scholarly journals Simple Metal and Binary Alloy Phases Based on the fcc Structure: Electronic Origin of Distortions, Superlattices and Vacancies

2017 ◽  
Author(s):  
Valentina F. Degtyareva ◽  
Nataliya S. Afonikova
Keyword(s):  
Binary Alloy ◽  
Complex Structures ◽  
Face Centered Cubic ◽  
Energy Contribution ◽  
Simple Metal ◽  
Fermi Sphere ◽  
The Face ◽  
Face Centered ◽  
The Stability ◽  
Fcc Structure

Crystal structures of simple metals and binary alloy phases based on the face-centered cubic (fcc) structure are analyzed within the model of Fermi sphere – Brillouin zone interactions to understand the stability of original cubic structure and derivative structures with distortions, superlattices and vacancies. Examination of the Brillouin-Jones configuration in relation to the nearly-free electron Fermi sphere for several representative phases reveals significance of the electron energy contribution to the phase stability. Representation of complex structures in the reciprocal space clarifies their relationship to the basic cubic cell.

scholarly journals Pt–Ti Alloy Coatings Deposited by DC Magnetron Sputtering: A Potential Current Collector at High Temperature

Coatings ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 224 ◽  
Author(s):  
Pascal Briois ◽  
Mohammad Arab-Pour-Yazdi ◽  
Nicolas Martin ◽  
Alain Billard
Keyword(s):  
Ostwald Ripening ◽  
Substrate Surface ◽  
Annealing Treatment ◽  
Current Collector ◽  
Titanium Content ◽  
Face Centered Cubic ◽  
Reducing Atmosphere ◽  
The Face ◽  
Face Centered ◽  
Fcc Structure

Metallic platinum–titanium coatings were deposited by co-sputtering of two metallic Pt and Ti targets in pure argon atmosphere. The titanium concentrations varied from 0 to 47 atomic percent and were adjusted as a function of the current applied to the titanium target. The structural and chemical features of these films were assessed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). All as-deposited coatings exhibit a perfect covering of the alumina pellets’ substrate surface. The coatings containing more than 4 at.% Ti are amorphous, whereas the others crystallize in the face-centered cubic (fcc) structure of platinum. After an annealing treatment under air for 2 h, all of the coatings adopt the fcc structure with a crystallization temperature depending on the titanium content. For titanium concentrations higher than 32 at.%, the TiO2 phase appears during the annealing treatment. For the smaller film thickness of Pt–Ti alloys (15 nm), the Ostwald ripening mechanism is observed by SEM increasing the annealing temperature regardless of the content of Ti. The film resistivity measured at room temperature is lower than 7 × 10−4 Ω·cm and increases with the temperature to achieve an insulating behavior (in air and reducing atmosphere Ar-H2 (90-10) at 1123 K the resistivity is ρ ≈ 10+36 Ω·cm). When the thickness of intermetallic Pt3Ti layer is higher than 50 nm, the coating is continuous and the resistivity is below 5 × 10−4 Ω·cm in air and in reducing atmosphere (Ar with 10% of H2) up to 1273 K.

CHALKOGENIDES OF THE TRANSITION ELEMENTS: II. EXISTENCE OF THE π PHASE IN THE M9S8 SECTION OF THE SYSTEM Fe–Co–Ni–S

1961 ◽  
Vol 39 (2) ◽  
pp. 297-317 ◽  
Author(s):  
Osvald Knop ◽  
Mohammad Anwar Ibrahim
Keyword(s):  
Crystal Structure ◽  
Cobalt Content ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Transition Elements ◽  
Maximum Increase ◽  
The Face ◽  
Face Centered ◽  
The Stability ◽  
Stability Limits

The face-centered cubic phase π(Fe,Co,Ni,S) has been shown to exist, at room temperature, within wide composition limits in or close to the M9S8 section of the quaternary system Fe–Co–Ni–S. The M:S ratio of the binary phase π (Co,S) is 9:8 with very narrow homogeneity ranges on both sides of Co9S8, but in π (Fe,Co,Ni,S) the ratio is somewhat higher and appears to increase with decreasing cobalt content. Stoichiometric Co9S8 probably contains a small number of vacancies in both sublattices. It is quite lilcely that the sulphur sublattice is nearly fully occupied and that departures from stoichiometry are caused by the varying degree of occupancy of the metal sublattice.The crystal structure, which was proposed for Co9S8 and for the mineral pentlandite by Lindqvist etal., has been confirmed for these two substances and for π (Fe,Co,Ni,S) in general by X-ray and neutron powder diffraction. The present evidence does not support the crystal structure suggested for natural pentlandite by Eliseev; Eliseev's model does not, in fact, account for the diffraction data of any of the substances examined in this work.Replacement of cobalt in π (Co,S) by iron or nickel or both results in an expansion of the unit cell, the maximum increase in a(π) amounting to about 3%. Cobalt in π (Co,S) cannot be replaced completely by iron or by nickel in samples prepared by dry synthesis, but if the substitution is simultaneous, the π structure will be preserved over a considerable range of compositions even on total replacement. The stability limits of π (Fe,Ni,S) have been found somewhat wider than those stated by Lundqvist.In π phases with the compositions Co8MS8 the metal atoms can conceivably be present in ordered sublattices. This possibility was explored by neutron diffraction in slowly cooled Co8NiS8. Unlike in spinels, where nickel shows a strong preference for octahedral co-ordination, the cobalt and nickel atoms were found to be distributed at random.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

MINIMAL KNOTTING NUMBERS

2009 ◽  
Vol 18 (08) ◽  
pp. 1159-1173 ◽  
Author(s):  
CASEY MANN ◽  
JENNIFER MCLOUD-MANN ◽  
RAMONA RANALLI ◽  
NATHAN SMITH ◽  
BENJAMIN MCCARTY
Keyword(s):  
The Body ◽  
Computer Algorithm ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Body Centered Cubic Lattice

This article concerns the minimal knotting number for several types of lattices, including the face-centered cubic lattice (fcc), two variations of the body-centered cubic lattice (bcc-14 and bcc-8), and simple-hexagonal lattices (sh). We find, through the use of a computer algorithm, that the minimal knotting number in sh is 20, in fcc is 15, in bcc-14 is 13, and bcc-8 is 18.

Poisson's Ratio for Central-Force Polycrystals

1976 ◽  
Vol 31 (12) ◽  
pp. 1539-1542 ◽  
Author(s):  
H. M. Ledbetter
Keyword(s):  
Electron Energy ◽  
Poisson Ratio ◽  
The Body ◽  
Central Force ◽  
Face Centered Cubic ◽  
Polycrystalline Aggregate ◽  
Body Centered Cubic ◽  
The Face ◽  
Predicted Values ◽  
Face Centered

Abstract The Poisson ratio υ of a polycrystalline aggregate was calculated for both the face-centered cubic and the body-centered cubic cases. A general two-body central-force interatomatic potential was used. Deviations of υ from 0.25 were verified. A lower value of υ is predicted for the f.c.c. case than for the b.c.c. case. Observed values of υ for twenty-three cubic elements are discussed in terms of the predicted values. Effects of including volume-dependent electron-energy terms in the inter-atomic potential are discussed.

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