Features of the Gas-Permeable Crystalline Phase of Poly-2,6-Dimethylphenylene Oxide

Poly-2,6-dimethylphenylene oxide (PPO) film samples with varying degrees of crystallinity (from 0 to 69%) were obtained by means of different techniques. The films were studied by various physicochemical methods (Fourier-transform infrared spectroscopy, positron annihilation lifetime spectroscopy, X-ray diffraction, and 1H nuclear magnetic resonance relaxation). Solubility coefficients of gases in the PPO samples were measured via sorption isotherms of gases by volumetric technique with chromatographic detection. The apparent activation energy of permeation and the activation energy of diffusion of all gases were estimated based on temperature dependences of gas permeability and diffusivity for amorphous and semi-crystalline PPO in the range of 20–50 °C. The peculiarities of free volume, density, and thermal properties of gas transport confirm the nanoporosity of the gas-permeable crystalline phase of PPO. So, the PPO can be included in the group of organic molecular sieves.

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Poly(ether imide)s: correlation of positron annihilation lifetime studies with polymer structure and gas permeability

Polymer ◽

10.1016/s0032-3861(98)00539-4 ◽

1999 ◽

Vol 40 (12) ◽

pp. 3605-3610 ◽

Cited By ~ 17

Author(s):

GeoffreyC. Eastmond ◽

JohnH. Daly ◽

AlexanderS. McKinnon ◽

RichardA. Pethrick

Keyword(s):

Positron Annihilation ◽

Gas Permeability ◽

Polymer Structure ◽

Positron Annihilation Lifetime ◽

Lifetime Studies

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Hybrid Ionic Liquid-Chitosan Membranes for CO2 Separation: Mechanical and Thermal Behavior

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2014-0109 ◽

2016 ◽

Vol 14 (3) ◽

pp. 713-718 ◽

Cited By ~ 10

Author(s):

Esther Santos ◽

Enrique Rodríguez-Fernández ◽

Clara Casado-Coterillo ◽

Ángel Irabien

Keyword(s):

Activation Energy ◽

Ionic Liquid ◽

Thermal Behavior ◽

Gas Permeability ◽

Co2 Separation ◽

Liquid Membranes ◽

Temperature Influence ◽

Supported Ionic Liquid ◽

Chitosan Membranes ◽

Supported Ionic Liquid Membranes

Abstract Pure chitosan (CS) and hybrid ionic liquid-chitosan membranes loaded with 5 wt% 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) ionic liquid were prepared in order to improve the thermal behavior of supported ionic liquid membranes (SILMs) for CO2 separation. Gas permeability, solubility and diffusivity were evaluated in the temperature range 298–323 K. The temperature influence was well described in terms of the Arrhenius–van’t Hoff exponential relationships. Activation energies were calculated and compared with those obtained for SILMs with the same ionic liquid. The introduction of this ionic liquid in the hybrid solid membrane decreases the permeability activation energy, leading to a lower influence of the temperature in the permeability and diffusivity. Moreover, the thermal behavior is similar to pure chitosan membranes, and the mechanical strength and flexibility were improved due to the introduction of the ionic liquid in the polymer matrix.

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Crystallization Behavior and Microstructure of B2O3-Al2O3-SiO2 Glass-Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.51.149 ◽

2008 ◽

Vol 51 ◽

pp. 149-154

Author(s):

Han Ning Xiao ◽

Tao Sun ◽

Hua Bin Liu ◽

Yin Cheng

Keyword(s):

Activation Energy ◽

Metal Oxides ◽

Crystalline Phase ◽

Crystallization Behavior ◽

Glass Ceramics ◽

Earth Metal ◽

Crystallization Activation Energy ◽

Alkali Earth Metal ◽

Alkali Earth ◽

Bulk Crystallization

The influences of B2O3/SiO2 ratio and different alkali earth metal oxides MO (M= Ba, Mg, Ca) on the crystallization behavior of B2O3-Al2O3-SiO2 (BAS) glass were investigated by means of DSC, XRD and SEM. With the reduction of B2O3/SiO2 ratio, the crystallization activation energy increases at first and then decreases, reaching the minimum value of 375.4 kJ·mol-1 when the B2O3/SiO2 ratio is 2.2. The crystalline indices (n) are all more than 4, which indicates that the glass is in bulk crystallization. When the glass was heated to 800°C, the primary precipitated crystalline phase was Al4B2O9. With the increase of temperature up to 1100°C, Al18B4O33 and Al5BO9 appeared and became the major crystalline phases in BAS glass-ceramics.

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Synthesis And Water Sorption Properties Of Aluminophosphate (AlPO4) And Silicoaluminophosphate (Sapo) Molecular Sieves

MRS Proceedings ◽

10.1557/proc-233-237 ◽

1991 ◽

Vol 233 ◽

Cited By ~ 2

Author(s):

P. B. Malla ◽

S. Komarneni

Keyword(s):

Molecular Sieves ◽

Water Sorption ◽

Hysteresis Loops ◽

Sorption Isotherms ◽

Cooperative Interaction ◽

Type I ◽

Relative Pressure ◽

Micropore Filling ◽

General Expectation ◽

Initial Adsorption

ABSTRACTAluminophosphate (AlPO4–5, AlPO4–11, AlPO4–17, AlPO4–20) and silicoaluminophosphate (SAPO-5, SAPO- 11, SAPO-17, SAPO-20) molecular sieves of varying pore sizes (3–8 Å) were synthesized and their water adsorption and desorption properties were studied. Water sorption isotherms of AlPO4 molecular sieves were characterized by unusual isotherm shapes, that is, little or no initial adsorption followed by extreme adsorption leading to volume filling by hydrogen bonding and cooperative interaction in micropores, apparently due to the nonpolar nature of pore surfaces coupled with weak (reversible upon evacuation) chemisorption of water, and hysteresis loops extending to very low pressures. Although micropore filling in AlPO2's and isostructural SAPO's was completed almost at the same relative pressure (p/po), SAPO's exhibited less extreme adsorption isotherms as a result of their slightly more polar nature of pore surfaces compared to AlPO4's. Neither AlPO4apos;s nor SAPO's exhibited Brunauer Type I isotherms with water, contrary to a general expectation of the hydrophilic microporous solids.

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Influence of Temperature on Intratrack Processes and Ps Formation and Behaviour in Liquid Water

Materials Science Forum ◽

10.4028/www.scientific.net/msf.607.213 ◽

2008 ◽

Vol 607 ◽

pp. 213-217 ◽

Cited By ~ 4

Author(s):

Sergey V. Stepanov ◽

Gilles Duplâtre ◽

Vsevolod Byakov ◽

V.S. Subrahmanyam ◽

Dmitry Zvezhinskiy ◽

...

Keyword(s):

Positron Annihilation ◽

Liquid Water ◽

Radical Reactions ◽

Influence Of Temperature ◽

Positron Annihilation Lifetime ◽

Temperature Range ◽

Diffusion Controlled ◽

Temperature Dependences ◽

Influence Of Temperature On

Positron annihilation lifetime (PAL) spectra are measured in liquid water in the temperature range 2 – 930C. The spectra are treated by taking into account intratrack reactions and assuming that radical reactions with Ps are diffusion-controlled (the respective temperature dependences obeying the Stokes-Einstein law). Equilibrium Ps bubble parameters are obtained.

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Positron Lifetime at Deep Donors of Radiation Origin in Proton - Irradiated FZ-Silicon Single Crystals

Materials Science Forum ◽

10.4028/www.scientific.net/msf.733.224 ◽

2012 ◽

Vol 733 ◽

pp. 224-227 ◽

Cited By ~ 1

Author(s):

Nikolai Yu. Arutynov ◽

Mohamed Elsayed ◽

Reinhard Krause-Rehberg ◽

Valentin V. Emtsev ◽

Gagik A. Oganesyan ◽

...

Keyword(s):

Activation Energy ◽

Room Temperature ◽

Positron Lifetime ◽

Shallow Donor ◽

Electrical Measurements ◽

Positron Annihilation Lifetime ◽

First Order ◽

Deep Donor ◽

Donor States ◽

Mev Protons

The recovery of shallow donor states of the atoms of phosphorus in n-FZ-Si:P material irradiated at the room temperature with 15 MeV protons was studied in the course of isochronal annealing. This process was investigated by the positron annihilation lifetime (PAL) spectroscopy and by low-temperature electrical measurements. The positron traps of a vacancy type manifesting themselves as deep donors have been revealed. These defects begin to anneal at ~ 593 K– 613 K; roughly estimated activation energy of the process is Ea ≈ 0.59 eV under the first order of reaction. The results suggest the involvement, at least, of one vacancy and the impurity atom of phosphorus in the microstructure of the deep donor.

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Activation Enthalpy of Dislocation Migration in Aircraft (Aerospace) (2024) Alloy by Positron Spectroscopy

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.278.11 ◽

2008 ◽

Vol 278 ◽

pp. 11-14 ◽

Cited By ~ 1

Author(s):

M.A. Abdel-Rahman ◽

M.S. Abdallah ◽

N.M. Hassan ◽

Emad A. Badawi

Keyword(s):

Activation Energy ◽

Aluminum Alloys ◽

Positron Annihilation ◽

Point Defects ◽

Isothermal Annealing ◽

Activation Enthalpy ◽

Positron Annihilation Lifetime ◽

Nuclear Techniques ◽

Positron Spectroscopy ◽

2024 Alloy

Positron annihilation lifetime is one of the most important nuclear techniques, used to study the isochronal and isothermal annealing in one of the most important engineering aluminum alloys which is 2024 alloy. Samples of 25 % deformation have been used for these studies. Two recovery stages during the isochronal annealing [1] were observed which were ascribed to the recovery of point defects and dislocations introduced by the deformation. The isothermal annealing measurements were performed at 583, 603, 623 and 643 K from which the activation energy obtained was 1.24 ± 0.08 eV.

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О термической устойчивости некоторых квазифуллеренов

Физика твердого тела ◽

10.21883/ftt.2019.03.47258.264 ◽

2019 ◽

Vol 61 (3) ◽

pp. 604

Author(s):

А.И. Подливаев ◽

Л.А. Опенов

Keyword(s):

Activation Energy ◽

Molecular Dynamics ◽

Thermal Stability ◽

Frequency Factor ◽

Arrhenius Law ◽

Method Of Molecular Dynamics ◽

Temperature Dependences ◽

Thermal Stability Of

AbstractThe thermal stability of recently predicted quasi-fullerenes С_20, С_42, С_48, and С_60 is studied by the method of molecular dynamics. The routes of their decomposition and the temperature dependences of their lifetimes are determined. The activation energy and frequency factor values that appear in the Arrhenius law are found. New isomers are detected.

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Unentangled Vitrimer Melts: Interplay between Chain Relaxation and Cross-link Exchange Controls Linear Rheology

10.26434/chemrxiv.13246823.v1 ◽

2020 ◽

Author(s):

RALM RICARTE ◽

Sachin Shanbhag

Keyword(s):

Activation Energy ◽

A Priori ◽

Relaxation Times ◽

Cross Link ◽

Time Dynamics ◽

Temperature Dependences ◽

Long Time ◽

Arrhenius Temperature Dependence ◽

Short Time ◽

Arrhenius Temperature

<div>Using this theoretical approach, we explore the influence of molecular structure and temperature on vitrimer linear</div><div>viscoelasticity. We observe that vitrimers with uniform and random cross-link distributions exhibit larger viscosities</div><div>and relaxation times than gradient and blocky types. Polydimethylsiloxane vitrimer (which has a flexible backbone) shows an Arrhenius temperature dependence for viscosity, while polystyrene vitrimers (which has rigid backbones) are only Arrhenius at high temperatures. During stress relaxation, the short time dynamics represent monomer friction, while the long time dynamics encompass a combination of network strand relaxation and cross-link exchange. Because of the different temperature dependences of the processes, time-temperature superposition fails. We also show that the effective rheological activation energy can be estimated a priori using only the cross-link exchange activation energy and the backbone Williams-Landel-Ferry parameters.</div><div><br></div><div>(Submitted to Macromolecules)</div>

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Туннельная проводимость и туннельное магнитосопротивление пленок Fe-SiO: корреляция магнитотранспортных и магнитных свойств

Физика твердого тела ◽

10.21883/ftt.2019.07.47835.408 ◽

2019 ◽

Vol 61 (7) ◽

pp. 1262

Author(s):

Д.А. Балаев ◽

А.Д. Балаев

Keyword(s):

Activation Energy ◽

Electrical Resistance ◽

Low Temperatures ◽

Magnetic Method ◽

Tunnel Mechanism ◽

Giant Magnetoresistive Effect ◽

Temperature Dependences ◽

Magnetoresistive Effect ◽

Dielectric Region ◽

Good Agreement

The paper presents the results of a study of the electrical properties of a system of nanogranular amorphous Fe-SiO films with a SiO concentration from 0 to 92 Vol.%. For samples with a low SiO content, metallic conductivity takes place. With an increase of the dielectric content, a concentration transition of conduction from the metallic regime to the tunnel regime at a dielectric concentration x  0.6 is observed. At the same concentration, a transition ferromagnet - superparamagnet occurs, which was previously investigated by the magnetic method. For compositions corresponding to the dielectric region, the temperature dependences of the electrical resistance (T) follow the law (T) ~ exp(2(С/kT)1/2), which is typical for the tunnel mechanism of conductivity. Estimation of the sizes of metal granules from the values of the tunneling-activation energy C showed a good agreement with the sizes obtained earlier from the analysis of magnetic properties. In the dielectric range of the compositions, a giant magnetoresistive effect was obtained, reaching 25% at low temperatures.

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