant by weight, mix and granulate; S4: Press the mixture under a pressure of 120-180MPa to obtain a ceramic green body; S5: Degrease the ceramic green body at 500-600℃ for 2-4 hours, with a heating rate of 1-3℃ / min; S6: After pre-sintering at 860-900℃ for 1-2 hours, continue to heat to 1350-1450℃ for sintering to obtain a ceramic matrix; S7: Coating the ceramic surface with a polyimide coating.

2. The method for preparing bulletproof ceramic according to claim 1, characterized in that, The starch-based pore-forming agent comprises corn starch and potato starch compounded in a weight ratio of (2.0-4.5):1, with a particle size controlled at 20-80 μm.

3. The method for preparing bulletproof ceramic according to claim 1, characterized in that, The alumina powder has an average particle size of 1-5 μm, and the talc powder has an average particle size of 10-30 μm; the glass powder is borosilicate glass powder.

4. The method for preparing bulletproof ceramic according to claim 1, characterized in that, The cellulose ether thickener is hydroxypropyl methylcellulose or sodium carboxymethyl cellulose.

5. The method for preparing bulletproof ceramic according to claim 1, characterized in that, The surfactant is prepared by compounding polyoxyethylene sorbitan monostearate and sodium dodecyl sulfate in a weight ratio of (1-2.6):

1.

6. The method for preparing bulletproof ceramic according to claim 1, characterized in that, The CaF2 has a particle size of 5-15 μm; the ceramic green body is left to stand for 12-24 hours after pressing.

7. The method for preparing bulletproof ceramic according to claim 1, characterized in that, In step S6, the sintering process includes: pre-sintering at 860-900℃ for 1-2 hours, and then heating to 1350-1450℃ at 2-5℃ / min and holding for 2-4 hours.

8. The method for preparing bulletproof ceramic according to claim 1, characterized in that, In step S7, the method for preparing the polyimide coating includes: applying a polyamic acid solution to the ceramic surface by spraying or dipping, then pre-curing at 150-200℃ for 30-60 minutes, and finally fully curing at 280-350℃ for 1-3 hours.

9. The method for preparing bulletproof ceramic according to claim 1, characterized in that, In step S3, the granulation process adopts spray granulation or extrusion granulation. After granulation, the particle size is controlled at 100-500μm and the moisture content is controlled at 8-12%.

10. The bulletproof ceramic prepared according to the method described in claims 1-9, characterized in that: Impact strength 240-350MPa, density 2.9-3.3g / cm³, porosity 10-16%.

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