Briltouin Scaterring And Raman Scaterring On Silicone Oil Under High-pressure

Silicon fluid is a kind of organic siloxane with different polymerization degreechain structure, which can be distinguished by different viscosities. Generally, itpossesses many merits, such as chemically stable, transparent, colorless (or canary),odorless, non-toxic and low volatile. As one of the regular pressure transmittingmedia used in diamond anvil cell (DAC) experiments, the hydrostaticity of siliconeoil has been highly concerned. However, there are no systematically reports on theacoustic velocity, Raman vibration and equation of state of silicone fluids withdifferent molecular structure and different viscosities under high pressure. Researchon the relationship between the hydrostatic limits of silicone oil and their viscosityand structure is important to the high-pressure experimental techniques and methods.In this thesis, using the DAC high pressure technique with ruby fluorescence R1line method for pressure calculation, we performed high-pressure Brillouin scatteringand Raman scattering measurements on three silicon fluids with differentviscosities(Silicon oil AP150wacker, Baysilone oil M1000and Baysilone oilM30000).1.By analyzing the Brillouin spectra of three different viscosity silicone oil underhigh pressure at room temperature, we obtained the pressure dependence of theacoustic velocity, refractive index and density for three samples with differentviscosities. At the same pressure, the less viscosity the oil possesses, the lower soundvelocity it has. the Silicone oil AP150wacker s acoustic velocity is lower than theother two; At around17GPa, the velocity in Silicone oil AP150wacker suddenlyincreases, this phenomena probably suggests an onset of structural densification underhigh-pressure.2.By analyzing the Raman spectra of three different viscosity silicone oil underhigh-pressure at room temperature, the pressure dependence of Raman frequency shiftfor three samples with different viscosities have been obtained, and the Ramanvibrations modes were identified. Solidification process was observed pat around0.27GPa for Baysilone oil M1000and0.1GPa for Baysilone oil M30000, respectively. The intensity reduction of Si-O stretching vibration and appearance of new Ramanvibration modes were found. Some Raman vibrations disappeared and vibration slopechanged for Silicon oil AP150wacker, Baysilone oil M1000and Baysilone oilM30000at around10GPa,8GPa and4.5GPa, respectively.3.Based on the pressure dependence of ruby fluorescence R1line width andR1-R2splitting, we analyzed the hydrostatic limits of silicone oil with differentviscosities, and found that Silicon oil AP150wacker with the lowest viscositypossess the highest hydrostaticity. The hydrostatic limits of Silicon oil AP150wacker,Baysilone oil M1000and Baysilone oil M30000were10GPa,8GPa and4.5GPa,respectively. This is consistent with the pressure dependence of Raman vibrationschange under high-pressure, suggesting possible internal structure changes in siliconfluid lead to hydrostatical change.