Abstract：Terahertz time-domain spectroscopy has been gradually used in the study of ores. Usually, the rock should be ground and mixed with a binder to prepare samples. Thecontent and particle size of rock will affect the test result. Therefore, in this paper, the quartz sand (different particle size) was mixed with polyethylene(PE) particles in different proportions, and made into suitablesamples for terahertz system by means of tableting. The purpose was to explore the effect of quartz sand content and its particle size on the experimental results. Firstly, the effect of scattering particles content on the experimental results was studied. Particle size of quartz sand remain unchanged. It can be found that the time delay and peak values of time-domain signals show a non-monotonic trend. To explore this phenomenon, the refractive indexs and absorption coefficients of samples were further analyzed. The results showed that the refractive indexs of samples will gradually increase with the increase of the content of quartz sand in samples. Because the refractive index of quartz sand was larger than that of PE, which can be explained by the effective medium theory applicable to this experiment phenomenon. However, the absorption coefficients of samples increased first and then decreased with the increase of quartz sand content, and reached the maximum value when the mass fraction of quartz sand was about 60%. In order to explainthis phenomenon, the microstructure of the sample was observed by scanning electron microscope(SEM). It can be found that with the increase of quartz sand content, the breakage of PE particles during the pressing caused the particle size of PE to become smaller. According to the principle of Mie scattering and Rayleigh scattering, with decreasing particle size of PE, the scattering intensitydecreased, resulting in the phenomenon that absorption coefficients first increased and then decreased. In this paper, the influence of particle size of quartz sand on experimental results was studied. Samples with different particle sizes of quartz sand were tested. It can be found that refractive indexs of samples remained constant with the change of particle size of quartz sand. However, with the gradual decrease of particle size of quartz sand, the absorption coefficients of samples under the same ratio showed gradual decrease. According to Mie scattering principle, it could be inferred that the scattering intensities of samples gradually decrease with the decrease of the silica sand particle, so that the absorption coefficients of samples decrease with the decrease of the quartz sand particle. The research in this paper showed that the volume fractionand the particle size of quartz sand affect the experimental results. Under the condition of the same particle size, the absorption coefficient of quartz sand increased first and then decreased with the increase of the quartz sand content. With the same quartz sand content, the absorption coefficients of the samples gradually decreased with the decrease of the particle size of quartz sand. While the refractive index of samples increased with the increase of content of quartz sand, but the refractive index was broadly stableto the particlesize of quartz sand. Through the analysis of the refractive index and the absorption coefficient of the quartz sand and the mixture of PE particles in this paper, it has a certain degree of significance to the preparation of the mineral sample and the experimental results of the mixture.
Key words：Effective medium theory; Scattering; The mixture; Quartz sand; Terahertz spectroscopy
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