Structural and magnetic properties of hydrothermally synthesized β-MnO2 and α-K MnO2 nanorods

Barudžija, Tanja; Kusigerski, Vladan; Cvjetićanin, Nikola; Šorgić, Saša; Perović, M.; Mitrić, Miodrag

doi:10.1016/j.jallcom.2016.01.024

Cited by 26 publications

(20 citation statements)

References 40 publications

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“…α -MnO 2 nanosheets were also formed by co-precipitation of MnCl 2 ·4H 2 O and MnC 2 O 4 ·2H 2 O in aqueous solution with addition of sodium hydroxide to control the pH of the solution [87]. Hydrothermal synthesis was applied to grow two types of MnO 2 nanorods: (i) rutile-type β -MnO 2 due to a redox reaction (135 °C for 12 h) between manganese(II) sulfate with ammonium persulfate and (ii) hollandite-type α -K x MnO 2 ( x = 0.15 and 0.18) due to the decomposition of potassium permanganate obtained in the presence of sulfuric acid added to water after stirring to form a solution (150 °C for 8 h) [88]. The EPR spectra of α -K x MnO 2 nanorods contain two signals.…”

Section: Synthesis Of Mno2 Nanomaterialsmentioning

confidence: 99%

“…Recently, the synthesis process to grow MnO 2 nanoneedles (NNs) forming nanourchin (NUs) architecture has been investigated by different groups [30,45,46,88]. As shown above, many factors like acidity of the solution, cationic species (nature and concentration), and additive metal ions (Co 2+ , Ni 2+ , Fe 3+ , Al 3+ , etc.)…”

Section: Mno2 Nanostructures: Example Of Nanourchinsmentioning

confidence: 99%

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Nanostructured MnO2 as Electrode Materials for Energy Storage

2017

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Manganese dioxides, inorganic materials which have been used in industry for more than a century, now find great renewal of interest for storage and conversion of energy applications. In this review article, we report the properties of MnO2 nanomaterials with different morphologies. Techniques used for the synthesis, structural, physical properties, and electrochemical performances of periodic and aperiodic frameworks are discussed. The effect of the morphology of nanosized MnO2 particles on their fundamental features is evidenced. Applications as electrodes in lithium batteries and supercapacitors are examined.

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Section: Synthesis Of Mno2 Nanomaterialsmentioning

confidence: 99%

Section: Mno2 Nanostructures: Example Of Nanourchinsmentioning

confidence: 99%

Nanostructured MnO2 as Electrode Materials for Energy Storage

2017

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“…48 Recently, a study for samples with x about 1.2 and 1.4 found that even for these concentrations, a spin glass was more likely at low temperature. 49 At room temperature, structural characterization of these samples points to a tetragonal structure (I4/m). Turning to other examples, the original report of Ag 1.8 Mn 8 O 16 synthesis and characterization reported a tetragonal structure.…”

Section: Discussionmentioning

confidence: 98%

“…42,43 For hollandite group manganese oxides, the magnetic measurements at low temperature have not been so clearcut, with the latest data interpreted to indicate a spinglass phase. [44][45][46][47][48][49] While naturally occurring cryptomelane exhibited a mild monoclinic distortion, 4 room temperature characterization of synthesized hollandite group oxides showed a tetragonal phase (I4/m) for K, Li and Ag cases. [49][50][51][52] In the Ba case, a monoclinic phase (I2/m) was found.…”

Section: Introductionmentioning

confidence: 99%

“…[44][45][46][47][48][49] While naturally occurring cryptomelane exhibited a mild monoclinic distortion, 4 room temperature characterization of synthesized hollandite group oxides showed a tetragonal phase (I4/m) for K, Li and Ag cases. [49][50][51][52] In the Ba case, a monoclinic phase (I2/m) was found. 47 However, no detailed studies at low temperature have been performed to our knowledge.…”

Section: Introductionmentioning

confidence: 99%

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Charge localization and ordering in A2Mn8O16 hollandite group oxides: Impact of density functional theory approaches

Kaltak

Fernández-Serra

Hybertsen

2017

Phys. Rev. Materials

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The phases of A2Mn8O16 hollandite group oxides emerge from the competition between ionic interactions, Jahn-Teller effects, charge ordering, and magnetic interactions. Their balanced treatment with feasible computational approaches can be challenging for commonly used approximations in Density Functional Theory. Three examples (A = Ag, Li and K) are studied with a sequence of different approximate exchange-correlation functionals. Starting from a generalized gradient approximation (GGA), an extension to include van der Waals interactions and a recently proposed meta-GGA are considered. Then local Coulomb interactions for the Mn 3d electrons are more explicitly considered with the DFT+U approach. Finally selected results from a hybrid functional approach provide a reference. Results for the binding energy of the A species in the parent oxide highlight the role of van der Waals interactions. Relatively accurate results for insertion energies can be achieved with a low U and a high U approach. In the low U case, the materials are described as band metals with a high symmetry, tetragonal crystal structure. In the high U case, the electrons donated by A result in formation of local Mn 3+ centers and corresponding Jahn-Teller distortions characterized by a local order parameter. The resulting degree of monoclinic distortion depends on charge ordering and magnetic interactions in the phase formed. The reference hybrid functional results show charge localization and ordering. Comparison to low temperature experiments of related compounds suggests that charge localization is the physically correct result for the hollandite group oxides studied here. Finally, while competing effects in the local magnetic coupling are subtle, the fully anisotropic implementation of DFT+U gives the best overall agreement with results from the hybrid functional.

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MnO₂‐Magnetic Core‐Shell Structured Polyaniline Dependent Enhanced EMI Shielding Effectiveness: A Study of VRH Conduction

et al. 2019

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The core-shell structured based Polyaniline/MnO 2 composites were synthesized by chemical oxidation method, wherein MnO 2 particles acts as a magnetic core while polyaniline chains wrapped over these particles acts as a shell. Four different loading concentrations of MnO 2 particles (10, 20, 30 and 40 wt %) were used to investigate the effect of MnO 2 concentration on the EMI shielding effectiveness. X-ray diffraction (XRD) studies performed on pristine MnO 2 and composite samples reveal the polycrystalline nature of the MnO 2 particles and semi-crystalline nature of the composites with a sharp peak around 25°over a broad hump. Vibrating sample magnetometry (VSM) studies performed on the pristine MnO 2 particles as well composite sample (S4) at higher loading (40 wt %) concentration of MnO 2 suggest the ferromagnetic nature at room temperature. The charge transport properties of the prepared samples have been investigated under variable range hopping (VRH) conduction. Mott's three dimensional VRH model has been found to be applicable for conduction in the present samples. The dc conductivity of the prepared samples is found to increase with MnO 2 loading concentrations, which suggest their possible validity for EMI shielding applications. Therefore, the prepared samples are analyzed for EMI shielding properties in the frequency range of 8.2 to 12.4 GHz (X-band). The sample prepared with 30 wt% of MnO 2 has as much as 50 dB shielding effectiveness, which is quite higher than that required for industrial application (∼ 30dB).[a] R. Pal, Prof.

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Structural and magnetic properties of hydrothermally synthesized β-MnO2 and α-K MnO2 nanorods

Cited by 26 publications

References 40 publications

Nanostructured MnO2 as Electrode Materials for Energy Storage

Nanostructured MnO2 as Electrode Materials for Energy Storage

Charge localization and ordering in A2Mn8O16 hollandite group oxides: Impact of density functional theory approaches

MnO₂‐Magnetic Core‐Shell Structured Polyaniline Dependent Enhanced EMI Shielding Effectiveness: A Study of VRH Conduction

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Structural and magnetic properties of hydrothermally synthesized β-MnO2 and α-K MnO2 nanorods

Cited by 26 publications

References 40 publications

Nanostructured MnO2 as Electrode Materials for Energy Storage

Nanostructured MnO2 as Electrode Materials for Energy Storage

Charge localization and ordering in A2Mn8O16 hollandite group oxides: Impact of density functional theory approaches

MnO2‐Magnetic Core‐Shell Structured Polyaniline Dependent Enhanced EMI Shielding Effectiveness: A Study of VRH Conduction

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Product

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MnO₂‐Magnetic Core‐Shell Structured Polyaniline Dependent Enhanced EMI Shielding Effectiveness: A Study of VRH Conduction