Design,Fabrication And Application Of Nacre-inspired Bulk Composites Based On Lamellar Continuous Ceramic Scaffold

Natural structural materials,though built from a relatively meager selection of components,exhibit an excellent combination of multiple mechanical properties.The underlying reason is the exquisite hierarchical micro/nano structures at multiple length scales.Numerous efforts for characterization and analysis have been made by researchers to decipher the intricate interplay of structure-enabled mechanisms in natural structural materials and extract bio-inspired design principles underneath.With these acquisitions,attempts have been further made,using abundant natural or artificial micro/nano building blocks to replicate natural hierarchical structures via multiple assembly strategies,in order to fabricate bio-inspired materials with unprecedented mechanical properties.Among them,nacre,the inner part of the abalone shell,had drawn much attention to its highly ordered ’brick-and-mortar’ structure and the consequent remarkable combination of strength and toughness.Progress has been achieved in both exploring the structure-enabled mechanisms and developing nacreinspired artificial materials.However,the development and application of highperformance nacre-inspired artificial materials are highly restricted by sophisticated manufacturing processes for scalable manufacturing and unsatisfied assembly techniques for high-level exquisite structure manipulation.In addition,the-state-of-art nacre-inspired materials are designed with homogeneous structures,despite of the fact that natural structural materials present heterogeneous site-specific structures to gain multiple properties.In a word,the conflict between fine structural manipulation and scalable manufacturing remains the major obstacle in the field of bio-inspired materials.Besides,most attention has been paid to the mechanical properties of nacre-like structures,letting the potential of structure-enabled functional properties largely unexplored.In this dissertation,we first review three typical natural structural materials,including shells,teeth,and lobster exoskeleton.Then we focus on the progress of nacreinspired artificial bulk materials,reviewing the assembly strategies,kinds,and functional applications.Based on this,we further developed several bottom-up assembly strategies to scalably,efficiently,and material-independently design and fabricate nacre-inspired ceramic-based composite with both enhanced mechanical properties and functional properties.The main findings are summarized as follows:1.Inspired by nacre-like lamella structure,we developed a bottom-up assembly strategy based on nanofiber-assisted evaporation-induced self-assembly,lamination,and sintering process,achieving the orientation arrangement of micro/nano platelets.Using alumina microplatelets as building blocks,we fabricate large-scale nacre-like porous ceramics with robust mechanical properties and excellent thermal insulation properties.This work paved a new way for the design and fabrication of advanced thermal protection materials.2.Inspired by the ’brick-and-mortar’ structure and mineral bridges of nacre,we developed an efficient approach based on former work,the nacre-like porous scaffold,to fabricate a nacre-like ceramic-based composite.This approach is materialindependent and can be applied to diverse two-dimensional micro/nano platelets,providing the possibility of scalable manufacturing of multiple nacre-like composites.In addition,the mineral bridges enabled continuous ceramic scaffold in nacre-like ceramic-based composite facilitated the synergistic enhancement of mechanical properties and thermal conductivity,even under elevated temperatures.This work provided insight into the design and fabrication of advanced electronic substrate materials.3.Inspired by heterogeneous structures in natural structural materials,based on former works,we further developed a strategy for scalable manufacturing of bioinspired heterogeneous composite.As a demonstration,we fabricate a heterogeneous nacre-like ceramic-based composite with a strong and tough nacre-like main body and a stiff and hard outer surface,which are connected by a gradient interlayer to alleviate the property mismatch.The as-fabricated composite exhibited a combination of low density,high strength,modulus,toughness,hardness,and impact resistance.This simple strategy effectively solved the conflict between fine structural manipulation and scalable manufacturing,laying a methodology foundation for the design and fabrication of advanced bio-inspired heterogeneous composite.