Synthesis and characterisation of a new hydrated bismuth (III) oxalate : Bi2_2(C2_2O4_4)3_3,6H2_2O

This study presents results on synthesis and crystal structure of a new hydrated bismuth(III) oxalate : Bi$_2$(C$_2$O$_{4}$)$_3$,6H$_2$O. This compound is obtained by precipitation from Bi(NO$_3$)$_3$ solution and oxalic acid. Its structure is determined by X-ray crystallographic analysis from a single crystal: it is monoclinic with a = 9.761(1)Å, b = 8.193(1)Å, c = 10.214(1)Å, $\beta$ = 99.66(1)$^{\circ}$, G.S. P2$_{1}$/n. Its chemical composition is confirmed by chemical analyses, FTIR and TG-DTA experiments

Mechanical properties of zinc and calcium phosphates

Recent studies on a variety of metal phosphates (MP) have revealed that MPs tend to be soft at ambient pressure if the coordination on the metal cation is low and the degree of hydration or hydrogenation is high, while they are stiff otherwise. In addition, the softer MPs were found to stiffen dramatically more quickly with increasing pressure than the stiffer MPs. Here we review these findings and support their relevance with new results on the mechanical properties of tribofilms aged in air of relative humidity, which were produced from commercial, zinc phosphate-containing lubricant packages via heating and rubbing. We find that the films can soften quite substantially after having been exposed to humidity, as to be expected from the studies of bulk MPs. Moreover, when the hydrated films are exposed to high loads, the force-distance withdrawal curve becomes identical to that of unaged, non-hydrated films. A straightforward explanation of this observation is that large pressure reverses the hydration of the tribofilms. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010