阅读说明：本技术 一种具有高电磁屏蔽性能镁锂基复合材料及其制备方法 (Magnesium-lithium-based composite material with high electromagnetic shielding performance and preparation method thereof ) 是由 巫瑞智 王佳豪 张朕 廖阳 庞建华 陈嘉庆 于 2019-10-15 设计创作，主要内容包括：本发明提供一种具有高电磁屏蔽性能镁锂基复合材料及其制备方法,成分及百分比含量如下：以双向镁锂合金为基体,Ni<Sub>0.4</Sub>Zn<Sub>0.4</Sub>Co<Sub>0.2</Sub>Fe<Sub>2</Sub>O<Sub>4</Sub>粉末作为层间添加物；其中镁锂合金中Li为5.7-10.3wt％,其余为Mg,其包括如下步骤：制备镁锂合金；制备吸波材料Ni<Sub>0.4</Sub>Zn<Sub>0.4</Sub>Co<Sub>0.2</Sub>Fe<Sub>2</Sub>O<Sub>4</Sub>粉末；累积叠轧制备镁锂基复合材料。本发明结合屏蔽体的电磁屏蔽机理,设计并制备一种镁锂基复合材料,通过累积叠轧加工工艺,在获得良好反射损耗R和多重反射损耗B的同时,在叠层间引入吸波材料Ni<Sub>0.4</Sub>Zn<Sub>0.4</Sub>Co<Sub>0.2</Sub>Fe<Sub>2</Sub>O<Sub>4</Sub>粉末,获得良好的吸收损耗,因此获得高电磁屏蔽性能镁锂基复合材料。(The invention provides a magnesium-lithium based composite material with high electromagnetic shielding performance and a preparation method thereof, and the magnesium-lithium based composite material comprises the following components in percentage by weight: using bidirectional Mg-Li alloy as matrix, Ni 0.4 Zn 0.4 Co 0.2 Fe 2 O 4 The powder is used as interlayer additive; wherein Li in the magnesium-lithium alloy accounts for 5.7-10.3 wt%, and the balance is Mg, and the method comprises the following steps: preparing a magnesium-lithium alloy; preparation of wave-absorbing material Ni 0.4 Zn 0.4 Co 0.2 Fe 2 O 4 Powder; and (4) preparing the magnesium-lithium based composite material by accumulative pack rolling. The invention designs and prepares a magnesium-lithium based composite material by combining the electromagnetic shielding mechanism of a shielding body and by an accumulative pack rolling processing technologyWhile obtaining good reflection loss R and multiple reflection loss B, the wave-absorbing material Ni is introduced between the laminated layers 0.4 Zn 0.4 Co 0.2 Fe 2 O 4 And (3) obtaining good absorption loss by powder, thus obtaining the magnesium-lithium based composite material with high electromagnetic shielding performance.)

1. A magnesium-lithium based composite material with high electromagnetic shielding performance is characterized by comprising the following components in percentage by weight: using bidirectional Mg-Li alloy as matrix, Ni_0.4Zn_0.4Co_0.2Fe₂O₄The powder is used as interlayer additive; wherein Li in the magnesium-lithium alloy accounts for 5.7-10.3 wt%, and the balance is Mg.

2. A preparation method of a magnesium-lithium based composite material with high electromagnetic shielding performance is characterized by comprising the following steps:

the method comprises the following steps: preparing a magnesium-lithium alloy;

step two: preparation of wave-absorbing material Ni_0.4Zn_0.4Co_0.2Fe₂O₄Powder;

step three: and (4) preparing the magnesium-lithium based composite material by accumulative pack rolling.

3. The preparation method of the magnesium-lithium based composite material with high electromagnetic shielding performance according to claim 2, wherein the third step is specifically: cutting a magnesium-lithium alloy ingot into block-shaped samples, removing an oxide layer on the surface of the samples, performing single-pass reduction by 20 percent at the temperature of 200 ℃ and the rolling speed of 300 r/min, and finally pressing the samples from the initial thickness of 10mmForming into 2mm plate-shaped sample, collecting three rolled plate-shaped samples, performing subsequent accumulative pack rolling treatment, and adding Ni 4-8 wt% into each layer before accumulative pack rolling_0.4Zn_0.4Co_0.2Fe₂O₄And (2) powder, namely putting the combined materials into a resistance furnace at 250 ℃ for heat preservation for 15min, then performing multi-pass cumulative overlapping rolling under the condition that the rolling speed is 300 r/min and the initial reduction is more than 50%, and finally preparing the magnesium-lithium-based composite board with the initial thickness of 6mm under the reduction.

4. The preparation method of the magnesium-lithium based composite material with high electromagnetic shielding performance according to claim 2, wherein the first step is specifically as follows: preparing raw materials according to the alloy components and mass percentage content of 5.7-10.3 wt% of Li and the balance of Mg, wherein the mass purity of each chemical substance is 99.9%; adding the prepared raw materials into a melting crucible of a vacuum melting furnace, closing a furnace cover of the vacuum induction melting furnace, extracting air in the furnace to ensure that the pressure in the furnace is below 1 x 10 < -2 > Pa, introducing argon into the vacuum induction furnace to ensure that the pressure in the furnace is maintained at 0.04-0.05MPa, starting a high-frequency induction heating device of the vacuum induction furnace, smelting at 700 +/-15 ℃, keeping the temperature for 8-10 minutes at constant temperature, finally pouring a magnesium-lithium alloy melt into an open-close type mold through a rocker arm, cooling along with the furnace, taking out a cast ingot, namely a magnesium-lithium alloy ingot, and preserving the temperature of the obtained magnesium-lithium alloy ingot in a heat treatment furnace at 220 ℃ for 8 hours for homogenization treatment.

5. The preparation method of the magnesium-lithium based composite material with high electromagnetic shielding performance according to claim 2, wherein the second step is specifically as follows: preparation of Ni by sol-gel spontaneous combustion method_0.4Zn_0.4Co_0.2Fe₂O₄Nanoparticle ferrite, in accordance with Ni²⁺:Zn²⁺:Co²⁺:Fe³⁺:C₆H₈O₇·H₂Preparing raw materials with the molar ratio of O to O of 0.4:0.4:0.2:2:3, dissolving the prepared raw materials in 100ml of deionized water, violently stirring and mixing the reactants together, and then mixing the reactantsAmmonia was added dropwise to adjust the PH of the suspension to around 7, the suspension was magnetically stirred continuously at 80 ℃ for about 6 hours until the solution viscosity increased to a dark-colored gelatinous liquid, followed by a series of heat treatment processes of, firstly, drying the dark-colored gelatinous liquid in an oven at 150 ℃ for 10 hours, secondly, igniting the dried gel to obtain a loose powder, and finally, calcining the loose powder at 1100 ℃ for 3 hours to decompose all organic substances, and then obtaining the desired ferrite by slowly cooling the powder to ambient temperature.

Technical Field

The invention relates to a magnesium-lithium based composite material and a preparation method thereof, in particular to a magnesium-lithium based composite material with high electromagnetic shielding performance and a preparation method thereof.

Background

At present, the development of modern science and technology enables various electronic devices to provide great convenience for social production and human life. Meanwhile, the electromagnetic radiation and interference generated by the electronic equipment in the working process can influence the production and life of people, so that the electromagnetic environment of the living space of people is increasingly worsened. Electromagnetic radiation has become a new pollution source which is subsequent to water sources, atmosphere and noise, has great harmfulness and is not easy to protect, not only affects the normal use of electronic equipment, but also directly threatens the health of human beings, and becomes a hot problem concerned by the society and the scientific community. The most effective measure for controlling electromagnetic radiation pollution is electromagnetic shielding, which is mainly aimed at preventing the influence of radio frequency electromagnetic waves and suppressing the radiation intensity within a safe range. Therefore, it is important for research and development of shielding materials.

The transmission line theory is a common analysis method for explaining the electromagnetic wave shielding mechanism due to its convenient calculation, high precision and easy understanding. The transmission line theory is that the material is regarded as a transmission line, and when the electromagnetic wave approaches the surface of the shielding body, the intrinsic impedance (Z) is obtained_r) Impedance (Z) with electromagnetic wave propagation medium₀) Instead, the electromagnetic wave is reflected at the outer surface for a portion (reflection loss R) and the remaining portion penetrates the shield and travels forward. The intensities of the reflected and transmitted waves depend on the impedance of the medium and material. During transmission, the electromagnetic wave is continuously attenuated by the shield (absorption loss A) and is reflected multiple times between two interfaces of the shield (multiple reflection loss B), and finally transmission is completed. Therefore, the electromagnetic shielding mechanism of the shield includes reflection loss R of the surface of the shield, and absorption of the shielding materialA collection loss a and a multiple reflection loss B inside the shield. In order to obtain a shield having excellent electromagnetic shielding performance, the above aspects should be considered.

Disclosure of Invention

The invention aims to provide a magnesium-lithium-based composite material with excellent electromagnetic shielding performance in a ultrahigh frequency band and a preparation method thereof.

The purpose of the invention is realized as follows:

a magnesium-lithium based composite material with high electromagnetic shielding performance comprises the following components in percentage by weight: using bidirectional Mg-Li alloy as matrix, Ni_0.4Zn_0.4Co_0.2Fe₂O₄The powder is used as interlayer additive; wherein Li in the magnesium-lithium alloy accounts for 5.7-10.3 wt%, and the balance is Mg;

a preparation method of a magnesium-lithium based composite material with high electromagnetic shielding performance comprises the following steps:

the method comprises the following steps: preparing a magnesium-lithium alloy;

step two: preparation of wave-absorbing material Ni_0.4Zn_0.4Co_0.2Fe₂O₄Powder;

step three: and (4) preparing the magnesium-lithium based composite material by accumulative pack rolling.

The invention also includes such features:

the third step is specifically as follows: cutting a magnesium-lithium alloy ingot into block-shaped samples, removing an oxide layer on the surface of the samples, reducing the sample by 20 percent in a single pass at the temperature of 200 ℃ and the rolling speed of 300 r/min, finally pressing the sample into a plate-shaped sample with the initial thickness of 10mm to be 2mm, taking three rolled plate-shaped samples to perform subsequent accumulative roll processing, and adding 4-8 percent of Ni in mass ratio into each layer before accumulative roll processing_0.4Zn_0.4Co_0.2Fe₂O₄Powder, namely putting the combined material into a resistance furnace at 250 ℃ for heat preservation for 15min, then performing multi-pass cumulative overlapping rolling when the initial reduction is more than 50% under the condition that the rolling speed is 300 revolutions per minute, and finally preparing a magnesium-lithium-based composite plate with the initial thickness of 6mm under the reduction condition;

the first step is specifically as follows: preparing raw materials according to the alloy components and mass percentage content of 5.7-10.3 wt% of Li and the balance of Mg, wherein the mass purity of each chemical substance is 99.9%; adding the prepared raw materials into a smelting crucible of a vacuum smelting furnace, closing a furnace cover of the vacuum induction smelting furnace, extracting air in the furnace to enable the pressure in the furnace to be below 1 x 10 < -2 > Pa, introducing argon into the vacuum induction furnace to enable the pressure in the furnace to be maintained at 0.04-0.05MPa, starting a high-frequency induction heating device of the vacuum induction furnace, smelting at 700 +/-15 ℃, keeping the temperature for 8-10 minutes at constant temperature, finally pouring a magnesium-lithium alloy melt into an open-close type mold through a rocker arm, cooling along with the furnace, taking out an ingot, namely a magnesium-lithium alloy ingot, and preserving the temperature of the obtained magnesium-lithium alloy ingot in a heat treatment furnace at 220 ℃ for 8 hours for homogenization treatment;

preparation of Ni by sol-gel spontaneous combustion method_0.4Zn_0.4Co_0.2Fe₂O₄Nanoparticle ferrite, in accordance with Ni²⁺:Zn²⁺:Co²⁺:Fe³⁺:C₆H₈O₇·H₂Preparing raw materials with a molar ratio of O to O of 0.4:0.4:0.2:2:3, dissolving the prepared raw materials in 100ml of deionized water, vigorously stirring and mixing the reactants together, then dropwise adding ammonia water to adjust the pH value of the suspension to about 7, continuously magnetically stirring the suspension at 80 ℃ for about 6 hours until the solution viscosity rises to a dark-colored gelatinous liquid, then performing a series of heat treatment processes, firstly, drying the dark-colored gelatinous liquid in an oven at 150 ℃ for 10 hours, secondly, igniting the dried gel to obtain loose powder, finally, calcining the loose powder at 1100 ℃ for 3 hours to decompose all organic substances, and then obtaining the required ferrite by slowly cooling the powder to ambient temperature.

Compared with the prior art, the invention has the beneficial effects that:

the magnesium-lithium based composite material obtained by the invention has excellent electromagnetic shielding performance, low cost and simple manufacture, and is beneficial to popularization;

in recent years, no report is found in the research of foreign scholars aiming at the aspect of magnesium alloy electromagnetic shielding at present, and the domestic scholars aim at the aspect of magnesium alloy electromagnetic shieldingThe shielding performance is mainly to improve the electromagnetic shielding performance by improving the conductivity performance of the alloy. The invention designs and prepares a magnesium-lithium based composite material by combining the electromagnetic shielding mechanism of a shielding body, obtains good reflection loss R and multiple reflection loss B by an accumulative pack rolling processing technology, and simultaneously introduces a wave-absorbing material Ni between laminated layers_0.4Zn_0.4Co_0.2Fe₂O₄And (3) obtaining powder, and obtaining the magnesium-lithium-based composite material with excellent electromagnetic shielding performance in a super-high frequency band due to good absorption loss.

Drawings

FIG. 1 shows a wave-absorbing material Ni_0.4Zn_0.4Co_0.2Fe₂O₄SEM image of powder;

FIG. 2 is a schematic structural diagram of the magnesium-lithium based composite material;

FIG. 3 is a graph of the shielding effectiveness of the magnesium-lithium based composite material at 30MHz to 3000 MHz.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The magnesium-lithium based composite material comprises the following components in percentage by weight:

1)Mg-(5.7-10.3wt％)Li；

2)Ni_0.4Zn_0.4Co_0.2Fe₂O₄powder:

Ni(NO₃)₂·6H₂O:Zn(NO₃)₂·6H₂O:Co(NO₃)₂·6H₂O:Fe(NO₃)₃·9H₂O:C₆H₈O₇·H₂the molar ratio of O is 0.4:0.4:0.2:2:3, 100ml of deionized water and a proper amount of ammonia water.

The preparation method of the magnesium-lithium-based composite material with excellent electromagnetic shielding performance comprises the following steps:

1) preparation of magnesium-lithium alloy

Preparing raw materials according to the alloy components and mass percentage content of Li (5.7-10.3 wt%), and the balance of Mg, wherein the mass purity of each chemical substance is 99.9%; adding the prepared raw materials into a melting crucible of a vacuum melting furnace, closing a furnace cover of the vacuum induction melting furnace, and extracting air in the furnace to ensure that the pressure in the furnace is below 1 multiplied by 10 < -2 > Pa. Then argon is introduced into the vacuum induction furnace to maintain the pressure in the vacuum induction furnace at 0.04-0.05 MPa. Starting a high-frequency induction heating device of the vacuum induction furnace, and keeping the melting temperature at 700 +/-15 ℃ for 8-10 minutes at the constant temperature. And finally, pouring the magnesium-lithium alloy melt into an open-close type mould through a rocker arm, cooling along with the furnace, and taking out the cast ingot, namely the magnesium-lithium alloy ingot. And (3) preserving the heat of the obtained magnesium-lithium alloy ingot in a heat treatment furnace at 220 ℃ for 8 hours for homogenization treatment.

2) Preparation of wave-absorbing material Ni_0.4Zn_0.4Co_0.2Fe₂O₄Powder of

Preparation of Ni by sol-gel spontaneous combustion method_0.4Zn_0.4Co_0.2Fe₂O₄A nanoparticle ferrite. According to Ni²⁺:Zn²⁺:Co²⁺:Fe³⁺:C₆H₈O₇·H₂The molar ratio of O is 0.4:0.4:0.2:2: 3. The prepared raw materials were dissolved in deionized water (100 ml). The reactants were mixed together with vigorous stirring and then aqueous ammonia was added dropwise to adjust the pH of the suspension to around 7. The suspension was magnetically stirred continuously at 80 ℃ for about 6 hours until the solution viscosity increased to a dark gel-like liquid. Followed by a series of heat treatment processes. First, the dark gel-like liquid was dried in an oven at 150 ℃ for 10 hours. Next, the dried gel was ignited to obtain a loose powder. Finally, the bulk powder was calcined at 1100 ℃ for 3 hours to decompose all organic material, and then the desired ferrite was obtained by slowly cooling the powder to ambient temperature. The microstructure of the obtained ferrite is shown in figure 1.

3) Preparation of magnesium-lithium based composite material by accumulative pack rolling

Before rolling, the magnesium-lithium alloy ingot is cut into block-shaped samples by wire cutting, and oxide layers on the surfaces of the samples are brushed by a steel wire brush. Under the conditions of 200 ℃ and the roller speed of 300 r/min, the plate-shaped sample is pressed by 20 percent in a single pass, and finally the plate-shaped sample is pressed into a plate-shaped sample with the initial thickness of 10 mm. Taking three rolled piecesThe plate-like test piece is subjected to a subsequent accumulative pack rolling treatment. Before the accumulative pack rolling, a steel wire brush is used for brushing off an oxide layer on the surface of a sample, and Ni with the mass ratio of 4-8 percent is added into each layer_0.4Zn_0.4Co_0.2Fe₂O₄And (3) powder. And (3) putting the combined material into a resistance furnace at 250 ℃ for heat preservation for 15min, then carrying out multi-pass accumulated rolling under the condition that the rolling speed is 300 revolutions per minute and the initial reduction is more than 50%, and finally preparing the magnesium-lithium-based composite board with the initial thickness of 2mm under the reduction of 6 mm.

4) Detection, analysis, characterization

And detecting, analyzing and representing the electromagnetic shielding performance of the prepared magnesium-lithium alloy plate.

The invention takes Mg- (5.7-10.3 wt%) Li alloy as a matrix, utilizes the excellent electromagnetic shielding performance of the two-phase magnesium-lithium alloy, and introduces a wave-absorbing material in the accumulation pack rolling, thereby further improving the electromagnetic shielding performance, and the structural schematic diagram of the material is shown in figure 2.

The electromagnetic shielding performance of the magnesium-lithium based composite material is 112.91dB at 30MHz, 109.20dB at 800MHz, 106.57dB at 1500MHz and 104.14dB at 3000 MHz. The electromagnetic shielding performance is obviously higher than that of the common accumulated and rolled Mg-9Li alloy plate, which is shown in figure 3. The wave absorbing material added between the accumulating and rolling layers is favorable for absorbing the electromagnetic waves entering the matrix, so that the absorption loss of the shielding body is increased, and a good shielding effect is achieved.

A magnesium-lithium based composite material with excellent electromagnetic shielding performance is characterized in that a biphase Mg-Li alloy ingot is cut into 125mm multiplied by 40mm multiplied by 10mm by wire cut by an electric spark, and the surface of a sample is polished after the cut. Then, the mixture was held at 200 ℃ for 15 minutes in a resistance furnace and rolled in a vertical mill at 300 revolutions per minute. The reduction amount of each pass is controlled to be 20 percent, the steel is rolled from 10mm to 2mm, and the total reduction amount is 80 percent. The three rolled plate-like samples were subjected to the subsequent accumulative double rolling treatment. Before the accumulative pack rolling, the oxide layer on the surface of the sample is brushed off by a wire brush, and Ni with the mass ratio of 4 percent is added into each layer_0.4Zn_0.4Co_0.2Fe₂O₄And (3) powder. And (3) putting the combined material into a resistance furnace at 250 ℃ for heat preservation for 15min, then under the condition that the roller speed is 300 revolutions per minute, the initial reduction is more than 50%, and finally, the magnesium-lithium based composite board with the initial thickness of 2mm is prepared by the reduction of 6 mm.

The unique α phase and β phase of the biphase Mg-Li alloy are used, the density of the phase interface is increased through the rolling process with large deformation amount, which is beneficial to completing multiple reflection loss of electromagnetic waves in the alloy, and the wave-absorbing material Ni0.4Zn0.4Co0.2Fe2O4 nano ferrite is added into the laminated layer by adopting the accumulative roll-lamination processing technology, so that the electromagnetic waves entering the matrix are effectively absorbed, the absorption loss of the electromagnetic waves is increased, and the shielding effect of the shielding body on the electromagnetic waves is increased by integrating the advantages.

The Mg-Li alloy is selected as a matrix, and the Mg-Li alloy comprises the components with the mass percentage of Li (5.7-10.3 wt%) and the balance of Mg. Preparation of wave-absorbing material Ni_0.4Zn_0.4Co_0.2Fe₂O₄Powder, all chemicals used here were 99.9% pure by mass. Cutting the Mg-Li alloy ingot into 125mm multiplied by 40mm multiplied by 10mm by wire-cut electrical discharge machining, and polishing the surface of the sample after cutting. Then, the mixture was held at 200 ℃ for 15 minutes in a resistance furnace and rolled in a vertical mill at 300 revolutions per minute. The reduction amount of each pass is controlled to be 20 percent, the steel is rolled from 10mm to 2mm, and the total reduction amount is 80 percent. The three rolled plate-like samples were subjected to the subsequent accumulative double rolling treatment. Before the accumulative pack rolling, the oxide layer on the surface of the sample is brushed off by a wire brush, and Ni with the mass ratio of 4 percent is added into each layer_0.4Zn_0.4Co_0.2Fe₂O₄And (3) powder. And (3) putting the combined material into a resistance furnace at 250 ℃ for heat preservation for 15min, then under the condition that the roller speed is 300 revolutions per minute, the initial reduction is more than 50%, and finally, the magnesium-lithium based composite board with the initial thickness of 2mm is prepared by the reduction of 6 mm. And carrying out metallographic observation, SEM observation, XRD phase analysis, VSM test and electromagnetic shielding performance test on the obtained magnesium-lithium based composite material. The results show that Ni is added between the layers_0.4Zn_0.4Co_0.2Fe₂O₄The magnesium-lithium based composite material of the powder has the electromagnetic shielding propertyThe shielding effectiveness at 30MHz is 112.91dB, the shielding effectiveness at 800MHz is 109.20dB, the shielding effectiveness at 1500MHz is 106.57dB, and the shielding effectiveness at 3000MHz is 104.14 dB. The electromagnetic shielding performance of the alloy plate is obviously higher than that of the common accumulated and rolled Mg-Li alloy plate.

In summary, the following steps: the invention provides a magnesium-lithium-based composite material with excellent electromagnetic shielding performance in a ultrahigh frequency band and a preparation method thereof, wherein the preparation method comprises the following steps: selecting a biphase Mg-Li alloy as a matrix and Ni_0.4Zn_0.4Co_0.2Fe₂O₄The magnesium-lithium-based composite material with excellent electromagnetic shielding performance is prepared by using nano ferrite powder as an interlayer additive through an accumulative pack rolling process. The magnesium-lithium based composite material obtained by the invention has excellent electromagnetic shielding performance, low cost and simple manufacture, and is beneficial to popularization.