Preparation method of highly-filled zinc oxide coated magnesium oxide composite powder material

Abstract

The invention discloses a preparation method of a high-filling zinc oxide coated magnesium oxide composite powder material, and aims to solve the problems that magnesium oxide is easy to hydrolyze, poor in compatibility with a polymer matrix and low in filling rate as a filler. Comprising the following steps: firstly, preparing a polyvinyl butyral ethanol solution, sequentially adding nano zinc oxide, borax and micron magnesium oxide, uniformly mixing, distilling to remove ethanol, and carrying out ball milling and calcining to obtain zinc oxide coated magnesium oxide composite powder; according to the method, a compact zinc oxide coating layer is formed on the surface of the magnesium oxide, the hydrolysis resistance of the magnesium oxide is effectively improved, meanwhile, the product is smooth in surface, compact in structure, high in sphere-like degree, low in specific surface area, low in oil absorption value and excellent in flowability, the compatibility and filling performance of the functional filler and a base material are improved, and the service life of the functional filler is prolonged. The comprehensive performance of the heat-conducting glue and the heat-conducting gasket which take magnesium oxide as a raw material is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of inorganic composite materials technology, specifically relating to a method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material. Background Technology

[0002] Magnesium oxide (MgO) is an important inorganic functional material. Due to its high melting point, high insulation, high thermal conductivity, and relatively low price, it is a crucial and widely used functional material in the field of thermal conductivity. However, MgO has a major drawback that severely restricts its development and application in thermal conductivity. MgO readily undergoes a hydration reaction with water molecules in the environment. This reaction typically involves two steps: first, MgO reacts with water to form magnesium hydroxide, accompanied by significant volume expansion; then, magnesium hydroxide reacts with carbon dioxide in the environment to form basic magnesium carbonate. This hydration reaction leads to caking of the MgO powder, poor filling properties, and a decrease in thermal conductivity. Furthermore, when MgO is used as a functional thermally conductive filler in the preparation of composite materials such as thermally conductive plastics and pads, the volume expansion and alkalinity changes caused by the hydration reaction generate significant internal stress within the composite material, leading to cracking, blistering, decreased insulation, and reduced thermal conductivity, severely shortening the lifespan of the composite material itself.

[0003] Currently, many studies have been conducted on the hydrolysis resistance of magnesium oxide. A common method is to modify the surface of magnesium oxide with organic molecules such as silane coupling agents, fatty acids, and phthalates. Although this method can improve the hydrolysis resistance of magnesium oxide, the thermal stability of the surface organic modification layer is extremely poor. Under the conditions of later processing or during long-term use, the organic layer is prone to decomposition and carbonization. At this time, not only is the modification effect lost and the magnesium oxide loses its hydrolysis resistance, but its decomposition products may also generate gases and pollute the matrix system, thereby affecting the comprehensive performance of the composite material and causing serious negative effects.

[0004] To address the above issues, this method utilizes a polyvinyl butyral ethanol solution to aid dispersion and adhesion, combined with subsequent ball milling and calcination processes, to form a dense zinc oxide coating layer on the surface of magnesium oxide powder. This significantly improves the hydrolysis resistance of magnesium oxide and enhances its compatibility with the substrate, expanding its applications in various fields. Summary of the Invention

[0005] Based on the problems mentioned in the background art regarding the application of magnesium oxide as a thermally conductive filler, this invention aims to provide a method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material. This method uses polyvinyl butyral, ethanol, nano-zinc oxide, borax, and micron-sized magnesium oxide as raw materials. Through processes such as ball milling and calcination, a dense and smooth zinc oxide layer is coated onto the surface of magnesium oxide, greatly improving the hydrolysis resistance of magnesium oxide. Furthermore, zinc, as a transition zone metal, possesses certain empty orbitals, which can accept free electrons from the substrate, significantly improving the compatibility between magnesium oxide and the substrate. For example, in the field of thermal conductivity, it can effectively improve the compatibility between magnesium oxide and silicone rubber substrates, significantly improving the condition of thermally conductive adhesives and pads prepared using magnesium oxide as a raw material. Simultaneously, the surface coating exhibits high sphericality and a smooth surface, thus greatly enhancing the filling capacity. Moreover, the raw materials used are readily available, the process is simple, the production equipment requirements are low, and it is easily industrialized.

[0006] The preparation method of the highly filled zinc oxide-coated magnesium oxide composite powder material of the present invention includes the following steps: (1) Add polyvinyl butyral to ethanol and stir to dissolve the polyvinyl butyral to obtain a polyvinyl butyral ethanol solution. (2) Add nano zinc oxide and borax to the polyvinyl butyral ethanol solution, stir and mix evenly to form a slurry. (3) Add micron-sized magnesium oxide to the slurry, stir and mix evenly, then heat and continue stirring to distill out ethanol to obtain powder A; (4) Place powder A into a ball mill jar, add a ball milling tool and ball mill to obtain coated powder B; (5) Place the coated powder B into an atmosphere furnace for calcination, cool it and take it out to obtain zinc oxide coated magnesium oxide composite powder.

[0007] In step (1), the amount of polyvinyl butyral added is 2-6% of the mass of ethanol.

[0008] In step (1), the stirring speed is 200-800 r / min and the stirring time is 20-40 min.

[0009] In step (2), the zinc oxide has a particle size of D50 of 0.1-1 micrometer and D100 of 0.1-4 micrometer, and the amount added is 15-30% of the mass of ethanol.

[0010] In step (2), the amount of borax added is 0.15-0.6% of the mass of ethanol.

[0011] In step (2), the stirring speed and stirring time are 400-800 r / min and the stirring time is 20-40 min.

[0012] In step (3), the magnesium oxide particle size D50 is 20-80 micrometers, and the amount added is 60%-100% of the mass of ethanol.

[0013] In step (3), the stirring speed is 600-800 r / min and the stirring time is 30 min-60 min. In step (3), the heating distillation temperature is 35-60℃. The stirring speed is not required during heating distillation, but the stirring speed will gradually increase as ethanol is distilled.

[0014] In step (4), the ball-to-material ratio is 2:1, the ball milling speed is 300-500 r / min, and the ball milling time is 20-60 min.

[0015] In step (5), the calcination temperature is 900-1050℃, the holding time is 30-150min, and the cooling method is furnace cooling.

[0016] The formation mechanism and process of the highly filled zinc oxide-coated magnesium oxide composite powder material of the present invention are as follows: First, the zinc oxide used for coating must be nano-sized, and the D50 of the micron-sized magnesium oxide should be 20-80 microns to ensure an effective coating structure with the zinc oxide nano / submicron particles. A viscous solution is formed by dissolving polyvinyl butyral in ethanol, and the nano-zinc oxide is dispersed in this solution. Then, micron-sized magnesium oxide is added. The polyvinyl butyral solution acts as an organic binder, effectively adsorbing and dispersing the nano-zinc oxide to prevent its aggregation. Subsequently, under high-speed stirring, the shear force causes the polyvinyl butyral-coated nano-zinc oxide to collide and mix violently with the micron-sized magnesium oxide, initially adhering to the magnesium oxide surface. Subsequently, the mixture was continuously stirred and heated, with ethanol slowly evaporated at 35-60℃. As the solvent was removed, the solution viscosity increased, causing the polyvinyl butyral molecular chains to shrink, thus more tightly coating the nano-zinc oxide already attached to the magnesium oxide surface. However, it should be noted that agglomeration and clumping are unavoidable in this process. Therefore, a specific ball milling process is required to break up the agglomerates and clumps, resulting in zinc oxide and polyvinyl butyral-coated magnesium oxide powder. At this point, the presence of polyvinyl butyral on the surface of the coated powder significantly reduces the powder's thermal conductivity and filling properties, necessitating subsequent heat treatment. Finally, a high-performance coating structure is achieved through calcination. A suitable calcination process removes polyvinyl butyral, while borax is introduced as an additive. Combined with the inherent surface and small-size effects of nano-zinc oxide, the nano-zinc oxide particles diffuse and sinter together at temperatures far below the melting point of magnesium oxide without melting the magnesium oxide. The molten and sintered zinc oxide layer tends to form a smooth surface with the lowest energy, thus forming a continuous, smooth, and dense zinc oxide shell on the magnesium oxide surface. This results in the final composite powder exhibiting an excellent near-spherical morphology.

[0017] The key technical points and beneficial effects of this invention are as follows: The zinc oxide-coated magnesium oxide composite powder prepared by this invention significantly improves the hydrolysis resistance of magnesium oxide by coating the surface of magnesium oxide powder with a dense zinc oxide layer. This solves the problem that ordinary magnesium oxide will rapidly hydrolyze in high temperature and humid environment, leading to powder deterioration and performance degradation, and effectively expands the application of magnesium oxide. 2. Zinc particles in zinc oxide have empty orbitals that can accept electrons, enabling them to interact with free electrons in the polymer matrix, thus exhibiting better compatibility with the substrate. To impart this property to magnesium oxide, this invention prepares zinc oxide-coated magnesium oxide composite powder by coating a dense zinc oxide layer on the surface of magnesium oxide. This allows the composite powder to exhibit the excellent interfacial properties of zinc oxide as a whole, thereby significantly improving the bonding force between the filler and the matrix, reducing interfacial defects, and improving the mechanical properties and reliability of the final composite material. 3. The zinc oxide-coated magnesium oxide composite powder prepared by this invention has a smooth surface, dense structure, and high degree of spheroidization, with an overall morphology tending towards spherical. Compared with ordinary magnesium oxide, the composite powder prepared by this invention has a lower specific surface area, lower oil absorption value, and better particle flowability, meaning that a higher proportion of powder can be filled into the matrix to achieve the same viscosity. High filling capacity is a key prerequisite for achieving high thermal conductivity as a thermally conductive filler, significantly improving the applicability of magnesium oxide as a thermally conductive filler and broadening its application fields. Attached Figure Description

[0018] Figure 1 Scanning electron microscope (SEM) images prepared in Example 1 of this method

[0019] Figure 2 The scanning electron microscope (SEM) image prepared for Comparative Example 1 using this method.

[0020] Figure 3 Energy dispersive spectroscopy (EDS) image of Example 1 of this method Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments. It is worth noting that the following description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications and substitutions based on the technical solutions and inventive concepts provided by the present invention should be covered within the protection scope of the present invention.

[0022] The specific implementation steps of this invention are as follows: Add 2-6% polyvinyl butyral to ethanol and stir at 200-800 rpm for 20-40 minutes to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 15-30% nano-zinc oxide and 0.15-0.6% borax (the zinc oxide has a particle size D50 of 0.1-1 μm and a D100 of 0.1-4 μm) to the polyvinyl butyral ethanol solution and stir at 400-800 rpm for 20-40 minutes to form a slurry. Add 60%-100% micron-sized magnesium oxide (the magnesium oxide...) to the slurry. The particles (D50 of which is 20-80 micrometers) are stirred at 600-800 r / min for 30-60 min, and then heated to 35-60℃ with continuous stirring to distill off the ethanol, yielding powder A. Powder A is placed in a ball mill jar, and a ball milling mill is added. The ball milling mill is then milled at 300-500 r / min for 20-60 min at a mass ratio of 2:1 (hereinafter referred to as the ball-to-powder ratio) to obtain coated powder B. Coated powder B is placed in an atmosphere furnace and calcined at 900-1050℃ for 30-150 min. After cooling, it is removed to obtain zinc oxide coated magnesium oxide composite powder.

[0023] Example 1 Add 2% polyvinyl butyral to ethanol and stir at 200 r / min for 40 min to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 15% nano-zinc oxide with a D50 of 0.8 μm and 0.15% borax to the polyvinyl butyral ethanol solution and stir at 400 r / min for 40 min to form a slurry. Add 60% 40 μm magnesium oxide to the slurry and stir at 600 r / min for 60 min. Then heat to 60℃ and continue stirring to distill off the ethanol, obtaining powder A. Place powder A in a ball mill jar, add a ball milling tool, with a ball-to-powder ratio of 2:1, and ball mill at 300 r / min for 20 min to obtain coated powder B. Place coated powder B in an atmosphere furnace and calcine at 900℃ for 150 min. After cooling, remove the powder to obtain zinc oxide coated magnesium oxide composite powder.

[0024] Example 2 Add 4% polyvinyl butyral to ethanol and stir at 500 r / min for 30 min to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 22.5% of 0.8 μm D50 zinc oxide nanoparticles and 0.375% borax to the polyvinyl butyral ethanol solution and stir at 600 r / min for 30 min to form a slurry. Add 80% of 45 μm magnesium oxide to the slurry and stir at 700 r / min for 45 min. Then heat to 46℃ and continue stirring to distill off the ethanol, obtaining powder A. Place powder A in a ball mill jar, add a ball milling tool, with a ball-to-particle ratio of 2:1, and ball mill at 400 r / min for 40 min to obtain coated powder B. Place coated powder B in an atmosphere furnace and calcine at 1000℃ for 100 min. After cooling, remove the powder to obtain zinc oxide coated magnesium oxide composite powder.

[0025] Example 3 Add 6% polyvinyl butyral to ethanol and stir at 800 r / min for 20 min to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 30% nano-zinc oxide with a D50 of 0.8 μm and 0.6% borax to the polyvinyl butyral ethanol solution and stir at 800 r / min for 20 min to form a slurry. Add 100% micron-sized magnesium oxide to the slurry and stir at 800 r / min for 30 min. Then raise the temperature to 35℃ and continue stirring to distill off the ethanol, obtaining powder A. Place powder A in a ball mill jar, add a ball milling tool, with a ball-to-powder ratio of 2:1, and ball mill at 500 r / min for 20 min to obtain coated powder B. Place coated powder B in an atmosphere furnace and calcine at 1050℃ for 30 min. After cooling, remove the powder to obtain zinc oxide coated magnesium oxide composite powder.

[0026] Comparative Example 1 Add 2% polyvinyl butyral to ethanol and stir at 200 r / min for 40 min to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 15% nano-zinc oxide with a D50 of 0.8 μm and 0.15% borax to the polyvinyl butyral ethanol solution and stir at 400 r / min for 40 min to form a slurry. Add 60% 40 μm magnesium oxide to the slurry and stir at 600 r / min for 60 min. Then raise the temperature to 60℃ and continue stirring to distill off the ethanol, obtaining powder A. Place powder A in a ball mill jar, add a ball milling machine with a ball-to-powder ratio of 2:1, and ball mill at 300 r / min for 20 min to obtain the final product.

[0027] Comparative Example 2 20% of nano zinc oxide with a D50 of 0.8 micrometers and 80% of magnesium oxide with a D50 of 40 micrometers were mixed by stirring at 600 r / min for 60 min.

[0028] Comparative Example 3 15% of 0.8 μm D50 nano-zinc oxide and 0.15% of borax were added to ethanol and stirred at 400 r / min for 40 min to form a slurry. 60% of 40 μm magnesium oxide was added to the slurry and stirred at 600 r / min for 60 min. The mixture was then heated to 60 °C and stirred continuously to distill off the ethanol, yielding powder A. Powder A was placed in a ball mill jar, and ball milling pellets were added at a ball-to-powder ratio of 2:1. The mixture was then ball milled at 300 r / min for 20 min to obtain coated powder B. Coated powder B was placed in an atmosphere furnace and calcined at 900 °C for 150 min. After cooling, the powder was removed to obtain the final product.

[0029] Comparative Example 4 Add 2% polyvinyl butyral to ethanol and stir at 200 r / min for 40 min to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 15% nano-zinc oxide with a D50 of 0.8 μm and 0.15% borax to the polyvinyl butyral ethanol solution and stir at 400 r / min for 40 min to form a slurry. Add 60% 40 μm magnesium oxide to the slurry and stir at 600 r / min for 60 min. Then raise the temperature to 60℃ and continue stirring to distill off the ethanol, obtaining powder A. Place powder A in an atmosphere furnace and calcine at 900℃ for 150 min. After cooling, remove the powder to obtain the final product.

[0030] Comparative Example 5 Add 2% polyvinyl butyral to ethanol and stir at 200 r / min for 40 min to dissolve the polyvinyl butyral, obtaining a polyvinyl butyral ethanol solution. Then add 15% nano-zinc oxide with a D50 of 0.8 μm to the polyvinyl butyral ethanol solution and stir at 400 r / min for 40 min to form a slurry. Add 60% 40 μm magnesium oxide to the slurry and stir at 600 r / min for 60 min. Then raise the temperature to 60℃ and continue stirring to distill off the ethanol, obtaining powder A. Place powder A in a ball mill jar, add a ball milling tool, with a ball-to-powder ratio of 2:1, and ball mill at 300 r / min for 20 min to obtain coated powder B. Place coated powder B in an atmosphere furnace and calcine at 900℃ for 150 min. After cooling, remove the powder to obtain the final product.

[0031] Blank example The blank example is ordinary 40-micron magnesium oxide without coating.

[0032] The products obtained in Examples 1-3, Comparative Example 1, and the blank example were subjected to performance tests and characterization (Table 1 and figures). The performance test and characterization methods are as follows: Morphology testing method: The micromorphology of the samples was observed using a COXEM desktop scanning electron microscope. Energy dispersive spectroscopy (EDS) method: The surface elemental distribution morphology of the sample was observed using a COXEM desktop scanning electron microscope coupled with an energy dispersive spectroscopy (EDS) instrument. Particle size testing method: The particle size of the sample was tested using an LS-609 laser particle size analyzer, with a focus on changes in D50. Oil absorption test method: The test was conducted according to the method for detecting the oil absorption value of micron-sized inorganic powders as described in patent ZL 202111578448.8. Hydrolysis resistance test: 600 parts of the test sample were filled into 350cp vinyl silicone oil to prepare a colloid. The colloid was then placed in an environment with 85% humidity and 85℃ to see how long it took for the colloid to turn into powder. Thermal conductivity test: 600 parts of the sample to be tested were filled into 350cp vinyl silicone oil to prepare a colloid, which was tested by Xiangtan DRL-11 thermal conductivity tester. The material thickness was 2mm. Maximum filling amount test: The test sample is gradually added to 350cp vinyl silicone oil in 50-part increments until the product becomes dry and hard and is no longer a complete colloid after the test sample is added. This is the maximum filling amount.

[0033] Table 1

[0034] From Table 1 and the figure, we can see that: (1) Regarding particle size: The products prepared according to the process of the present invention in Examples 1-3 have uniform particle size and relatively concentrated particle size distribution. Compared with Example 1, Comparative Example 1 did not calcine off the surface polyvinyl butyral, and the particle size was slightly larger; Comparative Example 2 was a physical mixture, and since there was no coating and bonding, it was a simple compounding of coarse and fine powders, and the overall particle size was significantly smaller; Comparative Example 3 did not add polyvinyl butyral as a binder, and the zinc oxide calcined and melted part agglomerated, while the magnesium oxide remained basically unchanged, and the particle size was also slightly smaller; Comparative Example 4 did not ball mill, and the product particle size was significantly larger; Comparative Example 5 did not add borax to aid melting, and the particle size detected by the laser particle size analyzer was larger. (2) Regarding oil absorption: Examples 1, 2, and 3 have a smooth and dense zinc oxide coating, so their oil absorption is significantly lower than that of the blank and comparative examples; Comparative Example 1 has a surface of polyvinyl butyral and zinc oxide, which is relatively rough, so its oil absorption is significantly higher than that of the blank example; Comparative Example 2 is only a physical mixture and contains nano zinc oxide, so its oil absorption is significantly higher than that of the blank example; Comparative Example 3 does not add polyvinyl butyral as a binder, and the zinc oxide in the product is calcined and melted, while the magnesium oxide remains basically unchanged, resulting in a smaller particle size, so its oil absorption is significantly higher than that of the blank example; Comparative Example 4 does not have ball milling, so the product has more pores, and its oil absorption is significantly higher than that of the blank example; Comparative Example 5 does not add borax to aid melting, so the zinc oxide is not sintered into a dense and smooth state, resulting in a rough surface, and its oil absorption is significantly higher than that of the blank example. (3) Regarding the maximum filling amount: Examples 1, 2, and 3 benefited from the smooth surface and good interfacial compatibility of the products, and had better compatibility with the polymer substrate. Therefore, the maximum filling amount of Examples 1, 2, and 3 reached 800-850 parts; while Comparative Example 1 had a rough surface, so the maximum filling amount was reduced to 500 parts; the maximum filling amount of the blank example was 600 parts; Comparative Example 2 had a combination of coarse and fine particles, and the maximum filling amount was higher than that of the blank example; Comparative Example 3 had a combination of zinc oxide particles and magnesium oxide, and the maximum filling amount was higher than that of the blank example; Comparative Example 4 had more pores, and the maximum filling amount decreased significantly; Comparative Example 5 had a rough surface, but was still coated with zinc oxide, which improved the compatibility, and the maximum filling amount was slightly increased. (4) Morphology: After adding the additives, Example 1 was calcined and the surface was coated with a dense and smooth zinc oxide layer, and the overall morphology was highly spherical; Comparative Example 1 had a layer of polyvinyl butyral and zinc oxide on the surface, the surface was relatively rough and the particle size uniformity was poor. (5) Hydrolysis resistance: The products of Examples 1, 2, 3 and Comparative Examples 1 and 5, due to the effective isolation of the magnesium oxide core by the coating layer, remained intact for 180 days in a double 85 environment after being prepared into colloids; the blank sample magnesium oxide colloid was already pulverized in only 6 days in a double 85 environment; the magnesium oxide of Comparative Examples 2 and 3 did not have zinc oxide coating on the surface, and their hydrolysis resistance was consistent with that of the blank example; Comparative Example 4 could not be filled to 600 parts (poor filling ability), so this performance data could not be tested. (6) Thermal conductivity: Based on 600 phr of silicone gel, the thermal conductivity of the product prepared in Example 1 is higher than that of the blank example, and the thermal conductivity increases with the increase of product particle size; the thermal conductivity of Comparative Example 1 is significantly reduced because the surface is a zinc oxide layer of polyvinyl butyral, which is basically non-thermal conductive, affecting the construction of thermal conductive channels in the colloid; the thermal conductivity of Comparative Example 2 is significantly lower than that of the blank example because nano zinc oxide introduces a large amount of interfacial thermal resistance; the thermal conductivity of Comparative Example 3 is slightly lower than that of the blank example because zinc oxide is calcined and melted in the product and magnesium oxide remains basically unchanged; the thermal conductivity of Comparative Example 4 is not filled to 600 parts (poor filling performance), and the thermal conductivity data at this filling amount cannot be tested; the thermal conductivity of Comparative Example 5 is comparable to that of Example 1.

Claims

1. A method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material, characterized in that, Includes the following steps: (1) Add polyvinyl butyral to ethanol and stir to dissolve the polyvinyl butyral to obtain a polyvinyl butyral ethanol solution. (2) Add nano zinc oxide and borax to the polyvinyl butyral ethanol solution, stir at 200-800 r / min for 20-40 min to mix evenly and form a slurry; (3) Add micron-sized magnesium oxide to the slurry, stir at 400-800 r / min for 20-40 min to mix evenly, then heat and continue stirring to distill out ethanol to obtain powder A; (4) Place powder A into a ball mill jar, add a ball milling tool and ball mill to obtain coated powder B; (5) Place the coated powder B into an atmosphere furnace for calcination, cool it and take it out to obtain zinc oxide coated magnesium oxide composite powder.

2. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The amount of polyvinyl butyral added in step (1) is 2-6% of the mass of ethanol.

3. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The nano zinc oxide in step (2) has a particle size D50 of 0.1-1 micrometer and a D100 of 0.1-4 micrometer, and the amount added is 15-30% of the mass of ethanol.

4. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The amount of borax added in step (2) is 0.15-0.6% of the mass of ethanol.

5. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The micron-sized magnesium oxide particles (D50) mentioned in step (3) have a particle size of 20-80 microns and are added in an amount of 60%-100% of the mass of ethanol.

6. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The stirring speed in step (3) is 600-800 r / min, and the stirring time is 30 min-60 min.

7. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The distillation temperature mentioned in step (3) is 35-60℃. There is no requirement for the stirring speed during the distillation, but the stirring speed will gradually increase as the ethanol is distilled.

8. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The ball-to-material ratio in step (4) is 2:1, the ball milling speed is 300-500 r / min, and the ball milling time is 20-60 min.

9. The method for preparing a highly filled zinc oxide-coated magnesium oxide composite powder material according to claim 1, characterized in that, The calcination temperature in step (5) is 900-1050℃, the holding time is 30-150min, and the cooling method is furnace cooling.

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