CN115196963B

CN115196963B - Method for coating metal net, heat-resistant ceramic coating thereof and metal net

Info

Publication number: CN115196963B
Application number: CN202210735168.1A
Authority: CN
Inventors: 谢振山; 翁国庆; 陈建波
Original assignee: Hunan Wisconsin New Materials Technology Co ltd
Current assignee: Hunan Wisconsin New Materials Technology Co ltd
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2023-08-22
Anticipated expiration: 2042-06-27
Also published as: CN115196963A

Abstract

The application belongs to the field of metal surface treatment, and particularly relates to a metal mesh coating method, a heat-resistant ceramic coating thereof and a metal mesh, wherein the method comprises the following steps: obtaining a treated metal net; obtaining ceramic powder with preset particle size distribution; mixing the ceramic powder, a dispersing agent, an organic solvent, a pH regulator and a charging agent to obtain a suspension; placing the suspension in an electrophoresis container, connecting the anode of the electrophoresis container with the treated metal mesh, and carrying out electrophoretic deposition to obtain a deposited ceramic metal mesh coated with a ceramic green body; drying, sintering and cooling the deposited ceramic metal mesh to obtain a target metal mesh; the surface of the target metal net is covered with a heat-resistant ceramic coating. Adopts ceramic powder with bimodal particle size distribution and an electrophoretic deposition method to prepare the heat-resistant ceramic coating with controllable thickness, uniform distribution and few cracks. The process is simple and practical to operate and low in cost; and solves the problem that the metal mesh is easy to block holes when being coated with the heat-resistant ceramic coating.

Description

Method for coating metal net, heat-resistant ceramic coating thereof and metal net

Technical Field

The application belongs to the field of metal surface treatment, and particularly relates to a metal mesh coating method, a heat-resistant ceramic coating thereof and a metal mesh.

Background

With the wide application of metal nickel screens in the electronic ceramic industry, higher requirements are put on the performance of the metal nickel screens. The sintering net in the sintering process has the characteristics of high heat conduction efficiency, good air permeability, no reaction with sintering materials and the like; but the sintering-resistant temperature of the pure metal net or the alloy net is low (< 1200 ℃), the metal net with too high temperature can be softened, the sintering-resistant metal net is deformed, and the service life is short. For electronic ceramic devices sintered at high temperature (more than 1300 ℃), the metal mesh is softened, and meanwhile, the metal diffusion speed is increased at high temperature, so that pollution to high-end electronic products is easy to cause. The existing coating prepared by adopting methods such as direct spraying, brushing, dipping and the like has the problems of non-uniformity and easiness in blocking meshes.

The electrophoretic deposition method is an old scientific technology, and the traditional electrophoretic technology is applied to the surface coating of automobiles, ships, daily hardware products and the like. Modern electrophoretic deposition technology is widely applied to preparing high-temperature resistant ceramics, wear-resistant ceramics, superconducting ceramics, biological ceramics, fuel cells, membrane materials and the like.

There is a need for a coating process that can produce a heat resistant metal mesh with excellent properties.

Disclosure of Invention

The application provides a metal net coating method, a heat-resistant ceramic coating and a heat-resistant metal net thereof, which are used for solving the technical problems that the surface of the existing metal net is coated with the heat-resistant ceramic coating unevenly and is easy to fall off during high-temperature sintering.

In a first aspect, the present application provides a method of coating a metal mesh, the method comprising the steps of:

obtaining a treated metal net;

obtaining ceramic powder with preset particle size distribution;

mixing the ceramic powder, a dispersing agent, an organic solvent, a pH regulator and a charging agent to obtain a suspension;

placing the suspension in an electrophoresis container, connecting the negative electrode of the electrophoresis container with the treated metal mesh, and performing electrophoretic deposition to obtain a deposited ceramic metal mesh coated with a ceramic green body;

drying, sintering and cooling the deposited ceramic metal mesh to obtain a target metal mesh; the surface of the target metal net is covered with a heat-resistant ceramic coating.

Optionally, the thickness of the heat-resistant ceramic coating is 10-100 μm.

Optionally, the particle diameter d of the ceramic powder ₅₀ <0.5-1.5μm，d ₉₀ <5-10 μm; the ceramic powder comprises the following components: at least one of alumina, calcium oxide, magnesium oxide and zirconium oxide; and/or the components of the ceramic powder further comprise rare earth oxide.

Optionally, the organic solvent comprises at least one of acetone, butanone, acetylacetone and ethylene glycol; and/or the organic solvent further comprises an organic monohydric alcohol.

Optionally, the dispersing agent comprises one of triethanolamine, glycol amine, polyvinyl butyral, polyethylenimine, sodium lignin sulfonate and sodium polyacrylate;

and/or the charging agent comprises one of iodine, nitric acid, hydrochloric acid, phosphoric acid, ammonia water and acetic acid; and/or the charging agent further comprises an organic ammonium salt.

Optionally, the obtained treated metal mesh specifically includes: and (3) removing oil from the initial metal net by an alkali method, removing rust by an acid method, washing with water, phosphating and drying to obtain the treated metal net.

Optionally, in the suspension, the mass fraction of the ceramic powder is 0.5% -20%, the mass fraction of the dispersing agent is 0.05% -0.2% of the ceramic powder, and the mass fraction of the charging agent is 0.01% -0.5% of the ceramic powder.

Optionally, the sintering stage includes: the first temperature rise and the second heat preservation are carried out; the first heating speed is 3-15 ℃/min, and the target temperature of the first heating is 1100-1400 ℃; the temperature of the second heat preservation is 1100-1400 ℃, and the time of the second heat preservation is 1-6 h.

In a second aspect, the application provides a heat-resistant ceramic coating, which is prepared by the method of any one of claims 1-8, and the thickness of the heat-resistant ceramic coating is 10-100 μm.

In a third aspect, the present application provides a metal mesh produced by the method of the first aspect; the surface of the metal net is covered with a heat-resistant ceramic coating, and the thickness of the heat-resistant ceramic coating is 10-100 mu m.

Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:

according to the method provided by the embodiment of the application, the ceramic powder, the dispersing agent, the organic solvent, the pH regulator and the charge agent are mixed to obtain a suspension;

placing the suspension in an electrophoresis container, connecting the anode of the electrophoresis container with the treated metal mesh, and carrying out electrophoretic deposition to obtain a deposited ceramic metal mesh coated with a ceramic green body; drying, sintering and cooling the deposited ceramic metal mesh to obtain a target metal mesh; the surface of the target metal net is covered with a heat-resistant ceramic coating; the ceramic powder with bimodal distribution and the electrophoretic deposition method are adopted to prepare the heat-resistant ceramic coating with controllable thickness, uniform distribution and less cracks. The process is simple and practical to operate and low in cost; and solves the problem that the metal mesh is easy to block holes when being coated with the heat-resistant ceramic coating.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.

FIG. 1 is a process flow diagram of a method for coating a heat resistant ceramic coating with a metallic nickel mesh provided by an embodiment of the present application;

FIG. 2 is a schematic diagram of an electrophoretic deposition device according to an embodiment of the present application;

FIG. 3 shows the particle size distribution of the ceramic powder according to the embodiment of the present application;

FIG. 4 is a graph showing comparative effects of suspension properties of alumina raw material powder provided in an embodiment of the present application;

FIG. 5 is a graphical representation of ceramic coatings prepared by different processes provided in examples and comparative examples of the present application, a spray coating, b brush coating, c dip coating, d electrophoretic deposition;

FIG. 6 is a scanning electron microscope image of a heat resistant ceramic coating provided by examples and comparative examples of the present application;

FIG. 7 is a surface, cross-section and microscopic view of a heat resistant metal mesh coating provided in example 1 of the present application;

fig. 8 is a diagram of a primary nickel screen, b after phosphating, c after coating, and d after sintering according to example 1 of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Throughout the specification, unless specifically indicated otherwise, the terms used herein should be understood as meaning as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In case of conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present application. For example, room temperature may refer to a temperature in the range of 10 to 35 ℃.

Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.

The technical scheme of the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:

according to an exemplary embodiment of the present application, there is provided a method of coating a metal mesh, as shown in fig. 1, the method including the steps of:

s1, obtaining a treated metal net;

specifically, the metal mesh is made of one of nickel, iron, molybdenum and titanium and a high-temperature alloy taking the nickel, the iron, the molybdenum and the titanium as matrixes.

S2, obtaining ceramic powder with preset particle size distribution;

specifically, powder with particle size in bimodal distribution is prepared by adopting a sand grinding-sedimentation grading-drying process, the particle size distribution of the powder can be determined according to the property of the material, the ceramic temperature of some powder is low, and the particle size can be properly adjusted. Sanding includes: adding powder into deionized water, stirring and dispersing to prepare slurry with 20-30% of solid content, adding the slurry into a sand mill, and sanding to obtain powder particle diameter d due to different particle diameter requirements of the powder ₅₀ The range is 0.5-1.5 μm. The sedimentation classification adopts a centrifugal sedimentation classification method to classify different particle sizes, and the particle sizes of the powder are classified>5 mu m particles, returning to the sanding process; and (3) uniformly blending the graded powder, and drying the powder in an oven at 110 ℃ to obtain refined powder.

S3, mixing the ceramic powder, a dispersing agent, an organic solvent, a pH regulator and a charging agent to obtain a suspension;

specifically, after mixing, a mechanical stirring and ultrasonic dispersion process can be adopted to prepare a suspension with uniform performance.

Specifically, the organic solvent comprises at least one of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, ethylene glycol, acetone, butanone and acetylacetone. The suspension is prepared by the organic reagent, part of the organic reagent is easy to volatilize, but the coating prepared by organic solvent electrophoresis is uniform and has no pores. The pH regulator may be any one of ammonia water, nitric acid and hydrochloric acid.

If an aqueous solvent is adopted, in the method, the electrophoresis method can be directly used for preparing ceramic green bodies, but the bonding stability of the sintered ceramic and a metal matrix is poor, and the sintered powder is in the form of granular ceramic particles to fall off; the ceramic coating is porous because it breaks down into oxygen and hydrogen at high voltages, resulting in poor bonding properties of the coating to the substrate.

S4, placing the suspension in an electrophoresis container, connecting the anode of the electrophoresis container with the treated metal mesh, and performing electrophoretic deposition to obtain a deposited ceramic metal mesh coated with a ceramic green body;

specifically, the electrophoretic deposition adopts a constant voltage type direct current electrophoretic deposition and drying process. Process parameters for electrophoretic deposition include, but are not limited to: the electrophoresis voltage is 5-600V, the electrophoresis temperature is 5-40 ℃, the electrophoresis time is 5-30 min, the polar distance is 1-5 cm, and the polar ratio is 1: 1-1: 4. the test is carried out by adopting direct current constant voltage equipment, the electrophoresis container can be an electrophoresis tank, and the specific connection mode is shown in figure 2; the three-electrode body mode can be adopted, so that the front and back surfaces of the metal mesh are uniformly coated, the distance between the electrodes is controlled to be 2-3 cm, short circuit is easy to occur between pole pieces when the pole distance is too close to the operation, throwing power is insufficient when the pole distance is too far, and even a uniform coating cannot be deposited. The method avoids the problems of mesh blockage and uneven coating caused by a spraying method, a brushing method and a dipping method, and can manufacture a ceramic coating with uniform distribution and controllable thickness on the surface of a metal nickel screen. And further sintering to obtain the high-temperature heat-resistant uniform ceramic coating.

S5, drying, sintering and cooling the deposited ceramic metal net to obtain a target metal net; the surface of the target metal net is covered with a heat-resistant ceramic coating.

Specifically, the deposited ceramic metal net can be dried before being dried, and can be naturally dried in the shade or air-dried; sintering is performed in a high temperature atmosphere furnace, gases in the high temperature atmosphere including but not limited to: argon, nitrogen and hydrogen. The cooling mode is furnace-mounted cooling, and the target temperature of cooling is room temperature.

In the embodiment of the application, the step S2 is only needed to be carried out before the step S3 to obtain the ceramic powder with the preset particle size distribution; s1, the treated metal net is obtained only by being carried out before the step S4; the order of steps S1 and S2 may be interchanged.

In some embodiments, the thickness of the heat resistant ceramic coating is 10-100 μm.

In some embodiments, the particle size d of the ceramic powder ₅₀ <0.5~1.5μm，d ₉₀ <The ceramic powder with the thickness of 5-10 μm comprises the following components: at least one of alumina, calcium oxide, zinc oxide, magnesium oxide, and zirconium oxide; and/or the components of the ceramic powder further comprise rare earth oxide.

Specifically, the rare earth elements include 17 kinds, the oxides of the rare earth elements have excellent heat resistance and are commonly used as ceramic additives, yttrium oxide is taken as an example of the rare earth oxides in the embodiment of the application, and other rare earth oxides have similarity in heat resistance and can be selectively popularized and used according to the dielectric property and the economic property of the rare earth oxides.

Specifically, d of particle size in ceramic powder ₉₀ <The powder with the particle size of 5 mu m accounts for more than 90%, can promote the stability of suspension, and has positive effects of improving the uniform stability and heat resistance of the heat-resistant ceramic coating by controlling the particle size distribution in the ceramic powder. The particle size distribution of the refined powder is shown in fig. 3, the particle size distribution of the refined powder is bimodal, and the particle size main body of the powder is distributed between 0.5 and 1.5 mu m.

To further illustrate the effect of powder particle size distribution on suspension stability. The 5% YSZ target raw material powder (particle diameter d ₅₀ About 20 μm), refined powder (d ₅₀ About 0.8 to 1.2 μm), coarse-grained powder (particle diameter d ₅₀ About 8 μm), 5g of powder is respectively put into a beaker, 100g of water is added, stirring is uniform, ultrasonic treatment is carried out for 10min, 50ml is respectively put into 50ml measuring cylinders with numbers of 1, 2 and 3 in sequence, standing is carried out for 90min, the powder is shown in figure 4a before standing for 60min, and the stable suspension property of the suspension phase of refined powder, raw material powder and coarse particle powder after fine selection is better than that of the suspension phase of the refined powder after standing for 60min, as shown in figure 4 b.

In some embodiments, the organic solvent comprises at least one of acetone, butanone, acetylacetone, ethylene glycol; and/or the organic solvent further comprises an organic monohydric alcohol.

In some embodiments, the dispersant comprises one of triethanolamine, ethyleneglycol amine, polyvinyl butyral, polyethyleneimine;

and/or the charging agent comprises one of iodine, nitric acid, hydrochloric acid, phosphoric acid, ammonia water and acetic acid; and/or, the charging agent further comprises an organic ammonium salt.

Generally, particles tend to settle under gravity and the suspension will settle and the suspension will be unevenly distributed. The dispersing agent and the charging agent can improve the Zeta potential of the powder, increase the mutual repulsive interaction of suspended particles, slow down sedimentation and make the suspended particles distributed more uniformly; the suspension with uniformly distributed suspended particles has positive effects on the stability of the electrophoretic deposition process and on the uniform stability of the heat-resistant ceramic coating.

In some embodiments, the resulting treated metal mesh specifically comprises: and (3) removing oil from the initial metal net by an alkali method, removing rust by an acid method, washing with water, phosphating and drying to obtain the treated metal net.

Preferably, the initial metal net is pretreated by adopting the processes of alkali degreasing, water washing, acid derusting, water washing, phosphating, water washing and drying, so that the treated metal net is obtained, and the subsequent electrophoretic deposition is facilitated.

Specifically, the alkali liquid formula for removing oil by an alkali method comprises the following components in percentage by mass: 5% -6% of NaOH, 2% -3% of Na ₂ SiO ₃ 、5~6%Na ₂ CO ₃ 2-5% of surfactant. The temperature of the alkaline degreasing is 80-90 ℃, the alkaline degreasing is soaked for 5-10 min before degreasing by subtraction, the stains are removed by brushing with a brush after soaking, and the alkaline degreasing is rinsed for 3 times with deionized water.

Specifically, the formula of the rust removing liquid for acid method rust removal is 5% -10% hydrochloric acid and 1% -3% surfactant. The temperature for acid rust removal includes, but is not limited to, room temperature, the acid rust removal can be performed for 3-5 minutes by soaking, and the soaking is rinsed with deionized water for 3 times.

Specifically, the specific operations of phosphating include: and (3) preparing the phosphating solution to a proper concentration, soaking for 3-10 min at normal temperature, and rinsing with deionized water for 3 times after soaking, wherein the phosphating solution of the phosphating solution is prepared by adding 8-10% of phosphating agent into water, and is also an aqueous solution. The phosphating agent generally comprises the following componentsPhosphoric acid, zinc dihydrogen phosphate film forming agent and NO added ₃ ^2- 、Cu ²⁺ And (3) serving as a phosphating accelerator.

Specifically, the specific operation of drying includes: and naturally drying the phosphated sample in the shade, and then placing the sample in an oven for drying at 85-110 ℃.

In some embodiments, in the suspension, the ceramic powder is 0.5% -20% by mass, the dispersant is 0.05% -0.2% by mass, and the charging agent is 0.01% -0.5% by mass of the ceramic powder.

By controlling the proportion of the ceramic powder dispersing agent and the charging agent in the suspension, the stability of the suspension can be increased, and the particles in the suspension can be stabilized in the solution for a period of time.

The preparation method of the suspension comprises the following steps: controlling the concentration of powder (solid content is 0.5-20%wt), stirring at room temperature (20-30 ℃), stirring at 300-500 r/min for 5-10 min, adding a dispersing agent, wherein the adding amount of the dispersing agent is 0.05-0.2%wt, adding a small amount of a charging agent is 0.01-0.5%, and continuously stirring for 30min. And (3) carrying out ultrasonic dispersion on the suspension for 30-60 min to obtain a stable suspension.

In some embodiments, the stage of sintering comprises: the first temperature rise and the second heat preservation are carried out; the first heating speed is 3-15 ℃/min, and the target temperature of the first heating is 1100-1400 ℃; the temperature of the second heat preservation is 1100-1400 ℃, and the time of the second heat preservation is 1-6 h.

According to another exemplary embodiment of the present application, there is provided a heat-resistant ceramic coating layer, which is manufactured by the method of any one of claims 1 to 8, and has a thickness of 10 to 100 μm.

According to another exemplary embodiment of the present application, there is provided a metal net manufactured by the above-described method; the surface of the metal net is covered with a heat-resistant ceramic coating, and the thickness of the heat-resistant ceramic coating is 10-100 mu m.

Compared with the common metal net, the metal net in the embodiment of the application has the advantages that the metal net is resistant to high temperature under the same condition, the temperature resistant range reaches 1350 ℃, the metal diffusion speed is slowed down because the metal atoms in the metal net are diffused and blocked by the ceramic coating, the risk of pollution to electronic products in the using process is reduced, and the service life of the metal net is prolonged because the metal diffusion speed is slowed down. The reason is that: the electrophoretic deposition method has better uniformity than the common spraying, brushing and dipping methods when the metal net is coated with the coating. The heat-resistant metal net prepared by the electrophoretic deposition method has the characteristics of high heat resistance, long service life and good coating uniformity.

The method of the present application will be described in detail with reference to examples, comparative examples and experimental data.

Example 1

The embodiment of the application provides a coating method of a metal nickel screen, which comprises the following steps:

removing oil from the initial metal net by an alkaline method, removing rust by an acid method, washing with water, phosphating and drying to obtain a treated metal net;

obtaining ceramic powder with preset particle size distribution;

placing the suspension in an electrophoresis container, connecting the anode of the electrophoresis container with the treated metal mesh, and performing electrophoretic deposition to obtain a deposited metal mesh containing ceramic green bodies;

drying, sintering and cooling the deposited metal mesh to obtain a target metal mesh; the surface of the target metal net is covered with a heat-resistant ceramic coating. The sintering stage comprises: heating in the first stage and preserving heat in the second stage; the temperature rising speed in the first stage is 3-15 ℃/min, and the target temperature of the first temperature rising is 1100-1400 ℃; the temperature of the second-stage heat preservation is 1100-1400 ℃, and the time of the second heat preservation is 1-6 h.

The method specifically comprises the following steps: the grain size distribution of the target ceramic powder is d ₉₀ <The powder with the particle size of 5 mu m accounts for more than 90%, the particle size distribution is bimodal, and the main particle size distribution of the powder is between 0.5 mu m and 1.5 mu m.

Preparing a treated metal nickel screen: the metal nickel screen used in the test is uniformly pretreated, firstly, the nickel screen is treated at 80-90 DEG CSoaking in hot alkali solution for 5min (alkali solution component 5% NaOH, 3% Na) ₂ SiO ₃ 、5%Na ₂ CO ₃ 2% of surfactant), cleaning and removing stains by adopting a brush after soaking, and rinsing with deionized water for 3 times. Putting the deoiled nickel screen into 10% hydrochloric acid with 1% of surfactant at room temperature of 25 ℃, soaking for 3min, and rinsing with deionized water for 3 times. The phosphating process adopts an iron phosphating agent to dilute to 15% of stock solution concentration, is soaked for 10min at normal temperature, is rinsed for 3 times by deionized water after soaking, and is dried and cooled at 110 ℃ for standby.

Preparing ceramic powder: the powder for the test is prepared by adopting a sanding method, water is used as a solvent, zirconia balls are used as grinding media, the solid content concentration of raw materials is controlled to be 20-30%, and the raw materials are ground to d ₅₀ <1.5 mu m, adopting a centrifugal sedimentation fractionation method to carry out powder particle size fractionation and coarse particle size>5 mu m, and the fine powder is graded and blended uniformly to obtain the particle diameter d of the powder ₉₀ <5 mu m, putting into a baking oven, baking at 110 ℃ for 4 hours, and cooling for standby.

Weighing 30g of 5% YSZ powder, adding into a 500mL beaker, adding 400g of acetylacetone, stirring for 10min at room temperature at 300r/min, adding 0.2g of triethanolamine as a dispersing agent, adding 0.1g of iodine, adding acetic acid to adjust the pH to 4, and continuously stirring for 20min; stirring uniformly, placing in an ultrasonic oscillator, and oscillating for 30min to obtain a stable suspension. Placing the prepared solution in an electrophoresis tank, setting direct-current voltage 280V, connecting a positive electrode with a titanium-plated electrode piece, connecting a negative electrode with a metal mesh, and connecting the electrode spacing of 2cm and the electrode ratio of 4:1, carrying out electrophoresis for 5min at room temperature to obtain the coating. Naturally drying in the shade at room temperature; sintering the nickel screen coating in an argon atmosphere furnace, heating to 1250 ℃ at a heating rate of 5 ℃/min, preserving heat for 150min, and then cooling to room temperature along with the furnace; samples were prepared.

The metal nets in different states are recorded as shown in figure 5, which are respectively a metal original net, b phosphorized, c coated and d sintered physical figures, which shows that the metal net coated by the heat-resistant ceramic coating has no hole blockage and uniform coating.

The heat-resistant ceramic coating of example 1 was observed with a scanning electron microscope as shown in fig. 7, wherein fig. 7a is a surface of the heat-resistant ceramic coating and fig. 7e is a microscopic surface of the heat-resistant ceramic coating, illustrating that the heat-resistant ceramic coating has a dense and uniform structure.

Fig. 8a is a surface of a heat-resistant ceramic coating, fig. 8b is a cross section of the heat-resistant ceramic coating, and fig. 8c is a microscopic surface of the heat-resistant ceramic coating, illustrating that the heat-resistant ceramic coating is dense and uniform in structure.

Example 2

Weighing 30g of alumina powder, adding 500mL of beaker, adding 500g of methanol, stirring at room temperature for 10min at 300r/min, adding 0.2g of triethanolamine as dispersing agent, adding 3 drops of nitric acid as a charging agent, adding ammonia water to adjust the pH to 9, and continuing stirring for 20min; stirring uniformly, placing in an ultrasonic oscillator, and oscillating for 30min to obtain a stable suspension. Placing the prepared solution in an electrophoresis tank, setting a direct current voltage of 100V, adopting metal nets as electrodes, and enabling the polar distance to be 4cm and the polar ratio to be 1:1, carrying out electrophoresis for 45min at room temperature to obtain the coating. Naturally drying in the shade, and drying in a 50 ℃ oven; sintering the nickel screen coating in an argon atmosphere furnace, heating to 1200 ℃ at a heating rate of 5 ℃/min, preserving heat for 150min, and then cooling to room temperature along with the furnace; samples were prepared.

Example 3

Weighing 25g of yttrium oxide powder, adding a 500mL beaker, adding 400g of ethanol, stirring at room temperature for 10min at 300r/min, adding 0.2g of triethanolamine as a dispersing agent, adding 3 drops of nitric acid as a charging agent, adding acetic acid to adjust the pH to 4, and continuously stirring for 20min; stirring uniformly, placing in an ultrasonic oscillator, and oscillating for 30min to obtain a stable suspension. Placing the prepared solution in an electrophoresis tank, setting a direct-current voltage of 100V, connecting a positive electrode with a graphite sheet, connecting a negative electrode with a nickel screen, and keeping the polar distance of 2cm and the polar ratio of 4:1, carrying out electrophoresis for 15min at room temperature to obtain the coating. Naturally drying the surface reagent in the shade, and drying in a drying oven at 65 ℃; sintering the nickel screen coating in an argon atmosphere furnace, heating to 1200 ℃ at a heating rate of 10 ℃/min, preserving heat for 150min, and then cooling to room temperature along with the furnace; samples were prepared.

Example 4

Weighing 30g of 8% YSZ powder, adding a 500mL beaker, adding 400g of acetone, stirring for 10min at room temperature at 300r/min, adding 0.2g of triethanolamine as a dispersing agent, adding 0.1g of iodine as a charging agent, adding acetic acid to adjust the pH to 4, and continuously stirring for 20min; stirring uniformly, placing in an ultrasonic oscillator, and oscillating for 30min to obtain a stable suspension. Placing the prepared solution in an electrophoresis tank, setting a direct-current voltage of 100V, connecting a positive electrode with a platinum electrode plate, connecting a negative electrode with a nickel screen, and connecting the electrode spacing of 2cm and the electrode ratio of 1:1, carrying out electrophoresis for 15min at room temperature to obtain the coating. Naturally drying the surface reagent in the shade, and drying in a 50 ℃ oven; sintering the nickel screen coating in an argon atmosphere furnace, heating to 1250 ℃ at a heating rate of 5 ℃/min, preserving heat for 150min, and then cooling to room temperature along with the furnace; samples were prepared.

The heat-resistant ceramic coating of example 4 was observed with a scanning electron microscope as shown in fig. 7, wherein fig. 7b is the surface of the heat-resistant ceramic coating and fig. 7f is the microscopic surface of the heat-resistant ceramic coating.

Example 5

Weighing 30g of 8% YSZ powder, adding a 500mL beaker, adding 400g of isopropanol, stirring for 10min at room temperature at 300r/min, adding 0.2g of Polyethyleneimine (PEI) as a dispersing agent, adding 0.1g of iodine, adding acetic acid to adjust the pH to 4, and continuously stirring for 20min; stirring uniformly, placing in an ultrasonic oscillator, and oscillating for 30min to obtain a stable suspension. Placing the prepared solution in an electrophoresis tank, setting a direct current voltage of 200V, adopting nickel screens as electrodes, and enabling the electrode spacing to be 2cm and the electrode ratio to be 4:1, carrying out electrophoresis for 45min at room temperature to obtain the coating. Naturally drying the surface reagent in the shade, and drying in a drying oven at 65 ℃; sintering the nickel screen coating in an argon atmosphere furnace, heating to 1380 ℃ at a heating rate of 5 ℃/min, preserving heat for 150min, and cooling to room temperature along with the furnace; samples were prepared.

The heat-resistant ceramic coating of example 5 was observed with a scanning electron microscope as shown in fig. 7, wherein fig. 7c is the surface of the heat-resistant ceramic coating and fig. 7g is the microscopic surface of the heat-resistant ceramic coating.

Comparative example 1

This comparative example illustrates the uniformity comparison of the spray coating process and the electrophoretic deposition process to produce a coating on a metal mesh: 30g of refined alumina powder is weighed and placed in a beaker, 500g of water is added, 0.25g of dispersing agent and 1 drop of defoaming agent are added by a spraying method, after stirring and dispersing uniformly, 5g of 10% PVB aqueous solution is added, stirring is carried out for 30min, the mixture is added into a spray gun, the spraying distance is controlled to be 15cm, uniform spraying is carried out, and the metal net real object is shown in figure 6a after drying.

Comparative example 2

This comparative example illustrates the uniformity comparison of the brush coating process and the electrophoretic deposition process to prepare a coating on a metal mesh: 30g of refined alumina powder is weighed and placed in a beaker, 500g of water is added, 0.25g of dispersing agent and 1 drop of defoaming agent are added by a spraying method, after stirring and dispersing uniformly, 5g of 10% PVB aqueous solution is added, stirring is carried out for 30min, the solution is dipped by a bristle brush, the solution is coated on a metal net, and the metal net real object is shown in figure 6b after drying.

Comparative example 3

This comparative example illustrates the uniformity comparison of dip coating and electrophoretic deposition to produce a coating on a metal mesh: weighing 30g of refined alumina powder, placing the refined alumina powder into a beaker, adding 500g of water, adding 0.25g of dispersing agent by a spraying method, adding 1 drop of defoaming agent, stirring and dispersing uniformly, adding 15g of 10% PVB aqueous solution, stirring for 30min, soaking a metal net with 10% PVB for 10min, drying to form dry gel on the metal net, immersing the sized metal net in the solution for 10min, taking out, drying, and repeatedly dip-coating for 5 times. The metal net real object after drying is shown in fig. 6c.

Comparative example 4

This comparative example differs from example 1 in that: deionized water is selected as a solvent, and the direct-current voltage is set to 20V, so that a uniform ceramic green body can be obtained, but the ceramic falls off from the metal mesh after sintering, and more air holes are formed in the coating.

Comparative example 5

This comparative example differs from example 1 in that: the smooth ceramic coating can be obtained by mixing water and acetylacetone (volume ratio of 1:1) as a solution, but the ceramic coating with proper thickness (50 μm) is prepared, the electrophoresis voltage is higher, the suspension current density is high due to the better conductivity of water, the solution heats, and the prepared coating is relatively loose.

Comparative example 6

This comparative example differs from example 1 in that: the sintering adopts direct heating, the speed of the first heating is 5 ℃/min, the target temperature of the first heating is 1000 ℃, the temperature is kept for 150min at 1000 ℃, the ceramic coating is not sintered after being cooled along with the furnace, and the powder is dropped after the coating is light by hands.

Comparative example 7

The comparative example was conducted in the same manner as in example 5 in terms of the coating preparation process, simulating the environment in which the heat-resistant metal mesh was used, and conducting a temperature resistance test: placing the prepared heat-resistant metal mesh in a nitrogen atmosphere furnace, heating to 1350 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 180min, cooling to 700 ℃ at a heating rate of 10 ℃/min, and then cooling to room temperature along with the furnace; repeated 5 times.

The heat-resistant ceramic coating of comparative example 7 was observed with a scanning electron microscope as shown in fig. 7, wherein fig. 7d is the surface of the heat-resistant ceramic coating and fig. 7h is the microscopic surface of the heat-resistant ceramic coating.

Performance detection

The coated metal mesh prepared in some examples and comparative examples was observed and characterized, and the results are shown in table 1.

Table 1 detection and characterization of coated wire mesh

Project	Uniformity of green body	Coating and web bonding	Apparent characteristics of the coating	Other features
					Example 1	Uniformity of	Good (good)	Surface flour body micro-shedding	The coating was uniform and dense as shown in FIG. 8
Example 4	Uniformity of	Good (good)	Uniform coating	The coating thickness is moderate, as shown in FIG. 6d
					Example 5	Uniformity of	Good (good)	Uniform coating	The surface of the coating has microcracks, as shown in FIG. 7c
Comparative example 1	Non-uniformity of	Preferably, it is	Coating severe hole blocking	Part of the ceramic powder is adhered to the mesh, the real object is shown in FIG. 6a
					Comparative example 2	Uniformity of	Preferably, it is	Thin coating, partial metal being exposed and uniform coating blocking hole	The coating is uniform but the holes are blocked, the real object is as shown in FIG. 6b
Comparative example 3	Non-uniformity of	Preferably, it is	The coating is thin, and the bottom is blocked by agglomerated powder	The bottom is blocked by agglomerated powder, the real object is shown in figure 6c
					Comparative example 4	Uniformity of	Difference of difference	Smooth surface and even coating	The surface of the coating is smooth, and the inside of the coating is provided with air holes
Comparative example 6	Uniformity of	Difference of difference	Uniform coating	Surface powder body is not sintered, and the powder is removed by hand touch
					Comparative example 7	Uniformity of	Good (good)	Uniform coating	The surface of the coating is completely uniform as shown in FIG. 7d

As can be seen from Table 1, in examples 1 to 5, uniform coatings were obtained, and in comparative examples 1 to 3, non-uniform coatings were obtained, which demonstrates that ceramic coated green bodies could be prepared on a metal mesh by electrophoretic deposition, which solves the problem of non-uniform coating preparation by spraying, brushing, and dipping methods.

Example 1 is compared with comparative examples 4 and 5 to demonstrate that the parameters of the electrophoretic deposition process are related to the type of solvent, wherein water is decomposed during the preparation of a dense coating due to its low decomposition voltage, and pores are easily formed in the ceramic.

The comparison of the example 1 with the comparative examples 6 and 7 shows that the sintering temperature of the prepared ceramic is higher, the sintering temperature is higher than 1000 ℃ in the preparation process of the ceramic, the ceramic can be circularly calcined at 1350 ℃, the ceramic coating does not fall off, and the use temperature of the metal mesh ceramic coating can reach 1350 ℃.

Comparison of example 2 with example 3 shows that the farther the pole pitch, the thinner the thickness of the coating during electrophoretic deposition at the same voltage, but too close the pole pitch increases the risk of shorting the positive and negative poles, so the test pole pitch is controlled at about 2 cm.

Example 4 is compared to example 5, demonstrating that the polar ratio during electrophoretic deposition has an effect on the uniformity of the electrophoretically deposited coating.

Example 4 is compared with comparative example 6, and illustrates that the electrophoretic deposition and high-temperature sintering process is adopted to obtain the heat-resistant ceramic coating with uniform coating and compact structure, and the sintering temperature of part of the coating material is higher than 1000 ℃.

It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of coating a metal mesh, the method comprising the steps of:

obtaining a treated metal net;

obtaining ceramic powder with preset particle size distribution, wherein the ceramic powder adopts a sand grinding-sedimentation grading-drying process to prepare ceramic powder with particle size in bimodal distribution; particle diameter d of the ceramic powder ₅₀ <0.5~1.5μm，d ₉₀ <5-10 mu m, wherein the ceramic powder comprises the following components: at least one of alumina, calcium oxide, magnesium oxide and zirconium oxide; the ceramic powder also comprises rare earth oxide;

placing the suspension in an electrophoresis container, connecting the negative electrode of a power supply with the treated metal mesh, and performing electrophoretic deposition to obtain a deposited ceramic metal mesh coated with a ceramic green body;

drying, sintering and cooling the deposited ceramic metal mesh to obtain a target metal mesh; the surface of the target metal net is covered with a heat-resistant ceramic coating, wherein sintering is performed in a high-temperature atmosphere furnace, and the gas in the high-temperature atmosphere comprises the following components: one or more of argon, nitrogen and hydrogen; the sintering stage comprises: the first temperature rise and the second heat preservation are carried out; the target temperature of the first heating is 1100-1400 ℃; the second heat preservation temperature is 1100-1400 ℃.

2. The method of claim 1, wherein the heat resistant ceramic coating has a thickness of 10-100 μm.

3. The method according to claim 1, wherein the organic solvent comprises at least one of acetone, butanone, acetylacetone, ethylene glycol; and/or the organic solvent further comprises an organic monohydric alcohol.

4. The method of claim 1, wherein the dispersant comprises at least one of triethanolamine, ethylene glycol amine, polyvinyl butyral, polyethylenimine, sodium lignin sulfonate, and sodium polyacrylate;

and/or the charging agent comprises at least one of iodine, nitric acid, hydrochloric acid, phosphoric acid, ammonia water and acetic acid; and/or, the charging agent further comprises an organic ammonium salt.

5. The method according to claim 1, characterized in that said treated metal mesh is obtained, in particular comprising: and (3) removing oil from the initial metal net by an alkali method, removing rust by an acid method, washing with water, phosphating and drying to obtain the treated metal net.

6. The method according to claim 1, wherein the ceramic powder is 0.5-20% by mass, the dispersant is 0.05-0.2% by mass, and the charging agent is 0.01-0.5% by mass of the ceramic powder in the suspension.

7. The method of claim 1, wherein the first temperature rise rate is 3-15 ℃/min and the second temperature holding time is 1-6 hours.

8. A heat resistant ceramic coating, characterized in that it is produced by the method of any one of claims 1 to 7, and has a thickness of 10 to 100 μm.

9. A metal mesh, characterized in that it is produced by the method according to any one of claims 1-7; the surface of the metal net is covered with a heat-resistant ceramic coating, and the thickness of the heat-resistant ceramic coating is 10-100 mu m.