Relaxation Behavior of Zr-Cu-Al Ternary Bulk Glassy Alloy Studied by Using Positron Annihilation Techniques

2010 ◽  
Vol 654-656 ◽  
pp. 1070-1073 ◽  
Author(s):  
Akito Ishii ◽  
Shinya Mineno ◽  
Akihiro Iwase ◽  
Yokoyama Yoshihiko ◽  
Toyohiko J. Konno ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Isothermal Annealing ◽  
Glassy Alloy ◽  
Volume Ratio ◽  
Charpy Impact ◽  
Volume Changes ◽  
Appreciable Change ◽  
Positron Annihilation Lifetime ◽  
Bulk Glassy Alloy

Zr-based bulk glassy (BG) alloys show high tensile strength and a high Charpy impact value. In this study, the free volume changes for the hypoeutectic Zr60Cu30Al10 BG alloy during isothermal annealing below glass transition temperature (Tg) have been investigated by positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements. The positron lifetime of hypoeutectic and eutectic BG alloys is almost the same, although the atomic volume ratio, estimated by the density for the eutectic BG alloy is different from that for the hypoeutectic BG alloy. The CDB spectra show a marked difference between eutectic and hypoeutectic BG alloys; that is, the spectrum of the hypoeutectic BG alloy is closes to that of Zr metal than that of the eutectic BG alloy. This result exhibits that the elemental fraction of Zr atoms around free volume in hypoeutectic BG alloy is greater than that in eutectic BG alloy. The CDB ratio profiles for the hypoeutectic BG alloy during annealing shows no appreciable change. The same trend was observed in the eutectic BG alloy.

Positron Annihilation Lifetime Studies on Free Volume Changes in Polymers by CO2 Conditioning

1994 ◽  
Vol 175-178 ◽  
pp. 789-792 ◽  
Author(s):  
K. Tanaka ◽  
M. Ito ◽  
Hideki Kita ◽  
Katsutomo Okamoto ◽  
Yasuo Ito
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Volume Changes ◽  
Positron Annihilation Lifetime ◽  
Lifetime Studies

Positron annihilation lifetime studies of free volume changes in polycarbonate under static tensile deformation

1992 ◽  
Vol 25 (9) ◽  
pp. 2407-2411 ◽  
Author(s):  
M. Y. Ruan ◽  
H. Moaddel ◽  
A. M. Jamieson ◽  
R. Simha ◽  
J. D. McGervey
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Tensile Deformation ◽  
Volume Changes ◽  
Positron Annihilation Lifetime ◽  
Static Tensile ◽  
Lifetime Studies

Free Volume Relaxation Process in Zr50Cu40Al10 Bulk Metallic Glass Studied by Positron Annihilation Techniques

2007 ◽  
Vol 1048 ◽  
Author(s):  
Akito Ishii ◽  
Fuminobu Hori ◽  
Akihiro Iwase ◽  
Yoshihiko Yokoyama ◽  
Toyohiko J Konno
Keyword(s):  
Metallic Glass ◽  
Positron Annihilation ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Structural Relaxation ◽  
Annealing Temperature ◽  
Volume Relaxation ◽  
Appreciable Change ◽  
Positron Annihilation Lifetime ◽  
Chemical Ordering

AbstractStructural relaxation around free volume in Zr50Cu40Al10 bulk metallic glass (BMG) during isothermal annealing at 473, 573 and 673 K which are below glass transition temperature Tg =675 K have been investigated by positron annihilation lifetime (PAL) and coincidence Doppler broadening (CDB) measurements. The trends of change in positron lifetime, which correspond to the size of free volume at each annealing temperature, have a good correlation with their density change. These annealing processes obey a stretched exponential relaxation function (KWW: Kohlrausch-Williams-Watts law). Fitting parameters of KWW function, with relaxation time t0 and β, in each temperature were determined. These relaxation parameters depend on the annealing temperature, suggesting the distribution of activation energy for structural relaxation. Moreover, the profile of electron momentum distribution around free volume derived by CDB spectrum during annealing showed no appreciable change at each temperature. These facts suggest that long range chemical ordering, particularly around the free volume, dose not take place essentially.

scholarly journals Positron Annihilation Lifetime Study on free Volume Changes in TLD by Gamma - irradiation

2004 ◽  
Vol 1 (1) ◽  
pp. 144-148
Author(s):  
Baghdad Science Journal
Keyword(s):  
Gamma Irradiation ◽  
Positron Annihilation ◽  
Free Volume ◽  
Volume Fraction ◽  
Gamma Dose ◽  
Volume Changes ◽  
Positron Annihilation Lifetime ◽  
Free Volume Fraction ◽  
First Time ◽  
Free Volume Hole

Positron annihilation lifetime has been utilized for the first time to investigate the free - volume hole properties in thermolumenscent dosimeter ( TLD ) as a function of gamma-dosc . The hole volume, free volume fraction determined form orthopsitronium lifetime are found to be ?lamatically increase to large values , and then to minimum values as a function ofgamma-dose . The free - volume holes size is found to be 0.163nm’ and to have maximum of 0.166nm^ at the gamma-dose of 0.1 and 0.8 Gy, respectively-

Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Source ◽  
Lifetime Component ◽  
Positron Annihilation Lifetime ◽  
Long Lifetime

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

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