Experimental and Theoretical Treatment of Molecular-scale Mechanisms of Crystal Growth on Baryte

1998 ◽  
Vol 62A (1) ◽  
pp. 134-134
Author(s):  
U. Becker
Keyword(s):  
Crystal Growth ◽  
Theoretical Treatment ◽  
Molecular Scale

Crystallization and the Relaxation of Stress in Stretched Natural-Rubber Vulcanizates

1955 ◽  
Vol 28 (1) ◽  
pp. 36-50 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Crystal Growth ◽  
Natural Rubber ◽  
Theoretical Treatment ◽  
Cross Link ◽  
Continuous Transition ◽  
First Approximation ◽  
Degree Of Crystallization ◽  
Chemical Groups ◽  
Natural Rubber Vulcanizates

Abstract Experiments are described in which the decrease of volume and simultaneous relaxation of stress in crystallizing extended samples of vulcanized natural rubber were followed with time at a temperature of −26° C. The theoretical treatment of Avrami is extended and shown to predict to a first approximation the time functions governing crystal growth in stretched vulcanizates. A continuous transition from polyhedral to aciform crystal growth on increasing the extension is indicated The relaxation of stress is found to be approximately proportional to the degree of crystallization throughout the process, the factor relating them being given by the theory of Flory at high extensions, that is, for aciform crystal growth. The retarding influence of vulcanization is attributed to a banned volume mechanism, whereby an element of volume around each cross-link is prohibited to nucleation, and an approximate value for the banned volume has been obtained. The influence of irregular chemical groups and prior heating on the rate of crystallization is also discussed.

Rethinking Classical Crystal Growth Models through Molecular Scale Insights: Consequences of Kink-Limited Kinetics

2009 ◽  
Vol 9 (12) ◽  
pp. 5135-5144 ◽  
Author(s):  
J. J. De Yoreo ◽  
L. A. Zepeda-Ruiz ◽  
R. W. Friddle ◽  
S. R. Qiu ◽  
L. E Wasylenki ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Growth Models ◽  
Molecular Scale ◽  
Classical Crystal

scholarly journals The bee Tetragonula builds its comb like a crystal

2020 ◽  
Vol 17 (168) ◽  
pp. 20200187 ◽  
Author(s):  
Silvana S. S. Cardoso ◽  
Julyan H. E. Cartwright ◽  
Antonio G. Checa ◽  
Bruno Escribano ◽  
Antonio J. Osuna-Mascaró ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Lattice Model ◽  
Stingless Bees ◽  
Nucleation And Growth ◽  
Coupled Map Lattice ◽  
Three Dimensions ◽  
Crystal Nucleation ◽  
Target Pattern ◽  
Brood Comb ◽  
Molecular Scale

Stingless bees of the genus Tetragonula construct a brood comb with a spiral or a target pattern architecture in three dimensions. Crystals possess these same patterns on the molecular scale. Here, we show that the same excitable-medium dynamics governs both crystal nucleation and growth and comb construction in Tetragonula , so that a minimal coupled-map lattice model based on crystal growth explains how these bees produce the structures seen in their bee combs.

Resolving the Control of Magnesium on Calcite Growth: Thermodynamic and Kinetic Consequences of Impurity Incorporation for Biomineral Formation

2000 ◽  
Vol 620 ◽  
Author(s):  
Kevin J. Davis ◽  
Patricia M. Dove ◽  
James J. De Yoreo
Keyword(s):  
Atomic Force Microscopy ◽  
Crystal Growth ◽  
Impurity Incorporation ◽  
Force Microscopy ◽  
Mineral Solubility ◽  
Atomic Force ◽  
Molecular Scale ◽  
Terrace Width ◽  
Impurity Models

ABSTRACTMagnesium is a key determinant in CaCO3 biomineral formation and has recently emerged as an important paleotemperature proxy. Atomic force microscopy (AFM) was used to determine the fundamental thermodynamic and kinetic controls of Mg2+ on calcite morphology and growth. Comparison of directly measured monomolecular step velocities (vs±) to theoretical crystal growth impurity models demonstrated calcite inhibition due to enhanced mineral solubility through Mg2+ incorporation. Terrace width (λ) measurements independently supported an incorporation mechanism by indicating a shift in the effective supersaturation (σeff) of the growth solutions in the presence of Mg2+. This study resolves the controversy over the molecular-scale mechanism of calcite inhibition by Mg2+ and provides an unambiguous model for the thermodynamic and kinetic consequences of impurity incorporation into CaCO3 biominerals.

scholarly journals Molecular-scale mechanisms of crystal growth in barite

Nature ◽  
10.1038/26718 ◽  
1998 ◽  
Vol 395 (6701) ◽  
pp. 483-486 ◽  
Author(s):  
Carlos M. Pina ◽  
Udo Becker ◽  
Peter Risthaus ◽  
Dirk Bosbach ◽  
Andrew Putnis
Keyword(s):  
Crystal Growth ◽  
Molecular Scale

Montmorillonite Dendrites

1974 ◽  
Vol 32 ◽  
pp. 454-455
Author(s):  
Necip Güven ◽  
Rodney W. Pease
Keyword(s):  
Crystal Growth ◽  
Growth Mechanism ◽  
Growth Front ◽  
Morphological Features ◽  
Dendritic Crystal ◽  
Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

Cristal-growth dynamics of n-doped gaAs

1992 ◽  
Vol 50 (2) ◽  
pp. 1544-1545
Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay
Keyword(s):  
Crystal Growth ◽  
Spatial Resolution ◽  
Epitaxial Layer ◽  
Outer Surface ◽  
Gaas Substrate ◽  
Structural Modification ◽  
Growth Dynamics ◽  
Argon Laser ◽  
High Anisotropy ◽  
Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

Sign in / Sign up

Export Citation Format

Share Document