Iron-rich Precipitates Research Articles

Enhancing Directed Energy Deposited AL5356 Through in Situ Workpiece Vibrations

This study explores an innovative method to enhance Directed Energy Deposition (DED) of aluminum 5356 products by integrating an electromagnetic vibration system into the DED setup. The application of vibrations significantly improved surface quality, reducing surface waviness and increasing building efficiency by 14%, from 78.5% to 92.25%.Gas porosity was reduced from 1.5 ± 0.04% in as-built (AB) components to 0.34 ± 0.07% in vibration-assisted (VA) parts. Tensile tests showed a marked reduction in anisotropy, with the tensile strength deviation between the x and z directions decreasing to less than 0.4% for vibration-assisted samples, compared to 7.9% for asbuilt ones. Additionally, secondary phase analysis revealed a homogenization effect, with magnesium- and iron-rich precipitates displaying a finer dispersion (3.57 ± 3.42 µm²) compared to 11.28 ± 12.49 µm² in as-built parts. Overall, the findings highlight the potential of vibration-assisted DED to improve part properties, reduce defects, and advance the DED manufacturing process.

Migration of transition metals and potential for carbon mineralization during acid leaching of processed kimberlite from Venetia diamond mine, South Africa

Carbonation of mafic and ultramafic rocks and mineral wastes provides a permanent way to sequester excess atmospheric CO2. Recent research has shown that this method also offers the potential for enhanced recovery of critical metals from mine tailings. In this study, processed kimberlite from the Venetia diamond mine (South Africa) was used in column acid leaching experiments to assess both its carbonation potential and whether critical metals such as nickel could be recovered during mineral carbonation. Processed kimberlite was treated daily with one pore volume of either deionized water or dilute hydrochloric acid (0.04 M, 0.08 M, 0.12 M and 0.16 M) for 28 days. Iron-rich yellow precipitates consistent with yellow ground formed during the experiments both at the top of the residue columns (corresponding to the inlets of the columns) and within the leachates collected from the bases of columns. The carbonation potential and mobility of transition metals were investigated using a combination of quantitative X-ray diffraction (XRD) using Rietveld refinements, inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM) coupled with EDXS, and synchrotron-based X-ray fluorescence microscopy (XFM). Our results show that the high proportion of clay minerals (e.g., lizardite, smectite, talc, chlorite) in the processed kimberlite act as the primary source for Mg and transition metals such as Ni; however, calcite dissolution is the main source for Ca. The amount of Mg and Ca extracted from processed kimberlite increases with HCl concentration. If acid leaching of processed kimberlite were used at Venetia, the amount of Mg leached from clay minerals would provide an estimated CO2 offset potential ranging from 2.1 to 15.8 % of the mine's total annual emissions. The leached Ca from silicate dissolution could also provide an estimated CO2 offset potential ranging from 2.1 to 8.1 % of the mine's total annual emissions. However, the amount of CO2 released by calcite dissolution during this process is equivalent to 2.1–14.3 % of total annual CO2 emissions at Venetia., thus resulting in a net estimated CO2 offset potential of 2.1–9.6 % if the Ca released from calcite could not be recarbonated. If all of the Ca could be reprecipitated as calcite, the acid leaching techniques employed in this study could offset 4.2–23.9 % of the Venetia mine's CO2 emissions. Ultimately, greater concentrations and/or amounts of acid may be used to access more of the offset potential of Mg phyllosilicates in kimberlite, but the CO2 released by calcite dissolution must also be won back by recarbonation.

Grain Refinement and Strengthening of an Aluminum Alloy Subjected to Severe Plastic Deformation through Equal-Channel Angular Pressing

In the present study, the microstructure, mechanical properties, and stored energy of an aluminum alloy containing iron-rich fine precipitates, subjected to severe plastic deformation through equal-channel angular pressing (ECAP), were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Up to four passes through ECAP resulted in significant nanometer-scale grain refinement, as well as the accumulation of lattice defects, such as dislocations and mesoscopic shear planes. This resulted in a noticeable enhancement in the Vickers microhardness and the flow stress after ECAP. Differential scanning calorimetry results showed that the ECAP’ed material exhibited two exothermal peaks at 222 ± 2 °C and 362 ± 2 °C, with total thermal effects of ΔH = 4.35 and 6.5 J/g, respectively. Slight increases in the ECAP’ed material microhardness and flow stress were observed at 200 °C. The heat release, at a relatively low temperature, and the slight improvement in the mechanical properties were attributed to the evolution of low- and high-angle misorientation, with the strain and the pinning of tangled dislocation caused by the existing fine particles. The second peak was attributed to grain growth, resulting in a significant softening of the material.

Mineralization process of ferrous ions from ZnSO4-FeSO4 solution at a temperature range of 368.15–423.15 K

The abiotic mineralization of ferrous ions for ZnSO4-FeSO4 solution at temperatures of 368.15–423.15 K was investigated. The effect of kinetic factors including oxygen partial pressure, temperature, agitation speed, with presence of a neutralizer or not, and seeding on the ferrous oxidation process was evaluated in detail. Also, the rate constants for the ferrous oxidation process were calculated by a second-order kinetic curve of the partial concentration of [Fe2+] with time to realize the effect of the different kinetic factors as variables. Furthermore, the morphology of the minerals was identified using scanning electron microscopy electron dispersive spectroscopy measurements (SEM-EDS), and the phase composition was characterized by the X-ray diffraction (XRD), the thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The research indicated that the ferrous oxidation process was accelerated by elevating temperature, increasing agitation speed, and adding a neutralizer. Conversely, increasing oxygen partial and seeding both decrease the rate constant of the oxidation process. The iron-rich precipitates produced comprise a wide range of chemical compositions, structures, sizes, and morphologies. They consisted primarily of goethite and hematite, with goethite being dominant below 403.15 K, and hematite above 403.15 K. Moreover, the iron-rich products were successfully obtained by abiotic mineralization of industrial ZnSO4 solution at 423.15 K, containing 59% of Fe and 1% of Zn, while the resultant ZnSO4 solution after removal of iron contained less than 1 g/L of iron ions. Thus, abiotic mineralization of ferrous ions for ZnSO4 is clean and energy-saving, and the iron-rich products can be used as raw materials for ironmaking.

Effect of composition on the tensile and corrosion performance of nickel aluminium bronze produced via laser powder bed fusion

Nickel Aluminium Bronze (NAB) is a key material for marine applications due to its combination of high strength and superior corrosion resistance in seawater. While wrought components show enhanced strength and corrosion resistance compared to their cast equivalent, casting is often required in order to achieve necessary component shapes. This study investigates the potential manufacturing of NAB components through laser powder bed fusion ( L -PBF), which is known for its ability to create highly complex designs. NAB powders with compositions C63000 (Cu-10.2Al-4.8Fe-5.0Ni-0.2Si, wt%) and C95800 (Cu-9.0Al-4.0Fe-4.6Ni-1.9Mn, wt%), were tested for their manufacturability, mechanical performance, and corrosion behaviour in both as-built and heat treated conditions. As-built NAB shows a dominant β′ martensitic structure, which is unique to L -PBF due to the rapid heating/cooling rates of laser processing and leads to very high strength in excess of 1100 MPa but brittle performance. After heat treatment, the β′ decomposes into lamellar κ III which breaks down into a dense mixture of laths and particles through spheroidization. This allows AM NAB to attain the same tensile and corrosion behaviour as the wrought equivalent. As built C95800 has greater elongation but lower strength and worse corrosion performance compared to NAB owing to the formation of continuous soft and ductile α bands around β′ grains. After heat treatment, the prior α regions correspond to globular nickel rich spheroids and iron rich precipitates similar to κ IV . This causes heat treated C95800 to show similar tensile performance to cast NAB, while the corrosion behaviour remains similar to wrought. • Laser powder bed fusion suitable for manufacturing nickel aluminium bronze (NAB). • Tensile and corrosion properties equivalent to conventionally processed NAB. • Increasing aluminium supresses α phase and favours martensitic β′ in as-built NAB. • Lowering aluminium reduces strength but increases ductility after heat treatment.

Properties of Alluvial Soils of Taiga Forest under Anthropogenic Salinisation

The environmental impact of deposit development can be indirect and can cause combined geochemical processes in ecosystems. These must be taken into consideration under environmental forecasting and environmental risk assessment. Soil degradation in the Taiga Forest is considered, within the area of Verkhnekamskoye potash deposit (Russia), as an example of such environmental transformation. Here, the mechanism and characteristics of the anthropogenic salinisation of alluvial soils under potash deposit development are newly described. It was found that there is a strong anthropogenic impact of the potash industry on valley soils where the contaminated Na-Cl groundwater discharges or is close to the surface. The valley soils are characterised by high salinity, and the sum of toxic salts in soils has reached 26%. Alluvial gley humic clay chloride saline soil (Gleyic Fluvisols (Salic, Loamic, Technic)) and secondary solonchak on alluvial humic clay soil sulphate-chloride gypsum-containing surface-gleyed (Chloridic Gleyic Fluvic Solonchak (Hypersalic, Loamic, Technic)) were formed in hydromorphic conditions. Morphological, physicochemical and mineralogical analyses were carried out. Under hydromorphic conditions, Chloridic Gleyic Fluvic Solonchak (Hypersalic, Loamic) was described to show a hydrotroillite layer and reddish-yellow iron-rich precipitates on its surface. The top soil horizon has the highest content of iron minerals (up to 84.9%) and Fe-bearing plant residues (up to 20%). Additionally, the spongy and gel-like organic materials, as well as the siliceous remains of diatoms, are enriched in Ca, Fe, Cl, K, Na, S and P. The lower soil horizon consists of black gel-like phases and hydrogen sulphide settings with a high content of plant residues. The insoluble part of the samples contains up to 84% hydrogoethite. The sources of iron in soils and bottom sediments include the iron-enriched Sheshma sediments speckled rocks, slurry material, halite wastes and soil minerals of alluvial gley soils.

Separation of Impurity Iron from Polysilicon by Pulsed Electric Current

The effect of using a pulsed electric current to remove impurity iron from molten polysilicon was investigated. Using optical microscopy observation and area statistics of iron-rich content, it was found that iron tends to accumulate at the bottom of an ingot under the action of a pulsed electric current. A new separation mechanism is proposed, based on the decreased solubility of iron in polysilicon under conditions including a pulsed electric current. Thermodynamic calculations indicate the theoretical possibility of the formation of iron-rich Si clusters. These clusters sink to the bottom of an ingot under the effect of gravity and form iron-rich precipitates with silicon, thereby achieving the iron removal. This technique provides a new method for purification of polysilicon.

Effects of solute content on microstructure of nano precipitate-fine grain synergistically reinforced copper alloys

ABSTRACT Alloying of Fe, Co was reported to tailor microstructure of copper alloys into a nanoprecipitate-fine grain (NPFG) structure, i.e. nano-sized iron-rich precipitates dispersed inside refined grains. Here, we investigate the solute effect of Sn, Zn on NPFG structure in as-cast copper samples. Mechanisms are proposed to account for the solute effect on precipitate and grain features. Solutes restrict coarsening but facilitate undesirable morphology transition from spherical to angular of iron-rich precipitates. Meantime, solutes allow more precipitates to be active in the nucleation of copper and consequently induce finer grains. Minor Sn is added to optimise NPFG structure and leads to an excellent strength–ductility combination in Cu–1.5Fe–0.1Sn (wt-%) alloy. This work provides a solute-alloying strategy to achieve desired mechanical properties in metals.

Precipitates-interaction capture of nano-sized iron-rich precipitates during copper solidification

ABSTRACTNano-sized iron-rich precipitates reinforced copper alloys achieve excellent mechanical properties. Capture mechanism of iron-rich precipitates into copper grains during solidification was described but needs further validation. Here, Cu-1.5Fe-0.5Co (wt-%) alloy is fabricated by gravity casting. Iron-rich precipitates in nano and submicron scale (mostly < 100 nm) are well dispersed in copper grain interior. Traditional pushing/engulfment transition (PET) models are used to interpret the capture process of iron-rich precipitates during copper solidification, but all fail to match the experimental results. The precipitates-interaction capture mechanism is most reasonable for describing the capture process.

Mechanical properties and microstructures in zirconium deposited by injected powder laser additive manufacturing

The use of laser additive manufacturing based on melting of injected zirconium powder under localized shielding was evaluated in terms of microstructures and mechanical properties of thin wall structures. The material was characterized in both the laser travel and the build directions. The microstructures, tensile properties and fracture behavior were assessed for deposits made using as-received and recycled powder. Electron backscattered diffraction and transmission electron microcopy revealed a fine structure of Zr-α laths with nano-scale iron-rich precipitates at the lath interfaces. The properties of the fabricated components, which were made using new as-received powder were comparable to a Zr-2.5Nb alloy substrate, with yield strengths of over 569 MPa and uniform strains up to the ultimate tensile stress ranging from 8.5 to 9.9%. However, when recycled powder was used, the ductility dropped with total strains to failure of 1.0–7.5%, as a result of porosity and unmelted powder particles serving as brittle inclusions in the deposited material.

Influence of Drainage with High Levels of Water-Soluble Salts on the Environment in the Verhnekamskoe Potash Deposit, Russia

Saline drainage from slurry storage facilities can deteriorate the properties of clay barriers in the beds of embankment dams and slurry ponds and cause saline drainage to infiltrate into groundwater. The chemistry of slurry material, drainage, springs, surface water, and soils was studied near the slurry storage facility of the Verhnekamskoe potash mine (Russia). Our study showed that the Na–Cl type mine drainage water, with high amounts of nitrogen compounds, increased the salinity of the groundwater and surface water, and the river valley ecosystems. As a result of ion exchange and leaching, the soil, groundwater, and surface water have elevated levels of \({\text{C}}{{\text{a}}^{2+}}\), \({\text{M}}{{\text{g}}^{2+}}\), \({\text{SO}}_{4}^{{2 - }},\) and \({\text{F}}{{\text{e}}_{{\text{total}}}}\), and extremely high \({\text{~N}}{{\text{a}}^+}\) and \({\text{C}}{{\text{l}}^ - }{\text{~}}\) values. Iron-rich precipitates and hydrogen sulfide tend to form down-gradient in the saline, water-logged seepage areas.

Schwertmannite formation and properties in acidic drain environments following exposure and oxidation of acid sulfate soils in irrigation areas during extreme drought

This paper describes the occurrences, mineralogical assemblages and environmental relevance of iron-rich precipitates derived from acidic (pH<4) waters containing dominantly schwertmannite from a diverse range of six physical settings across the Lower Murray Reclaimed Irrigation Area (LMRIA) in Australia, comprising: (1) suspended flocculated precipitates in ponded drain water, (2) moist coatings or pastes in drying ponds and drains, (3) hard cemented crusts and aggregates amongst Phragmites roots and stems, (4) dry coatings on concrete and wooden structures, (5) dry coatings on surface soils and vegetation and (6) suspended flocculated precipitates in the mixing zone of drain discharge into the River Murray. Schwertmannite formed in these acid drain environments following exposure and oxidation of deep (~0.5→3.5m) clayey hypersulfidic material (pH>4) that dried, cracked and acidified to form deep sulfuric materials (pH<4) due to river and groundwater levels falling by nearly 2m during the latter part of the Millennium Drought (2007 to 2010). Reflooding events occurred between 2011 and 2015. All samples displayed X-ray diffraction (XRD) patterns typical for schwertmannite. In some samples, additional weak reflections from small amounts of jarosite, natrojarosite, gypsum, hexahydrite, konyaite and halite indicated deposition under variable pH conditions and sulfate concentrations due to different flow or evaporation stages. SEM images indicated that morphological and compositional features of schwertmannite were dominated by: (1) framboid-like spheroidal clusters with Fe/S ratio>5 that were preserved after crystallization and likely formed by dissolution of pyrite and microbial oxidation of Fe2+ by acidophilic bacteria and (2) fibrous spheres (0.3–3μm) with filamentous morphology and a high degree of porosity. Speciation calculations (PHREEQC) using the dissolved metal and major ion concentrations in drain waters supported the XRD results as the saturation index (SI) exceeded zero for schwertmannite in many drains. The precipitates contained high concentrations of metals (Al>Cu>As>Zn>Pb>Co) and nutrients (e.g. P) due to co-precipitation/scavenging of these elements during the formation of schwertmannite. There was also spatial variability in concentrations of metal(loids) in precipitates between drains. A conceptual model explains and summarizes the morphological properties, mineralogy, geochemistry and environmental processes influencing the formation and relative stabilities of schwertmannite-rich precipitates from six diverse physical settings. The environmental relevance, which has significant implications for rehabilitation options is shown in three perspectives: (1) the conditions for schwertmannite formation have persisted in irrigation drains for over 7years, (2) the ability for schwertmannite-rich precipitates to reveal acid sulfate conditions and therefore act as a mineralogical indicator in irrigation systems and (3) the pollution potential of metals and metalloids scavenged by schwertmannite-rich precipitates.

Process design of matrix acidizing by antifouling agents

The novelty of this work is the process design of matrix acidizing in the field scale to investigate the role of antifouling agents on the performance of acid stimulation of carbonate formations. The main aim of this study was to improve the process design in order to reduce the fouling problems of matrix acid treatments such as accumulation of iron-rich precipitates in the downstream facilities and plugging the pore-volumes of reservoir formation near the wellbore area. In this work, the real time monitoring of 54 systematic acid treatments were assessed to propound a practical and scientific approach in order to manage the fouling tendency of spent acid mud in both rock-formation and downstream facilities. Two main chelators of EDTA and NTA (54 samples in the range of 200–800ppm) as well as their blends (EDTA/NTA 50:50) were examined in order to obtain the optimal injection rate and the fouling tendency of mud acid. The experimental results revealed that NTA (in average concentration of 157ppm) increased the yield of both acid treatment and wormholing, while it decreased the fouling of downstream facilities and the clogging of formation’s pore-volumes; all leading to increase the success of acid stimulation processes.

Synthesis and characterization of Fe-Ti-Sb intermetallic compounds: Discovery of a new Slater-Pauling phase

Compounds of Fe, Ti, and Sb were prepared using arc melting and vacuum annealing. ${\mathrm{Fe}}_{2}\mathrm{TiSb}$, expected to be a full Heusler compound crystallizing in the $\mathrm{L}{2}_{1}$ structure, was shown by XRD and SEM analyses to be composed of weakly magnetic grains of nominal composition ${\mathrm{Fe}}_{1.5}\mathrm{TiSb}$ with iron-rich precipitates in the grain boundaries. FeTiSb, a composition consistent with the formation of a half-Heusler compound, also decomposed into ${\mathrm{Fe}}_{1.5}\mathrm{TiSb}$ grains with Ti-Sb rich precipitates and was weakly magnetic. The dominant ${\mathrm{Fe}}_{1.5}\mathrm{TiSb}$ phase appears to crystallize in a defective $\mathrm{L}{2}_{1}$-like structure with iron vacancies. Based on this finding, a first-principles DFT-based binary cluster expansion of Fe and vacancies on the Fe sublattice of the $\mathrm{L}{2}_{1}$ structure was performed. Using the cluster expansion, we computationally scanned $g{10}^{3}$ configurations and predict a novel, stable, nonmagnetic semiconductor phase to be the zero-temperature ground state. This new structure is an ordered arrangement of Fe and vacancies, belonging to the space group $R3m$, with composition ${\mathrm{Fe}}_{1.5}\mathrm{TiSb}$, i.e., between the full- and half-Heusler compositions. This phase can be visualized as alternate layers of $\mathrm{L}{2}_{1}$ phase ${\mathrm{Fe}}_{2}\mathrm{TiSb}$ and $\mathrm{C}{1}_{b}$ phase FeTiSb, with layering along the [111] direction of the original cubic phases. Our experimental results on annealed samples support this predicted ground-state composition, but further work is required to confirm that the $R3m$ structure is the ground state.

Synchrotron-based analysis of chromium distributions in multicrystalline silicon for solar cells

Chromium (Cr) can degrade silicon wafer-based solar cell efficiencies at concentrations as low as 1010 cm−3. In this contribution, we employ synchrotron-based X-ray fluorescence microscopy to study chromium distributions in multicrystalline silicon in as-grown material and after phosphorous diffusion. We complement quantified precipitate size and spatial distribution with interstitial Cr concentration and minority carrier lifetime measurements to provide insight into chromium gettering kinetics and offer suggestions for minimizing the device impacts of chromium. We observe that Cr-rich precipitates in as-grown material are generally smaller than iron-rich precipitates and that Cri point defects account for only one-half of the total Cr in the as-grown material. This observation is consistent with previous hypotheses that Cr transport and CrSi2 growth are more strongly diffusion-limited during ingot cooling. We apply two phosphorous diffusion gettering profiles that both increase minority carrier lifetime by two orders of magnitude and reduce [Cri] by three orders of magnitude to ≈1010 cm−3. Some Cr-rich precipitates persist after both processes, and locally high [Cri] after the high-temperature process indicates that further optimization of the chromium gettering profile is possible.

Iron solubilization during anaerobic growth of acidophilic microorganisms with a polymetallic sulfide ore

Acidithiobacillus ferrooxidans at 30°C and Sulfobacillus thermosulfidooxidans at 47°C were selected from a preliminary screening of various acidophiles for their ferric iron reduction capacities during anaerobic, autotrophic growth on sulfur. The selected cultures were used with a polymetallic sulfide ore under anoxic conditions to demonstrate enhanced solubilization of iron during leaching in shaken flasks and enhanced removal of iron from laboratory ore-leaching columns, compared to leaching with continuous aeration. Ore-associated, ferric iron-rich precipitates, which were formed under previously oxidizing conditions, were a potential influence on extraction of target metals and percolation through ore columns and were available as the source of ferric iron for anaerobic sulfur oxidation. Over twice as much iron was removed by moderate thermophiles when anoxic phases were introduced during the leaching. Enhanced removal of iron and some improvement in extraction of base metals from ore fragments were also demonstrated with a selected “Sulfolobus”-like strain during growth and leaching with alternating periods of aeration and anoxic conditions at 70°C.

Characterisation of iron-rich precipitates from synthetic atmospheric nickel laterite leach solutions

Iron-rich precipitates from atmospheric nickel laterite leach solutions normally contain large amounts of poorly defined phases such as schwertmannite and ferrihydrite. This complicates mineralogical identification using routine X-ray Diffraction (XRD) technique. In the present study, the iron-rich precipitates from synthetic nickel laterite leach solutions were characterised by a combination of several techniques that include selective Acidified Ammonium Oxalate (AAO) dissolution, Differential X-ray Diffraction (DXRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infra-Red (FTIR) spectroscopy. These techniques in combination allowed reliable mineralogical identification for samples containing high proportions of schwertmannite and ferrihydrite. The effects of foreign metallic cations on the crystallization, dissolution behaviour and surface sulphate coordination were investigated. The results suggest that selective AAO dissolution is a good method to distinguish between poorly and highly structurally-ordered phases in a mixed assemblage. The presence of goethite in the iron-rich precipitates was only determined after removing the schwertmannite and/or ferrihydrite. Nickel, aluminium and chromium retarded the transformations of schwertmannite and/or ferrihydrite to goethite, but aluminium and chromium supressed the formation of 6-line ferrihydrite. Also, aluminium and chromium influenced the absorbed sulphate symmetry of iron-rich precipitates. The structural order of the phases became less pronounced with the presence of foreign metallic cations, particularly aluminium and chromium. Aluminium and chromium can strongly stabilize iron-rich precipitates making these resistant to leaching by AAO solution. FTIR analysis confirmed the presence of goethite in the bi-metallic precipitates and suggested that the sulphate is present to a greater extent in lower symmetry environments.

Mineralogy of Fe-Precipitates and Their Role in Metal Retention from an Acid Mine Drainage Site in India

Iron-rich precipitates from acid mine drainage (AMD) sites around the Jaintia Hills coalfield, India, were investigated. The ochreous precipitates mainly consist of schwertmannite, goethite, and jarosite. Sorption affinities suggest that Ni, Mn, Cr, Cd, Pb, and Zn are more significant in schwertmannite-bearing ochre than in more crystalline jarosite- and goethite-bearing ochres. The lower crystallinity and higher surface area of schwertmannite-bearing ochreous precipitate result in higher metal retention potential. Fe and Mn concentrations in water may also influence the sorption of metals in the precipitates. The results of the sequential extractions showed that metal mobility is mainly controlled by Fe and Mn oxyhydroxide phases. This information may aid understanding of the natural attenuation of trace metals by ochreous precipitates in AMD-contaminated water.

Impact of microgalvanic corrosion on the degradation morphology of WE43 and pure magnesium under exposure to simulated body fluid

Corrosion of magnesium alloys was studied during exposure to simulated body fluid (SBF). Microgalvanic processes dominate degradation morphology and formation of the corrosion/conversion layer. Localized corrosion with vigorous hydrogen evolution was observed at zirconium- and iron-rich precipitates that act as micro-cathodes. These are surrounded by volcano-shaped deposits of Mg(OH)2. Circular areas around cathodic centers were found to be protected from corrosion, while bulk degradation takes place in between. In SBF, conversion to a corrosion double layer was demonstrated. Differences observed for WE43 and pure magnesium (Mg) are discussed within the framework of a comprehensive model of the mechanisms of corrosion.

Magnetic Fe doped ZnO nanofibers obtained by electrospinning

We demonstrate structural and room temperature magnetic properties of Fe doped ZnO nanofibers (NFs) obtained by electrospinning followed by calcination. The observed NFs, formed from crystalographically oriented, approximately 4.5 nm particles conglomerates, were approximately 200 nm in diameter. The reported synthesis of room temperature ferromagnetic Fe doped ZnO NFs is both facile and economical, and is therefore suggested as a generic method of fabricating biocompatible magnetic materials. The major substrates selected for the NFs synthesis (Zn, Fe) comprised of relatively low toxicity materials. Incorporating 10% Fe into ZnO does not modify the wurtzite crystal structure of the host material. No evidence of impurity phase was detected by either X-ray or electron diffraction. Magnetometry studies and Magnetic Force Microscopy imaging reveal a local ferromagnetic order that persists up to room temperature. We suggest that the observed phenomenon is either due to a mechanism mediated by presence of oxygen vacancies and/or is related to iron-rich precipitates.