CN106800773B - PA11/SiC composite material and preparation method thereof - Google Patents

PA11/SiC composite material and preparation method thereof Download PDF

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CN106800773B
CN106800773B CN201710071684.8A CN201710071684A CN106800773B CN 106800773 B CN106800773 B CN 106800773B CN 201710071684 A CN201710071684 A CN 201710071684A CN 106800773 B CN106800773 B CN 106800773B
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composite material
silicon carbide
nylon
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CN106800773A (en
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王志强
石磊
雷青娟
胡国胜
李萍
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Shanxi zhongkong Automation Technology Co., Ltd
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North University of China
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/04—Ingredients treated with organic substances
    • C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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Abstract

The invention discloses a PA11/SiC composite material and a preparation method thereof, wherein the mass fraction of SiC in the composite material is respectively 5-15%, and the SiC is modified by an organic modification method. The composite material with 10% of filling mass has stronger absorption at the thickness of 2mm, which reaches-26 dB, and the frequency bandwidth with reflection attenuation lower than-10 dB (representing absorption of more than 90%) exceeds 4 GHz. Basically meets the requirements of 'wide, light, thin and strong' of the absorbing material, and can be used as an absorbing material with excellent microwave band. When the thickness t of the composite material with the filling mass proportion of 5 percent is 5mm, the best multiband absorption is realized, the reflection attenuation of 2 wave bands at 4.5 and 13GHz positions respectively reaches the strongest value of-21.5 and-8 dB, and the requirements of low-frequency and multiband absorption are met to a certain extent.

Description

PA11/SiC composite material and preparation method thereof
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a PA11/SiC composite material and a preparation method thereof.
Background
Nylon 11 has a chemical name of polyundecanolactam (polyundecanoamide), an English name of Poly (Undecanoylamide) (PA 11 for short), and a chemical formula of H [ NH (CH)2)10CO]nAnd (5) OH. The long carbon chain soft nylon synthesized by castor oil as raw material is a white semitransparent solid with relative density of 1.03, compared with other nylons, the odd carbon atoms of the long carbon chain soft nylon enable the phthalocyanine groups to be positioned on the same side to completely form intermolecular hydrogen bonds, and a longer methylene soft chain is arranged between the adjacent phthalocyanine groups, so that the long carbon chain soft nylon has lower water absorption, higher impact strength and good stress cracking resistance, when external force is removed, the nylon 11 can be restored to the original shape, is embedded into a metal part and is not easy to crack, and can meet the injection and extrusion processing of various melt viscosity ranges.
Nylon 11 was successfully developed by Socicte organic corporation, France, 1944, and was first industrially produced by Atochem, France, 1955. The initial use was to make synthetic fibers for use in engineering plastic products after the 70's of the 20 th century. Currently, the world production of nylon 11 is about 45000Kt/a, and the major production companies include Atochem in France, Atochem in the United states, Dr Plata in Germany, Erta in Belgium, and Dongli in Japan. All of these companies employ french technology.
Nylon 11 is a commercial polyamide plastic with excellent properties. Until now, there has been a history of about 70 years, and its application history is compared with other nylon materials, and further development and research are needed. The nylon 11 is developed in 70 years in the 20 th century, but the nylon 11 is expensive and inconsistent with the current national conditions, and the technology lags behind and is interrupted for years. The research work of nylon 11 is carried out at the beginning of the 90 s at the university of north and middle China (formerly North China's institute of technology), and through years of efforts, the polycondensation technology and the preparation research of nylon 11 resin are identified in 1996, and hundred-ton-class pilot-scale production experiments are completed, and at present, a thousand-ton-class nylon 11 production line is built and put into use.
At present, PA11/Au and PA11/Si nano composite materials are mainly researched abroad and a certain progress is achieved. For example, the average particle size of PA11/Au nano-material Au particles prepared by Kensuke et al is as small as 3.2-5.2 nm. Domestic research on this aspect is still blank.
Because the mechanical property of the pure nylon 11 is not high and the price is high, the research of alloying and blending of the nylon 11, which can improve the mechanical property of the material and reduce the production cost of the material, becomes a very valuable research direction in the future.
The main application field of nylon 11 in China is the automobile industry, particularly the nylon 11 hose production, and then electronic and electric appliances and engineering components. By 2000 years, the total demand of China for nylon 11 has reached 3000-. At present, the production technology is not mature, the cost is high, large-scale industrial production is not available so far, the yield of nylon 11 is low, the required products mainly depend on import, and the development and utilization prospect is wide.
Along with the development of the industries such as machinery, electronics, chemical engineering and the like in China, especially along with the rapid development of the automobile industry, the demand of the automobile industry is bound to be larger and larger. Moreover, the main raw material for producing nylon 11 is castor oil, while China is the second largest castor oil producing country in the world, and the raw material source is not a problem. Therefore, the nylon 11 has wide development and utilization prospects in China. The industrialization pace of nylon 11 resin synthesis should be accelerated, the situation that the nylon 11 resin relies on import for a long time is gradually changed, the application research of the nylon 11 resin is strengthened, and the application field of the nylon 11 resin is widened, so that the development of plastics and related industries in China is promoted, and the development of the planting and processing industry of castor oil can be promoted.
Silicon carbide, also known as carborundum or refractory sand, is an artificial material and only after the artificial synthesis of silicon carbide, the accidental presence of silicon carbide in meteorites and on the crust is confirmed. Because the basic structural unit of SiC is a regular tetrahedron formed by combining Si and C by covalent bonds, the SiC has the advantages of exceptional outstanding chemical stability and thermal stability, good mechanical and thermal conductivity, and wide application prospect in the fields of optoelectronics, high-temperature electronics, anti-radiation electronics and high-frequency high-power devices.
The resistivity of the silicon carbide is between that of metal and semiconductor, and belongs to a journal-type semiconductor α -SiC single crystal with the resistivity of 109～1010Resistivity of omega cm, β -SiC single crystal is more than 106The conductive type and the resistance value of the SiC can be adjusted by methods of B, P, Al, Si and O doping, annealing, neutron or electron radiation and the like, and the β -SiC wave-absorbing performance is superior to that of α -SiC, so β -SiC powder is selected as an absorbent, the conventional silicon carbide powder has low wave-absorbing performance and can be used only by further treatment when being used as the absorbent.
China is the first major country for SiC production, the annual output is more than 100 million tons, but most of produced silicon carbide is low in grade and is used for export in large quantity, and high-grade silicon carbide is imported in large quantity, so that China becomes a supplier of cheap raw materials for foreign manufacturers. The efficient utilization and digestion of domestic SiC are very critical works, and the SiC not only has the wave absorbing function and can weaken the infrared signal of an engine, but also has the characteristics of high temperature, small relative density, good toughness, high strength, high hardness, high resistivity, good oxidation resistance and the like. SiC has also been studied as a wave absorbing agent, is one of wave absorbing materials which are developed rapidly at home and abroad, and is a wave absorbing material with good development and application prospects.
Disclosure of Invention
In order to obtain the wave-absorbing material with excellent performance and simultaneously optimize the performance and the application of the nylon 11 and the SiC, the invention researches the wave-absorbing performance of the nano SiC composite material. Nylon 11 with excellent performance is used as a matrix material to design and prepare the nylon 11/SiC nano composite material, so that the composite material is expected to be widely applied to the military stealth technology and the civil field. Meanwhile, the performance of the nylon 11 is improved, the application range of the nylon is widened, the use of domestic silicon carbide is optimized, the production cost is reduced, and the development of social economy is promoted.
The technical scheme adopted by the invention is as follows:
the PA11/SiC composite material of the invention has SiC with the mass fraction of 5-15% respectively, and the SiC is modified by an organic modification method. Preferably: the mass fraction of SiC in the composite material is 10 percent respectively.
The preparation method of the PA11/SiC composite material comprises the following specific steps:
(1) silicon carbide surface treatment:
preparing silicon carbide powder and hydrochloric acid into a suspension, and stirring for 12-36 h; taking out, carrying out vacuum filtration and washing, and drying the solid substance in a vacuum oven at 100-150 ℃ for 12-36 h; after drying, calcining for 6-18 h in a muffle furnace at 300-500 ℃;
respectively adding toluene, KH550 and calcined SiC into a reaction vessel, stirring and mixing uniformly, then placing the mixture into an oil bath kettle, keeping the temperature at 80-100 ℃ for 3-7 h, continuously filling nitrogen, then taking out the mixture, and performing suction filtration while the mixture is hot by using a vacuum pump to obtain silicon carbide solid;
ultrasonically dispersing the silicon carbide solid in an aqueous medium, then centrifugally separating, washing with water, washing with an acetone aqueous solution, and then soaking the silicon carbide solid in the acetone aqueous solution; performing suction filtration, taking down the silicon carbide solid, drying in a vacuum oven at 100-120 ℃ for 10-15 h, taking out, bagging and sealing for later use;
(2) preparing a PA11/SiC nano composite material:
nylon 11 and the surface-treated nano SiC are respectively blended in an extruder and an injection molding machine by a melt blending method to obtain the nylon 11/SiC composite material.
Preferably: preparing silicon carbide powder and 5 wt% of hydrochloric acid into a suspension with the silicon carbide weight fraction of 15%, and stirring for 24 h.
Preferably: the solid material was dried in a vacuum oven at 120 ℃ for 24 h. After drying, the mixture was calcined in a muffle furnace at 400 ℃ for 12 hours.
Preferably: the volume mass ratio of the toluene to the KH550 to the calcined SiC is 80: 1: 50 ml/ml/g.
Preferably: the mixture was placed in an oil bath and kept at 90 ℃ for 5h and continuously charged with nitrogen.
Preferably: ultrasonically dispersing the silicon carbide solid in an aqueous medium for half an hour, then centrifugally separating, washing with water, washing with 30 wt% acetone aqueous solution, then soaking the silicon carbide solid in 30 wt% acetone aqueous solution for 4 hours, carrying out suction filtration, and taking down the silicon carbide solid.
Preferably: the silicon carbide solid is dried in a vacuum oven for 12h at 110 ℃.
The PA11/SiC composite material can be used as a microwave band absorption material.
The invention has the following positive effects:
the invention adopts an organic modification method to carry out surface treatment on the nano SiC, and then the nano SiC and the nylon 11 are melted and blended to prepare the nylon 11/SiC nano composite material. Under the influence of nano effect, the composite material has two loss mechanisms of electric loss and magnetic loss at the same time, and has good microwave absorption capacity. The composite material with 10% of filling mass has stronger absorption at the thickness of 2mm, which reaches-26 dB, and the frequency bandwidth with reflection attenuation lower than-10 dB (representing absorption of more than 90%) exceeds 4 GHz. Basically meets the requirements of 'wide, light, thin and strong' of the absorbing material, and can be used as an absorbing material with excellent microwave band. When the thickness t of the composite material with the filling mass proportion of 5 percent is 5mm, the best multiband absorption is realized, the reflection attenuation of 2 wave bands at 4.5 and 13GHz positions respectively reaches the strongest value of-21.5 and-8 dB, and the requirements of low-frequency and multiband absorption are met to a certain extent.
Drawings
FIG. 1 is a graph of complex permittivity, complex permeability and loss tangent for pure nylon 11;
a-the relative complex dielectric constant and dielectric loss tangent of nylon 11; b-complex permeability of nylon 11.
Figure 2 is a graph of reflection attenuation for different thicknesses of pure nylon 11.
FIG. 3 is a graph of the complex dielectric constant, complex permeability and loss tangent of a nylon 11/SiC nanocomposite with a 10% filler mass fraction and reflection attenuation for different thicknesses;
a-dielectric constant as a function of frequency; b-the functional relationship of magnetic permeability to frequency; c-the dielectric and magnetic loss tangent values vary with frequency; d-reflection loss at different thicknesses.
FIG. 4 is a graph of the reflection absorption of a composite material having a packing mass fraction of 5,10, 15%, respectively;
a-reflection loss of 5% filling mass of the composite material at different thicknesses; b-reflection loss of composite material with 10% of filling mass ratio under different thicknesses; c-reflection losses at different thicknesses of the composite material at a filling mass fraction of 15%.
Detailed Description
The following examples are further detailed descriptions of the present invention.
Example 1
The mass fraction of SiC in the PA11/SiC composite material is 15 percent respectively, and the SiC is modified by an organic modification method.
The preparation method of the PA11/SiC composite material comprises the following specific steps:
(1) silicon carbide surface treatment:
preparing silicon carbide powder and hydrochloric acid into a suspension, and stirring for 36 hours; taking out, carrying out vacuum filtration and washing, and drying the solid substance in a vacuum oven at 100 ℃ for 36 h; after drying, calcining for 18h in a muffle furnace at 300 ℃;
respectively adding toluene, KH550 and calcined SiC into a reaction vessel, stirring and mixing uniformly, then placing the mixture into an oil bath kettle, keeping the temperature at 80 ℃ for 7h, continuously filling nitrogen, taking out the mixture, and carrying out suction filtration while the mixture is hot by using a vacuum pump to obtain silicon carbide solid;
ultrasonically dispersing the silicon carbide solid in an aqueous medium, then centrifugally separating, washing with water, washing with an acetone aqueous solution, and then soaking the silicon carbide solid in the acetone aqueous solution; performing suction filtration, taking down the silicon carbide solid, drying in a vacuum oven at 100 ℃ for 15h, taking out, bagging and sealing for later use;
(2) preparing a PA11/SiC nano composite material:
nylon 11 and the surface-treated nano SiC are respectively blended in an extruder and an injection molding machine by a melt blending method to obtain the nylon 11/SiC composite material.
Preparing silicon carbide powder and 5 wt% of hydrochloric acid into a suspension with the silicon carbide weight fraction of 15%, and stirring for 24 h.
The volume mass ratio of the toluene to the KH550 to the calcined SiC is 80: 1: 50 ml/ml/g.
Ultrasonically dispersing the silicon carbide solid in an aqueous medium for half an hour, then centrifugally separating, washing with water, washing with 30 wt% acetone aqueous solution, then soaking the silicon carbide solid in 30% acetone aqueous solution for 4 hours, carrying out suction filtration, and taking down the silicon carbide solid.
Example 2
The PA11/SiC composite material of the invention has SiC with the mass fraction of 5 percent respectively, and the SiC is modified by an organic modification method.
The preparation method of the PA11/SiC composite material comprises the following specific steps:
(1) silicon carbide surface treatment:
preparing silicon carbide powder and hydrochloric acid into a suspension, and stirring for 12 hours; taking out, carrying out vacuum filtration and washing, and drying the solid substance in a vacuum oven at 150 ℃ for 12 h; after drying, calcining for 6 hours in a muffle furnace at 500 ℃;
respectively adding toluene, KH550 and calcined SiC into a reaction vessel, stirring and mixing uniformly, then placing the mixture into an oil bath kettle, keeping the temperature at 100 ℃ for 3 hours, continuously filling nitrogen, taking out the mixture, and carrying out suction filtration while the mixture is hot by using a vacuum pump to obtain silicon carbide solid;
ultrasonically dispersing the silicon carbide solid in an aqueous medium, then centrifugally separating, washing with water, washing with an acetone aqueous solution, and then soaking the silicon carbide solid in the acetone aqueous solution; performing suction filtration, taking down the silicon carbide solid, drying in a vacuum oven at 120 ℃ for 10h, taking out, bagging and sealing for later use;
(2) preparing a PA11/SiC nano composite material:
nylon 11 and the surface-treated nano SiC are respectively blended in an extruder and an injection molding machine by a melt blending method to obtain the nylon 11/SiC composite material.
Preparing silicon carbide powder and 5 wt% of hydrochloric acid into a suspension with the silicon carbide weight fraction of 15%, and stirring for 24 h.
The volume mass ratio of the toluene to the KH550 to the calcined SiC is 80: 1: 50 ml/ml/g.
Ultrasonically dispersing the silicon carbide solid in an aqueous medium for half an hour, then centrifugally separating, washing with water, washing with 30 wt% acetone aqueous solution, then soaking the silicon carbide solid in 30% acetone aqueous solution for 4 hours, carrying out suction filtration, and taking down the silicon carbide solid.
Example 3
The PA11/SiC composite material of the invention has SiC with the mass fraction of 10 percent respectively, and the SiC is modified by an organic modification method.
The preparation method of the PA11/SiC composite material comprises the following specific steps:
(1) silicon carbide surface treatment:
preparing silicon carbide powder and 5% hydrochloric acid into a suspension with the silicon carbide weight fraction of 15%, and stirring for 24 hours; taking out, carrying out vacuum filtration and washing, and drying the solid substance in a vacuum oven at 120 ℃ for 24 hours. After drying, calcining for 12 hours in a muffle furnace at 400 ℃; after drying, calcining for 6-18 h in a muffle furnace at 300-50 ℃;
respectively adding toluene, KH550 and calcined SiC into a reaction vessel, stirring and mixing uniformly, then placing the mixture into an oil bath kettle, keeping the temperature at 90 ℃ for 5 hours, continuously filling nitrogen, taking out the mixture, and carrying out suction filtration while the mixture is hot by using a vacuum pump to obtain silicon carbide solid;
ultrasonically dispersing the silicon carbide solid in an aqueous medium, then centrifugally separating, washing with water, washing with an acetone aqueous solution, and then soaking the silicon carbide solid in the acetone aqueous solution; performing suction filtration, taking down, placing the silicon carbide solid in a vacuum oven, drying for 12 hours at 110 ℃, taking out, bagging and sealing for later use;
(2) preparing a PA11/SiC nano composite material:
nylon 11 and the surface-treated nano SiC are respectively blended in an extruder and an injection molding machine by a melt blending method to obtain the nylon 11/SiC composite material.
The volume mass ratio of the toluene to the KH550 to the calcined SiC is 80: 1: 50 ml/ml/g.
Ultrasonically dispersing the silicon carbide solid in an aqueous medium for half an hour, then centrifugally separating, washing with water, washing with 30 wt% acetone aqueous solution, then soaking the silicon carbide solid in 30% acetone aqueous solution for 4 hours, carrying out suction filtration, and taking down the silicon carbide solid.
Test of wave-absorbing Property
The characterization method of the electromagnetic parameters mainly comprises a direct calculation method and an indirect calculation method. The direct calculation method is to calculate the electromagnetic parameters by using the magnetic polarization strength and the electric field strength of the wave-absorbing agent in the electromagnetic field. It has two main methods, one is that absorbent and adhesive are mixed to make coating or module sample form, its mu is measuredrAnd εr. The measured constant of the method is actually the constant of the composite medium, namely the relative complex dielectric constant and the relative complex permeability of the absorbent; the other is the relative complex electromagnetic parameter mu of the absorberrAnd εrMeasurement of (2) gives the μ thereof using the absorbent as a powder staterAnd εrThis is also the most intuitive way to characterize its electromagnetic properties.
The invention applies the second method, the relative complex electromagnetic constant of the PA11/SiC composite material under the frequency of 1-18GHz is measured by adopting a coaxial method, a testing instrument is an HP-8722ES network vector analyzer, the thickness of a sample is 2mm, and the reflection attenuation of the composite material to electromagnetic waves is calculated according to measured data.
Pure nylon 11 electromagnetic wave absorption analysis
Figure 1 shows the complex permittivity, complex permeability and loss tangent of pure nylon 11 as a function of frequency. It can be seen that the values of the 6 parameters in the figure vary very little over the entire frequency range of 1-18 GHz. In FIG. 1(a), the relative complex dielectric constant and the dielectric loss tangent tan. delta. of nylon 11ENo obvious change occurs in the whole frequency range, which shows that the dipole in the nylon 11 is stable at normal temperature. Dielectric constant
The imaginary part epsilon' and the dielectric loss tangent value are all maintained at values close to zero, and the dielectric loss of the nylon 11 is very weak and can be ignored. In FIG. 1(b), it can be seen that the complex permeability of nylon 11 is almost 1 and the magnetic loss tangent tan. delta. isMNear zero, nylon 11 can be considered to have negligible magnetic losses as well. From the above we believe that nylon 11 is a low loss type dielectric material.
Figure 2 shows the reflection attenuation of pure nylon 11 at different thicknesses. As can be seen from the figure, the reflection attenuation of nylon 11 is very weak, and is less than-1 dB, SiC can be considered as the attenuation in the composite material, and the nylon 11 plays a role in adjusting the impedance matching.
Experiments prove that many high molecular polymers (rubber, plastic and resin) have little microwave reflection, and most of the high molecular polymers are good wave-transmitting materials. As can be seen from FIGS. 1 and 2, the dielectric constant of the nylon 11 matrix is about 2.3, and the dielectric loss tangent tan. delta. isEOf the order of 10-2And the reflection attenuation is less than-1 dB, and the values can support that the nylon 11 also has good wave-transmitting performance. The wave-transparent essence is to provide a channel for the transmission of electromagnetic waves, and only the dielectric material with good wave-transparent property can be used as a wave absorber for broadbandThe band provides guarantee and creates conditions for all wave absorbing agents to fully exert wave absorbing function.
Electromagnetic wave absorption analysis of nylon 11/SiC nano composite material
FIG. 3(a) shows the dielectric constant as a function of frequency for a nylon 11/SiC nanocomposite having a 10% loading mass. Compared with pure nylon 11, the dielectric constant of the nylon 11/SiC nano composite material is increased by several times, and the electrical property of the nylon 11 is greatly influenced by the addition of the nano SiC. In fig. 3(b), we can observe that the real part of the permeability of the composite material is not changed greatly, but the imaginary part of the permeability is changed obviously, particularly in a low-frequency band, and the maximum value is close to 0.4. The increase of the imaginary part of the magnetic permeability can be explained as that SiC has a special nano effect after the size of the particle diameter is reduced to the nano magnitude, shows good microwave absorption performance and has stronger magnetic loss along with the reduction of the particle diameter. FIG. 3(c) depicts the dielectric loss tangent tan. deltaEAnd magnetic loss tangent tan deltaMCurve as a function of frequency. It can be known that the composite material still mainly has the electric loss, but the magnetic loss is not negligible any more, and the magnetic loss is dominant in a certain waveband, so that the composite material has two loss mechanisms of the electric loss and the magnetic loss. Nylon 11 and SiC both belong to electric loss type materials, and the composite materials thereof have certain strength of magnetic loss, so that the loss of electromagnetic waves is increased, and the reflection attenuation is improved. FIG. 3(d) shows the reflection loss of a nylon 11/SiC nanocomposite with a 10% packing mass ratio at different thicknesses. At matching thickness tmThe strongest microwave absorption occurs at 10.5GHz at 2mm, the strongest reflection loss is about-26 dB, and the bandwidth with reflection losses below-10 dB (representing more than 90% absorption) exceeds 4GHz at a thickness t 2 mm. At matching thickness tmAt 3mm, the strongest microwave absorption occurs at 6.5GHz, with the strongest reflection loss being about-33 dB. The bandwidth with reflection losses below-10 dB (representing more than 90% absorption) at a thickness t-3 mm is about 4 GHz.
As can be seen from FIG. 3, the nylon 11/SiC nano composite material with 10% filling ratio has more ideal absorption of microwave energy, and in order to find a more ideal filling ratio and study the essential reason of microwave absorption, we prepared composite materials of SiC nano particles with different filling ratios, tested their complex dielectric constants and complex magnetic permeabilities, and calculated reflection attenuation at different thicknesses.
Figure 4 shows the reflection loss for different filling mass ratios of the composite material at different thicknesses. The matching thicknesses of the composite materials with filling mass proportions of 5,10 and 15 percent are respectively tmAt 5, 3, 2mm and the strongest reflection losses of about-21, -33, -8dB Rmax, it can be seen that the best electromagnetic and impedance matching is achieved at a 10% filling mass ratio. In particular, a composite material with a mass fraction of 10% has a comparatively strong absorption at a thickness of 2mm, and a bandwidth with reflection losses below-10 dB (representing an absorption of more than 90%) at a thickness t of 2mm exceeds 4 GHz. When the thickness of the composite material with the filling ratio of 5 and 10 percent reaches 4mm, absorption peaks of 2 wave bands appear. The composite material with the filling proportion of 5% realizes the best multiband absorption when the thickness t is 5mm, and the strongest absorption of-21.5 and-8 dB can be achieved at 4.5GHz and 13GHz respectively in 2 wavebands.
In the experimental research, the best matching thickness is expected to be obtained for researching the electromagnetic property of the material, in the application process of the wave-absorbing material, the single-layer wave-absorbing material is required to be thinner and is generally not more than 2mm, and a test sample with the filling volume ratio of 10% obtains better property at a position of 2mm, so that the requirements of 'width, lightness, thinness and strength' of the wave-absorbing material are basically met, and the wave-absorbing material can be used as an excellent absorbing material for a microwave waveband.
The invention adopts an organic modification method to carry out surface treatment on the nano SiC, and then the nano SiC and the nylon 11 are melted and blended to prepare the nylon 11/SiC nano composite material with the filling mass ratio of 5,10 and 15 percent. And performing infrared characterization, analysis and comparison on the structures of the SiC before and after surface treatment. The electromagnetic property and the microwave absorption property of the pure nylon 11 and the nylon 11/SiC nano composite material are researched and discussed, and the following conclusion is obtained:
(1) after the surface treatment of SiC, one end of hydrolyzed silane coupling agent reacts with hydroxyl on the surface of SiC, thereby covering upThe original characteristics of SiC are realized, so that the surface of the silicon carbide shows the characteristics of a silane coupling agent, and-NH is connected to the other end of the hydrolyzed silane coupling agent2The modification was shown to be successful.
(2) The electromagnetic property of the pure nylon 11 is tested, and the real part mu 'of the magnetic permeability is approximately equal to 1, the imaginary part mu' is close to 0, the imaginary part of the dielectric constant is also close to 0, and the loss tangent value in the whole frequency range is close to 0, so that the pure nylon 11 is a low-loss dielectric material. However, this would also support nylon 11 possessing good wave permeability.
(3) The nylon 11/SiC nano composite material is prepared by a melt blending method, and the electromagnetic property of the nylon 11/SiC nano composite material is tested, so that the electrical property of the nylon 11 is changed by adding the nano SiC, and the real part and the imaginary part of the dielectric constant are increased by several times. Moreover, under the action of the special effect of the nano SiC, the change of the imaginary part of the magnetic permeability of the composite material is obvious, so that the magnetic loss of the composite material cannot be ignored. When the composite material with the filling mass proportion of 10% has stronger absorption at the thickness of 2mm, the absorption reaches-26 dB, and the frequency bandwidth with the reflection loss lower than-10 dB (representing the absorption of more than 90%) exceeds 4 GHz. Basically meets the requirements of 'wide, light, thin and strong' of the absorbing material, and can be used as an absorbing material with excellent microwave band.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (1)

  1. The application of the PA11/SiC composite material as a microwave band absorption material is characterized in that: SiC in the composite material is modified by an organic modification method;
    the preparation method of the PA11/SiC composite material comprises the following steps:
    (1) silicon carbide surface treatment:
    preparing silicon carbide powder and 5 wt% of hydrochloric acid into a suspension with the silicon carbide weight fraction of 15%, and stirring for 24 hours; taking out, carrying out vacuum filtration and washing, and drying the solid substance in a vacuum oven at 120 ℃ for 24 hours; after drying, calcining for 12 hours in a muffle furnace at 400 ℃;
    toluene, KH550 and calcined SiC are added into a reaction vessel respectively, and the volume mass ratio of the toluene to the KH550 to the calcined SiC is 80: 1: 50ml/ml/g, stirring and mixing uniformly, then placing the mixture in an oil bath pan, keeping the temperature at 90 ℃ for 5 hours, continuously filling nitrogen, taking out the mixture, and carrying out suction filtration while the mixture is hot by using a vacuum pump to obtain silicon carbide solid;
    ultrasonically dispersing the silicon carbide solid in an aqueous medium for half an hour, then carrying out centrifugal separation and water washing, then washing with 30 wt% of acetone aqueous solution, then soaking the silicon carbide solid in 30% of acetone aqueous solution for 4 hours, carrying out suction filtration, taking down the silicon carbide solid, drying in a vacuum oven at 110 ℃ for 12 hours, taking out, bagging and sealing for later use;
    (2) preparing a PA11/SiC nano composite material:
    nylon 11 and the surface-treated nano SiC are respectively blended in an extruder and an injection molding machine by a melt blending method to obtain the nylon 11/SiC composite material;
    the composite material comprises 10% of SiC by mass and 2mm of material thickness.
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