The Influence of the Carbide-Forming Metallic Additives (W, Mo, Cr, Ti) on the Microstructure and Thermal Conductivity of Copper–Diamond Composites
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-05-26 |
| Journal | Journal of Composites Science |
| Authors | Arina V. Ukhina, Dina V. Dudina, Maksim A. Esikov, Д. А. Самошкин, С. В. Станкус |
| Institutions | Lavrentyev Institute of Hydrodynamics, Institute of Solid State Chemistry and Mechanochemistry |
| Citations | 7 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”- Core Problem Addressed: Low wettability of diamond particles by the copper (Cu) matrix, leading to high interfacial thermal resistance and reduced thermal conductivity (TC) in Cu-Diamond (Cu-D) composites.
- Solution & Key Finding: Introducing carbide-forming metallic additives (W, Mo, Cr, Ti) into the Cu matrix significantly improved wettability; Titanium (Ti) was the most effective element.
- Maximum Performance: The optimal composite (Cu-0.7 vol% Ti) achieved a maximum TC of 420 ± 21 W m-1 K-1, which is 2.8 times higher than the baseline unmodified Cu-D composite (~150 W m-1 K-1).
- Mechanism of Improvement: Ti’s high solubility in Cu allows it to diffuse through the matrix to the diamond surface, forming a stable titanium carbide (TiC) layer that ensures close contact and low thermal resistance.
- Processing Advantage: Spark Plasma Sintering (SPS) consistently produced higher TC materials (420 W m-1 K-1) compared to Hot Pressing (HP) (178 W m-1 K-1) for the optimal Ti composition, likely due to enhanced diffusion kinetics from electric current passage.
- Concentration Sensitivity: Thermal conductivity is highly sensitive to additive concentration; increasing Ti content from 0.7 vol% to 2 vol% caused the TC to drop sharply from 420 W m-1 K-1 to 67 W m-1 K-1 due to the formation of thick, thermally insulating carbide coatings.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Thermal Conductivity (TC) | 420 ± 21 | W m-1 K-1 | Cu-0.7 vol% Ti composite (SPS) |
| Cr-Modified TC | 385 ± 19 | W m-1 K-1 | Cu-0.7 vol% Cr composite (SPS) |
| Baseline TC (Unmodified Cu-D) | ~150 | W m-1 K-1 | Reference value [28] |
| Diamond Concentration | 50 | vol% | Constant across all samples |
| Optimal Ti Additive Concentration | 0.7 | vol% | Yields maximum TC |
| Sintering Temperature (SPS/HP) | 920 | °C | Constant processing temperature |
| Uniaxial Pressure (SPS/HP) | 40 | MPa | Constant consolidation pressure |
| SPS Atmosphere | 10 | Pa | Forevacuum conditions |
| HP Atmosphere | 0.1 | MPa | Argon gas |
| TiC Gibbs Free Energy (ΔG°) | -87 | kJ/mol atoms | Most stable carbide formed at 920 °C |
| Maximum Cu Lattice Parameter | 3.623 ± 0.002 | Angstrom | Observed in Cu-2 vol% Ti (HP), indicating Ti dissolution |
| Diamond Particle Size | 100 | µm | Raw material specification (MBD10) |
Key Methodologies
Section titled “Key Methodologies”- Material Preparation: Powders of synthetic diamond (100 µm) and copper (40 µm) were mixed with carbide-forming additives (W, Mo, Cr, Ti) at concentrations ranging from 0.15 to 2.0 vol%.
- Hot Pressing (HP): Samples were consolidated at 920 °C for 15 minutes under a uniaxial pressure of 40 MPa in an argon atmosphere (0.1 MPa).
- Spark Plasma Sintering (SPS): Samples were consolidated at 920 °C for 3 or 10 minutes under a uniaxial pressure of 40 MPa in a forevacuum atmosphere (10 Pa). Heating was achieved via direct electric current passage.
- Microstructure Analysis: Scanning Electron Microscopy (SEM) was used to examine the fracture surfaces, focusing on pore formation and the quality of the copper-diamond interface wetting.
- Phase Composition Analysis: X-ray Diffraction (XRD) was performed to identify crystalline phases (Cu, Diamond, Additive, Carbides) and to measure the copper lattice parameter, confirming the dissolution of Ti into the Cu matrix.
- Thermal Property Measurement: Thermal diffusivity (α) was measured using the laser flash method (LFA-427). Thermal conductivity (λ) was calculated using the measured density and the specific heat capacity estimated by the rule of mixtures.
Commercial Applications
Section titled “Commercial Applications”The development of high-TC, low-CTE copper-diamond composites is critical for industries requiring advanced thermal management solutions:
- Microelectronic Heat Sinks: Manufacturing high-efficiency heat dissipation elements for high-performance computing (CPUs, GPUs), replacing traditional copper and aluminum sinks.
- High-Power Semiconductor Substrates: Use as substrates for wide-bandgap devices (e.g., GaN and SiC power electronics) where matching the low coefficient of thermal expansion (CTE) of the semiconductor while maximizing heat removal is essential.
- LED and Laser Diode Packaging: Providing thermally stable and conductive packaging materials to manage heat flux in high-brightness LED arrays and industrial laser systems.
- Aerospace and Defense Systems: Components for radar systems and avionics that require robust, lightweight materials capable of operating under high thermal loads.
- Abrasive and Cutting Tools: Utilizing the composite’s high hardness and thermal stability in specialized cutting inserts and abrasive materials.
View Original Abstract
In this study, carbide-forming metallic additives (W, Mo, Cr, Ti) were introduced into the copper matrix to improve the wettability of diamond particles in the copper-diamond composites. The samples were prepared by Spark Plasma Sintering (SPS) and Hot Pressing (HP) at 920 °C. The phase composition, microstructure and thermal conductivity of the samples were investigated. The influence of the carbide-forming additive concentration, the sintering method as well as the nature of the metal introduced into the copper matrix on the thermal conductivity of copper-diamond composites was determined. Titanium ensured a more significant wettability improvement at the copper-diamond interface. This is due to its higher solubility in copper in comparison with other metals (W, Mo, Cr) and the possibility of its diffusion through the copper matrix to the diamond surface resulting in the formation of a closer contact at the copper-diamond interface.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
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