CN110357144B - Flower-like zinc oxide/ferroferric oxide wave absorbing agent, preparation method thereof and wave absorbing material - Google Patents
Flower-like zinc oxide/ferroferric oxide wave absorbing agent, preparation method thereof and wave absorbing material Download PDFInfo
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- CN110357144B CN110357144B CN201910783909.1A CN201910783909A CN110357144B CN 110357144 B CN110357144 B CN 110357144B CN 201910783909 A CN201910783909 A CN 201910783909A CN 110357144 B CN110357144 B CN 110357144B
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- C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
Abstract
The invention provides a flower-like zinc oxide/ferroferric oxide wave absorbing agent, a preparation method thereof and a wave absorbing material, belonging to the technical field of wave absorbing materials. The flower-like zinc oxide/ferroferric oxide wave absorbing agent comprises a zinc oxide nano rod and ferroferric oxide particles attached to the surface of the zinc oxide nano rod. The zinc oxide nano rod of the invention is in a flower-like structure, thereby greatly prolonging the propagation path of electromagnetic waves on the interface of the zinc oxide nano rod and prolonging the electromagnetic energy attenuation time; the ferroferric oxide nano particles can improve the overall magnetic loss of the material; in addition, the unique structure of the wave absorbing agent leads to good compatibility and synergistic effect between ferroferric oxide and zinc oxide, so that the wave absorbing material prepared from the flower-like zinc oxide/ferroferric oxide wave absorbing agent has good wave absorbing performance, the thickness of a material coating can be effectively reduced, and the range of effective wave absorbing bandwidth is enlarged.
Description
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a flower-like zinc oxide/ferroferric oxide wave-absorbing agent, a preparation method thereof and a wave-absorbing material.
Background
With the rapid development of modern technological progress, in the current civil field, along with the development of the current electronic information technology, the derived electromagnetic wave radiation causes many complex problems such as electromagnetic pollution, electromagnetic interference, information disclosure and the like, and the development of the fields such as the information industry, the electronic industry and the like is hindered; for national defense construction, particularly for the emergence of microwave electronic technology and advanced radar, stealth is taken as an effective means for improving the survival, penetration and depth capabilities of a weapon system, and the stealth is one of the hot spots in the world of strong military and country-oriented military advanced fields. Therefore, the development of a material capable of absorbing electromagnetic waves in a specific frequency band is an effective means for solving the problems at present, and has high research value and application prospect.
The wave-absorbing material as an important electromagnetic wave material can absorb or greatly weaken the electromagnetic wave energy projected to the surface of the wave-absorbing material, reduce the electromagnetic wave interference, convert the loss of the material into heat energy, greatly ensure the health of human beings and reduce the harm caused by electromagnetism when being applied to the civil field; in the field of national defense construction, the influence of detection systems such as radar and infrared on a target can be weakened as much as possible, and the penetration, attack and survival capability of a weapon system or an aircraft can be obviously improved.
Zinc oxide (ZnO) has attracted considerable attention as an important multifunctional semiconductor material in the field of absorption of electromagnetic wave materials because of its advantages of non-toxicity, large surface area, long-term stability, wide band gap, excellent dielectric properties, and the like. The preparation methods of zinc oxide are many, but the wave-absorbing performance exhibited by single zinc oxide still has a certain difference with the final target 'thin, light, wide and strong' of electromagnetic wave-absorbing material development. Therefore, the improvement of the wave absorbing performance of the material by designing a novel zinc oxide composite material has become an effective way for remarkably improving the microwave absorbing capacity, such as forming a unique structure, combining with other materials and introducing different scales in a specific preparation process. However, the problems that the effective wave-absorbing bandwidth of the zinc oxide-based composite material coating is narrow, the thickness is required to ensure the performance, the wave-absorbing performance needs to be improved and the like are still great challenges in the field of wave-absorbing materials.
Disclosure of Invention
The invention aims to provide a flower-like zinc oxide/ferroferric oxide wave-absorbing agent, and the wave-absorbing material prepared by using the wave-absorbing agent in the preparation of the wave-absorbing material has good wave-absorbing performance, can effectively reduce the thickness of a material coating, and increases the range of effective wave-absorbing bandwidth.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a flower-like zinc oxide/ferroferric oxide wave absorbent, which comprises a zinc oxide nano rod and ferroferric oxide nano particles attached to the surface of the zinc oxide nano rod; the zinc oxide nano-rod forms a flower-like structure.
Preferably, the weight of the ferroferric oxide nano particles accounts for 5-50% of the weight of the wave absorbing agent.
Preferably, the ferroferric oxide nanoparticles are spherical and have the diameter of 10-120 nm.
Preferably, the diameter of the zinc oxide nano rod is 200-800 nm, and the length of the zinc oxide nano rod is 3-10 μm.
The invention provides a preparation method of a flower-like zinc oxide/ferroferric oxide wave absorbing agent in the scheme, which comprises the following steps:
sequentially adding a strong alkali solution and a soluble ferric salt into a soluble zinc salt solution to obtain a reaction solution;
carrying out hydrothermal reaction on the reaction solution to obtain a flower-like zinc oxide/ferroferric oxide precursor;
and carrying out heat treatment on the flower-like zinc oxide/ferroferric oxide precursor to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent.
Preferably, the mass ratio of the soluble zinc salt to the strong base to the soluble ferric salt is 1: (1-8): (0.05-0.6).
Preferably, the soluble ferric salt is added in solid form.
Preferably, the temperature of the hydrothermal reaction is 170-220 ℃, and the time is 8-17 h.
Preferably, the temperature of the heat treatment is 450-750 ℃, and the time is 1-5 h.
The invention provides a wave absorbing material which comprises a wave absorbing agent and a binder, wherein the wave absorbing agent is the wave absorbing agent prepared by the scheme or the wave absorbing agent prepared by the preparation method of the scheme.
The invention provides a flower-like zinc oxide/ferroferric oxide wave absorbent, which comprises a zinc oxide nano rod and ferroferric oxide particles attached to the surface of the zinc oxide nano rod; the zinc oxide nano-rod forms a flower-like structure. The zinc oxide nano rod of the invention forms a plump flower-like structure, and the special shape and structure greatly prolong the propagation path of electromagnetic waves on the interface of the zinc oxide nano rod and prolong the electromagnetic energy attenuation time; the ferroferric oxide nano particles can improve the overall magnetic loss of the material; in addition, the unique structure of the wave absorbing agent causes good compatibility and synergistic effect between ferroferric oxide and zinc oxide, and the polarization of charges on the interface of the zinc oxide nano rod and the ferroferric oxide nano particle is enhanced, so that the wave absorbing material prepared from the flower-like zinc oxide/ferroferric oxide wave absorbing agent has good wave absorbing performance, the thickness of a material coating can be effectively reduced, and the range of effective wave absorbing bandwidth is enlarged.
The results of the embodiment show that when the wave absorbing agent is used for preparing the wave absorbing material, the dielectric constant of the wave absorbing material is as follows under the condition that the wave absorbing frequency is 2-18 GHz: the real part is 4.77-15.14, and the imaginary part is 0.23-6.68; magnetic permeability: the real part is 1.03-1.61, and the imaginary part is 0.003-0.23; the reflection loss is-10.1 to-36.2 dB; the effective bandwidth is 0.45-4.02 GHz; the thickness of the material is 2.2-5.4 mm; the wave absorbing agent has good wave absorbing performance, can effectively reduce the thickness of a material coating, and increases the range of effective wave absorbing bandwidth.
The invention provides a preparation method of a flower-like zinc oxide/ferroferric oxide wave absorbent, which is simple and easy to operate.
Drawings
FIG. 1 is an SEM photograph of a flower-like zinc oxide/ferroferric oxide absorbent in example 1 of the present invention;
FIG. 2 is an SEM photograph of a flower-like zinc oxide/ferroferric oxide absorbent in example 2 of the present invention;
FIG. 3 is an SEM photograph of a flower-like zinc oxide/ferroferric oxide absorbent in example 3 of the present invention;
FIG. 4 is an SEM photograph of a flower-like zinc oxide/ferroferric oxide absorbent in example 4 of the present invention;
FIG. 5 is an SEM photograph of a product obtained in comparative example 1 of the present invention;
FIG. 6 is an SEM photograph of a product obtained in comparative example 2 of the present invention.
FIG. 7 is an SEM photograph of a product obtained in comparative example 3 of the present invention.
Detailed Description
The invention provides a flower-like zinc oxide/ferroferric oxide wave absorbent, which comprises a zinc oxide nano rod and ferroferric oxide nano particles attached to the surface of the zinc oxide nano rod.
In the invention, the diameter of the zinc oxide nanorod is preferably 200-800 nm, more preferably 200-600 nm, more preferably 300-500 nm, and the length is preferably 3-10 μm, more preferably 5-8 μm, more preferably 6-7 μm. In the present invention, the top surface of each zinc oxide nanorod is preferably a symmetrical hexagonal shape; the whole of each zinc oxide nanorod is preferably a hexagonal prism structure or a hexagonal prism structure with a pyramid tip, and more preferably a hexagonal prism structure with a pyramid tip.
In the invention, the mass of the ferroferric oxide nano particles is preferably 5-50% of that of the wave absorbing agent, more preferably 5-35%, and even more preferably 10-20%; the ferroferric oxide nanoparticles are preferably spherical, the diameter of the ferroferric oxide nanoparticles is preferably 10-120 nm, more preferably 10-50 nm, and even more preferably 15-45 nm. The invention controls the content of the ferroferric oxide nano particles within the range, and is beneficial to further improving the wave absorbing performance of the wave absorbing agent.
The zinc oxide nano rod of the invention forms a plump flower-like structure, and the special shape and structure greatly prolong the propagation path of electromagnetic waves on the interface of the zinc oxide nano rod and prolong the electromagnetic energy attenuation time; the ferroferric oxide nano particles can improve the overall magnetic loss of the material; in addition, the distribution form of the zinc oxide nano rod and the ferroferric oxide particles ensures that the whole wave absorbing agent is also in a flower-like structure, the unique structure of the wave absorbing agent causes good compatibility and synergistic effect between the ferroferric oxide and the zinc oxide, and the polarization of charges on the interface of the zinc oxide nano rod and the ferroferric oxide particles is enhanced, so that the wave absorbing material prepared from the flower-like zinc oxide/ferroferric oxide wave absorbing agent has good wave absorbing performance, the thickness of a material coating can be effectively reduced, and the range of effective wave absorbing bandwidth is enlarged.
The invention provides a preparation method of a flower-like zinc oxide/ferroferric oxide wave absorbing agent in the scheme, which comprises the following steps:
sequentially adding a strong alkali solution and a soluble ferric salt into a soluble zinc salt solution to obtain a reaction solution;
carrying out hydrothermal reaction on the reaction solution to obtain a flower-like zinc oxide/ferroferric oxide precursor;
and carrying out heat treatment on the flower-like zinc oxide/ferroferric oxide precursor to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent.
According to the invention, a strong alkali solution and a soluble ferric salt are sequentially added into a soluble zinc salt solution to obtain a reaction solution.
In the present invention, the mass ratio of the soluble zinc salt, the strong base and the soluble ferric salt is preferably 1: (1-8): (0.05 to 0.6), more preferably 1: (1.5-5): (0.05 to 0.2), more preferably 1: (4.5-5): (0.1 to 0.15), and most preferably 1:4.9: 0.13. In the invention, the dosage of the soluble ferric iron salt is preferably calculated according to the mass fraction of ferroferric oxide in the final product.
In the present invention, the soluble zinc salt is preferably zinc acetate or zinc nitrate hexahydrate; the concentration of the soluble zinc salt solution is preferably 10-15 g/L. When the soluble zinc salt is zinc nitrate hexahydrate, the mass purity of the zinc nitrate hexahydrate is preferably more than 99%, and the pH value of the zinc nitrate hexahydrate is preferably more than or equal to 3.5. In the invention, the pH value of the zinc nitrate hexahydrate refers to the pH value under the condition of 25 ℃ aqueous solution with the concentration of 50 g/L.
In the present invention, the strong alkaline solution is preferably a sodium hydroxide solution or a potassium hydroxide solution, more preferably a sodium hydroxide solution; the concentration of the strong alkali solution is preferably 2-4 mol/L. In the invention, the strong alkali solution is preferably added in a dropwise manner, the dropwise addition speed is not particularly required, and the reaction does not cause agglomeration. The method adopts a dropwise adding mode, which is beneficial to the full reaction of the soluble zinc salt and hydroxyl to obtain better appearance.
In the present invention, the soluble ferric salt is preferably ferric nitrate or ferric chloride, and more preferably ferric nitrate. When selecting the ferric nitrate, the mass purity of the ferric nitrate is preferably more than or equal to 98.5%. In the present invention, the soluble ferric salt is preferably added in a solid form, in the present invention, the soluble ferric salt is preferably in a granular form, and the present invention has no particular requirement on the particle size of the soluble ferric salt, and any commercially available product well known in the art can be used. The soluble ferric salt is added in a solid form, which is favorable for better regulating and controlling the reaction rate, so that the ferroferric oxide nano-particles uniformly attached to the surface of the zinc oxide nano-rod are obtained.
The invention firstly adds strong alkaline solution to lead Zn (OH)2Is easier to form and more complete in reaction, the PH value of the mixed solution becomes strong alkalinity before the soluble ferric salt is added, and then the soluble ferric salt is added, so that the ferric salt with strong electrolyte can be more complete with Zn (OH)2Reaction to produce Fe (OH)3. In the process of adding sodium hydroxide, Zn (OH) is firstly generated2The precipitate is ionized into liquid again due to the increase of the adding amount of the sodium hydroxide, so that the solution is changed into turbid white and then into clear and transparent liquid along with the addition of the sodium hydroxide, but the substances obtained by the reactions are not changed. According to the invention, ferric nitrate is preferably added when the solution after the sodium hydroxide is added becomes a clear and transparent liquid.
In the present invention, the addition of the strong alkali solution and the soluble ferric salt is preferably carried out under stirring. In the present invention, the stirring is preferably magnetic stirring. The invention has no special requirement on the power of the magnetic stirring and does not cause liquid splashing. According to the invention, preferably, the soluble zinc salt is stirred for 8-12 min to uniformly disperse the soluble zinc salt solution, then the strong alkali solution is added, and the time for adding the strong alkali solution and the soluble ferric salt is preferably controlled within 40min (which means the time counted from the beginning of stirring the soluble zinc salt solution).
After reaction liquid is obtained, the reaction liquid is subjected to hydrothermal reaction to obtain a flower-like zinc oxide/ferroferric oxide precursor.
In the invention, the temperature of the hydrothermal reaction is preferably 130-220 ℃, more preferably 170-200 ℃, and more preferably 180-200 ℃; the time of the hydrothermal reaction is preferably 8-17 h, more preferably 10-13 h, and even more preferably 11-13 h.
In the hydrothermal reaction process, zinc oxide and ferroferric oxide crystal grains are generated.
After the hydrothermal reaction, the method preferably further comprises the steps of carrying out solid-liquid separation and solid drying on a hydrothermal reaction product system to obtain the flower-like zinc oxide/ferroferric oxide precursor. The invention preferably adopts a centrifugal mode to carry out solid-liquid separation. The present invention does not require any particular embodiment of centrifugation, and centrifugation means well known in the art may be used. In the invention, the drying is preferably drying, the drying temperature is preferably 55-70 ℃, and the drying time is preferably 12-24 h.
After obtaining the flower-like zinc oxide/ferroferric oxide precursor, the flower-like zinc oxide/ferroferric oxide precursor is subjected to heat treatment to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent.
In the invention, the temperature of the heat treatment is preferably 450-750 ℃, and more preferably 600 ℃; the time of the heat treatment is preferably 1 to 5 hours, more preferably 1 to 3 hours, and even more preferably 2 to 3 hours.
According to the invention, the temperature is preferably raised from room temperature to the heat treatment temperature, and the heating rate is preferably 2.5-3.7 ℃/min. In the present invention, the heat treatment is preferably performed in an air atmosphere.
In the heat treatment process, the material is subjected to secondary growth, and due to the difference of the surface energy of each generated ZnO nanorod crystal, single, paired or multiple nanorods are combined to different degrees to form flower-like zinc oxide/ferroferric oxide, so that the material with more stable structure, appearance and performance is obtained.
After the heat treatment, the present invention preferably further comprises grinding the heat-treated product. The present invention has no special requirement on the granularity after grinding, and the skilled person can control the granularity according to experience.
The invention provides a wave absorbing material which comprises a wave absorbing agent and a binder, wherein the wave absorbing agent is the wave absorbing agent prepared by the scheme or the wave absorbing agent prepared by the preparation method of the scheme. The present invention does not require any particular kind of binder as shown, and any binder known in the art may be used. The amount of the wave absorber and binder used in the present invention is not particularly limited, and can be set by those skilled in the art according to the experience. The preparation method of the wave-absorbing material has no special requirement, and the preparation method is well known in the field.
The flower-like zinc oxide/ferroferric oxide wave absorbing agent, the preparation method thereof and the wave absorbing material provided by the invention are explained in detail with reference to the following examples, but the flower-like zinc oxide/ferroferric oxide wave absorbing agent and the preparation method thereof and the wave absorbing material are not to be construed as limiting the protection scope of the invention.
Example 1
Weighing 4.16g of zinc nitrate hexahydrate, measuring 320mL of deionized water in a beaker with the capacity of 500mL, adding the weighed zinc nitrate into the deionized water, and carrying out sufficient ultrasound in ultrasonic dispersion for 30 minutes to obtain a zinc nitrate hexahydrate solution;
weighing 16g of sodium hydroxide particles, adding the sodium hydroxide particles into a beaker containing 100mL of deionized water, carrying out ultrasonic dispersion for 20 minutes, and measuring 40mL of the prepared sodium hydroxide solution after the ultrasonic dispersion is finished;
weighing 208mg of ferric nitrate nonahydrate particles according to the weight ratio of ferroferric oxide accounting for 5 wt.% of the final product; stirring the zinc nitrate solution subjected to ultrasonic dispersion with magnetic particles, slowly dripping 40mL of sodium hydroxide solution into the zinc nitrate solution after the stirring time is 10 minutes, adding weighed ferric nitrate nonahydrate particles to continue stirring when the mixed solution is changed from clear to turbid white and finally changed into clear and transparent liquid, wherein the total stirring time of the magnetic particles is not more than 40 minutes, and storing the obtained reaction solution;
pouring the reaction liquid into a high-pressure reaction kettle with a polytetrafluoroethylene lining, transferring the reaction liquid into a high-temperature drying oven for hydrothermal reaction, setting the reaction temperature at 190 ℃ for 11h, and taking out the reaction kettle after the reaction time is over and the reaction kettle is naturally cooled. Pouring the obtained mixed solution into a cleaned centrifugal tube, adding absolute ethyl alcohol and ultrapure water, centrifuging and washing for multiple times, and drying in a 70 ℃ oven for one day to obtain flower-like zinc oxide/ferroferric oxide precursor powder;
pouring the flower-like zinc oxide/ferroferric oxide precursor powder into a ceramic crucible, carrying out heat treatment reaction in a tubular furnace, gradually heating from room temperature to 600 ℃, heating at the rate of 3 ℃/min, keeping the temperature at 600 ℃ for 3h, naturally cooling to room temperature after sintering, taking out the powder, and fully grinding to obtain the flower-like zinc oxide/ferroferric oxide wave absorbent with the ferroferric oxide content of 5 wt.%.
SEM test of the product obtained in example 1 is shown in FIG. 1. FIG. 1 shows that the zinc oxide nanorod is of a flower-like structure, the length of the zinc oxide nanorod is about 5 μm, the diameter of the zinc oxide nanorod is about 200-600 nm, and ferroferric oxide spherical nanoparticles are dispersed on the surface of the zinc oxide nanorod and the diameter of the zinc oxide nanorod is about 10-50 nm.
Example 2
Weighing 3.26g of zinc nitrate hexahydrate, weighing 240mL of deionized water in a beaker with the capacity of 500mL, adding the weighed zinc nitrate into the deionized water, and carrying out sufficient ultrasound in ultrasonic dispersion for 20 minutes to obtain a zinc nitrate hexahydrate solution;
weighing 16g of sodium hydroxide particles, adding the sodium hydroxide particles into a beaker containing 100mL of deionized water, carrying out ultrasonic dispersion for 30 minutes, and measuring 40mL of the prepared sodium hydroxide solution after the ultrasonic dispersion is finished;
weighing 416mg of ferric nitrate nonahydrate particles according to the weight ratio of ferroferric oxide accounting for 10 wt.% of the final product; stirring the zinc nitrate solution subjected to ultrasonic dispersion by magnetic particles, slowly dripping 40mL of sodium hydroxide solution into the zinc nitrate solution after the stirring time is 10 minutes, adding weighed ferric nitrate nonahydrate particles into the zinc nitrate solution and continuously stirring the mixture when the mixed solution is changed from clear to turbid white and finally changed into clear and transparent liquid, wherein the total stirring time is not more than 40 minutes, and storing the obtained reaction solution;
pouring the reaction liquid into a high-pressure reaction kettle with a polytetrafluoroethylene lining, transferring the reaction liquid into a high-temperature drying oven for hydrothermal reaction, setting the reaction temperature at 180 ℃ for 12 hours, and taking out the reaction kettle after the reaction time is over and the reaction kettle is naturally cooled. Evenly pouring the obtained mixed solution into a cleaned centrifugal tube, adding absolute ethyl alcohol and ultrapure water, centrifuging and washing for multiple times, and drying in a 65 ℃ oven for one day to obtain flower-like zinc oxide/ferroferric oxide precursor powder;
and then pouring the flower-like zinc oxide/ferroferric oxide precursor powder into a ceramic crucible, carrying out heat treatment reaction in a tubular furnace, gradually heating from room temperature to 600 ℃, wherein the heating rate is 3.7 ℃/min, keeping the temperature at 600 ℃ for 3h, naturally cooling to room temperature after sintering, taking out the powder, and fully grinding to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent with the ferroferric oxide content of 10 wt.%.
SEM test of the product obtained in example 2 is shown in FIG. 2. FIG. 2 shows that the zinc oxide nanorods are flower-like structures, each zinc oxide nanorod is a hexagonal prism structure with a pyramid-shaped tip, the length of each zinc oxide nanorod is about 5-8 μm, the diameter of each zinc oxide nanorod is about 200-600 nm, and ferroferric oxide spherical nanoparticles are uniformly dispersed on the surface of each zinc oxide nanorod and the diameter of each zinc oxide nanorod is about 10-50 nm.
Example 3
Weighing 4.16g of zinc nitrate hexahydrate, measuring 320mL of deionized water in a beaker with the capacity of 500mL, adding the weighed zinc nitrate into the deionized water, and carrying out sufficient ultrasound in ultrasonic dispersion for 20 minutes to obtain a zinc nitrate hexahydrate solution;
weighing 8g of sodium hydroxide particles, adding the sodium hydroxide particles into a beaker containing 50mL of deionized water, carrying out ultrasonic dispersion for 30 minutes, and measuring 40mL of the prepared sodium hydroxide solution after the ultrasonic dispersion is finished;
weighing 624mg of ferric nitrate nonahydrate particles according to the weight ratio of ferroferric oxide accounting for 15 wt.% of the final product; stirring the zinc nitrate solution subjected to ultrasonic dispersion by magnetic particles, slowly dripping 40mL of sodium hydroxide solution into the zinc nitrate solution after the stirring time is 10 minutes, adding weighed ferric nitrate nonahydrate particles into the zinc nitrate solution and continuously stirring the mixture when the mixed solution is changed from clear to turbid white and finally changed into clear and transparent liquid, wherein the total stirring time is not more than 40 minutes, and storing the obtained reaction solution;
pouring the reaction liquid into a high-pressure reaction kettle with a polytetrafluoroethylene lining, transferring the reaction liquid into a high-temperature drying oven for hydrothermal reaction, setting the reaction temperature at 200 ℃ for 13h, and taking out the reaction kettle after the reaction time is over and the reaction kettle is naturally cooled. Evenly pouring the obtained mixed solution into a cleaned centrifugal tube, adding absolute ethyl alcohol and ultrapure water, centrifuging and washing for multiple times, and drying in a 70 ℃ oven for one day to obtain flower-like zinc oxide/ferroferric oxide precursor powder;
and then pouring the flower-like zinc oxide/ferroferric oxide precursor powder into a ceramic crucible, carrying out heat treatment reaction in a tubular furnace, gradually heating from room temperature to 600 ℃, preserving heat for 3 hours at the temperature of 600 ℃, naturally reducing the temperature in the furnace to room temperature after sintering, taking out the powder, and fully grinding to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent with the ferroferric oxide content of 15 wt.%.
SEM test of the product obtained in example 3 is shown in FIG. 3. FIG. 3 shows that the zinc oxide nanorods are flower-like structures, each zinc oxide nanorod is a hexagonal prism structure, the length of each zinc oxide nanorod is about 5-8 μm, the diameter of each zinc oxide nanorod is about 200-600 nm, and ferroferric oxide spherical nanoparticles are uniformly dispersed on the surfaces of the zinc oxide nanorods and the diameter of each zinc oxide nanorod is about 10-50 nm.
Example 4
Weighing 4.16g of zinc nitrate hexahydrate, measuring 320mL of deionized water in a beaker with the capacity of 500mL, adding the weighed zinc nitrate into the deionized water, and carrying out sufficient ultrasound in ultrasonic dispersion for 30 minutes to obtain a zinc nitrate hexahydrate solution;
weighing 16g of sodium hydroxide particles, adding the sodium hydroxide particles into a beaker containing 100mL of deionized water, carrying out ultrasonic dispersion for 20 minutes, and measuring 40mL of the prepared sodium hydroxide solution after the ultrasonic dispersion is finished;
weighing 832mg of ferric nitrate nonahydrate particles according to the weight ratio of ferroferric oxide accounting for 20 wt.% of the final product; stirring the zinc nitrate solution subjected to ultrasonic dispersion with magnetic particles, slowly dripping 40mL of sodium hydroxide solution into the zinc nitrate solution after the stirring time is 10 minutes, adding weighed ferric nitrate nonahydrate particles to continue stirring when the mixed solution is changed from clear to turbid white and finally changed into clear and transparent liquid, wherein the total stirring time of the magnetic particles is not more than 40 minutes, and storing the obtained reaction solution;
pouring the reaction liquid into a high-pressure reaction kettle with a polytetrafluoroethylene lining, transferring the reaction liquid into a high-temperature drying oven for hydrothermal reaction, setting the reaction temperature at 200 ℃ for 12 hours, and taking out the reaction kettle after the reaction time is over and the reaction kettle is naturally cooled. Pouring the obtained mixed solution into a cleaned centrifugal tube, adding absolute ethyl alcohol and ultrapure water, centrifuging and washing for multiple times, and drying in a 65 ℃ oven for one day to obtain flower-like zinc oxide/ferroferric oxide precursor powder;
pouring the flower-like zinc oxide/ferroferric oxide precursor powder into a ceramic crucible, carrying out heat treatment reaction in a tubular furnace, gradually heating from room temperature to 600 ℃, wherein the heating rate is 3.7 ℃/min, keeping the temperature at 600 ℃ for 3h, naturally cooling to room temperature after sintering, taking out the powder, and fully grinding to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent with the ferroferric oxide content of 20 wt.%.
SEM test of the product obtained in example 4 is shown in FIG. 4. FIG. 4 shows that the zinc oxide nanorods are flower-like structures, each zinc oxide nanorod is a hexagonal prism structure, the length of each zinc oxide nanorod is about 5-8 μm, the diameter of each zinc oxide nanorod is about 200-600 nm, and ferroferric oxide spherical nanoparticles are uniformly dispersed on the surfaces of the zinc oxide nanorods and the diameter of each zinc oxide nanorod is about 10-50 nm.
Comparative example 1
The difference from the example 3 is that no ferric nitrate is added, and the specific steps are as follows:
weighing 4.16g of zinc nitrate hexahydrate, measuring 320mL of deionized water in a beaker with the capacity of 500mL, adding the weighed zinc nitrate into the deionized water, and carrying out sufficient ultrasound in ultrasonic dispersion for 20 minutes to obtain a zinc nitrate hexahydrate solution;
weighing 8g of sodium hydroxide particles, adding the sodium hydroxide particles into a beaker containing 50mL of deionized water, carrying out ultrasonic dispersion for 30 minutes, and measuring 40mL of the prepared sodium hydroxide solution after the ultrasonic dispersion is finished;
stirring the ultrasonically dispersed zinc nitrate solution with magnetic particles, slowly dripping 40mL of sodium hydroxide solution into the zinc nitrate solution after the stirring time is 10 minutes, continuing stirring after the mixed solution is changed from clear to transparent to turbid white and finally changed into clear and transparent liquid, wherein the total time is not more than 40 minutes, and storing the obtained reaction solution;
pouring the reaction liquid into a high-pressure reaction kettle with a polytetrafluoroethylene lining, transferring the reaction liquid into a high-temperature drying oven for hydrothermal reaction, setting the reaction temperature at 200 ℃ for 13h, and taking out the reaction kettle after the reaction time is over and the reaction kettle is naturally cooled. Averagely pouring the obtained mixed solution into a cleaned centrifugal tube, adding absolute ethyl alcohol and ultrapure water, centrifuging and washing for multiple times, and drying in an oven at 70 ℃ for one day to obtain ZnO powder;
and then pouring the ZnO powder into a ceramic crucible, carrying out heat treatment reaction in a tubular furnace, gradually heating from room temperature to 600 ℃, preserving heat for 3 hours at 600 ℃, naturally reducing the temperature in the furnace to room temperature after sintering, taking out the powder, and fully grinding to obtain the ZnO powder.
SEM observation of the product obtained in comparative example 1 is shown in FIG. 5. Fig. 5 shows that the zinc oxide nanorods are flower-like structures, but the surfaces of the zinc oxide nanorods do not have ferroferric oxide particles.
Comparative example 2
The difference from comparative example 1 is that the temperature of the heat treatment was 400 ℃.
SEM observation of the product obtained in comparative example 2 is shown in FIG. 6. Fig. 6 shows that the ductility is not well reflected because the plump and uniform structure morphology is not formed due to the low heat treatment temperature, and the structure is not beneficial to improving the wave absorbing performance of the wave absorbing agent.
Comparative example 3
The difference from comparative example 1 is that the temperature of the heat treatment was 800 ℃.
SEM observation of the product obtained in comparative example 3 showed that the result was shown in FIG. 7. Fig. 7 shows that the internal stress is reduced due to the over-high temperature, the ductility is damaged, the end face or the surface of the material is easy to break and defect, and the wave absorbing performance of the wave absorbing agent is reduced.
Performance testing
And mixing the products obtained in the examples 1-4 and the comparative example 1 with solid paraffin (binder) according to the mass ratio of 3:2, and pouring the mixture into a specific pressure ring mold to coaxially press the mixed powder to obtain the annular wave-absorbing material with the inner diameter of 3.04mm and the outer diameter of 7.00 mm. A vector network analyzer with the model number of N5232B, produced by Agilent (KEYSIGHT), is adopted to carry out performance detection under the condition of the test frequency of 2-18GHz, and the results are shown in Table 1.
TABLE 1 test results of examples 1 to 4 and comparative example 1
Note: the thickness of the material in table 1 refers to the corresponding thickness of the material when the optimal wave-absorbing performance occurs, and the corresponding effective bandwidth refers to the range of the effective bandwidth obtained by the thickness of the material in table 1.
From the results in table 1, when the wave absorbing agent of the present invention is used for preparing a wave absorbing material, the dielectric constant of the wave absorbing material is as follows under the condition of 2-18 GHz: the real part is 4.77-15.14, and the imaginary part is 0.23-6.68; magnetic permeability: the real part is 1.03-1.61, and the imaginary part is 0.003-0.23; the reflection loss is-10.1 to-36.2 dB; the thickness of the material is 2.2-5.4 mm; the corresponding effective bandwidth is 0.45-4.02 GHz; the wave absorbing agent has good wave absorbing performance, can effectively reduce the thickness of a material coating, and increases the range of effective wave absorbing bandwidth. And the comparative example 1 has no ferroferric oxide modification, the maximum reflection loss is only-5.01 dB, and the wave absorbing performance is basically not generated.
In addition, as can be seen from table 1, when the doping amount of the ferroferric oxide is 10-15% (examples 2 and 3), the obtained wave-absorbing material has larger reflection loss, higher effective bandwidth, thinner thickness and more excellent wave-absorbing performance.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A flower-like zinc oxide/ferroferric oxide wave absorbent is characterized by comprising a zinc oxide nano rod and ferroferric oxide nano particles attached to the surface of the zinc oxide nano rod; the zinc oxide nano rod forms a flower-like structure; the weight of the ferroferric oxide nano particles accounts for 10-15% of that of the wave absorbent; the ferroferric oxide nano particles are spherical, and the diameter of each ferroferric oxide nano particle is 10-120 nm; the diameter of the zinc oxide nano rod is 200-800 nm, and the length of the zinc oxide nano rod is 3-10 mu m.
2. The preparation method of the flower-like zinc oxide/ferroferric oxide absorbent according to claim 1, comprising the following steps:
sequentially adding a strong alkali solution and a soluble ferric salt into a soluble zinc salt solution to obtain a reaction solution; the mass ratio of the soluble zinc salt to the strong base to the soluble ferric salt is 1: (1-8): (0.05-0.6);
carrying out hydrothermal reaction on the reaction solution to obtain a flower-like zinc oxide/ferroferric oxide precursor;
and carrying out heat treatment on the flower-like zinc oxide/ferroferric oxide precursor to obtain the flower-like zinc oxide/ferroferric oxide wave absorbing agent.
3. The method of claim 2, wherein the soluble ferric salt is added in solid form.
4. The preparation method according to claim 2, wherein the hydrothermal reaction is carried out at 130-220 ℃ for 8-17 h.
5. The method according to claim 2, wherein the heat treatment is carried out at a temperature of 450 to 750 ℃ for 1 to 5 hours.
6. A wave absorbing material is characterized by comprising a wave absorbing agent and a binder, wherein the wave absorbing agent is the wave absorbing agent in claim 1 or the wave absorbing agent prepared by the preparation method in any one of claims 2 to 5.
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