CN102103918A - Thin low-frequency wave-absorbing material and preparation method thereof - Google Patents
Thin low-frequency wave-absorbing material and preparation method thereof Download PDFInfo
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- CN102103918A CN102103918A CN 200910241997 CN200910241997A CN102103918A CN 102103918 A CN102103918 A CN 102103918A CN 200910241997 CN200910241997 CN 200910241997 CN 200910241997 A CN200910241997 A CN 200910241997A CN 102103918 A CN102103918 A CN 102103918A
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Abstract
The invention provides a low-frequency wave-absorbing material. The material is characterized by being prepared by mixing 60-75vol.% of FeCo alloy powder with 25-40vol.% of phenolic resin powder and then hot-forming the mixture, wherein the average particle size of the FeCo alloy powder is 0.25-0.35mu m and the FeCo alloy powder is covered by an alumina layer with the thickness of 25-35nm. The invention also provides a preparation method of the low-frequency wave-absorbing material. The method comprises the following steps: (1) preparing the FeCo alloy powder with the average particle size of 0.25-0.35mu m; (2) covering the FeCo alloy powder with the alumina powder by a chemical method; and (3) wet-mixing the FeCo alloy powder covered by the alumina layer in the step (2) with the phenolic resin powder on a ball mill, drying the mixture after wet mixing and hot-forming the dried mixture, thus preparing the low-frequency wave-absorbing material. The material has higher magnetic conductivity and magnetic loss within the frequency range of 1-4GHz, and the material with the thickness of 1.1-2mm has the highest microwave-absorbing performance, namely minus 16dB, within the frequency range of 1-4GHz.
Description
Technical field
The present invention relates to a kind of slim microwave absorbing material and technology of preparing that is applied to aspects such as radar, electronic countermeasures, electronic device, circuit, belong to the electromagnetic compatibility technology field.
Background technology
Absorptive-type electromagnetic shielding material has unique purposes aspect Electromagnetic Compatibility of Power Electronics, it not only can prevent electromagnetic leakage, also reflection electromagnetic wave not, thus the components and parts of equipment itself are not produced interference.The form that this class material adopts macromolecule resin and absorbent to mix usually applies or is pasted on the position that electromagnetic wave is revealed.At present can be various as the material category of microwave absorption, as various ferrite powders, carbonyl iron dust (CIP), FeCo alloy powder, polycrystalline iron fiber, ultrafine metal powders etc.Fe family metal and alloy powder are that microwave absorption is more widely used in research both at home and abroad at present.The wave-absorbing effect of the absorbing material of this resin/Magnaglo preparation, 1 millimeters thick the highest can the realization-more than the 20dB in the 8-18GHz frequency range, and obtained application in radar wave camouflage, Electromagnetic Compatibility of Power Electronics.But for low-frequency range (1-4GHz), because the magnetic permeability and the magnetic loss of material are on the low side, absorbing property is relatively poor when thin thickness.
High performance microwave absorbing material requires the magnetic permeability and the magnetic loss height of material, and Ferrite Material is owing to the restriction of Snooker law, the value of its magnetic permeability when 1-4GHz lower (less than 2).Feeromagnetic metal absorbent (comprising iron powder, ferrocobalt powder, iron-nitride etc.) has higher saturation magnetization height, its intrinsic permeability height (the 1-4GHz calculated value is about 20) in the microwave section, but because it is a good conductor, must disperse be distributed among the dielectric, integral body presents insulation characterisitic, just can have the effect of the ripple of suction.Because medium must add mutually, and the magnetic permeability of composite material is significantly reduced.Theoretically, the many more increases that help magnetic permeability more of the addition of magnetic metal phase, but, after the addition of metal phase surpasses a certain numerical value (seepage flow threshold value), prepared metal-dielectric composite material will become conductor, similar with the reflection of bulk metal sample, strong microwave reflection radiation can not be used as microwave absorbing material.The seepage flow threshold value of composite material is closely-related with raw material and preparation technology, the volume fraction of metal powder, form, distribution are very big to the influence of magnetic permeability and dielectric constant, it is even more that metal and medium distribute mutually, and the seepage flow threshold value of metal-dielectric composite material is high more.
As being for epoxy resin/magnetic metal powder, adopt conventional mixed method, the seepage flow threshold value of composite material is difficult to surpass 45%, and after the adding proportion of metal powder was greater than this ratio, the metal powder particle flocked together easily and forms conductive network and make composite material integral body be conductive characteristic.Because the restriction of metal dust adding proportion, make the magnetic permeability of composite material on the low side (when 1GHz less than 5).
Improving the intrinsic permeability of magnetic metallic powder and increasing its loading is to improve the key of composite material at magnetic permeability, thereby is implemented in microwave absorbing rate high under the situation of thinner thickness.
Summary of the invention
The object of the present invention is to provide a kind of SMD microwave absorbing material, this material has higher magnetic permeability and magnetic loss at 1-4GHz, and the material that 1.1～2mm is thick is the highest in the 1-4GHz band limits to be had-microwave absorbing property of 16dB.
At this purpose, the technical solution used in the present invention is as follows:
A kind of low frequency absorbing material, this low frequency absorbing material is after phenolic resins (PF) 2123 (trade mark of the phenolic resins) powder by the FeCo alloyed powder of 60vol.%-75vol.% and 25vol.%-40vol.%, hot-forming and make, wherein, the particle mean size of FeCo alloyed powder is 0.25 μ m～0.35 μ m, and coating thickness is the alumina layer of 25nm～35nm on this FeCo alloyed powder.
Phenolic resins powder used in the present invention, the trade mark are 2123, and the particle mean size of phenolic resins (PF) powder is below 1 micron, can be by the further ball milling preparation of the PF powder on the market.
Wherein, the Fe of FeCo alloyed powder and the mol ratio of Co are 55～75: 25～45, and the mol ratio of Fe and Co is preferably 65: 35.
Fe used in the present invention
55～75Co
25～45Alloy (is preferably Fe
65Co
35Alloy) specific saturation magnetization is up to 240Am
2/ kg, higher at the intrinsic permeability of microwave section, the present invention passes through Fe
55～ 75Co
25～45Alloy (is preferably Fe
65Co
35Alloy) powder of submicron order carries out the surface and coat to handle, and by mixes the method for hot pressing afterwards with the phenolic resins powder, improves its filling ratio in dielectric, realizing high microwave magnetic permeability, and then is implemented in 1-4GHz thin layer high-absorbility.
Low frequency absorbing material of the present invention be shaped as chip (also claiming SMD), its thickness is 1.1～2mm thickness, is preferably 1.2mm.
A kind of method for preparing the low frequency absorbing material, this method comprises the steps:
(1), the preparation particle mean size is the FeCo alloyed powder of 0.25 μ m～0.35 μ m;
(2), with chemical method coated aluminum oxide powder on the FeCo alloyed powder, the alumina layer thickness that coats on this FeCo alloyed powder is 25nm～35nm;
(3), FeCo alloyed powder and the phenolic resins powder with the coated aluminum oxide layer that obtains in the step (2) carries out wet mixing on ball mill, wherein, the mixing ratio of FeCo alloyed powder and phenolic resins is the FeCo alloyed powder: phenolic resins is 60vol.%-75vol.%: 25vol.%-40vol.%; Drying after the wet mixing, hot-forming and make.
In described step (1), described particle mean size is that the preparation of the FeCo alloyed powder of 0.25 μ m～0.35 μ m is to take following process:
With CoCl
26H
2O and FeSO
47H
2O is dissolved in the deionized water, is mixed with the transparent salting liquid of metal ion, wherein Co
2+The percentage that accounts for total metal ion is 0.25%～0.45%, and the total concentration of metal ion is 0.2-2Mol/L; In hydrazine hydrate, add NaOH, make the mixed solution pH value be adjusted into 8～12; The mixed solution of above-mentioned hydrazine hydrate and NaOH is heated to 80～100 ℃, then salting liquid is added in the mixed solution of hydrazine hydrate and NaOH, be incubated 0.5～2 hour, there is gas to emit in the course of reaction, after the complete blackening of the color of solution, react completely, will use distilled water and absolute ethanol washing extremely neutral behind the sedimentation and filtration respectively to wash liquid, with the black powder drying that obtains, the powder that obtains after the drying is that particle mean size is the FeCo alloyed powder of 0.25 μ m～0.35 μ m.
In described step (2), described method with chemical method coated aluminum oxide powder on the FeCo alloyed powder is to take following process:
The FeCo alloy powder that obtains in the step (1) is immersed AlNO
3In the solution, AlNO
3The concentration of solution is 1-3mol/L, stir leave standstill more than 10 minutes after, will dry behind the powder filter, under dynamic condition He in the argon gas atmosphere, heat-treat again.Above step is repeated 1～5 time, obtain coating the FeCo alloyed powder of the aluminium oxide bed thickness of 25nm～35nm.
In described step (2), described heat treated temperature is 750 ℃～900 ℃, and the time of insulation is 1～5 hour.
In described step (2), described dynamic condition is that the powder after the oven dry is put into quartz ampoule, and in heat treatment process, quartz ampoule keeps rotating with 1～5 rev/min rotating speed.
In described step (3), the particle mean size of described phenolic resins powder is 1 micron.
In described step (3), the FeCo alloyed powder of described coated aluminum oxide layer and phenolic resins powder are to carry out wet mixing on three roller ball mills, are medium with the deionized water, and the wet mixing time is 5～24 hours.
In described step (3), hot-forming temperature is 180～250 ℃, and hot-forming pressure is 50～300MPa, is 15min～45min when hot-forming.
Advantage of the present invention is as follows:
1) adopting particle mean size is raw material at the ultra-fine FeCo alloyed powder of 0.3 μ m, and the saturation magnetization of this alloy powder is higher, helps improving the magnetic permeability in the microwave section of composite material.
2) adopt the chemical method coating technology to make aluminium oxide evenly be coated on the outer surface of particle, aluminum oxide film has very high insulation characterisitic, thereby avoids the appearance of conductive network in the absorbing material preparation process to greatest extent.
3) adopt hot extrusion briquetting technique to obtain fine and close phenolic resins/metal powder composite material, the absorbing material insulation property of preparation are good, have higher magnetic permeability in the microwave section.
Description of drawings
Fig. 1 is the SEM image of FeCo alloy powder.
Embodiment
The concrete grammar of preparation low frequency absorbing material of the present invention is as follows:
1) preparation of submicron order ferrocobalt powder
With CoCl
26H
2O and FeSO
47H
2O is according to Co
2+: Fe
3+=0.35: 0.65 ratio is dissolved in the deionized water, and being mixed with metal ion solubility is the transparent salting liquid of 1Mol/L; Appropriate amount of NaOH is joined in the hydrazine hydrate, and regulating the mixed solution pH value is alkalescence (that is, making the mixed solution pH value be adjusted into 8～12); With CoCl
26H
2O and FeSO
47H
2The mixed solution of O joins in the mixed solution of hydrazine hydrate and NaOH, reacts under 90 ℃, is incubated 1 hour.Have gas to emit in the course of reaction, the color of solution becomes milky gradually by indigo plant, and the back becomes ash, until blackening.After the complete blackening of the color of solution, react completely, use distilled water and absolute ethanol washing to neutral respectively solution, the black powder that obtains is put into 40 ℃ of dryings of vacuum drying chamber, treat to take out behind the powder drying.Accompanying drawing 1 is the alloy powder SEM image of preparation, and grain graininess is about 300nm.
2) technology of preparing of chemical method coated aluminum oxide powder
The FeCo alloy powder is soaked AlNO as 1mol/L
3In the solution, leave standstill 30 minutes after stirring after, will dry behind the powder filter, 800 ℃ of insulations 2 hours in quartz tube furnace are cooled to room temperature under argon gas atmosphere protection.Quartz ampoule rotates with 5 rev/mins rotating speed maintenance in heat treatment process, to prevent the bonding of powder.Repeat above process 3 times, obtain the ferrocobalt powder of coated aluminum oxide.The thickness of coated aluminum oxide layer is about 30nm.
3) technology of preparing of composite wave-suction material
The composition range of metal-dielectric composite microwave absorbing material of the present invention is: absorbent FeCo:60vol.%-75vol.%; Phenolic resins 25-40vol.%.
Get the Fe of above method preparation
65Co
35Cladding powder is as absorbed dose, and the phenolic resins (PF) of choosing particle mean size and be 1 micron is the medium phase.The ferrocobalt powder and PF (phenolic resins) powder of coated aluminum oxide are carried out wet mixing on three roller ball mills, be medium with the deionized water, mixes oven dry after 10 hours, hot-forming at 200 ℃ of following 200MPa * 45min.Size with above-mentioned block materials during by concrete use is processed, and promptly obtains being used for the absorbing material that electromagnetic compatibility is used.
4) measuring technology
Adopt BRIGHT A100 numeral metallomicroscope, S-4800 type field emission scanning electron microscope to observe the microstructure of composite material; Adopt the granularity of JL-1166 type fully-automatic laser particle size analyzer test powders raw material; Adopt XD-2 type X-ray diffractometer to carry out material phase analysis; Adopt the C of Agilent4284A type LCR auto testing instrument
p-R
pThe specific insulation of pattern specimen when 1MHz; Adopt the HP8510 network analyzer to measure the magnetic permeability and the dielectric constant of composite material microwave section.
Embodiment one
Mix by carrying out ball milling after the ferrocobalt powder of 60vol.% coated aluminum oxide, the 40vol.% phenolic resins powder batching.Adopting nylon jar and nylon ball, is abrasive media with the deionized water, on three roller batch mixers mixes 10 hour at 1: 1 according to ratio of grinding media to material, and rotating speed is 60 rev/mins.Behind the mixed powder slurry drying, 200 ℃ of following 200MPa * 15min are hot-forming.
Sample is carried out performance test, and the relative density that records sample is 100%, room temperature condition, and the resistivity during 1MHz is 1.4M Ω cm, the dielectric constant in 1～4GHz wave band and the test result of magnetic permeability are as shown in table 1.Sample is respectively 10 and 3 in the real part and the imaginary part of the magnetic permeability of 1GHz.The high-absorbility of the 1.2mm of electromagnetic parameters appears at 2.8GHz per sample, for-12dB.
Embodiment two
Mix by carrying out ball milling after the ferrocobalt powder of 70vol.% coated aluminum oxide, the 30vol.% phenol-formaldehyde resin powder batching.Adopting nylon jar and agate ball, is abrasive media with the deionized water, on three roller batch mixers mixes 10 hour at 1: 1 according to ratio of grinding media to material, and rotating speed is 60 rev/mins.Behind the mixed powder slurry drying, 200 ℃ of following 200MPa * 15min are hot-forming.
Sample is carried out performance test, and the relative density that records sample is 100%, and the resistivity under the room temperature condition during 1MHz is 1.0M Ω cm, and the dielectric constant in 1～4GHz wave band and the test result of magnetic permeability are as shown in table 2.Sample is respectively 12 and 3.2 in the real part and the imaginary part of the magnetic permeability of 1GHz.The high-absorbility of the 1.2mm of electromagnetic parameters appears at 2.0GHz per sample, for-16dB.
Embodiment three
Mix by carrying out ball milling after the ferrocobalt powder of 75vol.% coated aluminum oxide, the 25vol.% phenol-formaldehyde resin powder batching.Adopting nylon jar and agate ball, is abrasive media with the deionized water, on three roller batch mixers mixes 10 hour at 1: 1 according to ratio of grinding media to material, and rotating speed is 60 rev/mins.Behind the mixed powder slurry drying, 200 ℃ of following 200MPa * 15min are hot-forming.
Sample is carried out performance test, and the relative density that records sample is 100%, room temperature condition, and the resistivity during 1MHz is 0.4M Ω cm, the dielectric constant in 1～4GHz wave band and the test result of magnetic permeability are shown in 3.Sample is respectively 13.8 and 2.2 in the real part and the imaginary part of the magnetic permeability of 1GHz.The high-absorbility of the 1.2mm of electromagnetic parameters appears at 1.6GHz per sample, for-11dB.
The dielectric constant and the magnetic permeability of table 1 sample 1 (60vol.% coated composite powder/40vol.% phenolic resins)
| Frequency (GHz) | 1 | ?2 | ?3 | ?4 |
| μ′ | 10 | ?9 | ?8.5 | ?6 |
| μ″ | 3 | ?3.5 | ?3.3 | ?3 |
| ε′ | 35 | ?34 | ?33 | ?33 |
| ε″ | 6.1 | ?5.9 | ?6.0 | ?5.8 |
The dielectric constant and the magnetic permeability of table 2 sample 2 (70vol.% coated composite powder/30vol.% phenolic resins)
| Frequency (GHz) | 1 | ?2 | ?3 | ?4 |
| μ′ | 12 | ?10 | ?8.7 | ?6.5 |
| μ″ | 3.2 | ?3.8 | ?3.7 | ?3.2 |
| ε′ | 45 | ?42 | ?44 | ?41 |
| ε″ | 10.8 | ?8.2 | ?8.4 | ?7.8 |
The dielectric constant and the magnetic permeability of table 3 sample 3 (75vol.% coated composite powder/25vol.% phenolic resins)
| Frequency (GHz) | 1 | ?2 | ?3 | ?4 |
| μ′ | 13.8 | ?11 | ?10.4 | ?7.5 |
| μ″ | 2.2 | ?3.6 | ?3.2 | ?3.4 |
| ε′ | 55 | ?52 | ?48 | ?51 |
| ε″ | 15.8 | ?14.2 | ?13.9 | ?15.1 |
Claims (9)
1. low frequency absorbing material, it is characterized in that, this low frequency absorbing material is after being mixed by the phenolic resins powder of the FeCo alloyed powder of 60vol.%-75vol.% and 25vol.%-40vol.%, hot-forming and make, wherein, the particle mean size of FeCo alloyed powder is 0.25 μ m～0.35 μ m, and coating thickness is the alumina layer of 25nm～35nm on this FeCo alloyed powder.
2. a method for preparing the low frequency absorbing material is characterized in that, this method comprises the steps:
(1), the preparation particle mean size is the FeCo alloyed powder of 0.25 μ m～0.35 μ m;
(2), with chemical method coated aluminum oxide powder on the FeCo alloyed powder, the alumina layer thickness that coats on this FeCo alloyed powder is 25nm～35nm;
(3), FeCo alloyed powder and the phenolic resins powder with the coated aluminum oxide layer that obtains in the step (2) carries out wet mixing on ball mill, wherein, the mixing ratio of FeCo alloyed powder and phenolic resins powder is the FeCo alloyed powder: the phenolic resins powder is 60vol.%-75vol.%:25vol.%-40vol.%; Drying after the wet mixing, hot-forming and make.
3. the method for preparing the low frequency absorbing material according to claim 2 is characterized in that, in described step (1), described particle mean size is that the preparation of the FeCo alloyed powder of 0.25 μ m～0.35 μ m is to take following process:
With CoCl
26H
2O and FeSO
47H
2O is dissolved in the deionized water, is mixed with the transparent salting liquid of metal ion, wherein Co
2+The percentage that accounts for total metal ion is 0.25%～0.45%, and the total concentration of metal ion is 0.2-2Mol/L; In hydrazine hydrate, add NaOH, make the mixed solution pH value be adjusted into 8～12; The mixed solution of above-mentioned hydrazine hydrate and NaOH is heated to 80～100 ℃, then salting liquid is added in the mixed solution of hydrazine hydrate and NaOH, be incubated 0.5～2 hour, there is gas to emit in the course of reaction, after the complete blackening of the color of solution, react completely, will use distilled water and absolute ethanol washing extremely neutral behind the sedimentation and filtration respectively to wash liquid, with the black powder drying that obtains, the powder that obtains after the drying is that particle mean size is the FeCo alloyed powder of 0.25 μ m～0.35 μ m.
4. the method for preparing the low frequency absorbing material according to claim 2 is characterized in that, in described step (2), described method with chemical method coated aluminum oxide powder on the FeCo alloyed powder is to take following process:
The FeCo alloy powder that obtains in the step (1) is immersed AlNO
3In the solution, AlNO
3The concentration of solution is 1-3mol/L, stir leave standstill more than 10 minutes after, will dry behind the powder filter, under dynamic condition He in the argon gas atmosphere, heat-treat again.Above step is repeated 1～5 time, obtain coating the FeCo alloyed powder of the aluminium oxide bed thickness of 25nm～35nm.
5. the method for preparing the low frequency absorbing material according to claim 4 is characterized in that, in described step (2), described heat treated temperature is 750 ℃～900 ℃, and the time of insulation is 1～5 hour.
6. the method for preparing the low frequency absorbing material according to claim 4 is characterized in that, in described step (2), described dynamic condition, be that the powder after the oven dry is put into quartz ampoule, in heat treatment process, quartz ampoule keeps rotating with 1～5 rev/min rotating speed.
7. the method for preparing the low frequency absorbing material according to claim 2 is characterized in that, in described step (3), the particle mean size of described phenolic resins powder is 1 micron.
8. the method for preparing the low frequency absorbing material according to claim 2, it is characterized in that, in described step (3), the FeCo alloyed powder of described coated aluminum oxide layer and phenolic resins powder are to carry out wet mixing on three roller ball mills, with the deionized water is medium, and the wet mixing time is 5～24 hours.
9. the method for preparing the low frequency absorbing material according to claim 2 is characterized in that, in described step (3), hot-forming temperature is 180～250 ℃, and hot-forming pressure is 50～300MPa, is 15min～45min when hot-forming.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103406545A (en) * | 2013-07-15 | 2013-11-27 | 北京航空航天大学 | Preparation method of micron-particle-size FeCo particles |
| CN107325476A (en) * | 2016-04-29 | 2017-11-07 | 洛阳尖端技术研究院 | A kind of absorbing meta-material base material and preparation method thereof |
| CN110722153A (en) * | 2019-11-25 | 2020-01-24 | 西安航空学院 | Antioxidant absorbent and preparation method thereof |
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| CN1417264A (en) * | 2001-11-07 | 2003-05-14 | 株式会社盟德 | Soft magnetic resin composition and its producfion process and formed product |
| JP2003147404A (en) * | 2001-11-09 | 2003-05-21 | Kawasaki Steel Corp | Iron-cobalt alloy powder |
| JP2003332784A (en) * | 2002-05-10 | 2003-11-21 | Kitagawa Ind Co Ltd | Soft magnetic material composition and electromagnetic wave absorber |
| JP5133338B2 (en) * | 2007-04-17 | 2013-01-30 | 株式会社日立ハイテクノロジーズ | Composite filler for resin mixing |
| JP2009164317A (en) * | 2008-01-04 | 2009-07-23 | Mitsubishi Materials Pmg Corp | Method for manufacturing soft magnetism composite consolidated core |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103406545A (en) * | 2013-07-15 | 2013-11-27 | 北京航空航天大学 | Preparation method of micron-particle-size FeCo particles |
| CN103406545B (en) * | 2013-07-15 | 2015-05-27 | 北京航空航天大学 | Micron-particle-size FeCo particles and preparation method thereof |
| CN107325476A (en) * | 2016-04-29 | 2017-11-07 | 洛阳尖端技术研究院 | A kind of absorbing meta-material base material and preparation method thereof |
| CN110722153A (en) * | 2019-11-25 | 2020-01-24 | 西安航空学院 | Antioxidant absorbent and preparation method thereof |
| CN110722153B (en) * | 2019-11-25 | 2021-07-27 | 西安航空学院 | Antioxidant absorbent and preparation method thereof |
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Effective date of registration: 20190625 Address after: 101407 No. 11 Xingke East Street, Yanqi Economic Development Zone, Huairou District, Beijing Patentee after: Research Institute of engineering and Technology Co., Ltd. Address before: 100088, 2, Xinjie street, Beijing Patentee before: General Research Institute for Nonferrous Metals |