Diffusion and Effusion of Hydrogen in Microcrystalline Silicon

1997 ◽  
Vol 467 ◽  
Author(s):  
W. Beyer ◽  
P. Hapke ◽  
U. Zastrow
Keyword(s):  
Diffusion Coefficient ◽  
Infrared Absorption ◽  
Cyclotron Resonance ◽  
Hydrogen Diffusion ◽  
Electron Cyclotron Resonance ◽  
Microcrystalline Silicon ◽  
Hydrogen Diffusion Coefficient ◽  
Internal Surfaces ◽  
Substrate Temperatures ◽  
Hydrogen Effusion

ABSTRACTThe diffusion and effusion of hydrogen in hydrogenated microcrystalline silicon films deposited in an electron cyclotron resonance reactor were studied for various deposition temperatures Ts. For deposition temperatures below 250°C, hydrogen effusion is found to be dominated by desorption of hydrogen from internal surfaces followed by rapid out-diffusion of H2. Higher substrate temperatures result in an increased hydrogen stability suggesting the growth of a more compact material. For this latter type of samples, a hydrogen diffusion coefficient similar as in compact plasma-grown a-Si:H films is found despite a different predominant bonding of hydrogen according to infrared absorption.

Hydrogen-induced Changes of The Microscopic Structure of Microcrystalline Silicon

1998 ◽  
Vol 513 ◽  
Author(s):  
I. Kaiser ◽  
N. H. Nickel ◽  
W. Pilz ◽  
W. Fuhs
Keyword(s):  
Cyclotron Resonance ◽  
Lattice Strain ◽  
Electron Cyclotron Resonance ◽  
Hydrogen Plasma ◽  
Microcrystalline Silicon ◽  
Crystalline Fraction ◽  
Before And After ◽  
Induced Changes ◽  
Substrate Temperatures ◽  
Hydrogenation Treatment

ABSTRACTMicrocrystalline silicon samples were exposed to an electron cyclotron resonance (ECR) hydrogen plasma at various exposure times and substrate temperatures. Before and after each post-hydrogenation treatment the crystalline fraction, Xc, was determined from Raman backscattering spectra. The results reveal that the change of Xc strongly depends on the structural composition of the starting material. Amorphous samples exhibit an increase of Xc while for ltc-Si specimens the Xc decreases. The decrease of Xc is enhanced for specimens with a high initial crystalline fraction. The same plasma treatment of Si-wafers did not lead to amorphisation. We conclude that the presence of lattice strain is required to observe a H-induced decrease of Xc.

scholarly journals Hydrogen Diffusion Coefficient, Hydrogen Solution Coefficient and Hydrogen Permeability of Nb-TiNi Eutectic Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1131-1136
Author(s):  
Wei Liang Wang ◽  
Kazuhiro Ishikawa ◽  
Kiyoshi Aoki
Keyword(s):  
Diffusion Coefficient ◽  
Hydrogen Absorption ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeability ◽  
K Value ◽  
Hydrogen Flow ◽  
Hydrogen Diffusion Coefficient ◽  
High K ◽  
Pressure Region ◽  
The Difference

In general, hydrogen permeabilityΦ of the alloy membrane is expressed as the product of the hydrogen diffusion coefficient D and the hydrogen solution coefficient K. Therefore, to improve the hydrogen permeability efficiently, the values of K and D should be separately considered. In the present study, hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the hydrogen flow method and compared with those of palladium. The hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of hydrogen pressure and hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the hydrogen permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.

Investigation of hydrogen diffusion behavior in 12Cr2Mo1R(H) steel by electrochemical tests and first-principles calculation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiang Qiu ◽  
Kun Zhang ◽  
Qin Kang ◽  
Yicheng Fan ◽  
Hongyu San ◽  
...  
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Hydrogen Atom ◽  
Hydrogen Embrittlement ◽  
First Principles ◽  
Hydrogen Diffusion ◽  
First Principles Calculations ◽  
Content Type ◽  
Diffusion Behavior ◽  
Hydrogen Diffusion Coefficient

Purpose This paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage. Design/methodology/approach The hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects. Findings The results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe. Originality/value This article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

Influence of Phases Stability on the Hydrogen Diffusion Coefficient in Ti-6Al-4V

2020 ◽  
Vol 986 ◽  
pp. 33-40
Author(s):  
Mohammed Kasim Mohsun
Keyword(s):  
Heat Treatment ◽  
Diffusion Coefficient ◽  
Titanium Alloys ◽  
Hydrogen Diffusion ◽  
Volume Fraction ◽  
Substantial Effect ◽  
Diffusion Annealing ◽  
Hydrogen Treatment ◽  
Β Phase ◽  
Hydrogen Diffusion Coefficient

For a unique microstructure creation, thermo-hydrogen treatment (THT), using hydrogen as a temporary alloying element within the heat treatment, is applied. This advanced heat treatment requires reliable data about the hydrogen diffusion coefficient (DH) for understanding diffusion kinetics and its effect on the mechanical behavior of the resulted phases. In this research, three different homogeneous microstructures were established for the investigation using different homogenization parameters. After that, the concentration of hydrogen, charged in the half-length of thin titanium rods via electrochemical hydrogenation, is specified. Then, a diffusion annealing heat treatment was carried out at different temperatures, leading to hydrogen diffusion in the hydrogenated specimens. Furthermore, DH was systematically determined using two methods including the explicit finite difference method (EFDM) and Matano technique (MT). For this purpose, Abaqus software was employed for modeling the hydrogen gradient established in the specimens. Additionally, scanning electron microscopy (SEM) was used for the microstructure examination in order to specify the influence of different hydrogen concentrations on the hydrogenated specimens. The experimental outcomes reveal a substantial effect of the β phase stability and grains sizes of the β and α phases on the hydrogen diffusion. Correspondingly, the results confirm that DH was independent of the hydrogen concentration, and obeys an Arrhenius-type temperature dependence. Furthermore, hydrogen diffusion in the α+β titanium alloys Ti-6Al-4V was slower in comparison to the hydrogen diffusion in the metastable β titanium alloys Ti-10V-2Fe-3Al. In conclusion, it was observed that DH is influenced by the previously performed heat treatments that determine the resulted microstructure types, and a slight influence of the volume fraction of the α phase on DH was observed as well.

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