Correlation of Mechanical Properties with Defect Structure in Commercial Pure Al and Al-Mn Alloys Studied by Positron Annihilation Spectroscopy

2007 ◽  
Vol 546-549 ◽  
pp. 783-787
Author(s):  
Ehsan. A.H. Gomaa ◽  
M. Mohsen ◽  
A.S. Taha ◽  
M.M. Mostafa
Keyword(s):  
Mechanical Properties ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Vickers Microhardness ◽  
Complete Recovery ◽  
Positron Annihilation Spectroscopy ◽  
Annihilation Radiation ◽  
Positron Annihilation Lifetime ◽  
Complete Recrystallization ◽  
Cold Rolled

The variations during isochronal annealing of cold-rolled commercial pure Al (1050) and Al-Mn (3004) has been investigated between room temperature (RT) and 823 K. The annealing stages have been identified as recovery, partial recrystallization, complete recrystallization and grain growth using positron annihilation lifetime (PAL) spectroscopy, Doppler broadening of annihilation radiation (DBAR) spectroscopy and Vickers microhardness (Hv) measurements. The retardation of complete recovery in Al-Mn alloys is due to the presence of vacancy-Mn complexes. A positive correlation has been found between positron annihilation parameters (τav & Snor) and mechanical properties (Hv) for the two alloys under investigation.

Free-Volume Properties of Amorphous Polymers Probed by Positron Annihilation Spectroscopy

1990 ◽  
Vol 215 ◽  
Author(s):  
Y. C. Jean ◽  
F. Zandiehnadem ◽  
Q. Deng
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Amorphous Materials ◽  
Polymeric Materials ◽  
Positron Annihilation Spectroscopy ◽  
Atomic Scale ◽  
Annihilation Radiation ◽  
Positron Annihilation Lifetime ◽  
Additional Information ◽  
Volume Properties

AbstractPositron annihilation spectroscopy (PAS) has been developed to characterize the free-volume properties of polymers. Positron annihilation lifetime measurements give direct information about the dimension, content, and hole-size distributions of free-volume in amorphous materials. The angular correlation of positron annihilation radiation measurements give additional information about the shape of the free-volume holes in oriented polymeric materials. The unique capability of PAS to probe free-volume properties is from the fact that positronium atom is preferentially trapped in the atomic-scale holes which have a size ranging from 1 to 10 Å.

Probing Materials by Positron Annihilation Technique and Mossbauer Spectroscopy - Review

2011 ◽  
Vol 699 ◽  
pp. 1-37
Author(s):  
Mahuya Chakrabarti ◽  
S. Chattopadhyay ◽  
D. Sanyal ◽  
A. Sarkar ◽  
D. Jana
Keyword(s):  
Magnetic Properties ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Spectroscopic Studies ◽  
Spectroscopic Technique ◽  
Annihilation Radiation ◽  
Radiation Measurement ◽  
Doppler Broadening ◽  
Positron Annihilation Lifetime ◽  
Coincidence Doppler Broadening

Positron annihilation technique is a well known technique to characterize the defects in a material. These defects can be identified by positron annihilation lifetime and coincidence Doppler broadening of positron annihilation radiation measurement. In this chapter we report the room temperature positron annihilation lifetime for single crystalline ZnO. From our study it is confirmed that the present crystal contains VZn–hydrogen complexes with low open volumes. Another important nuclear solid technique is the Mossbauer Spectroscopic technique which has been used to probe the local magnetic properties of a solid. Here we have summarized Mossbauer spectroscopic studies on ferrites.

COMPATIBILITY STUDY OF NBR/PVC BLEND WITH GASOLINES AND ETHANOL FUEL

2012 ◽  
Vol 85 (2) ◽  
pp. 195-206 ◽  
Author(s):  
Vânya M. D. Pasa ◽  
Adriana V. Maciel ◽  
José C. Machado ◽  
Guilherme O. Barra
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Thermogravimetric Analysis ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Compatibility Study ◽  
Mechanical Behaviors ◽  
Ethanol Fuel ◽  
Elongation At Break ◽  
Positron Annihilation Lifetime

Abstract An NBR/polyvinyl chloride (PVC) blend changed by aging (20 weeks in different fuels at room temperature) was evaluated for weight, hardness, mechanical properties, and microstructure. The exposure tests were made with premium gasoline, regular gasoline, regular gasoline doped with a rubber solvent, and an oxygenated renewable biofuel (ethanol fuel). After the aging tests, all NBR/PVC blend samples increased in both hardness and elastic modulus, whereas both elongation at break and tension at break decreased, but in different proportions. As the NBR/PVC blends aged, they became less elastomeric and more rigid. The regular gasoline doped with a rubber solvent was the most aggressive of the fuels tested because it promoted the extraction of a large quantity of the blend constituents, thus making the blend harder. In general, NBR/PVC samples immersed in the fuels showed similar mechanical behaviors, except in the case of immersion in ethanol. The values of parameters τ3 and I3 were obtained by positron annihilation lifetime spectroscopy. The changes in the mechanical properties and the reduction of the values of parameters τ3 and I3 were related to extraction of the plasticizer, which was confirmed by thermogravimetric analysis.

scholarly journals Crystallization pathways, morphologies and structural defects of α-MnO2 nanomaterial synthesized under annealed temperatures

2020 ◽  
Author(s):  
Van-Phuc Dinh ◽  
Anh Tuyen Luu ◽  
Siemek Krzysztof ◽  
Denis Kozlenko ◽  
Le Khiem ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Structural Defects ◽  
Annihilation Radiation ◽  
Practical Applications ◽  
Positron Annihilation Lifetime ◽  
Inorganic Nanomaterials ◽  
Ft Ir ◽  
Composition Structure

Abstract Manganese dioxide, in particular α-MnO2, is one of the advanced inorganic nanomaterials having wide applications in many areas. Hence, understanding the crystallization pathways, morphologies, and formation mechanism of defects in its structure is of particular importance, not only for fundamental science but also for practical applications. Herein, different physically and chemically based methods, such as Neutron Diffraction (ND), XRD, SEM, TPR- H2, TGA-DSC, FT-IR, Positron Annihilation Lifetime (PAL), Doppler Broadening (DB) of positron annihilation radiation, and Electron-Momentum Distribution (EMD) measurements combined with theoretical calculations, were utilized to systematically investigate the composition, structure, and morphology of α-MnO2 nanomaterial under different annealed temperatures. The investigated material was synthesized at room temperature using a facile chemical method with potassium permanganate (KMnO4) and ethanol (C2H5OH), prior to being treated by temperatures of 100 oC – 800 oC. Results demonstrated, for the first time, that the α-MnO2 nucleation can be formed even at room temperature and gradually developed to α-MnO2 nanorods at 600 oC. This novel finding, which cannot be explored by conventional XRD, was confirmed by ND analysis. In addition, PAL analysis combined with theoretical ab initio calculations indicated the existence of H+ ions in the tunnel [1x1] of α-MnO2. At the same time, DB and EMD measurements explored the presence of Mn and O vacancies in α-MnO2 crystals at low temperatures. Finally, the present study reported a remarkable finding that organic molecules may act as reactants as well as templates, which are entirely decomposed and disappeared at highly annealed temperatures.

Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production

2012 ◽  
Vol 331 ◽  
pp. 41-52 ◽  
Author(s):  
Andreas Wagner ◽  
Wolfgang Anwand ◽  
Maik Butterling ◽  
Thomas E. Cowan ◽  
Fine Fiedler ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Linear Accelerator ◽  
Electron Accelerator ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Electron Linear Accelerator ◽  
Positron Annihilation Lifetime ◽  
Electron Bremsstrahlung ◽  
New Type ◽  
Set Up

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

Mechanical properties of nickel beryllides

1989 ◽  
Vol 4 (6) ◽  
pp. 1347-1353 ◽  
Author(s):  
T. G. Nieh ◽  
J. Wadsworth ◽  
C. T. Liu
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Elastic Properties ◽  
Room Temperature ◽  
Vickers Microhardness ◽  
Interstitial Oxygen ◽  
Equiatomic Composition ◽  
Room Temperature Ductility ◽  
Hardness Increase ◽  
Microhardness Tester

The elastic properties of nickel beryllide have been evaluated from room temperature to 1000 °C. The room temperature modulus is measured to be 186 GPa, which is relatively low by comparison with other B2 aluminides such as NiAl and CoAl. Hardness measurements were carried out on specimens that had compositions over the range from 49 to 54 at. % Be, using both a Vickers microhardness tester and a nanoindentor. It was found that the hardness of NiBe exhibits a minimum at the equiatomic composition. This behavior is similar to that of aluminides of the same crystal structure, e.g., NiAl and CoAl. The effect of interstitial oxygen on the hardness of NiBe has also been studied and the results show that the presence of oxygen in NiBe can cause a significant increase in hardness. It is demonstrated that the hardness increase for the off-stoichiometric compositions is primarily caused by interstitial oxygen and can only be attributed partially to anti-site defects generated in off-stoichiometric compositions. Nickel beryllides appear to have some intrinsic room temperature ductility, as evidenced by the absence of cracking near hardness indentations.

Positron Annihilation Lifetime Measurements in Collagen Biopolymer

1998 ◽  
Vol 530 ◽  
Author(s):  
S. Siles ◽  
G. Moya ◽  
X.H. Li ◽  
J. Kansy ◽  
P. Moser
Keyword(s):  
Positron Annihilation ◽  
Amorphous Region ◽  
Positron Annihilation Spectroscopy ◽  
Lifetime Data ◽  
Spectroscopy Technique ◽  
Lifetime Measurements ◽  
Lifetime Distributions ◽  
Positron Annihilation Lifetime ◽  
Coincidence System ◽  
Three Components

AbstractLifetime measurement in Positron Annihilation Spectroscopy (PAS) is applied to the study of free-volume collagen characteristics as a function of concentration. The lifetimes of positrons were obtained by a conventional fast-fast coincidence system. All lifetime data are fitted in three components by using the computer program POSITRON FIT and resolved. For each concentration, lifetime distributions were analyzed in order to obtain the different components, thus we have observed three components of which a long component τ3. This long lived component can be associated with a pick-off annihilation of ortho-positronium (o-Ps) trapped in free volumes of amorphous region. This investigation shows the potential of the positron annihilation spectroscopy technique in the study of biopolymer microstructures.

The Evolution Behavior of Defects in the Nanofilms of W/Cu and W Probed by Doppler Broadening Positron Annihilation Spectroscopy

2017 ◽  
Vol 373 ◽  
pp. 104-107
Author(s):  
Ling Wang ◽  
Ai Hong Deng ◽  
Kang Wang ◽  
Yong Wang ◽  
Xiao Bo Lu ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Storage Time ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Radio Frequency Magnetron Sputtering ◽  
Helium Ions ◽  
Near Surface ◽  
Evolution Behavior

W/Cu multilayer nanofilms and pure W nanofilms were prepared in pure Ar and He/Ar mixing atmosphere by radio frequency magnetron sputtering method. The defect evolution of the samples was characterized by Doppler broadening positron annihilation spectroscopy (DB-PAS).The results show that plenty of defects can be produced by introducing helium (He) into W/Cu multilayer nanofilms. With the natural storage time increasing, the helium located in the near surface of W/Cu multilayer nanofilm would be released gradually and induce the coalescence of the helium related defects due to the diffusion of the helium and defects. In addition, the pure W nanofilms were irradiated by 30 keV helium ions and 40 keV hydrogen (H) ions in sequence at room temperature. From the DB-PAS analysis, it can be shown that a large number of vacancy-type defects are produced due to the He and/or H irradiation. H ions would be trapped by He related defects and produced He-H-V complexes.

Structure and Mechanical Properties of Asymmetrically Rolled IF Steel Sheet

2010 ◽  
Vol 654-656 ◽  
pp. 1255-1258 ◽  
Author(s):  
Dmitry Orlov ◽  
Rimma Lapovok ◽  
László S. Tóth ◽  
Ilana B. Timokhina ◽  
Peter D. Hodgson ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Steel Sheet ◽  
Rolling Direction ◽  
If Steel ◽  
Asymmetric Rolling ◽  
Cold Rolled ◽  
Hot Rolled ◽  
If Steel Sheet

As-received hot-rolled 5.6 mm thick IF steel sheet was symmetrically/asymmetrically cold rolled at room temperature down to 1.9 mm. The asymmetric rolling was carried out in monotonic (an idle roll is always on the same side of the sheet) and reversal (the sheet was turned 180º around the rolling direction between passes) modes. Microstructure, texture and mechanical properties were analysed. The observed differences in structure and mechanical properties were modest, and therefore further investigation of the effects of other kinds of asymmetry is suggested.

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