High-temperature self-repairing inorganic conductive adhesive, and preparation method and curing method thereof

Abstract

The application relates to a high-temperature self-repairing inorganic conductive adhesive as well as a preparation method and a curing method thereof. The high-temperature self-repairing inorganic conductive adhesive comprises the following raw materials: a Si-O-Al-P quaternary composite inorganic matrix, a core-shell structure ceramic-based conductive filler, an in-situ whisker reinforcing agent, high-temperature self-repairing microcapsules, a composite curing accelerator and deionized water. The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: an aluminum modified acidic silica sol, an alkaline aluminum phosphate, a borate fluxing agent and a nano-stable oxide. The borate fluxing agent is compounded by sodium tetraborate and zinc borate at a mass ratio of 1:1. The nano-stable oxide is one or more of monoclinic phase nano, monoclinic phase nano and monoclinic phase nano. The high-temperature self-repairing inorganic conductive adhesive has the advantages of low-temperature curing, high-temperature resistance, high conductive stability, high thermal shock resistance and micro-crack self-repairing.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to a high-temperature self-healing inorganic conductive adhesive and its preparation and curing methods. Background Technology

[0002] Conductive adhesive is a functional composite material that combines adhesive and conductive properties. It can replace traditional soldering and bolting methods for conductive bonding and fixing of electronic devices and high-temperature equipment, and is widely used in microelectronic packaging, intelligent sensing, industrial measurement and control, and other fields. Currently available commercial conductive adhesives are mainly divided into two categories: organic conductive adhesives and inorganic conductive adhesives.

[0003] Organic conductive adhesives are made from epoxy resin and silicone resin as the matrix, combined with silver powder, copper powder and carbon-based fillers. Their advantages are low curing temperature, good toughness and excellent adhesion. However, their heat resistance limit is generally lower than 250℃. At high temperatures, the organic matrix is ​​prone to thermal decomposition and carbonization failure, and the conductive network is very easy to collapse. They cannot meet the requirements of extreme high temperature conditions above 300℃, such as aero-engines, high-temperature kilns and SiC / GaN power semiconductors.

[0004] Existing inorganic conductive adhesives mostly use a single silicate or phosphate ionic inorganic matrix, combined with conductive fillers such as metal fillers, graphite, and titanium carbide. While their temperature resistance is significantly improved compared to organic conductive adhesives, they still have several core drawbacks: First, traditional inorganic matrices have an ionic structure, resulting in poor thermal stability. At temperatures above 800℃, they are prone to crystal transformation and volume shrinkage, leading to cracking and detachment of the adhesive layer. Second, metal conductive fillers are easily oxidized and undergo electromigration at high temperatures, while carbon-based fillers are prone to oxidation and ablation, causing a significant decrease in conductivity. Third, inorganic adhesives are inherently brittle, with poor compatibility between their thermal expansion coefficients and those of metal and ceramic substrates. They are prone to microcracks under thermal cycling conditions, resulting in poor long-term service stability. Fourth, most inorganic conductive adhesives require sintering and curing at temperatures above 300℃, which can easily damage precision electronic devices and leads to poor mass production compatibility. Finally, existing high-temperature conductive adhesives generally lack self-healing capabilities; the continuous propagation of high-temperature microcracks can directly cause bonding failure, electrical breakage, and a short service life.

[0005] There is currently no inorganic conductive adhesive that simultaneously possesses low-temperature curing, high-temperature resistance, high conductivity stability, high thermal shock resistance, and microcrack self-healing properties, so there is an urgent need to improve existing technologies. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-temperature self-healing inorganic conductive adhesive and its preparation and curing methods. The high-temperature self-healing inorganic conductive adhesive has the advantages of low-temperature curing, high temperature resistance, high conductivity stability, high thermal shock resistance, and self-healing of microcracks.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows:

[0008] On the one hand, the present invention provides a high-temperature self-healing inorganic conductive adhesive, comprising the following raw materials by mass percentage: 25% to 45% Si-O-Al-P quaternary composite inorganic matrix, 15% to 30% core-shell structure ceramic-based conductive filler, 5% to 12% in-situ whisker reinforcing agent, 3% to 8% high-temperature self-healing microcapsules, 2% to 5% composite curing accelerator, and the balance being deionized water;

[0009] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials by mass percentage: 30%–50% aluminum-modified acidic silica sol, 25%–40% basic aluminum phosphate, 10%–20% borate flux, and 5%–15% nano-stabilized oxide; the borate flux is a mixture of sodium tetraborate and zinc borate in a 1:1 mass ratio; the nano-stabilized oxide is a monoclinic nano-phase... , One or more of them.

[0010] In this process, the quaternary composite inorganic matrix reacts with deionized water to form a continuous Si-O-Al-P quaternary covalent framework, ensuring the bonding strength under high temperature conditions.

[0011] Preferably, the aluminum-modified acidic silica sol has a solid content of 30wt% to 40wt%, a pH value of 3.5 to 5.0, and a particle size of 10 to 30 nm; the basic aluminum phosphate has a particle size of 200 to 500 nm; the borate flux has a particle size of 50 to 200 nm; and the nano-stabilized oxide has a particle size of 20 to 100 nm.

[0012] Furthermore, the core-shell structured ceramic-based conductive filler is... , , Any one or more of them.

[0013] The preparation method of core-shell structured ceramic-based conductive filler includes the following steps: 1) Take 200-400 nm TiC, ... , 1) Prepare nano-whiskers; 2) Add nano-whiskers to an ethanol-silane coupling agent solution with a mass ratio of 1:8 to 1:12, and activate them with intermittent ultrasonication using a power of 300W. Each cycle consists of 5 minutes of ultrasonic operation followed by a 2-minute break, for a total effective ultrasonic time of 10 minutes. After activation, filter and vacuum dry at 75°C for 40 minutes to obtain surface-activated nano-whiskers; 3) Immerse the three types of surface-activated nano-whiskers in aluminum sol, silica sol, and borate-urea precursor solutions with a mass ratio of 1:7 to 1:11, respectively, and age them at 45°C with low-speed stirring for 2 hours; 4) After aging, dry at 120°C to remove organic solvents, then introduce an inert argon atmosphere and calcine at a rate of 2°C / min to 580°C for 2 hours, followed by slow cooling to room temperature. After calcination, a layer of 5-20 mm thick material forms on the surface of the whiskers. The core-shell structure ceramic-based conductive filler has an aspect ratio of 30 to 100. The ethanol-silane coupling agent solution is prepared by mixing anhydrous ethanol, deionized water, and silane coupling agent KH560 in a mass ratio of 92:3:5. The pH is adjusted to 4.0 to 4.5 by adding glacial acetic acid, and the mixture is stirred and allowed to stand at room temperature for 30 min.

[0014] The obtained core-shell structure ceramic-based conductive filler showed no obvious oxidation or electromigration after being kept at 800℃ in air for 1000 hours, and the stability of the conductive network was significantly better than that of pure metal fillers and pure carbon fillers.

[0015] Furthermore, the in-situ whisker reinforcement is a rutile nano-type... One or more of hexagonal wurtzite-type nano ZnO.

[0016] Preferably, the in-situ whisker reinforcement has a particle size of 30–80 nm.

[0017] During the curing process at 150–200°C, the in-situ whisker reinforcing agent reacts in-situ with the phosphorus and silicon components in the matrix to generate titanate whiskers and zincate whiskers. The generated whiskers are 1–5 μm long and 50–200 nm in diameter, and are randomly interwoven at the interface between the inorganic matrix and the conductive filler to construct a three-dimensional interlocking reinforcing structure, which significantly improves the thermal shock resistance and interfacial bonding strength of the adhesive layer.

[0018] Furthermore, the high-temperature self-healing microcapsules are used in... The composite ceramic is a dense shell, and the borate low-temperature glass powder with a softening point of 500-700℃ is used as the core material; the high-temperature self-healing microcapsules have a particle size of 5-20μm and a shell thickness of 1-3μm.

[0019] Understandably, the high-temperature self-healing microcapsules do not break under normal stirring and dispersion conditions, but automatically rupture when high-temperature cracks occur at 600-800℃. The core material melts and flows to fill the microcracks and then solidifies again.

[0020] The preparation method of the high-temperature self-healing microcapsules includes the following steps:

[0021] (1) Preparation of borate glass powder: Take according to the mass ratio 42%, 28%, 12%, MgO 10%, 8%, mixed and melted at 1250℃, water quenched, and ball milled to obtain 5-18μm glass powder;

[0022] (2) Glass powder dispersion: Add glass powder to an ethanol-silane coupling agent solution with a mass ratio of 1:6 to 1:10, and activate it with intermittent ultrasonication using a power of 300W. A single cycle consists of 5 min of ultrasonic operation and 2 min of interruption, with a total effective ultrasonic time of 10 min for both cycles. Then, vacuum dry the glass powder. The ethanol-silane coupling agent solution is prepared by mixing anhydrous ethanol, deionized water, and silane coupling agent KH560 in a mass ratio of 92:3:5. Add glacial acetic acid to adjust the pH to 4.0 to 4.5, and stir and let stand at room temperature for 30 min.

[0023] (3) Preparation of composite aluminum silicate sol: Weigh tetraethyl orthosilicate, aluminum isopropoxide, anhydrous ethanol and deionized water in a mass ratio of 3:1:24:12. First mix anhydrous ethanol and deionized water, then add tetraethyl orthosilicate and aluminum isopropoxide in sequence under stirring at room temperature until completely dissolved. Add glacial acetic acid to adjust the pH of the system to 3.8-4.5, and continue stirring for 30 min to obtain a stable and transparent composite aluminum silicate sol.

[0024] (4) The glass powder obtained in step (2) is added to a composite aluminosilicate sol with a mass ratio of 1:8 to 1:12. The mixture is stirred and coated at 45°C and 300 r / min for 2.5 h, allowed to stand and age for 2 h, and then filtered to obtain a solid material. The solid material is washed with ethanol, dried under vacuum at 75°C, and then calcined at 580°C for 1.2 h in an Ar atmosphere to obtain a shell with a thickness of 1 to 3 μm. Ceramic-coated borate glass powder microcapsules were subjected to airflow classification to obtain 5–20 μm high-temperature self-healing microcapsules.

[0025] The encapsulation mechanism during microcapsule preparation is as follows:

[0026] The composite aluminum-silica sol is rich in Si-OH and Al-OH, which undergo heterogeneous dehydration and condensation with the hydroxyl groups on the surface of glass powder, forming a continuous amorphous Al-Si oxide gel film in situ on the surface of glass powder.

[0027] Furthermore, the composite curing accelerator is composed of aluminum fluoride, light magnesium oxide, and nano-alumina in a mass ratio of 2:1:1.

[0028] Preferably, the particle size of the composite curing accelerator is ≤100nm.

[0029] Among them, the composite curing accelerator can effectively reduce the crosslinking activation energy of Si-O-Al-P matrix, realize room temperature pre-forming and low temperature rapid curing, and eliminate the need for high temperature sintering throughout the process. The high temperature crosslinking and heat preservation curing cycle is ≤30min, which is suitable for bonding and encapsulating precision high temperature devices and avoids device damage caused by high temperature processes.

[0030] On the other hand, the present invention provides a method for preparing the above-mentioned high-temperature self-healing inorganic conductive adhesive, comprising the following steps:

[0031] S1. Preparation of matrix sol: Take aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxide according to the formula, add them to deionized water, stir at 800-1200 r / min for 30-60 min at room temperature, and then ultrasonically disperse at 300 W for 15-20 min to prepare Si-O-Al-P quaternary composite inorganic matrix sol;

[0032] Among them, the cross-linking reaction mechanism of the Si-O-Al-P quaternary composite inorganic matrix sol is a stepwise hydrolysis-cross-covalent condensation reaction pathway.

[0033] Stage 1: Liquid-phase hydrolysis activation

[0034] All powder precursors are dissociated and surface hydroxylated in deionized water to generate a variety of active hydroxyl monomers: Si-OH, Al-OH, P-OH, B-OH, and Zr-OH.

[0035] Stage 2: Room temperature cross-condensation

[0036] Dehydration condensation occurs between active hydroxyl monomers, forming covalent oxygen bridges (Si-O-Si, Si-O-Al, Si-OP, Al-OP, Zr-O-Si, BOP). This differs from the single-component ionic bond networks of traditional single silicates (Si-O-Si only) and single phosphates (Al-OP only), forming a continuous Si-O-Al-P quaternary covalent framework. Among these, Si-O-Si, Si-O-Al, Si-OP, and Al-OP constitute the core framework of the inorganic network, providing the main source of adhesive strength. Zr-O-Si and BOP serve only as a small number of crosslinked branches to fill network voids, reducing the gel's thermal expansion coefficient and inhibiting high-temperature shrinkage cracking. After curing, the Si-O-Al-P quaternary composite inorganic matrix forms mullite. Zirconium phosphate It has a stable crystalline phase, a thermal decomposition temperature ≥900℃, and a coefficient of thermal expansion ≤5ppm / K.

[0037] S2. Filler activation pretreatment: Disperse the core-shell structure ceramic-based conductive filler and in-situ whisker reinforcing agent in anhydrous ethanol, ultrasonically activate for 10-15 min, and vacuum dry at 60℃ for later use.

[0038] In this step, the purpose of ultrasonic activation is to remove surface dust and oxidized impurities, which effectively improves the dispersibility and interfacial bonding of the filler.

[0039] S3. Mixing the main adhesive solution: The core-shell structure ceramic-based conductive filler, in-situ whisker reinforcing agent, and composite curing accelerator obtained in step S2 are added sequentially to the Si-O-Al-P quaternary composite inorganic matrix sol. First, stir at 500 r / min for 20 min, then stir at 1000 r / min for 40 min, and then homogenize with ultrasonic power of 300W for 20 min to obtain the initial mixed adhesive solution.

[0040] S4. Self-healing function compound: Slowly add high-temperature self-healing microcapsules into the initial mixed adhesive solution, and stir for 10-12 minutes at 200-300 r / min using a low-shear anchor-type stirring paddle to obtain a composite conductive adhesive solution.

[0041] In this step, the selection of the stirring rate and the use of a low-shear anchored stirring paddle are intended to avoid the ceramic shell from breaking and to ensure the integrity of the self-healing structure.

[0042] S5. Vacuum defoaming and encapsulation: Place the composite conductive adhesive stock solution in a vacuum defoaming tank and defoam for 10 to 15 minutes under a vacuum of -0.08 to -0.1 MPa. After filtration through a 200-mesh filter, seal and encapsulate to obtain a high-temperature self-healing inorganic conductive adhesive.

[0043] Furthermore, the present invention provides a curing method for the above-mentioned high-temperature self-healing inorganic conductive adhesive, comprising the following steps:

[0044] The high-temperature self-healing inorganic conductive adhesive is pre-formed at room temperature for 20-30 minutes, then heated to 100℃ at a rate of 1-3℃ / min and held for 10 minutes, and then heated to 150-200℃ at a rate of 1-3℃ / min and held for 10-20 minutes for cross-linking and curing. After curing, it is naturally cooled in the oven at a rate of ≤2℃ / min.

[0045] This curing method eliminates the need for high-temperature sintering above 300℃ throughout the entire curing process, thus avoiding heat damage to precision devices such as SiC / GaN chips and micro high-temperature sensors. After curing, the adhesive layer is dense and free of bubbles and penetrating microcracks.

[0046] The present invention has the following beneficial effects:

[0047] The high-temperature self-healing inorganic conductive adhesive of the present invention uses a Si-O-Al-P quaternary covalent network matrix to replace the traditional ionic inorganic matrix. It has a thermal decomposition temperature of ≥900℃ and can achieve stable service in a wide temperature range of -50℃ to 1000℃. It can also maintain a high temperature of 800℃ for a long time without structural collapse, thus making up for the shortcomings of traditional inorganic conductive adhesives that have a temperature resistance of less than 800℃ and are prone to failure at high temperatures.

[0048] This inorganic conductive adhesive cures rapidly at low temperatures of 150–200°C, with a high-temperature cross-linking and curing cycle of ≤30 minutes. It does not require sintering at temperatures above 300°C and can be used for bonding and encapsulating high-temperature sensitive devices such as SiC / GaN third-generation semiconductors and precision high-temperature sensors, reducing process energy consumption and the risk of device damage.

[0049] This inorganic conductive adhesive uses a core-shell structured ceramic-based conductive filler, avoiding the high-temperature oxidation and electromigration problems associated with metal fillers. Its volume resistivity is ≤ [value missing] at 800℃. Ω·cm, resistance change rate after high and low temperature cycling ≤15%, the stability of the conductive network far exceeds that of traditional inorganic conductive adhesives.

[0050] This inorganic conductive adhesive forms a three-dimensional interlocking reinforced structure by combining an in-situ whisker reinforcing agent with a quaternary composite inorganic matrix, which greatly improves the brittleness of the inorganic adhesive. The high-temperature shear strength at 800℃ is ≥12MPa. After 50 extreme thermal cycles, it shows no cracking or peeling and has excellent interfacial bonding.

[0051] This inorganic conductive adhesive, through high-temperature self-healing microcapsules, can automatically repair high-temperature microcracks. After multiple thermal shocks, its shear strength retention rate is ≥80%, solving the problem of cumulative failure of inorganic conductive adhesives due to microcracks and significantly improving its service life under extreme working conditions. Detailed Implementation

[0052] To make the technical problem to be solved, the technical solution, and the technical advantages of the present invention clearer, a detailed description will be provided below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments. The described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0054] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market.

[0055] Preparation example:

[0056] The preparation method of core-shell structured ceramic-based conductive filler includes the following steps: 1) Take 200-400 nm TiC, ... , 1) Prepare nano-whiskers; 2) Add nano-whiskers to an ethanol-silane coupling agent solution at a mass ratio of 1:10, and activate them with intermittent ultrasonication using a power of 300W. Each cycle consists of 5 minutes of ultrasonic operation followed by a 2-minute break, for a total effective ultrasonic time of 10 minutes. After activation, filter and vacuum dry at 75℃ for 40 minutes to obtain surface-activated nano-whiskers; 3) Immerse the three types of surface-activated nano-whiskers in aluminum sol, silica sol, and borate urea precursor solutions at a mass ratio of 1:9, respectively, and age them at 45℃ with low-speed stirring for 2 hours; 4) After aging, dry at 120℃ to remove organic solvents, then introduce an inert argon atmosphere and calcine at a rate of 2℃ / min to 580℃ for 2 hours, followed by slow cooling to room temperature. After calcination, a layer of 5-20mm thick nano-whiskers forms on the surface of the whiskers. The core-shell structure ceramic-based conductive filler has an aspect ratio of 30 to 100. The ethanol-silane coupling agent solution is prepared by mixing anhydrous ethanol, deionized water, and silane coupling agent KH560 in a mass ratio of 92:3:5. The pH is adjusted to 4.0 to 4.5 by adding glacial acetic acid, and the mixture is stirred and allowed to stand at room temperature for 30 min.

[0057] The preparation method of high-temperature self-healing microcapsules includes the following steps:

[0058] (1) Preparation of borate glass powder: Take according to the mass ratio 42%, 28%, 12%, MgO 10%, 8%, mixed and melted at 1250℃, water quenched, and ball milled to obtain 5-18μm glass powder;

[0059] (2) Dispersion of glass powder: Add glass powder to an ethanol-silane coupling agent solution with a mass ratio of 1:8, and activate it by intermittent ultrasonication with a power of 300W. A single cycle consists of 5 min of ultrasonic operation and 2 min of interruption. The total effective ultrasonic time for the two cycles is 10 min. Then, vacuum dry the glass powder. The ethanol-silane coupling agent solution is prepared by mixing anhydrous ethanol, deionized water, and silane coupling agent KH560 in a mass ratio of 92:3:5. Add glacial acetic acid to adjust the pH to 4.0-4.5, and stir and let stand at room temperature for 30 min.

[0060] (3) Preparation of composite aluminum silicate sol: Weigh tetraethyl orthosilicate, aluminum isopropoxide, anhydrous ethanol and deionized water in a mass ratio of 3:1:24:12. First mix anhydrous ethanol and deionized water, then add tetraethyl orthosilicate and aluminum isopropoxide in sequence under stirring at room temperature until completely dissolved. Add glacial acetic acid to adjust the pH of the system to 3.8-4.5, and continue stirring for 30 min to obtain a stable and transparent composite aluminum silicate sol.

[0061] (4) The glass powder obtained in step (2) is added to a composite aluminosilicate sol at a mass ratio of 1:10. The mixture is stirred and coated at 45°C and 300 r / min for 2.5 h, allowed to stand and age for 2 h, and then filtered to obtain a solid material. The solid material is washed with ethanol, dried under vacuum at 75°C, and then calcined at 580°C for 1.2 h in an Ar atmosphere to obtain a shell with a thickness of 1-3 μm. Ceramic-coated borate glass powder microcapsules were subjected to airflow classification to obtain 5–20 μm high-temperature self-healing microcapsules.

[0062] Examples and comparative examples:

[0063] This invention relates to high-temperature self-healing inorganic conductive adhesives, and includes Examples 1-6 and Comparative Examples 1-2.

[0064] Example 1

[0065] A high-temperature self-healing inorganic conductive adhesive comprises the following raw materials by mass percentage: 35% Si-O-Al-P quaternary composite inorganic matrix, 22% core-shell structured ceramic-based conductive filler, 8% in-situ whisker reinforcing agent, 5% high-temperature self-healing microcapsules, 3% composite curing accelerator, and the balance being deionized water.

[0066] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxides. The mass ratio is 40:35:15:10; the core-shell structure ceramic-based conductive filler is... The in-situ whisker reinforcement is rutile nano-type. The high-temperature self-healing microcapsule shell is The composite ceramic has a core material of 600℃ softened borate glass powder and a composite curing accelerator composed of aluminum fluoride, light magnesium oxide, and nano alumina in a mass ratio of 2:1:1.

[0067] Among them, the aluminum-modified acidic silica sol is SW-40 aluminum-modified acidic silica sol; the basic aluminum phosphate has a particle size of 200-500 nm; the borate flux is a mixture of sodium tetraborate and zinc borate in a mass ratio of 1:1 with a particle size of 50-200 nm; the nano-stabilized oxide has a particle size of 20-100 nm; the in-situ whisker reinforcing agent has a particle size of 30-80 nm; and the composite curing accelerator has a particle size of ≤100 nm.

[0068] The preparation method of this conductive adhesive includes:

[0069] S1. Preparation of matrix sol: Take aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux and nano-stabilized oxide according to the ratio, add them to deionized water, stir at 1000 r / min for 40 min at room temperature, and then ultrasonically disperse for 18 min with an ultrasonic cleaner with an ultrasonic power of 300W to prepare a uniform Si-O-Al-P quaternary composite inorganic matrix sol.

[0070] S2. Filler activation pretreatment: Disperse the core-shell structure ceramic-based conductive filler and in-situ whisker reinforcing agent in anhydrous ethanol, ultrasonically activate for 12 min, and vacuum dry at 60℃ to remove ethanol and surface impurities for later use.

[0071] S3. Mixing the main adhesive solution: The core-shell structure ceramic-based conductive filler, in-situ whisker reinforcing agent, and composite curing accelerator obtained in step S2 are added sequentially to the Si-O-Al-P quaternary composite inorganic matrix sol. First, stir at 500 r / min for 20 min, then stir at 1000 r / min for 40 min. Then, homogenize with an ultrasonic cleaner with an ultrasonic power of 300W for 20 min to obtain the initial mixed adhesive solution.

[0072] S4. Self-healing function compound: The high-temperature self-healing microcapsules are slowly added to the initial mixed adhesive solution, and the mixture is stirred at 300r / min for 10min using a low-shear anchor-type stirring paddle to obtain the composite conductive adhesive solution.

[0073] S5. Vacuum defoaming and encapsulation: The composite conductive adhesive stock solution is placed in a vacuum defoaming tank and defoamed for 12 minutes under a vacuum of -0.09 MPa. After filtration through a 200-mesh filter, it is sealed and encapsulated to obtain a high-temperature self-healing inorganic conductive adhesive.

[0074] Curing process: The sample with high-temperature self-healing inorganic conductive adhesive is pre-shaped at room temperature for 25 min, then heated to 100℃ at a rate of 2℃ / min and held for 10 min, and then heated to 180℃ at a rate of 2℃ / min and held for 15 min for cross-linking curing. After curing, the sample is naturally cooled in the oven at a rate of ≤2℃ / min.

[0075] Sample preparation and performance testing methods:

[0076] Resistivity test sample preparation: GH3030 nickel-based high-temperature alloy sandwich two-electrode sample was used, with electrode specifications of 40mm×20mm×3mm and an effective conductive area of ​​20mm×20mm; the electrode bonding surface was roughened with sandpaper, ultrasonically degreased with ethanol and dried; 0.03mm alumina microspheres were added to the conductive adhesive to control the adhesive layer thickness of 0.02~0.05mm, and after stacking, uniform pressure of 0.3 MPa was applied and cured by a curing process.

[0077] Resistivity testing: The volume resistivity of the test sample was measured using a resistivity meter at room temperature, 800℃, and after thermal cycling. It should be understood that the volume resistivity test consisted of three independent groups of samples. All three groups of samples had identical substrates, dimensions, adhesive layer thicknesses, and curing processes, and were not reused.

[0078] 1) Room temperature resistivity sample: tested only at 23℃, without experiencing high temperatures throughout the process;

[0079] 2) 800℃ resistivity sample: heated to 800℃ and tested in situ under constant temperature. The sample will not be reused after testing.

[0080] 3) Resistivity sample after thermal cycling: First, record the initial room temperature resistivity, complete a total of 50 cycles of thermal cycling from -50℃ to 800℃, and after the cycle is completed, cool to room temperature and remeasure the resistance to calculate the rate of change of resistance. In each thermal cycle, the heating and cooling rate is 3℃ / min, and the low temperature and high temperature are held for 30min each. The complete duration of a single cycle is about 6h.

[0081] Preparation of adhesive bonding samples: The samples were made of 96% alumina ceramic and GH3030 nickel-based high-temperature alloy as single-overlap substrates, with a single piece size of 30 mm × 25 mm × 10 mm. The two overlapping substrates were overlapped with high-temperature self-healing inorganic conductive adhesive, with an overlap length of 12.5 mm, and then cured by curing process.

[0082] Shear strength test: The shear strength of the bonded specimens was tested according to GB / T 42910-2023 "Inorganic Adhesives - Test Method for High-Temperature Compression Shear Strength". The shear strength retention rate is the rate of change calculated from the test results before and after the high-temperature impact treatment.

[0083] High-temperature shock (thermal shock) conditions: The bonded sample is heated to 800℃ and kept at that temperature for 30 minutes, then cooled to room temperature to complete one high-temperature shock, and the cycle is repeated 5 times; after the cycle is completed, the sample is cooled to room temperature.

[0084] Performance test results: room temperature resistivity Ω·cm, resistivity at 800℃ Ω·cm, resistivity change rate of 11.2% after 50 thermal cycles, shear strength of 15.3MPa at 800℃, and shear strength retention rate of 83.5% after 5 high-temperature impacts.

[0085] Example 2

[0086] A high-temperature self-healing inorganic conductive adhesive comprises the following raw materials by mass percentage: 33% Si-O-Al-P quaternary composite inorganic matrix, 22% core-shell structured ceramic-based conductive filler, 8% in-situ whisker reinforcing agent, 5% high-temperature self-healing microcapsules, 3% composite curing accelerator, and the balance being deionized water.

[0087] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxides. The mass ratio is 40:35:15:10; the core-shell structure ceramic-based conductive filler is... The in-situ whisker reinforcement is hexagonal wurtzite-type nano-ZnO with a particle size of 40–70 nm; the high-temperature self-healing microcapsule shell is… The composite ceramic has a core material of 600℃ softened borate glass powder and a composite curing accelerator composed of aluminum fluoride, light magnesium oxide, and nano alumina in a mass ratio of 2:1:1.

[0088] Among them, the aluminum-modified acidic silica sol is SW-40 aluminum-modified acidic silica sol; the basic aluminum phosphate has a particle size of 200-500 nm; the borate flux is a mixture of sodium tetraborate and zinc borate in a mass ratio of 1:1 with a particle size of 50-200 nm; the nano-stabilized oxide has a particle size of 20-100 nm; the in-situ whisker reinforcing agent has a particle size of 30-80 nm; and the composite curing accelerator has a particle size of ≤100 nm.

[0089] The preparation method of this conductive adhesive is the same as in Example 1. The sample preparation method and performance testing method are the same as in Example 1.

[0090] Performance test results: room temperature resistivity Ω·cm, resistivity at 800℃ Ω·cm, resistivity change rate of 10.5% after 50 thermal cycles, shear strength of 14.8MPa at 800℃, and shear strength retention rate of 84.2% after 5 high-temperature impacts.

[0091] Example 3

[0092] A high-temperature self-healing inorganic conductive adhesive comprises the following raw materials by mass percentage: 28% Si-O-Al-P quaternary composite inorganic matrix, 28% core-shell structure ceramic-based conductive filler, 10% in-situ whisker reinforcing agent, 7% high-temperature self-healing microcapsules, 4% composite curing accelerator, and the balance being deionized water.

[0093] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxides. The mass ratio is 40:35:15:10; the core-shell structure ceramic-based conductive filler is... The in-situ whisker reinforcement is rutile nano-type. The high-temperature self-healing microcapsule shell is The composite ceramic has a core material of 600℃ softened borate glass powder and a composite curing accelerator composed of aluminum fluoride, light magnesium oxide, and nano alumina in a mass ratio of 2:1:1.

[0094] Among them, the aluminum-modified acidic silica sol is SW-40 aluminum-modified acidic silica sol; the basic aluminum phosphate has a particle size of 200-500 nm; the borate flux is a mixture of sodium tetraborate and zinc borate in a mass ratio of 1:1 with a particle size of 50-200 nm; the nano-stabilized oxide has a particle size of 20-100 nm; the in-situ whisker reinforcing agent has a particle size of 30-80 nm; and the composite curing accelerator has a particle size of ≤100 nm.

[0095] The preparation method of this conductive adhesive is the same as in Example 1. The sample preparation method and performance testing method are the same as in Example 1.

[0096] Performance test results: room temperature resistivity Ω·cm, resistivity at 800℃ Ω·cm, resistivity change rate after 50 thermal cycles is 8.7%, shear strength at 800℃ is 16.1MPa, and shear strength retention rate after 5 high-temperature impacts is 86.7%.

[0097] Example 4

[0098] A high-temperature self-healing inorganic conductive adhesive comprises the following raw materials by mass percentage: 45% Si-O-Al-P quaternary composite inorganic matrix, 15% core-shell structured ceramic-based conductive filler, 6% in-situ whisker reinforcing agent, 4% high-temperature self-healing microcapsules, 2% composite curing accelerator, and the balance being deionized water.

[0099] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxides. The mass ratio is 40:35:15:10; the core-shell structure ceramic-based conductive filler is... The in-situ whisker reinforcement is rutile nano-type. The high-temperature self-healing microcapsule shell is The composite ceramic has a core material of 600℃ softened borate glass powder and a composite curing accelerator composed of aluminum fluoride, light magnesium oxide, and nano alumina in a mass ratio of 2:1:1.

[0100] Among them, the aluminum-modified acidic silica sol is SW-40 aluminum-modified acidic silica sol; the basic aluminum phosphate has a particle size of 200-500 nm; the borate flux is a mixture of sodium tetraborate and zinc borate in a mass ratio of 1:1 with a particle size of 50-200 nm; the nano-stabilized oxide has a particle size of 20-100 nm; the in-situ whisker reinforcing agent has a particle size of 30-80 nm; and the composite curing accelerator has a particle size of ≤100 nm.

[0101] The preparation method of this conductive adhesive is the same as in Example 1. The sample preparation method and performance testing method are the same as in Example 1.

[0102] Performance test results: room temperature resistivity Ω·cm, resistivity at 800℃ Ω·cm, resistivity change rate after 50 thermal cycles is 14.1%, shear strength at 800℃ is 13.6MPa, and shear strength retention rate after 5 high-temperature impacts is 81.2%.

[0103] Example 5

[0104] A high-temperature self-healing inorganic conductive adhesive comprises the following raw materials by mass percentage: 25% Si-O-Al-P quaternary composite inorganic matrix, 25% core-shell structure ceramic-based conductive filler, 9% in-situ whisker reinforcing agent, 8% high-temperature self-healing microcapsules, 3% composite curing accelerator, and the balance being deionized water.

[0105] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxides. The mass ratio is 40:35:15:10; the core-shell structure ceramic-based conductive filler is... The in-situ whisker reinforcement is hexagonal wurtzite-type nano-ZnO; the high-temperature self-healing microcapsule shell is... The composite ceramic has a core material of 600℃ softened borate glass powder and a composite curing accelerator composed of aluminum fluoride, light magnesium oxide, and nano alumina in a mass ratio of 2:1:1.

[0106] Among them, the aluminum-modified acidic silica sol is SW-40 aluminum-modified acidic silica sol; the basic aluminum phosphate has a particle size of 200-500 nm; the borate flux is a mixture of sodium tetraborate and zinc borate in a mass ratio of 1:1 with a particle size of 50-200 nm; the nano-stabilized oxide has a particle size of 20-100 nm; the in-situ whisker reinforcing agent has a particle size of 30-80 nm; and the composite curing accelerator has a particle size of ≤100 nm.

[0107] The preparation method of this conductive adhesive is the same as in Example 1. The sample preparation method and performance testing method are the same as in Example 1.

[0108] Performance test results: room temperature resistivity Ω·cm, resistivity at 800℃ Ω·cm, resistivity change rate after 50 thermal cycles is 9.3%, shear strength at 800℃ is 14.5MPa, and shear strength retention rate after 5 high-temperature impacts is 87.1%.

[0109] Example 6

[0110] A high-temperature self-healing inorganic conductive adhesive comprises the following raw materials by mass percentage: 32% Si-O-Al-P quaternary composite inorganic matrix, 20% core-shell structure ceramic-based conductive filler, 12% in-situ whisker reinforcing agent, 6% high-temperature self-healing microcapsules, 5% composite curing accelerator, and the balance being deionized water.

[0111] The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials: aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxides. The mass ratio is 40:35:15:10; the core-shell structure ceramic-based conductive filler is... and The mixture is formulated at a mass ratio of 1:1; the in-situ whisker reinforcing agent is rutile nano-type. The high-temperature self-healing microcapsule shell is The composite ceramic has a core material of 600℃ softened borate glass powder and a composite curing accelerator composed of aluminum fluoride, light magnesium oxide, and nano alumina in a mass ratio of 2:1:1.

[0112] Among them, the aluminum-modified acidic silica sol is SW-40 aluminum-modified acidic silica sol; the basic aluminum phosphate has a particle size of 200-500 nm; the borate flux is a mixture of sodium tetraborate and zinc borate in a mass ratio of 1:1 with a particle size of 50-200 nm; the nano-stabilized oxide has a particle size of 20-100 nm; the in-situ whisker reinforcing agent has a particle size of 30-80 nm; and the composite curing accelerator has a particle size of ≤100 nm.

[0113] The preparation method of this conductive adhesive is the same as in Example 1. The sample preparation method and performance testing method are the same as in Example 1.

[0114] Performance test results: room temperature resistivity Ω·cm, resistivity at 800℃ Ω·cm, resistivity change rate after 50 thermal cycles is 7.9%, shear strength at 800℃ is 16.8MPa, and shear strength retention rate after 5 high-temperature impacts is 88.3%.

[0115] Comparative Example 1

[0116] A traditional high-temperature resistant inorganic conductive adhesive comprises the following raw materials by weight percentage: 45% basic aluminum phosphate powder (particle size 300–500 nm), 28% conductive filler pure TiC nanocrystals, 17% filler alumina powder, 10% high-temperature curing aid magnesium oxide powder, and the balance being deionized water. The pure TiC nanocrystals have a diameter of 200–400 nm and an aspect ratio of 30–100, without an anti-oxidation ceramic coating; the alumina powder is… The particle size is 300–500 nm; the magnesium oxide powder is lightly calcined magnesium oxide with a particle size of 200–400 nm.

[0117] The preparation method of this conductive adhesive includes:

[0118] S1. Matrix dispersion: Add basic aluminum phosphate powder to deionized water, stir at 1000 r / min for 40 min at room temperature, and then ultrasonically disperse at 300 W for 10 min to obtain the matrix;

[0119] S2. Pre-treatment of filler activation: Disperse the conductive filler in anhydrous ethanol, ultrasonically activate for 12 min, and vacuum dry at 60℃ for later use.

[0120] S3. Mixing and stirring: Add the conductive filler, alumina powder filler and high-temperature curing agent obtained in step S2 to the matrix, and stir at 1000 r / min for 30 min to obtain the composite collagen solution.

[0121] S4. Vacuum defoaming and encapsulation: The composite collagen solution is placed in a vacuum defoaming tank and defoamed for 15 minutes under a vacuum of -0.09 MPa. After filtration through a 200-mesh filter, it is sealed and encapsulated to obtain inorganic conductive adhesive.

[0122] Curing process: The sample with inorganic conductive adhesive is pre-shaped at room temperature for 10 min, and then heated to 300℃ at a rate of 4℃ / min and held for 60 min for high-temperature sintering and curing. After curing, it is cooled to room temperature with the furnace.

[0123] Sample preparation:

[0124] Resistivity test sample preparation: GH3030 nickel-based high-temperature alloy sandwich two-electrode sample was used, with electrode specifications of 40mm×20mm×3mm and an effective conductive area of ​​20mm×20mm; the electrode bonding surface was roughened with sandpaper, ultrasonically degreased with ethanol and dried; 0.03mm alumina microspheres were added to the conductive adhesive to control the adhesive layer thickness of 0.02~0.05mm, and after stacking, uniform pressure of 0.3 MPa was applied and cured by a curing process.

[0125] Preparation of adhesive bonding samples: The samples were made of 96% alumina ceramic and GH3030 nickel-based high-temperature alloy as single-overlap substrates, with a single piece size of 30 mm × 25 mm × 10 mm. The two overlapping substrates were overlapped with inorganic conductive adhesive, with an overlap length of 12.5 mm, and then cured by curing process.

[0126] The performance testing method is the same as in Example 1.

[0127] Performance test results: room temperature resistivity Ω·cm, resistivity increases to at 800℃ Ω・cm; after 20 cycles of hot and cold, numerous microcracks appeared in the adhesive layer; the conductive network completely failed after high-temperature impact; it is not suitable for high-temperature conditions of 800℃.

[0128] Comparative Example 2

[0129] A conventional silicate-based silver-based inorganic conductive adhesive comprises the following raw materials by weight percentage: 40% sodium silicate water, 32% conductive filler micron-sized spherical silver powder (particle size 2-5 μm), 18% inert filler alumina, 10% high-temperature curing aid zinc oxide powder, and the balance being deionized water. The inert filler alumina is... The particle size is 300–500 nm; the high-temperature curing aid is a lightweight active zinc oxide powder with a particle size of 200–400 nm.

[0130] The preparation method of this conductive adhesive includes:

[0131] S1. Matrix dispersion: Sodium silicate water is added to deionized water and stirred at 1000 r / min for 40 min at room temperature. Then it is ultrasonically dispersed at 300 W for 10 min to obtain the matrix.

[0132] S2. Filler pretreatment: Micron-sized spherical silver powder conductive filler and alumina inert filler are simply mechanically mixed to obtain a filler mixture;

[0133] S3. Mixing and stirring: Add the filler mixture obtained in step S2 and the high-temperature curing agent zinc oxide powder to the matrix, and stir at 1000 r / min for 30 min to obtain the composite collagen solution.

[0134] S4. Vacuum defoaming and encapsulation: The composite collagen solution is placed in a vacuum defoaming tank and defoamed for 15 minutes under a vacuum of -0.09 MPa. After filtration through a 200-mesh filter, it is sealed and encapsulated to obtain inorganic conductive adhesive.

[0135] Curing process: The sample with inorganic conductive adhesive is left to stand at room temperature for 20 minutes to complete the initial shaping. The temperature is then increased to 260℃ at a rate of 3.5℃ / min and held for 40 minutes for cross-linking and curing. After curing, the sample is cooled to room temperature in the oven.

[0136] Sample preparation:

[0137] Resistivity test sample preparation: GH3030 nickel-based high-temperature alloy sandwich two-electrode sample was used, with electrode specifications of 40mm×20mm×3mm and an effective conductive area of ​​20mm×20mm; the electrode bonding surface was roughened with sandpaper, ultrasonically degreased with ethanol and dried; 0.03mm alumina microspheres were added to the conductive adhesive to control the adhesive layer thickness of 0.02~0.05mm, and after stacking, uniform pressure of 0.3 MPa was applied and cured by a curing process.

[0138] Preparation of adhesive bonding samples: The samples were made of 96% alumina ceramic and GH3030 nickel-based high-temperature alloy as single-overlap substrates, with a single piece size of 30 mm × 25 mm × 10 mm. The two overlapping substrates were overlapped with inorganic conductive adhesive, with an overlap length of 12.5 mm, and then cured by curing process.

[0139] The resistivity testing method is the same as in Example 1.

[0140] Thermal shock conditions: The bonded sample is heated to 300℃ and kept at that temperature for 30 minutes, then cooled to room temperature to complete one high-temperature shock, and the cycle is repeated 5 times; after the cycle is completed, the sample is cooled to room temperature.

[0141] Performance test results: room temperature resistivity The conductive network completely fails at 800℃ (Ω·cm); after five 300℃ thermal shocks, the thermal expansion coefficients of the adhesive layer and the ceramic / metal substrate are mismatched, resulting in large-area cracking and detachment; the adhesive layer cannot bond at 800℃ and has no conductivity, making it unsuitable for high-temperature conditions at 800℃.

[0142] The performance comparison analysis of the above embodiments and comparative examples shows that, compared with traditional single phosphate-based inorganic conductive adhesives and silicate-based inorganic conductive adhesives, this invention achieves multiple performance breakthroughs such as low-temperature curing, ultra-high temperature resistance, high conductivity stability, high thermal shock resistance, and microcrack self-repair through the combination of four core innovative components: quaternary composite inorganic matrix, core-shell structure ceramic-based conductive filler, in-situ whisker reinforcing agent, and high-temperature self-healing microcapsules. It solves the industry pain points of existing products such as high-temperature failure, process limitations, and short lifespan, and has extremely high application value and promotion prospects in the field of extreme high-temperature equipment.

[0143] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0144] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0145] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A high temperature self-healing inorganic conductive adhesive, characterized in that, The preparation materials contain the following percentages by mass: 25%–45% Si-O-Al-P quaternary composite inorganic matrix, 15%–30% core-shell structure ceramic-based conductive filler, 5%–12% in-situ whisker reinforcing agent, 3%–8% high-temperature self-healing microcapsules, 2%–5% composite curing accelerator, and the balance being deionized water. The Si-O-Al-P quaternary composite inorganic matrix comprises the following raw materials by mass percentage: 30%–50% aluminum-modified acidic silica sol, 25%–40% basic aluminum phosphate, 10%–20% borate flux, and 5%–15% nano-stabilized oxide; the borate flux is a mixture of sodium tetraborate and zinc borate in a 1:1 mass ratio; the nano-stabilized oxide is a monoclinic nano-phase... , One or more of them.

2. The high-temperature self-healing inorganic conductive adhesive according to claim 1, characterized in that, The core-shell structured ceramic-based conductive filler is , , Any one or more of them.

3. The high-temperature self-healing inorganic conductive adhesive according to claim 1, characterized in that, The in-situ whisker reinforcing agent is a rutile nano-type. One or more of hexagonal wurtzite-type nano ZnO.

4. The high-temperature self-healing inorganic conductive adhesive according to claim 1, characterized in that, The high-temperature self-healing microcapsules are The composite ceramic is a dense shell, and the borate low-temperature glass powder with a softening point of 500-700℃ is used as the core material; the high-temperature self-healing microcapsules have a particle size of 5-20μm and a shell thickness of 1-3μm.

5. The high-temperature self-healing inorganic conductive adhesive according to claim 1, characterized in that, The composite curing accelerator is composed of aluminum fluoride, light magnesium oxide, and nano aluminum oxide in a mass ratio of 2:1:

1.

6. A method for preparing a high-temperature self-healing inorganic conductive adhesive as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of matrix sol: Take aluminum-modified acidic silica sol, basic aluminum phosphate, borate flux, and nano-stabilized oxide according to the formula, add them to deionized water, stir at 800-1200 r / min for 30-60 min at room temperature, and then ultrasonically disperse at 300 W for 15-20 min to prepare Si-O-Al-P quaternary composite inorganic matrix sol; S2. Filler activation pretreatment: Disperse the core-shell structure ceramic-based conductive filler and in-situ whisker reinforcing agent in anhydrous ethanol, ultrasonically activate for 10-15 min, and vacuum dry at 60℃ for later use. S3. Mixing the main adhesive solution: The core-shell structure ceramic-based conductive filler, in-situ whisker reinforcing agent, and composite curing accelerator obtained in step S2 are added sequentially to the Si-O-Al-P quaternary composite inorganic matrix sol. First, stir at 500 r / min for 20 min, then stir at 1000 r / min for 40 min, and then homogenize with ultrasonic power of 300W for 20 min to obtain the initial mixed adhesive solution. S4. Self-healing function compound: Slowly add high-temperature self-healing microcapsules into the initial mixed adhesive solution, and stir for 10-12 minutes at 200-300 r / min using a low-shear anchor-type stirring paddle to obtain a composite conductive adhesive solution. S5. Vacuum defoaming and encapsulation: Place the composite conductive adhesive stock solution in a vacuum defoaming tank and defoam for 10 to 15 minutes under a vacuum of -0.08 to -0.1 MPa. After filtration through a 200-mesh filter, seal and encapsulate to obtain a high-temperature self-healing inorganic conductive adhesive.

7. A curing method for a high-temperature self-healing inorganic conductive adhesive as described in any one of claims 1-5, characterized in that, Includes the following steps: The high-temperature self-healing inorganic conductive adhesive is pre-formed at room temperature for 20-30 minutes, then heated to 100℃ at a rate of 1-3℃ / min and held for 10 minutes, and then heated to 150-200℃ at a rate of 1-3℃ / min and held for 10-20 minutes for cross-linking and curing. After curing, it is naturally cooled in the oven at a rate of ≤2℃ / min.

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