Optical Microscopy inside a Heating Capillary

Abstract

This paper presents a heating-capillary video-microscopy system that allows visual observation and quantification of phenomena involving biphasic dispersions with interfaces at high temperatures. The cylindrical capillaries were made to have inside diameters of ∼200 μm, while their exterior was coated with a transparent tin-doped indium oxide film that acted as an electrically heating jacket. The produced capillaries achieved temperatures ranging from ambient to at least 287 °C, the boiling temperature of n-hexadecane, a high boiling point hydrocarbon used in the temperature-calibration experiments. The generated temperatures may oscillate, with maximum deviations of about 3 °C from ambient to 80 °C, 9 °C from 80 to 170 °C, and 45 °C from 170 to 265 °C. In the range of 100−265 °C, the desired temperatures were attained at a rate from 75 to 198 °C/s and could be easily adjusted by changing the applied ac voltage with a variable transformer. Two examples of using the heating-capillary technique for interfac...