Ink-jet printing method for metal ink on surface of ceramic membrane

Abstract

The invention relates to an ink-jet printing method for metal ink on the surface of a ceramic membrane. The ink-jet printing method comprises the following steps of S1, wet membrane preparation, S2, initial heating, drying and shaping, S3, high-temperature sintering and molding and S4, high-temperature rapid reduction. The preparation method has the advantages that the wet film layer is formed on the surface of the ceramic flat sheet membrane in an ink-jet printing mode, and then the conductive membrane which is firm in combination, good in conductivity, has a filtering function and is rich in pores is formed on the surface of the ceramic flat sheet membrane through the steps of initial heating, drying and shaping, high-temperature sintering forming and high-temperature rapid reduction in sequence; in the preparation process, inert gas is continuously introduced into the inner cavity of the ceramic flat sheet membrane, so that the original pores of the ceramic membrane are prevented from being blocked by metal ink as much as possible, and the pores are formed on the sprayed ink layer when gas is discharged outwards, and decomposed substances during sintering are carried and transferred in time; the method has the characteristics of simplicity, easiness in operation and low material cost, the surface of the finished ceramic membrane is functionalized, the original preparation process and equipment of the ceramic membrane do not need to be adjusted, and the method is easy to popularize and use.

Description

Technical Field

[0001] The invention relates to the field of conductive functionalization of ceramic film surfaces, and in particular to a method for inkjet printing of metal ink on ceramic film surfaces. Background Art

[0002] The ceramic membrane with conductive function is used for water treatment. On the one hand, it can filter out impurities and pollutants. On the other hand, after the ceramic membrane is energized, it can effectively remove organic matter, colloids, etc. in the water that are difficult to remove by filtering alone, and can greatly reduce the adhesion and pollution of pollutants to the membrane. Existing conductive ceramic membranes generally use conductive materials to dope ceramic slurry, and then sinter to form conductive ceramic membranes with conductive functions. The shortcomings are: the conductive material is evenly dispersed in the entire ceramic membrane, so the amount of conductive material is large, resulting in a high cost of conductive ceramic membranes; due to the change in the composition of the ceramic slurry, the process parameters and equipment requirements during production are changed, resulting in the original process and equipment cannot be used, and the investment cost of process and equipment improvement is high.

[0003] Using metal ink to form a conductive film on the surface of a ceramic membrane is an effective method to make the ceramic membrane conductive so that it can have the dual functions of filtering and removing impurities and electrochemically removing pollutants. However, using conventional methods to form a conductive film on the surface of a ceramic membrane with metal ink will have an adverse effect on the filtration function of the ceramic membrane. Therefore, it is necessary to study new inkjet printing methods to ensure that a conductive layer with good conductivity is formed on the surface of the ceramic membrane and the original filtration performance of the ceramic membrane is basically retained. Summary of the invention

[0004] The present invention provides a method for inkjet printing of metal ink on the surface of a ceramic membrane, aiming to overcome the deficiencies in the prior art and ensure that the metal ink can form a conductive layer with good conductivity on the surface of the ceramic membrane and substantially retain the original filtering performance of the ceramic membrane.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: a method for inkjet printing of metal ink on the surface of a ceramic film, comprising the following steps:

[0006] S1. Wet film preparation: inkjet printing is performed on both sides of the ceramic flat film using a metal ink as a raw material to form a wet film layer;

[0007] S2. Initial heat drying and shaping: Place the ceramic flat membrane in a closed box, connect the inlet ports at both ends of the ceramic flat membrane to the inert gas pipeline, continuously introduce inert gas, maintain the gas pressure in the ceramic flat membrane cavity at 0.15-0.35MPa, slowly heat to 190℃, and continue drying for 3-5h;

[0008] S3. High temperature sintering: After drying, the pressure in the inner cavity of the ceramic flat membrane is increased to 0.5-0.7 MPa and maintained, and then the temperature is slowly raised to 350°C, and the high temperature sintering and curing is maintained at 350°C for 1.5-2.5 hours;

[0009] S4. High temperature rapid reduction: After sintering and curing, quickly heat up to 420℃, maintain high temperature at 420℃ for 2-3min, then naturally cool to 350℃, then quickly heat up to 420℃, and continue to reduce for 2-3min. Repeat several times, and then naturally cool to room temperature. The metal ink inkjet printing of the ceramic flat film is completed.

[0010] On the basis of the above technical solutions, the present invention can also have the following further specific options.

[0011] Specifically, during inkjet printing in S1, the nozzle of the inkjet printing device sprays ink toward the plane of the ceramic flat film at an angle.

[0012] Specifically, the thickness of the wet film layer formed by inkjet printing on the surface of the ceramic flat film in S1 is 1-5 μm.

[0013] Specifically, the inert gas in S2 is nitrogen or argon.

[0014] Specifically, the ceramic flat membranes in S2 and S3 are placed vertically in a closed box.

[0015] Specifically, the heating rate in S2 and S3 is controlled to be 1-3°C / min.

[0016] Specifically, the heating rate in S4 is controlled at 5-8°C / min.

[0017] Specifically, the temperature in S4 is raised to 420° C. for reduction and the reduction is repeated 3-5 times.

[0018] Specifically, the metal ink used in S1 contains organic copper salt, organic amine, inorganic ammonium salt, graphene oxide and polyimide ultrafine powder.

[0019] Specifically, the polyimide ultrafine powder is a thermosetting resin, and the average particle size is 30-40 μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention adopts inkjet printing to first form a wet film layer on the surface of a ceramic flat membrane, and then sequentially forms a conductive film with strong bonding, good conductivity and abundant pores with filtering function on the surface of the ceramic flat membrane through initial heat drying and shaping, high temperature sintering and high temperature rapid reduction steps. During the preparation process, an inert gas is continuously passed into the inner cavity of the ceramic flat membrane, which not only avoids the metal ink from blocking the original pores of the ceramic membrane as much as possible, but also ensures that pores are formed on the sprayed ink layer when the gas is released and the decomposed substances are transferred in time during sintering. The inkjet printing method provided by the present invention forms a conductive layer on the surface of a ceramic membrane, which has the characteristics of simple method, easy operation and low material cost. At the same time, it is a functionalization of the surface of the finished ceramic membrane, and there is no need to adjust the original slurry components, molding process and molding equipment of the ceramic membrane, so it is easy to be promoted and used in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a flow chart of a method for inkjet printing of metallic ink on a ceramic film surface. DETAILED DESCRIPTION

[0023] The principles and features of the present invention are described below in conjunction with the accompanying drawings and specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0024] like Figure 1 As shown, the present invention provides a method for inkjet printing of metal ink on the surface of a ceramic membrane, which includes the steps of wet film layer preparation, initial heat drying and shaping, high-temperature sintering and high-temperature rapid reduction in sequence, and can form a conductive membrane with abundant pores that is firmly bonded, has good conductivity and has a filtering function on the surface of the ceramic flat membrane. During the preparation process, an inert gas is continuously passed into the inner cavity of the ceramic flat membrane. The continuous passage of the inert gas can both avoid the metal ink from blocking the original pores of the ceramic membrane as much as possible, and ensure that pores are formed on the sprayed ink layer when the gas is released, protect the copper and graphene conductive components formed by reduction at high temperature from being oxidized by the air, and carry the decomposed substances during sintering to transfer in time.

[0025] It should be noted that the continuous flow of inert gas in a closed box will gradually increase the air pressure in the box. Therefore, after a certain amount of inert gas is initially introduced, the ventilation is switched to internal circulation. The existing inert gas in the box and the gas produced by decomposition are used as a mixed gas source to continuously ventilate the inner cavity of the ceramic membrane by the booster circulation component. The gas pressure is indicated by a barometer. During the preparation process, the inner cavity of the ceramic membrane is ventilated, and the gas rushes out of the membrane surface from the inside to the outside. Although the ink is sprayed obliquely to the membrane surface during inkjet printing, it is inevitable that some ink components will enter the original pores of the ceramic flat membrane. Reverse ventilation before solidification can cause this part of the ink to be discharged from the pores. At the same time, the gas passing through the wet film layer will also form pores in the wet film layer. Combined with the thermal decomposition of the inorganic ammonium salt in the ink of the wet film layer, it can be ensured that the film layer after initial drying and shaping has relatively abundant pores. Subsequently, during high-temperature sintering, the polyimide in the ink undergoes a process of first softening and melting, and then During the cross-linking and curing process, reverse ventilation can prevent the softened molten polyimide from blocking the pores until the cross-linking and curing are complete and the pores are fully formed. In the high-temperature rapid reduction stage, repeated intermittent high-temperature reduction treatment is used. The high temperature of 420°C can accelerate the decomposition of ammonia to reduce graphene oxide and copper ions, and avoid continuous damage to the solidified part of the polyimide due to excessively high temperatures. In the high-temperature rapid reduction stage, in order to enhance the reduction and save the time of repeated high-temperature treatment, a small amount of ammonia or hydrogen can be additionally introduced into the closed box during actual production.

[0026] The metal ink used in the present invention is specifically composed of soluble organic copper salt, organic amine, inorganic ammonium salt, graphene oxide, polyimide ultrafine powder, ethanol and water, wherein the mass ratio of inorganic ammonium salt, graphene oxide, polyimide ultrafine powder and soluble organic copper salt is (0.05-0.08): (0.02-0.04): (0.03-0.06): 1, the volume ratio of ethanol and water is 0.3-0.5: 1, the dosage ratio of soluble organic copper salt and water is 0.12-0.25g: 1mL, and the molar ratio of copper ions of soluble organic copper salt to organic amine is 1: 1-4. Among them, the soluble organic copper salt is copper acetate; the organic amine is preferably ethylenediamine or ethanolamine; the inorganic ammonium salt is ammonium chloride; the graphene oxide is preferably single-layer graphene; the polyimide is preferably an ultrafine powder with an average particle size of 30-40μm, and a thermosetting resin is selected.

[0027] The following is described in conjunction with specific embodiments. To avoid redundancy, the drugs used in the following embodiments are all commercially available products unless otherwise specified, and the methods used are all conventional methods in the art unless otherwise specified.

[0028] Example 1

[0029] A method for inkjet printing of metallic ink on a ceramic film surface, comprising the following steps:

[0030] S1. Wet film preparation: inkjet printing is performed on both sides of the ceramic flat film using metal ink as raw material to form a wet film layer. The ink is sprayed at a certain angle to avoid vertical spraying. The thickness of the wet film layer is controlled to be 3-5 μm;

[0031] S2. Initial heat drying and shaping: Place the ceramic flat membrane in a vertical state in a closed box, connect the inlets at both ends of the ceramic flat membrane to the nitrogen pipeline, continuously introduce nitrogen, maintain the pressure in the inner cavity of the ceramic flat membrane at 0.30-0.35MPa, slowly heat up to 190℃, and continue drying for 5h;

[0032] S3. High temperature sintering: After drying, the pressure in the inner cavity of the ceramic flat membrane is increased to 0.7 MPa and maintained, and then the temperature is slowly increased to 350°C at a heating rate of 1°C / min, and the high temperature sintering and curing at 350°C is maintained for 2.5 hours;

[0033] S4. High temperature rapid reduction: After sintering and curing, quickly heat up to 420℃, with a heating rate of 8℃ / min, maintain high temperature of 420℃ for continuous reduction for 2-3min, then naturally cool to 350℃, then quickly heat up to 420℃, and continue to reduce for 2-3min. Repeat this process 5 times, and then naturally cool to room temperature. The metal ink inkjet printing of the ceramic flat film is completed.

[0034] Example 2

[0035] A method for inkjet printing of metallic ink on a ceramic film surface, comprising the following steps:

[0036] S1. Wet film preparation: inkjet printing is performed on both sides of the ceramic flat film using metal ink as a raw material to form a wet film layer. The ink is sprayed at a certain angle to avoid vertical spraying. The thickness of the wet film layer is controlled to be 1-3 μm;

[0037] S2. Initial heat drying and shaping: Place the ceramic flat membrane in a vertical state in a closed box, connect the inlets at both ends of the ceramic flat membrane to the nitrogen pipeline, continuously introduce nitrogen, maintain the pressure in the inner cavity of the ceramic flat membrane at 0.15-0.25MPa, slowly heat up to 190℃, and continue drying for 3h;

[0038] S3. High temperature sintering: After drying, the gas pressure in the inner cavity of the ceramic flat membrane is increased to 0.5 MPa and maintained, and then the temperature is slowly raised to 350°C at a heating rate of 3°C / min, and the high temperature sintering and curing at 350°C is maintained for 1.5 hours;

[0039] S4. High temperature rapid reduction: After sintering and curing, quickly heat up to 420℃, with a heating rate of 5℃ / min, maintain high temperature of 420℃ for continuous reduction for 2-3min, then naturally cool to 350℃, then quickly heat up to 420℃, and continue to reduce for 2-3min. Repeat this process 3 times, and then naturally cool to room temperature. The metal ink inkjet printing of the ceramic flat film is completed.

[0040] Example 3

[0041] A method for inkjet printing of metallic ink on a ceramic film surface, comprising the following steps:

[0042] S1. Wet film preparation: inkjet printing is performed on both sides of the ceramic flat film using metal ink as a raw material to form a wet film layer. The ink is sprayed at a certain angle to avoid vertical spraying. The thickness of the wet film layer is controlled to be 2-4 μm.

[0043] S2. Initial heat drying and shaping: Place the ceramic flat membrane in a vertical state in a closed box, connect the inlets at both ends of the ceramic flat membrane to the nitrogen pipeline, continuously introduce nitrogen, maintain the pressure in the inner cavity of the ceramic flat membrane at 0.2-0.3MPa, slowly heat up to 190℃, and continue drying for 4h;

[0044] S3. High temperature sintering: After drying, the gas pressure in the inner cavity of the ceramic flat membrane is increased to 0.6 MPa and maintained, and then the temperature is slowly raised to 350°C at a heating rate of 2°C / min, and the high temperature sintering and curing at 350°C is maintained for 2 hours;

[0045] S4. High temperature rapid reduction: After sintering and solidification, quickly heat up to 420℃, with a heating rate of 6℃ / min, maintain high temperature of 420℃ for continuous reduction for 2-3min, then naturally cool to 350℃, then quickly heat up to 420℃, and continue to reduce for 2-3min. Repeat this process 4 times, and then naturally cool to room temperature. The metal ink inkjet printing of the ceramic flat film is completed.

[0046] After inspection, the ceramic flat membranes in the above embodiments, after undergoing the above-mentioned inkjet printing treatment, have formed a conductive layer with strong bonding and good conductivity on the upper surface. The obtained ceramic flat membranes were installed on ceramic membrane filters for water treatment tests. It was found that compared with the original time without inkjet treatment, the time taken to treat the same sewage using the ceramic flat membrane filter of the present invention was only slightly increased, and the increase in time did not exceed 5%, indicating that the ceramic membrane with a conductive layer prepared using the method of the present invention has better water treatment capacity; after the ceramic flat membrane of the present invention is powered on, the small molecular organic pollutants that were originally difficult to remove are effectively removed in the purified water obtained. After long-term use, it is found that the surface dirt of the energized ceramic flat membrane is significantly less than that of the ceramic flat membrane that has not been inkjet treated.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for inkjet printing of metallic ink on a ceramic film surface, characterized in that: The steps include: S1. Wet film preparation: inkjet printing is performed on both sides of the ceramic flat film using a metal ink as a raw material to form a wet film layer; S2. Initial heat drying and shaping: Place the ceramic flat membrane in a closed box, connect the inlet ports at both ends of the ceramic flat membrane to the inert gas pipeline, continuously introduce inert gas, maintain the gas pressure in the ceramic flat membrane cavity at 0.15-0.35MPa, slowly heat to 190℃, and continue drying for 3-5h; S3. High temperature sintering: After drying, the pressure in the inner cavity of the ceramic flat membrane is increased to 0.5-0.7 MPa and maintained, and then the temperature is slowly raised to 350°C, and the high temperature sintering and curing is maintained at 350°C for 1.5-2.5 hours; S4. High temperature rapid reduction: After sintering and curing, quickly heat up to 420℃, maintain high temperature at 420℃ for 2-3min, then naturally cool to 350℃, then quickly heat up to 420℃, and continue to reduce for 2-3min. Repeat several times, and then naturally cool to room temperature. The metal ink inkjet printing of the ceramic flat film is completed.

2. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: During inkjet printing in S1, the nozzle of the inkjet printing device sprays ink toward the plane of the ceramic flat film at an angle.

3. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: The thickness of the wet film layer formed by inkjet printing on the surface of the ceramic flat film in S1 is 1-5 μm.

4. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: The inert gas in S2 is nitrogen or argon.

5. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: The ceramic flat membranes in S2 and S3 are placed vertically in a closed box.

6. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: The heating rate in S2 and S3 was controlled at 1-3°C / min.

7. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: In S4, the heating rate is controlled at 5-8°C / min.

8. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 1, characterized in that: In S4, the temperature is raised to 420° C. for reduction and this is repeated 3-5 times.

9. The method for inkjet printing of metal ink on a ceramic film surface according to any one of claims 1 to 8, characterized in that: The metal ink used in S1 contains organic copper salt, organic amine, inorganic ammonium salt, graphene oxide and polyimide ultrafine powder.

10. The method for inkjet printing of metallic ink on the surface of a ceramic film according to claim 9, characterized in that: Polyimide ultrafine powder is a thermosetting resin with an average particle size of 30-40μm.

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