Publications (5)17.12 Total impact
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Article: The role of ammonium citrate washing on the characteristics of mechanochemical-hydrothermal derived magnesium-containing apatites.
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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.Journal of Materials Science Materials in Medicine 08/2007; 18(7):1413-21. · 2.32 Impact Factor -
Article: Preparation of magnesium-substituted hydroxyapatite powders by the mechanochemical-hydrothermal method.
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ABSTRACT: Magnesium-substituted hydroxyapatite (Mg-HAp) powders with different crystallinity levels were prepared at room temperature via a heterogeneous reaction between Mg(OH)(2)/Ca(OH)(2) powders and an (NH(4))(2)HPO(4) solution using the mechanochemical-hydrothermal route. The as-prepared products contained unreacted Mg(OH)(2) and therefore had to undergo purification in ammonium citrate aqueous solutions at room temperature. X-ray diffraction, infrared spectroscopy, thermogravimetric and chemical analyses were performed and it was determined that the purified powders were phase-pure Mg-HAp containing 0.24-28.4 wt% of Mg. The concentration of Mg was slightly lower near the surface than in the bulk of the HAp crystals as indicated by X-ray photoelectron spectroscopy. Dynamic light scattering revealed that the median particle size of the room temperature Mg-HAp powders was in the range of 102 nm-1.2 microm with a specific surface area between 91 and 269 m(2)/g. Scanning electron microscopy confirmed that the Mg-HAp powders consisted of submicron agglomerates of nanosized crystals, less than approximately 20 nm.Biomaterials 09/2004; 25(19):4647-57. · 7.40 Impact Factor -
Article: Mechanochemical-hydrothermal synthesis of carbonated apatite powders at room temperature.
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ABSTRACT: Crystalline carbonate- and sodium-and-carbonate-substituted hydroxyapatite (CO3HAp and NaCO3HAp) powders were prepared at room temperature via a heterogeneous reaction between Ca(OH)2/CaCO3/Na2CO3 and (NH4)2HPO4 aqueous solution using the mechanochemical hydrothermal route. X-ray diffraction, infrared spectroscopy, thermogravimetry, and chemical analysis were performed. Room temperature products were phase-pure CO3HAp and NaCO3HAp containing 0.8-12 wt% of carbonate ions in the lattice. Dynamic light scattering revealed that the median agglomerate size of the room temperature CO3HAp and NaCO3HAp powders was in the range of 0.35-1.6 microm with a specific surface area between 82 and 121 m2/g. Scanning and transmission electron microscopy confirmed that the carbonated HAp powders consisted of mostly submicron aggregates of nanosized, approximately 20 nm crystals. The synthesized carbonated apatite powders exhibit chemical compositions and crystallinities similar to those of mineral constituents of hard tissues and therefore are promising for fabrication of bone-resembling implants.Biomaterials 03/2002; 23(3):699-710. · 7.40 Impact Factor -
Article: Mechanochemical-hydrothermal preparation of crystalline hydroxyapatite powders at room temperature
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ABSTRACT: Crystalline hydroxyapatite (HAp) powders were prepared at room temperature from heterogeneous reaction between Ca(OH)2powders and (NH4)2HPO4 solutions via the mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, thermogravimetric characterization, and chemical analysis were performed, and it was determined that the room temperature products were phase-pure, thermally stable HAp with a nearly stoichiometric composition. Dynamic light scattering revealed that the dispersed particle size distribution of the room temperature HAp powders was in the range of 0.15–3.0 μm with a specific surface area of ≈90 m2/g. Both specific surface area measurements and scanning electron microscopy confirmed that the HAp powders consisted of agglomerates containing hundreds of ≈20 nm HAp crystals.Journal of Materials Research. 04/2001; 16(05):1231 - 1234. -
Article: Design, Synthesis, and Characterization of Hydroxyapatite Particulates
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ABSTRACT: New hydrothermal technology for the preparation of hydroxyapatite designer particulates has been developed. Phase diagrams were constructed for the pH dependent equilibrium between monetite and HA from 50 to 200°C. Thermodynamic calculations were completed using temperature dependent functions for the relevant solution phase and solid-liquid equilibria and solute species activity coefficients. Model accuracy was evaluated through experiment at 50, 100, and 200°C and pHs between 2.2 and 8.9. The thermodynamic calculations and experimental results are in good agreement. Stoichiometric, crystalline HA has also been prepared by heterogeneous reaction of Ca(OH)2 powder and aqueous (NH4)2HPO4 at room temperature using mechanochemical-hydrothermal methods. This method appears to have very good reproducibility in terms of crystallinity and chemical composition.MRS Proceedings. 12/1999; 662.
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Institutions
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2002–2007
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Rutgers, The State University of New Jersey
New Brunswick, NJ, USA
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