Metakaolin geopolymer with high dielectric constant and preparation method thereof

Abstract

A preparation method of a metakaolin geopolymer with a high dielectric constant comprises the following steps: preparing geopolymer slurry: uniformly mixing an alkali activator, water and fly ash according to a certain proportion, and maintaining for a certain time to obtain the geopolymer slurry; doping of high-thermal-conductivity substances: adding the high-thermal-conductivity substances boron nitride and aluminum nitride into the geopolymer slurry, and fully and uniformly mixing; and curing: putting the uniformly mixed slurry into a mold, and curing at a proper temperature. According to the invention, a metakaolin geopolymer is used as a filler matrix, and geopolymer slurry is mixed with heat-conducting filler spherical boron nitride and aluminum nitride in a certain proportion. The composite material with high dielectric constant and good thermal conductivity can be obtained by mixing the high dielectric constant of the geopolymer matrix with the high-thermal-conductivity filler. The mixed composite geopolymer is used for filling and coating a required packaging material in the form of slurry, and maintenance is carried out for several days, so that the packaging effect is realized.

Description

Technical Field

[0001] The invention relates to a high dielectric constant metakaolin geological polymer and a preparation method thereof, belonging to the technical field of building materials. Background Art

[0002] The power system is rapidly developing towards high voltage levels, large-capacity transmission, and intelligent control. The research and development and use of insulating materials are becoming increasingly important, and the development of the power industry has led to higher and higher performance requirements for insulating materials. Traditional insulating materials use epoxy resins, silicone rubber, polyimide, etc. Due to the insufficient dielectric constant (ε_r<10) of insulating materials such as epoxy resins and silicone rubber, it is difficult to achieve uniform electric field control, which can easily lead to space charge accumulation and surface flashover. The matrix material of the insulating material provides insulation and mechanical support for power devices. In addition, the matrix must have good thermal conductivity to effectively dissipate the heat generated during the operation of the device. However, polyimide as an organic matrix is relatively expensive, and the dielectric constant cannot meet the requirements under high-voltage conditions. In addition, its compressive strength and corrosion resistance are not as good as geopolymers, and its service life is short.

[0003] Therefore, it is very necessary to find a method for preparing a composite material with high dielectric constant and good thermal conductivity, which combines high dielectric constant, good thermal conductivity and excellent compressive strength in the field of high-voltage power electronic device packaging. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention provides a method for preparing a high-dielectric-constant metakaolin geopolymer. The method uses the metakaolin geopolymer as a filler matrix and mixes a geopolymer slurry with thermally conductive fillers such as spherical boron nitride and aluminum nitride in a specific ratio. By combining the high dielectric constant of the geopolymer matrix with the high thermally conductive fillers, a composite material with a high dielectric constant and excellent thermal conductivity is obtained. The resulting composite geopolymer is then coated with the desired encapsulation material in the form of a slurry and cured for several days to achieve the desired encapsulation effect.

[0005] One of the objectives of the present invention is to provide a high dielectric constant metakaolin geopolymer, the raw materials of which include the following components in parts by weight: 10-20 parts of metakaolin, 5-12 parts of acid activator, 0.1-0.2 parts of boron nitride, 0.1-0.2 parts of aluminum nitride, and 3-8 parts of water.

[0006] Furthermore, 15 parts of metakaolin, 9.84 parts of acid activator, 0.15 parts of boron nitride, 0.15 parts of aluminum nitride, and 4.72 parts of water.

[0007] A method for preparing a high dielectric constant metakaolin geological polymer comprises the following steps:

[0008] (1) Preparation of geopolymer slurry: taking a certain proportion of alkali activator, water, and fly ash, mixing them evenly, and curing them for a certain period of time to obtain geopolymer slurry;

[0009] (2) Adding high thermal conductivity: adding high thermal conductivity boron nitride and aluminum nitride to the geopolymer slurry obtained in step (1) and mixing thoroughly;

[0010] (3) Curing: The uniformly mixed slurry obtained in step (2) is placed in a mold and cured at an appropriate temperature.

[0011] Furthermore, in step (1), the ratio of the metakaolin, the acid activator and the water is (10-20): (5-12): (3-8).

[0012] Furthermore, the ratio of the metakaolin, acid activator and water is 3:2:1.

[0013] Furthermore, in step (1), the curing step is to allow the mixed geopolymer to stand for 20-30 minutes.

[0014] In step (2), the total amount of boron nitride and aluminum nitride added is 0.25% to 1.25% of the mass of the metakaolin.

[0015] Furthermore, the ratio of the addition amount of the boron nitride and aluminum nitride is 1:1.

[0016] Furthermore, the particle size of the boron nitride is 50-80 microns, and the particle size of the aluminum nitride is 1-5 microns.

[0017] Furthermore, in step (3), the curing temperature is 35-45° C., and the curing time is 5-10 days.

[0018] This application addresses the modification of geopolymers. Using geopolymers as a matrix, a multi-scale filler composite design is used to construct a novel insulating material that combines dielectric adaptability, high breakdown strength, low loss, and directional thermal conductivity. Geopolymers are inorganic gelled materials with an amorphous three-dimensional network structure, formed through the condensation polymerization of silicon and aluminum raw materials. They possess excellent properties such as high strength, high temperature resistance, corrosion resistance, and high insulation. Geopolymer composite modification meets the electrical insulation, high thermal conductivity, and good mechanical properties required for electronic packaging.

[0019] Boron nitride and aluminum nitride have excellent thermal conductivity, and this application uses them to fill modified geopolymers. This approach primarily involves using a polymer as a matrix material and adding a high-conductivity thermal filler to enhance thermal conductivity. This approach also offers advantages such as low cost and ease of processing, addressing the issues of traditional metal heat dissipation materials, such as their heavy weight, corrosion susceptibility, and poor insulation properties.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This application solves the problem of low thermal conductivity and difficulty in co-optimizing dielectric properties of traditional polymer materials through the collaborative design of spherical BN / AlN composite fillers, constructs a three-dimensional thermal conductive network structure, and increases the thermal conductivity of the composite material to the order of 0.7-0.8W / mK. It provides a new environmentally friendly packaging material solution that can replace epoxy resin for scenarios such as 5G high-frequency circuit substrates and IGBT module packaging.

[0022] 2. Compared with traditional thermal conductive plastics (requiring a processing temperature of more than 300°C), the geopolymer can reduce energy consumption by 80% in the room temperature acid excitation molding process.

[0023] 3. In this application, aluminum nitride and boron nitride with high thermal conductivity are added to the geopolymer. Their high thermal conductivity greatly improves the thermal conductivity of the geopolymer, and their addition to the geopolymer using different particle size ratios has a grading effect, which can improve the density and strength of the base material.

[0024] 4. This construction method is simple to operate, economical and has high construction efficiency, and is suitable for wide promotion. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments, and do not limit the scope of protection of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application. Any modifications, equivalent substitutions, etc. made within the spirit and scope of the present invention should be included in the scope of protection of the present invention.

[0026] In the description of the present application, “multiple” means two or more, unless otherwise clearly and specifically defined.

[0027] The embodiments of the present application are as follows: A high dielectric constant metakaolin geopolymer, whose raw materials include the following components in parts by weight: 10-20 parts of metakaolin, 5-12 parts of acid activator, 0.1-0.2 parts of boron nitride, 0.1-0.2 parts of aluminum nitride, and 3-8 parts of water.

[0028] Furthermore, 15 parts of metakaolin, 9.84 parts of acid activator, 0.15 parts of boron nitride, 0.15 parts of aluminum nitride, and 4.72 parts of water.

[0029] A method for preparing a high dielectric constant metakaolin geological polymer comprises the following steps:

[0030] (1) Preparation of geopolymer slurry: taking a certain proportion of alkali activator, water, and fly ash, mixing them evenly, and curing them for a certain period of time to obtain geopolymer slurry;

[0031] (2) Adding high thermal conductivity: adding high thermal conductivity boron nitride and aluminum nitride to the geopolymer slurry obtained in step (1) and mixing thoroughly;

[0032] (3) Curing: The uniformly mixed slurry obtained in step (2) is placed in a mold and cured at an appropriate temperature.

[0033] As a further preferred embodiment, in step (1), the ratio of the metakaolin, the acid activator and the water is (10-20): (5-12): (3-8).

[0034] As a further preferred embodiment, the ratio of metakaolin, acid activator and water is 3:2:1.

[0035] As a further preferred embodiment, in step (1), the curing step is to allow the mixed geopolymer to stand for 20-30 minutes.

[0036] As a further preferred embodiment, in step (2), the total amount of boron nitride and aluminum nitride added is 0.25% to 1.25% of the mass of the metakaolin.

[0037] As a further preferred embodiment, the ratio of the addition amount of boron nitride and aluminum nitride is 1:1.

[0038] As a further preferred embodiment, the particle size of the boron nitride is 50-80 microns, and the particle size of the aluminum nitride is 1-5 microns.

[0039] As a further preferred embodiment, in step (3), the curing temperature is 35-45° C., and the curing time is 5-10 days.

[0040] The specific implementation of the present invention is as follows:

[0041] Example 1

[0042] Step 1: Add 9.84 g of 98% phosphoric acid and 4.72 g of water to 15 g of metakaolin and stir evenly to obtain a geopolymer slurry.

[0043] Step 2: Take 0.15g of spherical boron nitride and 0.15g of aluminum nitride powder and add them to the geopolymer slurry and mix them thoroughly.

[0044] Step 3: Place the mixed slurry into a mold and cure at 40°C for 5 days.

[0045] Example 2

[0046] Step 1: Add 9.84 g of 98% phosphoric acid and 4.72 g of water to 15 g of metakaolin and stir evenly to obtain a geopolymer slurry.

[0047] Step 2: Add 0.075g of spherical boron nitride and 0.075g of aluminum nitride powder to the geopolymer slurry and mix thoroughly.

[0048] Step 3: Place the mixed slurry into a mold and cure at 40°C for 5 days.

[0049] Example 3

[0050] Step 1: Add 9.84 g of 98% phosphoric acid and 4.72 g of water to 15 g of metakaolin and stir evenly to obtain a geopolymer slurry.

[0051] Step 2: Add 0.0225 g of spherical boron nitride and 0.0225 g of aluminum nitride powder to the geopolymer slurry and mix thoroughly.

[0052] Step 3: Place the mixed slurry into a mold and cure at 40°C for 5 days.

[0053] Comparative Example 1

[0054] Step 1: Add 9.84 g of 98% phosphoric acid and 4.72 g of water to 15 g of metakaolin and stir evenly to obtain a geopolymer slurry.

[0055] Step 2: Place the mixed slurry into a mold and cure at 40°C for 5 days.

[0056] Comparative Example 2

[0057] Step 1: Add 9.84 g of 98% phosphoric acid and 4.72 g of water to 15 g of metakaolin and stir evenly to obtain a geopolymer slurry.

[0058] Step 2: Take 0.3g of spherical boron nitride powder and add it to the geopolymer slurry and mix thoroughly.

[0059] Step 3: Place the mixed slurry into a mold and cure at 40°C for 5 days.

[0060] Comparative Example 3

[0061] Step 1: Add 9.84 g of 98% phosphoric acid and 4.72 g of water to 15 g of metakaolin and stir evenly to obtain a geopolymer slurry.

[0062] Step 2: Take 0.3 g of graphene and add it to the geopolymer slurry and mix it thoroughly.

[0063] Step 3: Place the mixed slurry into a mold and cure at 40°C for 5 days.

[0064] The geopolymers obtained in Examples 1-3 and Comparative Examples 1-3 were tested for thermal conductivity, % improvement in thermal conductivity compared to the pure geopolymer matrix, compressive strength, dielectric constant, and dielectric loss. Comparative Example 1 shows that the thermal conductivity of the pure geopolymer matrix is 0.181 W / (mK). The test data are as follows:

[0065]

[0066] In Examples 1-3, geopolymer is used as the thermal conductive matrix, spherical boron nitride (50 microns) and aluminum nitride (1 micron) of different scales, and the binary filler is synergistically modified through multi-scale and multi-dimensional filler combination and interface optimization to construct a low thermal resistance and high connectivity thermal conductive network, breaking through the performance bottleneck of a single filler. The binary filler is synergistically modified to construct a thermal conductive network, thereby greatly increasing the thermal conductivity. The best effect is when the filling amount of the high thermal conductive material is 2%. In Comparative Example 1, no high thermal conductive material is added, in Comparative Example 2, only boron nitride is added as a high thermal conductive material, and in Comparative Example 3, only graphene is added as a high thermal conductive material. From the test data, the improvement of the thermal conductivity of the geopolymer is not obvious, so only the geopolymer prepared according to the method of the present application can fully improve the thermal conductivity.

[0067] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high dielectric constant metakaolin geopolymer, characterized in that: The raw materials include the following components in parts by mass: 10-20 parts of metakaolin, 5-12 parts of acid activator, 0.1-0.2 parts of boron nitride, 0.1-0.2 parts of aluminum nitride and 3-8 parts of water.

2. The high dielectric constant metakaolin geopolymer according to claim 1, characterized in that: 15 parts of metakaolin, 9.84 parts of acid activator, 0.15 parts of boron nitride, 0.15 parts of aluminum nitride, and 4.72 parts of water.

3. A method for preparing a high dielectric constant metakaolin geopolymer, characterized in that: The following steps are involved: (1) Preparation of geopolymer slurry: taking a certain proportion of alkali activator, water, and fly ash, mixing them evenly, and curing them for a certain period of time to obtain geopolymer slurry; (2) Adding high thermal conductivity: adding high thermal conductivity boron nitride and aluminum nitride to the geopolymer slurry obtained in step (1) and mixing thoroughly; (3) Curing: The uniformly mixed slurry obtained in step (2) is placed in a mold and cured at an appropriate temperature.

4. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 3, characterized in that: In step (1), the ratio of the metakaolin, the acid activator and the water is (10-20): (5-12): (3-8).

5. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 4, characterized in that: The ratio of the metakaolin, acid activator and water is 3:2:

1.

6. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 1, characterized in that: In step (1), the curing step is to allow the mixed geopolymer to stand for 20-30 minutes.

7. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 1, characterized in that: In step (2), the total amount of boron nitride and aluminum nitride added is 0.25% to 1.25% of the mass of the metakaolin.

8. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 5, characterized in that: The ratio of the added amounts of boron nitride and aluminum nitride is 1:

1.

9. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 6, characterized in that: The particle size of the boron nitride is 50-80 microns, and the particle size of the aluminum nitride is 1-5 microns.

10. The method for preparing a high dielectric constant metakaolin geopolymer according to claim 1, characterized in that: In step (3), the curing temperature is 35-45° C., and the curing time is 5-10 days.

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