UNCORRECTED PROOF Journal of Materials Science & Technology xxx (xxxx) xxx-xxx Contents lists available at ScienceDirect Journal of Materials Science & Technology journal homepage: www.elsevier.com Ice-templated porous tungsten and tungsten carbide inspired by natural wood Yuan Zhang a, b , Guoqi Tan a, c , Da Jiao a , Jian Zhang a , Shaogang Wang a , Feng Liu b , Zengqian Liu a, c, ⁎, Longchao Zhuo d, ⁎⁎ , Zhefeng Zhang a, c, ⁎, Sylvain Deville e , Robert O. Ritchie f a Laboratory of Fatigue and Fracture for Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China b School of Mechanical Engineering, Liaoning Shihua University, Fushun 113001, China c School of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China d School of Materials Science and Engineering, Xi'an University of Technology, Xi'an, 710048, China e Laboratoire De Synthèse Et Fonctionnalisation Des Céramiques, UMR3080 CNRS/Saint-Gobain CREE, Saint-Gobain Research Provence, Cavaillon 84306, France f Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA 94720, USA ARTICLE INFO Article history: Received 14 September 2019 Received in revised form 18 October 2019 Accepted 18 October 2019 Available online xxx Keywords: Ice-templating Tungsten Scaffolds Fracture mechanisms Bioinspired materials ABSTRACT 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%, 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 freez- ing. The processing, structural characteristics and mechanical properties of the resulting scaffolds were inves- tigated 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 nature-inspired multifunctional materials, as represented by W/WC-Cu composites. © 2020. 1. Introduction Tungsten (W) and tungsten carbide (WC) have ultrahigh melting points, high hardness, and outstanding resistance to wear and electri- cal erosion. These advantages can be combined with the high ther- mal and electrical conductivity of copper (Cu) by forming W/WC-Cu composites [1–6]. The excellent combinations of properties make the composites highly attractive for multifunctional applications. A com- mon use, especially for the W-Cu system, is to serve as high-volt- age electrical contacts to resist the stringent arc erosion created by completing or interrupting the circuit, while simultaneously ensuring an efficient electrical conduction [3–8]. Another good case in point is their potential as heat sinks for highly-loaded plasma facing com- ponents in nuclear fusion devices owing to their good thermal con- ductivity and superior mechanical properties at elevated temperatures [9–11]. WC-Cu composites are also promising candidates for thermal ⁎ Corresponding authors at: Laboratory of Fatigue and Fracture for Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China. ⁎⁎ Corresponding author. Email addresses: zengqianliu@imr.ac.cn (Z. Liu); zhuolongchao@xaut.edu.cn (L. Zhuo); zhfzhang@imr.ac.cn (Z. Zhang) barriers between plasma facing components and copper-based heat sinks [12,13]. Other applications include the warhead and nozzle lin- ers of missiles or rockets which utilize high densities and the unique thermophysical-mechanical properties of the composites [14,15]. A viable approach to fabricate W/WC-Cu composites is to infil- trate a Cu melt into the open pores of W/WC scaffolds [1–6]. This is made possible by the large gap in the melting temperatures of W/WC and Cu (the melting points are 3422 °C and 2870 °C for W and WC, respectively, but is only 1083 °C for Cu) and the minimal mutual sol- ubility or interfacial reaction between them [14,16]. In this scenario, the structure of W/WC scaffolds can be eventually inherited by the composites which can play a key role in dictating their final proper- ties. These scaffolds are most commonly processed with powder met- allurgical techniques because of the refractory nature of W and WC [1–15]. Despite its good applicability, such a method encompasses several shortcomings that may downgrade the performance of result- ing composites. Firstly, the scaffolds generally contain a limited frac- tion of pores, with porosity typically smaller than 50 vol.% [1–15], to maintain their integrity during processing. This leads to a low Cu content in the infiltrated composites and accordingly restricts their thermal and electrical conductivity. Secondly, the pores in the scaf- folds are essentially isometric in geometry and randomly distributed. This makes the conduits for thermal and electrical transport rather https://doi.org/10.1016/j.jmst.2019.10.021 1005-0302/ © 2020.