Differenzierung von Mangan(II)‐manganit und δ‐MnO<sub>2</sub> durch Oberflächenmessung nach Brunauer‐Emmet‐Teller

Buser, Walter; Graf, Patricia

doi:10.1002/hlca.19550380327

Cited by 33 publications

(18 citation statements)

References 6 publications

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“…[29,31] These two kinds of OMS materials do not support ion-exchange activity. [37] After an overnight ion exchange with 300 mL of 0.5 M sodium sulfate solution, pyrolusite and c-MnO 2 showed similar Cr/Mn ratios of about 0.10 from EDXS results (Table 2). Therefore, the only possibility for chromium to be present with such a high percentage in the total manganese seems to be the incorporation of Cr 3+ cations into the framework of pyrolusite and c-MnO 2 because the cations in the tunnels can be ion-exchanged with the cations in the solution and the Cr/Mn ratio should be decreased after ion exchange.…”

Section: Primary Study On the Incorporation Of Chromium Ions In The Omentioning

confidence: 80%

Hydrothermal Synthesis of Structure‐ and Shape‐Controlled Manganese Oxide Octahedral Molecular Sieve Nanomaterials

Yuan

Shen

et al. 2006

Adv Funct Materials

217

127

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Highly uniform single‐crystal Na‐OMS‐2 (OMS: octahedral molecular sieve), pyrolusite, and γ‐MnO2 nanostructures with an interesting 3D urchinlike morphology have been successfully prepared using a hydrothermal method based on a mild and direct reaction between sodium dichromate and manganese sulfate. The crystal phases, shapes, and tunnel sizes of the manganese dioxide nanostructures can be tailored. Reaction temperature, concentrations of the reactants, and acidity of the solution play important roles in controlling the synthesis of these manganese dioxides. Field‐emission scanning electron microscopy and transmission electron microscopy (TEM) studies show that the nanomaterials obtained are constructed of self‐assembled nanorods. X‐ray diffraction and TEM results indicate that the constituent manganese dioxide particles are single‐crystalline materials. Energy dispersive X‐ray analysis and magnetic studies imply that chromium cations may be incorporated into the framework and/or tunnels of the manganese dioxides. A mechanism for the growth of manganese dioxides with urchinlike architectures is proposed.

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Section: Primary Study On the Incorporation Of Chromium Ions In The Omentioning

confidence: 80%

Hydrothermal Synthesis of Structure‐ and Shape‐Controlled Manganese Oxide Octahedral Molecular Sieve Nanomaterials

Yuan

Shen

et al. 2006

Adv Funct Materials

217

127

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“…Previous authors (16)(17)(18)(19) have noted differences in the BET surface area of various samples of MnO~. The concept of increasing the surface area of a sample of MnO~ by grinding the particles to smaller and smaller diameters has often been proposed.…”

Section: Surface Area Of Mno~ Samplesmentioning

confidence: 99%

The Influence of the Active Surface on the Cathodic Reduction of MnO[sub 2]

Cahoon¹,

Korver²

1962

J. Electrochem. Soc.

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The surface area of samples of manganese dioxide is shown to be an important factor in influencing its behavior. Four samples of MnO~ of widely different origins, electrolytic, activated, natural ore, and synthetic pyrolusite, with total surface area values of 52.8, 50.5, 7.4, and 1.6 mS/g, respectively, are used as examples. The rates of the recuperation reaction at temperatures of 21~ 50~ are shown to be related to the total surface area of the oxides by a complex relation, dependent on temperature and other factors. The product of the reaction MnOOH develops on the surface and in the pores of the original MnO~ particle, thus increasing the diameter and resulting in reduced pore volume, respectively. The MnOOH made under these conditions, from all four starting materials, appears as rod-shaped units in electron micrographs.

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“…with SSA values that range from 120 to 315 m 2 g −1 , 2,17,28,[30][31][32] and MnĲIII) content varying between 0 and 31%. 2,33 While the MnĲIII) content of the products stems from the MnĲVII) : MnĲII) ratio employed in the synthesis, 2 the underlying cause for the large variations observed in SSA values is not known.…”

Section: Introductionmentioning

confidence: 99%

Crystal growth and aggregation in suspensions of δ-MnO₂nanoparticles: implications for surface reactivity

Marafatto

Lanson

Peña

2018

Environ. Sci.: Nano

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a Birnessite (layer-type Mn oxide) is a key reactive phase in soils and sediments and its sorption and oxidative properties render it attractive for use in technical applications. The most widely used synthetic analog of natural and biogenic birnessite in laboratory studies is nanocrystalline δ-MnO 2 . However, a wide range of physicochemical properties have been reported in the literature for δ-MnO 2 . In this study, we produced several batches of δ-MnO 2 and identified the mechanisms leading to significant variations in particle size, as probed by X-ray diffraction (3 to 7 nm), dynamic light scattering (85 to 501 nm) and N 2 Ĳg) BET specific surface area (SSA: 119 to 259 m 2 g −1) measurements. Both the coherent scattering domain (CSD) size in the ab plane and the wet-aggregate size decreased with increasing suspension pH and Na content, which is consistent with base-catalyzed oxidation and nucleation at high pH and growth by oriented attachment at low pH. The increase in the CSD size upon sample acidification but not basification provides further evidence for OA as a crystal growth mechanism. Finally, the sample SSA was not related to the crystallite size, but instead was inversely correlated to the suspension pH and Na : Mn content. The surface charge and counter-cation content of δ-MnO 2 control the aggregate structure, where low pH (low Na : Mn) favored high surface area structures and high pH (high Na : Mn) favored low surface area structures. The reversibility of SSA upon the acidification or basification of parent suspensions and the crystal growth only upon suspension acidification confirmed that the primary crystallite size and the aggregate/agglomerate size are highly sensitive to solution chemistry and surface charge and has direct implications for δ-MnO 2 nanoparticle reactivity towards organic and inorganic contaminants in environmental systems that can encompass a dynamic range of pH values and ionic compositions.

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Differenzierung von Mangan(II)‐manganit und δ‐MnO₂ durch Oberflächenmessung nach Brunauer‐Emmet‐Teller

Cited by 33 publications

References 6 publications

Hydrothermal Synthesis of Structure‐ and Shape‐Controlled Manganese Oxide Octahedral Molecular Sieve Nanomaterials

Hydrothermal Synthesis of Structure‐ and Shape‐Controlled Manganese Oxide Octahedral Molecular Sieve Nanomaterials

The Influence of the Active Surface on the Cathodic Reduction of MnO[sub 2]

Crystal growth and aggregation in suspensions of δ-MnO₂nanoparticles: implications for surface reactivity

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Differenzierung von Mangan(II)‐manganit und δ‐MnO2 durch Oberflächenmessung nach Brunauer‐Emmet‐Teller

Cited by 33 publications

References 6 publications

Hydrothermal Synthesis of Structure‐ and Shape‐Controlled Manganese Oxide Octahedral Molecular Sieve Nanomaterials

Hydrothermal Synthesis of Structure‐ and Shape‐Controlled Manganese Oxide Octahedral Molecular Sieve Nanomaterials

The Influence of the Active Surface on the Cathodic Reduction of MnO[sub 2]

Crystal growth and aggregation in suspensions of δ-MnO2nanoparticles: implications for surface reactivity

Contact Info

Product

Resources

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Differenzierung von Mangan(II)‐manganit und δ‐MnO₂ durch Oberflächenmessung nach Brunauer‐Emmet‐Teller

Crystal growth and aggregation in suspensions of δ-MnO₂nanoparticles: implications for surface reactivity