scholarly journals Kinetic Study of Calcium Phosphate Precipitation in the System H3PO4-Ca(OH)2-H2O at 30°C

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
K. Labgairi ◽  
A. Borji ◽  
M. Kaddami ◽  
A. Jourani
Keyword(s):  
Calcium Concentration ◽  
Calcium Phosphates ◽  
Stability Domain ◽  
Dicalcium Phosphate ◽  
Precipitation Reaction ◽  
X Ray Diffraction ◽  
The Stability ◽  
Kinetics Of ◽  
Calcium Phosphate Precipitation ◽  
Hydroxide Water

The precipitation kinetics of calcium phosphates, namely, hydroxyapatite (HAP), dicalcium phosphate dihydrate (DCPD), dicalcium phosphate anhydrous (DCPA), and monocalcium phosphate monohydrate (MCPM), were studied at 30°C by mixing calcium hydroxide, water, and phosphoric acid. The studied mixture was selected according to the stability domain of different calcium phosphates by referring to the phase diagram of the ternary system of H3PO4-Ca(OH)2-H2O at 30°C. The precipitation reaction has been monitored by following the changes in the conductivity, pH, and calcium concentration. The solid phases formed at different stages of this precipitation were characterized by X-ray diffraction.

Effects of citrate and NaCl on size, morphology, crystallinity and microstructure of calcium phosphates obtained from aqueous solutions at acidic or near-neutral pH

2012 ◽  
Vol 79 (2) ◽  
pp. 238-248 ◽  
Author(s):  
Omar Mekmene ◽  
Thierry Rouillon ◽  
Sophie Quillard ◽  
Paul Pilet ◽  
Jean-Michel Bouler ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Inhibitory Effect ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
Phosphate Dihydrate ◽  
Constant Ph ◽  
Starting Solutions ◽  
Calcium Phosphate Precipitation

Precipitation of calcium phosphates occurs in dairy products and depending on pH and ionic environment, several salts with different crystallinity can form. The present study aimed to investigate the effects of NaCl and citrate on the characteristics of precipitates obtained from model solutions of calcium phosphate at pH 6·70 maintained constant or left to drift. The ion speciation calculations showed that all the starting solutions were supersaturated with respect to dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP) in the order HAP>OCP>DCPD. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses of the precipitates showed that DCPD was formed at drifting pH (acidic final pH) whereas poor crystallised calcium deficient apatite was mainly formed at constant pH (6·70). Laser light scattering measurements and electron microscopy observations showed that citrate had a pronounced inhibitory effect on the crystallisation of calcium phosphates both at drifting and constant pH. This resulted in the decrease of the particle sizes and the modification of the morphology and the microstructure of the precipitates. The inhibitory effect of citrate mainly acted by the adsorption of the citrate molecules onto the surfaces of newly formed nuclei of calcium phosphate, thereby changing the morphology of the growing particles. These findings are relevant for the understanding of calcium phosphate precipitation from dairy byproducts that contain large amounts of NaCl and citrate.

In situ high-energy synchrotron X-ray diffraction revealing precipitation reaction kinetics of silver ions with mixed halide ions

2015 ◽  
Vol 3 (28) ◽  
pp. 7492-7498 ◽  
Author(s):  
Qi Liu ◽  
Zheng Li ◽  
John S. Okasinski ◽  
Yang Ren ◽  
Yugang Sun
Keyword(s):  
Reaction Kinetics ◽  
Silver Ions ◽  
High Energy ◽  
Precipitation Reaction ◽  
Halide Ions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Kinetics Of

Quantitative reaction kinetics involved in the precipitation of silver ions with mixed halogen ions that are capable of forming uniform silver chlorobromide nanocubes has been studied by in situ high-energy synchrotron X-ray diffraction.

A Novel Method to Synthesize Nanocrystalline Calcium Phosphates

2008 ◽  
Vol 47-50 ◽  
pp. 956-959
Author(s):  
Ren Long Xin ◽  
Fu Zeng Ren ◽  
Guang Jie Huang ◽  
Yang Leng
Keyword(s):  
Calcium Phosphates ◽  
Dicalcium Phosphate ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Phosphate Dihydrate ◽  
Transmission Electron ◽  
Temperature Ranges ◽  
Novel Method

This study reports a novel method for the preparation of several biologically important calcium phosphate (Ca-P) phases such as hydroxyapatite (HA), dicalcium phosphate dihydrate (DCPD) and dicalcium phosphate anhydrous (DCPA). X-ray diffraction (XRD) results showed that phase pure DCPD, DCPA and HA nano-crystals could be produced in the Ca2+/PO4 3- solutions with the presence of EDTA at 120 oC, 180 oC and 210 oC, respectively. Transmission electron microscope (TEM) micrographs revealed that all the Ca-P precipitates were needle-like or rod-like. Most of the precipitates ranged from 100 ~ 200 nm in length. Selected area electron diffraction confirmed that the longitude direction of the rod-like HA precipitates were along c-axis and the flat surface was (110). Thermal gravimetric analysis of the DCPD precipitates revealed that phase transformations of DCPD to DCPA and DCPA to HA occurred at 139 oC and 195 oC, respectively, which resulted in the different Ca-P phases during hydrothermal synthesis at different temperature ranges.

scholarly journals Selenium-Enriched Brushite: A Novel Biomaterial for Potential Use in Bone Tissue Engineering

2018 ◽  
Vol 19 (12) ◽  
pp. 4042 ◽  
Author(s):  
Aleksandra Laskus ◽  
Anna Zgadzaj ◽  
Joanna Kolmas
Keyword(s):  
Bone Tissue ◽  
Calcium Phosphates ◽  
Release Kinetics ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ionic Substitution ◽  
Starting Point ◽  
Kinetics Of ◽  
Potential Use

In this study, a novel biomaterial, i.e., brushite containing 0.67 wt% of selenium (Se-Bru) was synthesized via a wet precipitation method. Pure, unsubstituted brushite (Bru) was synthesized via the same method and used as a reference material. Different techniques of instrumental analysis were applied to investigate and compare physicochemical properties of both materials. Fourier-Transform Infrared Spectroscopy confirmed the chemical identity of both materials. Scanning Electron Microscopy (SEM) was used to study the morphology and indicated that both samples (Bru and Se-Bru) consisted of plate-like microcrystals. Powder X-ray Diffraction (PXRD) showed that Bru, as well as Se-Bru were crystallographically homogenous. What is more, the data obtained from PXRD studies revealed that the substitution of selenite ions into the crystal structure of the material had clearly affected its lattice parameters. The incorporation of selenium was also confirmed by solid-state 1H→31P CP MAS kinetics experiments. Additionally, studies on the release kinetics of the elements forming Se-Bru and preliminary cytotoxicity tests were conducted. This preliminary research will favor a better understanding of ionic substitution in calcium phosphates and may be a starting point for the development of selenium-doped brushite cements for potential use in bone tissue impairments treatment.

A TEM investigation of a hyper-eutectic lead-tin alloy

1988 ◽  
Vol 46 ◽  
pp. 562-563
Author(s):  
John A. Sutliff
Keyword(s):  
Volume Diffusion ◽  
Eutectic Mixture ◽  
Precipitation Reaction ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diffusion Controlled ◽  
Discontinuous Precipitation Reaction ◽  
Controlled Precipitation

Near-eutectic Pb-Sn alloys are important solders used by the electronics industry. In these solders, the eutectic mixture, which solidifies last, is the important microstructural consituent. The orientation relation (OR) between the eutectic phases has previously been determined for directionally solidified (DS) eutectic alloys using x-ray diffraction or electron chanelling techniques. In the present investigation the microstructure of a conventionally cast, hyper-eutectic Pb-Sn alloy was examined by transmission electron microscopy (TEM) and the OR between the eutectic phases was determined by electron diffraction. Precipitates of Sn in Pb were also observed and the OR determined. The same OR was found in both the eutectic and precipitation reacted materials. While the precipitation of Sn in Pb was previously shown to occur by a discontinuous precipitation reaction,3 the present work confirms a recent finding that volume diffusion controlled precipitation can also occur.Samples that are representative of the solder's cast microstructure are difficult to prepare for TEM because the alloy is multiphase and the phases are soft.

Fractionation of polymethylene chains: An electron crystallographic investigation

1986 ◽  
Vol 44 ◽  
pp. 794-795
Author(s):  
Douglas L. Dorset
Keyword(s):  
Cross Section ◽  
Binary Systems ◽  
Linear Chain ◽  
Pure Component ◽  
Organic Substrates ◽  
Crystallographic Investigation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molecular Sizes ◽  
The Stability

A variety of linear chain materials exist as polydisperse systems which are difficultly purified. The stability of continuous binary solid solutions assume that the Gibbs free energy of the solution is lower than that of either crystal component, a condition which includes such factors as relative molecular sizes and shapes and perhaps the symmetry of the pure component crystal structures.Although extensive studies of n-alkane miscibility have been carried out via powder X-ray diffraction of bulk samples we have begun to examine binary systems as single crystals, taking advantage of the well-known enhanced scattering cross section of matter for electrons and also the favorable projection of a paraffin crystal structure posited by epitaxial crystallization of such samples on organic substrates such as benzoic acid.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

Sign in / Sign up

Export Citation Format

Share Document