High-thermal-conductivity BN-based TiB2 composite conductive ceramic and preparation method thereof

Abstract

The high-thermal-conductivity BN-based TiB2 composite conductive ceramic is prepared from the following materials in percentage by mass: 57-85% of boron nitride, 12-38% of titanium boride and 3-5% of an interface modifier, and the preparation method of the high-thermal-conductivity BN-based TiB2 composite conductive ceramic comprises the steps of dry mixing, forming and hot pressed sintering. Through collaborative optimization of the components and the process, the triple characteristics of high heat conduction, controllable electric conduction and ultrahigh thermal shock resistance are achieved, BN serves as a main phase, the content of TiB is optimized to ensure the connectivity of a conductive network, the thermal shock resistance is improved through the high heat conduction and low thermal expansion characteristics of BN, and the thermal shock resistance delta T is larger than or equal to 1000 DEG C; the dry mixing process controls TiB particles to be distributed in gaps of BN lamellas, a three-dimensional conductive network is formed, TiB is directionally distributed, solvent pollution is avoided, the anisotropic structure of BN is reserved, the heat conductivity is improved, the volume resistivity is adjustable, the requirements of different scenes are met through the TiB content gradient design, and the application field is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of functional ceramic materials, and specifically relates to a high thermal conductivity BN-based TiB2 composite conductive ceramic and a preparation method thereof. Background Art

[0002] Evaporation boat is a general term for all evaporation vessels, which are usually used in vacuum evaporation coating processes as a container for holding evaporation source materials and heating them for evaporation. However, traditional evaporation boat materials have the following defects: 1. Graphite evaporation boats are easily oxidized at high temperatures and have a short lifespan; TiB2-C materials have good electrical conductivity but high brittleness and insufficient thermal shock resistance; 2. Bottleneck of BN-based composite materials: Existing BN-based composite materials (such as BN-AlN) have high insulation properties and are difficult to be directly used in conductive scenarios; 3. Mixing process problems: Wet ball milling introduces solvent contamination and easily leads to the destruction of BN flake structure, affecting the anisotropic thermal conductivity of the material. Summary of the invention

[0003] The purpose of the present invention is to provide a composite ceramic with BN as the main phase and a uniform distribution of TiB2 conductive network achieved through a dry mixing process, so as to solve the problems of high brittleness, poor thermal shock resistance and limited insulation of traditional conductive ceramics.

[0004] The technical solution of the present invention: A high thermal conductivity BN-based TiB2 composite conductive ceramic, composed of the following materials by mass percentage: Boron Nitride (BN) 57-85% Titanium boride (TiB2) 12-38% Interface modifier 3-5%.

[0005] Further preferably, the boron nitride is in the form of flakes, with an aspect ratio of >50 and a purity of ≥99%.

[0006] Further preferably, the titanium boride has a particle size of 0.5-5 μm and a purity of ≥99.5%.

[0007] Further preferably, the interface modifier is at least one of nano-Si3N4, h-BN-coated TiB2 particles or chopped carbon fibers.

[0008] A method for preparing a high thermal conductivity BN-based TiB2 composite conductive ceramic comprises the following steps: 1. Dry Mixing Adding boron nitride, titanium boride, an interface modifier, and a dispersant into a three-dimensional motion mixer or a V-type mixer to mix the materials to obtain a mixture; 2. Molding The mixed material obtained in step 1 is subjected to molding treatment; 3. Hot Pressing Sintering The formed blank obtained in step 2 is placed in a hot pressing sintering furnace and subjected to segmented sintering treatment to obtain the high thermal conductivity BN-based TiB2 composite conductive ceramic of the present invention.

[0009] Further preferably, the mixing speed is 10-30 rpm and the mixing time is 1-4 h.

[0010] Further preferably, the dispersant is stearic acid, and the added amount is 0.1-0.5% of the total amount of boron nitride, titanium boride, and interface modifier. The purpose of adding the dispersant is to avoid agglomeration of BN sheets. Further preferably, the forming is isostatic pressing or tape casting, and the pressure during the isostatic pressing treatment is 150-200 MPa.

[0011] Further preferably, the segmented sintering includes the following steps: low temperature section: under N2 atmosphere, heating to 600~900℃, keeping warm for 1 hour, removing organic impurities, high temperature section: pressure of 25-35 Mpa, keeping pressure for 2~3 hours, Ar atmosphere, heating to 1850~2100℃, heating rate of 3~10℃ / min, keeping warm for 2~6 hours, promoting TiB2-BN interface bonding. Beneficial effects of the invention: The invention realizes the triple characteristics of "high thermal conductivity + controllable electrical conductivity + ultra-high thermal shock resistance" through coordinated optimization of components and processes: taking BN (>50%) as the main phase, optimizing the TiB2 content to ensure the connectivity of the conductive network, and utilizing the high thermal conductivity (≥300 W / m·K) and low thermal expansion characteristics of BN to improve the thermal shock resistance, and the thermal shock resistance can reach ΔT≥1000℃; controlling the distribution of TiB2 particles in the gaps between BN layers through a dry mixing process to form a three-dimensional conductive network, and directional distribution of TiB2 to break through the performance ceiling of traditional composite materials; the dry mixing process avoids solvent contamination, retains the anisotropic structure of BN, improves thermal conductivity, and has adjustable volume resistivity (10⁻³~10⁻¹ Ω·cm); and meeting the needs of different scenarios through the TiB2 content gradient design, expanding the application field, and being suitable for extreme working conditions such as high-temperature vacuum evaporation coating (such as evaporation boats) and semiconductor heaters that require high thermal conductivity, electrical conductivity and thermal shock resistance, effectively solving the material problems of high-end equipment such as evaporation boats and semiconductor heaters. DETAILED DESCRIPTION

[0012] The present invention is further described below with reference to the embodiments.

[0013] Example 1 (Evaporation Boat Application) Component composition: BN 70%, TiB2 26%, nano-Si3N4 4%; process: three-dimensional mixing (20 rpm / 2h) → tape casting → sintering. The sintering process is as follows: under N2 atmosphere, the room temperature is raised to 600℃, the heating rate is 8℃ / min, and the temperature is kept for 1h. The temperature is raised from 600℃ to 1950℃ at a heating rate of 5℃ / min, and sintered at 1950℃ (Ar atmosphere) for 4h. Interface modifier: Nano-Si3N4 reacts with BN at high temperature to form a Si-BN interface layer, which enhances the bonding strength of the two. The performance of the prepared BN-based TiB2 composite conductive ceramics was tested: Resistivity: 9×10 -3 Ω·cm (parallel to the BN sheet direction); Thermal conductivity: 270 W / m·K (in-plane direction); Evaporation coating life: 300h continuous operation without cracking (compared with 80h for graphite boat).

[0014] Example 2 (Evaporation Boat Application) Composition: BN 61%, TiB2 35%, interface modifier: 4% (Al powder and Y2O3 are mixed in a ratio of 3:2), three-dimensional mixing (20 rpm / 2h) → isostatic pressing → hot pressing sintering, the pressure during isostatic pressing is 180MPa, and the hot pressing sintering process is as follows: under N2 atmosphere, room temperature rises to 600℃, the heating rate is 8℃ / min, and the temperature is kept for 1h, and the temperature is raised from 600℃ to 1950℃, the heating rate is 5℃ / min, and sintered at 1850℃ (Ar atmosphere) for 3h, and the pressure is 35MPa. Mold treatment: The surface of the graphite mold is pre-coated with a boron nitride isolation layer to prevent adhesion.

[0015] Performance test results: Resistivity: 5×10 -3 Ω·cm.

[0016] Thermal conductivity: 280 W / m·K (in-plane direction) Resistance to aluminum liquid corrosion: The continuous working life in 800℃ aluminum liquid is up to 400 hours (the traditional graphite boat is about 80 hours, which is 4 times higher).

[0017] Example 3 Composition: BN 85%, TiB2 12%, interface modifier 3% (Y2O3 single-phase sintering aid), V-type mixing (20 rpm / 2h) → isostatic pressing (150MPa) → hot pressing sintering process: under N2 atmosphere, room temperature rises to 600℃, heating rate is 8℃ / min, keep warm for 1h, 600℃ to 1950℃, heating rate is 5℃ / min, sintering at 1950℃ (Ar atmosphere) for 3h, pressure: 25MPa. Mold treatment: The surface of the graphite mold is pre-coated with a boron nitride isolation layer to prevent adhesion.

[0018] Performance test results: Resistivity: 12×10 -3 Ω·cm.

[0019] Resistance to aluminum liquid corrosion: The service life in 800℃ aluminum liquid is up to 500 hours (5 times that of graphite boat).

[0020] High temperature stability: thermal expansion coefficient ≤3×10⁻ at 1400℃ 6 / K, excellent thermal shock resistance (no cracking after 100 cycles).

[0021] Example 4 (Applications with high conductivity requirements) Composition: BN 60%, TiB2 37%, h-BN coated TiB2 3%; Process: V-type mixing (15rpm / 3h) → isostatic pressing (200MPa) → hot pressing sintering. The hot pressing sintering process is as follows: under N2 atmosphere, the room temperature is raised to 600℃, the heating rate is 8℃ / min, and the temperature is kept for 1h. The temperature is raised from 600℃ to 2050℃, the heating rate is 5℃ / min, and sintered at 2050℃ (Ar atmosphere) for 3h. The pressure is: 35MPa.

[0022] Performance test results: resistivity 8×10⁻ 4 Ω·cm, flexural strength 620MPa. Example 5 Components: BN 60%, TiB2 35%, interface modifier 5% (Al powder and carbon nanotubes composite, ratio 3:2).

[0023] Process: V-type mixing (15rpm / 3h) → isostatic pressing (180MPa) → hot pressing sintering. The hot pressing sintering process is as follows: under N2 atmosphere, the room temperature is raised to 600℃, the heating rate is 8℃ / min, and the temperature is kept for 1h. The temperature is raised from 600℃ to 2000℃ at a heating rate of 5℃ / min, and sintered at 2000℃ (Ar atmosphere) for 3h. The pressure is 30MPa.

[0024] Performance Testing and Results Volume resistivity: 3×10⁻³ Ω·cm (close to the theoretical value of pure TiB2, suitable for precise control of semiconductor coating); High temperature stability: resistivity fluctuation <5% at 1400°C, thermal expansion coefficient 4.8×10⁻ 6 / K (excellent thermal shock resistance).

[0025] Example 6 Composition: BN 57%, TiB2 38%, interface modifier 5% (Al powder and Y2O3 composite, ratio 4:1).

[0026] Process: V-type mixing (15rpm / 3h) → isostatic pressing (200MPa) → hot pressing sintering (35MPa). The hot pressing sintering process is as follows: under N2 atmosphere, the room temperature is raised to 600℃, the heating rate is 8℃ / min, and the temperature is kept for 1h. The temperature is then raised from 600℃ to 1850℃ at a heating rate of 5℃ / min. Sintering is carried out at 1850℃ (Ar atmosphere) for 2h, and the pressure is 35MPa.

[0027] Performance Testing and Results Volume resistivity: 1.2×10⁻³ Ω·cm (close to the conductivity of metal aluminum, meeting the needs of large current rapid evaporation); Resistance to aluminum liquid corrosion: The continuous working life in 800℃ aluminum liquid is up to 450 hours (the traditional graphite boat is about 80 hours, which is 5 times higher).

[0028] The present invention uses BN (content>50%) as the main phase, optimizes the TiB2 content to ensure the connectivity of the conductive network, and breaks through the performance ceiling of traditional composite materials through a dry mixing process; the components and processes are synergistically optimized to achieve the triple characteristics of "high thermal conductivity + controllable conductivity + ultra-high thermal shock resistance", and the thermal shock resistance can reach ΔT≥1000℃, and the volume resistivity is adjustable (10⁻³~10⁻¹ Ω·cm); it effectively solves the material problems of high-end equipment such as evaporation boats and semiconductor heaters, and expands the application field. It is suitable for high-temperature vacuum evaporation coating (such as evaporation boats, which use high thermal conductivity to achieve rapid heat absorption, and the TiB2 conductive network is directly powered on for heating. After vacuum coating tests, the life of the evaporation boat is 3-5 times longer than that of traditional graphite materials), semiconductor equipment (wafer heating plates, electrostatic chuck (ESC) substrates, nuclear fusion reactor first wall materials (resistant to high temperature plasma scouring and neutron irradiation), etc.

Claims

1. A high thermal conductivity BN-based TiB2 composite conductive ceramic, characterized in that: By mass percentage, it is composed of the following materials: Boron Nitride (BN) 57-85% Titanium boride (TiB2) 12-38% Interface modifier 3-5%.

2. A high thermal conductivity BN-based TiB2 composite conductive ceramic as claimed in claim 1, characterized in that: The boron nitride is in flake form, with an aspect ratio of >50 and a purity of ≥99%.

3. A high thermal conductivity BN-based TiB2 composite conductive ceramic as claimed in claim 1, characterized in that: The titanium boride has a particle size of 0.5-5 μm and a purity of ≥99.5%.

4. A high thermal conductivity BN-based TiB2 composite conductive ceramic as claimed in claim 1, characterized in that: The interface modifier is at least one of nano-Si3N4, h-BN-coated TiB2 particles or chopped carbon fibers.

5. The method for preparing a high thermal conductivity BN-based TiB2 composite conductive ceramic according to claim 1, characterized in that: The steps include:

1. Dry Mixing Adding boron nitride, titanium boride, an interface modifier, and a dispersant into a three-dimensional motion mixer or a V-type mixer to mix the materials to obtain a mixture; 2. Molding The mixed material obtained in step 1 is subjected to molding treatment; 3. Hot Pressing Sintering The formed blank obtained in step 2 is placed in a hot pressing sintering furnace and subjected to segmented sintering treatment to obtain the high thermal conductivity BN-based TiB2 composite conductive ceramic of the present invention.

6. The method for preparing a high thermal conductivity BN-based TiB2 composite conductive ceramic according to claim 1, characterized in that: The mixing speed is 10-30 rpm, and the mixing time is 1-4 h.

7. The method for preparing a high thermal conductivity BN-based TiB2 composite conductive ceramic according to claim 1, characterized in that: The dispersant is stearic acid, and the added amount is 0.1-0.5% of the total amount of boron nitride, titanium boride and interface modifier. The purpose of adding the dispersant is to prevent the agglomeration of BN sheets.

8. A method for preparing a high thermal conductivity BN-based TiB2 composite conductive ceramic capacitor as claimed in claim 1, characterized in that The molding is isostatic pressing or tape casting, and the pressure during isostatic pressing is 150-200 MPa.

9. The method for preparing a high thermal conductivity BN-based TiB2 composite conductive ceramic according to claim 1, characterized in that: The segmented sintering includes the following steps: low temperature stage: in N2 atmosphere, heating to 600-900°C, keeping warm for 1 hour, removing organic impurities; high temperature stage: pressure of 25-35 MPa, keeping pressure for 2-3 hours, Ar atmosphere, heating to 1850-2100°C, heating rate of 3-10°C / min, keeping warm for 2-6 hours, promoting TiB2-BN interface bonding.