scholarly journals Effect of glass composition on activation energy of viscosity in glass-melting-temperature range

2012 ◽  
Vol 358 (15) ◽  
pp. 1818-1829 ◽  
Author(s):  
Pavel Hrma ◽  
Sang-Soo Han
Keyword(s):  
Activation Energy ◽  
Melting Temperature ◽  
Glass Composition ◽  
Glass Melting ◽  
Temperature Range

scholarly journals The low-frequency conductivity of snow near the melting temperature

2001 ◽  
Vol 32 ◽  
pp. 14-18 ◽  
Author(s):  
Iwao Takei ◽  
Norikazu Maeno
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Melting Temperature ◽  
Low Frequency ◽  
Dielectric Dispersion ◽  
Average Particle ◽  
Temperature Range ◽  
Ice Surfaces ◽  
Increasing Temperature ◽  
Snow Samples

AbstractDielectric measurements of snow were carried out in the temperature range –15° to 0°C and in the frequency range 50 Hz to 5 MHz. The snow samples (about 400 kg m–3 density) used were stored snow (average particle size: 2 mm) and hoar-frost (particle size: <1 to 5 mm). The frequency characteristics of dielectric parameters showed a dielectric dispersion (Davidson-Cole type) around 30 kHz and a low-frequency dielectric dispersion (Cole-Cole circular law type). The a.c. conductivity showed a dielectric dispersion around 30 kHz and two characteristic constant values in the frequency ranges above 1 MHz and below 100 Hz (the high-frequency conductivity σ∞ and the low-frequency conductivity σLOW). The low-frequency conductivity σLOW showed a peak at about –2°C. This behavior has never been noted by previous researchers. The σLOW showed an activation energy of about 1 eV below –5°C. This means that the σLOW is mainly caused by a surface conduction. The activation energy increased with increasing temperature above –5°C. This means that the σLOW in this temperature range is affected by the quasi-liquid layer on ice surfaces. The σLOW above –2°C decreased with increasing temperature. The apparently curious behavior near the melting temperature is attributed to the numerous free ice surfaces within the porous snow. This conclusion was reached because our measurements without the free ice surfaces showed no such conductivity peaks for solid polycrystalline ice samples and for snow samples soaked with kerosene in the cooling process.

Viscosity Measurements for La-Al-Ni liquid Alloys by an Oscillating Crucible Method

1998 ◽  
Vol 554 ◽  
Author(s):  
Tohru Yamasaki ◽  
Tomohiro Tatibana ◽  
Yoshikiyo Ogino ◽  
Akihisa Inoue
Keyword(s):  
Activation Energy ◽  
Viscous Flow ◽  
Melting Temperature ◽  
Glass Forming Ability ◽  
Liquid Alloys ◽  
Temperature Range ◽  
Glass Forming ◽  
Ni Alloys ◽  
Ni Content ◽  
Ni Alloy

AbstractThe viscosity of liquid lanthanum-based and aluminum-based La-Al-Ni alloys has been measured by an oscillating crucible method of the inverse suspending type in the temperature range from melting temperature (Tm) up to about 1400 K. In the case of La55Al45-xNix (x = 10∼40 at. %) alloys, the viscosity increased with increasing Ni content up to about 20 at. % Ni and then decreased with increasing the Ni content, while the activation energy for viscous flow decreased to a minimum value at about 20 at. % Ni. This composition is well consistent with that of the La-Al-Ni alloy having largest glass-forming ability.

scholarly journals High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 581
Author(s):  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Threshold Stress ◽  
Activation Energies ◽  
Temperature Deformation ◽  
High Temperature Range ◽  
Temperature Range ◽  
True Activation Energy ◽  
Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

About the Electrical Activation of 1×1020 cm-3 Ion Implanted Al in 4H-SiC at Annealing Temperatures in the Range 1500 - 1950°C

2018 ◽  
Vol 924 ◽  
pp. 333-338 ◽  
Author(s):  
Roberta Nipoti ◽  
Alberto Carnera ◽  
Giovanni Alfieri ◽  
Lukas Kranz
Keyword(s):  
Activation Energy ◽  
Sheet Resistance ◽  
Annealing Time ◽  
Thermal Activation ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Thermal Activation Energy ◽  
Electrical Activation ◽  
Temperature Range ◽  
Annealing Temperatures

The electrical activation of 1×1020cm-3implanted Al in 4H-SiC has been studied in the temperature range 1500 - 1950 °C by the analysis of the sheet resistance of the Al implanted layers, as measured at room temperature. The minimum annealing time for reaching stationary electrical at fixed annealing temperature has been found. The samples with stationary electrical activation have been used to estimate the thermal activation energy for the electrical activation of the implanted Al.

scholarly journals SYNTHESIS AND ELECTRICAL CONDUCTIVITY OF SOLID SOLUTIONS OF THE SYSTEM RbF-PbF2-SnF2

2019 ◽  
Vol 85 (5) ◽  
pp. 60-68
Author(s):  
Yuliay Pogorenko ◽  
Anatoliy Omel’chuk ◽  
Roman Pshenichny ◽  
Anton Nagornyi
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Solid Solutions ◽  
Basic Structure ◽  
Elementary Cell ◽  
Initial Structure ◽  
Fluoride Ions ◽  
Temperature Range ◽  
Order Of Magnitude

In the system RbF–PbF2–SnF2 are formed solid solutions of the heterovalent substitution RbxPb0,86‑xSn1,14F4-x (0 < x ≤ 0,2) with structure of β–PbSnF4. At x > 0,2 on the X-ray diffractograms, in addition to the basic structure, additional peaks are recorded that do not correspond to the reflexes of the individual fluorides and can indicate the formation of a mixture of solid solutions of different composition. For single-phase solid solutions, the calculated parameters of the crystal lattice are satisfactorily described by the Vegard rule. The introduction of ions of Rb+ into the initial structure leads to an increase in the parameter a of the elementary cell from 5.967 for x = 0 to 5.970 for x = 0.20. The replacement of a part of leads ions to rubium ions an increase in electrical conductivity compared with β–PbSnF4 and Pb0.86Sn1.14F4. Insignificant substitution (up to 3.0 mol%) of ions Pb2+ at Rb+ at T<500 K per order of magnitude reduces the conductivity of the samples obtained, while the nature of its temperature dependence is similar to the temperature dependence of the conductivity of the sample β-PbSnF4. By replacing 5 mol. % of ions with Pb2+ on Rb+, the fluoride ion conductivity at T> 450 K is higher than the conductivity of the initial sample Pb0,86Sn1,14F4 and at temperatures below 450 K by an order of magnitude smaller. With further increase in the content of RbF the electrical conductivity of the samples increases throughout the temperature range, reaching the maximum values at x≥0.15 (σ573 = 0.34–0.41 S/cm, Ea = 0.16 eV and σ373 = (5.34–8.16)•10-2 S/cm, Ea = 0.48–0.51 eV, respectively). In the general case, the replacement of a part of the ions of Pb2+ with Rb+ to an increase in the electrical conductivity of the samples throughout the temperature range. The activation energy of conductivity with an increase in the content of RbF in the low-temperature region in the general case increases, and at temperatures above 400 K is inversely proportional decreasing. The nature of the dependence of the activation energy on the concentration of the heterovalent substituent and its value indicate that the conductivity of the samples obtained increases with an increase in the vacancies of fluoride ions in the structure of the solid solutions.

scholarly journals Determination of the Activation Energy of Polar Firn by D.C. Resistivity Measurements

1967 ◽  
Vol 6 (48) ◽  
pp. 911-915 ◽  
Author(s):  
M. P. Hochstein ◽  
G. F. Risk
Keyword(s):  
Activation Energy ◽  
Resistivity Measurements ◽  
Temperature Range

The activation energy ϵe1 of polar firn samples determined by D.C. resistivity measurements is a function of temperature and density. In the temperature range −2° C. to −10° C. ϵe1 decreases with decreasing temperature reaching a nearly constant value for temperatures colder than −10°C.; in the temperature range −10°C. to −21°C. ϵe1 was found to decrease with increasing density and to lie between 0.7 eV. and 0.4 eV.

Correlation between Activation Energy and Melting Temperature of Solids

1996 ◽  
Vol 223-224 ◽  
pp. 199-204
Author(s):  
P. Kuchhal ◽  
R.J. Kumar ◽  
N. Dass
Keyword(s):  
Activation Energy ◽  
Melting Temperature

Te Induced AlAs/GaAs Superlattice Mixing

1988 ◽  
Vol 126 ◽  
Author(s):  
P. Mel ◽  
S. A. Schwarz ◽  
T. Venkatesan ◽  
C. L. Schwartz ◽  
E. Colas
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Diffusion Coefficient ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Secondary Ion Mass Spectrometry ◽  
Chemical Vapor ◽  
Temperature Range ◽  
The Relationship ◽  
Secondary Ion

ABSTRACTTe enhanced mixing of AlAs/GaAs superlattice has been observed by secondary ion mass spectrometry. The superlattice sample was grown by organometallic chemical vapor deposition and doped with Te at concentrations of 2×1017 to 5×1018 cm−.3 In the temperature range from 700 to 1000 C, a single activation energy for the Al diffusion of 2.9 eV was observed. Furthermore, it has been found that the relationship between the Al diffusion coefficient and Te concentration is linear. Comparisons have been made between Si and Te induced superlattice mixing.

Study on the Crystallization Activation Energy of Poly (L-lactic acid) Nucleated with P-tert-butylcalix[8]arene

2018 ◽  
Vol 26 (2) ◽  
pp. 169-175
Author(s):  
Yaoqi Shi ◽  
Liang Wen ◽  
Zhong Xin
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crystallization Temperature ◽  
Nucleating Agent ◽  
Crystallization Activation Energy ◽  
Temperature Range ◽  
Chain Mobility

The crystallization activation energy (Δ E) of a polymer comprises the nucleation activation energy Δ F and the transport activation energy Δ E*. In this paper, the Δ E of poly (L-lactic acid) (PLLA) nucleated with nucleating agent p- tert-butylcalix[8]arene (tBC8) was calculated. The results showed that the Δ E of nucleated PLLA was 165.97 kJ/mol, which is higher than that of pure PLLA. The reason why Δ E of PLLA increased when incorporating nucleating agent was studied. The increment of glass transition temperature ( Tg) for nucleated PLLA revealed that the polymer chain mobility was restricted by tBC8, which was considered as the reason for the increase of Δ E*. Further, polyethylene glycol (PEG) was added to improve the chain mobility, thus eliminated the variation of the transport activation energy Δ E* caused by tBC8. Then the effect of the increment of crystallization temperature range on the increase of Δ F was also taken into consideration. It was concluded that both decreasing the mobility of chain segments and increasing the crystallization temperature range caused an increase of Δ E for PLLA/tBC8.

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