Anisotropy of Hydrogen Diffusivity in ZnO

2013 ◽  
Vol 333 ◽  
pp. 39-49 ◽  
Author(s):  
Jakub Čížek ◽  
František Lukáč ◽  
Marián Vlček ◽  
Martin Vlach ◽  
Ivan Procházka ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Hydrogen Concentration ◽  
Hydrogen Diffusion ◽  
Surface Region ◽  
Nuclear Reaction Analysis ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
Slow Positron ◽  
X Ray

Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work by X-ray diffraction combined with slow positron implantation spectroscopy and electrical resistometry. ZnO crystals were covered by a thin Pd over-layer and electrochemically charged with hydrogen. It was found that absorbed hydrogen causes plastic deformation in a sub-surface region. The depth profile of hydrogen concentration introduced into the crystal was determined by nuclear reaction analysis. Enhanced hydrogen concentration was found in the sub-surface region due to excess hydrogen atoms trapped at defects introduced by plastic deformation. Hydrogen diffusion in ZnO crystals with various orientations was studied by in-situ electrical resistometry. It was found that hydrogen diffusion in the c-direction is faster than hydrogen diffusion in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.

scholarly journals Elastic and Plastic Deformation Behavior Studied by In-Situ Synchrotron X-ray Diffraction in Nanocrystalline Nickel

2016 ◽  
Vol 57 (9) ◽  
pp. 1447-1453 ◽  
Author(s):  
Hiroki Adachi ◽  
Yui Karamatsu ◽  
Shota Nakayama ◽  
Tomotaka Miyazawa ◽  
Masugu Sato ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Behavior ◽  
X Ray Diffraction ◽  
Nanocrystalline Nickel ◽  
X Ray ◽  
Plastic Deformation Behavior ◽  
Elastic And Plastic Deformation

In situ X-ray diffraction study of stacking fault formation in the near-surface region of transformation induced plasticity steels

2013 ◽  
Vol 530 ◽  
pp. 105-112 ◽  
Author(s):  
David Rafaja ◽  
Christina Krbetschek ◽  
Daria Borisova ◽  
Gerhard Schreiber ◽  
Volker Klemm
Keyword(s):  
Diffraction Study ◽  
Surface Region ◽  
Stacking Fault ◽  
X Ray Diffraction ◽  
Near Surface ◽  
Transformation Induced Plasticity ◽  
X Ray

Diffusivity of Hydrogen in ZnO Single Crystal

2012 ◽  
Vol 326-328 ◽  
pp. 459-464 ◽  
Author(s):  
Jakub Čížek ◽  
František Lukáč ◽  
Marián Vlček ◽  
Ivan Procházka ◽  
Franziska Traeger ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Single Crystal ◽  
Hydrogen Diffusion ◽  
Subsurface Layer ◽  
Nuclear Reaction Analysis ◽  
High Concentration ◽  
Resistivity Measurements ◽  
Zno Single Crystal ◽  
Very High

Hydrogen diffusivity in ZnO (0001) single crystal was investigated using electrical resistometry and nuclear reaction analysis (NRA). ZnO crystals were covered with a thin Pd over-layer and electrochemically charged with hydrogen. The net concentration of hydrogen determined by NRA was found to be in a reasonable agreement with the value estimated from the transported charge using the Faradays law. The hydrogen diffusion coefficient in ZnO was estimated from in-situ electrical resistivity measurements. Moreover, NRA investigations revealed existence of a subsurface layer with very high concentration of hydrogen (up to 40 at.%). Typical surface modification observed on hydrogen loaded crystal by light microscope indicates hydrogen-induced plastic deformation realized by a slip in the c-direction. Open-volume defects introduced by hydrogen-induced plastic deformation trap diffusing hydrogen and cause an enhancement of hydrogen concentration in the deformed subsurface layer.

Hydrogen concentration gradients in cathodically charged austenitic stainless steel

1987 ◽  
Vol 2 (3) ◽  
pp. 305-312 ◽  
Author(s):  
D. G. Ulmer ◽  
C. J. Altstetter
Keyword(s):  
Stainless Steel ◽  
Hydrogen Concentration ◽  
X Ray Diffraction ◽  
Concentration Gradients ◽  
Diffraction Profile ◽  
X Ray ◽  
Charging Time ◽  
Concentration Depth Profile ◽  
Profile Changes

An x-ray diffraction technique has been developed to make in-situ measurements of hydrogen concentration profiles from which diffusivity and solubility values are calculated. Hydrogen is supplied to the metal surface by cathodically polarizing it in a bath of 1N H2SO4 electrolyte. The incident x-ray beam penetrates a thin layer of electrolyte solution at the surface of the sample, thus, x-ray diffraction profile changes can be recorded as a function of charging time and temperature. The applied potential prevents outgassing of the specimen during the measurement. The x-ray diffraction profiles are deconvoluted to remove the α1/α2 doublet and noncompositional broadening effects. Composition-depth profiles are then obtained from an intensity band transformation of the deconvoluted data. A diffusion coefficient is determined by fitting a solution to Fick's second law to the concentration-depth profile. The technique described here was used to measure hydrogen diffusivity in stainless steel in the temperature range 20°–80°C.

scholarly journals Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 467
Author(s):  
William Lemos Bevilaqua ◽  
Jérémy Epp ◽  
Heiner Meyer ◽  
Juan Dong ◽  
Hans Roelofs ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Thermomechanical Processing ◽  
High Energy ◽  
Isothermal Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Post Process ◽  
Dynamic Transformation ◽  
Bainitic Microstructure

In this work, the microstructural evolution during the dynamic transformation of austenite to bainite was directly observed by in-situ high energy synchrotron X-ray diffraction measurements during warm uniaxial compression performed at the P07 beamline of PETRA III, DESY (Deutsches Elektronen-Synchrotron). Plastic deformation triggers the phase transformation, which is continuously stimulated by the introduction of dynamic dislocations into the austenite. This scenario accelerates the kinetics of bainite formation in comparison with conventional isothermal treatment. No mechanical stabilization of austenite was observed during dynamic transformation. Evidence of carbon partitioning between phases during plastic deformation was obtained. Further post-process investigations suggest that the bainitic microstructure developed during compression is oriented perpendicular to the loading direction. The findings open up new possibilities to design carbide-free bainitic microstructures directly via thermomechanical processing.

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