Effect of Pulsed Magnetic Fields on Crystallization of Polymers

2002 ◽  
Vol 734 ◽  
Author(s):  
Mark N. Levin
Keyword(s):  
Magnetic Field ◽  
Polyethylene Oxide ◽  
Crystalline State ◽  
Structural Modification ◽  
Pulsed Magnetic Fields ◽  
Flexible Chain ◽  
Increased Sensitivity ◽  
Controlled Crystallization ◽  
Crystallization Of Polymers ◽  
Kinetics Of

ABSTRACTThe effect of pre-crystallization pulsed magnetic field (PMF) treatment of linear flexible-chain polymers on kinetics of their crystallization and structure in the crystalline state has been studied in polydimethylsiloxane (PDMS) and polyethylene oxide (PEO). It was established that the PMF treatment can destruct the initial net of non-chemically bonded “physical nodes” of the polymer and thus turn the melt into a metastable state with the increased sensitivity to regimes of crystallization. The effect revealed can lay the foundation for the development of new effective methods of controlled crystallization of the flexible-chain polymers, including fractionation and crystallization of polymorphic polymers in the chosen structural modification.

scholarly journals The influence of an external magnetic field on the dynamics of magnetite reduction with hydrogen

RSC Advances ◽  
2021 ◽  
Vol 11 (25) ◽  
pp. 15422-15427
Author(s):  
Petr A. Chernavsky ◽  
Nellie V. Kim ◽  
Victor A. Andrianov ◽  
Yurii D. Perfiliev ◽  
Alla A. Novakova ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Hydrogen Reduction ◽  
Kinetics Of

The kinetics of hydrogen reduction of magnetite was investigated in different magnetic fields.

scholarly journals Demicellization of Polyethylene Oxide in Water Solution under Static Magnetic Field Exposure Studied by FTIR Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Emanuele Calabrò ◽  
Salvatore Magazù
Keyword(s):  
Magnetic Field ◽  
Aqueous Solution ◽  
Ftir Spectroscopy ◽  
Static Magnetic Field ◽  
Polyethylene Oxide ◽  
Water Solution ◽  
Infrared Region ◽  
Bending Vibrations ◽  
Field Exposure ◽  
Methylene Groups

FTIR spectroscopy was used to investigate the alterations of the vibration bands in the mid-infrared region of Polyethylene oxide in aqueous solution at 25 mg/mL concentration under exposure up to 4 h to a static magnetic field at 200 mT. FTIR spectroscopic analysis of PEO solution in the range 3500–1000 cm−1 evidenced the stretching vibrations of ether band, C–H symmetric-antisymmetric and bending vibrations of methylene groups, and the C–O–C stretching band. A significant decrease in intensity of symmetric and asymmetric stretching CH2 vibration bands occurred after 2 h and 4 h of exposure, followed by a significant decrease in intensity of scissoring bending in plane CH2 vibration around 1465 cm−1. Finally, the C–O–C stretching band around 1080 cm−1 increased in intensity after 4 h of exposure. This result can be attributed to the increase of formation of the intermolecular hydrogen bonding that occurred in PEO aqueous solution after SMF exposure, due to the reorientation of PEO chain after exposure to SMF. In this scenario, the observed decrease in intensity of CH2 vibration bands can be understood as well considering that the reorientation of PEO chain under the applied SMF induces PEO demicellization.

Phase Change Materials - From Structures to Kinetics

2006 ◽  
Vol 918 ◽  
Author(s):  
Matthias Wuttig ◽  
Wojciech Welnic ◽  
Ralf Detemple ◽  
Henning Dieker ◽  
Johannes Kalb ◽  
...  
Keyword(s):  
Phase Change ◽  
Crystalline State ◽  
Phase Change Materials ◽  
Amorphous State ◽  
Structural Difference ◽  
Fast Time ◽  
Optical Contrast ◽  
Fast Time Scale ◽  
Kinetics Of ◽  
Structure Properties

AbstractPhase change materials possess a unique combination of properties which include a pronounced property contrast between the amorphous and crystalline state, i.e. a high electrical and optical contrast. In particular the latter observation is indicative for a considerable structural difference between the amorphous and crystalline state. At the same time the crystallization of the amorphous state proceeds on a fast time scale. This raises the question how structure, properties and kinetics are related in phase change alloys. It will be demonstrated that only a small group of covalent semiconductors with octahedral-like coordination has the required property combination. This is related to their thermodynamic properties which govern the kinetics of crystallization.

An Interpretation on Kinetics of Martensitic Transformation

2011 ◽  
Vol 172-174 ◽  
pp. 90-98 ◽  
Author(s):  
Tomoyuki Kakeshita ◽  
Takashi Fukuda ◽  
Yong-Hee Lee
Keyword(s):  
Magnetic Field ◽  
Hydrostatic Pressure ◽  
Martensitic Transformation ◽  
Magnetic Fields ◽  
Martensitic Transformations ◽  
Phenomenological Theory ◽  
Time Dependent ◽  
Isothermal Process ◽  
Kinetics Of ◽  
Transformation Processes

We have investigated athermal and isothermal martensitic transformations (typical displacive transformations) in Fe–Ni, Fe–Ni–Cr, and Ni-Co-Mn-In alloys under magnetic fields and hydrostatic pressures in order to understand the time-dependent nature of martensitic transformation, that is, the kinetics of martensitic transformation. We have confirmed that the two transformation processes are closely related to each other, that is, the athermal process changes to the isothermal process and the isothermal process changes to the athermal one under a hydrostatic pressure or a magnetic field. These findings can be explained by the phenomenological theory, which gives a unified explanation for the two transformation processes previously proposed by our group.

Kinetics of oxidation of subsurface layers of 29Si-enriched silicon in a magnetic field

2014 ◽  
Vol 56 (7) ◽  
pp. 1443-1448 ◽  
Author(s):  
O. V. Koplak ◽  
A. I. Dmitriev ◽  
R. B. Morgunov
Keyword(s):  
Magnetic Field ◽  
Kinetics Of Oxidation ◽  
Subsurface Layers ◽  
Kinetics Of

scholarly journals Martensitic transformation in the systems based on Fe-Ni compositions in strong pulsed magnetic fields

2021 ◽  
pp. 22-29 ◽  
Author(s):  
I. Zolotarevskii
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
Magnetic Fields ◽  
Temperature Dependence ◽  
Strong Magnetic Field ◽  
Low Temperatures ◽  
Strong Dependence ◽  
Magnetic Interaction ◽  
Iron Alloys ◽  
Pulsed Magnetic Fields

Purpose of work. To ascertain the causes of the abnormally large displacement of the martensitic point in steels and iron alloys in strong pulsed magnetic fields at low temperatures. Research methods. Generalization of experimental and theoretical investigations of the strong magnetic field influence on the martensitic transformation in steels and iron alloys, taking into account the magnetic state of austenite. The obtained results. The distributions of the martensitic point displacement ΔMS from the content of the main component - iron and the temperature of the martensitic γ → α- transformation beginning (martensitic point MS) in different experiments are obtained. It is shown that the obtained temperature dependence ΔMS(MS) in a strong magnetic field at low temperatures decomposes into two components, one of which correlates with the generalized Clapeyron-Clausius equations, and the other is opposite to it. In addition, it was found that steels and alloys with intense γ → α- transformation in a magnetic field contain at least 72.5% iron (wt), which at low temperatures in the fcc structure is antiferromagnetic. Scientific novelty. The anomalous temperature dependence of the distribution ΔMS(MS) in a strong magnetic field is explained on the basis of quantum representations of the magnetic interaction of atoms in the Fe-Ni system. This effect is associated with a number of other invar effects, in particular, with an abnormally large spontaneous and forced magnetostriction, a strong dependence of the resulting exchange integral on the interatomic distance. The point of view according to which in these alloys in a magnetic field γ → α- transformation occurs by the type of “magnetic first kind phase transformation” is substantiated. It is assumed that the nucleation of the martensitic phase in a magnetic field occurs in (at) local regions of γ- phase with disoriented atomic magnetic moments (with high compression and increased forced magnetostriction). Practical value. The information obtained in this work provides grounds for explaining the kinetic features of the transformation of austenite into martensite in steels and iron alloys.

scholarly journals In-situ kinetics of modifications induced by swift heavy ions in Al2O3: Colour centre formation, structural modification and amorphization

2017 ◽  
Vol 140 ◽  
pp. 157-167 ◽  
Author(s):  
C. Grygiel ◽  
F. Moisy ◽  
M. Sall ◽  
H. Lebius ◽  
E. Balanzat ◽  
...  
Keyword(s):  
Heavy Ions ◽  
Structural Modification ◽  
Colour Centre ◽  
Swift Heavy Ions ◽  
Kinetics Of
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