scholarly journals On the role of surface energy in the flattening of a crystal face

2005 ◽  
Vol 3 (1) ◽  
pp. 188-197
Author(s):  
Christo Nanev
Keyword(s):  
Free Energy ◽  
Crystal Growth ◽  
Surface Energy ◽  
Atomic Scale ◽  
Crystal Face ◽  
Screw Dislocations ◽  
The Face ◽  
Kinetic Effects ◽  
Face Morphology

AbstractThe question addressed in this paper is the flattening of the valley separating two growth hillocks emanating from screw dislocations during crystal growth. It is argued that both thermodynamic and kinetic effects contribute to this result, at least on a quasi-atomic scale. If performed under low enough supersaturation the growth leads to the formation of the face morphology corresponding to the minimum of the surface free energy. Accelerated step annihilation in the valley floor is a universal factor, which favors face flatting under any supersaturation.

scholarly journals Термодинамическая модель зародышеобразования кристаллов n-терфенила с анизотропией поверхностной энергии на межфазной границе жидкость-воздух

2019 ◽  
Vol 61 (12) ◽  
pp. 2432
Author(s):  
В.А. Постников ◽  
А.А. Кулишов ◽  
А.А. Островская ◽  
А.С. Степко ◽  
П.В. Лебедев-Степанов
Keyword(s):  
Free Energy ◽  
Crystal Growth ◽  
Surface Energy ◽  
Force Field ◽  
Structural Data ◽  
Field Method ◽  
Experimental Information ◽  
Growth From Solutions ◽  
Atomic Force ◽  
Air Interface

An analysis of the change in the Gibbs free energy ∆G upon the formation of a flat nucleus of a p-terphenyl crystal at the liquid – air interface is presented, taking into account the anisotropy of the surface energy of the faces. The surface energy values of the p-terphenyl crystal faces were calculated by the atomic force field method OPLS, based on structural data. Experimental information on crystal growth from solutions and their surface properties was used to analyze the model.

The study of crystal growth with the electron microscope IV. The nucleation and growth of n -propyl n -pentacontanoate

1955 ◽  
Vol 228 (1175) ◽  
pp. 539-548 ◽  
Keyword(s):  
Electron Microscope ◽  
Crystal Growth ◽  
Nucleation And Growth ◽  
Twist Boundary ◽  
Crystal Face ◽  
Screw Dislocations ◽  
Perfect Lattice ◽  
Lattice Disorder ◽  
Monomolecular Films ◽  
Rotational Slip

The study of long-chain paraffin derivatives in the electron microscope has been extended to include the fatty acid ester n -propyl n -pentacontanoate, n -C 53 H 106 o 2 . Examination of crystals prepared by previously described methods has given information on two further aspects of crystal growth. In the first place micrographs have been obtained at a much earlier stage in the growth of the crystals, before recognizable growth-steps have developed. It would appear that growth arises from sheet nuclei consisting of small condensed monomolecular films of 0.25 to 20μ 2 area. Screw dislocations arise at the edge of these sheets through the condensation of molecules in positions of incomplete lattice register. Growth thereafter continues around these dislocation centres, and the resultant spiral is built in towards the centre of the crystal face. This information modifies the Frank (1951) concept of a buckling mechanism for the formation of screw dislocations in crystals, since it places the emphasis on the importance of edge condensation in the formation of lattice disorder and minimizes the importance of strain in the growing perfect lattice. The second finding has been that these crystals frequently occur with a twist boundary parallel to {001}. This effect cannot properly be described as rotational slip of the type discussed by Wilman (1951), since it does not arise through deformation of an already formed crystal but occurs during growth itself. This twist boundary is penetrated by a screw dislocation or by a group of screw dislocations.

Role of screw dislocations in electrolytic crystal growth

1977 ◽  
Vol 12 ◽  
pp. 83 ◽  
Author(s):  
Vesselin Bostanov ◽  
Evgeni Budevski ◽  
Georgi Staikov
Keyword(s):  
Crystal Growth ◽  
Screw Dislocations

The observation of spiral growth-steps in n -paraffin single crystals in the electron microscope

1951 ◽  
Vol 206 (1087) ◽  
pp. 555-562 ◽  
Keyword(s):  
Electron Microscope ◽  
Crystal Growth ◽  
Single Crystals ◽  
Long Range ◽  
Electron Micrographs ◽  
Spiral Growth ◽  
Crystal Face ◽  
Screw Dislocations ◽  
Range Migration ◽  
Visual Confirmation

Electron micrographs of single crystals of the n -paraffin, n -hexatriacontane, C 36 H 74 , show clearly the successive monomolecular steps on the growing face of the crystal. Examination of the edge of these molecular steps shows, in many crystals, not a succession of closed terraces, but a continuous spiral on the crystal face. The results thus afford direct visual confirmation of the theory of crystal growth by spiral growth-steps ending on screw dislocations. There is no evidence of the long-range migration of molecules over the growing face of the crystals. The molecules appear to condense only on the developing edge.

Теория гетерогенного катализа. Теория хемосорбции

2021 ◽  
Author(s):  
Василий Садовников
Keyword(s):  
Heterogeneous Catalysis ◽  
Potential Energy ◽  
Publishing House ◽  
Cell Number ◽  
Oil Refining ◽  
Lateral Interaction ◽  
Reaction Products ◽  
Crystal Face ◽  
Independent Particle ◽  
The Face

This monograph is a continuation of the monograph by V.V. Sadovnikov. Lateral interaction. Moscow 2006. Publishing house "Anta-Eco", 2006. ISBN 5-9730-0017-6. In this work, the foundations of the theory of heterogeneous catalysis and the theory of chemisorption are more easily formulated. The book consists of two parts, closely related to each other. These are the theoretical foundations of heterogeneous catalysis and chemisorption. In the theory of heterogeneous catalysis, an experiment is described in detail, which must be carried out in order to isolate the stages of a catalytic reaction, to find the stoichiometry of each of the stages. This experiment is based on the need to obtain the exact value of the specific surface area of the catalyst, the number of centers at which the reaction proceeds, and the output curves of each of the reaction products. The procedures for obtaining this data are described in detail. Equations are proposed and solved that allow calculating the kinetic parameters of the nonequilibrium stage and the thermodynamic parameters of the equilibrium stage. The description of the quantitative theory of chemisorption is based on the description of the motion of an atom along a crystal face. The axioms on which this mathematics should be based are formulated, the mathematical apparatus of the theory is written and the most detailed instructions on how to use it are presented. The first axiom: an atom, moving along the surface, is present only in places with minima of potential energy. The second axiom: the face of an atom is divided into cells, and the position of the atom on the surface of the face is set by one parameter: the cell number. The third axiom: the atom interacts with the surrounding material bodies only at the points of minimum potential energy. The fourth axiom: the solution of the equations is a map of the arrangement of atoms on the surface. The fifth axiom: quantitative equations are based on the concept of a statistically independent particle. The formation energies of these particles and their concentration are calculated by the developed program. The program based on these axioms allows you to simulate and calculate the interaction energies of atoms on any crystal face. The monograph is intended for students, post-graduate students and researchers studying work and working in petrochemistry and oil refining.

Questions on the role of biofilms for the adaptation of microorganisms to unfavorable environmental factors by the example of P. aeruginosa

2020 ◽  
Vol 99 (4) ◽  
pp. 379-383
Author(s):  
Vasily N. Afonyushkin ◽  
N. A. Donchenko ◽  
Ju. N. Kozlova ◽  
N. A. Davidova ◽  
V. Yu. Koptev ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Environmental Factors ◽  
Barrier Function ◽  
Infectious Agent ◽  
Antagonistic Activity ◽  
The Body ◽  
Main Function ◽  
Pathogenic Potential ◽  
The Face

Pseudomonas aeruginosa is a widely represented species of bacteria possessing of a pathogenic potential. This infectious agent is causing wound infections, fibrotic cystitis, fibrosing pneumonia, bacterial sepsis, etc. The microorganism is highly resistant to antiseptics, disinfectants, immune system responses of the body. The responses of a quorum sense of this kind of bacteria ensure the inclusion of many pathogenicity factors. The analysis of the scientific literature made it possible to formulate four questions concerning the role of biofilms for the adaptation of P. aeruginosa to adverse environmental factors: Is another person appears to be predominantly of a source an etiological agent or the source of P. aeruginosa infection in the environment? Does the formation of biofilms influence on the antibiotic resistance? How the antagonistic activity of microorganisms is realized in biofilm form? What is the main function of biofilms in the functioning of bacteria? A hypothesis has been put forward the effect of biofilms on the increase of antibiotic resistance of bacteria and, in particular, P. aeruginosa to be secondary in charcter. It is more likely a biofilmboth to fulfill the function of storing nutrients and provide topical competition in the face of food scarcity. In connection with the incompatibility of the molecular radii of most antibiotics and pores in biofilm, biofilm is doubtful to be capable of performing a barrier function for protecting against antibiotics. However, with respect to antibodies and immunocompetent cells, the barrier function is beyond doubt. The biofilm is more likely to fulfill the function of storing nutrients and providing topical competition in conditions of scarcity of food resources.

The Modern Aristotle: Michael Polanyi’s Search for Truth against Nihilism

2018 ◽  
Author(s):  
Ronald Hoinski ◽  
Ronald Polansky
Keyword(s):  
Philosophy Of Science ◽  
Modern Science ◽  
Michael Polanyi ◽  
Contemporary Philosophy ◽  
The Face ◽  
Human Desire ◽  
The Mind ◽  
Theoretical Science

David Hoinski and Ronald Polansky’s “The Modern Aristotle: Michael Polanyi’s Search for Truth against Nihilism” shows how the general tendencies of contemporary philosophy of science disclose a return to the Aristotelian emphasis on both the formation of dispositions to know and the role of the mind in theoretical science. Focusing on a comparison of Michael Polanyi and Aristotle, Hoinski and Polansky investigate to what degree Aristotelian thought retains its purchase on reality in the face of the changes wrought by modern science. Polanyi’s approach relies on several Aristotelian assumptions, including the naturalness of the human desire to know, the institutional and personal basis for the accumulation of knowledge, and the endorsement of realism against objectivism. Hoinski and Polansky emphasize the promise of Polanyi’s neo-Aristotelian framework, which argues that science is won through reflection on reality.

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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