In this study, using first-principles calculations, we investigated the interfacial nature between single-walled carbon nanotubes (CNTs) and clean Al2O3(0001) surfaces. The calculation results showed that the adhesive energy of CNTs and clean Al2O3(0001) depends on the diameter of CNTs. The structures of the CNTs adsorbed on Al-terminated Al2O3(0001) do not drastically change from those before adsorbing. C atoms of CNTs interacted with the topmost Al atom of Al2O3(0001) by forming covalent bonding. In the case of the O-terminated Al2O3(0001), small-diameter CNTs have strong interaction, which comes from the opening of CNTs catalytically induced by the O-terminated surface and the subsequent formation of mixed covalent-ionic bonding between C and O atoms. This strong interfacial interaction also leads to significant charge transfer from the CNTs to the O-terminated Al2O3(0001). The strong interfacial interaction of small diameter CNTs with the O-terminated Al2O3(0001) would be a possible mechanism for the successful Al2O3 composite reinforced with CNTs.

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.

First principle calculation is performed to investigate structural and electronic properties of strained silicene (silicon analogue of graphene) when absorbing the hydrogen sulfide molecule gas. Two configuration of silicene-H2S system, center and hollow configuration, is checked under 0% (pure), 5%, and 10% uniaxial engineering strain. We report that the silicene-H2S system in center configuration has larger binding energy compare to the silicene-H2S system in hollow configuration. The results show that H2S is physisorbed on silicene. In this work, we also find the change of band gap energy (~60 meV) is appearing when H2S interacted with silicene in center configuration, whereas the band gap energy of silicene has no change when interacted with H2S in hollow configuration.