scholarly journals Prediction of Sodium Substitution Sites in Octacalcium Phosphate: The Relationships of Ionic Pair Ratios in Reacting Solutions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 240-248
Author(s):  
Yuki Sugiura ◽  
Masanori Horie
Keyword(s):  
Dicarboxylic Acid ◽  
Experimental Studies ◽  
Ionic Species ◽  
Octacalcium Phosphate ◽  
Pair Formation ◽  
Formation Processes ◽  
Ionic Pair ◽  
Substitution Process ◽  
Sodium Substitution ◽  
Acidic Conditions

Octacalcium phosphate (OCP) is widely used in biomaterial fabrication by virtue of its unique crystal structure and low environmental loading. Although various ion and molecule substitution methods into the OCP unit lattice have been introduced, it remains unclear which factors and mechanisms dominate the substitution process. Experimental studies have indicated that Na alkali metal ions are substituted at the P3 PO4 conjugated site in acidic to weakly acidic conditions and the P5 PO4 conjugated site in neutral to weak basic conditions. Ionic species calculation methods have indicated that the pair ratios of Na and HPO42− (NaHPO4−) are small in acidic reacting solutions but large under weakly basic conditions. Consequently, the roles played by NaHPO4− and ionic pair formation processes are thought to dominate ion and molecule substitution into the OCP unit lattice. Such ionic pair formation strongly inhibits dicarboxylic acid substitution into the OCP unit lattice due to the replacement of the Ca ion, which conjugates P5 PO4 as an anchor of dicarboxylic acid.

Development of calix[4]arenes modified at their narrow- and wider-rims as potential metal ions sensor layers for microcantilever sensors: further studies

2021 ◽  
Author(s):  
Paris E. Georghiou ◽  
Shofiur Rahman ◽  
Yousif Assiri ◽  
Gopi Kishore Valluru ◽  
Melita Menelaou ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Computational Study ◽  
Aqueous Media ◽  
Experimental Studies ◽  
Ionic Species ◽  
Alkoxy Group ◽  
Self Assembled Monolayers ◽  
Microcantilever Sensors ◽  
Assembled Monolayers

The development of a microcantilever (MCL) sensing device capable of simultaneously detecting several metal ionic species in aqueous media with low limits of detection requires a variety of sensing layers which are ion-specific. Calix[4]arenes are robust molecules which can be easily modified and have been extensively studied for their ion binding properties. They are also capable of forming self-assembled monolayers (SAMs) onto the gold layers of MCLs and are capable of detecting various metal ions with different anionic counterions in aqueous solutions. In this paper we report on the effect of the alkoxy group in the narrow rim [O-(alkoxycarbonyl)methoxy] substituents of bimodal calix[4]arenes which have been used as metal ion MCL sensing layers, using classical solution state experimental studies. A DFT computational study to compare the experimental results with several metal ions is also reported herein.

scholarly journals Phosphoserine Functionalized Cements Preserve Metastable Phases, and Reprecipitate Octacalcium Phosphate, Hydroxyapatite, Dicalcium Phosphate, and Amorphous Calcium Phosphate, during Degradation, In Vitro

2019 ◽  
Vol 10 (4) ◽  
pp. 54 ◽  
Author(s):  
Joseph Lazraq Bystrom ◽  
Michael Pujari-Palmer
Keyword(s):  
Calcium Phosphate ◽  
Amorphous Calcium Phosphate ◽  
Octacalcium Phosphate ◽  
Ionic Concentration ◽  
Strong Adhesion ◽  
Acidic Conditions ◽  
Rapid Transformation ◽  
Comparable Mass

Phosphoserine modified cements (PMC) exhibit unique properties, including strong adhesion to tissues and biomaterials. While TTCP-PMCs remodel into bone in vivo, little is known regarding the bioactivity and physiochemical changes that occur during resorption. In the present study, changes in the mechanical strength and composition were evaluated for 28 days, for three formulations of αTCP based PMCs. PMCs were significantly stronger than unmodified cement (38–49 MPa vs. 10 MPa). Inclusion of wollastonite in PMCs appeared to accelerate the conversion to hydroxyapatite, coincident with slight decrease in strength. In non-wollastonite PMCs the initial compressive strength did not change after 28 days in PBS (p > 0.99). Dissolution/degradation of PMC was evaluated in acidic (pH 2.7, pH 4.0), and supersaturated fluids (simulated body fluid (SBF)). PMCs exhibited comparable mass loss (<15%) after 14 days, regardless of pH and ionic concentration. Electron microscopy, infrared spectroscopy, and X-ray analysis revealed that significant amounts of brushite, octacalcium phosphate, and hydroxyapatite reprecipitated, following dissolution in acidic conditions (pH 2.7), while amorphous calcium phosphate formed in SBF. In conclusion, PMC surfaces remodel into metastable precursors to hydroxyapatite, in both acidic and neutral environments. By tuning the composition of PMCs, durable strength in fluids, and rapid transformation can be obtained.

scholarly journals Modeling of structuring processes at hardening of expanding cements and concretes on their basis

2018 ◽  
Vol 196 ◽  
pp. 04035 ◽  
Author(s):  
Igor Kharchenko ◽  
Alexander Panchenko ◽  
Alexey Kharchenko ◽  
Vyacheslav Alekseev
Keyword(s):  
Theoretical Analysis ◽  
Rheological Model ◽  
Experimental Studies ◽  
High Strength ◽  
Cementitious Materials ◽  
Cement Stone ◽  
Formation Processes ◽  
Structure And Properties ◽  
Potential Index ◽  
Kinetics Of

This paper reports the results of experimental research of the effect of strain-restriction conditions on the structure and properties of sulfoaluminate expanding cementitious materials. Theoretical analysis of the development of pattern formation processes is performed by applying the developed rheological model, illustrating features of the kinetics of structure-forming processes according to the ratio of the potential index of extension with linear, flat and volumetric limitation of deformations of the extension. The results show that rheological model adequately correlates with the results of experimental studies and can be described mathematically. Found that with the volume limitation of deformations arising when mixing crystallographic phases with high density and strength, the pore structure of the cement stone contains mainly gel pores. This is the main prerequisite for obtaining a dense, high-strength and durable structure of cement stone and concrete on its basis.

Relaxation of Misfit Dislocations at Nodes

2014 ◽  
Vol 783-786 ◽  
pp. 515-520 ◽  
Author(s):  
Shuai Shao ◽  
Jian Wang ◽  
Amit Misra ◽  
Richard G. Hoagland
Keyword(s):  
Misfit Dislocation ◽  
Mechanical Stability ◽  
Experimental Studies ◽  
Atomistic Simulations ◽  
Misfit Dislocations ◽  
Formation Processes ◽  
Coherent Interface ◽  
Core Energy ◽  
Structures And Properties ◽  
Coherent Interfaces

Experimental studies proved that structures and properties of misfit dislocations and their intersections (nodes) in semi-coherent interfaces strongly affect thermal and mechanical stability of interface. Employing atomistic simulations, we reveal that misfit dislocation lines can exhibit a spiral pattern (SP) or remain straight in association with dislocation character at nodes. By analyzing nodes formation processes in terms of kinetics and energetics, we found that the variation is ascribed to the competition between core energy of misfit dislocation and interface stacking fault energy with respect to coherent interface.

Laboratory Study of Weak Acid Fracturing Fluid

2012 ◽  
Vol 550-553 ◽  
pp. 598-602
Author(s):  
Yan Min Lou ◽  
Zhi Liu
Keyword(s):  
Guar Gum ◽  
Experimental Studies ◽  
Weak Acid ◽  
High Moisture Content ◽  
Cross Link ◽  
High Moisture ◽  
Fracturing Fluid ◽  
Reservoir Permeability ◽  
Acidic Conditions ◽  
Cross Linker

At present, most of the fields have entered the stage with high moisture content. So fracturing as an important stimulation is particularly important. Through a lot of theoretical analysis and experimental studies. The water insoluble matter of modified guar gum we composed is much lower than before. It has a better tackifier performance. The GHPG can cross-link with cross-linker in weakly acidic conditions. So it can avoid the damage of the fracturing fluid to the formation of desensitization. And the fracturing fluid has higher strength, stability. It has a better gel breaking performance after which the viscosity is 1.87 mPa·s. So it can reduce the damage to reservoir permeability greatly

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