Terahertz spectrum characteristics of bituminous coal

In order to study the spectrum characteristics of bituminous coal under terahertz frequency band,7 kinds of Chinese bituminous coal were tested by using terahertz time domain spectroscopy ( THz-TDS). The absorption spec- trum and refractive index spectrum of the 7 kinds of bituminous coal were obtained. The effects of ash content,volatile matter,metamorphism degree and other factors of different bituminous coals on terahertz spectrum characteristics were analyzed. The results show that when the thickness of sample is 2 mm,the effective spectral bandwidth of bituminous coal is 1. 2 ~ 1. 8 THz,and no obvious absorption peak has been found in the effective bandwidth. With the increase of bituminous coal metamorphism degree,the absorption effect of bituminous coal gradually decreases,and its refractive index becomes smaller. With the increase of ash content in bituminous coal,the absorption effect of bituminous coal gradually increases,and the refractive index becomes bigger. Although the absorption effect and refraction index differ- ence of different bituminous coals in terahertz band are synthetically caused by the difference in composition of bitumi- nous coal,the results show that the ash content and metamorphism degree of bituminous coal are the major factors af- fecting the spectral characteristics. The accurate classification of different bituminous coals can be achieved by using THz-TDS.