scholarly journals Homogeneous Nucleation of Hydroxyapatite, Ca5OH(PO4)3, at 37 °C

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 695 ◽  
Author(s):  
Hans Erik Lundager Madsen
Keyword(s):  
Free Energy ◽  
Light Scattering ◽  
Calcium Phosphate ◽  
Surface Free Energy ◽  
Classical Theory ◽  
Homogeneous Nucleation ◽  
Crystal Surface ◽  
Small Particles ◽  
Large Particles

Precipitation of the calcium phosphate hydroxyapatite, Ca5OH(PO4)3, is studied by simple mixing of reagent solutions and measurement of light scattering (turbidimetry) at six different wavelengths from 300 to 800 nm. Measured turbidities are analyzed using Mie’s theory of light scattering from small particles. Results are interpreted in terms of classical theory of homogeneous nucleation, and from this the surface free energy of crystals is determined. The low value thus found is explained as the effect of protonation of the strongly basic anions hydroxide and phosphate at the crystal surface. Relatively large particles registered by turbidimetry are shown to be not monocrystals, but aggregates of nanocrystals.

A Multilayer Approach to the Design of Fine Dispersed Metallic two Component Materials

1995 ◽  
Vol 382 ◽  
Author(s):  
C. Eisenmenger-Sittner ◽  
R. Behr ◽  
A. Bergauer ◽  
A. Hejl ◽  
W. Bauer
Keyword(s):  
Free Energy ◽  
Large Class ◽  
Surface Free Energy ◽  
Phase Distribution ◽  
Small Particles ◽  
Theoretical Concepts ◽  
Two Component ◽  
The Common ◽  
Critical Nuclei ◽  
Deposition Techniques

ABSTRACTIn the common applications of multilayer materials a strict separation of the single layers as well as very sharply defined interlayer interfaces are highly desired. On the otherhand there exists a large class of materials which consist of small particles dispersed in a matrix with mechanically different properties.In this paper the theoretical concepts of producing this second class of materials via a multilayer deposition approach are presented. Although the focus is on the preparation ofsputter deposited immiscible metallic two component materials, the concepts presented arevalid for a greater variety of materials and deposition techniques.The phase distribution as well as the roughness evolution of a material consisting of oneisland- and one layer forming component is quantitatively described by considerations about the minimization of the surface free energy of the whole system. On the atomistic level the formation of critical nuclei on an arbitrarily shaped surface is briefly discussed and a connection to the thermodynamic minimization of the surface free energy is made.

Stratospheric Aerosol Determinations

1974 ◽  
Vol 52 (8) ◽  
pp. 1519-1526 ◽  
Author(s):  
D. J. Hofmann
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Stratospheric Aerosol ◽  
Small Particles ◽  
Particle Detectors ◽  
The Past ◽  
Body Of Knowledge ◽  
Large Particles ◽  
Comparison Of The Results ◽  
Lidar Observations

This review consists of a summary and comparison of the results of ongoing programs to study the stratospheric aerosol by a variety of techniques. In view of the considerable degree of disagreement among various experimental techniques in the past, the importance of comparative studies is emphasized. Many of the results are still in preliminary form, and only relatively new results are presented.Both remote and insitu measurements are discussed; the former consist mainly of lidar observations while the latter comprise impactor sampling and light-scattering particle detectors. Discussion is divided along traditional lines, i.e., by particle size, with "small" particles those of radii ≤0.1 µm and "large" particles those of radii ≥ 0.1 µm, with emphasis on the latter because of the considerably greater body of knowledge available for these particles.

Simulations of the Structure and Properties of the Polyethylene Crystal Surface

1995 ◽  
Vol 408 ◽  
Author(s):  
J. L. Wilhelmi ◽  
G. C. Rutledge
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Crystal Surface ◽  
Excess Entropy ◽  
Free Energy Calculations ◽  
Intermolecular Potential ◽  
Free Energies ◽  
Free Energy Surface ◽  
Lattice Mode ◽  
Molecular Layers

AbstractThe structures and thermodynamic properties of the (100), (010), and (110) lateral surfaces of extended-chain polyethylene crystals between 0 K and 300 K were determined by free energy minimization using consistent quasi-harmonic lattice dynamics. Slight rotations of the outermost chains from their corresponding orientations in the bulk were observed. These deviations from bulk structure were confined to the first three molecular layers (approximately 10 Å) at the surface. Surface free energy calculations found the (110) surface to be the most stable over the entire temperature range modeled, with free energies ranging from 95.4 erg/cm2 to 103.5 erg/cm2, at temperatures of 0 K and 300 K, respectively. Surface free energies of the (100) and (010) surfaces were found to be at least 15% higher than the (110) surface, with the (100) surface slightly more stable than the (010) surface, over all temperatures considered. Surface free energy increases as the density of chains at the surface decreases. The surface free energy at low temperatures was determined predominantly by intermolecular potential energy; at higher temperatures, excess entropy accounted for nearly half the surface free energy. Surface entropy was almost entirely due to lattice mode motions.

Smectic A-Smectic B interface : faceting and surface free energy measurement

1989 ◽  
Vol 50 (24) ◽  
pp. 3527-3534 ◽  
Author(s):  
P. Oswald ◽  
F. Melo ◽  
C. Germain
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Energy Measurement ◽  
Smectic A

Examination of the lubricant storing and releasing ability of thermally sprayed surfaces

2011 ◽  
Vol 2 (2) ◽  
pp. 101-105
Author(s):  
L. Fazekas ◽  
Z. S. Tiba ◽  
G. Kalácska
Keyword(s):  
Free Energy ◽  
Surface Energy ◽  
Surface Free Energy ◽  
Essential Role ◽  
Index Number ◽  
Adhesion Ability ◽  
Thermally Sprayed ◽  
Proper Operation

Abstract The lubricant storing and releasing ability of the thermally sprayed surfaces plays an essential role in the proper operation of the components. In the case of porous sprayed surfaces the lubricant storing and releasing ability depends mainly on porosity and the surface energy (adhesion susceptibility). The adhesion ability can also be expressed indirectly with an index number that is by determining the surface free energy.

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