a b s t r a c tThe present study investigated the role of alloy microstructure and surface roughness on wear and friction behavior of leaded and unleaded tin bronzes. Ball-on-disk experiments were carried out under dry conditions with steel balls sliding against bronze disks. Scanning electron microscopy (SEM), energy dispersive electron microscopy (EDX), x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy were performed to analyze the sliding tracks and the ball scars. The wear reducing effect of lead was associated to the formation of an oxidized lead rich layer. When no such film formed on the leaded bronze wear was more severe than in case of unleaded bronze. Nevertheless, the presence of lead in the alloy was a necessary but not sufficient condition to obtain a smeared layer and thus a lubricating effect of the leaded alloy. Two mechanistic hypotheses were formulated to explain the formation of the smeared layer.

Adsorption studies of counterions carried by the ruthenium(II) complexes (Bu4N)2[Ru(Hdcbpy)2(NCS)2] (1), (Bu4N)4[Ru(dcbpy)2(NCS)2] (2), and [Ru(H2dcbpy)2(NCS)2] (3) (dcbpy = 2,2‘-bipyridyl-4,4‘-dicarboxylate, Bu4N = tetrabutylammonium) on TiO2 have been carried out by using thermoanalytical techniques, NMR, and ATR−FTIR spectroscopic methods. The thermogravimetric analysis (TGA) data of the adsorbed complexes 1 and 2 on TiO2 show the presence of 1 and ≤1.3 cations coadsorbed per ruthenium center, respectively. These complexes in the adsorbed state on TiO2 show remarkable stability in air atmospheres at high temperatures up to 180 °C. The only process that is observed at lower temperatures is the dehydration, which occurs between 40 and 110 °C. At high temperature the processes are deamination of the tetrabutylammonium counterion as well as decarboxylation and decomposition of the complex between 200 and 400 °C. The NMR data of the desorbed complexes 1 and 2 from the TiO2 surface show the presence of 1 and ≤1.5 cations, which is in close agreement with the TGA data. Comparative analysis of the ATR−FTIR spectra of complexes 1 and 2 between the free and the adsorbed forms also indicates the presence of 1 and ≤1.5 cations per ruthenium center, respectively.