title: The role of ammonium citrate washing on the characteristics of mechanochemical-hydrothermal derived magnesium-containing apatites.
abstract: The role of citrate washing on the physical and chemical characteristics of magnesium-substituted apatites (HAMgs) was performed. HAMgs were synthesized by a mechanochemical-hydrothermal route at room temperature in as little as 1 h, which is five times faster than our previous work. Magnesium-substituted apatites had concentrations as high as 17.6 wt% Mg with a corresponding specific surface area (SSA) of 216 m(2)/g. A systematic study was performed to examine the influence of increasing magnesium content on the physical and chemical characteristics of the reaction products. As the magnesium content increased from 0 to 17.6 wt%, magnesium-doped apatite crystallite size decreased from 12 to 8.8 nm. The Mg/(Mg + Ca) ratio in the product was enriched relative to that used for the reacting precursor solution. During mechanochemical-hydrothermal reaction, magnesium doped apatites co-crystallize with magnesium hydroxide. Citrate washing serves to remove the magnesium hydroxide phase. The concomitant increase in surface area results because of the removal of this phase. Possible mechanisms for magnesium hydroxide leaching are discussed to explain the measured trends.
authors.affiliation: Department of Ceramic and Materials Engineering, Rutgers University, 607 Taylor Road, Piscataway, NJ 08854, USA. c_wchen@hotmail.com
authors.forename: Chun-Wei
authors.initials: CW
authors.lastname: Chen
authors.forename: Wojciech L
authors.initials: WL
authors.lastname: Suchanek
authors.forename: Pavel
authors.initials: P
authors.lastname: Shuk
authors.forename: Kullaiah
authors.initials: K
authors.lastname: Byrappa
authors.forename: Charles
authors.initials: C
authors.lastname: Oakes
authors.forename: Richard E
authors.initials: RE
authors.lastname: Riman
authors.forename: Kelly
authors.initials: K
authors.lastname: Brown
authors.forename: Kevor S
authors.initials: KS
authors.lastname: Tenhuisen
authors.forename: Victor F
authors.initials: VF
authors.lastname: Janas
mesh_terms: D001031:Apatites / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D004548:Elasticity; D006358:Hot Temperature; D008274:Magnesium / Q000737:chemistry*; D008422:Materials Testing; D010316:Particle Size; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D001031:Apatites; D001672:Biocompatible Materials; D000644:Quaternary Ammonium Compounds; D014867:Water; D019343:Citric Acid; C481046:ammonium citrate; D008274:Magnesium