A carbonized ceramic conductive film and a method for preparing the same

Abstract

The application provides a carbonized ceramic conductive film and a preparation method thereof, and relates to the technical field of conductive films.The application adopts phase inversion technology to dissolve polyacrylonitrile and mix the polyacrylonitrile with ceramic particles, to prepare a polyacrylonitrile polymer ceramic film precursor through phase inversion, and then to convert the polyacrylonitrile polymer in the ceramic film precursor into a graphite carbon structure with high conductivity through low-temperature pre-oxidation and high-temperature carbonization, so as to prepare the carbonized ceramic conductive film.The preparation method can adjust the film structure and the film hole size, significantly reduce the film resistance, and make the film have good mechanical properties and stability.

Description

Technical Field

[0001] This invention relates to the field of conductive film technology, and in particular to a carbide ceramic conductive film and its preparation method. Background Technology

[0002] Traditional nanofiltration and reverse osmosis membranes are effective at retaining small-sized pollutants but have low permeation flux. Traditional microfiltration and ultrafiltration membranes, while having high permeation flux, struggle to retain small-sized pollutants. This is because small-sized pollutants often carry different charges. Conductive membranes can introduce charges into the membrane surface and interior through an external power source, enhancing the electrostatic interaction between the membrane and small-molecule pollutants, thereby improving the membrane's retention capacity for these pollutants. This breaks the trade-off effect between the membrane's pollutant rejection rate and permeation flux, achieving both high flux and high small-molecule pollutant rejection performance.

[0003] Existing conductive films mainly fall into two categories: organic polymer conductive films and inorganic conductive films. The preparation of organic polymer conductive films primarily involves three methods: using conductive polymer materials, adding conductive materials to the material, and preparing a conductive functional layer on the surface. Polymer conductive films prepared using these methods generally suffer from high resistance due to the inherent insulation of the polymer, have few electrocatalytic sites, and are prone to damage and detachment of the surface conductive functional layer. Inorganic conductive films mainly include three types: metal films, carbon films, and conductive ceramic films. Traditional processes for preparing metal films, carbon films, and conductive ceramic films typically involve extrusion molding, leading to difficulties in controlling the film structure and poor mechanical properties. Furthermore, metal films and carbon films are easily electrochemically corroded and exhibit poor stability when used as electrochemical anodes. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a carbide ceramic conductive film and its preparation method. This method can adjust the film structure and pore size, while significantly reducing the film's resistance and giving it good mechanical properties and stability.

[0005] The method for preparing the conductive film of the carbide ceramic film of the present invention includes the following steps:

[0006] S1. Dissolve the polymer material in a solvent. After complete dissolution, add ceramic particles and stir until homogeneous to obtain the casting solution.

[0007] S2. After the casting solution is allowed to stand to remove bubbles, pour it onto a clean glass plate and scrape the film. Immediately after scraping, immerse the glass plate with the casting solution into the coagulation bath and wait for complete phase transformation.

[0008] S3. Remove the membrane that has undergone complete phase inversion from the coagulation bath, freeze it, and then vacuum dry it.

[0009] S4. After the dried film is cut, it is sandwiched between two layers of ceramic sheets for pre-oxidation. After pre-oxidation, it is carbonized at high temperature. After carbonization, it is naturally cooled to room temperature to obtain the carbonized ceramic conductive film.

[0010] Furthermore, the polymer material is one or more of polypropylene, polysulfone, polyacrylonitrile, polyimide, and polyvinylidene fluoride.

[0011] Preferably, the polymer material is polyacrylonitrile.

[0012] Furthermore, the solvent is one or more of DMAc, DMF, NMP, and DMSO.

[0013] Preferably, the solvent is DMF.

[0014] Furthermore, the ceramic particles are one or more of alumina, silicon dioxide, zirconium oxide, silicon carbide, and kaolin.

[0015] Preferably, the ceramic particles are alumina.

[0016] Furthermore, the polymer material content in the casting solution is 5wt%-20wt%, the ceramic particle content is 30wt%-50wt%, and the remainder is solvent.

[0017] Preferably, the casting solution contains 6.25 wt% polymer material, 37.5 wt% ceramic particles, and the remainder is solvent.

[0018] Furthermore, the coagulation bath is a pure water coagulation bath, an ethanol coagulation bath, or a mixed coagulation bath with an ethanol to water mass ratio of 3:7.

[0019] Preferably, when the pore structure of the carbide ceramic conductive film is finger-shaped, the coagulation bath is a pure water coagulation bath.

[0020] Preferably, when the pore structure of the carbide ceramic conductive film is a sponge-like pore, the coagulation bath is an ethanol coagulation bath.

[0021] Furthermore, the thickness of the film after scraping is 300-1000 μm.

[0022] Preferably, the thickness of the film after scraping is 550 μm.

[0023] Furthermore, the pre-oxidation is carried out in an air atmosphere, with a heating rate of 2℃ / min, a pre-oxidation temperature of 100℃-300℃, and a holding time of 150min.

[0024] Preferably, the pre-oxidation temperature is 230°C.

[0025] Furthermore, the high-temperature carbonization is carried out under a nitrogen atmosphere, with a heating rate of 3℃ / min, a high-temperature carbonization temperature of 800℃-1600℃, and a holding time of 60min.

[0026] Preferably, the high-temperature carbonization temperature is 1200°C.

[0027] The present invention also provides a carbide ceramic conductive film prepared according to the above method.

[0028] This invention employs phase inversion technology to first dissolve polyacrylonitrile and mix it with ceramic particles to prepare a polyacrylonitrile polymer ceramic membrane precursor. Then, after low-temperature pre-oxidation, high-temperature carbonization is carried out to transform the polyacrylonitrile polymer in the ceramic membrane precursor into a graphitic carbon structure with high electrical conductivity, thereby realizing the preparation of a carbonized ceramic conductive membrane and giving the carbonized ceramic membrane high electrical conductivity (resistance less than 20Ω) and high electrocatalytic performance.

[0029] This invention controls the pore size and structure of carbonized ceramic membranes by adjusting phase inversion process parameters. When pure water is used as the coagulation bath, the solvent-water exchange rate is fast, and instantaneous phase separation occurs on the membrane surface during the phase inversion process. A difference in deposition rate between the polymer phase inside and on the surface results in an asymmetric membrane structure with a dense surface and finger-like macropores inside. When ethanol is used as the coagulation bath, the solvent-ethanol exchange rate is relatively slow, allowing for delayed phase separation during the phase inversion process. The difference in deposition rate between the polymer phase on the membrane surface and inside is smaller, resulting in a sponge-like pore structure similar to the surface and interior. As the amount of polymer material added increases, the viscosity of the casting solution increases, leading to a denser membrane formed by the phase inversion. The increased graphite carbon produced after carbonization further contributes to the density of the carbonized ceramic membrane. By controlling the choice of the phase inversion coagulation bath and the amount of polymer material added, the membrane pore size can be controlled between 180-400 nm, the porosity between 65%-80%, and the membrane structure between sponge-like and finger-like pores.

[0030] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0031] The conductive membrane of the carbide ceramic membrane of this invention, coupled with an external power source, not only possesses high permeation flux but also exhibits excellent removal performance for small molecule pollutants. Furthermore, the carbide ceramic membrane prepared by this invention has an adjustable membrane structure, pore size, low resistivity, and good mechanical properties and stability. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 The images shown are SEM images of the surface morphology of the carbide ceramic conductive film in Examples 1-6 of this invention.

[0034] Figure 2 The images shown are SEM images of the cross-sectional morphology of the carbide ceramic conductive films in Examples 1-6 of this invention.

[0035] Figure 3 The carbonized ceramic conductive film resistors are those described in Examples 1-6 of this invention;

[0036] In the diagram, the number after M represents the amount of polyacrylonitrile added, H represents the pure water phase conversion, and E represents the ethanol phase conversion. Detailed Implementation

[0037] The technical solution provided by the present invention will be further described below with reference to the embodiments.

[0038]

[0039]

[0040] The preparation methods of Examples 1-6 are as follows:

[0041] In a ball mill jar, polyacrylonitrile is dissolved in DMF. After complete dissolution, alumina particles are added, and an appropriate amount of grinding balls are added. The mixture is then ball milled and stirred at 300 r / min for 48 h to ensure uniform mixing of the casting solution.

[0042] After the mixture is completely mixed, remove the ball mill jar and place it in an ultrasonic machine for ultrasonication for 30 minutes. Then let it stand for more than 4 hours to ensure complete degassing.

[0043] Pour the degassed casting solution onto a clean, flat glass plate. Use a scraper to adjust the thickness to 550 μm and scrape the film. Then place the glass plate in a pure water or ethanol coagulation bath for 24 hours to ensure complete phase inversion.

[0044] After the phase inversion is complete, the membrane is removed, placed in a freezer and frozen completely, and then placed in a freeze dryer for drying.

[0045] After drying, the membrane is removed and cut into 28mm diameter sheets. The sheets are sandwiched between two ceramic plates and placed in a tube furnace. Under air atmosphere, the membrane is heated to 230℃ at a heating rate of 2℃ / min and held for 150 minutes. It is then allowed to cool naturally to room temperature. Next, in a tube furnace under nitrogen atmosphere, the temperature is raised to 1200℃ at a controlled heating rate of 3℃ / min, held for 60 minutes, and then allowed to cool naturally to room temperature to obtain a carbonized ceramic conductive film.

[0046] pass Figure 1 and Figure 2 It can be seen that the present invention can control the membrane pore size and membrane structure by adding polyacrylonitrile and selecting the coagulation bath. The prepared carbonized ceramic membrane has high conductivity and low resistance. When the carbonization temperature reaches 1200℃, the resistance of the carbonized ceramic membrane is less than 20Ω.

[0047] Test Example 1

[0048] The dye retention performance of the conductive membranes in Examples 1-6 was tested using Congo Red (CR), Rhodamine b (Rhb), Methylene Blue (MB), and Methyl Orange (MO) dye solutions. The dye concentration in the dye solutions was 20 mg / L, and the sodium sulfate concentration was 7.2 g / L. Under an applied voltage of 1.5 V, the membrane was used as a filtration unit and simultaneously as an anode to filter and remove the dye solutions. The absorbance of the CR, Rhb, MB, and MO dye solutions and the filtrate at wavelengths of 498 nm, 554 nm, 592 nm, and 464 nm was measured using a UV spectrophotometer. The dye retention rate was calculated, and the results are as follows:

[0049] Sample naming Pure water flux Average removal rate of four dyes Example 1 14133LMH / bar 97.6％ Example 2 8213 LMH / bar 99.5％ Example 3 6404 LMH / bar 99.5％ Example 4 2577.5 LMH / bar 99.5％ Example 5 1610 LMH / bar 99.8％ Example 6 977LMH / bar 99.8％

[0050] Comparative Example 1

[0051] A method for preparing an organic polymer conductive film:

[0052] Carbon nanotubes and polyvinylidene fluoride (PVDF) cohexafluoropropylene were mixed at a mass ratio of 1:1, and nano-zeolite (60% of the mass of the carbon nanotubes) was added. The mixture was then ultrasonically dispersed in a water-ethanol (1:1 volume ratio) solvent for 10 min. The resulting dispersion was then vacuum filtered onto filter paper and treated at 160℃ for 1 h to integrate PVDF cohexafluoropropylene into the nano-zeolite and carbon nanotube structures. The membrane was then removed and tested. The results are as follows:

[0053] The membrane has a pore size of 50 nm, a resistance of 200 Ω, a porosity of 40%, a pure water flux of 210 LMH / bar, and a dye removal rate of 60% at 1.5V.

[0054] Comparative Example 2

[0055] A method for preparing an organic polymer-ceramic composite conductive film:

[0056] The ceramic support layer was immersed in a solution of reduced graphene oxide (5wt%), polypyrrole (30wt%), and ethanol (65wt%) at 40℃ for 30 min, and then heated at 110℃ for 4 h to enhance the bonding force between the ceramic support and the reduced graphene oxide. After that, the film was removed for testing, and the results are as follows:

[0057] The membrane has a pore size of 300 nm, a resistance of 1 KΩ, a porosity of 50%, a pure water flux of 3523 LMH / bar, and a dye removal rate of 12% at 1.5V.

[0058] Comparative Example 3

[0059] A method for preparing an organic polymer conductive film

[0060] First, 0.36 g of zinc acetate and 0.24 g of urea were dissolved in a mixture of 160 mL of deionized water and 24 mL of ethanolamine. The solution was ultrasonically dispersed for 1 h to obtain a homogeneous solution. Then, 0.04 g of reduced graphene oxide (rGO) was added to the solution and ultrasonically dispersed. The solution was heated at 120 °C for 12 h in a hydrothermal reactor. The collected gray precipitate was washed by centrifugation and finally dried at 60 °C to obtain rGO-ZnO.

[0061] 16% polysulfone, 1% polyvinylpyrrolidone, and 1.5% rGO-ZnO (based on the amount of polysulfone) were added to DMAc (83%). The mixture was ultrasonically dispersed at 60 W for 30 min, then stirred at 60 °C until a homogeneous casting solution was obtained. A film was scraped onto a clean glass plate and subjected to phase inversion in a pure water coagulation bath. The film was then removed and tested. The results are as follows:

[0062] The membrane has a pore size of 78 nm, a resistance of 405 Ω, a porosity of 60%, a pure water flux of 283 LMH / bar, and a dye rejection rate of 40% at 1.5V.

[0063] Comparative Example 4

[0064] A method for preparing a carbon conductive film

[0065] Coal was ground into fine particles (4μm), then mixed with polyvinyl alcohol binder (5wt%), and extruded into a 30mm diameter membrane under a hydraulic press pressure of 3MPa. After drying in air, the membrane was carbonized in argon at 900℃ for 1 hour. The final product was then naturally cooled to room temperature for testing, and the results are as follows:

[0066] The membrane has a pore size of 500 nm, a resistivity of 18 Ω, a porosity of 43.8%, a pure water flux of 632 LMH / bar, and a dye rejection rate of 70% at 1.5V.

[0067]

[0068] Test Example 2

[0069] The dye rejection performance of the conductive membrane in Comparative Example 5-8 was tested using dye solutions of Congo Red (CR), Rhodamine b (Rhb), Methylene Blue (MB), and Methyl Orange (MO). The dye concentration in the dye solution was 20 mg / L, and the dye solution was prepared with 7.2 g / L sodium sulfate. Under an applied voltage of 1.5 V, the membrane was used as a filter unit and simultaneously as an anode to filter and remove the dye solution. The dye rejection rate was calculated, and the results are as follows:

[0070]

[0071]

[0072] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a carbonized ceramic conductive film, characterized in that, Includes the following steps: S1. Dissolve the polymer material in dimethylformamide. After complete dissolution, add ceramic particles and stir evenly to obtain the casting solution. S2. After the casting solution is allowed to stand and degas, it is poured onto a clean glass plate for coating. After coating, the glass plate with the casting solution is immediately immersed in a coagulation bath until the phase transformation is complete. The thickness of the coating after coating is 300-1000 μm. S3. Remove the membrane that has undergone complete phase inversion from the coagulation bath, freeze it, and then vacuum dry it. S4. After the dried film is cut, two ceramic sheets are used to sandwich the film in the middle for pre-oxidation. After pre-oxidation, high-temperature carbonization is carried out. After carbonization, the film is naturally cooled to room temperature to obtain the carbonized ceramic conductive film. The coagulation bath is a pure water coagulation bath or an ethanol coagulation bath; The pre-oxidation is carried out in an air atmosphere, with a heating rate of 2℃ / min, a pre-oxidation temperature of 100℃-300℃, and a holding time of 150 min. The high-temperature carbonization was carried out under a nitrogen atmosphere, with a heating rate of 3℃ / min, a high-temperature carbonization temperature of 1200℃, and a holding time of 60 min.

2. The method for preparing a carbide ceramic conductive film according to claim 1, characterized in that, The polymer material is one or more of polypropylene, polysulfone, polyacrylonitrile, polyimide, and polyvinylidene fluoride.

3. The method for preparing a carbide ceramic conductive film according to claim 1, characterized in that, The ceramic particles are one or more of alumina, silicon dioxide, zirconium oxide, silicon carbide, and kaolin.

4. The method for preparing a carbide ceramic conductive film according to claim 1, characterized in that, The casting solution contains 5wt%-20wt% polymer material, 30wt%-50wt% ceramic particles, and the remainder is solvent.

5. A carbonized ceramic conductive film, characterized in that, Prepared by the method described in any one of claims 1-4.

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