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5. Experimental techniques in high temperature research

Aims: To illustrate the most important experimental techniques used to attain, control and measure high temperatures both in laboratory experiments and in industry; to describe the main methods employed in the measurement of thermodynamic and kinetic properties at high temperatures.

5.1 Generation, temperatures

measurement

and

utilization

of

high

and

very

high

Topic description and teaching suggestions: The concept and definition of thermodynamic temperature should be introduced. Temperature scales and International practical Temperature Scale (ITS-90) should be described also in their historical evolution. Examples of primary and secondary thermometers should be given. Among the methods to produce high temperatures, in addition to the classical resistance, radiation and radiofrequency induction heating techniques, mention should be made of laser heating and the exploding wire technique for generating extremely high temperatures (6000K+). Among the most used devices for temperature measurement, of special interest are resistance thermometers, various types of thermocouples, monochromatic optical pyrometers and total radiation pyrometers. Remarks on the suitability of different groups of materials for use as containers in experiments at high temperature under various chemical environments (vacuum-inert, reducing or oxidising atmosphere). Containerless processing techniques provide non- contact conditions; therefore, they are particularly useful to study liquid or glassy-state samples avoiding interaction of the sample with environment. Give a description of various levitation techniques: electromagnetic levitation, aerodynamic levitation, acoustic levitation, microgravity levitation in space coupled with various modes of heating such as by induction, incandescent radiator, or laser irradiation. Remember that “at high temperature anything reacts with anything else”; therefore, these techniques are conveniently used for the measurement of thermophysical properties of advanced

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