CN101899234A - Preparation method of glucose-based mesoporous carbon-coated ZnFeO for electromagnetic wave absorbing coatings - Google Patents

Abstract

The invention discloses a preparation method of glucose-based mesoporous carbon-coated ZnFeO for electromagnetic wave absorbing paint, which belongs to the preparation process of electromagnetic wave absorbing paint. The present invention combines solvothermal method and high-temperature calcination to form a carbon coating layer on the surface of zinc ferrite, which can not only improve the monodispersity and stability of ferrite, reduce the density of ferrite, but also further increase the effectiveness of electromagnetic waves. Absorption is conducive to expanding the absorption frequency band and achieving the goal of "thin, light, wide, and strong". It can be widely used in civilian and military applications, and is more practical.

Description

Preparation method of glucose-based mesoporous carbon-coated ZnFeO for electromagnetic wave absorbing coatings

technical field

The invention relates to a preparation technology of glucose-based mesoporous carbon-coated ZnFeO used in electromagnetic wave absorbing coatings, and belongs to the technical field of electromagnetic wave absorbing coating preparation.

technical background

Zinc ferrite material is a material with a large loss tangent value. It not only has a high electrical loss rate, but also absorbs and attenuates electromagnetic waves through magnetic polarization mechanisms such as hysteresis loss, domain wall resonance and aftereffect loss. It is widely used in the field of electromagnetic absorbing materials. Composite zinc ferrite is usually made by doping metal elements in order to broaden its absorption band, but the disadvantage of high ferrite density cannot be avoided.

Combining ferrite with light-weight dielectric loss absorbing material not only has multiple absorbing properties, but also can further reduce the density of the material. Therefore, the application prospect of carbon materials with low density and relatively simple preparation process in lightweight absorbing materials is very promising. Such as the report [Shen G Z, Xu M, Xu Z.Double-layer microwave absorber based on ferrite and short carbon fiber composites.Mater.Chem.Phys.,2007,105(2- 3): 268-272.], found that although the incorporation of carbon fiber has no obvious effect on the intensity of the absorption peak of the sample, it can significantly reduce the matching thickness of the coating. Carbon nanotubes are coated with magnetic materials or filled with magnetic materials, which can absorb and attenuate electromagnetic waves through various mechanisms of magnetic loss and dielectric loss, and have strong broadband absorption performance. However, the preparation and purification process of carbon nanotubes is relatively complicated, and surface modification is required to increase the filling rate, which is expected to further enhance electromagnetic wave absorption. Shen et al [Shen Y, Lin Y H, Li M, et al. Adv. Mater., 2007, 19(10): 1418-1422.] prepared a carbon-shell-coated silver core-shell structure by a simple hydrothermal reaction , filled with epoxy resin to form a composite material. The carbon shell acts as an interface between the silver core and the organic matrix, reducing the tunneling current between adjacent silver cores and localizing the free electrons of the silver core. Through the study of the dielectric properties of the Ag/C epoxy composite material, the carbon shell improves the dielectric constant of the composite material, and at the same time, the dielectric constant can also be effectively controlled by adjusting the thickness of the carbon shell.

Ferrite has a good shielding effect on electromagnetic waves. Forming a carbon coating on the surface of zinc ferrite can not only improve the monodispersity and stability of ferrite, reduce the density of ferrite, but also further increase the effectiveness of electromagnetic waves. Absorption is conducive to expanding the absorption frequency band and achieving the goal of "thin, light, wide and strong".

Contents of the invention

The purpose of the present invention is to propose a preparation method of glucose-based mesoporous carbon-coated ZnFeO with simple process and excellent electromagnetic wave absorption performance.

The invention comprises the following steps: (1), dissolving a certain amount of metal salt in 80mL of ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2g of polyethylene glycol PEG2000 to it, and after stirring, encapsulate the reaction mixture in a polytetrafluoroethylene kettle for solvothermal reaction at 200°C for 12h; the above metal salt is FeCl ₃ 6H ₂ O and/or ZnCl _2. The total molar amount of metal atoms is 0.01mol～0.03mol, and spherical ZnFeO particles are obtained; (2), the obtained product is separated, washed, and dried; (3), the ZnFeO particles are taken, added to the glucose solution, and dispersed by ultrasonic waves. Then hydrothermally react in a polytetrafluoroethylene kettle at 160°C for 4h; (4), the obtained product is washed, dried, and heat-treated in a nitrogen-protected atmosphere tube furnace, the heat-treatment temperature is from 250°C to 1000°C, and the heating rate is 1-10°C/min, keep warm at the target temperature for 2-6h, and then obtain glucose-based mesoporous carbon-coated ZnFeO.

In the present invention, a layer of mesoporous carbon is coated on the outside of ferrite nanoparticles to obtain a glucose-based mesoporous carbon-coated ZnFeO material. Ferrite has a good shielding effect on electromagnetic waves. Forming a carbon coating on the surface of zinc ferrite can not only improve the monodispersity and stability of ferrite, reduce the density of ferrite, but also further increase the effectiveness of electromagnetic waves. Absorption is conducive to expanding the absorption frequency band and achieving the goal of "thin, light, wide and strong". The preparation technology is simple and the obtained glucose-based mesoporous carbon-coated ZnFeO material has excellent electromagnetic wave absorption performance.

Description of drawings

Figure 1 is the XRD pattern of ZnFeO (1:1) before and after coating.

Figure 2 is the TEM images before and after ZnFeO (1:1) coating: (2-a) ZnFeO (1:1); (2-b) G-ZnFeO (1:1).

Figure 3 is the N2 adsorption and desorption curves before and after ZnFeO (1:1) coating.

Fig. 4 is the reflectance variation curve of different Zn/Fe molar ratio samples ZnFeO-500 with thickness: (4-a) 0: 1; (4-b) 1: 2; (4-c) (1: 1); (4-d) 2:1; (4-e) 1:0.

Figure 5 is the reflectance curve of G-ZnFeO (1:2) samples with different heat treatment temperatures as a function of thickness: (5-a) 250°C; (5-b) 750°C; (5-c) 1000°C.

Detailed ways

Specific embodiment one:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 0:1 and heat treatment at 500 °C after glucose coating

(1) Dissolve 2.70g FeCl ₃ ·6H ₂ O in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The resulting sample is denoted as ZnFeO (0:1), where (0:1) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 5° C./min and kept at 500° C. for 6 hours.

The sample is marked as G-ZnFeO(0:1)-500, where G is coated with glucose.

G-ZnFeO(0:1)-500 and epoxy resin are made into absorbing test samples at a mass ratio of 4:6. When the sample thickness is 2mm, the reflection loss absorption peak is -7.3dB; when the sample thickness is 7mm, its The reflection loss absorption peak reaches -28.0dB, and the frequency width less than -10dB reaches 3.2GHz.

Specific embodiment two:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 1:2 and heat treatment at 500 °C after glucose coating

(1) 5.40g FeCl ₃ ·6H ₂ O and 1.36g ZnCl ₂ were dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The obtained sample is recorded as ZnFeO (1:2), (1:2) being the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 5° C./min and kept at 500° C. for 6 hours.

The sample is marked as G-ZnFeO(1:2)-500, where G is coated with glucose.

G-ZnFeO(1:2)-500 and epoxy resin are made into absorbing test samples at a mass ratio of 4:6. When the sample thickness is 2mm, the reflection loss absorption peak is -4.3dB; when the sample thickness is 7mm, its The reflection loss absorption peak reaches -22.2dB, and the frequency width less than -10dB reaches 2.4GHz.

Specific embodiment three:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 1:1 and heat treatment at 500 °C after glucose coating

(1) 2.70g FeCl ₃ ·6H ₂ O and 1.36g ZnCl ₂ were dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The obtained sample is recorded as ZnFeO (1:1), where (1:1) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 5° C./min and kept at 500° C. for 6 hours.

The sample is marked as G-ZnFeO(1:1)-500, where G is coated with glucose.

The method is simple and easy, and the preparation cost is low. The diffraction peaks of the obtained ZnFeO (1:1) sample correspond to the JCPDS standard card (82-1042), which is zinc ferrite with a spinel structure. After glucose hydrothermal coating, the hydrothermally generated amorphous carbon did not affect the crystal structure of zinc ferrite. (see picture 1). It can be seen from Figure 2-a that the nanoparticles obtained by the hydrothermal reaction are spherical with a relatively uniform size, and the particle size is about 100nm. After hydrothermal coating with glucose, there is a layer of amorphous carbon around each nanoparticle (Fig. 2-c), which improves the dispersion of ZnFeO particles. The surface of the ferrite particles is rough, and the particles are piled up into balls, and its BET specific surface area is 20m ² /g. After hydrothermal coating with glucose, the surface is smooth and the specific surface area is only 6m ² /g. G-ZnFeO(1:1)-500 and epoxy resin obtained after heat treatment at 500°C were made into absorbing test samples at a mass ratio of 4:6. When the thickness of the sample was 2mm, the reflection loss absorption peak was -7.4dB; the sample When the thickness is 7mm, its reflection loss absorption peak reaches -17.7dB, and the frequency width less than -10dB reaches 2.2GHz.

Specific embodiment four:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 2:1 and heat treatment at 500 °C after glucose coating

(1) 2.70g FeCl ₃ ·6H ₂ O and 2.72g ZnCl ₂ were dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The resulting sample is noted as ZnFeO (2:1), where (2:1) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 5° C./min and kept at 500° C. for 6 hours.

The sample is denoted as G-ZnFeO (2:1), where G is coated with glucose.

G-ZnFeO (2:1) and epoxy resin are made into absorbing test samples at a mass ratio of 4:6. When the sample thickness is 2mm, the reflection loss absorption peak is -4.3dB; when the sample thickness is 7mm, the reflection loss is The absorption peak reaches -22.2dB, and the frequency width less than -10dB reaches 2.4GHz.

Specific embodiment five:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 1:0 and heat treatment at 500 °C after glucose coating

(1) 1.36g ZnCl ₂ was dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The obtained sample is recorded as ZnFeO (1:0), where (1:0) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 5° C./min and kept at 500° C. for 6 hours.

The sample is marked as G-ZnFeO(1:0)-500, where G is coated with glucose.

G-ZnFeO(1:0)-500 and epoxy resin are made into absorbing test samples at a mass ratio of 4:6. When the sample thickness is 2mm, the reflection loss absorption peak is -0.8dB; when the sample thickness is 7mm, its The reflection loss absorption peak reaches -4.9dB.

Table 1 Electromagnetic wave absorption properties of ZnFeO-500 samples with different Zn/Fe molar ratios

Specific embodiment six:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 1:2 and heat treatment at 250 °C after glucose coating

(1) 5.40g FeCl ₃ ·6H ₂ O and 1.36g ZnCl ₂ were dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The resulting sample is noted as ZnFeO (2:1), where (2:1) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 1° C./min and kept at 250° C. for 6 hours.

The sample is marked as G-ZnFeO(2:1)-250, where G is coated with glucose.

G-ZnFeO(2:1)-250 and epoxy resin were made into absorbing test samples at a mass ratio of 4:6. When the thickness of the sample was 2 mm, the reflection loss absorption peaks of G-ZnFeO(2:1)-250 were respectively It is -8.8dB; when the sample thickness is 7mm, its reflection loss absorption peak reaches -15.1.

Specific embodiment seven:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 1:1 and heat treatment at 750 °C after glucose coating

(1) 2.70g FeCl ₃ ·6H ₂ O and 1.36g ZnCl ₂ were dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The obtained sample is recorded as ZnFeO (1:1), where (1:1) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The sample is denoted as G-ZnFeO (1:1), where G is coated with glucose.

G-ZnFeO(1:1)-750 and epoxy resin are made into absorbing test samples at a mass ratio of 4:6. When the sample thickness is 2mm, the reflection loss absorption peak is -9.6dB; when the sample thickness is 7mm, its The reflection loss absorption peak reaches -12.7dB, and the frequency width less than -10dB reaches 0.4GHz.

Specific embodiment eight:

Preparation of glucose-based mesoporous carbon-coated ZnFeO materials with a molar ratio of Zn and Fe of 1:2 and heat treatment at 1000 °C after glucose coating

(1) 5.40g FeCl ₃ ·6H ₂ O and 1.36g ZnCl ₂ were dissolved in 80mL ethylene glycol to form a transparent solution. Add 7.2g of sodium acetate and 2.0g of polyethylene glycol PEG2000 to it, and stir vigorously for 6h.

(2) Encapsulate the reaction mixture into a polytetrafluoroethylene kettle, and perform solvothermal reaction at 200° C. for 12 hours.

(3) The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C. The resulting sample is noted as ZnFeO (2:1), where (2:1) is the molar ratio of Zn and Fe.

(4) Take 0.5 g of ZnFeO particles, add it to 80 mL of glucose solution (0.5 M), and disperse it by ultrasonic wave for 30 min.

(5) Pour the mixture into a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 160° C. for 4 hours. The obtained product was separated by centrifugation, washed three times with distilled water and ethanol, and dried under vacuum at 60°C.

(6) The product was heat-treated in a nitrogen-protected atmosphere tube furnace at a heating rate of 10° C./min and kept at 1000° C. for 2 hours.

The sample is marked as G-ZnFeO(2:1)-1000, where G is coated with glucose.

G-ZnFeO(2:1)-1000 and epoxy resin were made into absorbing test samples at a mass ratio of 4:6. When the thickness of the sample was 2 mm, the reflection loss absorption peaks of G-ZnFeO(2:1)-1000 were respectively It is -14.3dB; when the sample thickness is 7mm, its reflection loss absorption peak reaches -11.0dB.

Table 2G—Electromagnetic wave absorption properties of ZnFeO (1:2) samples with different heat treatment temperatures.

Claims (1)

1. A preparation method for glucose-based mesoporous carbon-coated ZnFeO of electromagnetic wave absorbing coating, is characterized in that comprising the following steps: (1) Dissolve a certain amount of metal salt in 80mL ethylene glycol to form a transparent solution, add 7.2g sodium acetate and 2g polyethylene glycol PEG2000 to it, and after stirring, encapsulate the reaction mixture into a polytetrafluoroethylene kettle Solvothermal reaction at 200°C for 12 hours; the above metal salt is FeCl ₃ 6H ₂ O and/or ZnCl ₂ , and the total molar amount of metal atoms is 0.01mol~0.03mol, and spherical ZnFeO particles are obtained; (2), the product obtained is separated, washed and dried; (3) Take ZnFeO particles, add them to the glucose solution, disperse them by ultrasonic waves, and then conduct a hydrothermal reaction at 160°C in a polytetrafluoroethylene kettle for 4 hours; (4) The obtained product is washed, dried, and heat-treated in a nitrogen-protected atmosphere tube furnace. The heat treatment temperature is from 250°C to 1000°C, the heating rate is 1-10°C/min, and the temperature is kept at the target temperature for 2-6h. That is, the glucose-based mesoporous carbon-coated ZnFeO was obtained.

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