Effect Of MnO Research Articles

The effect of MnO2 additive on the microstructure and mechanical properties of magnesium aluminate spinel

AbstractIn this study, varying amounts of MnO2 up to 5 wt.% were added to magnesium aluminate spinel (MA) bodies using a solid‐state sintering method at 1200–1600°C. The effect of MnO2 addition on the phase composition, microstructure, distribution of elements, and ionic valence of MA was investigated via X‐ray diffraction, scanning electron microscopy, energy‐dispersive spectroscopy, and X‐ray photoelectron spectroscopy, respectively. The results showed that Mg2+ ions in MA crystals were replaced by Mn2+ ions, resulting in the formation of the (Mg1‐xMnx)Al2O4 solid solution. The distorted crystal structures promoted the sintering reactions, and the mechanical characteristics of MA were greatly improved by the solid solution strengthening process. When the additive amount of MnO2 was 5 wt.% and the sintered temperature reached at 1600°C, excess manganese ions hardly dissolved into the lattice of MA. And these ions were only distributed at the grain boundaries of MgAl2O4, forming a “barrier” that hindered the migration and diffusion of particles, thereby suppressing the sintering process and weakening the mechanical strength of MA.

Effect of MnO2 on crystallization behavior and specific capacity of phosphate glass anode

AbstractIn recent years, glass anodes have been widely studied. However, self‐crystallization often occurs during glass preparation, which leads to a reduction in the cycle stability of the glass anode. In this work, SnO–P2O5–MnO2 glass anode materials were prepared using the melt‐quenching method. By increasing the concentration of MnO2, the specific capacity (after 800 cycles) of the glass anode was increased by 62%, from 234.9 to 381.3 mAh g−1. The result indicates that the introduction of MnO2 makes the glass structure more compact and suppresses the glass's ability of self‐crystallization, which is beneficial for the long‐cycle performance of lithium‐ion batteries. In addition, with the introduction of MnO2 in glass, manganese–tin synergistic discharge disperses the internal stress during the alloying process, which further enhances the cycling stability of the glass anode. This research is to propose a new reference for improving the cycle life and specific capacity of glass anode materials.

Effects of MnO on the smelting process of vanadium titanomagnetite pre-reduced pellets in an electric furnace

MnO is proven as an effective fluxing additive for high-temperature pyrometallurgy processes. The effects of MnO on the electric furnace smelting of vanadium titanomagnetite pre-reduced pellets were systematically studied in this study. The results indicated that MnO addition could reduce the titanium slag viscosity. The activities of titania and silica in the slag decreased with the increasing MnO content. The external views of slag-iron separation showed that the addition of MnO was beneficial for the separation of iron from the slag. The EPMA results indicated that the reduction degree of vanadium oxides was improved with the MnO additions of 1 wt% and 2 wt%, but mitigated with the further increase of MnO. Moreover, the reduction of titanium oxides was suppressed with the increasing MnO content. Finally, it was concluded that the suitable addition of MnO was 2 wt% under the present smelting conditions.

The effect of MnO<SUB align="right">2 concentration on the formation of MnO<SUB align="right">2/ZnO thin films with bifunctional thermal insulation and photocatalytic self-cleaning performance

This study focuses on fabricating manganese dioxide/zinc oxide (MnO2/ZnO) thin films using a two-stage chemical bath deposition (CBD) technique. The concentration effect of MnO2 thin film for the second stage deposition will be optimised and selected based on their thermal conductivity behaviour. It was found out that the wettability showed an increase in the contact angle (CA) after the addition of ZnO, with the highest CA of 14.5°C for 12% of ZnO. The same sample also demonstrated commendable thermal performance after reaching a constant temperature of 35.9°C in 65 minutes compared to the uncoated glass substrate. All thin films indicated low photocatalytic activity, where the best sample (12% of ZnO loading) yielded only 6% degradation efficiency of 10 mgL-1 malachite green (MG) as a model pollutant within 90 minutes. The porosity and agglomeration gradually increased following second stage deposition and ZnO introduction.

Thermodynamic activity of FeO in CaO–SiO2–MnO–FeO–MgO molten slags

ABSTRACT To understand the thermodynamic characteristics of the melting process for high manganese twinning-induced plasticity steel, the activity coefficient of FeO in molten slag of MnO–CaO–SiO2–FeO–MgO slag system with up to 52 mass% MnO was measured at 1450°C by the experiments of the iron equilibrium between liquid silver and molten slag under the mixed gas atmosphere of CO, CO2 and Ar. The effects of MnO, FeO and the basicity on the activity coefficient of FeO in molten slag were discussed. The relationships between the activity coefficients of FeO, the concentrations of FeO and MnO and the basicity ((mass% CaO + mass% MgO)/mass% SiO2) were investigated by the regression analysis method. The results show that the activity coefficient of FeO was proportional to the reciprocal of FeO concentration, and increased slightly with the increasing MnO, but slowly decreased by increasing the basicity under the research conditions.

Effect of MnO and CaO substitution for BaO on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO-MnO slag

The effect of MnO and CaO substitution for BaO on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO-MnO slag was investigated using the rotating cylinder method and the structure was analyzed by employing FT-IR and XPS. The results showed that the viscosity at various temperatures decreased gradually when MnO content increased from 0wt% to 3wt%, and increased with BaO content rising from 0wt% to 5wt%, which was consistent with the corrected optical basicity (Λcorr). The activation energy for viscous flow (Eη) showed the similar trend. FT-IR and XPS spectra analysis indicated that both [SiO4]-tetrahedral and [AlO4]-tetrahedral were influenced by MnO and BaO content. The [SiO4]-tetrahedral and [AlO4]-tetrahedral network structures were depolymerized due to an increase in the relative fraction of free oxygen (O2−) and decrease of bridging oxygen (O0) with the increasing MnO content. As a larger amount of CaO was substituted by BaO, the trough depth of [SiO4]-tetrahedral and [AlO4]-tetrahedral bands became deeper, indicating the complexity of network structure and polymerization degree of slag increased, which led to an increase in viscosity.

Effect of MnO and Substituting CaO with BaO on the Desulfurization Ability of Blast Furnace Slag

Effect of MnO and Substituting CaO with BaO on the Desulfurization Ability of Blast Furnace Slag

Pt/MnO<sub>2</sub> catalyst for high-efficiency catalytic wet oxidation of formaldehyde wastewater at low temperature

<p indent="0mm">Formaldehyde wastewater, which is mainly from plastics, paper, resin and other industries, not only causes serious environmental problems, but also gives harmful effects to human health. With the increasing environmental concerns, the abatement of formaldehyde wastewater has become an urgent problem. Compared with the conventional technologies, such as the biological treatment, catalytic wet air oxidation (CWAO) has been shown to be an effective and environmentally-friendly way to remove the formaldehyde in water. CWAO technology uses air or oxygen as the oxidant, where the organic can be directly oxidized into CO₂ and H₂O or partially converted to the less toxic compounds by suitable catalysts at elevated temperature and pressure. The key issue of CWAO is to develop a promising catalyst that can work efficiently at low temperature. MnO₂ is widely applied in the complete oxidation reactions due to its variable valence and abundant crystal structures, but is rarely used in the treatment of formaldehyde wastewater. In this article, Pt/R-MnO₂ (Pt supported on rod-like-MnO₂) with very low precious metal content (Pt, 0.1wt%) was prepared by impregnation method. For comparison, Pt/TiO₂ and Pt/CeO₂ catalysts were also prepared. The three catalysts with different supports were investigated in the CWAO of formaldehyde wastewater. Pt/TiO₂ showed the lowest activity and the TOC conversion is less than 35% even at the temperature of 100°C. Pt/CeO₂ exhibited better catalyst performance. As the reaction temperature increased from 30 to 100°C, the TOC conversion rose from 19.1% to 83.0%. Pt/R-MnO₂ displayed the most excellent catalytic performance compared with Pt/TiO₂ and Pt/CeO₂. At the reaction temperatures of 50 and 80°C, the TOC conversions of Pt/R-MnO₂ are 82.2% and 89.0%, respectively. MnO₂ possesses abundant morphologies, which may affect its catalytic performance. The effect of MnO₂ morphologies on the catalytic performance of Pt/MnO₂ in formaldehyde wastewater was investigated and the cocoon-like- and sheet-like-MnO₂ were also prepared. It was found that Pt/C-MnO₂ catalyst (Pt supported on cocoon-like-MnO₂) exhibited the best catalytic performance among the prepared Pt/MnO₂ catalysts. At the temperature of 50°C, Pt/C-MnO₂ can achieve TOC conversion of 88.1%. TOC conversion can be retained at a level higher than 80% even after four consecutive runs. Pt/S-MnO₂ (Pt supported on sheet-like-MnO₂) and Pt/R-MnO₂ (Pt supported on rod-like-MnO₂) showed lower activity and quicker deactivation with the reaction proceeding. After four consecutive runs, TOC conversion is decreased from 82.4% and 82.2% to 35.6% and 16.3% for Pt/S-MnO₂ and Pt/R-MnO₂, respectively. The Pt/C-MnO₂ showed the most excellent activity and stability for CWAO of aqueous formaldehyde at low temperature. Various characterizations were used to analyze the catalysts of Pt/C-MnO₂, Pt/R-MnO₂ and Pt/S-MnO₂. The measurement of dispersion indicated that Pt/C-MnO₂ catalyst has better dispersion, which is up to 36.0%, higher than 21.2% for Pt/S-MnO₂ and 17.3% for Pt/R-MnO₂. The results of XPS and O₂-TPD showed that Pt/C-MnO₂ contains more reactive oxygen species. H₂-TPR revealed that Pt/C-MnO₂ can be reduced at lower temperature and thus possesses better oxidizing ability. ICP analysis implied that Pt/C-MnO₂ has a better ability to inhibit the leaching of Pt. The Pt content of Pt/S-MnO₂ and Pt/R-MnO₂ is severely lost after four reactions, which caused a sharp decrease in the activity of the two catalysts. Better dispersion, more reactive oxygen species, higher oxidizing ability and better anti-leaching capability contribute to the excellent performance of Pt/C-MnO₂ in CWAO of aqueous formaldehyde reaction.

Effect of MnO on the crystallization, microstructure, and properties of MgO-Al2O3-SiO2 glass-ceramics

The Mn-doped MgO-Al2O3-SiO2 (MAS) glass-ceramics were prepared by the melt quenching technique. The effect of MnO on the crystallization, microstructure, and properties of MAS was discussed. XRD results showed that MnO promotes the phase transformation from indialite to Mg0.6Al1.2Si1.8O6 and enstatite. Crystallization kinetics suggested that MnO inhibits the precipitation of indialite. Both the crystallization index and SEM photographs proved that the bulk crystallization plays an important role in the Mn-doped MAS system. EDS analyses indicated that the large grain corresponds to Mg0.6Al1.2Si1.8O6 and the small grain corresponds to the magnesium-rich phase. Due to the addition of 0.5 wt% MnO, the flexural strength was enhanced from 146 to 247 MPa, and the coefficient of thermal expansion was increased from 3.52 × 10−6/°C to 5.41 × 10−6/°C. • Mn-modified MAS glass-ceramic with high flexural strength and low thermal expansion was developed. • Small addition of MnO markedly improved the flexural strength and Young’s modulus. • The relation between CTE values and crystal phases was revealed. • Crystallization kinetics suggested that MnO inhibited the precipitation of indialite.

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.

Effect of MnO on the microstructure and electrical properties of SnO2–Zn2SnO4 ceramic composites

This work presents the microstructure and electrical properties of MnO-doped SnO2–Zn2SnO4 ceramic composites prepared through conventional ceramic processing. Scanning electron microscopy images reveal that all samples have a compact structure. With increasing MnO content, the grains grow larger and the grain boundaries become unsharp. Energy dispersive spectroscopy results for the sample doped with 0.1 mol% MnO indicate that Mn distributes randomly on the grain surfaces. X-ray diffraction patterns exhibit that all the samples are composed of SnO2 and Zn2SnO4, and the relative intensity of the diffraction peak for Zn2SnO4 increases with increasing MnO content. The relations between the electric field and current density show that all the samples have varistor properties. For the samples doped with 0.2 and 0.3 mol% MnO, the breakdown electric field is so large that it exceeds the measuring range of the instrument, whereas the relative permittivity is as low as about 30 at 100 Hz. In the electric modulus spectra, two sets of relaxation peaks were observed and the corresponding activation energies are enhanced greatly by doping MnO. The effect of MnO on the microstructure and electrical properties indicates that the space charges trapped by oxygen vacancies are the origin of the great permittivity and varistor properties for SnO2–Zn2SnO4 ceramic composites.

Effect of MnO on the fusing temperature and the viscosity of high titanium slag

The fusing temperature and the viscosity are important physical properties of high titanium slag. The Einstein-Roscoe equation was used to study the thermodynamic simulation of high titanium slag via FactSage software. The effects that the MnO had on the fusing temperature and the viscosity of high titanium slag were studied, and the reliability of the thermodynamic simulation method is verified by experiments. The results showed that the fusing temperature and the viscosity of high titanium slag decreased when the MnO content increased. The fusing temperature of high titanium slag was 1626.17∼1691.24 °C. After the high titanium slag was completely melted, the viscosity of high titanium slag was 86∼127 mPa · s. When the temperature was lower than the fusing temperature, the high titanium slag precipitated into solid-phase particles. The amount of precipitation increased when the temperature decreased, which in turn increased the viscosity of the high titanium slag.

Measurements and Model Estimations of Viscosities of the MnO-CaO-SiO2-MgO-Al2O3 Melts

The viscosities of the MnO (0 to 55 mass pct)-CaO-SiO2-MgO (5 mass pct)-Al2O3 (20 mass pct) melts were measured by rotating cylinder method in the temperature range from 1573 K to 1873 K (1300 °C to 1600 °C). The measurements were carried out in the atmosphere of flowing CO/CO2 gas mixture with a volume ratio of 99/1, and molybdenum crucible and spindle were adopted. The results reveal that MnO is a viscosity reducing component, and the effect of MnO is more notable in the melts with higher ratio of CaO to SiO2. For example, in the melts with the mass ratio of CaO to SiO2 equal to 0.6, the addition of 5 mass pct MnO only slightly reduced the viscosities. Comparatively, the addition of 5 mass pct MnO made the viscosities of the melts with the mass ratio of CaO to SiO2 equal to 1.0 and 1.5 decrease remarkably. Based on the measured data, the viscosities estimation model proposed in our previous study was extended to the system containing MnO, and the model parameters were determined. The model can estimate and predict the viscosities of the aluminosilicate melts containing MnO well, and then some iso-viscosity contours of this system were calculated. From the iso-viscosity contours, it can be seen that MnO is almost equivalent to CaO in reducing the viscosities in the melt with high SiO2 content, while with the decrease of the SiO2 content MnO becomes more effective than CaO.

Effect of MnO2 Phase Structure on the Oxidative Reactivity toward Bisphenol A Degradation.

Manganese dioxides (MnO2) are among important environmental oxidants in contaminant removal; however, most existing work has only focused on naturally abundant MnO2. We herein report the effects of different phase structures of synthetic MnO2 on their oxidative activity with regard to contaminant degradation. Bisphenol A (BPA), a frequently detected contaminant in the environment, was used as a probe compound. A total of eight MnO2 with five different phase structures (α-, β-, γ-, δ-, and λ-MnO2) were successfully synthesized with different methods. The oxidative reactivity of MnO2, as quantified by pseudo-first-order rate constants of BPA oxidation, followed the order of δ-MnO2-1 > δ-MnO2-2 > α-MnO2-1 > α-MnO2-2 ≈ γ-MnO2 > λ-MnO2 > β-MnO2-2 > β-MnO2-1. Extensive characterization was then conducted for MnO2 crystal structure, morphology, surface area, reduction potential, conductivity, and surface Mn oxidation states and oxygen species. The results showed that the MnO2 oxidative reactivity correlated highly positively with surface Mn(III) content and negatively with surface Mn average oxidation state but correlated poorly with all other properties. This indicates that surface Mn(III) played an important role in MnO2 oxidative reactivity. For the same MnO2 phase structure synthesized by different methods, higher surface area, reduction potential, conductivity, or surface adsorbed oxygen led to higher reactivity, suggesting that these properties play a secondary role in the reactivity. These findings provide general guidance for designing active MnO2 for cost-effective water and wastewater treatment.

Effect of MnO2 on the Properties of Mullite-based Ceramics

Low-density mullite-based ceramic proppants were prepared from recycled coal fly ash, bauxite, and additives (feldspar, talcum, BaCO3, and MnO2). The effects of MnO2 content and sintering temperature on properties and morphologies of resultant proppants were investigated. Results showed that the performance of proppants have approved significantly at sinter temperature around 1380 °C when the content of MnO2 equals to 4 wt %, such as low apparent density(2.70 g cm−3) and low breakage ratio (3.10% under 52 MPa pressure). The low-density mullite-based ceramic proppant therefore is assumed to be a promising proppant material for the hydraulic fracturing production of petroleum.

Effect of MnO on High-Alumina Slag Viscosity and Corrosion Behavior of Refractory in Slags

Effect of MnO on High-Alumina Slag Viscosity and Corrosion Behavior of Refractory in Slags

Effect of MnO on Mineral Composition of CaO-SiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-MgO-Al&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;-Cr&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; System

The chromium leaching from stainless steel slag highly depends on the occurrence of chromium. The effect of MnO on the mineral composition of stainless steel slag was investigated through CaO-SiO2-MgO-Al2O3-Cr2O3 synthetic slags. The experiments were performed in a conductive furnace, and the samples collected during tests were analyzed using X-ray Diffrac-tion (XRD) and Scanning Electron Microscope (SEM) equipped Energy Dispersive Spectroscopy (EDS). The results show that the addition of MnO significantly reduces the solidus temperature of oxide systems from 1204oC to 950oC, promotes the spinel precipitation and increases the size of spinel crystals. The fraction of chromium contained in non-spinel mineral phases decreases and the amount of larnite dissolved into spinel phase slightly reduces with the content of MnO increasing. In addition, the amorphous phase forms when the content of MnO is up to 6 wt%. Hence, the addition of MnO is beneficial to suppress chromium leaching from slag.

Effect of MnO&lt;SUB&gt;2&lt;/SUB&gt; Doping on Optical and FTIR Spectra of Lead Phosphate Glasses

Effect of MnO&lt;SUB&gt;2&lt;/SUB&gt; Doping on Optical and FTIR Spectra of Lead Phosphate Glasses

Ba0.85Ca0.15Ti0.90Zr0.10O3 Lead-free Ceramics with a Sintering Aid of MnO

Effects of MnO on the microstructure and electrical properties of Ba0.85Ca0.15Ti0.90 Zr0.10O3 (BCTZ) ceramics were investigated. Its sintering temperature decreases, a phase boundary shifts to a higher temperature, and a denser microstructure is induced by introducing MnO. Double P-E loops were observed in BCTZ with x ≥ 0.30 wt% MnO due to the involvement of more defects. Piezoelectric properties are degraded by doping MnO, but the temperature stability of piezoelectric properties is improved with a low dielectric loss of ∼ 0.63%. As a result, BCTZ ceramics with x = 0.15 wt% MnO have optimum electrical properties: d 33 ∼ 382 pC/N, k p ∼ 44.5%, ϵ r ∼ 2611, and tan δ ∼ 0.63%.

Effects of MnO2 doping on structure, dielectric and piezoelectric properties of 0.825NaNbO3–0.175Ba0.6(Bi0.5K0.5)0.4TiO3 lead‐free ceramics

AbstractLead‐free ceramics 0.825NaNbO3–0.175Ba0.6(Bi0.5K0.5)0.4TiO3 + xmol% MnO2 were prepared by an ordinary sintering technique and the effects of MnO2 doping on the structure, dielectric, and piezoelectric properties of the ceramics were studied. The ceramics with perovskite structure are transformed from tetragonal to pseudocubic phases by increasing the doping level of MnO2. After the addition of MnO2, the Curie temperature TC of the ceramics decreases and the ferroelectric–paraelectric phase transition at TC becomes more diffusive. Because of the donor and acceptor doping effects of Mn ions simultaneously, the piezoelectric constant d33, electromechanical coupling coefficient kp, relative permittivity εr, and mechanical quality factor Qm are enhanced considerably after the addition of 1 mol% MnO2. The ceramic with 1 mol% MnO2 doping possesses the optimum piezoelectricity (d33 = 131 pC/N and kp = 21.8%) and relatively high Qm = 627.