Ceramics are famous for being hard but easy to break. Now, researchers have demonstrated that adding carbon nanotubes to a ceramic material can nearly triple its resistance to fracturing.
Since carbon nanotubes were discovered a decade ago, ceramics researchers have tried to exploit the tiny tubes' extraordinary strength and flexibility to make much more fracture-resistant materials.
Such durable materials could eventually replace conventional ceramics or even metals in countless products, says Joshua D. Kuntz of the University of California, Davis. For instance, engineers might use the toughened ceramic to make gears, bearings, or other parts for everything from racecars to industrial food-processing equipment.
In the new research, Kuntz, Amiya K. Mukherjee, and their UC-Davis coworkers aimed to toughen a ceramic made of alumina crystals only nanometers wide. Such nanocrystalline ceramics are particularly hard, but they're brittle and fracture easily.
In previous work, other researchers had added carbon nanotubes to alumina during processing. The best of these attempts improved the resulting composite's fracture resistance, or toughness, by only 24 percent. That experiment used multiwall carbon nanotubes, which resemble a set of nested straws.
The UC-Davis researchers suspected that high processing temperatures damaged many of the added nanotubes. They also predicted that single-wall carbon nanotubes would work better than the multiwall kind. …