Study on the Structural Relaxation in Supercooled Liquids and Glasses

本课题研究了过冷液晶态和玻璃态的结构弛豫。选择了氯化物和氧化物的玻璃形成系统作为研究对象。在含氯化锌的二元体系中进行了超声光谱分析。在这些二元熔体中，声波在过冷区有明显的频散现象。本文对三种二元熔体进行了瑞利-布里渊散射实验，分别为：氯化锌-氯化钠、氯化锌-氯化钾和氯化锌-氯化铯。在550-1000K的温度范围内，获得了每个二元熔体的瑞利-布里渊光谱的完整轮廓。观察到光谱形状随温度和组成的变化而显著变化，并认为这是由于熔体的结构弛豫所致。在高超声速区域的熔体中，观察到声波传播的色散。在单弛豫假设下，用粘弹性理论对光谱进行了分析。确定了极限低频和高频下的驰豫时间和速度随温度和碱氯化物组成的函数。用纯的氯化锌、氯化锌-溴化钾和氯化锌-碘化钾制备了玻璃样品。在玻璃态下得到的光谱与在过冷液体中的光谱相似。玻璃态下，在GHz频段没有结构弛豫。

The structural relaxation in the super cooled liquid and glass states has been studied in present project. The glass forming systems of chlorides and oxides has been selected as the objects. Ultrsonic spectroscopy has been carried out in binary systems containing zinc chloride. In those binary melts, the dispersion of sound wave has been found in the super cooled temperature region.Rayleigh-Brillouin scattering experiment has been carried out for ZnCl_2-NaCl, ZnCl_2-KCl and ZnCl_2 ZnCl_2-CsCl binary melts. The complete profiles of Rayleigh-Brillouin spectra were obtained for each binary melt, and at temperatures ranging from 550 to 1000K.The remarkable change in the shape of the spectrum with the variations in temperature and composition has been observed and has been concluded to be due to a structural relaxation in the melts. A dispersion of sound wave propagation was observed in the melts at the hypersonic region. The spectra have been analyzed by the viscoelastic theory with the assumption of the single relaxation. The relaxation time and the velocities at limiting low frequency and high frequency were determined as functions of temperature and of alkali chloride composition.The experiment has also been done for glass state. The samples of pure ZnCl_2, ZnCl_2-KBr and ZnCl_2-KI has been used for preparing glass samlpes. The spectra obtained in glass state was similar to those in super cooled liquids. In the glass state there was not structural relaxation in the frequency region of GHz.