CN111285671B - Low-frequency wave-absorbing material and preparation method thereof - Google Patents
Low-frequency wave-absorbing material and preparation method thereof Download PDFInfo
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
- C04B2235/3232—Titanium oxides or titanates, e.g. rutile or anatase
- C04B2235/3234—Titanates, not containing zirconia
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/628—Coating the powders or the macroscopic reinforcing agents
- C04B35/62802—Powder coating materials
- C04B35/62805—Oxide ceramics
Abstract
The invention provides a low-frequency wave-absorbing material and a preparation method thereof. The low-frequency wave-absorbing material comprises: the core is carbonyl iron powder; the shell layer is coated on the surface of the core and is barium titanate; the molar ratio of barium titanate to carbonyl iron powder is 1: 10-50, the low-frequency wave-absorbing material and the setting agent are mixed according to the mass ratio of 6-8.5: 1 to prepare a ring with the thickness of 1.5-3 mm, the measured reflection loss of the ring with the thickness of 3mm at 1.32GHz reaches-30.5 dB, and the reflection loss at 0.82-4.25GHz is less than-10 dB. According to the low-frequency wave absorbing material, the barium titanate and the carbonyl iron are compounded, so that the impedance matching performance of electromagnetic waves is effectively improved, and the low-frequency wave absorbing performance is further improved.
Description
Technical Field
The invention relates to the field of composite materials, in particular to a low-frequency wave-absorbing material and a preparation method thereof.
Background
With the rapid development of modern electrical and electronic technology, the surrounding electromagnetic environment is increasingly deteriorated, so that the absorption type electromagnetic shielding material is widely regarded and deeply researched. Carbonyl iron as a typical magnetic loss type wave-absorbing material has high magnetic conductivity and thermal stability, and has certain absorption potential in a low-frequency S band (2-4 GHz), but due to the problems of high density, poor oxidation resistance and single loss mechanism, the carbonyl iron is more and more difficult to meet the increasing application requirements.
The effective absorption of low-frequency electromagnetic waves is always a difficult point in the research of wave-absorbing materials. Researches find that the carbonyl iron and the dielectric loss material are compounded, so that the electromagnetic wave matching performance of the wave-absorbing material can be effectively improved, and the low-frequency wave-absorbing performance of the wave-absorbing material is further improved. Barium titanate in the dielectric loss material is a perovskite ferroelectric with high dielectric constant and excellent piezoelectricity, and is a good dielectric loss type wave-absorbing material under the action of an electromagnetic field, and loss of electromagnetic waves is mainly dependent on oriented polarization and interface polarization of electric dipoles.
At present, the composite research on barium titanate and carbonyl iron at home and abroad mostly adopts a physical mixing mode, for example, Jinghongxia and the like research the influence of different barium titanate addition amounts on the electromagnetic performance of a barium titanate/carbonyl iron mixed material, and obtain the influence of different barium titanate addition amounts on the low-frequency absorption effect. Qing Yuchang et al studied the problem of optimal proportioning of barium titanate carbonyl iron mixture to obtain a barium titanate addition of 20% with maximum absorption strength. However, the barium titanate and the carbonyl iron are physically mixed, and the combination effect is poor, so that the surface activity and the stability of the obtained composite material are poor, and the wave-absorbing performance of the composite material is influenced.
Disclosure of Invention
The invention mainly aims to provide a low-frequency wave-absorbing material and a preparation method thereof, and aims to solve the problem that the wave-absorbing material formed by mixing barium titanate and carbonyl iron in the prior art is unstable in wave-absorbing performance.
In order to achieve the above object, according to one aspect of the present invention, there is provided a low frequency wave-absorbing material, including: the core is carbonyl iron powder; the shell layer is coated on the surface of the core and is barium titanate; the molar ratio of barium titanate to carbonyl iron powder is 1: 10-50, the low-frequency wave-absorbing material and the setting agent are mixed according to the mass ratio of 6-8.5: 1 to prepare a ring with the thickness of 1.5-3 mm, the measured reflection loss of the ring with the thickness of 3mm at 1.32GHz reaches-30.5 dB, and the reflection loss at 0.82-4.25GHz is less than-10 dB.
Furthermore, the particle size of the core of the low-frequency wave-absorbing material is 2-10 μm, and the particle size of the low-frequency wave-absorbing material is 4-12 μm.
According to another aspect of the present invention, a preparation method of a low frequency wave-absorbing material is provided, which comprises: step S1, mixing and ball-milling the first organic solvent dispersed with carbonyl iron powder, the titanium precursor solution and the barium precursor solution to obtain a suspension; step S2, washing and carrying out solid-liquid separation on the suspension to obtain a solid-phase product; and step S3, carrying out heat treatment on the solid-phase product to obtain a low-frequency wave-absorbing material, wherein carbonyl iron powder in the low-frequency wave-absorbing material is taken as a core, and barium titanate is taken as a shell layer to coat the surface of the carbonyl iron powder.
Further, the step S1 includes: step S11, performing ball milling on the first organic solvent dispersed with carbonyl iron powder to obtain a first ball milling dispersion liquid; step S12, mixing the first ball-milling dispersion liquid with one of a titanium precursor liquid and a barium precursor liquid, and then carrying out ball milling to obtain a second ball-milling dispersion liquid; step S13, mixing the second ball milling dispersion liquid and the other one of the barium precursor liquid and the titanium precursor liquid, and then carrying out ball milling to obtain a suspension; preferably, a surfactant is added during any ball milling process of step S1, more preferably the surfactant is selected from one or more of polyvinyl alcohol, polyethylene glycol, and cetyltrimethylammonium bromide.
Further, the titanium precursor liquid comprises a titanium source and a second organic solvent, and the barium precursor liquid comprises a barium source and a third organic solvent; the molar ratio of the titanium source to the barium source to the carbonyl iron powder is 1:1: 10-50, the first organic solvent, the second organic solvent and the third organic solvent are mutually soluble, the addition amount of the surfactant is 2-4% of the carbonyl iron powder in percentage by mass, preferably, the titanic acid is selected from butyl titanate, titanium isopropoxide or titanium tetrapentyloxy, and the barium source is selected from barium acetate, barium hydroxide or barium chloride.
Further, the ball milling balls adopted in the ball milling process are selected from zirconia balls or silicon nitride balls, and the diameter of the ball milling balls is preferably 2-10 mm.
Further, the above preparation method further comprises a step of forming a titanium precursor solution, the step of forming the titanium precursor solution comprising: placing a titanium source in a second organic solvent, and then dropwise adding a hydrochloric acid solution into the second organic solvent to obtain a titanium precursor solution, wherein the volume of the hydrochloric acid is the same as that of the second organic solvent, the concentration of the hydrochloric acid solution is selected from 1-2 mol/L, and the second organic solvent is preferably selected from one or more of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene and benzyl alcohol; more preferably, the amount of the second organic solvent added is 300 to 400mL per 1mol of the titanium source.
Further, the preparation method further comprises a step of forming a barium precursor solution, wherein the step of forming the barium precursor solution comprises the following steps: placing a barium source in a third organic solvent, and stirring in a water bath to obtain a barium precursor solution, wherein the water bath temperature is 35-45 ℃, and preferably the third organic solvent is one or more selected from ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene and benzyl alcohol; more preferably, the amount of the third organic solution added is 250 to 350mL per 1mol of the barium source.
Further, the first organic solvent is selected from one or more of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene and benzyl alcohol; preferably, the mass ratio of the carbonyl iron powder to the first organic solvent is 1: 2-1: 3; the mass ratio of the total mass of the carbonyl iron powder and the first organic solvent to the ball-milling balls is 1: 20-1: 80.
Further, the step S1 includes: ball-milling the first organic solvent dispersed with the carbonyl iron powder for 0.2-1.5 h to obtain a first ball-milling dispersion liquid; preferably, mixing the first ball-milling dispersion liquid with the titanium precursor liquid, and then carrying out ball milling for 0.1-0.5 h to obtain a second ball-milling dispersion liquid; preferably, the second ball-milling dispersion liquid and the barium precursor liquid are mixed and then ball-milled for 2-24 hours to obtain a suspension.
Further, step S2 includes: washing the suspension to obtain a washed solid-phase product; and drying the washed solid-phase product to obtain the solid-phase product, wherein the preferable drying is drying at 60-80 ℃.
Further, in step S3, the heat treatment step includes: and calcining the solid-phase product to obtain the low-frequency wave-absorbing material, wherein the calcining temperature is 800-1200 ℃, and the calcining time is 1-4 hours.
By applying the technical scheme of the invention, the barium titanate is coated on the surface of the carbonyl iron powder to form the low-frequency composite material, so that the wave-absorbing performance, the oxidation resistance and the thermal stability of the carbonyl iron powder are fully exerted; meanwhile, the high dielectric constant and the excellent piezoelectric property of the good dielectric loss wave-absorbing material barium titanate can be fully exerted, so that the low-frequency wave-absorbing material formed by the coating mode can effectively improve the impedance matching performance of electromagnetic waves, further improves the low-frequency wave-absorbing performance, and ensures that the low-frequency wave-absorbing performance is more stable and outstanding. The method comprises the steps of mixing the low-frequency wave-absorbing material with a setting agent (preferably paraffin) according to a mass ratio of 6-8.5: 1 to prepare a ring with the thickness of 1.5-3 mm, and measuring the electromagnetic parameters of the ring, wherein the low-frequency wave-absorbing effect of the obtained wave-absorbing material is directly influenced by different proportions of barium titanate and carbonyl iron powder, and the wave-absorbing material with the electromagnetic parameters of-30.5 dB at 1.32GHz and less than-10 dB at 0.82-4.25GHz under the thickness of 3mm can be obtained within the provided molar proportion range.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the wave-absorbing material formed by mixing barium titanate and carbonyl iron powder in the prior art has the problem of unstable wave-absorbing performance. In order to solve the problem, the application provides a low-frequency wave-absorbing material and a preparation method thereof.
The low-frequency wave-absorbing material comprises a core and a shell layer coated on the surface of the core, wherein the core is carbonyl iron powder, the shell layer is barium titanate, and the molar ratio of the barium titanate to the carbonyl iron powder is 1: 10-50; the low-frequency wave-absorbing material and the setting agent are mixed according to the mass ratio of 6-8.5: 1 to prepare a ring with the thickness of 1.5-3 mm, the reflection loss of the ring with the thickness of 3mm at 1.32GHz reaches-30.5 dB, and the reflection loss at 0.82-4.25GHz is less than-10 dB.
According to the scheme provided by the application, the barium titanate is coated on the surface of the carbonyl iron powder to form the low-frequency composite material, so that the wave-absorbing performance, the oxidation resistance and the thermal stability of the carbonyl iron powder are fully exerted; meanwhile, the high dielectric constant and the excellent piezoelectric property of the good dielectric loss wave-absorbing material barium titanate can be fully exerted, so that the low-frequency wave-absorbing material formed by the coating mode can effectively improve the impedance matching performance of electromagnetic waves, further improves the low-frequency wave-absorbing performance, and ensures that the low-frequency wave-absorbing performance is more stable and outstanding. The low-frequency wave absorbing effect of the obtained wave absorbing material is directly influenced by different proportions of barium titanate and carbonyl iron powder, and the wave absorbing material with the reflection loss of a ring with the thickness of 3mm reaching-30.5 dB at 1.32GHz and the reflection loss of less than-10 dB at 0.82-4.25GHz can be obtained within the provided molar proportion range. The testing method comprises the steps of mixing the low-frequency wave-absorbing material and the setting agent (preferably paraffin) according to the mass ratio of 6-8.5: 1 to prepare a circular ring with the thickness of 1.5-3 mm, and measuring the electromagnetic parameters of the circular ring.
In a preferred embodiment, the particle size of the core of the low-frequency wave-absorbing material is 2-10 μm, and the particle size of the low-frequency wave-absorbing material is 4-12 μm. Because the carbonyl iron powder has very small particles, the size of the spherical carbonyl iron powder particles is generally 2-5 mu m, the size of the flaky carbonyl iron powder particles obtained after the spherical carbonyl iron powder is flaked in the wave-absorbing material is generally 2-10 mu m, and the thickness of the coating layer is required to be very small in order to ensure the mass fraction of the carbonyl iron powder in the wave-absorbing material, the size of the wave-absorbing material is preferably 4-12 mu m, so that the anti-oxidation performance of the wave-absorbing material is favorably provided, and the wave-absorbing performance of the carbonyl iron is not influenced.
In another exemplary embodiment, the present application provides a method for preparing a low-frequency wave-absorbing material, where the preparation includes: step S1, mixing and ball-milling the first organic solvent dispersed with carbonyl iron powder, the titanium precursor solution and the barium precursor solution to obtain a suspension; step S2, washing and carrying out solid-liquid separation on the suspension to obtain a solid-phase product; and step S3, carrying out heat treatment on the solid-phase product to obtain a low-frequency wave-absorbing material, wherein carbonyl iron powder is taken as a core in the low-frequency wave-absorbing material, and barium titanate is taken as a shell layer to coat the surface of the carbonyl iron powder.
The ball-milling equipment utilizes the first organic solvent, the titanium precursor liquid and the barium precursor liquid which are dispersed with carbonyl iron powder to carry out mixed ball milling, so that the titanium precursor liquid and the barium precursor liquid are coated on the surface of the carbonyl iron powder when carrying out chemical reaction to form barium titanate in the ball-milling process, and the barium titanate and the carbonyl iron powder are compounded more uniformly and more firmly. And then, suspension obtained by ball milling is subjected to washing, impurity removal, solid-liquid separation and surface oxidation by heat treatment in sequence, so that the problem of poor oxidation resistance of carbonyl iron is further avoided, and the stability of the wave absorption performance of the low-frequency wave absorbing material is improved. The barium titanate is coated on the surface of the carbonyl iron powder, so that the oxidation resistance and the thermal stability of the carbonyl iron powder are fully exerted; meanwhile, the high dielectric constant and the excellent piezoelectric property of the barium titanate which is a good dielectric loss wave-absorbing material can be fully exerted, so that the low-frequency wave-absorbing material in the coating form obtained by the preparation method can effectively improve the matching performance of electromagnetic waves, and the low-frequency wave-absorbing material is more stable and outstanding in performance. Therefore, the low-frequency wave-absorbing material prepared by the preparation method has the advantages of simple process, easiness in operation and low cost, can realize large-scale production, and meanwhile, the prepared low-frequency wave-absorbing material has stable electromagnetic property, wide wave-absorbing frequency band and good wave-absorbing property, and has good application prospect in the fields of electromagnetic shielding and electromagnetic wave absorption.
In a preferred embodiment, the step S1 includes: step S11, dispersing carbonyl iron powder in a first organic solvent, and then performing ball milling to obtain a first ball milling dispersion liquid; s12, mixing the first ball-milling dispersion liquid with one of the barium precursor liquid and the titanium precursor liquid, and then carrying out ball milling to obtain a second ball-milling dispersion liquid; s13, mixing the second ball-milling dispersion liquid and the other one of the barium precursor liquid and the titanium precursor liquid, and then carrying out ball milling to obtain a suspension; preferably, a surfactant is added during any ball milling process of step S1, and more preferably, the surfactant is selected from one or more of polyvinyl alcohol, polyethylene glycol, and cetyltrimethylammonium bromide.
Because the wave-absorbing performance of the flaky barium titanate is more excellent, the carbonyl iron powder is flaked by performing ball milling treatment on the carbonyl iron powder, which is beneficial to improving the low-frequency magnetic conductivity of the carbonyl iron powder as a wave-absorbing material and further promoting the low-frequency absorption effect, and on the other hand, the shape of the carbonyl iron powder coated with the flaky barium titanate is also flaked; meanwhile, the particle size of the flaky carbonyl iron powder can be controlled by ball milling, so that the particle size of the generated barium titanate is controlled. And secondly, the barium titanate is more uniformly coated on the surface of the carbonyl iron powder by virtue of the energy transferred by ball milling, so that the barium titanate and the carbonyl iron powder are better combined. And then adding the titanium precursor liquid and the barium precursor liquid for continuous ball milling, reducing the reaction activation energy of the surface of the material and improving the combination effect between the two materials by inducing the change of the structures and the performances of the barium titanate and the carbonyl iron through ball milling, so that the barium titanate is combined with the carbonyl iron after being synthesized and is coated on the surface of the carbonyl iron. A small amount of surfactant is added in the ball milling process, so that better physical crosslinking can be formed between carbonyl iron powder and barium titanate, and the barium titanate is more uniformly distributed on the surface of the carbonyl iron powder. Meanwhile, in the subsequent high-temperature calcination process, the surfactant is heated and decomposed, so that the interior of the obtained low-frequency wave-absorbing material is porous, and the loss of electromagnetic waves in the holes can be increased through multiple reflection and refraction, so that the wave-absorbing performance is further improved.
In a preferred embodiment, the titanium precursor solution comprises a titanium source and a second organic solvent, and the barium precursor solution comprises a barium source and a third organic solvent; the molar ratio of the titanium source to the barium source to the carbonyl iron powder is 1:1: 10-50, and the first organic solvent, the second organic solvent and the third organic solvent can be mutually soluble. The molar ratio of the titanium source, the barium source and the carbonyl iron powder is not limited in the range provided by the invention, but the numerical ratio in the range is favorable for improving the ratio of barium titanate and carbonyl iron in the finally obtained low-frequency wave-absorbing material, and is favorable for improving the low-frequency wave-absorbing performance of the wave-absorbing material. Meanwhile, the first organic solvent, the second organic solvent and the third organic solvent are controlled to be mutually soluble, so that the contact mixing performance of the carbonyl iron powder, the titanium precursor liquid and the barium precursor liquid is better, and the mutual reaction activity is improved. The method comprises the steps of combining a titanium source in a titanium precursor liquid with a barium source in a barium precursor liquid to generate barium titanate, wherein the titanium source and the barium source in the precursor liquid can be combined to generate barium titanate through ball milling treatment, and the barium titanate can be used as raw materials of the titanium precursor liquid and the barium precursor liquid; when the titanium source is titanium isopropoxide, the barium source is selected from barium hydroxide or barium chloride; when the titanium source may be titanium tetratetriteoxide, the titanium source is barium oxyxide.
In a preferred embodiment, the ball milling process is performed by using zirconia beads or silicon nitride beads. Because there is the loss to the ball-milling in-process always, when consequently carrying out the selection of ball-milling ball, need consider the influence of the material of ball-milling ball to low frequency absorbing material, choose for use zirconia pearl or silicon nitride ball as ball-milling ball can avoid simultaneously acquireing the convenience to absorbing material performance's influence. And meanwhile, hard alloy balls can be selected, so that the ball grinding balls are not easy to lose in the ball milling process, and the influence on the generated barium titanate is small. In addition, because the size of the ball milling ball is greatly related to substances needing ball milling, and because the particles of carbonyl iron powder, titanium precursor liquid and barium precursor liquid are all small, in order to perform ball milling treatment on the three substances, modification treatment on the materials is facilitated, and meanwhile, the combination of barium titanate and carbonyl iron powder is promoted, the diameter of the ball milling ball is preferably 2-10 mm.
In a preferred embodiment, the step of forming the titanium precursor solution includes: first, a titanium source is added to a second organic solvent, and then a hydrochloric acid solution is dropped thereto to obtain a titanium precursor solution. Wherein the volume of the hydrochloric acid is the same as that of the second organic solvent, the concentration of the hydrochloric acid solution is 1-2 mol/L, and the second organic solvent is preferably one or more selected from ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene and benzyl alcohol; more preferably, the amount of the second organic solvent added is 300 to 400mL per 1mol of the titanium source. The titanium source is added into the organic solvent, so that the titanium source is dispersed in the organic solvent and hydrolyzed to obtain titanic acid, subsequent reaction with barium in the barium precursor liquid is facilitated to obtain barium titanate, the addition of hydrochloric acid is facilitated to dissolve the titanium source in the organic solvent, and the selection of the concentration of the hydrochloric acid is in certain correlation with the addition amount of the hydrochloric acid. The second organic solvent is not limited to the range provided above, as long as it is miscible with the first organic solvent and the third organic solvent. The organic solvent provided by the method is more convenient to obtain and has lower cost.
In a preferred embodiment, the step of forming the barium precursor liquid includes: firstly, adding a barium source into a third organic solvent, and then stirring in a water bath at 30-50 ℃ to obtain a barium precursor solution. Preferably, the third organic solvent is selected from one or more of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene and benzyl alcohol; more preferably, the amount of the third organic solution added is 250 to 350mL per 1mol of the barium source, and the amount of the surfactant added is 2 to 4% by mass of the carbonyl iron powder. The barium source is added into the organic solvent, so that the barium is dispersed in the organic solvent, the subsequent reaction with the titanic acid in the titanium precursor liquid is facilitated to obtain the barium titanate, and the barium source is mixed in the third organic solvent by water bath heating. The third organic solvent is not limited to the range provided above, as long as it is miscible with the first and second organic solvents. The organic solvent provided by the method is more convenient to obtain and has lower cost.
In a preferred embodiment, the first organic solvent is selected from one or more of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene, and benzyl alcohol; preferably, the mass ratio of the carbonyl iron powder to the first organic solvent is 1: 2-1: 3; the mass ratio of the carbonyl iron powder to the ball grinding balls is 1: 20-1: 80. The first organic solvent is not limited to the above range, and may be selected so long as it can be mixed with the second organic solvent and the third organic solvent. The addition amount of the ball milling balls is related to the mass of the required ball milling substances, and the mass of the ball milling balls with the proportion is preferably favorable for realizing the flaking treatment of the carbonyl iron powder, promoting the combination of the barium titanate and the carbonyl iron powder and modifying the barium titanate.
In a preferred embodiment, the above preparation method further comprises: firstly, ball-milling a first organic solvent dispersed with carbonyl iron powder for 0.2-1.5 h to obtain a first ball-milling dispersion liquid; preferably, mixing the first ball-milling dispersion liquid with the titanium precursor liquid, and then carrying out ball milling for 0.1-0.5 h to obtain a second ball-milling dispersion liquid; preferably, the second ball-milling dispersion liquid and the barium precursor liquid are mixed and then ball-milled for 2-24 hours to obtain a suspension. The first organic solvent in which the carbonyl iron powder is dispersed is subjected to ball milling for 0.2-1.5 h, so that the sheet-shaped carbonyl iron powder with a proper width-thickness ratio is obtained. And then mixing the first ball-milling dispersion liquid obtained after the first ball-milling with the titanium precursor liquid, and continuing ball-milling for 0.1-0.5 h, so that the titanic acid and carbonyl iron in the titanium precursor liquid are favorably and fully mixed, and the subsequent generated barium titanate is favorably coated on the surface of the carbonyl iron powder. And finally, performing third ball milling on the mixed solution of the second ball milling dispersion liquid and the barium precursor liquid for 2-24 hours, so that the combination of barium titanate and carbonyl iron powder is promoted.
In a preferred embodiment, step S2 includes: firstly, washing the suspension obtained after ball milling to obtain a washed solid-phase product; and then drying the washed solid-phase product to obtain the solid-phase product, wherein the preferable drying is drying at 60-80 ℃. Residual impurities can be removed by washing the turbid liquid, and then the turbid liquid is dried to obtain the solid wave-absorbing material. The drying process adopts the drying with simple operation.
In a preferred embodiment, in the step S3, the step of heat-treating includes: and calcining the solid-phase product at 800-1200 ℃ for 1-4 h to obtain the low-frequency wave-absorbing material. The calcining heat treatment can oxidize the surface of the wave-absorbing material, so that the oxidation resistance and the wave-absorbing performance of the wave-absorbing material are further improved, and meanwhile, in the calcining temperature and the calcining time, impurities doped in the wave-absorbing material in the preparation process are further removed to improve the purity of the wave-absorbing material, so that the wave-absorbing performance and the electromagnetic performance of the wave-absorbing material are further improved.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
34.032g (0.1mol) of butyl titanate is weighed and added into 30mL of ethanol solution, and 30mL of 1mol/L hydrochloric acid solution is slowly added into the ethanol solution to dissolve the butyl titanate, so that titanium precursor solution is obtained; 25.541g (0.1mol) of barium acetate is weighed and added into 25mL of ethanol solution, and the solution is stirred in a water bath at the temperature of 35 ℃ to be dissolved, so that barium precursor solution is obtained; 559.2g (2.85mol) of carbonyl iron powder is weighed and dispersed into 1398mL of ethanol solution (the mass ratio of the carbonyl iron powder to the ethanol is 1:2), then the mixture is added into a ball milling pot, 11184g of zirconia beads with the diameter of 2-8 mm (the mass ratio of the carbonyl iron powder to the zirconia beads is 1:20) are placed into the ball milling pot, and the first ball milling is carried out for 0.2 h. And then mixing the first ball-milling dispersion liquid obtained after the first ball-milling with the titanium precursor liquid, and carrying out second ball-milling for 0.1 h. And mixing the second ball-milling dispersion liquid obtained by the second ball-milling with the barium precursor liquid, and carrying out third ball-milling (at the moment, the molar ratio of the butyl titanate, the barium acetate and the carbonyl iron powder in the ball-milling tank is 1:1:28.5) for 24 hours. And then washing the suspension obtained after the third ball milling by using ethanol, drying at 60 ℃ to obtain a solid phase product, and finally calcining the solid phase product at 800 ℃ for 1h to obtain the low-frequency wave-absorbing material.
Example 2
In contrast to example 1, the molar ratio of butyl titanate, barium acetate and carbonyl iron powder added was 1:1: 10.
Example 3
In contrast to example 1, the molar ratio of butyl titanate, barium acetate and carbonyl iron powder added was 1:1: 50.
Example 4
Different from example 1, in the process of preparing the titanium precursor solution, 40mL of hydrochloric acid solution with a concentration of 2mol/L was added together with 40mL of ethanol.
Example 5
Unlike example 1, the amount of ethanol added during the preparation of the barium precursor solution was 35mL, and the solution was stirred in a water bath at 45 ℃.
Example 6
Different from the example 1, carbonyl iron powder is dispersed in 2097mL of ethanol (the mass ratio of the carbonyl iron powder to the ethanol is 1:3), and 44736g of zirconia beads with the diameter of 4-10 mm (the mass ratio of the carbonyl iron powder to the zirconia beads is 1:80) are added into a ball milling pot.
Example 7
Different from the example 1, the time of the first ball milling is 1.5h, the time of the second ball milling is 0.5h, and the time of the third ball milling is 24 h.
Example 8
In contrast to example 1, 11.18g (2% of carbonyl iron powder) of polyvinyl alcohol was added as a surfactant during the third ball milling.
Example 9
In contrast to example 1, during the heat treatment, the solid phase product was calcined at 1200 ℃ for 4 h.
Example 10
In contrast to example 1, butyl titanate was dissolved in propylene glycol, barium acetate was dissolved in propylene glycol, and carbonyl iron was dissolved in propylene glycol.
Example 11
In contrast to example 1, butyl titanate was dissolved in methanol, barium acetate in isopropanol and carbonyl iron in benzyl alcohol.
Example 12
In contrast to example 1, titanium isopropoxide was dissolved in propylene glycol, barium hydroxide was dissolved in propylene glycol, and iron carbonyl was dissolved in propylene glycol.
Comparative example 1
Different from the embodiment 1, the low-frequency wave-absorbing material is obtained by mixing barium titanate and carbonyl iron, performing ball milling, and calcining at 800 ℃ for 2 hours.
The test method comprises the following steps: the low-frequency wave-absorbing materials of the embodiments and the comparative examples are mixed with paraffin according to the mass ratio of 8.5:1 to prepare a circular ring with a certain thickness, electromagnetic parameters (dielectric constant and magnetic permeability) are measured by an Agilent E5071C vector network analyzer, and then reflection loss is calculated and simulated. The test results are shown in Table 1.
TABLE 1
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
the barium titanate is coated on the surface of the carbonyl iron powder to form the low-frequency composite material, so that the wave-absorbing performance, the oxidation resistance and the thermal stability of the carbonyl iron powder are fully exerted; meanwhile, the high dielectric constant and the excellent piezoelectric property of the good dielectric loss wave-absorbing material barium titanate can be fully exerted, so that the low-frequency wave-absorbing material formed by the coating mode can effectively improve the impedance matching performance of electromagnetic waves, further improves the low-frequency wave-absorbing performance, and ensures that the low-frequency wave-absorbing performance is more stable and outstanding. The low-frequency wave absorbing effect of the obtained wave absorbing material is directly influenced by different proportions of barium titanate and carbonyl iron powder, and the wave absorbing material with the measured reflection loss of a ring with the thickness of 3mm reaching-30.5 dB at 1.32GHz and the reflection loss of less than-10 dB at 0.82-4.25GHz can be obtained within the provided molar proportion range. The testing method comprises the steps of mixing the low-frequency wave-absorbing material and the setting agent (preferably paraffin) according to the mass ratio of 6-8.5: 1 to prepare a circular ring with the thickness of 1.5-3 mm, and measuring the electromagnetic parameters of the circular ring.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (19)
1. A preparation method of a low-frequency wave-absorbing material is characterized by comprising the following steps:
step S1, mixing and ball-milling the first organic solvent dispersed with carbonyl iron powder, the titanium precursor solution and the barium precursor solution to obtain a suspension;
step S2, washing and carrying out solid-liquid separation on the suspension to obtain a solid-phase product; and
step S3, carrying out heat treatment on the solid-phase product to obtain the low-frequency wave-absorbing material, wherein carbonyl iron powder is taken as a core in the low-frequency wave-absorbing material, and barium titanate is taken as a shell layer to coat the surface of the carbonyl iron powder;
the step S1 includes:
step S11, performing ball milling on the first organic solvent dispersed with the carbonyl iron powder to obtain a first ball milling dispersion liquid;
step S12, mixing the first ball-milling dispersion liquid with one of the titanium precursor liquid and the barium precursor liquid, and then carrying out ball milling to obtain a second ball-milling dispersion liquid;
step S13, mixing the second ball-milling dispersion liquid with the other one of the barium precursor liquid and the titanium precursor liquid, and then carrying out ball milling to obtain a suspension;
adding a surfactant during any ball milling process of the step S1, wherein the surfactant is selected from one or more of polyvinyl alcohol, polyethylene glycol and cetyl trimethyl ammonium bromide.
2. The method according to claim 1, wherein the titanium precursor liquid includes a titanium source and a second organic solvent, and the barium precursor liquid includes a barium source and a third organic solvent; the molar ratio of the titanium source to the barium source to the carbonyl iron powder is 1:1: 10-50, the first organic solvent, the second organic solvent and the third organic solvent are mutually soluble, and the addition amount of the surfactant is 2-4% of the carbonyl iron powder in percentage by mass.
3. The method according to claim 2, wherein the titanium source is selected from butyl titanate, titanium isopropoxide or titanium teterpenteoxide and the barium source is selected from barium acetate, barium hydroxide or barium chloride.
4. The preparation method according to claim 1, wherein the ball milling balls used in the ball milling process are selected from zirconia balls or silicon nitride balls.
5. The method according to claim 4, wherein the ball grinding balls have a diameter of 2 to 10 mm.
6. The method of manufacturing according to claim 2, further comprising the step of forming the titanium precursor liquid, the step of forming the titanium precursor liquid comprising:
and (3) adding a hydrochloric acid solution into the titanium source after the titanium source is placed in the second organic solvent to obtain the titanium precursor solution, wherein the volume of the hydrochloric acid is the same as that of the second organic solvent, and the concentration of the hydrochloric acid solution is selected from 1-2 mol/L.
7. The method according to claim 6, wherein the second organic solvent is one or more selected from the group consisting of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene, and benzyl alcohol.
8. The production method according to claim 6, wherein the second organic solvent is added in an amount of 300 to 400mL relative to 1mol of the titanium source.
9. The method of manufacturing according to claim 2, further comprising the step of forming the barium precursor liquid, the step of forming the barium precursor liquid comprising:
and (3) placing the barium source in the third organic solvent, and stirring under a water bath condition to obtain the barium precursor solution, wherein the water bath temperature is 35-45 ℃.
10. The method of claim 9, wherein the third organic solvent is selected from one or more of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene, and benzyl alcohol.
11. The method according to claim 9, wherein the third organic solution is added in an amount of 250 to 350mL per 1mol of the barium source.
12. The method according to claim 4, wherein the first organic solvent is one or more selected from the group consisting of ethanol, methanol, isopropanol, propylene glycol, acetylacetone, benzene, and benzyl alcohol.
13. The preparation method according to claim 12, wherein the mass ratio of the carbonyl iron powder to the first organic solvent is 1:2 to 1: 3; the mass ratio of the total mass of the carbonyl iron powder and the first organic solvent to the ball grinding ball is 1: 20-1: 80.
14. The method for preparing a composite material according to claim 1, wherein the step S1 includes:
and ball-milling the first organic solvent dispersed with the carbonyl iron powder for 0.2-1.5 h to obtain the first ball-milling dispersion liquid.
15. The preparation method according to claim 14, wherein the first ball-milled dispersion liquid and the titanium precursor liquid are mixed and then ball-milled for 0.1 to 0.5 hours to obtain the second ball-milled dispersion liquid.
16. The preparation method according to claim 14, wherein the second ball-milled dispersion liquid and the barium precursor liquid are mixed and then ball-milled for 2 to 24 hours to obtain the suspension.
17. The method for preparing a composite material according to claim 1, wherein the step S2 includes:
washing the suspension to obtain a washed solid-phase product;
and drying the washed solid-phase product to obtain a solid-phase product.
18. The method according to claim 17, wherein the drying is drying at 60 to 80 ℃.
19. The method according to claim 1, wherein in the step S3, the heat treatment step includes: and calcining the solid-phase product to obtain the low-frequency wave-absorbing material, wherein the calcining temperature is 800-1200 ℃, and the calcining time is 1-4 hours.
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