Colossal negative thermal expansion over a wide temperature span in dynamically self-assembled MnCo(Ge,Si)/epoxy composites

The achievement of significant negative thermal expansion (NTE) over a wide temperature range (ΔTNTE) has posed a formidable challenge for NTE materials. In the present study, textured MnCo(Ge,Si)/epoxy composites were prepared by magnetic field-assisted dynamic self-assembly of multi-component Mn0.945Co1.055Ge1-xSix particles. The utilization of multi-component particles with tunable transition temperatures significantly amplifies the temperature range over which the NTE occurs, surpassing the limitations of conventional single-component composites. The textured microstructure enables the extension of lattice-level NTE to reach the macroscopic level, which is manifested by a remarkably large NTE coefficient of −328.7 × 10−6/K between 288.2 and 431.1 K.