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

We report the results of measurements of adsorption isotherms of deute rium hydride (HD) adsorbed onto boron nitride. From this data we deriv e both the two-dimensional critical point temperatures (using Larher's method) and the heat of adsorption for the first few layers of this s ystem. These results are compared with similar measurements of ND adso rbed onto graphite and MgO. While substantial substeps within some adl ayer steps are evident in the adsorption isotherms of HD on graphite a nd 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.