| An experimental method which can be called Reed-vibration Mechanical Spectroscopy for Liquids (RMS-L) has been invented newly in Huang Yi-neng’s group. Utilizing this method, the mechanical spectra of typical small molecular glass-former glycerol and propylene carbonate are obtained. Experimental results and analysis preliminarily indicate that the RMS-L method can effectively detect the mechanical spectra from the liquid to the solid state in real-time, so that it could provide physical information of soft condensed matter. The application of this method in research of physical processes of liquids and soft condensed matters, as well as the confirmation of its effectivity, remains researchable questions for this new method. In this work, parts of the questions above were probed.Firstly, the experimental method and repeatability of RMS-L was studied. We performed a detection of cooling and heating circle for each 16 kinds of glycerol samples, and the resultes shows that RMS-L is highly repeatable. Moreover, the complex Young’s modulus of glycerol during -relaxation was taken as the checkout parameter, we performed RMS-L measurements of cooling and heating circle for 18 kinds of glycerol samples, and found out that the repeatability of home-made temperature controller was pretty good. Besides, the mechanical spectra of a series of dimethyl phthalate samples were measured, and the results proved that RMS-L is a reliable and effective method to study some physical processes for liquids. The results also reveals the abnormal phenomenon of the relationship between glass transition temperature and internal freedom of molecules, and the possible mechanism was analyzed, as well.Secondly, the application of RMS-L in research of recrystallization and melting processes of supercooled liquids was explored, in this work. We measured the recrystallization of supercooled dimethyl phthalate (DP) and 1,3-propanediol (PD) samples using this method. The mechanical spectroscopic analysis shows that there was no crystallization in the cooling supercooled liquid (CSL) for DP and PD, but the heating supercooled liquid (HSL) can be crystallized. The HSL crystallization is driven by thermal activation. According to the Jeziorny-Johnson-Mehl-Avrami (JJMA) equation, we analysed the mechanical spectra during nucleation and crystal growth of propylene carbonate (PC) and 1,3-propanediol (PD) samples, and the results show that there is a crossover of the driven force from low temperature thermal activation to high temperature thermal activation, and the melting of crystals driven by high and low temperature thermal activation are both collective behaviors of molecules. In addition, we discussed about the melting method according to the Jeziorny-Johnson-Mehl-Avrami (JJMA) equation for heterothermal heterogeneous transition.Thirdly, a new method to detect the crack creating and healing of solids in real time based upon the RMS-L was designed, called RMS-L-CH. And a new scheme to pre-produce simple cracks was developed as well. A series of molecular liquids and three crystals were measured by the RMS-L-CH method, the results indicate that the RMS-L-CH method can effectively detect, in real time, the crack creating and healing processes of glass-formers and crystals, and some regular knowledge of the crack healing is obtained:1) the crack healing rate shows a single peak with increasing temperature, and the peak temperature can be taken as the characteristic temperature of the crack healing process Tch. The rate peak is non-symmetric, and the lower temperature side is wide but the higher is narrow, which shows that the cracks start to heal at relatively low temperature and healing amount is large. And contrarily, the higher temperature healing region is small so that the healing amount is small as well; 2) the crack healing temperature coincides with the onset glass temperature Tg, i.e. Tch=Tg independent of the liquid fragility. The law of Tch=Tg shows that the crack healing processes in glasses are closely related to the glass transition, and it could be concluded that it is the glass transition which leads to the crack healing in glass. These results further indicate that, the measurements of the crack healing in glass can provide a new means to characterize the glass transition processes and investigate the glass transition mechanisms; 3) the characteristic temperature of crack healing for crystals Tchc is higher than the one for glassformers Tchg, but it is lower than the recrystallization temperature for supercooled liquid Trc. The half-width of crack healing peak in crystal △Tchc is larger than that in glassformer Tchg,so the crack healing of crystal is much different from normal crystallization. As a result, we presented a crack healing model to describe the recrystallzation of liquid-like surface on cracks; 4) the dynamical processes of crack healing in glassformers are obviously different for simple and complex cracks. Compared to the crack healing in crystals, there is no nucleation and growth, but a process of overall coordination.For the fourth, the solidification course of modified two-component acrylic structural adhesive and epoxy glue were detected by the Reed-vibration Mechanical Spectroscopy for Liquids (RMS-L) in this work, and results show that there are four sequential processes of mechanical spectra with time. Deep analysis indicates that RMS-L can detect the generation and disappearance of active free radicals in real-time, as wells as the formation of chemical cross-link in the adhesive. Therefore, the RMS-L can provide effective information and become an approach to detect chemical reaction process.The fifth, the reed-vibration mechanical spectroscopy for liquids (RMS-L) was applied to measure and analyze the dehydration denaturation process of egg white and yelk, one kind of typical protein hydrogels, in this work. The results show that, with the reduction of water content, egg white at least has four states successively. The steric configuration denaturation of protein mainly happens in the mixed state in which the protein with bond water transforms to binding protein by losing the water. The mechanical spectrosopic results of thermal induced denaturation of egg white reveal that there are at least 5 states during heating. The denaturation of proteins include the transformation from the natural protein state to the extended protein state, and from protein with bond water to binding protein by losing the water. This indicates that the dehydration denaturation process of egg white and yelk, and the thermal induced denaturation of egg white can be effectively detected by RMS-L. The results about the mechanism of denaturation and protein hydrogels could be used as a reference for the related researches.Finally, reed-vibration mechanical spectroscopy for liquids (RMS-L) was used to measure the mechanical spectrum of the hydration process of ordinary Portland cement for the first time. The measured results show that there are seven sub-processes during the hydration of cement paste in order. The process of cement hydration is analyzed based on the existing conclusions of cement hydration and the measurement theory of mechanical spectroscopy. The results above show that RMS-L is a feasible method, and systematic and in-depth researches are thought to provide some possible clues to the unsolved problems of cement hydration. |
PDF Full Text Request