A Mössbauer study of the oxidation state of Fe in silicate melts

Jayasuriya, K.D.; O’Neill, Hugh St. C.; Berry, Andrew; Campbell, S. J.

doi:10.2138/am-2004-11-1203

Cited by 196 publications

(162 citation statements)

References 36 publications

Supporting

Mentioning

142

Contrasting

Unclassified

Order By: Relevance

“…glasses in the range of 3% to 60% Fe ++ /Fe total and as previously verified in silicate melts [14], there is no significant difference between the recoil-free fractions of Fe 2+ and Fe 3+ and the redox ratio was calculated from the areas of the corresponding doublets.…”

Section: Methodssupporting

confidence: 81%

Vanadium and chromium redox behavior in borosilicate nuclear waste glasses

McKeown

Muller

Gan

et al. 2011

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

X-ray absorption spectroscopy (XAS) was used to characterize vanadium (V) and chromium (Cr) environments in low activity nuclear waste (LAW) glasses synthesized under a variety of redox conditions. V 2 O 5 was added to the melt to improve sulfur incorporation from the waste; however, at sufficiently high concentrations, V increased melt foaming, which lowered melt processing rates. Foaming may be reduced by varying the redox conditions of the melt, while small amounts of Cr are added to reduce melter refractory corrosion. Three parent glasses were studied, where CO-CO 2 mixtures were bubbled through the corresponding melt for increasing time intervals so that a series of redox-adjusted-glasses was synthesized from each parent glass. XAS data indicated that V and Cr behaviors are significantly different in these glasses with respect to the cumulative gas bubbling times: V 4+ /V total ranges from 8 to 35%, while Cr 3+ /Cr total can range from 15 to 100% and even to population distributions including Cr 2+. As Nacontent decreased, V, and especially, Cr became more reduced, when comparing equivalent glasses within a series. The Na-poor glass series show possible redox coupling between V and Cr, where V 4+ populations increase after initial bubbling, but as bubbling time increases, V 4+ populations drop to near the level of the parent glass, while Cr becomes more reduced to the point of having increasing Cr 2+ populations.

show abstract

Section: Methodssupporting

confidence: 81%

Vanadium and chromium redox behavior in borosilicate nuclear waste glasses

McKeown

Muller

Gan

et al. 2011

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

show abstract

“…50−100 mg of powder that was enclosed in a 20-mm-diameter cylindrical plastic sample holder, the size of which has been determined to optimize the absorption. We observe doublets and sextets in the Mössbauer spectra of the samples which are characteristic of quadrupole and magnetic dipole interactions, respectively, the doublets being associated to the presence of iron in the silicate network and the sextets to oxide phases with magnetic signature (Ferreira da Silva et al 1992;Jayasuriya et al 2004). The Mössbauer spectra of samples E10 to E40 show a single doublet characteristic of FeIII in silicates whereas the spectra of the E10R to E40R samples show two doublets characteristic of FeIII and FeII.…”

Section: Sample Characterizationmentioning

confidence: 87%

Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

Demyk

Meny

Leroux

et al. 2017

A&A

View full text Add to dashboard Cite

Context. To model the cold dust emission observed in the diffuse interstellar medium, in dense molecular clouds or in cold clumps that could eventually form new stars, it is mandatory to know the physical and spectroscopic properties of this dust and to understand its emission. Aims. This work is a continuation of previous studies aiming at providing astronomers with spectroscopic data of realistic cosmic dust analogues for the interpretation of observations. The aim of the present work is to extend the range of studied analogues to iron-rich silicate dust analogues. Methods. Ferromagnesium amorphous silicate dust analogues were produced by a sol-gel method with a mean composition close to Mg 1−x Fe x SiO 3 with x = 0.1, 0.2, 0.3, 0.4. Part of each sample was annealed at 500• C for two hours in a reducing atmosphere to modify the oxidation state of iron. We have measured the mass absorption coefficient (MAC) of these eight ferromagnesium amorphous silicate dust analogues in the spectral domain 30−1000 µm for grain temperature in the range 10−300 K and at room temperature in the 5−40 µm range. Results. The MAC of ferromagnesium samples behaves in the same way as the MAC of pure Mg-rich amorphous silicate samples. In the 30−300 K range, the MAC increases with increasing grain temperature whereas in the range 10−30 K, we do not see any change of the MAC. The MAC cannot be described by a single power law in λ −β . The MAC of the samples does not show any clear trend with the iron content. However the annealing process has, on average, an effect on the MAC that we explain by the evolution of the structure of the samples induced by the processing. The MAC of all the samples is much higher than the MAC calculated by dust models. Conclusions. The complex behavior of the MAC of amorphous silicates with wavelength and temperature is observed whatever the exact silicate composition (Mg vs. Fe amount). It is a universal characteristic of amorphous materials, and therefore of amorphous cosmic silicates, that should be taken into account in astronomical modeling. The enhanced MAC of the measured samples compared to the MAC calculated for cosmic dust model implies that dust masses are overestimated by the models.

show abstract

“…If incorporated into the glass structure as tetrahedra, they will act as network formers; if, however, they change coordination and form octahedra, then they will act as network modifi ers, disrupting the glass network. Naturally these cations are very important in silicate melt studies, as they are commonly found in natural melts, and there have been many studies on melts and glasses incorporating one or more of these elements (Fe: Jayasuriya et al 2004, Magnien et al 2004, Ti: Henderson et al 2003, Roskosz et al 2004, Al: Lee et al 2004, Neuville et al 2004a. However, many of these authors have utilized compositions that are inherently complex structurally.…”

Section: Intermediate Oxides (Al Ti Fe)mentioning

confidence: 99%

The Structure of Silicate Melts: A Glass Perspective

Henderson

2005

The Canadian Mineralogist

128

View full text Add to dashboard Cite

Glasses are widely used as analogues for the study of silicate melts. Although they are solid materials, their structure is inherently complex and diffi cult to study. However, progress has been made in elucidating this structure, its relationship to composition, and how it behaves at high temperatures and pressures. Recent research has brought to light some new fi ndings with important implications for natural melts. These include the observation that the structure is dependent upon the type and size of alkali or alkaline-earth cations incorporated into the glass network, with Li behaving very differently than other alkali cations. In addition, the presence of more than one type of alkali cation can cause non-linear physical behavior. Elements such as Al, Ti and Fe, which play important roles in petrological phenomena, can exhibit coordination environments (e.g., 5-fold) or polyhedral arrangements (e.g., triclusters) that are not common in crystalline phases. Furthermore, polyamorphic phase-transitions may occur at high temperature and pressures; the application of new theoretical models like mean fi eld-constraint hypothesis suggests that several glass phenomena, and probably melt phenomena as well, may be related to stress-rigid to fl oppy transitions. The state of understanding of glass structure, although still rudimentary relative to crystalline materials, has grown exponentially over the last few decades, often with geological researchers at the forefront.Keywords: melts, structure, glasses, petrology, spectroscopy, behavior, model. SOMMAIREOn se sert couramment des verres pour étudier les bains fondus silicatés. Quoiqu'ils sont des matériaux solides, leur structure est naturellement complexe et diffi cile à étudier. Toutefois, des progrès ont été faits dans l'étude de cette structure, sa relation à la composition, et son comportement à températures et pressions élevées. Les projets de recherche récents font ressortir les implications importantes aux bains fondus naturels. A titre d'exemple, la structure dépendrait de la sorte et la taille d'ion alcalin ou alcalino-terreux qui se trouve incorporé dans le réseau du verre. Le Li se comporte de façon très différente des autres alcalins. De plus, la présence de plus d'une sorte d'alcalin peut causer des comportements physiques non-linéaires. Les élements tels Al, Ti et Fe, dont l'importance pétrologique est évidente, peuvent adopter une coordinence inhabituelle, cinq par exemple, et un arrangement polyédrique, des groupements par trois, par exemple, qui ne sont pas communs dans les phases cristallines. De plus, des transitions de phases polyamorphiques pourraient avoir lieu à températures et à pressions élevées. L'application de nouveaux modèles théoriques, par exemple le modèle de contrainte moyenne du champ, fait penser que plusieurs phénomènes impliquant les verres, et tout probablement les bains fondus, pourraient résulter de transitions de matériau rigide face aux contraintes à maté-riau déformable. Quoique les connaissances de la structure du ve...

show abstract

A Mössbauer study of the oxidation state of Fe in silicate melts

Cited by 196 publications

References 36 publications

Vanadium and chromium redox behavior in borosilicate nuclear waste glasses

Vanadium and chromium redox behavior in borosilicate nuclear waste glasses

Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues

The Structure of Silicate Melts: A Glass Perspective

Contact Info

Product

Resources

About