Preparation methods significantly influence the thermophysical properties of diamond/copper composites. Common techniques include high-temperature high-pressure (HTHP) synthesis, liquid-phase infiltration, discharge plasma sintering, and vacuum hot-press sintering.
The high-temperature high-pressure method melts copper powder into a molten copper phase at elevated temperatures, then applies high pressure using a six-sided press to produce dense diamond/copper composites. This technique yields materials with high density, high diamond volume fraction, and ultra-high thermal conductivity, while offering short processing times and high efficiency. However, it requires stringent preparation conditions, incurs high costs, and is limited to smaller dimensions.
Liquid-phase infiltration involves preparing diamond particles into preforms with sufficient strength, then filling the gaps between these particles with molten copper through capillary action or pressure. The composite is formed upon cooling. Non-pressure infiltration requires prolonged heating of the composite above the base metal's melting point, relying on capillary action for infiltration. However, this process demands good wettability between the reinforcement and matrix, and exhibits low infiltration efficiency.
Spark Plasma Sintering (SPS) enables dense sintering of powdered materials below their melting points with short processing times and high efficiency. This technique involves applying pulsed high-energy currents and pressure to a diamond-copper mixture, generating plasma between particles. The high-speed particle flow expels adsorbed gases from the powder surface and disrupts surface oxide layers. The pulsed current activates and purifies the mixed powder, enabling the formation of a dense diamond/copper composite at lower sintering temperatures and shorter sintering times.
