Fabrication of Graphene-reinforced Alumina Ceramic Composites<italic> via </italic>Adsorption-precipitation Self-assembly Combined with Spark Plasma Sintering

Alumina ceramics are widely utilized as structural materials, yet their inherent brittleness and monofunctionality limit their application in high-stress scenarios. Strategic integration of two-dimensional graphene sheets, characterized by their excellent mechanical, thermal and electrical properties, into ceramic matrix can facilitate grain refinement through interface engineering, thereby achieving performance optimization. Conventional physical blending methods result in poor uniformity and integrity of 2D sheets, thereby impeding advancements in graphene-ceramic composites. Herein, a novel adsorption-precipitation self-assembly (APSA) method was proposed for the nondestructive integration of graphene oxide (GO) sheets with submicron Al2O3 particles. A homogeneous precursor is obtained by uniform deposition of Al3+ ions adsorbed on GO surface, followed by low-temperature rapid densification via spark plasma sintering (SPS). For the resultant composites, the incorporated graphene is aligned parallel to the alumina grains, facilitating grain refinement and significantly enhancing the mechanical properties through synergistic effect of various toughening mechanisms, including pull-out, crack extension and bridging. In comparison to monolithic alumina ceramics, the ceramic composites exhibit a 43% enhancement in flexural strength ((428±87) MPa) and a 34% improvement in fracture toughness ((4.40±0.13) MPa·m1/2). Furthermore, the strength and toughness values also increase by 15% respectively, compared to specimens made from the conventional ball-milling mixing process, confirming the efficacy and advancement of such a manufacturing approach.