CN112828280B

CN112828280B - Preparation method of metal membrane with gradient pore diameter structure

Info

Publication number: CN112828280B
Application number: CN202110010469.3A
Authority: CN
Inventors: 俞健; 杨佳辉; 张玉冬; 徐玫瑰
Original assignee: Nanjing Tech University
Current assignee: Nanjing Tech University
Priority date: 2021-01-06
Filing date: 2021-01-06
Publication date: 2022-09-09
Anticipated expiration: 2041-01-06
Also published as: CN112828280A

Abstract

The invention relates to a preparation method of a metal membrane with a gradient aperture structure, which comprises the following steps: uniformly stirring small-particle-size metal powder and a binder solution to prepare slurry; uniformly coating the slurry on a smooth flat plate, drying, and stripping a metal mold blank from the flat plate to obtain a metal mold blank which is wound into a cylindrical shape and tightly attached to the inner wall of a rigid outer mold; filling metal powder with different thicknesses into a cavity between the rigid outer mold and the elastic inner mold, sealing two ends of the cavity by using elastic seal heads, and removing the elastic inner mold and the elastic seal heads after cold isostatic pressing; and fourthly, placing the rigid external mold and the blank in an atmosphere furnace for high-temperature sintering, and removing the rigid external mold after cooling to obtain the asymmetric metal film. The process is simple, the cost is low, and the prepared metal membrane has large aperture gradient, large flux and high filtration precision.

Description

Preparation method of metal film with gradient pore diameter structure

Technical Field

The invention belongs to the technical field of membrane materials, and particularly relates to a preparation method of a metal membrane with a gradient pore diameter structure.

Technical Field

With the rapid development of membrane science and technology, membrane separation, as a novel and efficient separation technology, has been widely applied in many fields such as energy, petrochemical industry, biology, health and medicine, environment, metallurgy, food, and the like. At present, common membrane materials mainly comprise metal, ceramic and high molecular organic materials, and porous metal has high mechanical strength and good processing, welding and sealing properties and is superior to the ceramic and the organic materials in many fields.

The porous metal film is classified into a symmetrical porous metal film and an asymmetrical porous metal film. The asymmetric gradient pore size structure is formed by combining a substrate layer for supporting and a separation layer for filtering, has high filtering precision and large permeation flux, and is the development direction of porous metal materials. Then, as the number of the film layers increases, the more complicated the preparation process of the porous metal material becomes, and the cost increases. The conventional preparation method of the metal membrane with the gradient pore diameter structure comprises a suspended particle sintering method, a wet powder spraying method, a centrifugal forming method and the like, and patent CN103691330A discloses a preparation process of porous stainless steel. Patent CN103386486A discloses a method for preparing an unsupported porous metal film, which comprises ball-milling and mixing metal powder and aqueous solution of polyvinyl alcohol uniformly, coating the slurry on the surface of a substrate, drying, peeling to obtain a metal film blank, and placing ceramic filler and the blank into a sintering mold for sintering and molding. The method is characterized in that a metal film layer prepared on the curved surface in a coating mode is uneven in thickness and more in defects, the weight of metal particles is mainly large, if the viscosity of slurry preparation is too large, the fluidity is poor, a film cannot be formed, and if the viscosity of the slurry is too small, the wall is difficult to hang, so that the defects and the thickness are uneven. The flat plate is coated without being influenced by gravity, and the preparation difficulty of the film layer is very small.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings of the prior art, solve the problems of defects and uneven thickness of a tubular metal membrane layer with a gradient pore diameter structure and provide a preparation method of a metal membrane with a gradient pore diameter structure.

In order to achieve the purpose, the invention adopts the following technical scheme: a preparation method of a metal membrane with a gradient pore diameter structure comprises the following specific steps:

the method comprises the following steps: mixing metal powder and a binder solution according to the mass ratio of 1 (2-5), and uniformly stirring to prepare slurry; the mass content of the binder is 0.2-2 wt%;

step two: uniformly preparing the slurry on a smooth flat plate by adopting a coating method, peeling a metal film blank from the flat plate after drying, and rolling the obtained metal film blank into a cylindrical shape to be tightly attached to the inner wall of a rigid outer die;

step three: forming a die by the rigid outer die, the elastic inner die and the elastic end enclosure, mixing two metal powders with different particle sizes in proportion, filling the mixture into a cavity between the rigid outer die and the elastic inner die, and removing the elastic inner die and the elastic end enclosure after cold isostatic pressing;

step four: and sintering the rigid outer die and the blank in a vacuum or inert atmosphere furnace, cooling, and removing the rigid outer die to obtain the asymmetric metal film.

Preferably, the metal powder in the first step is made of stainless steel, nickel, copper or titanium; the particle size of the metal powder is 0.5-50 μm; the binder solution is polyvinyl butyral, polymethyl cellulose or polyvinyl alcohol solution.

Preferably, the coating method in the second step is a spraying method or a doctor blade method. Preferably, the thickness of the metal film blank in the second step is 0.05-2 mm. Preferably, the two kinds of metal powder in the second step are both made of stainless steel, nickel, copper or titanium; the grain diameter of the large-grain diameter metal powder is 50-500 mu m, and the grain diameter of the small-grain diameter metal powder is 0.5-50 mu m; the size and the grain diameter are mixed according to the volume ratio of (1-10) to 1.

Preferably, the rigid outer mold in the third step is made of quartz, ceramic or corundum; the rigid elastic inner membrane and the elastic end socket are made of silica gel or rubber.

Preferably, the asymmetric metal obtained in step four has a thickness of 0.5 to 10 mm.

Preferably, the inert gas is argon or nitrogen; the vacuum is generally between 0.001 and 0.1Pa absolute.

Preferably, the sintering temperature is 800-1200 ℃, and the heat preservation time is 0.5-10 h; the heating rate is 1-5 ℃/min.

Has the advantages that:

according to the preparation method of the metal film with the gradient aperture structure, the film layer is prepared on the flat plate in advance through a coating method, so that the problems of defects, uneven thickness and the like of the film layer can be effectively reduced; the method can realize one-time co-sintering of the film layer and the substrate, and obviously reduce energy consumption.

Drawings

FIG. 1 is a schematic diagram of the structure of an asymmetric metal film blank and a preparation mold; wherein 1, the elastic inner mold; 2. an elastic end enclosure; 3. a metal powder; 4. a metal film blank; 5, a rigid external mold;

FIG. 2 is a metallographic image of a cross section of the metal film obtained in example 1;

FIG. 3 is a diagram showing the pore size distribution of the metal film obtained in example 1.

Detailed Description

The present invention will be described in detail with reference to specific examples. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

The following examples relate to asymmetric metal film blanks and preparation molds schematically shown in figure 1.

Example 1

1. 1g of polymethyl cellulose was dissolved in 80g of water, and 20g of stainless steel powder having an average particle size of 5 μm was slowly added thereto, followed by stirring for 24 hours to prepare a suspension. The slurry was uniformly applied to a smooth glass plate by a doctor blade method, the thickness of the cross-sectional metallographic image was about 0.058mm, and after drying at room temperature, the metal film blank was peeled off from the glass plate.

2. The obtained blank is rolled into a cylinder with the outer diameter of 50mm, and is placed in an outer mold of a quartz tube with the diameter of 70 x 10mm and is tightly attached to the inner wall of the quartz tube. Selecting a rubber tube with an elastic inner membrane of phi 40 x 10mm, fully and uniformly mixing stainless steel powder with the grain sizes of 100 microns and 5 microns according to the volume ratio of 10:1, filling the mixture into cavities of a rigid outer mold and an elastic inner mold, sealing two ends of the mixture by using rubber elastic end sockets (phi 50 x 10mm) after filling, and removing the elastic inner membrane and the elastic end sockets after cold isostatic pressing.

3. And (2) placing the obtained blank and the die into a high-temperature furnace to be sintered under the argon atmosphere, wherein the sintering temperature is 950 ℃, the heating rate is 1 ℃/min, the temperature is kept for 0.5h, cooling, taking out, and then removing the rigid external die to obtain the metal film with the gradient pore diameter structure (the section metallographic diagram of the metal film is shown in figure 1), the thickness of the metal film is 5mm, as can be seen from figure 2, the thickness of the separation layer with the highly asymmetric structure of the metal film is about 0.05mm, the average pore diameter is 0.4 mu m, the maximum pore diameter is 0.73 mu m, the minimum pore diameter is 0.12 mu m, and the pore diameter is mainly concentrated between 0.35 and 0.42 mu m.

Example 2

1. 2g of polymethyl cellulose is dissolved in 100 g of ethanol, 30g of titanium powder with the average particle size of 50 mu m is slowly added, and the mixture is stirred for 24 hours to prepare suspension. The slurry is evenly coated on a smooth glass plate by adopting a spraying method, the thickness of the glass plate is 1.96mm, and after the glass plate is dried at room temperature, the metal film blank is peeled off from the glass plate.

2. The obtained blank is rolled into a cylinder with the outer diameter of 60mm, and is placed in an external mold of a corundum tube with the diameter of 80 x 10mm and is tightly attached to the inner wall of the corundum tube. Selecting a silicone tube with an elastic inner membrane of phi 40 x 10mm, fully and uniformly mixing titanium powder with the grain sizes of 500 microns and 50 microns according to the volume ratio of 5:1, filling the mixture into cavities of the rigid outer mold and the elastic inner mold, sealing two ends of the mixture by using a silica gel elastic end socket (phi 60 x 15mm) after filling, and removing the elastic inner membrane and the elastic end socket after cold isostatic pressing.

3. And (3) placing the obtained blank and the die into a high-temperature furnace to be sintered in a nitrogen atmosphere, wherein the sintering temperature is 1200 ℃, the heating rate is 5 ℃/min, the temperature is kept for 10h, the blank is cooled and taken out, then the rigid outer die is removed, the metal film with the gradient pore diameter structure and the thickness of 10mm can be obtained, the thickness of a separation layer is obtained by observing through a metallographic microscope, the average pore diameter is 5.3 mu m and the maximum pore diameter is 12.6 mu m, and the pore diameter is mainly concentrated between 4 and 7 mu m.

Example 3

1. 0.5g of polyvinyl butyral is dissolved in 100 g of water, 50g of nickel powder with the average particle size of 0.5 mu m is slowly added, and the mixture is stirred for 24 hours to prepare suspension. And uniformly coating the slurry on a smooth glass plate by adopting a doctor blade method, wherein the thickness of the glass plate is 0.5mm, and stripping the metal film blank from the glass plate after the glass plate is dried at room temperature.

2. The obtained blank is rolled into a cylinder with the outer diameter of 30mm, and is placed in an external mold of a phi 50 x 10mm corundum tube to be tightly attached to the inner wall of the corundum tube. Selecting a silicone tube with an elastic inner film of phi 26 x 5mm, fully and uniformly mixing nickel powder with the particle sizes of 50 microns and 0.5 micron respectively according to the volume ratio of 1:1, filling the mixture into cavities of a rigid outer die and an elastic inner die, sealing two ends of the mixture by using a silicone elastic end socket (phi 60 x 15mm) after filling, and removing the elastic inner film and the elastic end socket after cold isostatic pressing.

3. And putting the obtained blank and the die into a high-temperature furnace for sintering under vacuum, wherein the absolute pressure is 0.01Pa, the sintering temperature is 800 ℃, the heating rate is 2 ℃/min, preserving heat for 5h, cooling, taking out, removing the rigid outer die to obtain the metal film with the gradient pore diameter structure and the thickness of about 2mm, observing through a metallographic microscope to obtain the thickness of a separation layer of about 0.2mm, and measuring the average pore diameter of 0.17 mu m and the maximum pore diameter of 0.39 mu m by using a bubble pressure method, wherein the pore diameter is mainly concentrated between 0.1 and 0.22 mu m.

Claims

1. A preparation method of a metal membrane with a gradient pore diameter structure comprises the following specific steps:

the method comprises the following steps: mixing metal powder and a binder solution according to a mass ratio of 1 (2-5), and uniformly stirring to prepare slurry; the mass content of the binder is 0.2-2 wt%;

step three: forming a die by the rigid outer die, the elastic inner die and the elastic end enclosure, mixing two metal powders with different particle sizes in proportion, filling the mixture into a cavity between the rigid outer die and the elastic inner die, and removing the elastic inner die and the elastic end enclosure after cold isostatic pressing; wherein the two kinds of metal powder are made of stainless steel, nickel, copper or titanium; the grain diameter of the large-grain diameter metal powder is 50-500 mu m, and the grain diameter of the small-grain diameter metal powder is 0.5-50 mu m; mixing the particle sizes according to the volume ratio of (1-10) to 1;

step four: and sintering the rigid external mold and the blank in a vacuum or inert atmosphere furnace, cooling, and removing the rigid external mold to obtain the asymmetric metal film.

2. The method of claim 1, wherein: the metal powder in the first step is made of stainless steel, nickel, copper or titanium; the particle size of the metal powder is 0.5-50 μm; the binder solution is polyvinyl butyral, polymethyl cellulose or polyvinyl alcohol solution.

3. The method of claim 1, wherein: and the coating method in the second step is a spraying method or a doctor blade method.

4. The method of claim 1, wherein: the thickness of the metal film blank in the second step is 0.05-2 mm.

5. The method of claim 1, wherein: the rigid outer mold in the third step is made of ceramic; the elastic inner die and the elastic end socket are made of rubber.

6. The production method according to claim 1, characterized in that: the thickness of the asymmetric metal film obtained in the fourth step is 0.5-10 mm.

7. The production method according to claim 1, characterized in that: the sintering temperature is 800-1200 ℃, and the heat preservation time is 0.5-10 h; the heating rate is 1-5 ℃/min.