Redox State and Transition Metal Concentration Effects on Microstructure of Simulated Simplified Glasses for Waste Immobilization

1995 ◽  
Vol 412 ◽  
Author(s):  
C.-W. Kim ◽  
I. S. Muller ◽  
A. C. Buechele ◽  
I. L. Pegg ◽  
P. B. Macedo
Keyword(s):  
Solubility Limit ◽  
Aluminosilicate Glass ◽  
Enthalpies Of Solution ◽  
Concentration Effects ◽  
Redox Ratio ◽  
Redox States ◽  
Waste Immobilization ◽  
Temperature Transformation ◽  
Using Data ◽  
Iron Redox

AbstractChromium, iron, and nickel are present in many waste-streams from DOE sites. This study considers a simplified lime-aluminosilicate glass system, similar to one proposed for high temperature (1250–1450°C) vitrification of soil and wastes from DOE sites, in which concentrations of Cr, Fe. and Ni are being varied and different redox states induced for selected melting conditions. The solubilities of Cr 2O3 and NiO in the simplified system are determined at 1350°C, 1400°C, and 1450°C. The enthalpies of solution calculated from the solubility data for Cr2O3 and NiO are 12.2 and 15.2 kcal/mol, respectively. The iron redox ratio, Fe2+/Fetotal in selected glasses is determined by Mössbauer Spectroscopy and related to changes in microstructure. The crystallization of eskolaite (Cr2O3) seems to be favored at intermediate states of reduction (Fe2+/Fetotal ≈0.8) in Cr-containing glass at near the solubility limit. Pseudoternary diagrams are plotted for melts in air at 1450°C in which Fe2O3 + SiO2 + X (X = NiO or Cr2O33) is held constant. Time-Temperature-Transformation (TTT) curves are plotted using data from heat treatment studies. Liquidus temperatures of base, 1.5 wt% Cr2O3 glass and 8 wt% NiO, 7 wt% Fe2O3 glass are found to be 1150°C, 1175°C, and 1175°C, respectively.

Investigation of iron redox ratio in zinc borate glass prepared in microwave heating and comparison with conventional glass

2016 ◽  
Vol 450 ◽  
pp. 12-17 ◽  
Author(s):  
Biswajit Mandal ◽  
Avik Halder ◽  
Prasanta Kumar Sinha ◽  
Ranjan Sen ◽  
Ashis Kumar Mandal
Keyword(s):  
Microwave Heating ◽  
Borate Glass ◽  
Zinc Borate ◽  
Redox Ratio ◽  
Iron Redox

scholarly journals The effect of phosphorus on the iron redox ratio, viscosity, and density of an evolved ferro-basalt

1994 ◽  
Vol 117 (3) ◽  
pp. 293-304 ◽  
Author(s):  
M. J. Toplis ◽  
D. B. Dingwell ◽  
G. Libourel
Keyword(s):  
Redox Ratio ◽  
Iron Redox

Redox Systematics in Model Glass Compositions from West Valley

1992 ◽  
Vol 294 ◽  
Author(s):  
Henry D. Schreiber ◽  
Charlotte W. SCHREIBER ◽  
Cary C. Ward
Keyword(s):  
Waste Glass ◽  
Processing Temperature ◽  
Active Components ◽  
Redox Ratio ◽  
Metal Precipitation ◽  
Model Glass ◽  
Redox Active ◽  
Iron Redox ◽  
Glass Compositions

ABSTRACTAt a processing temperature of 1150°C for model West Valley glass compositions, the prescribed range of oxygen fugacities needed to achieve an [Fe2+]/[Fe3+] of 0.1 to 0.5 is 10−4 to 10−7 atm. Establishment of the Fe2+-Fe0 equilibrium, resulting in metal precipitation from the melt, occurs at oxygen fugacities lower than 10−11 atm at this temperature. The target processing range as defined by the iron redox ratio is equally valid at both lower and higher temperatures (±100°C). Elevations of the concentrations of redox-active components to I wt% Cr2O3, 1 wt% NiO, 1 wt% CuO, 1 wt% CeO2, and 4 wt% Mn2O3 in the waste glass will not affect the redox limits as established by the iron redox ratio of 0.1 to 0.5; these limits provide sufficiently large margins of safety to assure no stabilization of reduced or oxidized forms of these elements.

Crystallization of an Yttrium Aluminosilicate Glass for Nuclear Waste Immobilization

2012 ◽  
Vol 1475 ◽  
Author(s):  
Diana Carolina Lago ◽  
Diana Garcés ◽  
Miguel Oscar Prado
Keyword(s):  
Particle Size ◽  
Cross Sections ◽  
Glass Particle ◽  
Aluminosilicate Glass ◽  
Glassy Matrix ◽  
Borosilicate Glasses ◽  
Aluminosilicate Glasses ◽  
Waste Immobilization ◽  
Yttrium Disilicate ◽  
Nuclear Waste Immobilization

ABSTRACTSiO2-Al2O3-Y2O3 glasses exhibit high glass transition temperatures, water corrosion resistance and good mechanical properties. These properties suggest that yttrium aluminosilicate glasses could potentially replace the borosilicate glasses usually used for immobilization of nuclear wastes. At the same time, yttrium can be used to simulate actinides.During waste immobilization, crystallization of the glassy matrix must be avoided or at least controlled, thus, the understanding of glass crystallization kinetics is essential.We found by XRD that the crystalline phases present on heat treatments are yttrium disilicate and sillimanite/mullite. By optical microscopy on polished cross-sections we could only identify highly yttrium enriched crystals which we associate with yttrium disilicate crystals.In this paper we measure the surface density of nucleation sites Ns in as obtained splat cooled pieces obtaining values of about 1.5 · 1011 nucleus · m-2. Crystal growth rate U in the temperature range 1000-1040 oC varies in the range 8-13 μm · h-1. These data are useful for designing sintering or melting thermal paths of YAS glasses in order to control their microstructure. We show the effect of glass particle size on DTA results: crystallization peaks moves towards lower temperatures for smaller particle size, which confirms that mainly surface nucleation is taking place on heating.

scholarly journals The reaction of ascorbic acid with different heme iron redox states of myoglobin

FEBS Letters ◽  
1993 ◽  
Vol 332 (3) ◽  
pp. 287-290 ◽  
Author(s):  
Cecilia Giulivi ◽  
Enrique Cadenas
Keyword(s):  
Ascorbic Acid ◽  
Heme Iron ◽  
Redox States ◽  
Iron Redox

scholarly journals Disproportionation of H2O2 Mediated by Diiron-Peroxo Complexes as Catalase Mimics

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4501
Author(s):  
Dóra Lakk-Bogáth ◽  
Patrik Török ◽  
Flóra Csendes ◽  
Soma Keszei ◽  
Beatrix Gantner ◽  
...  
Keyword(s):  
Formation Rate ◽  
Enzyme Reaction ◽  
Critical Issue ◽  
Hydrogen Atom Transfer ◽  
Heme Iron ◽  
Fine Tuning ◽  
Redox Potentials ◽  
Redox States ◽  
Functional Models ◽  
Iron Redox

Heme iron and nonheme dimanganese catalases protect biological systems against oxidative damage caused by hydrogen peroxide. Rubrerythrins are ferritine-like nonheme diiron proteins, which are structurally and mechanistically distinct from the heme-type catalase but similar to a dimanganese KatB enzyme. In order to gain more insight into the mechanism of this curious enzyme reaction, non-heme structural and functional models were carried out by the use of mononuclear [FeII(L1–4)(solvent)3](ClO4)2 (1–4) (L1 = 1,3-bis(2-pyridyl-imino)isoindoline, L2 = 1,3-bis(4′-methyl-2-pyridyl-imino)isoindoline, L3 = 1,3-bis(4′-Chloro-2-pyridyl-imino)isoindoline, L4 = 1,3-bis(5′-chloro-2-pyridyl-imino)isoindoline) complexes as catalysts, where the possible reactive intermediates, diiron-perroxo [FeIII2(μ-O)(μ-1,2-O2)(L1-L4)2(Solv)2]2+ (5–8) complexes are known and well-characterized. All the complexes displayed catalase-like activity, which provided clear evidence for the formation of diiron-peroxo species during the catalytic cycle. We also found that the fine-tuning of iron redox states is a critical issue, both the formation rate and the reactivity of the diiron-peroxo species showed linear correlation with the FeIII/FeII redox potentials. Their stability and reactivity towards H2O2 was also investigated and based on kinetic and mechanistic studies a plausible mechanism, including a rate-determining hydrogen atom transfer between the H2O2 and diiron-peroxo species, was proposed. The present results provide one of the first examples of a nonheme diiron-peroxo complex, which shows a catalase-like reaction.

scholarly journals Effect of the Iron Reduction Index on the Mechanical and Chemical Properties of Continuous Basalt Fiber

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2472 ◽  
Author(s):  
Lida Luo ◽  
Qichang Zhang ◽  
Qingwei Wang ◽  
Jiwen Xiao ◽  
Jin Liu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Iron Reduction ◽  
Basalt Fiber ◽  
Chemical Properties ◽  
Aluminosilicate Glass ◽  
Photometric Method ◽  
X Ray ◽  
Iron Redox ◽  
And Chemical Properties ◽  
Redox Index

Basalt glass belongs to the iron-rich aluminosilicate glass system; thus, the iron content and the iron redox index (IRI=Fe2+/Fetotal) influence the viscosity, density, mechanical and chemical properties of basalt fiber (BF). In this work, continuous BFs with IRIs ranging from 0.21–0.87 were prepared by adding a different amount of redox agents. An economical and easily accessible testing method—the spectral photometric method with 1,10-phenanthroline—is applied to measure the IRI with convinced accuracy, which has been approved by Mössbauer spectra and X-ray fluorescence analysis. The tensile strength of the BF samples increases approximately linearly with increasing IRI as a function of σ = 227.9 IRI + 780.0 . The FT-IR results indicate that, with increasing IRI, the ferric ions are replaced by the much stronger network formers (Al3+ and Si4+), hence the increased the tensile strength. The X-ray diffraction results show an amorphous nature of BF samples. Moreover, the tensile strength is significantly decreased after the alkali corrosion, which is partly attributed to the severe surface damaging according to the SEM results. This work proved the feasibility of mechanical property improvement in BF production by controlling the iron redox index.

Polar Magnetic Field Reversals of the Sun in Maunder Minimum

2000 ◽  
Vol 179 ◽  
pp. 193-196
Author(s):  
V. I. Makarov ◽  
A. G. Tlatov
Keyword(s):  
Magnetic Field ◽  
Maunder Minimum ◽  
The Sun ◽  
Annual Rings ◽  
Field Reversal ◽  
Polar Magnetic Field ◽  
Pine Trees ◽  
Using Data ◽  
Magnetic Field Reversal

AbstractA possible scenario of polar magnetic field reversal of the Sun during the Maunder Minimum (1645–1715) is discussed using data of magnetic field reversals of the Sun for 1880–1991 and the14Ccontent variations in the bi-annual rings of the pine-trees in 1600–1730 yrs.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

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