Chemical pavement modifications to reduce ice adhesion

The formation of ice and snow on road pavement surfaces is a recurring problem, creating hazardous driving conditions, restricting public mobility as well as having adverse economic effects. It would be desirable to develop new and improved ways of modifying the pavement surface, to prevent or at least delay the build-up of ice and to weaken the pavement–ice bond, and making the ice which forms easier to remove. This development could lead to economic, environmental and safety benefits for winter service providers and road users. This paper describes how environmental scanning electron microscopy was used to examine the mechanism by which de-icing chemicals, added as a filler replacement to bituminous materials, can be transferred to the pavement surface. The paper assesses the potential for chemical modifications to reduce the adhesion between ice and the pavement surface by means of work of adhesion calculations, based on surface energy parameters and a new physical ice bond test. The paper also examines the influence that the chemical modifications have on the durability of the pavement surface course

An investigation of ZnSe growth by chemical beam epitaxy using modulated beam scattering and related techniques

Mechanistic aspects pertaining to the CBE growth of ZnSe on GaAs from dimethyl-zinc and diethyl-selenium precursors have been investigated using modulated beam scattering techniques in combination with other surface sensitive methods. The Gp VI precursor requires pre-cracking to form Se on either the GaAs substrate or on the ZnSe growth surface. In contrast, dimethyl zinc decomposes readily on GaAs although it also displays a negligible reactive sticking probability on ZnSe. ZnSe CBE growth is possible, however, since the decomposition efficiency of this precursor rises to unity over a wide temperature range in the presence of a simultaneous Se flux. The reactivity patterns observed in III-V and II-VI CBE are compared and contrasted. The results suggest that ALE-type growth approaches should be more successful in the case of the II-VI compounds and that compositional control of the growth matrix may also be more readily achieved for such materials in comparison to the case for the III-V semiconductors