Hyperfine Interactions and ESCA Data

Shirley, D. A.

doi:10.1088/0031-8949/11/3-4/002

Cited by 46 publications

(10 citation statements)

References 16 publications

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“…17 This would lead to the formation of Mn 2 O 3 as a surface product. The corresponding separation of peak energies (⌬E) is described in terms of the exchange interaction energy 24,30,31 ⌬E ϭ ͑ 2S ϩ 1͒K͓3s, 3d͔ ͓2͔ This can, nevertheless, explain the Mn 3ϩ -rich surface formed during storage of the electrodes.…”

Section: Resultsmentioning

confidence: 99%

Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

Eriksson

Gustafsson

Thomas

2002

Electrochem. Solid-State Lett.

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Section: Resultsmentioning

confidence: 99%

Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

Eriksson

Gustafsson

Thomas

2002

Electrochem. Solid-State Lett.

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“…[1][2][3]5,7 In the synthesis of Cu-OMS-2, the sol-gel method was not very advantageous compared to the reflux method in incorporating Cu 2+ ions. 23 Paramelaconite, a copper oxide, is readily formed in the sol-gel method based on XRD analysis of the product. The amount of Cu incorporated in OMS-2 by the reflux method is very minute.…”

Section: Resultsmentioning

confidence: 99%

“…centered at 641.97 eV, suggesting that the Mn is close to the Mn 3+ state. 23 The Mn 3s multiplet splitting indicates the presence of multivalent Mn. XPS spectra for Cu-OMS-2 in the Mn 3s region show multiplet splitting with B.E.…”

Section: Scanning Electron Microscopymentioning

confidence: 99%

Effects of Cu²⁺ Ions on the Structure and Reactivity of Todorokite- and Cryptomelane-Type Manganese Oxide Octahedral Molecular Sieves

et al. 1999

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The concentration effects on Cu uptake into the structures and reactivity of manganese oxide octahedral molecular sieves (OMS) were investigated. Two sets of 3 × 3-tunnel structure OMS designated as OMS-1 were synthesized by hydrothermal treatment at 160 °C for 48 h. The Cu-OMS-1 series of materials (tunnel substituted) were prepared by incorporating Cu 2+ ions into OL-1, which has a layered structure, at 60 °C for 24 h. [Cu]-OMS-1 materials (framework substituted) were prepared by ion exchanging Cu 2+ ions into the tunnels of OMS-1 under similar conditions. Cu-OMS-2 materials characterized by 2 × 2 tunnels were prepared by the reflux method. ICP analysis shows a Cu/Mn molar ratio of 0.278 for Cu-OMS-1 labeled C as the substitution limit for a pure sample based on its XRD pattern. The Cu(II) ions easily substitute for the divalent cations (Mg 2+ , Mn 2+ ) either in tunnel or framework sites when exchange was done before hydrothermal treatment. The presence of Cu 2+ ions decreases the Mn 2+ /Mn 4+ ratio in Cu-OMS-1 samples as suggested by an increasing trend in the average oxidation state of Mn and decreasing amounts of total Mn. XPS data reveal that Cu remains in the 2 + state in all of the materials as indicated by the shake-up peaks associated with Cu in such valency. EPR spectra of Cu-containing OMS-1 materials show the six peaks of Mn 2+ with a hyperfine splitting constant of 97 G, indicating an octahedral environment. The TGA profiles of [Cu]-OMS-1 show that these samples have the same thermal stability as OMS-1 but the amount of lattice oxygen evolved decreases slightly with the amount of Cu 2+ in the tunnel. The thermal stability of the Cu-OMS-1 and Cu-OMS-2 structures decrease as the amount of Cu incorporated increases. The copper ions that substitute for Mn 2+ in the framework are considered as defects in the structure of the crystallites which make them less stable than OMS-1 containing Mg 2+ in the framework where it exhibits a stabilizing effect. Resistivity measurements show a decrease and leveling off as the concentration of Cu increases in the Cu-OMS-1 series, which is a trend consistent with doping. The resistivity of the OMS-2 structure increases with the amount of copper incorporated. Cu(II) ions replacing the divalent cations in the framework during hydrothermal synthesis possibly account for the properties observed in the Cu-OMS-1 materials. An increased catalytic activity was observed for this set of materials as the Cu/Mn ratio increased for the oxidative dehydrogenation of ethylbenzene to styrene at 300 °C at 1 atm.

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“…High degree of vacuum provided the releasing of the studied samples from adsorbed water due to which the spectra of as prepared and dry samples were identical. During the further treatment, the background was subtracted basing on Shirley method [34]. Quantification of atomic content was provided using sensitivity factors provided by the elemental library of CasaXPS.…”

Section: Ultimate Analysismentioning

confidence: 99%

sp amorphous carbons in view of multianalytical consideration: Normal, expeсted and new

Golubev

Rozhkova

Кабачков

et al. 2019

Journal of Non-Crystalline Solids

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The suggested approach "Selected set of samples + selected set of analytical tools" occurred quite efficient when applying to sp 2 amorphous carbons, thus providing a transformation of 'amorphous' representation of the issue, based on particulars, into a 'crystalline' one based on a limited set of fixed commonalities. The slogan first part implies a set of different-origin solid samples. The second part concerns analytical tools, the most suitable to achieve the goal. The parts combining means the application of each tool to the whole set of samples. In the current study, two natural sp 2 amorphous carbons, namely, shungite carbon and antraxolite, as well as two engineered products -carbon blacks CB632 and CB624, all of the four bodies belonging to the elitist highest-carbon-content sp 2 species, were subjected to analytical study by using modern structural and compositional analytical techniques. The approach has allowed disclosing the following steady points that are common to the whole class of this carbon allotrope and that may lay the foundation of consolidate, more 'crystalline' representation of what are sp 2 amorphous carbons:1. sp 2 Amorphous carbons are products of particular chemical reactions related to their basic structural units. Further macroscopic agglomeration of the latter plays a subsidiary role. 2. The units represent framed graphene molecules of 1-2 nm and 1-x*10 (x=1-3) nm in size in the case of natural and engineered products, respectively.3. Framing of graphene molecules, predominantly incomplete with respect to the number of vacant places, concerns only edge atoms and is implemented by the related chemical additives, such as hydrogen, oxygen, nitrogen, sulfur and halogens which are attached to the carbon core via chemical bonding. 4. The molecules small size provides a countable number of newly formed chemical bonds.INS and XPS allow attributing the bonds to chemical compositions restricted by number while QCh ensures reliable support. 5. Temperature and pressure as well as physical state and chemical content of surrounding media are the main factors governing geochemistry and technical chemistry of carbon products. 6. Graphene molecules, laying the foundation of sp 2 amorphous carbons, are strongly radicalized due to which the latter acquire a new facet in the space of their properties, being the largest repository of stable radicals.

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Hyperfine Interactions and ESCA Data

Cited by 46 publications

References 16 publications

Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

Effects of Cu²⁺ Ions on the Structure and Reactivity of Todorokite- and Cryptomelane-Type Manganese Oxide Octahedral Molecular Sieves

sp amorphous carbons in view of multianalytical consideration: Normal, expeсted and new

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Hyperfine Interactions and ESCA Data

Cited by 46 publications

References 16 publications

Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

Surface Structure of LiMn[sub 2]O[sub 4] Electrodes

Effects of Cu2+ Ions on the Structure and Reactivity of Todorokite- and Cryptomelane-Type Manganese Oxide Octahedral Molecular Sieves

sp amorphous carbons in view of multianalytical consideration: Normal, expeсted and new

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Effects of Cu²⁺ Ions on the Structure and Reactivity of Todorokite- and Cryptomelane-Type Manganese Oxide Octahedral Molecular Sieves