Elastic Behavior, Birefringence, and Swelling of Amorphous Polyethylene Networks

1968 ◽  
Vol 41 (5) ◽  
pp. 1182-1193
Author(s):  
A. N. Gent ◽  
V. V. Vickroy
Keyword(s):  
Optical Anisotropy ◽  
Crystalline State ◽  
Amorphous State ◽  
Elastic Behavior ◽  
Molten State ◽  
Γ Irradiation ◽  
Linear Polyethylene ◽  
Solvent Interaction ◽  
Γ Radiation ◽  
Equilibrium Swelling

Abstract Polyethylene networks were prepared by γ-irradiation of linear polyethylene, both molten and crystalline. Elastic and. photoelastic properties of the networks were studied at high temperatures, i.e., in the molten state. Equilibrium swelling was also measured in several solvents. Values of the crosslinking efficiency G of γ-radiation, the molecular weight Me between entanglements, the optical anisotropy α of the equivalent random link, and the polymer-solvent interaction parameter μ are deduced. Samples prepared by irradiation in the amorphous state showed markedly nongaussian elastic behavior. The presence of a large nongaussian term in the optical anisotropy is also deduced. The value of α obtained for swollen samples, which showed substantially gaussian elastic behavior, was 3.9×10−24, about one half of that obtained for dry samples. It corresponds to an equivalent random link of only about 5 CH2 units, on the basis of Denbigh's values for bond polarizabilities. The samples prepared by irradiation in the crystalline state also showed lower values for α, depending on the degree of crosslinking. This is attributed to the nonrandom chain configurations prevailing at the time of crosslinking. The same samples were found to show more nearly gaussian elastic behavior, which is attributed to the same cause.

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.

Effects of initial concentration and irradiation dose to degradation of di butyl phthalate from phosphoric acid (30 % P2O5)

2018 ◽  
Vol 106 (11) ◽  
pp. 909-916
Author(s):  
Louisa Bounemia ◽  
Abdelhamid Mellah
Keyword(s):  
Organic Matter ◽  
Phosphoric Acid ◽  
Optimal Recovery ◽  
Γ Irradiation ◽  
Γ Radiation ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics ◽  
Butyl Phthalate

Abstract The pretreatment of the phosphoric acid is a stage of utmost importance leading to an optimal recovery of the uranium present in this acid. To this end, the degradation of the organic matter which obstructs considerably this recovery was tested by γ irradiation. This study lies within the scope of the radiation/matter interaction; concerning the use of the γ irradiator as proceed of phosphoric acid purification by the degradation of di butyl phthalate (DBP). Studies of the interaction of γ radiation with phosphoric acid solutions polluted by an organic matter concern the study of the influence of some parameters such as: dose rate (0.5–35 kGy), initial concentration (50–500 mg/L) of the pollutant, pH and % in P2O5 on the degradation of organic matter by γ irradiation. The reactions followed pseudo first order kinetics for different initial concentrations. The results made it possible to say that the degradation of di butyl phthalate by γ irradiation is dependent on the amount of the concentration of DBP and pH. The G-values decreased with absorbed doses, and increased with higher initial concentrations.Purification of phosphoric acid by γ radiation does not degrade the quality of this acid.

scholarly journals The Effect of Channel Length on Phase Transition of Phase Change Memory

2018 ◽  
Vol 7 (3.11) ◽  
pp. 25
Author(s):  
M S. A.Aziz ◽  
F H. M.Fauzi ◽  
Z Mohamad ◽  
R I. Alip
Keyword(s):  
Phase Transition ◽  
Silicon Carbide ◽  
Phase Change ◽  
Pulse Width ◽  
Crystalline State ◽  
Phase Change Memory ◽  
Amorphous State ◽  
Channel Length ◽  
Change Memory

The phase transition of germanium antimony tellurium (GST) and the temperature of GST were investigated using COMSOL Multiphysic 5.0 software. Silicon carbide was using as a heater layer in the separate heater structure of PCM. These simulations have a different channel of SiC. The temperature of GST and the phase transition of GST can be obtained from the simulation. From the simulation, the 300 nm channel of SiC can change the GST from amorphous to crystalline state at 0.7V with 100 ns pulse width. The 800 nm channel of SiC can change the GST from amorphous to crystalline state at 1.1V with 100 ns pulse width. Results demonstrated that the channel of SIC can affecting the temperature of GST and the GST changes from amorphous state to crystalline state. As the channel of SiC decreased, the temperature of GST was increased and the GST was change to crystalline state quickly.  

Efficient monitoring of dosimetric behaviour for copper nanoparticles through studying its optical properties

2019 ◽  
Vol 107 (6) ◽  
pp. 523-529 ◽  
Author(s):  
Mohamad Bekhit ◽  
Asmaa Sobhy ◽  
Zakaria I. Ali ◽  
Sameh M. Gafar
Keyword(s):  
Copper Nanoparticles ◽  
Metal Ion ◽  
Copper Ions ◽  
Dose Range ◽  
Ion Concentration ◽  
Nanocomposite Films ◽  
Poly Vinyl Alcohol ◽  
High Dose ◽  
Γ Irradiation ◽  
Γ Radiation

Abstract A novel high-dose dosimeter based on γ radiation reduction of copper ions and formation of copper metal inside polymer matrix were investigated. γ radiation induced synthesis of copper nanoparticles (CuNPs) in poly vinyl alcohol films were studied by UV-Visible Spectrophotometer, X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The optical absorption spectra showed that the Cu/PVA nanocomposite films have surface plasmon resonance (SPR) of copper nanoparticles which depending on irradiation doses. Upon γ irradiation these films turns its color from faint blue to deep reddish brown depending on metal ion concentration. The XRD pattern and FTIR spectrum confirm the formation of the CuNPs. The response of Cu/PVA nanocomposite dosimeters depends on both the irradiation doses and concentration of copper precursor. The dose range for these films was from 50 to 650 kGy, revealing its important applications for high dose dosimetry. Cu/PVA nanocomposites films exhibit good post-irradiation stability in dark and light.

Thermodynamic Properties and Polymer Solvent Interaction Parameters for Silicone Rubber Networks

1968 ◽  
Vol 41 (3) ◽  
pp. 608-620 ◽  
Author(s):  
R. D. Seeley
Keyword(s):  
Thermodynamic Properties ◽  
Network Structure ◽  
Silicone Rubber ◽  
Volume Fraction ◽  
Swelling Behavior ◽  
Effective Number ◽  
Solvent Interaction ◽  
Molecular Weights ◽  
Linear Relationships ◽  
Equilibrium Swelling

Abstract The relationships of the volume fraction of rubber (silica reinforced silicone rubber vulcanizates) at equilibrium swelling to a corresponding solvent-rubber interaction parameter have been found to agree quite well with theory throughout the entire range of volume fractions investigated. Composite sigmoidal curves were constructed from the ϕrs versus μ data for the different vulcanizates. Temperature and solvent effects were found to merely shift the plotting points along the curves for the respective vulcanizates. Contrary to other work linear relationships between ϕrs and μ were found in this investigation only in the range of moderate dilations. Such relationships could lead to serious misinterpretations if the investigations involved ϕrs versus μ data near an inflection point. Thus, the value of μ relative to a corresponding ϕrs not only depend upon solvent (s) and temperature, but also upon the level of vulcanization at moderate to high dilations. The entropy, enthalpy, and free energy changes associated with the configurational changes occurring in the network structure of the rubber were calculated. The thermodynamic properties were found to be consistent and uniform throughout the dilation range. Limiting osmotic pressures were determined to obtain effective number average molecular weights of the crosslinked chains. The molecular weight values were found to average slightly less than three times those obtainable from ve/Vr data. Finally, this investigation has shown that reinforced silicone rubber vulcanizates at equilibrium swelling in a variety of solvents exhibit the swelling behavior predicted by theory. However, swelling behavior at moderate to high swelling was found to be unrelated to the rubber in general, but related more specifically to the network structure of the vulcanizate. At low dilations, the characteristics of the silicone rubber species control the swelling behavior.

Radiation Chemical Conversions in Fluorine Containing Elastomers under Different γ-Irradiation Conditions

1974 ◽  
Vol 47 (2) ◽  
pp. 282-284 ◽  
Author(s):  
A. B. Kryukova ◽  
A. S. Kuz'minskii ◽  
N. S. Gilinskaya ◽  
F. A. Galil-Ogly ◽  
G. A. Sankina
Keyword(s):  
Stressed State ◽  
Vinyl Ether ◽  
High Temperatures ◽  
Vinylidene Fluoride ◽  
Chemical Crosslinking ◽  
Γ Irradiation ◽  
Radiation Chemical ◽  
Γ Radiation ◽  
Copolymer 1

Abstract Rates of radiation chemical crosslinking and scission of fluorine containing elastomers based on copolymers of vinylidene fluoride with trifluorochloroethylene (Copolymer 1), with hexafluoropropylene (Copolymer 2), and with a perfluoroalkyl vinyl ether (Copolymer 3) and also the behavior of their radiation vulcanizates in the stressed state at high temperatures are determined both by the type of polymer and by the irradiation conditions. Crosslinking rates of Copolymers 2 and 3 are higher than those of Copolymer 1; oxygen of the air inhibits crosslinking by γ-radiation; by irradiation in the presence of oxygen of the air, the sol fraction is 8–10 times higher than in its absence, Copolymer 3 vulcanizates obtained by irradiation in the absence of air appear to be optimal.

scholarly journals Thermoelastic Properties and Elastocaloric Effect in Rapidly Quenched Ribbons of Ti2NiCu Alloy in the Amorphous and Crystalline State

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 949
Author(s):  
Evgeny Morozov ◽  
Dmitry Kuznetsov ◽  
Vladimir Kalashnikov ◽  
Koledov Victor ◽  
Vladimir Shavrov
Keyword(s):  
Mechanical Stress ◽  
Coefficient Of Thermal Expansion ◽  
Relative Elongation ◽  
Landau Theory ◽  
Amorphous State ◽  
External Action ◽  
Elastic Behavior ◽  
Specific Power ◽  
Thermoelastic Properties ◽  
Elastocaloric Effect

The thermoelastic properties and the elastocaloric effect (ECE) were studied in rapidly quenched ribbons of the Ti2NiCu alloy samples in amorphous and crystalline states under periodic mechanical tension with a frequency of up to 50 Hz. In the amorphous samples, elastic behavior is observed, described by Hooke’s law, with a high coefficient of thermal expansion α = 1.7 × 10−4 K−1. Polycrystalline ribbons of the Ti2NiCu alloy have the classical shape memory effect (SME), the temperatures of the forward and reverse thermoelastic martensitic transitions being Ms = 345 K, Mf = 325 K, As = 332 K, and Af = 347 K and the coefficient of the dependence of the transition temperature on mechanical stress being β = 0.12 K/MPa. The experimentally measured value of the adiabatic temperature change under the action of mechanical stress (ECE) in the amorphous state of the alloy at room temperature (Tr = 300 K) was ΔT = −2 K, with a relative elongation of ε = 1.5% and a mechanical stress of σ = 243 MPa. For crystalline samples of Ti2NiCu alloy ribbons, the ECE is maximum near the completion temperature of the reverse thermoelastic martensitic transformation Af, and its value was 21 K and 7 K under cyclic mechanical loads of 300 and 100 MPa, respectively. It is shown that the ECE value does not depend on the frequency of external action in the range from 0 to 50 Hz. The specific power of the rapidly quenched ribbon was evaluated as a converter of thermal energy at an external mechanical stress of 100 MPa; its value was 175 W/g at a frequency of 50 Hz. The thermodynamic model based on the Landau theory of phase transitions well explains the properties of both amorphous ribbons (reverse ECE) and alloy ribbons with EPF (direct ECE).

scholarly journals Radiation Resistance of a Structural Material Based on Modified Titanium Hydride

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
R. N. Yastrebinsky ◽  
V. I. Pavlenko ◽  
A. A. Karnauhov ◽  
N. I. Cherkashina ◽  
A. V. Yastrebinskaya ◽  
...  
Keyword(s):  
Structural Material ◽  
Portland Cement ◽  
Radiation Resistance ◽  
Titanium Hydride ◽  
Structural Phase ◽  
Absorbed Dose ◽  
Phase Changes ◽  
Cement Matrix ◽  
Γ Irradiation ◽  
Γ Radiation

This work investigates the radiation resistance of a structural material based on modified titanium hydride and a Portland cement in a flux of neutron and γ-radiation. An assessment of the geometric and physicomechanical properties is given, along with the surface structure of irradiated cement composites, and the phase composition of the main hydrosilicates of the hydrated cement matrix during its γ-irradiation. It is shown that the use of a shot of titanium hydride increases the radiation resistance of radiation shielding based on a cement matrix, in comparison with the unmodified shot. A composite based on a modified shot of titanium hydride retains its basic properties after γ-irradiation, at an absorbed dose of up to 10 MGy. At an absorbed dose of 2 MGy in the Portland cement matrix of a composite based on a modified shot of titanium hydride, the formation of suolunite hydrosilicates occurs. It was established using X-ray fluorescence that, in the titanium hydride, a redistribution of the electron density occurs at an absorbed dose of γ radiation of 5 MGy, caused by structural phase changes due to the ongoing dehydrogenation processes.

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