Hydroxyapatite phase analysis

First stage encompassed phase analysis of the powders. X-ray quality analysis of hydroxyapatite powder revealed its 100% crystallinity and presence of hexagonal phase of HA with the following parameters of the cell a = b = 9,418 nm, c= 6,884 nm, space group... 

Several chemical reactions, including calcium carbonate and hydroxyapatite precipitation, have been studied to determine their relationship to observed water column and sediment phosphorus contents in hard water regions of New York State. Three separate techniques have been used to Identify reactions important in the distribution of phosphorus between the water column and sediments 1) sediment sample analysis employing a variety of selective extraction procedures 2) chemical equilibrium calculations to determine ion activity products for mineral phases involved in phosphorus transport and 3) seeded calcium carbonate crystallization measurements in the presence and absence of phosphate ion. 

At relatively high supersaturations, compounds that include hydrophilic cations (such as Ca, Al, Fe, etc.) are likely to form highly hydrated amorphous precipitates via homogeneous nucleation and subsequent flocculation. A number of important crystalline compounds, such as hydroxyapatite or zeolites, are formed by phase transformation via amorphous and/or gel-like precursor phases. Thermal analysis techniques yield information on the amount of incorporated water, and mechanism and strength of bonding, and pore sizes of such amorphous and poorly crystalline materials. In some cases they have been successfully used to detect the initiation of phase transformation, such as the formation of ordered subunits of a quasicrystalline zeolite phase within amorphous alumosilicate precursors. 

The conducted analysis allows to observe that addition of zirconium phase impacts on rise in temperature of hydroxyapatite decomposition, which manifests in decline in CaO and... 

Addition of hydroxyapatite modified with a silane coupling agent was introduced into PHBV by Tang et al. [255] in an effort to understand the influence of the bioceramic phase on water absorption, solubility, and biodegradation. They concluded that, compared to neat PHBV, diffusion coefficients for the bionanocomposites decreased, whereas the sorption coefficients and the solubility show an opposite tendency. In another work [256], the dynamic mechanical properties, thermal properties, and bioactivity of these bionanocomposite were examined, indicating that better mechanical properties and improved bioactivity were achieved with the introduction of hydroxyapatite. Moreover, thermal analysis revealed that when incorporating hydroxyapatite nanoparticles, the decomposition of PHBV was accelerated at the initial stage but retarded thereafter. 

Degradation and complete removal of the organic component of bone is accompanied by mass loss of about 20-29% [9, 28-30, 32], emission of carbon dioxide (identified by mass spectrometry coupled with thermogravimetric analysis [7, 31]), and the release of water, associated in some studies to the bone organic phase decomposition [7] or loss of water from the hydroxyapatite crystal structure [30, 43]. Mass loss varies depending on the place of sampling [19,43], tissue type (cortical or cancellous) [30] or tissue health state [31,43]. 

This phase transformation is accompanied by a bone expansion, as indicated by the dilatometry analysis presented in Figure 16.2 (1260-1360 °C range) [28]. Traces of calcium oxide and magnesium oxide have been identified [11] in bone specimens (originating to different species) thermally treated at 1400 °C. They were not considered as products of hydroxyapatite decomposition, but reported as mineral phases. 

Abstract— Thermal analysis of hydroxyapatite formation through dry mechanochemical method has heen stndied. The calcium phosphate was synthesized using calcinm hydroxide and di-ammonium hydrogen phosphate as the precnrsors. The ball milling of 1/6 ball-powder mass ratio was employed on mixtures of calcium hydroxide and di-ammoninm hydrogen phosphate in three different speeds 170, 270 and 370 rpm for 15 h. As ball-milled powders were then sintered at 1150, 1250 and 1350°C for 2 h, then subjected to TGA, XRD and FTIR for phase characterization. Calcium phosphates with ammonium are phases of the material. The ammonium is trace of phosphorus precursor. Choosing condition of the process and type of precursors determines type of reactions and its products. 

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