Abstract
Abstract With regard to the mechanism of electromagnetic radiation (EMR) excited by deformation and failure of coal and rock, the present study employed the optical microscope, digital microhardness tester and atomic force microscopy (AFM) to measure surface morphology, surface microhardness and electro-mechanical characteristics, including elastic modulus and surface potential of coal. The results show that micro-mineral composition and micro-mechanical properties of coal are clearly heterogeneous. The elastic modulus values measured are 62.3 MPa–4.0 GPa and the surface potential values tested are 21.2–166.2 mV. The proportion distributions of the two parameters mentioned follow the normal distribution, which indicates the electro-mechanical characteristics of coal are clearly inhomogeneous at the micro- and nanoscales. Finally, the effects of the inhomogeneous elastic modulus and surface potential on the EMR from the microscopic perspective were analyzed. In this experiment, the change of the micro-elastic modulus and the existence of the surface potential on the coal surface were directly observed. The findings reveal the mechanism of EMR induced by deformation and failure of coal and rock.
Highlights
In mines, coal and rock dynamic disasters frequently occur that seriously threaten the safe development of mines
The typical force–separation curve obtained during atomic force microscopy (AFM) imaging by peak-force quantitative nano-mechanical (PF–QNM) is shown in figure 3, while the abscissa is the distance between the probe tip and the sample, the ordinate represents the force between the probe tip and the sample
When the tip of the AFM probe falls on the inherent damage point or region of coal samples, the micro-elastic modulus values tested are smaller
Summary
Coal and rock dynamic disasters (such as rock burst, coal and gas outburst, etc.) frequently occur that seriously threaten the safe development of mines. The electro-mechanical properties of coal and rock at the micro- and nanoscales have not been studied in detail yet. Atomic force microscopy (AFM), as an instrument with atomic-level precision in the field of material science, has been widely used in the research into electro-mechanical properties of solid materials at the micro- and nanoscales. The results and conclusions above provide useful references for studying the electro-mechanical properties of coal and rock at the micro- and nanoscale. The reasons from the microscopic perspective for inhomogeneous failure and the generation of surface potential of coal were explored Their influence on the EMR excited by deformation and failure of coal was analyzed so as to give an insight into the research on the mechanism of EMR on the micro-basis. The micro-mechanical and electrical characteristics of rock will be conducted in future research
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