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Ultralight, Strong Three Dimensional SiC Structures Sakineh Chabi, Victoria G Rocha, Esther Garcia-Tunton, Claudio Ferraro, Eduardo Saiz, Yongde Xia, and Yanqiu Zhu ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.5b05533 • Publication Date (Web): 18 Nov 2015 Downloaded from http://pubs.acs.org on November 23, 2015
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ACS Nano
Ultralight, Strong Three Dimensional SiC Structures
Sakineh Chabi1, Victoria G. Rocha2, Esther Garcia-Tunon2, Claudio Ferraro2, Eduardo Saiz2, Yongde Xia1, Yanqiu Zhu1* 1
College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
2
Centre for Advanced Structural Ceramics, Department of Materials, Imperial College London, London SW7 2AZ, UK
*Email:
[email protected] Abstract Ultralight and strong three-dimensional (3D) silicon carbide (SiC) structures have been generated by the carbothermal reduction of SiO with a graphene foam (GF). The resulting SiC foams have an average height of 2 mm, and density ranging between 9-17 mg cm-3. They are the lightest reported SiC structures. They consist of hollow struts made from ultrathin SiC flakes, and long 1D SiC nanowires growing from the trusses, edges and defect sites between layers. AFM results revealed an average flake thickness of 2-3 nm and lateral size of 2 µm. In-situ compression tests in the scanning electron microscope (SEM) shown that, compared with most of the existing lightweight foams, the present 3D SiC exhibited superior compression strengths and significant recovery after compression strains of about 70%.
Keywords: Silicon carbide, three dimensional, 2D SiC, Ultralight, recoverable ceramic
Cellular
foam ceramics are well-known for their high specific strength and excellent
resistance to temperature, aggressive chemical environments and thermal shock. 1 ACS Paragon Plus Environment
ACS Nano
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Traditionally, direct foaming, gel casting and template-assisted replica methods have been the main approaches for the production of ceramic foams, with direct foaming allowing the synthesis of both open and closed-cell structures.1-3 In general, the morphological and microstructural features of the foam, including the cell types and dimensions, strut sizes and void configurations can change significantly, depending on the manufacturing processes, and they can be tuned to suit different applications. For example, ordered hierarchical structures can be achieved via template-assisted synthesis,3 whereas the sol-gel process suits large and scalable template-free industrial level manufacturing.4 The porosity level of the foam is yet another key parameter that can be modified by varying the synthesis routes,5 e.g. the replica method produces foams with a cells size in the millimetre range, whereas the sol-gel method can result in nanometre size pores.6 Among many cellular ceramic foams, SiC and its composites have attracted much attention, and both open and closed cell foams have been synthesised.5,7 In contrast to the sealed pores in the closed-cell foam, the open-cell SiC foams have an interconnected porous network, and are suitable for use as catalyst support,8 insulating modulus,9 ceramic filters,5 shock energy damping,10 and solar receivers.10,11 The concept of lightweight conventionally refers to structures with a density (ρ) range of 0.3 5 g cm-3. The new generation of lightweight structures however, is three orders of magnitude lighter than conventional foams. Graphene foams (GFs),8 CNT-graphene aerogels,9 silica aerogel (ρ > 1.5 mg cm-3), metallic foams (ρ > 10 mg cm-3),10 nano-fibrous aerogels (NFAs) (5.3
