Nacre‐Inspired Structural Composites: Performance‐Enhancement Strategy and Perspective

Abstract

fabricated a montmorillonite clay (MTM)/poly(diallydimethylammonium) chloride polycation (PDDA) composite with nacre-like layer structure for the first time through sequential adsorption of organic and inorganic dispersions, [13] a typical layer-by-layer (LBL) method. The MTM/PDDA hybrid film with layer structure shows a fracture strength and strain of 105 MPa and 1%, respectively, approximately equal to that of nacre. Since then, more clay-based nacre-like films have been synthesized through the LBL method, and the mechanical properties are promoted by modifying the MTM [14] or crosslinking the polymer. [15] However, the thickness of the nacre-inspired films synthesized by the LBL method is limited to sub-10 µm as LBL is extremely time-consuming. [4] To increase the thickness of nacre-like films, efficient methods such as vacuum-assisted filtration, [16,17] electrophoretic-assisted deposition, [18] evaporation, [19,20] and dip-coating [21] have been developed in the following years. For example, the nacre-like MTM/poly(vinyl alcohol) (PVA) film with a thickness of over 200 µm, which is dozens of times thicker than films fabricated by LBL, can be synthesized through vacuum-assisted filtration, and its fracture strength and strain can be up to 160 MPa and 1%, respectively. [16] Recently, a much thicker clay-PVA composite (up to several millimeters) could be achieved by compressing and heating thin-layered films synthesized by evaporation. [22] Another typical method to produce bulk composites with layer structure is freeze-casting. [23][24][25][26] For instance, a lamellar Al 2 O 3 /poly(methyl methacrylate) (PMMA) composite with a size of dozens of centimeters showed a high combination of strength (flexural strength of 210 MPa) and toughness (32 MPa m 0.5 ), further surpassing the traditional structural materials. [23] In general, several methods have been developed since 2003 to synthesize nacre-inspired artificial composites with layer structures. However, the limitation of binary inorganic/organic hybrids still hinders further improvement of the mechanical properties of nacre-like artificial structural composites. [27] Recent progress in the synthesis of novel nacre-inspired structural materials, including ternary artificial nacre, artificial nacre reinforced by bridges, and those with a high content of hard phase, is discussed next, here, as a reference of the novel strategies for fabricating lighter, stronger, and tougher nacre-inspired structural materials. To give a comprehensive understanding, the perspective to develop next-generation lightweight and high-performance structural materials and their challenges is also included.For modern material engineering, one of the most ambitious goals is to develop lightweight structural materials with superior strength and toughness. Nacre, a typical biomaterial with high mechanical performance, has always inspired synthesis of high-performance structural composites. Here, the synthesis strategies for further enhancing the strength and toughness of novel nacre-insp...

Nature‐Inspired Nacre‐Like Composites Combining Human Tooth‐Matching Elasticity and Hardness with Exceptional Damage Tolerance

“…Additionally, despite the implementation of bioinspired designs in mineral-organic composites for structural applications, nacre-like lamellar and brick-and-mortar architectures have rarely been realized in biomedical systems, specifically for dental applications. [39,[42][43][44][54][55][56][57][58] Here we clarify the architectural design principles of the current composites composed of 3Y-TZP and dental resin in generating their tooth-matching stiffness. The lamellar composites, although having a parallel arrangement of constituents, display a Young's modulus lower than that predicted by the rule-of-mixtures following the Voigt model.…”

Strategic Design of Clay‐Based Multifunctional Materials: From Natural Minerals to Nanostructured Membranes

“…In the past few decades, clay minerals have been considered as important industrial components or precursors in geology, agriculture, and construction. In addition to their conventional uses in ceramics, paper coatings, plastics and rubbers, and catalysis, clay nanosheets have found many novel applications when they are properly handled . In this section, we summarize some unique nanotechnology‐driven phenomena and features of clay‐based functional materials, compare the exfoliation methods, the size of nanosheets, the assembly methods, and the related properties and applications ( Table 2 ).…”

Beyond Seashells: Bioinspired 2D Photonic and Photoelectronic Devices

“…By looking at the iridescent strips (Figure b) and the highly ordered layered microstructure (Figure d) of the seashells, this type of structural colors is mostly from the interference of light from aragonite–collagen (fresh) or aragonite–air (dry) multilayers, but not as those from 3D opal‐like photonic crystal structures in butterfly wings and some beetles . To achieve the metallic bioinspired colors of the multilayers, the aragonite‐like layer in the structure must be very dense or free of particulate defects . The optical properties of the nacre structure are very sensitive to the particulate defects with the size over the half wavelength of visible light, equaling to around 190 nm, as shown in the first schematic drawing of Figure a, which will be significantly scattering the incident light into different directions through refractions or diffuse reflections.…”