scholarly journals The Creep Activation Energies of Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 429-444 ◽  
Author(s):  
D. R. Homer ◽  
J. W. Glen
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Creep Deformation ◽  
Tensile Axis ◽  
Strain Rates ◽  
Boundary Slip ◽  
Creep Tests ◽  
Creep Activation Energy ◽  
Single Grain ◽  
Image Position

AbstractMonocrystals and bicrystals of ice have been creep tested at temperatures between 4 and — 30°C. The bicrystals had a single grain boundary running parallel to the tensile axis; this configuration inhibited grain-boundary slip between the two grains. The creep tests, which were carried out at constant stress σ and temperature T, yielded data of strain ϵ for time elapsed since the start of the test. These data showed accelerating creep for both monocrystals and bicrystals at all strain levels. Strain-rates were derived at strains of 0.01, 0.05. and 0.10, and these rates were fitted to the expressionk is Boltzmann’s constant and E is the creep activation energy. Derived values of n were 1.9 for monocrystals and 2.9 for bicrystals. The creep activation energy was found to be 78 kJ/mol for monocrystals and 75 kJ/mol for bicrystals. The processes of creep deformation in mono-, bi- and polycrystals are discussed.

scholarly journals The Creep Activation Energies of Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 429-444 ◽  
Author(s):  
D. R. Homer ◽  
J. W. Glen
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Creep Deformation ◽  
Tensile Axis ◽  
Strain Rates ◽  
Boundary Slip ◽  
Creep Tests ◽  
Creep Activation Energy ◽  
Single Grain ◽  
Image Position

Abstract Monocrystals and bicrystals of ice have been creep tested at temperatures between 4 and — 30°C. The bicrystals had a single grain boundary running parallel to the tensile axis; this configuration inhibited grain-boundary slip between the two grains. The creep tests, which were carried out at constant stress σ and temperature T, yielded data of strain ϵ for time elapsed since the start of the test. These data showed accelerating creep for both monocrystals and bicrystals at all strain levels. Strain-rates were derived at strains of 0.01, 0.05. and 0.10, and these rates were fitted to the expression k is Boltzmann’s constant and E is the creep activation energy. Derived values of n were 1.9 for monocrystals and 2.9 for bicrystals. The creep activation energy was found to be 78 kJ/mol for monocrystals and 75 kJ/mol for bicrystals. The processes of creep deformation in mono-, bi- and polycrystals are discussed.

The microstructure and creep deformation of hot-pressed Si3N4 with different amounts of sintering additives

1996 ◽  
Vol 11 (1) ◽  
pp. 120-126 ◽  
Author(s):  
Sang-Young Yoon ◽  
Takashi Akatsu ◽  
Eiichi Yasuda
Keyword(s):  
Activation Energy ◽  
Silicon Nitride ◽  
Creep Rate ◽  
Grain Boundary ◽  
Apparent Activation Energy ◽  
Creep Test ◽  
Creep Deformation ◽  
Glassy Phase ◽  
Microstructural Observation ◽  
Rate Limiting

Compressive creep deformation of hot-pressed silicon nitride with different amounts of grain boundary glassy phase was investigated at 1300–1400 °C under 30–100 MPa. The stress exponent of the creep rate was determined to be nearly unity. The apparent activation energy of silicon nitride with a larger amount of glassy phase was measured to be about 700 kJ/mole, and that with a smaller amount of glassy phase was found to be 400 kJ/mole. In addition, the microstructural observation found that no cavity appeared and grain boundary glass was recrystallized during creep test. Thus, the rate-limiting steps in solution/precipitation creep mechanism change from the solution-reprecipitation of Si3N4 grains to the diffusion through the grain boundary with increasing the amount of glassy phase.

Impression Creep Behaviour of Extruded Mg-Sn Alloy

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
V. Thenambika ◽  
S. Jayalakshmi ◽  
R.A. Singh ◽  
J.K. Nidhi ◽  
M. Gupta
Keyword(s):  
Activation Energy ◽  
Stress Exponent ◽  
Creep Deformation ◽  
Creep Behaviour ◽  
Impression Creep ◽  
Temperature Dependent ◽  
Creep Tests ◽  
Automobile Engine ◽  
Creep Curves ◽  
Mg2sn Phase

Mg-Sn alloys contain thermally stable Mg2Sn phase, and are proposed as heat-resistant alloys for automobile engine applications. In this study, the creep behaviour of Mg-5Sn alloy was investigated using impression creep technique. The impression creep tests were carried out under constant punching stress in the range of 80-320 MPa at temperatures 373-573 K, for dwell times up to 5 hours. The results highlight that creep of Mg-5Sn alloy was load and temperature dependent, i.e. increasing the load and temperature resulted in larger creep deformation and hence to higher creep rates. From the creep curves, the stress exponent and the activation energy were estimated and the creep mechanism was identified.

Investigations on a New Failure Model for Electromigration

1991 ◽  
Vol 225 ◽  
Author(s):  
J. Kitchin ◽  
J. R. Lloyd
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Cumulative Distribution Function ◽  
Cumulative Distribution ◽  
Failure Model ◽  
Line Segments ◽  
Standard Normal ◽  
The Mean ◽  
Image Position ◽  
Line P

A new statistical model for electromigration failure in fine-line thin film conductors is developed in [1] by extending [2] to incorporate the statistics of microstructure and concomitant variations in the activation energy for grain boundary diffusion. The resulting distribution of time t to failure is well-approximated bywhere N is the number of line segments that are potential independent failure elements, 1μ and σ are, respectively, the mean and standard deviation of an assumed normal distribution of activation energy in grain boundaries, γ is a scaling constant, T is in degrees Kelvin, j is the current density in the line, p1 is the fraction of line segments for which exactly one grain boundary occurs between two blocking boundaries, and Φ is the standard normal cumulative distribution function. (Note: .)

Creep of Si3N4 Based Ceramics for Thermo-Mechanical Applications

2008 ◽  
Vol 591-593 ◽  
pp. 667-672
Author(s):  
Claudinei dos Santos ◽  
Kurt Strecker ◽  
M.J.R. Barboza ◽  
Francisco Piorino Neto ◽  
Olivério Moreira Macedo Silva ◽  
...  
Keyword(s):  
Activation Energy ◽  
Rare Earth ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Phase Content ◽  
Creep Tests ◽  
Intergranular Phase ◽  
Aspect Ratios ◽  
Compressive Stresses ◽  
N2 Atmosphere

Commercial α−Si3N4, Al2O3 and a mixed yttrium and rare earth oxides, RE2O3, were used as starting-powders. Powder batches were milled using different Al2O3/RE2O3 contents, as additive. Hot-pressing was done at 1750oC-30 min-20MPa in N2 atmosphere. Specimens neat to 6x3x3mm3 were polished and characterized by XRD and SEM. Specimens were submitted to creep tests, under compressive stresses between 100 and 350 MPa at temperatures ranging from 1250 to 1300oC in air. Higher additive amounts resulted in larger grains of higher aspect ratios and in a decreased anisotropy in the hot-pressed ceramics. The compressive creep behavior depends on the intergranular phase content. While higher amounts of additives resulted in higher creep rates, • ε , and higher stress exponents, n, the activation energy Qss, has been inferior for samples with lower additive contents. Grain sliding has been identified to be the predominant mechanism responsible for creep deformation of these ceramics.

Analysis of defect formation in Nb-doped SrTiO3 by impedance spectroscopy

2001 ◽  
Vol 16 (1) ◽  
pp. 192-196 ◽  
Author(s):  
Seong-Ho Kim ◽  
Jung-Ho Moon ◽  
Jae-Hwan Park ◽  
Jae-Gwan Park ◽  
Yoonho Kim
Keyword(s):  
Activation Energy ◽  
Impedance Spectroscopy ◽  
Grain Boundary ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Thermal Activation ◽  
Oxygen Vacancies ◽  
Defect Formation ◽  
Activation Energies ◽  
Single Grain

The thermal activation energies for conduction of Nb-doped SrTiO3 grains and grain boundaries have been investigated by impedance spectroscopy. First, to observe the effect of electrode/SrTiO3 bulk interface, the varied impedances of SrTiO3 single crystal were measured with temperatures. The activation energy of an electrode/bulk interface was determined to be 1.3 eV, whereas that of bulk was 0.8 eV. When the impedances of Nb-doped SrTiO3 ceramics were measured, it was suggested that the more precise impedance values of a single grain and a single grain to grain junction be obtained using a microelectrode method. The activation energies for a grain, a grain boundary, and an electrode/bulk interface were determined to be about 0.8, 1.3, and 1.5 eV, respectively. From these measured results, it was suggested that the activation energy, 0.8 eV, measured in grain was originated from oxygen vacancies and the activation energy, 1.3 eV, in grain boundary was from strontium vacancies.

Creep Behavior of Two Series Magnesium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1596-1601 ◽  
Author(s):  
Yang Shan Sun ◽  
Jing Bai ◽  
Feng Xue
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Stress Exponent ◽  
Magnesium Alloys ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Grain Boundary Sliding ◽  
Creep Tests ◽  
Sharp Drop ◽  
Creep Properties

The creep behavior of two series of magnesium alloys, Mg-4Al based alloys with strontium addition and binary Mg-Nd alloys, has been studied. Results show that the high creep properties achieved by the Mg-Nd alloys are attributed to the precipitation of tiny dispersed β’ particles, which form and effectively restrict the dislocation slipping and climb during creep deformation. In terms of values of the stress exponent and apparent activation energy gained from systematic creep tests, the mechanism responsible for creep deformation of the Mg-Nd alloys is inferred as dislocation climb, which is supported by TEM observations performed on the Mg-2Nd alloy after creep test. For the Mg-4Al based alloys, however, microstructural observations reveal that the significant improvement on creep properties caused by Sr addition is accounted for the formation of an interphase network consisting of Al4Sr and a Mg-Al-Sr ternary compound distributing at grain boundaries. The breakage of the interphase network after extrusion results in a sharp drop of creep properties, indicating the creep deformation of the alloy is controlled mainly by grain boundary sliding, which is in contradiction to the mechanism for creep of the alloys inferred by the classical criterions based on the values of stress exponent and apparent activation energy.

Temperature Dependence of High-Mobility Poly-Si Tft with Single Grain Boundary

2002 ◽  
Vol 715 ◽  
Author(s):  
In-Hyuk Song ◽  
Cheon-Hong Kim ◽  
Min-Koo Han
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Single Crystal ◽  
Field Effect ◽  
High Mobility ◽  
Drain Current ◽  
Field Effect Mobility ◽  
Single Grain ◽  
Increasing Temperature ◽  
Channel Region

AbstractWe have fabricated high-mobility TFTs with large lateral grains and investigated the variation of drain current with increasing temperature. The activation energy of drain current in large grain TFTs is found to be higher under the off-state and lower under the on-state than that in small grain TFTs. The field-effect mobility during the on-state is reduced with increasing temperature due to a lattice scattering inside grain. Because the proposed device has large lateral grain in the channel region, the lattice scattering inside the grain would be dominant, which is similar to single crystal Si MOSFETs.

Short Channel Poly-Si TFT with Single Grain Boundary by Excimer Laser Annealing on Al-masked a-Si Layer

2002 ◽  
Vol 715 ◽  
Author(s):  
Sang-Hoon Jung ◽  
Jae-Hoon Lee ◽  
Min-Koo Han
Keyword(s):  
Grain Boundary ◽  
Laser Annealing ◽  
Thin Film Transistor ◽  
High Mobility ◽  
Silicon Layer ◽  
Silicon Thin Film ◽  
Short Channel ◽  
Excimer Laser Annealing ◽  
Boundary Density ◽  
Single Grain

AbstractA short channel polycrystalline silicon thin film transistor (poly-Si TFT), which has single grain boundary in the center of channel, is reported. The reported poly-Si TFT employs lateral grain growth method through aluminum patterns, which acts as a selective beam mask and a lateral heat sink during the laser irradiation, on an amorphous silicon layer. The electrical characteristics of the proposed poly-Si TFT have been considerably improved due to grain boundary density lowered. The reported short channel poly-Si TFT with single grain boundary exhibits high mobility as 222 cm2/Vsec and large on/off current ratio exceeding 1 × 108.

Grain Boundary Atomic Structures in SrTiO3 and BaTiO3

2007 ◽  
Vol 558-559 ◽  
pp. 851-856 ◽  
Author(s):  
Takahisa Yamamoto ◽  
Teruyasu Mizoguchi ◽  
S.Y. Choi ◽  
Yukio Sato ◽  
Naoya Shibata ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Annealing Temperature ◽  
Unit Length ◽  
Rate Dependency ◽  
Atomic Structures ◽  
Current Voltage ◽  
Single Grain ◽  
Current Voltage Characteristics ◽  
Theoretical Results

SrTiO3 bicrystals with various types of grain boundaries were prepared by joining two single crystals at high temperature. By using the bicrystals, we examined their current-voltage characteristics across single grain boundaries from a viewpoint of point defect segregation in the vicinity of the grain boundaries. Current-voltage property in SrTiO3 bicrystals was confirmed to show a cooling rate dependency from annealing temperature, indicating that cation vacancies accumulate due to grain boundary oxidation. The theoretical results obtained by ab-initio calculation clearly showed that the formation energy of Sr vacancies is the lowest comparing with Ti and O vacancies in oxidized atomosphere. The formation of a double Schottky barrier (DSB) in n-type SrTiO3 is considered to be closely related to the accumulation of the charged Sr vacancies. Meanwhile, by using three types of low angle boundaries, the excess charges related to one grain boundary dislocation par unit length was estimated. In this study, we summarized our results obtained in our group.

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