Formation characteristics of calcium phosphate deposits on a metal surface by H2O2-electrolysis reaction under various conditions

Dispersion and stability mechanism of Pt nanoparticles on transition-metal oxides

The heterogeneous catalysts of Pt/transition-metal oxides are typically synthesized through calcination at 500 °C, and Pt nanoparticles are uniformly and highly dispersed when hydrogen peroxide (H₂O₂) is applied before calcination. The influence of H₂O₂ on the dispersion and the stability of Pt nanoparticles on titania-incorporated fumed silica (Pt/Ti-FS) supports was examined using X-ray absorption fine structure (XAFS) measurements at the Pt L₃ and Ti K edges as well as density functional theory (DFT) calculations. The local structural and chemical properties around Pt and Ti atoms of Pt/Ti-FS with and without H₂O₂ treatment were monitored using in-situ XAFS during heating from room temperature to 500 °C. XAFS revealed that the Pt nanoparticles of H₂O₂-Pt/Ti-FS are highly stable and that the Ti atoms of H₂O₂-Pt/Ti-FS support form into a distorted-anatase TiO₂. DFT calculations showed that Pt atoms bond more stably to oxidized-TiO₂ surfaces than they do to bare- and reduced-TiO₂ surfaces. XAFS measurements and DFT calculations clarified that the presence of extra oxygen atoms due to the H₂O₂ treatment plays a critical role in the strong bonding of Pt atoms to TiO₂ surfaces.

Magnesium Doped Hydroxyapatite-Based Coatings Obtained by Pulsed Galvanostatic Electrochemical Deposition with Adjustable Electrochemical Behavior

The aim of this study was to adapt the electrochemical behavior in synthetic body fluid (SBF) of hydroxyapatite-based coatings obtained by pulsed galvanostatic electrochemical deposition through addition of Mg in different concentrations. The coatings were obtained by electrochemical deposition in a typical three electrodes electrochemical cell in galvanic pulsed mode. The electrolyte was obtained by subsequently dissolving Ca(NO3)2·4H2O, NH4H2PO4, and Mg(NO3)2·6H2O in ultra-pure water and the pH value was set to 5. The morphology consists of elongated and thin ribbon-like crystals for hydroxyapatite (HAp), which after the addition of Mg became a little wider. The elemental and phase composition evidenced that HAp was successfully doped with Mg through pulsed galvanostatic electrochemical deposition. The characteristics and properties of hydroxyapatite obtained electrochemically can be controlled by adding Mg in different concentrations, thus being able to obtain materials with different properties and characteristics. In addition, the addition of Mg can lead to the control of hydroxyapatite bioactive ceramics in terms of dissolution rate.