Steady State Conduction Behaviour of Liquid Crystalline Polyurethane

2013 ◽  
Vol 856 ◽  
pp. 210-214
Author(s):  
Jitender Kumar Quamara ◽  
Satish Kumar Mahna ◽  
Sohan Lal ◽  
Pushkar Raj
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Temperature Region ◽  
Liquid Crystalline ◽  
Ionic Conduction ◽  
Schottky Type ◽  
Order Of Magnitude ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Type Conduction

The steady state measurements in Liquid crystalline polyurethane (LCPU) have been investigated for different fields (4 - 45 kV/cm) and temperatures (50°-220°C). The nature of conduction processes has been determined by estimating ion jump distances (a) and Schottky coefficients. The order of magnitude of a in the temperature region 150°C and below does not seem to support an ionic conduction. However the magnitude of a at higher temperatures (180°C and above) indicates the possibility of ionic conduction. There is a definite possibility of a Schottky type conduction at lower temperature and a Poole Frankel type conduction at higher temperature (100°C). The activation energy associated with the high temperature region lies between 0.26 eV and 0.65 eV depending on the field whereas in the low temperature region the activation energy lies between 0.82 eV and 0.95 eV depending on the applied electric field. The dual slopes in the log I versus 1/T curves indicate the presence of more than one type of trapping levels.

EFFECTS OF COPPER DOPING ON DIELECTRIC AND A.C. CONDUCTIVITY IN LAYERED SODIUM TRI-TITANATE CERAMIC

2013 ◽  
Vol 27 (22) ◽  
pp. 1350114 ◽  
Author(s):  
SHRIPAL ◽  
SHAILJA DWIVEDI ◽  
RAKESH SINGH ◽  
R. P. TANDON
Keyword(s):  
Ionic Conduction ◽  
Relaxation Times ◽  
Paramagnetic Resonance ◽  
Temperature Range ◽  
Higher Temperature ◽  
Polaron Conduction ◽  
Tan Δ ◽  
Lower Temperature ◽  
Electron Paramagnetic ◽  
Derivatives Of

Electron paramagnetic resonance (EPR) spectra of 0.01, 0.1 and 1.0 molar percentage (mp) of CuO doped derivatives of layered Na 2 Ti 3 O 7 ceramic have been reported. The results show that copper substitutes as Cu 2+ at Ti 4+ octahedral sites. From the dependence of loss tangent ( tan δ) and the relative permittivity (ε′) on temperature and frequency, it is concluded that all the derivatives are of polar nature. The relaxation peaks at lower temperatures have been attributed to the presence of different types of dipoles, whereas peaks in the higher temperature region indicate possible ferroelectric phase transition. The dependence of conductivity on temperature show that electron hopping (polaron) conduction exists in a wide span of temperature range. However, the associated interlayer ionic conduction exists in a small temperature range. Interlayer alkali ion hopping mechanism of conduction has been proposed toward higher temperatures. The conductivity versus frequency plots reveal that the polaron conduction plays a prominent role toward the lower temperature side that diminishes with the rise in temperature. The most probable relaxation times for 0.01 and 0.1 mp CuO doped derivatives are almost same but it records an increased value for 1.0 mp doped material. This again attributes to the possible change in the symmetry of copper environment.

scholarly journals Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Solid Earth ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. 233-245 ◽  
Author(s):  
Lidong Dai ◽  
Wenqing Sun ◽  
Heping Li ◽  
Haiying Hu ◽  
Lei Wu ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Temperature Region ◽  
Ionic Conduction ◽  
Complex Impedance ◽  
Weight Percent ◽  
Spectroscopic Technique ◽  
Ultrahigh Pressure ◽  
Chemical Compositions ◽  
Metamorphic Belt ◽  
Lower Temperature

Abstract. The electrical conductivity of gneiss samples with different chemical compositions (WA = Na2O + K2O + CaO  =  7.12, 7.27 and 7.64 % weight percent) was measured using a complex impedance spectroscopic technique at 623–1073 K and 1.5 GPa and a frequency range of 10−1 to 106 Hz. Simultaneously, a pressure effect on the electrical conductivity was also determined for the WA = 7.12 % gneiss. The results indicated that the gneiss conductivities markedly increase with total alkali and calcium ion content. The sample conductivity and temperature conform to an Arrhenius relationship within a certain temperature range. The influence of pressure on gneiss conductivity is weaker than temperature, although conductivity still increases with pressure. According to various ranges of activation enthalpy (0.35–0.52 and 0.76–0.87 eV) at 1.5 GPa, two main conduction mechanisms are suggested that dominate the electrical conductivity of gneiss: impurity conduction in the lower-temperature region and ionic conduction (charge carriers are K+, Na+ and Ca2+) in the higher-temperature region. The electrical conductivity of gneiss with various chemical compositions cannot be used to interpret the high conductivity anomalies in the Dabie–Sulu ultrahigh-pressure metamorphic belt. However, the conductivity–depth profiles for gneiss may provide an important constraint on the interpretation of field magnetotelluric conductivity results in the regional metamorphic belt.

Computer Simulation of Annealing after Cluster Ion Implantation

1998 ◽  
Vol 532 ◽  
Author(s):  
Z. Insepov ◽  
T. Aoki ◽  
J. Matsuo ◽  
I. Yamada
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Computer Simulation ◽  
Ion Implantation ◽  
Temperature Region ◽  
Diffusion Coefficients ◽  
Metropolis Monte Carlo ◽  
Cluster Ion ◽  
Higher Temperature ◽  
Substrate Temperatures

ABSTRACTMolecular Dynamics (MD) and Metropolis Monte-Carlo (MMC) models of monomer B and decaborane implantation into Si and following rapid thermal annealing (RTA) processes have been developed in this paper. The implanted B dopant diffusion coefficients were obtained for different substrate temperatures. The simulation of decaborane ion implantation has revealed the formation of an amorphized area in a subsurface region, much larger than that of a single B+ implantation, with the same energy per ion. The B diffusion coefficient shows an unusual temperature dependence with two different activation energies. Low activation energy, less than 0.2, was obtained for a low-temperature region, and a higher activation energy, ˜ 3 ev, for a higher-temperature region which is typical for the RTA processing. The higher activation energy is comparable with the equilibrium activation energy, 3.4 ev, for B diffusion in Si.

Effects of Microstructure on the Electrical Conductivity of SrCo0.8Fe0. 2O3_δ

1999 ◽  
Vol 575 ◽  
Author(s):  
K. Zhang ◽  
M. Miranova ◽  
Y. L. Yang ◽  
A. J. Jacobson ◽  
K. Salama
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Size Effect ◽  
Temperature Region ◽  
Grain Size Effect ◽  
Average Grain Size ◽  
Lower Temperature ◽  
Lower Temperature Region ◽  
Test Temperature Range

ABSTRACTThe effect of microstructure on the electrical conductivity of SrCO0.8Fe0.2O3_δ (SCFO) was investigated in air using a four-point dc method. In the test temperature range of 200 to 900 °C, the electrical conductivity of this material was observed to increase with the increase of the average grain size in the lower temperature region where the conductivity increases with the increase of the temperature. The activation energy is decreased with the increase of the grain size in this region, 0.04 ± 0.004 ev for 4.1μm sample and 0.01 ± 0.001 ev for 14.8 μm sample. When temperature is further increased, the conductivity of this material decreases with the increase of the temperature, and the grain size effect becomes less noticeable.

On the Sintering Activation Energy of α-Al2O3

2008 ◽  
Vol 368-372 ◽  
pp. 686-687 ◽  
Author(s):  
Wei Quan Shao ◽  
Shaou Chen ◽  
Da Li ◽  
Ping Qi ◽  
Yong Wan ◽  
...  
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Temperature Interval ◽  
High Purity ◽  
Powder Compact ◽  
Isothermal Condition ◽  
Particle Sizes ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Increasing Temperature

The sintering activation energy of high-purity alumina powders with different particle sizes was evaluated under non-isothermal condition. It was found that, during sintering, the activation energy for the lower temperature stage is higher than that for higher temperature stage. The value of the activation energies for the powder compact with larger particle size was higher than that for the powder compact with smaller particle size. If the selected temperature interval for calculation was narrow enough, the evaluated activation energy values varied with the increasing temperature continuously.

Synthesis of ZnO Nanostructures by Thermal Evaporation on Graphite

2007 ◽  
Vol 124-126 ◽  
pp. 575-578
Author(s):  
Kon Bae Lee ◽  
Ki Seop Cho ◽  
Won Hee Lee ◽  
Hoon Kwon
Keyword(s):  
Temperature Region ◽  
Thermal Evaporation ◽  
Metal Catalyst ◽  
Zno Nanostructures ◽  
Zno Nanowire ◽  
Zno Particles ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Zno Powder ◽  
Lower Temperature Region

ZnO nanostructures have been synthesized on graphite substrates by thermal evaporation of ZnO powder without a metal catalyst at a temperature of 1300. The colors of the as-synthesized products gradually change from white and brown to gray as the distance from the source material increases. ZnO particles were formed at higher temperature region. ZnO particles gradually changed into ZnO nanowire as the temperature decreased. Finally, ZnO nanowires disappeared completely and only Zn particles were observed at lower temperature region.

scholarly journals The FA Polymerization Disruption by Protic Polar Solvent

2018 ◽  
Author(s):  
Guillaume Falco ◽  
Nathanael Guigo ◽  
Luc Vincent ◽  
Nicolas Sbirrazzuoli
Keyword(s):  
Activation Energy ◽  
Isopropyl Alcohol ◽  
Polar Solvent ◽  
Water System ◽  
Polar Solvents ◽  
Continuous Increase ◽  
Exponential Factor ◽  
Rubbery State ◽  
Higher Temperature ◽  
Lower Temperature

Furfuryl alcohol (FA) is a biobased monomer derived from lignocellulosic biomass. The present work describes its polymerization in presence of protic polar solvents, i.e. water or isopropyl alcohol (IPA), using maleic anhydride (MA) as acidic initiator. The polymerization was followed from the liquid to the rubbery state by combining DSC and DMA data. In the liquid state, IPA disrupts the expected reactions during all the FA polymerization due to a stabilization of the furfuryl carbenium center. This causes the initiation of the polymerization at higher temperature, which is also reflected by higher activation energy. In water system, the MA opening allows to start the reaction at lower temperature. A higher pre-exponential factor value is obtained in that case. The DMA study of final branching reaction occurring in the rubbery state has highlighted continuous increase of elastic modulus until 290 °C. This increasing tendency of modulus was exploited to obtain activation energy dependences (Eα) of FA polymerization in the rubbery state.

scholarly journals Electrical Conduction in Some Nickelates

2011 ◽  
Vol 8 (1) ◽  
pp. 83-90
Author(s):  
Kanchan Gaur ◽  
Shalini Shalini ◽  
Satyendra Singh
Keyword(s):  
Temperature Region ◽  
Conduction Mechanism ◽  
Charge Carriers ◽  
Band Model ◽  
Orthorhombic Unit Cell ◽  
Dominant Conduction Mechanism ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Lower Temperature Region ◽  
Band Type

This paper reports electrical conductivity (s) and Seebeck coefficient (s) study on rare-earth nickelates RNiO3 where R = Nd, Sm and Eu in the temperature range 400-1200 K. They have orthorhombic unit cell. The majority charge carriers are holes throughout the measurement. Both s and S variations show three regions. In higher temperature region (Above 1000K) dominant conduction mechanism is intrisic band type whereas below this temperature, hopping of holes from Ni3+ to Ni2+ centres takes place. In lower temperature region, the electrical conductions is taken over by acceptor type impurities. The conduction mechanism is explained on the basis of every band model. Break temperatures as well as mobility have also been evaluated.

Two Phases of Ageing in Drosophila Subobscura

1961 ◽  
Vol 38 (3) ◽  
pp. 679-684
Author(s):  
JEAN M. CLARKE ◽  
J. MAYNARD SMITH
Keyword(s):  
Steady State ◽  
Life Span ◽  
Low Temperatures ◽  
Initial Value ◽  
Male And Female ◽  
Higher Temperature ◽  
Two Phases ◽  
Lower Temperature ◽  
The Individual

1. Male and female D. subobscura were kept for varying periods at low temperatures 3-20° C.) and then transferred to a higher temperature (26-30° C.) and kept there until they died. 2. It was found that during the early part of the life span, over the range 15-30° C., every day spent at a low temperature reduced the expectation of life at a higher temperature by approximately 1 day. Later, when the expectation of life at the higher temperature had fallen to about half its initial value, little further change in this expectation occurred with increasing age at a lower temperature. 3. It is concluded that the life span can be divided into two phases, (i) an irreversible ‘ageing’ process whose rate is approximately independent of temperature from 15 to 30° C., but which is slower at 3° C., and (ii) a ‘dying’ process which is initiated when ageing has proceeded to a stage at which the individual is no longer capable of maintaining a steady state at the temperature at which it is living, although the same individual would be capable of maintaining a steady state at some lower temperature. 4. The rate of the dying process is highly dependent on temperature, and it can be reversed in flies transferred to lower temperatures.

Isothermal oxidation kinetics and oxidation behavior of nickel slag

2020 ◽  
Vol 117 (6) ◽  
pp. 603
Author(s):  
Xiaoming Li ◽  
Xinyi Zhang ◽  
Yi Li ◽  
Xiangdong Xing
Keyword(s):  
Activation Energy ◽  
Oxidation Behavior ◽  
Model Fitting ◽  
Three Dimensional ◽  
Oxidation Kinetic ◽  
Isothermal Oxidation ◽  
Model Free ◽  
Random Nucleation ◽  
Higher Temperature ◽  
Lower Temperature

To improve the reduction effect of nickel slag in preparing Fe–Co–Ni–Cu alloy, an oxidization pretreatment was carried out to changing the structure and phase of silicate and sulfide for the nickel slag before the reducing process. The oxidation behavior and kinetics of nickel slag under different temperature and time conditions were discussed. The results shown that in the oxidation process of nickel slag, the part of Fe2SiO4 was oxidized to Fe3O4 and further to Fe2O3, and the other part of Fe2SiO4 directly oxidized to Fe2O3. Meanwhile, the nickel, cobalt and copper in the form of silicate and sulfide were changed into oxides. The changes of the phases are beneficial to the subsequent reduction of nickel slag. The oxidation degree of nickel slag reached 98% under suitable oxidation conditions (900 °C, 15 min). The oxidation kinetic model of nickel slag obtained by Ln–Ln analysis and Model-fitting method was three-dimensional diffusion at lower temperature (300 °C, 400 °C and 500 °C) and random nucleation at higher temperature (700 °C, 900 °C and 1000 °C) respectively. The activation energies obtained by the model method and the model-free method were 28.58 kJ.mol−1 and 26.28 kJ.mol−1 at lower temperature (300 °C, 400 °C and 500 °C) respectively, and the corresponding value were 81.98 kJ.mol−1 and 78.36 kJ.mol−1 at higher temperature (700 °C, 900 °C and 1000 °C) respectively. The activation energy calculated by the two methods was relatively close, and both can be used to calculate the activation energy.

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