Method for enhancing toughness and heat conductivity of heat-conducting aluminum oxide

Abstract

The invention discloses a method for enhancing toughness and heat conductivity of heat-conducting aluminum oxide, and particularly relates to the technical field of heat-conducting materials. The method comprises the following steps: S1, preparation of nano heat-conducting fibers, S2, modification of heat-conducting aluminum oxide powder, and S3, preparation of a heat-conducting composite material. According to the method for enhancing the toughness and the heat conductivity of the heat-conducting aluminum oxide, through high length-diameter ratio and surface functionalization treatment of the nano heat-conducting fibers, an interface between aluminum oxide particles and a matrix can be effectively bridged, a fiber-aluminum oxide-matrix synergistic heat-conducting network is formed, phonon scattering is reduced, and the heat-conducting property is greatly enhanced; the superfine nano heat-conducting fibers are added into the heat-conducting aluminum oxide powder to form a special heat-conducting channel with the organic silicon matrix, so that the interface thermal resistance is remarkably reduced, and the comprehensive heat-conducting property of the material is greatly improved. 2-3.5% of nano heat-conducting fibers are added into the heat-conducting silicone grease, so that the heat conductivity can be improved by 2.5-5 W / (m.K); and 3-3.5% of the additive is added into heat-conducting silica gel, so that the heat conductivity can be improved by 2.8-6 W / (m.K).

Description

Technical Field

[0001] This invention relates to the field of thermally conductive materials technology, specifically a method for enhancing the toughness and thermal conductivity of thermally conductive alumina. Background Technology

[0002] Alumina is widely used in thermally conductive silicone and thermal grease due to its low price, high filler content, and high thermal conductivity, making it a common material in various thermal conductive products. However, its thermal conductivity is always affected by morphology and alpha conversion rate, limiting its application in high-end thermal conductive products. Improving the thermal conductivity of conventional alumina products by more than 2W would have immeasurable market value. Thermally conductive alumina is widely used in thermally conductive silicone and thermal grease due to its low price, high filler content, and good thermal conductivity. However, its thermal conductivity has long been limited by the following issues: 1. Morphological defects: Traditional spherical or near-spherical alumina particles are prone to agglomeration in the matrix due to uneven particle size distribution and rough surface, forming local thermal resistance.

[0003] 2. Low α-phase conversion rate: During the high-temperature sintering process, alumina is prone to generating impurity phases such as δ-phase and θ-phase, which leads to a decrease in thermal conductivity.

[0004] 3. Poor interfacial compatibility: Insufficient interfacial adhesion between alumina and the organosilicon substrate leads to a break in the heat conduction path.

[0005] In existing technologies, surface modification (such as silane coupling agents) or composite fillers (such as aluminum nitride and graphene) can partially improve thermal conductivity, but these methods generally suffer from high costs, complex processes, or limited performance improvements. Therefore, there is an urgent need for an efficient and low-cost method to overcome the technical bottlenecks of thermally conductive alumina. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a method for enhancing the toughness and thermal conductivity of thermally conductive alumina, thereby improving the thermal conductivity and mechanical properties of materials such as thermally conductive silicone and thermally conductive grease.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for enhancing the toughness and thermal conductivity of thermally conductive alumina, specifically comprising the following steps: S1. Preparation of nano-thermal conductive fibers: Nano-thermal conductive fibers of the required diameter are prepared by vapor deposition or electrospinning technology, and the fiber surface is functionalized to enhance the interfacial bonding force with alumina and organosilicon matrix. S2. Modification of thermally conductive alumina powder: The thermally conductive nanofibers prepared in step S1 are mixed with thermally conductive alumina powder according to the mass ratio of silicone grease or silicone. Then, the nanofibers are uniformly coated on the surface of alumina particles by mechanical grinding or ultrasonic dispersion technology to form a "fiber-alumina" composite structure. S3. Preparation of thermally conductive composite material: The composite powder modified in step S2 is added to the organosilicon matrix, and thermally conductive silicone grease or silicone is formed by high-speed stirring and vacuum degassing process. Then, by controlling the orientation and distribution of nanofibers, continuous thermally conductive channels are constructed to reduce interfacial thermal resistance, thereby constructing a three-dimensional thermally conductive network.

[0010] Preferably, the nano-thermal conductive fibers in step S1 are boron nitride or silicon carbide, and their surfaces are coated with a silane coupling agent.

[0011] Preferably, in step S2, the amount of nano-thermal conductive fibers added to the thermal grease is 2-3.5%.

[0012] Preferably, in step S2, the particle size of the thermally conductive alumina powder is 1-5 μm, and the α phase content is ≥99%.

[0013] Preferably, the mechanical grinding in step S2 is a honeycomb mill.

[0014] Preferably, the organosilicon matrix in step S3 is one of silicone oil, silicone rubber, or vinyl-terminated silicone resin.

[0015] Preferably, the thermally conductive nanofibers prepared in step S1 by vapor deposition or electrospinning have a diameter of 50-200 nm and a length of 1-5 μm.

[0016] Preferably, in step S2, the amount of nano-thermal conductive fibers added to the thermally conductive silicone is 3-3.5%.

[0017] (III) Beneficial Effects

[0018] This invention provides a method for enhancing the toughness and thermal conductivity of thermally conductive alumina. Compared with existing technologies, it has the following advantages: (1) This method for enhancing the toughness and thermal conductivity of thermally conductive alumina utilizes the high aspect ratio and surface functionalization of nano-thermal conductive fibers to effectively bridge the interface between alumina particles and the matrix, forming a synergistic thermal conductive network of "fiber-alumina-matrix". This reduces phonon scattering and significantly enhances thermal conductivity. By adding ultrafine nano-thermal conductive fibers to thermally conductive alumina powder, a special thermal conductive channel is formed with the organosilicon matrix, significantly reducing interfacial thermal resistance and thus greatly improving the overall thermal conductivity of the material. Adding 2-3.5% nano-thermal conductive fibers to thermally conductive silicone grease can increase thermal conductivity by 2.5-5 W / (m·K); adding 3-3.5% to thermally conductive silicone can increase thermal conductivity by 2.8-6 W / (m·K). This invention solves the bottleneck of thermal conductivity in traditional thermally conductive alumina caused by morphological defects and low α-phase conversion rate, and has both high cost-effectiveness and industrial feasibility.

[0019] (2) The method of enhancing the toughness and thermal conductivity of thermally conductive alumina significantly improves the impact resistance and fatigue resistance of the material by utilizing the stress dispersion and crack deflection effect of the fiber in the matrix, thereby greatly improving the toughness. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 The present invention provides five technical solutions: a method for enhancing the toughness and thermal conductivity of thermally conductive alumina, specifically including the following embodiments: Example 1: A method for enhancing the toughness and thermal conductivity of thermally conductive alumina, specifically including the following steps: S1. Preparation of nano-thermal conductive fibers: Nano-thermal conductive fibers of the required diameter are prepared by vapor deposition or electrospinning technology. The nano-thermal conductive fibers have a diameter of 120 nm and a length of 2.5 μm. The fiber surface is functionalized to enhance the interfacial bonding force with alumina and organosilicon matrix. The nano-thermal conductive fibers are boron nitride or silicon carbide, and their surface is coated with silane coupling agent. S2. Modification of thermally conductive alumina powder: The nano-thermal conductive fibers prepared in step S1 are mixed with thermally conductive alumina powder according to the mass ratio of silicone grease or silicone. Then, the nano-fibers are uniformly coated on the surface of alumina particles by mechanical grinding or ultrasonic dispersion technology to form a "fiber-alumina" composite structure. The amount of nano-thermal conductive fibers added in the thermally conductive silicone grease is 2.5%, and the amount of nano-thermal conductive fibers added in the thermally conductive silicone is 3.25%. The particle size of the thermally conductive alumina powder is 3μm, the α phase content is ≥99%, and the mechanical grinding is honeycomb milling. S3. Preparation of thermally conductive composite material: The composite powder modified in step S2 is added to the organosilicon matrix and thermally conductive silicone grease or silicone is formed by high-speed stirring and vacuum degassing process. Then, by controlling the orientation and distribution of nanofibers, continuous thermally conductive channels are constructed to reduce interfacial thermal resistance, thereby constructing a three-dimensional thermally conductive network. The organosilicon matrix is ​​silicone oil.

[0023] Example 2: A method for enhancing the toughness and thermal conductivity of thermally conductive alumina, specifically including the following steps: S1. Preparation of nano-thermal conductive fibers: Nano-thermal conductive fibers of the required diameter are prepared by vapor deposition or electrospinning technology. The nano-thermal conductive fibers have a diameter of 50 nm and a length of 1 μm. The fiber surface is functionalized to enhance the interfacial bonding force with alumina and organosilicon matrix. The nano-thermal conductive fibers are boron nitride or silicon carbide, and their surface is coated with silane coupling agent. S2. Modification of thermally conductive alumina powder: The nano-thermal conductive fibers prepared in step S1 are mixed with thermally conductive alumina powder according to the mass ratio of silicone grease or silicone. Then, the nano-fibers are uniformly coated on the surface of alumina particles by mechanical grinding or ultrasonic dispersion technology to form a "fiber-alumina" composite structure. The amount of nano-thermal conductive fibers added in the thermally conductive silicone grease is 2%, and the amount of nano-thermal conductive fibers added in the thermally conductive silicone is 3%. The particle size of the thermally conductive alumina powder is 1μm, the α phase content is ≥99%, and the mechanical grinding is honeycomb milling. S3. Preparation of thermally conductive composite material: The composite powder modified in step S2 is added to the organosilicon matrix. Thermally conductive silicone grease or silicone is formed by high-speed stirring and vacuum degassing process. Then, by controlling the orientation and distribution of nanofibers, continuous thermally conductive channels are constructed to reduce interfacial thermal resistance, thereby constructing a three-dimensional thermally conductive network. The organosilicon matrix is ​​silicone rubber.

[0024] Example 3: A method for enhancing the toughness and thermal conductivity of thermally conductive alumina, specifically including the following steps: S1. Preparation of nano-thermal conductive fibers: Nano-thermal conductive fibers of the required diameter are prepared by vapor deposition or electrospinning technology. The nano-thermal conductive fibers have a diameter of 200 nm and a length of 5 μm. The fiber surface is functionalized to enhance the interfacial bonding force with alumina and organosilicon matrix. The nano-thermal conductive fibers are boron nitride or silicon carbide, and their surface is coated with silane coupling agent. S2. Modification of thermally conductive alumina powder: The nano-thermal conductive fibers prepared in step S1 are mixed with thermally conductive alumina powder according to the mass ratio of silicone grease or silicone. Then, the nano-fibers are uniformly coated on the surface of alumina particles by mechanical grinding or ultrasonic dispersion technology to form a "fiber-alumina" composite structure. The amount of nano-thermal conductive fibers added in the thermally conductive silicone grease is 3.5%, and the amount of nano-thermal conductive fibers added in the thermally conductive silicone is 3.5%. The particle size of the thermally conductive alumina powder is 5μm, the α phase content is ≥99%, and the mechanical grinding is honeycomb milling. S3. Preparation of thermally conductive composite material: The composite powder modified in step S2 is added to the organosilicon matrix. Thermally conductive silicone grease or silicone is formed by high-speed stirring and vacuum degassing process. Then, by controlling the orientation and distribution of nanofibers, continuous thermally conductive channels are constructed to reduce interfacial thermal resistance, thereby constructing a three-dimensional thermally conductive network. The organosilicon matrix is ​​vinyl-terminated silicone resin.

[0025] Example 4: Preparation of thermal grease: Raw material ratio: Thermally conductive alumina powder (α phase, particle size 3μm): 92.0%; Nano-sized BN fibers (100 nm in diameter, 3 μm in length): 3.0%; Silicone oil matrix (viscosity 1000 cSt): 5.0%.

[0026] Preparation steps: Nano-BN fibers and alumina powder were mixed in a certain proportion and then dry-ground using a honeycomb mill (1000 rpm, 30 min).

[0027] The modified powder was added to the silicone oil and stirred at high speed (1500 rpm, 30 min), followed by vacuum degassing (-0.1 MPa, 30 min).

[0028] Thermal conductivity test: 3.34 W / (m·K) → increased to 5.84 W / (m·K) (an increase of 2.5 W / (m·K)).

[0029] Example 5: Preparation of thermally conductive silicone: Raw material ratio: Thermally conductive alumina powder (α phase, particle size 1 μm): 87.0%; Nano-SiC fibers (80 nm in diameter, 2 μm in length): 3.5%; Silicone rubber matrix (vinyl end cap): 9.5%.

[0030] Preparation steps: Nano-SiC fibers and alumina powder were ultrasonically dispersed (500W, 30min), then mixed with silicone rubber and vulcanized (150℃, 10min).

[0031] Thermal conductivity test: 2.10 W / (m·K) → increased to 6.90 W / (m·K) (an increase of 4.8 W / (m·K)).

[0032] In summary, this invention, through the high aspect ratio and surface functionalization of nano-thermal conductive fibers, effectively bridges the interface between alumina particles and the matrix, forming a synergistic thermal conductive network of "fiber-alumina-matrix," reducing phonon scattering and significantly enhancing thermal conductivity. By adding ultrafine nano-thermal conductive fibers to thermally conductive alumina powder, a special thermal conductive channel is formed with the organosilicon matrix, significantly reducing interfacial thermal resistance and thus greatly improving the overall thermal conductivity of the material. Adding 2-3.5% nano-thermal conductive fibers to thermally conductive silicone grease can increase thermal conductivity by 2.5-5 W / (m·K); adding 3-3.5% to thermally conductive silicone can increase thermal conductivity by 2.8-6 W / (m·K). This invention solves the bottleneck of thermal conductivity in traditional thermally conductive alumina caused by morphological defects and low α-phase conversion rate, possessing both high cost-effectiveness and industrial feasibility. By utilizing the stress dispersion and crack deflection effects of fibers in the matrix, the impact resistance and fatigue resistance of the material are significantly improved, resulting in a significant increase in toughness.

[0033] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for enhancing the toughness and thermal conductivity of thermally conductive alumina, characterized in that: Specifically, the following steps are included: S1. Preparation of nano-thermal conductive fibers: Nano-thermal conductive fibers of the required diameter are prepared by vapor deposition or electrospinning technology, and the fiber surface is functionalized to enhance the interfacial bonding force with alumina and organosilicon matrix. S2. Modification of thermally conductive alumina powder: The thermally conductive nanofibers prepared in step S1 are mixed with thermally conductive alumina powder according to the mass ratio of silicone grease or silicone. Then, the nanofibers are uniformly coated on the surface of alumina particles by mechanical grinding or ultrasonic dispersion technology to form a "fiber-alumina" composite structure. S3. Preparation of thermally conductive composite material: The composite powder modified in step S2 is added to the organosilicon matrix, and thermally conductive silicone grease or silicone is formed by high-speed stirring and vacuum degassing process. Then, by controlling the orientation and distribution of nanofibers, continuous thermally conductive channels are constructed to reduce interfacial thermal resistance, thereby constructing a three-dimensional thermally conductive network.

2. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: In step S1, the nano-thermal conductive fibers are boron nitride or silicon carbide, and their surfaces are coated with a silane coupling agent.

3. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: In step S2, the amount of nano-thermal conductive fibers added to the thermal grease is 2-3.5%.

4. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: In step S2, the thermally conductive alumina powder has a particle size of 1-5 μm and an α phase content of ≥99%.

5. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: The mechanical grinding in step S2 is a honeycomb mill.

6. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: In step S3, the organosilicon matrix is ​​one of silicone oil, silicone rubber, or vinyl-terminated silicone resin.

7. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: The nanofibers prepared in step S1 by vapor deposition or electrospinning have a diameter of 50-200 nm and a length of 1-5 μm.

8. The method for enhancing the toughness and thermal conductivity of thermally conductive alumina according to claim 1, characterized in that: In step S2, the amount of nano-thermal conductive fibers added to the thermally conductive silicone is 3-3.5%.

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