Fe Pd Research Articles

Orientation dependence of martensite variants during loading of Fe–Pd shape memory alloy

Abstract A simple analysis based upon infinitesimal deformation theory is applied to the prediction of the orientation dependence of martensite variant fractions in Fe–Pd shape memory alloy. The predictions are in good agreement with previously presented neutron diffraction data.

Synthesis of Fe–Pd and Fe–Pd∕Ta magnetic nanocomposites by severe plastic deformation

Severe plastic deformation (SPD) and cyclic codeformation were used to prepare bulk magnetic nanocomposite of ordered L10Fe-Pd phase and soft α-Fe following an atomic ordering and precipitation reaction. Enhanced coercivity and remanence have been achieved with this method. Layering of Ta foils with the Fe–34at.%Pd foils was explored in an effort to minimize nanocomposite grain size by confinement. Faster kinetics and improvement in the remanence resulted from Ta layering.

Formation of L10-type Ordered FePd Phase in Multilayers Composed of Fe and Pd

We have investigated the magnetic properties and structure of [Fe (2.50 nm)/Pd (tPd nm)]8 multilayers for a series of Pd layer thicknesses in order to study the formation of the L10-type ordered FePd phase in Fe/Pd multilayers as a function of annealing temperature. It is found that the bcc-Fe phase and fcc-Pd phase in the as-deposited Fe/Pd multilayer do not transform to the disordered Fe–Pd phase or L12-type ordered FePd3 phase but transform directly to the L10-type ordered FePd phase with increasing annealing temperature above 673 K for the Pd layer thickness range between 3.00 nm and 3.50 nm. The value of (SLattice)2 for a 3.25-nm-thick Pd layer, namely, the degree of order obtained for specific lattice parameters is evaluated to be approximately 0.17 at the annealing temperature of 673 K, and is then enhanced to nearly 1.0 with increasing annealing temperature above 823 K. The formation temperature of the L10-type ordered FePd phase in the Fe/Pd multilayer becomes low. The thickness range of the Pd layer for the formation of the fully L10-type ordered FePd phase in the Fe/Pd multilayer becomes narrow.

Structure and magnetic properties of Fe–Pd silica composites prepared by sequential ion implantation

The nanostructural and magnetic properties of Fe–Pd/SiO2 granular solids prepared by sequential ion implantation have been investigated. Nanostructural features depend on the relative Pd/Fe implanted dose and, in particular, in the Pd50Fe50 sample 2–6nm size nanoparticles with the disordered FCC structure are formed. At low temperatures Fe–Pd composites have open hysteresis loops with coercivity fields of some mT and large magnetic moment per Fe atom (2.8μB). In only-Fe and Fe–Pd composites the nanoparticles are superparamagnetic at room temperature and the blocking temperature increases from 20K, for the only-Fe sample, to 110K, for Fe50Pd50 sample.

Magnetic field-induced reversible variant rearrangement in Fe–Pd single crystals

Variant rearrangements induced by external magnetic field in Fe–Pd FCT martensite transformed from FCC austenite single crystals have been investigated by means of optical microscopy. Fe–Pd single crystals in fully martensite state contain two large correspondence variants, and a kink due to {1 0 1} twinning is observed at the twinning boundary of the variants. The twinning boundary exhibits both large reversible and small irreversible movement by applying magnetic field as a result of variant rearrangement, and 0.49% of reversible strain is obtained. The variant rearrangement is not completed even though magnetic flux density is increased to maximum of an electromagnet used. The boundary also moves reversibly by application of external compression stress, however, the direction of the boundary movement is opposite with respect to the movement induced by magnetic field and the variant rearrangment is not completed. The reversible strain of 2.8% was also observed when the specimen was compressed.

The effect of interstitial hydrogen on the electronic structure of Fe–Pd alloys

The electronic structure and bonding in Fe–Pd alloys were computed using a tight binding method. Two phases have been identified for these alloys, a high temperature fcc and a low temperature fct structure. The hydrogen absorption turns out to be a favorable process in both structures. The hydrogen at tetrahedral interstitial site for the fct structure is 2.2 eV more stable than that impurity atom located at an octahedral interstitial site in the fcc structure. The density of states curves show a peak below the d metal band which is made up mostly of hydrogen based states (>50% H 1s) while the metal contribution includes mainly s and p orbitals. In the fcc structure, both Fe–H and Pd–H bonds are developed while the Fe–Pd interface shows antibonding filled states near the Fermi level. When the fct phase is considered, the Fe–H overlap population (OP) decreases, while the Pd–H remains similar to the previous case. The Fe–Fe OP decreases and the Pd–Pd bonds are almost unaltered. The interfacial Fe–Pd bonds are almost unaffected by hydrogen. The band structure of the hydrogenated alloys in the fcc and fct phases were also computed.

First-principles investigation of L10-disorder phase equilibria of Fe–Ni, –Pd, and –Pt binary alloy systems

FLAPW total energy electronic structure calculations are combined with cluster variation method in order to perform first-principles investigation of phase equilibria for three kinds of Fe-based binary alloy systems, Fe–Ni, Fe–Pd, and Fe–Pt. A particular focus of the present investigation is placed on L10-disorder phase equilibria. The lattice vibration effects are incorporated within the quasi-harmonic approximation via Debye–Gruneisen model. The ground state analysis revealed that magnetism plays a crucial role in the phase stability of each system. The calculated transition temperatures for Fe–Pd and Fe–Pt systems are in close agreement with experimental ones. The lattice vibration effects further improves the accuracy, and it is found that magnetic fine structure also affects the resultant transition temperature in Fe–Pt system. Although L10-ordered phase does not appear as a stable ordered phase in a conventional phase diagram of Fe–Ni system, the present first-principles calculation suggests the possibility of the stabilization of this phase. The effect of the second nearest neighbor pair interactions as well as multibody interactions are investigated.

Effects of atomic ordering on the Curie temperature of FePd L1 type alloys

In this work, we systematically studied the effects of atomic ordering on the Curie temperature of FePd alloys in the composition region of L10 phase. The Curie temperatures of the bulk Fe–50 at. % Pd, Fe–55 at. % Pd, Fe–60 at. % Pd alloys for both ordered and disordered structures have been measured. Unlike the Curie temperatures reported in the literature, atomic ordering decreases the Curie temperature by about 30 K for each of the compositions. Using a molecular field model, we calculated the Curie temperatures of Fe–Pd alloys. The simulation results show that the difference of the Curie temperature of the disordered and ordered states arises from the change of the nearest-neighbor occupation probabilities and the change of atomic interactions.

Magnetic properties of Fe–∼30 at% Pd films

Fe–Pd alloys with about 30 at% of Pd belong to the group of alloys exhibiting a thermoelastic martensitic transformation. The magnetic properties of the Fe–∼30 at% Pd thin films with the disordered FCC structure were examined. A relatively high coercive force of the films was measured. In one of the film samples, a case of out-of-plane magnetization occurred.

Suzuki Cross‐Coupling in Aqueous Media Catalyzed by a 1,1′‐N‐Substituted Ferrocenediyl Pd(II) Complex.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Neutron diffraction study of stress-induced martensitic transformation and variant change in Fe–Pd shape memory alloy

Neutron diffraction spectra were recorded during tensile testing of Fe–30.5 at.% Pd shape memory alloy at temperatures above Ms and below Mf. Peak intensity changes indicate that the application of tensile stress to initially fully austenitic material results in the preferential martensitic transformation of grains oriented with austenite 〈100〉 parallel to the tensile axis. Tensile stress applied to initially fully martensitic material causes the greatest extent of reorientation in those variants oriented with martensite 〈001〉 lying parallel to the tensile axis. These results are interpreted using a simple elasticity-based theory. Additionally, diffraction peak shifts provide information on the development of lattice strain in differently oriented grain families during loading. This indicates that above Ms the alloy exhibits high single crystal elastic anisotropy. Below Mf the apparent stiffnesses of different grain families suggest that axially compressive internal stresses develop in those grain families in which most variant reorientation occurs. These stresses act to reverse the variant changes upon subsequent unloading.

Effects of grain size on coercivity of combined-reaction-processed FePd intermetallics

The evolution of the microstructure and the coercivity of cold-deformed ferromagnetic Fe–Pd intermetallics with equiatomic composition during isothermal annealing at 500 and 600 °C has been studied by X-ray diffraction, scanning and transmission electron microscopy and vibrating sample magnetometry. The deformation-processed alloys exhibit morphologically essentially equiaxed microstructures and up to about fivefold increased coercivity compared with conventionally processed bulk L1 0-ordered FePd. An inverse linear relationship between the coercivity and the average grain size has been established, which for grain sizes in the range of about 0.4–1.0 μm has been attributed to a nucleation-type coercivity mechanism.

An Analysis of Lattice Strain due to Disclination Dipole Walls in Fe-Pd Martensite

The martensite structure in Fe–Pd is shown to possess disclination dipole walls, which induce a locally fluctuating residual stress field. In a polycrystal, the residual stress averaged over each (former austenite) grain vanishes, since the average t

The Activity of Fe–Pd Alloys for the Water–Gas Shift Reaction

The role of Fe promoters has been investigated on Pd/ceria, Pt/ceria and Rh/ceria catalysts for the water–gas shift (WGS) reaction in 25 torr of CO and H2O under differential reaction conditions. While no enhancement was observed with Pt and Rh, the activity of Pd/ceria increased by as much as an order of magnitude upon the addition of an optimal amount of Fe. Similarly, the addition of 1 wt% Pd to an Fe2O3 catalyst increased the WGS rate at 453 K by a factor of 10 over that measured on Fe2O3 alone, while the addition of Pt or Rh to Fe2O3 had no effect on rates. The amount of Fe that was necessary to optimize the rates increased with Pd loading but was independent of the order in which Fe and Pd were added to the ceria. Increased WGS activity was also observed upon the addition of Fe to Pd supported on Ce0.5Zr0.5O2. XRD measurements, performed after running the catalyst under WGS conditions, show the formation of a Fe–Pd alloy, even though similar measurements on an Fe/ceria catalyst showed that Fe3O4 was the stable phase for Fe in the absence of Pd. Possible implications of these results on the development of new WGS catalysts are discussed.

Thermomechanical and magnetic properties of the as-spun Fe–Pd SMA ribbons

Fe–Pd with approximately 30 at.% of Pd belongs to ferromagnetic shape memory alloys. Thermal loading and some magnetic properties such as magnetostriction and saturation magnetization of Fe–Pd melt-spun ribbons have been examined.

THE EFFECT OF H ON THE ELECTRONIC STRUCTURE OF AN Fe(110)–Pd(100) INTERFACE

The ion-driven mechanism in hydrogen permeation is substantially modified when iron is coated with palladium. A detailed knowledge of the electronic structure at the metal–metal interfaces is a prerequisite for understanding the process of H permeation. We have selected two low-Miller-index surfaces as a simple model for the interface. The system under consideration has 148 metallic atoms forming an Fe–Pd cluster distributed in six metallic layers. We have investigated the interaction of atomic hydrogen with the Fe (110)– Pd (100) interface using the semiempirical atom superposition and electron delocalization (ASED-MO) method. The changes in the electronic structures, density of states (DOS) and crystal overlap orbital population (COOP) in two different Fe–Pd interfaces were compared with the bulk ground states of both metals. The interfacial Fe–Pd distance results in about 1.74 Å, whereas for the Fe–Pd first neighbors distance it is about 1.85 Å. An important conclusion is that the metal–metal bonds at the interface are stronger than those bonds in the pure metal bulk. A favorable metal adhesion is observed, as revealed by the energetic stabilization of the composite metal system. H is stabilized near the FePd interface and stopped at the first Pd layer. A H–metal bond is developed with both Fe and Pd atoms while Fe–Pd bonding at the interface remains unaltered.

Effects of the spinning wheel velocity on the microstructure of Fe–Pd shape memory melt-spun ribbons

Fe–Pd with approximately 30 at.% of Pd shape memory ribbons have been manufactured by the free jet melt-spinning method with various wheel velocities. The microstructure of the as-spun ribbons have been investigated.

Suzuki cross-coupling in aqueous media catalyzed by a 1,1 ′- N-substituted ferrocenediyl Pd(II) complex

Reaction of PdCl 2(MeCN) 2 with Fe[η-C 5H 4NC(H)Ph–N] 2 ( 1) at MeOH at r.t. gives air-stable PdCl 2Fe[η-C 5H 4NC(H)Ph–N] 2 ( 2; yield 84%). X-ray single-crystal diffraction analyses show that 2 is a Pd(II) square planar complex with N, N ′ chelation of the ferrocenediyl ligand, without Fe–Pd bond. It effectively catalyzes Suzuki cross-coupling reactions of aryl iodides and bromides with aryl boronic acids in aqueous media under non-homogeneous conditions in which the products can be easily isolated. The reaction conditions including choice of base, catalytic load and catalyst recoverability have been investigated and reported.

Neutron diffraction study of stress-induced martensitic transformation and variant change in Fe–Pd

Neutron diffraction spectra have been recorded in situ during tensile testing of polycrystalline Fe–30.5 at % Pd at a range of temperatures, in order to investigate stress-induced martensitic transformation and variant changes. The selective transformation of preferentially oriented austenite grains and martensite variants is identified and related to elasticity-based theory. Rietveld refinement is applied to determine the variation of elastic stiffness with temperature, revealing a significant increase in stiffness upon transformation to the martensite phase, in contrast to macroscopic measurements.

Magnetic age hardening of cold-deformed bulk equiatomic Fe–Pd intermetallics during isothermal annealing

The interplay between the ordering reaction with recovery and recrystallization of the as-deformed state leads to combined reactions (CRs) during annealing of cold-deformed disordered Fe–Pd intermetallics at temperatures below the critical ordering temperature. CRs can be exploited to control the scale and morphology of the Fe–Pd alloy microstructures in order to optimize alloy properties. Here, the magnetic age hardening behavior and microstructural evolution of cold-deformed (cold rolled to 97% reduction in thickness) binary equiatomic Fe–Pd has been studied for isothermal annealing at temperatures of 400°C, 500°C, and 600°C. The evolution of the microstructure during the annealing treatments has been characterized by a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magnetic age hardening behavior, the evolution of the coercivity as a function of annealing time, has been determined using a vibrating sample magnetometer (VSM). The microstructures of the transforming material have been characterized quantitatively using computer assisted image analysis methods. The CR transformed microstructures are morphologically equiaxed with average grain sizes in the sub-micron range and show coercivity up to five-fold larger than for conventionally processed equiatomic bulk Fe–Pd. During annealing the coercivity increases up to a maximum peak value and has been correlated with the increasing fraction of ordered material. The maximum coercivity obtains, as the ordering phase transformation is complete. With respect to conventionally processed material the ordering transformation in the cold-deformed material exhibits accelerated kinetics and is facilitated by a CR, which involves heterogeneous nucleation and growth processes akin to a ‘massive ordering’ reaction. Further annealing leads to decreasing coercivity, which has been attributed to the onset of grain growth in the population of CR-transformed grains. The characteristic magnetic age hardening response has been rationalized in terms of the microstructural observations.