|Bachelorprojekt, 1. modul, 2011, id:271|
|Findes på RUb:||Ja|
This report introduces an approach to characterizing thermal and mechanical properties of viscous liquids, by using a specific set up utilizing the coupling of a piezoelectric bulk modulus gauge (PBG) and a thermistor placed on a transverse wire through the PBG. More specifically we are using this set-up to investigate the temperature response to a pressure change of a supercooled liquid at the dynamic glass transition, as is also stated in the title. Physically this is achieved by applying a voltage on the liquid filled PBG, causing a volume displacement, which then in turn creates a pressure difference in the sphere. The report includes an introduction to supercooled liquids, viscosity and the glass transition. An introduction is also given to the energy bond formalism we use to derive a model for the experimental system (expressed in circuit diagrams). Based on this we derive transfer matrices that characterize the energy couplings of the thermodynamic, mechanical and electrical variables. Experiments are conducted with an empty PBG, a liquid-filled PBG and the latter utilizing the special conditions from the set-up with the thermistor and PBG coupling. From these experiments coupled with some approximations and generalized modelling, we are able to characterize various properties like capacitance and adiabatic compressibility. This data is used in conjunction with data determined in previous research to characterize the inverse of the adiabatic pressure coefficient. A significant amount of noise is detected in some experimental data. Also some unexpected development was detected in the frequency dependence of temperature change (formel) and the inverse adiabatic pressure coefficient (formel). Hovewer - concurrent independent experiments that use the same equipment but in a different manner show similar abnormalities in the data. This is indicating some "exo-model" influence that we have not accounted for. In spite of various abnormalities, the model is deemed viable for continued development, due to consistency with other similar studies and results.