Investigation of the Fabrication of Diamond/SiC Composites Using α-Si3N4/Si Infiltration

At a Glance

Metadata	Details
Publication Date	2023-09-17
Journal	Materials
Authors	Bo Xing, Yingfan Zhang, Jinzhui Zhao, Jianyu Wang, Guoqin Huang
Institutions	Huaqiao University, Zhengzhou Institute of Machinery
Citations	3
Analysis	Full AI Review Included

Executive Summary

This analysis summarizes the fabrication and optimization of Diamond/Silicon Carbide (Dia/SiC) composites using pressureless silicon infiltration, focusing on achieving high density and solving critical manufacturing adhesion issues.

Core Value Proposition: Successful preparation of high-density Dia/SiC composites (ideal for electronic packaging/heat sinks) using a cost-effective, low-pressure vacuum infiltration method, avoiding expensive High-Temperature High-Pressure (HTHP) sintering.
Optimal Diamond Packing: A multiscale diamond ratio optimization model, based on the Dinger-Funk particle stacking theory, determined the optimal volume ratio for D20, D50, and D90 µm particles to be 1:3:6.
Performance Metrics: The optimized composite (Dia/SiC-8) achieved a maximum density of 2.73 g/cm³ and a minimum porosity of 0.6%.
Anti-Adhesion Solution: Adhesion of the product to molten silicon was effectively prevented by using a mixed bedding powder of alpha-Si₃N₄ and Si.
Infiltration Parameters: Optimal low-pressure siliconizing was performed at 1600 °C under a high vacuum (0.01 Pa).
Mechanism of Action (Bedding Powder): Alpha-Si₃N₄ acts as a silicon source and reacts at high temperatures to form silicon carbide (SiC), preventing the liquid silicon from wrapping and adhering to the sample. Optimal Si content in the bedding mixture was 60-70%.

Technical Specifications

Parameter	Value	Unit	Context
Optimal Diamond Volume Ratio	1:3:6	D20:D50:D90	Based on Dinger-Funk particle stacking theory.
Highest Density Achieved	2.73	g/cm³	Dia/SiC-8 composite (8% reduction ratio).
Lowest Porosity Achieved	0.6	%	Dia/SiC-8 composite.
Optimal Sintering Temperature	1600	°C	Vacuum infiltration sintering.
Sintering Vacuum Degree	0.01	Pa	Required for low-pressure siliconizing.
Carbonization Temperature	1100	°C	Preform preparation in Argon atmosphere.
Hot Pressing Force	50	kN	Used for pottery blank fabrication (at 100 °C).
Raw Material Volume Ratio	40:20:20:20	Dia:Graphite:Si:Resin	Used to prepare the initial composite mixture.
Optimal Bedding Powder Si Content	60-70	%	Silicon content in alpha-Si₃N₄/Si mixture.
Si₃N₄ Content Change (1500 °C to 1700 °C)	28% to 12%	%	Decrease in buried powder composition.

Key Methodologies

The Dia/SiC composites were prepared using a two-step process: prefabricated porous preform creation followed by vacuum infiltration sintering.

Raw Material Preparation:
- Diamond particles (D20, D50, D90 µm) were mixed at the optimized 1:3:6 volume ratio.
- The composite mixture consisted of Diamond, Graphite, Silicon powder (5 µm average size), and Phenolic Resin binder at a 40:20:20:20 volume ratio.
Pottery Blank Molding:
- The mixture was hot-pressed using constant volume molding at 100 °C and 50 kN.
- The final density and porosity were controlled by regulating the feeding amount, corresponding to reduction ratios (h/H) of 0% (Dia/SiC-0) to 10% (Dia/SiC-10).
Preform Carbonization:
- The pottery blank was carbonized in an argon furnace at 1100 °C. This process converted the phenolic resin into activated carbon, providing strength and additional carbon source for SiC formation.
Bedding Powder System:
- A mixed powder of alpha-Si₃N₄ and elemental Silicon (Si) was used as the bedding material, with Si content optimized at 60-70%.
- Function: The alpha-Si₃N₄ reacts at high temperatures to form SiC, preventing the liquid silicon from adhering to the sample surface, a common issue with pure Si bedding.
Vacuum Infiltration Sintering:
- The preform was buried in the mixed bedding powder inside a graphite crucible.
- Sintering was performed in a high-temperature vacuum furnace (ZT-40-21Y) at a vacuum degree of 0.01 Pa.
- Optimal sintering temperature was 1600 °C, allowing molten Si to spontaneously infiltrate the porous preform via capillary pressure and react with carbon to form the SiC matrix.

Commercial Applications

Dia/SiC composites are highly valued in industries requiring superior thermal management due to their high thermal conductivity and low coefficient of thermal expansion (CTE).

Electronic Packaging: Used extensively as high-efficiency heat sinks and thermal spreaders for high-power density electronic equipment (e.g., CPUs, power modules, LEDs).
High Heat Flux Devices: Applications in situations demanding rapid and efficient heat dissipation, such as high-frequency microwave devices and laser diode arrays.
Aerospace and Defense: Components requiring materials with high strength, low density, and excellent thermal stability under extreme conditions.
Substrate Materials: Used as substrates for mounting semiconductor chips where thermal mismatch must be minimized (low CTE is critical).
Advanced Ceramics: Fabrication of dense, strong ceramic matrix composites for structural applications where wear resistance and high thermal performance are necessary.

View Original Abstract

Diamond/SiC (Dia/SiC) composites possess excellent properties, such as high thermal conductivity and low thermal expansion coefficient. In addition, they are suitable as electronic packaging materials. This study mainly optimized the diamond particle size packing and liquid-phase silicon infiltration processes and investigated a method to prevent the adhesion of the product to molten silicon. Based on the Dinger-Funk particle stacking theory, a multiscale diamond ratio optimization model was established, and the volume ratio of diamond particles with sizes of D20, D50, and D90 was optimized as 1:3:6. The method of pressureless silicon infiltration and the formulas of the composites were investigated. The influences of bedding powder on phase composition and microstructure were studied using X-ray diffraction and scanning electron microscopy, and the optimal parameters were obtained. The porosity of the preform was controlled by regulating the feeding amount through constant volume molding. Dia/SiC-8 exhibited the highest density of 2.73 g/cm3 and the lowest porosity of 0.6%. To avoid adhesion between the sample and buried powder with the bedding silicon powder, a mixed powder of α-Si3N4 and silicon was used as the buried powder and the related mechanisms of action were discussed.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma16186252

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