CN115445888A - Magnesium alloy based layered composite material and preparation method thereof - Google Patents
Magnesium alloy based layered composite material and preparation method thereof Download PDFInfo
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- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
- B05D5/12—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain a coating with specific electrical properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
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- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
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- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/194—After-treatment
Abstract
The invention provides a magnesium alloy based layered composite material and a preparation method thereof, wherein the preparation method comprises the following steps: dispersing carboxylated graphene in a solvent to obtain a graphene dispersion liquid; dispersing carbon nanotubes in a solvent to obtain a carbon nanotube dispersion liquid; sequentially spraying and depositing the carbon nanotube dispersion liquid, the graphene dispersion liquid and the carbon nanotube dispersion liquid on the surface of the magnesium foil to obtain a magnesium-based composite sheet layer containing a spraying layer; and crushing the magnesium-based composite sheet layer into a layered element, and putting the layered element into a die to sequentially perform vacuum hot-pressing sintering and hot extrusion to obtain the magnesium alloy-based layered composite material. The magnesium alloy-based layered composite material provided by the invention realizes the synergistic enhancement of mechanical property and electromagnetic shielding effectiveness, and widens the application of magnesium alloy in the field of electromagnetic shielding.
Description
Technical Field
The invention relates to the technical field of metal composite materials, in particular to a magnesium alloy based layered composite material and a preparation method thereof.
Background
The magnesium-based composite material not only has the advantages of high specific strength, high specific rigidity, good wear resistance and the like, but also has good electromagnetic shielding performance, so that the magnesium-based composite material is widely applied to the fields of riding, aerospace, electronic products and the like. However, the magnesium alloy has good shielding effect only on low-frequency electromagnetic waves (less than or equal to 300MHz, namely the range of radio waves), and has not ideal shielding effect on high-frequency and ultrahigh-frequency electromagnetic waves, so that the magnesium alloy is difficult to resist the attack of high-frequency and ultrahigh-frequency electronic station weapons, and the electromagnetic shielding capability of electronic warfare weaponry determines the battlefield viability, even influences the success or failure of warfare. Therefore, the application of the magnesium alloy in the field of national defense electromagnetic shielding is seriously hindered by the defect of narrow shielding frequency band of the existing magnesium alloy.
Disclosure of Invention
The embodiment of the invention provides a magnesium alloy-based layered composite material and a preparation method thereof.
In a first aspect, the present invention provides a method for preparing a magnesium alloy-based layered composite material, the method comprising:
dispersing carboxylated graphene in a solvent to obtain a graphene dispersion liquid; dispersing carbon nanotubes in the solvent to obtain a carbon nanotube dispersion liquid;
sequentially spraying and depositing the carbon nano tube dispersion liquid, the graphene dispersion liquid and the carbon nano tube dispersion liquid on the surface of a magnesium foil to obtain a magnesium-based composite sheet layer containing a spraying layer;
and crushing the magnesium-based composite sheet layer into a layered element, and placing the layered element in a mold to sequentially perform vacuum hot-pressing sintering and hot extrusion to obtain the magnesium alloy-based layered composite material.
Preferably, the carboxylated graphene is obtained by acid-washing graphene nanosheets.
Preferably, the size of the graphene nano-sheet is 0.5-5 μm.
More preferably, the graphene nanoplatelets have a thickness of 0.8 to 1.2nm.
Preferably, the diameter of the carbon nanotube is 30 to 80nm.
Preferably, the length of the carbon nanotubes is less than 10 μm.
Preferably, the preparation method of the carboxylated graphene comprises the following steps: and (3) placing the graphene nanosheet in an acid solution, and stirring for 4-6 h at the temperature of 60-80 ℃.
More preferably, the preparation method of the carboxylated graphene comprises the following steps: and (3) placing the graphene nanosheet in an acid solution, performing ultrasonic treatment for 20-40 min, and stirring for 4-6 h at the temperature of 60-80 ℃.
Preferably, the carbon nanotubes are obtained by the acid washing; the acid washing comprises the steps of placing the carbon nano tube in the acid solution and stirring for 4-6 h at the temperature of 60-80 ℃.
More preferably, the carbon nanotubes are acid-washed; the acid washing comprises the steps of placing the carbon nano tube in the acid solution, carrying out ultrasonic treatment for 20-40 min, and stirring for 4-6 h at the temperature of 60-80 ℃.
Preferably, the acid solution is a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1.
Preferably, the mass concentration of the carboxylated graphene in the graphene dispersion liquid is 0.5 to 0.7g/L.
More preferably, the mass concentration of the carboxylated graphene in the graphene dispersion liquid is 0.6g/L.
Preferably, the mass concentration of the carbon nanotubes in the carbon nanotube dispersion liquid is 0.2 to 0.4g/L.
More preferably, the mass concentration of the carbon nanotubes in the carbon nanotube dispersion liquid is 0.3g/L.
Preferably, the solvent is absolute ethanol.
Preferably, before the performing the spray deposition, the method further comprises:
polishing the magnesium foil, and heating the magnesium foil to 80-100 ℃.
Preferably, the spraying pressure of the spraying deposition is 0.2-0.4 MPa.
More preferably, the spray pressure of the spray deposition is 0.3MPa.
Preferably, the spray layer comprises a carbon nanotube layer, a carboxylated graphene layer and a carbon nanotube layer which are connected in sequence.
Preferably, the mass of the sprayed layer is 0.45 to 0.55wt% of the mass of the magnesium foil.
More preferably, the mass ratio of the carbon nanotube layer, the carboxylated graphene layer and the carbon nanotube layer in the spray layer is 1.
Preferably, the size of the layered element is 1.5 to 2.5mm, and the thickness is 45 to 55 μm.
Preferably, the temperature of the vacuum hot-pressing sintering is 625-635 ℃, the pressure is 45-55 MPa, the time is 5.5-6.5 h, and the vacuum degree is 4 multiplied by 10 -3 ～6×10 -3 Pa。
More preferably, the temperature of the vacuum hot-pressing sintering is 630 ℃, the pressure is 50MPa, and the time is 6h.
Preferably, the hot extrusion temperature is 380-420 ℃, the volume-pressure ratio is (25-30): 1, and the extrusion speed is 0.1-0.3 mm/s.
More preferably, the hot extrusion temperature is 400 ℃, the pressure ratio is 29.
In a second aspect, the present invention provides a magnesium alloy-based layered composite material prepared by the preparation method of the first aspect.
Preferably, the magnesium alloy-based layered composite material is obtained by performing vacuum hot-pressing sintering and hot extrusion on layered elements; the layered element is a magnesium-based composite sheet layer with a spraying layer on the surface, and the spraying layer comprises a carbon nano tube layer, a carboxylated graphene layer and carbon nano tubes which are sequentially connected.
Compared with the prior art, the invention at least has the following beneficial effects:
firstly, preparing a magnesium-based composite sheet layer containing a nano carbon layer, enhancing the mechanical property of a magnesium foil through carboxylated graphene and carbon nano tubes, and forming the nano carbon layer with the bottom and the top being the carbon nano tubes and the middle being the carboxylated graphene on the surface of the magnesium-based composite sheet layer; then, the magnesium-based composite sheet layer is crushed to obtain a layered element, the layered element is subjected to vacuum hot-pressing sintering and hot extrusion to obtain the magnesium alloy-based layered composite material, and the existence of the nano carbon layer enables the mechanical property and the electromagnetic wave shielding property of the composite material to be remarkably improved, so that the integration of the light weight, the mechanics and the shielding function is realized.
In the invention, the carboxylated graphene and the carbon nano tubes in the nano carbon layer form a three-dimensional net-shaped communicating structure, so that the transmission path of electromagnetic waves in the nano carbon layer is more complicated and roundabout, and the loss of the electromagnetic waves in the transmission process is enhanced. The magnesium alloy-based layered composite material prepared by the invention is prepared from layered elements, electromagnetic waves are reflected among the layered composite material for multiple times, and the absorption loss of the electromagnetic waves is further enhanced, so that the electromagnetic shielding efficiency is obviously improved, and the application of the magnesium alloy in the electromagnetic shielding field is widened.
Drawings
FIG. 1 is a flow chart of a method for preparing a magnesium alloy-based layered composite material according to an embodiment of the present invention;
FIG. 2 is an SEM electron micrograph of a sprayed layer distributed on the surface of a magnesium foil according to example 1 of the present invention;
FIG. 3 is an SEM (scanning Electron microscope) image of a spray layer provided by comparative example 2 of the invention distributed on the surface of a magnesium foil;
FIG. 4 is an SEM electron micrograph of a sprayed layer provided by comparative example 3 of the present invention distributed on the surface of a magnesium foil;
FIG. 5 is an optical microscope photograph of an extruded pure magnesium substrate according to comparative example 1 of the present invention;
FIG. 6 is an optical microscope photograph of a magnesium alloy-based layered composite material provided in example 1 of the present invention;
FIG. 7 is an SEM electron micrograph of a magnesium alloy-based layered composite material provided in example 1 of the present invention;
FIG. 8 is a TEM electron micrograph of a magnesium alloy-based layered composite material provided in example 1 of the present invention;
FIG. 9 is a stress-strain plot of materials provided in inventive example 1 and comparative examples 1 to 3;
FIG. 10 is a graph of the total shielding effectiveness in the X-band for the materials provided in example 1 of the present invention and comparative examples 1 to 3;
FIG. 11 is a wave absorption loss curve diagram of the materials provided in example 1 and comparative examples 1 to 3 of the present invention in the X band;
FIG. 12 is a graph showing reflection loss in the X-band of the materials provided in example 1 of the present invention and comparative examples 1 to 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.
The embodiment of the invention provides a preparation method of a magnesium alloy-based layered composite material, which comprises the following steps of:
step 1: dispersing carboxylated graphene in a solvent to obtain a graphene dispersion liquid; dispersing carbon nanotubes in a solvent to obtain a carbon nanotube dispersion liquid;
step 2: sequentially spraying and depositing the carbon nanotube dispersion liquid, the graphene dispersion liquid and the carbon nanotube dispersion liquid on the surface of the magnesium foil to obtain a magnesium-based composite sheet layer containing a spraying layer;
and step 3: and crushing the magnesium-based composite sheet layer into layered elements, and sequentially performing vacuum hot-pressing sintering and hot extrusion on the layered elements in a mold to obtain the magnesium alloy-based layered composite material.
It should be noted that, in step 1, the solvent is a volatile solvent, which is convenient for dispersing the carboxylated graphene and the carbon nanotubes and is easy to remove during the jet deposition. In step 2, the same spray deposition operation needs to be performed on both surfaces of the magnesium foil.
Firstly, preparing a magnesium-based composite sheet layer containing a nano carbon layer, enhancing the mechanical property of a magnesium foil through carboxylated graphene and carbon nano tubes, and forming the nano carbon layer with the bottom and the top being the carbon nano tubes and the middle being the carboxylated graphene on the surface of the magnesium-based composite sheet layer; then, the magnesium-based composite sheet layer is crushed to obtain a layered element, the layered element is subjected to vacuum hot-pressing sintering and hot extrusion to obtain the magnesium alloy-based layered composite material, and the existence of the nano carbon layer enables the mechanical property and the electromagnetic wave shielding property of the composite material to be remarkably improved, so that the integration of the light weight, the mechanics and the shielding function is realized.
According to some preferred embodiments, the carboxylated graphene is acid-washed from graphene nanoplatelets.
According to some preferred embodiments, the preparation method of the carboxylated graphene comprises: placing the graphene nanosheets in an acid solution, and stirring for 4-6 h at 60-80 ℃; the acid solution is a mixed solution of concentrated sulfuric acid and concentrated nitric acid with the volume ratio of 3:1.
Specifically, the graphene nanoplatelets are subjected to acid washing and ultrasonic treatment in an acid solution for 20-40 min (for example, 20min, 25min, 30min, 35min or 40 min), then heated in a water bath to 60-80 ℃ (for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃) and stirred for 4-6 h (for example, 4h, 4.5h, 5h, 5.5h or 6 h), and then washed with distilled water until the pH of the washed graphene nanoplatelets is 7, so as to obtain the carboxylated graphene.
In the invention, the oxygen-containing functional groups are added on the surfaces of the graphene nano sheets, so that the van der Waals force among the graphene nano sheets is reduced, and the agglomeration among the graphene nano sheets is reduced, so that the graphene nano sheets can be uniformly dispersed on the magnesium foil during the subsequent spray deposition, and the agglomeration is reduced.
According to some preferred embodiments, the graphene nanoplatelets have a size of 0.5 to 5 μm (e.g., can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm).
According to some preferred embodiments, the graphene nanoplatelets have a thickness of 0.8 to 1.2nm (e.g. may be 0.8nm, 0.85nm, 0.9nm, 0.95nm, 1nm, 1.05nm, 1.1nm, 1.15nm or 1.2 nm).
The size of the carboxylated graphene is the same as that of the graphene nanoplatelets. The size of the graphene nanoplatelets is specifically referred to as the diameter of the graphene nanoplatelets.
According to some preferred embodiments, the carbon nanotubes have a diameter of 30 to 80nm (e.g., may be 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, or 80 nm).
According to some preferred embodiments, the carbon nanotubes have a length of less than 10 μm (e.g., may be 9.9 μm, 9.5 μm, 9 μm, 8.5 μm, 8 μm, 7.5 μm, 7 μm, 6.5 μm, 6 μm, 5.5 μm, 5 μm, etc.).
According to some preferred embodiments, the carbon nanotubes are acid-washed; the acid washing comprises placing the carbon nano tube in acid solution and stirring for 4-6 h at 60-80 ℃.
Specifically, the carbon nanotubes are subjected to acid washing and ultrasonic treatment in an acid solution for 20 to 40min (for example, 20min, 25min, 30min, 35min or 40 min), then heated in a water bath to 60 to 80 ℃ (for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃) and stirred for 4 to 6h (for example, 4h, 4.5h, 5h, 5.5h or 6 h), and then washed with distilled water until the pH of the carbon nanotubes is 7, so as to obtain the carbon nanotubes.
In the invention, impurities and amorphous carbon in the carbon nanotubes are removed by acid washing, and oxygen-containing functional groups are introduced to the surfaces of the carbon nanotubes, so that Van der Waals force among the carbon nanotubes is reduced, and agglomeration among the carbon nanotubes is reduced.
In the invention, the sizes of the graphene nanosheets and the carbon nanotubes are limited within the range, so that agglomeration and difficult dispersion can be avoided when the sizes are too small; meanwhile, the mechanical property and electromagnetic shielding performance of the finally prepared magnesium alloy-based layered composite material caused by the difficulty in hot-press bonding of subsequent adjacent layer-mounted elements due to accumulation when the dimension is too large can be avoided.
According to some preferred embodiments, the mass concentration of carboxylated graphene in the graphene dispersion is 0.5 to 0.7g/L (e.g., may be 0.5g/L, 0.52g/L, 0.55g/L, 0.58g/L, 0.6g/L, 0.62g/L, 0.65g/L, 0.68g/L, or 0.7 g/L).
According to some more preferred embodiments, the mass concentration of the carboxylated graphene in the graphene dispersion is 0.6g/L.
In the invention, as the graphene nanosheets are of a two-dimensional lamellar structure, when the concentration of the graphene dispersion liquid is too low, the carboxylated graphene deposited on the surface of the magnesium foil is dispersed too sparsely; when the concentration of the graphene dispersion liquid is too high, the nozzle of the spray gun is easily blocked, and the agglomeration of the carboxylated graphene is easily caused.
According to some preferred embodiments, the mass concentration of carbon nanotubes in the carbon nanotube dispersion is 0.2 to 0.4g/L (e.g., can be 0.2g/L, 0.22g/L, 0.25g/L, 0.28g/L, 0.3g/L, 0.32g/L, 0.35g/L, 0.38g/L, or 0.4 g/L).
According to some more preferred embodiments, the mass concentration of carbon nanotubes in the carbon nanotube dispersion is 0.3g/L.
In the invention, experiments prove that when the concentration of the carbon nanotube dispersion liquid is too low, the carbon nanotubes deposited on the surface of the magnesium foil are dispersed too sparsely; when the concentration of the carbon nanotube dispersion is too high, the nozzle of the spray gun is easily blocked, and the carbon nanotube is easily agglomerated.
In order to uniformly disperse the carboxylated graphene and the carbon nanotubes in the solvent, the method further comprises performing ultrasonic treatment on the graphene dispersion liquid and the carbon nanotube dispersion liquid for 10 to 13 hours (for example, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours or 13 hours), wherein the ultrasonic power is 200w, and the ultrasonic frequency is 40kHz.
According to some preferred embodiments, in step 1, the solvent is absolute ethanol.
According to some preferred embodiments, before performing the spray deposition, further comprising:
the magnesium foil is subjected to a grinding process and heated to 80 to 100 ℃ (for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃).
The magnesium foil is subjected to a polishing treatment to remove an oxide film on the surface thereof, for example, 350# sandpaper. The magnesium foil is heated to rapidly volatilize the solvent in the carbon nanotube dispersion liquid or the graphene dispersion liquid sprayed and deposited on the surface of the magnesium foil, so as to further prevent the carboxylated graphene or the carbon nanotubes from agglomerating.
According to some preferred embodiments, in step 2, the spray pressure of the spray deposition is 0.2 to 0.4MPa (e.g., may be 0.2MPa, 0.25MPa, 0.3MPa, 0.35MPa, or 0.4 MPa).
Specifically, the nozzle used in the spray deposition of the present invention is a slit-type linear nozzle, and the spray distance is 30 to 50cm (for example, 30cm, 35cm, 40cm, 45cm, or 50 cm).
According to some more preferred embodiments, in step 2, the spray pressure of the spray deposition is 0.3MPa.
Experiments prove that if the spray pressure is low during spray deposition, the atomization of the graphene dispersion liquid or the carbon nanotube dispersion liquid is not facilitated, and the initial liquid drops deposited on the surface of the magnesium foil are large, so that the rapid volatilization of a solvent is not facilitated, and the agglomeration of graphene or carbon nanotubes is caused; if the spray pressure is high during spray deposition, the graphene dispersion liquid or the carbon nanotube dispersion liquid is excessively atomized, so that the solvent is volatilized in the air before the graphene dispersion liquid or the carbon nanotube dispersion liquid is deposited on the surface of the magnesium foil, and thus the graphene or the carbon nanotube cannot be effectively deposited on the surface of the magnesium foil.
According to some preferred embodiments, the spray layer comprises a carbon nanotube layer, a carboxylated graphene layer, and a carbon nanotube layer connected in sequence.
According to some preferred embodiments, the mass of the sprayed layer is 0.45 to 0.55wt% (e.g., may be 0.45wt%, 0.46wt%, 0.48wt%, 0.5wt%, 0.52wt%, 0.54wt%, or 0.55 wt%) of the mass of the magnesium foil.
According to some more preferred embodiments, the mass of the sprayed layer is 0.5wt% of the mass of the magnesium foil.
According to some more preferred embodiments, the mass ratio of the carbon nanotube layer, the carboxylated graphene layer and the carbon nanotube layer in the jetted layer is 1.
Specifically, in the invention, during the first spray deposition, only the carbon nanotube dispersion liquid is sprayed and deposited on the surface of the magnesium foil to obtain the carbon nanotube layer, and the mass of the carbon nanotube deposited on the layer is recorded as m 1 (ii) a During the second spraying deposition, spraying and depositing graphene dispersion liquid on the deposited carbon nanotube layer to obtain a carboxylated graphene layer, wherein the mass of the carboxylated graphene deposited on the layer is recorded as m 2 (ii) a And during the third time of spray deposition, spraying and depositing carbon nanotube dispersion liquid on the deposited carboxylated graphene layer to obtain a carbon nanotube layer, wherein the mass of the carbon nanotubes deposited on the layer is recorded as m 3 . And finally, forming a spraying layer on the surface of the magnesium foil, namely forming a nano carbon film with a sandwich hybrid structure, wherein the middle layer of the nano carbon film is carboxylated graphene, and the bottom and the top of the nano carbon film are carbon nano tubes. Preferably, the ratio of the masses deposited each time is m 1 :m 2 :m 3 1 (i.e., the mass ratio of the carbon nanotube layer, the carboxylated graphene layer, and the carbon nanotube layer in the jetted layer is 1.
In the invention, the total mass of the carboxylated graphene and the carbon nano tubes increased after the three times of deposition is 0.45-0.55 wt% of the mass of the magnesium foil. Experiments prove that if the mass fraction is low, the introduced interlayer nano carbon material is less, and the reinforcing effect of the carboxylated graphene or the carbon nano tube cannot be effectively exerted; on the contrary, if the mass fraction is higher, the interlayer nano carbon material is easy to agglomerate, the interface combination between adjacent layered elements is not facilitated, and the mechanical property of the prepared magnesium alloy-based layered composite material is seriously influenced.
According to some preferred embodiments, the lamellar elements have a size of 1.5 to 2.5mm (e.g., may be 1.5mm, 1.6mm, 1.8mm, 2mm, 2.1mm, 2.2mm, 2.4mm, or 2.5 mm) and a thickness of 45 to 55 μm (e.g., may be 45 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, or 55 μm).
According to some preferred embodiments, in step 3, the temperature of vacuum hot-pressing sintering is 625-635 ℃ (for example, 625 ℃, 626 ℃, 62 ℃ may be adoptedAt 8 ℃, 630 ℃, 632 ℃ or 635 ℃), at a pressure of 45 to 55MPa (for example, 45MPa, 46MPa, 48MPa, 50MPa, 51MPa, 52MPa, 54MPa or 55 MPa), for a time of 5.5 to 6.5h (for example, 5h, 5.2h, 5.5h, 5.8h, 6h, 6.2h or 6.5 h), and at a vacuum of 4X 10 -3 ～6×10 -3 Pa(4×10 -3 Pa、4.5×10 -3 Pa、5×10 -3 Pa、5.5×10 -3 Pa or 6X 10 -3 Pa)。
According to some more preferred embodiments, in step 3, the temperature of the vacuum hot-pressing sintering is 630 ℃, the pressure is 50MPa, and the time is 6h.
According to some preferred embodiments, in step 3, the temperature of the hot extrusion is 380 to 420 ℃ (for example, may be 380 ℃, 385 ℃, 390 ℃, 395 ℃, 400 ℃, 405 ℃, 410 ℃, 415 ℃ or 420 ℃), the backlog ratio is (25 to 30): 1 (for example, 1.
According to some more preferred embodiments, in step 3, the temperature of hot extrusion is 400 ℃, the pressure ratio is 29.
In the invention, the layered element with the carbon nanotube layer-carboxylated graphene layer-carbon nanotube layer is placed in a mould, and the magnesium alloy-based layered composite material is obtained through vacuum hot-pressing sintering and hot extrusion in sequence, so that the prepared composite material has a layered structure of the layered element, and the mechanical property and the electromagnetic wave shielding property of the composite material are obviously improved due to the existence of the nano carbon layer, thereby realizing the integration of light weight, mechanics and shielding functions.
In the invention, the carboxylated graphene and the carbon nano tubes in the nano carbon layer form a three-dimensional net-shaped communicating structure, so that the transmission path of electromagnetic waves in the nano carbon layer is more complicated and roundabout, and the loss of the electromagnetic waves in the transmission process is enhanced. The magnesium alloy-based layered composite material prepared by the invention is prepared from layered elements, and electromagnetic waves are reflected among the layered composite material for multiple times, so that the absorption loss of the electromagnetic waves is further enhanced, the electromagnetic shielding efficiency is obviously improved, and the application of the magnesium alloy in the electromagnetic shielding field is widened.
The invention also provides the magnesium alloy-based layered composite material prepared by the preparation method.
In order to more clearly illustrate the technical scheme and advantages of the present invention, a magnesium alloy-based layered composite material and a preparation method thereof are described in detail by several examples.
In the following examples and comparative examples, a magnesium foil having a thickness of 50 μm was used.
Example 1
(1) Putting a graphene nanosheet with the diameter of 0.5-5 mu m and the thickness of 0.8-1.2 nm into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with the volume fraction ratio of 3:1 for ultrasonic treatment for 30min, then heating in a water bath to 70 ℃, stirring for 5h, finally washing and filtering the pickled graphene nanosheet with distilled water until the pH value is 7, and obtaining carboxylated graphene; dispersing the carboxylated graphene in absolute ethyl alcohol, and performing ultrasonic treatment for 12 hours to obtain a graphene dispersion liquid with the mass concentration of the carboxylated graphene being 0.6g/L;
putting a carbon nano tube with the diameter of 30-80 nm and the length of less than 10 mu m into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with the volume fraction ratio of 3:1 for ultrasonic treatment for 30min, then heating the mixture to 70 ℃ in a water bath, stirring the mixture for 5h, and finally washing and filtering the acid-washed graphene nano sheet by using distilled water until the pH value of the acid-washed graphene nano sheet is 7 to obtain the acid-washed carbon nano tube; dispersing the carbon nano tube in absolute ethyl alcohol, and performing ultrasonic treatment for 12 hours to obtain carbon nano tube dispersion liquid with the mass concentration of the carbon nano tube of 0.3g/L;
wherein the ultrasonic power of the ultrasonic treatment is 200w, and the frequency is 40kHz;
(2) And grinding the magnesium foil by using No. 350 sand paper to remove the oxide film on the surface of the magnesium foil. Placing the magnesium foil subjected to grinding treatment on a heating table, heating to 90 ℃, and then sequentially spraying and depositing the carbon nanotube dispersion liquid, the graphene dispersion liquid and the carbon nanotube dispersion liquid prepared in the step (1) on the surface of the magnesium foil for three times to obtain a magnesium-based composite sheet layer containing a spraying layer; wherein the injection pressure is 0.3MPa;
first-time spray deposition: spraying and depositing the carbon nano tube dispersion liquid on the surface of the magnesium foil to obtain a first carbon nano tube layer, wherein the mass of the carbon nano tubes deposited on the layer is recorded as m 11 ；
And (3) second-time spray deposition: spraying and depositing graphene dispersion liquid on the deposited first carbon nanotube layer to obtain a carboxylated graphene layer, and recording the mass of the carboxylated graphene deposited on the layer as m 21 ；
Third time spray deposition: spraying and depositing carbon nanotube dispersion liquid on the deposited carboxylated graphene layer to obtain a second carbon nanotube layer, wherein the mass of the carbon nanotubes deposited on the layer is recorded as m 31 ；
The structure of the spraying layer is a first carbon nano tube layer, a carboxylated graphene layer and a second carbon nano tube layer; and m is 11 :m 21 :m 31 1, the mass of the sprayed layer is 0.5wt% of the mass of the magnesium foil;
(3) Crushing Mg-base composite sheet into laminated elements of 1.5-2.5 mm x 1.5-2.5 mm thickness and 45-55 micron thickness, and setting the laminated elements in isostatic graphite mold at 630 deg.c and 50MPa and 5 x 10 -3 Vacuum hot pressing and sintering for 6 hours under Pa to obtain
The cylindrical block body of (2); and carrying out hot extrusion deformation on the cylindrical block, wherein the hot extrusion temperature is 400 ℃, the extrusion ratio is 29.
Example 2
Example 2 is substantially the same as example 1 except that:
in the step (1), preparing a graphene dispersion liquid with the mass concentration of carboxylated graphene being 0.5 g/L; preparing carbon nano tube dispersion liquid with the mass concentration of the carbon nano tube of 0.4g/L.
Example 3
Example 3 is substantially the same as example 1, except that:
in the step (1), preparing a graphene dispersion liquid with the mass concentration of carboxylated graphene being 0.7 g/L; preparing carbon nano tube dispersion liquid with the mass concentration of the carbon nano tube of 0.2 g/L.
Example 4
Example 4 is essentially the same as example 1, except that:
in the step (2), the injection pressure is 0.2MPa.
Example 5
Example 5 is essentially the same as example 1, except that:
in the step (2), the injection pressure is 0.4MPa.
Example 6
Example 6 is essentially the same as example 1, except that:
in step (2), the mass of the sprayed layer was 0.45wt% of the mass of the magnesium foil.
Example 7
Example 7 is essentially the same as example 1, except that:
in step (2), the mass of the sprayed layer was 0.55wt% of the mass of the magnesium foil.
Comparative example 1
Is directly to
The cylindrical block pure magnesium is placed in an isostatic graphite mould at 630 ℃, 50MPa and 5 multiplied by 10 -3 Vacuum hot-pressing sintering is carried out for 6 hours under Pa; and (3) carrying out hot extrusion deformation on the cylindrical block, wherein the hot extrusion temperature is 400 ℃, the extrusion ratio is 29.
Comparative example 2
Comparative example 2 is substantially the same as example 1 except that: in the step (2), the graphene dispersion liquid prepared in the step (1) is sprayed and deposited on the surface of a magnesium foil by adopting the spraying pressure of 0.3MPa to obtain a magnesium-based composite sheet layer containing a spraying layer; wherein the structure of the spray layer is only a carboxylated graphene layer; and the mass of the sprayed layer was 0.5wt% of the mass of the magnesium foil.
Comparative example 3
Comparative example 3 is substantially the same as example 1 except that: in the step (2), the carbon nano tube dispersion liquid prepared in the step (1) is sprayed and deposited on the surface of the magnesium foil by adopting the spraying pressure of 0.3MPa to obtain a magnesium-based composite sheet layer containing a spraying layer; wherein, the structure of the spraying layer is only a carbon nano tube layer; and the mass of the sprayed layer was 0.5wt% of the mass of the magnesium foil.
The magnesium alloy-based layered composite material prepared in example 1, the extruded pure magnesium matrix prepared in comparative example 1, and the magnesium alloy-based layered composite materials prepared in comparative examples 2 and 3 were subjected to material characterization and performance tests, wherein the mechanical performance test results are shown in table 1.
Specifically, the distribution of the nanocarbon material in the sprayed layer on the surface of the magnesium foil and the layered structure of the magnesium alloy-based layered composite material were observed using a field emission Scanning Electron Microscope (SEM), as shown in fig. 2, 3, 4 and 7. The layered structure of the extruded pure magnesium matrix and magnesium alloy matrix layered composite was observed using an Optical Microscope (OM), as shown in fig. 5 and 6. The interface structure of the magnesium alloy-based layered composite material was observed with a transmission microscope (TEM), as shown in fig. 8. The tensile property of the material is tested by adopting an electronic universal drawing machine, the size of a gauge length section of a tensile sample is 15 multiplied by 6 multiplied by 2mm, and the tensile speed is 0.5mm/min. The electromagnetic shielding effectiveness of the material in an X wave band (8.2-12.4 GHz) is tested by a waveguide method by adopting a network vector analyzer, and the size of a sample is 22.86 multiplied by 10.16 multiplied by 5mm.
As can be seen from fig. 2 to 4, after the spray deposition, the nanocarbon material in the spray layer is uniformly dispersed on the surface of the magnesium foil, and no obvious stacking phenomenon occurs; furthermore, as shown in fig. 2, the surface of the layered unit prepared by the invention has a three-dimensional network communication structure composed of carboxylated graphene nanosheets and carbon nanotubes.
As can be seen from fig. 5 and 6, compared with fig. 5, the micro-nano layered structure formed by stacking the micro-magnesium layer and the nano-carbon material layer by layer is successfully constructed in fig. 6. After hot extrusion, the layered structure converts equiaxed grains of the pure magnesium matrix into brick-like rectangular grains. The direction of the magnesium layer was parallel to the Extrusion Direction (ED), and it was noted that the thickness of the initial magnesium foil was reduced from 50 μm to about 22 μm after hot extrusion deformation, as shown in FIG. 7. No obvious impurities and defects were observed between the adjacent magnesium layers, which indicates that the nanocarbon material/magnesium interface in the magnesium alloy-based layered composite material prepared by the present invention was well bonded, as shown in fig. 8.
TABLE 1
As can be seen from Table 1 and FIG. 9, the magnesium alloy-based layered composite material prepared in example 1 according to the present invention has an increased yield strength from 93MPa to 142MPa, an increased tensile strength from 154MPa to 237MPa, and an increased elongation from 6.5% to 10.1%, in which the yield strength is increased by as much as 53%, as compared to the extruded pure magnesium matrix prepared in comparative example 1. Moreover, the yield strength and the tensile strength of the composite material are obviously improved compared with those of the magnesium alloy-based layered composite materials of comparative example 2 and comparative example 3 with the same content of the nano-carbon material, and the elongation is still higher.
As can be seen from FIGS. 10 to 12, the magnesium alloy-based layered composite material prepared in example 1 of the present invention exhibited a higher SE than that of the extruded pure magnesium matrix prepared in comparative example 1 T And SE A Value, however, SE R The value is not obviously changed, so that the micro-nano layered structure designed by the invention is mainly used for increasing the electromagnetic shielding efficiency by increasing the absorption loss. SE of the magnesium alloy-based layered composite material prepared in example 1 of the present invention, compared with the extruded pure magnesium matrix prepared in comparative example 1 T The increase from 30dB to 70dB SE A From 20dB to 65dB. Wherein SE T For characterizing the total shielding effectiveness, SE A For characterizing absorption losses, SE R For characterizing the reflection loss. Obviously, this is very different from the traditional shielding metal material, which improves the electromagnetic shielding effectiveness mainly by reflecting the electromagnetic wave on the metal surface. In addition, the magnesium alloy-based layered composite material prepared by the invention has obviously higher absorption loss to electromagnetic waves than the magnesium alloy-based layered composite materials prepared by comparative examples 2 and 3, which shows that the spraying layer with the sandwich structure is not only favorable for improving the mechanical property of the composite material, but also favorable for improving the mechanical property of the composite materialThe absorption of electromagnetic waves is also facilitated. Therefore, the magnesium alloy-based layered composite material prepared by the invention realizes the integration of mechanics and shielding functions.
In summary, the electromagnetic shielding effectiveness of the magnesium alloy-based layered composite material prepared by the present invention is mainly attributed to the enhancement of the absorption loss of the electromagnetic wave, and the enhancement of the absorption loss of the electromagnetic wave is mainly attributed to the multiple reflection of the electromagnetic wave between the internal interlayer structures of the composite material. In the process of multiple reflections of the electromagnetic wave in the laminated structure, different transmission paths of the electromagnetic wave in the micro-nano layer provide different phase offsets for the propagation of the electromagnetic wave, so that the original electromagnetic plane wave loses phase coherence (phase mismatching), and a special electromagnetic wave absorption mechanism is formed. In addition, the carboxylated graphene nanosheets and the carbon nanotubes have ultrahigh dielectric constants, can effectively reflect and incident electromagnetic waves, and are recognized as a potential electromagnetic shielding material. Due to the existence of the graphene nano-sheets and the carbon nano-tubes in the composite material, the propagation path of incident electromagnetic waves is further increased. In addition, the interface between the two conductive materials with huge impedance difference, namely the nano carbon material and the magnesium matrix, can further enhance the back-and-forth reflection of the electromagnetic wave on the interface. All of these factors, as described above, enhance the dissipation of electromagnetic wave energy in the nanocarbon/magnesium layered composite. In addition, due to the spraying layer with the sandwich structure, the carboxylated graphene nanosheets and the carbon nanotubes form a communicated three-dimensional net structure, so that the transmission path of electromagnetic waves in the carbon nano-layer is more complicated and roundabout, and the loss of the electromagnetic waves in the transmission process is enhanced, so that the electromagnetic shielding effectiveness of the composite material is higher than that of the composite material only added with the carboxylated graphene nanosheets or only added with the carbon nanotubes.
In fig. 5 to 8, the directions of the magnesium layers in fig. 6 to 8 are parallel to the Extrusion Direction (ED), and are the same as those in fig. 5. In FIGS. 9 to 12, bulk Mg is used to characterize the extruded pure magnesium matrix prepared in comparative example 1, CNTs/Mg is used to characterize the magnesium alloy-based layered composite prepared in comparative example 3, GNs/Mg is used to characterize the magnesium alloy-based layered composite prepared in comparative example 2, and Hybrid/Mg is used to characterize the magnesium alloy-based layered composite prepared in example 1.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention. The invention has not been described in detail and is in part known to those of skill in the art.
Claims (10)
1. The preparation method of the magnesium alloy-based layered composite material is characterized by comprising the following steps of:
dispersing carboxylated graphene in a solvent to obtain a graphene dispersion liquid; dispersing the carbon nano tube in the solvent to obtain carbon nano tube dispersion liquid;
sequentially spraying and depositing the carbon nanotube dispersion liquid, the graphene dispersion liquid and the carbon nanotube dispersion liquid on the surface of a magnesium foil to obtain a magnesium-based composite sheet layer containing a spraying layer;
and crushing the magnesium-based composite sheet layer into a layered element, and placing the layered element in a mold to sequentially perform vacuum hot-pressing sintering and hot extrusion to obtain the magnesium alloy-based layered composite material.
2. The method of claim 1, wherein:
the carboxylated graphene is obtained by pickling graphene nanosheets; preferably, the size of the graphene nanosheet is 0.5 to 5 μm, and the thickness is preferably 0.8 to 1.2nm; and/or
The diameter of the carbon nano tube is 30-80 nm, and the length of the carbon nano tube is preferably less than 10 mu m.
3. The production method according to claim 2, characterized in that:
the preparation method of the carboxylated graphene comprises the following steps: placing the graphene nanosheets in an acid solution, and stirring for 4-6 h at the temperature of 60-80 ℃; and/or
The carbon nano tube is obtained by acid washing; the acid washing comprises the steps of placing the carbon nano tube in the acid solution, and stirring for 4-6 hours at the temperature of 60-80 ℃;
preferably, the acid solution is a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1.
4. The production method according to claim 1, characterized in that:
the mass concentration of the carboxylated graphene in the graphene dispersion liquid is 0.5-0.7 g/L, and preferably 0.6g/L; and/or
The mass concentration of the carbon nano tube in the carbon nano tube dispersion liquid is 0.2-0.4 g/L, and preferably 0.3g/L;
preferably, the solvent is absolute ethanol.
5. The production method according to claim 1, characterized in that:
before the spray deposition, the method further comprises the following steps:
polishing the magnesium foil, and heating the magnesium foil to 80-100 ℃;
and/or the presence of a gas in the atmosphere,
the spraying pressure of the spraying deposition is 0.2-0.4 MPa, and is preferably 0.3MPa.
6. The production method according to claim 1, characterized in that:
the spraying layer comprises a carbon nano tube layer, a carboxylated graphene layer and a carbon nano tube layer which are sequentially connected;
preferably, the mass of the sprayed layer is 0.45 to 0.55wt% of the mass of the magnesium foil;
more preferably, the mass ratio of the carbon nanotube layer, the carboxylated graphene layer and the carbon nanotube layer in the spray layer is 1.
7. The method of claim 1, wherein:
the size of the layered element is 1.5-2.5 mm, and the thickness is 45-55 μm.
8. The production method according to any one of claims 1 to 7, characterized in that:
the temperature of the vacuum hot-pressing sintering is 625-635 ℃, the pressure is 45-55 MPa, the time is 5.5-6.5 h, and the vacuum degree is 4 multiplied by 10 -3 ～6×10 -3 Pa。
9. The production method according to any one of claims 1 to 7, characterized in that:
the hot extrusion temperature is 380-420 ℃, the pressure ratio is (25-30): 1, and the extrusion speed is 0.1-0.3 mm/s.
10. A magnesium alloy-based layered composite material characterized by being produced by the production method according to any one of claims 1 to 9.
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