Research On Crystallization Of Water Induced By Fused Quartz Under Shock Compression

Water is considered to be the source of life since it not only is the most common substance in nature, but water is essential to both humans and other life forms as it is the most important component of all organisms. Water is always caused much attention of scientists because it has many unusual physical and chemical properties. The pressure-induced liquid-solid phase transition of water has been researched in static high-pressure experiments in the past, and the existences of dozens of phases have been confirmed. The question now is whether water can also freeze in a dynamic loading process of shock compression. However, shock-induced solidification still remains a challenge because some technique difficulties are needed to be overcome. Shock loading is an adiabatic and transient process. To obtain the structural information of a material in a very short period of time is a very difficult task. To accomplish this, well-designed experimental setups, experimental equipment with high sensitivity diagnostic and highly accurate synchronization techniques are needed. The rapid crystallization of water has been successfully performed in molecular dynamics simulations, but not enough direct evidence in terms of freezing occurring in nanosecond time scales. Thus far, only works conducted by Dolan have been reported, but their results of water freezing were only observed in the case of using a silicon-glass window. However, the freezing point of water changes by the effect of external conditions. So attention should be paid to the following problems. Firstly, whether the freezing of water still need to undergo supercooling under the role of silica glass? Secondly, the effect of silica glass induced to freezing was an indirect or direct effect? Thirdly, what was the mechanism of the silica glass during the induced freezing? In this thesis, we further studied the water freezing under shock compression with a novel technique using light transmission measurements and obtained the following conclusions:(1) A measurement technique employing optical transmission under shock loading conditions was developed, in which the speeds of projectile is up to 700 meters per second. Fused quartz was to maintain good transparency below pressure of 4.5GPa, and was confirmed during that the shock compression and unloading process. Shock wave velocity of fused quartz was found is to be constant during elastic compressions with an average speed of 5.99 kilometers every second.(2) Rapid crystallization of water occurred when water came into contact with the fused quartz at 1.28GPa. This pressure was lower than the results which were reported by Dolan. The liquid-solid phase transition occurred very rapidly and produced the scattering effect of incident light within dozens of nanosecond.(3) According to kinetics of phase transition theory, water must first be supercooled to certain degree before the liquid-solid phase transition can occur. However, we observed the phase transition occuring in the liquid region of the phase diagram. This phenomenon is not explained by traditional theory. The rate of crystallization did not differ when different paths were chosen to cross the liquid-solid phase transition boundary. For this reason, the conclusion is that the freezing phenomena can not be completely attributed to supercooling.(4) By experiment with other types of window materials to be in contact with water, it was found that freezing only happened during the presence of fused quartz windows. Such phenomena can be explained as follows:First, in accordance to the interface nucleation theory, the particles near the interface were coronary that the required nucleation energy is less than that of spherical nucleation. Secondly, the static electric field of the interface make water molecules appear to form a hydrogen-bonding network with intermingled regions of ordered structures; Thirdly, the freezing point of water becomes higher under the effect of an electric field. Therefore, ice nucleation occurs more easily at water-fused quartz interfaces under multi-shock compressions.