A dramatic improvement in the tensile strength of fullerene needle-like crystals

Needle-like crystals consisting of a solid solution of C₆₀-C₇₀ fullerene were synthesized by a liquid-liquid interfacial precipitation method using toluene and 2-propanol as solvents. A machined crystal with a V-notch was placed in a focused ion beam scanning electron microscope where it was bent until fracture by pushing it with a molybdenum probe to measure its mechanical properties and its fracture surface was examined. The crystals had a tensile strength of 58-71 MPa, which is much higher than C₆₀ fullerene needle-like crystals and slightly larger than alumina, and a fracture toughness of 1.1-1.3 MPa m^1/2. Moreover, it is possible to change the plasticity and fracture toughness of the C₆₀-C₇₀ crystals by solvation of different numbers of fullerene molecules. The C₆₀-C₇₀ fullerene crystals have the potential for use as electrodes, anchors for brittle materials, and ductile wires to carry electricity.