EXPERIMENTAL STUDIES OF HYDROGEN ON BORON-NITRIDE .1. ADSORPTION-ISOTHERMS OF HD

We report the results of measurements of adsorption isotherms of deuterium hydride (HD) adsorbed onto boron nitride. From this data we derive both the two-dimensional critical point temperatures (using Larher's method) and the heat of adsorption for the first few layers of this system. These results are compared with similar measurements of ND adsorbed onto graphite and MgO. While substantial substeps within some adlayer steps are evident in the adsorption isotherms of HD on graphite and MgO and have been shown to indicate a two-dimensional liquid-solid transition within the layer, no substep is evident at the level of one percent of a step level for HD adsorbed onto BN.