石英砂-聚乙烯二元混合体系的太赫兹光谱特性研究

太赫兹时域光谱技术目前逐渐应用于对岩石的研究中。在制备样品时通常需要将岩石磨碎后与粘合剂混合压片，岩石的含量、粒径等都会对测试结果造成影响。将自然界中常见的石英砂粉末（不同粒径）与聚乙烯（PE）微粒以不同的比例混合，通过压片的手段将其制成适用于太赫兹系统测试的样品，用以探究样品中石英砂的含量以及其粒径对实验结果的影响。首先研究石英砂含量对实验结果造成的影响。在保持样品中石英砂的粒径不变的情况下，发现不同石英砂含量样品的时域光谱图中，时间延迟以及峰值都呈现出非单调的变化趋势。为了探究出现这种现象的原因，对样品的折射率以及吸收系数做了进一步的分析。结果表明样品的折射率会随着样品中石英砂含量的增加而逐渐增大，通过适用于本实验的有效介质理论能够解释这一现象。样品对于太赫兹波段的吸收系数随着石英砂含量的增加呈现出先增大后减小的现象，并且在石英砂质量分数为60%时达到最大值。为了解释这一现象产生的原因，利用扫描电子显微镜对样品的微观形貌进行观察，发现随着石英砂含量的增加，在压制样品时PE颗粒破碎程度加剧，导致PE的粒径变小。根据米氏散射以及瑞利散射的原理，石英砂粒径不变而PE粒径减小，随之降低的散射强度与石英砂的吸收效应发生竞争，从而导致了吸收系数先增大后减小的现象。进一步研究了石英砂粒径对实验结果的影响，对不同粒径的石英砂样品进行测试，发现折射率不随石英砂粒径的变化而改变，但其吸收系数随着石英砂粒径的减小而逐渐减小。根据米氏散射，样品吸收系数的变化是由于散射强度随石英砂粒径的减小而逐渐减小。研究表明，样品中石英砂的含量和粒径都会对实验结果产生影响。石英砂粒径相同时，样品的吸收系数随石英砂含量的增加呈现先增大后减小的趋势，样品的折射率随石英砂含量的增加而逐渐增大；石英砂含量相同时，样品的吸收系数随石英砂粒径的减小而逐渐减小，而样品的折射率基本不变。这一结论对矿物样品的制备以及对混合物的实验结果分析有一定程度的指导意义。

Spectroscopy Studies on Quartz Sand-Polyethylene Hybrid Systemin the Terahertz Range

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.