First-principles calculation of diamond/Al interface properties and study of interface reaction
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Ping Zhu, Qiang Zhang, Huasong Gou, Pingping Wang, Puzhen Shao |
| Citations | 8 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Value Proposition: This research combines Density Functional Theory (DFT) and experimental methods to systematically analyze and optimize the interface properties and long-term stability of diamond/aluminum (Al) composites for advanced thermal management applications.
- Interface Superiority: DFT calculations confirm that the Diamond(100)/Al(111) interface is significantly stronger, exhibiting 41% higher adhesion work (5.85 J/m2) compared to the Diamond(111)/Al(111) interface (4.14 J/m2).
- Bonding Mechanism: The enhanced bonding on the (100) face is driven by greater charge transfer and a stronger tendency for Al-C chemical bond formation, which promotes C-C bond formation at the interface.
- Interface Reaction Product: The reaction product, aluminum carbide (Al4C3), preferentially forms on the highly reactive Diamond{100} surface, confirmed by experimental observation of needle-like pits after etching.
- Stability Degradation: While Al4C3 initially improves mechanical bonding, its susceptibility to hydrolysis during heat-moisture treatment (70 °C, 90% R.H.) severely compromises composite integrity.
- Performance Loss: After 60 days of heat-moisture treatment, the composite experienced a 29.9% decrease in thermal conductivity and a 40.1% reduction in bending strength.
- Design Guidance: Inhibiting Al4C3 formation and promoting selective, stable bonding on the less-reactive Diamond{111} face is crucial for ensuring long-term reliability in complex, humid environments.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond(100)/Al(111) Adhesion Work (Wad) | 5.85 | J/m2 | Calculated (unmodified interface) |
| Diamond(111)/Al(111) Adhesion Work (Wad) | 4.14 | J/m2 | Calculated (unmodified interface) |
| Modified (Al-C bond) Wad | 9.72 | J/m2 | Calculated (Diamond(100)/Al(111) with Al-C bond) |
| Initial Thermal Conductivity (λ) | 610.2 | W/(m·K) | Composite average (before treatment) |
| Thermal Conductivity Decrease | 29.9 | % | After 60 days heat-moisture treatment |
| Initial Bending Strength | 247.6 | MPa | Composite average (before treatment) |
| Bending Strength Decrease | 40.1 | % | After 60 days heat-moisture treatment |
| Diamond Lattice Constant | 3.568 | Angstrom | Calculated value |
| Aluminum Lattice Constant | 4.047 | Angstrom | Calculated value |
| Optimal Al-C Bond Length (in Al4C3) | 1.94 | Angstrom | Calculated value |
| Diamond(100)/Al(111) Mismatch | 6.8 | % | Lattice mismatch |
| Diamond(111)/Al(111) Mismatch | 1.3 | % | Lattice mismatch |
| Heat-Moisture Test Temperature | 70 | °C | Environmental testing condition |
| Heat-Moisture Test Humidity | 90 | % R.H. | Environmental testing condition |
| Composite Reinforcement Volume Fraction | ~60 | % | Diamond particle content |
Key Methodologies
Section titled âKey MethodologiesâThe study utilized a combined computational and experimental approach to characterize the composite interfaces:
I. First-Principles Calculation (DFT)
Section titled âI. First-Principles Calculation (DFT)â- Software: Materials Studio 2017 (CASTEP module).
- Functional: Generalized Gradient Approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE) form.
- Pseudopotentials: Ultrasoft pseudopotentials.
- Convergence Criteria:
- Energy: 1 x 10-5 eV/atom.
- Force: less than 0.03 eV/Angstrom.
- Interface Models: Diamond(111)/Al(111) and Diamond(100)/Al(111) were modeled, including a 15 Angstrom vacuum layer.
- Analysis: Calculation of adhesion work (Wad), differential charge density, partial density of states (PDOS), and atomic orbital population analysis.
II. Composite Fabrication
Section titled âII. Composite Fabricationâ- Method: Vacuum Gas Pressure Infiltration.
- Raw Materials:
- Matrix: Industrial pure aluminum (99.99% mass fraction).
- Reinforcement: MBD4 synthetic monocrystalline diamond (100 ”m particle size).
- Process Parameters: Infiltration temperature of 700 °C for 30 minutes.
III. Characterization and Testing
Section titled âIII. Characterization and Testingâ- Microstructure Analysis:
- Scanning Electron Microscopy (SEM, Helios Nanolab600i) for overall morphology and Al4C3 etch pits.
- Atomic Force Microscopy (AFM, Dimension Icon) for surface roughness (Ra) of diamond faces.
- Transmission Electron Microscopy (TEM, Talos F200x) for high-resolution interface structure and phase relationships.
- Thermal Property Testing: Thermal diffusivity measured using LFA467Nanoflash. Thermal conductivity (λ) calculated using the mixing rule (λ = k * Ï * c).
- Mechanical Testing: Three-point bending strength measured using an INSTRON-5569 electronic universal testing machine.
- Environmental Stability Testing:
- Method: Heat-Moisture Treatment (SMC-150PF constant temperature and humidity chamber).
- Conditions: 70 °C, 90% R.H.
- Duration: Tested at intervals up to 60 days.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings directly impact the reliability and design of high-performance materials used in demanding thermal environments:
- High-Power Electronics Packaging: Designing stable substrates and heat sinks for devices like Insulated Gate Bipolar Transistors (IGBTs) and high-frequency power modules where thermal cycling and humidity exposure are common.
- Advanced Thermal Management: Manufacturing composite materials with predictable long-term thermal performance (e.g., thermal spreaders) for CPUs, GPUs, and other microelectronic components.
- Aerospace and Defense Systems: Utilizing lightweight, high-conductivity composites in systems exposed to varying atmospheric conditions, requiring resistance to moisture-induced degradation.
- Electric Vehicle (EV) Power Systems: Developing reliable cooling components for EV battery packs and inverters, where stability against environmental factors is paramount for safety and longevity.
- Material Interface Engineering: Providing a theoretical basis for surface modification techniques (e.g., pre-coating diamond particles) aimed at suppressing the formation of brittle, hydrolyzable phases like Al4C3 and promoting stable, non-reactive interfaces (e.g., favoring the Diamond{111} face).
View Original Abstract
First-principles calculation and experimental methods are used to study the interfacial properties and reaction of diamond/Al composites. Based on the first-principles method, the interfacial adhesion work (<i>W</i><sub>ad</sub>), electronic structure and charge transfer of diamond/Al models are calculated systematically. The results show that the adhesion work of diamond(100)/Al(111) is 41% higher than that of diamond(111)/Al(111), therefore, the interface bonding of diamond(100)/Al(111) interface is stronger. According to the analysis of the electronic structure, there are more charges transferring at the diamond(100)/Al(111) interface, and the high charge density is distributed on the side of C atoms. The redistribution of charges at the interface is conducive to the formation of AlâC bond, so that the tendency of forming AlâC bonds is greater. The introduction of AlâC bond can promote the formation of CâC bond at the diamond(100)/Al(111) interface and improve the interfacial adhesion work. In addition, the diamond/Al composites are fabricated by vacuum gas pressure infiltration, and multi-scale characterization of the interface structure of diamond/Al composites is carried out. The interfacial debonding occurs mainly on the diamond {111}. Meanwhile, the interface product Al<sub>4</sub>C<sub>3</sub> is easier to form on the diamond {100}. The experimental phenomenon is consistent with the calculated results. Moreover, the influence of the interfacial reaction on the properties and stability of diamond/Al composites are further discussed through heat-moisture treatment. The study finds that the performance degradation in heat-moisture environment is related mainly to the hydrolysis of the interface product Al<sub>4</sub>C<sub>3</sub>. After 60 daysâ heat-moisture, the thermal conductivity of the diamond/Al composites decreases by 29.9%, and the bending strength is reduced by 40.1%. The large attenuation of performance is not conducive to the stability of composites in complex environments. Therefore, inhibiting the formation of Al<sub>4</sub>C<sub>3</sub> and improving interfacial selectivity are of great importance in developing the performance and stability of diamond/Al composites. The research in this paper not only lays a theoretical foundation for the first-principles calculation of the interface properties of diamond/metal, but also possesses important guidance significance in designing the diamond/metal composites.