High-conductivity high-temperature-resistant ceramic electrode with multi-layer gradient composite structure and preparation method of high-conductivity high-temperature-resistant ceramic electrode

Abstract

A high-conductivity high-temperature-resistant ceramic electrode with a multilayer gradient composite structure sequentially comprises a bottom supporting layer, a middle transition layer and a surface conductive layer from bottom to top, the bottom supporting layer is a porous supporting layer, the middle transition layer is doped with metal nanowires in a gradient mode to form a three-dimensional conductive network, the surface conductive layer is made of high-conductivity ceramic, and the surface conductive layer is made of high-conductivity ceramic. The preparation method of the high-conductivity high-temperature-resistant ceramic electrode comprises the following steps: (1) tape casting; and (2) hot pressed sintering. The multi-layer gradient composite structure design is adopted, the surface conductive layer is made of high-conductivity ceramic and reduces bulk resistance, the middle transition layer is doped with metal nanowires in a gradient mode to form a three-dimensional conductive network, the bottom supporting layer is a high-strength porous ceramic matrix, the mechanical performance is improved, and thermal stress is relieved; interlayer seamless combination is achieved through the tape casting and hot pressing sintering integrated forming technology, the interface defect of a traditional lamination technology is avoided, and the industrial problem that it is difficult to collaboratively optimize the conductivity, strength and high-temperature resistance of conductive ceramic is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive ceramic materials, and relates to a ceramic electrode material, in particular to a high-conductivity and high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure and a preparation method thereof. Background Art

[0002] Conductive ceramics refer to ceramic materials with conductive properties. They not only retain the excellent properties of ceramics but also have good electrical conductivity, thus expanding the application scope of ceramic materials. Existing conductive ceramics (such as titanium boride TiB 2 , silicon carbide SiC, indium tin oxide ITO, etc.) have the following disadvantages: 1. The contradiction between electrical conductivity and mechanical strength: Improving electrical conductivity often requires sacrificing the material density, resulting in a decrease in strength; 2. Insufficient high-temperature stability: Grain boundary oxidation or thermal stress cracking under long-term high temperature; 3. High interfacial contact resistance: The traditional single-layer structure is prone to generate interfacial resistance when connected to other materials. Therefore, it is urgent to develop a ceramic electrode that improves electrical conductivity, mechanical strength, and high-temperature resistance. Summary of the Invention

[0003] In view of the deficiencies in the background art, the present invention has studied and designed a high-conductivity and high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure and a preparation method thereof, aiming to: provide a high-conductivity and high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure that improves electrical conductivity, optimizes mechanical strength, and enhances high-temperature resistance and a preparation method thereof.

[0004] The technical solution of the present invention:

[0005] A high-conductivity and high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure includes, from bottom to top in sequence: a bottom support layer, an intermediate transition layer, and a surface conductive layer. The bottom support layer is a porous support layer, the intermediate transition layer is gradient-doped with metal nanowires to form a three-dimensional conductive network, and the surface conductive layer is a high-conductivity ceramic.

[0006] Preferably, the porous support layer is an Al 2 O 3 -ZrO 2 porous ceramic matrix.

[0007] Preferably, in the porous support layer, by mass percentage, the amounts of each substance are: Al 2 O 3 is 53%-55%, ZrO 2 (3Y-TZP) is 35%-37%, and graphite powder is 9%-11%.

[0008] Preferably, the intermediate transition layer is a SiC matrix gradient-doped with Ag nanowires, the diameter of the Ag nanowires is 50 nm, and the aspect ratio > 100.

[0009] Preferably, the porosity of the porous support layer is 20-30%, and the pore size distribution is 1-10 μm.

[0010] Preferably, in the intermediate transition layer, by mass percentage, the amounts of each substance are: 95%-99.5% of the SiC matrix and 0.5%-5% of the Ag nanowires, that is, the doping concentration of the Ag nanowires decreases linearly or non-linearly from 5% to 0.5% in the direction from the surface conductive layer to the bottom support layer.

[0011] Preferably, the surface conductive layer is TiB 2 -SiC composite ceramic.

[0012] Preferably, in the surface conductive layer, by mass percentage, the amounts of each substance are: TiB 2 is 68%-70%, SiC is 28%-30%, and Y 2 O 3 is 1%-2%.

[0013] A preparation method of a highly conductive and high-temperature resistant ceramic electrode with a multi-layer gradient composite structure includes the following steps:

[0014] (I) Tape casting

[0015] Preparation of the surface conductive layer: TiB 2 and SiC are ball-milled and mixed in the above ratio for 24 h, and Y 2 O 3 is added as a sintering aid; tape casting: the coating thickness of the slurry is 200 μm, and after drying, nano-SiO 2 sol (concentration 5%) is sprayed on the surface as an interfacial agent;

[0016] Preparation of the intermediate transition layer: the SiC matrix and the Ag nanowires are mixed in the above gradient ratio; tape casting: the thickness is 150 μm, and nano-SiO 2 sol is sprayed synchronously between layers;

[0017] Preparation of the bottom support layer: Al 2 O 3 and ZrO 2 are mixed in the above ratio, graphite powder is added as a pore-forming agent, and ball-milled for 12 h; tape casting: the thickness is 300 μm, and a porous structure is formed after drying.

[0018] (II) Hot pressing and sintering

[0019] Stack the three-layer film materials prepared in step (I), place them in a graphite mold, sinter at 1580-1620 °C for 2 h under argon protection, with a pressure of 30-35 MPa, cut into electrode sheets after cooling, and perform surface polishing treatment to obtain the ceramic electrode material of the present invention.

[0020] Preferably, in the step (1), the viscosity of the slurry is controlled to be 3000-5000 mPa·s, and the tape casting speed is 70 mm / min.

[0021] Advantages of the present invention: The present invention adopts a multi-layer gradient composite structure design. The surface conductive layer is a high-conductivity ceramic (TiB 2 -SiC composite layer), which reduces the bulk resistance. The intermediate transition layer is gradient-doped with metal nanowires (silver nanowires) to form a three-dimensional conductive network. The bottom support layer is a high-strength porous ceramic matrix (Al 2 O 3 -ZrO 2 ), which improves the mechanical properties and relieves the thermal stress. The seamless bonding between layers is achieved through an integrated tape casting and hot pressing sintering process, avoiding the interface defects of the traditional lamination process. The ceramic electrode prepared by the present invention has improved conductivity. The resistivity of the surface conductive layer is <10 -5 Ω·m. The nanowire network of the intermediate transition layer reduces the interface contact resistance by more than 30%. The mechanical strength of the bottom porous support layer is optimized, and the flexural strength is ≥450 MPa, which is 2 times higher than that of the traditional single-layer TiB 2 . In terms of high-temperature resistance performance: it can continuously work at 1800°C for 100 h without cracking, and the oxidation resistance is improved (oxidation weight gain <1.5%). It solves the industry problem that it is difficult to synergistically optimize the conductivity, strength and high-temperature resistance performance of conductive ceramics, and is especially suitable for the field of high-temperature electrochemical devices with strict requirements for reliability and life. It can be applied to scenarios such as high-temperature sensors, solid oxide fuel cell (SOFC) electrodes, and arc furnace electrodes, and can be further extended to high-end scenarios such as nuclear reactor electrodes and spacecraft thermal protection systems in the future. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the multi-layer gradient composite ceramic electrode of the present invention.

[0023] Wherein: 1. Surface conductive layer, 2. Intermediate transition layer, 3. Bottom support layer. Specific Embodiments

[0024] The following further describes the present invention with reference to the embodiments.

[0025] Embodiment 1

[0026] Material components:

[0027] Surface conductive layer: TiB 2 70%, SiC 29%, Y 2 O 3 1%;

[0028] Intermediate transition layer: 97% SiC, 3% Ag nanowires (gradient decreasing: 3% in the surface conductive layer → 0.5% in the bottom support layer);

[0029] Bottom support layer: Al 2 O 3 54%, ZrO 2 (3Y-TZP) 36%, 10% graphite powder.

[0030] Preparation process:

[0031] Preparation of the surface conductive layer: TiB 2 and SiC are ball-milled and mixed in the above ratio for 24 h, adding Y 2 O 3 as a sintering aid; Tape casting: The coating thickness of the slurry is 200 μm, and nano-SiO 2 sol (concentration 5%) is sprayed on the surface after drying as an interfacial agent, and the tape casting speed is 70 mm / min.

[0032] Preparation of the intermediate transition layer: The SiC matrix and Ag nanowires (diameter 50 nm, aspect ratio > 100) are mixed in a gradient ratio (3% Ag in the surface layer, gradually decreasing to 0.5% in the bottom support layer); Tape casting: The thickness is 150 μm, and nano-SiO 2 sol is sprayed synchronously between layers, and the tape casting speed is 70 mm / min.

[0033] Preparation of the bottom support layer: Al 2 O 3 is mixed with ZrO 2 in the above ratio, adding graphite powder as a pore-forming agent, ball-milling for 12 h and tape casting: The thickness is 300 μm, the tape casting speed is 70 mm / min, and a porous structure (porosity 25%, pore diameter 5 - 8 μm) is formed after drying.

[0034] Hot press sintering:

[0035] Stack the above three-layer films, place them in a graphite mold, sinter at 1620 °C for 2 h under argon protection, with a pressure of 30 MPa, cut into electrode sheets after cooling, and perform surface polishing treatment to obtain the ceramic electrode of the present invention.

[0036] Perform performance tests on the ceramic electrode prepared in Example 1:

[0037] Conductivity: Resistivity 9.5×10 -6 Ω·m;

[0038] Mechanical strength: Flexural strength 520 MPa, and the pores in the support layer are evenly distributed;

[0039] High temperature resistance: No cracking after being kept at 1800 °C for 100 h, and the oxidation weight gain is 0.8%.

[0040] Example 2

[0041] Material components:

[0042] Surface conductive layer: TiB 2 68%, SiC 30%, Y 2 O 3 2%;

[0043] Intermediate transition layer: SiC 95%, Ag nanowires 5% (gradient decreasing: surface conductive layer 5% → bottom support layer 0.5%);

[0044] Bottom support layer: Al 2 O 3 53%, ZrO 2 37%, graphite powder 10%.

[0045] Optimization of the preparation process. The main method and process of the preparation process are the same as those in Example 1, and the following parameters are optimized:

[0046] Adjustment of ball milling time: The ball milling time of the surface conductive layer is extended to 30 h to improve the uniformity of the TiB 2 -SiC mixture.

[0047] Optimization of sintering pressure: The hot pressing sintering pressure is increased to 35 MPa to enhance the interlayer densification.

[0048] Perform performance tests on the ceramic electrode prepared in Example 2:

[0049] Conductivity: Resistivity 8.2×10 -6 Ω·m;

[0050] Mechanical strength: Flexural strength 490 MPa;

[0051] High temperature resistance: Oxidation weight gain of 1.2% at 1800°C.

[0052] Example 3

[0053] Material components:

[0054] Surface conductive layer: TiB 2 69%, SiC 29.5%, Y 2 O 3 1.5%;

[0055] Intermediate transition layer: SiC 99%, Ag nanowires 1% (gradient decreasing: surface conductive layer 1% → bottom support layer 0.5%);

[0056] Bottom support layer: Al 2 O 3 55%, ZrO 235%, graphite powder 10%.

[0057] Optimization of the preparation process. The main method and process of the preparation process are the same as those in Example 1, and the following parameters are optimized:

[0058] Interface agent enhancement: nano-SiO 2 The sol concentration is increased to 8%, and the spraying amount is increased by 20% to enhance the interfacial bonding force. Fine-tuning of the sintering temperature: The hot-pressing sintering temperature is reduced to 1580 °C, and the pressure is 33 MPa to reduce Al 2 O 3 -ZrO 2 Interface reaction.

[0059] Perform performance tests on the ceramic electrodes prepared in Example 3:

[0060] Conductivity: Resistivity 0.9×10 -5 Ω·m;

[0061] Mechanical strength: Flexural strength 510 MPa;

[0062] High temperature resistance: Oxidation weight gain of 0.7% at 1800 °C.

[0063] Example 4

[0064] Material components:

[0065] Surface conductive layer: TiB 2 70%, SiC 28.5%, Y 2 O 3 1.5%;

[0066] Intermediate transition layer: SiC 98%, Ag nanowires 2% (gradient decreasing: surface conductive layer 2% → bottom support layer 0.5%);

[0067] Bottom support layer: Al 2 O 3 54%, ZrO 2 36%, graphite powder 10%.

[0068] Optimization of the preparation process. The main method and process of the preparation process are the same as those in Example 1, and the following parameters are optimized:

[0069] Optimization of the pore-forming agent: The particle size of the graphite powder is adjusted to 5 μm (original 10 μm), and the pore size distribution of the support layer is more uniform (1 - 5 μm);

[0070] Doctor blade coating speed: Reduced to 50 mm / min to reduce internal bubbles in the film layer.

[0071] Perform performance tests on the ceramic electrodes prepared in Example 4:

[0072] Conductivity: resistivity of 9.8×10 -6 Ω·m;

[0073] Mechanical strength: flexural strength of 505 MPa;

[0074] High temperature resistance: oxidation weight gain of 0.9% at 1800°C.

[0075] Example 5

[0076] Material components:

[0077] Surface conductive layer: TiB 2 69.5%, SiC 29%, Y 2 O 3 1.5%;

[0078] Intermediate transition layer: SiC 96.5%, Ag nanowires 3.5% (gradient decreasing: 3.5% in the surface conductive layer → 0.5% in the bottom support layer);

[0079] Bottom support layer: Al 2 O 3 54%, ZrO 2 35%, graphite powder 11%.

[0080] Optimization of the preparation process. The main method and process of the preparation process are the same as those in Example 1, and the following parameters are optimized:

[0081] Gradient doping process: The gradient design of Ag nanowires is changed to non-linear decreasing (3.5% in the surface conductive layer → 2% in the intermediate transition layer → 0.5% in the bottom support layer) to optimize the interfacial resistance distribution;

[0082] Post-sintering treatment: Annealing treatment in argon after sintering (holding at 1200°C for 1 h) to eliminate residual stress.

[0083] Performance testing of the ceramic electrode prepared in Example 5:

[0084] Conductivity: resistivity of 8.9×10 -6 Ω·m;

[0085] Mechanical strength: flexural strength of 495 MPa;

[0086] High temperature resistance: oxidation weight gain of 0.85% at 1800°C.

[0087] The gradient composite design of the present invention takes into account electrical conductivity, strength and thermal matching, breaking through the performance bottleneck of traditional single-layer materials; process simplification: integrated molding reduces processing steps and lowers production costs (15% lower than traditional processes); tape casting: the slurry viscosity is controlled at 3000 - 5000 mPa·s to ensure a uniform and defect-free film layer; hot pressing sintering: the temperature range is 1580 - 1620 °C and the pressure is 30 - 35 MPa to balance densification and interlayer bonding; gradient design: the Ag nanowire gradient decreases (5% → 0.5%) or non-linearly decreases to achieve the combination of low interface resistance and high strength; pore control: adjusting the particle size and content of graphite powder, the porosity of the support layer is 20 - 30% and the pore diameter is 1 - 10 μm to balance gas diffusion and mechanical strength; the present invention can customize and adjust the proportion of each layer of material to adapt to the requirements of different high-temperature and highly corrosive scenarios, such as the anode of a solid oxide fuel cell: the porous structure of the support layer promotes gas diffusion, and the conductive layer efficiently transports electrons; the electrode of a high-temperature sensor: it can withstand extreme temperature fluctuations, and the surface conductive layer can integrate a Pt temperature measurement circuit, with wide applications.

[0088] The above-described embodiments merely represent the preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure, characterized in that: From bottom to top, it includes: a bottom support layer, an intermediate transition layer, and a surface conductive layer. The bottom support layer is a porous support layer, the intermediate transition layer is gradiently doped with metal nanowires to form a three-dimensional conductive network, and the surface conductive layer is a highly conductive ceramic.

2. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: The porous supporting layer is an Al2O3-ZrO2 porous ceramic matrix.

3. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: In the porous support layer, the amount of each substance, calculated by mass percentage, is: Al2O3 is 53%-55%, ZrO2 (3Y-TZP) is 35%-37%, and graphite powder is 9%-11%.

4. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: The intermediate transition layer is a SiC substrate doped with gradient Ag nanowires, the Ag nanowires have a diameter of 50 nm and an aspect ratio of >100.

5. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: The porosity of the porous support layer is 20-30%, and the pore size distribution is 1-10 μm.

6. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: In the intermediate transition layer, the amount of each substance is as follows, by mass percentage: SiC matrix is ​​95%-99.5%, Ag nanowire is 0.5%-5%, that is, the doping concentration of Ag nanowire decreases gradually or nonlinearly from 5% to 0.5% from the surface conductive layer to the underlying support layer.

7. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: The surface conductive layer is TiB2-SiC composite ceramic.

8. A high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 1, characterized in that: In the surface conductive layer, the amount of each substance, calculated by mass percentage, is: TiB2 is 68%-70%, SiC is 28%-30%, and Y2O3 is 1%-2%.

9. A method for preparing a high-conductivity, high-temperature-resistant ceramic electrode with a multi-layer gradient + composite structure as claimed in claim 1, characterized in that: The steps include: (I) Tape casting Preparation of surface conductive layer: TiB2 and SiC were ball-milled and mixed for 24 hours according to the above proportion, and Y2O3 was added as a sintering aid; tape casting: the slurry was coated with a thickness of 200 μm, and after drying, nano-SiO2 sol (concentration 5%) was sprayed on the surface as an interface agent; Preparation of intermediate transition layer: SiC matrix and Ag nanowires are mixed in the above gradient ratio; tape casting: thickness 150 μm, nano-SiO2 sol is sprayed between layers simultaneously; Preparation of the bottom support layer: Al2O3 and ZrO2 were mixed in the above proportions, graphite powder was added as a pore-forming agent, and ball milling was performed for 12 hours; tape casting was performed to form a film with a thickness of 300 μm, and a porous structure was formed after drying; (ii) Hot pressing sintering The three-layer film prepared in the lamination step 1 is placed in a graphite mold, sintered at 1580-1620° C. for 2 hours under argon protection and a pressure of 30-35 MPa, and cut into electrode sheets after cooling and surface polishing to obtain the ceramic electrode material of the present invention.

10. The method for preparing a high-conductivity and high-temperature resistant ceramic electrode with a multi-layer gradient composite structure as claimed in claim 9, characterized in that: In the step (i), the slurry viscosity is controlled to be 3000-5000 mPa·s, and the tape casting speed is 70 mm / min.

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