Amorphous calcium phosphate phase-mediated crystal nucleation kinetics and pathway

2015 ◽  
Vol 179 ◽  
pp. 451-461 ◽  
Author(s):  
Shuqin Jiang ◽  
Haihua Pan ◽  
Yan Chen ◽  
Xurong Xu ◽  
Ruikang Tang
Keyword(s):  
Calcium Phosphate ◽  
Heterogeneous Nucleation ◽  
Amorphous Calcium Phosphate ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Nucleation Kinetics ◽  
Solution Interface ◽  
Precursor Phase ◽  
Phosphate Phase ◽  
Polymorph Transformation

Generally, a solution nucleation model is used to study biomineralization kinetics. However, we found that the amorphous calcium phosphate (ACP)-mediated hydroxyapatite (HAP) nucleation in simulated body fluids (SBF) had a different profile from the linear relationship between ln J and ln−2 S (J, nucleation rate; S, supersaturation). This behaviour was alternatively explained by a developed heterogeneous nucleation theory, which indicated that HAP was nucleated at the ACP–solution interface via a polymorph transformation. Based upon this new model, we demonstrated experimentally that the embedded polymer molecules inside ACP were inert on HAP nucleation kinetics; rather, the polymers adsorbed on ACP surface could inhibit HAP nucleation from ACP. It further confirmed the heterogeneous nucleation pathway of HAP on the precursor phase. The present study provides an in-depth understanding of HAP formation for ACP-mediated crystallization.

scholarly journals Heterogeneous Crystal Nucleation from the Melt in Polyethylene Oxide Droplets on Graphite: Kinetics and Microscopic Structure

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 924
Author(s):  
Muhammad Tariq ◽  
Thomas Thurn-Albrecht ◽  
Oleksandr Dolynchuk
Keyword(s):  
Optical Microscopy ◽  
Polyethylene Oxide ◽  
Heterogeneous Nucleation ◽  
Polarized Light ◽  
Contact Angles ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Graphite Substrate ◽  
Nucleation Kinetics

It is well known that the crystallization of liquids often initiates at interfaces to foreign solid surfaces. In this study, using polarized light optical microscopy, atomic force microscopy (AFM), and wide-angle X-ray scattering (WAXS), we investigate the effect of substrate–material interactions on nucleation in an ensemble of polyethylene oxide (PEO) droplets on graphite and on amorphous polystyrene (PS). The optical microscopy measurements during cooling with a constant rate explicitly evidenced that the graphite substrate enhances the nucleation kinetics, as crystallization occurred at approximately an 11 °C higher temperature than on PS due to changes in the interactions at the solid interface. This observation allowed us to conclude that graphite induces heterogeneous nucleation in PEO. By employing the classical nucleation theory for analysis of the data with reference to the amorphous PS substrate, the obtained results indicated that the crystal nuclei with contact angles in the range of 100–117° were formed at the graphite interface. Furthermore, we show that heterogeneous nucleation led to a preferred orientation of PEO crystals on graphite, whereas PEO crystals on PS had isotropic orientation. The difference in crystal orientations on the two substrates was also confirmed with AFM, which showed only edge-on lamellae in PEO droplets on graphite compared to unoriented lamellae on PS.

scholarly journals Nucleation Behavior of a Single Al-20Si Particle Rapidly Solidified in a Fast Scanning Calorimeter

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2920
Author(s):  
Qin Peng ◽  
Bin Yang ◽  
Benjamin Milkereit ◽  
Dongmei Liu ◽  
Armin Springer ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Rapid Solidification ◽  
Heterogeneous Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Solidification Behavior ◽  
Nucleation Kinetics ◽  
Nucleation Behavior ◽  
Nucleation Undercooling ◽  
Primary Si

Understanding the rapid solidification behavior characteristics, nucleation undercooling, and nucleation mechanism is important for modifying the microstructures and properties of metal alloys. In order to investigate the rapid solidification behavior in-situ, accurate measurements of nucleation undercooling and cooling rate are required in most rapid solidification processes, e.g., in additive manufacturing (AM). In this study, differential fast scanning calorimetry (DFSC) was applied to investigate the nucleation kinetics in a single micro-sized Al-20Si (mass%) particle under a controlled cooling rate of 5000 K/s. The nucleation rates of primary Si and secondary α-Al phases were calculated by a statistical analysis of 300 identical melting/solidification experiments. Applying a model based on the classical nucleation theory (CNT) together with available thermodynamic data, two different heterogeneous nucleation mechanisms of primary Si and secondary α-Al were proposed, i.e., surface heterogeneous nucleation for primary Si and interface heterogenous nucleation for secondary α-Al. The present study introduces a practical method for a detailed investigation of rapid solidification behavior of metal particles to distinguish surface and interface nucleation.

Nucleation and Glass Formation

1985 ◽  
Vol 57 ◽  
Author(s):  
D. R. Uhlmann ◽  
M. C. Weinberg
Keyword(s):  
Glass Formation ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Oxide Glass ◽  
Classical Nucleation Theory ◽  
Nucleation Kinetics ◽  
Formation Behavior ◽  
Homogeneous Crystal ◽  
Exponential Factors

AbstractThe role of nucleation kinetics in affecting glass formation behavior is discussed. Also considered are measurements of homogeneous crystal nucleation in a variety of liquids. For a number of oxide glass-forming liquids, available data indicate pre-exponential factors which are larger than those predicted from classical nucleation theory by factors of 1017 to 1049. Possible sources of this discrepancy are discussed.

Stabilizing amorphous calcium phosphate phase by citrate adsorption

CrystEngComm ◽  
2014 ◽  
Vol 16 (10) ◽  
pp. 1864-1867 ◽  
Author(s):  
Yan Chen ◽  
Wenjia Gu ◽  
Haihua Pan ◽  
Shuqin Jiang ◽  
Ruikang Tang
Keyword(s):  
Calcium Phosphate ◽  
Amorphous Phase ◽  
Amorphous Calcium Phosphate ◽  
Surface Reaction ◽  
Phosphate Phase ◽  
Calcium Phosphate Phase

Citrate controls nucleation by association with a precursor amorphous phase, which inhibits the surface reaction for nucleation.

A Comparative Study of Pathological Nanomineral Aggregates with Distinct Morphology in Human Aortic Atherosclerotic Plaques

2021 ◽  
Vol 21 (1) ◽  
pp. 547-554
Author(s):  
Yuan Li ◽  
Changqiu Wang ◽  
Anhuai Lu ◽  
Kang Li ◽  
Xiao Cheng ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Calcium Phosphate ◽  
Amorphous Calcium Phosphate ◽  
Microscopic Analysis ◽  
Atherosclerotic Plaques ◽  
Carbonate Hydroxyapatite ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Precursor Phase ◽  
Exact Difference

Calcification exists in atherosclerotic plaques in the form of nanomineral aggregates and is closely related to the development of atherosclerosis. Spheroidal and massive calcification are two major types of calcification found in atherosclerotic tissue. However, the exact difference between these two types of calcification is still not clear. Samples composed entirely of spheroidal calcifications and massive calcifications were isolated from aortic atherosclerotic plaques and tested using both bulk and microscopic analysis techniques. Scanning electron microscopy and transmission electron microscopy showed that spheroidal calcifications had a core–shell structure. Massive calcifications were composed of randomly arranged nanocrystals. Synchrotron radiation X-ray diffraction, Raman spectroscopy and selected area electron diffraction showed amorphous calcium phosphate, whitlockite and carbonate hydroxyapatite all existing in spheroidal calcification, while massive calcification only consisted of carbonate hydroxyapatite. We conclude that amorphous calcium phosphate may act as a precursor phase of spheroidal calcifications that eventually transforms into a crystalline phase, while whitlockite in lesions could aggravate the progression of atherosclerosis.

Surface Induced Calcium Phosphate Nucleation and Growth

1995 ◽  
Vol 414 ◽  
Author(s):  
L. Song ◽  
A. A. Campbell ◽  
X. S. Li ◽  
B. C. Bunker
Keyword(s):  
Calcium Phosphate ◽  
Phase Formation ◽  
Octacalcium Phosphate ◽  
Crystal Nucleation ◽  
X Ray Diffraction ◽  
Nucleation Kinetics ◽  
Constant Composition ◽  
Phosphate Dihydrate ◽  
Induction Times

AbstractCalcium phosphate nucleation on colloidal oxide surfaces, such as TiO2, SiO2 and Al2MO3, has been studied as a model system to understand the role of surface chemistry on crystal nucleation kinetics and phase formation. The nucleation induction times have been measured using Constant Composition (CC) technique and calcium phosphate phases formation have been determined mainly by X-ray diffraction. The results indicated TiO2 not only significantly reduces the nucleation induction time and interfacial energy but also stimulates octacalcium phosphate formation over dicalcium phosphate dihydrate. SiO2 and Al2O3 have little effect on both nucleation kinetics and phase formation.

scholarly journals PRECIPITATION OF HYBRID HYDROXYAPATITE / AUTOFIBRIN NANOCOMPOSITES

2021 ◽  
pp. 818-828
Author(s):  
Илья Евгеньевич Глазов ◽  
Валентина Константиновна Крутько ◽  
Роман Алексеевич Власов ◽  
Ольга Николаевна Мусская ◽  
Людмила Викторовна Кульбицкая ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Simulated Body Fluid ◽  
Amorphous Calcium Phosphate ◽  
Body Fluid ◽  
Hybrid Composites ◽  
Model Solution ◽  
Hybrid Nanocomposites ◽  
Biomimetic Apatite ◽  
Phosphate Phase ◽  
Calcium Phosphate Phase

Синтезированы гибридные нанокомпозиты на основе гидроксиапатита и аутофибрина в форме фибринового сгустка либо цитратной плазмы путем осаждения при pH 9. «Мягкие» условия осаждения и быстрое выделение нанокомпозитов способствовали сохранению биополимерной матрицы аутофибрина. Дестабилизация дополнительной фазы аморфного фосфата кальция с образованием стехиометрического гидроксиапатита обусловлена влиянием макромолекул фибрина. Формирование кальцийдефицитного гидроксиапатита с x« 0,1 и Ca / P 1,65 происходило в среде цитратной плазмы, который после 800 °С превращался в смесь гидроксиапатит / 3 -трикальцийфосфат. Синтез композитов на основе биомиметического апатита осуществляли при добавлении 30 об.% модельного раствора Simulated Body Fluid (SBF). Влияние ионов Mg, CO~, входящих в состав SBF, способствовало стабилизации аморфного фосфата кальция и образованию карбонатзамещенного гидроксиапатита, устойчивого к термическим превращениям до 800°С. Совокупное влияние аутофибрина и ионов введенного SBF позволило управлять составом минеральной составляющей гибридных нанокомпозитов без разрушения биополимерной матрицы. Hybrid composites based on hydroxyapatite and autofibrin were synthesized by precipitation in a medium with pH = 9. Soft precipitation conditions and rapid isolation of the composite precipitates favored preservation of a biopolymer matrix of autofibrin. An effect of fibrin macromolecules contributed to destabilization of the amorphous calcium phosphate phase and formation of stoichiometric hydroxyapatite. The medium of the citrated plasma stimulated precipitation of calcium-deficient hydroxyapatite with x « 0,1 and the Ca / P ration of 1,65 which transformed into the mixture of hydroxyapatite / 3 -tricalcium phosphate at 800 °С. Biomimetic apatite composites were synthesized with an addition of 30 vol. % of a Simulated Body Fluid (SBF) model solution. The effect of Mg, CO~ ions of SBF promoted the stabilization of amorphous calcium phosphate and formation of carbonated hydroxyapatite that exhibited thermal stability up to 800 °С. The cummulative effect of autofibrin and ions of induced SBF provided controlling composition of the mineral part of hybrid nanocomposites without disruption of an autofibrin matrix.

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