A bionic gradient ceramic material and its preparation method and application

Abstract

The invention relates to a gradient ceramic material based on bionics and a preparation method and application thereof, belonging to the technical field of ceramic-based composite materials, and solving the problems of insufficient hardness and heavy weight of existing protective gear preparation materials. The invention first prepares boron carbide particles, and then uses the boron carbide particles, Al2O3 powder, Y2O3 powder, carbon powder and phenolic resin as raw materials, pours each raw material into a corresponding steel mold cavity, compacts the raw materials in the steel mold by a servo motor and a compaction structure, and prepares a plurality of layered blanks with shell bionic structures; the layered blanks with different components are arranged vertically and neatly in a graphite crucible in turn, and sintered by a segmented heating and temperature raising method, so as to obtain a gradient ceramic material based on bionics, which has the advantages of excellent mechanical properties, light weight, high stability and low corrosion resistance, and can be used to manufacture protective equipment with higher quality, lighter weight and adaptability to natural environments.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic-based composite materials, and in particular to a gradient ceramic material based on bionics and a preparation method and application thereof. Background Art

[0002] In nature, there are many organisms with special structures that can achieve good performance with less biological energy. Bionic gradient structure is an excellent biological structure that combines materials with different mechanical properties to produce a structural gradient inside the material. The gradient structure can adapt to the different properties between different materials and provide good toughness and wear resistance. It is currently widely used in the field of armor preparation.

[0003] For protective gear, its material and structure are the key factors that determine its protective effect. Currently, Kevlar, ceramics, polyethylene and other materials are used to make protective gear, but these materials have the disadvantages of insufficient hardness and heavy weight, resulting in the protective gear currently produced still being difficult to have the characteristics of high hardness and light weight. Summary of the invention

[0004] In order to solve the problems of insufficient hardness and heavy weight of materials used in manufacturing protective gear, the present invention provides a bionics-based gradient ceramic material and a preparation method and application thereof.

[0005] To solve the above problems, the present invention adopts the following technical solutions:

[0006] A method for preparing a gradient ceramic material based on bionics comprises the following steps:

[0007] Step 1: granulating boron carbide powder using a vertical high-speed ball mill to prepare boron carbide particles;

[0008] Step 2: Boron carbide particles, Al2O3 powder, Y2O3 powder, carbon powder and phenolic resin are respectively used as raw materials, and each raw material is poured into a corresponding steel mold cavity, the bottom of the mold cavity is a transfer pad, the mold cavity and the transfer pad form a shell bionic structure, and then the raw materials in the steel mold are compacted by a servo motor and a compaction structure driven by the servo motor to prepare a plurality of layered blanks with a shell bionic structure;

[0009] Step 3: The layered green blanks of different compositions obtained in step 2 are placed vertically and neatly in a graphite crucible in sequence, and the graphite crucible and the layered green blanks therein are sintered by a segmented heating method to obtain a bionic gradient ceramic material after sintering.

[0010] The present invention also provides a bionics-based gradient ceramic material prepared by the above-mentioned preparation method.

[0011] The present invention also provides application of the above-mentioned bionics-based gradient ceramic material in protective gear.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention utilizes bionic technology and combines the good gradient of the surface of the razor clam shell to obtain a higher quality and higher performance gradient ceramic material in a hierarchical manner through component design, gradient blank production, sintering and other processes. The gradient ceramic material has the advantages of excellent mechanical properties, light weight, high stability and low corrosion resistance. The bionic gradient ceramic material can be used to prepare protective equipment that is higher quality, lighter and more adaptable to the natural environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0015] Figure 1 This is a schematic diagram of the principle of the preparation method described in an embodiment of the present invention;

[0016] Figure 2 Schematic diagram of the structure of bionic-based gradient ceramic materials. DETAILED DESCRIPTION

[0017] In order to more clearly describe the technical problems, technical solutions and advantages to be solved by the present invention, the technical solutions of the present invention are described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] The present invention first establishes a mapping relationship between biological models and protective equipment through the analysis of biological prototype materials from the aspects of characterization and analysis of the microscopic morphology of razor clam shells, testing of the mechanical properties of razor clam shell materials, and testing and realization principle research of the protective function of razor clam shells. Among them, the protective performance test of the biological prototype mainly refers to the use of relevant observation equipment to test the protective performance of the organism, and analyze whether the protective performance of the organism meets the needs of high quality and lightweight protective equipment. The research on the realization principle of the protective function of the biological prototype mainly refers to the analysis of the microscopic morphology, structure, chemical composition material parameters, etc. of the organism after the biological material meets the performance test, and the relationship between the structure of the organism and its excellent protective performance is obtained to guide the preparation of gradient ceramic materials based on bionics.

[0019] The main steps for characterizing and analyzing the microscopic morphology of the back plate of the scaly clam shell are as follows:

[0020] a. Select adult live razor clams and place them in a beaker. Add an appropriate amount of ether solution into the beaker, seal the beaker and let stand for 8 minutes.

[0021] b. Remove biological tissues from the shells of razor clams and use chemical cleaning methods to remove stains and impurities on the surface of the shells;

[0022] c. Soak the razor clam shell sample in liquid nitrogen for a certain period of time with tweezers, take it out and cut it to obtain a razor clam shell section of ideal size;

[0023] d. Fix the cross-section sample of the razor clam shell on the microscope stage, spray-coat the cross-section sample with gold, and finally observe it with a scanning electron microscope to obtain a cross-section structure image of the razor clam shell.

[0024] The main process of mechanical property testing of scaly clam shell material is as follows: the sample is tested using a nanoindenter, and the test conditions are: loading time is 120s, holding time is 8s, unloading time is 80s, maximum loading force is 10mN, and Poisson's ratio is 0.3. It can be concluded that there are fine channels distributed in the scaly clam shell, and the direction of the channels changes from the middle layer to the inner layer, which can be used to analyze the formation direction of the lamellar structure during the growth process of the scaly clam shell.

[0025] The research on the principle of the protective function of the scaly clam shell mainly includes the following contents: the main components of the scaly clam shell are determined by elemental content analysis, and the structure is observed by scanning electron microscopy. The results show that the main component of the scaly clam shell is calcium carbonate, and a structure similar to the "pearl layer" is formed on one side of its inner surface. The transition between this layer of material and the lamellar structure is characterized by the fact that when the material is damaged, it will not form cracks extending along the direction of its arrangement like the scaly clam shell with a clear lamellar structure. For the scaly clam, due to its behavioral habits and the structure of the scaly clam shell, the force on the scaly clam shell when it is damaged always starts from the outer surface and points to the inner surface. Because of this unique force direction, the structure formed by the material on the inner surface of the scaly clam shell reduces the risk of damage to the scaly clam shell and improves the defense ability of the scaly clam shell.

[0026] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a gradient ceramic material based on bionics, which finally obtains a high-performance gradient ceramic material through processes such as component design, gradient green billet production and sintering.

[0027] Step 1: Raw material composition design and granulation.

[0028] The raw materials of the bionic gradient ceramic material in this embodiment include boron carbide (B4C), Al2O3, Y2O3, carbon powder, and phenolic resin. The boron carbide needs to be granulated to form boron carbide particles, and the other four materials do not need to be granulated. Al2O3 and Y2O3 use chemically pure powders, and the specific surface area of ​​the carbon powder is greater than or equal to 260m 2 / g, the concentration of phenolic resin can be 45%-50%.

[0029] Boron carbide ceramics, as a ceramic material composed of boron carbide crystals, have high hardness, as well as extremely high wear resistance, high temperature stability and chemical stability, and are not easily corroded.

[0030] In this embodiment, a vertical high-speed ball mill is used to granulate boron carbide powder to prepare boron carbide particles. Specifically, the granulation process includes the following steps:

[0031] Put the boron carbide powder into a vertical high-speed ball mill, and add additives such as sintering aids; add deionized water in a ratio of 2:1 between boron carbide and deionized water, add dispersant in a ratio of 30:1 between boron carbide and dispersant, and start ball milling. After high-speed ball milling dispersion for 2 hours, add a binder in a ratio of 3:1 between boron carbide and binder, and continue high-speed ball milling for 4-6 hours. The total ball milling time is 6-8 hours, and the solid content is controlled at 45%-50%; wait for After the ball milling is completed, the slurry is pumped to the mixing barrel for continuous stirring; then the centrifugal spray drying tower is used for granulation. The slurry flows through the ball mill pipeline into a vibrating screen with a mesh size of more than 200 to remove impurities and iron, and then is transported to the atomizer on the top of the tower by a diaphragm pump through a voltage regulator tube. The slurry is atomized into a "water drop shape" by a high-speed centrifugal disk with a linear speed of 55m / s-65m / s, and rotates and falls in contact with a 200℃ heat flow in the tower to dry, and obtain boron carbide spherical particles with a water content of 0.8-1.2% and a size of about 0.10mm. The water content of boron carbide particles can be detected by a moisture meter.

[0032] Step 2: Preparation of gradient green billet.

[0033] Boron carbide particles, Al2O3 powder, Y2O3 powder, carbon powder and phenolic resin are used as raw materials, and each raw material is poured into the corresponding steel mold cavity. The bottom of the cavity is a transfer pad. The cavity and the transfer pad form a shell bionic structure. The raw materials in the steel mold are compacted by a servo motor and a compaction structure driven by the servo motor, and finally a plurality of layered blanks with shell bionic structures are prepared. It should be pointed out that Figure 1In the present invention, only a flat layered green billet is used as an example to illustrate the preparation process of this embodiment. However, the specific structural shape of the layered green billet is determined by the shape of the contact surface of the compacting structure, the shape of the transfer pad, and the shape of the steel mold cavity. For a layered green billet composed of Al2O3 powder, Y2O3 powder, and carbon powder, its structure is Figure 2 The middle three layers have the same rib structure, while for the top layer (or bottom layer) and the bottom layer (or top layer) composed of boron carbide particles and phenolic resin, the two opposite surfaces have rib structures and the other surfaces are flat.

[0034] Before preparing the layered green billet, a steel mold is made according to the linear shrinkage characteristics and three-dimensional structural characteristics of the raw material granulation material, and the contact surface between the steel mold and the granulation material needs to be polished. The granulation powder is placed in the steel mold and laid in layers, and vibration and pressure are used to prepare the layered green billet with gradient composition. The shape of the layered green billet is guaranteed by the shape of the contact surface of the loading mold, the shape of the transfer pad and the cavity structure. The thickness of the layered laying is guaranteed by the feed servo motor and the compaction structure.

[0035] Then put the granulated powder into the V-shaped groove, which will pour the granulated powder into the cavity of the steel mold driven by the servo motor. The bottom of the cavity is a transfer pad. After the shell simulation structure is formed by the cavity and the pad, the servo motor and the compaction structure are used with vibration to ensure compaction. The shape of the layered blank is determined by the shape of the contact surface of the loading mold of the compaction structure, the shape of the transfer pad and the cavity structure. The thickness of the layered blank is determined by the feed servo motor and the compaction structure. Among them, the pressure of the compaction structure is controlled at 1.3-1.8 tons / cm 2 , the holding time is 20s-60s. As the number of layers of the layered billet increases, the holding time increases, and the holding time is appropriately adjusted according to the compaction density of the layered billet. The compaction density of the layered billet is determined according to the standard (GB3850-1983) and the Archimedes drainage method is used. The instrument used is a high-precision solid-liquid specific gravity meter of model DAHODH-120T with an accuracy of 0.1mg. Before the measurement, the layered billet sample to be tested is cleaned, and acetone is used as the medium. The layered billet to be tested is placed in an ultrasonic instrument for cleaning for 30 minutes, and then kept at 250℃ for 2 hours to fully dry.

[0036] Step 3: Segmented heating and sintering.

[0037] In this step, the layered blanks of different compositions obtained in step 2 are placed vertically and neatly in a graphite crucible in sequence, with the height not exceeding the height of the crucible. The graphite crucible containing the layered blanks is neatly stacked in a horizontal vacuum furnace, the furnace door is closed and the vacuum pump is turned on. After 25 minutes, the heating program is run, and the heating program is run by a segmented heating method.

[0038] Sintering temperature is an important factor affecting the microstructure of boron carbide ceramic materials. If the temperature is too high, grain coarsening and abnormal growth will occur inside the sintered body, affecting the mechanical properties of the boron carbide ceramic material. If the temperature is too low, the structure is fine but the porosity is high, the density of the sintered body does not meet the requirements, and high-performance boron carbide ceramic materials cannot be obtained.

[0039] The sintering process in this embodiment adopts a staged heating method, which specifically includes the following steps: when heating from room temperature to 1200°C, the heating rate is (5-6)°C / min; when heating from (1201-1600)°C, the heating rate is (3-4)°C / min; since boron carbide ceramics begin to shrink near a temperature of 1800°C, in order to ensure that the boron carbide ceramics are fully sintered and densified, when heating from 1600°C to the set sintering temperature, the heating rate is (1-2)°C / min, and optionally, the sintering temperature is set to 2260±10°C; after the temperature reaches the set sintering temperature, the holding time is set to 45min, and then cooled to room temperature with the furnace, thereby completing the sintering preparation of the bionic gradient ceramic material.

[0040] The structure of the gradient ceramic material prepared by the preparation method described in the above embodiment is as follows: Figure 2 As shown, the gradient ceramic material applies the rib structure of the razor clam shell in the preparation process. To ensure the consistency of strength at different positions, the gradient ceramic material is divided into 5 layers, namely B4C, Al2O3, Y2O3, carbon powder, and phenolic resin, to form a simulated reinforced structure.

[0041] The present invention also provides the application of the above-mentioned bionic gradient ceramic material in protective gear. The specific application method is not particularly limited, and the application method of the material in protective gear in the prior art can be referred to.

[0042] The above is only a preferred embodiment of the present invention. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a gradient ceramic material based on bionics, It is characterized in that The following steps are involved: Step 1: granulating boron carbide powder using a vertical high-speed ball mill to prepare boron carbide particles; Step 1 includes the following steps: Put the boron carbide powder into a vertical high-speed ball mill and add a sintering aid; Deionized water is added in a ratio of 2:1 between boron carbide and deionized water, and dispersant is added in a ratio of 30:1 between boron carbide and dispersant, and ball milling is started. After high-speed ball milling dispersion for 2 hours, a binder is added in a ratio of 3:1 between boron carbide and binder, and high-speed ball milling is continued for 4-6 hours. The total ball milling time is 6-8 hours, and the solid content is controlled at 45%-50%; After the ball milling is completed, the slurry is pumped into the mixing barrel for continuous stirring; The granulation is carried out by a centrifugal spray drying tower. The slurry flows through the ball mill pipeline into a vibrating screen with a mesh size of 200 or above to remove impurities and iron. Then, it is transported to the atomizer on the top of the tower by a diaphragm pump through a voltage regulator tube. The slurry is atomized by a high-speed centrifugal disk with a linear speed of 55m / s-65m / s. In the tower, it is contacted with a 200℃ heat flow and rotated and dropped to dry to obtain boron carbide particles. Step 2: Boron carbide particles, Al 2 O 3 Powder, Y 2 O 3 Powder, carbon powder and phenolic resin are used as raw materials, and each raw material is poured into a corresponding steel mold cavity, the bottom of the mold cavity is a transfer pad, and the mold cavity and the transfer pad form a shell bionic structure, and then the raw materials in the steel mold are compacted by a servo motor and a compaction structure driven by the servo motor to prepare a plurality of layered blanks with shell bionic structures; Step 3: placing the layered green sheets with different compositions obtained in step 2 in a graphite crucible in sequence and in a vertical and orderly manner, and sintering the graphite crucible and the layered green sheets therein by a segmented heating method, and obtaining a gradient ceramic material based on bionics after sintering; The stepwise heating method in step 3 comprises the following steps: When heating from room temperature to 1200°C, the heating rate is 5-6°C / min; When heating from 1201 to 1600°C, the heating rate is 3 to 4°C / min; When heating from 1600°C to the set sintering temperature, the heating rate is 1-2°C / min, and the set sintering temperature is 2260±10°C; After the temperature reaches the set sintering temperature, the holding time is set to 45 minutes, and then it is cooled to room temperature with the furnace.

2. A method for preparing a biomimetic gradient ceramic material according to claim 1, It is characterized in that Carbon powder specific surface area is greater than or equal to 260m 2 / g, the concentration of phenolic resin is 45%-50%.

3. A method for preparing a biomimetic gradient ceramic material according to claim 1, It is characterized in that When the compaction structure compacts the raw materials in the steel mold, the pressure is controlled at 1.3-1.8 tons / cm 2 , the holding time is 20s-60s.

4. The method for preparing a biomimetic gradient ceramic material according to claim 1, It is characterized in that After the layered green billet is prepared, step 2 further includes the following steps: using a high-precision solid-liquid hydrometer to measure the compaction density of the layered green billet.

5. A method for preparing a biomimetic gradient ceramic material according to claim 4, It is characterized in that Before measuring the compaction density of the layered green billet, the layered green billet to be measured was cleaned in an ultrasonicator using acetone as a medium for 30 minutes and then kept at 250° C. for 2 hours to be fully dried.

6. A gradient ceramic material based on bionics, It is characterized in that The method is described in any one of claims 1 to 5.

7. An application of the bionic gradient ceramic material as claimed in claim 6 in protective gear.

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