Increasing Fe Content Research Articles

EFFECT OF Fe CONTENT ON THE STRUCTURAL AND MAGNETIC PROPERTIES OF TERNARY (Ni60Co40)100−xFex NANOMATERIALS SYNTHESIZED BY HYDROTHERMAL ROUTE

The effect of iron content on the structure, morphology and magnetic properties of (Ni[Formula: see text]Co[Formula: see text])[Formula: see text]Fe[Formula: see text] powders synthesized by hydrothermal method has been studied. Several samples have been elaborated for different Fe content ([Formula: see text] = 0, 3, 5, 7, 10 and 13.5). The as- prepared samples have been characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometry (VSM). From XRD spectra and for all Fe content, we have shown the presence of both face centered cubic (FCC) and Hexagonal (HCP) nanosized phases. The lattice parameter increases with increasing Fe content and the grains size varies with Fe content to reach a minimum value of 32 nm for (Co[Formula: see text]Ni[Formula: see text])[Formula: see text]Fe[Formula: see text]. From hysteresis curves, we have extracted the saturation magnetization, Ms, and the coercivity, Hc. We noticed that Ms increases and then decreases as a function of Fe content. The values of Hc vary from 156 Oe to 186 Oe depending on the particles shape.

Visible light induced self‐cleaning performance of iron‐doped TiO2 nanoparticles for surface applications

AbstractThis study aimed to enhance the visible light photosensitivity of TiO2 nanoparticles for self‐cleaning applications by doping with Fe3+. Nanocrystalline undoped and Fe‐doped TiO2 (Ti1 − xFexO2, x = .01–.04) were synthesized via sol–gel method. The results demonstrated that Fe‐doped TiO2 nanoparticles exhibited visible light sensitivity and self‐cleaning properties. An increased Fe concentration resulted in a red shift in the absorption band edge. Fe0.03‐doped TiO2 with an average particle size of ∼21 nm, a crystallite size of ∼12 nm, and a band gap of ∼2.86 eV showed the highest photocatalytic activity (60% methylene blue degradation) and super‐hydrophilicity (water droplet contact angle 9°) under visible light radiation. These findings highlight the potential of Fe‐doped TiO2 nanoparticles as a promising material for self‐cleaning applications.

Topological Hall effect and the transition of the anomalous Hall effect mechanism in hexagonal alloys Mn3.1− xFexGe0.9 (x = 1.6, 1.8, 2.0)

Hexagonal Mn3Ge, with both kagome lattice and triangular antiferromagnetism, has gained significant attention due to its large anomalous Hall effect (AHE), resulting from the non-vanishing Berry phase. In this study, we present the magnetic and anomalous transport properties of a series hexagonal D019 type Fe-doped Mn3Ge alloys with the composition of Mn3.1−xFexGe0.9 (x = 1.6, 1.8, 2.0). The ferromagnetic interactions gradually increase with increasing Fe content. The longitudinal resistivity of all alloys exhibits a typical metallic behavior, increasing with temperature from 5 to 390 K. The residual resistivity decreases from 120.4 to 67.8 μΩ·cm as x increases from 1.6 to 2.0. A temperature-driven Lifshitz transition and a spin reorientation have been observed in the x = 1.6 alloy. Topological Hall effect accompanied by the spin reorientation is demonstrated. The maximum value of the topological Hall resistivity ρxyT is approximately 0.16 μΩ·cm. The relationship of ρxyA∝ ρxx in x = 1.6 alloy suggests that the extrinsic skew scattering predominantly contributes to the AHE mechanism. In the case of x = 1.8 and 2.0, both intrinsic and extrinsic factors contribute to the AHE. The anomalous Hall conductivity of our polycrystalline samples at room temperature is comparable to that of single crystal Mn3Ge, which is advantageous for practical applications. This study reveals the effectiveness of chemical engineering in tailoring nontrivial spin textures and the AHE.

Valorisation of acid mine drainage waste for synthesis of ferric ammonium sulfate (FAS)

Green and sustainable production of secondary products from waste sources is needed for a global circular economy. The primary aim of this work was to produce ferric ammonium sulfate (FAS) from acid mine drainage (AMD). AMD with a Fe content of approximately 240 mg/L was used as a matrix to model FAS formation under different solution concentrations of Fe and S (as ferric sulfate and sulfuric acid). This approach offered the benefit of identifying boundary conditions for FAS synthesis from wastes, so that the results of this study can be applied to many different AMD compositions. Results showed that increased Fe concentrations were associated with higher crystal yields and more selective crystallisation. Fe, S, and Al were more selectively incorporated over other elements present in AMD, however, XRD analysis did not show additional Al-bearing alum products. FAS was produced for AMD solutions where Fe was above 2500 mg/L, which demonstrates that FAS could be formed from iron-rich waste solutions.

Dissolved organic matter and Fe/Mn enhance the combination and transformation of As in Lake Chaohu Basin

The phenomenon of algal blooms resulting from lake eutrophication has the potential to increase the concentration of dissolved organic matter (DOM) and consequently influence the environmental behaviour of arsenic (As). In the subtropical region, the interplay between DOM, Fe/Mn and As becomes complex as Fe/Mn-rich substances from soils and sediments enter eutrophic lakes. The mechanisms by which DOM-Fe/Mn interactions affect the transformation of As species remain uncertain. Therefore, the Chaohu Lake Basin was selected as a representative case study site to investigate the levels of DOM, As, Fe and Mn in the water and to establish their associations. In addition, the interaction mechanism between DOM-Fe/Mn and As was investigated by elucidating the transformation behaviour of DOM-Fe/Mn on As species in a controlled laboratory environment. The results showed that in cases where the coexistence of Fe and Mn concentrations was relatively low (e.g. Fe < ∼0.5 mg/L and Mn < ∼0.6 mg/L), the concentration of As in water would increase proportionally with the simultaneous increase of both Fe and Mn concentrations (As < 5 μg/L). However, when the concentration of either Fe or Mn reached 10 mg/L, the proportion of As complexed by DOM increased significantly, reaching 99.73% and 99.66%, respectively. In the configuration of a metallic bridge, the elements Fe and Mn act as connectors between negatively charged DOM and As, thereby increasing the adsorption capacity of DOM for As. The alcohol and alkene functional groups present on the DOM-Fe/Mn surface show a preference for binding with free species of As in aqueous environments. In addition, the reductive groups on the surface of DOM not only directly convert As(V) to As(III), but also facilitate the reduction of Fe(III) to Fe(II), resulting in the indirect conversion of As(V) to As(III). Thus, this study provides a comprehensive understanding of the transport and transformation processes of arsenic in subtropical eutrophic lakes.

Relationship among intrinsic magnetic parameters and structure and crucial effect of metastable Fe3B phase in Fe-metalloid amorphous alloys

The intrinsic heterogeneity of an amorphous structure originates from composition, and the structure determines the magnetic properties and crystallization models of amorphous magnets. Based on classical Fe–B binary magnetic amorphous alloys, the relationship between the structure and magnetic properties was extensively studied. The stacking structure of Fe–B binary amorphous alloys exhibit discontinuous changes within the range of 74–87 at.% Fe. The structural feature can be expressed as Amor. Fe3B matrix + Fe atoms are transforming into Amor. Fe matrix + B atoms with the increase of Fe content. The solute atoms are uniformly distributed in the amorphous matrix holes, similar to a single-phase solid solution structure. The transition point corresponds to the eutectic crystallization model composition (Fe82B18 to Fe83B17). A high Fe content will amplify magnetic moment sensitivity to temperature. Under a given service temperature, the disturbance effect of magnetic moment self-spinning will offset the beneficial effect of increasing Fe content and induce the saturation magnetization (Ms) value to decrease. Binary amorphous Fe–B alloys obtain the maximum Curie temperature near 75 at.% Fe, which is slightly smaller than that of the corresponding metastable Fe3B phase, i.e., the amorphous short-range order structure maintains the highest similarity to the Fe3B phase. The chemical short-range ordering (SRO) structure of amorphous alloys exhibits heredity to corresponding (meta)stable crystal phases. The unique spatial orientation structure of the metastable Fe3B phase is the structural origin of the amorphous nature. This study can guide the composition design of Fe-metalloid magnetic amorphous alloys. The design of materials with excellent magnetic properties originates from a deep understanding of precise composition control and temperature disturbance mechanism.

Effect of Fe addition in W-Ni-Cu heavy alloy processed through powder metallurgy on microstructure and mechanical properties

In the present investigation, effect of Fe addition to 90 W-aNi-bCu-xFe, (where a/b was 6/4; x = 0, 0.5, 1.0, 1.5, and 2.0) on the microstructure and mechanical behaviour of Tungsten heavy alloys (WHAs) was undertaken. WHAs were fabricated via powder metallurgy processing. Sintering of green compact was done with a horizontal tubular furnace at 1400 °C under hydrogen atmosphere for 60 min. A synergetic effect of Fe dissolution in Ni-Cu binder on densification response was observed. The tungsten solubility in the matrix was measured using EPMA and found to decrease with the increase of Fe content. The tungsten particle size reduction of up to 20%, compared to 90 W-6Ni-4Cu heavy alloy, was observed. The bulk hardness measurements showed a maximum of about 332 HV5 for 2.0 wt% Fe containing W-Ni-Cu alloy. The mechanical properties, such as compressive and flexural/bending strength were determined by employing the uniaxial compression and three-point bend test and found to be 1732 ± 36 MPa and 1147 ± 22 MPa, respectively. Because of Fe content in the WHAs, lower volume % of the matrix and higher W-W contiguity in the microstructure resulted leading to superior compressive strength. Detailed fractography was done on all sintered WHA samples to understand the failure response during transverse loading. Fractography on fracture surface of bend tested samples was carried out. The separation of the W-W interface and W/W trans-granular failure was the predominant fracture mechanism observed.

Increase in iron-bound organic carbon content under simulated sea-level rise: A “marsh organ” field experiment

Rising sea levels have increased the risk of intense flooding in tidal wetlands, potentially leading to rises in soil iron-bound organic carbon (Fe-OC) contents by inhibiting microbial activity. However, flooding-induced Fe-OC accumulation may be attenuated by root activities of tidal wetland plants, which remains under-investigated in tidal wetlands. Here we established manipulative “marsh organ” filed experiments with soils collected from an oligohaline tidal wetland and introduced the indigenous plant species Phragmites australis (Cav.) Trin. ex Steud. These “marsh organ” mesocosms were then subjected to three flooding water-level treatments over a period of 3.5 years. Overall, root biomass, root porosity, and rhizosphere ferric iron-to-ferrous iron [Fe(III):Fe(II)] ratio increased with flooding levels, indicating that enhanced flooding promotes root oxygen loss of tidal wetland plants. The abundances of Fe-oxidizing bacteria (Gallionella) and Fe-reducing bacteria (Geobacter) increased, whereas the abundance of sulfate-reducing bacteria (dsrA gene) decreased with increased flooding, indicating a diversion of Fe from Fe-sulfur associations towards microbially-mediated Fe redox cycling. The soil organic carbon (SOC) pool did not change with increased flooding; however, the Fe-OC-to-SOC ratio (fFe-OC) increased from 9 to 18%. The fFe-OC was strongly related to soil amorphous Fe(III) concentrations and the activities of soil C-acquiring enzymes, both of which were affected by rhizosphere Fe(III):Fe(II) ratios. Thus, increased root oxygen loss, along with enhanced flooding, facilitated increases in amorphous Fe(III) concentrations and C-acquiring enzyme activity. Increased soil amorphous Fe(III) concentrations further promoted Fe-OC accumulation, whereas increased soil C-acquiring enzyme activities reduced the labile organic C pool. Overall, the dominance of the Fe-OC pool increased under enhanced flooding, owing to increased oxygen loss from the roots. Therefore, we outlined that soil C stability will increase in tidal wetland ecosystems that are exposed to future sea-level rise.

Microstructure and magnetic properties in nanocrystalline Pr2Co7-xFex alloys: Experimental and theoretical study

We report on an experimental and theoretical investigation of the microstructural and magnetic properties in nanocrystalline Pr2Co7-xFex compounds. The exchange interactions (Jij) and Curie temperature (TC) values were theoretically determined using mean field theory (MFT), and the results were found to be in excellent agreement with experimental data. The dependence of macroscopic and microscopic magnetic properties on the Fe content (x) was investigated, considering the model of random magnetic anisotropy. The saturation approach (SA) was utilized to analyze magnetization curves (M(H)), and various magnetic parameters, including random anisotropy fields (Ha) and local random anisotropy constant (K1), were studied. It was observed that these parameters increase with increasing Fe content up to x = 0.5 and then decreased for x > 0.5. Moreover, the coercivity (HC) was analyzed using the Herzer model by taking into account the grain size (D) and exchange correlation length (Rf). The experimental HC values were consistent with those derived from the random anisotropy model. Electronic structure calculations based on density functional theory (DFT) were performed to further understand the impact of Fe substitution and the improvements in magnetic performance. The collective findings provide valuable insights into the magnetic properties and behavior of nanocrystalline Ce2Ni7-type Pr2Co7-xFex compounds, aiding in the understanding and design of advanced magnetic materials.

Minority-spin conducting states in Fe substituted pyrite CoS2

There has been a longstanding debate whether the pyrite CoS2 or its alloys with FeS2 are half metallic. We argue using first principles calculations that there is a finite occupation of minority-spin states at the Fermi level throughout the series CoFe x S2. Although the exchange–correlation functional influences the specifics of the electronic structure, we observe a similar trend with increasing Fe concentration in both local density approximation and generalized gradient approximation calculations. Specifically, even as band filling is decreased through Fe substitution, the lowest-lying conduction band in the minority-spin channel broadens such that these states keep getting lowered relative to the Fermi level, which is contrary to the expectations from a rigid band picture. Furthermore, the exchange splitting decreases as more Co atoms are replaced by Fe, and this again brings the minority-spin states closer to the Fermi level. These two mechanisms, in conjunction with the experimental observation that minority-spin bands cross the Fermi level in stoichiometric CoS2, indicate that minority-spin charge carriers will always be present in CoFe x S2.

Improved magnetic properties of Fe substituted La2CoMnO6 for spintronic applications

A detailed study of magnetic behaviour of double perovskites was carried out by developing La2Co1-xFexMnO6; (x = 0.0, 0.2, 0.5, 0.8 and 1.0) via sol–gel technique. All samples showed single magnetic transition except pure LCMO (x = 0.0) and LCFMO2 (x = 0.5). Temperature dependent inverse magnetic susceptibility (χ-1) was fitted in accordance with Curie-Weiss law. μeff (effective magnetic moment) was determined for all the developed samples. Pure LCMO showed a downward divergence from Curie-Weiss law below 230 K but above transition temperature which indicates the characteristics of Griffiths phase. Saturation magnetization (Ms) increased initially and then decreased, whereas coercive field (Hc) was found to be monotonous decreased with increase in Fe content. LCFMO1 (x = 0.2) was noticed to have maximum Ms (38.87 emu/g) which indicated that the magnetic properties of pure LCMO were improved with Fe substitution, but for lower substitution only. Magnetization vs. field (M−H) curves were not well saturated even at a magnetic field of 60 kOe, therefore, values of Ms for all the samples were estimated using law of approach to saturation. With increase in Fe content, an increased anti-site disorder among Mn and Co strengthened antiferromagnetic (AFM) super exchange interactions and weakened ferromagnetism (FM). Therefore, substitution of Fe on Co-site was responsible for systematic decrease in saturation magnetization when × exceeded 0.2.

A new method to determine composition of sphalerite without secondary pollution based on CIELAB color space

AbstractCurrently, most of the methods for mineral materials analysis generate secondary pollution, which is detrimental to human health. For instance, traditional methods for sphalerite analysis in the zinc (Zn) smelting industry including chemical titration, atomic absorption spectrometry, and inductively coupled atomic emission spectroscopy. Colored indicators and toxic heavy metals are used in the analytical processes, causing severe pollution. For some methods, liquid is transformed into gaseous plasma, which is more dangerous to human health. Due to large quantities of sphalerite being used, secondary pollution cannot be ignored. This study proposes a green analysis method for the detection of sphalerite based on colorimetry, which does not generate secondary pollution. The results show that the strong substitution ability of iron (Fe) for Zn contributes to their inverse correlation in contents. The lattice parameters decrease with the increasing Fe content, resulting in a darker coloration. Here, key colorimetry parameters of L*, a*, and b* show clear linear correlations with the Zn and Fe contents. Compared with traditional approaches, this new method is environmental friendly with high sensitivity and accuracy. The relative error and relative standard deviation were less than 10% and 5%, respectively. This study provides a significant reference for nonpollution determination of other mineral materials.

Magnetism of 3d electrons in YCo12-xFexB6 compounds

The magnetic properties of the polycrystalline YCo12-xFexB6 alloys are thoroughly investigated through the scope of the Kuz’min model describing the thermal evolution of the spontaneous magnetization. The analysis of this behavior reveals a strong composition dependence of the magnetization as well as its thermal evolution. This is interpreted as an evolution from first neighbor ferromagnetic (FM) interactions with progressively reinforced antiferromagnetic (AFM) interactions. The magnetization in the ordered state decreases when increasing Fe content from 0.45 µB/f.u. down to 0.11 µB/f.u. for x = 0 and x = 4, respectively. The Inoue-Shimizu s-d model has also been used close to the ordering temperature to investigate the evolution of the Landau coefficients and study in detail the order of the magnetic transition and have some insights on the magnetovolume coupling in this series of compounds. It revealed that Fe for Co substitution causes the already weak magnetovolume exchange to become even weaker.

Silicon ameliorates iron deficiency in sour orange seedlings grown under different pHs

Iron (Fe) is an essential element for all plants while silicon (Si) is non-essential but has some beneficial roles for reducing iron deficiency stresses in plants. Soil pH affect iron solubility and availability and thus plant Fe nutrition however, little is known on how high or low pHs affect Si efficiency in alleviating Fe deficiency stress. In this research the interactive effects of root zone pH and Si nutrition on the alleviation of Fe deficiency in sour orange (Citrus aurantium) seedlings were investigated. Citrus seedlings were grown for three months in Fe-sufficient (control), Fe-deficient and Fe-zero media supplied with or without Si (0.7 mM), adjusted to pHs 6.5 and 8.0 and analyzed subsequently. Fe deficiency resulted in declined tissue Fe, proteins, chlorophylls, carotenoids and the activities of catalase, soluble and cell wall peroxidase associated with increased hydrogen peroxide and lipid peroxidation. Higher pH compromised plant growth associated with depleted tissue Fe in both Fe-deficient and Fe-sufficient plants and imposed chlorophylls and soluble proteins reduction. Si nutrition increased plant growth in Fe-deficient and Fe-sufficient plants under both pH treatments. It also improved tissue Fe content, soluble proteins, chlorophylls, carotenoids and the activities of antioxidant enzymes while decreased tissue hydrogen peroxide and lipid peroxidation levels. These results suggest that Si nutrition can reduce the harmful effects of soil Fe deficiency and higher pHs in sour orange plants via increase of Fe content and reduction of oxidative stress; however, in the absence of Fe, the applied Si cannot mitigate plant nutrient stress symptoms.

Labile Fe(III) phase mediates the electron transfer from Fe(II,III) (oxyhydr)oxides to carbon tetrachloride

Labile Fe(III) phase (includes Fe(III)aq, Fe(III)ads, or Fe(III)s species) is an important intermediate during the interaction between Fe(II) and Fe(III) (oxyhydr)oxides, but how does labile Fe(III) influence the electron transfer from Fe(II) to oxidant environmental pollutant during this Fe(II)-Fe(III) interaction is unclear. In this work, the dynamic change of Fe(II,III) (oxyhydr)oxides at the same time scale is simulated by synthesizing Fe(III)-Fe(II)-I (Fe(III)+NaOH+Fe(II)+NaOH) with different Fe(II)/Fe(III) ratios. CCl4 is used as a convenient probe to test the reduction kinetics of mixed valence Fe(II,III)(oxyhydr)oxides with different Fe(II):Fe(III) ratios. The Mössbauer spectra results reveal the Fe(III)labile in the solid phase is in octahedral coordination. The electron-donating capability of Fe(II) was improved with increasing Fe(III) content, but suppressed when [Fe(III)] ≥ 30 mM. The reductive dechlorination of CT by Fe(III)-Fe(II)-I decreased gradually with the increase of Fe(III) content, because more amount Fe(III)labile in solid phase is accumulated. This shows that the electron transfer from Fe(II) to Fe(III)labile rather than to CT is enhanced with increasing Fe(III) content. FTIR data shows that the hydroxylation of Fe(II) with Fe(OH)3 occurs preferentially in the non-hydrogen bonded hydroxyl group, causing the decrease of its reductive reactivity. The presence of [Fe(III)-O-Fe(II)]+ in Fe(III)-Fe(II)-I can stabilize the dichlorocarbene anion (:CCl2−), favouring the conversion of CT to CH4 (13.1%). The aging experiment shows that Fe(III)labile surface may maintain the reductive reactivity of Fe(II) during aging when [Fe(III)] = 5-20 mM. This study deepens our understanding of the mass transfer pathway of iron oxyhydroxides induced by Fe(II) and its impact on the reductive dechlorination of CT.

Manipulate A2/B2 Structures in AlCrFexNi Alloys for Improved Mechanical Properties and Wear Resistance

Precipitation strengthening of body-center cubic (A2) alloys via ordered B2 nanoprecipitates is expected to achieve a desirable combination of strength and ductility. In this work, the A2/B2 configuration is manipulated by adjusting Fe content in medium-entropy AlCrFexNi (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) alloys fabricated via arc-melting for improved mechanical properties and wear resistance. As Fe content increases, the fraction of A2 phase increases, and A2 nanoprecipitates in the B2 matrix change to a weave-like A2/B2 structure. Continuously increasing Fe content leads to a mixture of BMAP (B2 matrix with A2 precipitates) and AMBP (A2 matrix with B2 precipitates), and finally to a complete AMBP structure. The yield strength decreases and fracture strain increases with increasing Fe content except x = 0. The alloy of x = 0 displays slightly higher hardness because of its relatively brittle B2 matrix. Cracks tend to propagate along A2/B2 interfaces. AMBP structure exhibits greater toughness than the BMAP structure. The alloy of x = 0 displays the second-greatest wear volume loss due to its relatively brittle B2 matrix. When Fe is added, the wear volume loss decreases considerably but shows a trend of an upward parabola with respect to the Fe content. After achieving the highest volume loss at x = 1.5 with a mixture of AMBP and BMAP, the volume loss decreases again. A completely uniform AMBP structure at x = 3.0 shows the least volume loss.

Tolerance of Al–Mg–Si Wrought Alloys for High Fe Contents: The Role of Effective Si

Aluminum scrap is often contaminated with steel parts, leading to accumulation of Fe in recycled Al alloys. Consequently, low limits for Fe in Al wrought alloys are difficult to meet by recycling without dilution with primary Al. Wrought alloys with a higher tolerance for Fe could help overcome this problem and improve the sustainability of Al wrought products. Here we study the effects of increasing the Fe content in EN AW-6060, 6005A, and 6082 from 0.2 to 0.7 wt pct. The microstructure and mechanical properties of the alloys after extrusion and artificial ageing are compared to the standard alloys. We found that 6082 is more tolerant to above-standard Fe contents than 6005A, which in turn is more tolerant than 6060: the strength of the 6082-based alloy with increased Fe content is comparable to that of standard 6082 and the elongation at break is increased. In contrast, the artificial ageing potential of the 6060-based alloy with more Fe is drastically reduced compared to 6060. This data and literature values show that the effective Si content is a good overall predictor of alloy strength. Effective Si is not bound in AlFeSi-type phases and is available for precipitation hardening. Additional effects of increased Fe levels are discussed.

Towards a Correlation Between Iron/Cobalt Content, Support Pore Size and Metal Particle Size in Supported Catalysts

AbstractFe−Co‐based catalysts supported on γ‐Al2O3, Aerosil 200 silica and zeolite 4A were prepared by co‐precipitation of the respective nitrates in the presence of ammonium hydroxide. The objective was to demonstrate the influence of Fe/Co mass ratio and support pore size on metal particle size. Catalysts were characterized by thermogravimetric analysis (TGA), X‐ray diffraction (XRD), N2 physisorption, Fourier‐transformed infrared spectroscopy (FTIR), and scanning (SEM) and transmission (TEM) microscopies. It was demonstrated that the minimal presence of Fe was enough to reduce the average particle diameters by half. Increasing Fe content did not cause proportional decreases in the average particle diameter. The support pore diameter probably played a role in the crystallization step of bimetallic and Fe monometallic catalysts, whose particle diameters were similar to those observed for the pores. This phenomenon was not observed for Co monometallic catalysts.

Effect of C14 Laves/BCC on microstructure and hydrogen storage properties of (Ti32.5V27.5Zr7.5Nb32.5) 1-xFex (x = 0.03, 0.06, 0.09) high entropy hydrogen storage alloys

In order to explore the effect of C14 Laves/BCC on the hydrogen storage properties of high entropy hydrogen storage alloys, (Ti32.5V27.5Zr7.5Nb32.5) 1-xFex (x = 0.03, 0.06, 0.09) high entropy hydrogen storage alloys are prepared. The C14 Laves/BCC rises with the increase of Fe content. The C14 Laves phase provides a path for the diffusion of hydrogen atoms, so that defects with higher hydrogen binding energy capture more hydrogen atoms to ensure the increase of initial hydrogen absorption content in the activation process. The appropriate ratio of C14 Laves/BCC ensures that the main hydrogen absorbing phase BCC phase of high entropy hydrogen storage alloy plays a full role. The (Ti32.5V27.5Zr7.5Nb32.5) 0.94Fe0.06 high entropy hydrogen storage alloy possesses the best hydrogen absorption capacity of 3.19 wt% at 150 °C under 3 MPa hydrogen pressure. The gradual increase of Fe content makes the VEC value of C14 Laves phase rise, so that the hydrogen binding energy decreases. The factor reduces the thermal stability of metal hydrides. The reversible phase transition of BCC phase + metal C14 Laves phase → FCC phase + metal hydride C14 Laves phase → BCC phase + metal C14 Laves phase occurs in the whole cycle.

The beneficial effect of minor iron additions on the crack susceptibility of rapidly solidified aluminum alloy 6060 toward additive manufacturing applications

Solidification cracking presents a challenge for additive manufacturing of many materials, such as heat treatable aluminum alloys. The objectives of this article are to demonstrate the beneficial effect of minor Fe additions on crack elimination in rapidly solidified Al alloy 6060 and to elucidate the underlying mechanism. Blocks of 6060 + xFe (0 ≤ x ≤ 0.5) were cast and single-track laser melting trials were performed on the surface of the blocks to emulate solidification rates characteristic of additive manufacturing. Analysis of the melt pool cross sections revealed that cracks were present in all processing conditions for the baseline 6060 alloy, but a monotonic decrease in cracking was observed with increasing Fe content with no cracks observed in any conditions for the 6060 + 0.5Fe sample. Serial SEM imaging and FIB milling were used to reveal the 3D morphology of nanoscale particles in the melt pools, while TEM analysis was used to identify the phases. Discrete and nodular δ-AlFeSi particles were observed in samples containing 0.1–0.2 wt% Fe, while elongated and branched α-AlFeSi particles were observed in the 6060 + 0.5Fe sample. The crack mitigation mechanism is proposed to be due to bridging of the Al matrix by the AlFeSi particles, through the formation of a strong interface and mechanical interlocking, thereby resisting the thermally induced loads. It is concluded that minor Fe additions can effectively eliminate cracking in Al 6060, and that this cannot be explained by conventional mechanisms such as grain refinement or an increase in eutectic liquid.