Interfacial Interaction between Carbon Nanotube and Stoichio- and Nonstoichiometric Ceramic Surfaces by <i>Ab-Initio</i> Calculations

Abstract

This work deals with the interfacial interaction between single-walled carbon nanotubes (CNTs) and ceramic surfaces of SiC(0001) and ZrO 2 (111) based on the density functional theory. The ab-initio calculations show that the adhesive energy per the projected contact area on the ceramic surfaces depends on not only the diameter of CNTs but also the stoichiometry of the surfaces. For stoichiometric surfaces, such as the Oterminated ZrO 2 (111), the structures of the adsorbed CNTs do not drastically change from the original cylindrical shape and the interfacial interaction is relatively weak. In the case of nonstoichiometric surfaces, such as Si-and C-terminated SiC surfaces and Zr-terminated ZrO 2 surface, they have a strong interaction. Especially for the small-diameter CNTs, the structure was transformed into an arch-like shape. The strong interaction arises from the formation of the mixed covalent-ionic bonding and the subsequent opening of CNTs, which is catalytically induced by the nonstoichiometric surfaces. The covalent and ionic characteristics of the interfacial bonding states are discussed in terms of the integrated crystal orbital Hamilton populations calculation and the Bader charge transfer analysis. These properties of the interface might be related with how a crack propagates on the interface and how large fracture toughness the composite has. CNT-SiC, which has the lower adhesive energy and relatively large covalent strength, results in the slightly increased fracture toughness. And CNT-ZrO 2 with the same lower adhesive energy but the lower covalent strength does in the decreased, as seen in the experimental data.

Adsorption Site Preference Determined by Triangular Topology: Application of the Method of Moments to Transition Metal Surfaces

“…90−92 The ICOHP is known to be a good measure of covalent bond strength. 1,4,93,94 LOBSTER was also used to perform the Mulliken population analysis. We performed extended Huckel calculations 95 to understand the results of the DFT calculations in connection with the simple models presented in the Theoretical Background section, using ATK-SE 96 implemented in QuantumATK 97 and YAeHMOP 98 implemented in Avogadro.…”

“…Surface structures shown in this paper were drawn using VESTA . To estimate the strength of the bonding of the adsorbates to the surface, we calculated the integrated COHP (ICOHP) − using LOBSTER v4.0.0. − The ICOHP is known to be a good measure of covalent bond strength. ,,, LOBSTER was also used to perform the Mulliken population analysis.…”