Characterization of the Structure of a Novel Refractory Alloy Glass – Ni60Nb37Sn3

2002 ◽  
Vol 754 ◽  
Author(s):  
Michelle L. Tokarz ◽  
Matt Daniels ◽  
John C. Bilello ◽  
Zofia Rek
Keyword(s):  
Radial Distribution ◽  
Metallic Glasses ◽  
Hard Sphere ◽  
Nearest Neighbor ◽  
Refractory Alloy ◽  
Scattering Data ◽  
Distribution Analysis ◽  
X Ray ◽  
Nearest Neighbor Distances

ABSTRACTBulk forms of Refractory Alloy Glasses (RAGs) of the composition Ni60Nb37Sn3 have recently been synthesized as part of a larger project for potential use in structural applications. Modeling efforts of such metallic glasses have traditionally involved the use of hard sphere models without regard to potential electron density fluctuations of individual components. X-ray characterization of these materials (in both reflection and transmission modes) provided scattering data necessary for subsequent radial distribution analysis, which gives structural information such as nearest neighbor distances and packing characteristics. A model radial distribution function (RDF) was constructed based upon a hard sphere space filling assumption and compared to the RDFs obtained from experimental scattering data. The experimental RDFs showed no difference from the model RDF within the limit of experimental error, with regard to nearest neighbor distances and coordination numbers of the first two nearest neighbors.Additionally, transmission mode scattering experiments from a white beam x-ray source (E = 2 to 40 keV) demonstrated a through thickness amorphous structure of 2mm thick samples. Converted line profiles from the two-dimensional diffraction patterns from this experiment also showed agreement with reflection mode experiments. Samples of Vitreloy-106 (Zr57Nb5Cu15.4Ni12.6Al10) of similar thicknesses were used as standards due to the well-known behavior of this particular class of metallic glasses.

On the Structural Characterization of a Series of Novel Ni-Nb-Sn Refractory Alloy Glasses

2003 ◽  
Vol 806 ◽  
Author(s):  
Michelle L. Tokarz ◽  
John C. Bilello
Keyword(s):  
Radial Distribution ◽  
Hard Sphere ◽  
Alloy Composition ◽  
Distribution Functions ◽  
Refractory Alloy ◽  
Distribution Analysis ◽  
X Ray Diffraction ◽  
Characterization Methods ◽  
X Ray ◽  
Hard Sphere Models

ABSTRACTRecently refractory alloy glasses of varying Ni, Nb and Sn concentrations were prepared and studied via several characterization methods, including x-ray diffraction via standard lab and synchrotron radiation sources, SEM, and other complementary techniques. A comparison between x-ray diffraction results obtained from synchrotron sources vs. standard lab sources shows the necessity of a low-divergence source in order to distinguish nanoscale crystallites present within an amorphous matrix. The divergence of both sources was determined by comparing the diffraction patterns of a LaB6standard and noting the deviation from ideal or theoretical Bragg peaks. The crystallites in these glasses comprised between 0 and 7.5 percent by volume, depending upon the specific composition. The results presented here also show a very good sample-to-sample consistency for any given alloy composition. While x-ray diffraction results give information about the average structure, SEM was also performed to understand aspects of individual crystallite size and distribution. By studying results of varying alloy concentrations, it is seen that a very small composition range exists for near-perfect glass formers (as defined by a near zero percentage crystallinity). Radial distribution analysis was also performed for each composition and compared to hard sphere models for each alloy composition. This analysis indicated the presence of intermediate range order beyond the first nearest neighbors as indicated by the divergence of the experimental reduced radial distribution functions from that predicted by the accompanying hard sphere models.

Exafs and Exelfs Study of the Structure of Pd-Ni-P Bulk Metallic Glasses

2000 ◽  
Vol 644 ◽  
Author(s):  
Faisal M. Alamgir ◽  
Himanshu Jain ◽  
David B. Williams ◽  
Gilles Hug ◽  
Ricardo B. Schwarz ◽  
...  
Keyword(s):  
Fine Structure ◽  
Metallic Glasses ◽  
Nearest Neighbor ◽  
Bulk Metallic Glasses ◽  
Weighted Average ◽  
Ternary Alloys ◽  
X Ray ◽  
Efficient Packing ◽  
X Ray Absorption ◽  
Nearest Neighbor Distances

AbstractWe have explored the short-range order around all three constituent atoms in (Pd-Ni)80P20 bulk metallic glasses (BMGs), a system that is a prototype for a whole class of BMG formers containing 80% transition metal and 20% metalloid. We have examined the changes in the nearest neighbor environments around the transition metals in (Pd-Ni)80P20 glasses using extended X-ray absorption fine structure (EXAFS) in comparison to their binary counterparts. We have done similar studies around the coordination of P using extended energy loss fine structure (EXELFS). The environment around the all the atoms in Pd60Ni20P20 and Pd30Ni50P20are very similar to those of the binary phosphides at the ends of the composition range. However, the (Pd-Ni)80P20 glasses are not simply solid solutions of the phases. The nearest neighbor distances of the metals are reduced in the ternary alloys with respect to those of the binary phosphides. The best glass former in this series, Pd40Ni40P20 is nearly isostructural to Pd30Ni50P20 but shows shorter distances at the 2nd and 3rd coordination shells, which we believe is due to more efficient packing in this glass. The metal environments in Pd40Ni40P20, on the other hand, are better described by a weighted average of those of Pd30Ni50P20 and Pd60Ni20P20.

The analytical evaluation of the first-order density cluster integral in the radial distribution function

1970 ◽  
Vol 320 (1542) ◽  
pp. 323-348 ◽  
Keyword(s):  
Hard Sphere ◽  
Virial Coefficient ◽  
Second Virial Coefficient ◽  
Scattering Data ◽  
X Ray ◽  
Lennard Jones ◽  
X Ray Scattering ◽  
Cluster Integrals ◽  
Square Well ◽  
Three Body

It is shown how to evaluate the two-body, and three-body cluster integrals, ɳ 3 , ɳ * 3 , β 3 , β * 3 (equations (1.1) to (1.4)) for the hard-sphere, square-well and Lennard-Jones ( v :½ v ) potentials; the three-body potential used is the dipole-dipole-dipole potential of Axilrod & Teller. Explicit expressions are presented for the integrals ɳ * 3 , β * 3 using the above potentials; in the case of the first integral, its values for both small and large values of the separation distance are also given, for the Lennard-Jones ( v :½ v ) potential. Similar considerations have been carried out for ɳ 3 and β 3 , except that explicit expressions for the hard-sphere, and square-well potentials are not given, since these had been done before by other authors. The intermediate expressions for the four cluster integrals, are in terms of single integrals, and such expressions are valid for any continuous potential. Numerical results based on some of the expressions in this paper are compared with the results of numerical evaluation of the above integrals by other authors, and the agreement is seen to be good. Making use of the Mikolaj-Pings relation, the above results are used to obtain relationships between the second virial coefficient, and X-ray scattering data, as well as a means of deducing the pair potential at large separations, directly from a knowledge of X-ray scattering data, and the second virial coefficient.

Characterization of structures from X-ray scattering data using genetic algorithms

1999 ◽  
Vol 357 (1761) ◽  
pp. 2827-2848 ◽  
Author(s):  
Matthew Wormington ◽  
Charles Panaccione ◽  
Kevin M. Matney ◽  
D. Keith Bowen
Keyword(s):  
Genetic Algorithms ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals On the Use of a Modified Radial Distribution Analysis for Indexing Powder Patterns

1962 ◽  
Vol 6 ◽  
pp. 18-24
Author(s):  
A. F. Berndt
Keyword(s):  
Radial Distribution ◽  
Unit Cell ◽  
Powder Pattern ◽  
Distribution Analysis ◽  
Trial And Error ◽  
Orthorhombic Unit Cell ◽  
X Ray ◽  
Tetragonal Unit Cell ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

AbstractA modification of the theory of X-ray radial distribution analysis is presented. This modification can serve as a guide to the values of the unit cell dimensions and may be useful in indexing powder patterns of unknown structures, although the use of trial and error methods is not eliminated. This technique is shown to give consistent results with known structures and is applied to the indexing of powder patterns of Pu3Ru and Pu5Ru3. The powder pattern of Pu3Ru can be indexed on the basis of an orthorhombic unit cell with a0 = 6.216 Å, b0 = 6.924 Å, and c0 = 8.093 Å, and Pu5Ru3 on the basis of a tetragonal unit cell with a0 = 8.092 Å and c0 - 10.023 Å.

Structure and Electrical Conductivity of Amorphous ZnTe and CdTe

1972 ◽  
Vol 50 (20) ◽  
pp. 2512-2519 ◽  
Author(s):  
H. M. Brown ◽  
D. E. Brodie
Keyword(s):  
Electrical Conductivity ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Annealing Temperature ◽  
Nearest Neighbor ◽  
Electron Diffraction Data ◽  
Distribution Analysis ◽  
Amorphous Films ◽  
Higher Temperature ◽  
Nearest Neighbor Distances

Amorphous films of ZnTe and CdTe have been prepared and studied. Electron microscope studies have shown the films to have crystallite diameters of about 25 Å. A radial distribution analysis of the electron diffraction data for ZnTe shows that the first and second nearest neighbor distances are the same as in the bulk crystal and they are consistent with the basic crystalline tetrahedral units being retained in the amorphous phase.The electrical conductivity of ZnTe films has a temperature dependence which varies with the annealing temperature. This is explained by assuming that the extrinsic range is caused by acceptor-like dangling bonds which anneal at lower temperatures (100 °C), but that at higher temperature anneals (400 °C) the film re-crystallizes.

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