阅读说明：本技术 一种微波磁控管用陶瓷支持体及其制备方法 (Ceramic support for microwave magnetron and preparation method thereof ) 是由 方豪杰 贺亦文 张晓云 曾雄 于 2020-04-25 设计创作，主要内容包括：本发明公开一种微波磁控管用陶瓷支持体及其制备方法,涉及金属化陶瓷加工技术领域。本发明公开的微波磁控管用陶瓷支持体,包括陶瓷基体和金属化层,其中陶瓷基体用碳化硅-三唑硅烷-氮化铝网状基体、高炉矿渣、分散剂和除泡剂等原料,经碳化硅-三唑硅烷-氮化铝网状覆膜基体的制备、混料、造粒和烧结等步骤而制成；金属化层原料包括钛粉、铜粉、黏土和粘结剂,并公开了用金属化层和陶瓷基体组成的陶瓷支持体的制备方法。本发明提供的微波磁控管用陶瓷支持体,具有高的致密度和抗拉强度,具有优异的抗拉强度、韧性、耐高温性能和热导性,并能降低原料成本,达到节能环保的目的。(The invention discloses a ceramic support for a microwave magnetron and a preparation method thereof, and relates to the technical field of metallized ceramic processing. The ceramic support for the microwave magnetron disclosed by the invention comprises a ceramic substrate and a metallization layer, wherein the ceramic substrate is prepared by preparing, mixing, granulating, sintering and the like a silicon carbide-triazole silane-aluminum nitride net-shaped coated substrate, blast furnace slag, a dispersing agent, a defoaming agent and the like; the raw materials of the metallized layer comprise titanium powder, copper powder, clay and a binder, and the preparation method of the ceramic support body consisting of the metallized layer and the ceramic matrix is disclosed. The ceramic support for the microwave magnetron provided by the invention has high density and tensile strength, excellent tensile strength, toughness, high temperature resistance and thermal conductivity, and can reduce the cost of raw materials and achieve the purposes of energy conservation and environmental protection.)

1. The ceramic support for the microwave magnetron comprises a ceramic substrate and a metallization layer, and is characterized in that the ceramic substrate is prepared from the following raw materials in parts by weight: 75-90 parts of silicon carbide-triazole silane-aluminum nitride mesh matrix, 5-20 parts of blast furnace slag, 3-5 parts of dispersing agent and 1-3 parts of defoaming agent, wherein the dispersing agent and the defoaming agent are respectively sodium hexametaphosphate and alkyl silicone oil;

the preparation method of the ceramic matrix sequentially comprises the following steps:

a1, preparation of a silicon carbide-triazole silane-aluminum nitride net-shaped film coating substrate:

placing the aluminum nitride ceramic powder in 5% oxygen atmosphere, oxidizing at 1000 ℃ for 30min to obtain an aluminum oxide film on the surface of the aluminum nitride ceramic, and preparing oxidized aluminum nitride ceramic;

adding 15% sodium ethoxide solution into 100mL of mixed solution of 1-phenyl-3-hydroxy-1, 2, 4-triazole and ethyl acetate at room temperature, heating to 70-90 ℃, stirring for 0.5-1h, then adding 3-chloropropyltrimethoxysilane, stirring for 10h at 50-70 ℃, and finishing the reactionAfter completion, the mixture was cooled to room temperature, filtered, and the filter cake was made with 2% NaHCO₃Cleaning the solution and deionized water to be neutral, and drying to obtain a triazole silane compound; the mass ratio of the 1-phenyl-3-hydroxy-1, 2, 4-triazole to the sodium ethoxide solution to the 3-chloropropyltrimethoxysilane is 1 (1-2) to 1-2.

Soaking silicon carbide powder and the prepared triazole silane compound in 1mol/L NaOH solution for 6-8 h at 50-60 ℃, filtering and drying to obtain surface modified silicon carbide, wherein the mass ratio of the silicon carbide powder to the triazole silane compound is 1 (2-3);

mixing oxidized aluminum nitride and surface modified silicon carbide, and reacting for 6-8 h at 80-120 ℃ under the pressure of 5-10 MPa in an inert atmosphere to obtain a silicon carbide-triazole silane-aluminum nitride net-shaped coated film matrix, wherein the mass ratio of the surface modified silicon carbide to the oxidized aluminum nitride is 1 (7-10);

a2, mixing: drying the blast furnace slag in parts by weight at 120 ℃ for 1-2 h, and then ball-milling for 5-10 h to prepare blast furnace slag particles with the average particle size of 2-3 mu m; adding blast furnace slag particles and a dispersing agent into the silicon carbide-triazole silane-aluminum nitride net-shaped film-coated substrate prepared in the step A1, stirring for 0.5-1h, adding a defoaming agent and absolute ethyl alcohol with the mixing ratio of 3:1, mixing for 2-3 h to obtain slurry, and performing high-speed ball milling for 10-12 h to obtain the slurry;

a3, granulating: drying the ground slurry in a drying oven at 70-80 ℃ for 1h, and then processing the dried slurry into granular ceramic powder with the average particle size of 20-40 mu m by using an organic solvent spray dryer for later use;

a4, sintering: and B, loading the ceramic powder obtained in the step A3 into a hot-pressing die, sintering at 1700-1850 ℃ under normal pressure by taking nitrogen as protective gas, keeping the temperature for 4-6 h, cooling to room temperature along with a furnace, taking out, and polishing on a surface grinding machine to obtain the ceramic matrix to be metallized.

2. The ceramic support for microwave magnetrons of claim 1, wherein said blast furnace slag of step a2 has a ball milling rate of 360r/min and a ball to feed ratio of 12: 1.

3. The ceramic support for microwave magnetrons of claim 1, wherein the ball milling rate of the slurry of step a2 is 240r/min and the ball-to-material ratio is 10:1 during the ball milling process.

4. A method for manufacturing a ceramic support for microwave magnetrons according to any of claims 1 to 3, characterized in that it comprises the following steps:

b1, clay pretreatment: drying clay at 100 ℃ for 2-4 h, and then ball-milling for 4-6 h to prepare clay particles with the average particle size of 2-3 mu m;

b2, preparation of a metallization paste: weighing 8-20 parts of titanium powder, 60-70 parts of copper powder, 10-20 parts of clay particles and 1-3 parts of binder, and uniformly mixing the titanium powder, the copper powder, the clay particles and the binder to prepare a metallization paste;

b3, silk-screen printing: ultrasonically cleaning the surface of the ceramic matrix to be metalized, which is prepared in the claim 1, by absolute ethyl alcohol, and then uniformly coating the metallization paste on the surfaces to be treated at two ends of the ceramic matrix by a screen printing method, wherein the printing thickness of the metallization paste is 40-50 μm;

b4, metallization treatment: and sintering the prepared ceramic substrate coated with the metallization paste under the protection of vacuum or inert gas, wherein the sintering temperature is 1100-1200 ℃, and the sintering heat preservation time is 1-2 h, so that the ceramic support for the microwave magnetron is obtained.

5. The method of claim 4, wherein the binder used in step B2 is terpineol: the polyvinyl alcohol is formed by mixing (1-3) parts by weight.

Technical Field

The invention belongs to the technical field of metallized ceramic processing, and particularly relates to a ceramic support body used on a magnetron in a microwave oven and a preparation method thereof.

Background

With the development of technology, magnetrons are widely used in the fields of electronics, electric power, chemical engineering, and the like, and the demand for ceramic supports, which are one of the core components, tends to increase year by year. At present, the ceramic support used in the microwave magnetron is composed of a metallized ceramic tube, and materials used in the metallization process mainly include alumina, silica, silicon carbide, silicon nitride, etc., wherein the most widely used material is mainly alumina, and then the ceramic is metallized, so that the metal layer and the ceramic matrix need to have good wettability. In the existing alumina ceramic supporter, the alumina content is more than 95 percent, the alumina ceramic has poor toughness, is easy to break and has unsatisfactory sealing strength with a metal layer; the thermal conductivity of the alumina ceramic is lower, only 15W/mK-20W/mK, and with the increasing power density of the current integrated circuit, the heat dissipation problem becomes a key problem which must be solved in the design and manufacture of the microwave magnetron, and the traditional alumina ceramic cannot meet the requirement.

The aluminum nitride ceramic is [ AlN ]₄]The tetrahedron is a covalent bond compound with a structural unit, has a wurtzite structure, has a decomposition temperature of 2450 ℃, and has excellent stability and thermal shock resistance in a high-temperature non-oxide atmosphere within 2000 ℃. The alumina ceramic has the characteristics of low atomic weight, strong interatomic bonding, simple crystal structure, high lattice oscillation harmony and the like, thereby having extremely high thermal conductivity which can reach 150W/mK-200W/mK and is about 10 times of that of the alumina ceramic, and the thermal expansion coefficient is small and is close to that of silicon. The aluminum nitride ceramic has the characteristics of being not corroded by aluminum, other molten metals and gallium arsenide, and has good erosion resistance, good electrical insulation and dielectric properties. The aluminum nitride ceramic has good mechanical property, the breaking strength is higher than that of aluminum oxide ceramic and beryllium oxide ceramic, the aluminum nitride ceramic is a high-temperature insulating structural ceramic material with excellent performance, and the aluminum nitride ceramic can be applied to electronic devices, optical devices, high-temperature materials, wear-resistant materials and the like.

However, aluminum nitride is easily hydrolyzed in a humid atmosphere and oxidized in a high-temperature environment, which affects the preparation and use of aluminum nitride ceramic, causes the thermal conductivity of aluminum oxide ceramic to be reduced, and affects the sealing effect of aluminum nitride ceramic and metal. Since aluminum nitride ceramics have excellent erosion resistance to most molten metals (such as Al, Cu, Ag, Pb, etc.), the aluminum nitride ceramics have poor wettability of the interface between the aluminum nitride ceramics and the metal and low bonding strength, and thus, the aluminum nitride ceramics are rarely used for the ceramic support of the microwave magnetron.

The sintering aid in the existing aluminum nitride ceramic generally adopts high-purity metal oxide, and the preparation method of the high-purity metal oxide is complex and has higher cost, so that the preparation cost of the aluminum nitride ceramic is correspondingly increased. The metallization of the surface of the aluminum nitride ceramic generally comprises a direct copper-coating method, an active sealing method, a thick film method, a thin film method and the like. The traditional method mostly adopts an active sealing method with Mo, MnO and Al₂O₃、SiO₂And CaO and other metallization raw materials, ethanol, terpineol and ethyl cellulose are prepared into an organic solvent according to the weight ratio of 6:24:1, and then the mixture is sintered under certain conditions to obtain the Mo-Mn metallization layer. However, the metallization layer often has the defects of bubbling, low bonding strength and the like, and the airtightness and effective sealing of the ceramic metallization layer are difficult to ensure. The existing metallization raw materials generally adopt high-purity metal oxides, and the preparation cost is higher, so that the manufacturing cost of the metallization ceramic is increased.

Chinese invention patent CN103762181B discloses a method for preparing an aluminum oxide copper-clad ceramic substrate, which adds a metal modified layer containing copper oxide between aluminum nitride and copper sheet of pre-oxidized aluminum oxide, so that the aluminum nitride and the copper sheet are tightly combined, and the problem of surface bubble of AlN-DBC is effectively solved. However, the sealing effect of the aluminum nitride ceramic and metallization can not meet the sealing requirement of the ceramic support of the microwave magnetron, and the problem that the aluminum nitride ceramic is easy to oxidize at high temperature is not solved.

Disclosure of Invention

The invention provides a metallized ceramic and a preparation method thereof, which are used on a ceramic support of a microwave magnetron, and mainly aims to provide a metallized ceramic with high thermal conductivity, improve the sealing strength between a ceramic substrate and the metallized layer, solve the problem that aluminum nitride ceramic is easy to oxidize at high temperature and reduce the preparation cost.

In order to achieve the purpose of the invention, the invention provides a ceramic support for a microwave magnetron, which comprises a ceramic substrate and a metallization layer, wherein the ceramic substrate is prepared from the following raw materials in parts by weight: 75-90 parts of silicon carbide-triazole silane-aluminum nitride mesh matrix, 5-20 parts of blast furnace slag, 3-5 parts of dispersing agent and 1-3 parts of defoaming agent, wherein the dispersing agent and the defoaming agent are respectively sodium hexametaphosphate and alkyl silicone oil;

the preparation method of the ceramic matrix sequentially comprises the following steps:

a1, preparation of a silicon carbide-triazole silane-aluminum nitride net-shaped film coating substrate:

placing the aluminum nitride ceramic powder in 5% oxygen atmosphere, oxidizing at 1000 ℃ for 30min to obtain an aluminum oxide film on the surface of the aluminum nitride ceramic, and preparing oxidized aluminum nitride ceramic;

adding 15% sodium ethoxide solution into 100mL of mixed solution of 1-phenyl-3-hydroxy-1, 2, 4-triazole and ethyl acetate at room temperature, heating to 70-90 ℃, stirring for 0.5-1h, then adding 3-chloropropyltrimethoxysilane, stirring for 10h at 50-70 ℃, cooling to room temperature after reaction is completed, filtering, and using 2% NaHCO for filter cakes₃Cleaning the solution and deionized water to be neutral, and drying to obtain a triazole silane compound; the mass ratio of the 1-phenyl-3-hydroxy-1, 2, 4-triazole to the sodium ethoxide solution to the 3-chloropropyltrimethoxysilane is 1 (1-2) to 1-2.

Soaking silicon carbide powder and the prepared triazole silane compound in 1mol/L NaOH solution for 6-8 h at 50-60 ℃, filtering and drying to obtain surface modified silicon carbide, wherein the mass ratio of the silicon carbide powder to the triazole silane compound is 1 (2-3);

mixing oxidized aluminum nitride and surface modified silicon carbide, and reacting for 6-8 h at 80-120 ℃ under the pressure of 5-10 MPa in an inert atmosphere to obtain a silicon carbide-triazole silane-aluminum nitride net-shaped coated film matrix, wherein the mass ratio of the surface modified silicon carbide to the oxidized aluminum nitride is 1 (7-10);

a2, mixing: drying the blast furnace slag in parts by weight at 120 ℃ for 1-2 h, and then ball-milling for 5-10 h to prepare blast furnace slag particles with the average particle size of 2-3 mu m; adding blast furnace slag particles and a dispersing agent into the silicon carbide-triazole silane-aluminum nitride net-shaped film-coated substrate prepared in the step A1, stirring for 0.5-1h, adding a defoaming agent and absolute ethyl alcohol with the mixing ratio of 3:1, mixing for 2-3 h to obtain slurry, and performing high-speed ball milling for 10-12 h to obtain the slurry;

a3, granulating: drying the ground slurry in a drying oven at 70-80 ℃ for 1h, and then processing the dried slurry into granular ceramic powder with the average particle size of 20-40 mu m by using an organic solvent spray dryer for later use;

a4, sintering: and B, loading the ceramic powder obtained in the step A3 into a hot-pressing die, sintering at 1700-1850 ℃ under normal pressure by taking nitrogen as protective gas, keeping the temperature for 4-6 h, cooling to room temperature along with a furnace, taking out, and polishing on a surface grinding machine to obtain the ceramic matrix to be metallized.

Further, the ball milling speed of the blast furnace slag in the step A2 is 360r/min, and the ball-to-feed ratio is 12: 1.

Further, in the ball milling process of the slurry in the step A2, the ball milling speed is 240r/min, and the ball-to-material ratio is 10: 1.

A method for preparing the ceramic support for the microwave magnetron, which is characterized by comprising the following steps:

b1, clay pretreatment: drying clay at 100 ℃ for 2-4 h, and then ball-milling for 4-6 h to prepare clay particles with the average particle size of 2-3 mu m;

b2, preparation of a metallization paste: weighing 8-20 parts of titanium powder, 60-70 parts of copper powder, 10-20 parts of clay particles and 1-3 parts of binder, and uniformly mixing the titanium powder, the copper powder, the clay particles and the binder to prepare a metallization paste;

b3, silk-screen printing: ultrasonically cleaning the surface of the ceramic matrix to be metalized, which is prepared in the claim 1, by absolute ethyl alcohol, and then uniformly coating the metallization paste on the surfaces to be treated at two ends of the ceramic matrix by a screen printing method, wherein the printing thickness of the metallization paste is 40-50 μm;

b4, metallization treatment: and sintering the prepared ceramic substrate coated with the metallization paste under the protection of vacuum or inert gas, wherein the sintering temperature is 1100-1200 ℃, and the sintering heat preservation time is 1-2 h, so that the ceramic support for the microwave magnetron is obtained.

Further, in the step B2, the binder is terpineol: the polyvinyl alcohol is formed by mixing (1-3) parts by weight.

The invention achieves the following beneficial effects:

1. the sodium hexametaphosphate belongs to an anionic hydrophilic group surfactant, the sodium hexametaphosphate can be ionized in water to form anions which are adsorbed by the surface of an oxide in blast furnace slag, so that an electric double layer is formed on the interface of oxide molecules in contact with water, and the oxide has negative charges because the surface adsorbs the anions. The oxides with the same charges are subjected to electrostatic repulsion, so that mutual aggregation of the particles is prevented, and the dispersion effect of the oxides is improved.

2. The invention adopts alkyl silicone oil as the defoaming agent, is used for solving the problem of bubbles generated during high-temperature sintering of aluminum nitride ceramics, improves the compactness and the heat conductivity of the ceramic matrix, and removes the bubbles generated between the ceramic matrix and the metallization layer, thereby improving the sealing strength between the ceramic matrix and the metallization layer.

3. The invention adopts blast furnace slag as sintering aid, and the main components of the blast furnace slag are CaO and SiO₂、Al₂O₃、MgO、TiO₂、Fe₂O₃When oxides, the oxides in the blast furnace slag form a glass phase during high-temperature sintering, which is beneficial to grain boundary diffusion and migration, and the blast furnace slag is used as a sintering aid to remarkably improve the density and mechanical properties of the ceramic matrix. In addition, the blast furnace slag is used as an industrial byproduct generated in the blast furnace ironmaking process, has high yield and generates huge burden on the ecological environment, and the application of the blast furnace slag in the invention reduces the cost of raw materials and the cost of energy consumption on the basis of improving the performance of ceramics, thereby achieving the effects of energy conservation and environmental protection.

4. The titanium powder in the metallization paste has strong chemical activity and has great affinity to oxides such as silicon oxide, magnesium oxide, aluminum oxide and the like in clay. The titanium powder and the oxide in the clay form liquid-phase active alloy which permeates to the surface of the ceramic matrix easily at the sintering temperature to form a very compact and uniform metal layer, so that the ceramic matrix and the metal layer are sealed with high strength and high air tightness, and the wettability of the ceramic matrix is greatly improved.

5. When the clay in the metallization paste is sintered at high temperature, eutectic substances in the clay begin to melt to form a liquid phase, the liquid phase is filled between copper powder particles and unmelted particles in the clay, and the solid particles are further closed due to the action of the surface tension of the liquid phase, so that the volume is sharply shrunk, the porosity is reduced, the density is improved, and the density of the metallization paste is enhanced. In addition, the clay has wide sources and low price, and the raw material cost of the invention is reduced.

6. According to the invention, triazole silane is used for acting silicon carbide powder in aluminum nitride ceramic to prepare a silicon carbide-triazole silane-aluminum nitride net-shaped coating substrate, wherein triazole rings in the triazole silane interact with silicon carbide and aluminum nitride to form chemical bonds, alkoxy silane in the triazole silane is chemically bonded with aluminum oxide to form a net-shaped structure, and the silicon carbide is chemically converted and coated on the surface of the aluminum nitride to form a silicon carbide layer, so that the aluminum nitride ceramic is protected from being oxidized at high temperature and is not easy to hydrolyze at normal temperature; moreover, because the silicon carbide powder has high thermal conductivity, the silicon carbide powder is coated on the surface of the aluminum nitride ceramic, so that the silicon carbide ceramic has high thermal conductivity; the net structure is beneficial to the densification of the ceramic matrix, and the temperature resistance and the mechanical property of the ceramic matrix are greatly improved; the triazole silane component in the silicon carbide-triazole silane-aluminum nitride reticular coated matrix can be used as a binder of a ceramic matrix, so that blast furnace slag is uniformly dispersed in the reticular structure of the silicon carbide-triazole silane-aluminum nitride reticular coated matrix under the action of a dispersing agent, a compact ceramic matrix is formed under the action of triazole silane, the ceramic matrix has good flexibility, and the bending strength is further improved;

7. in the sintering process of the metallization layer, oxides in titanium powder and clay form a glass phase, and the glass phase migrates towards copper powder particles, so that the copper powder is adjusted in position and is closely arranged again, and the density of the metallization layer is high; meanwhile, the copper powder is driven to permeate into the ceramic matrix by the glass phase in the metallization layer under the action of surface tension, and the glass phase of the metallization layer can be more easily migrated into the ceramic matrix by the network structure of the ceramic matrix, so that the connection between the ceramic matrix and the metallization layer is enhanced, and the wettability of the ceramic matrix is enhanced; the oxide in the blast furnace slag is easy to react with the oxides such as silicon oxide, silicon oxide and the like in the clay at high temperature, and the wettability of the ceramic matrix to the metalized layer is further improved.

8. According to the invention, the silicon carbide-triazole silane-aluminum nitride net-shaped coated substrate is adopted, and blast furnace slag is used as a sintering aid, so that the ceramic substrate with high density is obtained, and has high thermal conductivity, excellent bending property, fracture toughness, insulativity and high temperature resistance, and the raw material cost is reduced; the ceramic support body prepared by adopting titanium powder, copper powder, clay and the like as the metallization paste to carry out metallization treatment on the ceramic matrix has good compactness, and the metallization paste and the ceramic matrix have good sealing effect, so that the ceramic support body has high tensile strength and excellent high-temperature resistance, the cost of raw materials is reduced, and the purposes of energy conservation and environmental protection are achieved.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The ceramic support for a microwave magnetron and the method for producing the same according to the present invention will be described with reference to the following specific examples.