Pressure-Composition-Temperature (PCT) Measurements
Pressure-Composition-Temperature (PCT) measurement provides scientists with a source of important information related to thermodynamical properties of hydrides. PCT measurement is generally performed at isothermal conditions, where the pressure in a function of concentration of hydrogen in a hydride is collected at a constant temperature (Fig. 1). As a result, PCT measurement is also known as Pressure-Composition-Isotherm (PCI). Thermodynamic properties of different hydride systems, such as enthalpy or entropy, can be compared using their PCT data.
A fully-automatic, and computer-controlled volumetric apparatus (known as Sieverts apparatus, or PCT apparatus) has been installed in our lab to perform PCT measurement (Fig.2 and 3b). It is capable of measuring isotherms from 25 to 500oC to a maximum hydrogen pressure of 100 bar. On-going projects at MSEL Hydrogen Storage Materials Program include the modification of PCT apparatus for small volume/mass samples, and combination of PCT measurement with other methods for measuring hydrogen capacity (In-situ PCT with Raman spectroscopy or in-situ PCT with infrared (IR) imaging measurement).
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