Session: 16-01-01: NSF-funded Research (Grad & Undergrad)

Paper Number: 77083

Start Time: Wednesday, 02:25 PM

77083 - Interfacial Sliding of Graphene Versus Hexagonal Boron Nitride on Silica Substrates 

Graphene and hexagonal boron nitride (hBN) flakes or nanotubes are promising reinforcing additives in ceramic matrix nanocomposites, but the interfacial strength properties have remained largely unexplored. Our recent single nanotube pull-out force measurements show that the interfacial shear strength of boron nitride nanotubes in silica (silicon dioxide) substrates is ~20% higher than that of carbon nanotubes in silica substrates. Here, we present the results of our recent density function theory (DFT) calculations characterizing the interfacial strength properties between graphene and silica as well as between hBN and silica to explain these intriguing nanomechanical experiments. We show that the interfacial interactions are highly sensitive to the end-terminations of the silica substrate. The O₂-terminated α-quartz has a ~20 times stronger adhesion energy on hBN or graphene than the Si- or O-terminated α-quartz. The equilibrium separation distance of hBN or graphene on the Si- or O-terminated α-quartz, on the other hand, is ~2 times larger than that of O₂-terminated α-quartz. These results suggest that very strong covalent bonds are formed between O₂-terminated α-quartz and hBN or graphene, while these atomic sheets are only weakly physisorbed on O-terminated or Si-terminated α-quartz which permit interfacial sliding without fracture of the atomic sheets. Reconstruction of the sliding energy landscape by nudged elastic band methods reveals that the sliding of graphene on O- or Si-terminated α-quartz is largely directional independent, i.e. the barrier energies are largely similar in all sliding orientations. This is in contrast to the anisotropic sliding of hBN on O- or Si-terminated α-quartz resulting in high barrier energies along specific sliding orientations. This directional dependence stems from the differing interactions between the termination atom of α-quartz and the B or N atoms in hBN versus the single C atom type in graphene. In particular, the highest energy barrier along the sliding energy landscape for the interface between Si-terminated α-quartz and hBN is ~0.0306 J/m², which is ~36% larger than that the highest barrier energy of 0.0225 J/m² formed along the interface between Si-terminated α-quartz and graphene. Similarly, the highest barrier energy between O-terminated α-quartz and hBN is 70.1% larger than that between O-terminated α-quartz and graphene. This higher energy barriers for interfacial sliding between hBN and silica versus graphene and silica plausibly explains the higher pull-out force measured on boron nitride nanotube-silica interfaces in our nanomechanical experiments. These results have significant implications in the optimal design of atomistic interfacial structures to mitigate and ultimately control interfacial failure of ceramic nanocomposites.

Presenting Author: Ning Li University of Illinois at Urbana-Champaign

Authors:

Ning Li University of Illinois at Urbana-Champaign
Christopher Dmuchowski State University of New York at Binghamton
Yingchun Jiang State University of New York at Binghamton
Chenglin Yi State University of New York at Binghamton
Feilin Gou State University of New York at Binghamton
Changhong Ke State University of New York at Binghamton
Huck Beng Chew University of Illinois at Urbana-Champaign