Effect of SiC-coated diamond and its size on the relative density and thermal conductivity of diamond/W composites

Tungsten (W) is a promising plasma-facing material (PFM) for fusion reactor divertors but suffers from relatively low thermal conductivity (173 W·m⁻¹·K⁻¹), leading to overheating, recrystallization, and thermal fatigue under extreme heat loads.

Incorporating high thermal conductivity reinforcements such as diamond can enhance heat transfer, yet direct W–diamond contact produces brittle WC/W₂C phases with poor thermal transport. Surface coatings are therefore essential to stabilize the interface. In this study, a nanoscale SiC coating was deposited on diamond particles (100–400 μm) by magnetron sputtering and used to fabricate diamond(SiC)/W composites via spark plasma sintering (SPS). The SiC layer exhibited good uniformity at 150 W sputtering power for 16 h, with a thickness of ~0.53 μm. For 200 μm diamonds, moderate additions (≤40 vol%) promoted W–SiC interfacial reactions, improving bonding, densification, and thermal conductivity. 

However, excessive diamond additions (50–60 vol%) caused fragmentation and migration of the WC–SiC layer under thermal and electrical stresses, increasing interfacial defects and reducing conductivity. The optimal 40 vol% diamond(SiC)/W composite achieved 152 W·m⁻¹·K⁻¹. Increasing diamond size further enhanced densification and heat transfer, with 40 vol% composites containing 400 μm diamonds reaching 225 W·m⁻¹·K⁻¹ at 96.8% relative density. 

These results demonstrate that SiC coatings and diamond size optimization can effectively improve the thermal performance of W-based composites for fusion applications.

#diamond(SiC)/W composite

#SiC diamond 

#Diamond and silicon carbide composite