No abstract

The adhesive interphase formed between brass plated steel cord and sulfur crosslinked rubber is known to be a complex layer of metal oxides, sulfides, and rubber. Hostile aging of this system produces changes in the structure, morphology, thickness, and mechanical properties of this layer. In a previous publication it has been shown that the overall thickness of the sulfide layer as measured by depth profiling with Auger electron spectroscopy could be used to characterize the degradation of the adhesive bond [G. E. Hammer et al., J. Vac. Sci. Technol. A 12, 2388 (1994)]. In this work multivariate statistical analysis of the sulfur Auger electron spectra was used to produce chemical depth profiles of the individual copper and zinc sulfide layers. These chemical depth profiles give new insight into the adhesion degradation mechanism on the nanometer scale. Particularly, the percentage of copper sulfide in the layer was found to be an accurate predictor of adhesion degradation.

The oxidation of zinc in air at 294 K has been studied for exposure times from 1 min to 150 h. The fraction of zinc in the Zn+2 valence state has been determined by high resolution Auger electron spectroscopy. Surface oxide thickness was measured by using AES with argon ion sputter etching. The adsorbed oxygen was shown by x-ray photoelectron spectroscopy to be in two states, one corresponding to O−2 in ZnO, the other being chemisorbed oxygen. The two O1s photoelectron peaks were partially resolved by means of a van Cittert-type deconvolution calculation and the relative separation was found to be 1.7 eV, in agreement with that for low level O2 adsorption of polycrystalline zinc under UHV conditions.1 The effect of temperature was also determined in the range of 294–573 K. The fraction of zinc in the Zn+2 valence state after 1 h exposure was found to increase nearly linearly with temperature, with ZnO formation complete at 573 K.

The adhesive interphase formed between brass and sulfur crosslinked rubber is known to be a complex layer of metal oxides, sulfides, and rubber. Hostile aging of this system produces changes in the structure, morphology, thickness, and mechanical properties of this layer. In this work it has been demonstrated that the overall thickness of the sulfide film can be used to characterize the degradation of the adhesive layer. The thickness of the sulfide film was measured from depth profiles of the brass-plated steel surface obtained by using Auger electron spectroscopy with ion sputter etching following cryogenic fracture of the bond. Aging under several conditions indicated an inverse relationship between adhesion and interfacial sulfide thickness, with magnitude dependent upon properties of the rubber compound formulation.

The effect of ion bombardment on the near-surface composition of brass has been investigated over a bulk composition range including single-phase a (fcc) brass and two-phase, a + p (bcc) brass. Auger electron spectroscopy has been used to determine the equilibrium near-surface composition after ion sputtering with argon and xenon at ion energies between 1 and 4 keV. Preferential removal of the zinc was found under all conditions. X-ray photoelectron spectroscopy has been used to investigate variations in composition in the first atomic layers by comparison of the intensities and escape depths of the 2p and 3p photoemission peaks. The near-surface composition was primarily a function of ion energy in the single a phase, with higher ion energy increasing the preferential removal of zinc; no change was detected comparing data from information depths of 5 vs. 10 monolayers. In the mixed a + p phase, surface zinc concentration decreased with increasing ion energy and mass, and depletion of zinc was greater nearer to the surface.