Different Amounts Of Mn Research Articles

Optimizing physical properties of BiFe1-xMnxO3 perovskite thin films via a low-temperature sol-gel method

Multiferroic materials have recently attracted great attention for possible use in photovoltaic and photocatalytic devices. In this study, pure-phase BiFe1-xMnxO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) thin films were deposited on glass substrates via low-temperature sol-gel assisted spin coating procedure. We found that the thin films undergo a rhombohedral to cubic structural transition. From FESEM images, it was observed that different amount of Mn affects the surface morphology and grain size of the studied samples. For all samples, the absorption coefficient was in the range of 105 cm−1, and the refractive index and extinction coefficient of samples were about 1.15–1.50 and 0.2–0.9, respectively. BiFe0.8Mn0.2O3 thin film has the lowest bandgap energy due to the highest absorption coefficient at the wavelengths of 400–1100 nm denoted by its lowest transmittance. Structural and magnetic results show the substitution of low-spin smaller Mn ions for high-spin larger Fe ions. The best photocatalytic activity was observed for BiFe0.8Mn0.2O3 thin film with a removal efficiency of 78.83% in the photodegradation of methylene blue.

Rational Regulation of Reducibility and Acid Site on Mn-Fe-BTC to Achieve High Low-Temperature Catalytic Denitration Performance.

Selective catalytic reduction with ammonia is the mainstream technology of flue gas denitration (de-NOx). The reducibility and acid site are two important factors affecting the de-NOx performance, and effective regulation between them is the key to obtain a highly efficient de-NOx catalyst. Herein, a series of Mn-Fe-BTC with different ratios of Mn and Fe are synthesized, among which 2Mn-1Fe-BTC with 2:1 molar ratio of Mn and Fe has excellent low-temperature (LT) de-NOx performance (above 90% NO conversion between 60 and 270 °C) and good tolerance to H2O and SO2 poisoning (88% NO conversion at 150 °C with 100 ppm of SO2 and/or 6% H2O). It is revealed that the reducibility properties and acid sites of Mn-Fe-BTC can be flexibly tuned by the ratio of Mn and Fe. The difference in electronegativity between Fe and Mn leads to the redistribution of valence electrons, which enables the controllable reducibility of Mn-Fe-BTC. Furthermore, different amounts of Mn and Fe lead to different electron transport, which determines the type and number of acid sites. The synergistic effect of Mn and Fe endows Mn-Fe-BTC with enhanced surface molecular adsorption capacity and enables the catalyst to selectively chemisorb NH3 and NO at different active sites. This research provides guidance for the flexible regulation of reducibility and acid site of LT de-NOx catalyst.

Effects of Mn and Microalloying Composition on Corrosion and Hydrogen-Induced Cracking of API 5L X65 Steels

The corrosion and hydrogen-induced cracking (HIC) resistance as well as hydrogen permeation behavior of two API 5L X65 steels with different amounts of Mn and microalloying elements were compared. The corrosion behavior of both steels, evaluated using electrochemical impedance spectroscopy and polarization curves in solution A of NACE TM0284-16 standard with and without H2S saturation (sour medium), showed no relevant differences in each medium, which can be ascribed to their similar microstructures; however, the corrosion resistance of both steels was lower in the sour medium. The investigation of resistance to hydrogen-induced failures disclosed better performance for the low Mn steel. This was confirmed using a harsher HIC test performed in an HCl acidified sour medium and was ascribed to the presence of Nb carbides nanoprecipitates, as revealed by the scanning transmission electron microsccopy analysis.

Effect of manganese incorporation on the excitonic recombination dynamics in monolayer MoS2

Using x-ray photoelectron spectroscopy, atomic force microscopy, and Raman spectroscopy techniques, we investigate the incorporation of manganese (Mn) in monolayer (1L)-MoS2 grown on sapphire substrates by microcavity based chemical vapor deposition method. These layers are coated with different amounts of Mn by pulsed laser deposition technique. The study reveals two contrasting Mn-incorporation regimes. Below a threshold deposition amount, thin Mn-coating with large area coverage is found on MoS2 layers where substitution of Mo ions by Mn is detected through XPS. Dewetting takes place when Mn deposition crosses the critical mark, resulting in the formation of Mn-droplets on MoS2 layers. In this regime, substitutional incorporation of Mn is suppressed, while the Raman study suggests an enhancement of disorder in the lattice with the Mn deposition time. This knowledge can help us in tackling the challenge of doping of 2D transition metal dichalcogenides in general. From the temperature dependent photoluminescence study, it has been found that, even though Mn deposition enhances the density of non-radiative recombination channels for the excitons, the thermal barrier height for such recombinations to take place also rises. The study attributes these non-radiative transitions to Mo-related defects (Mo-vacancies and/or distorted Mo–S bonds), which are believed to be generated in large numbers during Mn-droplet formation stage.

Effect of introducing manganese as additive on microstructure, hydrogen storage properties and rate limiting step of Ti–Cr alloy

TiCr2 with adding different amount of Mn (0, 2, 4 and 8 wt.%) alloys have been investigated. All alloys have C14-type main phase (gray color in SEM) and Ti minor phase (dark gray color in SEM). Rietveld fitting results proved that the lattice parameter a and cell volume of C14-type phase decreased with increasing Mn content. The first hydrogenation measurement manifest that all alloys have best activation properties and could be activated without any prior heat treatment and hydrogen exposure. However, introducing Mn led to the decrease of the first hydrogen absorption rate of TiCr2 alloy, which may be due to the decrease of cell volume of C14-type main phase. The first hydrogenation properties at low temperature and effect of air exposure of the alloy were discussed. The results showed that the maximum hydrogen absorption capacity at 0 °C was obviously higher than that at room temperature. In addition, TiCr2 alloy doped with minor amounts of Mn after long-time air exposure showed better hydrogenation performance. This may be due to the Mn additive acting as a deoxidizer. Finally, the first hydrogenation kinetic mechanisms of all alloys at different temperature were also studied by using the rate limiting step.

Magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism in FeCoNiZMnx (Z = Si, Al, Sn, Ge) high entropy alloys

We design high entropy alloys (HEAs) with different induction elements (Si/Al/Sn). In order to keep the crystal structure invariant and to investigate how the increment in saturation magnetization (Ms) is caused only by the change of electron spin state, each set of HEAs contains a different amount of Mn. Synergistic effects among induction elements that induce the magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism are found. Ms of added Mn reduces when a particular induction element (Si0.4/Al0.4/Sn0.4) exists, while a larger increment of Ms appears when two induction elements coexist, Si0.4Al0.4 (25.79 emu/g) and Sn0.4Al0.4 (15.43 emu/g). This is reflected in the microcosmic magnetic structure for the emergence of closed domains due to large demagnetization energy, which is confirmed by the Lorentz transmission electron microscope (LTEM) data. The calculated magnetic moments and the exchange integral constants from density functional theory based on the Exact Muffin-Tin Orbits formalism reveal that the magnetic state and the strength of ferromagnetic and anti-ferromagnetic coupling determine the variation of Ms in different chemical environments. The difference in energy levels of coexisting multiple induction elements also leads to a larger increment of Ms, Si0.4Al0.4Sn0.4 (29.78 emu/g), and Si0.4Al0.4Ge0.4Sn0.4 (31.00 emu/g).

Tunable surface charge of Fe, Mn substituted polyoxometalates/hydrotalcites for efficient removal of multiple dyes

Mn, Fe substituted Keggin type polyoxometalate/hydrotalcites hybrids were synthesized by anion exchange method. The structures and morphologies of the samples were determined by XRD, FTIR, SEM, TG and BET. The samples were used as heterogeneous catalysts for the Fenton reaction process and displayed high activity for degradation organic dyes in aqueous solution. The experimental parameters such as pH value, H2O2 concentration and type of dyes were studied. Especially, the surface charges of the catalysts could be changed by inserting different amount of Mn, Fe substituted polyoxometalate in the interlamination of hydrotalcites. Considering electrostatic forces between dyes and catalysts, tunable surface charge of catalyst was beneficial to deal with different types of dyes. The results demonstrated that the synthesized material could be served for the removal of mixed dyes from water. The experimental results also showed that the presence of Fe3+/Fe2+, Mn3+/Mn2+ pair at the surface of the catalysts promoted the degradation reactions, and W element from polyoxometalate also played a key role in this reaction. The catalytic activity was maintained after fourth cycles of reaction, which proved reusability and stability of the catalysts.

Transition metal substitution effects in sol-gel derived Mg3-xMx/Al1 (M = Mn, Co, Ni, Cu, Zn) layered double hydroxides

In the present study the transition metal substitution effects in Mg3-xMx/Al1 (M = Mn, Co, Ni, Cu, Zn) layered double hydroxides (LDHs) were investigated. For the synthesis of the mentioned compounds a newly developed sol-gel synthesis method has been applied. It was demonstrated that different amounts of Mn, Co, Ni, Cu and Zn could be introduced to the sol-gel derived LDHs without destroying the layered structure. The synthesis products were characterized using X-ray powder diffraction (XRD) analysis, infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The specific surface area of differently substituted Mg3-xMx/Al1 LDH specimens was also estimated. The synthesized LDHs could be tested for different medical applications and could be used as precursor material for the preparation of nanostructured mixed-metal oxides with a variety of useful properties.

The effect of alloying elements on fracture resistance of E7010-P1 cellulosic welding electrodes

In this paper, Assessment for fracture resistance of three different cellulosic welding electrodes (type E7010-P1) with various chemical compositions is made. This assessment is done by using Failure Assessment Diagram (FAD) method and based on the principles of fracture mechanics in accordance with BS 7910-2015 standard. The mechanical and fracture toughness properties of weld materials have been determined carrying out tensile test as well as CTOD fracture toughness test. The results are then used for finite element (FE) simulations in ABAQUS commercial software to compute stress intensity factor (SIF) along the crack front in the weld material. These results are then used to plot FAD curves and assessment points for each welding electrode to evaluate the existing crack in simulation. The analysis reveals that the presence of different amount of Mn in the weld metal influences directly on the resistance to fracture in weld metal at moderate temperature applications.

Effect of Dopant Loading on the Structural and Catalytic Properties of Mn-Doped SrTiO3 Catalysts for Catalytic Soot Combustion

Soot particles have been associated with respiratory diseases and cancer. To decrease these emissions, perovskite-mixed oxides have been proposed due to their thermal stability and redox surface properties. In this work, SrTiO3 doped with different amounts of Mn were synthesized by the hydrothermal method and tested for soot combustion. Results show that at low Mn content, structural distortion, and higher Oads/Olat ratio were observed which was attributed to the high content of Mn3+ in Ti sites. On the other hand, increasing the Mn content led to surface segregation of manganese oxide. All synthesized catalysts showed mesopores in the range of 32–47 nm. In the catalytic combustion of soot, the samples synthesized in this work lowered the combustion temperature by more than 100 °C compared with the uncatalyzed reaction. The sample doped with 1 wt % of Mn showed the best catalytic activity. The activation energy of these samples was also calculated, and the order of decreasing activation energy is as follows: uncatalyzed > Mn0 > Mn8 > Mn4 > Mn1. The best catalytic activity for Mn1 was attributed to its physicochemical properties and the mobility of the oxygen from the bulk to the surface at temperatures higher than 500 °C.

Promotional effect of Ce on the SCR of NO with NH3 at low temperature over MnO x supported by nitric acid-modified activated carbon

Different amounts of Mn and Ce oxides were loaded onto nitric acid-modified activated carbon (ACN) by wet impregnation. The series of catalysts were employed for the selective catalytic reduction of NO x by NH3 at temperatures between 100 and 250 °C. Cerium-modified catalysts exhibited higher de-NO x performance than those modified with Mn/ACN, even with the same total loadings. The precursor solution with a molar ratio for Ce/(Mn + Ce) of 0.4 exhibited the highest catalytic activity. Enhanced resistance to SO2 and H2O and better stability were observed for 10%Mn–Ce(0.4)/ACN relative to 10%Mn/ACN. The catalysts were further characterized by N2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed desorption of ammonia (NH3-TPD). The N2 physisorption and XRD results suggested that co-doping Ce with Mn increased the surface area and promoted the dispersion of Mn–Ce binary metal oxides. H2-TPR the NH3-TPD results demonstrated that the interaction between manganese oxide and cerium oxide species enhanced the redox and surface acidity of 10%Mn–Ce(0.4)/ACN.

New insights into the effects of Mn and Li on the mechanistic pathway for CO hydrogenation on Rh-Mn-Li/SiO2 catalysts

It has been reported widely that Rh-Mn-Li/SiO2 catalysts can exhibit high selectivity to C2+ oxygenates during CO hydrogenation, with promoters of Mn and Li playing an important role in this behavior. In this study, a series catalysts of Rh-Mn-Li/SiO2 with different amounts of Mn and Li were prepared, and the new insights into the effects of Mn and Li on the mechanistic pathway for C2+ oxygenates synthesis from syngas were investigated. The XPS analysis showed that Rh existed mainly as metallic Rh after reduction, however partially positively charged Rhδ+ atoms appeared on the surface of Mn-containing catalyst due to the interaction of Rh-Mn. The results of H2-TPR indicated that both of Li and Mn can inhibit the reduction of Rh2O3. With the increase in the ratio of Mn/Rh, the most effective interaction, associated to the presence of two reduction centers of Rh2O3, was obtained when the ratio of Mn/Rh=1. In situ-FTIR was used to probe the effects of Mn and Li on CO absorption and hydrogenation. With regards to the CO adsorption, the doping of Mn can enhance the CO adsorption ability of Rh and weaken the CO-Rh bond strength very effectively when the amount of Mn reached 1.5wt.%. Improved capacity of CO adsorption is conducive to increase of CO conversion, while the weakening of CO-Rh bond is beneficial to the CO insertion reaction, thus contributing to the generation of C2+ oxygenates. Moreover, the low amount of Li (≤0.075wt.%) can also enhance the CO adsorption, resulting in the improvement of reactivity. On the other hand, Mn and Li promoted dissociation of H2, which is favorable to an increase in the rate of hydrogenation. But an opposite effect appeared at high content of Mn (>1.5wt.%). As the optimized results, when Rh, Mn, Li content was 1.5wt.%, 1.5wt.% and 0.075wt.%, the catalyst for CO hydrogenation of C2+ oxygenates achieved the best performance of C2+ oxygenates synthesis.

Wear Resistance of Two Nanostructural Bainitic Steels with Different Amounts of Mn and Ni

Extremely valuable mechanical properties in combination with acceptable wear resistance can make nanostructural bainitic steels to be used extensively in different engineering and tribological applications. However, it is critical to characterize the contributed factors to investigate the wear response of these high-strength materials. This work aims to study the wear behavior of two nanostructural bainitic steels with different amount of austenite stabilizer elements Mn and Ni. For this purpose, wear resistances of the materials were evaluated using the pin-on-disk method. The results indicated that the hardness of the sample is a critical factor affecting the tribological behavior, and the volume fraction and morphology of high-carbon retained austenite are also of considerable importance. It has also been demonstrated that transformation-induced plasticity effect during the wear test and oxide formation at worn surfaces are critical factors.

Improved electrical properties for Mn-doped lead-free piezoelectric potassium sodium niobate ceramics

The un-doped and doped lead-free piezoelectric potassium sodium niobate (K0.5Na0.5NbO3, KNN) ceramics with different amounts of Mn were prepared. The decreased dielectric losses and the improved electrical properties were observed in the Mn-doped KNN ceramics. However, the variation of electrical properties with the Mn contents was not continuously. The 0.5 mol.% Mn-doped KNN ceramic shows the highest dielectric loss and the worst electrical properties. The KNN ceramics doped with less than and more than 0.5 mol.% Mn all show improved electrical properties. The change of lattice position of Mn ions in KNN ceramics was the main reason. When the Mn content is less than 0.5 mol.%, the Mn ions occupied the cation vacancies in A-site. When the Mn content is higher than 0.5 mol.%, the Mn ions entered B-site of KNN perovskite structure and formed the defect complexes (MnNb″−VO⋅⋅) and (MnNb′−VO⋅⋅−MnNb′). They both led to a lower defect concentration. However, When the Mn content is up to 1.5 mol.%, the electrical properties of KNN ceramic became degraded because of the accumulation of Mn oxides at grain boundaries.

Study of the interaction between human serum albumin and Mn-doped ZnS quantum dots

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but very little known is about interaction of quantum dots with biological molecules. In this study, interactions of ZnS quantum dots doped with different amounts of Mn (1, 2 and 3 %) with human serum albumin (HSA) were studied by fluorescence and UV–Vis spectroscopic techniques. It was observed that fluorescence of HSA was strongly quenched by ZnS QDs. The results of fluorescence quenching at different temperatures and UV–Vis absorption spectra experiments indicated that the quenching mechanism of serum albumin by QDs is static quenching through formation of the complex of QDs–HSA. According to the modified Stern–Volmer equations at different temperatures, the thermodynamic parameters, ΔH 0, ΔS 0 and ΔG 0 were determined. The number of binding sites (n) was also obtained. It was found that hydrogen bonding and van der Waals interaction played a key role in the interaction process.

Removal of NO(x) at low temperature over mesoporous alpha-Mn2O3 catalyst.

Low-temperature selective catalytic reduction was carried out over various kinds of manganese oxide (MnOx) catalysts. Mesoporous alpha-Mn2O3, commercial bulk Mn2O3, and Mn/SBA-15 were used as the catalyst. The NOx removal performances of the catalysts were compared. Three different amounts of Mn (5, 10, and 15 wt%) were impregnated on SBA-15 to synthesize Mn/SBA-15. The physical and chemical properties of the catalysts were examined by Brunauer-Emmett-Teller, X-ray diffraction, X-ray photoelectron spectroscopy, and H2-temperature programmed reduction analyses. Of all catalysts examined, mesoporous alpha-Mn2O3 exhibited the highest low-temperature SCR de-NOx efficiency, reaching about 90% at 175 degrees C. This is attributed to strong reducing ability and high oxygen mobility of mesoporous alpha-Mn2O3 and well dispersed Mn2O3 in its mesoporous framework.

Electromechanical Properties of Acceptor‐Doped Lead‐Free Piezoelectric Ceramics

We have studied the processing and electromechanical properties of Mn and Fe‐doped 0.88[Bi0.5Na0.5TiO3]–0.08[Bi0.5K0.5TiO3]–0.04[Bi0.5Li0.5TiO3] piezoelectric ceramics prepared by the mixed oxide route. Different amounts of Mn (0.01, 0.014, 0.015, 0.016, 0.017, 0.02, 0.022) or Fe (0.0125, 0.015, 0.0175) were doped to this lead‐free piezoelectric composition. Ceramics were sintered at different temperatures (1075°C–1150°C) to achieve the highest density and mechanical quality factor. Mn or Fe doping resulted in a considerable enhancement of Qm in both planar and thickness resonance modes. In 1.5 mol% Mn‐doped ceramics sintered at 1100°C, a planar Qm of about 970 and tanδ of 0.88% were obtained. In Fe‐doped ceramics, a planar Qm as high as 900 was achieved. Acceptor dopants also resulted in decreasing the coupling coefficients, the piezoelectric charge coefficient, and the dielectric constant.

전이금속을 함침한 γ-Al2O3촉매의 Toluene 분해

Alumina-supported catalysts containing different transition metals such as Cu, Cr, Mn, Zn, Co, W were investigated for their activity in the selective oxidation of toluene. Catalytic oxidation of toluene was investigated at atmospheric pressure in a fixed bed flow reactor system over transition metals with <TEX>$Al_2O_3$</TEX> catalyst. The result showed the order of catalytic activities for the complete oxidation of toluene was Mn > Cu> Cr> Co> W> Zn for 5wt.% transition <TEX>$metals/Al_2O_3$</TEX>. <TEX>$Mn/Al_2O_3$</TEX> catalysts containing different amount of Mn were characterized by X-ray diffraction spectroscopy for decision of loading amount of metal to alumina. 5 wt.%<TEX>$Mn/Al_2O_3$</TEX> catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of <TEX>$289^{\circ}C$</TEX>.

Impurity band conduction in the thermoelectric material ZnSb

ZnSb is favourable as a thermoelectric material, from both an environmental and a global resources point of view. Its efficiency can possibly be improved by the reduction of the thermal conductivity through nanostructuring and optimization of doping. These tasks require a better understanding of the material and, in particular, of the interplay between preparation techniques and material properties. We have prepared bulk polycrystalline samples and report on low-temperature electrical transport measurements (6 K to room temperature). The data have been interpreted in terms of hole impurity band conduction: intrinsic acceptor defects creating bands that are conducting when there are also compensating donors. Modelling the transport reveals qualitatively good agreement. Quantitative differences are discussed in terms of the structure of the samples, which has been studied by using x-ray diffraction, a scanning electron microscope and an electron microprobe. The systematics of adding different amounts of Mn and Cr to ZnSb has been studied and has the effect of varying the density of states in impurity bands and varying the hole concentrations.

Study of the Microstructure and Strain Induced Precipitation during Thermomechanical Processing of Low Carbon Microalloyed Steels

A series of anisothermal multipass hot torsion tests were carried out to simulate hot rolling on three high-strength low-carbon steels with different amounts of Mn, Mo, Nb and Ti and designed for pipeline construction. Mean Flow Stress was graphically represented against the inverse of temperature to characterize the evolution of austenite microstructure during rolling. The effect of austenite strengthening obtained at the end of thermomechanical processing on the final microstructure obtained after cooling was studied. Higher levels of austenite strengthening before cooling promote a refinement of final microstructure but can also restrict the fraction of low-temperature transformation products such as acicular ferrite. This combined effect gives rise to a wide range of final microstructures and mechanical properties depending on the composition, processing schedule and cooling rates applied. On the other hand, the precipitation state obtained at diverse temperatures during and at the end of hot rolling schedule was evaluated by means of transmission electron microscopy (TEM) in two microalloyed steels. It was found that two families of precipitates with different morphology, composition and mean size can coexist in microalloyed steels.