Addition Of MnO2 Research Articles

The Effects of MnO2 Addition on the Physical Properties of Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3-Pb(Mg1/2W1/2)O3-BiFeO3 Ceramics

In this paper, for the application to multi-layer piezoelectric devices capable of being used in piezoelectric speakers, Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3-BiFeO3 ceramics substituted with Pb(Mg1/2W1/2)O3 were manufactured according to MnO2 addition, and their physical properties were studied. At non-doped MnO2 added specimen, the maximum values of piezoelectric properties were shown, respectively: the εr of 2182, d33 of 513 pC/N, and kp of 0.634. When taking into consideration the low dielectric constant and high d33 in case of increasing the numbers of multilayer in ceramics, the x = 0.2 composition ceramics was suitable for the device application such as speaker using low-temperature sintering multilayer piezoelectric actuators.

Corrosion protection performance and interfacial interactions of polythiophene/silanes/MnO2 nanocomposite coatings on magnesium alloy in marine environment

The silane functionalized MnO2 nanoparticles were incorporated in polythiophene (PT) to produce PT/silanes/MnO2 nanocomposites. The surfaces of MnO2 nanoparticles were modified with ethyltrimethoxysilane (ETMS), 3-glycidyloxypropyltrimethoxysilane (GPTMS), and 3-aminopropyltrimethoxysilane (APTMS) and characterized by X-ray diffraction (XRD) studies. The corrosion resistance of newly synthesized PT, PT-ETMS/MnO2, PT-GPTMS/MnO2, and PT-APTMS/MnO2 composite coatings of magnesium alloy (AZ91A) was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) studies, and scanning electrochemical microscopy (SECM) immersed in natural seawater for several days. The PT-APTMS/MnO2 nanocomposite coatings showed an excellent resistance against corrosion with a charge transfer resistance of over 7517.85 kΩ cm2, which were higher than that of the PT coating (548.25 kΩ cm2) after 80 days immersion in seawater. The coating with MnO2 nanoparticles modified by APTMS, GPTMS, and ETMS groups showed no significant penetration by corrosive ions during 80 days’ immersion due to the strong chemical bonding between amino/epoxide/ethyl groups on MnO2 and the sulfur of PT. Decreased current was detected at the scratch of investigated nanocomposite coatings by SECM analysis. The affinity between PT and silanes/MnO2 nanoparticles is enhanced due to their interfacial interactions, which improves the dispersion of silane functionalized MnO2 nanoparticles in PT to produce uniform coatings. Scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and XRD technique of synthesized nanocomposite coatings confirmed the presence of corrosion products which block the dissolution of Mg alloy. Excellent mechanical properties are shown by the investigated coatings. Highlights Newly synthesized polythiophene (PT), PT-ETMS/MnO2, PT-GPTMS/MnO2, and PT-APTMS/MnO2 composite coatings on magnesium alloy (AZ91A) was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) studies, and scanning electrochemical microscopy (SECM) immersed in natural seawater for several days. The addition of MnO2 in the polymer resulted in the reduction of porosity of the coatings significantly. The silane functionalized MnO2 nanoparticles loaded nanocomposite coatings demonstrated excellent resistance against corrosion than that of the MnO2-free PT coating after 80 days of immersion. The corrosion resistance of the coatings was considerably improved due to enhanced interfacial interactions between silane functionalized MnO2 nanoparticles and PT by chemical bonding. The coating with MnO2 nanoparticles modified by amino (APTMS), epoxide (GPTMS), and ethyl (ETMS) groups showed no significant penetration by corrosive ions during 80 days’ immersion due to the strong chemical bonding between amino/epoxide/ethyl groups on MnO2 and a sulfur heterocycles of PT without changing the original crosslinking structure of PT. Interfacial interaction between phases also plays a key role in the affinity between MnO2 and PT, which determines the dispersion of MnO2 in coatings and uniform morphology of composite coatings.

Enhanced energy density and electric cycling reliability via MnO2 modification in sodium niobate‐based relaxor dielectric capacitors

Sodium niobate (NaNbO3)‐based dielectrics have received much attention for energy storage applications due to their low‐cost, lightweight, and nontoxic nature. The field‐induced metastable ferroelectric phase in NaNbO3‐based dielectrics, however, leads to a large hysteresis of the polarization–electric field (P–E) loops and hence deteriorate the energy storage performance. In this study, the hysteresis was successfully reduced by introducing Bi3+ and Ti4+ into A‐site and B‐site of NaNbO3, respectively. MnO2 addition was added to further increase the ceramic density and enhance the cycling reliability. As a result, a high recoverable energy density of 4.3 J/cm3 and a high energy efficiency of 90% were simultaneously achieved in the ceramic capacitor at an applied electric field of 360 kV/cm. Of particular importance is that the ceramic capacitor exhibits a stable energy storage properties over a wide temperature range of −70 to 170 °C, with much improved electric cycling reliability up to 105 cycles.

Effect of MnO2 Dopant on Properties of Na+-β/β"-Al2O3 Solid Electrolyte Prepared by a Synthesizing-cum-sintering Process

In order to simplify the complexity of the conventional solid-state reaction process, Na+-β/β″-Al2O3 as a fast Na+-ionic conductive solid electrolyte was fabricated using a synthesizing-cum-sintering process combined with the double-zeta method, which is able to distribute a small amount of Li2O more homogeneously in the Na2O-Al2O3-Li2O system. Additionally, in order to enhance the ionic conductivity, MnO2 was used as a dopant to increase the Na+-ion concentration on the conduction plane in the Na+-β/β″-Al2O3 crystal structure. The relative sintered density increased with the synthesis temperature, ultimately reaching 99.7 % after synthesis at 1400 °C. The phase formation showed an overall β″-phase fraction over 90 %. The addition of MnO2 had a positive effect on the phase formation, but a negative influence on the relative density resulting from the grain growth promotion effect. The highest ionic conductivity was observed at 1.74 × 10-1 S/cm (350 °C) for the sample sintered at 1600 °C with 0.5 wt.% MnO2.

Composition and strain engineered AgNbO3-based multilayer capacitors for ultra-high energy storage capacity

With strain engineer and MnO2 addition, an ultra-high energy-storage density Wrec = 7.9 J cm−3 and efficiency η = 71% were achieved in Ag(Nb0.85Ta0.15)O3 + 0.25 wt% MnO2 multilayer capacitors.

Enhanced thermal conductivity and photo-to-thermal performance of diatomite-based composite phase change materials for thermal energy storage

With abundant reserves and natural high porosity, diatomite has been a candidate material in the matrix of composite phase change materials (PCMs). Diatomite-based composite phase change materials (PCMs) were fabricated by blending lauric acid-stearic acid (LA-SA) and diatomite matrix via the vacuum impregnation method. To improve the thermal conductivity and photo-to-thermal performance, the purified diatomite (Dp) was designed by a hydrothermal reaction to synthesize MnO2-decorated diatomite (Dp-M). Scanning electron microscopy and X-ray photoelectron spectroscopy analysis verified the existence of MnO2 in the diatomite surface. The LA-SA/Dp-M2 with 42.2% loadage of LA-SA melts at 26.81 °C and releases 66.74 J g−1 of heat, and the thermal conductivity was increased by 89.5% due to the addition of MnO2. Particularly, LA-SA/Dp-M2 has the best photo-to-thermal conversion ability compared with pure LA-SA and LA-SA/Dp, making it the potential to use solar energy efficiently. Meanwhile, LA-SA/Dp-M2 with higher thermal conductivity has an excellent performance in the heat storage/release process and transient temperature response. Therefore, the prepared composite possesses a potential application for thermal energy storage in the building envelope.

Effects of MnO2 addition on the structure and electrical properties of PIN-PZN-PT ceramics with MPB composition

A two-step fabrication route was used to synthesize piezoelectric ceramics 0.35Pb(In1/2Nb1/2)O3-0.40Pb(Zn1/3Nb2/3)O3-0.25PbTiO3-xwt% MnO2 (PIN-PZN-PT-xMn, x = 0.0–2.0), and the corresponding structural changes and variations in electrical parameters caused by Mn modification were also investigated. The addition of MnO2 was quite effective to reduce the sintering temperature of PIN-PZN-PT ceramics. A pure perovskite structure was obtained in all sintered samples by XRD tests. The Curie temperature TC, piezoelectric constant d33, dielectric loss tanδ and planar electromechanical coupling coefficient kp gradually decreased as the MnO2 addition content increases, while the mechanical quality factor Qm increased. The diffusive phase transition behavior became strong with increasing the MnO2 doping content. A relatively high Qm value on the order of 420 has been obtained at the 2 wt% MnO2-added ceramic, which is six times higher than that of the undoped PIN-PZN-PT sample. These results indicate that Mn-doped PIN-PZN-PT ceramics show a broad prospect in the applications of electromechanical device requiring high power and high temperature.

Leaching of Pure Chalcocite with Reject Brine and MnO2 from Manganese Nodules

Chalcocite (Cu2S) has the fastest kinetics of dissolution of Cu in chlorinated media of all copper sulfide minerals. Chalcocite has been identified as having economic interest due to its abundance, although the water necessary for its dissolution is scarce in many regions. In this work, the replacement of fresh water by sea water or by reject brine with high chloride content from desalination plants is analyzed. Additionally, the effect of adding MnO2 from available manganese nodules in vast quantities at the bottom of the sea is studied. Reject brine shows better results than sea water, and the addition of MnO2 to the brine significantly increases the kinetics of chalcocite dissolution in a short time. H2SO4 concentration is found to be irrelevant when working at high concentrations of chloride and MnO2. The best results, 71% Cu extractions in 48 h, are obtained for reject brine, 100 mg of MnO2 per 200 g of mineral and H2SO4 0.5 mol/L. The results are expected to contribute to a sustainable process of dissolution of chalcocite by using the reject brine from desalination plants.

Improved ferroelectric, piezoelectric, and magnetic properties in BiFeO3–(Ba0.85Ca0.15)TiO3 ceramics through Mn addition

Integrating multiple functions in a single compound is still attractive and necessary to meet the demand of device miniaturization. In this work, we systemically modulate multifunctional properties in the 0.74BiFeO3–0.26(Ba0.85Ca0.15)TiO3–x wt. % MnO2 solid solution with the addition of MnO2. A highly rectangular and saturated polarization–hysteresis (P–E) loop is obtained with a large remanent polarization Pr of 49.5 μC/cm2 as x=0.8. Furthermore, the piezoelectric coefficient d33 also obviously improved with an optimized d33=137 pC/N by the introduction of MnO2 due to the grain size effect, the improvement of insulation, and relaxation regulation. With the addition of MnO2, the remanent magnetization Mr increases monotonically because of the enhanced exchange interactions between Fe2+and Fe3+. The results may provide an effective way to explore promising multifunctional materials in BiFeO3-based ceramics.

Pure hydrogen production by steam‐iron process: The synergic effect of MnO 2 and Fe 2 O 3

In the energy transition from fossil to clean fuels, hydrogen plays a key role. Proton-exchange membrane fuel cells (PEMFCs) represent the most promising hydrogen application, but they require a pure hydrogen stream (CO < 10 ppm). The steam iron process represents a technology for the production of pure H2, exploiting iron redox cycles. If renewable reducing agents are used, the process can be considered completely green. In this context, bio-ethanol can be an interesting solution that is still not thoroughly explored. In this work, the use of ethanol as a reducing agent in the steam iron process will be investigated. Ethanol, at high temperature, decomposes mainly in syngas but can also form coke, which can compromise the process effectiveness, reacting with water and producing CO together with H2. In this work, the deposition of coke is avoided by controlling the duration of the reduction step; in fact, the data demonstrated that coke deposition is significantly dependent on reduction time. Tests were carried out in a fixed bed reactor using hematite (Fe2O3) as raw iron oxide adopting several reduction times (7 minutes-25 minutes), which correspond to different amount of ethanol fed (5 mmolC2H5OH/gFe2O3-17,95 mmolC2H5OH/gFe2O3). The effect of the addition of MnO2 to increase the reduction degree of iron oxides was explored using different amount of MnO2 (10 wt% and 40 wt% with respect to Fe2O3). The tests were performed at fixed temperatures of 675°C and atmospheric pressure. The optimization of the reduction time, in the chosen operating condition, performed only with Fe2O3, shows that, feeding an amount of 5 mmolC2H5OH/gFe2O3, coke deposition is avoided and, therefore, a pure H2 stream in oxidation is obtained. The addition of MnO2 leads to increased H2 yield and process efficiency, confirming its positive effect on the reduction degree of the solid bed. A reaction pathway to demonstrate the synergic effect of Fe2O3 and MnO2 in the reduction step was proposed in this article.

Effect of multi-oxidants on mechanical response and reactive characteristics of PTFE/Al reactive material under dynamic impact

PTFE/Al/Fe2O3, PTFE/Al/MnO2 and PTFE/Al/MoO3 reactive materials specimens were fabricated by referring to the traditional thermite and adding PTFE as matrix. Split Hopkinson pressure bar system tests were carried out to investigate the effect of multi-oxidants on mechanical response and reactive characteristics of PTFE/Al reactive material under dynamic impact. The results show that three oxidants have significant influence on the mechanical behavior and reactive characteristics of the reactive materials. PTFE/Al/Fe2O3 had the highest strength while PTFE/Al/MoO3 exhibited the lowest strength. The reaction time and reaction thresholds of PTFE/Al/Fe2O3, PTFE/Al/MnO2 and PTFE/Al/MoO3 were measured to be 2.5 ms, 2.9 ms, 1.9 ms and 6250 s−1, 5600 s−1, 6500 s−1, respectively. The addition of MnO2 could dramatically improve the explosion intensity, prolong the reaction time and reduce reaction threshold of PTFE/Al reactive material. All the results indicate that MnO2 has great potential for serving as an additive into PTFE/Al system to improve the energy release rate.

Enhancing of low-temperature OHC-SCR activity of Ag/TiO2 with addition of MnO2 nanoparticles, and performance evaluation using diesel engine exhaust gases

The purpose of this study is to investigate the NO x removal activity of Ag/TiO 2 catalyst with addition of MnO 2 to improve the low temperature activity in the SCR system. The catalysts were prepared using washcoating method and were characterized with SEM, BET, XRD and FT-IR analyzes. According to results of SEM analysis, the catalysts exhibited a regular structure and fine particles dispersed over the surface and pores. BET analysis showed that the surface area and pore volume of catalysts decreased significantly with increasing of Mn amount. A strong interaction between catalytic materials and TiO 2 was determined by XRD analysis. FT-IR results indicated the presence of loading catalytic species on the catalyst surface. The effects of MnO 2 amount, reaction temperature, space velocity and engine load on catalytic performance were investigated by using ethanol as the reductant. The results indicated that Ag–Mn (3%)/TiO 2 catalyst was very effective in the temperature range of 170–290 °C. NO x conversion on the Ag–Mn (3%)/TiO 2 catalyst reached 92.9% at 290 °C and 30000 h −1 space velocity. The NO x removal performance of Ag/TiO 2 catalyst with high amount of MnO 2 decreased at low temperatures. In general, NO x conversion ratios of the catalysts reduced at 50000 h − 1 . • NO x removal performance of Ag based catalysts are insufficient at low temperatures. • Ag–Mn (3%)/TiO 2 catalyst shows highest NO x conversion ratios at low temperatures. • High MnO 2 loading reduces catalytic activity at low temperatures. • Increasing of GHSV decreases activity of catalysts.

Immobilizing chromium in stainless steel slags with MnO addition

AbstractThis work investigates the stabilizing impact of MnO on the leaching behavior of hazardous Cr‐containing CaO‐SiO2‐Al2O3‐Cr2O3‐MnO stainless steel slags after equilibrating at various elevated temperatures and evaluates the potential immobilization of Cr into a MnCr2O4 spinel phase from the existing Cr2O3 phase. The MnCr2O4 spinel phase was found to be an excellent Cr‐stabilizer in stainless steel slags, where the leaching tendency of potentially hazardous Cr‐related ions decreased with higher MnO content and lower equilibration temperatures within the range of 0 to 15 mass pct. and 1500 to 1300°C, respectively. Thermodynamic calculations by conducting the phase stability diagram also showed that the MnCr2O4 spinel phase was relatively stable and the Ca3Si2O7 (Ca3‐xMnxSi2O7) phase was relatively unstable compared with other crystal phases in acid extractant with pH value of 3.2. Combined with the scanning electron microscopy and X‐ray powder diffraction results along with the thermodynamic calculations, the leached Cr‐related ions was predominantly originating from the unstable amorphous glass phase.

Effects of stabilizers on sustainability, activity and decolorization performance of Manganese Peroxidase enzyme produced by Phanerochaete chrysosporium

Manganese Peroxidase (MnP), is one of the most promising lignin depolymerization enzymes, which has been widely used for degradation purposes. Nevertheless, MnP tends to lose activity rapidly during its maintenance phase and degradation process, especially in the inevitable presence of hydrogen peroxide. This study aimed to improve MnP efficiency produced by Phanerochaete chrysosporium, via enhancing its sustainability. In this context, the effects of MnO2, Fe3O4, PEG, Veratryl Alcohol (VA), and DMSO as stabilizing agents on MnP activity were explored both in vivo and in vitro. During in vivo experiments, heterogeneous Fe3O4 was found to be the desirable choice to enhance MnP production, obtaining a maximum MnP activity of 2149 U/L, which was a 67 % boost over the stock configuration. Also, in vitro studies demonstrated a noticeable increase in the stability of the extracted MnP from 8 days up to 14, 23, 23, 25, and 26 days by the addition of MnO2, VA, Fe3O4, PEG, and DMSO stabilizers, respectively. The efficiency of stabilizers on degradation ability of MnP was also examined; optimum conversion of model dyes viz., AO7 and CV, were improved 36.17 and 126.51 % in response to stabilizers, respectively. The inclusion of stabilizers managed to improve sustainability, performance, and cost-effectiveness of the biological water treatment process.

Effect of TiO2 and TiN on the Viscosity, Fluidity, and Crystallization of Fluorine‐Free Mold Fluxes for Casting Ti‐Bearing Steels

TiN inclusions are known to exacerbate slag rimming and nozzle clogging during continuous casting of Ti‐bearing steels. Herein, the effect of TiO2 and TiN on the viscosity and fluidity of a fluorine‐free (F‐free) mold flux, as well as the corresponding precipitated crystalline phase is studied. Higher TiO2 is found to lower the viscosity and increase the strip length of the molten slag at TiO2 contents less than 10 wt%, whereas the viscosity increases suddenly and the strip length decreases rapidly at TiO2 contents above 10 wt%, due to the precipitation of CaTiO3 crystals, resulting in a solid–liquid coexisting melt. TiN has a low solubility in F‐free mold fluxes without MnO additions, and TiN is distributed in the molten slag as solid particles. TiN addition significantly increases the viscosity and shortens the strip length of the molten slag. On the other hand, F‐free mold fluxes containing MnO dissolves TiN into the molten slag through the oxidization of TiN to TiO2. However, beyond the solubility limit of TiN in fluorine‐free mold fluxes containing 5 wt% MnO, excess TiN is not completely dissolved. Then, the precipitation of Ca2Ti2O6 crystals is promoted.

Influence of malonic acid and manganese dioxide on humic substance formation and inhibition of CO2 release during composting

The aim of thisstudy was to explore the effects of malonic acid (MA), manganese dioxide (MnO2), malonic acid combined with manganese dioxide (MA + MnO2) additionon reducing CO2 emission and promoting humic substance (HS) formation during composting. The result showed that the addition of MA and MnO2 were an efficient way to reduce CO2 emission. Meanwhile, the CO2 emissions in the MA + MnO2 treatment was 36.8% less than that of the CK, and the amount of humic acid (HA) produced in the MnO2 treatment was 38.7% higher than that of the CK. Structural equation models demonstrated that the addition of exogenoussubstance promoted the conversion of amino acids and reducing sugars to HA. The addition of exogenous substances was the main reason for influencing the concentration of HA. In general, this research provided theoretical supports for the addition of exogenous substances to promote HA formation during composting.

Comparison of MnO2 and ZnO Additives on Zircon Decomposition and Formation of Solid Solution

In this paper, the effects of MnO2 and ZnO additives on zircon decomposition were investigated. The substitution of Mn and Zn into zircon lattices and the formation of solid solutions are discussed. The additives were added at 0–4 wt.% to zircon. The phase composition, physical properties, and microstructural changes for the sintered samples were characterized. Results of Rietveld refinement analysis showed that 1 wt.% of both additives retarded the decomposition of zircon. Further addition of additives slightly accelerated the zircon decomposition and improved sample densification. X-ray diffraction peaks of zircon were shifted to higher angles by the addition of MnO2, whereas ZnO did not alter zircon peaks. Energy dispersive spectroscopy analysis detected the presence of Mn and Zn in zircon grains. ZnO has a lower solubility than MnO2 in zircon, leading to the formation of a higher fraction of secondary phases, in turn leading to the suppression of grain growth.

Preparation of New Nano-MnO2 and Its Molybdenum Adsorption in Manganese Sulfate Solution

Manganese sulfate solution was in this study oxidized, using H2O2 as oxidant, to obtain new Nano-MnO2 in situ. The characterization of new MnO2 was carried out by XRD, SEM, FT-IR and BET. The effect of new manganese dioxide adsorpting molybdenum ion in manganese sulfate solution was also studied. Results showed that the main crystal form of the new MnO2 was γ type, and there was agglomeration of nanospheres with 200∼300 nm diameter from the microscopic morphology, which had abundant surface hydroxyl groups, and its specific surface area was as high as 146 m2/g. MnO2 addition was 1.0 g under optimal adsorption conditions when the pH was 2, and the reaction time was 30 min, with removal rate of 99.2% molybdenum and 0.26 ppm residual amount of molybdenum in manganese sulfate solution, which met the quality standard for high purity manganese sulfate (HG/T4823-2015) with ≤5 ppm molybdenum content. Moreover, the thermodynamics and kinetics of molybdenum adsorption by new manganese dioxide were also studied. The experiments showed that the adsorption process was in accordance with the Freundlich adsorption equation. The adsorption process of molybdenum on manganese dioxide could be described with pseudo second order kinetic model, and the internal diffusion was a controlling link of adsorption rate.

Structural and Electric Properties of MnO2-Doped KNN-LT Lead-Free Piezoelectric Ceramics

Structural, ferroelectric, dielectric, and piezoelectric properties of K0.5Na0.5NbO3-LiTaO3-xmol%MnO2 lead-free piezoelectric ceramics with 0.0 ≤ x ≤ 0.3 were studied. The ceramic samples were synthesized through the conventional solid-state reaction method. The MnO2 addition can reduce the sintering temperature of KNLNT ceramics. Compared with undoped KNLNT ceramic, the piezoelectric measurements showed that piezoelectric properties of K0.5Na0.5NbO3-LiTaO3-xMnO2 were improved (d33 = 251 pC/N) when x = 0.1. In addition, KNLNT-xMnO2 ceramics have larger Pr(20.59~21.97 μC/cm2) and smaller Ec(10.77~6.95 kV/cm), which indicates MnO2 has excellent softening property, which improves the ferroelectric properties of KNLNT ceramics This work adds relevant information regarding of potassium sodium niobate K0.5Na0.5NbO3 (KNN) when doped Li, Ta, Mn at the B-site.

Perspectives in the Recycling of High Sulphatized Electrodes from Lead Acid Batteries

The structural modifications of the infrared (IR) bands induced by the CuO and MnO2 addition in the recycled Pb-PbO2 host matrix are due to the bending modes of Pb-O-Pb linkages, the decrease of intensity of sulfate ions and the random intercalation of the [CuO n ] and [MnO n ] structural units. Electron paramagnetic resonance (EPR) measurements show that the copper ions exist in two stable valence states as Cu+1 and Cu+2 ions. The cyclic voltammogram of the electrode containing 5 mol % CuO does not show hydrogen evolution reactions and produces a removal of passivation phenomena by an increase in the residual current across the potential range between 0 and 2 V.