scholarly journals Studies of stainless steel exposed to sandblasting

Nukleonika ◽  
2015 ◽  
Vol 60 (4) ◽  
pp. 721-724 ◽  
Author(s):  
Paweł Horodek ◽  
Marat K. Eseev ◽  
Andrey G. Kobets
Keyword(s):  
Stainless Steel ◽  
Diffusion Length ◽  
Applied Pressure ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Time Duration ◽  
Force Microscopy ◽  
Atomic Force ◽  
Positron Lifetimes ◽  
Variable Energy

Abstract The influence of sandblasting on surface and subsurface of stainless steel is investigated using variable energy positron beam (VEP), positron annihilation spectroscopy (PAS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Samples of stainless steel were blasted using 110 μm particles of Al2O3 under different pressure and time duration. In the case of sandblasting for 90 s, the reduction of positron diffusion length depending on the applied pressure was observed. Sandblasting during 30 s leads only to the reduction of positron diffusion length to about 60 nm for all samples. Positron lifetimes close to 170 ps measured using positrons emitted directly from the source point to the presence of vacancies on the dislocation lines. SEM and AFM images show that surface roughness depends rather on pressure of sandblasting than time of exposition.

scholarly journals Slow positron beam at the JINR, Dubna

Nukleonika ◽  
2015 ◽  
Vol 60 (4) ◽  
pp. 725-728 ◽  
Author(s):  
Paweł Horodek ◽  
Andrey G. Kobets ◽  
Igor N. Meshkov ◽  
Alexey A. Sidorin ◽  
Oleg S. Orlov
Keyword(s):  
Diffusion Length ◽  
Nuclear Research ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Low Energy ◽  
Positron Energy ◽  
Slow Positron ◽  
Tungsten Foil ◽  
Sample Chamber ◽  
Variable Energy

Abstract The Low Energy Positron Toroidal Accumulator (LEPTA) at the Joint Institute for Nuclear Research (JINR) proposed for generation of positronium in flight has been adopted for positron annihilation spectroscopy (PAS). The positron injector generates continuous slow positron beam with positron energy range between 50 eV and 35 keV. The radioactive 22Na isotope is used. In distinction to popular tungsten foil, here the solid neon is used as moderator. It allows to obtain the beam intensity of about 105 e+/s width energy spectrum characterized by full width at half maximum (FWHM) of 3.4 eV and a tail to lower energies of about 30 eV. The paper covers the characteristic of variable energy positron beam at the LEPTA facility: parameters, the rule of moderation, scheme of injector, and transportation of positrons into the sample chamber. Recent status of the project and its development in the field of PAS is discussed. As an example, the measurement of the positron diffusion length in pure iron is demonstrated.

Micromechanisms of Hydrogen-Assisted Cracking in Super Duplex Stainless Steel Investigated by Scanning Probe Microscopy

2014 ◽  
Author(s):  
Bai An ◽  
Takashi Iijima ◽  
Chris San Marchi ◽  
Brian Somerday
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Scanning Tunneling ◽  
Super Duplex Stainless Steel ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Hydrogen Assisted Cracking ◽  
Cracking Mechanisms ◽  
Localized Plastic Deformation

Understanding the micromechanisms of hydrogen-assisted fracture in multiphase metals is of great scientific and engineering importance. By using a combination of scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and magnetic force microscopy (MFM), the micromorphology of fracture surface and microcrack formation in hydrogen-precharged super duplex stainless steel 2507 are characterized from microscale to nanoscale. The results reveal that the fracture surfaces consist of quasi-brittle facets with riverlike patterns at the microscale, which exhibit rough irregular patterns or remarkable quasi-periodic corrugation patterns at the nanoscale that can be correlated with highly localized plastic deformation. The microcracks preferentially initiate and propagate in ferrite phase and are stopped or deflected by the boundaries of the austenite phase. The hydrogen-assisted cracking mechanisms in super duplex stainless steel are discussed according to the experimental results and hydrogen-enhanced localized plasticity theory.

Hydrogen Transport and Hydrogen-Assisted Cracking in SUS304 Stainless Steel During Deformation at Low Temperatures

2015 ◽  
Author(s):  
Lin Zhang ◽  
Bai An ◽  
Takashi Iijima ◽  
Chris San Marchi ◽  
Brian Somerday
Keyword(s):  
Stainless Steel ◽  
Hydrogen Embrittlement ◽  
Room Temperature ◽  
Hydrogen Release ◽  
Hydrogen Transport ◽  
Force Microscopy ◽  
Atomic Force ◽  
Strain Induced Martensite ◽  
Hydrogen Assisted Cracking ◽  
Slip Planes

The behaviors of hydrogen transport and hydrogen-assisted cracking in hydrogen-precharged SUS304 austenitic stainless steel sheets in a temperature range from 177 to 298 K are investigated by a combined tensile and hydrogen release experiment as well as magnetic force microscopy (MFM) based on atomic force microscopy (AFM). It is observed that the hydrogen embrittlement increases with decreasing temperature, reaches a maximum at around 218 K, and then decreases with further temperature decrease. The hydrogen release rate increases with increasing strain until fracture at room temperature but remains near zero level at and below 218 K except for some small distinct release peaks. The MFM observations reveal that fracture occurs at phase boundaries along slip planes at room temperature and twin boundaries at 218 K. The role of strain-induced martensite in the hydrogen transport and hydrogen embrittlement is discussed.

EFFECT OF ETCHING TIME ON OPTICAL AND MORPHOLOGICAL FEATURES OF N-TYPE POROUS SILICON PREPARED BY PHOTO-ELECTROCHEMICAL METHOD

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Asad A. Thahe ◽  
Noriah Bidin ◽  
Mohammed A. Al-Azawi ◽  
Naser M. Ahmed
Keyword(s):  
Porous Silicon ◽  
Gravimetric Method ◽  
Constant Current ◽  
Etching Time ◽  
Absorption Data ◽  
Time Duration ◽  
Constant Current Density ◽  
Force Microscopy ◽  
Atomic Force ◽  
Structure Properties

Achieving efficient visible photoluminescence from porous-silicon (PSi) is demanding for optoelectronic and solar cells applications. Improving the absorption and emission features of PSi is challenging. Photo-electro-chemical etching assisted formation of PSi layers on n-type (111) silicon (Si) wafers is reported. Samples are prepared at constant current density (~30 mA/cm2) under varying etching times of 10, 15, 20, 25, and 30 min. The influence of etching time duration on the growth morphology and spectral properties are inspected. Room temperature photoluminescence (PL) measurement is performed to determine the optical properties of as-synthesized samples. Sample morphologies are imaged via Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The thickness and porosity of the prepared samples are estimated using the gravimetric method. The emission and absorption data is further used to determine the samples band gap and electronic structure properties. Results and analyzed, interpreted with different mechanisms and compared.  

Electrochemical Atomic Force Microscopy Study of the Dissolution Kinetics of 304 Stainless Steel

1996 ◽  
Vol 451 ◽  
Author(s):  
T. J. Mckrell ◽  
J. M. Galligan
Keyword(s):  
Stainless Steel ◽  
Electrical Potential ◽  
Dissolution Kinetics ◽  
Microscopy Study ◽  
304 Stainless Steel ◽  
Electrochemical Characteristics ◽  
Surface Kinetics ◽  
Chemical Surface ◽  
Force Microscopy ◽  
Atomic Force

ABSTRACTAn electrochemical atomic force microscope (ECAFM) has been employed to observe, in situ, the topographical and electrical changes that occur on 304 stainless steel as a function of an electrical potential. The concurrent acquisition of a polarization curve and topographical data allows direct correlation of variations in the surface roughness with the electrochemical characteristics of the passivation process. Also, the large AFM scan size, employed in this study, allows for the delineation and determination of the interdependence of the surface kinetics at various regions of the surface. Simultaneous measurements of topographical and electrical changes at these regions have established a correspondence of the competing kinetics between the reactions of dissolution and passivation. This provides a way to relate chemical surface reactions to surface topography.

POSITRON INTERACTION IN POLYMERS

2004 ◽  
Vol 19 (23) ◽  
pp. 3951-3959 ◽  
Author(s):  
CORINE BAS ◽  
N. DOMINIQUE ALBÉROLA ◽  
MARIE-FRANCE BARTHE ◽  
JÉRÉMIE De BAERDEMAEKER ◽  
CHARLES DAUWE
Keyword(s):  
Positron Annihilation ◽  
Chemical Structure ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Hole Size ◽  
Doppler Broadening ◽  
Positron Source ◽  
Positron Annihilation Lifetime ◽  
Doppler Broadening Spectra ◽  
Variable Energy

A series of dense copolyimide membranes was characterized using positron annihilation spectroscopy. The positron annihilation lifetime spectroscopy performed on film with a classical positron source gives informations on the positronium fraction formed and also on the hole size within the film. The Doppler broadening spectra (DBS) of the gamma annihilation rays coupled with a variable energy positron beam allow the microstructural analyses as a function of the film depth. Experimental data were also linked to the chemical structure of the polyimides. It was found that the presence of the fluorine atoms strongly affects the positron annihilitation process and especially the DBS responses.

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