scholarly journals Morphological Features and Sorption Performance of Materials Based on Birnessite Exposed to Various Reductive Conditions

2018 ◽  
Vol 2 (4) ◽  
pp. 70
Author(s):  
Arseniy Portnyagin ◽  
Andrey Egorin ◽  
Alexey Golikov ◽  
Eduard Tokar ◽  
Vitaliy Mayorov ◽  
...  
Keyword(s):  
Porous Structure ◽  
Kinetic Analysis ◽  
Manganese Oxide ◽  
Structural Changes ◽  
Xrd Analysis ◽  
Operating Regime ◽  
Repeated Use ◽  
Temperature Programmed ◽  
Amorphous Surface ◽  
Sorption Characteristics

The article is devoted to the evolution of structural, morphological, and sorption characteristics of layered manganese oxide (birnessite) under various conditions close to the real operating regime of the sorbents for radioactive waste processing. To identify the phase composition in the birnessites, we implemented XRD analysis, while SEM and temperature-programmed reduction (TPR) were used to study morphological and redox features of the materials, respectively. Structural changes after various kinds of treatment of birnessites were tracked using low temperature nitrogen sorption. Sorption characteristics were assessed under static and in dynamic conditions on the efficiency of Sr2+ removal from simulated seawater. TPR combined with kinetic analysis revealed the decrease of particle sizes in the birnessites after repeated use in sorption-regeneration cycle and reduction with hydrazine. Despite the fact that the porous structure of the materials remains preserved, the surface morphology of birnessite changes drastically depending on the reducing agent. Hydrazine treatment increases the sorption performance of the birnessite followed by degradation of mechanical properties, thus, preventing such sorbent from repeated use. Kinetic analysis of TPR allows quantifying differences in morphology and porous structure of manganese oxide materials. The specific surface area, amorphous surface structure, and accessibility of Mn+3 sites are the most important factors for birnessite sorption performance.

Synthesis and Characterization of Reduced Graphene Oxide

2013 ◽  
Vol 678 ◽  
pp. 56-60 ◽  
Author(s):  
Cherukutty Ramakrishnan Minitha ◽  
Ramasamy Thangavelu Rajendrakumar
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Graphite Oxide ◽  
High Performance ◽  
Structural Changes ◽  
Epoxy Group ◽  
Xrd Analysis ◽  
Si Substrates ◽  
Reduced Graphene ◽  
Reduced Graphite Oxide

Reduced graphene oxide is an excellent candidate for various electronic devices such as high performance gas sensors. In this work Graphene oxide was prepared by oxidizing graphite to form graphite oxide. From XRD analysis the peak around 11.5o confirmed that the oxygen was intercalated into graphite. By using hydrazine hydrate, the epoxy group in graphite oxide was reduced then the solution of reduced graphite oxide (rGO) is exfoliated. Raman spectrum of rGO contains both G band (1580 cm-1), D band (1350 cm-1). The remarkable structural changes reveals that reduction of graphene oxide from the values of ID/IG ratio that increase from 0.727 (GO) to 1.414 (rGO). The exfoliated reduced graphite oxide solution is spin coated on to the SiO2/Si substrates.

scholarly journals Yttrium doped phosphate-based glasses: structural and degradation analyses

2020 ◽  
Vol 6 (1) ◽  
pp. 34-49
Author(s):  
Abul Arafat ◽  
Sabrin A. Samad ◽  
Jeremy J. Titman ◽  
Andrew L. Lewis ◽  
Emma R. Barney ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Xrd Analysis ◽  
Calcium Pyrophosphate ◽  
Ion Release ◽  
Subsequent Increase ◽  
Structural Characterisation ◽  
Release Studies ◽  
Degradation Properties

AbstractThis study investigates the role of yttrium in phosphate-based glasses in the system 45(P2O5)–25(CaO)– (30-x)(Na2O)–x(Y2O3) (0≤x≤5) prepared via melt quenching and focuses on their structural characterisation and degradation properties. The structural analyses were performed using a combination of solid-state nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). 31P NMR analysis showed that depolymerisation of the phosphate network occurred which increased with Y2O3 content as metaphosphate units (Q2) decreased with subsequent increase in pyrophosphate species (Q1). The NMR results correlated well with structural changes observed via FTIR and XPS analyses. XRD analysis of crystallised glass samples revealed the presence of calcium pyrophosphate (Ca2P2O7) and sodium metaphosphate (NaPO3) phases for all the glass formulations explored. Yttrium-containing phases were found for the formulations containing 3 and 5 mol% Y2O3. Degradation analyses performed in Phosphate buffer saline (PBS) and Milli-Q water revealed significantly reduced rates with addition of Y2O3 content. This decrease was attributed to the formation of Y-O-P bonds where the octahedral structure of yttrium (YO6) cross-linked phosphate chains, subsequently leading to an increase in chemical durability of the glasses. The ion release studies also showed good correlation with the degradation profiles.

Probing Porous Structure of Single Manganese Oxide Mesorods with Ionic Current

2013 ◽  
Vol 117 (47) ◽  
pp. 24836-24842 ◽  
Author(s):  
Trevor Gamble ◽  
Eleanor Gillette ◽  
Sang Bok Lee ◽  
Zuzanna S. Siwy
Keyword(s):  
Porous Structure ◽  
Manganese Oxide ◽  
Ionic Current

scholarly journals Catalytic Abatement of Volatile Organic Compounds and Soot over Manganese Oxide Catalysts

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4534
Author(s):  
Miguel Jose Marin Figueredo ◽  
Clarissa Cocuzza ◽  
Samir Bensaid ◽  
Debora Fino ◽  
Marco Piumetti ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Low Temperature ◽  
Manganese Oxide ◽  
Organic Compounds ◽  
Catalytic Performance ◽  
Oxide Catalysts ◽  
X Ray ◽  
Manganese Oxide Catalysts ◽  
Volatile Organic ◽  
Temperature Programmed

A set of manganese oxide catalysts was synthesized via two preparation techniques: solution combustion synthesis (Mn3O4/Mn2O3-SCS and Mn2O3-SCS) and sol-gel synthesis (Mn2O3-SG550 and Mn2O3-SG650). The physicochemical properties of the catalysts were studied by means of N2-physisorption at −196 °C, X-ray powder diffraction, H2 temperature-programmed reduction (H2-TPR), soot-TPR, X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FESEM). The high catalytic performance of the catalysts was verified in the oxidation of Volatile Organic Compounds (VOC) probe molecules (ethene and propene) and carbon soot in a temperature-programmed oxidation setup. The best catalytic performances in soot abatement were observed for the Mn2O3-SG550 and the Mn3O4/Mn2O3-SCS catalysts. The catalytic activity in VOC total oxidation was effectively correlated to the enhanced low-temperature reducibility of the catalysts and the abundant surface Oα-species. Likewise, low-temperature oxidation of soot in tight contact occurred over the Mn2O3-SG550 catalyst and was attributed to high amounts of surface Oα-species and better surface reducibility. For the soot oxidation in loose contact, the improved catalytic performance of the Mn3O4/Mn2O3-SCS catalyst was attributed to the beneficial effects of both the morphological structure that—like a filter—enhanced the capture of soot particles and to a probable high amount of surface acid-sites, which is characteristic of Mn3O4 catalysts.

scholarly journals An alternative approach to kinetic analysis of temperature-programmed reaction data

RSC Advances ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 3286-3295 ◽  
Author(s):  
A. S. Portnyagin ◽  
A. P. Golikov ◽  
V. A. Drozd ◽  
V. A. Avramenko
Keyword(s):  
Particle Size ◽  
Kinetic Analysis ◽  
Kinetic Parameters ◽  
Isothermal Reaction ◽  
Alternative Approach ◽  
Reaction Data ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

Presented method of kinetic analysis of non-isothermal reaction data provides precise kinetic parameters for different materials with different morphology and particle size.

scholarly journals Reddish-Orange Luminescence from BaF2:Eu3+ Fluoride Nanocrystals Dispersed in Sol-Gel Materials

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3735 ◽  
Author(s):  
Natalia Pawlik ◽  
Barbara Szpikowska-Sroka ◽  
Joanna Pisarska ◽  
Tomasz Goryczka ◽  
Wojciech A. Pisarski
Keyword(s):  
Glass Ceramic ◽  
Structural Changes ◽  
Sol Gel ◽  
Ceramic Materials ◽  
Xrd Analysis ◽  
Luminescence Spectra ◽  
Silica Network ◽  
Scanning Calorimetry ◽  
Glass Ceramic Materials ◽  
Reddish Orange

Nanocrystalline transparent BaF2:Eu3+ glass-ceramic materials emitting reddish-orange light were fabricated using a low-temperature sol-gel method. Several experimental techniques were used to verify structural transformation from precursor xerogels to sol-gel glass-ceramic materials containing fluoride nanocrystals. Thermal degradation of xerogels was analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry method (DSC). The presence of BaF2 nanocrystals dispersed in sol-gel materials was confirmed by the X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). In order to detect structural changes in silica network during annealing process, the infrared spectroscopy (IR-ATR) was carried out. In particular, luminescence spectra of Eu3+ and their decays were examined in detail. Some spectroscopic parameters of Eu3+ ions in glass-ceramics containing BaF2 nanocrystals were determined and compared to the values obtained for precursor xerogels. It was observed, that the intensities of two main red and orange emission bands corresponding to the 5D0→7F2 electric-dipole transition (ED) and the 5D0→7F1 magnetic-dipole (MD) transition are changed significantly during transformation from xerogels to nanocrystalline BaF2:Eu3+ glass-ceramic materials. The luminescence decay analysis clearly indicates that the measured lifetime 5D0 (Eu3+) considerably enhanced in nanocrystalline BaF2:Eu3+ glass-ceramic materials compared to precursor xerogels. The evident changes in luminescence spectra and their decays suggest the successful migration of Eu3+ ions from amorphous silica network to low-phonon BaF2 nanocrystals.

Humidity Controlled Diffractometry and its Applications

1992 ◽  
Vol 36 ◽  
pp. 439-449 ◽  
Author(s):  
Radko A. Kühnel ◽  
Sjerry J. van der Gaast
Keyword(s):  
Structural Changes ◽  
Basic Research ◽  
Xrd Analysis ◽  
Reaction Rates ◽  
Hydrous Minerals ◽  
X Ray ◽  
Special Attachment ◽  
Potential Applications ◽  
Total Structure ◽  
Structure Collapse

AbstractHumidity sensitive mineral phases change their structure when humidity varies resulting in X-ray pattern changes in intensity, position, and shape of lines. These structural changes in hydrous minerals are induced by dehydration and rehydration, which can lead to phase transformations or to steady depletion which may result in a total structure collapse. By means of X-ray diffraction with a special attachment, such reactions can be followed. The controlled relative humidity is provided in situ, in a closed cell, by a flow of moistened helium gas which is flushed through the cell during the XRD analysis. Humidity diffractometry allows studies of reaction rates of dehydration-rehydration reactions and their reversibilities, as well as effects of additives and impurities on these reactions. Potential applications in basic research and in industry are demonstrated using montmorilionite, ettringites, sodium carbonates and calcium sulfates.

scholarly journals Effect of Soil Solution pH during the Tetracycline Intercalation on the Structural Properties of a Dioctahedral Smectite: Microstructural Analysis

2019 ◽  
Vol 2019 ◽  
pp. 1-17
Author(s):  
Walid Oueslati
Keyword(s):  
Soil Solution ◽  
Structural Changes ◽  
Ph Value ◽  
Microstructural Analysis ◽  
Xrd Analysis ◽  
Deformation Bands ◽  
Solution Ph ◽  
Hydration Properties ◽  
In Situ Xrd

The aim of this work is to quantitatively characterize the structural response to a chemical disruption of saturated montmorillonite crystallites by organic molecules (tetracycline (TC)), derived from pharmaceutical waste. The chemical disturbance is performed by varying the surrounding soil solution pH. To show the effect of this chemical perturbation on the interlamellar space (IS) configuration and the hydration properties, an “in situ” XRD analysis, based on the modeling of the 00l reflections, is carried out. The “in situ” XRD analysis is performed by varying the relative humidity conditions (%RH). FTIR SEM and BET- (Brunauer-Emmett-Teller-) BJH (Barrett-Joyner-Halenda) analyses are used as complementary techniques to confirm the structural changes accompanying the intercalation process. Results showed a dependence between solution acid character and the TC adsorption mechanism. From pH values close to 7, the deprotonation of the TC molecule within IS is accelerated by an increasing %RH rate. IR spectroscopy shows that the structure is preserved versus pH value and only a shift of the water deformation bands ascribed to interlamellar water molecule abundance and TC conformation is observed. The surface morphology studied by SEM shows the increase in the surface porosity by increasing the pH value. BET-specific surface area and BJH pore size distribution (PSD) analyses confirm the SEM observations.

scholarly journals Kinetic Analysis of Temperature-Programmed Autoxidation of Ethyl Eicosapentaenoate and Ethyl Docosahexaenoate

1999 ◽  
Vol 63 (8) ◽  
pp. 1336-1339 ◽  
Author(s):  
Hidefumi YOSHII ◽  
Takeshi FURUTA ◽  
Takatoki ITOH ◽  
Yoshihisa MISAWA ◽  
Noriaki HATA ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Temperature Programmed ◽  
Ethyl Docosahexaenoate
Sign in / Sign up

Export Citation Format

Share Document