Preparation method and application of FexOy / TiO2 / C composite microwave absorbing material

Abstract

The invention discloses a preparation method and application of a FexOy / TiO2 / C composite microwave absorbing material, belongs to the field of solid waste utilization and microwave absorbing materials, and solves the technical problem of high-value utilization of rare earth waste residues and red mud. According to the technical scheme, the method comprises the following steps: firstly, drying, ball-milling and screening rare earth waste residues or red mud; secondly, mixing the solid waste powder with soluble starch to prepare mixed powder; thirdly, dropwise adding deionized water into a mixed solution prepared from tetrabutyl titanate, glacial acetic acid and absolute ethyl alcohol to prepare sol, adding the mixed powder into the sol, magnetically stirring and uniformly mixing, and aging to obtain gel; and finally, drying the gel, and roasting the dried gel in an N2 atmosphere to prepare the FexOy / TiO2 / C composite microwave absorbing material. The composite wave-absorbing material is prepared from the solid waste, the tetrabutyl titanate, the soluble starch and the barium acetate as main raw materials, a new thought is provided for comprehensive utilization of the rare earth waste residues and the red mud, and meanwhile the microwave-absorbing material is prepared at low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste utilization and microwave absorbing materials, and specifically relates to a Fe x O y Preparation method and application of / TiO2 / C composite microwave absorbing material. Background Art

[0002] Metal smelting produces many solid wastes that are difficult to utilize and harmful to the ecological environment, and red mud is one of them. During the alumina refining process, the bauxite slag produced is called red mud. However, the comprehensive utilization of red mud is not optimistic. At present, the main disposal method for red mud is to build reservoirs for storage or stack storage. This method will cause a great waste of resources and economic losses. In addition, red mud has fine particles and may enter the atmosphere with airflow, causing air pollution. In general, red mud poses a threat to the environment and also restricts the development of the aluminum industry to a certain extent. Therefore, it is imperative to seek a reasonable method to recycle red mud and make comprehensive use of it.

[0003] In addition, rare earth plays an increasingly important role in the national economy as an "industrial vitamin". It is widely used in many fields such as electronic information, advanced manufacturing, green chemical industry, functional materials and devices, clean energy and "dual carbon" technology. However, in the process of extracting rare earth, "three wastes" will be generated, namely waste slag, waste water and waste gas. Among them, the output of waste slag is large, and the waste slag contains a large amount of metal, so the waste slag has a high recycling value. Among the many rare earth waste slags, NdFeB rare earth waste slag shows greater utilization potential due to its high iron content. At present, the recycling and utilization technologies of NdFeB waste slag include pyrometallurgical recycling process, wet recycling process, physical recycling, hydrogen explosion method, biological leaching method, electrochemical method, etc., but the above methods will be accompanied by high pollution, high energy consumption, immature process, low product added value and other problems in the recycling process; in order to overcome the shortcomings of the above methods, high-value recycling production technologies such as wet-pyrometallurgical combined process and Magnet-to-Magnet process are gradually favored, but the processes of these two methods are relatively complicated. It can be seen from this that it is necessary to effectively improve the high-value utilization of rare earth waste, and then realize the recycling of NdFeB waste, high-quality green development, and low-carbon transformation of social economy.

[0004] With the rapid development of modern electronic information technology, more and more electronic devices have become indispensable tools in life and work. The development of new and efficient electromagnetic absorbing materials to suppress the harmful effects of electromagnetic waves has become a research hotspot. The preparation of microwave absorbing materials with thinner coating thickness, lighter weight, wider absorption band and stronger absorbing performance has gradually become a hot topic. At the same time, better absorbing materials should also take into account the advantages of low raw material price and simple preparation process, and ensure the adaptability of materials in different environments.

[0005] According to numerous scientific studies, carbon materials have excellent dielectric properties and low density, and are dielectric loss-type absorbing materials with good performance. However, a single carbon material cannot meet application requirements, and a high complex dielectric constant will lead to impedance mismatch, which in turn affects the absorbing performance, so it is necessary to compound TiO2 to adjust the complex dielectric constant and optimize the absorbing performance. As an important inorganic functional material, TiO2 has high photocatalytic activity, good weather resistance, corrosion resistance, moisture sensitivity, gas sensitivity, strong ultraviolet shielding ability, and can produce unique properties such as peculiar color effects. It has attracted much attention in many fields such as environmental protection, wastewater treatment, sunscreen and skin care, coatings and automotive industry, sensors, functional ceramics, photocatalysts, sensitive devices and optoelectronic materials. In recent years, it has become a rising star in absorbing materials due to its good dielectric properties.

[0006] In summary, the rational development and utilization of red mud and rare earth waste residue to prepare Fe x O y / TiO2 / C composite microwave absorbing material can not only effectively alleviate the environmental problems caused by a large amount of red mud and rare earth waste, but also avoid the waste of resources. Finally, it can also reduce the cost of composite absorbing materials, truly realizing the high-value utilization of rare earth waste and the low-cost production of absorbing materials. Summary of the invention

[0007] The main purpose of the present invention is to overcome the shortcomings of the prior art and solve the problem of resource utilization of red mud and rare earth waste residue. The present invention provides a Fe x O y The preparation method and application of / TiO2 / C composite microwave absorbing materials provide new ideas for the high-value and large-scale application of red mud and rare earth waste, and at the same time realize the low-cost preparation of composite microwave absorbing materials.

[0008] In order to achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is: Fe x O y The preparation method of the / TiO2 / C composite microwave absorbing material comprises the following steps: S1. Drying the solid waste in an oven at a drying temperature of 60°C to 130°C for 6 to 10 hours; then ball-milling the solid waste and sieving it through a standard sieve of 80 to 300 meshes to obtain solid waste powder; the solid waste is rare earth waste residue or red mud; S2, mixing the solid waste powder after drying in step S1 with soluble starch in a mass ratio of 1: (0.5-2) to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of (1-9):(1-4):(0-30) to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 1%-5% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, and when the solid waste is rare earth waste residue, the mass ratio of the rare earth waste residue in the mixed powder to the tetrabutyl titanate in the sol is 1:(2-15); when the solid waste is red mud, the mass ratio of the red mud in the mixed powder to the tetrabutyl titanate in the sol is 1:(1-6); the mixture is mixed uniformly by magnetic stirring; finally, a gel is obtained after aging; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 60°C to 120°C for a drying time of 6 to 12 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 400°C to 1000°C for a calcination time of 2 hours, and then cooled to room temperature with the furnace to obtain Fe x O y / TiO2 / C composite microwave absorbing material.

[0009] Furthermore, the composition and mass percentage of the rare earth waste slag are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%; the composition and mass percentage of the red mud are: Fe2O3: 43.36%~44.86%, Al2O3: 19.06%~19.85%, SiO2: 19.92%~20.42%, Na2O: 6.83%~7.33%, TiO2: 4.96%~5.26%, CaO: 3.58%~4.58%.

[0010] Furthermore, in step S3, the rotation speed of the magnetic stirring is 100-400 r / min.

[0011] Furthermore, in the step S3, the aging is carried out at room temperature, and the aging time is 8-18 hours.

[0012] The Fe prepared by the above-mentioned preparation method x O y Application of / TiO2 / C composite microwave absorbing materials in microwave absorption process.

[0013] Furthermore, the Fe x O y The effective phase for microwave absorption in the / TiO2 / C composite microwave absorbing material is Fe x O y , TiO2 and C, the Fex O y is Fe or Fe3O4; among which, Fe x O y As magnetic components, TiO2 and C serve as dielectric components.

[0014] Further, in the Fe x O y In the / TiO2 / C composite microwave absorbing material, the dielectric component TiO2 is wrapped around the magnetic component Fe x O y Outside the composite absorbing material, the dielectric component C is evenly distributed in the composite absorbing material.

[0015] The beneficial effects of the present invention are: 1. During the roasting process, Fe2O3 (playing the main role) in red mud and rare earth waste reacts with soluble starch to produce Fe x O y Acting as a magnetic component, it optimizes the microwave absorption performance of the composite material, reduces the cost of the microwave absorption material, and is conducive to the low-cost production of microwave absorption materials; 2. In the carbon thermal reaction process, red mud and rare earth waste are mainly used as iron sources to provide the magnetic component of the composite material. Soluble starch participates in the reaction as a reducing agent. The soluble starch not consumed in the reaction can be converted into carbon, which together with the generated TiO2 serves as the dielectric component of the composite material. The two work synergistically with the magnetic component to improve the microwave absorption performance of the material. At the same time, the strong alkaline substances in the red mud will activate the carbon components in the system, increase the pore structure of the material, facilitate multiple reflections and scattering of electromagnetic waves in the material, and at the same time help to make the material lighter. 3. The present invention uses TiO2 as a dielectric component, which together with carbon provides dielectric loss and synergistically enhances the microwave absorption performance of the material; on this basis, TiO2 has excellent thermal stability, and coating TiO2 on the surface of the magnetic component can improve the thermal stability of the composite microwave absorption material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The microwave reflection loss curve of the Fe3O4 / TiO2 / C composite microwave absorbing material prepared using rare earth waste as raw material in Example 1; Figure 2 The Raman spectrum of the Fe / TiO2 / C composite microwave absorbing material prepared using rare earth waste as raw material in Example 2; Figure 3 The Raman spectrum of TiO2 in the Fe / TiO2 / C composite microwave absorbing material prepared using rare earth waste as raw material in Example 3; Figure 4This is the XRD spectrum of the Fe3O4 / TiO2 / C composite microwave absorbing material prepared using rare earth waste as raw material in Example 4.

[0017] Figure 5 The microwave reflection loss curve of the Fe3O4 / TiO2 / C composite microwave absorbing material prepared using red mud as raw material in Example 5; Figure 6 The Raman spectrum of TiO2 in the Fe / TiO2 / C composite microwave absorbing material prepared using red mud as raw material in Example 6; Figure 7 The Raman spectrum of carbon in the Fe3O4 / TiO2 / C composite microwave absorbing material prepared using red mud as raw material in Example 7; Figure 8 This is the X-ray diffraction spectrum of the Fe3O4 / TiO2 / C composite microwave absorbing material prepared using red mud as raw material in Example 8. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Example 1

[0019] The preparation method of Fe3O4 / TiO2 / C composite microwave absorbing material comprises the following steps: S1. The rare earth waste residue is ball-milled, and the chemical composition and mass percentage of the rare earth waste residue are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%; the rare earth waste residue is ball-milled and sieved through a 120-mesh standard sieve, and the sieved rare earth waste residue powder is placed in an oven for drying at a drying temperature of 80° C. for a drying time of 6 hours, and is reserved for use in the subsequent step; S2, mixing the rare earth waste residue after drying in step S1 with soluble starch in a mass ratio of 1:0.5 to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1.2:0.2 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 2% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of the rare earth waste residue in the mixed powder to the tetrabutyl titanate in the sol is 1:4, and the mixture is mixed uniformly by magnetic stirring at a speed of 100-200 r / min; finally, the gel is obtained after aging at room temperature for 8 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 80°C for 12 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 700°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / TiO2 / C composite microwave absorbing material.

[0020] The Fe3O4 / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 1 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe3O4, TiO2 and C, wherein Fe3O4 is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0021] like Figure 1 As shown, when the Fe3O4 / TiO2 / C composite microwave absorbing material prepared in Example 1 is used in the microwave absorption process, when the coating thickness is 1.5 mm, its effective bandwidth is 4.2 GHz and the minimum reflection loss is -40.1 dB. Example 2

[0022] The preparation method of Fe / TiO2 / C composite microwave absorbing material comprises the following steps: S1. The rare earth waste residue is ball-milled, and the chemical composition and mass percentage of the rare earth waste residue are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%; the rare earth waste residue is ball-milled and sieved through a 150-mesh standard sieve, and the sieved rare earth waste residue powder is placed in an oven for drying at a drying temperature of 80° C. for 8 hours, and is reserved for use in the subsequent step; S2, mixing the rare earth waste residue dried in step S1 with soluble starch in a mass ratio of 1:1.5 to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:2.5:0.5 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 3% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of rare earth waste in the mixed powder to tetrabutyl titanate in the sol is 1:8, and the mixture is mixed uniformly by magnetic stirring at a speed of 200-300 r / min; finally, the gel is obtained after aging at room temperature for 12 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 80°C for 10 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 900°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe / TiO2 / C composite microwave absorbing material.

[0023] The Fe / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 2 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe, TiO2 and C, wherein Fe is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0024] like Figure 2 As shown, the Raman spectrum of the Fe / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 2 has D peak and G peak, which proves that after the carbothermal reduction reaction, there is still excess carbon inside the Fe / TiO2 / C composite material. Example 3

[0025] The preparation method of Fe / TiO2 / C composite microwave absorbing material comprises the following steps: S1. The rare earth waste residue is ball-milled, and the chemical composition and mass percentage of the rare earth waste residue are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%; the rare earth waste residue is ball-milled and sieved through a 200-mesh standard sieve, and the sieved rare earth waste residue powder is placed in an oven for drying at a drying temperature of 100° C. for 6 hours, and is reserved for use in the subsequent step; S2, mixing the rare earth waste residue after drying in step S1 with soluble starch in a mass ratio of 1:1 to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1.8:0.5 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 4% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of the rare earth waste residue in the mixed powder to the tetrabutyl titanate in the sol is 1:4, and the mixture is mixed uniformly by magnetic stirring at a speed of 300-400 r / min; finally, the gel is obtained after aging at room temperature for 10 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 80°C for 12 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 900°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe / TiO2 / C composite microwave absorbing material.

[0026] The Fe / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 3 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe, TiO2 and C, wherein Fe is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0027] Depend on Figure 3 It can be seen that the Raman spectrum of the Fe / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 3 has a characteristic peak of rutile phase TiO2, which proves that TiO2 with good dielectric properties can be successfully prepared by the sol-gel method. Example 4

[0028] The preparation method of Fe3O4 / TiO2 / C composite microwave absorbing material comprises the following steps: S1. The rare earth waste residue is ball-milled, and the chemical composition and mass percentage of the rare earth waste residue are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%; the rare earth waste residue is ball-milled and sieved through a 120-mesh standard sieve, and the sieved rare earth waste residue powder is placed in an oven for drying at a drying temperature of 80° C. for 10 hours, and is reserved for use in the subsequent step; S2, mixing the rare earth waste residue after drying in step S1 with soluble starch in a mass ratio of 1:1 to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1.2:0.2 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 3.5% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of the rare earth waste residue in the mixed powder to the tetrabutyl titanate in the sol is 1:11, and the mixture is mixed uniformly by magnetic stirring at a speed of 250-350 r / min; finally, the gel is obtained after aging at room temperature for 18 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 80°C for 12 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 500°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / TiO2 / C composite microwave absorbing material.

[0029] The Fe3O4 / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 4 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe3O4, TiO2 and C, wherein Fe3O4 is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material. Example 5

[0030] The preparation method of Fe3O4 / TiO2 / C composite microwave absorbing material comprises the following steps: S1. Drying the red mud in an oven at a drying temperature of 70° C. for 6 hours; then ball-milling the solid waste and sieving it through a 120-mesh standard sieve to obtain red mud powder; the composition and mass percentage of the red mud are: Fe2O3: 43.36% to 44.86%, Al2O3: 19.06% to 19.85%, SiO2: 19.92% to 20.42%, Na2O: 6.83% to 7.33%, TiO2: 4.96% to 5.26%, CaO: 3.58% to 4.58%; S2, mixing the red mud powder dried in step S1 with soluble starch of equal mass to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 9:2:10 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 2.5 of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of red mud in the mixed powder to tetrabutyl titanate in the sol is 1:5.0, and the mixture is mixed uniformly by magnetic stirring, and the speed of the magnetic stirrer is controlled at 200-300 r / min; finally, the gel is obtained after aging at room temperature for 12 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a drying temperature of 100°C for 10 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a calcination temperature of 700°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / TiO2 / C composite microwave absorbing material.

[0031] The Fe3O4 / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 5 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe3O4, TiO2 and C, wherein Fe3O4 is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0032] like Figure 5 As shown, when the Fe3O4 / TiO2 / C composite microwave absorbing material prepared in Example 5 is used in the microwave absorption process, when the coating thickness is 3.0 mm, its effective bandwidth is 3.2 GHz and the minimum reflection loss value is -35.87 dB. Example 6

[0033] The preparation method of Fe / TiO2 / C composite microwave absorbing material comprises the following steps: S1. Drying the red mud in an oven at a drying temperature of 80° C. for 10 hours; then ball-milling the solid waste and sieving it through a 120-mesh standard sieve to obtain red mud powder; the composition and mass percentage of the red mud are: Fe2O3: 43.36% to 44.86%, Al2O3: 19.06% to 19.85%, SiO2: 19.92% to 20.42%, Na2O: 6.83% to 7.33%, TiO2: 4.96% to 5.26%, CaO: 3.58% to 4.58%; S2, mixing the red mud powder dried in step S1 with soluble starch of equal mass to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 9:4:20 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 3.5% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of red mud in the mixed powder to tetrabutyl titanate in the sol is 1:4, and the mixture is mixed uniformly by magnetic stirring at a speed of 150-250 r / min; finally, the gel is obtained after aging at room temperature for 15 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 110°C for 12 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 900°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe / TiO2 / C composite microwave absorbing material.

[0034] The Fe / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 6 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe, TiO2 and C, wherein Fe is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0035] like Figure 6 As shown, the characteristic peak of TiO2 rutile phase can be seen in the Raman spectrum of the Fe / TiO2 / C composite microwave absorbing material prepared in Example 6, proving that the Fe / TiO2 / C composite microwave absorbing material prepared in Example 6 contains TiO2 phase. Example 7

[0036] The preparation method of Fe3O4 / TiO2 / C composite microwave absorbing material comprises the following steps: S1. Drying the red mud in an oven at a drying temperature of 80° C. for 9 hours; then ball-milling the solid waste and sieving it through a 150-mesh standard sieve to obtain red mud powder; the composition and mass percentage of the red mud are: Fe2O3: 43.36%-44.86%, Al2O3: 19.06%-19.85%, SiO2: 19.92%-20.42%, Na2O: 6.83%-7.33%, TiO2: 4.96%-5.26%, CaO: 3.58%-4.58%; S2, mixing the red mud powder dried in step S1 with soluble starch of equal mass to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 2:1:4 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 4% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of red mud in the mixed powder to tetrabutyl titanate in the sol is 1:2, and the mixture is mixed uniformly by magnetic stirring at a speed of 100-200 r / min; finally, the gel is obtained after aging at room temperature for 15 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 100°C for 8 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 500°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / TiO2 / C composite microwave absorbing material.

[0037] The Fe3O4 / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 7 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe3O4, TiO2 and C, wherein Fe3O4 is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0038] like Figure 7 As shown, obvious D peaks and G peaks can be seen in the Raman spectrum of the Fe3O4 / TiO2 / C composite microwave absorbing material prepared in Example 7, indicating that residual carbon still exists in the system after the carbothermal reduction reaction. Example 8

[0039] The preparation method of Fe3O4 / TiO2 / C composite microwave absorbing material comprises the following steps: S1. Drying the red mud in an oven at a drying temperature of 100° C. for 9 hours; then ball-milling the solid waste and sieving it through a 200-mesh standard sieve to obtain red mud powder; the composition and mass percentage of the red mud are: Fe2O3: 43.36% to 44.86%, Al2O3: 19.06% to 19.85%, SiO2: 19.92% to 20.42%, Na2O: 6.83% to 7.33%, TiO2: 4.96% to 5.26%, CaO: 3.58% to 4.58%; S2, mixing the red mud powder dried in step S1 with soluble starch of equal mass to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 9:4:15 to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 5% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, the mass ratio of red mud in the mixed powder to tetrabutyl titanate in the sol is 1:1.8, and the mixture is mixed uniformly by magnetic stirring at a speed of 300-400 r / min; finally, the gel is obtained after aging at room temperature for 18 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 90°C for 9 hours to obtain a precursor dry gel; then, the precursor dry gel is placed in a tubular furnace and calcined at a constant temperature in a N2 atmosphere at a temperature of 500°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / TiO2 / C composite microwave absorbing material.

[0040] The Fe3O4 / TiO2 / C composite microwave absorbing material prepared by the preparation method described in Example 8 is used in the microwave absorption process, wherein the effective phases for microwave absorption are Fe3O4, TiO2 and C, wherein Fe3O4 is used as a magnetic component, TiO2 and C are used as dielectric components, and the dielectric component TiO2 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0041] like Figure 8 As shown, the X-ray diffraction spectrum of the Fe3O4 / TiO2 / C composite microwave absorbing material prepared in Example 8 has characteristic peaks of Fe3O4 and TiO2, which proves that TiO2 can be successfully prepared by the sol-gel method and Fe2O3 can be successfully carbon thermally reduced to Fe3O4.

[0042] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. Fe x O y The preparation method of / TiO2 / C composite microwave absorbing material is characterized in that: The following steps are involved: S1. Drying the solid waste in an oven at a drying temperature of 60°C to 130°C for 6 to 10 hours; then ball-milling the solid waste and sieving it through a standard sieve of 80 to 300 meshes to obtain solid waste powder; the solid waste is rare earth waste residue or red mud; S2, mixing the solid waste powder after drying in step S1 with soluble starch in a mass ratio of 1: (0.5-2) to obtain a mixed powder for use in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of (1-9):(1-4):(0-30) to obtain a mixed solution; secondly, deionized water is added dropwise into the mixed solution, and the volume of the added deionized water accounts for 1%-5% of the total volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S2 is weighed and added to the sol, and when the solid waste is rare earth waste residue, the mass ratio of the rare earth waste residue in the mixed powder to the tetrabutyl titanate in the sol is 1:(2-15); when the solid waste is red mud, the mass ratio of the red mud in the mixed powder to the tetrabutyl titanate in the sol is 1:(1-6); the mixture is mixed uniformly by magnetic stirring; finally, a gel is obtained after aging; S4. First, the gel prepared in step S3 is placed in an oven and dried at a temperature of 60°C to 120°C for 6 to 12 hours to obtain a precursor dry gel; Then, the precursor dry gel was placed in a tubular furnace and calcined at a constant temperature of 400°C to 1000°C in a N2 atmosphere for 2 h, and then cooled to room temperature to obtain Fe x O y / TiO2 / C composite microwave absorbing material.

2. Fe according to claim 1 x O y The preparation method of / TiO2 / C composite microwave absorbing material is characterized in that: The composition and mass percentage of the rare earth waste slag are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%; the composition and mass percentage of the red mud are: Fe2O3: 43.36%~44.86%, Al2O3: 19.06%~19.85%, SiO2: 19.92%~20.42%, Na2O: 6.83%~7.33%, TiO2: 4.96%~5.26%, CaO: 3.58%~4.58%.

3. Fe according to claim 1 x O y The preparation method of / TiO2 / C composite microwave absorbing material is characterized in that: In the step S3, the rotation speed of the magnetic stirring is 100-400 r / min.

4. Fe according to claim 1 x O y The preparation method of / TiO2 / C composite microwave absorbing material is characterized in that: In the step S3, the aging is carried out at room temperature, and the aging time is 8-18 hours.

5. Fe prepared by the preparation method as claimed in claim 1 x O y Application of / TiO2 / C composite microwave absorbing materials in microwave absorption process.

6. The use according to claim 5, characterized in that: The Fe x O y The effective phase for microwave absorption in the / TiO2 / C composite microwave absorbing material is Fe x O y , TiO2 and C, the Fe x O y Fe or Fe3O4; Among them, Fe x O y As magnetic components, TiO2 and C serve as dielectric components.

7. The use according to claim 6, characterized in that: In the Fe x O y In the / TiO2 / C composite microwave absorbing material, the dielectric component TiO2 is wrapped around the magnetic component Fe x O y Outside the composite absorbing material, the dielectric component C is evenly distributed in the composite absorbing material.

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