Carbon-metal oxide-metal ternary hollow microsphere absorbent and its preparation method

Abstract

The present invention discloses a carbon-metal oxide-metal three-component hollow microsphere microwave absorber, which consists of a hollow inner core and a spherical shell; wherein, the hollow inner core is an air cavity; the spherical shell structure is composed of carbon as the continuous phase and metal oxide-metal composite particles as the dispersed phase. When used as a microwave absorber, the heterogeneous composite spherical shell and the hollow inner core structure of the microsphere have the following advantages: firstly, the hollow inner core has a lower density than traditional electromagnetic functional materials, which can reduce the density of the microsphere microwave absorber; secondly, the dispersion of oxide and metal particles can be improved through the supporting and dispersing effect of the carbon material. Combining the certain permeability of the carbon material to electromagnetic waves, electromagnetic waves can be induced to enter the hollow cavity for multiple reflections, and cooperate with the components with different electromagnetic characteristics inside the spherical shell to increase the electromagnetic wave loss and enhance the electromagnetic wave absorption ability. The present invention also provides a preparation method for the hollow microsphere microwave absorber.

Description

Technical Field

[0001] The present invention relates to the field of functional materials. More specifically, it relates to a carbon-metal oxide-metal three-component hollow microsphere wave absorber and a preparation method thereof. Background Art

[0002] Electromagnetic wave absorption and shielding materials are widely used to address the increasingly serious problem of electromagnetic wave pollution and the survival threat posed by electromagnetic detection to equipment. With the development of society and the progress of science and technology, lightweight has increasingly become an important consideration in the upgrading process of various facilities and equipment. As the saying goes, one generation of materials gives rise to one generation of equipment, and materials undoubtedly play a crucial role in the lightweight of various equipment. For electromagnetic wave absorption and shielding materials, there is also a need for lightweight and performance improvement. For lightweight, since most wave-absorbing materials are composites composed of wave absorbers and matrix materials, their lightweight can be achieved through matrix foaming and lightweight design of wave absorbers. However, the foaming of the matrix usually leads to a reduction in the effective components in the system, loss of functionality, and generally poor controllability of the foam pores. Moreover, the presence of pores will significantly reduce the mechanical strength of the composite material, which is not conducive to the practical application of wave-absorbing materials. Relatively speaking, lightweight design of wave absorbers is a more effective method.

[0003] On the other hand, to effectively achieve the loss of electromagnetic waves, more and more research tends to compound wave-absorbing functional components with different electromagnetic properties, and regulate the overall matching and wave-absorbing ability of the material through the synergistic effect between the components. For the compounding of wave-absorbing functional components with different electromagnetic properties, compared with simple mixing, combining the components into a macroscopically uniform single wave absorber with a heterogeneous structure inside is a more effective way. The reason is that heterogeneous compounding has more advantages in realizing the microscopic scale compounding of each wave-absorbing component, introducing heterogeneous interfaces with different electromagnetic properties, and improving the application convenience of the composite structure wave absorber. Therefore, heterogeneous compounding within a macroscopically uniform single wave absorber is an important direction for developing new high-performance wave absorbers. However, on the one hand, it is still very difficult to carry out collaborative design of heterogeneous compounding and lightweight, and the available material systems and structures are limited; on the other hand, the synthesis methods of current heterogeneous composite structure wave absorbers generally involve multi-step synthesis processes, which are not only cumbersome and time-consuming, not suitable for large-scale production, but also not conducive to the efficient compounding of heterogeneous functional components and the formation of multiple interfaces. Summary of the Invention

[0004] The first object of the present invention is to provide a carbon-metal oxide-metal three-component hollow microsphere absorber, the functional characteristics of the absorber are mainly brought by its micro-nanoscale mixed multi-components, the spherical shell has a triple interface and high dispersibility, and the composition and electromagnetic parameters of the hollow microspheres in the absorber can be conveniently controlled within a wide range; at the same time, the absorber overcomes the shortcomings of traditional absorbers such as high density, weak loss capacity, complicated preparation process, and poor economy.

[0005] Another object of the present invention is to provide a method for preparing a carbon-metal oxide-metal three-component hollow microsphere absorber.

[0006] In order to achieve the above first object, the present invention adopts the following technical scheme:

[0007] A carbon-metal oxide-metal three-component hollow microsphere absorber consists of a hollow core and a spherical shell; wherein the hollow core is an air cavity; and the spherical shell structure consists of carbon as a continuous phase and metal oxide-metal composite particles as a dispersed phase.

[0008] Furthermore, the particle size of the hollow microsphere absorber is 5-60 μm and the density is 0.7-2.1 g / cm 3 .

[0009] Furthermore, in the hollow microsphere absorber, the shell thickness is 0.3-1.8 μm.

[0010] Furthermore, in the hollow microsphere absorber, the mass ratio of carbon, metal oxide and metal is 20-70:5-20:5-30.

[0011] Furthermore, the metal is selected from a single metal, a metal alloy or a mixture of different single metals; the metal oxide can be a single metal oxide or a composite oxide of two or more metals.

[0012] Furthermore, the metal element in the metal or metal oxide is selected from one or more of nickel, iron, cobalt and copper.

[0013] Furthermore, the metal oxide is Fe2O3.

[0014] Furthermore, the metal and the metal element in the metal oxide have the same source.

[0015] Furthermore, the metal component is obtained by reducing and converting the initially added metal oxide nanoparticles and water-soluble metal salt.

[0016] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0017] A preparation method of a carbon-metal oxide-metal three-component hollow microsphere absorbent, comprising the following steps:

[0018] (1) Mix metal oxide nanoparticles, an organic carbon source, and a water-soluble metal salt, and stir evenly to obtain a spray slurry;

[0019] (2) Atomize and dry the slurry to obtain spherical intermediates;

[0020] (3) Heat-treat the intermediates in an inert atmosphere to obtain the carbon-metal oxide-metal three-component hollow microsphere absorbent.

[0021] Further, the ratio of the carbon source, oxide nanoparticles, water-soluble metal salt to deionized water in the slurry is (50-250) g:(10-30) g:(25-180) g:(300-500) g.

[0022] Further, the organic carbon source is selected from one or more of water-soluble glucose, sucrose, starch, citric acid, dopamine.

[0023] Further, the water-soluble metal salt includes but is not limited to metal chlorides, sulfates, nitrates, acetates, and other water-soluble organic metal salts.

[0024] Further, the conditions for atomizing and drying are: the inlet temperature is 200-350 °C, and the drying atmosphere is air.

[0025] Further, the heat treatment temperature is 400-700 °C, and the heat preservation time is 1-10 h.

[0026] The beneficial effects of the present invention are as follows:

[0027] The carbon-metal oxide-metal three-component hollow microsphere absorbent with a hollow structure provided by the present invention can reduce the density of the absorbent through the internal hollow cavity; secondly, in-situ carbothermal reduction of the metal and dispersion of pre-added oxide nanoparticles can be achieved. On the one hand, the electromagnetic wave absorption can be enhanced through the multiple interface effects and multiple loss mechanisms of carbon, metal, and oxide, and on the other hand, the relatively large micron-scale macroscopic size of the hollow microspheres can prevent the aggregation of nanoparticles, facilitating the use of the absorbent.

[0028] In the preparation method provided by the present invention, oxides generated by the oxidation and corrosion of metal materials in the environment (such as Fe2O3) can be used as initial reactants, providing a method for the resource utilization of solid waste after metal corrosion; in addition, this preparation method can overcome the problems of cumbersome and time-consuming preparation processes, high costs, and being unfavorable for large-scale production of traditional composite lightweight absorbents. Description of the Drawings

[0029] The following further elaborates on the specific embodiments of the present invention in conjunction with the accompanying drawings.

[0030] Figure 1 Shows a schematic diagram of the preparation process of the carbon-metal oxide-metal three-component hollow microsphere absorbent in the present invention.

[0031] Figure 2 Shows the X-ray diffraction (XRD) pattern of the carbon-metal oxide-metal three-component hollow microsphere absorbent prepared in Example 1.

[0032] Figure 3 Shows the scanning electron microscope (SEM) image of the carbon-metal oxide-metal three-component hollow microsphere absorbent prepared in Example 1.

[0033] Figure 4 Shows the SEM image of the carbon-metal oxide-metal three-component hollow microsphere absorbent prepared in Example 1.

[0034] Figure 5 Shows the transmission electron microscope (TEM) image of the carbon-metal oxide-metal three-component hollow microsphere absorbent prepared in Example 1. Specific Embodiments

[0035] To more clearly illustrate the present invention, the following further describes the present invention in conjunction with preferred embodiments and the accompanying drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0036] Example 1

[0037] Take 120 g of nickel nitrate, 80 g of citric acid, and 150 g of soluble starch, add them to 350 g of water, and stir well to dissolve; then add 25 g of iron oxide nanoparticles (particle size 60 nm) under stirring to obtain a spray slurry. The prepared slurry is subjected to atomization drying treatment, using a pneumatic atomization drying device, with an inlet temperature of 200 °C, an outlet temperature of 120 °C, and a drying atmosphere of air to obtain precursor microspheres. Then, the obtained microspheres are heat-treated and calcined in a nitrogen atmosphere. Initially, the temperature is raised to 150 °C at a heating rate of 3 °C / min, held for 20 min, then raised to 550 °C at a heating rate of 5 °C / min, and held for 4 h. After cooling in a nitrogen atmosphere, a carbon-metal oxide-metal three-component hollow microsphere absorbent is obtained. The mass ratio of carbon, metal oxide, and metal in this hollow microsphere absorbent is 61:16:24, the density is 1.93 g / cm3, the shell thickness is 1650 nm, and the average particle size is 7 μm.

[0038] Example 2

[0039] Take 100 g of cobalt nitrate, 110 g and 100 g of soluble starch, add them to 400 g of water, and stir well to dissolve. Then, while stirring, add 21 g of ground iron oxide nanoparticles (particle size 70 nm) to obtain a spray slurry. Atomize and dry the prepared slurry using a pneumatic atomization drying device with an inlet temperature of 230 °C, an outlet temperature of 140 °C, and a drying atmosphere of air to obtain precursor microspheres. Then, heat-treat the obtained microspheres by calcining in a nitrogen atmosphere. Initially, heat up to 150 °C at a heating rate of 3 °C / min, hold for 20 min, then heat up to 630 °C at a heating rate of 5 °C / min, and hold for 3 h. After cooling in a nitrogen atmosphere, a carbon-metal oxide-metal three-component hollow microsphere absorbent is obtained. The mass ratio of carbon, metal oxide, and metal in this hollow microsphere absorbent is 63:12:25, the density is 1.15 g / cm3, the shell thickness is 610 nm, and the average particle size is 13 μm.

[0040] Example 3

[0041] Take 30 g of cobalt nitrate, 75 g of copper nitrate, 80 g of dopamine, and 80 g of soluble starch, add them to 400 g of water, and stir well to dissolve. Then, while stirring, add 18 g of ground iron oxide nanoparticles (particle size 70 nm) to obtain a spray slurry. Atomize and dry the prepared slurry using a pneumatic atomization drying device with an inlet temperature of 280 °C, an outlet temperature of 160 °C, and a drying atmosphere of air to obtain precursor microspheres. Then, heat-treat the obtained microspheres by calcining in a nitrogen atmosphere. Initially, heat up to 200 °C at a heating rate of 3 °C / min, hold for 20 min, then heat up to 600 °C at a heating rate of 5 °C / min, and hold for 3 h. After cooling in a nitrogen atmosphere, a carbon-metal oxide-metal three-component hollow microsphere absorbent is obtained. The mass ratio of carbon, metal oxide, and metal in this hollow microsphere absorbent is 50:10:26, the density is 1.27 g / cm3, the shell thickness is 680 nm, and the average particle size is 15 μm.

[0042] Example 4

[0043] Take 48 g of cobalt nitrate, 42 g of nickel nitrate, 60 g of sucrose, 70 g of soluble starch, and 50 g of citric acid and add them to 300 g of water. Stir well to dissolve. Then, while stirring, add 28 g of copper oxide nanoparticles (particle size 55 nm) to obtain a spray slurry. Atomize and dry the prepared slurry using a pneumatic atomization drying device. The inlet temperature is 210 °C, the outlet temperature is 110 °C, and the drying atmosphere is air to obtain precursor microspheres. Then, heat-treat the obtained microspheres by calcining in a nitrogen atmosphere. Initially, heat up to 200 °C at a heating rate of 3 °C / min, hold for 20 min, then heat up to 650 °C at a heating rate of 5 °C / min, and hold for 1 h. After cooling in a nitrogen atmosphere, a carbon-metal oxide-metal three-component hollow microsphere absorbent is obtained. In this hollow microsphere absorbent, the mass ratio of carbon, metal oxide, and metal is 52:19:24, the density is 1.75 g / cm3, the shell thickness is 1250 nm, and the average particle size is 11 μm.

[0044] Example 5

[0045] Take 170 g of iron nitrate, 90 g of soluble starch, and 70 g of citric acid and add them to 350 g of water. Stir well to dissolve. Then, while stirring, add 15 g of nickel oxide nanoparticles (particle size 50 nm) to obtain a spray slurry. Atomize and dry the prepared slurry using a pneumatic atomization drying device. The inlet temperature is 310 °C, the outlet temperature is 170 °C, and the drying atmosphere is air to obtain precursor microspheres. Then, heat-treat the obtained microspheres by calcining in a nitrogen atmosphere. Initially, heat up to 200 °C at a heating rate of 3 °C / min, hold for 20 min, then heat up to 500 °C at a heating rate of 5 °C / min, and hold for 9 h. After cooling in a nitrogen atmosphere, a carbon-metal oxide-metal three-component hollow microsphere absorbent is obtained. In this hollow microsphere absorbent, the mass ratio of carbon, metal oxide, and metal is 32:11:26, the density is 0.85 g / cm3, the shell thickness is 450 nm, and the average particle size is 17.5 μm.

[0046] Example 6

[0047] Take 55 g of nickel nitrate, 65 g of copper nitrate, 100 g of sucrose and 120 g of citric acid, add them to 500 g of water, and stir well to dissolve. Then, add 17 g of cobalt oxide nanoparticles (particle size 60 nm) under stirring to obtain a spray slurry. Atomize and dry the prepared slurry using a pneumatic atomization drying device with an inlet temperature of 250 °C, an outlet temperature of 130 °C, and a drying atmosphere of air to obtain precursor microspheres. Then, heat-treat the obtained microspheres by calcining in a nitrogen atmosphere. Initially, heat up to 150 °C at a heating rate of 3 °C / min, hold for 20 min, then heat up to 600 °C at a heating rate of 5 °C / min, and hold for 5 h. After cooling in a nitrogen atmosphere, a carbon-metal oxide-metal three-component hollow microsphere absorbent is obtained. The mass ratio of carbon, metal oxide, and metal in the hollow microsphere absorbent is 65:13:25.5, the density is 0.67 g / cm3, the shell thickness is 310 nm, and the average particle size is 10.5 μm.

[0048] Performance test:

[0049] Test the electromagnetic properties of the products prepared in the above-mentioned examples. The test method is as follows: Mix the hollow composite microspheres (absorbing materials) prepared in each example with paraffin at a mixing mass ratio of 30%-50% to prepare a coaxial ring with an inner diameter of 3 mm, an outer diameter of 7 mm, and a thickness of 2 mm. Then, use a vector network analyzer to test the electromagnetic parameters and analyze their electromagnetic properties. The results are shown in Table 1.

[0050] Table 1 Performance parameters of the samples in each example

[0051]

[0052] Obviously, the above-mentioned examples of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A carbon-metal oxide-metal three-component hollow microsphere microwave absorber, characterized in that, It consists of a hollow core and a spherical shell; wherein the hollow core is an air cavity; the spherical shell structure is composed of carbon as a continuous phase and metal oxide-metal composite particles as a dispersed phase; The particle size of the hollow microsphere wave absorber is 5 - 60 μm, and the density is 0.7 - 2.1 g / cm 3 ; In the hollow microsphere absorber, the shell thickness is 0.3-1.8 μm; The preparation method of the wave absorbing agent comprises the following steps: (1) mixing metal oxide nanoparticles, an organic carbon source and a water-soluble metal salt, and stirring them uniformly to obtain a spray slurry; (2) atomizing and drying the slurry to obtain a spherical intermediate; (3) heat treating the intermediate in an inert atmosphere to obtain the carbon-metal oxide-metal three-component hollow microsphere absorber; The ratio of the carbon source, the oxide nanoparticles, the water-soluble metal salt and the deionized water in the slurry is (50-250) g: (10-30) g: (25-180) g: (300-500) g; The heat treatment temperature is 400-700°C and the insulation time is 1-10h; The metal element in the metal or metal oxide is selected from one or more of nickel, iron, cobalt and copper.

2. The hollow microsphere microwave absorber according to claim 1, characterized in that, In the hollow microsphere absorber, the mass ratio of carbon, metal oxide and metal is 20-70:5-20:5-30.

3. The hollow microsphere microwave absorber according to claim 1, characterized in that, The metal is selected from a metal element, a metal alloy or a mixture of different metal elements; the metal oxide can be a single metal oxide or a composite oxide of two or more metals.

4. The hollow microsphere microwave absorber according to claim 1 or 3, characterized in that, The metal oxide is Fe2O3.

5. The hollow microsphere microwave absorber according to claim 1, characterized in that, The organic carbon source is selected from one or more of water-soluble glucose, sucrose, starch, citric acid and dopamine.

6. The hollow microsphere microwave absorber according to claim 1, characterized in that, The conditions of the atomization drying are: the inlet temperature is 200-350° C., and the drying atmosphere is air.

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