Adhesion characteristics of gold surfaces

Abstract

Measurement of the contact area between a gold coated glass ball and a polyurethane surface during a pull-off test at constant load allows one to show that the energy of adhesion corresponds to that of a low energy surface. These results, which seem equally valid for other elastomers, rubber-based adhesives and even epoxy adhesives, throw doubt on our understanding of the adhesion process. If the cause of the low surface energy measured over inorganic surfaces is an adsorbed layer, the latter is not displaced by the adhesive.Surface energy is a determining factor in adhesion. If the surface energy of a substrate is low, its ability to form strong adhesive bonds (the adhesive strength) is also low, and the converse.In a recent review article published in this journal (1), it was shown that gold has a low surface energy, involving essentially dispersive, rather than polar, interactions. This low surface energy could not be increased in spite of a variety of cleaning methods being used.However, from the nature of metals their surface energies should be high, as is the case for molten gold.When a metal or inorganic solid has a low surface energy, this is usually attributed to the adsorption of substances which lower the surface energy. As the observed adhesive strength of metals is usually high, it indicates that the adhesives displace the adsorbed layer.Polyurethane has been used in the study presented below to determine the energy of adhesion, and, by inference, gold's surface properties. As polyurethane has surface properties similar to other rubber-like materials, its adhesive strength to gold should be the same as that of all rubber or rubber-based adhesives.From the kinetics of the breaking of adhesion between an elastomer and a gold surface, it can be shown that either gold has a low surface energy, or the adsorbed surface layers are not readily displaced by adhesives.Furthermore, as similar results were obtained for a drop of epoxy adhesive on gold, this argument is probably valid for other adhesives in contact with gold.

Study of the Interfacial Shear Strength Pressure Dependence by Modulated Lateral Force Microscopy

“…Our measurements on these four samples thus seem to confirm that the hypothesis of Barquins, i.e. the friction force is the sum of an adhesive contribution and a ploughing contribution, is valid for a nanocontact such as an AFM tip−sample contact.…”

“…For randomly rough surfaces, the contact area increases in direct proportion to the normal applied load and the macroscopic Amonton's law is recovered. A second hypothesis, first proposed by Barquins for macroscopic contact, considers that the friction force is the sum of an adhesion contribution τ 0 A and a ploughing contribution F L F N , i.e. : with μ L the friction factor and F N = F n + F ad the total normal load applied to the surface.…”

Evaluating the Influence of Current on the Wear Processes of Au/Cr-Au/MWCNT Switching Surfaces

“…it causes layers and is the result of the w between the layers. [18] In between the contact resistance discussed. The trends of R c failure: unstable, stable, rising stage, the fine transfer mechan resistance and number of boun image of the Au/MWCNT su mulate the switching action of a tact force was set to 1 mN.…”

Overview of Silane-Based Polymer Coatings and Their Applications

“…The bond between the main and side chains is Si-O. Silicone has a relatively low surface tension as a liquid and a low surface free energy (20 mJ/m 2 ) as solid when compared with those of epoxy resin (about 40 mJ/m 2 ), urethane resin (about 50 mJ/m 2 ), and acrylic resin (about 40 mJ/m 2 ) [ 7 ]. Therefore, they tend to detach from the substrates as a solid fi lm, even though they might be easy to get wet and stretch out on substrates as a liquid.…”