Carbon nanotubes may toughen ceramic matrix composites

Japanese researchers explore what has hindered CNT performance and new discoveries that produce CMCs with unprecedented properties.

As reported in,  Ever since their discovery, carbon nanotubes (CNTs) have been considered the ultimate additive to improve the mechanical properties of structural ceramics, such as aluminum oxide, silicon nitride and zirconium dioxide. Yet despite the remarkable strength and stiffness of CNTs, many studies have reported only marginal improvements or even the degradation of mechanical properties after these super-materials were added. Indeed, the ability of CNTs to directly reinforce a ceramic material has been strongly questioned and debated in the last ten years.

In a review paper titled, "Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites" published in the journal Science and Technology of Advanced Materials, researchers at the National Institute for Materials Science in Japan explore what is preventing the reinforcing ability of CNTs from being exploited in a ceramic matrix.

The authors briefly review recent studies that address the key questions involved and discuss a recently discovered reinforcing mechanism at the nanoscale, which is responsible for unprecedented, simultaneous mechanical improvements including strengthening, toughening and softening of the ceramic host matrix.

The authors also highlight a new processing method that enables the fabrication of defect-free CNT-concentrated ceramics and CNT-graded composites with unprecedented properties, for applications ranging from biomedical implants and tissue engineering to thermoelectric power generation.