Bio-based wave-absorbing agent based on vinasse and preparation method and application of bio-based wave-absorbing agent

Abstract

The invention provides a vinasse-based bio-based wave absorbing agent as well as a preparation method and application thereof. According to the technical scheme provided by the invention, the high-performance wave absorbing agent derived based on the vinasse biomass material is developed, and a multi-stage pore structure combining micropores, mesopores and macropores and functional doping of heteroatoms are formed by regulating and controlling carbonization conditions (step-by-step heating calcination treatment) and adding an activating agent; the performance optimization of the wave-absorbing material and the greenization of the preparation process are realized. The multistage pore structure (the synergistic effect of micropores, mesopores and macropores) is an important design strategy for improving the performance of the wave-absorbing material. The micropores provide a larger specific surface area and are used for adsorbing and capturing electromagnetic waves; the middle hole provides a channel for propagation and diffusion of electromagnetic waves, and the transmission path of the electromagnetic waves is effectively prolonged; the macro holes improve the overall loss performance of the wave-absorbing material by enhancing multiple scattering of electromagnetic waves. According to the bio-based wave absorbing agent provided by the invention, the effective absorption bandwidth is 4.16 GHz when the matching thickness is 1.5 mm, and the minimum reflection loss is-65.7 dB when the matching thickness is 2.2 mm. Meanwhile, the vinasse derived carbon material is low in density, and the lightweight requirement of modern wave-absorbing materials is met.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic shielding, and particularly relates to a bio-based microwave absorber based on distillers' grains, its preparation method and application. Background Art

[0002] With the rapid popularization of modern communication technologies, radar stealth technologies, unmanned aerial vehicles, 5G communication devices, and various electronic products, the problem of electromagnetic wave pollution has become a global challenge. Electromagnetic wave pollution not only interferes with the normal operation of communication devices but may also have potential negative impacts on the ecological environment and human health, such as causing signal disorders in electronic devices, affecting the stability of medical devices, and endangering the cell functions of organisms. Thus, electromagnetic wave absorbing materials have emerged. Traditional electromagnetic wave absorbing materials are mainly based on metals and their oxides, such as ferrites, carbides, and certain metal alloys. These materials have excellent microwave absorption properties in the high-frequency band, but they have high density, high preparation costs, and are prone to corrosion during long-term use, resulting in performance degradation. In addition, the production processes of these materials are usually accompanied by high energy consumption and environmental pollution, making it difficult to meet the current requirements of green and sustainable development.

[0003] Considering the above, biomass materials, as a widely existing renewable resource in nature, have great application prospects in the field of new functional materials due to their rich sources, degradability, low cost, and environmental friendliness. Distillers' grains are a large number of by-products generated during the liquor manufacturing process. Its main components include cellulose, hemicellulose, and lignin. In addition, it also contains a certain amount of protein, sugars, and minerals. Due to the porous internal structure of distillers' grains and the presence of a variety of active functional groups, it is an ideal precursor for carbon materials. The invention patent with the application number CN202410802114.1 discloses a biochar-metal composite microwave absorber from white liquor distillers' grains and its preparation method. The biochar-metal composite material from white liquor distillers' grains uses biochar from white liquor distillers' grains as the matrix material, and metal nanoparticles are deposited on the surface of the biochar from white liquor distillers' grains by atomic layer deposition. Its disadvantages are that the product prepared by the technical solution has a complex preparation process, difficult-to-control pore structure, and single material function. Summary of the Invention

[0004] In order to make up for the deficiencies of the prior art, the present invention provides a bio-based microwave absorber based on distillers' grains. The technical solution is as follows: A preparation method of a bio-based microwave absorber based on distillers' grains, the preparation steps of the preparation method are as follows: Mix the distillers grains raw material evenly with an acidic activator, and then obtain the acid-activated distillers grains through drying and crushing (processed into granular or powder form); the acidic activator is one of hydrochloric acid, sulfuric acid, phosphoric acid or citric acid; the hydrochloric acid is selected from hydrochloric acid with a concentration of 5-20%; the sulfuric acid is selected from sulfuric acid with a concentration of 10-30%; the phosphoric acid is selected from phosphoric acid with a concentration of 30-50%; the citric acid is selected from citric acid with a concentration of 5-20%.

[0005] Mix and dry the acid-activated distillers grains with a mixed activator; then subject the dried product to stepwise temperature-rising calcination treatment; add a sulfur source or a phosphorus source during the stepwise temperature-rising calcination treatment; The mixed activator is selected from one of the mixed solutions of potassium hydroxide and zinc chloride, potassium hydroxide and phosphoric acid, sodium hydroxide and zinc chloride, potassium hydroxide and ferric chloride, zinc chloride and phosphoric acid, potassium hydroxide and urea, sodium carbonate and potassium hydroxide.

[0006] Preferably, the stepwise temperature-rising calcination treatment is as follows: under a nitrogen or inert gas atmosphere, heat to 400-450°C at a heating rate of 3-10°C / min for calcination treatment for 2-5 h, and add a sulfur source or a phosphorus source; then heat to 800-850°C at a heating rate of 5-10°C / min and introduce an active gas for calcination treatment for 1-3 h; then heat to 1000-1100°C at a heating rate of 2-5°C / min for calcination treatment for 0.5-3 h.

[0007] Preferably, the active gas is a mixed gas of H2 and N2, where the volume fraction of H2 is 3%-10%, and the rest is N2.

[0008] Preferably, the sulfur source is added in a mass ratio of sulfur source:distillers grains raw material of (0.1-0.5):1; the phosphorus source is added in a mass ratio of phosphorus source:distillers grains raw material of (0.1-0.5):1.

[0009] Preferably, the sulfur source is selected from one of thiourea, 1,3-dimethylthiourea or N-methylthiourea and phenylthiourea; the phosphorus source is selected from one of potassium dihydrogen phosphate or phosphoric acid.

[0010] Preferably, the mixed activator is selected from the mixed solution of potassium hydroxide and zinc chloride, where the molar ratio of potassium hydroxide to zinc chloride is 1:(1-2); Or it is selected from the mixed solution of potassium hydroxide and phosphoric acid, where the molar ratio of potassium hydroxide to phosphoric acid is 1:(0.5-2); Or it is selected from the mixed solution of sodium hydroxide and zinc chloride, where the molar ratio of sodium hydroxide to zinc chloride is 1:(1-3); Or selected from a mixed solution of potassium hydroxide and ferric chloride, wherein the molar ratio of potassium hydroxide to ferric chloride is 1:(0.2 - 1); Or selected from a mixed solution of zinc chloride and phosphoric acid, wherein the molar ratio of zinc chloride to phosphoric acid is 1:(0.5 - 1.5); Or selected from a mixed solution of potassium hydroxide and urea, wherein the molar ratio of potassium hydroxide to urea is 1:(1 - 4); Or selected from a mixed solution of sodium carbonate and potassium hydroxide, wherein the molar ratio of sodium carbonate to potassium hydroxide is 1:(1 - 2).

[0011] Preferably, the distillers grains raw material and the acidic activator are mixed in a ratio of 1 g of distillers grains dissolved in 10 - 20 ml of acidic activator, and stirred at 20 - 60 °C for 1 - 12 h.

[0012] Preferably, the acid-activated distillers grains and the mixed activator are mixed and stirred in a ratio of 1 g of acid-activated distillers grains dissolved in 10 - 20 ml of mixed activator for 10 - 12 h, and then dried at 80 - 120 °C for 6 - 12 h.

[0013] The bio-based wave absorber based on distillers grains prepared according to the technical solution of the present invention is applied to the field of electromagnetic wave absorption.

[0014] Beneficial effects The present invention provides a bio-based wave absorber based on distillers grains and a preparation method thereof. The technical solution provided by the present invention aims to develop a high-performance wave absorber derived from distillers grains biomass materials. By regulating the carbonization conditions (stepwise heating calcination treatment) and the addition of activators, a hierarchical pore structure combining micropores, mesopores and macropores and the functional doping of heteroatoms are formed, so as to realize the performance optimization of the wave-absorbing material and the greening of the preparation process. The hierarchical pore structure (the synergistic effect of micropores, mesopores and macropores) is an important design strategy for improving the performance of wave-absorbing materials. Micropores provide a large specific surface area for adsorbing and capturing electromagnetic waves; mesopores provide channels for the propagation and diffusion of electromagnetic waves, effectively extending the transmission path of electromagnetic waves; macropores improve the overall loss performance of the wave-absorbing material by enhancing the multiple scattering of electromagnetic waves. The bio-based wave absorber provided by the present invention has an effective absorption bandwidth of 4.16 GHz at a matching thickness of 1.5 mm and a minimum reflection loss of -65.7 dB at 2.2 mm. At the same time, the density of the distillers grains-derived carbon material is low, meeting the lightweight requirements of modern wave-absorbing materials.

[0015] The technical solution provided by the present invention converts distillers grains into a high-performance wave-absorbing material, which not only effectively realizes the resource utilization of waste, but also solves the environmental pollution problem. At the same time, the present invention adopts an activator treatment and carbonization process with low energy consumption, avoiding the use of harmful chemical reagents, which conforms to the concept of sustainable development.

[0016] The technical solution provided by the present invention has the advantages of low cost and simple preparation process. Distiller's grains are a large amount of solid waste generated during the production of liquor, and its main components (such as cellulose, lignin) are good precursors of carbon materials. Distiller's grains are widely sourced and inexpensive. Compared with traditional high-performance microwave absorbing materials (such as metal oxides, ferrites), the raw material cost is significantly reduced. The process flow of the present invention is simplified, without complex multi-step processing and expensive equipment, and is easy to scale up production, further reducing the overall cost. Brief Description of the Drawings

[0017] Figure 1 It is a test chart of the microwave absorbing performance of the product obtained in Example 1.

[0018] Figure 2 It is a test chart of the microwave absorbing performance of the product obtained in Comparative Example 1.

[0019] Figure 3 It is a test chart of the microwave absorbing performance of the product obtained in Comparative Example 2.

[0020] Figure 4 It is a test chart of the microwave absorbing performance of the product obtained in Comparative Example 3.

[0021] Figure 5 It is one of the SEM electron microscope scanning images of the multi-level pore structure of the product obtained in Example 1.

[0022] Figure 6 It is the second SEM electron microscope scanning image of the multi-level pore structure of the product obtained in Example 1.

[0023] Figure 7 It is the SEM electron microscope scanning image of the products obtained in Example 1 and Comparative Examples 1 - 3. Detailed Description of the Embodiments

[0024] To describe in detail the technical content, structural features, achieved objectives and effects of the technical solution, the following is a detailed description in combination with specific embodiments and accompanied by the drawings.

[0025] Example 1 A bio-based microwave absorber based on distiller's grains, the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare hydrochloric acid with a concentration of 5% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distiller's grains raw material, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery acid-activated distiller's grains; the distiller's grains raw material is sourced from fermented barley in a brewery. Step 2, treating the raw materials with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and zinc chloride, where the molar ratio of potassium hydroxide to zinc chloride is 1:1; Step 3, place the product obtained from the treatment in Step 2 under a nitrogen atmosphere and treat the raw materials by three-stage gradual heating: The first stage, heat to 400 °C at a heating rate of 5 °C / min, add 2 g of thiourea and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; The second stage, heat to 800 °C at a heating rate of 8 °C / min, and introduce an active gas at this time for calcination treatment for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reactions or phase transformations in the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; The third stage, heat to 1000 °C at a heating rate of 3 °C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0026] Comparative Example 1 A bio-based microwave absorber based on distillers grains, the preparation steps are as follows: Step 1, pre-treating the raw materials with an acid activator: Prepare hydrochloric acid with a concentration of 5% as the acid activator, take 100 ml of the acid activator and mix it with 10 g of distillers grains raw materials, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and crush after drying to obtain powdery acid-activated distillers grains; the distillers grains raw materials are from fermented barley in a brewery; Step 2, treating the raw materials with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and zinc chloride, where the molar ratio of potassium hydroxide to zinc chloride is 1:1; Step 3, place the product obtained from the treatment in Step 2 under a nitrogen atmosphere and heat to 600 °C at a heating rate of 5 °C / min, add 2 g of thiourea and calcine for 3 h.

[0027] Comparative Example 2 A bio-based microwave absorber based on distillers grains, the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare hydrochloric acid with a concentration of 5% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distillers grains raw material, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery distillers grains after acidic activation; the distillers grains raw material is from fermented barley in a brewery; Step 2, treat the raw material with a mixed activator: Immerse the distillers grains after acidic activation obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and zinc chloride, where the molar ratio of potassium hydroxide to zinc chloride is 1:1; Step 3, place the product obtained in Step 2 in an active gas and heat it to 1000 °C at a heating rate of 5 °C / min, and add 2 g of thiourea for calcination treatment for 3 h. The active gas is a mixed gas of 5% H2 and 95% N2 by volume.

[0028] Comparative Example 3 A bio-based wave-absorbing agent based on distillers grains, the preparation steps are as follows: Step 1, dry 10 g of distillers grains raw material at 50 °C for 12 h, and after drying, crush to obtain powdery distillers grains; the distillers grains raw material is from fermented barley in a brewery; Step 2, place the product obtained in Step 1 in an active gas and heat it to 1000 °C at a heating rate of 5 °C / min, and add 2 g of thiourea for calcination treatment for 3 h. The active gas is a mixed gas of 5% H2 and 95% N2 by volume.

[0029] Example 2 A bio-based wave-absorbing agent based on distillers grains, the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare hydrochloric acid with a concentration of 10% as the acidic activator. Take 150 ml of the acidic activator and mix it with 10 g of distillers grains raw material, and stir at 20 °C for 10 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery distillers grains after acidic activation; the distillers grains raw material is from fermented barley in a brewery; Step 2, treat the raw material with a mixed activator: Immerse the distillers grains after acidic activation obtained in Step 1 in 200 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 2 h; the mixed activator is a mixed solution of potassium hydroxide and zinc chloride, where the molar ratio of potassium hydroxide to zinc chloride is 1:2; Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw material by three-stage gradual heating: In the first stage, heat to 420°C at a heating rate of 3°C / min, add 2 g of phosphoric acid and calcine for 5 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat to 850°C at a heating rate of 5°C / min, and introduce an active gas at this time for calcination treatment for 3 h; the active gas is a mixed gas of 10% H2 and 90% N2 by volume fraction; this stage is to promote solid-phase reaction or phase transformation of the material, and the reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation and improve the performance of the material; In the third stage, heat to 1000°C at a heating rate of 2°C / min and calcine for 3 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0030] Example 3 A bio-based microwave absorber based on distillers grains, and the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare hydrochloric acid with a concentration of 20% as the acidic activator, take 200 ml of the acidic activator and mix it with 10 g of distillers grains raw material, and stir at 40°C for 4 h; then dry at 50°C for 12 h, and crush after drying to obtain powdery acid-activated distillers grains; the distillers grains raw material is derived from fermented barley in a brewery; Step 2, treat the raw material with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 150 ml of the mixed activator and stir for 12 h, and then dry at 100°C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and zinc chloride, and the molar ratio of potassium hydroxide to zinc chloride is 1:1.5; Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw material by three-stage stepwise heating: In the first stage, heat to 420°C at a heating rate of 3°C / min, add 4 g of thiourea and calcine for 5 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat to 850°C at a heating rate of 5°C / min, and introduce an active gas at this time for calcination treatment for 3 h; the active gas is a mixed gas of 10% H2 and 90% N2 by volume fraction; this stage is to promote solid-phase reaction or phase transformation of the material, and the reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation and improve the performance of the material; In the third stage, heat to 1000°C at a heating rate of 2°C / min and calcine for 3 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0031] Example 4 A bio-based microwave absorber based on distillers grains, and the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare sulfuric acid with a concentration of 10% as the acidic activator. Take 200 ml of the acidic activator and mix it with 10 g of distillers grains raw materials, and stir at 60 °C for 11 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery acid-activated distillers grains; the distillers grains raw materials are from fermented barley in a brewery; Step 2, treat the raw materials with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 120 °C for 10 h; the mixed activator is a mixed solution of potassium hydroxide and phosphoric acid, where the molar ratio of potassium hydroxide to phosphoric acid is 1:0.5; Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw materials by three-stage gradual heating: The first stage, heat to 400 °C at a heating rate of 8 °C / min, add 2 g of potassium dihydrogen phosphate and calcine for 5 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; The second stage, heat to 850 °C at a heating rate of 10 °C / min, and introduce an active gas at this time for calcination for 3 h; the active gas is a mixed gas of 8% H2 and 92% N2 by volume; this stage is to promote solid-phase reaction or phase transformation of the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; The third stage, heat to 1050 °C at a heating rate of 2 °C / min and calcine for 3 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0032] Example 5 A bio-based microwave absorber based on distillers grains, and the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare phosphoric acid with a concentration of 30% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distillers grains raw materials, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery acid-activated distillers grains; the distillers grains raw materials are from fermented barley in a brewery; Step 2, treat the raw materials with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 150 ml of the mixed activator and stir for 12 h, and then dry at 80 °C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and phosphoric acid, where the molar ratio of potassium hydroxide to phosphoric acid is 1:1; Step 3: Place the product obtained from Step 2 under a nitrogen atmosphere and treat the raw material by gradually heating it in three stages: In the first stage, heat it to 400°C at a heating rate of 5°C / min, add 5 g of phenylthiourea and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat it to 800°C at a heating rate of 8°C / min, and introduce an active gas at this time for calcination treatment for 2 h; the active gas is a mixed gas of 4% H2 and 96% N2 by volume; this stage is to promote solid-phase reaction or phase transformation of the material, and the reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; In the third stage, heat it to 1000°C at a heating rate of 3°C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0033] Example 6 A bio-based wave absorber based on distiller's grains, and the preparation steps are as follows: Step 1: Pretreat the raw material with an acidic activator: Prepare citric acid with a concentration of 5% as the acidic activator, take 100 ml of the acidic activator and mix it with 10 g of distiller's grains raw material, and stir at 50°C for 12 h; then dry at 50°C for 12 h, and crush after drying to obtain powdery acid-activated distiller's grains; the distiller's grains raw material is derived from fermented barley in a brewery; Step 2: Treat the raw material with a mixed activator: Immerse the acid-activated distiller's grains obtained in Step 1 in 200 ml of the mixed activator and stir for 12 h, and then dry at 100°C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and phosphoric acid, and the molar ratio of potassium hydroxide to phosphoric acid is 1:2; Step 3: Place the product obtained from Step 2 under a nitrogen atmosphere and treat the raw material by gradually heating it in three stages: In the first stage, heat it to 400°C at a heating rate of 5°C / min, add 5 g of 1,3-dimethylthiourea and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat it to 800°C at a heating rate of 8°C / min, and introduce an active gas at this time for calcination treatment for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reaction or phase transformation of the material, and the reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; In the third stage, heat it to 1000 °C at a heating rate of 3 °C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0034] Example 7 A bio-based microwave absorber based on distiller's grains, and the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare sulfuric acid with a concentration of 30% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distiller's grains raw material, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery acid-activated distiller's grains; the distiller's grains raw material is from fermented barley in a brewery. Step 2, treat the raw material with a mixed activator: Immerse the acid-activated distiller's grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 100 °C for 12 h; the mixed activator is a mixed solution of sodium hydroxide and zinc chloride, and the molar ratio of sodium hydroxide to zinc chloride is 1:1. Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw material by three-stage gradual heating: In the first stage, heat it to 400 °C at a heating rate of 5 °C / min and calcine 1 g of 1,3-dimethylthiourea for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material. In the second stage, heat it to 800 °C at a heating rate of 8 °C / min, and at this time introduce an active gas and calcine for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reaction or phase transformation of the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material. In the third stage, heat it to 1000 °C at a heating rate of 3 °C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0035] Example 8 A bio-based microwave absorber based on distiller's grains, and the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare sulfuric acid with a concentration of 20% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distiller's grains raw material, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and after drying, crush to obtain powdery acid-activated distiller's grains; the distiller's grains raw material is from fermented barley in a brewery. Step 2, treating the raw material with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of sodium hydroxide and zinc chloride, where the molar ratio of sodium hydroxide to zinc chloride is 1:3; Step 3, place the product obtained from the treatment in Step 2 under a nitrogen atmosphere and treat the raw material with three-stage gradual heating: The first stage, heat to 400 °C at a heating rate of 5 °C / min, add 1 g of potassium dihydrogen phosphate and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; The second stage, heat to 800 °C at a heating rate of 8 °C / min, and introduce an active gas at this time for calcination treatment for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reaction or crystal-phase transformation of the material, and the reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; The third stage, heat to 1000 °C at a heating rate of 3 °C / min and calcine for 2 h; this stage is to promote sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0036] Example 9 A bio-based wave absorber based on distillers grains, the preparation steps are as follows: Step 1, pretreat the raw material with an acid activator: Prepare phosphoric acid with a concentration of 50% as the acid activator, take 100 ml of the acid activator and mix it with 10 g of distillers grains raw material, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and crush after drying to obtain powdery acid-activated distillers grains; the distillers grains raw material is from fermented barley in a brewery; Step 2, treating the raw material with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and iron chloride, where the molar ratio of potassium hydroxide to iron chloride is 1:0.2; Step 3, place the product obtained from the treatment in Step 2 under a nitrogen atmosphere and treat the raw material with three-stage gradual heating: The first stage, heat to 420 °C at a heating rate of 8 °C / min, add 1 g of N-methylthiourea and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat it to 820°C at a heating rate of 6°C / min, and introduce an active gas for calcination treatment for 2 h at this time; the active gas is a mixed gas of 5% H2 and 95% N2 by volume fraction; this stage promotes solid-phase reactions or phase transformations in the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; In the third stage, heat it to 1000°C at a heating rate of 3°C / min for calcination treatment for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0037] Example 10 A bio-based microwave absorber based on distillers' grains, and the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distillers' grains raw materials, and stir at 50°C for 12 h; then dry at 50°C for 12 h, and crush after drying to obtain powdery acid-activated distillers' grains; the distillers' grains raw materials are derived from fermented barley in a brewery; Step 2, treat the raw materials with a mixed activator: Immerse the acid-activated distillers' grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 100°C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and iron chloride, and the molar ratio of potassium hydroxide to iron chloride is 1:1; Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw materials by three-stage stepwise heating: In the first stage, heat it to 400°C at a heating rate of 5°C / min, add 4 g of N-methylthiourea for calcination treatment for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat it to 800°C at a heating rate of 8°C / min, and introduce an active gas for calcination treatment for 2 h at this time; the active gas is a mixed gas of 5% H2 and 95% N2 by volume fraction; this stage promotes solid-phase reactions or phase transformations in the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; In the third stage, heat it to 1000°C at a heating rate of 3°C / min for calcination treatment for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0038] Example 11 A bio-based microwave absorber based on distillers' grains, and the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distiller's grains raw materials, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and crush after drying to obtain powdery acidic-activated distiller's grains; the distiller's grains raw materials are from fermented barley in a brewery. Step 2, treat the raw materials with a mixed activator: Immerse the acidic-activated distiller's grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of zinc chloride and phosphoric acid, where the molar ratio of zinc chloride to phosphoric acid is 1:0.5. Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw materials by three-stage gradual heating: The first stage, heat to 400 °C at a heating rate of 5 °C / min, add 5 g of N-methylthiourea and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material. The second stage, heat to 800 °C at a heating rate of 8 °C / min, and introduce an active gas at this time for calcination for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reactions or phase transformations in the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material. The third stage, heat to 1000 °C at a heating rate of 3 °C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0039] Example 12 A bio-based microwave absorber based on distiller's grains, the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distiller's grains raw materials, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and crush after drying to obtain powdery acidic-activated distiller's grains; the distiller's grains raw materials are from fermented barley in a brewery. Step 2, treat the raw materials with a mixed activator: Immerse the acidic-activated distiller's grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, then dry at 100 °C for 12 h; the mixed activator is a mixed solution of zinc chloride and phosphoric acid, where the molar ratio of zinc chloride to phosphoric acid is 1:1.5. Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw materials by three-stage gradual heating: In the first stage, heat it to 400°C at a heating rate of 5°C / min, add 5 g of phenylthiourea and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat it to 800°C at a heating rate of 8°C / min, and introduce an active gas at this time for calcination treatment for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reaction or phase transformation of the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation and improve the performance of the material; In the third stage, heat it to 1100°C at a heating rate of 5°C / min and calcine for 3 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0040] Example 13 A bio-based microwave absorber based on distillers grains, and the preparation steps are as follows: Step 1, pretreat the raw material with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator, take 100 ml of the acidic activator and mix it with 10 g of distillers grains raw material, and stir at 50°C for 12 h; then dry at 50°C for 12 h, and after drying, crush it to obtain powdery acid-activated distillers grains; the distillers grains raw material is derived from fermented barley in a brewery; Step 2, treat the raw material with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 100°C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and urea, and the molar ratio of potassium hydroxide to urea is 1:1; Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw material by three-stage gradual heating: In the first stage, heat it to 400°C at a heating rate of 5°C / min, add 5 g of potassium dihydrogen phosphate and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat it to 850°C at a heating rate of 10°C / min, and introduce an active gas at this time for calcination treatment for 3 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reaction or phase transformation of the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation and improve the performance of the material; In the third stage, heat it to 1000°C at a heating rate of 3°C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0041] Example 14 A bio-based wave absorber based on distillers' grains, and the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distillers' grains raw materials, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and crush after drying to obtain powdery acidic-activated distillers' grains; the distillers' grains raw materials are from fermented barley in a brewery; Step 2, treat the raw materials with a mixed activator: Immerse the acidic-activated distillers' grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 100 °C for 12 h; the mixed activator is a mixed solution of potassium hydroxide and urea, and the molar ratio of potassium hydroxide to urea is 1:4; Step 3, place the product obtained in Step 2 under a nitrogen atmosphere and treat the raw materials by three-stage gradual heating: The first stage, heat to 400 °C at a heating rate of 5 °C / min, add 1 g of phosphoric acid and calcine for 3 h; the function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; The second stage, heat to 800 °C at a heating rate of 10 °C / min, and introduce an active gas at this time for calcination treatment for 2 h; the active gas is a mixed gas of 5% H2 and 95% N2 by volume; this stage is to promote solid-phase reaction or crystal-phase transformation of the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; The third stage, heat to 1000 °C at a heating rate of 5 °C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0042] Example 15 A bio-based wave absorber based on distillers' grains, and the preparation steps are as follows: Step 1, pretreat the raw materials with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator. Take 100 ml of the acidic activator and mix it with 10 g of distillers' grains raw materials, and stir at 50 °C for 12 h; then dry at 50 °C for 12 h, and crush after drying to obtain powdery acidic-activated distillers' grains; the distillers' grains raw materials are from fermented barley in a brewery; Step 2, treat the raw materials with a mixed activator: Immerse the acidic-activated distillers' grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 100 °C for 12 h; the mixed activator is a mixed solution of sodium carbonate and potassium hydroxide, and the molar ratio of sodium carbonate to potassium hydroxide is 1:1; Step 3: Place the product obtained from Step 2 under a nitrogen atmosphere and treat the raw material by gradually increasing the temperature in three stages: In the first stage, heat to 450°C at a heating rate of 10°C / min, add 5 g of phosphoric acid and calcine for 3 h. The function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat to 800°C at a heating rate of 8°C / min, and at this time introduce an active gas and calcine for 2 h. The active gas is a mixed gas of 5% H2 and 95% N2 by volume fraction. This stage is to promote solid-phase reactions or phase transformations in the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; In the third stage, heat to 1000°C at a heating rate of 3°C / min and calcine for 2 h. This stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0043] Example 16 A bio-based wave absorber based on distillers grains, and the preparation steps are as follows: Step 1: Pretreat the raw material with an acidic activator: Prepare citric acid with a concentration of 20% as the acidic activator, take 100 ml of the acidic activator and mix it with 10 g of distillers grains raw material, and stir at 50°C for 12 h; then dry at 50°C for 12 h, and after drying, crush to obtain powdery acid-activated distillers grains; the distillers grains raw material is derived from fermented barley in a brewery; Step 2: Treat the raw material with a mixed activator: Immerse the acid-activated distillers grains obtained in Step 1 in 100 ml of the mixed activator and stir for 12 h, and then dry at 100°C for 12 h; the mixed activator is a mixed solution of sodium carbonate and potassium hydroxide, and the molar ratio of sodium carbonate to potassium hydroxide is 1:2; Step 3: Place the product obtained from Step 2 under a nitrogen atmosphere and treat the raw material by gradually increasing the temperature in three stages: In the first stage, heat to 400°C at a heating rate of 5°C / min, add 5 g of potassium dihydrogen phosphate and calcine for 3 h. The function of this stage is to remove moisture and organic matter in the material and ensure the structural stability of the material; In the second stage, heat to 800°C at a heating rate of 8°C / min, and at this time introduce an active gas and calcine for 2 h. The active gas is a mixed gas of 5% H2 and 95% N2 by volume fraction. This stage is to promote solid-phase reactions or phase transformations in the material. The reducing atmosphere of hydrogen helps to adjust the chemical state of the material, prevent oxidation, and improve the performance of the material; In the third stage, heat it to 1000 °C at a heating rate of 3 °C / min and calcine for 2 h; this stage is to promote the sintering and densification of the material and improve its mechanical strength and electrical conductivity.

[0044] Test Example 1 Samples were prepared by mixing the product obtained in Example 1 with paraffin at a mass ratio of 6:4. All samples were pressed into a standard annulus by the same mold , in order to maintain the certainty of the geometric shape. The thickness of all annuli was maintained at 2.5 mm. The Agilent PNA software automatically outputs the relevant electromagnetic parameter test items and test results according to the Nicolson and Ross and Weir algorithms as follows: (1) Specific surface area: 800–1200 m² / g; (2) Minimum reflection loss: -65.7 dB (thickness 2.5 mm); (3) Effective absorption bandwidth: 7.8 GHz (RL ≤ -10 dB); (4) Thermal stability: retain 80% wave absorption performance at 600 °C; (5) Dielectric constant: ε’ ≈ 15 –20 , ε’’ ≈ 10 –18 (at 12 GHz); (6) Density: 0.58 g / cm³.

[0045] Test Example 2 The wave absorption performance of the products obtained in Example 1 and Comparative Examples 1-3 was tested. The test standard was based on GB / T 32596-2016, and a network analyzer (VNA, N5245A, Agilent, USA) was used to test in the 2-18 GHz frequency band.

[0046] The test results are as Figures 1 to 4 shown; it can be seen from the Figures 1 - 4 figure that the lowest reflection losses corresponding to the products obtained in Example 1 and Comparative Examples 1-3 were -65.7 dB, -20.1 dB, -54.6 dB, and -31.8 dB, respectively; the effective absorption bandwidths were 4.16 GHz, 3.72 GHz, 3.28 GHz, and 3.88 GHz, respectively.

[0047] The above results show that distiller's grains, as a kind of biomass waste, have been transformed into a high-performance wave absorption material through reasonable carbonization and activation treatment.

[0048] As Figures 6 to 7As shown, the bio-based microwave absorber prepared in Example 1 has a hierarchical pore structure (manifested as a combination of micropores, mesopores, and macropores), and this hierarchical pore structure can provide a large specific surface area and enhance the diffusion and reflection of electromagnetic waves, thereby effectively improving the microwave absorption performance.

[0049] Meanwhile, the distiller's grains itself is rich in organic components, and during the carbonization process, elements such as nitrogen, sulfur, and phosphorus can be doped to further enhance the dielectric loss and magnetic loss capabilities of the material and improve the energy absorption ability of electromagnetic waves.

[0050] In addition, by controlling the carbonization temperature and activation conditions, the graphitization degree and pore structure of the distiller's grains can be optimized to further improve its microwave absorption performance.

[0051] Test Example 3 The products prepared in Example 1 and Comparative Examples 1-3 were subjected to SEM electron microscopy structure detection, and the obtained results are as Figures 5 to 7 shown. From Figures 5 to 6 it can be seen the hierarchical pore structure of the product obtained in Example 1, and different-sized micropore structures are clearly shown in the figure. From Figure 7 it can be seen that the porosity can be further regulated through energy-level heating and activation regulation.

[0052] It should be noted that although the above embodiments have been described in this article, the patent protection scope of the present invention is not limited thereby. Therefore, based on the innovative concept of the present invention, any changes and modifications made to the embodiments described in this article, or equivalent structural or equivalent process transformations made using the content of the specification and drawings of the present invention, and directly or indirectly applying the above technical solutions to other related technical fields, are all included in the patent protection scope of the present invention.

Claims

1. A method for preparing a bio-based absorber based on wine lees, characterized in that: The preparation steps of the preparation method are as follows: The vinasse raw material and the acidic activator are mixed evenly, and then dried and crushed to obtain the acid-activated vinasse; the acidic activator is one of hydrochloric acid, sulfuric acid, phosphoric acid or citric acid; The acid-activated distiller's grains are mixed with a mixed activator and dried; and the dried product is calcined by gradually increasing the temperature; Adding a sulfur source or a phosphorus source during the step-by-step temperature increase calcination process; The mixed activator is selected from a mixed solution of potassium hydroxide and zinc chloride, a mixed solution of potassium hydroxide and phosphoric acid, a mixed solution of sodium hydroxide and zinc chloride, a mixed solution of potassium hydroxide and ferric chloride, a mixed solution of zinc chloride and phosphoric acid, a mixed solution of potassium hydroxide and urea, and a mixed solution of sodium carbonate and potassium hydroxide.

2. The preparation method according to claim 1, characterized in that: The step-by-step temperature rise calcination treatment is as follows: in a nitrogen or inert gas atmosphere, heating to 400-450°C at a heating rate of 3-10°C / min, adding a sulfur source or a phosphorus source, and calcining for 2-5 hours; then heating to 800-850°C at a heating rate of 5-10°C / min, introducing an active gas, and calcining for 1-3 hours; and then heating to 1000-1100°C at a heating rate of 2-5°C / min, and calcining for 0.5-3 hours.

3. The preparation method according to claim 2, characterized in that: The active gas is a mixed gas of H2 and N2, wherein the volume fraction of H2 is 3% to 10% and the rest is N2.

4. The preparation method according to claim 1, characterized in that: The sulfur source is added at a mass ratio of sulfur source to distiller's grains raw material of (0.1-0.5):1; the phosphorus source is added at a mass ratio of phosphorus source to distiller's grains raw material of (0.1-0.5):

1.

5. The preparation method according to claim 4, characterized in that: The sulfur source is selected from one of thiourea, 1,3-dimethylthiourea or N-methylthiourea and phenylthiourea; the phosphorus source is selected from one of potassium dihydrogen phosphate or phosphoric acid.

6. The preparation method according to claim 1, characterized in that: The mixed activator is selected from a mixed solution of potassium hydroxide and zinc chloride, wherein the molar ratio of potassium hydroxide to zinc chloride is 1:(1-2); Or selected from a mixed solution of potassium hydroxide and phosphoric acid, wherein the molar ratio of potassium hydroxide to phosphoric acid is 1:(0.5-2); Or selected from a mixed solution of sodium hydroxide and zinc chloride, wherein the molar ratio of sodium hydroxide to zinc chloride is 1:(1-3); Or selected from a mixed solution of potassium hydroxide and ferric chloride, wherein the molar ratio of potassium hydroxide to ferric chloride is 1:(0.2-1); Or selected from a mixed solution of zinc chloride and phosphoric acid, wherein the molar ratio of zinc chloride to phosphoric acid is 1:(0.5-1.5); Or selected from a mixed solution of potassium hydroxide and urea, wherein the molar ratio of potassium hydroxide to urea is 1:(1-4); Or it can be selected from a mixed solution of sodium carbonate and potassium hydroxide, wherein the molar ratio of sodium carbonate to potassium hydroxide is 1:(1-2).

7. The preparation method according to claim 1, characterized in that: The vinasse raw material and the acidic activator are mixed in a ratio of 10-20 ml of the acidic activator per 1 g of vinasse, and stirred at 20-60° C. for 10-12 hours.

8. The preparation method according to claim 1, characterized in that: The acid-activated vinasse and the mixed activator are mixed and stirred for 10-12 hours in a ratio of 10-20 ml of the mixed activator per 1 g of the acid-activated vinasse, and then dried at 80-120° C. for 6-12 hours.

9. A bio-based absorber based on wine lees, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. Use of the bio-based radar absorber based on vinasse obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The bio-based wave absorber based on wine lees is applied in the field of electromagnetic wave absorption.

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