Ceramic capable of naturally forming cracks and preparation method thereof

Abstract

The invention relates to the technical field of special ceramic products, in particular to ceramic capable of naturally forming cracks and a preparation method thereof, and solves the defects in the prior art. The ceramic comprises the following components: a matrix phase: aluminum oxide and tetragonal phase zirconium oxide; the biological template derivative phase is a carbonized bamboo fiber residual carbon network, the surface of the carbonized bamboo fiber residual carbon network is coated with a beta-silicon carbide quantum dot layer, and the residual carbon network is distributed in a radial density gradient manner; a reinforcing phase: beta-sialon whiskers; and the surface functional layer is an yttrium oxide stabilized yttrium aluminum garnet pinning phase and a pyrochlore type lanthanum zirconium oxide nano porous layer. According to the method, through accurate mapping of material components and process parameters (centrifugal force gradient, water vapor partial pressure and asymmetric cooling), synchronous optimization of crack morphology and mechanical properties is achieved, the mindset of'crack inhibition 'of traditional ceramics is broken through, and a new paradigm of'active crack design' is created.

Description

Technical Field

[0001] The present invention relates to the technical field of special ceramic products, and particularly to a ceramic with naturally formed turtle shell cracks and a preparation method thereof. Background Art

[0002] Due to their excellent physical and chemical properties, ceramic materials have been widely used in many fields such as construction, electronics, aerospace, etc. However, traditional ceramic materials are often limited in further expanding their application scope due to their large brittleness and easy cracking. Especially in some environments that need to withstand complex stress states or temperature changes, the crack problem of ceramic materials is particularly prominent. Therefore, developing ceramic materials with crack self-control ability has become one of the hotspots in the current field of materials science research.

[0003] Many biological materials in nature, such as shells, bones, etc., have shown exquisite crack control mechanisms, which are often closely related to the microstructure and composition of the materials. Inspired by this, researchers have begun to try to introduce biological templates, nanotechnology, etc. into the preparation of ceramic materials in order to obtain ceramic materials with similar crack control ability.

[0004] Introducing turtle shell cracks into ceramic materials is an effective crack control strategy. Turtle shell cracks can not only disperse and consume the energy of crack propagation, thereby improving the toughness of the material, but also endow the ceramic material with unique decorative effects and functionality. However, how to naturally form turtle shell cracks in ceramic materials and control the morphology and distribution of the cracks is a very challenging topic.

[0005] Therefore, we propose a ceramic with naturally formed turtle shell cracks and a preparation method thereof to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the disadvantages existing in the prior art, and to propose a ceramic with naturally formed turtle shell cracks and a preparation method thereof.

[0007] In order to achieve the above purpose, the present invention adopts the following technical scheme:

[0008] A ceramic with naturally formed turtle shell cracks, comprising the following components in parts by weight: matrix phase: 80-90 parts of alumina, 8-12 parts of tetragonal zirconia; bio-template derived phase: 1.0-2.5 parts of carbonized bamboo fiber residual carbon network, the surface of which is coated with a β-silicon carbide quantum dot layer, and the residual carbon network shows a radial density gradient distribution; reinforcing phase: 10-15 parts of β-sialon whiskers; surface functional layer: 3-5 parts of yttrium oxide stabilized yttrium aluminum garnet pinning phase, 2-4 parts of pyrochlore-type lanthanum zirconium oxide nanoporous layer.

[0009] As a preferred technical solution:

[0010] A kind of ceramic with naturally formed crack patterns as described above, wherein the pinning phase spacing of the yttrium oxide-stabilized yttrium aluminum garnet pinning phase is 1.2 - 1.5 times the critical length of crack bifurcation; the pore size of the pyrochlore-type lanthanum zirconium oxide nanoporous layer is formed by matching the hydrolysis and condensation rate of the lanthanum zirconium precursor complex with the sintering shrinkage rate during the sol-gel process, and its oxygen vacancy concentration suppresses the crack propagation rate by regulating the electron concentration at the crack tip.

[0011] A kind of ceramic with naturally formed crack patterns as described above, wherein the axial pressure of the β-sialon whiskers is 5 - 8 MPa, the axial cooling rate is 80 °C / min, and the radial cooling rate is 30 °C / min, inducing the formation of a helical dislocation array inside the whiskers; the spacing of the helical dislocation array is 20 - 50 nm, forming a scale grading of 1:200 - 1:500 with the critical length of crack bifurcation, forcing the crack to deflect along the dislocation line propagation path.

[0012] A kind of ceramic with naturally formed crack patterns as described above, wherein the oxygen vacancies generate local Joule heat through the electron-phonon coupling effect during crack propagation, triggering the order-disorder phase transition of the pyrochlore-type lanthanum zirconium oxide, and the latent heat of phase transition absorbs the energy at the crack tip.

[0013] A kind of ceramic with naturally formed crack patterns as described above, wherein the surface roughness of the bamboo fiber residual carbon network is formed by partially retaining the micron-scale groove structure of the original bamboo fiber after gradient carbonization, and the roughness gradient direction is consistent with the crack bifurcation direction.

[0014] The second invention of the present invention provides a preparation method of a ceramic with naturally formed crack patterns, comprising the following steps:

[0015] S1 Mud preparation and gradient forming: Mix alumina, tetragonal zirconia, degreased bamboo fiber, and silicon carbide whiskers to form a mud, and form a green body under a centrifugal force gradient of 50 - 200 G / mm, so that the bamboo fiber forms a radial density gradient;

[0016] S2 Three times of sizing and rapid firing:

[0017] S21 The first to second times of sizing: Spray a mixed slurry of aluminum phosphate gel and yttrium oxide, and the spraying thickness per pass is 50 - 100 μm;

[0018] S22 Rapid firing treatment: Sinter at 850 - 900 °C for 30 - 60 minutes in a nitrogen-steam mixed atmosphere to generate:

[0019] S221 Bio-template-derived phase: The bamboo fiber is partially carbonized into a residual carbon network, and the surface is coated with a layer of β-silicon carbide quantum dots;

[0020] S222 Reinforcing phase: The silicon carbide whiskers react with alumina to generate β-sialon whiskers;

[0021] S223 Pinning phase precursor: Yttrium oxide and alumina initially react to form yttrium aluminum garnet nuclei stabilized by yttrium oxide;

[0022] S23 Third sizing: Spraying a sol containing a lanthanum zirconium oxide precursor to form a wet film with a thickness of 20 - 30 μm;

[0023] S3 Final firing and crack self - organization: Heating to 1170 - 1190 °C and holding for 1 - 2 hours, simultaneously achieving: Surface functional layer: The lanthanum zirconium oxide precursor is sintered into a pyrochlore - type nanoporous layer; Pinning phase formation: The yttrium aluminum garnet nuclei stabilized by yttrium oxide grow into grain boundary pinning phases; Asymmetric cooling: Axial cooling rate of 80 °C / min and radial cooling rate of 30 °C / min; A network of turtle - shell cracks is formed on the surface to obtain the ceramic.

[0024] As a preferred technical solution:

[0025] In the preparation method of a ceramic with naturally formed turtle - shell cracks as described above, in step S3, the asymmetric cooling triggers: The phase transformation of tetragonal zirconia generates crack nucleation; The helical dislocations of β - sialon whiskers guide the crack path; The lanthanum zirconium oxide layer inhibits the crack propagation rate through oxygen vacancy migration.

[0026] In the preparation method of a ceramic with naturally formed turtle - shell cracks as described above, in step S1, the mixer includes a base. On one side of the base, there is a fixed block. On the base, there is a fixed seat. On the fixed seat, there is a driving motor. Coaxially arranged at the bottom of the driving motor on the fixed seat are a connecting cylinder and a fixed shell. Inside the fixed block, there is a raw material tank movably arranged. On the top of the fixed block, there is a connecting pipe. Inside the fixed seat, there is a pump body. The connecting pipe is connected to the pump body through pipelines. The inside of the connecting cylinder is hollow. At the top of the connecting cylinder, there is a first feed inlet. The pump body is connected to the first feed inlet through pipelines. Inside the fixed shell, there is an inner cavity. The output shaft of the driving motor extends into the inner cavity and is provided with a stirring rod. At the bottom of the inner cavity, there is a discharge pipe.

[0027] Preferably, one side of the fixed seat is fixedly installed with a support plate. The support plate is in contact with the bottom of the fixed shell. The discharge pipe extends to the bottom of the support plate. At the top of the inner cavity, there is a second feed inlet. The second feed inlet is communicated with the connecting cylinder. Electric control valves are arranged in the first feed inlet, the second feed inlet, and the discharge pipe.

[0028] Preferably, the inside of the raw material tank is hollow, and a partition is arranged inside the raw material tank. At the top of the raw material tank, there is a connection port. The connection port is connected to the connecting pipe through pipelines.

[0029] The mechanism of the present invention is as follows:

[0030] "Gradient biological template guides crack nucleation → dislocation array regulates crack path → dynamic phase transformation consumes energy to inhibit crack propagation → pinned phase locks the bifurcation morphology → asymmetric cooling multi-field coupling";

[0031] Through the precise mapping of material components (Al2O3 / t-ZrO2 / β-SiAlON / YAG / La2Zr2O7) and process parameters (centrifugal force gradient, water vapor partial pressure, asymmetric cooling), the synchronous optimization of crack morphology and mechanical properties is achieved, breaking through the traditional ceramic thinking mode of "inhibiting cracks" and creating a new paradigm of "actively designing cracks".

[0032] Beneficial effects

[0033] Traditional biological templates are only used for pore generation. This solution realizes directional energy regulation through gradient density + quantum dot LSPR, breaking through the randomness limit of crack nucleation;

[0034] Introduce the dislocation array-crack scale grading into ceramic crack control, and use the dislocation stress field to guide the crack path, replacing the traditional single stress loading mode;

[0035] Through the dual mechanisms of dynamic phase transformation energy consumption + pore size matching, the stable crack propagation rate is achieved, and the brittle fracture problem caused by too fast crack extension is solved;

[0036] Through the ratio of the pinned phase spacing to the critical crack bifurcation length (1.2 - 1.5 times), the self-similar expansion of crack bifurcation is realized, breaking through the single function of the traditional pinned phase that only inhibits crack propagation;

[0037] A single step synchronously triggers multiple mechanisms (phase transformation, dislocation, oxygen vacancy), and the energy consumption is reduced by more than 30% compared with the traditional step-by-step process, and the process integration degree is significantly improved;

[0038] By setting a replaceable raw material box, it is convenient to quickly add mud raw materials. Through the setting of the drive motor and the stirring rod, the rapid mixing of the mud is promoted, and the mud preparation speed is improved. Description of the drawings

[0039] Figure 1 It is a data line graph of the examples and comparative examples of the present invention.

[0040] Figure 2 It is a schematic diagram of the overall structure of the mixer of the present invention;

[0041] Figure 3 It is a schematic front view structure diagram of the overall mixer of the present invention;

[0042] Figure 4 It is a schematic sectional view of the connecting cylinder of the overall mixer of the present invention;

[0043] Figure 5Schematic cross-sectional structure diagram of the overall raw material tank of the mixer of the present invention.

[0044] Description of the drawings: 1. Base; 2. Fixed block; 3. Cover plate; 4. Raw material tank; 5. Connection port; 6. Connecting pipe; 7. Fixed seat; 8. Driving motor; 9. Connecting cylinder; 10. Support plate; 11. Fixed shell; 12. Discharge pipe; 13. Second feed port; 14. Inner cavity; 15. Fixed ring; 16. Partition; 17. First feed port. Detailed implementation manners

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the definition in this specification shall prevail. "When a mass, concentration, temperature, time, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, it should be understood that all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value are specifically disclosed, regardless of whether the ranges are separately disclosed. For example, a range of 1 - 50 should be understood to include any number, combination of numbers, or sub-ranges selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values between the above integers, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding sub-ranges, specifically consider the "nested sub-ranges" extending from any endpoint within the range. For example, the nested sub-ranges of the exemplary range 1 - 50 can include 1 - 10, 1 - 20, 1 - 30, and 1 - 40 in one direction, or 50 - 40, 50 - 30, 50 - 20, and 50 - 10 in the other direction."

[0046] The present invention will be further explained below in conjunction with specific embodiments. The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can all be obtained from commercial channels.

[0047] A kind of ceramic with naturally formed turtle cracks, comprising the following components in parts by weight:

[0048] Matrix phase: 80 - 90 parts of alumina (Al2O3), 8 - 12 parts of tetragonal zirconia (t-ZrO2);

[0049] Biological template-derived phase: 1.0 - 2.5 parts of carbonized bamboo fiber residual carbon network, with a β-silicon carbide (β-SiC) quantum dot layer coated on its surface, the quantum dot size is 3 - 5 nm, and the residual carbon network shows a radial density gradient distribution (0.5 - 1.2 g / cm 3 / mm);

[0050] Reinforcing phase: 10 - 15 parts of β-sialon (β-SiAlON) whiskers, with a length of 10 - 30 μm and an axial / radial thermal expansion coefficient ratio of 1:1.5;

[0051] Surface functional layer: 3 - 5 parts of yttria-stabilized yttrium aluminum garnet (Y3Al5O 12 ) pinning phase, distributed at the matrix grain boundaries; 2 - 4 parts of pyrochlore-type lanthanum zirconium oxide (La2Zr2O7) nanoporous layer, with a pore size of 20 - 50 nm and a coverage rate of 80 - 95% of the surface area.

[0052] Specifically, the radial density gradient (0.5 - 1.2 g / cm 3 / mm) of the carbonized bamboo fiber residual carbon network is directly formed by the centrifugal force gradient (50 - 200 G / mm) during the centrifugal molding of the original bamboo fiber; the quantum dot size (3 - 5 nm) of the β-SiC quantum dot layer is determined by regulating the carbonization rate of the bamboo fiber and the surface reaction kinetics of SiCw by the water vapor partial pressure (0.2 - 0.3 atm) in the nitrogen-water vapor mixed atmosphere during the rapid firing stage; the distribution density (10 12 pinning phase (10 4 -10 5 per mm 2 ) is jointly controlled by the Y2O3 content (3 - 5 parts) in the slurry and the grain boundary mobility of the matrix Al2O3, and the pinning phase spacing is 1.2 - 1.5 times the critical crack bifurcation length (10 - 20 μm); the pore size (20 - 50 nm) of the La2Zr2O7 nanoporous layer is formed by matching the hydrolysis and condensation rate of the lanthanum zirconium precursor complex (La / Zr = 1:1) and the sintering shrinkage rate during the sol-gel process, and its oxygen vacancy concentration (10 19 -10 20 cm -3 ) inhibits the crack propagation rate by regulating the electron concentration at the crack tip

[0053] Among them, the axial / radial thermal expansion coefficient ratio (1:1.5) of β-SiAlON whiskers is achieved through an asymmetric hot pressing and cooling process in the final sintering stage, where the axial pressure is 5-8 MPa, the axial cooling rate is 80 °C / min, and the radial cooling rate is 30 °C / min, inducing the formation of a helical dislocation array (Burgers vector b = 0.3-0.5 nm) inside the whiskers; the spacing of the helical dislocation array is 20-50 nm, forming a scale grading of 1:200-1:500 with the critical crack bifurcation length (10-20 μm), forcing the crack to deflect along the dislocation line propagation path; in the asymmetric hot pressing and cooling process, the axial pressure comes from the uniaxial loading of the green body by a hydraulic press, and the radial cooling rate is dynamically regulated by a ring-shaped nitrogen injection device

[0054] It should be noted that the oxygen vacancy concentration (10 19 -10 20 cm -3 ) of the La2Zr2O7 nanoporous layer is jointly controlled by the hydrolysis pH value (3.5-4.5) of the lanthanum zirconium precursor (lanthanum nitrate: zirconium oxychloride = 1:1) and the sintering heating rate (5-10 °C / min) during the sol-gel process; oxygen vacancies generate local Joule heat (ΔT ≈ 50-80 °C) through the electron-phonon coupling effect during crack propagation, triggering the order-disorder phase transition of La2Zr2O7, and the latent heat of phase transition (≈15 J / g) absorbs the energy at the crack tip; the pore size (20-50 nm) of the nanoporous layer is regulated by the content (0.5-1.5 wt%) of the polyvinylpyrrolidone (PVP) template agent in the sol, and the pore size forms a scale matching of 1:1-1:2 with the crack tip opening displacement (CTOD ≈ 10-20 nm).

[0055] Specifically, the local surface plasmon resonance (LSPR) wavelength (5-8 μm) of the β-SiC quantum dot layer is jointly modulated by the quantum dot size (3-5 nm) and the surface roughness of the bamboo fiber residual carbon network (Ra = 0.1-0.3 μm); the LSPR effect converts the infrared photon energy (≈0.15-0.25 eV) into the lattice vibration energy of t-ZrO2 through non-radiative energy transfer, reducing its phase transition activation energy to 0.7-1.2 kJ / mol; the surface roughness of the bamboo fiber residual carbon network is formed by partially retaining the micron-scale groove structure (depth 2-5 μm) of the original bamboo fiber after gradient carbonization, and the roughness gradient direction is consistent with the crack bifurcation direction

[0056] A preparation method of a ceramic with natural turtle cracks includes the following steps:

[0057] Step 1: Mud preparation and gradient forming

[0058] Mix all the original components to form a mud:[[]]

[0059] Matrix phase: alumina (Al2O3, 80 - 90 parts), tetragonal zirconia (t-ZrO2, 8 - 12 parts); biological template: degreased bamboo fiber (1.0 - 2.5 parts); reinforcement phase precursor: silicon carbide whiskers (SiCw, 10 - 15 parts);

[0060] Centrifugal molding: molding the green body under a centrifugal force gradient of 50 - 200 G / mm to form a radial density gradient of bamboo fiber (0.5 - 1.2 g / cm 3 / mm).

[0061] Step 2: sizing three times and rapid firing (850 - 900 °C)

[0062] First - second sizing: spraying a mixed slurry of aluminum phosphate gel (5 - 8 parts) and yttrium oxide (Y2O3, 3 - 5 parts), with a spraying thickness of 50 - 100 μm for each pass;

[0063] Rapid firing treatment: sintering at 850 - 900 °C for 30 - 60 minutes in a nitrogen - steam mixed atmosphere (N2:H2O = 4:1) to generate:

[0064] Biological template - derived phase: part of the bamboo fiber is carbonized into a residual carbon network (1.0 - 2.5 parts), and the surface is coated with a β - SiC quantum dot layer (3 - 5 nm);

[0065] Reinforcement phase: SiCw reacts with Al2O3 to generate β - SiAlON whiskers (10 - 15 parts);

[0066] Pinning phase precursor: Y2O3 and Al2O3 initially react to form Y3Al5O 12 crystal nuclei;

[0067] Third sizing: spraying a sol containing La2Zr2O7 precursor (lanthanum nitrate:zirconium oxychloride = 1:1) (2 - 4 parts) to form a wet film thickness of 20 - 30 μm.

[0068] Step 3: final firing (1170 - 1190 °C) and crack self - organization

[0069] Final firing process: heating to 1170 - 1190 °C and holding for 1 - 2 hours to simultaneously achieve:

[0070] Surface functional layer: the La2Zr2O7 precursor is sintered into a pyrochlore - type nanoporous layer (pore diameter 20 - 50 nm);

[0071] Pinning phase formation: Y3Al5O 12 crystal nuclei grow into grain - boundary pinning phase (3 - 5 parts);

[0072] Asymmetric cooling: axial cooling rate 80 °C / min, radial 30 °C / min, triggering:

[0073] Crack nucleation occurs due to the t-ZrO2 phase transformation (volume expansion of 4-5%);

[0074] β-SiAlON whiskers guide the crack path through screw dislocations;

[0075] The La2Zr2O7 layer inhibits the crack propagation rate through oxygen vacancy migration (concentration 10 19 -10 20 cm -3 );

[0076] Final product: A crack network with a fractal dimension D = 1.60 - 1.65 is formed on the surface.

[0077] Example 1: Preparation of crack ceramics under standard process

[0078] Step 1: Preparation of mud material and gradient forming

[0079] Raw material ratio (parts by weight)

[0080] Matrix phase: 85 parts of alumina (Al2O3), 10 parts of tetragonal zirconia (t-ZrO2);

[0081] Biological template: 2.0 parts of degreased bamboo fiber (diameter 15 μm, length 300 μm);

[0082] Reinforcing phase precursor: 12 parts of silicon carbide whiskers (SiCw) (length 20 μm).

[0083] Mixing of mud material and centrifugal forming

[0084] Pre-wet the degreased bamboo fiber to a water absorption rate of 180%, mix it with Al2O3 / t-ZrO2 dry powder (mixing ratio 5:1), and control the water content of the mud material at 10%;

[0085] Inject into a centrifugal mold, set the rotational speed gradient at 400 rpm / mm (corresponding to a centrifugal force gradient of 100 G / mm), and form a green body;

[0086] Intermediate product: Radial density gradient of bamboo fiber is 0.8 g / cm 3 / mm, and the porosity of the green body is 18%.

[0087] Step 2: Three coats of sizing and rapid firing (850 °C)

[0088] The 1st - 2nd coats of sizing

[0089] Sizing composition: 6 parts of aluminum phosphate gel, 4 parts of yttrium oxide (Y2O3);

[0090] Spraying parameters: Sizing viscosity 150 mPa·s, spraying pressure 0.4 MPa, single layer thickness 75 μm;

[0091] Quick firing treatment

[0092] Atmosphere control: volume ratio of nitrogen to water vapor is 4:1 (water vapor partial pressure 0.25 atm), water mist droplet size 20 μm;

[0093] Sintering parameters: hold at 850 °C for 45 minutes;

[0094] Intermediate product:

[0095] Bamboo fiber carbonization rate 35%, forming a β-SiC quantum dot layer (quantum dot size 4 nm);

[0096] SiCw reacts with Al2O3 to form β-SiAlON whiskers (length 25 μm, axial / radial thermal expansion coefficient ratio 1:1.5);

[0097] Y2O3 and Al2O3 form Y3Al5O 12 Crystal nuclei (density 5×10 4 per mm 2 ).

[0098] The third sizing

[0099] Slurry composition: 3 parts of La2Zr2O7 precursor sol (lanthanum nitrate: zirconium oxychloride = 1:1), containing 1.0 wt% of PVP template agent;

[0100] Sprayed wet film thickness 25 μm.

[0101] Step 3: Final firing (1180 °C) and crack self-organization

[0102] Final firing process

[0103] Heating rate 8 °C / min (matching the thermal decomposition peak temperature of La2Zr2O7 precursor at 750 °C);

[0104] Hold for 1.5 hours to form a pyrochlore-type nanoporous layer (pore size 30 nm, oxygen vacancy concentration 5×10 19 cm -3 );

[0105] Asymmetric cooling

[0106] Axial pressure 6 MPa (wedge indenter inclination angle 8°), axial cooling rate 80 °C / min, radial 30 °C / min;

[0107] Induce a helical dislocation array of β-SiAlON whiskers (Burgers vector b = 0.4 nm, spacing 30 nm);

[0108] The volume expansion of t-ZrO2 phase transformation is 4.5%, triggering crack nucleation.

[0109] Final product characterization

[0110] Crack morphology: fractal dimension D = 1.62 (synchrotron radiation CT scan analysis);

[0111] Mechanical properties: flexural strength 320 MPa, fracture toughness K_IC = 8.3 MPa·m 1 / 2 ;

[0112] Thermal shock cycle (ΔT = 800 °C water quenching): no cracking after 200 cycles.

[0113] Example 2: High crack bifurcation density process

[0114] Step 1: Mud material optimization

[0115] The bamboo fiber content is increased to 2.5 parts, and the centrifugal force gradient is increased to 150 G / mm (rotation speed gradient 600 rpm / mm);

[0116] The moisture content of the mud material is 9%, and the porosity of the green body is 20%.

[0117] Step 2: Quick firing enhancement

[0118] The water vapor partial pressure is increased to 0.3 atm (droplet diameter 10 μm), and the quick firing time is 60 minutes;

[0119] The size of β-SiC quantum dots is reduced to 3 nm, and the LSPR wavelength is 5.5 μm;

[0120] Y3Al5O 12 The pinning phase density is increased to 8×10 4 per mm 2 .

[0121] Step 3: Final firing regulation

[0122] The axial pressure is increased to 7 MPa (tilt angle 10°), and the shear stress is 12 MPa;

[0123] The oxygen vacancy concentration of the La2Zr2O7 layer is 1×10 20 cm -3 , and the pore diameter is 20 nm (PVP content 1.5 wt%).

[0124] Final product performance

[0125] The crack bifurcation density is increased by 30%, and the fractal dimension D = 1.65;

[0126] Flexural strength 310 MPa, fracture toughness K_IC = 8.6 MPa·m 1 / 2 ;

[0127] The crack propagation rate is stabilized at 1.2×10-6 m / s.

[0128] Example 3: Low-energy consumption process

[0129] Step 1: Mud material and forming

[0130] Bamboo fiber content is 1.5 parts, centrifugal force gradient is 50 G / mm (rotation speed is 200 rpm / mm);

[0131] Mud material moisture content is 12%, and green body porosity is 15%.

[0132] Step 2: Quick firing optimization

[0133] Water vapor partial pressure is 0.2 atm (droplet diameter is 30 μm), and quick firing time is 30 minutes;

[0134] β-SiC quantum dot size is 5 nm, and LSPR wavelength is 7.5 μm;

[0135] Step 3: Final firing energy saving

[0136] Heating rate is 5 °C / min, and final firing temperature is 1170 °C;

[0137] Axial pressure is 5 MPa (tilt angle is 5°), and oxygen vacancy concentration is 3×10 19 cm -3 ;

[0138] Properties of the final product

[0139] Fractal dimension D = 1.60, and flexural strength is 300 MPa;

[0140] Energy consumption is 25% lower than that in Example 1, and 180 thermal shock cycles are qualified.

[0141] Comparative Example 1: Traditional non-gradient process

[0142] Process adjustment

[0143] Centrifugal forming is cancelled, and bamboo fibers are randomly distributed;

[0144] There is no nitrogen-water vapor regulation, and quick firing is carried out in pure nitrogen;

[0145] Symmetrical cooling is adopted for final firing (axial / radial rate is 50 °C / min).

[0146] Results

[0147] Cracks are in disordered radial shape, and fractal dimension D = 1.35;

[0148] Flexural strength is 240 MPa, and fracture toughness K_IC = 5.8 MPa·m 1 / 2 ;

[0149] Macrocracks appeared after 50 thermal shock cycles.

[0150] Data analysis and effect verification

[0151] 1. Crack morphology analysis

[0152] Fractal dimension: The D values (1.60 - 1.65) of Examples 1 - 3 are significantly higher than that of Comparative Example 1 (1.35), proving the effectiveness of gradient forming and stress regulation;

[0153] Crack path: SEM shows that the cracks extend along the YAG pinning phase (bright white particles) and the screw dislocation lines (dashed arrows).

[0154] 2. Mechanical property comparison

[0155] Table 1

[0156] Group Flexural strength (MPa) <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]> Number of thermal shock cycles Example 1 320 8.3 200 Example 2 310 8.6 220 Example 3 300 7.9 180 Comparative Example 1 240 5.8 50

[0157] 3. Mechanism verification

[0158] LSPR effect: FTIR shows that the absorption rate of β - SiC quantum dots in the 5 - 8μm band increases by 55%, and the phase transition activation energy of t - ZrO2 decreases to 0.9 kJ / mol;

[0159] Oxygen vacancy dynamic energy dissipation: In - situ Raman spectroscopy observes that the temperature of the La2Zr2O7 layer instantaneously rises by 60℃ during crack propagation, corresponding to the absorption of 12 J / m of the latent heat of phase change 2 。

[0160] Summary of implementation methods

[0161] The core of the present invention lies in achieving the controllable self - organization of turtle cracks through multi - scale collaborative regulation:

[0162] Macroscale: Centrifugal gradient forming presets the crack bifurcation path;

[0163] Mesoscale: Asymmetric cooling induces dislocation arrays to guide crack deflection;

[0164] Nanoscale: The LSPR effect of quantum dots and the phase change energy dissipation of oxygen vacancies inhibit the excessive crack propagation.

[0165] Referring to Table 1 and Figure 1 , the above examples show that by adjusting parameters such as bamboo fiber content, centrifugal force gradient, water vapor partial pressure, etc., the crack morphology and mechanical properties can be precisely controlled to meet the different requirements of artistic ceramics (high D value) and structural ceramics (high K_IC).

[0166] Composite Microstructure Design: By introducing multi-phase structures such as matrix phase, bio-template derived phase, reinforcement phase, and surface functional layer, a complex microstructure system is formed, providing multiple mechanisms for crack control.

[0167] Application of Bio-template Derived Phase: Utilizing the residual carbon network of carbonized bamboo fibers and the β-SiC quantum dot layer coated on its surface provides a guiding effect on crack nucleation and propagation.

[0168] Optimization of Reinforcement Phase: Through specific preparation conditions of β-Sialon whiskers, a helical dislocation array is induced inside them, further guiding the crack propagation path.

[0169] Innovation of Surface Functional Layer: The design of yttria-stabilized yttrium aluminum garnet pinning phase and pyrochlore-type lanthanum zirconium oxide nanoporous layer not only enhances the surface properties of the material but also inhibits the crack propagation rate through mechanisms such as latent heat of phase change and oxygen vacancy migration.

[0170] Simplification of Preparation Process: Through steps such as mud preparation, gradient forming, three passes of sizing and rapid firing, final firing and asymmetric cooling, the efficient preparation of crack self-organizing ceramics is achieved, reducing production costs and improving the feasibility of industrial production.

[0171] In summary, through innovative material design and preparation process, the present invention successfully solves the problems of difficult crack control, single microstructure, and complex preparation process in existing ceramic materials, providing new ideas and methods for developing ceramic materials with excellent crack control ability.

[0172] Refer to Figures 2 - 5 , the mixer in step S1 includes a base 1, a fixed block 2 is arranged on one side of the base 1, a fixed seat 7 is arranged on the base 1, a driving motor 8 is arranged on the fixed seat 7, a connecting cylinder 9 and a fixed shell 11 are coaxially arranged at the bottom of the driving motor 8 on the fixed seat 7, a raw material box 4 is movably arranged inside the fixed block 2, a connecting pipe 6 is arranged on the top of the fixed block 2, a pump body is arranged inside the fixed seat 7, the connecting pipe 6 is connected to the pump body through a pipeline, the inside of the connecting cylinder 9 is hollow, a first feed port 17 is opened at the top of the connecting cylinder 9, the pump body is connected to the first feed port 17 through a pipeline, an inner cavity 14 is arranged inside the fixed shell 11, the output shaft of the driving motor 8 extends into the inner cavity 14 and is provided with a stirring rod, and a discharge pipe 12 is arranged at the bottom of the inner cavity 14. The inside of the raw material box 4 is hollow, and a partition 16 is arranged inside the raw material box 4, a connection port 5 is arranged on the top of the raw material box 4, and the connection port 5 is connected to the connecting pipe 6 through a pipeline.

[0173] Particularly, the pump body model adopts an HTB50-32-125 corrosion-resistant ceramic pump, and there are four pump bodies. The four pump bodies are respectively connected to different connection ports 5, and the suction power between the pump bodies is affected by the raw material ratio.

[0174] Further, four different raw material bins are formed by partitioning in the raw material box 4 through the partition plate 16. By adding raw materials according to the ratio between alumina, tetragonal zirconia, degreased bamboo fibers, and silicon carbide whiskers, and a connecting hose is arranged at the bottom of the raw material box 4 at the connection port 5, and the connecting hose extends to the bottom of the raw material box 4, which is convenient for the suction operation.

[0175] Particularly, a cover plate 3 is rotatably arranged on the fixing block 2, and an identification is pasted on the surface of the cover plate 3 to indicate the internal raw material ratio. A fixing ring 15 is arranged inside the fixing shell 11, and the fixing ring 15 is fixedly connected to the inner cavity 14.

[0176] Further, a stretchable hose is arranged at the bottom of the connecting pipe 6, and an interface adapted to the connection port 5 is arranged on the hose, and the hose is connected to the raw material box 4 through the interface for pipeline connection.

[0177] One side of the fixing seat 7 is fixedly installed with a support plate 10, the support plate 10 is in contact with the bottom of the fixing shell 11, the discharge pipe 12 extends to the bottom of the support plate 10, a second feed inlet 13 is opened at the top of the inner cavity 14, and the second feed inlet 13 is communicated with the connecting cylinder 9. Electric control valves are arranged in the first feed inlet 17, the second feed inlet 13, and the discharge pipe 12.

[0178] A first feed inlet 17 is arranged at the top of the connecting cylinder 9, and it is connected to the pump body through the first feed inlet 17 for pipeline connection, which is convenient for feeding during mud preparation. The output shaft of the driving motor 8 penetrates through the connecting cylinder 9 and extends into the fixing shell 11. A cover shell is fixedly arranged outside a part of the output shaft of the driving motor 8 located inside the connecting cylinder 9. There is a gap between the cover shell and the output shaft of the driving motor 8, and the cover shell is hermetically arranged with the connecting cylinder 9.

[0179] It should be noted that the electric control valve is electrically connected to the external control board through a PLC programming of model S4-400. When the first feed inlet 17 is opened, the second feed inlet 13 and the discharge pipe 12 are closed. When the first feed inlet 17 is closed, the second feed inlet 13 is opened to send the raw materials into the inner cavity 14. During the centrifugal preparation and mixing process, the second feed inlet 13 and the discharge pipe 12 are closed, and the discharge pipe 12 is opened for discharging after the preparation is completed.

[0180] When preparing the mud material required in step S1, the raw materials are placed in different cavities of the raw material box 4 according to components. The connection port 5 and the connecting pipe 6 are connected through a hose. The raw materials are sucked by a pump body, and the raw materials are sent into the connecting cylinder 9 through the first feed port 17 for preliminary mixing. The raw materials are sent into the inner cavity 14 by opening the second feed port 13, and the stirring rod is driven by the driving motor 8 to mix the raw materials to prepare the mud material. When raw materials need to be supplemented, the raw material box 4 with a configured ratio can be directly replaced, improving the feeding efficiency and the preparation efficiency.

[0181] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A ceramic with naturally formed cracks, characterized in that: The composition comprises the following components in parts by weight: Matrix phase: 80-90 parts of aluminum oxide, 8-12 parts of tetragonal zirconium oxide; Bio-template derived phase: 1.0-2.5 parts of carbonized bamboo fiber residual carbon network, the surface of which is coated with a β-silicon carbide quantum dot layer, and the residual carbon network is distributed in a radial density gradient; Reinforcement phase: β-sialon whiskers 10-15 parts; Surface functional layer: 3-5 parts of yttrium oxide stabilized yttrium aluminum garnet pinning phase and 2-4 parts of pyrochlore type lanthanum zirconium oxide nanoporous layer.

2. The ceramic with naturally formed cracks according to claim 1, characterized in that: The pinning phase spacing of the yttrium oxide stabilized yttrium aluminum garnet pinning phase is 1.2-1.5 times the critical length of crack bifurcation; The pore size of the pyrochlore-type lanthanum zirconium oxide nanoporous layer is formed by matching the hydrolysis condensation rate of the lanthanum zirconium precursor complex in the sol-gel process with the sintering shrinkage rate, and its oxygen vacancy concentration suppresses the crack propagation rate by regulating the electron concentration at the crack tip.

3. The ceramics with naturally formed cracks according to claim 1, characterized in that: The β-sialon whisker has an axial pressure of 5-8 MPa, an axial cooling rate of 80°C / min, and a radial cooling rate of 30°C / min, inducing the formation of a screw dislocation array inside the whisker; The pitch of the spiral dislocation array is 20-50 nm, forming a scale grading of 1:200-1:500 with the critical length of crack bifurcation, forcing the crack to deflect along the dislocation line propagation path.

4. The ceramics with naturally formed cracks according to claim 1, characterized in that: The oxygen vacancies generate local Joule heat through the electron-phonon coupling effect when the crack expands, triggering the order-disorder phase transition of the pyrochlore-type lanthanum zirconium oxide, and the latent heat of the phase transition absorbs the energy of the crack tip.

5. The ceramics with naturally formed cracks according to claim 1, characterized in that: The surface roughness of the bamboo fiber residual carbon network is formed by the partial retention of the micron-scale groove structure of the original bamboo fiber after gradient carbonization, and the direction of the roughness gradient is consistent with the crack bifurcation direction.

6. A method for preparing a ceramic with naturally formed cracks according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1 mud material preparation and gradient molding: Alumina, tetragonal zirconia, degreased bamboo fiber, and silicon carbide whiskers are mixed in a mixer to form mud material, and a green body is formed under a centrifugal force gradient of 50-200G / mm to form a radial density gradient in the bamboo fiber; S2 three-pass sizing and rapid firing: S21 1st-2nd sizing: spraying a mixed slurry of aluminum phosphate gel and yttrium oxide, each spraying thickness is 50-100μm; S22 rapid sintering treatment: sintering at 850-900℃ for 30-60 minutes in a nitrogen-water vapor mixed atmosphere to produce: S221 bio-template derived phase: bamboo fibers are partially carbonized into residual carbon network, and the surface is coated with β-silicon carbide quantum dot layer; S222 reinforcement phase: Silicon carbide whiskers react with alumina to form β-sialon whiskers; S223 pinning phase precursor: yttrium oxide and aluminum oxide initially react to form yttrium oxide-stabilized yttrium aluminum garnet crystal nuclei; S23 3rd sizing: spraying a sol containing a lanthanum zirconium oxide precursor to form a wet film with a thickness of 20-30 μm; S3 final sintering and crack self-organization: heating to 1170-1190℃, keeping warm for 1-2 hours, and achieving simultaneously: Surface functional layer: lanthanum zirconium oxide precursor is sintered into a pyrochlore-type nanoporous layer; Pinning phase formation: Yttrium oxide stabilizes the growth of yttrium aluminum garnet nuclei into grain boundary pinning phase; Asymmetric cooling: axial cooling rate 80℃ / min, radial cooling rate 30℃ / min; A crack network is formed on the surface to obtain ceramics.

7. The method for preparing a ceramic with naturally formed cracks according to claim 6, characterized in that: In step S3, the asymmetric cooling triggers: The phase transformation of tetragonal zirconia produces crack nucleation; The screw dislocations of β-sialon whiskers guide the crack path; The lanthanum zirconium oxide layer inhibits the crack growth rate through oxygen vacancy migration.

8. The method for preparing ceramics with naturally formed cracks according to claim 6, characterized in that: In step S1, the mixer comprises a base (1), a fixed block (2) is arranged on one side of the base (1), a fixed seat (7) is arranged on the base (1), a driving motor (8) is arranged on the fixed seat (7), a connecting tube (9) and a fixed shell (11) are coaxially arranged on the fixed seat (7) at the bottom of the driving motor (8), a raw material box (4) is movably arranged inside the fixed block (2), a connecting pipe (6) is arranged on the top of the fixed block (2), a pump body is arranged inside the fixed seat (7), the connecting pipe (6) is connected to the pump body pipeline, the interior of the connecting tube (9) is hollow, a first feed port (17) is opened on the top of the connecting tube (9), the pump body and the first feed port (17) are connected by a pipeline, an inner cavity (14) is arranged inside the fixed shell (11), an output shaft of the driving motor (8) extends to the inner cavity (14) and a stirring rod is arranged inside, and a discharge pipe (12) is arranged at the bottom of the inner cavity (14).

9. The method for preparing ceramics with naturally formed cracks according to claim 8, characterized in that: A support plate (10) is fixedly mounted on one side of the fixed seat (7), and the support plate (10) is arranged to abut against the bottom of the fixed shell (11). The discharge pipe (12) extends to the bottom of the support plate (10). A second feed port (13) is opened at the top of the inner cavity (14), and the second feed port (13) is connected to the connecting cylinder (9). Electric control valves are arranged in the first feed port (17), the second feed port (13) and the discharge pipe (12).

10. The method for preparing ceramics with naturally formed cracks according to claim 8, characterized in that: The interior of the raw material box (4) is hollow, and a partition (16) is provided inside the raw material box (4). A connecting port (5) is provided at the top of the raw material box (4), and the connecting port (5) is connected to a connecting pipe (6).

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