Interfacial Modification and Heat Transfer Mechanisms in Diamond/Copper Composites

Diamond/Cu composites are promising thermal management materials due to their ultrahigh intrinsic thermal conductivity and tunable coefficient of thermal expansion (CTE). However, their effective thermal conductivity remains far below theoretical predictions because of poor interfacial bonding, severe phonon mismatch, and weak electron–phonon coupling at the Cu/diamond interface.

1. Theoretical and Experimental Insights

Using the Differential Effective Medium (DEM) model:

$K_c = f(k_d, k_m, V_f, h_k)$

where $k_d$ and $k_m$ are the conductivities of diamond (~2200 W m⁻¹ K⁻¹) and copper (~400 W m⁻¹ K⁻¹), $V_f$ is the diamond volume fraction, and $h_k$ is interfacial thermal conductance.
Theoretical $K_c$ (>1000 W m⁻¹ K⁻¹) is drastically reduced in practice (~200–450 W m⁻¹ K⁻¹) due to high interfacial resistance arising from weak van der Waals bonding and large phonon impedance mismatch ( $Zdiamond=4.7×107Z_{diamond}=4.7×10⁷$ , $ZCu=2.5×107Z_{Cu}=2.5×10⁷$ kg m⁻² s⁻¹).

2. Interfacial Engineering Strategies

Interfacial Engineering Strategies for Diamond Cu Composites.jpg

(1) Chemical Bonding Enhancement

Surface metallization: Ti, Cr, W, Mo, or Zr coatings form carbide layers (e.g., TiC, Cr₃C₂) improving adhesion and phonon transmission.
Cu matrix alloying: Cu–X (X = Cr, Ti, Zr, B) alloys generate controlled reaction layers, enhancing interfacial integrity and electronic coupling.
Nanointerlayers: Multilayer (Ti/W/Cu) or graded (Cu–C, TiN/TiC) structures provide lattice and energy-band transition to suppress phonon scattering.

Optimized designs can increase interfacial thermal conductance by 1–2× while improving mechanical reliability.

(2) Carrier and Phonon Coupling Regulation

Electron–phonon coupling: Formation of metal–carbon chemical bonds (e.g., Ti–C, Cr–C) increases local density of states and electron-to-phonon energy transfer efficiency.
Phonon spectrum bridging: Transition layers (e.g., TiC, WC) smooth phonon spectra across the interface, enhancing phonon transmission as validated by MD simulations.

3. Future Directions

Atomic-level interface design via in-situ growth or ALD.
Multiscale simulation integrating ab initio, MD, and FEM.
High-throughput and AI-assisted optimization of interfacial chemistry and reaction layer thickness.
Application to high-power modules, SiC devices, and radar T/R units.

Conclusion

The effective thermal performance of Diamond/Cu composites is dominated by interfacial properties. Synergistic strategies combining chemical bonding enhancement and phonon/electron coupling optimization can significantly reduce interfacial resistance, potentially achieving bulk thermal conductivities above 800 W m⁻¹ K⁻¹.

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11/3/2025

Interfacial Modification and Heat Transfer Mechanisms in Diamond/Copper Composites