title: Thermal and structural characterization of synthetic and natural nanocrystalline hydroxyapatite.
abstract: The aim of this work was to study the thermal stability on heating and to obtain the processing parameters of synthetic and bone-derived hydroxyapatite over temperatures between room temperature and 1400°C by thermal analysis (thermogravimetry (TG)/differential scanning calorimetry (DSC) and thermo-mechanical analysis-TMA). Structural and surface modifications related to samples origin and calcination temperature were investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy, X-ray diffraction (XRD) and BET method. FTIR spectra indicated that the organic constituents and carbonate are no longer present in the natural sample calcined at 800°C. Raman spectra highlighted the decomposition products of the hydroxyapatite. The calcination treatment modifies the processes kinetics of the synthetic samples, being able to isolate lattice water desorption processes of decarbonization and the dehydroxylation processes. Shrinkage of calcined synthetic sample increases by 10% compared to uncalcined synthetic powder. From the TMA correlated with TG analysis and heat capacity data it can be concluded that sintering temperature of the synthetic samples should be chosen in the temperature range of the onset of dehydroxylation and the temperature at which oxyapatite decomposition begins.
authors.affiliation: Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 060021 Bucharest, Romania.
authors.forename: Ancuta M
authors.initials: AM
authors.lastname: Sofronia
authors.affiliation: National Research Institute for Electrochemistry and Condensed Matter, 300224 Timisoara, Romania.
authors.forename: Radu
authors.initials: R
authors.lastname: Baies
authors.affiliation: Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 060021 Bucharest, Romania.
authors.forename: Elena M
authors.initials: EM
authors.lastname: Anghel
authors.affiliation: Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 060021 Bucharest, Romania. Electronic address: alcorina@chimfiz.icf.ro.
authors.forename: Cornelia A
authors.initials: CA
authors.lastname: Marinescu
authors.affiliation: Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 060021 Bucharest, Romania.
authors.forename: Speranta
authors.initials: S
authors.lastname: Tanasescu
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry*; D006358:Hot Temperature; D015394:Molecular Structure; D049329:Nanostructures; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D017886:Durapatite
keywords: Fourier Transform Infrared spectroscopy; Hydroxyapatite; Raman spectroscopy; Thermal analysis