Composite powders are powders composed of two or more different components, exhibiting core-shell structure characteristics, and are classified into mixed and coated types. Coated composite powders achieve particle-scale mixing through the bonding of the central particle and the coating layer; preparation methods include spray conversion and chemical precipitation. Nano-tungsten carbide cobalt composite powder is prepared using the spray conversion method; centrifugal speed significantly affects the loose packing density, with higher speeds maintaining the WC grain size below 200 nm. Adding Al₂O₃-ZrO₂ composite powder to a zirconia-based sizing nozzle can reduce the cubic ZrO₂ content, forming a columnar zirconia reinforcing phase, which reacts with MgO to form magnesium aluminum spinel.
Typical composite powder structures include copper/nickel/silver core-shell composite powders and graphene-coated metal/ceramic/polymer substrate composite powders, used in electronic pastes, thermal spraying, and 3D printing. Nickel-coated aluminum composite powders are prepared via liquid-phase deposition pressurized hydrogen reduction, requiring controlled reduction temperature (150-175℃). Graphene-coated composite powders can achieve a 30%-50% increase in strength and a 20%-40% increase in conductivity, making them suitable for applications in rail transportation and aerospace. ZrO₂-TiO₂ composite powders prepared by the sol-gel method form ZrTiO₄ nanocrystals at 650℃, and the luminescence intensity changes with increasing ZrO₂ content.
