阅读说明：本技术 一种制备纳米核壳结构γ-Fe2O3@SiO2铁氧硅复合吸波材料的方法 (Preparation of nano core-shell structure gamma-Fe2O3@SiO2Method for preparing ferrite-silicon composite wave-absorbing material ) 是由 张紫莹 高东光 李灵玥 戴婷 洪昶 刘珍 姚晋珍 朱聪聪 谢宇 李诗琪 于 2021-05-12 设计创作，主要内容包括：本发明提供了一种制备纳米壳核结构的γ-Fe-(2)O-(3)@SiO-(2)具有低频吸波性能的铁氧硅复合物吸波材料的方法,该方法以六水合氯化铁、硫酸亚铁铵、硅酸四乙酯等为主要原料,采用化学沉淀法制备γ-Fe2O3纳米铁氧体前躯体,然后进行包覆处理方法采用溶胶-凝胶法制备在酸性条件下制备出具有低频吸波性能的γ-Fe2O3@SiO2纳米复合材料。经过复合SiO2之后,增加矫顽力产生的磁滞损耗,纳米γ-Fe2O3@SiO2复合材料同时拥有了电磁损耗和磁滞损耗,再加上也还发生界面极化,产生极化弛豫损耗,复合后的材料其吸波性能较单体吸波性能好,在微波吸收材料以及电磁防护等领域有很好的应用前景。(The invention provides a method for preparing gamma-Fe with a nano shell-core structure 2 O 3 @SiO 2 The method for preparing the ferrite silicon composite wave-absorbing material with the low-frequency wave-absorbing performance comprises the steps of preparing a gamma-Fe 2O3 nano ferrite precursor by using ferric chloride hexahydrate, ammonium ferrous sulfate, tetraethyl silicate and the like as main raw materials through a chemical precipitation method, and then preparing the gamma-Fe 2O3@ SiO2 nano composite material with the low-frequency wave-absorbing performance under an acidic condition through a coating treatment method and a sol-gel method. After the composite SiO2, the hysteresis loss generated by coercive force is increased, the nano gamma-Fe 2O3@ SiO2 composite material has electromagnetic loss and hysteresis loss at the same time, and in addition, interfacial polarization also occurs to generate polarization relaxation loss, and the composite material has the advantages of high magnetic conductivity, high magnetic conductivity and low magnetic resistanceThe wave-absorbing performance is better than that of a monomer, and the composite material has good application prospect in the fields of microwave absorbing materials, electromagnetic protection and the like.)

1. A method for preparing a nano core-shell structure gamma-Fe [email protected] SiO2 ferrite silicon composite wave-absorbing material is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: 3.277g of ferric trichloride (FeCl3 & 6H2O) is respectively weighed by an analytical balance to prepare 100ml of solution I; ammonium ferrous sulfate ((NH4)2Fe (SO4) 2.6H 20)3.9445g is prepared into 100ml of solution (II); 3.3335g of sodium hydroxide (NaOH) to prepare 100ml of solution (c); mixing the solution (r) and the solution (c) to obtain a solution (r), adding the solution (c) into an oil bath at 60 ℃ while stirring, quickly adding the solution (c) within a few seconds, magnetically stirring the obtained solution (c) in the oil bath for half an hour, then preserving the heat in the oil bath for two hours, taking out the solution for natural cooling, carrying out reduced pressure suction filtration and washing for multiple times to remove Cl-, Na +, SO42-, NH4+ and the like, carrying out vacuum drying at 60 ℃ for 24 hours to obtain crystalline Fe3O4, grinding the crystalline Fe3O4 into powder, oxidizing the powder for 2 hours at 300 ℃, taking out and grinding the powder to obtain gamma-Fe 2O3 particles.

Step two: the method comprises the following steps of coating the dried and calcined reddish brown nano gamma-Fe 2O3 particles by adopting an improved Sol-gel method, weighing 0.06g of gamma-Fe 2O3 in 50ml of ethanol in specific experimental steps, adding 5ml of 250g/L PEG-600 aqueous solution, and carrying out ultrasonic treatment until the gamma-Fe 2O3 is uniformly dispersed. The mixture was transferred to a 250ml round bottom flask and 1.7ml of ammonia was added under magnetic stirring. A mixture of 30ml of absolute ethanol and a quantity of tetraethyl silicate was slowly added dropwise to the round bottom flask using a constant pressure funnel. After the dropwise addition, the reaction is carried out for 12h at 30 ℃, the product is washed by deionized water, and after centrifugal separation, the product is dried for 3h at 60 ℃ to obtain a yellowish-brown product, namely the finally obtained core-shell structure gamma-Fe [email protected] SiO2 particles.

2. The method of claim 1, wherein: in the first step, the nanoparticles prepared by the oxidation reaction at 300 ℃ by the coprecipitation method are most preferred.

3. The method of claim 1, wherein: in step one, the optimal molar ratio of FeCl3 & 6H2O, (NH4)2Fe (SO4)2 & 6H2O is 1.2: 1.

4. The method of claim 1, wherein: in step two, the particle size of γ [email protected] SiO2 was controlled by ultrasonic dispersion.

5. The method of claim 1, wherein: in the second step, a coating reaction is carried out, and the optimal reaction temperature is 30 ℃.

6. A nanometer gamma-Fe [email protected] SiO2 composite material with low-frequency wave absorption is characterized in that: prepared by the process according to claims 1-5.

7. The nano gamma-Fe [email protected] SiO2 composite material with low frequency wave absorption according to claim 6.

8. Use according to claim 7, characterized in that: the nano gamma-Fe [email protected] SiO2 composite material with the low-frequency wave absorption performance is applied to the fields of microwave absorption materials, electromagnetic protection and the like.

Technical Field

The invention belongs to the field of microwave absorbing material preparation, and particularly relates to a gamma-Fe [email protected] SiO2 ferrooxygen silicon composite wave absorbing material with low-frequency wave absorbing performance and a preparation method thereof.

Background

With the rapid development of modern technologies such as microwave technology, electronic technology, stealth radar and the like, more and more electromagnetic devices are filled in the living space of people, which causes certain harm to human health and living environment, and causes wide attention of countries in the world. The scientists predict: in the 21 st century, the electromagnetic pollution of the earth ecological environment caused by electromagnetic waves will become the first-generation physical pollution. The wave-absorbing material can be widely used in the fields of EMI resistant materials (electromagnetic compatibility) and microwave absorbing materials, and can even be extended to stealth materials from sound waves to infrared rays. The wave-absorbing material has the main function of enabling incident waves to enter the material to the maximum extent and losing electromagnetic energy through energy conversion. The gamma-Fe 2O3 is an n-type semiconductor with a narrow forbidden band width, and has the advantages of stable structure, low price, no toxicity, environmental protection and the like. The nano gamma-Fe 2O3 is widely concerned due to the unique property, the microstructure changes when the size of the gamma-Fe 2O3 is reduced to the nano size, and the optical, electrical and magnetic properties and the like which are peculiar to some nano materials are presented at the same time, in addition, the properties of the nano materials are closely related to the appearance, and the gamma-Fe 2O3 core-shell structure microspheres have potential application value in the fields of catalysts, magnetic materials, wave-absorbing materials, dye adsorption, alkali ion batteries, gas sensors and the like due to low density, large specific surface area and good cycle stability.

The radar wave-absorbing material can be divided into an electric loss type and a magnetic loss type according to a wave-absorbing principle, wherein the electric loss type comprises resistance loss and dielectric loss; according to the forming process and the bearing capacity, the method can be divided into a structural type and a coating type. The electric loss type wave-absorbing material comprises graphite, carbon black, carbon nano tubes, carbon fibers, silicon carbide fibers and the like. The magnetic loss type wave-absorbing material comprises ferrite, magnetic metal micro powder, polycrystalline fiber and the like.

Ferrite is the most mature wave absorbent studied at present, has both magnetic loss capacity and dielectric loss capacity, and the ferrite wave absorbing material is an important electromagnetic wave absorbent. The ferrite material is a double-complex dielectric material, so that the ferrite material has magnetism and dielectricity. The nano gamma-Fe 2O3 has unique semiconductor characteristics, and can be excited by ultraviolet rays, visible light and infrared rays, so that the nano gamma-Fe 2O3 is expected to be used as a wave-absorbing material and has potential application values in coating, ultraviolet protection and infrared absorption, however, the currently reported infrared absorption performance of the nano gamma-Fe 2O3 is far away from application. In addition, it is considered that γ -Fe2O3 may have microwave absorption characteristics, depending on its magnetic loss and the characteristics of the nano magnetic oxide. The composite material with SiO2 can effectively improve the wave-absorbing performance of ferrite gamma-Fe 2O 3.

Disclosure of Invention

The invention provides a method for preparing a nano core-shell structure gamma-Fe [email protected] SiO2 ferrite silicon composite wave-absorbing material.

The invention adopts the following technical scheme:

a method for preparing a nano core-shell structure gamma-Fe [email protected] SiO2 ferrite silicon composite wave-absorbing material comprises the following steps:

the method comprises the following steps: preparation of gamma-Fe 2O3 by coprecipitation method

3.277g of ferric trichloride (FeCl3 & 6H2O) is respectively weighed by an analytical balance to prepare 100ml of solution I; ammonium ferrous sulfate ((NH4)2Fe (SO4) 2.6H 20)3.9445g is prepared into 100ml of solution (II); 3.3335g of sodium hydroxide (NaOH) to prepare 100ml of solution (c); mixing the solution (r) and the solution (c) to obtain a solution (r), adding the solution (c) into an oil bath at 60 ℃ while stirring, quickly adding the solution (c) within a few seconds, magnetically stirring the obtained solution (c) in the oil bath for half an hour, then keeping the temperature in the oil bath for two hours, taking out the solution for natural cooling, washing the solution for multiple times by reduced pressure suction filtration to remove Cl-, Na +, SO42-, NH4+ and the like, performing vacuum drying at 60 ℃ for 24 hours to obtain crystalline Fe3O4, grinding the crystalline Fe3O4 into powder, oxidizing the powder for 2 hours at 300 ℃, taking out and grinding the powder to obtain gamma-Fe 2O3 particles.

Step two: compounding with SiO2 by sol-gel method

The method comprises the following steps of coating the dried and calcined reddish brown nano gamma-Fe 2O3 particles by adopting an improved Sol-gel method, weighing 0.06g of gamma-Fe 2O3 in 50ml of ethanol in specific experimental steps, adding 5ml of 250g/L PEG-600 aqueous solution, and carrying out ultrasonic treatment until the gamma-Fe 2O3 is uniformly dispersed. The mixture was transferred to a 250ml round bottom flask and 1.7ml of ammonia was added under magnetic stirring. A mixture of 30ml of absolute ethanol and a quantity of tetraethyl silicate was slowly added dropwise to the round bottom flask using a constant pressure funnel. After the dropwise addition, the reaction is carried out for 12h at 30 ℃, the product is washed by deionized water, and after centrifugal separation, the product is dried for 3h at 60 ℃ to obtain a yellowish-brown product, namely the finally obtained core-shell structure gamma-Fe [email protected] SiO2 particles.

Preferably, in step one, the optimum molar ratio of FeCl3 · 6H2O, (NH4)2Fe (SO4)2 · 6H2O obtained from experiments is 1.2: 1.

Preferably, in step one, the optimal addition amount of ethanol is 30 mL.

Preferably, in the first step, the optimal temperature for the coprecipitation oxidation reaction is 300 ℃.

Preferably, in the second step, the optimal temperature for performing the composite coating in the sol-gel method is 30 ℃.

The invention has the advantages that: the method has the advantages that the operation steps are relatively simple and safe, the synthesized gamma-Fe 2O3 is nanoparticles, the particles are small, the dispersity is good, the magnetic loss performance of the prepared gamma-Fe [email protected] SiO2 is general, the monomer shows resistance loss, and the compound shows dielectric loss generated by interface polarization. Compared with other ferrites, the gamma-Fe [email protected] SiO2 composite material with the nano shell-core structure and the low-frequency wave absorption performance, which is prepared by the method, has good wave absorption performance and ferromagnetic behavior. Therefore, the invention has high practical application value.

Drawings

FIG. 1: reflection loss curves of different thicknesses of gamma-Fe 2O3

FIG. 2: reflection loss curves for different ethyl silicate-added gamma-Fe [email protected] SiO2

FIG. 3: XRD patterns of gamma-Fe 2O3 and gamma-Fe [email protected] SiO2

FIG. 4: hysteresis loop diagrams of gamma-Fe 2O3 and gamma-Fe [email protected] SiO2

Detailed Description

The invention is further described below with reference to fig. 1-4, without limiting the scope of the invention.

In the following description, for purposes of clarity, not all features of an actual implementation are described, well-known functions or constructions are not described in detail since they would obscure the invention with unnecessary detail, it being understood that in the development of any actual embodiment, numerous implementation details must be set forth in order to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, changing from one implementation to another, and it being recognized that such development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art.

Example 1

The method comprises the following steps: preparation of gamma-Fe 2O3 by coprecipitation method

3.277g of ferric trichloride (FeCl3 & 6H2O) is respectively weighed by an analytical balance to prepare 100ml of solution I; ammonium ferrous sulfate ((NH4)2Fe (SO4) 2.6H 20)3.9445g is prepared into 100ml of solution (II); 3.3335g of sodium hydroxide (NaOH) to prepare 100ml of solution (c); mixing the solution (r) and the solution (c) to obtain a solution (r), adding the solution (c) into an oil bath at 60 ℃ while stirring, quickly adding the solution (c) within a few seconds, magnetically stirring the obtained solution (c) in the oil bath for half an hour, then keeping the temperature in the oil bath for two hours, taking out the solution for natural cooling, washing the solution for multiple times by reduced pressure suction filtration to remove Cl-, Na +, SO42-, NH4+ and the like, performing vacuum drying at 60 ℃ for 24 hours to obtain crystalline Fe3O4, grinding the crystalline Fe3O4 into powder, oxidizing the powder for 2 hours at 300 ℃, taking out and grinding the powder to obtain gamma-Fe 2O3 particles.

Step two: compounding with SiO2 by sol-gel method

The method comprises the following steps of coating the dried and calcined reddish brown nano gamma-Fe 2O3 particles by adopting an improved Sol-gel method, weighing 0.06g of gamma-Fe 2O3 in 50ml of ethanol in specific experimental steps, adding 5ml of 250g/L PEG-600 aqueous solution, and carrying out ultrasonic treatment until the gamma-Fe 2O3 is uniformly dispersed. The mixture was transferred to a 250ml round bottom flask and 1.7ml of ammonia was added under magnetic stirring. A mixture of 30ml of absolute ethanol and 0.07ml of tetraethyl silicate was slowly added dropwise to the round bottom flask using a constant pressure funnel. After the dropwise addition, the reaction is carried out for 12h at 30 ℃, the product is washed by deionized water, and after centrifugal separation, the product is dried for 3h at 60 ℃ to obtain a yellowish-brown product, namely the finally obtained core-shell structure gamma-Fe [email protected] SiO2 particles.

Example 2

The method comprises the following steps: preparation of gamma-Fe 2O3 by coprecipitation method

3.277g of ferric trichloride (FeCl3 & 6H2O) is respectively weighed by an analytical balance to prepare 100ml of solution I; ammonium ferrous sulfate ((NH4)2Fe (SO4) 2.6H 20)3.9445g is prepared into 100ml of solution (II); 3.3335g of sodium hydroxide (NaOH) to prepare 100ml of solution (c); mixing the solution (r) and the solution (c) to obtain a solution (r), adding the solution (c) into an oil bath at 60 ℃ while stirring, quickly adding the solution (c) within a few seconds, magnetically stirring the obtained solution (c) in the oil bath for half an hour, then keeping the temperature in the oil bath for two hours, taking out the solution for natural cooling, washing the solution for multiple times by reduced pressure suction filtration to remove Cl-, Na +, SO42-, NH4+ and the like, performing vacuum drying at 60 ℃ for 24 hours to obtain crystalline Fe3O4, grinding the crystalline Fe3O4 into powder, oxidizing the powder for 2 hours at 300 ℃, taking out and grinding the powder to obtain gamma-Fe 2O3 particles.

Step two: compounding with SiO2 by sol-gel method

The method comprises the following steps of coating the dried and calcined reddish brown nano gamma-Fe 2O3 particles by adopting an improved Sol-gel method, weighing 0.06g of gamma-Fe 2O3 in 50ml of ethanol in specific experimental steps, adding 5ml of 250g/L PEG-600 aqueous solution, and carrying out ultrasonic treatment until the gamma-Fe 2O3 is uniformly dispersed. The mixture was transferred to a 250ml round bottom flask and 1.7ml of ammonia was added under magnetic stirring. A mixture of 30ml of absolute ethanol and 0.10ml of tetraethyl silicate was slowly added dropwise to the round bottom flask using a constant pressure funnel. After the dropwise addition, the reaction is carried out for 12h at 30 ℃, the product is washed by deionized water, and after centrifugal separation, the product is dried for 3h at 60 ℃ to obtain a yellowish-brown product, namely the finally obtained core-shell structure gamma-Fe [email protected] SiO2 particles.

Embodiment 3

The method comprises the following steps: preparation of gamma-Fe 2O3 by coprecipitation method

3.277g of ferric trichloride (FeCl3 & 6H2O) is respectively weighed by an analytical balance to prepare 100ml of solution I; ammonium ferrous sulfate ((NH4)2Fe (SO4) 2.6H 20)3.9445g is prepared into 100ml of solution (II); 3.3335g of sodium hydroxide (NaOH) to prepare 100ml of solution (c); mixing the solution (r) and the solution (c) to obtain a solution (r), adding the solution (c) into an oil bath at 60 ℃ while stirring, quickly adding the solution (c) within a few seconds, magnetically stirring the obtained solution (c) in the oil bath for half an hour, then keeping the temperature in the oil bath for two hours, taking out the solution for natural cooling, washing the solution for multiple times by reduced pressure suction filtration to remove Cl-, Na +, SO42-, NH4+ and the like, performing vacuum drying at 60 ℃ for 24 hours to obtain crystalline Fe3O4, grinding the crystalline Fe3O4 into powder, oxidizing the powder for 2 hours at 300 ℃, taking out and grinding the powder to obtain gamma-Fe 2O3 particles.

Step two: compounding with SiO2 by sol-gel method

The method comprises the following steps of coating the dried and calcined reddish brown nano gamma-Fe 2O3 particles by adopting an improved Sol-gel method, weighing 0.06g of gamma-Fe 2O3 in 50ml of ethanol in specific experimental steps, adding 5ml of 250g/L PEG-600 aqueous solution, and carrying out ultrasonic treatment until the gamma-Fe 2O3 is uniformly dispersed. The mixture was transferred to a 250ml round bottom flask and 1.7ml of ammonia was added under magnetic stirring. A mixture of 30ml of absolute ethanol and 0.12ml of tetraethyl silicate was slowly added dropwise to the round bottom flask using a constant pressure funnel. After the dropwise addition, the reaction is carried out for 12h at 30 ℃, the product is washed by deionized water, and after centrifugal separation, the product is dried for 3h at 60 ℃ to obtain a yellowish-brown product, namely the finally obtained core-shell structure gamma-Fe [email protected] SiO2 particles.

Example 4

The method comprises the following steps: preparation of gamma-Fe 2O3 by coprecipitation method

3.277g of ferric trichloride (FeCl3 & 6H2O) is respectively weighed by an analytical balance to prepare 100ml of solution I; ammonium ferrous sulfate ((NH4)2Fe (SO4) 2.6H 20)3.9445g is prepared into 100ml of solution (II); 3.3335g of sodium hydroxide (NaOH) to prepare 100ml of solution (c); mixing the solution (r) and the solution (c) to obtain a solution (r), adding the solution (c) into an oil bath at 60 ℃ while stirring, quickly adding the solution (c) within a few seconds, magnetically stirring the obtained solution (c) in the oil bath for half an hour, then keeping the temperature in the oil bath for two hours, taking out the solution for natural cooling, washing the solution for multiple times by reduced pressure suction filtration to remove Cl-, Na +, SO42-, NH4+ and the like, performing vacuum drying at 60 ℃ for 24 hours to obtain crystalline Fe3O4, grinding the crystalline Fe3O4 into powder, oxidizing the powder for 2 hours at 300 ℃, taking out and grinding the powder to obtain gamma-Fe 2O3 particles.

Step two: compounding with SiO2 by sol-gel method

The method comprises the following steps of coating the dried and calcined reddish brown nano gamma-Fe 2O3 particles by adopting an improved Sol-gel method, weighing 0.06g of gamma-Fe 2O3 in 50ml of ethanol in specific experimental steps, adding 5ml of 250g/L PEG-600 aqueous solution, and carrying out ultrasonic treatment until the gamma-Fe 2O3 is uniformly dispersed. The mixture was transferred to a 250ml round bottom flask and 1.7ml of ammonia was added under magnetic stirring. A mixture of 30ml of absolute ethanol and 0.15ml of tetraethyl silicate was slowly added dropwise to the round bottom flask using a constant pressure funnel. After the dropwise addition, the reaction is carried out for 12h at 30 ℃, the product is washed by deionized water, and after centrifugal separation, the product is dried for 3h at 60 ℃ to obtain a yellowish-brown product, namely the finally obtained core-shell structure gamma-Fe [email protected] SiO2 particles.

Conclusion

Wave-absorbing performance diagram: using a vector network analyzer and a Fourier infrared spectrometer (FTIR) to test and analyze the microwave and infrared absorption characteristics and the wave absorption performance of a sample, carrying out the research on the wave absorption performance of the composite material by using a monomer and four groups of different composite proportions of SiO2 and gamma-Fe 2O3 to obtain the wave absorption performance graphs shown in figures 1 and 2, the quantity of ethyl silicate added in the sequence from left to right to top in figure 2 is 0.07ml,0.10ml,0.12ml and 0.15ml respectively, and the comparison and analysis of the wave-absorbing performance graphs in figure 1 and figure 2 proves that the wave-absorbing material of the patent has larger absolute value of wave-absorbing loss in the 2-18GHz frequency band, comparing the compounding of SiO2 and gamma-Fe 2O3 under four groups of different proportion conditions, the compound of 0.10ml of ethyl silicate is added to obtain the gamma-Fe [email protected] SiO2 which has the lowest peak value, the lowest reflection loss and the larger absolute value of wave-absorbing loss in the 2-18GHz frequency band.

XRD pattern: a group and a monomer with the best wave-absorbing performance research proportion are selected for morphological structure characterization, an X-ray diffractometer (XRD) performance test is carried out to obtain an XRD pattern shown in figure 3 after SiO2 and gamma-Fe 2O3 are compounded, a SiO2 amorphous diffraction peak with weak intensity is obviously seen in the XRD pattern at about 20-30 degrees, the peak shape of gamma-Fe 2O3 is basically kept unchanged, the original gamma-Fe 2O3 monomer is not damaged after the gamma-Fe 2O3 and SiO2 are compounded, and the overall morphological structure of the gamma-Fe 2O3 is complete.

Vibration magnetometer chart: the magnetic strength test is carried out by the vibrating magnetometer to obtain the vibrating magnetometer shown in figure 4, a single magnetic hysteresis loop passes through the origin of coordinates and has no hysteresis loss, which shows that a sample has superparamagnetism and poor wave-absorbing performance, and the hysteresis loss generated by coercive force is increased after the sample passes through the composite SiO2, so that the nano gamma-Fe [email protected] SiO2 composite material has electromagnetic loss and hysteresis loss at the same time, and in addition, interface polarization also occurs to generate polarization relaxation loss, and the wave-absorbing performance of the composite material is better than that of the single body.

Although the invention has been described and illustrated in some detail, it should be understood that various modifications may be made to the described embodiments or equivalents may be substituted, as will be apparent to those skilled in the art, without departing from the spirit of the invention.