A Study for Measurement of Thermophysical Properties using Thermal Fluctuations

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The results obtained from the present research are summarized as follows.(1)In order to detect very weak scattered light from thermally excited surface wave (ripplon), we have developed an heterodyne detection apparatus using a grating having a100 mum period. By employing n-pentane as an sample liquid near room temperature, we found that the apparatus has enough ability to detect the signal from ripplon.(2)Through experimental considerations, we have found optimum conditions for the incident angel of laser beam on the liquid surface and the order of diffracted beam from the grating. It was confirmed that, in principle, we are able to calculate the surface tension and the kinematic viscosity from the power spectrum of ripplons.(3)As the first step towards measurement on high temperature melts, we have designed a trough for molten Si using BN.We also have designed a high temperature furnace system up to 1600 ﾟC by using an infrared imaging furnace.(4)In order obtain much stronger scattered light from ripplon, we have employed a 200 mum-optical grating. By using this grating, we were able to detect much better S/N ratio signals and the reproducibility was improved : surface tension (〕SY.+-.〔)0.4% and kinematic viscosity (〕SY.+-.〔)11%.(5)Due to the improvement of reproducibility, we were able to detect the change of surface tension as a function of time because of degradation of liquid surface.