Fe-P Alloys Research Articles

Novel FeNiP–FeNi–C nanofiber as an outstanding electrocatalyst for oxygen evolution reaction

Developing stable, highly active, and economical non-precious metal catalysts for the oxygen evolution reaction (OER) has been highly demanded in the new energy field since it can meet the industrial demands of large-scale electrocatalytic water splitting. A novel FeP/Ni2P/Fe0.64Ni0.36/C (FeNiP–FeNi–C) nanofiber was prepared by electrospinning and high-temperature phosphating. Notably, the good dispersion of FeP, Ni2P, and FeNi alloy nanoparticles in the nanocarbon fiber greatly increased the number of electroactive sites, and the synergistic effect between the FeP/Ni2P heterogeneous interface and FeNi alloy significantly improved the inherent activity of each site. Moreover, the carbon nanofibers enhanced the long-term durability of the catalyst by preventing the corrosion of the FeP, Ni2P, and FeNi alloy particles. Therefore, the optimal FeNiP–FeNi–C catalyst revealed exceptionally high OER activity, with overpotentials of 364 mV and 236 mV at 50 mA cm−2 and 10 mA cm−2 respectively, and the slope of Tafel of 61.00 mV·dec−1. This catalyst performs significantly better than commercial RuO2 catalysts in alkaline electrolytes. The results of this study offer a novel perspective for the mass production of non-precious metal OER high-efficiency electrocatalysts.

Modelling and optimization of electrodeposited amorphous Fe-P alloys using central composite design and response surface method

Central composite circumscribed (CCC) design and response surface methodology (RSM) were used to model and optimize the electrodeposition of amorphous Fe-P alloys. Based on our previous single-factor experimental results, the significance of influencing factors was ranked using analysis of variance (ANOVA) method. Three factors, significantly impacting the P content in deposits, hardness and corrosion current density, were identified, including bath temperature, pH values and H2PO2− concentration. The statistic relationships between process parameters and individual responses were established based on the CCC experimental data and RSM. The optimal parameters for each response were derived and the influences of interaction terms were investigated. The predicted maximum P content of 26.35 wt% was achieved at a bath temperature of 60℃, a pH of 1.2 and H2PO2− concentration of 60 g/L. The predicted highest microhardness was 534 HV0.1 under the optimal conditions of temperature of 60 ℃, pH value of 1.6 and H2PO2− concentration of 49 g/L. The lowest corrosion current density was predicted to be 1.34 μA·cm−2 under the conditions of a bath temperature of 60℃，a pH value of 1.2, and a H2PO2− concentration of 53 g/L. A desirability function was applied to explore the optimal comprehensive performance of both high hardness and low corrosion current density. The optimal parameter combination for comprehensive performance was bath temperature of 60℃, pH of 1.4, and H2PO2− concentration of 49 g/L, and the resulting hardness and corrosion current density were 527 HV0.1 and 2.40 μA·cm−2, respectively. Due to the complex electrodeposition mechanism of amorphous Fe-P alloys, the predicted P content in deposits largely deviated from the experimental result, but the hardness, corrosion current density and comprehensive performances show high prediction accuracy.

Modulating Fe/P ratios in Fe-P alloy through smelting reduction for long-term electrocatalytic overall water splitting

Owing to strong Fe-P interaction that differs the electron distribution beneath metal/phosphide interface of Fe-P alloy, the charge transfer of Fe-P alloy has been accelerated during the electrocatalytic oxidation process and improved the efficiency and durability of overall water splitting. In this work, a novel metallurgical technology in combination with smelting reduction and Single Roller Melting Spinning (SRMS) for the purpose of electrochemical overall water splitting where High-phosphorus Oolitic Iron Ore (HPOIO) has been directly used as the main raw material is developed for preparing amorphous Fe-P alloys strips. The rational modulation on the Fe/P ratio can alter the crystal structure and crystallinity of Fe-P alloy, favor electron transfer, and further trap the positively charged H+. The obtained FeP electrocatalyst exhibits 436 and 527 mV at 10 mA cm−1 with Tafel slopes of 102.3 and 77.2 mV dec−1 for HER and OER in 1.0 mol/L KOH solution, respectively, especially with long-term stability (∼207 h for HER and ∼42 h for OER). Specifically, the DFT calculation displaying structural advantages and componential superiorities exhibited that P in Fe-P amorphous alloy regulated by systematic P addition optimization might increase the energy density in the Fermi level. Furthermore, the phosphorus content brought about high active surface areas, low impedance, and variable reaction paths-caused low reaction energy barriers with the improved amorphicity and absorption and desorption of intermediates, thereby boosting the overall water splitting activity. This study displays a novel strategy to develop Fe-P amorphous alloy for the stable and efficient overall water splitting.

Electrodeposition behavior and characterization of Fe-P alloys at different pH values

Fe-P alloys were electrochemically deposited at various pH values from a chloride bath. The electrodeposition behavior was examined through cathodic polarization, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that at low pH values (1.2 and 1.5), Fe is first deposited and then follows P deposition, while at high pH values (1.8–2.4), Fe and P are codeposited simultaneously, but the existing form of Fe2+ species is different. The morphology and phase structure transformed from amorphous to crystalline as the bath pH increased, which is closely related to the P content regardless of the deposition path. The maximum P content in Fe-P alloy deposits (19.66 wt%) was obtained at pH 1.8.

Resource-saving production of Fe-based amorphous alloys from carbothermal reduction of high-phosphorus oolitic iron ore

Energy-saving and resource-friendly production of Fe-based soft-magnetic materials is of paramount importance for the development of green economy. In this study, an innovative process for fabricating Fe-based amorphous alloys from high-phosphorus oolitic iron ore was developed with the combination of ironmaking and melt-spinning techniques. By using the developed process, iron and phosphorus in high-phosphorus oolitic iron ore can be simultaneously utilized. During the direct carbothermal reduction process of high-phosphorus oolitic iron ore, oolitic hematite and apatite were first reduced to form liquid iron phase and absorb P2 gas, resulting in the enrichment of P element in iron phase. Fe-P alloys with different P and C content can be easily obtained by tailoring the C/O ratio. The reduced Fe-P alloys with high εFe of 96.4% and εP of 70.7% are ideal raw materials for preparing Fe-based soft-magnetic alloys. Fe80P10C9Si1 amorphous alloy was successfully obtained after composition adjustment. The high AFA of rod sample with diameter up to 1 mm and good magnetic softness of the ribbon samples including high Bs of 1.54 T, low Hc of 3.6 A/m, high μe of 30 × 103 with excellent frequency stability prove the effectiveness of the designed process. These findings are of great significance to lay the foundation for the recycling of resources and preparation of high performance soft-magnetic alloys from iron ores.

Synchronous enrichment of phosphorus and iron from a high-phosphorus oolitic hematite ore to prepare Fe-P alloy by direct reduction-magnetic separation process

Synchronous enrichment of phosphorus and iron from a high-phosphorus oolitic hematite ore to prepare Fe-P alloy by direct reduction-magnetic separation process

Critical Evaluation and Thermodynamic Optimization of the Fe-P System

Thermodynamic optimization of the Fe-P system was performed using the CALculation of PHAse Diagrams (CALPHAD) method based on critical evaluation of all available phase equilibria and thermodynamic data. The Gibbs energies of liquid phase and solid solutions were described using the Modified Quasichemical Model and Compound Energy Formalism, respectively. The Fe-P phase diagram, thermodynamic properties of P in liquid Fe and stability of intermediate iron phosphides (Fe3P, Fe2P, FeP and FeP2) in the entire composition range were reoptimized for resolving the discrepancies left in the previously optimized database. Several problems in previous assessments were resolved, and a more accurate and consistent description of the Fe-P system was achieved compared to experimental data. The distribution of P between molten Fe-P alloys and slag at different temperatures was also calculated to present the applicability of the present work to steel dephosphorization calculation.

Effect of recovery and recrystallization on microstructure and magnetic properties of Fe-0.4P rolled sheets

Powder metallurgical processing of the soft magnetic Fe-P alloys is well known. In recent times, the wrought metallurgical processing of these alloys is gaining importance due to the possibility of achieving a good combination of soft magnetic properties by optimising the microstructure through carefully designed heat treatment. The Fe-P alloys are mainly focussed towards realizing an alternative and cost effective alloy to conventional electrical steels. Since not much work on bulk Fe-P alloy system has been reported, we have put efforts on processing Fe-P alloy by wrought metallurgy route to bring out comprehensively the dependence of the microstructure on magnetic properties. Fe-0.4 wt.% P alloy sheets (~0.5 mm) were prepared by adopting the conventional melting, forging and rolling, and heat treated at various temperatures (500 – 1000 °C). Recovery and recrystallization behaviour was investigated using electron back scattered diffraction technique and correlated with the microstructural parameters and mechanical/magnetic properties. Transmission electron microscopy studies revealed the formation of Fe3P nanoprecipitates (2-4 nm) leading to a reduction in lattice strain as confirmed from X-Ray diffraction data analysis. Heat treatment at 1000 °C/1h resulted in the formation of fully recrystallized coarse grain structure with coercivity of 80 A/m. Upon further aging at 300 - 500 °C/0.5 h, the coercivity reduced to 43 A/m with a core loss of 347 W/kg. The attractive combination of soft magnetic properties was attributed to the coarse grain and nanoprecipitate microstructure with reduction in lattice strain. The results were also compared with commercial non-oriented Si-steels (M700-50A and M400-50A).

Investigation of electrochemical deposition of Fe-P alloys on polycrystalline platinum from an alkaline bath

The electrodeposition process of the Fe-P alloy on platinum substrate was investigated at room temperature using a moderately alkaline bath containing FeCl3, NaH2PO2 and Na3NTA (trisodium nitrilotriacetate), which stabilized the Fe(III) ions in the bath at pH 8.0. Cyclic voltammetry was used to analyze the electrochemical behavior of the Fe(III)-NTA species in the electrodeposition bath, and two cathodic and two anodic processes were found. Hydrodynamic studies suggested that the reduction processes are mainly controlled by mass transport. Energy dispersive X-ray spectrometry analysis showed that Fe and P co-deposited. Scanning electron microscopy micrographs revealed electrodeposits without cracks or dendritic crystallites. The Fe and Fe3P phases could be observed by X-ray diffraction in the Fe-P electrodeposits produced from alkaline NTA bath. Confocal laser scanning microscopy showed that roughness of Fe-P electrodeposits, produced with deposition charge density of 40.0 C cm−2, decreased from 0.046 µm to 0.024 µm, depending on the deposition potential.

Effects of Fe3P Addition on Sintering Behaviors and Magnetic Properties of Fe-P Alloys Sintered at Low Temperatures

In this paper, we demonstrate that trace amounts of P addition can activate the sintering of carbonyl powder and influence the magnetic properties of the sintered materials. Fe-x P (x = 0, 0.6, 0.8, 1.0, 1.2, 1.4, and 1.6 wt.%) samples were fabricated by doping carbonyl powder with different amounts of Fe3P. They were sintered at 1000 °C in argon for 2 h. The sintering of the Fe-0 wt.% P sample was interrupted by the ferrite-austenite transformation at 912 °C due to the low diffusion rate of the austenite. The addition of P can stabilize the ferrite, and suppress the ferrite-austenite transformation. Therefore, all the P-containing samples shrank continuously throughout the whole sintering process, which showed improved sintering densities compared to the P-free sample. However, the sintering density did not increase monotonously with increasing P content. The Fe-1.4 wt.% P and Fe-1.6wt.% P samples easily got oxidized during sintering, and the densification process was thus influenced by the P-containing oxide particles. As a result, the Fe-1.2 wt.% P sample exhibited the highest sintering density (7.664 g/cm3) and the best magnetic properties (coercive force 172 A/m).

Study of mechanical properties of an iron phosphorus based alloys under various aging time

We reported to Fe-P based alloys are observed as one of the promising materials which could replace Si-steel on the basis of two factors: i) the cost of Fe-P based alloys are well expected to be about 20% lower than Fe-Si alloys. ii) Phosphorous addition enhances the soft magnetic properties of pure Fe. Elemental Fe with Fe-P and Fe-Si master alloys were taken in suitable weight ratios and induction melted to obtain Fe-0.4wt.% P-0.85wt.%Si alloy. Fe-P based alloys can be produced conventionally by powder Metallurgical route. The optical micrographs of Fe-P-Si alloys were aged at 500 °C with different aging time. Aged samples strength has increased due to the interaction of the moving dislocations with dispersed precipitates. The mechanical properties of the Fe-P-Si aged samples were increasing with aging time up to the peak aged then decrease for the over aged samples. TEM reveals the presence of two phases: Fe3P phase in α-Fe matrix phase. The sizes of the precipitates were increasing from ∼ 1.2 nm to ∼ 2.2 nm with aging time.

Chemical, morphological and corrosion characterisations of electrodeposited Ni-Fe-P coatings

Fe-P, Ni-P and Ni-Fe-P alloys were prepared by galvanostatic electrodeposition over copper electrodes in aqueous media in order to obtain a corrosion resistant layer. All electrodeposits were prepared in optimized conditions at acidic medium (pH < 2.0), using 80 mA cm−2 for Fe-P and Ni-P alloys and 60 mA cm−2 for Ni-Fe-P alloy at 55 °C. The morphology of the electrodeposits was evaluated by scanning electron microscopy, which revealed a nodular, hemispheric grains in Ni-P and Ni-Fe-P alloys and the same grains with cracks in Fe-P alloy. X-ray diffraction (XRD) measurements showed characteristic peaks for Fe and Ni, and P incorporation was observed due to characteristic peak at 2θ ≈ 50°, which means that P atoms amorphized the structure of the electrodeposits. Energy Dispersive X-Ray Spectroscopy (EDS) measurements showed the following composition for all alloys (mass percentage): Fe91.1%-P4.3%, Ni88.5%-P9.7%, Ni46.5%-Fe39.4%-P12.6%. Linear potentiodynamic polarization showed the following order for crescent nobility corrosion potential: Ecorr (Fe-P) < Ecorr (Ni-P) < Ecorr (Ni-Fe-P). Although Ni-P presented lower anodic current values than Ni-Fe-P in polarization curves, the analysis of E-Ecorr polarization curves in these studies showed that Ni-Fe-P and Fe-P coatings had the lowest and highest anodic current values, respectively, among the three electrodeposits. The same trend was observed in electrochemical impedance spectroscopy when a nested circuit for two capacitance events was applied, having Ni-Fe-P layer the highest polarization resistance value among the three and Fe-P the lowest polarization resistance, showing the viability of anticorrosion properties of Ni-Fe-P layers.

Mechanical properties of electrodeposited amorphous/crystalline multilayer structures in the Fe-P system

Amorphous/crystalline multilayer structures of Fe-P alloys were deposited electrochemically using the single bath technique. Hall-Petch behavior of microhardness with respect to sublayer thickness was observed down to a sublayer thickness of 15nm. For thinner sublayers, a hardness plateau was obtained. The transition at a sublayer thickness of 15nm coincides with the loss of the multilayer structure as observed in transmission electron microscopy. The transition is a possible result of a change in the amorphous to crystalline sublayer thickness ratio and the interface roughness development during the deposition process. Additionally, crack deflection at the interfaces was observed for the layered structures with small sublayer thickness in microbending experiments.

Simultaneous Recovery of Iron and Phosphorus from a High-Phosphorus Oolitic Iron Ore to Prepare Fe-P Alloy for High-Phosphorus Steel Production

Unlike previous dephosphorization studies, the present work complies with a concept to recover phosphorus within the utilization of high-phosphorus oolitic iron ores to prepare Fe-P alloy for high-phosphorus steel production. Simultaneous enrichment of iron and phosphorus can be achieved by directly alloying the high-phosphorus oolitic iron ore at high reduction temperatures (≥1623 K). Neither fluxes nor other special additives need to be used. Consequently, the phosphorus element migrates from original apatite to the slag phase with the elevating temperature from 1323 K to 1473 K, and it further moves into metallic iron and forms Fe3P at 1623 K. A metalized iron-phosphorus alloy with assaying of 96.51% iron and 2.03% phosphorus content was obtained at 1623 K for 10 min at corresponding iron and phosphorus recovery rates of 97.50% and 64.51%, respectively. This process exhibits high economic efficiency and is practicable as a stepping-stone for the efficient and direct utilization of high-phosphorus iron ore resources.

Effect of Annealing on Mechanical Properties and Formability of Cold Rolled Thin Sheets of Fe-P P/M Alloys

Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1–0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.

Electrodeposited Fe-P nanowire arrays in hard-anodic aluminum oxide templates with controllable magnetic properties by thermal annealing

The highly ordered uniform amorphous Fe-P alloy nanowire arrays are fabricated by potentiostatic electrodeposition in hard-anodic aluminum oxide (H-AAO) templates with diameter and pore distance about 110 nm and 265 nm, respectively. The deposited Fe-P nanowire arrays gradually change from crystalline to amorphous phase as the phosphorus content in the nanowire arrays increases. The phosphorus content and nanowire growth rate are sensitive to the applied potential and sodium hypophosphite concentration in electrolyte. Subsequently, the as-deposited amorphous Fe-P alloy nanowire arrays are annealed with different temperature. And the original and annealed samples reveal different crystallographic structures and magnetic properties. The results show that both the coercivity and squareness have been improved significantly, while the magnetic anisotropy become weak with the increasing of annealing temperature, which mainly attributes to the competition of shape anisotropy, stress anisotropy and the strengthening of magnetocrystalline anisotropy.

An investigation on effect of heating mode and temperature on sintering of Fe-P alloys

The present study examines the effect of sintering temperature and heating mode on densification, microstructure and mechanical properties of Fe-P alloys. The green compacts were heated conventionally and in microwave under 95%N2–5%H2 (forming gas) at 1120°C and 1250°C for 60min. Both the compositions (Fe-1.5P and Fe-3P in wt%) were found to couple well in microwave field with rapid heating (~40°Cmin−1) and resulted in reduction of overall processing time by about 90% in comparison of conventional heating. Microwave sintering resulted in higher densification in case of Fe-P alloys. Moreover, an important feature of microwave and conventionally sintered samples was that their microstructures exhibited distinctly rounded pores. This resulted into improved corrosion and mechanical properties in general.

P114] Grain-boundary segregation transition in the binary Fe-P alloy

P114] Grain-boundary segregation transition in the binary Fe-P alloy

AC Magnetic Properties and Core Loss Behavior of Fe–P Soft Magnetic Sheets

AC magnetic properties and core loss behavior of differently prepared Fe-P sheets have been analyzed in this paper. Furthermore, the results have been compared with non-oriented silicon (Si) steel. The coercivity, magnetic flux density, and permeability measurements in dc magnetic field show Fe-P has better soft magnetic properties than Si steel. The ac magnetic behavior of both the samples has been studied in the frequency range from dc to 1 kHz for a range of flux density values. The above studies indicate that crystalline Fe-P alloys can be the replacement of so-called Si steel for low-power device applications.

Development of Thin Sheets from Fe-P Alloys through P/M Technique

Cracks due to segregation of Fe3P along the grain boundaries is a major problem in working of Fe-P alloys, processed in conventional wrought route. The present work deals with development of binary Fe-P alloys with varying content of phosphorus (in the range 0.1-0.35%) through powder metallurgical technique to obtain better mechanical properties without the problem of segregation. These alloys were processed into thin sheets by hot forging and rolling. The developed Fe-P alloy sheets were characterized in terms of microstructure, porosity and mechanical properties. Strength and hardness of Fe-P alloys increased with increase in phosphorus content and ductility slightly decreased. It has been observed that thin sheets of Fe-P alloys (with phosphorus as high as 0.25wt %) with high strength and moderate ductility can be obtained through powder metallurgy route and these alloys are free from embrittlement during working due to elimination of segregation problem.