Long-Range Diffusion of Hydrogen in Solid-Solution PdCe Alloys as Deduced from Absorption Experiments

2008 ◽  
Vol 273-276 ◽  
pp. 381-387 ◽  
Author(s):  
Giovanni Mazzolai
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Thermal Decomposition ◽  
Diffusion Coefficient ◽  
High Temperature ◽  
Diffusion Constant ◽  
Absorption Data ◽  
Friction Measurements ◽  
And Diffusion ◽  
Diffusion Of Hydrogen

The diffusion of H and the thermal decomposition of hydrides have been investigated at high temperatures in two PdCe alloys of composition 5% and 9% Ce. It has been found that the H diffusion coefficient obeys an Arrhenius-type of law with the following values of the activation energy W and diffusion constant D0, ( )     = ± × = ± − s m D W eV 2 7 0 2 2 10 0.20 0.02 (Pd95Ce5 alloy) ( )     = ± × = ± − s m D W eV 2 7 0 2 1 10 0.24 0.01 (Pd91Ce9 alloy) The high-temperature absorption data match the low-temperature ones deduced from internal friction measurements, indicating that Ce atoms do not act as strong trapping centres for H. Thermal decomposition of hydrides in the Pd95Ce5H0.008 alloy occurs in a single stage showing a homogeneous solid solution state of the H-Me system.

Diffusion Constant and Diffusion Coefficient

Science ◽  
1955 ◽  
Vol 121 (3137) ◽  
pp. 215-216 ◽  
Author(s):  
J. VERDUIN
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Constant ◽  
And Diffusion

Simultaneous measurement of vaporisation rate and diffusion coefficient in the Ni-V solid solution

1980 ◽  
Vol 30 (4) ◽  
pp. 465-468 ◽  
Author(s):  
V. I. Patoka ◽  
V. I. Silantjev ◽  
V. N. Kolesnik ◽  
J. Vřešťál ◽  
B. Million
Keyword(s):  
Solid Solution ◽  
Diffusion Coefficient ◽  
Simultaneous Measurement ◽  
And Diffusion

The influence of monomer and polymer properties on the removal of organic vehicle from ceramic and metal moldings

1995 ◽  
Vol 10 (8) ◽  
pp. 2060-2072 ◽  
Author(s):  
S.A. Matar ◽  
J.R.G. Evans ◽  
M.J. Edirisinghe ◽  
E.H. Twizell
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Degradation Products ◽  
Diffusion Constant ◽  
Enthalpy Of Vaporization ◽  
Organic Vehicle ◽  
Polymer Properties ◽  
Plastic Forming ◽  
Successful Removal ◽  
Ceramic Suspensions

This paper describes the effects of monomer and polymer properties on the competition between degradation of organic vehicle and transport of degradation products in ceramic moldings during pyrolysis. An experimentally tested model is studied systematically for ranges of material and process parameters characteristic of known polymers and their degradation products. The work highlights the properties having the greatest influence on the successful removal of organic vehicle from molded ceramics. The polymer properties controlling the diffusion constant are linked to the temperature dependence of viscosity of the molten suspension. Enthalpy of vaporization of the organic vehicle and the activation energy for the diffusion coefficient have a commanding influence on the critical heating rate for avoidance of defects. Preliminary guidelines emerge for the design of polymers for plastic forming of ceramic suspensions.

Interface Controlled Diffusional Creep of Cu + 2.8 at.% Co Solid Solution

2012 ◽  
Vol 322 ◽  
pp. 33-39 ◽  
Author(s):  
Sergei Zhevnenko ◽  
Eugene Gershman
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Surface Tension ◽  
High Temperature ◽  
Creep Behavior ◽  
Pure Copper ◽  
Diffusional Creep ◽  
High Temperature Creep ◽  
Temperature Range ◽  
Different Temperatures

High-temperature creep experiments were performed on a Cu-2.8 ат.% Co solid solution. Cylindrical foils of 18 micrometers thickness were used for this purpose. Creep tests were performed in a hydrogen atmosphere in the temperature range of about from 1233 K to 1343 K and at stresses lower than 0.25 MPa. For comparison, a foil of pure copper and Cu-20 at.% Ni solid solution were investigated on high temperature creep. Measurements on the Cu foil showed classical diffusional creep behavior. The activation energy of creep was defined and turned out to be equal 203 kJ/mol, which is close to the activation energy of bulk self-diffusion of copper. There was a significant increase in activation energy for the Cu-20 at.% Ni solid solution. Its activation energy was about 273 kJ/mol. The creep behavior of Cu-Co solid solution was more complicated. There were two stages of diffusional creep at different temperatures. The extremely large activation energy (about 480 kJ/mol) was determined at relatively low temperature and a small activation energy (about 105 kJ/mol) was found at high temperatures. The creep rate of Cu-Co solid solution was lower than that of pure copper at all temperatures. In addition, the free surface tension of Cu-2.8 ат.% Co was measured at different temperatures from 1242 K to 1352 K. The surface tension increases in this temperature range from 1.6 N/m to 1.75 N/m. There were no features on the temperature dependence of the surface tension.

Diffusion Behavior of Carbon Atoms in Austenite Region of SCM435 Steel

2016 ◽  
Vol 850 ◽  
pp. 266-270 ◽  
Author(s):  
Dong Xu ◽  
Bing Zheng ◽  
Xing Liang Gao ◽  
Miao Yong Zhu
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Arrhenius Equation ◽  
Diffusion Constant ◽  
Carbon Diffusion ◽  
Diffusion Activation Energy ◽  
Diffusion Behavior ◽  
Scm435 Steel ◽  
The Relationship ◽  
Diffusion Activation

The research on the decarbonizing behavior of the austenite region of SCM435 steel was carried out. And the experimental results shewed that the relationship between the diffusion coefficient and temperature totally agreed with the Arrhenius equation and that the diffusion constant and the diffusion activation energy were uniform within the temperature range of 900-1100°C. However, when the austenite reached certain temperature, the carbon diffusion coefficient decreased significantly as temperature increased and its relationship with temperature no longer agreed with the Arrhenius equation.

Effect of Stress on Creep at High Temperatures

1957 ◽  
Vol 24 (2) ◽  
pp. 207-213
Author(s):  
H. Laks ◽  
C. D. Wiseman ◽  
O. D. Sherby ◽  
J. E. Dorn
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
High Temperature ◽  
Creep Rate ◽  
Pure Aluminum ◽  
Dislocation Climb ◽  
Experimental Investigations ◽  
High Temperature Creep ◽  
Self Diffusion ◽  
Temperature Creep

Abstract Experimental investigations on pure aluminum and its dilute solid-solution alloys revealed that the high-temperature creep rate ϵ̇ is related to the stress σ by ϵ̇ ∼ σn for low stresses and ϵ̇ ∼ eBσ for high stresses where n and B are constants independent of the creep strain and temperature. According to a preliminary dislocation-climb model for high-temperature creep, the activation energy for creep is that for self-diffusion, the effect of stress on the creep rate depends on the number of active Frank-Read sources, and the rate of climb depends on the structure as determined by the pattern of climbing dislocations. Many of the experimental observations on high-temperature creep can be accounted for by this model.

Diffusion Constant and Diffusion Coefficient

Science ◽  
1955 ◽  
Vol 121 (3137) ◽  
pp. 215-216
Author(s):  
Jacob Verduin
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Constant ◽  
And Diffusion

Diffusion of Hydrogen in 6H Silicon Carbide

1996 ◽  
Vol 423 ◽  
Author(s):  
M. K. Linnarsson ◽  
J. P. Doyle ◽  
B. G. Svensson
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Silicon Carbide ◽  
Diffusion Coefficient ◽  
Secondary Ion Mass Spectrometry ◽  
Depth Profiling ◽  
Defect Complexes ◽  
Induced Defects ◽  
Secondary Ion ◽  
Diffusion Of Hydrogen

Abstract6H polytype silicon carbide (SiC) samples of n-type have been implanted with 50 keV H+ ions and subsequently annealed at temperatures between 200 °C and 1150 °C. Using depth profiling by secondary ion mass spectrometry motion of hydrogen is observed in the implanted region for temperatures above 700 °C. A diffusion coefficient of ∼10−14 cm2/s is extracted at 800°C with an approximate activation energy of ∼3.5 eV. Hydrogen displays strong interaction with the implantation-induced defects and stable hydrogen-defect complexes are formed. These complexes anneal out at temperatures in excess of 900°C and are tentatively identified as Carbon-Hydrogen centers at a Si vacancy.

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