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Ca/P Molar Ratio (p + molar_ratio)
Selected AbstractsPreparation of Nano Carbonate-Substituted Hydroxyapatite from an Amorphous PrecursorINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008Yanbao Li Carbonated amorphous calcium phosphate (CACP) precursors were precipitated by the wet chemical method at 5°C in the presence of poly(ethylene glycol) and carbonates. The nano carbonate-substituted hydroxyapatite (HAp) was obtained after heat treat CACP precursors at a low temperature (800°C) for 3 h. The calcium phosphates were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma, thermal gravimetric and differential thermal analysis, transmission electron microscopy, and scanning electron microscopy. The results show that calcium phosphate particles with a Ca/P molar ratio of 1.73 are AB-type carbonate-substituted HAp with about 50 nm in diameter. [source] Preparation and characterization of novel biphasic calcium phosphate powders (,-TCP/HA) derived from carbonated amorphous calcium phosphatesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Yanbao Li Abstract Novel biphasic calcium phosphate (BCP) powders composed of ,-tricalcium phosphate (,-TCP) and hydroxyapatite (HA) were prepared by thermal decomposition of carbonated amorphous calcium phosphates (CACP). At first, the CACP precipitates were synthesized by adding ammonium carbonate in the presence of poly(ethylene glycol) at pH 10 with an initial Ca/P molar ratio of 1.60 at 5°C. The Ca/P molar ratios of the CACP precursors are between 1.50 and 1.67 investigated by ICP. Then BCP (,-TCP/HA) powders were obtained after heating the CACP precursors at relatively low temperature (800°C) for 3 h. ,-TCP/HA powders were characterized by X-ray diffractometry, Fourier transform infrared spectra, transmission electron microscopy/scanning electron microscopy, and sedimentation experiment. The results show that ,-TCP and HA phases form in one powder, ,-TCP/HA powders are sphere with the diameter of 300 nm to less than 100 nm varied with their chemical compositions and the ratio of ,-TCP and HA in the powders can be adjusted by the adding amount of carbonates. The possible formation process of biphasic ,-TCP/HA powders was proposed. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Theoretical Defect Energetics in Calcium Phosphate BioceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Katsuyuki Matsunaga Vacancies, impurities, and foreign ions dissolving in calcium phosphate bioceramics play an important role in the biological properties of the materials. However, little is known about the thermodynamic stability of the defects. In this regard, point defects in hydroxyapatite (HAp) and octacalcium phosphate (OCP) were calculated in a first-principles manner, and the chemical-potential dependence of the defect formation energies was revealed. In particular, because calcium phosphates are usually subjected to an aqueous solution, a methodology to evaluate ionic chemical potentials under chemical equilibrium of the solid,aqueous solution was introduced. In the present article, recent results based on such a methodology (the solution pH dependence of Ca/P molar ratio of HAp and the ion-exchange ability with foreign cations in HAp and OCP) were reviewed. [source] Effect of temperature and soluble reactive phosphorus on abundance of Aphanizomenon flos-aquae (Cyanophyceae)PHYCOLOGICAL RESEARCH, Issue 1 2000Keishi Takano SUMMARY Filament density of Aphanizomenon flos-aquae (Lemmerm.) Ralfs, water temperature and soluble reactive phosphorus (SRP) were measured from April to August in 1993,1996 in Lake Barato, Hokkaido, Japan. In addition, growth characteristics and internal phosphorus (P) utilization of Aph. flos-aquae were evaluated under P limitation at three temperatures (15, 20 and 25,C) to clarify the role of internal accumulated P for its growth in the incubation experiment. The filament density was highest in early July 1994, when SRP concentration had not yet decreased and the water temperature was high. These are important factors favoring an increase in abundance of this species in L. Barato. During batch culture, the time course of the stationary phase was shortest at 25,C and longest at 15,C; the cellular C:P molar ratio was 111 under P sufficiency and increased eight- to 12-fold under P limitation. As the C:P ratio was significantly higher in the decreasing phase at 15,C, Aph. flos-aquae may be more adaptable to Plimitation at 15,C than at 20,C and 25,C. However, the low temperatures did not favor the abundance of Aph. flos-aquae in 1996. This indicates that the filament density of Aph. flos-aquae decreases before it reaches the maximum value for some reason under P limitation in L. Barato. [source] | ||||||||||