Results 201 to 210 of about 9,908 (221)

Positron Annihilation Lifetime and Doppler Broadening Spectroscopy of polymers

Radiation Physics and Chemistry, 2020
Abstract Positron Annihilation Lifetime and Doppler Broadening spectroscopy of positron annihilation radiation are performed in four different polymers. The size of elementary free volume sites and their chemical environments are determined. It is shown that polymers with different groups of C–H, C O, and C–F can be distinguished by their orbital ...
A. Biganeh, O. Kakuee, H. Rafi-Kheiri, M. Lamehi-Rachti, N. Sheikh, E. Yahaghi   +5 more
openaire   +1 more source

Porosity characterization of aerogels using positron annihilation lifetime spectroscopy

Journal of Non-Crystalline Solids, 2004
Abstract We utilized positron annihilation lifetime spectroscopy (PALS) for non-destructive characterization of porosity in aerogels, using positronium (Ps; an electron–positron bound state) as a probe. PALS measures Ps lifetime in pores and uses models to translate that into a spatial measure (mean free path), which can then be converted to pore ...
I. Mincov, M.P. Petkov, P. Tsou, T. Troev   +3 more
openaire   +1 more source

Investigation of SPPO Membranes by Positron Annihilation Lifetime Spectroscopy

Plasma Science and Technology, 2006
Positron annihilation lifetime spectroscopy (PALS) is a powerful technique to study the free volume in polymers. The lifetime of ortho-positronium (o-Ps), a bound state of an electron and a positron, can be used to assess the pore size while the intensity can be used to characterize the number of pores. On the basis of the values of the long-lived o-Ps
Htwe Htwe Yin, Yin Zejie, Tang Shibiao, Huang Huan   +3 more
openaire   +1 more source

Positron annihilation lifetime spectroscopy of nano/macroporous bioactive glasses

Journal of Materials Research, 2012
Abstract
Roman Golovchak, Shaojie Wang, Himanshu Jain, Adam Ingram   +3 more
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Acidity Effects in Positron Annihilation Lifetime Spectroscopy of Zeolites

The Journal of Physical Chemistry C, 2018
Positron annihilation lifetime spectroscopy (PALS) is a tool used to study pore networks in zeolites, as the diffusion of metastable ortho-positronium (o-Ps, an electron–positron bound pair) provides insights into connectivity that cannot be obtained by other techniques.
Robbie Warringham, Lars Gerchow, David Cooke, Paolo Crivelli, Richard S. Vallery, Sharon Mitchell, Javier Pérez-Ramírez   +6 more
openaire   +1 more source

Study of Chemical Carcinogens by Positron Annihilation Lifetime Spectroscopy

Journal of Applied Spectroscopy, 2013
We have used positron annihilation lifetime spectroscopy to study the carcinogens C21H20BrN3, C4H7Cl2O4P, CCl4, CHCl3, AlF3, C8H12N4O, C6H4Cl2 and the non-carcinogens H2O, AlCl3, CH2Cl2, C2H6OS. We have established a correlation between the annihilation characteristics of the studied compounds and their degree of carcinogenicity.
A. A. Pivtsaev, V. I. Razov, A. O. Karasev   +2 more
openaire   +1 more source

Design of a slow pulsed positron beam for positron annihilation lifetime spectroscopy

2007 IEEE Nuclear Science Symposium Conference Record, 2007
Positron annihilation spectroscopy provides a useful tool for the non-destructive study of subsurface microscopic defects. Variations in the electronic environment, from that of the bulk of the material, caused by defects introduce Coulombic forces which cause positrons to localize at the site of defects. This lifetime can vary from nanoseconds, if the
Alfred G. Hathaway, Jeremy Moxom, Ayman I. Hawari, Jun Xu   +3 more
openaire   +1 more source

Antiplasticization of a polyamide: a positron annihilation lifetime spectroscopy study

Polymer, 2004
Abstract In order to modify the transport properties of the amorphous polyamide Trogamid-T™, several additives with structural characteristics that produce antiplasticization have been tested. Positron annihilation lifetime spectroscopy (PALS) has been used to determine both the size of free volume holes and the number of holes (free fractional free ...
A. Garcia, M. Iriarte, C. Uriarte, J.J. Iruin, A. Etxeberria, J.del Rio   +5 more
openaire   +1 more source

A fast detector for single-shot positron annihilation lifetime spectroscopy

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
Abstract When an intense sub-nanosecond positron pulse impinges upon a target, a pulse of γ-rays is created which can yield information concerning electron–positron pairs just prior to annihilation. Many conventional γ-ray detectors are unable to exploit the timing information contained within such pulses, and we describe here the development of a ...
D.B. Cassidy, A.P. Mills
openaire   +1 more source

Characterization of ZnO varistor degradation using lifetime positron-annihilation spectroscopy

Journal of Applied Physics, 1991
Positron-annihilation spectroscopy (PAS) was used in the lifetime mode to study changes in the grain-boundary defect equilibrium associated with dc-bias-induced degradation of a ZnO varistor. The PAS lifetime spectra were collected while the sample was under an applied bias ranging from 100 V ( ∼ 400 V/cm) to 500 V ( ∼ 2000 V/cm).
M. S. Ramanachalam, A. Rohatgi, J. P. Schaffer, T. K. Gupta   +3 more
openaire   +1 more source