Influence of the zero motion of a positron on positron lifetime in a metal lattice due to higher Fourier components of its Bloch function

2005 ◽  
Vol 71 (24) ◽  
Author(s):  
H. Stachowiak ◽  
E. Boroński
Keyword(s):  
Positron Lifetime ◽  
Bloch Function ◽  
Metal Lattice

Positron-lifetime study of electrically hydrogen charged Ni, austenitic stainless steel and Fe

2000 ◽  
Vol 283-287 ◽  
pp. 858-862 ◽  
Author(s):  
H Ohkubo ◽  
S Sugiyama ◽  
K Fukuzato ◽  
M Takenaka ◽  
N Tsukuda ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Positron Lifetime

Nanometer size pores in ionic liquid loaded silica gel characterized by positron lifetime spectroscopy

2015 ◽  
Vol 213 (1) ◽  
pp. 165-169 ◽  
Author(s):  
Christian Herold ◽  
Hubert Ceeh ◽  
Thomas Gigl ◽  
Markus Reiner ◽  
Marco Haumann ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Silica Gel ◽  
Positron Lifetime ◽  
Nanometer Size ◽  
Positron Lifetime Spectroscopy

First Stages of Nano-Crystallization of Amorphous Fe75.5Cu1Si12.5B8 Studied by the Positron Annihilation Lifetime Technique

1993 ◽  
Vol 321 ◽  
Author(s):  
A. J. Kruk ◽  
H. Schut ◽  
J. Sietsma ◽  
A. Van Veen
Keyword(s):  
Positron Annihilation ◽  
Crystallization Process ◽  
Positron Lifetime ◽  
Early Stage ◽  
Average Density ◽  
Crystalline Material ◽  
Positron Annihilation Lifetime ◽  
Resistivity Measurements ◽  
Nano Crystalline ◽  
Crystallisation Process

ABSTRACTThe first stages of the nano-crystallization process of amorphous Fe75.5Cu1Nb3Si12.5B8 into a nano-crystalline structure are investigated by the positron annihilation lifetime technique. Samples have been isothermally annealed at 643 K for times varying between 600 and 105 seconds. The positron lifetime spectra have been analyzed allowing for three lifetimes. The shortest and the longest lifetime, τ1 = 150 ± 2 ps and τ3 = 1500–2000 ps respectively, are attributed to annihilation of positrons in the amorphous phase and to the formation and annihilation of ortho-positronium at the surface of the stacked foils and did not change significantly upon the annealing. The intermediate positron lifetime τ2 increased from 324 ps to 387 ps. The intensity of this component increased from 5 to 15%. Comparison with resistivity measurements indicates that the change of this lifetime component occurs at an early stage in the crystallisation process, i.e. when the fraction of crystalline material is on the order of 10−3. The increase of τ2 is attributed to positrons annihilating in a region with lower average density surrounding the small crystallite.

Defects in electron irradiated GaP studied by positron lifetime spectroscopy

1995 ◽  
Vol 60 (6) ◽  
pp. 541-544 ◽  
Author(s):  
A. Polity ◽  
Th. Abgarjan ◽  
R. Krause-Rehberg
Keyword(s):  
Positron Lifetime ◽  
Positron Lifetime Spectroscopy

Positron lifetime studies in organic media

1971 ◽  
Vol 4 (2) ◽  
pp. 261-268 ◽  
Author(s):  
K P Singh ◽  
R M Singru ◽  
C N R Rao
Keyword(s):  
Positron Lifetime ◽  
Organic Media ◽  
Lifetime Studies

Mechanical and microstructural properties of polystyrene based composites: positron lifetime spectroscopic and DSC studies

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Abdullah Mohammed Ali Mohammed Altaweel ◽  
Jaya Madhu Raj ◽  
Malalvalli Nagarajaiah Chandrashekara ◽  
Puttegowda Ramya ◽  
Parthasarathy Sampathkumaran ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Free Volume ◽  
Positron Lifetime ◽  
Tensile Modulus ◽  
Silica Content ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Microstructural Property ◽  
Calcium Aluminosilicate

Abstract Polystyrene (PS) based composites respectively with cenosphere (CS) and calcium aluminosilicate (CAS) as fillers were studied using the positron lifetime technique to reveal the correlation between free volume, a microstructural property, and mechanical properties of the composites (tensile strength and tensile modulus). The thermal stability of the composites was determined using differential scanning calorimetry. The results showed that addition of CAS filler lead to a significant improvement in the mechanical properties of the composite, whereas addition of CS resulted in improvement in tensile modulus only. Both PS/CAS and PS/CS composites showed enhancement in thermal stability compared with that of the pure PS matrix. The positron results showed that the average free volume size for the PS/CAS composite (at 40 phr CAS) was reduced significantly compared with that of the pure PS. These results are understood in terms of the influence of silica content, filler-matrix interaction, and particle size.

Insights into the synergistic role of metal–lattice oxygen site pairs in four-centered C–H bond activation of methane: the case of CuO

2016 ◽  
Vol 6 (11) ◽  
pp. 3984-3996 ◽  
Author(s):  
Jithin John Varghese ◽  
Quang Thang Trinh ◽  
Samir H. Mushrif
Keyword(s):  
Activation Energy ◽  
Copper Oxide ◽  
Bond Activation ◽  
Lattice Oxygen ◽  
Oxide Surfaces ◽  
Energy Barriers ◽  
Metal Lattice ◽  
Oxygen Site ◽  
Site Pair

Of the three mechanisms for activation of methane on copper and copper oxide surfaces, the under-coordinated Cu–O site pair mediated mechanism on CuO surfaces has the lowest activation energy barriers.

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