Mixture Of Mn3O4 Research Articles

Revealing oxygen transfer between Mn3O4 and CuMn2O4 and its effect on enhanced catalytic oxidization of VOCs

Hybrid catalysts are widely utilized in various environmental catalysis, such as catalytic oxidization and reduction. However, most works usually treat a hybrid catalyst as a whole, and seldom report explores interface behavior of active species between components in the hybrid. In this work, we investigated mechanism for enhanced catalytic oxidization of toluene by a mixture of Mn3O4 and CuMn2O4. The mixture removed 99% of toluene at 240 °C, far bigger than CuMn2O4 (53%) and Mn3O4 (23%). In brief, Mn3O4 had plenty of bulk lattice oxygens, which were inactive for toluene catalytic oxidization. After forming an interface between Mn3O4 and CuMn2O4, oxygen vacancy formed on the interface during the catalysis, and transferred the bulk lattice oxygen to the interface, forming active lattice oxygen. Therefore, the number of active sites was increased, resulting in an enhanced catalytic performance. This conclusion was verified in other hybrids, including Mn3O4/CuFeOx, Mn3O4/CuCeOx, and Mn3O4/CuCoOx. The main result of this work helps to understand the catalytic mechanism of volatile organic compounds by hybrid oxides. These results are also in favor of designing and optimizing catalysts.

High-Density Drilling Fluids for Managed Pressure Drilling: Lab Development and Field Trial

Abstract Managed pressure drilling (MPD) offers a closed-loop circulation system in which formation fracture pressure, bottom hole pressure, and pore pressure are considered and managed at surface. The right choice of drilling fluid used during MPD operation facilitates proper mud management and treatment. Lab formulation and field trial of a high-density water-based drilling fluid comprising a mixture of barite (BaSO4) and manganese tetroxide (Mn3O4) as weighting agents have been described in this paper. Drilling fluids having a mixture of Mn3O4 and BaSO4 as weighting agents would have lower equivalent circulating density (ECD), better sag, better acid solubility, and lower fluid cost as compared to conventional BaSO4-based fluids. This paper describes the formulation of three different water-based drilling fluids viz. 100, 120, and 150 pcf drilling fluids having a mixture of Mn3O4 and BaSO4 and hot rolled at temperatures of 270, 250, and 300 °F, respectively. Rheological properties, sag resistance, and high pressure-high temperature (HPHT) filtration properties of the three fluids have been described in the paper. Data obtained from the field trial of 160 pcf high-density drilling fluids having a mixture of Mn3O4 and BaSO4 for wells with a 300 °F bottom hole static temperature have been described. HPHT operations across naturally fractured formations with 0.5–1.0 pcf drilling fluid window have been described in the paper. During the field trial, the fluid having a mixture of Mn3O4 and BaSO4 showed good rheological, filtration, and sag properties thereby resulting in successful drilling of the well with no issues. MPD operation became more successful and practical with high-density drilling fluids having a mixture of Mn3O4 and BaSO4 as it facilitated better drilling fluid management and treatment in comparison to conventional fluids.

The foaming mechanism of glass foams prepared from the mixture of Mn3O4, carbon and CRT panel glass

Cathode ray tube (CRT) panel glass is processed into glass foams by using carbon and Mn3O4 as foaming agents. We investigate the foaming ability and foaming mechanism of the mixture by varying the composition and the temperature. Carbon load of 5 wt% inhibits the sintering of the glass powder, while 2 wt% carbon promotes the coalescence of pores during foaming. Carbon load of ≤0.4 wt% is suitable for achieving low density foams (0.15–0.23 g cm-3) with closed pores (75–100%). Foaming is initiated by the reaction between carbon and Mn3O4 and this is the main source of melt expansion. Reduction of cations in the glass melt, including Mn3+ dissolved from Mn3O4, makes an important contribution to the melt foaming at >800 °C. The main gaseous product is CO2 (67–95 vol%). CO appears above 800 °C and the concentration increases with temperature.

One-step electrosynthesis of MnO2/rGO nanocomposite and its enhanced electrochemical performance

We present a facile one-step electrochemical approach to generate MnO2/rGO nanocomposite from a mixture of Mn3O4 and graphene oxide (GO). The electrochemical conversion of Mn3O4 into MnO2 through potential cycling is expedited in the presence of GO while the GO is reduced into reduced graphene oxide (rGO). The MnO2 nanoparticles are evenly distributed on the rGO nanosheets and act as the spacer to prevent rGO nanosheets from restacking. This unique structure provides high electroactive surface area (1173 m2 g−1) that improves ions diffusion within the MnO2/rGO structure. As a result, the MnO2/rGO nanocomposite exhibits high specific capacitance of 473 F g−1 at 0.25 A g−1, which is remarkably higher (3 times) than the Mn3O4/GO prior conversion. In addition, the electrosynthesized nanocomposite shows higher conductivity and excellent potential cycling stability of 95% at 2000 cycles.

CuMn1.8O4 protective coatings on metallic interconnects for prevention of Cr-poisoning in solid oxide fuel cells

Cr-poisoning of the cathodes due to the presence of metallic interconnects is detrimental to the performance of intermediate temperature solid oxide fuel cell stacks. Applying a protective coating on the interconnect is an effective solution to preventing Cr-poisoning. In this study, the application of a protective CuMn1.8O4 spinel coating is explored. Dense coatings are deposited on both metallic flat plates and meshes by electrophoretic deposition followed by thermal densification steps. The coating is found to be a mixture of Mn3O4 and cubic spinel phases at room temperature but is a pure cubic spinel phase between 750 °C and 850 °C. A reaction layer between the Cr2O3 scale at the coating/interconnect interface and CuMn1.8O4 coating is found to be a mixture of (Cu,Mn,Cr)3-xO4 cubic spinel phases with Cr-rich precipitates believed to be Cr2O3, indicating that the coating layer acts as a Cr getter. Solubility experiments show that 1 mol of the CuMn1.8O4 phase can getter at least 1.83 mol of Cr2O3 at 800 °C. Electrochemical testing of cells in the presence of coated interconnects show that the CuMn1.8O4 coating getters Cr effectively for 12 days at 800 °C, leading to no performance loss of the cell due to Cr-poisoning.

SUPPORT EFFECT ON THE STRUCTURE AND PROPERTIES OF MANGANESE OXIDE ELECTRODE MATERIALS

The composite electrode material of manganese oxide supported on poly glucose (PGS) was prepared by using KMnO4 as manganese source. In order to study the influence of the support on the structure and properties of the composite electrode materials, the changes of the composition of the composite electrode materials were investigated in different weight ratio of KMnO4/PGS (3:1, 3:3, 3:5, 3:7, 3:9). The characterization results of XRD, Raman special and XPS indicated the composition of manganese oxides was greatly influenced by the content of PGS. When the PGS content is lower, the composition of manganese oxide in hybrid material is single-component oxide (MnOOH or Mn3O4). With the increasing PGS content, a mixture of Mn3O4 and MnCO3 was observed, furthermore proportion of MnCO3 in mixture also increased, and up to higher PGS content (KMnO4/PGS=3:9), single-component MnCO3 was founded on hybrid material. In addition, the change of composition of hybrid materials also led to an obvious difference in electrochemical performance. With the increase of PGS content, the specific capacitance of hybrid materials increases firstly, and reaches the maximum with the weight ratio of KMnO4/PGS equal to 3:3, and then gradually decreases. This was attributed to the higher electrochemical performance of Mn3O4 than that of MnOOH and MnCO3.

Facile decolorization of methylene blue with flower-like manganese wads

Flower-like manganese wads (MWs) were synthesized via a simple and inexpensive ultrasonic irradiation method for the first time. MWs were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and transmission electronic microscopy. The decolorization efficiency of MWs for methylene blue (MB) azo dye was examined as a function of pH, stirring time, MW dosage and initial concentration of the MB solution. Results show that MWs have excellent decolorization performance for MB with a higher efficiency (and without using H2O2 or other devises such as UV light and ultrasonic irradiation) compared to other catalysts, such as the mixture of Mn3O4 and H2O2 (with a maximum decolorization rate of 99.7% in 3 h), ZnS and CdS under light irradiation (with a maximum decolorization rate of 73% in 6 h), and sulfate modified titania under solar radiation (with a maximum decolorization rate of nearly 100% in 4 h).

MnOx/SWCNT macro-films as flexible binder-free anodes for high-performance Li-ion batteries

We present a low-temperature synthetic route toward the binder-free MnOx (the mixture of Mn3O4 and MnO2)/single-walled carbon nanotube (SWCNT) macro-films, which could be employed as the single component of anodes in Li-ion batteries. Morphological characterizations reveal that the interconnected network of SWCNT macro-films in the free-standing MnOx/SWCNTs intrinsically possesses high electrical conductivity and exhibits good mechanical adhesion on Cu foils (current collectors). The MnOx nanoparticles directly grown onto the external surface of SWNT macro-films have very strong bonds with the nanotubes, avoiding agglomeration during their electrochemical operations. These MnOx/SWNT macro-films are evidenced to possess an excellent capacity of ∼1000mAhg−1, showing promise as flexible anode materials for light weight and high performance Li-ion batteries.

Effect of Hydrothermal Time, pH, and Alkali on Crystal Phase and Morphology of Manganese Oxides

γ‐MnOOH nanowires and Mn3O4 nanoparticles were prepared in the hydrothermal process. The effect of hydrothermal time, pH, and alkali on morphology and composition of manganese oxides was investigated. The results of XRD, TEM, and SEM showed that the γ‐MnOOH prepared in shorter hydrothermal time was a mixture of nanocubes and nanowires, while in longer hydrothermal time was pure nanowires. Interestingly, increasing the pH of the reaction system from 8 to 10, the mixture of γ‐MnOOH nanowires and Mn3O4 nanoparticles was obtained. Alkali types also were discussed in directing the reaction and crystallization of manganese oxides. The product was pure γ‐MnOOH when using NaOH in the system, but a mixture of Mn3O4 and γ‐MnOOH was obtained when using NH3 · H2O.

Preparation of Spherical Spinel LiMn<sub>2</sub>O<sub>4</sub> Cathode Material for Lithium Ion Batteries

A novel process was proposed for preparing spinel LiMn2O4 with spherical particles from cheap materials of MnSO4, NaOH, NH3•H2O and LiOH. Its successful preparation started with a carefully controlled crystallization of Mn3O4, leading to the spherical shape of its particles and a high tap density. The mixture of Mn3O4 and LiOH was sintered to produce LiMn2O4 with spherical particle size retention. The spherical particles of spinel LiMn2O4 were of excellent fluidity and dispersivity, and had tap density as high as 2.14 g cm-3 and the initial discharge capacity reaching 128 mAh g-1. Its 15th cycle capacity kept to be 125 mAh g-1.

Effect of Hydrothermal on the Crystalline Phase and Morphology of Manganese Oxide Nanocrystals

The effect of hydrothermal on the crystalline phase and morphology of manganese oxide nanocrystals was studied. The Mn3O4 nanoparticles were transformed into γ‐MnOOH nanowires after hydrothermal treatment. The pH plays an important role in the transformation of crystalline phases. The whole nanowires of γ‐MnOOH were formed at pH 8 and pH 9 while the crystalline phase of Mn3O4 was still remained in the mixture of Mn3O4 and γ‐MnOOH at pH 10.