Preparation method and application of FexOy / BaTiO3 / C composite microwave absorbing material

Abstract

The invention discloses a preparation method and application of a FexOy / BaTiO3 / C composite microwave absorbing material, belongs to the technical field of solid waste recycling and microwave absorbing materials, and solves the technical problem of comprehensive utilization of red mud and rare earth waste residues. The solution is as follows: firstly, red mud or rare earth waste residues are subjected to drying, ball milling and screening treatment and then mixed with soluble starch, and mixed powder is prepared; secondly, preparing a barium acetate aqueous solution; thirdly, adding the barium acetate aqueous solution into a mixed solution prepared from tetrabutyl titanate, glacial acetic acid and absolute ethyl alcohol to prepare 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 / BaTiO3 / C composite microwave absorbing material. The composite microwave absorbing material is prepared by taking the red mud, the rare earth waste residues and the tetrabutyl titanate as raw materials, a new way is provided for resource utilization of solid wastes, and low-cost preparation of the microwave absorbing material is also realized.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste recycling and microwave absorbing materials, and specifically relates to a Fe x O y Preparation method and application of / BaTiO3 / C composite microwave absorbing material. Background Art

[0002] Modern technology has been developed to a large extent using energy forms, the most relevant of which is electricity. Power stations generate alternating current with a frequency of 50~60Hz, which is transmitted through high-voltage transmission lines, but these lines are usually close to buildings where people live or work. In addition, household appliances that use alternating current can also expose people to electromagnetic fields. Static magnetic fields are also generated in trams, electric trains, and industrial production processes. Electromagnetic fields produce non-ionizing radiation and cause so-called electromagnetic wave pollution. Therefore, many researchers focus their research on the research and development of electromagnetic wave absorbing materials. Most of the electromagnetic wave absorbing materials on the market are currently prepared from pure materials, which are costly and limit their large-scale production. Therefore, achieving low-cost preparation of electromagnetic wave absorbing materials has become a hot issue of concern to researchers.

[0003] Red mud is a polluting solid waste discharged after alumina is extracted from bauxite. Due to different production processes and ore sources, 0.6 to 1.8 tons of red mud will be produced for every ton of alumina produced. As a major solid waste discharged during the alumina production process, the comprehensive utilization rate of red mud does not exceed 5%. At present, the treatment of red mud is basically carried out by open-air storage, which occupies a large amount of land. In addition, the heavy metal ions contained in red mud have caused serious pollution to the surrounding environment and groundwater. Therefore, it is urgent to find a method to utilize red mud resources and use it on a large scale.

[0004] Since the birth of the third generation of rare earth permanent magnet material, NdFeB, it has been widely used due to its excellent magnetic properties, and its output and consumption have also increased day by day. However, in the production process of NdFeB magnetic materials, NdFeB waste of no less than 30% of the raw material weight will be produced, of which about 30% is rare earth, more than 60% is iron, and there is also a part of waste slag containing cobalt, aluminum, copper and other elements. This waste slag is generally called "primary waste slag". After further purification of the primary waste slag, the rare earth is extracted to obtain secondary waste slag, and the iron content in the secondary waste slag will reach 80%. At present, there are many studies on primary waste slag, mainly focusing on the enrichment and refining of rare earth in waste slag, but the utilization of secondary waste slag is less, which will cause waste of resources and environmental pollution. Therefore, the rational and efficient use of rare earth waste slag can not only alleviate environmental pressure, but also promote the healthy development of the rare earth industry.

[0005] Barium titanate (BaTiO3) is a typical ABO3 type functional material. It is widely used in a variety of electronic devices in the ceramic industry due to its high dielectric constant, significant ferroelectric, piezoelectric, thermoelectric properties and energy harvesting properties, such as multilayer ceramic capacitors, dynamic random access memory, thermistors, etc. Wang et al. prepared Au / BaTiO3 nanocomposite films by sol-gel method, mixing barium acetate, titanium isopropoxide and tetrachlorogold trihydrate, adding an equal molar amount of acetylacetone as a stabilizer, and aging to form a stable BaTiO3 sol. Finally, the Au / BaTiO3 nanocomposite film was obtained after annealing and other treatments, but the preparation cost is relatively high.

[0006] In summary, the rational recycling of red mud and rare earth waste residues to prepare Fe x O y / BaTiO3 / C composite microwave absorbing material can not only reduce the adverse impact on the environment and society caused by improper solid waste disposal, but also significantly reduce the production cost of microwave 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 / BaTiO3 / C composite microwave absorbing material provide new ideas for the high value-added 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 / BaTiO3 / C composite microwave absorbing material comprises the following steps: S1. Drying solid waste in an oven, wherein the solid waste is red mud or rare earth waste residue, the drying temperature is 60°C to 120°C, and the drying time is 4 to 10 hours; the dried solid waste is ball-milled and sieved through a 100-mesh to 300-mesh standard sieve to obtain solid waste powder; then, the solid waste powder is mixed evenly with soluble starch in a mass ratio of 1:(0.5-2) to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a barium acetate aqueous solution with a mass concentration of 20% to 45%, which will be used in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:(0-4):(2-8) to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, and the volume of the barium acetate aqueous solution accounts for 10%-30% of the volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, when the solid waste is red mud, the mass ratio of the red mud powder in the mixed powder to the tetrabutyl titanate in the sol is 1:(0.5-2), 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 is 1:(1-5), and 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 70°C to 100°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 / BaTiO3 / C composite microwave absorbing material.

[0009] Furthermore, the composition of the red mud and its mass percentage 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%; the composition of the rare earth waste slag and its mass percentage are: Fe2O3: 92.1%, CoO: 1.7%, SiO2: 1.3%, Al2O3: 1.0%, LOI: 3.9%.

[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 10-24 hours.

[0012] The Fe prepared by the above-mentioned preparation method x O y Application of / BaTiO3 / C composite microwave absorbing materials in microwave absorption process.

[0013] Furthermore, the Fe x O y The effective phase for microwave absorption in the / BaTiO3 / C composite microwave absorbing material is Fe x O y, BaTiO3 and C, the Fe x O y is Fe or Fe3O4; among which, Fe x O y As a magnetic component, BaTiO3 and C serve as a dielectric component.

[0014] Further, in the Fe x O y In the / BaTiO3 / C composite microwave absorbing material, the dielectric component BaTiO3 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 carbon thermal reaction, red mud or rare earth waste is used as an iron source to provide the magnetic component of the composite material, and soluble starch is used as a reducing agent to participate in the reaction. The remaining soluble starch not consumed by the carbon thermal reduction reaction and BaTiO3 in the composite material exist together as the dielectric component of the composite material, and synergize with the magnetic component to improve the microwave absorption performance of the material; 2. The main raw material red mud used in the present invention is solid waste. The strong alkaline substances in it can activate the carbon in the system, better participate in the reaction process of carbon thermal reduction, and at the same time increase the pore structure of the material, which is conducive to multiple reflection and scattering of electromagnetic waves in the material, and at the same time is conducive to the lightweight of the material; 3. Fe2O3 in rare earth waste or red mud can undergo carbothermal reduction reaction with soluble starch to generate Fe x O y As a magnetic component, it optimizes the microwave absorbing performance of the composite material, reduces the cost of the microwave absorbing material, and is conducive to the low-cost production of microwave absorbing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the microwave reflection loss curve of the Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared in Example 1.

[0017] Figure 2 This is the Raman spectrum of carbon in the Fe / BaTiO3 / C composite microwave absorbing material prepared in Example 2.

[0018] Figure 3 This is the X-ray diffraction spectrum of the Fe / BaTiO3 / C composite microwave absorbing material prepared in Example 3.

[0019] Figure 4 This is a microwave reflection loss curve of the Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared in Example 4.

[0020] Figure 5 This is the Raman spectrum of the Fe / BaTiO3 / C composite microwave absorbing material prepared in Example 5.

[0021] Figure 6 This is the XRD spectrum of the Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared in Example 6. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Example 1

[0023] The preparation method of Fe3O4 / BaTiO3 / C composite microwave absorbing material comprises the following steps: S1. Weigh red mud and place it in an oven for drying at a drying temperature of 80°C for 10 hours. After ball milling, the dried red mud is sieved through a 120-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%; then, the red mud powder is mixed evenly with soluble starch of equal mass to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a 35% barium acetate aqueous solution for later use; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1:5 to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is measured and added dropwise to the mixed solution, the volume of the barium acetate aqueous solution accounts for 19% of the volume of the mixed solution, to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, the mass ratio of red mud powder 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 100-200 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 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 calcination temperature of 700°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / BaTiO3 / C composite microwave absorbing material.

[0024] The Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared by the preparation method described in Example 1 is used in the microwave absorption process, and the effective phases for microwave absorption are Fe3O4, BaTiO3 and C, wherein Fe3O4 is used as a magnetic component, BaTiO3 and C are used as dielectric components, and the dielectric component BaTiO3 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0025] like Figure 1 As shown, when the Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared in Example 1 is used in the microwave absorption process, when the coating thickness is 2.0 mm, its effective bandwidth is 3.04 GHz and the minimum reflection loss value is -32.64 dB. Example 2

[0026] The preparation method of Fe / BaTiO3 / C composite microwave absorbing material comprises the following steps: S1. Weigh red mud and place it in an oven for drying at a drying temperature of 90°C for 8 hours. After ball milling, the dried red mud is sieved 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%; then, the red mud powder is mixed evenly with soluble starch of equal mass to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a 40% barium acetate aqueous solution for later use; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1:6 to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, the volume of the barium acetate aqueous solution accounts for 23% of the volume of the mixed solution, to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, the mass ratio of red mud powder 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 10 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 90°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 / BaTiO3 / C composite microwave absorbing material.

[0027] The Fe / BaTiO3 / C composite microwave absorbing material prepared by the preparation method described in Example 2 is used in the microwave absorption process, and the effective phases for microwave absorption are Fe, BaTiO3 and C, wherein Fe is used as a magnetic component, BaTiO3 and C are used as dielectric components, and the dielectric component BaTiO3 is wrapped around the outside of the magnetic component Fe, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0028] Depend on Figure 2 It can be seen that the Raman spectrum of the Fe / BaTiO3 / C composite microwave absorbing material prepared in Example 2 shows obvious D peak and G peak, indicating that there is still residual carbon in the system after the carbothermal reduction reaction. Example 3

[0029] The preparation method of Fe / BaTiO3 / C composite microwave absorbing material comprises the following steps: S1. Weigh the red mud and place it in an oven for drying at a drying temperature of 100°C for 6 hours. After the dried red mud is ball-milled, it is sieved through a 180-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%; then, the red mud powder is mixed evenly with soluble starch of equal mass to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a 30% barium acetate aqueous solution for later use; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1:6 to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, and the volume of the barium acetate aqueous solution accounts for 20% of the volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, and the mass ratio of the red mud powder in the mixed powder to the tetrabutyl titanate in the sol is 1:1.8, 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 15 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 / BaTiO3 / C composite microwave absorbing material.

[0030] The Fe / BaTiO3 / C composite microwave absorbing material prepared by the preparation method described in Example 3 is used in the microwave absorption process. The effective phases for microwave absorption are Fe, BaTiO3 and C, wherein Fe is used as a magnetic component, BaTiO3 and C are used as dielectric components, and the dielectric component BaTiO3 is wrapped around the outside of the magnetic component Fe, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0031] like Figure 3 As shown, the X-ray diffraction spectrum of the Fe / BaTiO3 / C composite microwave absorbing material prepared in Example 3 has obvious BaTiO3 and Fe characteristic peaks, which proves that BaTiO3 is successfully prepared by the sol-gel method and Fe2O3 is successfully carbon thermally reduced to Fe. Example 4

[0032] The preparation method of Fe3O4 / BaTiO3 / 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 100-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 8 hours. The dried rare earth waste residue is evenly mixed with soluble starch at a mass ratio of 1:1 to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a 37.5% barium acetate aqueous solution for later use; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:0.7:3.4 to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, and the volume of the barium acetate aqueous solution accounts for 24.5% of the volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, and the mass ratio of the mixed powder to tetrabutyl titanate is 1:1.5, 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 drying temperature of 100°C for 6 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 / BaTiO3 / C composite microwave absorbing material.

[0033] The Fe3O4 / BaTiO3 / 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, BaTiO3 and C; wherein Fe3O4 is used as a magnetic component, BaTiO3 and C are used as dielectric components, and the dielectric component BaTiO3 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0034] like Figure 4 As shown, when the Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared in Example 4 is used in the microwave absorption process, when the coating thickness is 1.5 mm, its effective bandwidth is 3.4 GHz, and the minimum reflection loss is -30.4 dB; when the coating thickness is 2.5 mm, its effective bandwidth is 3.0 GHz, and the minimum reflection loss is -35.3 dB. Example 5

[0035] The preparation method of Fe / BaTiO3 / 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 10 hours. The dried rare earth waste residue is evenly mixed with soluble starch at a mass ratio of 1:0.5 to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a 37.5% barium acetate aqueous solution for later use; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1:5.2 to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, and the volume of the barium acetate aqueous solution accounts for 17.5% of the volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, and the mass ratio of the mixed powder to tetrabutyl titanate 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 20 hours; S4. First, the gel prepared in step S3 is placed in an oven for drying at a temperature of 80°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 900°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe / BaTiO3 / C composite microwave absorbing material.

[0036] The Fe / BaTiO3 / 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 Fe, BaTiO3 and C; wherein Fe is used as a magnetic component, BaTiO3 and C are used as dielectric components, and the dielectric component BaTiO3 is wrapped around the outside of the magnetic component Fe, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0037] like Figure 5 As shown, the Raman spectrum of the Fe / BaTiO3 / C composite microwave absorbing material prepared by the preparation method described in Example 5 has D peak and G peak, which proves that after the carbothermal reduction reaction, there is still excess carbon inside the Fe / BaTiO3 / C composite material, which can be used as a dielectric component to improve the microwave loss capacity of the material. Example 6

[0038] The preparation method of Fe3O4 / BaTiO3 / 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 a drying time of 10 hours. The dried rare earth waste residue is evenly mixed with soluble starch at a mass ratio of 1:1.5 to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a 33.3% barium acetate aqueous solution for later use; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:1:6.9 to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, the volume of the barium acetate aqueous solution accounts for 16.9% of the volume of the mixed solution, to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, the mass ratio of the mixed powder to tetrabutyl titanate is 1:3, 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 drying 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 calcination temperature of 700°C for 2 hours, and then cooled to room temperature with the furnace to obtain a Fe3O4 / BaTiO3 / C composite microwave absorbing material.

[0039] The Fe3O4 / BaTiO3 / 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 Fe3O4, BaTiO3 and C; wherein Fe3O4 is used as a magnetic component, BaTiO3 and C are used as dielectric components, and the dielectric component BaTiO3 is wrapped around the outside of the magnetic component Fe3O4, and the dielectric component C is uniformly distributed in the composite absorbing material.

[0040] like Figure 6 As shown, the X-ray diffraction spectrum of the Fe3O4 / BaTiO3 / C composite microwave absorbing material prepared in Example 6 has BaTiO3 characteristic peaks, proving that the BaTiO3 crystal phase with good dielectric properties can be successfully prepared by the sol-gel method.

[0041] 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 / BaTiO3 / C composite microwave absorbing material is characterized in that: The following steps are involved: S1. Drying solid waste in an oven, wherein the solid waste is red mud or rare earth waste residue, the drying temperature is 60°C to 120°C, and the drying time is 4 to 10 hours; the dried solid waste is ball-milled and sieved through a 100-mesh to 300-mesh standard sieve to obtain solid waste powder; then, the solid waste powder is mixed evenly with soluble starch in a mass ratio of 1:(0.5-2) to obtain a mixed powder, which is reserved for use in the subsequent step; S2. Prepare a barium acetate aqueous solution with a mass concentration of 20% to 45%, which will be used in the next step; S3. First, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol are mixed uniformly in a volume ratio of 1:(0-4):(2-8) to obtain a mixed solution; secondly, the barium acetate aqueous solution prepared in step S2 is added dropwise to the mixed solution, and the volume of the barium acetate aqueous solution accounts for 10%-30% of the volume of the mixed solution to obtain a sol; thirdly, the mixed powder prepared in step S1 is weighed and added to the sol, when the solid waste is red mud, the mass ratio of the red mud powder in the mixed powder to the tetrabutyl titanate in the sol is 1:(0.5-2), 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 is 1:(1-5), and 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 70°C to 100°C for a drying time of 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 / BaTiO3 / C composite microwave absorbing material.

2. Fe according to claim 1 x O y The preparation method of / BaTiO3 / C composite microwave absorbing material is characterized in that: 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%; 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%.

3. Fe according to claim 1 x O y The preparation method of / BaTiO3 / 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 / BaTiO3 / 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 10-24 hours.

5. Fe prepared by the preparation method as claimed in claim 1 x O y Application of / BaTiO3 / 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 / BaTiO3 / C composite microwave absorbing material is Fe x O y , BaTiO3 and C, the Fe x O y Fe or Fe3O4; Among them, Fe x O y As a magnetic component, BaTiO3 and C serve as a dielectric component.

7. The use according to claim 6, characterized in that: In the Fe x O y In the / BaTiO3 / C composite microwave absorbing material, the dielectric component BaTiO3 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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