The Meyer–Neldel Rule in Conduction Mechanism of the Electrospun ZnO Nanofibers

NANO ◽  
2016 ◽  
Vol 11 (03) ◽  
pp. 1650025 ◽  
Author(s):  
Andrzej Stafiniak ◽  
Marek Tłaczała
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Conduction Mechanism ◽  
Deep Level ◽  
Electrical Measurements ◽  
Thermally Activated ◽  
Theoretical Assumptions ◽  
Different Temperatures ◽  
Zno Nanofibers ◽  
Improved Model

An analytical model describing the conductivity of ZnO nanofibers depending on the grains size is proposed. The research is based on the thermal dc electrical measurements of a single electrospun ZnO nanofiber calcined at different temperatures. In the our previous research, we showed that electrical conduction of ZnO nanofibers is mainly thermally activated. The activation energy of conductivity was strongly dependent on the grain size, which in turn depended on the calcination temperature. This could be due to migration of a point defect in the grain of ZnO and could change the carrier concentration. Our recent studies have shown that ZnO nanofibers behavior is consistent with the Meyer–Neldel rule. This indicates an exponential energy distribution of deep level traps in the material. Based on the theoretical assumptions and experimental data, the improved model of conductivity in a single ZnO nanofiber calcined at different temperatures was proposed.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

scholarly journals Drying kinetics of baru flours as function of temperature

2018 ◽  
Vol 22 (10) ◽  
pp. 713-719 ◽  
Author(s):  
Douglas R. Reis ◽  
Fabrício B. Brum ◽  
Eduardo J. O. Soares ◽  
Jessiana R. Magalhães ◽  
Fabrício S. Silva ◽  
...  
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Food Industry ◽  
Nutritional Value ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Statistical Parameters ◽  
Noticeable Effect ◽  
Different Temperatures ◽  
Kinetics Of

ABSTRACT Several types of seeds have been initially used in the food industry due to the great potential that vegetable proteins have. Baru is a fruit commonly found in the Cerrado biome, having a high nutritional value. This paper aimed to determine and analyze the drying kinetics of whole and defatted baru almond flours at different temperatures. The flour resulting from almond milling was defatted using petroleum ether. The drying processes were performed at temperatures of 40, 50 and 60 ºC. The mathematical models of Page, Henderson and Pabis, Midilli & Kucuk, Thompson and Approximation of Diffusion were fitted to the experimental data. The results showed a noticeable effect of air temperature on the drying kinetics of whole and defatted baru almond flours. According to the statistical parameters of analysis, the models Midilli & Kucuk and Page were the ones with the best fits to the experimental data. The effective diffusivity values found ranged from 8.02 × 10–10 to 19.90 × 10–10 m2 s-1 and for the activation energy were 22.39 and 39.37 KJ mol-1 for whole and defatted almonds, respectively.

Mössbauer effect study on the mixed valence state of iron in tourmaline

1988 ◽  
Vol 52 (365) ◽  
pp. 221-228 ◽  
Author(s):  
E. A. Ferrow ◽  
H. Annersten ◽  
R. P. Gunawardane
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Valence State ◽  
Mixed Valence ◽  
Effect Study ◽  
High Activation ◽  
Charge Delocalization ◽  
Thermally Activated ◽  
Different Temperatures ◽  
Iron Bearing

AbstractMössbauer spectra of iron-bearing tourmaline, obtained at different temperatures, show the existence of thermally-activated charge delocalization among clusters of iron atoms situated in the Y and Z octahedra of the tourmaline structure. The temperature dependence indicates an unusually high activation energy for the delocalization process which suggests that the process takes place between crystallographically non-equivalent sites. Annealing of the tourmaline in hydrogen is observed to inhibit the delocalization process, thus localizing the electron into the Z-site.

Impact of Electric Field on Thermoemission of Carriers from Shallow Dislocation-Related Electronic States

2013 ◽  
Vol 205-206 ◽  
pp. 299-304 ◽  
Author(s):  
M. Trushin ◽  
Oleg F. Vyvenko
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Electric Field ◽  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Dislocation Line ◽  
Electronic States ◽  
Energy Reduction ◽  
Transient Spectroscopy ◽  
Internal Charge

Shallow dislocation-related electronic states near the bottom of the conduction band in n-type Si bonded sample have been investigated with deep-level transient spectroscopy (DLTS), isothermal transient spectroscopy (ITS) and energy-resolved DLTS. The effect of thermoemission (TE) enhancement in external electric field was found and the dependence of the TE activation energy reduction as a function of the filling grade was obtained for these states. A new model of dislocation-strain-related Poole-Frenkel effect that accounts for the own electric field of internal charge of dislocation line is suggested and compared with the experimental data.

scholarly journals Ultrasonic relaxation of some CdO boro-tellurate glasses

2016 ◽  
Vol 94 (10) ◽  
pp. 1008-1016 ◽  
Author(s):  
M.S. Gaafar ◽  
I.S. Mahmoud
Keyword(s):  
Activation Energy ◽  
Relaxation Process ◽  
Ultrasonic Attenuation ◽  
Operating Frequency ◽  
Thermally Activated ◽  
Different Temperatures ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Double Well Potential ◽  
Solid Type

50B2O3–(50-x)TeO2–xCdO glass system, with x = 0, 10, 20, 30, 40, and 50 mol% have been prepared, to measure the longitudinal ultrasonic attenuation at frequencies of 2, 4, 6, and 14 MHz in the temperature range from 120 to 300 K. Well-defined broad peaks of the absorption curves were observed at different temperatures depending on the glass composition and the operating frequency. The maximum peaks shifted to higher temperatures with the increase of the operating frequency implying the presence of some kind of relaxation process. This process is suggested as due to the thermally activated relaxation process. The variation of the average activation energy of the process mainly depends on the CdO mol% content. Such dependence was analyzed in terms of the loss of standard linear solid type, with low dispersion and a broad distribution of Arrhenius type relaxation with temperature independent relaxation strength. The obtained acoustic activation energy values were quantitatively interpreted in terms of the number of loss centers (number of oxygen atoms that vibrate in the double well potential).

scholarly journals Radiation-produced defects in germanium: experimental data and models of defects

2017 ◽  
Vol 51 (12) ◽  
pp. 1632
Author(s):  
V.V. Emtsev ◽  
D.S. Poloskin ◽  
G.A. Oganesyan ◽  
V.V. Kozlovski
Keyword(s):  
Experimental Data ◽  
Defect Formation ◽  
Deep Level ◽  
Minor Role ◽  
Radiation Defects ◽  
Electrical Measurements ◽  
Group V ◽  
Before And After ◽  
Transient Spectroscopy ◽  
A Minor

The problem of radiation-produced defects in n-Ge before and after n-> p conversion is discussed in the light of electrical data obtained by means of Hall effect measurements as well as Deep Level Transient Spectroscopy. The picture of the dominant radiation defects in irradiated n-Ge before n-> p conversion appears to be complicated, since they turn out to be neutral in n-type material and unobserved in the electrical measurements. It is argued that radiation-produced acceptors at ~ EC-0.2 eV previously ascribed to vacancy-donor pairs (E-centers) play a minor role in the defect formation processes under irradiation. Acceptor defects at ~ EV+0.1 eV are absolutely dominating in irradiated n-Ge after n-> p conversion. All the radiation defects under consideration were found to be dependent on the chemical group-V impurities. Together with this, they are concluded to be vacancy-related, as evidenced positron annihilation experiments. A detailed consideration of experimental data on irradiated n-Ge shows that the present model of radiation-produced defects adopted in literature should be reconsidered. DOI: 10.21883/FTP.2017.12.45178.8599

Determination of the Electrical Capture Process of the EH6-Center in n-Type 4H-SiC

2013 ◽  
Vol 740-742 ◽  
pp. 377-380 ◽  
Author(s):  
Jonas Weber ◽  
Svetlana Beljakowa ◽  
Heiko B. Weber ◽  
Gerhard Pensl ◽  
Bernd Zippelius ◽  
...  
Keyword(s):  
Cross Section ◽  
Deep Level Transient Spectroscopy ◽  
Capture Cross Section ◽  
Deep Level ◽  
Schottky Contacts ◽  
Capture Process ◽  
Thermally Activated ◽  
Different Temperatures ◽  
Transient Spectroscopy

Deep Level Transient Spectroscopy (DLTS) investigations at different temperatures and with various filling pulse lengths were performed on n-type 4H-SiC epitaxial layers using Iridium Schottky contacts to determine the electrical capture process of the EH6-center. The temperature dependence of the electrical capture cross section σ ~ T-2.0 suggests a cascade capture process, which is not thermally activated. Together with earlier work by Zippelius et al. [4] this proves the acceptor-type of the EH6-center.

Note: Color development rate in dulce de leche

1995 ◽  
Vol 1 (2-3) ◽  
pp. 137-140 ◽  
Author(s):  
M.S. Pauletti ◽  
E. Castelao ◽  
N. Sabbag ◽  
Y S. Costa
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Formation Process ◽  
Arrhenius Equation ◽  
Development Rate ◽  
Sensorial Analysis ◽  
Color Formation ◽  
Color Development ◽  
Global Rate ◽  
Different Temperatures

The time necessary to obtain the characteristic dulce de leche color at different temperatures was studied. Samples were held at constant temperature until they reached a standard prescribed color. Sensorial analysis of the final color of the samples was performed in order to detect any difference. Results showed that color among samples was not significantly different (p = 0.95). Arrhenius equation was used to correlate the kinetics results. Variance analysis showed a very good correlation of experimental data (r2 = 0.98). The apparent activation energy values for both studied systems were similar (13.88–14.45 kcal mol–1) but somewhat smaller than those given by other authors for similar systems. The global rate constant value of color formation process at any temperature was slightly larger when the protein/carbohydrate ratio was higher.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Development of High Permeability Core Materials for Embeddable Inductors in Flexible Organic Substrates

2003 ◽  
Vol 769 ◽  
Author(s):  
C. K. Liu ◽  
P. L. Cheng ◽  
S. Y. Y. Leung ◽  
T. W. Law ◽  
D. C. C. Lam
Keyword(s):  
Low Temperature ◽  
Sol Gel ◽  
Circuit Board ◽  
Organic Substrates ◽  
Circuit Boards ◽  
High Permeability ◽  
Electrical Measurements ◽  
Different Temperatures ◽  
Spiral Inductors ◽  
Ceramic Tape

AbstractCapacitors, resistors and inductors are surface mounted components on circuit boards, which occupy up to 70% of the circuit board area. For selected applications, these passives are packaged inside green ceramic tape substrates and sintered at temperatures over 700°C in a co-fired process. These high temperature processes are incompatible with organic substrates, and low temperature processes are needed if passives are to be embedded into organic substrates. A new high permeability dual-phase Nickel Zinc Ferrite (DP NZF) core fabricated using a low temperature sol-gel route was developed for use in embedded inductors in organic substrates. Crystalline NZF powder was added to the sol-gel precursor of NZF. The solution was deposited onto the substrates as thin films and heat-treated at different temperatures. The changes in the microstructures were characterized using XRD and SEM. Results showed that addition of NZF powder induced low temperature transformation of the sol-gel NZF phase to high permeability phase at 250°C, which is approximately 350°C lower than transformation temperature for pure NZF sol gel films. Electrical measurements of DP NZF cored two-layered spiral inductors indicated that the inductance increased by three times compared to inductors without the DP NZF cores. From microstructural observations, the increase is correlated with the changes in microstructural connectivity of the powder phase.

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