Preparation method and application of core-shell structure biochar / CoFe2O4 anti-electromagnetic radiation material

Abstract

The invention relates to the technical field of novel anti-electromagnetic radiation materials, and discloses a preparation method and application of a core-shell structure biochar / CoFe2O4 anti-electromagnetic radiation material, and the preparation method comprises the following steps: firstly, activating dry yeast powder under a certain condition, depositing iron ions and cobalt ions on a yeast cell membrane through the metabolism process of yeast cells, and preparing a core-shell structure biochar / CoFe2O4 anti-electromagnetic radiation material; participating in a biological mineralization process of yeast cells; then, through high-temperature carbonization treatment, CoFe2O4 nanoparticles are generated from iron ions and cobalt ions under the action of a complexing agent while yeast cells are carbonized, so that the biochar / CoFe2O4 composite material is prepared by a one-step method. The anti-electromagnetic radiation material prepared by the invention has both electrical loss and magnetic loss, and has better anti-electromagnetic radiation performance. The yeast powder used in the preparation method is low in price and easy to obtain, complex processes and use of a large amount of solvents are avoided in the material preparation process, and the method is green and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of novel anti-electromagnetic radiation materials, and particularly to a preparation method and application of a core-shell structured biochar / CoFe 2 O 4 anti-electromagnetic radiation material. Background Art

[0002] Electromagnetic radiation pollution has become one of the pollutions in contemporary society. The electromagnetic radiation affecting the human living environment is mainly divided into natural electromagnetic radiation pollution sources and artificial electromagnetic radiation pollution sources. Long-term exposure of the human body to electromagnetic radiation will affect the human immune system, reproductive system, cardiovascular system, etc. through heat effect, non-thermal effect and cumulative effect ways, inducing diseases such as decreased immunity and impaired hearing, and electromagnetic radiation will also affect aircraft navigation systems, TV and network signals, etc. Therefore, the demand for anti-electromagnetic radiation materials with light weight, wide absorption frequency band and high absorption efficiency is becoming more and more urgent.

[0003] Traditional wave-absorbing materials mainly include iron-based wave-absorbing materials, carbon-based wave-absorbing materials, ceramic-based wave-absorbing materials, etc., which can absorb and dissipate electromagnetic waves and electromagnetic radiation through dielectric loss, resistive loss and magnetic loss. Among them, CoFe 2 O 4 ferrite has broad application prospects in the field of microwave absorption due to its excellent magnetic properties, chemical stability, unique structure and other advantages. However, the ferrite material has small dielectric loss and narrow absorption frequency band. Moreover, the ferrite material has a relatively large specific gravity, which limits its practical application. Summary of the Invention

[0004] Object of the Invention: Aiming at the problems existing in the prior art, the present invention provides a preparation method and application of a core-shell structured biochar / CoFe 2 O 4 anti-electromagnetic radiation material. By compounding yeast cells with CoFe 2 O 4 precursor and preparing the biochar / CoFe 2 O 4 anti-electromagnetic radiation material by one-step carbonization method. On the one hand, the present invention realizes the low-cost and green preparation of novel anti-electromagnetic radiation materials; on the other hand, it can not only broaden the wave-absorbing bandwidth of ferrite materials but also reduce the specific gravity of the composite material, thus broadening the application range of ferrite.

[0005] Technical Solution: On the one hand, the present invention provides a preparation method of a core-shell structured biochar / CoFe 2 O 4 anti-electromagnetic radiation material, comprising the following steps: S1. Activate yeast cells to obtain a yeast cell solution; S2. Bio - mineralization process of metal ions in yeast cells: Add cobalt chloride hexahydrate and ferric chloride hexahydrate into the yeast cell solution for bio - mineralization, so that metal ions are deposited in the yeast cell membrane; Subsequently, add tartaric acid and adjust the pH value of the solution to 5 - 7; Then, after constant - temperature water - bath and stirring evaporation to form a gel, dry it to obtain a honeycomb - shaped dry gel, which is the yeast cell / CoFe 2 O 4 precursor; S3: Yeast cell / CoFe 2 O 4 Carbonization heat - treatment of the precursor: Carbonize and heat - treat the yeast cell / CoFe 2 O 4 precursor in a nitrogen atmosphere, and cool it naturally to obtain the bio - carbon / CoFe 2 O 4 anti - electromagnetic radiation material.

[0006] Preferably, in S1, the specific steps for activating the yeast cells are: Place dry yeast powder in a glucose solution for cultivation, centrifuge and wash to obtain an activated yeast cell solution.

[0007] Furthermore, the mass ratio of the dry yeast powder to glucose and deionized water in the glucose solution is 1∶0.5 - 3∶30 - 100; The specific conditions for the cultivation are: the cultivation temperature is 30 - 40 °C, and the cultivation time is 0.5 - 2 h.

[0008] Furthermore, in S2, the mass ratio of the yeast cells, cobalt chloride hexahydrate, and ferric chloride hexahydrate is 3∶1 - 10∶2 - 20.

[0009] Furthermore, in S2, the specific conditions for the bio - mineralization are: the mineralization temperature is 30 - 40 °C, and the mineralization time is 12 - 48 h.

[0010] Furthermore, in S2, the addition amount of tartaric acid is 25% - 75% of the total amount of the substance of metal ions.

[0011] Preferably, in S2, the temperature of the constant - temperature water - bath is 70 - 80 °C; In S2, the drying temperature is 80 - 120 °C.

[0012] Furthermore, in S3, the specific conditions for the carbonization heat - treatment are: the heating rate is 5 - 20 °C / min, the highest temperature is 600 - 900 °C, and the heat - preservation time is 1 - 4 h.

[0013] On the other hand, the present invention provides an application of the material prepared by the method described in any one of the above in anti - electromagnetic radiation.

[0014] The preparation principle of the present invention is as follows: In the present invention, dry yeast powder is first activated under certain conditions. Iron ions and cobalt ions are deposited on the yeast cell membrane through the metabolic process of yeast cells and participate in the biomineralization process of yeast cells. Subsequently, through high-temperature carbonization treatment, while the yeast cells are carbonized, iron ions and cobalt ions react with a complexing agent to generate CoFe 2 O 4 nanoparticles, thereby preparing a biochar / CoFe 2 O 4 composite material in one step. In the present invention, the yeast cell wall is negatively charged, which enables yeast cells to combine with positively charged metal ions through electrostatic attraction. Therefore, the activated yeast cells have a strong ability to adsorb metal ions. Thus, cobalt ions and iron ions can be adsorbed by them. Yeast cells have the characteristics of biomineralization, and the adsorbed metal ions are mineralized in the yeast cells to achieve a phase transformation. Then, high-temperature carbonization treatment is carried out. Under a nitrogen atmosphere, the yeast cells are transformed into biochar microspheres, and cobalt ions and iron ions react with the complexing agent to generate CoFe 2 O 4 ferrite, which is deposited on the surface of the carbon microspheres to form a core-shell structure biochar / CoFe 2 O 4 anti-electromagnetic radiation material.

[0015] Carbonizing yeast cells and compounding them with ferrite enables the composite anti-electromagnetic radiation material to have both dielectric loss and magnetic loss, increases the loss forms, broadens the absorption frequency band of the ferrite material, and enhances its absorption efficiency. Moreover, after the yeast cells are carbonized, carbon microspheres are formed, and the ferrite is deposited on the surface of the carbon microspheres to form a shell layer. The finally formed composite material has a core-shell structure, and its formation mechanism is as Figure 1 shown. The composite material has the advantage of light weight, which expands the application range of the ferrite material. The anti-electromagnetic radiation material prepared by the present invention can be used in fields such as stealth coatings, electronic communications, and new energy vehicles.

[0016] Beneficial effects: Compared with the prior art, the present invention uses a one-step carbonization method to prepare a core-shell structure biochar / CoFe 2 O 4 anti-electromagnetic radiation material, which has the following advantages: 1) The yeast cells used in the present invention are easily available, the components are safe and environmentally friendly, and the preparation cost is relatively low. And the preparation process does not involve the use of a large amount of solvents, is economical and environmentally friendly, the technology is simple, easy to operate, and can realize the low-cost and green preparation of anti-electromagnetic radiation materials.

[0017] 2) The present invention uses a one-step carbonization method to prepare an anti-electromagnetic radiation material. While the yeast cells are carbonized, the ferrite crystallizes, saving energy and having a simple process.

[0018] 3) Ferrite nanoparticles are deposited on the surface of the microspheres formed after the carbonization of yeast cells, forming a multiphase interface, which in turn increases the dielectric loss of the composite material. The ferrite acts as a shell, making it easier for electromagnetic waves to enter the interior of the material and be dissipated by the biological carbon, improving the electromagnetic wave absorption performance of the composite material and thus enhancing its anti-electromagnetic radiation performance.

[0019] 4) Preparing a core-shell structure composite material by combining ferrite and biological carbon can reduce the specific gravity of the composite material.

[0020] 5) No one has prepared an anti-electromagnetic radiation material by carbonizing yeast cells and combining them with ferrite in domestic and foreign papers, patents and other literatures. The applicant uses green and environmentally friendly yeast cells as a biological carbon source to prepare a composite material. Not only is the preparation process green and environmentally friendly, but the prepared anti-electromagnetic radiation material has the characteristics of high absorption efficiency and small specific gravity. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a formation mechanism diagram of the core-shell structure biological carbon / CoFe 2 O 4 in the present invention; Figure 2 It is an XRD pattern of the core-shell structure biological carbon / CoFe 2 O 4 in Embodiment 3; Figure 3 It is a curve of the reflectivity of the core-shell structure biological carbon / CoFe 2 O 4 changing with frequency in Embodiment 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be described in detail below in conjunction with the embodiments.

[0023] Embodiment 1: (1) Activation of yeast cells: First, 3 g of dry yeast powder is placed in a glucose solution (6 g of glucose and 150 mL of water), and cultured at 37 °C for 30 min to restore the biological activity of the yeast cells. After centrifugation and washing, an activated yeast cell solution is obtained.

[0024] (2) Biomineralization process of metal ions in yeast cells: At a temperature of 37 °C, 1.0135 g of cobalt chloride hexahydrate and 2.3059 g of iron chloride hexahydrate were added to the yeast cell solution activated in step (1). The metal ions will be deposited in the yeast cell membrane through biomineralization, and the deposition and mineralization time is 24 h. Subsequently, the solution was heated to 50 °C, 0.9596 g of complexing agent tartaric acid was added, the pH of the solution was adjusted to about 5 with ammonia water, the solution was placed in a constant temperature water bath at 70 - 80 °C, and after heating and evaporation to form a gel with continuous stirring, it was dried at 110 °C for 24 h and then transformed into a honeycomb-like dry gel, which is the yeast cell / CoFe 2 O 4 precursor.

[0025] (3) Yeast cell / CoFe 2 O 4 Carbonization heat treatment of the precursor: The yeast cell / CoFe 2 O 4 precursor was loaded into an alumina boat and placed in a tubular furnace. Under a nitrogen atmosphere, it was heated to 700 °C at a heating rate of 5 °C / min and held for 1 h. After the carbonization reaction ended, it was naturally cooled to room temperature, which is the biochar / CoFe 2 O 4 anti-electromagnetic radiation material.

[0026] Embodiment 2: (1) Activation of yeast cells: First, 1 g of dry yeast powder was placed in a glucose solution (2 g of glucose and 50 mL of water), and cultured at 37 °C for 30 min to restore the biological activity of the yeast cells. After centrifugation and washing, an activated yeast cell solution was obtained.

[0027] (2) Biomineralization process of metal ions in yeast cells: At a temperature of 37 °C, 1.0135 g of cobalt chloride hexahydrate and 2.3059 g of iron chloride hexahydrate were added to the yeast cell solution activated in step (1). The metal ions will be deposited in the yeast cell membrane through biomineralization, and the deposition and mineralization time is 24 h. Subsequently, the solution was heated to 50 °C, 0.9596 g of complexing agent tartaric acid was added, the pH of the solution was adjusted to about 5 with ammonia water, the solution was placed in a constant temperature water bath at 70 - 80 °C, and after heating and evaporation to form a gel with continuous stirring, it was dried at 110 °C for 24 h and then transformed into a honeycomb-like dry gel, which is the yeast cell / CoFe 2 O 4 precursor.

[0028] (3) Yeast cell / CoFe 2 O 4 Carbonization heat treatment of the precursor: The yeast cell / CoFe 2 O 4The precursor was loaded into an alumina boat and placed in a tube furnace. Under a nitrogen atmosphere, it was heated to 700 °C at a heating rate of 5 °C / min and held for 1 h. After the carbonization reaction ended, it was naturally cooled to room temperature to obtain biochar / CoFe 2 O 4 anti-electromagnetic radiation material.

[0029] Embodiment 3: (1) Activation of yeast cells: First, 1 g of dry yeast powder was placed in a glucose solution (2 g of glucose and 50 mL of water) and cultured at 37 °C for 30 min to restore the biological activity of the yeast cells. After centrifugation and washing, an activated yeast cell solution was obtained.

[0030] (2) Biomineralization process of metal ions in yeast cells: At a temperature of 37 °C, 3.0405 g of cobalt chloride hexahydrate and 6.9177 g of iron chloride hexahydrate were added to the activated yeast cell solution obtained in step (1). The metal ions will be deposited in the yeast cell membrane through biomineralization, and the deposition and mineralization time is 24 h. Subsequently, the solution was heated to 50 °C, 2.8788 g of the complexing agent tartaric acid was added, the pH of the solution was adjusted to about 5 with ammonia water, and the solution was placed in a constant temperature water bath at 70 - 80 °C. After heating and evaporation with continuous stirring to form a gel, it was dried at 110 °C for 24 h and then transformed into a honeycomb-like dry gel, which is the yeast cell / CoFe 2 O 4 precursor.

[0031] (3) Carbonization heat treatment of yeast cell / CoFe 2 O 4 precursor: The yeast cell / CoFe 2 O 4 precursor was loaded into an alumina boat and placed in a tube furnace. Under a nitrogen atmosphere, it was heated to 700 °C at a heating rate of 5 °C / min and held for 1 h. After the carbonization reaction ended, it was naturally cooled to room temperature to obtain biochar / CoFe 2 O 4 anti-electromagnetic radiation material.

[0032] The materials prepared in this Embodiment 3 were characterized, and the results are as follows: Figure 2 For the XRD pattern of the core-shell structured biochar / CoFe 2 O 4 anti-electromagnetic radiation material in Embodiment 3. As can be seen from the figure, characteristic diffraction peaks of CoFe 2 O 4 appeared in the XRD pattern, indicating that CoFe 2 O 4Successfully synthesized. In addition, a small number of diffraction peaks of biochar appeared in the XRD pattern, indicating that at this carbonization temperature, a small amount of biochar was crystallized. It shows that the biochar / CoFe 2 O 4 composite material was successfully synthesized.

[0033] The electromagnetic radiation resistance of biochar / CoFe 2 O 4 can be evaluated by the reflectivity of the material to electromagnetic waves. Figure 3 Figure 17 is the curve of the reflectivity of the biochar / CoFe 2 O 4 electromagnetic radiation resistant material in Embodiment 3 changing with frequency. As can be seen from the figure, for biochar / CoFe 2 O 4 when the thickness is 3.0 mm and 4.0 mm, the minimum reflectivity value reaches -10 dB. And at this thickness, the bandwidth of biochar / CoFe 2 O 4 less than -5 dB reaches 5 GHz, showing a relatively large bandwidth. It is worth pointing out that when the thickness is 2.0 mm, the reflectivity of biochar / CoFe 2 O 4 is less than -5 dB in the range of 13 - 18 GHz, showing a strong ability to absorb electromagnetic waves, indicating that the biochar / CoFe 2 O 4 at this thickness can be applied to the absorption of electromagnetic radiation in the high-frequency band. In summary, the biochar / CoFe 2 O 4 composite material shows good electromagnetic wave absorption ability and has great application potential as an electromagnetic radiation resistant material.

[0034] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material, characterized in that: The following steps are involved: S1. Activating yeast cells to obtain yeast cell solution; S2. Biomineralization process of metal ions in yeast cells: cobalt chloride hexahydrate and ferric chloride hexahydrate are added to the yeast cell solution for biomineralization, so that the metal ions are deposited in the yeast cell membrane; then, tartaric acid is added, and the pH value of the solution is adjusted to 5-7; then, a constant temperature water bath is placed, stirred and evaporated to form a gel, and then dried to obtain a honeycomb dry gel, which is a yeast cell / CoFe2O4 precursor; S3: Carbonization heat treatment of yeast cell / CoFe2O4 precursor: Carbonization heat treatment of the yeast cell / CoFe2O4 precursor is performed in a nitrogen atmosphere, and naturally cooled to obtain a biochar / CoFe2O4 anti-electromagnetic radiation material.

2. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 1, characterized in that: In S1, the specific steps of activating the yeast cells are: placing dry yeast powder in a glucose solution for cultivation, centrifuging, and washing to obtain an activated yeast cell solution.

3. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 2, characterized in that: The mass ratio of the dry yeast powder to the glucose and deionized water in the glucose solution is 1:0.5-3:30-100; The specific conditions of the culture are: the culture temperature is 30-40° C., and the culture time is 0.5-2 h.

4. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 1, characterized in that: In S2, the mass ratio of the yeast cells, cobalt chloride hexahydrate and ferric chloride hexahydrate is 3:1-10:2-20.

5. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 1, characterized in that: In S2, the specific conditions of the biomineralization are: the mineralization temperature is 30-40°C, and the mineralization time is 12-48 hours.

6. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 1, characterized in that: In S2, the added amount of tartaric acid is 25% to 75% of the total amount of metal ion substances.

7. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 1, characterized in that: In S2, the temperature of the constant temperature water bath is 70-80°C; In S2, the drying temperature is 80-120°C.

8. The method for preparing the core-shell structured biochar / CoFe2O4 anti-electromagnetic radiation material according to claim 1, characterized in that: In S3, the specific conditions of the carbonization heat treatment are: a heating rate of 5 to 20°C / min, a maximum temperature of 600 to 900°C, and a holding time of 1 to 4 hours.

9. Use of a material prepared by the method according to any one of claims 1 to 8 in resisting electromagnetic radiation.

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