Aragonite crystals grown on bones by reaction of CO2 with nanostructured Ca(OH)2 in the presence of collagen. Implications in archaeology and paleontology.

The loss of mechanical properties affecting archeological or paleontological bones is often caused by demineralization processes that are similar to those driving the mechanisms leading to osteoporosis. One simple way to harden and to strengthen demineralized bone remains could be the in situ growth of CaCO3 crystals in the aragonite polymorph - metastable at atmospheric pressure -which is known to have very strong mechanical strength in comparison with the stable calcite. In the present study the controlled growth of aragonite crystals was achieved by reaction between atmospheric CO2 and calcium hydroxide nanoparticles in the presence of collagen within the deteriorated bones. In a few days the carbonation of Ca(OH)2 particles led to a mixture of calcite and aragonite, increasing the strength of the mineral network of the bone. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared (FT-IR) spectrometry showed that aragonite crystallization was achieved. The effect of the aragonite crystal formation on the mechanical properties of the deteriorated bones was investigated by means of X-rays microtomography, helium porosimetry, atomic force microscopy (AFM), and Vickers microhardness techniques. All these data enabled to conclude that the strength of the bones increased of a factor of 50-70% with respect to the untreated bone. These results could have immediate impact for preserving archeological and paleontological bone remains

The curious effect of potassium fluoride on glycerol carbonate. How salts can influence the structuredness of organic solvents

Glycerol carbonate (4-hydroxymethyl-1,3-dioxolan-2-one, shortly GC) is a dense, viscous, water soluble solvent. The high dielectric constant and dipole moment make it a suitable non-aqueous green solvent for several salts in different applications. GC dissolves significant amounts of inorganic salts such as KF. The saturation of GC with KF leads to the formation of a viscous liquid at room temperature. In this paper, we report on conductivity, rheology, differential scanning calorimetry and infrared spectroscopy experiments that indicate the formation of a glassy liquid where GC molecules and KF ion pairs are intercalated in a firm and ordered tridimensional structure, stabilized by hydrogen bonding and strong ion-dipole interactions

Chelators confined into 80pvac-borax highly viscous dispersions for the removal of gypsum degradation layers

AbstractIn this paper a new method for the removal of gypsum degradation layers from carbonatic matrices in cultural heritage conservation, using aqueous Highly Viscous Polymeric Dispersions (HVPDs) based on partially hydrolyzed poly(vinyl acetate) and borax, embedded with chelators, is presented. Due to their interesting viscoelasticity, these systems guarantee a good adhesion to the treated surface and easiness of removal in one step, minimizing the residues. Thus, they can potentially overcome the "residue question" limit associated to traditional methodologies that use thickened solutions of chelators. Here the rheological properties of HVPDs containing different amounts of selected chelating agents are explored and their efficacy in the extraction of gypsum is verified through cleaning tests onto artificially sulfated travertine tiles. The homogeneous removal of gypsum across the surface was checked non-invasively via Fourier Transform Infrared Spectroscopy (FTIR) 2D Imaging. An analytical protocol for the pre-treatment and the analysis of HVPD samples by means of Ion Cromatography (IC) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) was set up and the approximate amount of calcium sulfate removed was determined