High Pressure Volumetric Sorption Measurements On Small Samples At Low Temperatures*

With recent efforts to develop new hydrogen storage materials needed for the hydrogen economy, fast and accurate hydrogen capacity measurements are needed to screen the numerous types of test samples. Having an ability to perform such measurements on small masses facilitates the research both by reducing the effort required to produce enough material for testing and by increasing measurement throughput since small samples have process faster. Here, we report on improvements to the volumetric method that allows measurements at high pressures ($\sim $ 80 bar) and low temperature (77 K). Critical components for the exact control of temperature gradients from room temperature to the LN2 bath as well as methods used to minimize the effect of the falling LN2 level will be described. Experimental procedure, instrument calibration, accuracy estimates, and instrument verification will be discussed. Finally, example data with samples will be used to show the functioning of the instrument.