Ceramic precursor and method for microwave field enhanced synthesis of ceramic precursor, applications

Abstract

This invention provides a method and application for synthesizing ceramic precursors using microwave field enhancement. The method includes: uniformly and densely mixing metal oxide powder and microwave absorbing medium powder to obtain a composite material; subjecting the composite material to microwave irradiation under a CO2 atmosphere at a temperature range of 300°C to 500°C; and cooling after the microwave irradiation reaction to obtain the ceramic precursor. This method is the first to propose and realize a novel approach for synthesizing ceramic precursors by directly conducting a large-scale solid-phase reaction between flowing CO2 and solid metal oxides under microwave field assistance and low-temperature (300°C to 500°C) conditions. Utilizing the unique effect of the microwave field, the method precisely activates oxygen or defect sites in the metal oxide lattice, significantly improving the solid-gas reaction rate and efficiency; and achieving one-step synthesis of ceramic precursors with specific morphology, high specific surface area, and uniform composition.

Description

Technical Field

[0001] This invention belongs to the field of ceramic material preparation technology, specifically relating to a method and application of ceramic precursor and microwave field-enhanced synthesis of ceramic precursor. Background Technology

[0002] Traditional methods for preparing carbonate or ceramic precursors utilize solid-state reactions of CO2 with metal oxides (such as ZnO, ZrO2, and Al2O3), typically requiring high temperatures (often above 600°C to 800°C) and long reaction times. High temperatures easily lead to coarsening of product particles, severe agglomeration, and a decrease in specific surface area, and also result in high energy consumption, which is detrimental to obtaining highly reactive nanomaterials. Solution methods (such as coprecipitation and hydrothermal methods) can synthesize precursors at lower temperatures, but these processes are usually complex, involving solvent use and post-processing, potentially introducing impurities, and making it difficult to achieve the preparation of certain special phases or morphologies. Large-scale production also faces cost and environmental pressures. Microwave heating, a bulk heating method, offers advantages such as rapid, uniform, and selective heating with high energy efficiency. It can directly couple to the dipoles or ions of materials, inducing internal molecular frictional heating, thereby potentially activating reactants at the molecular / atomic scale and lowering the reaction activation energy. Currently, there are no publicly available reports on using the bulk heating and selective heating characteristics of microwave fields specifically to drive the direct and efficient solid-phase carbonization / carbonation reaction of CO2 and solid metal oxides at low temperatures (<500°C) to prepare ceramic precursors with special microstructures and high sintering activity in a one-step process.

[0003] To address the aforementioned issues, it is necessary to propose a method and application for designing a reasonably sound and effective ceramic precursor and for microwave field-enhanced synthesis of ceramic precursors. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a method and application for the synthesis of ceramic precursors and microwave field-enhanced ceramic precursors.

[0005] One aspect of the present invention provides a method for microwave field-enhanced synthesis of ceramic precursors, the method comprising: Step 1: The metal oxide powder and the microwave absorbing medium powder are uniformly and densely physically mixed to obtain the composite material; Step 2: The composite raw material is subjected to microwave irradiation reaction under CO2 atmosphere protection at a temperature range of 300°C to 500°C; Step 3: After completing the microwave irradiation reaction, the mixture is cooled to obtain the ceramic precursor.

[0006] Optionally, the microwave irradiation reaction in step two can be carried out for a period of 10 min to 2 h.

[0007] Optionally, the mass ratio of the metal oxide powder to the microwave absorbing medium powder in step one is in the range of 1:(0.1 ~ 2).

[0008] Optionally, step two specifically includes: The composite material is placed in a ball mill equipped with a microwave emitter and subjected to microwave irradiation reaction under a continuously or intermittently flowing CO2 atmosphere.

[0009] Optionally, the metal oxide powder includes zinc oxide powder or aluminum oxide powder.

[0010] Optionally, the microwave absorbing medium powder includes silicon carbide powder or activated carbon powder.

[0011] Optionally, after completing step three, the method further includes: The microwave absorbing medium is removed from the ceramic precursor by acid washing or heat treatment.

[0012] Optionally, the particle size of the metal oxide powder in step one is submicron, and the particle size of the microwave absorbing medium powder is similar to or slightly larger than that of the metal oxide powder.

[0013] Another aspect of the present invention provides a ceramic precursor, which is prepared by the microwave field-enhanced synthesis method for ceramic precursors described above.

[0014] The application of a ceramic precursor as described above in the preparation of functional ceramics or functional materials.

[0015] This invention provides a method and application for synthesizing ceramic precursors using microwave field enhancement. This method, for the first time, proposes and realizes a novel approach to synthesizing ceramic precursors by directly reacting flowing CO2 with solid metal oxides under microwave field assistance and low-temperature (300°C ~ 500°C) conditions, achieving large-scale solid-phase reaction. Utilizing the unique effect of the microwave field, it precisely activates lattice oxygen or defect sites in the metal oxide, significantly improving the solid-gas reaction rate and efficiency. It synthesizes ceramic precursors with specific morphology, high specific surface area, and uniform composition in a one-step process. By introducing a composite raw material of microwave-absorbing medium and metal oxide, the efficient absorption and conversion of microwave energy by the medium creates a localized high-temperature field around the reactant particles, potentially generating plasma. This precisely and selectively activates lattice oxygen or defects on the surface of the metal oxide, thereby achieving efficient adsorption and activation conversion of CO2 molecules at an overall low temperature. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a method for synthesizing ceramic precursors using microwave field strengthening, according to an embodiment of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, one aspect of the present invention provides a method S100 for microwave field-enhanced synthesis of ceramic precursors, the method comprising: Step 1: The metal oxide powder and the microwave absorbing medium powder are uniformly and densely mixed to obtain the composite material.

[0019] Specifically, the metal oxide powder and the microwave absorbing medium powder are uniformly and densely physically mixed at a mass ratio ranging from 1:(0.1 to 2) to form a composite material. The metal oxide powder has a submicron particle size, and the microwave absorbing medium powder has a particle size similar to or slightly larger than that of the metal oxide powder to ensure uniform mixing.

[0020] In this embodiment, by controlling the mass ratio of metal oxide to microwave absorbing medium to be 1:0.1 to 1:2, both microwave absorption efficiency and uneven heating caused by excessive dilution of reactants or insufficient absorption medium are ensured.

[0021] In step one, the metal oxide powder may include zinc oxide powder or aluminum oxide powder. Of course, the metal oxide can be other types; this embodiment does not impose specific limitations and selection can be made as needed. Using zinc oxide or aluminum oxide as the metal oxide raw material is representative and widely applicable. Both are common basic raw materials for functional ceramics, and the synthesized precursors can be used to prepare high-hardness, high-stability ceramic materials, such as ZnO-based antibacterial materials or Al2O3-based structural ceramics, expanding the application scope of this method.

[0022] In step one, the microwave absorbing medium powder may include silicon carbide powder or activated carbon powder. Similarly, other types of microwave absorbing media can also be used; this embodiment does not impose specific limitations and selection can be made according to actual needs. Silicon carbide and activated carbon, as microwave absorbing media, possess excellent microwave coupling ability and thermal stability. They can rapidly heat up in a microwave field, forming localized high-temperature hotspots, activating the oxide surface, promoting CO2 adsorption and conversion, and are easily removed in post-processing, ensuring product purity.

[0023] Preferably, in this embodiment, the microwave absorbing medium is silicon carbide, whose particle size is similar to or slightly larger than that of metal oxides, to ensure uniform mixing.

[0024] In this embodiment, a microwave absorbing medium with submicron-sized metal oxides and matching particle size was selected to ensure mixing uniformity and interfacial contact efficiency. Similar particle sizes help to form a uniform local thermal field, avoiding uneven heating or incomplete reaction caused by particle size differences, and improving the consistency of product structure.

[0025] Step 2: The composite raw material is subjected to microwave irradiation reaction under CO2 atmosphere protection at a temperature range of 300°C to 500°C.

[0026] Specifically, the composite raw material is placed in a ball mill equipped with a microwave emitter. Through programmed temperature control, the reaction system is rapidly heated and maintained within the target temperature range of 300°C to 500°C. The microwave irradiation reaction is carried out under a continuously or intermittently flowing CO2 atmosphere. The duration of the microwave irradiation reaction ranges from 10 minutes to 2 hours.

[0027] The composite raw materials were placed in a ball mill equipped with a microwave emitter and reacted under a flowing CO2 atmosphere, achieving dual enhancement through microwave heating and mechanical stirring. The ball milling process helps to continuously update the reaction interface, prevent particle agglomeration, improve gas-solid contact efficiency, and further accelerate the carbonization reaction rate. Limiting the microwave irradiation reaction time to 10 minutes to 2 hours ensures sufficient reaction while avoiding over-burning or structural damage to the product due to excessive time. The short reaction time helps maintain the nanostructure and morphology of the product, improves production efficiency, and is suitable for continuous industrial production.

[0028] This step provides a method for the direct reaction of CO2 as a carbon source with metal oxides at temperatures far below conventional solid-state reaction temperatures, specifically between 300°C and 500°C. Utilizing the unique effect of a microwave field, the method precisely activates oxygen or defect sites in the metal oxide lattice, significantly improving the solid-gas reaction rate and efficiency. This one-step method synthesizes carbonate / basic carbonate precursors with specific morphologies (e.g., porous, plate-like), high specific surface area, and uniform composition.

[0029] Step 3: After completing the microwave irradiation reaction, the mixture is cooled to obtain the ceramic precursor.

[0030] Specifically, after the microwave irradiation reaction is completed, the mixture is cooled in an inert atmosphere or air to obtain a ceramic precursor (i.e., a metal carbonate or a basic carbonate). Then, the microwave absorbing medium is removed by acid washing or heat treatment to further obtain a pure precursor powder.

[0031] In this step, the microwave-absorbing medium is removed by acid washing or heat treatment, ensuring the purity of the final ceramic precursor. This step is simple and controllable, suitable for the separation needs of different media, and facilitates direct use in subsequent ceramic sintering or functional material preparation, thereby enhancing the application value of the product.

[0032] This invention provides a method for synthesizing ceramic precursors using a microwave field-enhanced approach. This method, for the first time, proposes and implements a novel approach for synthesizing ceramic precursors through large-scale solid-phase reactions of flowing CO2 and solid metal oxides under microwave field assistance and low-temperature (300°C ~ 500°C) conditions. Utilizing the unique effect of the microwave field, it precisely activates lattice oxygen or defect sites in the metal oxide, significantly improving the solid-gas reaction rate and efficiency. It achieves one-step synthesis of ceramic precursors with specific morphology, high specific surface area, and uniform composition. By introducing a composite material of microwave-absorbing medium and metal oxide, the efficient absorption and conversion of microwave energy by the medium creates a localized high-temperature field around the reactant particles, potentially generating plasma. This precisely and selectively activates lattice oxygen or defects on the surface of the metal oxide, thereby achieving efficient adsorption and activation conversion of CO2 molecules at an overall low temperature.

[0033] Another aspect of the present invention provides a ceramic precursor, which is prepared using the microwave field-strengthened synthesis method S100 described above. The specific steps of this microwave field-strengthened synthesis method S100 have been described in detail above and will not be repeated here.

[0034] In this embodiment, the ceramic precursor prepared by the method of the present invention has a high specific surface area, uniform composition, and special microstructure (such as porous and lamellar), exhibiting excellent structural stability and reactivity. This precursor is suitable for subsequent low-temperature sintering to prepare high-performance nanoceramics, or can be used directly as a functional material.

[0035] The ceramic precursor prepared by this invention can be used to prepare nano-ceramic powders with high sintering activity, or directly used as functional materials (such as antibacterial agents and ultraviolet shielding agents), realizing the high added value transformation of raw materials into functional materials.

[0036] The following specific embodiments illustrate the detailed process of the microwave field-enhanced synthesis method for ceramic precursors provided by the present invention.

[0037] Example 1 50 g of zinc oxide (ZnO) powder with an average particle size of 30 nm and 50 g of silicon carbide (SiC) powder with an average particle size of 50 nm were mixed in a planetary ball mill for 2 hours to obtain a uniform composite powder. 10 g of the composite powder was spread evenly in an alumina crucible and placed in a multimode microwave reaction chamber. Pure CO2 gas was introduced into the chamber at a flow rate of 50 mL / min to purge air. The microwave was turned on, and the temperature was programmed to rise to 400°C at a rate of 20°C / min and maintained at this temperature for 30 minutes. The microwave power was automatically adjusted based on temperature feedback. After the reaction was completed, the microwave was turned off, and the mixture was cooled to room temperature under a CO2 gas flow. The product was washed with dilute hydrochloric acid to remove SiC, then washed with water and dried to obtain a white powder, which was then calcined to obtain a ceramic precursor. The hardness of the prepared ceramic precursor was tested; the hardness of the ceramic precursor prepared in Example 1 was 5.0 GPa.

[0038] Example 2 The heating rate was changed to 10°C / min, with other parameters remaining the same as in Example 1. The hardness of the prepared ceramic precursor was tested, and the hardness of the ceramic precursor in Example 2 was 5.3 GPa.

[0039] Example 3 The heat treatment time was extended to 60 min, while the other parameters remained the same as in Example 1. The hardness of the ceramic precursor was tested, and the hardness of the ceramic precursor in Example 3 was 5.5 GPa.

[0040] Example 4 The CO2 flow rate was increased to 100 mL / min, with other parameters remaining the same as in Example 1. The hardness of the ceramic precursor was tested, and the hardness of the ceramic precursor in Example 4 was 5.2 GPa.

[0041] Example 5 ZnO with an average particle size of 20 nm and SiC with an average particle size of 40 nm were used, with other parameters the same as in Example 1. The hardness of the ceramic precursor was tested, and the hardness of the ceramic precursor in Example 5 was 5.8 GPa.

[0042] Example 6 The ZnO powder was replaced with Al2O3 powder with an average particle size of 30 nm, and the other parameters were the same as in Example 1. The hardness of the ceramic precursor was tested, and the hardness of the ceramic precursor in Example 5 was 8.1 GPa.

[0043] As shown above, the hardness of conventionally prepared ZnO ceramics is generally in the range of 3 GPa to 5 GPa, while the hardness of the ZnO-based ceramics prepared by this invention can reach 5.0 GPa to 5.8 GPa, which is superior to or reaches the hardness of ceramics prepared by existing technologies. The hardness of Al2O3 ceramics prepared by existing technologies is in the range of 8 GPa to 12 GPa, while the hardness of the Al2O3 ceramics prepared by this invention reaches a medium-to-high level. In other words, the hardness of the ceramic precursors prepared by the microwave field-strengthened synthesis method of ceramic precursors provided by this invention all meet the requirements of high-performance ceramic materials and exhibit excellent mechanical properties.

[0044] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for microwave field-enhanced synthesis of ceramic precursors, characterized in that, The method includes: Step 1: The metal oxide powder and the microwave absorbing medium powder are uniformly and densely physically mixed to obtain the composite material; Step 2: The composite raw material is subjected to microwave irradiation reaction under CO2 atmosphere protection at a temperature range of 300°C to 500°C; Step 3: After completing the microwave irradiation reaction, the mixture is cooled to obtain the ceramic precursor.

2. The method according to claim 1, characterized in that, The microwave irradiation reaction in step two takes place over a period of 10 minutes to 2 hours.

3. The method according to claim 1, characterized in that, The mass ratio of the metal oxide powder to the microwave absorbing medium powder in step one is in the range of 1: (0.1 ~ 2).

4. The method according to claim 1, characterized in that, Step two specifically includes: The composite material is placed in a ball mill equipped with a microwave emitter and subjected to microwave irradiation reaction under a continuously or intermittently flowing CO2 atmosphere.

5. The method according to claim 1, characterized in that, The metal oxide powder includes zinc oxide powder or aluminum oxide powder.

6. The method according to claim 1, characterized in that, The microwave absorbing medium powder includes silicon carbide powder or activated carbon powder.

7. The method according to claim 1, characterized in that, After completing step three, the method further includes: The microwave absorbing medium is removed from the ceramic precursor by acid washing or heat treatment.

8. The method according to claim 1, characterized in that, The particle size of the metal oxide powder in step one is in the submicron range, and the particle size of the microwave absorbing medium powder is similar to or slightly larger than that of the metal oxide powder.

9. A ceramic precursor, characterized in that, The precursor is prepared by the method of microwave field strengthening synthesis of ceramic precursor as described in any one of claims 1 to 8.

10. The application of the ceramic precursor as described in claim 9 in the preparation of functional ceramics or functional materials.

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