Study On The Shock Induced Phase Transition Characteristic Of Water By Optical Transparency Back Observation Technology

The phase transition behavior of shocked water was studied by employing an optical transparency back observation technique in this paper.Based on the light scattering theory and phase transformation kinetics,the phase transformation kinetics mechanism of water under multiple shocks is discussed.The experimental data indicate that the evolution of light transmittance of the shocked-water can be broadly divided into three stages,which are the phase transition relaxation stage,the decline stage,and the recovery stage in sequence.1.It is confirmed that the relaxation stage of the phase transition is completed in the nanosecond time scale.Analysis indicates that the higher the pressure,the greater degree of phase transition and the shorter relaxation time.Because the size of the new phase particles induced by quartz at the window/water interface at this stage is much smaller than the incident light wavelength,the scattering effect is not obvious,and the light transmittance of the sample in the phase transition relaxation stage remains stable.2.Signs of movement of the water/ice phase boundary to the liquid phase area under shock-wave loading conditions are observed.3.The physical mechanism corresponding to the transmittance decline stage and the recovery stage are suggested.In the early stage of multiple shock loading,driven by a substantial increase in shock pressure,the new phase grains grow up rapidly.Correspondingly,the transmittance of the sample in this stage shows a rapid decline.In the late stage of multiple shock loading,the growth rate of shock pressure slowed down,and the growth rate of new phase grains slowed down accordingly.In coordination with it,the transmittance of the sample in this stage shows a slow decline.When the transmittance reaches a minimum value,it represents that the size of the new phase particles at the moment is approximately equal to the wavelength of the given incident light.As the phase transition progresses,the size of the new phase particles gradually exceeds the wavelength of the incident light,causing the transmittance of the sample to recover.However,the progress of the phase transition also spawned more new phase particles that can act as a scattering source,which slowed down the speed of the sample's transmittance recovery.Therefore,the recovery rate in the measured transmittance curve is relatively slow.4.Liquid-solid coexistence state of water under high pressure was observed by employing the shock wave loading platform and the optical transmittance in-situ detection system.It appears that the final transmittance of the shocked sample has not yet recovered to1.This result shows that in the 6GPa pressure range,although the shock phase transition of water can occur in the nanosecond scale,the phase transition process is still not completed within 2500 ns.