High Purity Iron Research Articles

The improvement of dry sliding tribological properties by designing nano-primary cementite in bainitic/martensitic matrix microstructure in hypereutectoid PM components

The production of nano-sized primary cementite in bainite/martensite matrix (NCBM) microstructure was designed to improve the dry sliding wear properties of high carbon PM parts. A different heat treatment cycle was carried out for the production of novel the NCBM microstructure. High purity iron powder 1.5 wt%. natural graphite powder was added and it was compacted in the form of a dry sliding wear test specimen in a mold and sintered at 1200 °C in a pure Ar gas atmosphere. The novel NCBM microstructure in the PM material was produced by quenching at 950 °C, then annealing at 600 °C for 12 min, then quickly cooling from 730 °C to 250 °C in a salt bath and keeping it isothermal for 100 s. The friction coefficient of materials with NCBM microstructure was less than other samples. It was found that while the wear coefficient were higher in the tempered martensitic microstructure sample having higher hardness, they were less than in the sample having bainitic/martensitic microstructure with similar hardness.

Approach towards the Purification Process of FePO4 Recovered from Waste Lithium-Ion Batteries

The rapid development of new energy vehicles and Lithium-Ion Batteries (LIBs) has significantly mitigated urban air pollution. However, the disposal of spent LIBs presents a considerable threat to the environment. Recycling these waste LIBs not only addresses the environmental issues but also compensates for resource shortages and generates substantial economic benefits. Current recycling processes primarily focus on the extraction of valuable metals, often overlooking the treatment of residual waste post-extraction. This project targets the iron phosphate (FePO4) derived from waste lithium iron phosphate (LFP) battery materials, proposing a direct acid leaching purification process to obtain high-purity iron phosphate. This purified iron phosphate can then be used for the preparation of new LFP battery materials, aiming to establish a complete regeneration cycle that recovers lithium carbonate and iron phosphate from waste LFP materials for the production of LFP. The study investigates process parameters such as acid types and concentrations, leaching time, and the number of leaching cycles. The results demonstrate that, after purification, the levels of impurity metals decrease while the iron content increases correspondingly. Under optimized experimental conditions, the dilute sulfuric acid leaching rates of Al, Cu, Ca, and Ni reached 36.0%, 51.4%, 89.5%, and 90.9%, respectively. Furthermore, hydrothermal treatment in dilute phosphoric acid achieved leaching rates of 87.9%, 85.8%, 98.4%, and 99.1% for Al, Ca, Cu, and Ni, respectively. The microstructure characterization revealed significant changes in phase and grain morphology during the leaching process in dilute phosphoric acid, which are likely associated with the liberation of impurity atoms from the lattice. These findings indicate that acid leaching is highly effective in removing impurities from the iron phosphate recycled from waste LIBs.

Experimental Study on the Preparation of High-Purity Iron Oxide Red by Acid Leaching Iron from Coal Gangue.

Aiming at the problems of the large storage, complex composition, low comprehensive utilization rate, and high environmental impact of coal gangue, this paper carried out experimental research on the preparation of iron oxide red from high-iron gangue by calcination activation, acid leaching, extraction, and the hydrothermal synthesis of coal gangue. The experimental results show that when the calcination temperature of coal gangue is 500 °C, the calcination time is 1.5 h, the optimal concentration of iron removal is 6 mol/L, the acid leaching temperature is 80 °C, the acid leaching time is 1 h, and the liquid--solid mass ratio is 4:1; the iron dissolution rate can reach 87.64%. A solvent extraction method (TBP-SK-hydrochloric acid system) was used to extract the leachate, and a solution with iron content up to 99.21% was obtained. By controlling the optimum hydrothermal conditions (pH = 9, temperature 170 °C, reaction time 5 h), high-purity iron oxide red product can be prepared; the yield is 80.07%. The red iron oxide was characterized by XRD, SEM-EDS, particle-size analysis, and ICP-OES. The results show that the red iron oxide peak has a cubic microstructure, an average particle size of 167.16 μm, and a purity of 99.16%. The quality of the prepared iron oxide red product meets the requirement of 98.5% of the "YHT4 Iron oxide Standard for ferrite". It can be used as a raw material to produce high-performance soft magnetic ferrite. In summary, this experimental study on the preparation of iron oxide red from coal gangue is of great significance for the comprehensive utilization of coal gangue to realize the sustainable development of the environment and economy.

A Brief Review of Surface Modification of Carbonyl Iron Powders (CIPs) for Magnetorheological Fluid Applications

Magnetorheological fluids (MRFs) is a smart fluid system that exhibits swift and reversible alterations in their rheological characteristics when exposed to an external magnetic field. MRFs are used for applications in various areas, including automotive systems, robotics, aerospace, and civil engineering. The performance of MRFs depends on the behavior of the dispersed magnetic particles, necessitating thoughtful consideration of particle traits to optimize fluid performance. Carbonyl Iron Powders (CIPs), high purity iron (>98%) reduced from penta carbonyl iron, are widely employed in MRFs due to their exceptional magnetic characteristics. Nevertheless, the innate surfaces of CIPs tend to conglomerate, leading to compromises in fluid stability and rheological performance. To overcome the challenges, an intensive research has been devoted to advancing surface modification techniques that augment the dispersion, stability, and overall functionality of MRFs based on CIPs. This review describes the comprehensive approach to surface modification of CIPs for highly stable MRFs. We discuss the various surface modification methodologies that have been explored to optimize the behavior of carbonyl iron-based MRFs. Coating techniques, surfactant functionalization, magnetic coatings, and emerging approaches such as nanocoatings and electrochemical modification are also summarized. Moreover, insights into potential applications and future prospects of these modified MRFs are provided.

Aqueous hybrid iron-ion battery capacitors with ultra-long cycle life

With the over-exploitation of lithium resources, there is a tendency to find a new metal-ion energy storage device to replace lithium-ion batteries. In recent years, Fe-ion energy storage devices are acknowledged for their low cost, abundant resources, and safe characteristics, but their full potential has yet to be widely explored. Herein, we propose a new hybrid iron-ion battery capacitor (H-IIBC) energy storage device. The H-IIBC device prepared with nano flower-like activated carbon (FAC) as the cathode material, high-purity iron sheet as the anode material, and 1 M FeSO4 + NH4Cl aqueous solution as the electrolyte. After atomic molecular dynamics simulations and ex situ characterization analysis, ion adsorption/desorption occurs on the surface of the FAC cathode during the charging/discharging process, accompanied by the redox of iron ions. The stripping/deposition of iron occurs at the high-purity iron anode. With the charging/discharging process, the reaction at the anode favors the interconversion between Fe2+ and Fe3+ which requires less energy, thus ensuring that the high purity iron will not be depleted. Thus, the specific capacitance of prepared H-IIBC could reach 644 mF g−1 (399 mF cm−2) at a current density of 1 mA cm−2 in the voltage window of 0–1 V and shows ultra-high cycling stability at 3,000 cycles test. This economical, long-life and safe H-IIBC is expected to realize great potential in the field of energy storage in the near future.

Numerical Simulation of the Hydrogen-Based Directly Reduced Iron Melting Process

In the context of carbon reduction and emission reduction, the new process of electric arc furnace (EAF) steelmaking based on direct hydrogen reduction is an important potential method for the green and sustainable development of the steel industry. Within an electric furnace for the hydrogen-based direct reduction of iron, after hydrogen-based directly reduced iron (HDRI) is produced through a shaft furnace, HDRI is melted or smelted in an EAF to form final products such as high-purity iron or high-end special steel. As smelting proceeds in the electric furnace, it is easy for pieces of HDRI to bond to each other and become larger pieces; they may even form an “iceberg”, and this phenomenon may then worsen the smelting working conditions. Therefore, the melting of HDRI is the key to affecting the smelting cycle and energy consumption of EAFs. In this study, based on the basic characteristics of HDRI, we established an HDRI melting model using COMSOL Multiphysics 6.0 and studied the HDRI melting process, utilizing pellets with a radius of 8 mm. The results of our simulation show that the HDRI melting process can be divided into three different stages: generating a solidified steel layer, melting the solidified steel layer, and melting HDRI bodies. Moreover, multiple HDRI processes are prone to bonding in the melting process. Increasing the spacing between pieces of HDRI and increasing the preheating temperature used on the HDRI can effectively reduce the aforementioned bonding phenomenon. When the melting pool temperature is 1873 K, increasing the spacing of HDRI to 10 mm and increasing the initial HDRI temperature to 973 K was shown to effectively reduce or eliminate the bonding phenomenon among pieces of HDRI. In addition, with the increase in the melting pool temperature, the time required for melting within the three stages of the HDRI melting process shortened, and the melting speed was accelerated. With the increase in the temperature used to preheat the HDRI, the duration of the solidified steel layer’s existence was also shortened, but this had no significant impact on the time required for the complete melting of HDRI. This study provides a theoretical basis for the optimization of the HDRI process within EAFs.

Laser induced reduction of iron ore by silicon

Iron ore powder accompanied by Si-powder as a reducing agent, was melted using a high-power laser beam. During laser melting of the two different powder beds placed next to each other, silicon merged and diffused into the iron ore, forming a ternary melt phase Fe-O-Si of around 30–60–10 at%. High speed imaging of the laser melting process as well as subsequent SEM-analysis of the generated nuggets showed the formation of droplets that merge with the surrounding Si- or ore-powder and form distinct domains. Under certain circumstances, the solidifying nuggets, of the order of 0.5–5 mm in size, generated numerous small domains, up to 25 µm, of high purity iron, 90 + at%, surrounded by a matrix of the above mentioned slag. Many of these Fe-domains were created in the vicinity of regions of high Si-content.

Adsorption on UiO-66 for preconcentration, matrix separation, slurry sampling and in situ hydride generation-atomic fluorescence spectrometric determination of trace bismuth in alloy and water

The determination of trace bismuth in environmental or alloy samples are rather challenging due to the low abundance and interferences arising from complicated sample matrix including heavy metals. In this work, Zr-based metal organic frameworks (UiO-66) was prepared and utilized to selectively extract Bi(III) from water samples or digests of iron alloy. Following simple centrifugation separation, Bi(III)-adsorbed UiO-66 was re-suspended in dilute hydrochloric acid for direct slurry sampling and in-situ hydride generation for atomic fluorescence spectrometric (HG-AFS) detection of bismuth. Experimental conditions affecting the adsorption of Bi(III) on UiO-66 as well as the slurry sampling HG-AFS process were carefully investigated. Under the experimental conditions, a limit of detection (LOD) of 0.1 ng/mL was achieved for bismuth. Inspiringly, the method could resist interferences from transition metals like Cu(II), Ni(II) and Fe(III), and this ensured reliable analytical results for the determination of trace bismuth in high-purity iron alloy, seawater, and river water samples.

Iron Oxide Nanoparticles Produced by a Low-Energy Nd: YAG Laser Ablation Technique and Their Application as Contrast Agent for Magnetic Resonance Imaging

A magnetic resonance imaging contrast agent is proposed using iron oxide nanoparticles (IONPs) synthesized by a pulsed laser ablation technique. Experimentally, an Nd: YAG laser (1064 nm, 7 ns, 30 mJ) was directed and focused on a high-purity iron plate immersed in a liquid solution of deionized water and polyvinylpyrrolidone (PVP). After a few minutes of laser bombardment, iron oxide nanoparticles dispersed in the liquid were homogeneously produced. A reddish yellow color-colloidal IONPs are produced in the water, while its color changes to dark brown for the PVP solution. The characterization results demonstrated that IONPs in the form of Fe2O3 and Fe3O4 made in the PVP have an excellent dispersibility with a spherical shape that is significantly smaller than that of IONPs made in the deionized water at the same laser repetition rate. The produced IONPs are further applied as a contrast agent for the magnetic resonance imaging (MRI) modality by varying concentrations from 0.05 mM to 2.31 mM. The results demonstrated that images of the IONPs sample with a concentration of 2.31 mM showed the highest contrast enhancement (Cenh), with an enhancement factor of 221.875 % for T1-weighted images and 91.227 % for T2-weighted images. IONPs with a concentration of 2.31 mM had the highest signal-to-noise ratio (SNR) for a T1-weighted picture of 52.92, while IONPs with a concentration of 0.05 mM had the highest SNR for a T2-weighted image of 179.117.

Self–ion irradiation of high purity iron: Unveiling plasticity mechanisms through nanoindentation experiments and large-scale atomistic simulations

Ion irradiation may enhance material hardness through crystal defect nucleation and reorganization. In this study, we examine the nanomechanical behavior of high-purity iron samples, comparing the response of pristine specimen to those that have been self–irradiated with 5 MeV ions at 300∘C. We utilize spherical nanoindentation to investigate the nanomechanical response, and we focus on the comprehensive modeling of the self–irradiation effects in high-purity iron through large-scale molecular simulations. Transmission electron microscopy is used in the irradiated regions, at various depths below the nanoindentation imprint, to analyze the nucleation of dislocation networks and the plastic deformation mechanisms at room temperature. Large scale novel molecular dynamics simulations are conducted to simulate overlapping collision cascades reaching an irradiation dose with defect density similar to experiments, followed by nanoindentation simulations that display qualitative agreement to experiments. We find that irradiated sample requires higher critical load for the transition from elastic to plastic deformation due to interaction of dislocation lines with the dislocation loops and point defects formed during the irradiation, leading to hardening.

Study on the mechanism of preparing metallic iron from soluble anode

The optimization of the ironmaking process for the preparation of high-purity metallic iron has become an important part of the production of the iron and steel industry due to the increasing demand for steel in the modern industry. This article adopted the soluble anode molten salt electrolysis process to prepare a soluble anode with excellent conductivity by mixing Fe2O3 and C in a molar ratio of 1:3, sintering at 1073 K for 6 h. The metal iron was electrolytically deposited on the cathode by applying a constant current of 0.1 A for 6 h in the NaCl-CaCl2 molten salt system. The anode dissolution and cathode deposition mechanisms were analyzed based on the electrolysis U-t curve. The experimental results showed that the presence of C after sintering reduces the impedance value by reducing Fe2O3 to Fe3O4. During the electrolysis process, Fe2+ in Fe3O4 oxidized to Fe3+ and entered the molten salt, migrated to the vicinity of the cathode, and underwent the reduction process of Fe3+-Fe2+-Fe during the cathodic reduction process. The deposited Fe on the cathode exhibited a dendritic crystal structure with a purity of 99.51%.

High-throughput synthesis of high-purity and ultra-small iron phosphate nanoparticles by controlled mixing in a chaotic microreactor

High-purity FePO4 with small particle size is pivotal for improving electrochemical performance of LiFePO4-based lithium-ion batteries. Here, an oscillating feedback microreactor (OFM) based on chaotic advection was designed to prepare high-quality FePO4 by coprecipitation. Dye-tracer experiments and CFD simulations were adopted to investigate fluid mixing mechanism and to evaluate mixing efficiency in the reactor. The results indicated that a “flow-focused” OFM (FOFM) performed better than a “Y-junction” OFM in mixing performance, owing to enhanced premixing in focused inlet microchannel of the former. The results of Villermaux-Dushman experiments illustrated that almost complete mixing could be achieved in 0.16 ms in FOFM. Accordingly, FePO4 nanoparticles of good quality was synthesized using FOFM, and the particle size can be easily controlled by adjusting flow rate or reactant concentration. High-purity (P/Fe molar ratio: 0.95–1.04) and ultra-small FePO4 nanoparticles (9 nm) with narrow particle size distribution were generated at a high throughput of 180 mL/min.

The recovery of high purity iron phosphate from the spent lithium extraction slag by a simple phosphoric acid pickling

Recycling metal resources from spent lithium-ion batteries is promising for resource reuse and environmental conservationis, but there are challenges in obtaining high purity recovered materials. The alkaline solutions (NaOH) is employed to precipitate FePO4 from spent LiFePO4, however, the introduction of sodium leads to low purity and lattice defects in the recovered FePO4. Here, we propose an ultrasonic-centrifugal H3PO4 pickling method able to regenerate battery-grade FePO4 in the low Na/Fe environment. In a weak acid environment, the potential of NaH2PO4 increases and the NaH2PO4 attached to the outer layer of FePO4 is converted to FePO4 by H3PO4 pickling. When Na/Fe ≤ 0.8, sodium exists in the form of NaH2PO4, which can be removed by H3PO4 pickling to obtain perfectly crystalline FePO4. When Na/Fe ≥ 2, sodium co-exists in the form of NaH2PO4, NaFe3P3O12 and NaFeP2O7. The latter two impurities are too stable to be removed by pickling, resulting in lattice distortion of FePO4. In addition, the electrochemical performance of regenerated 0.8Na-FePO4 reached the level of commercial FePO4 (C-FePO4), meanwhile the cost of 0.8Na-FePO4 was calculated to be $2.08/kg. This is about 15 % lower than the cost of C-FePO4 ($2.45/kg). This work proposes a high value recovery method of FePO4 with considerable economic advantages and environmental benefits for engineering applications.

Enhanced oxidation and recovery of phosphorous from hypophosphite wastewater: Key role of heterogeneous E-Fenton system with MOFs derived hierarchical Mn-Fe@PC modified cathode

Hypophosphite has high solubility and stable chemical structure, however, the effective oxidation of hypophosphite wastewater with high purity phosphate by-product recovery remains a big challenge. In this work, hypophosphite was oxidized by heterogeneous Electro-Fenton system (hetero-EF) with Metal organic Frameworks (MOFs) derived Mn-Fe co-doped porous carbon (Mn-Fe@PC) modified cathode. The effects of cathode material, current intensity and pH value were investigated. The results indicated that the Mn-Fe@PC modified cathode performed much better on hypophosphite oxidation than Fe doped porous carbon (Fe@PC) or Mn doped porous carbon (Mn@PC) modified cathodes, and the optimal Mn/Fe doping ratio was 1: 2. In the hetero-EF system, H2PO2− (10 mM) was completely oxidized within 240 min at 10 mA/cm2 of current density and 3 of pH. The radical quenching experiments results indicated that •OH was the main active species on the oxidation of H2PO2− into H2PO4−. In addition, the actual wastewater tests confirmed the feasibility of recycling high-purity lithium iron phosphate and struvite from the phosphate solution after the oxidation of hypophosphite in hetero-EF oxidation process, which would provide a new green approach for recycling phosphorus from hypophosphite wastewater.

Extraction of high purity magnetite from bauxite residue

Bauxite residue is a byproduct of the alumina industry and is characterized by high alkalinity and very fine particle size. Currently, there is a low volume utilization of bauxite residue as an additive in the construction industries, and only 3–4 % of the total volume produced annually (160 million tons) is utilized effectively. Bauxite residue is mainly composed of iron oxide along with oxides of aluminum, calcium, sodium, silicon, and titanium. A high fraction of iron in bauxite residue makes it a potential alternative source. However, recovery of high purity iron products with high recovery is technically challenging. The present work is focused on the recovery of iron from bauxite residue in the form of high purity magnetite through a hydrometallurgical approach. Bauxite residue is first neutralized after leaching with mild hydrochloric acid, followed by the leaching of iron with oxalic acid and photochemical reduction of leach liquor to obtain ferrous oxalate precipitate, which is further converted to high purity magnetite. Three different bauxite residue samples with different mineralogical compositions were used, and a comparative study is presented to illustrate the flexibility of the process toward different grades of bauxite residue.

Self-ion irradiation effects on nanoindentation-induced plasticity of crystalline iron: A joint experimental and computational study

In this paper, experimental work is supported by multi-scale numerical modeling to investigate nanomechanical response of pristine and ion irradiated with Fe2＋ ions with energy 5 MeV high purity iron specimens by nanoindentation and Electron Backscatter Diffraction. The appearance of a sudden displacement burst that is observed during the loading process in the load–displacement curves is connected with increased shear stress in a small subsurface volume due to dislocation slip activation and mobilization of pre-existing dislocations by irradiation. The molecular dynamics (MD) and 3D-discrete dislocation dynamics (3D-DDD) simulations are applied to model geometrically necessary dislocations (GNDs) nucleation mechanisms at early stages of nanoindentation test; providing an insight to the mechanical response of the material and its plastic instability and are in a qualitative agreement with GNDs density mapping images. Finally, we noted that dislocations and defects nucleated are responsible the material hardness increase, as observed in recorded load–displacement curves and pop-ins analysis.

Grain boundary mobility of γ-Fe in high-purity iron during isothermal annealing

Grain boundary migration in pure electrolytic iron (Fe > 99.98 %) was studied under isothermal conditions at 1050 °C, 1150 °C, 1250 °C and 1350 °C. High-temperature laser scanning confocal microscopy (HT-LSCM) was used to observe the in-situ grain growth of austenite (γ-Fe) on the sample surface. The dependence of the arithmetic mean grain size on time and temperature were considered in a mathematical model according to classic grain growth theory. As no other effects, e.g., pinning by precipitation or impurity-induced solute drag, occur in pure Fe, the grain boundary mobility M was directly determined by fitting the experimental results. The temperature relationship followed an Arrhenius equation with M = 6.79*10−6*exp(-172750R−1T−1) m4J−1s−1. The mobility obtained differed by more than two orders of magnitude from Turnbull's postulation, which agreed with observations in the literature. The results matched published data extrapolated from a recent study on austenite grain growth in multicomponent steels.

Research Progress and Trends in Iron Metal Purification Processes

Traditional industrial pure iron can no longer meet the requirements of many core industries, such as aerospace, electronic information, and military industries. Thus, high-purity iron has attracted considerable interest. Pyrometallurgy, hydrometallurgy, and electrometallurgy provide extensive research platforms for purifying and developing novel processes for producing high-purity iron. In this paper, we review latest research advances in high-purity iron purification methods and production processes and summarize the merits of each purification method. Moreover, we propose a production process that ensures the production of high-purity iron while reducing carbon emissions. In this process, iron ore is leached using a hydrometallurgical process, high-purity iron is obtained by electrolysis from clean energy sources, such as photovoltaics and wind power, and the purity of iron is increased to over 5N with a pyrometallurgy process.

Experimental Investigation of the Porous Free Zone of Silicon Cemented Layer Obtained through Pack Cementation

The development of a porous free zone of the silicon cemented layer represents a scientific and technical challenge. The limitation of the effects of the Kirkendall–Frenkel phenomena requires the right control of the thermochemical processing parameters (temperature, time, and chemical) and thorough knowledge of the related interaction with the specific elements of the metallic matrix of the thermochemically processed product. Through the experimental programming method, the individual and cumulated effects of the thermochemical processing parameters on (Fe-Armco) high-purity iron cemented by silicon in ferrosilicon (FeSi75C) powdered solid media have been quantified. It was concluded that ferrosilicon with silicon concentrations higher than 60% (FeSi75C) represents a redoubtable active component, especially in a temperature range higher than 1100 °C. In the layer cemented with silicon, the presence of nitrogen was also observed, as a direct consequence of the composition of the medium used for cementation. The presence of this element is the predominant result of the manifestation of the ionic phenomenon of adsorption. The correlations between these parameters and the dimension of the porous free zone of the silicon cemented layer in the vicinity of the thermochemically processed surface have been determined.

ON THE INTERACTION OF ALLOYING ELEMENTS WITH GRAIN BOUNDARIES OF HIGH-PURITY NICKEL AND IRON

Purpose. Proof of the reality of the effect of displacement of some microadditives from the internal boundaries of the grains into their internal volumes for reasons of purely thermodynamic concepts.
 Research methods. The initial data were specially selected chemical compositions of model alloys based on high-purity nickel and iron, which are microalloyed with yttrium, lanthanum, zirconium and rhenium. The choice of nickel and iron as the basis for the alloys under study is due to the fact that they are the base for a large group of industrial alloys (heat-resistant nickel materials and a wide range of steels for various purposes).
 The lattice parameters of nickel and iron were determined using an improved DRON-1 type diffractometer in copper (nickel alloys) and iron (iron alloys) X-ray radiation with monochromatization of diffracted beams. The lattice parameters were determined, respectively, using the (420)a and (220)a lines, respectively, for nickel and iron alloys.
 Results. During recrystallization, migrating grain boundaries in nickel and iron retain impurity atoms and still partially “sweep” them out of the grain volume. The thickening of the boundary zones (that is, their "loosening") prevents the possibility of supersaturation of the interfaces with microalloying impurities.
 The effect of significant displacement of some microalloying elements (zirconium and rhenium) deep into the grains of the matrix phases (nickel and iron) has been established.
 It has been found that such microalloying elements as lanthanum (cerium) and yttrium have the most effective influence on the strength characteristics of the studied metallic materials.
 Scientific novelty. Graphs of changes in the chemical composition of microalloyed basic solutions (nickel and iron) are plotted while maintaining the fine structure of grain boundaries. If they are loosened, this crowding out effect disappears.
 Practical value. Since the effect of microalloying (as shown in the presented works) significantly affects the strength characteristics of materials, the results of the study showed which of the selected microalloying elements act most effectively in this direction.