Synchrotron X-ray radiation diffraction studies of thermal expansion, free volume change and glass transition phenomenon in Cu-based glassy and nanocomposite alloys on heating

In a preparatory study of structural relaxations and plastic flow in a two-dimensional idealized atomic glass, the process of melting and quenching through a glass transition has been studied by computer simulation using a molecular dynamics model. In this model, the transition from a solid to a melt was observed to take place when liquid-like structural elements composed of dipoles of five- and seven-sided Voronoi polygons percolate through the two-dimensional structure of distorted hexagons in the form of strings. Such dipoles constitute discrete elements of excess free volume within which liquid like behaviour is established in the sense of reduced cohesion or local elastic moduli. Upon quenching the melt, the percolation condition of liquid-like regions is retained for under-cooled melts between the melting point and a glass transition temperature below which the percolation condition is broken and the thermal expansion is sharply reduced. The simulation that has used empirical pair potentials characteristic of Cu and Zr has substantially underpredicted the melting and glass transition temperatures and overpredicted the thermal expansion of C u x Zr 1-x type glasses. These defects of the model can be partly attributed to the two-dimensional nature of the material, which stores larger concentrations of free volume than a corresponding three-dimensional material. In spite of these quantitative shortcomings, the model gives valuable insight into the topological features of the local atomic configurations at melting and upon vitrification.

Download Full-text

On the applicability of a free volume concept to glass-transition phenomenon in microheterogeneous polymeric systems

Journal of Polymer Science Polymer Symposia ◽

10.1002/polc.5070420235 ◽

2007 ◽

Vol 42 (2) ◽

pp. 855-857 ◽

Cited By ~ 2

Author(s):

Yu. S. Lipatov

Keyword(s):

Glass Transition ◽

Free Volume ◽

Polymeric Systems ◽

Transition Phenomenon

Download Full-text

Glass transition, thermal expansion and relaxation in B2O3 glass measured by time-resolved X-ray diffraction

Journal of Non-Crystalline Solids ◽

10.1016/j.jnoncrysol.2007.07.043 ◽

2008 ◽

Vol 354 (2-9) ◽

pp. 325-327 ◽

Cited By ~ 6

Author(s):

W.J. Botta ◽

K. Ota ◽

K. Hajlaoui ◽

G. Vaughan ◽

A.R. Yavari

Keyword(s):

Thermal Expansion ◽

Glass Transition ◽

X Ray Diffraction ◽

Time Resolved ◽

X Ray ◽

B2o3 Glass

Download Full-text

Thermal expansion of corium prepared from UO2 and Zircaloy-2

MRS Proceedings ◽

10.1557/opl.2012.1004 ◽

2012 ◽

Vol 1444 ◽

Cited By ~ 1

Author(s):

Shun Hirooka ◽

Masatoshi Akashi ◽

Teppei Uchida ◽

Kyoichi Morimoto ◽

Masato Kato

Keyword(s):

Thermal Expansion ◽

Phase Transformation ◽

Volume Change ◽

Thermal Vibration ◽

X Ray Diffraction ◽

Volume Changes ◽

X Ray ◽

Content Ratio ◽

Diffraction Patterns ◽

Ar Gas

ABSTRACTIn this study, sintered pellets were prepared from Zircaloy-2 oxide and UO2 as a parameter of content ratio (Zr contents were 0, 24.3, 49.0, 73.4, and 97.9 at% in metal). The sintered pellets were heated in 5%H2/Ar gas. UO2 pellets underwent simple thermal expansion caused by thermal vibration while Zircaloy-2 oxide pellets underwent thermal expansion and volume change with phase transformation. Finally, the 24.3, 49.0, and 73.5 at%Zr-UO2 pellet specimens showed both phenomena. However, phase transformation temperatures were lower than that of Zircaloy-2 oxide, and volume changes were much smaller. X-ray diffraction patterns obtained after thermal expansion measurements showed that the 24.3 at%Zr-UO2 specimen contained tetragonal and cubic (Zr, U)O2 while the 73.5 at%Zr-UO2 specimen contained mainly monoclinic ZrO2.

Download Full-text

Glass Transition Tg, and Quenched-In Free Volume in Bulk Metallic Glasses Measured by X-Ray Diffraction

Journal of Metastable and Nanocrystalline Materials ◽

10.4028/www.scientific.net/jmnm.20-21.23 ◽

2004 ◽

Vol 20-21 ◽

pp. 23-28 ◽

Cited By ~ 2

Author(s):

Alain Reza Yavari ◽

A. Le Moulec ◽

N. Nishiyama ◽

Akihisa Inoue ◽

G. Vaughan ◽

...

Keyword(s):

Glass Transition ◽

Free Volume ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

X Ray Diffraction ◽

X Ray

Download Full-text

Quenched-in Free Volume Vf, Deformation-induced Free Volume, the Glass Transition Tg and Thermal Expansion in glassy ZrNbCuNiAl measured by Time-resolved Diffraction in Transmission

MRS Proceedings ◽

10.1557/proc-806-mm3.5 ◽

2003 ◽

Vol 806 ◽

Cited By ~ 3

Author(s):

A. R. Yavari ◽

M. Tonegaru ◽

N. Lupu ◽

A Inoue ◽

E. Matsubara ◽

...

Keyword(s):

Heat Treatment ◽

Glass Transition ◽

Free Volume ◽

Supercooled Liquid ◽

Supercooled Liquid Region ◽

Liquid Region ◽

Time Resolved ◽

X Ray ◽

Excess Free Volume ◽

Rapidly Solidified

ABSTRACTUsing high-precision X-ray dilatometry, we have succeeded in directly measuring excess quenched-in free-volume Vf in metallic glasses. The method was applied to the very easy glass forming Zr57Nb5Cu15.4Ni12.6Al10 (Vit 106). The annealing out of the order of 0.5% free volume was observed during heat treatment of rapidly solidified glassy ribbons. Excess free volume was also generated by heavy deformation and observed to anneal out during heat treatment. Once the excess free volume anneals out, the glass transition Tg appears clearly as a break in the x-ray dilatation curves as the glass goes over to the supercooled liquid region prior to crystallization at Tx.

Download Full-text

Viscoelastic Properties of Polypropylene Reinforced with Mica in and Transition Zones

International Journal of Polymer Science ◽

10.1155/2011/427095 ◽

2011 ◽

Vol 2011 ◽

pp. 1-5 ◽

Cited By ~ 8

Author(s):

S. Farzaneh ◽

A. Tcharkhtchi

Keyword(s):

Thermal Expansion ◽

Glass Transition ◽

Free Volume ◽

Viscoelastic Properties ◽

Volume Fraction ◽

Loss Modulus ◽

Glassy State ◽

Transition Zones ◽

Wlf Equation ◽

Free Volume Fraction

The viscoelastic properties of mica-reinforced polypropylene (PP) was studied in temperature range between −30°C and 120°C. WLF equation permits determining the free volume fraction in and transitions regions. It was shown that the value of this parameter is lower for transition, indicating that the free volume and thermal expansion of region is more than that of region. At a 40% loading level, it was shown that the storage and loss modulus of mica-filled PP increases dramatically (in comparison with the pure polypropylene). The relative modulus does not change significantly at glassy state but it increases for the temperature higher than . It was also shown that mica does not affect the glass transition temperature but results in an increase in transition.

Download Full-text