Tailoring interfacial bonding states of highly thermal performance diamond/Al composites - Spark plasma sintering vs. vacuum hot pressing
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-09-17 |
| Journal | Composites Part A Applied Science and Manufacturing |
| Authors | Zhanqiu Tan, Gang Ji, Ahmed Addad, Zhiqiang Li, JeanâFrançois Silvain |
| Institutions | State Key Laboratory of Metal Matrix Composites, Institut de Chimie de la MatiÚre Condensée de Bordeaux |
| Citations | 57 |
| Analysis | Full AI Review Included |
Diamond/Aluminum Composites for Thermal Management: Sintering Control and Interfacial Engineering
Section titled âDiamond/Aluminum Composites for Thermal Management: Sintering Control and Interfacial EngineeringâAn Analysis of âTailoring interfacial bonding states of highly thermal performance diamond/Al composites: Spark plasma sintering vs. vacuum hot pressingâ
This technical documentation analyzes the critical factors governing Thermal Conductivity (TC) in diamond/aluminum Metal Matrix Composites (MMCs), specifically focusing on the superiority of Vacuum Hot Pressing (VHP) over Spark Plasma Sintering (SPS) due to tighter control over the diamond-metal interface.
Executive Summary
Section titled âExecutive SummaryâThe effectiveness of diamond/Al MMCs for high-power thermal management relies critically on achieving a low Interfacial Thermal Resistance (ITR). This study highlights the technical limitations of rapid sintering techniques and confirms the value of precise thermal control:
- VHP Superiority: Vacuum Hot Pressing (VHP) achieved significantly higher thermal conductivity (TC) than optimized Spark Plasma Sintering (SPS) composites, reaching 475 W/m K versus 330 W/m K for comparable density materials.
- Interfacial Control: The high TC in VHP samples is attributed to the creation of a unique, âcleanâ diffusion-bonded interface at the micrometer scale, facilitated by the large processing window and homogeneous thermal field.
- SPS Defect Mechanism: Rapid SPS heating generates substantial radial and axial thermal gradients, leading to a detrimental mixed bonding state (non-bonded, diffusion-bonded, and reaction-bonded).
- ITR Impact: The resulting heterogeneity in SPS led to an ITR ($1.08 \times 10^{-7} \text{ m}^{2} \text{ K/W}$) five times higher than that of the VHP counterparts ($0.2 \times 10^{-7} \text{ m}^{2} \text{ K/W}$).
- Reaction Products: Both VHP and SPS showed the formation of nanoscale Aluminum Carbide (Al4C3) and Aluminum Oxide (Al2O3) particles, but VHP minimizes these reaction layers at the micrometer scale, maximizing heat transfer.
- Technical Takeaway: For functional MMCs where TC is paramount, techniques prioritizing homogeneous thermal equilibrium (like VHP) are preferable to rapid sintering (SPS) methods which prioritize kinetics and fine grain structure.
Technical Specifications
Section titled âTechnical SpecificationsâKey performance metrics and process parameters extracted from the comparison of diamond/Al composites fabricated by VHP and SPS methods.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max TC Achieved (VHP) | 475 | W/m K | 40 vol.% diamond composite |
| Max TC Achieved (SPS) | 420 | W/m K | 50 vol.% diamond composite (optimized) |
| Relative Density (VHP) | 97 | % | Optimal conditions |
| Relative Density (SPS) | 96.7 | % | 40 vol.% diamond at 560 °C |
| ITR (VHP Estimate) | 0.2 x 10-7 | m2 K/W | Calculated via Differential Effective Medium (DEM) scheme |
| ITR (SPS Estimate) | 1.08 x 10-7 | m2 K/W | Calculated via DEM scheme |
| Diamond Initial TC | 1000-2000 | W/m K | Synthetic Diamond Range |
| Diamond CTE | 1-3 | ppm/K | Used in MMCs (Compatible with electronics <10 ppm/K) |
| Al Matrix Initial TC | ~240 | W/m K | Pure Al |
| Diamond Powder Size | 200 | ”m | Type HWD40 |
| Interfacial Product Thickness | ~10 | nm | Nanoscale Al4C3 layer on VHP {111} diamond |
| Al2O3 ITR Threshold (Amorphous) | ~30 | nm | Thickness above which ITR becomes detectable |
Key Methodologies
Section titled âKey MethodologiesâThe study compared two primary methods for consolidating diamond/Al composites, utilizing advanced characterization techniques to analyze the resultant interfacial bonding states.
- Starting Materials Preparation:
- Synthetic diamond powder (Type HWD40, 200 ”m average particle size) and pure Al powder (99.8% purity, 75-105 ”m size) were used.
- Vacuum Hot Pressing (VHP) Recipe:
- Sintering Temperature: 650 °C.
- Uniaxial Pressure: 67 MPa.
- Holding Time: 90 min.
- Result: Enabled a large processing window and homogeneous thermal field, promoting clean quasi-diffusion-bonded interfaces.
- Spark Plasma Sintering (SPS) Recipe:
- Sintering Temperature Range: 540-560 °C (Optimized for Al densification).
- Uniaxial Pressure: 50 MPa.
- Holding Time: 5 min (Rapid processing cycle).
- Result: Rapid heating-cooling generated radial and axial thermal gradients, resulting in mixed interfacial bonding states.
- Characterization Techniques:
- Surface Preparation: Triple Ion Beam (TIB) cutting was utilized to prepare nearly-perfect, artifact-free surfaces for subsequent analysis, overcoming the difficulty of polishing hard diamond and soft Al simultaneously.
- Microstructure: SEM (HITACHI S-4700) and TEM (Philips CM30, FEI Tecnai G2 FEG) equipped with EDX were used for multiscale interfacial characterization (macro to nanoscale).
- Phase Identification: X-ray Diffraction (XRD) was used to detect reaction products (notably Al4C3).
- Thermal Testing: Thermal diffusivity ($\alpha$) was measured using the laser flash technique (Netzsch LFA447) to calculate TC ($\lambda$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe findings confirm that the quality and preparation of the diamond material, particularly its surface chemistry and crystallographic consistency, are paramount to minimizing ITR in thermal management MMCs. 6CCVDâs advanced MPCVD diamond products and engineering capabilities directly address the technical requirements needed to replicate or surpass the high-performance VHP results.
| Requirement/Challenge from Research | 6CCVD Applicable Material & Service | Engineering Solution & Value Proposition |
|---|---|---|
| Material Purity & High Intrinsic TC | Optical Grade Single Crystal Diamond (SCD) Plates/Wafers. | Provides intrinsic TC up to 2000 W/m K. Starting with the highest purity SCD minimizes lattice defects that contribute to phonon scattering, ensuring the highest potential TC for the composite. |
| Surface Chemistry Control for Bonding | Custom Metalization Services: Au, Pt, Pd, Ti, W, Cu layers applied via internal capability. | This study confirms that pre-coating diamond with reactive elements (like Ti or W, as noted in previous research achieving 600 W/m K TC) is vital for promoting controlled diffusion bonding and limiting detrimental Al4C3 formation. 6CCVD provides tailored surface coatings to optimize wettability and ITR. |
| Complex Geometry & Integration | Custom Dimensions and Shaping: PCD/SCD wafers up to 125mm, thicknesses 0.1”m - 500”m. Laser cutting and grinding services. | Engineers can specify the exact dimensions and geometries needed for complex thermal sinks or integration into VHP dies, supporting the scale-up from lab samples ($\text{Ă}10 \times 3 \text{ mm}$) to semi-industrial parts ($\text{Ă}50 \times 10 \text{ mm}$). |
| Interfacial Characterization Preparation | Ultra-Fine Polishing Services: SCD (Ra < 1nm), PCD (Ra < 5nm). | High-quality polishing ensures a smooth, non-contaminated surface, eliminating preparation artifacts that necessitated complex TIB cutting in the published research. This allows for cleaner, more reliable post-sintering interface analysis (SEM/TEM/EDX). |
| Heterogeneity and Interface Engineering | Custom Crystallographic Orientation: SCD substrates with specified crystallographic face (e.g., {100} or {111}). | Since Al4C3 nucleation and dissolution kinetics are highly dependent on the diamond surface orientation, 6CCVD can supply SCD materials cut to specific planes, enabling researchers to isolate and study the most favorable interface for diffusion bonding. |
Engineering Support: 6CCVDâs in-house PhD team can assist with material selection, surface coating selection (Ti/W), and dimensional optimization for high-performance diamond-MMC thermal management projects, particularly those targeting military, aerospace, and high-power electronics applications where maximizing TC is critical.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2006 - The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method [Crossref]
- 2011 - Electric current activation of sintering: a review of the pulsed electric current sintering process [Crossref]
- 2005 - Fundamental investigations on the spark plasma sintering/synthesis process: I. Effect of dc pulsing on reactivity [Crossref]
- 2005 - Fundamental investigations on the spark plasma sintering/synthesis process: III. Current effect on reactivity [Crossref]
- 2005 - Fundamental investigations on the spark plasma sintering/synthesis process: II. Modeling of current and temperature distributions [Crossref]
- 2007 - Electron backscattering diffraction analysis of mechanically milled and spark plasma sintered pure aluminium [Crossref]
- 2008 - Synthesis of high-strength bimodally grained iron by mechanical alloying and spark plasma sintering [Crossref]
- 2007 - Processing dense hetero-nanostructured metallic materials by spark plasma sintering [Crossref]
- 2007 - A high-strength bulk nanocrystalline Al-Fe alloy processed by mechanical alloying and spark plasma sintering [Crossref]
- 2008 - Properties of mechanically milled and spark plasma sintered Al-15 at.%MgB2 composite materials [Crossref]