Mn Composition Research Articles

An Eco-approach synthesis of undoped and Mn doped ZnO nano-photocatalyst for prompt decoloration of methylene blue dye

The present work reports the synthesis of nano pure ZnO and Mn-doped ZnO in an Eco-approach using seed extract of Cassia angustifolia for the removal of methylene blue. The aqueous Phyto-molecules helps in the reduction of metal precursor to nano-photocatalyst zinc oxide and the changes in absorbance was noted in UV-DRS for varying the parameters to get optimized. Different concentrated dopant material manganese sulphate (0.001 M, 0.003 M, and 0.005 M) was introduced on ZnO to enhance the optical absorption and to generate a new Fermi level. The XRD data exhibit the same wurtzite pattern for pure ZnO and Mn-doped ZnO samples. The slight shift in peak positions was noted in Mn-doped ZnO samples compared to pure ZnO without additional peaks determines the incorporation of Mn2+ ions in the lattice of ZnO NPs. The peak appearance in FT-IR denotes the bond formation among functional groups and metal oxide. The structural morphology of ZnO and Mn-doped ZnO was observed in Field Emission Scanning Electron microscopy. The elemental composition of Mn in ZnO was predicted in the EDAX. The High-resolution transmission electron microscopy (HRTEM) denotes the reduced size and altered the crystallinity of ZnO when Mn was introduced as the dopant in the green route. The effective photocatalytic activity of nano ZnO, Mn-doped ZnO achieves 84 and 95% decoloration of water pollutant Methylene blue (MB) dye with H2O2 and UV radiation by changing parameters like dye concentration, amount of catalyst, and pH. Results from this study suggest that the nano- Mn-doped ZnO photocatalyst can be advantageous for dye removal compared to pure ZnO. The green synthesized Mn-doped ZnO using Cassia angustifolia seed might considerable for treating dye contaminated water and supports in water remediation.

Evolution of structural, magnetic and magnetocaloric effect in TmFe1-xMnxO3 (x≤0.3)

The influence of Mn doping on structure, magnetic behaviors and magnetocaloric effect in TmFeO3 polycrystalline ceramics has been explored. X-ray powder diffraction proves that TmFe1-xMnxO3 (x ≤ 0.3) ceramics maintain an orthorhombic structure, and the space group is Pbnm. Compared with the original TmFeO3 sample, structural parameters change slightly and magnetic properties are effectively tuned with the gradual substitution of Mn at Fe site. The spin reorientation temperature region shifts from 90.3 to 73.2 K for TmFeO3 to 180.0–156.0 K for TmFe0.7Mn0.3O3. Besides, for TmFe1-xMnxO3 (x ≤ 0.3), the maximum magnetic entropy changes dependent on the Mn composition are 6.29 J/kg K, 6.56 J/kg K, 6.79 J/kg K and 7.22 J/kg K for 0–70 kOe, respectively. The refrigeration capacities are 159.3 J/kg, 168.9 J/kg, 176.7 J/kg and 184.4 J/kg, respectively. For a better assessing the magnetocaloric performance of TmFe1-xMnxO3 (x ≤ 0.3), we have calculated the temperature average entropy change, refrigerant capacity and normalized refrigerant capacity, and their values become larger with increasing Mn doping. Our experimental results can provide valuable references for the application and development of RFeO3 (R = rare earth) as multifunctional materials.

Thermal instabilities of cobalt containing MnZn ferrite cores for medium (500 kHz) frequency applications

MnZn ferrites of the nominal composition (Mn0.81Zn0.19)Fe2.13O4, doped with cobalt, have been studied concerning the evolution of their medium (500 kHz) frequency power losses and initial magnetic permeabilities upon ageing at various temperatures for various times. Thermal ageing results to significant power loss reduction by about 50% at 400 kHz-50 mT (i.e. at 90 °C from initially 58–29 mW cm−3) and about 30% at 500 kHz–100 mT (i.e. at 90 °C from initially 690–480 mW cm−3), accompanied with a simultaneous decrease of the relative initial permeability from initially 1700–1200. The extent of power loss reduction depends on ageing time and temperature and can be described by a thermally activated process, during which Co2+ ions fall from a metastable high energy state to a stable lower energy state with an activation energy 0.33 eV/cation. Addition of TiO2 to an amount of 4000 ppm (wt.%) appears to retard the cobalt-induced ageing process by increasing the activation energy to 0.45 eV/cation, while equal amount additions of SnO2 did not seem to have any effect.

Magnetic nanoparticles for components of MRI diagnostics and electronic devices

The formation of single-phase solid solutions of iron oxide and manganese oxide with a spinel structure in MnxFe3 – xO4 system (x = 0; 0.3; 0.6; 0.8; 1.0; 1.2; 1.4; 1.8) has been established by methods of X-ray phase analysis and infrared spectroscopy. The maximum saturation magnetization was found for the composition Mn0.3 Fe2.7O4 (Ms = 68 A ⋅ m2 ⋅ kg−1 at 300 K and Ms = 85 A ⋅ m2 ⋅ kg−1 at 5 K), which is associated with a change in the cationic distribution over tetrahedral and octahedral voids. The materials obtained were stabilized in the form of colloidal solutions using a number of polyelectrolytes. It was found that poly(diallyldimethylammonium chloride) (PDDA) had the best stabilizing effect due to its structural features. A method for controlling the magnetic properties of magnetite by partial replacement of iron ions in the magnetite structure with manganese is proposed. Changing the magnitude of the magnetization and coercive force is possible by changing the degree of substitution. Relatively high values of specific magnetization, as well as uniformity of magnetic particles in size, can be of practical interest, for the manufacture of contrast agents in MRI diagnostics.

Characterisation of High Temperature Oxidation Phenomena during AISI 430 Stainless Steel Manufacturing under a Controlled H2 Atmosphere for Bright Annealing

Localised-in-the-edge oxidation of four AISI 430 alloys was investigated after an industrial bright annealing process. The oxidised surface of each specimen was characterised by X-ray photoelectron spectroscopy (XPS), Raman-spectroscopy and SEM. The results showed that the selective oxidation of Cr and Mn took place at the coil edges of AISI 430. This led to the formation of an oxide scale based on Cr2O3 and MnCr2O4. On the other hand, the formation of Cr(OH)3 and MnOOH in the outer part of the oxide scale was related to the effect of the H2–N2 environment on the annealing furnace. The results concluded that the composition of Cr and Mn in the alloy determined the composition of the oxidation products. However, the effect of annealing time was minor in this oxidation mechanism, which slightly contributed to an increase in the cation diffusion from the steel to the oxide. Finally, the results obtained indicate that the colouration of the coil edges displayed in each studied material varies according to the alloy chemical composition and annealing time.

Synthesis of A2+B3 type hyperbranched poly(amide-ether) block copolymer and its shape memory function

High-molecular-weight hyperbranched polyether-b-amides (hb-PEBA; number average molecular weight (Mn) = 29.2–96.2 kDa) were successfully prepared by polycondensation of NH2-terminated poly(ethylene oxide) (PEO; Mn = 3.35, 4.6, 8.0, and 10.0 kDa) as A2-type and COOH-terminated three-armed N-methylbenzamide pentamers (TMA-3MAB5) as B3-type macromonomers in N-methylpyrrolidone (NMP) at 35–60 °C for 6 h. TMA-3MAB5 was prepared by stepwise condensation of 4-N-methylaminobenzoic acid (MAB), trimesic acid (TMA), and thionyl chloride/NMP as the building block, core molecule, and condensation reagent, respectively. Transparent to opaque films were prepared from all polymer samples through the solvent casting method using CHCl3, and the crystallization of PEO segments (crystallization degree Xc 15%–66%) was confirmed using differential scanning calorimetry (DSC). The hb-PEBA films showed tensile strengths of 0.71–16.8 MPa, with breaking elongation of 40–350%, and tensile elastic moduli of 0.10–1.43 GPa, depending on Mn and polymer composition. The superior shape memory properties of hb-PEBA polymers compared with their linear counterparts were confirmed by deformation at 80 °C, shape retention (memory) at room temperature, and shape recovery by reheating. Overall, the well-controlled TMA-3MAB5 was undoubtedly effective for the synthesis of high Mnhb-PEBA, resulting in improved mechanical and shape memory properties.

Screen printing of multi-mode emission NaYF4:Yb,Er(Tm)/NaYF4:Ce,Mn composites for anti-counterfeiting applications

NaYF4:Yb,Er(Tm)/NaYF4:Ce,Mn composites were prepared by a hydrothermal method, and an anti-counterfeiting printed pattern can display different colors under different ambient lights.

Interrelation between cationic distribution and electromagnetic properties of vanadium-substituted Mn–Zn ferrites

This study manifests the outcomes of varying vanadium (V) concentration in Mn–Zn ferrites with the general composition Mn0.6Zn0.4VxFe2−xO4 (x = 0.00—0.10, in steps of 0.02) synthesized by the solid-state reaction method. X-ray diffraction (XRD) analysis of all the samples confirmed the formation of the spinel structure. The cell parameter slightly decreases with the increase in V content. The substitution of V noticeably enhanced densification in samples sintered at 1250 °C. The grain size of the starting compositions varied from 13.0 to 27.9 µm. The Fourier Transform Infrared (FTIR) spectra indicate the preference of vanadium ions at octahedral sites. The saturation magnetization (Ms) and the experimental magnetic moments nB (µB) are observed to increase for x = 0.02 with = $${M}_{\mathrm{S}}$$ 61.73 emu/g. This happens for the reduction of the A–B interaction in the AB2O4 spinel type ferrites. After that, Ms and nB (µB) values decreased for higher V contents. The magnetization obtained is explained by redistribution of cations in the tetrahedral and octahedral sites and spin canting due to weakening of exchange interaction. The magnetic permeability and dielectric constant show a decreasing trend with increasing V concentration. The Cole–Cole plots demonstrate the grain and grain boundary effects. The manifestation of single semicircle after x = 0.06 indicates the precedence of grains in the overall resistance. The complex modulus graphs were also studied to understand the mechanism of the electrical processes.

Regulating the Coordination of Co sites in Co3 O4 /MnO2 Compounding for Facilitated Oxygen Reduction Reaction.

Binary transition metal oxides as a promising oxygen reduction reaction (ORR) catalyst have received significant attention. However, their exact reaction mechanisms are often too complex to be discussed. Herein, novel Co-Mn composites with a well-defined nanostructure were developed for understanding the role of each component. The growth pattern of cobalt oxide and the effects of the coordination environment of Co sites during growth on the overall activity were investigated. Based on experimental and density functional theory studies, it was found that the decaying coordination number directly affected the expression of crystal planes of cobalt oxide, which further had a great influence upon limiting current density of Co-Mn catalysts. The cuboid-Co/Mn catalyst exhibited outstanding limiting current density and showed good stability, related to more highly active (110) planes exposed in Co3 O4 . These provided many references for the preparation of related nonprecious catalysts in various domains.

Bimetallic MOFs derived FeM(II)-alloy@C composites with high-performance electromagnetic wave absorption

• FeM@C (M = null, Co, Ni, Mn) composites are synthesized by facile pyrolysis technique from FeM-MIL-88B. • FeM@C composites show controllable and excellent microwave absorption performance. • A minimum RL of −71.4 dB and effective bandwidth to 14.2 GHz with low filler loading (25 wt%) are achieved. • The second metal is doped to optimize the pyrolysis procedure and the electromagnetic parameters. The realization of balance between relative permittivity and permeability is still a great challenge in the development of microwave absorption materials. Based on the controllable MOFs precursor, bimetallic Fe/M (M = Co, Ni, Mn) doped carbon derived from pyrolyzing bimetallic MOFs (FeM-MIL-88B) exhibits intriguing microwave absorption property. By tuning the second metal source and the ratio of Fe/M, in this work we realize impedance matching between free space and the absorber. Optimized FeCo 2 @C exhibits strong EMW absorption performance (-71.4 dB) and broad bandwidth (14.2 GHz) with a low filler loading of 25 wt%. The synergistic effect of the bimetal source on carbonization process and electric/magnetic properties prove that rationally doping the second metal source into the Fe-MOFs precursor to generate bimetallic magnetic nanoparticles/C material play an intensified role to tune the microwave absorption performance.

In situ structural study of manganese and iron oxide promoted rhodium catalysts for oxygenate synthesis

In situ x-ray diffraction (XRD) and absorption spectroscopy (XAS) was used to characterize the structure and phase composition of a novel Mn and Fe double-promoted Rh-based catalyst for CO hydrogenation to oxygenates. Catalysts with different Mn:Rh molar ratios were prepared by combining Mn and Rh precursors with Fe2O3 powder, which were then calcined in air and reduced under hydrogen. The resulting MnRh/Fe2O3 catalysts are found to be highly selective for ethanol synthesis (∼40 %) for CO hydrogenation under mild conditions (∼1 bar, 240 °C). Comparison of the reactivity results with quantitative phase information from in situ XRD measurements suggest that reduced metal oxides, MnO and FeOx, and metallic Rh co-exist as active phases to promote oxygenate selectivity. The results of this work also highlight the importance of in situ characterization for extracting meaningful information on the active phases of such complex, ternary catalysts which can vary under reaction conditions.

The effect of processing parameters and heat-treatment on the microstructure and mechanical properties of PM CoCrFeMnNiTi0.1 high-entropy alloy

CoCrFeMnNiTi0.1 high-entropy alloy (HEA) was fabricated using mechanical alloying (MA) and sintering. To synthesize the HEA, the equiatomic composition of Cr, Co, Fe, Mn, and, Ni powders and Ti powder (1.0. at%) were ball milled at different times and then pressed and sintered specimens were provided. To investigate the effect of heat-treatment on the structure, sintered samples were heat-treated. The powder morphology, microstructure, X-ray diffraction, phase identification, hardness, and compressive strength investigation were performed. The results showed; over time smaller grain size was approached which led to improving the mechanical properties of the HEA. HEA structure contains FCC phase and the disappearance of XRD peaks, intensity decrement, and peak broadening occurred during milling. Heat-treatment led to round edges for the Cr-rich phase due to the decrease in the distance between the lamellar structure. Grain boundary strengthening and precipitation hardening are considered to be the main reinforcement mechanisms due to the addition of Ti. The 20-h heat-treated sample was nominated as the optimum mechanical properties.

Synthesis of mesoporous nickel-cobalt-manganese sulfides as electroactive materials for hybrid supercapacitors

Nickel-cobalt-manganese sulfide (NiCoMn-S) with a mesoporous structure was synthesized as the electroactive battery materials for hybrid supercapacitors. The synergy between transition metals of NiCoMn-S was investigated theoretically by performing density functional theory calculations and experimentally by comparing the charge storage properties of sulfides with different transition metals. It is found that the Mn composition can activate the 3d electrons of Co and enhance affinity of NiCo–S with electrolyte ions, leading to synergy between transition metals for enhanced electrochemical activity and rate performance. The Mn composition also increases the specific area for more electroactive sites and reduces the charge transfer resistance of sulfides. In addition, it is found that the Mn and Ni compositions can greatly enhance the charge storage activity of sulfide, and the Co composition greatly improves the rate performance. The strong synergy between Ni, Co and Mn results in enhanced specific capacity, high rate performance and excellent cycling stability. The NiCoMn-S exhibits a specific capacity of 661 C g−1 at 1 A g−1, which retains 440 C g−1 at 50 A g−1. More significantly, the NiCoMn-S demonstrates well matched performance with the capacitive RGO electrode, and the resulting hybrid supercapacitor (HSC) demonstrates both high power and high energy performances. The HSC exhibits a specific energy of 42.1 Wh kg−1 at a specific power of 750 W kg−1, and showing a specific energy of 13.2 Wh kg−1 at a specific power of 22.5 kW kg−1.

Metal Contaminants Tracer for Modeling Marine Culture Environmental Quality - A Taiwanese Case Study

Shih, Y.C., 2020. Metal contaminants tracer for modeling marine culture environmental quality-A Taiwanese case study. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 648-654. Coconut Creek (Florida), ISSN 0749-0208.The study was undertaken to assess the marine environmental effects from feed and waste associated with marine culture activities in Taiwan. In the meanwhile, the work was undertaken to develop an approach for modelling the changes of sediment chemistry related to the accumulation of marine culture waste. Metal composition of sediment Cu, Zn, Mn, Al, Li (ug/g) and Fe (%) were used to determine the extent of detectable effects around the cage. The concentrations of Al decreased with increased accumulation of Cu at study sites. There is a trend among normalised metals related to normal, hypoxic and anoxic sediment conditions. The trends are useful for detecting and assessing the cumulative effects from aquaculture wastes to the marine environment. Principal components analysis (PCA) was carried out on the metals and to cluster the similarities of the variables to establish for assessing the environmental conditions.

Customized magnetic properties of (Mn0.5Zn0.5)[EuxNdxFe2-2x]O4 nanospinel ferrites synthesized via ultrasonic irradiation approach

The demand of the multifunctional nanospinel ferrites (NSFs) is ever-increasing for various advanced applications wherein the fundamental knowledge of the magnetic features became essential. In this view, high purity NSFs of composition (Mn0.5Zn0.5)[EuxNdxFe2-2x]O4 (0.00 ≤ x ≤ 0.05) were synthesized via the ultrasonic irradiation. The influence of the co-substituents (Eu3+/Nd3+) concentration on the microstructures, morphologies and magnetic behaviors of these as-prepared NSFs were evaluated. The samples were characterized thoroughly using diverse analytical instruments. The X-ray powder diffraction patterns of these NSFs verified their phase purity. The SEM and TEM analyses revealed the existence of spherical shaped grains with size around 20 nm. The produced NSFs showed a superparamagnetic (SPM) behavior at room temperature and ferromagnetic (FM) behavior at very low temperatures. Both saturation and remanent magnetization values of the studied NSFs were improved at lower Eu3+/Nd3+ contents up to x = 0.02 and then dropped beyond x > 0.02. It was shown that the magnetic traits of these NSFs can be tailored by controlling the Eu3+/Nd3+ concentrations.

Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation

PurposeMeibum from donors who have had hematological stem cell transplantations (MHSCT) are susceptible to severe dry eye symptoms and exhibit very high lipid order (stiffness) compared with meibum from donors without dry eye (Mn). Since lipid order could have functional consequences, we compared the rheology and composition of Mn and MHSCT to measure meibum compositional, structural and functional relationships. MethodsThe rheology and composition was measured using Langmuir trough and 1H NMR spectroscopy, respectively. ResultsMHSCT and Mn was studied from 16 to 43 donors, respectively, using NMR spectroscopy. MHSCT contained significantly 16% more straight chain and 24% less iso-chain hydrocarbons compared with Mn. The cholesteryl ester to wax ester molar ratio, and hydrocarbon chain unsaturation were not significantly different, for MHSCT compared with Mn.Surface pressure-area isotherms of meibum from 30 donors without dry-eye were grouped into 4 pools (PC) and meibum from 32 donors with dry eye who had hematopoietic stem cell transplantation (PT) were grouped into 3 pools. Above 15 years of age the Пmax and (Cs−1)max increased with age for both the PC and the PT cohorts. (Cs−1)max values were higher for PT samples compared with age matched PC samples, indicating they had higher elasticity and stiffness. A more ordered lipid could contribute to the formation of a discontinuous patchy tear film lipid layer, which in turn results in deteriorated spreading, and decreased surface elasticity. ConclusionsThe composition and rheology of meibum from donors with dry eye and who have had HSCT support the idea from other studies that more ordered meibum may contribute to or be a marker of dry eye.

Comparative study on the mechanical and dielectric properties of aramid fibrid, mica and nanofibrillated cellulose based binary composites

High-performance insulation materials are widely used in transformers, electric generators and insulated wires of the high-speed trains and airplanes. However, the relatively poor mechanical and dielectric properties of the traditional insulation materials severely limit their application fields, especially in the harsh conditions. In this study, we prepared three binary composite films, including aramid fibrid/mica (AM), aramid fibrid/nanofibrillated cellulose (AN) and mica/nanofibrillated cellulose (MN), through a vacuum-assisted filtration and thoroughly investigated their mechanical and dielectric properties. Due to the dense nacre-like lamellar structure and strong interfacial bonding strength between mica and nanofibrillated cellulose (NFC), the MN composites exhibit the highest tensile strength of 34.6 MPa and excellent dielectric breakdown intensity of 17.1 kV/mm. The AM composite film has good thermal stability owing to the inherent high temperature resistance of aramid fibrid and mica, but shows the lowest tensile strength and dielectric breakdown intensity. The AN composite film shows the compromise mechanical and dielectric properties.

Magnetic Property Enhancement of Spinel Mn-Zn Ferrite through Atomic Structure Control.

Temperature treatment of magnetic Mn-Zn ferrites with the composition Mn0.6Zn0.2Fe2.2O4 up to 1100 °C results in a tremendous enhancement of the saturation magnetization by more than 60%. Employing a robust combined Rietveld refinement of powder X-ray and neutron diffraction (PXRD and NPD) data, it is revealed how a reordering of the cations takes place during the annealing step, the extent of which depends on the annealing temperature. While Zn(II) exclusively occupies tetrahedral sites throughout the whole temperature range, as the annealing temperature increases up to 700 °C, the Mn(II) cation distribution shifts from 80(7)% of the total Mn content occupying the octahedral sites (partly inverse spinel) to Mn only being present on the tetrahedral sites (normal spinel). Above 700 °C, pronounced crystallite growth is observed, followed by an increase of the saturation magnetization. Complementary techniques such as energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) confirm an even cation distribution and the particle growth with annealing temperature. The structural changes caused by annealing of spinel ferrites directly alter the magnetic properties of the materials, thus serving as an easy handle for enhancing their magnetic properties.

Composition dependence of spin−orbit torque in Pt1−xMnx/CoFeB heterostructures

We investigate spin–orbit torques (SOTs) in heterostructures with Pt1−xMnx alloy and CoFeB as a function of Mn composition (x) by using an extended harmonic Hall measurement. Slonczewski-like and field-like SOT efficiencies (ξSL and ξFL) show non-monotonic variation and a different trend with respect to x, and considerably large ξSL up to 0.21 is obtained at x = 0.20. Compared to the x dependence of longitudinal resistivity, the Slonczewski-like SOT in the low x region is mainly attributed to an intrinsic spin-Hall mechanism, whereas a non-monotonic variation in the higher x region suggests the presence of additional factors. The present findings deliver useful clues to understand the physics behind SOT generation in antiferromagnetic heterostructures and offer a route to realize efficient devices.

Coupled Manganese Redox Cycling and Organic Carbon Degradation on Mineral Surfaces.

Minerals, natural organic matter (NOM), and divalent manganese (Mn(II)) often coexist in suboxic/oxic environment. Multiple adsorption and oxidation processes occur in this ternary system, which are coupled to affect the fate of both OM and Mn therein and alter their chemical reactivity toward metals and other pollutants. However, the details about the coupling are poorly known although much has been gained for the binary systems. We determined the mutual influence of surface-catalyzed Mn(II) oxidation and humic acid (HA) adsorption and oxidation in a Fe(III) oxide (goethite)-HA-Mn(II) system at pH 5-8. The presence of Mn(II) substantially increased HA adsorption whereas HA greatly impaired the extent and rate of Mn(II) oxidation by O2 on goethite surfaces. The impacts were more pronounced at higher pH. Mn(II) oxidation produced β-MnOOH, γ-MnOOH, and Mn3O4 which in turn oxidized HA, producing small organic acids. The presence of HA markedly altered the composition of Mn(II) oxidation products by inhibiting the formation of β-MnOOH while favoring the production of γ-MnOOH and Mn(II) adsorbed on the HA-mineral assemblage. Nonconducting γ-Al2O3 exhibited similar but weaker effects than semiconducting goethite in the above processes. Our results suggest that similar to Mn-oxidizing microorganisms, mineral surfaces can drive the coupling of the Mn redox cycle with NOM oxidative degradation under suboxic/oxic and circumneutral/alkaline conditions.