Morphological and Chemical Characteristics of Oxide Scales Formed on δ-Phase Plutonium Metal Alloys II: 2.0 at% Ga

2021 ◽  
pp. 153473
Author(s):  
Scott B. Donald ◽  
Brandon W. Chung
Keyword(s):  
Metal Alloys ◽  
Chemical Characteristics ◽  
Oxide Scales ◽  
Δ Phase ◽  
Plutonium Metal

scholarly journals Time-dependent Local and Average Structural Evolution of δ-phase 239Pu-Ga Alloys

MRS Advances ◽  
2016 ◽  
Vol 1 (44) ◽  
pp. 3019-3025 ◽  
Author(s):  
Alice I. Smith ◽  
Katharine L. Page ◽  
Joan E. Siewenie ◽  
Adrian S. Losko ◽  
Sven C. Vogel ◽  
...  
Keyword(s):  
Room Temperature ◽  
Structural Integrity ◽  
Ambient Pressure ◽  
Structural Evolution ◽  
Time Dependent ◽  
Pressure Chemical ◽  
Δ Phase ◽  
Scattering Study ◽  
Plutonium Metal ◽  
Neutron Total Scattering

ABSTRACT Plutonium metal is a very unusual element, exhibiting six allotropes at ambient pressure, between room temperature and its melting point, a complicated phase diagram, and a complex electronic structure. Many phases of plutonium metal are unstable with changes in temperature, pressure, chemical additions, or time. This strongly affects structure and properties, and becomes of high importance, particularly when considering effects on structural integrity over long periods of time [1]. This paper presents a time-dependent neutron total scattering study of the local and average structure of naturally aging δ-phase 239Pu-Ga alloys, together with preliminary results on neutron tomography characterization.

Microscopy and Microanalysis of Plutonium Metal, Alloys and Oxides or the Problem With Pu

2000 ◽  
Vol 6 (S2) ◽  
pp. 932-933
Author(s):  
Rollin E. Lakis ◽  
Bradford G. Storey ◽  
Charles C. Davis
Keyword(s):  
Atomic Number ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Pure Metal ◽  
University Of California ◽  
Metal Alloys ◽  
Naturally Occurring ◽  
The University ◽  
Crystalline Forms ◽  
Plutonium Metal

Plutonium (Pu), with an atomic number of 94, is the highest atomic number naturally occurring element on Earth. It is formed when naturally occurring Uranium 238 captures a neutron that can be created by spontaneous fission and alphaneutron reactions. The natural abundance of terrestrial Pu is very small; its concentration is about one part in 10 of the uranium present in naturally occurring uranium ores. The first man-made plutonium was produced at the University of California cyclotron and identified on February 23, 1941. Just a few months after the first Pu was produced it became clear how metallurgically complex this material is. Plutonium is known to have six allotropes (crystalline forms) at atmospheric pressure, between room temperature and 640°C, the melting point of the pure metal. This is the largest number of allotropes known for any element.

scholarly journals Electronically driven collapse of the bulk modulus inδ-plutonium

2020 ◽  
Vol 117 (9) ◽  
pp. 4480-4485 ◽  
Author(s):  
Neil Harrison
Keyword(s):  
Thermal Expansion ◽  
Hydrostatic Pressure ◽  
Bulk Modulus ◽  
Elastic Moduli ◽  
Elevated Temperatures ◽  
Thermally Activated ◽  
Δ Phase ◽  
Electronic Configurations ◽  
Plutonium Metal ◽  
Good Agreement

Plutonium metal exhibits an anomalously large softening of its bulk modulus at elevated temperatures that is made all the more extraordinary by the finding that it occurs irrespective of whether the thermal expansion coefficient is positive, negative, or zero—representing an extreme departure from conventional Grüneisen scaling. We show here that the cause of this softening is the compressibility of plutonium’s thermally excited electronic configurations, which has thus far not been considered in thermodynamic models. We show that when compressible electronic configurations are thermally activated, they invariably give rise to a softening of the bulk modulus regardless of the sign of their contribution to the thermal expansion. The electronically driven softening of the bulk modulus is shown to be in good agreement with elastic moduli measurements performed on the gallium-stabilized δ phase of plutonium over a range of temperatures and compositions and is shown to grow rapidly at small concentrations of gallium and at high temperatures, where it becomes extremely sensitive to hydrostatic pressure.

The Microstructure of Nickel Oxide Scales

1981 ◽  
Vol 39 ◽  
pp. 86-87
Author(s):  
M. T. Tinker ◽  
L. W. Hobbs
Keyword(s):  
Electron Microscopy ◽  
Nickel Oxide ◽  
Ion Beam ◽  
Oxide Scales ◽  
Nickel Substrate ◽  
Outward Diffusion ◽  
Transmission Electron ◽  
Nickel Substrates ◽  
Nickel Base ◽  
Technological Interest

There is considerable technological interest in oxidation of nickel because of the importance of nickel-base superalloys in high-temperature oxidizing environments. NiO scales on nickel grow classically, by outward diffusion of nickel through the scale, and are among the most studied of oxidation systems. We report here the first extensive characterization by transmission electron microscopy of nickel oxide scales formed on bulk nickel substrates and sectioned both parallel and transversely to the Ni/NiO interface.Electrochemically-polished nickel sheet of 99.995% purity was oxidized at 1273 K in 0.1 MPa oxygen partial pressure for times between 5 s and 25 h. Parallel sections were produced using a combination of electropolishing of the nickel substrate and ion-beam thinning of the scale to any desired depth in the scale. Transverse sections were prepared by encasing stacked strips of oxidized nickel sheet in epoxy resin, sectioning transversely and ion-beam thinning until thin area spanning one or more interfaces was obtained.

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