Substitution Of Manganese Ions Research Articles

The type of current carriers in defective manganese sulfide and with cationic substitution by samarium ions

IR spectra and electrical resistance of defective manganese sulfide with the substitution of manganese ions with samarium ions in the of 80-500 K are investigated. The maxima of the temperature coefficient of electrical resistance and anomalies of conductivity are attributed to spin and lattice polarons. Absorption bands have been found in the IR spectra, that due to oscillations of octahedra and lattice polarons. From the Hall measurements, the type of current carriers, concentration and mobility of hole and electrons are estimated.

Facile synthesis of cobalt-doped sodium lithium manganese oxide with superior rate capability and excellent cycling performance for sodium-ion battery

In this work, cobalt-doped sodium lithium manganese oxide (NLMC) was synthesized by a solid-state reaction method. Crystal structure and morphology of the NLMC material were examined using X-ray diffraction, selected area electron diffraction, scanning eletron microscopy, transmission electron microscopy, energy dispersive spectroscopy, and inductively coupled plasma - optical emission spectrometry analysis. The NLMC material was utilized to fabricate CR2032-type coin cells, and later evaluated for its electrochemical characteristics. The partial substitution of manganese ions in the structure by cobalt and lithium ions is the main reason for the outstanding electrochemical properties. The NLMC material was delivers a specific capacity of 112 mAh/g at a current density of 0.1C; up to higher current density of 1C, it has retained a specific capacity of 63 mAh/g. In addition, the NLMC material exhibited an excellent cycling performance, it is able to remains up to 97.7% specific capacity over 100 cycles at the current density of 0.1C. The presented results provide new pathway of obtaining high electrochemical performance of the sodium manganese-based materials by employing other transitional elements to partially substitute manganese in the crystal structure.

Biochemical basis for hydrolysis of organophosphorus by a marine bacterial prolidase

Abstract Extensive application of synthesized organophosphorus compounds (OPs) leads to pollutant accumulation and enhanced eco-toxicity. Hydrolysis of phosphotriester bonds catalyzed by evolved microbial enzymes is a key step for detoxification of OPs. Here, a new marine bacterial prolidase OPAA4301 exhibiting promiscuous phosphotriesterase activity was isolated and systematically characterized. The homo-tetrameric enzyme OPAA4301 can catalyze the hydrolysis of both amido bond and phosphotriester bond. Manganese ions were observed to be essential for its catalytic integrity, and in vitro substitution of manganese ions by different metal cofactors led to decreased activity. We also revealed cooperation pattern of metal ligands and substrate-binding residues on OP hydrolysis by mutational analysis. Metal-binding sites together with Arg418 in the large-binding pocket of the enzyme were found to be indispensable for catalytic ability. Substitution mutation of small- and large-binding pocket residues caused significant variation in phosphotriesterase activity, and leaving group sites appeared to be involved in the catalytic process as substrate affinity regulators. Our study gave an overall biochemical understanding on the organophosphorus hydrolysis pattern of the newly identified marine bacterial prolidase and provided ideas for protein engineering to expand its application in the bioremediation field.

Does Ni and/or S Doping of Lithium-Manganese Spinel Enhance Surface Stability of a Cathode?

Around 18% of all of the commercial Li-ion batteries is based on lithium-manganese spinel LiMn2O4 (LMO). This material stands out among other cathode systems by its price and environmental friendliness [1]. Despite the fact that LMO is used to power electric tools, medical devices or powertrains, its applicability is greatly limited due to the LMO’s poor columbic efficiency. This limitation in electrochemical performance is connected with LMO structural instability. LMO at room temperatures can undergo reversible phase transition (caused by Jahn-Teller distortion of high-spin Mn3+ ions) from cubic (Fd-3m) to orthorhombic (Fddd) structure which is electrochemically inactive [2]. Moreover, in working Li-ion battery cell, the LMO can degrade through the reaction with components of liquid electrolyte [3]. The spinel disproportionation reaction with electrolyte (El) oxidation is presented below. LiMn2O4 + 3xLi+ + xEl → Li1+3xMn2-xO4 + xMn2+ + xEl+ To overcome the first of these problems and suppress the unfavorable phase transition in material the long range order in the spinel structure must be disordered. This can be achieved by partial substitution in cationic or anionic sublattice. Substitution of manganese ions with other transition metals (Co and Ni are most often used) leads to good stabilization but in the same time has negative impact on material cost [4]. Izoelectronic partial substitution of oxygen atoms in the spinel structure with sulfur gives the same result but does not influence the electrochemistry of the material or its cost [5]. In this studies we are taking a closer look on the surface of modified LMO spinels and theirs stability in Li-ion battery cell. The goal of this research is to analyze the influence of dopant presence in the cathode material’s structure on the stability of its surface against liquid electrolytes as well as the composition and stability of solid-electrolyte interface which is formed during electrochemical intercalation/deintercalation of Li+. Materials obtained via a sol-gel process with different compositions LiMn2-xNixO4-ySy, x = (0;0.5), y = (0;0.05) were studied in terms of materials corrosion and passivation in Li-ion half-cell. Besides the electrochemical studies (cyclic voltammetry, galvanostatic charge/discharge tests, electrochemical impedance spectroscopy), the analysis of passivation layer by X-ray photoelectron and infrared spectroscopy as well as transmission electron microscopy were conducted. The manganese dissolution in liquid electrolytes was evaluated using both electrochemical methods and atomic absorption/emission spectroscopy analysis. ACKNOWLEDGMENT This work is supported by National Centre for Research and Development, Poland under research grant No. LIDER/463/L-6/14/NCBR/2015.

The Influence of Sulfur Doping on Composition and Stability of Cathode Material-Electrolyte Interface Basing on Lithium-Manganese Spinel Studies

The solid-electrolyte interface (SEI) in lithium-ion batteries systems has crucial influence on the cell performance and its lifetime. The composition and properties of passivation layer which is formed at this interface depend on many factors like electrode material and electrolyte composition, the morphology of the electrode, potential range in which electrode is working or current densities. Therefore, appropriate selection of all of those parameters is essential to ensure the optimal properties of final battery. Lithium-manganese spinel LiMn2O4 (LMO) is relatively well known and successfully used cathode material in some commercial application (18% of whole cathode materials market according to Avicenne ENERGY reports from 2013). Despite the fact that LMO is used to power electric tools, medical devices or powertrains, its applicability is greatly limited due to the LMO’s poor capacity retention. This restricted cyclability is related to material’s structural lability and its limited stability versus organic solvents used in electrolytes for Li-ion batteries. LMO at room temperatures can undergo reversible phase transition from cubic (Fd-3m) to orthorhombic (Fddd) structure [1]. This transition which is related to the Jahn-Teller distortion of high-spin Mn3+ ions causes irreversible loss of capacity during subsequent charging/discharging cycles [1-6]. Stabilization of LMO is possible by distorting long-range order of crystalline structure. This can be achieved by partial substitution in cationic or anionic sublattice. Substitution of manganese ions with other transition metals (Co and Ni are most often used) leads to good stabilization but in the same time have negative impact on material cost. Izoelectronic partial substitution of oxygen atoms in spinel structure with sulfur seems to be better approach because it not only inhibit undesirable phase transition, which improves columbic efficiency of electrochemical reaction and cycle life of battery, but also significantly increase the capacity of the material [7]. Moreover, electrochemical impedance spectroscopy studies of the sulfur doped LMO (LiMn2O4-ySy) indicate that the surface of such modified material is more stable than pristine LMO. The goal of this studies is to analyze the influence of sulfur presence in the cathode material’s structure on the composition and stability of solid-electrolyte interface in working Li-ion battery cell. The stability and lifetime of working spinel electrode is strongly dependent on the properties of the material’s passivation layer. The composition of this interface and its stability in the electrolyte in the potential range of 3-4.5 V at different current densities were analyzed during electrochemical reaction for pristine LMO and sulfur doped samples. ACKNOWLEDGMENT This work is supported by National Centre for Research and Development, Poland under research grant No. LIDER/463/L-6/14/NCBR/2015. REFERENCES G. Li, Y. Iijima, Y. Kudo, H. Azuma Solid State Ionics, 146 (2002) 55-63G. Pistoia, A. Antonini, R. Rosati, D. Zane Electrochimica Acta, 41 (1996) 2683-2689G.G. Amatucci, C.N. Schmutz, A. Blyr, C. Sigala, A.S. Gozdz, D. Larcher, J.M. Tarascon Journal Power Sources, 69 (1997) 11-25A. Yamada, M. Tanaka, K. Tanaka, K. Sekai Journal Power Sources, 81-82 (1999) 73-78E. Iwata, K. Takahashi, K. Maeda, T. Mouri Journal Power Sources, 81-82 (1999) 430-433L. Yang, M. Takahashi, B. Wang Electrochimica Acta, 51 (2006) 3228-3234M. Molenda, M. Bakierska, D. Majda, M. Świętosławski, R. Dziembaj Solid State Ionics, 272 (2015) 127–132

Magnetic interactions in La0.7Sr0.3Mn1−xMexO3 (Me=Ga, Fe, Cr) manganites

Magnetic properties and crystal structure of La0.7Sr0.3Mn1−xMexO3 (Me=Ga, Fe, Cr; x≤0.3) have been studied by neutron powder diffraction and magnetization measurements. It is shown that substitution of manganese ions by chromium or gallium ions (x=0.3) leads to phase separation into antiferromagnetic and ferromagnetic phases whereas replacement by Fe ions stabilizes spin glass state (x=0.3). Ferromagnetic interactions in Cr-substituted compounds are much more pronounced than in Fe- and Ga-doped ones. Magnetic properties are discussed in the model assuming a dominance of superexchange interactions. It is considered that ferromagnetism in the Cr-substituted compositions is associated with nearly equal contributions from positive and negative components of the superexchange interaction between Mn3+ and Cr3+ ions as well as to mixed valence of chromium ions. The spin glass state observed for the Fe-doped sample (x=0.3) is associated with strong antiferromagnetic superexchange between Fe3+–O–Fe3+ and Fe3+–O–(Mn3+, Mn4+).

Effect of paramagnetic manganese ions doping on frequency and high temperature dependence dielectric response of layered Na1·9Li0·1Ti3O7 ceramics

The manganese doped layered ceramic samples (Na1·9Li0·1)Ti3O7 : XMn(0·01 ≤ X ≤ 0·1) have been prepared using high temperature solid state reaction. The room temperature electron paramagnetic resonance (EPR) investigations exhibit that at lower percentage of doping the substitution of manganese ions occur as Mn3+ at Ti4+ sites, whereas for higher percentage of doping Mn2+ ions occupy the two different interlayer sodium/lithium sites. In both cases, the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. The manganese doped derivatives of layered Na1·9Li0·1Ti3O7 (SLT) ceramics have been investigated through frequency dependence dielectric spectroscopy in this work. The results indicate that the dielectric losses in these ceramics are the collective contribution of electric conduction, dipole orientation and space charge polarization. Smeared peaks in temperature dependence of permittivity plots suggest diffuse nature of high temperature ferroelectric phase transition. The light manganese doping in SLT enhances the dielectric constant. However, manganese doping decreases dielectric loss due to inhibition of domain wall motion, enhances electron-hopping conduction, and impedes the interlayer ionic conduction as well. Manganese doping also gives rise to contraction of interlayer space.

Synthesis, characterization and electrical properties of the system LaMn xFe 1− xO 3

The system manganese substituted lanthanum ferrite viz. LaMn x Fe 1− x O 3 (1.0 ≤ x ≥ 0) was prepared by sol–gel autocombusion method. The structural characterization of the samples was carried out by X-ray diffraction technique and it is found that, the phase transfer from cubic to orthorhombic perovskite structure. The lattice parameter and crystallite size decrease with increasing Mn content. The phase formation of perovskite was revealed by thermal analysis technique. The surface morphology and elemental analysis of all the samples were carried out by scanning electron microscopy and energy dispersive X-ray spectroscopic technique, respectively. Electrical properties of the compounds show that, they exhibit semiconducting behavior. The substitution of manganese ions plays an important role in changing their structural, electrical and magnetic properties of lanthanum ferrite.

Investigation of structural and magnetic properties of nanocrystalline manganese substituted lithium ferrites

Nanocrystalline manganese substituted lithium ferrites Li 0.5Fe 2.5− x Mn x O 4 (2.5≤ x≥0) were prepared by sol–gel auto-combustion method. X-ray diffraction patterns revealed that as the concentration of manganese increased, the cubic phase changed to tetragonal. Magnetic properties were measured by hysteresis loop tracer technique. All the compositions indicated ferrimagnetic nature. The surface morphology of all the samples was studied by using scanning and transmission electron microscopy. The substitution of manganese ions in the lattice affected the structural as well as magnetic properties of spinels.

EPR and mixed electronic-ionic conductivity studies of pure and manganese doped layered Potassium–Lithium tetra titanates (K1.9Li0.1Ti4O9)

Lithium (5%) mixed layered K2Ti4O9 and its 0.01, 0.02, 0.05, 0.1 and 1.0 molar percentage MnO2, doped derivatives have been prepared and characterized through electrical conductivity studies in the temperature range 373–900 K and room temperature EPR investigation. Three distinct regions have been identified in the Log(σT) versus 1000/T plots. The lowest temperature region is attributed to electronic hopping conduction (except for K1.9Li0.1Ti4O9 (PLT) in which interlayer lithium ionic conduction is proposed) involving loose electrons from Ti4O 9 2− groups. The intermediate region to associated interlayer ionic conduction through dilated interlayer space and the highest temperature region to unassociated interlayer ionic conduction. The room temperature EPR investigations reveal that at a lower percentage of doping the substitution of manganese ions occur as Mn4+ at Ti4+ sites, whereas for higher percentage of doping Mn2+ ions predominantly occupy the two different interlayer alkali sites. The dilation of interlayer space has further been proposed to occur due to manganese ions substitution at octahedral Ti4+ sites. In both these cases the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice.

Thermoluminescence of aluminophosphate glasses in the metaphosphate composition

Potassium aluminum phosphate (KAP) glasses in the system xKPO 3–(100 − x)Al(PO 3) 3 with x = 10, 30 and 50 mol% were prepared in the metaphosphate composition. The glasses were doped with MnO 2 and their thermoluminescent (TL) response was investigated. Raman spectra showed that these glasses did not undergo structural changes with the substitution of manganese ions. The glass composition x = 50 mol% doped with 1.0 mol% of MnO 2 presented the best TL response. The material displayed good sensitivity for γ-rays, X-rays and UV light. The emission curves exhibited two TL peaks, one at a low temperature (∼150 °C) and the other at a high temperature (∼365 °C), whose positions were dependent on the type of exciting radiation applied. The results of the present study indicated that the high temperature peak is a good candidate for TL dosimetric investigations.

Adsorption of Heavy Metal Ions onto the Surface of Metal-Incorporated Hydrous Ferric Oxide Particles

The substitution of manganese ions for the lattice Fe 3+ ions in goethite (α-FeOOH) contributes to a preferential removal of Pb II from low-pH solutions. This effect was enhanced by the excess addition of manganese nitrate in the synthetic process for Mn-incorporated goethite particles. This enhancement was caused by the formation of the specific surface sites for the selective adsorption of Pb II .

Magnetic ordering in perovskites containing manganese and cobalt

The magnetization measurement of systems with the nominal formula (R = Eu, Gd, Tb, Y) has been made. It has been found that and are weak ferromagnets of Dzialoshinsky - Moriya type whereas is an antiferromagnet. The substitution of manganese ions by cobalt ones leads to the appearance of different magnetic states: cluster-spin-glass-like , inhomogeneous ferromagnets with well defined Curie temperatures and again a spin glass state . Spontaneous magnetizations and Curie temperatures reach maxima for compounds with x = 0.5. External magnetic field induces a metamagnetic transition in (R = Gd, Tb, Y). The transition becomes irreversible at low temperature in the Tb- and Y-based compounds. The annealing in vacuum of leads to the increase of the Curie temperature and to the appearance of a metamagnetic transition for the compound. The metamagnetic behaviour is interpreted taking into account the ionic ordering of and ions and possible 3d-orbital ordering in the sublattice.

Electrical conductivity and electron paramagnetic resonance investigations in manganese-doped polycrystalline Na2Ti3O7

D.c. electrical conductivity studies have been reported in Na2Ti3O7 in the temperature range 370–750 K. Three distinct regions have been identified in the log(σT) versus 1000/T plots, the lowest temperature region being proposed to be due to electronic hopping conduction involving loose electrons of Ti3O72− groups, the intermediate region to associated extrinsic ionic conduction through dilated interlayer space and the highest temperature region to modified interlayer ionic conduction, the modification being affected by loose oxygens from Ti3O72− groups. The room-temperature electron paramagnetic resonance (EPR) investigations have been interpreted in terms of manganese substitution in the lattice. For a lower percentage of doping the substitution of manganese ions occur as Mn3+ at Ti4+ sites, whereas for a higher percentage of doping, Mn2+ ions predominantly occupy the interlayer Na+ sites. The dilation of interlayer space has further been proposed to occur due to a Ti4+ substitution of manganese ions.