Highly conductive and low expansion molybdenum-copper composites synthesized by freeze-drying and infiltration

To tackle key issues of inhomogeneous microstructure distribution, poor thermal conductivity, and relatively high thermal expansion coefficient of molybdenum‑copper (MoCu) composites for electronic and engineering applications, in this study, heterogeneous MoCu composites were prepared using integrated freeze-drying and infiltration methods. With water used as the major solvent, molybdenum skeletons with different solid contents were successfully obtained using the freeze-drying method operated at −70 °C. Porous structures of the skeletons with an average pore diameter of ∼5 μm were isotropically and uniformly distributed in all directions, and the obtained compressive strengths of these skeletons were ranged from ∼149 to ∼232 MPa. After post-infiltration with copper at 1350 °C, the synthesized composites exhibited evenly distributed copper and molybdenum phases, achieving a high thermal conductivity of up to ∼235.2 W/(m·K) and a low thermal expansion coefficient of 6.1 × 10⁻⁶/°C. The intrinsic mechanisms underlying the high thermal conductivity and low coefficient of thermal expansion in MoCu composites were attributed to the formation of a relatively dense and interpenetrating network structure between the Mo and Cu phases, and an appropriate level of porosity effectively compensated for certain deformations induced by thermal expansion and contraction during temperature variations.