Absorption of Gases

Measuring Hydrogen Absorption by Metals

A CI microbalance has been incorporated in a computer-controlled apparatus designed to measure isotherms (hydrogen pressure versus hydrogen/metal ratios at a fixed temperature) for the absorption of hydrogen in a variety of metals and intermetallic materials. The traditional method of making these measurements is to introduce a fixed amount of hydrogen into the apparatus and to measure the resulting pressure drop (Sieverts method). This, however, leads to an accumulation of errors, and is also difficult to automate. It has recently been realised that the change in mass due to hydrogen absorption is easily measured on a microbalance, with an improved accuracy. Since the mass change is available as an analogue signal, automation is easy.

In this laboratory apparatus, the microbalance head has been mounted in a stainless steel caging so that hydrogen pressures of up to ten atmospheres can be used. The sample is suspended in a tube, which is mounted in a furnace at a controlled temperature, the hydrogen pressure is varied by changing the temperature of the hydrogen storage material. A computer reads temperatures and pressures through conventional transducers and ADC units. It can also change the hydrogen pressure between readings by altering the temperature of the hydrogen storage medium. Thus, it is possible to record pre-planned sets of data automatically.

High Pressure H-Solubility Studies on Various Metal-Hydrogen and Alloy-Hydrogen Systems

The use of a CI Microbalance allows the determination of P-C-T (Pressure Constant Temperature) data on various systems to be determined and also allows kinetic studies on hydrogen absorption and desorption.

The measurements are facilitated by connecting the balance, pressure and temperature to a PC, enabling the measurements to be automated and enabling the direct output of the P-C-T and kinetic data.

The temperature range involved is: 77K to 1273K. The pressure range is: Vacuum to 100 atmospheres.