Tribo-Induced Near-Infrared Light Emission between Metal and Quartz.

Triboluminescence (TL) refers to the luminescence phenomenon at the material surface under the action of pressure or shear. This fascinating phenomenon can directly convert mechanical energy into light emission without the need for other auxiliary components; therefore, it attracts more and more researchers to conduct research in different wavelength ranges, such as X-ray, ultraviolet, visible light, and terahertz. However, there have been few reports on the study of the near-infrared (NIR) range, which is very important in the integrity of the triboluminescence research. In this research, we found that NIR light with a wavelength ranging from 800 to 1000 nm was generated by friction between solid metals and a quartz crystal. Analysis of the cross section of the quartz disk after friction revealed that the TL phenomenon had a strong relationship with the doping of metal grains into the silica. Density functional theory (DFT) and X-ray photoelectron spectroscopy were also conducted to further identify the results. We infer that such light emission arises from the implantation of metal grains into the surface of the quartz, which forms a metal-insulator junction with amorphous silica. Moreover, electron transition between the metal and the insulator, followed by a transition at the center of the defects, causes near-infrared light emission. Our research reveals the infrared luminescence behavior from a different perspective, the transfer of materials, and perhaps deepens the understanding of the near-infrared emission mechanism.

Triboluminescence dominated by crystallographic orientation.

Triboluminescence (TL) is an optical phenomenon that has a long and varied history with broad applications, such as damage detection, X-ray source, and mass health monitoring sensor. So far, the properties and mechanisms of TL remain not completely understood. The TL properties emitted during the sliding contact between Al2O3 and SiO2 surfaces were studied along different crystallographic orientations. In this study, the TL intensity of Al2O3 was significantly enhanced as Al2O3 surface was along a particular crystallographic orientation, which is an unconventional phenomenon. TL enhancement of Al2O3 was not affected by air atmosphere and atomic stocking mode of Al2O3. The enhancement mechanism of Al2O3 may be influenced by the surface state of Al2O3. This work provides a new method to control the intensity of TL and novel ideas to elucidate the TL mechanism.

Enhancement of Triboluminescence in the Presence of CO2 by Sliding between Silica and Yttria-Stabilized Zirconia.

Triboluminescence (TL) has gained increasing attention in the past two decades due to its potential for many applications such as an in situ damage sensor, X-ray source, spectroscopic probe, and optical switch. So far the mechanisms by which TL is excited are not well understood. We have investigated the TL emitted during the sliding contact between silica wafer and YSZ (yttria-stabilized zirconia) wafers in CO2 gas, ambient air, and vacuum. We discovered that the mean intensity of photons emitted in CO2 gas is nearly a hundred times stronger than that in air. TL induced in the sliding experiment is proposed to be due to a combination of chemical luminescence, impurities and vacancies luminescence. In addition, the intensity of the light emission of YSZ may be controlled by changing the concentration of CO2 gas.