Silicon carbide / copper-manganese composite microspheres, and preparation method and application thereof

Abstract

The application belongs to the field of high infrared radiation materials, and particularly relates to a silicon carbide / copper manganate composite microsphere and a preparation method and application thereof. The cobalt-doped copper manganate wrinkle microsphere is accumulated by nanoparticles; the cobalt-doped copper manganate wrinkle microsphere has mesoporous characteristics, and a pore size is 2-40 nm; the preparation method adopts the following steps: adding silicon carbide powder into deionized water, ultrasonic dispersion, dissolving citric acid, a copper ion source and a manganese ion source in the dispersion liquid, performing spray drying treatment to obtain a precursor powder, and performing annealing treatment to obtain the silicon carbide / copper manganate composite microsphere. The preparation method has the advantages of low cost, easily available raw materials and simple operation, and is easy for large-scale preparation of the composite microsphere. The silicon carbide / copper manganate composite microsphere prepared by the application can effectively improve the infrared radiation performance of copper manganite while inhibiting the oxidation of silicon carbide, has excellent infrared radiation performance and thermal stability, and has a wide application prospect in high-temperature coatings.

Description

Technical Field

[0001] This invention belongs to the field of high infrared radiation materials technology, specifically relating to a silicon carbide / copper manganese oxide composite microsphere, its preparation method, and its application. Background Technology

[0002] The irreversible consumption and severe environmental pollution caused by traditional fossil fuels have made the rational utilization of renewable resources and the development of advanced energy-saving materials a current research hotspot. With increasing awareness of sustainable development, research on new energy-saving materials has become paramount. Among numerous research advances, high-infrared radiation materials, due to their excellent radiation power, high-temperature oxidation resistance, and high infrared emissivity, have been widely used in high-temperature industrial kilns, infrared heaters, aerospace vehicles, solar energy conversion, and electronic appliances. Although high-infrared radiation materials have wide applications in various fields, the high cost and poor high-temperature infrared radiation performance of existing high-infrared radiation materials still cannot fully meet the needs of practical applications. Therefore, further exploration of high-infrared radiation materials with low cost and excellent high-temperature performance is urgently needed.

[0003] As research progresses, spinel materials often exhibit excellent infrared radiation performance and thermal stability, thanks to the large number of tetrahedral and octahedral voids within them, which facilitate heteroatom doping and lattice distortion, thus affecting infrared radiation performance. Copper-manganese spinel, in particular, possesses a unique hybrid spinel structure with higher lattice distortion and free carrier concentration, exhibiting relatively outstanding performance across the entire wavelength range, as well as in the 3-5 μm and 8-14 μm wavelength ranges. However, the performance of copper-manganese spinel in the 3-5 μm wavelength range at low temperatures still has significant room for improvement. Silicon carbide is a typical gray-body radiating material, with a stable emissivity that varies with wavelength and exhibits high emissivity in the 3-5 μm wavelength range, making it suitable for a wide range of applications at high temperatures. However, this material is often unstable in oxidizing atmospheres and high-temperature environments, easily oxidized to carbon monoxide and silicon dioxide, resulting in a significant decrease in emissivity and thus limiting its high-temperature applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, one objective of this invention is to provide a silicon carbide / copper manganese oxide composite microsphere, wherein the silicon carbide / copper manganese oxide composite microsphere is formed by the stacking of nanoparticles; the cobalt-doped copper manganese oxide wrinkled microsphere has mesoporous characteristics with a pore size of 2-40 nm.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned silicon carbide / copper manganate composite microspheres, which has the advantages of simple process steps, short reaction time, low cost and readily available raw materials.

[0006] The third objective of this invention is to provide the application of the aforementioned silicon carbide / copper manganese oxide composite microspheres, which can effectively improve the infrared radiation performance of copper manganese spinel while inhibiting the oxidation of silicon carbide, exhibiting excellent infrared radiation performance and thermal stability, and have broad application prospects in high-temperature coatings.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A silicon carbide / copper manganate composite microsphere, wherein the surface of the silicon carbide / copper manganate composite microsphere is wrinkled and has obvious granular texture, silicon carbide powder is wrapped inside the microsphere and the microsphere has obvious mesoporous characteristics, and the pore size distribution of the mesopore is mainly between 2-40 nm.

[0009] The above-mentioned method for preparing silicon carbide / copper manganate composite microspheres comprises the following steps: μμ

[0010] (1) Add silicon carbide powder to deionized water and ultrasonically disperse it to obtain a dispersion;

[0011] (2) Dissolve citric acid, copper ion source and manganese ion source in the dispersion obtained in step (1) and spray dry to obtain precursor powder;

[0012] (3) The precursor powder obtained in step (2) is dried and then annealed to obtain the silicon carbide / copper manganate composite microspheres.

[0013] Further, in step (1), the mass fraction of the silicon carbide powder in the dispersion is 5%-15%; the particle size of the silicon carbide powder is 40-200nm; and the ultrasonic dispersion treatment time is 30-90min.

[0014] Furthermore, in step (2), the copper ion source is a divalent water-soluble copper source.

[0015] Furthermore, the copper source is at least one of copper acetate, copper nitrate, copper chloride, and copper sulfate.

[0016] Furthermore, in step (2), the manganese ion source is a divalent water-soluble manganese source.

[0017] Furthermore, the manganese source is manganese acetate, manganese nitrate, manganese chloride, or manganese sulfate.

[0018] Furthermore, the molar mass-volume ratio of the copper ion source, manganese ion source, citric acid, and deionized water is 0.003 mol: 0.006 mol: 1.891 g: 100 mL.

[0019] In this invention, citric acid acts as a complexing agent for metal ions such as copper and manganese ions, enabling ion complexation and overcoming the problems of weak intermolecular bonding in the precursor powder obtained by spray drying, which easily leads to structural collapse and uneven morphology during heat treatment.

[0020] Further, in step (2), the inlet temperature of the spray drying process is set to 180-250℃, the outlet temperature is controlled at 80-110℃, the peristaltic pump speed is 20-30%, and the air flow rate is 400-600 L·h. -1 .

[0021] Furthermore, in step (3), the drying temperature is 50-110℃ and the time is 5-12 h. The purpose of drying the precursor powder is to reduce the residual moisture in the precursor powder.

[0022] Furthermore, in step (3), the annealing temperature is 300-500℃, the time is 1-3 h, and the heating rate is 1℃ / min.

[0023] The above-mentioned silicon carbide / copper manganese oxide composite microspheres can be used to prepare heat dissipation coatings, and can effectively accelerate heat dissipation and significantly improve the cooling rate.

[0024] This invention involves spray-drying a solution containing silicon carbide, citric acid, and metal ions to produce a grayish-green powder, which is then further annealed to prepare silicon carbide / copper manganate composite microspheres. Since the intermolecular bonding forces within the microspheres obtained after spray drying are relatively weak, it is necessary to prevent structural deformation during heat treatment. Therefore, this invention uses citric acid as a metal ion complexing agent to enhance the bonding of Cu ions. 2+ Mn 2+ Ion complexation occurs between them, and citric acid, as an organic compound, also serves as a carbon source in this invention. After carbonization during annealing, it plays a role in stabilizing the microstructure of silicon carbide / copper manganate composite microspheres, preventing structural collapse of the silicon carbide / copper manganate composite microspheres due to stress changes during heat treatment.

[0025] This invention utilizes the rapid evaporation of solvent in droplets during spray drying and the formation of surface-wrinkled microspheres under continuously increasing capillary forces. The principle is as follows: the precursor solution enters the nozzle via a peristaltic pump, where it is dispersed and atomized to form initial spherical droplets; subsequently, as the droplets enter the drying glass cylinder, the solvent is rapidly evaporated and undergoes localized deformation under continuously increasing capillary forces; finally, the dried, surface-wrinkled spherical particles are collected in a container by a cyclone separator. Compared to other micromorphologies, spherical particles have a relatively smaller contact area, resulting in a higher emissivity and better infrared radiation performance.

[0026] Beneficial effects (1) The composite microspheres prepared by spray drying in this invention have obvious mesoporous characteristics. This rich pore structure can significantly improve the absorption characteristics of the material and further enhance the infrared emissivity of the material, thereby obtaining better infrared radiation performance.

[0027] (2) The present invention significantly simplifies the preparation method of silicon carbide / copper manganese oxide composite microspheres by using spray drying and annealing process, and prepares composite microspheres containing a large number of mesopores. The preparation method has the advantages of low cost, readily available raw materials and simple operation, and is easy to prepare composite microspheres on a large scale.

[0028] (3) The silicon carbide / copper manganate composite microspheres prepared by the present invention can effectively improve the infrared radiation performance of copper manganese spinel while inhibiting the oxidation of silicon carbide. They have excellent infrared radiation performance and thermal stability and have broad application prospects in high-temperature coatings. Attached Figure Description

[0029] Figure 1 XRD images of the materials prepared in Comparative Example 1 and Examples 1-3;

[0030] Figure 2 The images show SEM images of the silicon carbide / copper manganate composite microspheres and silicon carbide powder prepared in Example 2. Figure 2 a is a microscopic morphology diagram of silicon carbide powder. Figure 2 b is an image showing the overall morphology of the silicon carbide / copper manganate composite microspheres prepared in Example 2. Figure 2 c is a partial magnified view of the silicon carbide / copper manganate composite microspheres prepared in Example 2;

[0031] Figure 3 TEM image of the silicon carbide / copper manganate composite microspheres prepared in Example 2;

[0032] Figure 4 The figures show the nitrogen adsorption-desorption curves and pore size distribution curves of the silicon carbide / copper manganate composite microspheres prepared in Example 2. Figure 4 a is the nitrogen adsorption-desorption curve. Figure 4 b is the aperture distribution curve;

[0033] Figure 5 Thermogravimetric images of silicon carbide powder and silicon carbide / copper manganate composite microspheres prepared in Example 2. Figure 5 a is the thermogravimetric image of silicon carbide powder. Figure 5 b is a thermogravimetric image of the silicon carbide / copper manganate composite microspheres prepared in Example 2;

[0034] Figure 6 Infrared emissivity statistics of the materials prepared in Comparative Example 1 and Examples 1-3;

[0035] Figure 7 This is a morphology diagram of the high emissivity coating. Figure 7 a is a digital image of the high-emissivity coating. Figure 7 b is a low-magnification SEM image of the high-emissivity coating surface. Figure 7 c is a magnified SEM image of the high emissivity coating surface. Figure 7 d is the SEM image of the cross-section of the high emissivity coating. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Comparative Example 1 S1: 1.891 g of citric acid (C6H8O7) was dissolved in 100 mL of deionized water. After complete dissolution, 0.003 mol of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 0.006 mol of manganese nitrate tetrahydrate (Mn(NO3)2·4H2O) were added to the solution and stirred until completely dissolved to obtain a mixed solution.

[0038] S2. Before spray drying, set the inlet temperature to 180℃, the peristaltic pump speed to 25%, and the air flow meter to 500 L / h. -1 After the temperature reaches the preset temperature, the mixed solution prepared in step S1 is spray-dried to obtain the precursor powder.

[0039] S3. The precursor powder obtained in step S2 is dried in an oven at 80°C for 8 hours to remove residual moisture.

[0040] S4. The dried precursor powder sample from step S3 is placed in a muffle furnace for annealing: the annealing temperature is 300℃, the heating rate is 1℃ / min, and the holding time is 2 h. After completion, copper manganate microspheres are obtained.

[0041] Example 1 S1: Weigh 5% silicon carbide and stir it thoroughly in 100 mL of deionized water. Then sonicate for 30 min to make the dispersion more uniform. Then add 1.891 g of citric acid (C6H8O7) to the above dispersion. After it is completely dissolved, add 0.003 mol of copper chloride dihydrate (CuCl2·2H2O) and 0.006 mol of manganese chloride tetrahydrate (MnCl4·4H2O) to the solution and continue stirring until completely dissolved to obtain a mixed solution.

[0042] S2. Before spray drying, set the inlet temperature to 200℃, the peristaltic pump speed to 25%, and the air flow meter to 500 L / h. -1 After the temperature rises to the preset temperature, the mixed solution prepared in step S1 is spray-dried to obtain the precursor powder.

[0043] S3. The precursor powder obtained in step S2 is dried in an oven at 100°C for 6 hours to remove residual moisture.

[0044] S4. Place the dried precursor powder sample from step S3 into a muffle furnace for annealing: the annealing temperature is 400℃, the heating rate is 1℃ / min, and the holding time is 2 h. After completion, silicon carbide / copper manganate composite microspheres are obtained.

[0045] Example 2 S1: 10% silicon carbide was thoroughly stirred in 100 mL of deionized water and sonicated for 60 min to achieve a more uniform dispersion. Then, 1.891 g of citric acid (C6H8O7) was added to the dispersion. After complete dissolution, 0.003 mol of copper acetate dihydrate (Cu(CH3COO)2·2H2O) and 0.006 mol of manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O) were added to the solution and stirring continued until completely dissolved to obtain a mixed solution.

[0046] S2. Before spray drying, set the inlet temperature to 200℃, the peristaltic pump speed to 25%, and the air flow meter to 500 L·h. -1 After the temperature reaches the preset temperature, the mixed solution prepared in step S1 is spray-dried to obtain the precursor powder.

[0047] S3. The precursor powder obtained in step S2 is dried in an oven at 110°C for 6 h to remove residual moisture.

[0048] S4. Place the dried precursor powder sample from step S3 into a muffle furnace for annealing: the annealing temperature is 400℃, the heating rate is 1℃ / min, and the holding time is 3 h. After completion, silicon carbide / copper manganate composite microspheres are obtained.

[0049] Example 3 S1: 15% silicon carbide was thoroughly stirred in 100 mL of deionized water and sonicated for 90 min to make the dispersion more uniform. 1.891 g of citric acid (C6H8O7) was added to the above dispersion. After it was completely dissolved, 0.003 mol of copper sulfate pentahydrate (CuSO4·5H2O) and 0.006 mol of manganese sulfate (MnSO4·H2O) were added to the solution and the stirring was continued until it was completely dissolved to obtain a mixed solution.

[0050] S2. Before spray drying, set the inlet temperature to 250℃, the peristaltic pump speed to 25%, and the air flow meter to 500 L / h. -1 After the temperature rises to the preset temperature, the mixed solution prepared in step S1 is spray-dried to obtain the precursor powder.

[0051] S3. The precursor powder obtained in step S2 is dried in an oven at 80°C for 6 hours to remove residual moisture.

[0052] S4. The dried precursor powder sample from step S3 is placed in a muffle furnace for annealing: the annealing temperature is 450℃, the heating rate is 1℃ / min, and the holding time is 3 h. After completion, silicon carbide / copper manganate composite microspheres are obtained.

[0053] Performance testing:

[0054] (1) Figure 1 XRD images of the materials prepared in Comparative Example 1 and Examples 1-3, from... Figure 1 As can be seen, all diffraction peaks in Comparative Example 1 correspond to the standard card, indicating that impurity-free copper manganate material was successfully prepared. Furthermore, in Examples 1-3, the diffraction peaks corresponding to silicon carbide gradually increased with increasing silicon carbide composite content. Figure 1 The diffraction patterns all correspond to the diffraction peaks of silicon carbide and copper manganate, and there are no other impurity phases, which preliminarily indicates that a silicon carbide / copper manganate composite material has been synthesized.

[0055] (2) The microstructure of silicon carbide powder and silicon carbide / copper manganate composite microspheres prepared in Example 2 were further observed under a scanning electron microscope (SEM). Figure 2 SEM images of silicon carbide powder and silicon carbide / copper manganate composite microspheres prepared in Example 2. Figure 2 a is a microscopic morphology diagram of silicon carbide powder. Figure 2 b represents the overall morphology of the silicon carbide / copper manganate composite microspheres and Figure 2 c is a further magnified view of the local area; Figure 2 As can be seen from a, the silicon carbide powder is an irregular particle with a particle size of 40-200 nm. Figure 2 b shows that the composite microspheres have uniform wrinkles on their surface and an average particle size of 4 μm. The wrinkles on the surface of the microspheres are due to the rapid evaporation of the solvent in the droplets and the continuous enhancement of capillary forces after the droplets are ejected from the nozzle, which causes changes in the surface morphology of the microspheres. Figure 2 The magnified image of a single particle c shows that the surface of the microsphere is rough and has a granular texture, indicating that the spray-dried silicon carbide particles are uniformly wrapped inside the microsphere, which can avoid direct contact between silicon carbide and air and inhibit silicon carbide oxidation to a certain extent.

[0056] Figure 3 TEM image of the silicon carbide / copper manganate composite microspheres prepared in Example 2; Figure 4 The figures show the nitrogen adsorption-desorption curves and pore size distribution curves of the silicon carbide / copper manganate composite microspheres prepared in Example 2. Figure 4 a is the nitrogen adsorption-desorption curve. Figure 4 b is the aperture distribution curve. Figure 3 It can be seen that the microspheres have a distinct granular texture and obvious pore channels, and the specific surface area test further confirms their mesoporous characteristics. Figure 4 ).

[0057] Figure 2-4 The results show that Example 2 successfully prepared surface-wrinkled composite microspheres with a silicon carbide / copper manganate composition. The silicon carbide particles are encapsulated inside the copper manganate microspheres, exhibiting obvious mesoporous characteristics, with the pore size distribution mainly between 2-40 nm.

[0058] (3) Figure 5 The silicon carbide / copper manganate composite microspheres prepared in Example 2 of this invention ( Figure 5 a) with silicon carbide powder ( Figure 5 (b) Thermogravimetric image. Figure 5 As can be seen from a, when silicon carbide is calcined at high temperature in air, it begins to slowly increase in weight as the temperature rises, especially after 800℃, the reaction becomes more intense, and finally the weight gain can reach 38% at 1200℃. Figure 5 b. It can be seen that when the silicon carbide / copper manganate composite microspheres prepared in Example 2 are calcined at high temperature in air, the thermogravimetric curve rises slowly overall and finally only increases in weight by 11% at 1200℃. Figure 5 The results show that the silicon carbide / copper manganate composite microspheres prepared in this embodiment can effectively inhibit the oxidation of silicon carbide under high temperature and oxygen conditions.

[0059] (4) The infrared radiation performance of the materials prepared in Comparative Example 1 and Examples 1-3 was tested. Figure 6 The infrared emissivity statistics of the silicon carbide / copper manganate composite microspheres prepared in Comparative Example 1 and Examples 1-3 show that the cobalt-doped copper manganate wrinkled microspheres prepared in Examples 1-3 all exhibit outstanding emissivity values, indicating excellent infrared radiation performance. As the test temperature increases from room temperature to 300℃, the emissivity of the composite microspheres continuously increases; with further increases in temperature, the emissivity value of the composite microspheres slightly decreases, but remains at a high level. This indicates that the silicon carbide particles being encapsulated inside the microspheres can mitigate the drawback of a sharp decrease in emissivity caused by oxidation, and the performance of the composite microspheres is significantly improved compared to copper manganate alone.

[0060] (5) Using the cobalt-doped copper manganate wrinkled microspheres prepared in Example 2 as fillers for high infrared radiation coatings, silicon carbide / copper manganate composite microspheres, binder powder, and binder aqueous solution were mixed in a mass ratio of 3:1:2. An appropriate amount of deionized water was added, and the mixture was thoroughly ground in a mortar to form a uniform slurry. This slurry was then placed in an air spray gun and uniformly sprayed onto a high-nickel stainless steel substrate. After drying at room temperature for 24 h, it was cured at 500℃ for 1 h to obtain a dense and uniform coating (e.g., ...). Figure 7 ). Figure 7 a is a digital photograph of the coating. The coating is generally blackish-gray and the surface is uniform with no peeling. Figure 7 b is a low-magnification SEM image of the coating surface. The coating is dense and crack-free. Upon magnification, the composite microspheres are found to be intact and stacked, forming a large number of pore channels. Figure 7 c). Figure 7 Image d shows the microscopic interface of the coating. No fractures were found at the interface between the substrate and the coating, indicating a good interfacial bond between the coating and the substrate. The coating has a uniform thickness of approximately 150 μm. The resulting coating has a uniform and flat surface with numerous pores, which enhances its infrared absorption and thus improves its infrared emissivity. Furthermore, the porous structure effectively alleviates the interfacial stress between the coating and the substrate, resulting in good thermal shock resistance and significant retention of infrared radiation performance.

[0061] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing silicon carbide / copper manganate composite microspheres, characterized in that, The surface of the silicon carbide / copper manganate composite microspheres is composed of nanoparticles, and the silicon carbide / copper manganate composite microspheres have a porous structure; the preparation method of the composite microspheres adopts the following steps: (1) Add silicon carbide powder to deionized water and ultrasonically disperse it to obtain a dispersion; (2) Dissolve citric acid, copper ion source and manganese ion source in the dispersion obtained in step (1) and spray dry to obtain precursor powder; (3) The precursor powder obtained in step (2) is dried and then annealed to obtain the silicon carbide / copper manganate composite microspheres.

2. The preparation method according to claim 1, characterized in that, The pore size of the pore structure is 2-40 nm.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass fraction of the silicon carbide powder in the dispersion is 5%-15%; the particle size of the silicon carbide powder is 40-200 nm; and the ultrasonic dispersion time is 30-90 min.

4. The preparation method according to claim 1, characterized in that, In step (2), the copper ion source is at least one of copper acetate, copper nitrate, copper chloride, and copper sulfate; the manganese ion source is manganese acetate, manganese nitrate, manganese chloride, or manganese sulfate.

5. The preparation method according to claim 1, characterized in that, The molar mass-volume ratio of the copper ion source, manganese ion source, citric acid, and deionized water is 0.003 mol: 0.006 mol: 1.891 g: 100 mL.

6. The preparation method according to claim 1, characterized in that, In step (2), the inlet temperature of the spray drying process is set to 180-250℃, the outlet temperature is controlled at 80-110℃, the peristaltic pump speed is 20-30%, and the air flow rate is 400. 600 L h -1 .

7. The preparation method according to claim 1, characterized in that, In step (3), the drying temperature is 50-110℃ and the time is 5-12 h; The annealing temperature is 300-500℃, the time is 1-3 h, and the heating rate is 1℃ / min.

8. An application of silicon carbide / copper manganate composite microspheres prepared by the preparation method according to any one of claims 1-6, characterized in that, The silicon carbide / copper manganate composite microspheres are used to prepare a heat dissipation coating.

Images