Site-occupation tendencies for ternary additions (Fe, Co, Ni) in β-phase transition-metal aluminides

The known metal–C2O4 structures may be divided into two modifications, α and β. The α-modification has an order–disorder struxture, revealing one-dimensional disordering of the metal–oxalate chains, and the β-modification is ordered. The crystal structures of orthorhombic γ-MnC2O4 {poly[μ-oxalato-manganese(II)]; space group Pmna, a = 7.1333 (1), b = 5.8787 (1), c = 9.0186 (2) Å, V = 378.19 (1) Å3, Z = 4 and Dx = 2.511 Mg m−3} and γ-CdC2O4 {poly[μ-oxalato-cadmium(II)]; space group Pmna, a = 7.3218 (1), b = 6.0231 (1), c = 9.2546 (2) Å, V = 408.13 (1) Å3, Z = 4 and Dx = 3.262 Mg m−3} have been obtained from powder diffraction patterns. The structures are isostructural. Each metal atom in each structure is coordinated by seven O atoms which belong to five oxalate ions. The crystal packing, which contains noticeable cavities in the [101] and [001] directions, is not close packed and essentially differs from the known disordered α- and ordered β-modifications of transition metal oxalates. This modification seems to be metastable. It was found that a spontaneous γ→β phase transition takes place for γ-CdC2O4.

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Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165070 ◽

1996 ◽

Vol 54 ◽

pp. 522-523

Author(s):

G.A. Botton ◽

C.J. Humphreys

Keyword(s):

High Temperature ◽

Transition Metal ◽

Energy Loss ◽

Grain Boundaries ◽

Industrial Applications ◽

Edge Structure ◽

Structural Applications ◽

Yield Behaviour ◽

Late Transition ◽

Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

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Nanocrystalline, Mixed-Phase Transition Metal Oxide/Oxy-Chalcogenide Nanostructures for Efficient Hydrogen Evolution Electrocatalysis

10.29363/nanoge.ngfm.2019.250 ◽

2019 ◽

Author(s):

Giorgio Giuffredi ◽

Fabio Di Fonzo ◽

Andrea Perego ◽

Piero Mazzolini ◽

Greta Tirelli ◽

...

Keyword(s):

Phase Transition ◽

Transition Metal ◽

Metal Oxide ◽

Hydrogen Evolution ◽

Transition Metal Oxide ◽

Mixed Phase

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Strain Induced Phase Transition of WS2 by Local Dewetting of Au/Mica Film upon Annealing

Surfaces ◽

10.3390/surfaces4010001 ◽

2020 ◽

Vol 4 (1) ◽

pp. 1-8

Author(s):

Tomasz Kosmala ◽

Pawel Palczynski ◽

Matteo Amati ◽

Luca Gregoratti ◽

Hikmet Sezen ◽

...

Keyword(s):

Phase Transition ◽

Transition Metal ◽

Thermal Annealing ◽

Tensile Strain ◽

Structural Phase ◽

Transition Metal Dichalcogenides ◽

Proof Of Concept ◽

Threshold Strain ◽

Metal Dichalcogenides ◽

Phase Engineering

Here, we present a proof-of-concept experiment where phase engineering at the nanoscale of 2D transition metal dichalcogenides (TMDC) flakes (from semiconducting 2H phase to metallic 1T phase) can be achieved by thermal annealing of a TMDC/Au/mica system. The local dewetting of Au particles and resulting tensile strain produced on the TMDC flakes, strongly bound to the Au surface through effective S-Au bonds, can induce a local structural phase transition. An important role is also played by the defects induced by the thermal annealing: when vacancies are present, the threshold strain needed to trigger the phase transition is significantly reduced. Scanning photoelectron microscopy (SPEM) was revealed to be the perfect tool to monitor the described phenomena.

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The onset of ferromagnetism in transition metal alloys as a cooperative phase transition

Journal of Physics F Metal Physics ◽

10.1088/0305-4608/10/11/023 ◽

1980 ◽

Vol 10 (11) ◽

pp. 2515-2534 ◽

Cited By ~ 13

Author(s):

J C Ododo

Keyword(s):

Phase Transition ◽

Transition Metal ◽

Metal Alloys ◽

Transition Metal Alloys

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First-principle investigations of structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides

Materials Science-Poland ◽

10.1515/msp-2015-0033 ◽

2015 ◽

Vol 33 (2) ◽

pp. 251-258

Author(s):

Bendouma Doumi ◽

Allel Mokaddem ◽

Mustapha Ishak-Boushaki ◽

Miloud Boutaleb ◽

Abdelkader Tadjer

Keyword(s):

Transition Metal ◽

Electronic Properties ◽

Density Functional ◽

First Principle ◽

Generalized Gradient ◽

Metallic Behavior ◽

Plane Wave Method ◽

Structural And Electronic Properties ◽

The Difference ◽

Metal Aluminides

AbstractIn the present work, we have investigated the structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides in the B2 structure, using first-principle calculations of the density functional theory (DFT) based on the linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2k code, in which the energy of exchange and correlation are treated by the generalized gradient approximation (GGA), proposed in 1996 by Perdew, Burke and Ernzerhof (PBE). The ground state properties have been calculated and compared with other calculations, and the electronic structures of all FeAl, CoAl, and NiAl compounds exhibited a metallic behavior. It was depicted that the density of states is characterized by the large hybridization between the s-p (Al) and 3d (Fe, Co, and Ni) states, which creates the pseudogap in the region of anti-bonding states. Moreover, the band structures of FeAl, CoAl, and NiAl are similar to each other and the difference between them is in the energy level of each band relative to the Fermi level.

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