KR102316380B1 - Manufacturing method of heat-resistant and electromagnetic shielding composite coated with magnetic material and heat-resistant and electromagnetic shielding composite manufactured by the method - Google Patents

Abstract

The present invention relates to a method for manufacturing a heat dissipation-magnetic composite coated with a magnetic material, comprising: a first step of using aluminum as a heat dissipating material and mixing aluminum powder with a precursor powder of a magnetic material at 0 to 25° C. to prepare a mixed powder; a second step of preparing a heat dissipation-electromagnetic wave shielding composite in which an aluminum core is coated with a magnetic material by adding moisture as a reactant to the mixed powder and heating at 35 to 95°C; and a third step of washing and drying after step (2).

Description

Manufacturing method of heat-resistant and electromagnetic shielding composite coated with magnetic material and heat-resistant and electromagnetic shielding composite manufactured by the method

The present invention relates to a method for manufacturing a heat dissipation-electromagnetic wave shielding composite coated with a magnetic material, and more particularly, by mixing a precursor of a magnetic material using aluminum as a heat dissipating material at room temperature and adding moisture as a reactant to react, the aluminum heat dissipation material core It relates to a method of manufacturing a heat dissipation-electromagnetic wave shielding composite coated with a magnetic material, characterized in that the magnetic material-coated heat dissipation-electromagnetic wave shielding composite can be easily manufactured.

Recently, with the development of electronic and communication devices, the convenience of human life has greatly improved, and at the same time, the problem of harmfulness due to exposure to electromagnetic waves generated from electronic devices is gradually emerging.

In particular, as the weight reduction, miniaturization, and design of electronic devices are diversified, a housing material is being replaced from metal to plastic, and accordingly, electromagnetic waves generated inside the electronic device are easily leaked to the outside of the electronic device.

The leaked electromagnetic waves cause interference with other nearby electronic devices, causing the interfered electronic devices to malfunction or even adversely affect the human body. When exposed to strong electromagnetic waves for a long time, the hormone secretion system is disturbed. In particular, children, pregnant women, and the elderly with weak immune systems are vulnerable to electromagnetic waves, so a solution to these damages is needed.

Currently, electromagnetic wave shielding technologies for protecting the human body and various devices are spurring the development of electromagnetic wave shielding technologies in various fields including chemical engineering beyond the electronic information field.

Electromagnetic wave shielding refers to shielding electromagnetic wave interference that is incident from the outside, and when electromagnetic waves meet a material during the process, they are reflected or absorbed and disappear. The electromagnetic wave shielding effectiveness (SE) by a technology that reduces the electromagnetic response from one space to another by blocking unnecessary jammers appears as the sum of the reflective and absorbing capabilities of the shielding material. The better this and the better the permeability, the higher the absorption capacity.

Therefore, the electromagnetic wave shielding material should be electrically conductive or magnetic, and it is advantageous to have a large surface area. Accordingly, metals such as copper, iron, nickel, aluminum, tin, and zinc, which have good electromagnetic properties, are in the spotlight as a shielding material.

Among them, aluminum is the second most common element on Earth after oxygen and silicon, accounting for 8.2%, and its thermal conductivity is 327 W/m·K, which is widely used in industry as a heat dissipation material.

However, since aluminum is used as a solid fuel, the heat of combustion is large, so care is required in handling it.

In addition, aluminum has excellent reactivity with oxygen and is easily _{converted into aluminum oxide (Al 2} O ₃ ) in air to form a ceramic layer on its surface. It is significantly reduced compared to aluminum foil.

In addition, since the ceramic layer on the surface of the aluminum powder has low reactivity, it is impossible to impart physical properties such as metal or metal oxide coating through chemical reaction or magnetism through doping to the surface of the aluminum powder by the conventional hydrothermal synthesis method.

Accordingly, when aluminum is included as a heat dissipating material and a metal having excellent electromagnetic properties for shielding electromagnetic waves is included as a shielding material, a matrix is further included so that the components can be included on the matrix together.

In this regard, US Patent No. 7,608,326 (October 27, 2009) relates to a thermally conductive composite material for reducing electromagnetic emission generated from an electronic device, wherein the thermally conductive composite material is a thermally conductive material in the form of particles and particles. An electromagnetic energy absorbing material in the form of an electromagnetic energy absorbing material is dispersed in a matrix to shield thermally conductive electromagnetic waves, wherein the thermally conductive material may be aluminum nitride, and the electromagnetic energy absorbing material is carbonyl iron (carbonyl) iron).

In addition, U.S. Patent Publication No. 2016/0233173 (2016.08.11.) relates to a thermally conductive electromagnetic interference (EMI) absorber, wherein the absorber includes alumina, which is a thermally conductive particle, and carbonyl iron, which is an EMI absorption particle. And it is characterized in that the thermal conductivity is improved while maintaining the electromagnetic wave shielding rate by loading silicon carbide into the matrix.

As such, in the prior art, when aluminum powder is used as it is and a metal such as iron is included as a shielding material to supplement dielectric constant or magnetic permeability, there is a problem in that the manufacturing process is complex and the specific gravity of the composite is large.

US Registered Patent Publication No. 7,608,326 (2009.10.27) US Patent Publication No. 2016/0233173 (2016.08.11)

Accordingly, in order to solve the above problems, the present invention is to provide a method for manufacturing a heat dissipation-electromagnetic wave shielding composite coated with a magnetic material as a solution thereof.

In addition, the present invention, in order to solve another problem, characterized in that manufactured by the above manufacturing method, heat dissipation - to provide another solution to the electromagnetic wave shielding composite.

In order to solve the above problems, the present invention includes: a first step of preparing a mixed powder by mixing aluminum powder with a precursor powder of a magnetic material at 0 to 25° C. by using aluminum as a heat dissipating material; a second step of preparing a heat dissipation-electromagnetic wave shielding composite in which an aluminum core is coated with a magnetic material by adding moisture as a reactant to the mixed powder and heating at 35 to 95°C; and a third step of washing and drying after the step (2).

As an embodiment, in the second step, water may be water or water vapor, and water may be added to the mixed powder in a ratio of 1:0.05 to 0.5 based on parts by weight.

As an embodiment, 100 to 500 parts by weight of the magnetic precursor powder may be included with respect to 100 parts by weight of the aluminum powder.

Preferably, the precursor of the magnetic material is at least one selected from the group consisting of iron (II) chloride, iron (III) chloride, nickel chloride, cobalt chloride, iron (II) nitrate, iron (III) nitrate, nickel nitrate and cobalt nitrate. can

In another aspect for solving the above problem, the present invention provides a heat dissipation-electromagnetic wave shielding composite, characterized in that it is prepared by a method of manufacturing the magnetic material-coated heat-radiation-electromagnetic wave shielding composite.

In the present invention, by using aluminum as a heat dissipating material and adding a magnetic precursor to the aluminum powder, a heat dissipation-electromagnetic wave shielding composite can be manufactured by a simple dry process, thereby reducing cost and improving productivity.

In addition, the composite prepared by the present invention is in the form of a powder coated with a magnetic material on an aluminum core, and as it has both heat dissipation and magnetism, it can exhibit electromagnetic wave shielding performance by a magnetic material while maintaining the heat dissipation performance and low specific gravity of the aluminum powder. have.

1 shows a schematic diagram of a heat dissipation-electromagnetic wave shielding composite of the present invention.
Figure 2 1) shows the reaction scheme for preparing the heat dissipation-electromagnetic wave shielding composite of the present invention, and Figure 2 2) shows the reaction scheme for preparing the composite according to the conventional hydrothermal synthesis.
3 is an SEM photograph of a heat dissipation-electronic vehicle shielding composite according to an embodiment of the present invention.
4 is a photograph confirming magnetism according to an embodiment of the present invention.
5 is a graph showing the relative permeability (Re) and the investment loss ratio (Im) according to an embodiment of the present invention.
6 is a graph illustrating an EMI SE according to an embodiment of the present invention.

Conventionally, in the case of a composite including a magnetic material and aluminum, it was prepared by hydrothermal synthesis.

Figure 2 2) shows the formation of a complex by a precursor of alumina and a magnetic material according to the hydrothermal synthesis method.

In the case of the synthesis method, sufficient energy to oxidize aluminum cannot be applied, so even if the precursor metal becomes a metal oxide, a bond cannot be formed with the aluminum powder, and even if a bond is formed, a new crystal that does not _{exhibit magnetism in the form of MeAl 2} O ₄ indicates gender. Accordingly, the composite prepared by the above method is mainly used as a catalyst.

Accordingly, the present invention provides a method of manufacturing a heat dissipation-electromagnetic wave shielding composite coated with a magnetic material by a simple process by reacting aluminum and a magnetic metal precursor by a dry method.

Hereinafter, a method for manufacturing a heat dissipation-electromagnetic wave shielding composite coated with a magnetic material according to the present invention will be described in detail. The terms or words used below should not be construed as being limited to conventional or dictionary meanings, and those having substantially the same configuration as the technical idea and achieving the same operational effects are included in the technical scope of the present invention. In addition, in the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

According to an aspect of the present invention, by using aluminum as a heat dissipating material, and mixing the aluminum powder with the precursor powder of the magnetic material at 0 to 25 ℃, a first step of preparing a mixed powder; a second step of preparing a heat dissipation-electromagnetic wave shielding composite in which an aluminum core is coated with a magnetic material by adding moisture as a reactant to the mixed powder and heating at 35 to 95°C; and a third step of washing and drying after the step (2).

In the present invention, the first step is a step of preparing a mixed powder by mixing the aluminum powder and the precursor powder of the magnetic material, and the temperature is set to 0 to 25 °C during mixing.

This is because, when the mixing temperature is less than 0 ° C, water may form due to condensation, and when it exceeds 25 ° C, some reactions occur during mixing, so that the aluminum powder and the precursor powder of the magnetic material cannot be sufficiently mixed.

Preferably, the aluminum powder and the precursor powder of the magnetic material are mixed at 0 to 15 °C, more preferably 5 to 15 °C, and the mixing time is not particularly limited, but it is preferably carried out for at least 10 minutes.

In addition, at this time, it is characterized in that it contains 100 to 500 parts by weight of the magnetic precursor powder with respect to 100 parts by weight of the aluminum powder.

This is, when the precursor powder of the magnetic material is included in less than 100 parts by weight, the electromagnetic wave shielding performance is insignificant because it cannot sufficiently exhibit magnetism, and when it exceeds 500 parts by weight, the aluminum content that can react with the precursor of the magnetic material As this is not sufficient, the precursor of the magnetic material cannot be formed as an oxide, and heat dissipation performance is deteriorated due to a decrease in the aluminum content.

Accordingly, preferably, 100 to 250 parts by weight of the magnetic precursor powder is included with respect to 100 parts by weight of the aluminum powder. More preferably, 100 to 150 parts by weight of the magnetic precursor powder is included with respect to 100 parts by weight of the aluminum powder.

In addition, at this time, the precursor powder of the magnetic material may be used as long as it is a magnetic material, so it is not limited to a specific material, but preferably iron (II) chloride, iron (III) chloride, nickel chloride, cobalt chloride, iron (II) nitrate, It may be at least one selected from the group consisting of iron (III) nitrate, nickel nitrate and cobalt nitrate, and more preferably nickel chloride and/or cobalt chloride.

In addition, at this time, the aluminum is characterized in that it is in a state in which it is difficult to chemically modify the powder surface or to coat or dope a metal precursor because the surface is oxidized in a spherical shape and is very stable and has little conductivity, so the reactivity is very low. In addition, although the size is not limited, it is preferably characterized in that it is 0.1 mm or less.

Next, in the second step, by adding moisture as a reactant to the mixed powder and heating it at 35 to 95° C., a magnetic material is coated on an aluminum core to prepare a heat dissipation-electromagnetic wave shielding composite.

In detail, the second step may be described with reference to FIG. 2 1 ).

Figure 2 1) shows the reaction formula when the heat dissipation-electromagnetic wave shielding composite is prepared according to the present invention. Referring to this, in the second step, by adding moisture as a reactant to the mixed powder, aluminum is heated at 35 to 95 ° C. Silver is oxidized to move electrons from the aluminum, and the precursor of the magnetic material receives oxygen from moisture to become an oxide (magnetic metal oxide), and at the same time, the oxide is bonded to the surface of the spherical aluminum.

In more detail, the composite prepared in the second step may be described with reference to FIG. 1 .

1 is a schematic representation of the composite prepared by the present invention. Referring to this, in the second step, a heat dissipation-electromagnetic wave shielding composite in which an aluminum core is coated with a magnetic material is prepared, and the magnetic material is an oxidized precursor of the magnetic material. As the magnetic metal oxide, it is preferably characterized in that at least one selected from iron, nickel, and cobalt is an oxidized magnetic metal oxide.

In the step (2) of preparing the composite as described above, the moisture is water or water vapor, and after supplying oxygen atoms so that the precursor of the magnetic material can be formed as an oxide by being included in the second step as a reactant, hydrogen gas is produced. It is characterized by generating

In addition, the moisture is characterized in that a small amount is included in the mixed powder. Preferably, a ratio of the mixed powder and water is added in a ratio of 1:0.05 to 0.5 based on parts by weight. This is because when water is added to less than 0.05, oxygen atoms cannot be smoothly supplied to the precursor of the magnetic material, and when it exceeds 0.5, water does not act as a reactant but dissolves all the precursors of the magnetic material and acts as a solvent. am.

In addition, the heating in the second step is characterized in that made at 35 to 95 ℃. This is because, when the precursor of the magnetic material is generated as a magnetic metal oxide in the second step, the reaction does not occur easily when the reaction is less than 35 ° C. because the activation energy of the reaction is high, and when it exceeds 95 ° C. This is because the reaction does not proceed easily due to evaporation.

Accordingly, preferably, the heating is characterized in that 50 to 90 ℃, more preferably made at 60 to 80 ℃.

In addition, since aluminum exhibits a rapid exothermic reaction as it is oxidized in the second step, it is preferable not to increase the temperature above the above temperature through cooling after the reaction is started at 60 to 80 °C.

In this case, the heating and reaction time is sufficient for 1 to 2 minutes, but may be carried out for 5 minutes or more in some cases.

Next, the third step is a step of washing and drying after step (2). The washing is performed 2-3 times with distilled water, and the distilled water is removed using a vacuum pump and a filter or after washing with distilled water for quick drying. The washing may be performed with acetone, but the washing and drying methods are not limited thereto.

In addition, the manufactured composite may recover the composite powder prepared by using a magnet in a powder form, but is not limited thereto.

According to another aspect of the present invention, the heat dissipation-electromagnetic wave shielding composite, characterized in that manufactured by the above manufacturing method is provided.

Hereinafter, examples will be given for a more detailed description of the present invention. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto.

<Example>

Example 1

After adding 3 g of a magnetic precursor powder (FeCl ₂ ·4H ₂ O) to 2.0 g of the untreated aluminum, it was mixed at a temperature lower than room temperature at 15° C. using a tool such as a rod.

Next, after adding 0.5 to 1.0 g of distilled water to the mixed powder, it was heated to 60 °C, and if the reaction did not occur within 1 to 2 minutes, it was heated to 80 °C to induce a reaction.

After the reaction was completed, it was washed with distilled water and acetone and dried to prepare a heat dissipation-electromagnetic wave shielding composite powder, which was referred to as Example 1.

Example 2

A heat dissipation-electromagnetic wave shielding composite was prepared as a powder in the same manner as in Example 1 except that 5 g of the magnetic precursor powder (FeCl ₂ ·4H _{2 O) was added, and this was referred to as Example 2.}

Example 3

A heat dissipation-electromagnetic wave shielding composite was prepared as a powder in the same manner as in Example 1, except _{that CoCl 2} ·6H ₂ O powder was used as a precursor of the magnetic material, and this was referred to as Example 3.

Comparative Example 1

2 g of untreated aluminum powder was used as Comparative Example 1.

Comparative Example 2

In 50 g of water (solvent), _{2.0 g of alumina Al 2} O _{3 and 3 g of FeCl 2} 4H ₂ O as a precursor of a magnetic material were added to completely dissolve the precursor, and then heated at 120 ° C for 2 hours in a pressurized container using a Teflon liner. did. Accordingly, a powder including aluminum and FeAl ₂ O ₄ was prepared, but FeAl ₂ O ₄ was not coated on the aluminum powder.

Comparative Example 3

In 50 g of water (solvent), _{2.0 g of alumina Al 2} O _{3 and 3 g of CoCl 2} .6H ₂ O as a precursor of a magnetic material were added and the precursor was completely dissolved. A powder coated with _{CoAl 2} O ₄ on an aluminum core was prepared.

< Analysis >

1. Surface Analysis

3 is a scanning electron microscope (SEM) photograph of the composite powder of Examples 1 and 3;

Referring to this, in each of Examples 1 and 3, it can be seen that FeO and CoO as magnetic materials were coated on a spherical aluminum core, respectively.

2. Magnetic

4 is a photograph confirming the magnetism of Examples 1, 3, and Comparative Examples 1 to 3;

Referring to this, in Examples 1 and 3, when a magnet is brought into contact with the outer wall of the container containing each of the composite powders, as each composite powder moves toward the magnet and is attached to the outer wall, Examples 1 and 3 3, it can be confirmed that it has magnetism.

On the other hand, Comparative Example 1 composed only of Al and Comparative Examples 2 and 3 prepared by hydrothermal synthesis did not show any reaction to the magnet, so it could be confirmed that they did not have magnetism.

In Comparative Examples 2 and 3, the ones that did not have magnetism despite including Fe and Co having magnetism were prepared by a hydrothermal synthesis method using water as a solvent, unlike Examples 1 and 3, so that the aluminum coating layer This is because the material of FeAl ₂ O ₄ and CoAl ₂ O ₄ are non-magnetic.

3. Permeability

The permeability was confirmed for Examples 1 and 2 and Comparative Example 1, and is shown in Table 1 below.

Aluminum (g) FeCl ₂ 4H ₂ O permeability Comparative Example 1 2.0 - 8 Example 1 2.0 3.0 12 Example 2 2.0 5.0 14 or more

Referring to Table 1, it can be seen that the heat dissipation-electromagnetic wave shielding composite powder prepared including the precursor powder of the magnetic material exhibits a permeability increased by 1.5 times or more compared to the powder prepared including only aluminum.

In addition, it can be seen that the magnetic permeability can be further improved by adjusting the content of the precursor of the magnetic material included together with aluminum.

4. Permeability and investment loss rate

5 is a graph showing the relative permeability (Relative Permeability (Re)) and the investment loss ratio (Permeability (Im)) for Examples 1 and 2 and Comparative Example 1.

In the graph, the permeability is calculated by substituting the S-parameter and the phase difference into the NRW (Nicolson-Ross-Weir) equation with a vector network analyzer (VNA), and means the degree of magnetization in a magnetic field.

In addition, in the graph, the investment loss ratio Im means energy loss due to magnetization.

Referring to FIG. 5 , it can be seen that Examples 1 and 2 in which an aluminum core is coated with a magnetic shell exhibit increased magnetization (Re) in a magnetic field compared to Comparative Example 1 including only aluminum, and the aluminum core is coated By controlling the content of the magnetic material, it is believed that the degree of magnetization (Re) can be further improved.

In addition, it can be seen that Examples 1 and 2 exhibit a higher degree of magnetization than Comparative Example 1, and thus an energy loss rate due to magnetization, that is, an investment loss rate Im, is also increased.

The complex permeability calculation formula is as follows.

5. Shielding efficiency

6 is an EMI SE (Electromagnetic interference shielding effectiveness) graph for Examples 1, 2 and Comparative Example 1.

Referring to this, it can be confirmed that Examples 1 and 2, which are composites in which an aluminum core is coated with a magnetic material, exhibit improved electromagnetic wave shielding efficiency than Comparative Example 1 made of only aluminum.

In addition, it is determined that the electromagnetic wave shielding efficiency can be further improved by adjusting the ratio of aluminum and magnetic material constituting the composite.

Claims (5)

A first step of preparing a mixed powder by using aluminum as a heat dissipating material and mixing the aluminum powder with the magnetic precursor powder at 0 to 25°C;
a second step of preparing a heat dissipation-electromagnetic wave shielding composite in which an aluminum core is coated with a magnetic material by adding moisture as a reactant to the mixed powder and heating at 35 to 95°C; and
After step (2), a third step of washing and drying;
In the second step, the moisture is water or water vapor, and the moisture to the mixed powder is added in a ratio of 1: 0.05 to 0.5 based on parts by weight.
delete The method of claim 1,
The magnetic precursor is at least one selected from the group consisting of iron (II) chloride, iron (III) chloride, nickel chloride, cobalt chloride, iron (II) nitrate, iron (III) nitrate, nickel nitrate and cobalt nitrate. A method of manufacturing a heat dissipation-electromagnetic wave shielding composite coated with a magnetic material.
The method of claim 1,
A method of manufacturing a magnetic material-coated heat dissipation-electromagnetic wave shielding composite, characterized in that it comprises 100 to 500 parts by weight of the magnetic precursor powder based on 100 parts by weight of the aluminum powder.
Claims 1, 3, and characterized in that manufactured by the method according to any one of claims 4, heat dissipation-electromagnetic wave shielding composite.

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