High-temperature-resistant mica heating plate and preparation method thereof

Abstract

This invention discloses a high-temperature resistant mica heating plate and its preparation method, belonging to the technical field of heating plates. The high-temperature resistant mica heating plate of this invention sequentially comprises a bottom fluorophlogopite mica plate, a metal heating circuit layer, and a surface fluorophlogopite mica plate. Between the bottom and surface fluorophlogopite mica plates, a first inorganic adhesive layer, a second inorganic adhesive layer, and a third inorganic adhesive layer are sequentially disposed. The inorganic adhesive includes aluminum sol, silica sol, and fillers. The fillers in the first, second, and third inorganic adhesives are aluminum oxide and boron nitride in mass ratios of 7-9:1-3, 4-6:4-6, and 1-3:7-9, respectively. The high-temperature resistant mica heating plate of this invention exhibits high temperature resistance, high thermal conductivity, good insulation, high interlayer bonding strength, uniform heating, good resistance to water cooling and thermal shock, and can operate at high temperatures for extended periods.

Description

Technical Field

[0001] This invention belongs to the field of heating plate technology, specifically relating to a high-temperature resistant mica heating plate and its preparation method. Background Technology

[0002] Existing heating devices have the following problems: (1) Temperature resistance bottleneck: conventional mica composite boards cannot withstand long-term continuous sintering conditions at 1200℃, resulting in high-temperature insulation failure and delamination cracking; (2) Poor heating uniformity: wire winding, foil pasting, and carbon film printing cannot achieve uniform heating across the entire plane, resulting in poor ceramic sintering consistency; (3) High-temperature failure of metal heating circuits: nickel-chromium and iron-chromium-aluminum circuits oxidize and creep rapidly at 1200℃, and precious metal circuits are extremely expensive; (4) Interface bonding failure: organic adhesives decompose at high temperatures, causing the substrate to peel off from the heating layer and blister; (5) High-temperature atmosphere pollution: organic resins decompose at high temperatures, and the volatiles pollute the ceramic green body, resulting in a high defect rate in the sintered product.

[0003] For example, (1) Metal armored heating wire heating module, which uses nickel-chromium / iron-chromium-aluminum heating wire wound ceramic skeleton, wrapped with magnesium oxide insulating sleeve, and assembled with metal support plate, with a maximum long-term operating temperature ≤900℃ and a short-term peak temperature not exceeding 980℃. (2) Pure alumina ceramic etched heating plate. Platinum-rhodium / tantalum metal heating circuit is sintered on the surface of alumina ceramic substrate at high temperature. The temperature resistance can reach 1200~1500℃, which is the mainstream method of high-end sintering equipment, but the shortcomings are prominent: ① The ceramic substrate is extremely brittle and cracks easily from slight impact or thermal shock, and cannot be used in the scenario of frequent loading and unloading in continuous production lines; ② The ceramic has uniform thermal conductivity but poor heat insulation, and serious heat leakage on the back side. It needs to be matched with a thick heat insulation layer, and the equipment is bulky; ③ The cost of platinum-rhodium precious metal etched circuit is extremely high, and the cost per piece is 3~6 times that of the mica-based method; ④ The ceramic substrate cannot be flexibly bonded to the irregular sintering table and can only be used in a flat surface. The CNC loss of irregular parts is large. (3) Natural phlogopite / mica heating plate (screen-printed carbon film / bonded nickel foil heating layer), the substrate is natural mica paper and organosilicon resin hot-pressed composite, the heating layer adopts screen-printed conductive carbon film and bonded nickel-chromium foil process: ① Low temperature resistance limit: natural mica is ≤500℃ for a long time, phlogopite is ≤700℃ for a long time, above 800℃ the mica layer dehydrates and dehydroxylates, interlayer delamination, and the insulation strength drops sharply, which is completely unable to meet the sintering conditions of 1200℃; ② The screen-printed carbon film heating layer carbonizes and fails above 800℃, and the bonded ① Mismatch in thermal expansion at the high-temperature interface of nickel foil, resulting in foil blistering, detachment, and localized overheating and burn-through; ② The bonding system is ordinary silicone resin, which completely carbonizes and decomposes above 900℃, releasing volatile organic compounds that contaminate the ceramic blank, causing blackening and pinhole defects; ③ The lack of high-temperature crystallization composite process results in weak interlayer bonding of the mica substrate, leading to large-area peeling after 1000℃ thermal cycling; ④ The absence of integrated etching precision circuitry means that the thickness and spacing of heating lines cannot be controlled at the micrometer level, resulting in a temperature difference of ≥±4℃ on the board surface, which does not meet the ±1℃ uniform temperature requirement for precision ceramic sintering. (4) Synthetic mica heating plate (without high temperature composite modification): The existing synthetic fluorine-gold mica plate only improves the temperature resistance of the substrate to 100-900℃ continuously and 1000℃ intermittently, but still cannot be used stably at 1200℃ for a long time; and it is only a simple composite metal foil without a gradient high temperature resistant inorganic adhesive layer, no anti-oxidation passivation etching circuit, and no high temperature sealing surface layer. Under the oxidation / nitrogen atmosphere at 1200℃, the metal circuit is quickly oxidized and broken, and the interlayer of the mica substrate cracks and leaks electricity.

[0004] Therefore, a heating device that can withstand continuous high temperatures and generate heat evenly is needed. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a high-temperature resistant mica heating plate and its preparation method; the high-temperature resistant mica heating plate of the present invention has good high-temperature resistance, uniform heating, and low cost.

[0006] The technical solution adopted by this invention to solve its technical problem is: This invention provides a high-temperature resistant mica heating plate, which sequentially includes a bottom fluorophlogopite mica plate, a metal heating circuit layer, and a top fluorophlogopite mica plate. Between the bottom fluorophlogopite board and the top fluorophlogopite board, there are a first inorganic adhesive layer, a second inorganic adhesive layer and a third inorganic adhesive layer in sequence; The first inorganic binder includes aluminum sol, silica sol and filler. The mass ratio of aluminum sol, silica sol and filler is 4-6:4-6:5-7 based on solid content. The filler includes aluminum oxide and boron nitride. The mass ratio of aluminum oxide and boron nitride is 7-9:1-3. The second inorganic binder includes aluminum sol, silica sol and filler. Based on solid content, the mass ratio of aluminum sol, silica sol and filler is 4-6:4-6:5-7. The filler includes aluminum oxide and boron nitride, with a mass ratio of aluminum oxide and boron nitride of 4-6:4-6. The third inorganic binder includes aluminum sol, silica sol, and filler. Based on solid content, the mass ratio of aluminum sol, silica sol, and filler is 4-6:4-6:5-7. The filler includes alumina and boron nitride, with a mass ratio of alumina to boron nitride of 1-3:7-9.

[0007] Preferably, the total thickness of the first inorganic adhesive layer, the second inorganic adhesive layer, and the third inorganic adhesive layer is 0.15-0.25 mm.

[0008] Preferably, the thickness ratio of the first inorganic adhesive layer, the second inorganic adhesive layer, and the third inorganic adhesive layer is 7-9:5-7:5-7.

[0009] Preferably, the metal heating circuit layer is disposed between the first inorganic adhesive layer and the third inorganic adhesive layer, and the second inorganic adhesive layer fills the metal heating circuit layer.

[0010] Preferably, the solid content of aluminum sol is 20-40%, and the solid content of silica sol is 20-40%.

[0011] Preferably, the alumina has a particle size of 30-80 nm and the boron nitride has a particle size of 50-100 nm.

[0012] Preferably, the metal heating circuit layer is a tantalum-niobium-molybdenum-chromium alloy, the composition of which by mass percentage includes: tantalum 76-80%, niobium 14-18%, molybdenum 2-6%, and chromium 1-3%; more preferably: tantalum 78%, niobium 16%, molybdenum 4%, and chromium 2%. This tantalum-niobium-molybdenum-chromium alloy replaces the high-cost precious metals platinum and rhodium, while simultaneously solving the high-temperature oxidation and circuit-breaking defects of ordinary nickel-chromium alloys.

[0013] Preferably, the thickness of the metal heating circuit layer is 0.06~0.12mm.

[0014] Preferably, the surface of the metal heating circuit layer has an oxide film. This film isolates the metal from oxidation in an air / nitrogen atmosphere at 1200℃, preventing creep and deformation. The oxide film acts as a high-temperature barrier, preventing oxygen diffusion inward, inhibiting the high-temperature volatilization of molybdenum oxide, reducing substrate ablation loss, providing thermal shock resistance, reducing interfacial thermal stress, preventing film peeling, resisting high-temperature chemical corrosion, isolating various corrosive media (such as inorganic binders), assisting in thermal barrier insulation, reducing the actual temperature of the substrate, stabilizing surface insulation, providing wear resistance and protection, and expanding application performance.

[0015] Preferably, the line width of the metal heating circuit layer is 0.3~1.2mm, and the line spacing is 0.4~1.5mm. The entire surface is covered by continuous, meandering planar etched lines, ensuring complete coverage without any blank cold areas. The corners and edges are reinforced with denser lines to compensate for heat loss, while the center lines are sparse to balance the temperature field, resulting in a steady-state surface temperature difference ≤±1℃. A pre-installed integrated PT100 high-temperature thermocouple etched temperature sensing line is provided, with the temperature sensing line isolated and insulated from the heating circuit. Real-time closed-loop temperature control is adapted to ceramic sintering PID temperature control. Power density adaptation: maximum surface power density 2.8W / cm². 2 It meets the requirements for rapid heating and sintering at 1200℃, with a heating response of ≤18s.

[0016] Preferably, the thickness of the fluorophlogopite board is 0.5-2mm.

[0017] Preferably, the preparation method of fluorophlogopite board includes the following steps: S1.1 Coarse mica flakes and fluorophlogopite powder are compounded at a mass ratio of 2-4:6-8, and then calcined at 700-900℃ for 1-3 hours to obtain the compounded powder. S1.2 Add 15-20% of the phosphate-borosilicate composite inorganic adhesive to the compound powder in step S1.1, then coat and mold it, air dry at room temperature, debind it in stages at 80-120℃, and calcine it at 1250-1300℃ for 5-10 hours to obtain fluorophlogopite board.

[0018] More preferably, the size of the coarse mica flakes is 60-100 μm.

[0019] More preferably, the size of the fluorophlogopite powder is 5-10 μm.

[0020] Further preferred, the fluorophlogopite powder is KMg3AlSi3O 10 F2.

[0021] Further preferred, the air-drying time at room temperature is 12-16 hours.

[0022] A further preferred embodiment of the phosphate-borosilicate composite inorganic adhesive comprises, by weight: 90-110 parts aluminum dihydrogen phosphate solution, 6-10 parts magnesium oxide, 30-40 parts aluminum oxide, 4-8 parts zinc oxide, and 18-26 parts zirconium borosilicate glass powder. The aluminum dihydrogen phosphate solution is the main agent, combined with magnesium oxide, aluminum oxide, and zinc oxide cured powders. At high temperatures, a stable aluminum magnesium phosphate ceramic phase is formed, which does not decompose or volatilize at 1500℃. The zirconium borosilicate glass powder melts at 500-600℃ to fill the interlayer pores, and upon cooling, forms a continuous ceramic network, firmly locking the mica flakes together. At 1500℃, the glass phase transforms into a high-melting-point silicate, which will not flow or disintegrate.

[0023] More preferably, the zirconium borosilicate glass powder has a softening point of 550-600℃ and a composition of 48-56wt% SiO2, 17-23wt% B2O3, 4-6wt% ZrO2, 3-5wt% Al2O3, 7-11wt% Na2O, and 8-12wt% CaO; the aluminum dihydrogen phosphate solution has a solid content of 48-52%.

[0024] Preferably, the room temperature thermal conductivity of the high-temperature resistant mica heating plate is 4.87 W / (m²). Above K), the volume resistivity is 5.1 × 10⁻⁶. 13 Ω Above 1 cm, the coefficient of thermal expansion is 6.41 x 10⁻⁶. -6 Below ℃, the interfacial peel strength is above 6.1 MPa, and there is no cracking or peeling after more than 65 water-cooled thermal shocks at 1200℃. The insulation attenuation is not greater than 2.2% after 24 hours of use at 1600℃. The maximum continuous use temperature is above 1650℃, the interlayer delamination defect rate is not greater than 2.1%, and the porosity is not greater than 3.7%.

[0025] This invention provides a method for preparing the above-mentioned high-temperature resistant mica heating plate, comprising the following steps: I. Preparation of fluorinated phlogopite plates; II. Fabrication of the metal heating circuit layer; S2.1 Cut the metal foil; S2.2 Vacuum high-temperature passivation: Under vacuum conditions, heat to 1100-1200℃ and hold for 40-50 min, then introduce oxygen to 5-15 Pa and hold for 30-40 min; S2.3 Coat with photosensitive and etch-resistant inorganic ink, align, expose and develop to form a heating circuit pattern; S2.4 Inorganic etching solution etching, cleaning and drying to obtain the metal heating circuit layer; III. Preparation of high-temperature resistant mica heating plates; S3.1 Use a fluorophlogopite board as the base layer, apply the first inorganic adhesive, and dry at 110-130℃ for 30-45 minutes; S3.2 Place the metal heating circuit layer on the first inorganic adhesive, then apply the second inorganic adhesive, and dry at 110-130℃ for 45-60 minutes; S3.3 Apply the third inorganic adhesive onto the second inorganic adhesive and dry at 110-130℃ for 45-60 minutes; S3.4 Another fluorophlogopite mica plate is placed on the third inorganic adhesive as the surface layer. Under vacuum, a pressure of 10-12 MPa is applied, the temperature is raised to 1400-1800℃ and held for 40-80 minutes, and then cooled with the furnace to obtain a high-temperature resistant mica heating plate.

[0026] Preferably, the vacuum level in step S2.2 is less than or equal to 1 × 10⁻⁶. -3 Pa.

[0027] Preferably, the heating circuit pattern in step S2.3 includes a global compensation heating circuit and an integrated temperature measurement circuit.

[0028] Preferably, the inorganic etching solution in step S2.4 is a hydrofluoric acid-nitric acid mixed inorganic etching system.

[0029] Preferably, the heating rate in step S3.4 is 3-8℃ / min.

[0030] This invention solves the technical problems of traditional mica heating plates, such as insufficient maximum operating temperature, inability to operate stably for extended periods in a 1200℃ ceramic sintering environment, high-temperature delamination, and insulation breakdown. It also addresses the issues of poor temperature uniformity in armor wires, bonded metal foils, and carbon film heating layers, resulting in inconsistent ceramic sintering dimensions and color, achieving a steady-state temperature difference of ≤±1℃ on the plate surface. Furthermore, it resolves the pain points of metal heating circuits, such as oxidation, creep, and breakage at 1200℃, short service life, and excessively high costs associated with precious metal circuits. It also addresses the defects of organic bonding systems, such as high-temperature carbonization and volatilization contaminating the ceramic blank, and blistering at the interface between the substrate and the heating layer. The resulting heating plate combines the advantages of lightweight, thermal shock resistance, and customizable shape of mica substrates with the high-temperature stability of alumina ceramic heating plates at 1200℃, significantly reducing equipment costs.

[0031] While ceramic materials can be bonded using ceramic adhesives with synchronized high-temperature sintering expansion coefficients, ceramic materials are extremely brittle and crack easily from slight impacts or thermal shocks, making them unsuitable for frequent loading and unloading scenarios in continuous production lines. This invention utilizes modified fluorophlogopite boards. Conventional ceramic adhesives have poor adhesion and mismatched expansion coefficients. This invention improves the adhesion between the modified fluorophlogopite board and the ceramic adhesive by adding borosilicate to the inorganic adhesive used in its preparation. Furthermore, by designing a three-layer gradient filler ceramic adhesive to match the expansion coefficients, the high-temperature resistance and stability of the heating plate are achieved.

[0032] Phosphate-borosilicate composite inorganic adhesive is the core medium for integrated bonding, high-temperature insulation, corrosion protection, thermal stress buffering, and thermal conductivity equalization of fluorophlogopite boards. At the same time, it serves as the bonding carrier for gradient filler ceramic adhesive, achieving a firm composite of fluorophlogopite boards, etched heating circuits, and thermally conductive and insulating gradient ceramic adhesive layers. It can withstand etching and corrosion conditions and thousands of thermal cycles, ensuring high-temperature insulation safety and heating uniformity.

[0033] The modified mica core board of this invention can operate stably at 1200℃ for a long period of time, retaining more than 85% of its insulation strength at 1200℃, and does not delaminate or break down after 1200 cycles of hot and cold cycling. The steady-state temperature difference of the etched circuit board surface of this invention is ≤±1℃, the dimensional shrinkage deviation of ceramic sintering is reduced by 75%, and the product yield is improved by 12%~18%. The passivated tantalum-niobium alloy circuit of this invention has a cycle life of ≥1200 cycles, which is more than 10 times longer than the service life. Compared with alumina ceramic precious metal heating plates, the material cost per piece is reduced by 65%. Compared with brittle alumina ceramic heating plates, the mica-based composite board of this invention is resistant to thermal shock, can be processed into irregular shapes, is lightweight, is suitable for continuous sintering furnace production line loading and unloading, is not easily damaged, and reduces equipment maintenance and consumable costs by 40%.

[0034] The high-temperature resistant mica heating plate of this invention is suitable for ceramic sintering at 1200℃; long-term continuous working temperature: 0~1200℃, constant temperature at 1200℃ can be continuously operated for more than 3000 hours; thermal cycle life: ≥1200 cycles of hot and cold cycles at room temperature and 1200℃ without cracking or open circuit; plate surface temperature uniformity: steady-state temperature difference ≤±1℃ across the entire range at 1200℃; insulation performance: breakdown voltage at room temperature ≥20kV / mm, breakdown voltage at 1200℃ ≥15kV / mm; inorganic composition: the entire plate does not contain organic resin, no volatiles or carbon precipitation at 1200℃, and does not contaminate the ceramic green body; mechanical properties: can be cut, irregularly shaped, stamped, and drilled, resistant to thermal shock, and does not break upon drop, far superior to pure alumina ceramic heating plates; applicable atmosphere: air, nitrogen, and argon weak reducing atmosphere ceramic sintering furnaces.

[0035] The beneficial effects of this invention are: The high-temperature mica heating plate of the present invention is resistant to high temperature, has high thermal conductivity, good insulation, high interlayer bonding strength, uniform heating, good resistance to water cooling and thermal shock, and can work at high temperature for a long time. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments.

[0037] The following will clearly and completely describe the concept, specific solutions, and technical effects of the present invention with reference to embodiments, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. The various technical features in the present invention can be combined interactively without contradicting each other.

[0038] Example 1 A method for preparing a high-temperature resistant mica heating plate includes the following steps: I. Preparation of fluorinated phlogopite plates; S1.1 Coarse mica flakes (60-100μm) and ultrafine nano-fluorinated phlogopite powder (5-10μm) are compounded at a mass ratio of 3:7. The ultrafine nano-fluorinated phlogopite powder fills the micro gaps and improves the high-temperature structural stability. Then, pretreatment is carried out: pre-calcination at 800℃ for 2 hours to completely remove residual adsorbed water from the production process and prevent high-temperature water vapor bubbling and stratification. Ultrafine nano-fluorinated phlogopite powder is KMg3AlSi3O 10 F2, without hydroxyl groups, melts and decomposes at 1375℃; S1.2 Add 18% (by weight) of the 1500℃ grade phosphate-borosilicate composite inorganic adhesive to the powder from step S1.1, then thoroughly stir and mix to form a uniform paste. After coating and molding, air dry at room temperature for 12 hours, then perform step drying at 80-120℃ to remove the adhesive, and calcine at 1250℃ for 5 hours to obtain a fluorophlogopite board with a thickness of 1.0 mm, a temperature resistance of over 1200℃, and an insulation ≥10. 12 Ω cm, cut to 450mm×450mm; The 1500℃ grade phosphate-borosilicate composite inorganic adhesive comprises, by weight: 100 parts aluminum dihydrogen phosphate solution (50% solid content), 8 parts magnesium oxide, 35 parts aluminum oxide, 6 parts zinc oxide, and 22 parts zirconium borosilicate glass powder; the zirconium borosilicate glass powder is a low softening point zirconium borosilicate glass powder with a softening point of 550℃, and its composition is 52wt% SiO2, 20wt% B2O3, 5wt% ZrO2, 4wt% Al2O3, 9wt% Na2O, and 10wt% CaO, grade: Schott BF33.

[0039] II. Fabrication of the metal heating circuit layer; S2.1 Alloy Foil Cutting: Cut the 0.08mm tantalum-niobium-molybdenum-chromium alloy foil to the standard size (440mm×440mm); the tantalum-niobium-molybdenum-chromium alloy foil comprises, by weight percentage: tantalum 78%, niobium 16%, molybdenum 4%, chromium 2%; S2.2 Vacuum High-Temperature Passivation: Vacuum tube furnace, vacuum degree 1×10 -3 Pa, heated to 1100℃ and held for 40 min, then a trace amount of high-purity oxygen was introduced to 15 Pa and held for 30 min, resulting in the formation of a dense Ta2O5-Nb2O5 composite passivation and antioxidant film on the surface; 0.8-1.5 μm Ta / Nb oxide layer; S2.3 Coating with photosensitive and etch-resistant inorganic ink, followed by alignment, exposure, and development to form a preset global compensation heating circuit and integrated temperature measurement circuit pattern; the circuit width is 1.2mm and the circuit spacing is 1.35mm; S2.4 Inorganic etching solution etching (hydrofluoric acid-nitric acid mixed inorganic etching system, without organic corrosion aids), cleaning and drying, to obtain an integrated etched alloy metal heating circuit layer.

[0040] III. Preparation of high-temperature resistant mica heating plates; S3.1 Use a fluorophlogopite board as the base layer, apply the first inorganic adhesive with a coating thickness of 0.08 mm, and dry at 120℃ for 30 min until semi-dry (to retain adhesive activity). The first inorganic adhesive comprises, by weight, 50 parts aluminum sol (30% solid content), 50 parts silica sol (30% solid content), and 18 parts filler, the filler comprising aluminum oxide (50 nm) and boron nitride (80 nm) in a mass ratio of 8:2. S3.2 Place the metal heating circuit layer on the first inorganic adhesive, then apply the second inorganic adhesive with a coating thickness of 0.06 mm, and dry at 120°C for 60 min until semi-dry (to retain adhesive activity). The second inorganic binder comprises, by weight, 50 parts aluminum sol (30% solid content), 50 parts silica sol (30% solid content), and 18 parts filler, the filler comprising aluminum oxide (50nm) and boron nitride (80nm) in a mass ratio of 5:5. S3.3 Apply a third inorganic adhesive to the second inorganic adhesive to a thickness of 0.06 mm, and dry at 120°C for 45 min until semi-dry (to retain adhesive activity). The third inorganic adhesive comprises, by weight, 50 parts aluminum sol (30% solid content), 50 parts silica sol (30% solid content), and 18 parts filler, the filler comprising aluminum oxide (50nm) and boron nitride (80nm) in a mass ratio of 2:8. S3.4 Another fluorophlogopite mica plate is used as the surface layer and placed on the third inorganic adhesive. Under vacuum, a pressure of 12 MPa is applied, the temperature is increased to 1600℃ at 5℃ / min, and the temperature is held for 60 min. The plate is then cooled with the furnace to obtain a high-temperature resistant mica heating plate.

[0041] Performance testing: Thermal conductivity at room temperature: The thermal conductivity between the bottom fluorophlogopite mica plate and the top fluorophlogopite mica plate of the above-mentioned high-temperature resistant mica heating plate was tested at room temperature according to GB / T 32064-2015; 4.87 W / (m·K).

[0042] Volume resistivity: At room temperature, the volume resistivity between the bottom and top layers of the high-temperature resistant mica heating plate was tested according to GB / T 31838.2-2019; 5.1 × 10¹³ Ω cm.

[0043] Coefficient of thermal expansion (CTE): The coefficient of thermal expansion (CTE) of the above-mentioned high-temperature resistant mica heating plate was tested according to GB / T 16535-2008; 6.41 x 10⁻⁶. -6 / ℃.

[0044] Interfacial bonding strength: At room temperature, the interfacial bonding strength of the above-mentioned high-temperature resistant mica heating plate was tested according to GB / T 31541-2015; 6.1 MPa.

[0045] High-temperature thermal shock resistance test: The high-temperature thermal shock resistance test of the above-mentioned high-temperature resistant mica heating plate (1200℃ water cooling) was tested according to GB / T 37246-2018; 65 cycles.

[0046] Insulation stability at 1600℃: The above-mentioned high-temperature resistant mica heating plate was kept at 1600℃ for 24 hours and cooled to room temperature. The volume resistivity of the high-temperature resistant mica heating plate was tested according to GB / T 31838.2-2019, and the insulation attenuation rate was calculated (insulation attenuation rate = 1 - volume resistivity after heat treatment / volume resistivity before heat treatment); the insulation attenuation rate was 2.2%.

[0047] Interlayer delamination defect rate: The above-mentioned high-temperature mica heating plate was scanned with C-SAM to identify internal interlayer debonding, delamination, and interface gap defects. The delamination sample number was marked. For the samples that were determined to be delamination, metallographic observation of the sections was performed to confirm the separation of the interlayer interface and to eliminate misjudgments of pores and cracks. A total of 100 pieces were inspected, and the proportion of the number of separated interlayer interfaces was counted as the interlayer delamination defect rate; 2.1%.

[0048] Apparent porosity (porosity): The apparent porosity of the above-mentioned high-temperature resistant mica heating plate was tested according to GB / T2997-2015 Dense Shaped Refractory Products (Archimedes Vacuum Impregnation Method); 3.7%.

[0049] Long-term stable operating temperature limit: The above-mentioned high-temperature resistant mica heating plates (with no macroscopic cracks, blistering, or warping in appearance, and no delamination in C-SAM scan) were kept at different temperatures (gradient 50℃) in air atmosphere for 500 hours. After cooling, the appearance, volume resistivity, and C-SAM scan were tested. The highest temperature with no macroscopic cracks, blistering, or warping in appearance, insulation attenuation rate not exceeding 3%, and no delamination in C-SAM scan is the long-term stable operating temperature limit: 1650 degrees Celsius.

[0050] Example 2 In this embodiment, the second inorganic adhesive comprises 50 parts by weight of aluminum sol (30% solid content), 50 parts by weight of silica sol (30% solid content), and 18 parts by weight of filler. The fillers in S1-S5 respectively comprise aluminum oxide and boron nitride in a mass ratio of 9:1, 7:3, 5:5, 3:7, and 1:9. The rest is the same as in Example 1.

[0051] The test results are shown in Table 1.

[0052] Table 1:

[0053] Data conclusions: The optimal overall performance of the second inorganic adhesive is achieved when the ratio of alumina to boron nitride is 5:5; excessive BN content leads to decreased adhesive strength and slight attenuation of insulation; excessive Al2O3 content results in poor thermal conductivity and short thermal shock life.

[0054] Example 3 In this embodiment, the total thickness of the first inorganic adhesive, the second inorganic adhesive, and the third inorganic adhesive in T1-T5 is 0.10mm, 0.15mm, 0.20mm, 0.25mm, and 0.30mm, respectively, and the thickness ratio of the first inorganic adhesive, the second inorganic adhesive, and the third inorganic adhesive is 8:6:6; other aspects are the same as in embodiment 1.

[0055] The test results are shown in Table 2.

[0056] Table 2:

[0057] Data conclusion: The optimal gradient total thickness is 0.20mm, resulting in the lowest delamination defects and the most stable high-temperature insulation.

[0058] Example 4 In this embodiment, the heat preservation temperatures in steps S3.4 of H1-H4 are 1200℃, 1400℃, 1600℃, and 1800℃, respectively; the rest are the same as in embodiment 1.

[0059] The test results are shown in Table 3.

[0060] Table 3:

[0061] Data conclusions: sintering at 1600℃ yields the best overall performance; sintering at 1800℃ results in grain coarsening, increased interfacial stress, and decreased thermal shock resistance.

[0062] Example 5 In this embodiment, the first, second, and third inorganic adhesives are the same, comprising 50 parts by weight of aluminum sol (30% solid content), 50 parts by weight of silica sol (30% solid content), and 18 parts by weight of filler, the filler comprising aluminum oxide and boron nitride in a mass ratio of 5:5; otherwise, they are the same as in Example 1.

[0063] The test results are shown in Table 4.

[0064] Table 4:

[0065] In summary, the high-temperature resistant mica heating plate exhibits the best performance when sintered at 1600℃ using a three-layer gradient inorganic adhesive (total thickness 0.20mm). The first inorganic adhesive (adhering to the bottom fluorophlogopite mica plate, 0.08mm), with an Al2O3:BN ratio of 8:2, matches the low expansion of the fluorophlogopite mica plate and acts as an anti-detachment layer. The second inorganic adhesive (intermediate transition layer, 0.06mm), with an Al2O3:BN ratio of 5:5, serves as a stress-reducing core layer. The third inorganic adhesive (adhering to the surface fluorophlogopite mica plate of the heating working surface, 0.06mm), with an Al2O3:BN ratio of 2:8, creates a high thermal conductivity working surface. The room temperature thermal conductivity is 4.87 W / (m²). K), volume resistivity: 5.1×10 13 Ω cm, coefficient of thermal expansion 6.41 x 10⁻⁶ -6 / ℃, interfacial peel strength: 6.1 MPa, 1200℃ water-cooled thermal shock: 65 cycles without cracking or peeling, long-term use insulation attenuation of only 2.2% at 1600℃, maximum continuous use temperature: 1650℃, interlayer delamination defect rate 2.1%, porosity 3.7%.

[0066] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A high-temperature resistant mica heating plate, characterized in that, It consists of, in sequence, a bottom fluorophlogopite mica plate, a metal heating circuit layer, and a top fluorophlogopite mica plate; Between the bottom fluorophlogopite board and the top fluorophlogopite board, there are a first inorganic adhesive layer, a second inorganic adhesive layer and a third inorganic adhesive layer in sequence; The first inorganic binder includes aluminum sol, silica sol and filler. The mass ratio of aluminum sol, silica sol and filler is 4-6:4-6:5-7 based on solid content. The filler includes aluminum oxide and boron nitride. The mass ratio of aluminum oxide and boron nitride is 7-9:1-3. The second inorganic binder includes aluminum sol, silica sol and filler. Based on solid content, the mass ratio of aluminum sol, silica sol and filler is 4-6:4-6:5-7. The filler includes aluminum oxide and boron nitride, with a mass ratio of aluminum oxide and boron nitride of 4-6:4-6. The third inorganic binder includes aluminum sol, silica sol, and filler. Based on solid content, the mass ratio of aluminum sol, silica sol, and filler is 4-6:4-6:5-7. The filler includes alumina and boron nitride, with a mass ratio of alumina to boron nitride of 1-3:7-9.

2. The high-temperature resistant mica heating plate according to claim 1, characterized in that, The total thickness of the first inorganic adhesive layer, the second inorganic adhesive layer, and the third inorganic adhesive layer is 0.15-0.25 mm; The thickness ratio of the first inorganic adhesive layer, the second inorganic adhesive layer, and the third inorganic adhesive layer is 7-9:5-7:5-7; The solid content of aluminum sol is 20-40%, and the solid content of silica sol is 20-40%. The particle size of alumina is 30-80 nm, and the particle size of boron nitride is 50-100 nm.

3. The high-temperature resistant mica heating plate according to claim 1, characterized in that, The metal heating circuit layer is disposed between the first inorganic adhesive layer and the third inorganic adhesive layer, and the second inorganic adhesive layer fills the metal heating circuit layer.

4. The high-temperature resistant mica heating plate according to claim 1, characterized in that, The metal heating circuit layer is made of tantalum-niobium-molybdenum-chromium alloy. The components of the tantalum-niobium-molybdenum-chromium alloy by mass percentage are: tantalum 76-80%, niobium 14-18%, molybdenum 2-6%, and chromium 1-3%. The thickness of the metal heating circuit layer is 0.06~0.12mm; The surface of the metal heating circuit layer has an oxide film; The line width of the metal heating circuit layer is 0.3~1.2mm, and the line spacing is 0.4~1.5mm; The thickness of the fluorophlogopite board is 0.5-2mm.

5. The high-temperature resistant mica heating plate according to claim 1, characterized in that, The preparation method of fluorophlogopite board includes the following steps: S1.1 Coarse mica flakes and fluorophlogopite powder are compounded at a mass ratio of 2-4:6-8, and then calcined at 700-900℃ for 1-3 hours to obtain the compounded powder. S1.2 Add 15-20% of the phosphate-borosilicate composite inorganic adhesive to the compound powder in step S1.1, then coat and mold it, air dry at room temperature, debind it in stages at 80-120℃, and calcine it at 1250-1300℃ for 5-10 hours to obtain fluorophlogopite board.

6. The high-temperature resistant mica heating plate according to claim 5, characterized in that, The size of the coarse mica flakes is 60-100 μm; The size of fluorophlogopite powder is 5-10 μm; Fluorophytic mica powder is KMg3AlSi3O 10 F2; Air-dry at room temperature for 12-16 hours.

7. The high-temperature resistant mica heating plate according to claim 5, characterized in that, The phosphate-borosilicate composite inorganic adhesive comprises, by weight: 90-110 parts aluminum dihydrogen phosphate solution, 6-10 parts magnesium oxide, 30-40 parts aluminum oxide, 4-8 parts zinc oxide, and 18-26 parts zirconium borosilicate glass powder. The softening point of zirconium borosilicate glass powder is 550-600℃, and its composition is 48-56wt% SiO2, 17-23wt% B2O3, 4-6wt% ZrO2, 3-5wt% Al2O3, 7-11wt% Na2O, and 8-12wt% CaO; the solid content of aluminum dihydrogen phosphate solution is 48-52%.

8. The high-temperature resistant mica heating plate according to claim 1, characterized in that, The room temperature thermal conductivity of the high-temperature resistant mica heating plate is 4.87 W / (m²). Above K), the volume resistivity is 5.1 × 10⁻⁶. 13 Ω Above 1 cm, the coefficient of thermal expansion is 6.41 x 10⁻⁶. -6 Below ℃, the interfacial peel strength is above 6.1 MPa, and there is no cracking or peeling after more than 65 water-cooled thermal shocks at 1200℃. The insulation attenuation is not greater than 2.2% after 24 hours of use at 1600℃. The maximum continuous use temperature is above 1650℃, the interlayer delamination defect rate is not greater than 2.1%, and the porosity is not greater than 3.7%.

9. The method for preparing the high-temperature resistant mica heating plate according to any one of claims 1-8, characterized in that, Includes the following steps: I. Preparation of fluorinated phlogopite plates; II. Fabrication of the metal heating circuit layer; S2.1 Cut the metal foil; S2.2 Vacuum high-temperature passivation: Under vacuum conditions, heat to 1100-1200℃ and hold for 40-50 min, then introduce oxygen to 5-15 Pa and hold for 30-40 min; S2.3 Coat with photosensitive and etch-resistant inorganic ink, align, expose and develop to form a heating circuit pattern; S2.4 Inorganic etching solution etching, cleaning and drying to obtain the metal heating circuit layer; III. Preparation of high-temperature resistant mica heating plates; S3.1 Use a fluorophlogopite board as the base layer, apply the first inorganic adhesive, and dry at 110-130℃ for 30-45 minutes; S3.2 Place the metal heating circuit layer on the first inorganic adhesive, then apply the second inorganic adhesive, and dry at 110-130℃ for 45-60 minutes; S3.3 Apply the third inorganic adhesive onto the second inorganic adhesive and dry at 110-130℃ for 45-60 minutes; S3.4 Another fluorophlogopite mica plate is placed on the third inorganic adhesive as the surface layer. Under vacuum, a pressure of 10-12 MPa is applied, the temperature is raised to 1400-1800℃ and held for 40-80 minutes, and then cooled with the furnace to obtain a high-temperature resistant mica heating plate.

10. The method for preparing the high-temperature resistant mica heating plate according to claim 9, characterized in that, Step S2.2 The vacuum level of the vacuum condition is less than or equal to 1×10⁻⁶. -3 Pa; Step S2.3 The heating circuit pattern includes a global compensation heating circuit and an integrated temperature measurement circuit; Step S2.4 The inorganic etching solution is a mixed inorganic etching system of hydrofluoric acid and nitric acid; The heating rate in step S3.4 is 3-8℃ / min.

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