Design of ultra-efficient and automatically temperature-variable cycle (TVC) Sieverts apparatus for testing sorption properties of hydrogen storage materials

Abstract

The evaluation of hydrogen sorption properties in materials is crucial for their widespread applications. However, existing volumetric apparatuses often suffer from low accuracy and efficiency due to inadequate calibration techniques, temperature gradients, and limited automation. To address these limitations, a Temperature-Variable Cycle (TVC) Sieverts apparatus has been developed. Besides conventional tests, the device is capable of efficiently performing TVC tests, such as TVC Pressure-Composition-Temperature (PCT) isotherm and kinetics, through the integration of RS485 serial communication and automatic dosing techniques. The instrument's component selection and configuration were described in detail. Furthermore, novel methods for volume calibration and anti-thermal gradient were presented, where a continuous function was proposed to overcome temperature gradients across the entire range of test temperatures. Finally, a series of tests were conducted using La0.5Ce0.5Ni4Co alloy and Mg material as benchmark materials to validate the setup and methods. The accuracy of volumes and the feasibility of the methods were confirmed through null PCT tests and data comparisons of PCT with kinetic of La0.5Ce0.5Ni4Co alloy, respectively. By employing these methods, the accuracy of null tests is improved by nearly tenfold. The efficiency and robustness of the unit were demonstrated through Temperature-Programmed Desorption/Absorption (TPD/TPA), TVC PCT, and TVC kinetics tests on MgH2 powder. The results produced by the TVC system align well with the reliable data in literature.