Sarah Petit

Fonction et rattachement

Doctorant / CNRS

Carrière

Au LRS depuis le 15 octobre 2014

Publications

Incorporation of vanadium into the framework of hydroxyapatites: importance of the vanadium content and pH conditions during the precipitation step

By: Petit, Sarah; Gode, Thrimurthulu; Thomas, Cyril; Dzwigaj, Stanislaw; Millot, Yannick; Brouri, Dalil; Krafft, Jean-Marc; Rousse, Gwenaelle; Laberty-Robert, Christel; Costentin, Guylene

Physical Chemistry Chemical Physics - Volume19 - Issue14 - Pages 9630-9640

Even though vanadium-​modified hydroxyapatite (V-​HAp) samples are promising systems for oxidative dehydrogenation of propane, the incorporation of vanadium into the hydroxyapatite framework was reported to be limited and to lead to over-​stoichiometric compds.  Here, the synthesis of a Ca₁₀(PO₄)​_6-​x(VO₄)​_x(OH)​₂ stoichiometric solid soln. using a co-​pptn. method is monitored in the whole compn. range (0 ≤ x ≤ 6) by controlling the pH of the pptn. medium, with continuous (the first series of samples) or periodic (the second series of samples) addn. of NH₄OH during the pptn. step or during the maturation step, resp.  The changes in pH conditions result in materials of a substantial difference in terms of the final compn.  From x-​ray diffraction patterns and Rietveld refinements, a solid soln. V-​HAp phase was exclusively obtained for the first series of samples for x varying from 0 to 6.  This also occurred in the second series of samples but only for x lower than 4.  For 4 ≤ x ≤ 5.22, the materials were composed of a mixt. of V-​HAp and Ca₂V₂O₇, whereas for a x value of 6 only Ca₂V₂O₇ was formed.  The predominance of polymeric V species in soln. at a high vanadium concn. deduced from the diagram of speciation of vanadium accounts for the preferential formation of Ca₂V₂O₇ under these particular conditions.  However, provided that a higher pH value was maintained, isolated VO₃(OH)​^2-​ species are predominant, which accounts for the incorporation of isolated vanadates into the hydroxyapatite framework and for the well-​controlled stoichiometry with Ca​/(P + V) ratios close to 1.67.  Such a good accommodation of vanadium in the hydroxyapatite framework is illustrated by the characterization of the local surrounding of phosphorus and vanadium species using ³¹P and ⁵¹V NMR, Raman and UV-​vis spectroscopies.

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