DENSIFICATION PROCESS AND PROPERTIES OF DIAMOND/SiC COMPOSITES BY PRESSURELESS VAPOUR INFILTRATION
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-04-04 |
| Journal | Ceramics - Silikaty |
| Authors | Xulei Wang |
| Institutions | Zhengzhou University of Aeronautics, University of Science and Technology Beijing |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research successfully developed high-density Diamond/SiC composites using a cost-effective, scalable Pressureless Si Vapour Infiltration (PVI) method, targeting advanced thermal management applications.
- Peak Performance: Optimal material composition (60 vol.% diamond) achieved a maximum thermal conductivity (TC) of 536 W·m-1·K-1.
- Mechanical Strength: The composite demonstrated superior mechanical properties, reaching a peak bending strength of 348.67 MPa.
- Thermal Matching: The material exhibits a low thermal expansion coefficient (TEC) ranging from 1.0 to 3.25 ppm·K-1 (50-500 °C), ensuring excellent thermal compatibility with silicon components.
- Densification Mechanism: A three-stage densification process was identified: Si-C reaction on the diamond surface, pore filling, and subsequent growth and accumulation of SiC nanowires.
- Microstructure for TC: The SiC phase forms a continuous three-dimensional skeleton embedded with diamond, establishing the preferred path for high heat conduction.
- Phase Purity: XRD analysis confirmed the presence of Diamond, SiC, and free Si, with no evidence of diamond graphitization under the optimized 1650 °C PVI conditions.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Peak Thermal Conductivity (TC) | 536 | W·m-1·K-1 | Composite with 60 vol.% diamond |
| Peak Bending Strength | 348.67 | MPa | Composite with 60 vol.% diamond |
| Thermal Expansion Coefficient (TEC) Range | 1.0 to 3.25 | ppm·K-1 | Measured range (50-500 °C) |
| PVI Infiltration Temperature | 1650 | °C | Used for Si vapor reaction |
| PVI Infiltration Time (Complete) | 60 | minutes | Time required for full densification |
| Green Body Forming Pressure | 30 | MPa | Applied during wet-mixing and forming |
| Diamond Raw Material TC | 1738 | W·m-1·K-1 | Single crystal, 148 µm average size |
| TEC Matching Temperature Range | 523-673 | K | Range where composite TEC matches Si TEC (2.5-2.6 ppm·K-1) |
| Ultimate Vacuum (PVI) | 1 | Pa | Vacuum furnace condition |
Key Methodologies
Section titled “Key Methodologies”- Raw Material Preparation: Single crystal diamond (148 µm, -100 mesh) was used as reinforcement. Phenolic resin (binder/carbon source), silicon powder (< 10 µm), and graphite powder (< 50 µm) were added.
- Green Body Formation: Raw materials were calculated based on desired volume fraction (40 to 80 vol.% diamond), wet-mixed, and formed into blanks (Φ = 30 x 3 mm2) under 30 MPa pressure.
- Pre-treatment (Pyrolysis): Green bodies were heat-treated at 1100 °C under high-purity argon protection to pyrolyze the phenolic resin and prepare the porous structure.
- Pressureless Vapour Infiltration (PVI): Si infiltration was performed in a vacuum furnace (1 Pa ultimate vacuum) at 1650 °C. Infiltration times of 30 and 60 minutes were tested, with 60 minutes ensuring complete densification.
- Densification Analysis: The mechanism was studied via FE-SEM/EDS on partially reacted samples (30 minutes infiltration), revealing three stages: Si-C reaction on diamond, pore filling, and SiC nanowire growth.
- Property Measurement:
- Density (ρ) via Archimedes drainage method.
- Thermal Diffusivity (α) via Netzsch LFA 467 HyperFlash®.
- Specific Heat Capacity (Cp) calculated using the compound rule.
- Thermal Conductivity (λ) calculated using the formula: λ = ρ · α · Cp.
- Bending strength measured using a WDW-100 electron universal testing machine.
Commercial Applications
Section titled “Commercial Applications”The superior thermophysical and mechanical properties of the Diamond/SiC composites make them ideal candidates for high-performance electronic and structural applications:
- High-Power Electronic Packaging: Used as heat dissipation materials and substrates for high-power components and chips, where high TC is critical for reliability.
- Advanced Communication Systems: Applicable in civil 5G communication units, which require highly integrated and miniaturized components with efficient heat removal.
- Military and Aerospace Devices: Suitable for high-power devices such as military radar, lasers, and high-power microwave systems where thermal stability and high strength are mandatory.
- New Energy Vehicles (NEVs): Potential use in power electronic components and heat exchangers within NEVs.
- Semiconductor Manufacturing: Candidate material for advanced semiconductor substrates due to high TC and stable chemical properties.
View Original Abstract
Diamond/silicon carbide (SiC) composites with different diamond contents were prepared by pressureless silicon (Si) vapour infiltration. The densification process of the Si infiltration of the composites was analysed. Three densification process were put forward. The densification degree of the composites was determined by the concentration of the Si vapour. The three-dimensional skeleton of the SiC composite embedded with diamond constitutes the best path for the heat conduction of composites. With an increase of diamond content, the thermal conductivity (TC) of the composites increases at first and then decreases, reaching a maximum value at a diamond 60 vol.%, with the TC of 536 W/(m·K). In the temperature range of 50~500 °C, the thermal expansion coefficient of the composite varies from 1.0 to 3.25 ppm/K. The bending strength of the composite reached a maximum value of 334.52 MPa. The composite has a low thermal expansion coefficient, superior thermal conductivity and bending strength, and can be used as an alternative thermal management material.