Preparation method of porous conductive ceramic carrier through hydrogen fluoride gas phase etching

Abstract

According to the method for preparing the porous conductive ceramic carrier through hydrogen fluoride gas phase etching, the conductive ceramic is etched through hydrogen fluoride generated through decomposition of ammonium fluoride in a tubular furnace, so that pore forming is achieved, the size and distribution of pores are accurately controlled, and a more uniform pore structure is obtained; the method has the advantages of being environment-friendly, simple and convenient to operate, controllable in pore structure and the like, is suitable for various conductive ceramic materials, and provides an effective way for optimizing the pore structure of the conductive ceramic carrier material for the fields of energy conversion, storage and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of the regulation of porous conductive ceramic carriers, and particularly relates to a preparation method of a porous conductive ceramic carrier by using hydrogen fluoride gas-phase etching. Background Art

[0002] In recent years, creating pores on the surface of catalyst carriers to increase their specific surface area has become an effective means to improve the performance of catalysts. The porous structure can significantly increase the specific surface area, thereby providing more active sites and enhancing the mass transfer efficiency, which is crucial for the performance of catalysts. Nano-conductive ceramics have become one of the commonly used catalyst carriers due to their excellent properties such as corrosion resistance, conductivity, and high-temperature resistance. However, there are certain challenges in creating pores on the surface of ceramic materials, and traditional pore-forming methods have many limitations. For example, the high-temperature calcination pore-forming method forms pores by decomposing pore-forming agents during the sintering process, but it is difficult to achieve uniform distribution of pores, which may lead to inconsistencies in porosity and pore size. The chemical corrosion method may pollute the environment and is difficult to control. The sol-gel method forms pores through solvent evaporation and gel aging, but it is difficult to control the pore structure and size, and the process is relatively cumbersome. The pore size and shape of the freeze-drying method are greatly affected by the freezing conditions and are difficult to precisely control. Therefore, there is an urgent need to develop new methods for creating pores in conductive ceramic carriers to overcome the deficiencies of existing methods. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a preparation method of a porous conductive ceramic carrier by using hydrogen fluoride gas-phase etching in view of the above problems, generating hydrogen fluoride at high temperature by ammonium fluoride, and etching the conductive ceramic in a tube furnace to achieve the pore-forming effect.

[0004] The embodiments of the present application are implemented as follows: The embodiments of the present application provide a preparation method of a porous conductive ceramic carrier by using hydrogen fluoride gas-phase etching, which is characterized by including the following steps: Step a, align and stick a long crucible with a lid and a short crucible without a lid with transparent silicone glue, and place them in an oven to dry and remove moisture; Step b, weigh an appropriate amount of conductive ceramic and place it evenly on the lid of the long crucible, and place an appropriate amount of ammonium fluoride in the short crucible; Step c, push the prepared crucibles into the tube furnace, continuously introduce argon into the tube furnace, and maintain an appropriate flow rate; Step d, according to the set temperature-rising program of the tube furnace, maintain a certain initial temperature for a certain period of time to remove the air inside the furnace, thereby maintaining an argon environment, raise the temperature at a certain rate, reach 190 - 200 °C, maintain a sufficient reaction time, and then start the temperature-lowering program; Step e: After the tubular furnace has cooled down to room temperature, turn off the argon gas, take out the crucible, collect the conductive ceramics on the long crucible cover, add them to hydrochloric acid, then add a magnetic rotor, stir with a magnetic stirrer, and then centrifuge. After washing and centrifuging several times with water, put the sample into an oven, evacuate it, and dry it overnight to obtain a porous conductive ceramic support.

[0005] In some alternative embodiments, the crucible described in step a is a high-temperature resistant alumina crucible.

[0006] In some alternative embodiments, the argon gas flow rate in step c is based on the number of bubbles generated in the anti-backflow bottle.

[0007] In some alternative embodiments, the initial temperature in step d is 25 - 30 °C and is maintained for 30 - 45 min.

[0008] In some alternative embodiments, the heating rate in step d is 5 °C per minute.

[0009] In some alternative embodiments, the reaction time in step d is 30 min - 1 h.

[0010] In some alternative embodiments, the mass concentration of the hydrochloric acid described in step e is 37%, and the mass ratio of the conductive ceramics to the hydrochloric acid is 1:1.

[0011] In some alternative embodiments, the stirring duration of the magnetic stirrer in step e is 1 - 2 h.

[0012] In some alternative embodiments, the operating temperature of the oven described in step a is 105 - 190 °C, and the drying duration is 2 - 3 h.

[0013] In some alternative embodiments, the argon gas flow rate is 1 - 2 bubbles generated per second in the anti-backflow bottle.

[0014] The beneficial effects of this application are as follows: 1. A preparation method of a porous conductive ceramic support using hydrogen fluoride gas-phase etching provided by this application adopts a pore-forming technology for conductive ceramic supports based on hydrogen fluoride gas phase. We can etch the required pore structure by controlling the reaction time or the amount of reactants, which can not only significantly increase the specific surface area of the conductive ceramic support, but also enhance the dispersion of the catalyst and improve its loading capacity; 2. It can be carried out at a relatively low temperature, avoiding the possible destruction of the material structure caused by high temperature, and at the same time, it can more precisely control the size and distribution of the pores to obtain a more uniform pore structure; 3. It does not produce harmful by-products and is applicable to a variety of conductive ceramic materials, having a wide range of application prospects; by optimizing the pore structure, the loading capacity of the catalyst can be significantly improved, enabling it to play a greater role in fields such as energy conversion and storage. Description of the Drawings

[0015] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for the embodiments will be briefly introduced below. It should be understood that the following accompanying drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related accompanying drawings can also be obtained based on these drawings.

[0016] Figure 1a 、 Figure 1b are respectively the effect diagrams before and after gas-phase etching in Embodiment 2 of the present application; Figure 2 is the nitrogen adsorption-desorption isotherm and the pore size distribution diagram of zirconium carbide before and after hydrogen fluoride treatment in Embodiment 2 of the present application. Detailed Embodiments

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in 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. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0019] It should be understood that the magnitudes of the sequence numbers of the steps in the embodiments do not mean the order of execution. The execution order of each process should be determined by its function and internal logic and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0020] It should be noted that similar reference numerals and letters indicate similar items in the following accompanying drawings. Therefore, once an item is defined in one accompanying drawing, it does not need to be further defined and explained in subsequent accompanying drawings.

[0021] The features and performance of the present application will be further described in detail below in combination with the embodiments.

[0022] Aiming at the defects of the existing methods for creating pores in catalyst carriers, a method for creating pores based on gas-phase corrosion of conductive ceramic carriers by hydrogen fluoride is provided, which can provide porous nano-conductive ceramic carrier materials.

[0023] Embodiment 1 Taking zirconium carbide conductive ceramic as an example.

[0024] A method for preparing a conductive ceramic porous carrier by using hydrogen fluoride vapor etching, the specific steps are as follows: 1) Use transparent silicone glue to align and stick a 100×30×15mm long crucible with a lid and a 30×20×15mm short crucible without a lid, put them in an oven at 105℃ for 2 hours to remove moisture, and then let them cool to room temperature.

[0025] 2) Weigh 0.13g of zirconium carbide and place it on the long crucible cover, spread it evenly, and put 0.35g of ammonium fluoride in the short crucible. Ammonium fluoride can continuously decompose hydrogen fluoride during the high temperature period.

[0026] 3) Push the crucible prepared in step 2) into the tube furnace, and continuously introduce argon gas into the tube furnace. The argon flow rate depends on the number of bubbles generated in the anti-backflow bottle, and about one bubble per second is sufficient. Control the argon flow rate to ensure that the hydrogen fluoride has enough time to contact and etch the conductive ceramic, so that it will not be quickly carried out by the argon gas and not be etched in time.

[0027] 4) Set the temperature program of the tube furnace, keep it at 25℃ for 30 minutes to remove the air inside the furnace, so as to maintain the argon environment, and heat it at a rate of 5℃ per minute to 190℃, keep it at 190℃ for 30 minutes, and then start the cooling program. The temperature program reacts at 190℃, because at this temperature ammonium fluoride begins to decompose hydrogen fluoride, and it is maintained for a sufficient reaction time. 5) When the tube furnace cools to room temperature, turn off the argon gas, carefully take out the crucible, collect the conductive ceramic on the long crucible cover, add it to 37% hydrochloric acid, the mass ratio of the two is 1:1, then add the rotor, stir with a magnetic stirrer for 2 hours. The conductive ceramic pickling process is to remove impurities and obtain clean conductive ceramics. After pickling, centrifuge, wash with water and centrifuge several times, put the sample into an oven for vacuum, and dry it at 60°C overnight to obtain a porous zirconium carbide conductive ceramic carrier.

[0028] Example 2 Take zirconium carbide conductive ceramics as an example.

[0029] A method for preparing a conductive ceramic porous carrier by using hydrogen fluoride vapor etching, the specific steps are as follows: 1) Use transparent silicone glue to align and stick a 100×30×15mm long crucible with a lid and a 30×20×15mm short crucible without a lid, put them in an oven at 105℃ for 2 hours to remove moisture, and then let them cool to room temperature.

[0030] 2) Weigh 0.13g of zirconium carbide and place it on the lid of the long crucible, spreading it evenly. Put 0.55g of ammonium fluoride in the short crucible.

[0031] 3) Push the crucible prepared in step 2) into the tube furnace, continuously introduce argon into the tube furnace, and adjust the argon flow rate according to the number of bubbles generated in the anti-backflow bottle, about 1 bubble per second is fine.

[0032] 4) Set the heating program of the tube furnace. Keep it at 25°C for 30 minutes to remove the air inside the furnace, so as to maintain an argon environment. Then heat it at a rate of 5°C per minute until it reaches 190°C, and keep it at 190°C for 1 hour. Then start the cooling program. 5) When the tube furnace cools down to room temperature, turn off the argon, carefully take out the crucible, collect the conductive ceramics on the long crucible cover, add them to hydrochloric acid with a mass concentration of 37%, with a mass ratio of 1:1 between them. Then add a rotor, stir with a magnetic stirrer for 2 hours, and then centrifuge. After washing and centrifuging several times with water, put the sample into an oven, evacuate it, and dry it overnight at 60°C to obtain a porous zirconium carbide conductive ceramic support.

[0033] Figure 1a and Figure 1b are schematic diagrams of the conductive ceramics before and after hydrogen fluoride treatment. From Figure 1a , Figure 1b it can be observed that the appearance of the conductive ceramic support treated by hydrogen fluoride gas phase has no obvious change, and it remains in powder form before and after treatment. Comparative analysis was carried out on zirconium carbide before and after hydrogen fluoride treatment, and the results are shown in detail in Figure 2 . We evaluated the effect of hydrogen fluoride treatment on the surface structural characteristics of zirconium carbide powder through nitrogen adsorption-desorption isotherm tests and BET analysis. Zirconium carbide treated by hydrogen fluoride showed a higher porosity and a specific pore structure in the adsorption-desorption isotherm test. According to the data in Table 1, the specific surface area of zirconium carbide after hydrogen fluoride treatment increased significantly from 46 m2 / g to 83 m2 / g. The pore size distribution diagram determined by BJH analysis shows that the pore volume increased significantly in the range of 3 - 4 nm, especially reaching the maximum value at about 3.6 nm (see the inset in Figure 2 ), indicating that pores of about 3.6 nm were successfully created.

[0034] Table 1 Comparison of specific surface area of zirconium carbide conductive ceramics before and after hydrogen fluoride gas phase treatment

Claims

1. A method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching, characterized in that: The steps include: Step a, aligning and gluing a long crucible with a cover and a short crucible without a cover with transparent silicone glue, and placing them in an oven to dry and remove moisture; Step b, weighing an appropriate amount of conductive ceramic and placing it on the long crucible cover, spreading it evenly, and placing an appropriate amount of ammonium fluoride in the short crucible; Step c, pushing the prepared crucible into a tube furnace, and continuously introducing argon gas into the tube furnace at a proper flow rate; Step d, according to the setting of the tubular furnace heating program, the initial temperature is maintained for a certain period of time to remove the air inside the furnace, thereby maintaining the argon environment, and the temperature is increased at a certain rate to reach 190-200°C, and sufficient reaction time is maintained, and then the cooling program is started; Step e, when the tube furnace is cooled to room temperature, the argon gas is turned off, the crucible is taken out, the conductive ceramic on the long crucible cover is collected, added to hydrochloric acid, and then a magnetic rotor is added, stirred with a magnetic stirrer, and then centrifuged. After washing and centrifuging several times, the sample is placed in an oven for evacuation and dried overnight to obtain a porous conductive ceramic carrier.

2. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 1, characterized in that: The crucible described in step a is an alumina high temperature resistant crucible.

3. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 1 or 2, characterized in that: The argon gas flow rate described in step c is based on the number of bubbles generated in the anti-backflow bottle.

4. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 3, characterized in that: The initial temperature in step d is 25-30° C. and maintained for 30-45 min.

5. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 4, characterized in that: The heating rate in step d is 5° C. per minute.

6. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 5, characterized in that: The reaction time in step d is 30 min-1 h.

7. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 6, characterized in that: The mass concentration of the hydrochloric acid in step e is 37%, and the mass ratio of the conductive ceramic to the hydrochloric acid is 1:

1.

8. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 7, characterized in that: The stirring time of the magnetic stirrer described in step e is 1-2h.

9. The method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching according to claim 1 or 8, characterized in that: The working temperature of the oven described in step a is 105-190° C., and the drying time is 2-3 hours.

10. A method for using the method for preparing a porous conductive ceramic carrier using hydrogen fluoride vapor etching as claimed in claim 3, characterized in that: The argon gas flow rate is such that 1-2 bubbles are generated in the anti-backflow bottle in 1 second.

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