Hyperelasticity of three-dimensional carbon nanotube sponge controlled by the stiffness of covalent junctions |
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| Affiliation: | 1. Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, United States;2. Center for Composite Materials, University of Delaware, Newark, DE 19716, United States;3. Department of Chemistry, Indiana University, Bloomington, IN 47405, United States;4. Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, 104 Davey Lab, University Park, PA 16802-6300, United States;5. Department of Materials Science and Engineering, The Pennsylvania State University, 104 Davey Lab, University Park, PA 16802-6300, United States;6. Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, United States;7. Research Center for Exotic Nanocarbons (JST), Shinshu University, Wakasato 4-17-1, Nagano 380-8553, Japan;8. Department of Polymer Science and Engineering, Department of Energy Science, Sungkyunkwan University, 300 Chunchun-dong, Jangan-gu, Suwon 440-746, South Korea;1. Laboratory of Physics, Vin?a Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia;2. INFN-Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati, Italy;1. Institute of Problems of Mechanical Engineering, V.O., Bolshoj pr. 61, St. Petersburg 199178, Russia;2. Ioffe Institute, Politekhnicheskaya 26, St. Petersburg 194021, Russia;3. Helmholtz_Zentrum Berlin fur Materialen und Energie, Elektronenspeicherring BESSY II D, 12489 Berlin, Germany;1. Universidade Federal do Rio Grande do Norte, Departamento de Física, Caixa Postal 1641, 59078-900 Natal, RN, Brazil;2. Universidade Federal da Paraíba, Departamento de Física,CCEN, Caixa Postal 5008, 58051-970 João Pessoa, PB, Brazil |
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| Abstract: | To expand the applications of carbon nanotubes (CNTs) at macroscale, a heteroatom doping technique has been employed to fabricate isotropic 3-D CNT architectures by inducing elbow-like covalent junctions into multiwalled CNTs. As the junctions modify the topology of each CNT by favoring the stable bends in CNTs, junction stiffness and the consequence of junction-related morphology changes in sponge's hyperelasticity remain largely elusive. In this study, two types of 3-D multiwalled CNT sponges were fabricated by inducing boron-doped or nitrogen-doped covalent junctions into CNTs. Hyperelastic properties of the sponges were experimentally quantified as the functions of CNT morphology. A novel microstructure informed continuum constitutive law was developed specifically for such isotropic CNT sponges with junctions. Analyzing the experimental data with the new theory demonstrated that, for the first time, the effective modulus of boron-doped junctions (～100 GPa) is higher than that of nitrogen-doped junctions (～20 GPa), and the junction stiffness is a key factor in regulating the hyperelastic compressive modulus of the material. Theoretical analysis further revealed that increased number of junctions and shorter segments on each individual CNT chain would result in stronger hyperelastic 3-D CNT networks. This study has established a fundamental knowledge base to provide guidance for the future design and fabrication of 3-D CNT macrostructures. |
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