Investigation of a factor on the luminescence induced by a mechanoluminescence of rocks

The objective of the present study is to investigate a factor on luminescence of rock induced by mechanical action such as fracture and/or sliding. The luminescence was caused by 3-points destructive test and sliding slip test. It was observed by an electron multiplication cooled charged-coupled device camera, i.e., EM-CCD camera. The intensity of the luminescence was also detected by a luminescence analyzer employing a photomultiplier tube. In order to reveal the role of SiO2 as a factor of piezoelectric effect, tensile strength and ambient gas plasma, SiO2 amount was measured using X-ray diffraction analysis. The test was carried out in air, nitrogen or oxygen. In addition, a spectrum analysis was done during slide slip test to verify the role of ambient gas on the luminescence. From the obtained results, it was revealed that the luminescence appears by fracture loaded by the 3-points bending and also the sliding slip test. The spot-like luminescence can be observed by the EM-CCD camera. The luminescence intensity depends on SiO2 amount in rocks and its tensile strength. When nitrogen is used as ambient gas, the luminescence becomes stronger. The luminescence of rock can be generated by plasma of ambient gas induced by piezoelectric effect in mechanical action, i.e., fracture and/or sliding.