title: Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.
abstract: Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process.
authors.affiliation: Research Center in Biomedical Engineering, Biomaterials Division, Department of Materials Science and Metallurgy, Technological University of Catalonia (UPC), Avda. Diagonal 647, Barcelona E-08028, Spain.
authors.forename: Carolina
authors.initials: C
authors.lastname: Mochales
authors.forename: Hassane
authors.initials: H
authors.lastname: El Briak-BenAbdeslam
authors.forename: Maria Pau
authors.initials: MP
authors.lastname: Ginebra
authors.forename: Alain
authors.initials: A
authors.lastname: Terol
authors.forename: Josep A
authors.initials: JA
authors.lastname: Planell
authors.forename: Philippe
authors.initials: P
authors.lastname: Boudeville
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000737:chemistry; D018786:Bone Substitutes / Q000138:chemical synthesis* / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D002617:Chemical Industry / Q000295:instrumentation* / Q000379:methods*; D003198:Computer Simulation; D017276:Friction; D006882:Hydroxyapatites / Q000138:chemical synthesis* / Q000737:chemistry; D007700:Kinetics; D008422:Materials Testing; D008956:Models, Chemical; D009038:Motion; D010087:Oxides / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D017610:Calcium Compounds; D002130:Calcium Phosphates; D006882:Hydroxyapatites; D010087:Oxides; C016538:lime; C485829:calcium phosphate, dibasic, anhydrous