Mn Solid Solution Research Articles

Radiation Resistance of High-Entropy Alloys CoCrFeNi and CoCrFeMnNi, Sequentially Irradiated with Kr and He Ions.

This work studied the effect of sequential irradiation by krypton and helium ions at room temperature on the composition and structure of CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Irradiation of the HEAs by 280 keV Kr14+ ions up to a fluence of 5 × 1015 cm-2 and 40 keV He2+ ions up to a fluence of 2 × 1017 cm-2 did not alter their elemental distribution and constituent phases. Blisters formed on the nickel surface after sequential irradiation, where large blisters had an average diameter of 3.8 μm. The lattice parameter of the (Co, Cr, Fe and Ni) and (Co, Cr, Fe, Mn and Ni) solid solutions increased by 0.17% and 0.37% after sequential irradiation, respectively. Irradiation by Kr ions led to a decrease in tensile macrostresses in the HEAs in the region of krypton ion implantation (Region I) and the formation of compressive macrostresses in the region behind the peak of implanted krypton (Region II). Sequential irradiation formed large compressive stresses in Ni and HEAs equal to -131.5 MPa, -300 MPa and -613.5 MPa in Ni, CoCrFeNi and CoCrFeMnNi, respectively, in the Region II. Irradiation by krypton ions decreased the dislocation density by 1.6-2.3 times, and irradiation with helium ions increased it by 11-15 times relative to unirradiated samples for CoCrFeNi and CoCrFeMnNi, respectively. Sequentially irradiated CoCrFeMnNi HEA had higher macrostresses and dislocation density than CoCrFeNi.

Constructing Ce–Mn/Al2O3 with different active components for low temperature catalytic degradation of chlorobenzene in soil

Soil remediation containing numerous organic contaminants is of great significance to ecological environment. Herein, the synergetic effects of Ce–Mn/Al2O3 with different active components on catalytic thermal desorption of chlorobenzene in soil were investigated. The optimized Ce–Mn/Al2O3 drastically enhance the desorption efficiency of chlorobenzene, and the corresponding conversion reaches 100% within 1 h at a low temperature of 120 °C. The superior performance is ascribed to the formation of Ce–Mn solid solution during the calcination process, resulting in a certain lattice change to the generation of abundant oxygen vacancies and acidic sites. Combining with the analysis of in-situ diffuse reflectance infrared spectroscopy and gas chromatography-mass spectrometry, the final products of chlorobenzene are decomposed into CO2, H2O, Cl2 and HCl. This work sheds light on the rational design of highly-active catalysts for practical applications of sustainable soil remediation.

Magnetic properties and structure of the Fe63.5Mn10Cu1Nb3Si13.5B9 alloy nanocrystallized under tensile stresses

The influence of introduction of 10 at. % Mn for Fe in the classical Finemet (Fe73.5Cu1Nb3Si13.5B9) on its magnetic properties, magnetic anisotropy, and structure is studied after nanocrystallization annealing at 520°C with varying duration from 10 min to 4 h in the presence of tensile stresses (σ = 200 MPa) (SA) and without them (NA). It is established that in the Fe63.5Mn10Cu1Nb3Si13.5B9 alloy (Mn10-alloy), just as in the classical Finemet, SA results in the induction of transverse magnetic anisotropy, yet, the constant of induced magnetic anisotropy is decreased by a factor of 4. The coercivity of the Mn10-alloy grows with increasing annealing time upon both SA and NA, while that of Finemet virtually does not change. Unlike Finemet, in the Mn10-alloy, along with the α-Fe(Si, Mn) solid solution and Fe3Si phase, there form borides already after 10-min treatment. This results in the change in the volume fractions of structure components with a negative magnetostriction, α-Fe(Si, Mn) and Fe3Si, which are responsible for the induction of transverse magnetic anisotropy, and positive magnetostriction, FeB, Fe2B, Fe3B, and hence, most likely, causes decrease in the constant of IMA of the Mn10-alloy. Besides, unlike Finemet, the average grain size in the alloy with Mn increases with the time of annealing, which, together with the formation of borides, increases the coercivity.

Optical properties of Zn0.75Mg0.25O:Mn ceramics

Mn-doped ZnO, MgO and Zn0.75Mg0.25O samples ([Mn] = 0.1 at.%) were produced by conventional solid-state technique and investigated by means of XRD, EPR, absorption, photocurrent, photo- and cathodoluminescence methods. It was shown that Zn0.75Mg0.25O solid solution with hexagonal structure has the bandgap of Eg ∼3.65 eV. The quenching of host defect-related luminescence in ZnO:Mn and in hexagonal Zn0.75Mg0.25O:Mn was observed, while the Mn-related emission being absent. The energy level of MnZn2+ center in hexagonal Zn0.75Mg0.25O:Mn was found to be at 2.16 eV below conduction band (c-band) bottom and all excited states of MnZn2+ ions, including the lowest one, reside in c-band, as it takes place in ZnO:Mn. It is concluded that the necessary condition to obtain Mn-related light emission in Mn-doped alloys is to make deeper the lowest excited level of MnZn2+ ions. One of the solutions is to produce Zn1-xMgxO:Mn solid solution with the bandgap energy larger than 4.0 eV using nonequilibrium fabrication approaches.

Calculation of critical shear stress for binary magnesium alloys: A first-principles study

The selection of alloying elements with the effect of “Solid solution strengthening and ductilizing” (SSDD) is an important way to develop high-performance magnesium (Mg) alloys recently, and the critical shear stress (CRSS) is an intrinsic parameter that characterizes the effect of SSDD. In this study, the CRSS of four slip systems in Mg-X (X = Al, Zn, Ca, Li, Mn, Sn, Bi, Ag Ga, In, Zr), all of which have a solid solubility (>0.5 at%) in Mg, are calculated using a combination of first-principles and the Peierls-Nabarro (P–N) model, and the SSDD effect of the alloying elements is studied systematically and experimentally verified. Calculations indicate that solid solutions of Mn, Ag, and Li can increase the CRSS of basal system and reduce the difference between the three non-basal and basal systems. Solid solutions of Zn, Ca and Zr can narrow the CRSS gap between at least one non-basal slip system and the basal slip system, but other elements have no positive effect. A smaller equilibrium volume and larger charge density around Mn or Ag element than that of Li, which makes CRSS larger. At the same time, the simulation results are validated by experiment. Mg–Ag alloy exhibits improved strength and plasticity, as well as a large number of <c+a> dislocations under TEM, which is consistent with the calculation finding that Ag promotes < c+a> dislocation slip. This study can provide guidance for the selection of solid solution elements for Mg alloys.

Clarification of the anodic dissolution behavior of metallurgical structures during electrorefining of Al-Mn alloys in a 1-ethyl-3-methyl-imidazolium chloride-AlCl3 ionic liquid

Recycling Al is crucial to reduce the energy and environmental costs of Al manufacturing; however, the reclamation efficiency of high-quality Al from Al alloys is limited by the co-deposition of impurities during the electrorefining process. To address this issue, the anodic dissolution behavior of metallurgical structures within various Al-Mn binary alloys in 1-ethyl-3-methyl-imidazolium chloride-AlCl3 ionic liquid was investigated. During the constant-potential electrolysis of Al-1.5%Mn cast and cold-rolled plate alloys, an enriched layer derived from Mn solid solution was formed at an electrorefining potential of 0.2 V; this was attributed to preferential dissolution of Al in the matrix phase, followed by Mn accumulation at the Al surface. Furthermore, dissolution of the Al-Mn-Fe and Al-Mn intermetallic compounds occurred at 0.6 and 1.0 V, respectively; thus, the dissolution behavior of Mn in the Al-Mn alloys differed between the Mn solid solution in the matrix phase and the Mn-containing intermetallic compounds. These results indicate that by controlling the microstructure of the Al-Mn alloy and the applied anodic potential, the dissolution of Mn into the 1-ethyl-3-methyl-imidazolium chloride-AlCl3 electrolyte can be suppressed, thus preventing its co-deposition with Al on the cathode. This development is therefore anticipated to inform the development of electrorefining processes to obtain high-quality recycled Al for numerous manufacturing applications.

Development of high strength-ductility Mg-Er extruded alloys by micro-alloying with Mn

This work systematically investigated the influence of the micro-Mn addition on the microstructures and mechanical properties of Mg-Er alloys. To investigate their deformation mechanisms during tensile testing, electron back-scattered diffraction, transmission electron microscopy, slip trace analysis, and visco-plastic self-consistent polycrystal constitutive (VPSC) modeling were used. The study showed that the as-solid solution samples only consist of the α-Mg phase. All samples exhibit a complete dynamic recrystallized (DRXed) microstructure with an average grain size of 2.79 µm after hot extrusion. The ductility first increases from 26.02 % to 35.34 % and then remains unchanged with the increment of Mn content. Meanwhile, the yield strength significantly increases from 95 MPa to 200 MPa. According to VPSC results, the initial slip resistance (τ0) difference between prismatic and basal slips decreases from 109 MPa to 92 MPa and τ0 between pyramidal and basal slip systems from 129 MPa to 112 MPa. Both the VPSC and two-beam diffraction results confirmed that pyramidal<c+a>slip and<a>slip were activated during tensile deformation. The quantitative analysis of the slip trace line verified that the volume of non-basal slip reached 65 % when the content of Mn was increased to 0.9 wt%. Mn in solid solution increased the activity of pyramidal<c+a>and prismatic<a>dislocations during deformation, which is beneficial for accommodating c-axis strain. Consequently, the ambient ductility of Mg-2Er alloy with Mn addition is improved.

Graphitic carbon nitride (g-C3N4) as a super support for Mn–Ce based NH3-SCR catalyst: Improvement of catalytic performance and H2O/SO2 tolerance for NOx removal

Low temperature NH3 selective catalytic reduction (NH3-SCR) technology is an efficient and economical strategy for NOx removal. In this study, Mn–Ce oxides supported on graphitic carbon nitride (g-C3N4) was applied to the NH3-SCR of NOx at low temperature compared with Mn–Ce oxides supported on commercial TiO2, γ-Al2O3, and montmorillonite (MNT). The NOx conversion and H2O/SO2 tolerance of 8% Mn–Ce/g–C3N4–300 were superior to those of 8% Mn–Ce/TiO2-300, 8% Mn–Ce/γ-Al2O3-300 and 8% Mn–Ce/MNT-300 in the temperature window of 100–300 °C, and more than 95% NOx conversion could be obtained within the whole temperature range. According to the experimental and characteriazation results, the superior low temperature NH3-SCR performance of 8% Mn–Ce/g–C3N4–300 could be attributed to the formation of Ce–O–Mn solid solution structure, the higher concentrations of the surface elements, the optimun low-temperature reduction behavior, the largest amount of total acid sites, the highest (Mn4++Mn3+)/(Mn4++Mn3++Mn2+) and (Ce3+)/(Ce3++Ce4+) ratios, and the modest Oα/(Oα+Oβ) ratio.

Ce–Mn Oxide Nanocomposites for Catalytic Removal of H2S

The development of efficient and stable nanocatalysts is crucial for the catalytic removal of H2S through selective oxidation to sulfur. Inspired by the different catalytic activity and selectivity of CeO2 and MnO2 for the reaction, cerium–manganese (Ce–Mn) nanocomposite oxides with tunable phase structure and unique surface properties were constructed to optimize the catalytic performance. By regulating the molar ratio of Ce and Mn components, a novel catalyst structure comprising Ce–Mn solid solution and amorphous CeO2 is synthesized from Ce–Mn oxide with nCe/nMn ratio of 0.5 (50Ce–Mn). Compared with the unmodified MnO2, the tailored 50Ce–Mn possesses a high specific surface area, which facilitates the access of reactants to active sites and the desorption of formed sulfur. More importantly, strong Ce–Mn interaction and abundant surface-active oxygen species are generated, contributing to the regeneration of Mn4+/Ce4+ active sites, facilitating the formation of sulfur, and inhibiting the accumulation of sulfates during the reaction. Consequently, 50Ce–Mn presents a superior catalytic activity (T100 of 150 °C), stability, and sulfur selectivity even under relatively high weight hourly space velocity conditions (23,000 mL·g–1·h–1). This study provides an example of how catalytic performance can be boosted through phase structure regulation on nanocomposites.

焼戻マルテンサイト鋼の高C化による粒界破壊強度の向上

Effect of carbon (C) content (0.05 mass% to 0.3 mass%) on critical intergranular fracture stress of tempered martensite steel was investigated using 3 mass% manganese (Mn) steel. The critical intergranular fracture stress was obtained by calculating the maximum principal stress at fracture in a circumferential notched specimen tensile test using elastoplastic finite element analysis. As a result, critical intergranular fracture stress of tempered martensite steel increased with increasing C content. Therefore, the dominant factors of critical intergranular fracture stress were examined from the viewpoints of the amount of segregation of each element on prior-austenite grain boundaries and the grain size of the martensite substructure. The first result was found to be the effect of reducing the amount of Mn segregation by increasing C content. This was thought to be because cementite acts as a solid solution site for Mn, and the amount of Mn in solid solution in the matrix phase is reduced by increasing the C content. The second result was found to be the effect of refining the substructure of martensite surrounded by high angle grain boundaries by increasing the C content. This indicates that grain size also affects crack initiation resistance in intergranular fracture by determining the stress concentration at the grain boundaries as the distance of dislocation accumulation.

Ferromagnetic and antiferromagnetic orders in low dimensional PbBiFe1-xMxO4 (M = Mn and Co) solid solutions

A new solid solution of composition PbBiFe1-xMxO4 (M ​= ​Mn and Co, 0 ​≤ ​x ​≤ ​0.15–0.2) with low structural dimensions has been synthesized by solid-state reaction at 873–923 ​K. The crystal structures have been investigated using X-ray and neutron diffraction. The presence of Co2+/Co3+ on the Fe3+ sites and oxygen vacancies in PbBiFe1-xCoxO4 is revealed by its unusual volume increase and TGA, while the volume contraction of PbBiFe1-xMnxO4 indicates the substitution of Mn4+/Mn3+ on the Fe3+ sites. This leads to unexpected greater and smaller metal-metal distances inside the chains for the Co and Mn case, respectively, compared with the undoped materials. All the PbBiFe1-xMxO4 materials display long-range antiferromagnetic order but are suppressed by cationic substitution, as evidenced by a decrease in TN. Additional intrinsic short-range ferro- (or ferri-) magnetic transitions in the Co-doped materials are evidenced by magnetic hysteresis and frequency-dependent χ’ peak around TF. The introduction of ferromagnetic intrachain clusters in PbBiFe1-xCoxO4 is rationalized through a competitive mechanism between direct AFM exchange interaction and 90°- type FM superexchange interactions, which provided insights to tune the magnetic properties and design low dimensional functional materials.

Insights into mixed metal sulfides of MnxSn1-xS2 for high-performance supercapacitors

• Substitutional solid solution Mn x Sn 1-x S 2 can be easily synthesized. • Mn 0.33 Sn 0.67 S 2 delivers the highest capacitance electrochemical performances. • The content of Mn plays a crucial role in the lattice parameter and electrochemical properties. • Mn 0.33 Sn 0.67 S 2 //AC achieves excellent energy density of 15.68 Wh kg −1 at 0.15 kW kg −1 . A variety of mixed metal sulfides of Mn x Sn 1-x S 2 nanoflowers were synthesized by a facile one-step template-free solvothermal method and their ability of capacitive energy storage were evaluated as potential supercapacitor electrode materials. Substitutional solid solutions of Mn x Sn 1-x S 2 with various chemical compositions can easily be produced by varying the Mn/Sn molar ratio in the reactants. Among these sulfides, Mn 0.33 Sn 0.67 S 2 exhibits the highest electrochemical performance with a high specific capacitance of 1118.92 F g −1 at 1 A g −1 , great rate capacity and superb cycling stability. Because of its increased electrochemical active sites, altered microstructure, and improved electrical conductivity brought on by lattice distortion and the synergistic effect of elemental substitution, Mn 0.33 Sn 0.67 S 2 exhibits good performance. What’s more, an asymmetric supercapacitor of Mn 0.33 Sn 0.67 S 2 //AC (activated carbon) possesses a high energy density (15.68 Wh kg −1 at 150.1 W kg −1 ). Thus, Mn doped tin sulfides highlight widely applicable to advance high-performance energy storage technology.

Achieving opto-responsive multimode luminescence in Zn1+xGa2−2xGexO4:Mn persistent phosphors for advanced anti-counterfeiting and information encryption

Optical characteristics of phosphors, e.g. color output, decay process and external field stimulation mode (including opto-, thermo- and mechano-stimulation), play an important role in the areas of information storage, anti-counterfeiting and bio-imaging applications. Persistent luminescence (PersL) phosphors are particularly suitable for such applications owing to their multimodal luminescence features such as photoluminescence (PL), PersL, photostimulated luminescence and mechanoluminescence. However, conventional PersL phosphors are suffering from a huge challenge to develop a single material for multicolor anti-counterfeiting. Herein, the Zn1+xGa2−2xGexO4:Mn (0 ≤ x ≤ 1) solid solution phosphors are synthesized, which can emit from green to yellow, golden, pink, and red PL. In addition, the phosphors also show the thermo-mechano-opto-stimulated green PersL after irradiation of a UV 254/365 nm lamp. Based on the multimode and multicolor luminescence features, the advanced anti-counterfeiting and optical data storage are designed. Results show that the multimodal luminescence feature with high information capacity can be conveniently identified by using a luggable ultraviolet lamp or NIR laser diode. This extraordinary material will make anti-counterfeiting more sophisticated and show advanced security in the applications of data encryption.

Intermetallic compounds of the Cr–Mn system investigated using in situ powder neutron diffraction: The reported order-disorder transformation of the σ phase elucidated

Cr–Mn system is very important for many applications. In the present work, the reported intermetallic compounds have been studied using in situ high temperature neutron powder diffraction. For the first time, site occupancies in a σ phase are obtained as a function of temperature by Rietveld analysis. They are compared with calculated data obtained from DFT. The previously reported order-disorder transition in the σ phase around 1000 °C is shown to be in fact a congruent phase transformation to the bcc Cr–Mn solid solution. This solid solution is probably continuous between pure Cr and δ-Mn. The second reported intermetallic α’ phase (Cr2Mn3) phase is shown to be in fact a ternary nitride of the Cr–Mn–N system that should not appear in the binary phase diagram. The present work clarifies and explains all the features of the previous literature on this system and brings major revisions to the phase diagram. General conclusions are drawn concerning mistakes that can be done in the evaluations of phase diagrams.

Two dimensional porous Ni12P5 sheet modified Mn0.5Cd0.5S for efficient photo-catalytic hydrogen production

In this paper, solid solution Mn 0.5 Cd 0.5 S (MCS) nanocrystals is modified by two-dimensional (2D) porous Ni 12 P 5 sheet to form Ni 12 P 5 /MCS composite, which shows photo-catalytic hydrogen production rate as high as 63.22 mmol g −1 h −1 . Compared with pure Mn 0.5 Cd 0.5 S, the hydrogen production performance is nearly 9 times improved. As a non-noble metal co-catalyst, the 2D structure and unique electronic properties of Ni 12 P 5 not only promoted the absorption of light, but also effectively inhibited the recombination process of photo-generated carriers. The successful preparation of Ni 12 P 5 /MCS composite provided an effective way for improving the photo-catalytic performance of semiconductor materials. Ni 12 P 5 /Mn 0.5 Cd 0.5 S composite photocatalyst were firstly synthesized using a simple low-cost ultrasound assisted method with high hydrogen evolution rate and stability. • 2D Ni 12 P 5 sheet with porous structure was successfully synthesized for the first time by hydrothermal method. • Ni 12 P 5 /Mn 0.5 Cd 0.5 S exhibited an excellent photocatalytic hydrogen evolution rate. • Coupling the multiple effects to boost the photocatalytic activity.

A strategy to regulate the microstructure and properties of Mg-2.0Zn-1.5Mn magnesium alloy by tracing the existence of Mn element

The role of Mn existence types on microstructure and mechanical properties of extruded Mg-2.0Zn-1.5Mn magnesium alloy is investigated. Four different Mn existence types in Mg-2.0Zn-1.5Mn magnesium alloy are obtained by different heat treatment. The four types include: (1) solid solution Mn atoms, (2) nanoscale α-Mn phase, (3) solid solution atoms + micron scale α-Mn phase, (4) micron scale α-Mn phase + nanoscale α-Mn phase, respectively. The result shows pre-existed nanoscale α-Mn particles present good pinning effect for refining grains. The micron scale α-Mn phase activates the particle stimulated nucleation (PSN) mechanism. The combination of micron scale α-Mn phase + nanoscale α-Mn phase state presents the best grain refining effect with an average grain size of 1.3 µm. The mechanical properties are significantly enhanced, the tensile yield strength, tensile strength and fracture elongation are 267 MPa, 305 MPa, 28.6%, respectively. Based on the results, four basic rules for preparing fine grained Mn-containing Mg alloys are proposed and an ideal pre-extrusion state of Mn-containing alloy is obtained: namely, direct extrusion in the as-cast-aging state. Besides has great potential for grain refinement, this state also can be regulated by the coordination of PSN effect and pinning effect in Mn-containing Mg alloy.

Solute-induced strengthening during creep of an aged-hardened Al-Mn-Zr alloy

We examine the precipitation and creep behavior of Al-0.5Mn-0.02Si (at.%) alloys, with and without the L12-forming elements Zr and Er (0.09 and 0.05 at.%, respectively), utilizing isochronal aging experiments as well as compressive and tensile creep tests performed between 275 and 400 °C. The Al-0.5Mn-0.09Zr-0.05Er-0.05Si alloy exhibits an unusually high creep resistance in the peak-aged state, which is significantly better than that observed generally in its Mn-free L12-strengthened counterparts; for example, the creep threshold stresses at 300 °C are 34-37 MPa, about three times higher than those in a Mn-free Al-0.11Zr-0.005Er-0.02Si alloy. Scanning transmission electron microscopy illustrates that nanoscale Al3(Zr,Er) L12-precipitates are formed in the dendritic cores and micron-sized Al(Mn,Fe)Si α-precipitates in the interdendritic channels. Moreover, the Al(f.c.c.)-matrix remains supersaturated with randomly distributed Mn solute atoms, as determined by atom-probe tomography and electrical conductivity measurements, for months at creep temperatures. Creep experiments on the Zr- and Er-free Al-0.5Mn-0.02Si solid-solution alloy reveal a small primary creep strain, a high apparent stress exponent, na ∼9-7, and a threshold-stress-type behavior. After ruling out other possible mechanisms, we provide evidence that the threshold stress in this precipitate-free alloy originates from dislocation/solute elastic interactions leading to a strong drag force exerted on edge dislocations, hindering their ability to climb. The relatively high creep resistance of Al-0.5Mn-0.09Zr-0.05Er-0.05Si is interpreted in terms of the synergy between this solute-induced threshold stress (SITS, from Mn in solid-solution) and the known precipitate-bypass threshold stress (from the L12-nanoprecipitates).

Catalytic Combustion of Toluene Over Broccoli‐Shaped Ce1Mn3Ox Solid Solution

AbstractCe1Mn3Ox with broccoli morphology were synthesized by simple redox‐precipitation. A series of Ce−Mn‐based catalysts with different activities were obtained by changing calcination time. The catalytic activity of Ce−Mn solid solution was greatly improved compared with that of pure oxides. Ce1Mn3Ox‐1 (C1M3‐1) briefly calcined at 400 °C showed the optimal catalytic performance (WHSV=60000 mL h−1 g−1, Toluene concentration=3000 ppm, T100%=180 °C). The characterization results unambiguously identified that C1M3‐1 had a large amount of Ce3+, Mn3+ and surface adsorbed oxygen. This work emphasized the preparation of Ce−Mn‐based solid solution with strong interaction by simple redox precipitation, and the activity of the catalyst was regulated by changing the calcination time. The advantages of low cost, high efficiency, good stability, and recycling indicated that the catalyst had the possibility of industrial application.

In-situ TEM Investigation of Solid Phase Transformations and Reactions

In this paper, an example of phase analysis during annealing is presented using in-situ TEM. The example is demonstrated on amorphous Cu-Mn/C thin films focusing on phase identification in a multicomponent system. The transient states following the crystallization of the amorphous Cu-Mn alloy and the reaction with the C substrate were analyzed by evaluating the diffraction patterns recorded at different temperatures. The camera constant was calibrated using the internal standard method. The change in composition of the Cu(Mn) solid solution was calculated by separating the effect of thermal expansion and solute concentration. Identification of the forming phases was aided by analyzing and comparing the probability of formation of all phases in the Cu-Mn-C-O system. After the crystallization of amorphous Cu-Mn alloy into Cu(Mn) and α-Mn-based solid solutions, the formation of the following carbide phases was observed: Mn23C6, Mn5C2 and Mn7C3.

Electrodeposition of Fe–Mn alloys from chloride-based bath: A preliminary study for biomedical applications

Abstract Fe–Mn alloys are promising candidates for less-invasive and temporary implants such as bioabsorbable stents. However, their composition and microstructure must be tailored to assess an adequate corrosion rate for the desirable lifespan of the stent. This study aimed to evaluate the development of Fe–Mn alloy and its structure and properties correlation when processed by electrodeposition. Planar samples were produced by potentiostatic deposition at two different potentials, −1.3 and −1.7 V vs. Ag/AgCl, from a chloride-based acidic electrolyte with different amounts of NH4Cl. It was verified that, in more negative deposition potentials, the deposition interface changes from planar to dendritic, leading to more ramified deposits with a high level of defects like cracks and pores. More negative potentials also increased the Mn content in the deposit from 0.8 to 5.2 wt.% Mn. The microstructure was composed of a single phase of (Fe, Mn) solid solution in the −1.3 V vs. Ag/AgCl deposit, while the deposit obtained at −1.7 V vs. Ag/AgCl exhibit two phases, one rich in Mn and the other rich in Fe. A higher concentration of NH4Cl in the electrolyte leads to an increase in the Mn content (5.2 wt.% Mn), maintaining the monophasic microstructure. Although several challenges still remain, these results prove that is possible to obtain Fe–Mn bioabsorbable alloys by electrodeposition, which opens a new processing route for these alloys.