LIGHT-PULSES EMITTED AT MICROFRACTURES FORMED BY FRICTION BETWEEN 2 SOLID MATERIALS

Short-duration light pulses have been observed to be emitted at the mo ment of microfracture (pit size of 10-20 mu m) when two solids are rub bed against each other, When a fused silica sample is scratched by a d iamond grain, the observed light pulses have a rise time of less than 10 ns and pulse width of 10-20 ns. A continuous spectrum at 500-800 nm is observed, suggesting 3000 degrees C material part. At 300-400 nm, intense line spectra are observed, which suggests the existence of gas eous O-2 molecules desorbed from SiO2. When the solid fractures, the fractured part heats up to a very high temperature almost instantaneou sly, and cools down within 10-20 ns.