Precipitation in thin foils of al-4wt.% Cu alloy, 11. Growth kinetics of θ precipitates

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

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The Ordered Phase Formation in Ti-Al-Ga Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069193 ◽

1970 ◽

Vol 28 ◽

pp. 440-441

Author(s):

Shiro Fujishiro ◽

Harold L. Gegel

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Titanium Alloys ◽

Growth Kinetics ◽

Stoichiometric Composition ◽

Good Potential ◽

Alpha Titanium ◽

Cold Rolled ◽

Kinetics Of ◽

Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

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Influence of ion-milling on the T2 phase in Al-2.5%Li-2.5%Cu alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153415 ◽

1989 ◽

Vol 47 ◽

pp. 288-289

Author(s):

J. R. Reed ◽

D. J. Michel ◽

P. R. Howell

Keyword(s):

Thin Foil ◽

Icosahedral Symmetry ◽

Ion Milling ◽

Cu Alloy ◽

Thin Foils ◽

Heat Treated ◽

Aluminum Solid Solution ◽

In Situ Heating ◽

The Stability

The Al6Li3Cu (T2) phase, which exhibits five-fold or icosahedral symmetry, forms through solid state precipitation in dilute Al-Li-Cu alloys. Recent studies have reported that the T2 phase transforms either during TEM examination of thin foils or following ion-milling of thin foil specimens. Related studies have shown that T2 phase transforms to a microcrystalline array of the TB phase and a dilute aluminum solid solution during in-situ heating in the TEM. The purpose of this paper is to report results from an investigation of the influence of ion-milling on the stability of the T2 phase in dilute Al-Li-Cu alloy.The 3-mm diameter TEM disc specimens were prepared from a specially melted Al-2.5%Li-2.5%Cu alloy produced by conventional procedures. The TEM specimens were solution heat treated 1 h at 550°C and aged 1000 h at 190°C in air to develop the microstructure. The disc specimens were electropolished to achieve electron transparency using a 20:80 (vol. percent) nitric acid: methanol solution at -60°C.

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Growth Kinetics of Quantum Size ZnO Particles

MRS Proceedings ◽

10.1557/proc-536-347 ◽

1998 ◽

Vol 536 ◽

Author(s):

E. M. Wong ◽

J. E. Bonevich ◽

P. C. Searson

Keyword(s):

Growth Kinetics ◽

Ostwald Ripening ◽

Chemical Potential ◽

Colloidal Suspensions ◽

Green Emission ◽

Blue Shift ◽

Constant Current ◽

Mass Model ◽

Zno Particles ◽

Kinetics Of

AbstractColloidal chemistry techniques were used to synthesize ZnO particles in the nanometer size regime. The particle aging kinetics were determined by monitoring the optical band edge absorption and using the effective mass model to approximate the particle size as a function of time. We show that the growth kinetics of the ZnO particles follow the Lifshitz, Slyozov, Wagner theory for Ostwald ripening. In this model, the higher curvature and hence chemical potential of smaller particles provides a driving force for dissolution. The larger particles continue to grow by diffusion limited transport of species dissolved in solution. Thin films were fabricated by constant current electrophoretic deposition (EPD) of the ZnO quantum particles from these colloidal suspensions. All the films exhibited a blue shift relative to the characteristic green emission associated with bulk ZnO. The optical characteristics of the particles in the colloidal suspensions were found to translate to the films.

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