Shape of α'R. Zn Rich Precipitatesin Al Zn Alloys. Effect of an Uniaxial Stress on Decomposition

1982 ◽  
Vol 21 ◽  
Author(s):  
F. Livet
Keyword(s):  
Cross Section ◽  
Small Angle ◽  
Strain Field ◽  
Small Angle Neutron Scattering ◽  
Uniaxial Stress ◽  
Mean Value ◽  
Initial Composition ◽  
The Matrix ◽  
C Value ◽  
Zn Alloys

ABSTRACTDuring the first stages of decomposition of Al Zn alloys, spherical GP zones are observed. On further ageing of the samples, the precipitates have the shape of flat ellipsoids, the small axis of which are in the various <111> directions.We have followed such an evolution in single crystals by small angle neutron scattering. From the asymptotic behavior of the cross section, we have calculated the size (c) of the small semiaxis of the ellipsoids. We show that c is almost independent of the initial composition of our samples (5.3, 6.8, 12.1 at Zn %), independent of the other dimensions of the “α'R” precipitates and very sharply distributed around its mean value (c = 24.5 ± 2 Å at 293°C).The strain field in the matrix must clearly be involved in the limitation of the c value. We have studied the effect of a uniaxial [110] compressive stress applied during ageing. Neutron small angle experiments, carried on an Al-12.1 at % Zn single crystal show that the c value remains the same. The scattering in the [111] and [11] directions is much higher than in the [111] and [111] directions. This is mainly due to the fact that the stress favors the number of [111] and [111] type of α'R precipitates.

An in situ small angle neutron scattering study of expanded graphite under a uniaxial stress

Carbon ◽  
2013 ◽  
Vol 57 ◽  
pp. 460-469 ◽  
Author(s):  
Félix Balima ◽  
Vittoria Pischedda ◽  
Sylvie Le Floch ◽  
Annie Brûlet ◽  
Peter Lindner ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Expanded Graphite ◽  
Uniaxial Stress ◽  
Scattering Study ◽  
Neutron Scattering Study

scholarly journals Magnetic field dependent small-angle neutron scattering on a Co nanorod array: evidence for intraparticle spin misalignment

2014 ◽  
Vol 47 (3) ◽  
pp. 992-998 ◽  
Author(s):  
A. Günther ◽  
J.-P. Bick ◽  
P. Szary ◽  
D. Honecker ◽  
C. D. Dewhurst ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Scattering ◽  
Cross Section ◽  
Field Dependence ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Strong Field ◽  
Structural Parameters ◽  
Nanorod Array ◽  
Field Dependent

The structural and magnetic properties of a cobalt nanorod array have been studied by means of magnetic field dependent small-angle neutron scattering (SANS). Measurement of the unpolarized SANS cross section dΣ/dΩ of the saturated sample in the two scattering geometries where the applied magnetic fieldHis either perpendicular or parallel to the wavevectorkiof the incoming neutron beam allows one to separate nuclear from magnetic SANS, without employing the usual sector-averaging procedure. The analysis of the SANS data in the saturated state provides structural parameters (rod radius and centre-to-centre distance) that are in good agreement with results from electron microscopy. Between saturation and the coercive field, a strong field dependence of dΣ/dΩ is observed (in both geometries), which cannot be explained using the conventional expression of the magnetic SANS cross section of magnetic nanoparticles in a homogeneous nonmagnetic matrix. The origin of the strong field dependence of dΣ/dΩ is believed to be related to intradomain spin misalignment, due to magnetocrystalline and magnetoelastic anisotropies and magnetostatic stray fields.

Elastic Modulus Measurements in Plasma Sprayed Deposits

1997 ◽  
Author(s):  
J.S. Wallace ◽  
J. Ilavsky
Keyword(s):  
Elastic Modulus ◽  
Surface Area ◽  
Cross Section ◽  
Small Angle ◽  
Zirconium Oxide ◽  
Small Angle Neutron Scattering ◽  
Small Areas ◽  
Scattering Measurements ◽  
Spherical Ball ◽  
Plasma Sprayed

Abstract A technique has been developed to characterize the elastic modulus of zirconium oxide - 8 % yttrium oxide plasma sprayed deposits. A commercial hardness indenter has been modified to record load - displacement as a spherical ball is elastically loaded onto the surface of the material to be measured. The resulting data are used to calculate the elastic modulus. Since the loads used are in the elastic region, the technique is, in theory, nondestructive. Relatively small areas of the material, approximately 50 μm in diameter, are sampled by the indenter, allowing local mapping of elastic modulus variations throughout the deposit. Using this technique, elastic modulus variations have been measured through the thickness of the deposit. Also, different moduli were measured in the cross-section and through the thickness and these differences are correlated with the microstructure. Finally, significant increases in elastic modulus have been found in samples annealed for 2.5 h at 1100°C. These changes have been correlated with small angle neutron scattering measurements of void surface area.

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.

Double-Bent-Crystal Small-Angle Neutron Scattering Setting and its Applications

1997 ◽  
Vol 30 (5) ◽  
pp. 844-848 ◽  
Author(s):  
P. Strunz ◽  
J. Saroun ◽  
P. Mikula ◽  
P. Lukás ◽  
F. Eichhorn
Keyword(s):  
Data Analysis ◽  
Neutron Scattering ◽  
Cross Section ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Indirect Method ◽  
Data Evaluation ◽  
Measured Intensity ◽  
Bent Crystal

Theoretical relations for optimum adjustments of two arrangements of a double-bent-crystal (DBC) small-angle neutron scattering (SANS) diffractometer are discussed. Results of several experiments demonstrate the applicability of DBC SANS in the investigation of some technologically important materials in the range of scattering-vector sizes 0.0002–0.02 Å−1. Formulas derived for data analysis, which describe the transformation of the SANS cross section to the measured intensity, indicate that water calibration is not required and that the indirect method of data evaluation is the most appropriate.

Absolute Calibration of Small-Angle Neutron Scattering Data of a Double-Crystal Diffractometer

1997 ◽  
Vol 30 (5) ◽  
pp. 857-861 ◽  
Author(s):  
F. Carsughi ◽  
D. Bellmann ◽  
J. Kulda ◽  
M. Magnani ◽  
M. Stefanon
Keyword(s):  
Neutron Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Scattering Data ◽  
Absolute Calibration ◽  
Double Crystal ◽  
Similar Materials ◽  
Double Crystal Diffractometer

Small-angle neutron scattering (SANS) experiments generally provide the absolute SANS cross sections and this allows quantitative results to be obtained; however, data collected at double-crystal diffractometers are frequently not normalized to absolute cross sections and they are used only for qualitative analysis. In point-geometry diffractometers, the normalization is done by comparing the scattered intensities to those of samples of known cross sections or by measuring the direct-beam intensity; in the double-crystal diffractometer, the incident flux information is contained in the rocking curve measured without a sample and this feature can therefore be used to normalize the scattered intensities to the SANS cross sections. A sample of thickness 1 mm of the Ni-based superalloy UDIMET 520 was analyzed at a double-crystal diffractometer; the SANS cross section obtained by the proposed procedure compares well with the SANS cross section found for similar materials by using conventional point-geometry diffractometers and calibrated by light water.

Dissolution and Growth of Precipitates Under Electron Irradiation in an Al-11.8 at % Zn Alloy by Small Angle Neutron Scattering.

1994 ◽  
Vol 376 ◽  
Author(s):  
M.R. Baig
Keyword(s):  
Neutron Scattering ◽  
Electron Irradiation ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Diffusion Mechanism ◽  
Precipitate Size ◽  
Low Doses ◽  
Radiation Enhanced Diffusion ◽  
The Matrix ◽  
Zn Alloy

ABSTRACTDissolution and growth of precipitates in a room temperature aged Al-11.8 at % Zn alloy have been studied under electron irradiation using small angle neutron scattering (SANS). A series of electron irradiations were performed on each sample and SANS measurements were made on each irradiation. In general for low doses the results show an initial decrease in the magnitude of the scattering, but associated with an increase in the precipitate size. This is followed on prolonged irradiation by an increase in the magnitude of the scattering with a continued increase in precipitate size. It is believed, that at low doses some precipitate grow in size but others may dissolve in the matrix, which then becomes supersaturated. With the enhanced rate of diffusion as a result of the irradiation, the remaining precipitates grow rapidly. As the supersaturation reduces, a coarsening mechanism takes over, via a radiation enhanced diffusion mechanism.

scholarly journals Structural Aspects of Stabilization of Magnetic Fluids by Mono-Carboxylic Acids

2009 ◽  
Vol 152-153 ◽  
pp. 182-185 ◽  
Author(s):  
M.V. Avdeev ◽  
Doina Bica ◽  
L. Vekas ◽  
V. L. Aksenov ◽  
A.V. Feoktystov ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Size Distribution ◽  
Carboxylic Acids ◽  
Magnetite Nanoparticles ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Magnetic Fluids ◽  
Mean Value ◽  
Chain Lengths ◽  
Structural Aspects

The structure of magnetic fluids (magnetite in decahydronaphtalene) stabilized with saturated mono-carboxylic acids of different chain lengths (lauric, myristic, palmitic and stearic acids) is studied by means of magnetization analysis and small-angle neutron scattering. It is shown that magnetite nanoparticles are dispersed in the carrier approximately with the same size distribution whose mean value and width are significantly less as compared to the classical stabilization with non-saturated oleic acid. The found thickness of the surfactant shell around magnetite is analyzed with respect to stabilizing properties of mono-carboxylic acids.

The use of multiple-scattering data to enhance small-angle neutron scattering experiments

1999 ◽  
Vol 55 (3) ◽  
pp. 500-507 ◽  
Author(s):  
T. M. Sabine ◽  
W. K. Bertram
Keyword(s):  
Neutron Scattering ◽  
Multiple Scattering ◽  
Cross Section ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Scattering Data ◽  
Specimen Thickness ◽  
Neutron Wavelength ◽  
The Cross ◽  
Small Angle Region

Multiple scattering of neutrons by the inhomogeneities responsible for small-angle neutron scattering (SANS) during the passage of the beam through the specimen can be used to provide valuable information about the shape of the objects and the absolute value of the contrast between the scattering particles and the matrix. The neutrons emerging from the specimen are classified into those that have been scattered n times. The index n ranges from zero to infinity. The remnant of the incident beam is the group of neutrons for which n equals zero. Each group contributes separately to the scattering profile. The small-angle scattering cross section is independent of the neutron wavelength for n = 1 only. Thus collection of data as a function of specimen thickness and of neutron wavelength will provide a number of different profiles describing the same physical situation. Simultaneous analysis of these profiles provides absolute values of the cross section for scattering into the small-angle region and of the cross section for removal of neutrons from the small-angle region. So that the method can be used generally, a profile function that is a very good approximation to those in the literature is introduced. The implications for time-of-flight SANS are discussed.

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