Quantification and promotion of interfacial interactions between carbon nanotubes and polymer derived ceramics

Carbon nanotubes (CNTs) have been considered an ideal reinforcement for light-weight and high-strength ceramic matrix composites. Understanding the interfacial properties between CNTs and the matrix is crucial for engineering the desired properties in such composites. Here in-situ pull-out experiments with a polymer derived ceramic (PDC) matrix are carried out with both pristine CNTs and CNTs coated with Al2O3 (CNT/Al2O3) produced by Atomic Layer Deposition (ALD), using micro-fabricated devices in a scanning electron microscope. This carefully designed comparative study makes it possible to better understand the interfacial interactions between CNTs and PDC matrices. The interfacial shear strength (IFSS) of CNT-PDC is 9.99 +/- 2.84 MPa, while the IFSS of (CNT/Al2O3)/PDC with similar to 3 nm Al2O3 coating thickness is 14.52 +/- 2.66 MPa, demonstrating a 45.3% improvement. The non-linear failure observed with the coated CNTs is also indicative of energy dissipation mechanisms that promote toughening in ceramic matrix composites. The improved properties in (CNT/Al2O3)/PDC are believed to originate from increased surface roughness, which leads to mechanical interlocking at the interface during the pull-out process. The combination of special interlayer structures such as ALD Al2O3 and strong CNTs opens up interesting opportunities for improving the mechanical properties of ceramic nanocomposites reinforced by CNTs. (C) 2015 Elsevier Ltd. All rights reserved.