A Tian-Calvet heat-flux microcalorimeter for measurement of differential heats of adsorption

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Abstract
A Tian-Calvet heat-flux microcalorimeter system is described for measurement of heats of adsorption and reaction on solid surfaces. Heat-flux signals are measured in transducer assemblies consisting of several hundred Seebeck-effect thermoelements connected in series and arranged in a thimble configuration. These transducers surround quartz calorimeter cells connected to a high-vacuum, volumetric adsorption system. The sensitivity of the calorimeter can be calibrated with a Joule-effect device or by measurement of heats of adsorption for known processes. Microcalorimetric measurements have been conducted at temperatures from 300 to 473 K, and operation at temperatures from about 200 to 573 K is possible. Calorimeter cells are described that facilitate sample handling under controlled atmosphere conditions, allowing studies of freshly treated materials and samples that have been exposed to catalytic reaction conditions.