FePd Alloy Research Articles

Responsive Magnetic Particle Imaging Tracer: Overcoming "Always-On" Limitation, Eliminating Interference, and Ensuring Safety in Adaptive Therapy.

Magnetic particle imaging (MPI) has emerged as a novel technology utilizing superparamagnetic nanoparticles as tracers, essential for disease diagnosis and treatment guidance in preclinical animal models. Unlike other modalities, MPI provides high sensitivity, deep tissue penetration, and no signal attenuation. However, existing MPI tracers suffer from "always-on" signals, which complicate organ-specific imaging and hinder accuracy. To overcome these challenges, we have developed a responsive MPI tracer using pH-responsive PdFe alloy particles coated with a gatekeeper polymer. This tracer exhibits pH-sensitive Fe release and modulation of the MPI signal, enabling selective imaging with a higher signal-to-noise ratio and intratumoral pH quantification. Notably, this responsive tracer facilitates subtraction-enhanced MPI imaging, effectively eliminating interference from liver uptake and expanding the scope of abdominal imaging. Additionally, the tracer employs a dual-function mechanism for adaptive cancer therapy, combining pH-switchable enzyme-like catalysis with dual-key co-activation of ROS generation, and Pd skeleton that scavenges free radicals to minimize Fe-related toxicity. This advancement promises to significantly expand MPI's applicability in diagnostics and therapeutic monitoring, marking a leap forward in imaging technology.

Molecular beam epitaxy of Pd-Fe graded alloy films for standing spin waves control

This study demonstrates capabilities of a molecular beam epitaxy method for the deposition of ferromagnetic Pd–Fe alloy thin films with variable compositions across film thickness. It is proposed as a technological route to synthesize graded magnetic materials possessing unusual physical properties. A particular approach to realize a concentration profile through temperature control of an effusion cell during deposition is described in detail. Using this technique, graded ferromagnetic films were synthesized and characterized to reveal the possibility of controlling the spectrum of standing spin waves in them. Limitations of creating Pd–Fe films magnetically profiled across the thickness are discussed, associated with the thermal inertia of effusion cells and possible phase separation.

Effect of tetragonality on the magnetic preference, elasticity and magnetocrystalline anisotropy of L10-FeM(M = Ni, Pd, Pt) alloys

The effect of tetragonality on the magnetocrystalline anisotropy of L10-FeM(M = Ni, Pd and Pt) ordered alloys is widely concerned, but its effect on other physical properties is not well understood. In this paper, the impact of tetragonality on the magnetic preference, lattice dynamics and elasticity, as well as magnetocrystalline anisotropy of these L10 ordered alloys are systematically investigated based on the first-principles methods. The antiferromagnetic FeNi and FePd alloys are metastable within appropriate axial ratio c/a range, although the ferromagnetic state is ground-state stable. The reduced axial ratio c/a favors the antiferromagnetic state over the ferromagnetic state for the FePt alloy. The tetragonality has a non-monotonic effect on the Young’s modulus and shear modulus, while the bulk modulus is almost tetragonality independent for all L10 ordered alloys. The uniaxial magnetocrystalline anisotropy increases with tetragonality in the fe rromagnetic state, while it shows different trends in the antiferromagnetic state. Interestingly, the antiferromagnetic FePt exhibits planar magnetocrystalline anisotropy in a wide axial ratio c/a range, and a transition between hard magnetic and semi-hard magnetic at c/a = 1.45 is discovered for the FePd alloy. These intriguing properties induced by tetragonality provide us a deeper understanding of the potential rare-earth-free permanent magnet L10 alloys.

Microstructure and Magnetic Properties of Fe67.6-Pd32-In0.4 (at.%) Shape Memory Melt-Spun Ribbons.

Fe-~30 at.%Pd is a ferromagnetic shape memory alloy (SMA) with a reversible thermoelastic fcc-fct phase transformation. The advantage of adding a small amount of Indium to Fe-Pd SMAs is, among other things, the upward shift of the transformation temperatures, which allows us to maintain the material in the martensitic state (fct structure) at room temperature. In this work, we study the microstructure and the magnetic properties of nominally Fe67.6-Pd32-In0.4 (at.%) melt-spun ribbons. Energy-dispersive spectroscopy analysis showed a certain level of non-uniformity of Indium distribution in the as-spun ribbon. However, the attempt to homogenize the ribbon by annealing at 1273 K for 120 h resulted in an unfavoured structural change to bct martensite. Magneto strains induced by a 9 kOe magnetic field reached over 400 ppm for certain field orientations, which is around four times more than the magneto strains of near-binary Fe-Pd shape memory alloys.

Wetting of L10 twin and antiphase boundaries by nanometer-scale L12 in Fe-Pd alloys

This paper reports microstructure associated with the L10 and L12 two-phase coexistence region in magnetic Fe-Pd alloys and analyzes the observed complex nanometer scale wetting layer structures. Fe - 61.8 at% Pd samples were continuously cooled from the disordered A1 phase through the eutectoid isotherm and aged at 650 °C for various times. X-ray diffraction reveals that the samples first order to L12 then transform to L10-dominant L10 + L12 two-phase mixture. It is shown that L10 forms {110} polytwin microstructure with straight {11¯0} antiphase boundaries (APBs), where L12 exists as nanometer-scale wetting layers along the twin boundaries and APBs. The variant selection for L12/L10 wetting layers is discussed, and evidence of closed/open APB structures is shown with high-resolution transmission electron microscopy.

Field-free magnetic rotation in FePd alloy films controlled by reversible hydrogenation

In this study, we performed magneto-optical Kerr effect (MOKE) microscope measurements and X-ray diffraction to examine the hydrogenation effect on the magnetic anisotropy (MA) of Fe40Pd60/Al2O3 thin films and its correlation with crystalline structure. The change in magnetic coercivity was observed and attributed to the rotation of MA, which is characterized by the azimuthal angle-dependent MOKE. Hydrogen-enhanced magnetic moment was confirmed by X-ray magnetic circular dichroism. Multi-step etching processes were used to lower the thickness of the FePd alloy coating, and the hydrogenation process triggered the magnetic easy axis to always be parallel to the same direction. The magnetic anisotropy energy (MAE) of FePd film originates from the volume and the interface-contributed MAE. When the MAEs prefer different orientations, the film thickness and the hydrogen absorption will change the dominant term, resulting in the MA rotation. Furthermore, the reversible rotation of magnetism was achieved through hydrogen absorption and desorption without an external magnetic field. These observations are applicable to the development of field-free switched spintronic devices.

PdFe Alloy-Fe5C2 interfaces for efficient CO2 hydrogenation to higher alcohols

Direct CO2 hydrogenation to higher alcohols (HA) is a promising route for high-value utilization of waste CO2, but developing active and stable catalysts remains a grand challenge. For this reaction, constructing multifunctional interfaces as active sites is required to fulfill controllable C-C coupling of alkyl and CO*/CHxO* species. Herein, we report a PdFe catalyst with abundant PdFe alloy-Fe5C2 interfaces via a PdFe alloy induced FeOx carbidization process, which can achieve HA yield of 86.5 mg gcat−1 h−1 with 26.5% selectivity at 300 ºC, 5 MPa, and 6000 mL gcat−1 h−1. The accelerated deactivation test unveils the PdFe catalyst exhibits better durability than the widely studied CuFe based catalysts against harsh conditions. Multiple in-situ characterization results unveil a synergetic mechanism for HA synthesis at the PdFe alloy-Fe5C2 interfaces, where PdFe alloy is responsible for CO formation and non-dissociative activation, while Fe5C2 phase promotes CO dissociation and chain propagation.

Boosting hydrogen evolution performance of nanoporous Fe-Pd alloy electrocatalyst by metastable phase engineering

Nanoporous Fe-Pd alloy with metastable face-centered cubic (fcc Fe-Pd) phase is prepared by electrochemical dealloying as an electrocatalyst for hydrogen evolution reaction (HER). The nanoporous fcc Fe-Pd alloy achieves an overpotential of 58 mV at 10 mA cm−2 in 1 M KOH, outperforming those of stable body-centered cubic Fe-Pd alloy (bcc Fe-Pd) and commercial Pt/C catalyst. Density functional theory calculation reveals that the metastable fcc structure can tailor the coordination environment and electronic structure of Pd active sites in Fe-Pd alloy. As a result, the d‐band center of Pd active site shifts away from the Fermi level, which weakens the Pd-H interaction and reduces the energy barrier of water dissociation. In addition, the fcc Fe-Pd exhibits good mechanical properties, which maintains the catalytic performance in the deformation state. This work broadens the idea for designing and preparing HER catalysts via metastable phase structure design.

PdFe alloy nanoparticles supported on nitrogen-doped carbon nanotubes for electrocatalytic upcycling of poly(ethylene terephthalate) plastics into formate coupled with hydrogen evolution

PdFe alloy nanoparticles supported on nitrogen-doped carbon nanotubes, is proposed for the electrochemical upcycling of polyethylene terephthalate waste at the anode with simultaneous generation of hydrogen at the cathode.

Origin of the Magnetic-Optical Properties of Palladium Compounds, an Ab Intio Study

Abstract: The structural, magnetic, and magneto-optical properties of the PdM (M=Fe, Co, Ni) alloy are investigated using first-principles calculations with the exciting code. The study employs the full potential linearized augmented plane wave method (FP-LAPW) based on density functional theory (DFT). The exchange-correlation energy is described in the generalized gradient approximation developed by Perdew-Burke-Ernzerhof (PBE-GGA). The calculated lattice parameters are in good agreement with theoretical and experimental results. The magnetic properties reveal a ferromagnetic stability phase for all compounds. Additionally, the total (TDOS) and partial (PDOS) density of states, along with the band structure, indicate that PdM (M = Fe, Co, Ni) exhibits metallic behavior. The total and local magnetic moments are investigated. We conducted a study on the polar magneto-optical Kerr effect and calculated Kerr spectra. The microscopic origins of the peaks found in Kerr's angle are interpreted as interband transitions, primarily arising from the states (d to d) in the PdNi and (S to d) in the PdFe and PdCo alloys. Keywords: P-MOKE, DFT, GGA-PBE, Intermetallic.

Synthesis and catalytic activity of porous Fe–Pd alloys in the decomposition of C2–C4 hydrocarbons

Synthesis and catalytic activity of porous Fe–Pd alloys in the decomposition of C2–C4 hydrocarbons

Direct evidence of the shockley tetragonal L1’ phase in a bulk Fe-Pd alloy

Direct evidence is provided for the existence of the tetragonal L1’ phase, first predicted by Shockley in 1938, in bulk Fe - 62 at% Pd alloys aged at 525 ∘C. L1’ existence as the dominant phase is supported by quantitative x-ray diffraction analysis. This is combined with transmission electron microscopy of the polytwinned microstructure, examining the diffracted intensities in specific superlattice reflections where the complete extinction in L10 is relaxed in L1’. Ordering to L1’ appears to occur directly from the A1 parent phase at 525 ºC, while aging at 650 ºC only produces L10. The possibility of L1’ ordering may have consequences for the ferromagnetic properties of classic and important binary alloy systems where L10 is the assumed equilibrium phase.

Green Chemistry for the Transformation of Chlorinated Wastes: Catalytic Hydrodechlorination on Pd-Ni and Pd-Fe Bimetallic Catalysts Supported on SiO2

Monometallic catalysts based on Fe, Ni and Pd, as well as bimetallic catalysts based on Fe-Pd and based on Ni-Pd supported on silica, were synthesized using a sol-gel cogelation process. These catalysts were tested in chlorobenzene hydrodechlorination at low conversion to consider a differential reactor. In all samples, the cogelation method allowed very small metallic nanoparticles of 2-3 nm to be dispersed inside the silica matrix. Nevertheless, the presence of some large particles of pure Pd was noted. The catalysts had specific surface areas between 100 and 400 m2/g. In view of the catalytic results obtained, the Pd-Ni catalysts are less active than the monometallic Pd catalyst (<6% of conversion) except for catalysts with a low proportion of Ni (9% of conversion) and for reaction temperatures above 240 °C. In this series of catalysts, increasing the Ni content increases the activity but leads to an amplification of the catalyst deactivation phenomenon compared to Pd alone. On the other hand, Pd-Fe catalysts are more active with a double conversion value compared to a Pd monometallic catalyst (13% vs. 6%). The difference in the results obtained for each of the catalysts in the Pd-Fe series could be explained by the greater presence of the Fe-Pd alloy in the catalyst. Fe would have a cooperative effect when associated with Pd. Although Fe is inactive alone for chlorobenzene hydrodechlorination, when Fe is coupled to another metal from the group VIIIb, such as Pd, it allows the phenomenon of Pd poisoning by HCl to be reduced.

Computational and Experimental Design of the Octahedral PdFe Alloy Nanocatalyst for Hiyama Cross-Coupling and Environmental Pollutant Degradation

The research on various bimetallic nanoparticles (NPs) is rapidly expanding due to their widespread applications. However, the formation of bimetallic nanostructures in a facile way remains challenging. In the present study, an octahedral (Oh) PdFe alloy nanostructure was designed by following an aqueous medium synthesis strategy. Different metal precursor ratios were varied to observe the change in the shape and distribution of the Oh PdFe alloy nanostructure. Surprisingly, increasing the Fe content directed the finer growth of Oh morphology. However, increasing the Pd amount resulted in an uneven Oh PdFe alloy shape. The catalytic activity of the optimized Oh PdFe alloy was examined for Hiyama cross-coupling, and the degradation of dyes was scrutinized at different pH. The suggested alloy nanostructured catalyst exhibited improved catalytic behavior compared to other nanocatalysts, such as commercial catalyst Pd/C (95%), monometallic Pd Oh (98%), Fe NPs (15%), and PdFe NPs (85%), for the Hiyama cross-coupling reaction. The optimized alloy catalyst with less Pd and more Fe demonstrated 98% yield and excellent reusability up to the fifth consecutive cycle, conveying 80% yield. The stability of the Oh PdFe alloy nanocatalyst and the mechanistic aspects of Hiyama cross-coupling was supported by density functional theory. The degradation of both anionic dyes, Congo red, Eosin Y, and cationic rhodamine B, was performed under normal along with acidic and basic conditions. The degradation reaction was completed in an adequate time interval for all the dyes with no change in the morphology of the synthesized catalyst.

Effect of the thermodynamic factor on the intrinsic and tracer diffusivities in binary mixtures.

One of the Darken equationsgives a relationship between the intrinsic and the tracer diffusion coefficients, D_{A} and D_{A}^{*}, of species A in a solid binary mixture. In its original formulation, the equationreads D_{A}=D_{A}^{*}Γ, with Γ the thermodynamic factor. The question addressed in this paper is how D_{A} and D_{A}^{*} depend separately on Γ. Using a recent result for transition probabilities in terms of the excess chemical potential [M. Di Muro and M. Hoyuelos, Phys. Rev. E 104, 044104 (2021)2470-004510.1103/PhysRevE.104.044104], it is shown that the intrinsic diffusivity does not depend on Γ. This approach simplifies a previous theoretical analysis that reaches the same result. Experimental results of diffusion in Ni-Pd and Fe-Pd alloys [M. J. H. van Dal et al., Acta Mater. 48, 385 (2000)1359-645410.1016/S1359-6454(99)00375-4] are used to check the theory. Numerical simulations of Ni-Pd were performed to show that the migration energy is the main factor responsible for the increase in diffusivity at intermediate concentrations.

Pd-Fe alloy film with high magnetic gradient: structural and magnetic properties

An epitaxial film of the Pd-Fe alloy 116 nm thick with an iron concentration varying in depth from 2 at.% to 50 at.% has been synthesized. An experimental depth distribution profile of iron was obtained as a result of stepwise etching of the film surface with Ar+ ions. Profiling has shown that, as a result of annealing, the impurity was redistributed in the film, and a layer of the L10-phase with a constant concentration was formed near the film surface. After removal of the L10-phase, the film exhibits &amp;quot;easy-plane&amp;quot; anisotropy. The study of spin-wave resonance spectra showed the presence of several modes of standing spin waves, the number of which depends on the residual film thickness. Keywords: graded magnetic materials, molecular beam epitaxy, palladium-iron alloys, X-ray diffraction, spin-wave resonance.

Пленка сплава Pd-Fe с большим градиентом магнитной примеси: структурные и магнитные свойства

An epitaxial film of the Pd-Fe alloy 116 nm thick with an iron concentration varying in depth from 2 at.% to 50 at.% has been synthesized. An experimental depth distribution profile of iron was obtained as a result of stepwise etching of the film surface with Ar+ ions. Profiling showed that, as a result of annealing, the impurity was redistributed in the film, and a layer of the L10-phase with a constant concentration was formed near the film surface. After removal of the L10-phase, the film exhibits easy-plane anisotropy. The study of spin-wave resonance spectra showed the presence of several modes of standing spin waves, the number of which depends on the residual film thickness.

High performance magnetostriction of Fe-Cu-Pd ferromagnetic strain glass:Local chemical ordering induced martensitic nanodomains morphology with low modulus

Large magnetostriction with low saturation magnetic field was recently reported in Fe-Pd ferromagnetic strain glass alloys. Such behaviour is highly desirable for miniaturized sensor and actuator applications. The origin of high performance magnetostriction in Fe-Pd ferromagnetic strain glass is suggested to stem from its martensitic nanodomains. However, the atomic formation mechanism underlying these nanodomains and their associated local crystal symmetry breaking have not been well revealed. Moreover, accumulating experimental results indicate that the nano-structure can lead to a small saturation field but cannot guarantee large magnetostriction. Consequently, the necessary conditions for low field triggered large magnetostriction of Fe-Pd ferromagnetic strain glass alloys still remain unclear. In this paper, the chemistry, structure and transformation properties of the Fe98-xCu2Pdx (x = 28.5 ∼ 31) system are systematically explored to discover the origin of the high performance magnetostriction of ferromagnetic strain glass alloys. We found that the structure of ferromagnetic strain glass consists of local chemical order. This leads to tetragonal martensitic nanodomains with the local crystal symmetry breaking. The local chemical order also induces strong local phonon softening and a low modulus during the strain glass transition. Further investigation shows that the combination of martensitic nanodomains and low modulus are the necessary conditions to achieve both large magnetostriction and a low saturation field, because they can result in small energy barriers for the rotation of nanodomains. These findings provide an effective guideline to design high performance magnetostrictive materials and devices.

Bimetallic PdFe catalysts in hydrodechlorination of diclofenac: Influence of support nature, metal deposition sequence and reduction condition

Monometallic palladium and bimetallic palladium-iron catalysts (1 wt% Pd, 10 wt% Fe) were prepared by sequential (denoted as “-s”) and co- (denoted as “-c“) impregnation of alumina and silica – zirconia (ZS) supports with metal nitrates. After reduction with H2 at 320 and 30 °C the catalysts were tested in hydrodechlorination of diclofenac in water at 30 °C in batch and flow-type reactors. The alumina-supported catalysts were more active than the ZS-supported ones, while the bimetallic catalysts were more efficient than the monometallic Pd ones. The co-impregnated bimetallic catalysts showed higher efficiencies than the catalysts prepared by the sequential deposition of metals. Pd/Al2O3 and PdFe/Al2O3-c provided the same rate of DCF conversion in the batch reactor after both types of preliminary reduction, opening the way for energy saving. The catalysts were studied by XRD, TEM, SEM-EDX, low-temperature N2 physisorption, Mössbauer spectroscopy, DRIFT-CO and by XPS after in situ reduction at 320 °C and ex-situ reduction at 30 °C. The improvements in catalyst efficiency resulted from wider pores, formation of PdFe alloys or Pd-Fe-Ox species on the surface, high Pd0/Pd2+ ratio, low extent of Pd encapsulation with the support and especially its coordinately unsaturated sites. The encapsulation degree was the lowest in the co-impregnated catalysts.

Highly selective hydrogenation of CO2 to C5+ hydrocarbons over Fe catalysts copromoted by K with Pd

CO2 hydrogenation to liquid fuels is significant to reduce CO2 emissions and replace fossil fuels. Herein, we reported that Fe catalysts promoted by combination of K and Pd showed a three-synergistic catalytic effect to high selectivity of C5+ hydrocarbons in CO2 hydrogenation reaction. The catalysts were prepared using an impregnation method and characterized with physical adsorption, XRD, XPS, HRTEM, H2-TPR, H2-TPD and CO2-TPD. The results indicated that K0.016Pd0.12Fe catalysts showed K-overlapped PdFe-like alloy structure which enhanced H2 activation behaviors and moderately chemisorption of CO2. K addition promoted Fe to activate carbide species while active H originated from H2 pool generated by PdFe alloy spilled to Fe species surface, consequently boosting not only conversion of CO2 to 41.8% but also selectivity of C5+ hydrocarbon to 70.6%. The maximum yield of long-chain C5+ hydrocarbon reached up to 20.0% under high space velocity 6000 mL gcat−1 h−1. These results provide a new insight to develop highly selective Fe based catalysts for long-chain hydrocarbons via CO2 hydrogenation.