Bioinspired fish-scale-like magnesium composites strengthened by contextures of continuous titanium fibers:Lessons from nature

Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made materials.Here bioinspired magnesium composites with fish-scale-like orthogonal plywood and double-Bouligand architectures were developed by pressureless infiltration of a magnesium melt into the woven contextures of continuous titanium fibers.The composites exhibit enhanced strength and work-hardening ability compared to those estimated from a simple mixture of their constituents at ambient to elevated temperatures.In particular,the double-Bouligand architecture can effectively deflect cracking paths,alleviate strain localization,and adaptively reorient titanium fibers within the magnesium matrix during the deformation of the composite,representing a successful implementation of the property-optimizing mechanisms in fish scales.The strength of the composites,specifically the effect of their bioinspired architectures,was interpreted based on the adaptation of classical laminate theory.This study may offer a feasible approach for developing new bioinspired metal-matrix composites with improved performance and provide theoretical guidance for their architectural designs.

Bioinspired tungsten-copper composites with Bouligand-type architectures mimicking fish scales

The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in metals.Here bioinspired tungsten-copper composites with different Bouligand-type architectures mimicking fish scales were fabricated by infiltrating a copper melt into woven contextures of tungsten fibers.These composites exhibit a synergetic enhancement in both strength and ductility at room temperature along with an improved resistance to high-temperature oxidization.The strengths were interpreted by adapting the classical laminate theory to incorporate the characteristics of Bouligand-type architectures.In particular,under load the tungsten fibers can reorient adaptively within the copper matrix by their straightening,stretching,interfacial sliding with the matrix,and the cooperative kinking deformation of fiber grids,representing a successful implementation of the optimizing mechanisms of the Bouligand-type architectures to enhance strength and toughness.This study may serve to promote the development of new high-performance tungsten-copper composites for applications,e.g.,as electrical contacts or heat sinks,and offer a viable approach for constructing bioinspired architectures in metallic materials.

Ice-templated porous tungsten and tungsten carbide inspired by natural wood

The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional applications.However,it is challenging to construct and control the architectures by means of self-assembly in W/WC systems because of their large densities.Here we present the development of unidirectionally porous architectures,with high porosities exceeding 65 vol.%,for W and WC scaffolds which in many respects reproduce the design motif of natural wood using a direct ice-templating technique.This was achieved by adjusting the viscosities of suspensions to retard sedimentation during freezing.The processing,structural characteristics and mechanical properties of the resulting scaffolds were investigated with the correlations between them explored.Quantitative relationships were established to describe their strengths based on the mechanics of cellular solids by taking into account both inter-and intra-lamellar pores.The fracture mechanisms were also identified,especially in light of the porosity.This study extends the effectiveness of the ice-templating technique for systems with large densities or particle sizes.It further provides preforms for developing new natureinspired multifunctional materials,as represented by W/WC-Cu composites.

Friction and wear behavior of bioinspired composites with nacre-like lamellar and brick-and-mortar architectures against human enamel

Friction and wear performance is critical for dental materials which are inevitably subject to reciprocating friction against opposing teeth in applications.Here in-vitro friction and wear behavior of bioinspired ceramic-polymer composites,which possess nacre-like lamellar and brick-and-mortar architectures and resemble human teeth in their stiffness and hardness,against human tooth enamel were quantitatively investigated to imitate actual service conditions in line with standardized testing configuration.The composites were revealed to exhibit different wear mechanisms and lead to differing extents of wear to the opposing tooth enamel depending on their specific architectural types and orientations.In particular,the brick-and-mortar architecture displayed much less wear than the lamellar one,without obviously roughening the contact surfaces with enamel owing to its high ceramic content,and as such did not accelerate the wear of enamel as compared to smooth ceramics.Such characteristics,combined with its unique stiffness and hardness matching those of human enamel as well as the good fracture toughness and machinability,endow the composite with a promising potential for dental applications.This work may provide an experimental basis to this end and may also give insights towards designing new bioinspired wear-resistant materials for reducing friction and wear.

连续冰模板法制备均匀定向多孔材料

冰模板技术为在材料中构筑有序定向多孔结构提供了一种有效的途径,然而其通常存在制备效率低、过程难以调控以及制得的样品尺寸小、结构均匀性差等局限.本文开发了一种新型的连续式冰模板工艺,通过将冷冻固-液界面连续下降浸入到冷却介质中以抵消其向上的生长,成功在界面前沿建立了大而稳定的双向温度梯度,从而制备得到了具有均匀定向结构的多孔材料.与传统的静置式冰模板技术相比,该工艺的制备效率显著提升,制得的样品尺寸明显增加.以多孔氧化锆陶瓷为例,其多孔结构变得更加细密而均匀,陶瓷片层的定向性和连通性均明显提升,这使得材料在相同孔隙率条件下表现出更高的压缩强度,并且强度沿样品高度方向也更加稳定.本研究有助于推动冰模板技术的放大,并促进新型高性能材料的开发与应用.