scholarly journals Small Angle Neutron Scattering from Nanocrystalline Pd and Cu Compacted at Elevated Temperatures

1994 ◽  
Vol 351 ◽  
Author(s):  
P.G. Sanders ◽  
J.R. Weertman ◽  
J.G. Barker ◽  
R.W. Siegel
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Prompt Gamma Activation Analysis ◽  
Impurity Level ◽  
Prompt Gamma ◽  
Gas Condensation ◽  
Hardness Increase

ABSTRACTNanocrystalline (n-) Cu and Pd, prepared by inert gas condensation (IGC) and in situ room temperature (RT) and elevated temperature (warm) compactions, have been studied by small angle neutron scattering (SANS). Previous work [1] on room temperature compacted and subsequently annealed n-Pd seemed to show that all the scattering could be accounted for by a distribution of pores. Analysis of more extensive SANS measurements, together with the results of prompt gamma activation analysis (PGAA), indicates that the SANS can be explained by the presence of pores and hydrogen. Warm compaction reduces the hydrogen impurity level, while increasing the bulk density and decreasing the pore size. This can lead to a dramatic hardness increase in these materials.

scholarly journals Structure of nanocrystalline palladium and copper studied by small angle neutron scattering

1996 ◽  
Vol 11 (12) ◽  
pp. 3110-3120 ◽  
Author(s):  
P. G. Sanders ◽  
J. R. Weertman ◽  
J. G. Barker
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Room Temperature ◽  
Prompt Gamma Activation Analysis ◽  
Prompt Gamma ◽  
Number Density ◽  
Warm Compaction ◽  
Gas Condensation ◽  
Micrometer Size

The structure of nanocrystalline palladium and copper, made by inert gas condensation and compaction, was studied using small angle neutron scattering (SANS), optical microscopy, and scanning electron microscopy. The effects of annealing and warm compaction were also examined with these techniques. The SANS results were interpreted using a maximum entropy routine, combined with knowledge of the Archimedes density and hydrogen concentration determined by prompt gamma activation analysis (PGAA). Similar hydrogen concentrations were detected by SANS and PGAA. This hydrogen content, which was approximately 5 at. % in samples compacted at room temperature, was reduced by both annealing and warm compaction. Defects in several size classes were observed, including missing grain pores (≈1−50 nm diameter) and defects of micrometer size. Warm compaction produced a lower number density of pores in nanocrystalline palladium, which led to increased density. The observed structure was correlated with Vickers microhardness and fracture surface morphology.

scholarly journals Small Angle Neutron Scattering from Nanophase Titanium As A Function of Oxidation

1988 ◽  
Vol 132 ◽  
Author(s):  
J. A. Eastman ◽  
J. E. Epperson ◽  
H. Hahn ◽  
T. E. Klippert ◽  
A. Narayanasamy ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Scattering Length ◽  
Contrast Variation ◽  
Gas Condensation ◽  
Pressure Oxygen ◽  
Scattering Centers ◽  
Scattering Lengths ◽  
Contrast Matching

ABSTRACTNanophase titanium, prepared by the gas-condensation method both as aggregated powder and in lightly compacted discs, has been studied by conventional small angle neutron scattering, and by use of contrast variation methods. The contrast has been changed (a), isotopically, by means of deuterated/protonated solvents distilled into the specimen and (b) by progressive incremental oxidation of the Ti particles using fixed doses of low-pressure oxygen. It was shown that some evolution of the small angle pattern for lightly compacted nanophase Ti occurred over a period of several months at 300 K. Contrast matching by external solvent works well and has allowed the scattering lengths of oxidized and unoxidized specimens to be followed. The results imply that the scattering from metal and oxide can be separated under suitable conditions. The partial oxidation experiments indicate that there is both a fast and slow oxidation at 300 K. Also, during slow oxidation, high scattering length density scattering centers were formed whose number increased, but whose size remained the same at about 2 nm; these centers are tentatively assumed to be TiO2.

Sans Measurement of Deuterium-Dislocation Correlation in Palladium

1989 ◽  
Vol 166 ◽  
Author(s):  
Brent J. Heuser ◽  
G.C. Summerfield ◽  
J.S. King ◽  
J.E. Epperson
Keyword(s):  
Neutron Scattering ◽  
Cross Section ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Room Temperature ◽  
Gas Pressure ◽  
Solution Phase ◽  
Pressure Cell ◽  
Scattering Cross ◽  
The Difference

ABSTRACTSmall angle neutron scattering (SANS) measurements have been made on deformed polycrystal palladium samples with and without deuterium dissolved in the solution phase (a) at room temperature. Concentrations were held constant during SANS experiments by an equilibrium gas pressure cell. The difference scattering cross section for the same sample with and without deuterium loading has a 1/Q behavior (Q=4Φ/λsinθ/2) at intermediate values of Q. At very low values of Q the dependence is much stronger than 1/Q. The 1/Q behavior is attributed to deuterium trapping close to long dislocation cores forming rod-like scattering structures.

Probing the Room Temperature Spatial Distribution of Hydrogen in Nanoporous Carbon by Use of Small-Angle Neutron Scattering

2010 ◽  
Vol 114 (47) ◽  
pp. 19895-19900 ◽  
Author(s):  
Cheng-Si Tsao ◽  
Mingda Li ◽  
Yang Zhang ◽  
Juscelino B. Leao ◽  
Wei-Shan Chiang ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Room Temperature ◽  
Nanoporous Carbon

Small-angle neutron scattering and phase separation in alloys

2003 ◽  
Vol 218 (2) ◽  
Author(s):  
G. Kostorz
Keyword(s):  
Phase Separation ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Elevated Temperatures ◽  
Hexagonal Phase ◽  
Scattering Data ◽  
Two Phase ◽  
Basic Principles ◽  
Two Stages

AbstractThe basic principles of small-angle neutron scattering and the two-phase model, frequently used for the interpretation of scattering data, are presented. Some studies on phase separation in alloy single crystals serve to illustrate the possibilities of the method. Small-angle neutron scattering of Ni-rich Ni—Ti studied during ageing at elevated temperatures indicates a complex sequence of phases during decomposition, involving two stages of metastable coherent precipitation preceding the formation of the stable hexagonal phase.

Dependence of small-angle neutron scattering contrast on the difference in thermal expansions of phases in two-phase alloys

2009 ◽  
Vol 42 (6) ◽  
pp. 981-989 ◽  
Author(s):  
Pavel Strunz ◽  
Ralph Gilles ◽  
Debashis Mukherji ◽  
Michael Hofmann ◽  
Dominique del Genovese ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Integral Intensity ◽  
Two Phase ◽  
The Difference ◽  
The Individual

Theoretical expressions describing small-angle neutron scattering (SANS) contrast dependence on temperature in the region where no phase-composition changes occur were derived for two-phase Ni superalloys. The theory is based on the difference in thermal expansion of the two primary phases, γ and γ′. The simulations show that the scattering contrast temperature evolution is significant enough to be considered inin situSANS experiments with superalloys at elevated temperatures. The simulations performed show that the magnitude of the scattering contrast at room temperature is firmly connected with the particular shape of the scattering contrast temperature dependence. This fact can be used for determination of the scattering contrast without a knowledge of the compositions of the individual phases. The theoretical expressions derived for scattering contrast were proven experimentally on an Ni–Fe-base alloy, DT706. The evolution of lattice parameters of both the matrix and the precipitate phases was obtained from anin situwide-angle neutron diffraction experiment. The theoretical scattering contrast dependence was then successfully fitted to the measured SANS integral intensity.

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