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Pavel R Hrma - One of the best experts on this subject based on the ideXlab platform.
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a method for determining bulk density material density and porosity of melter feed during nuclear waste vitrification
Journal of the American Ceramic Society, 2016Co-Authors: Zachary J Hilliard, Pavel R HrmaAbstract:Abstract Glass making efficiency largely depends on heat transfer to reacting Glass Batch (melter feed), which in turn is influenced by the bulk density (ρb) and porosity (Φ) as functions of temperature (T). Neither b(T) nor Φ(T) functions are readily accessible to direct measurement, but they can be determined based on monitoring the profile area of heated Glass Batch pellets and material density of Batches quenched at various stages of conversion via pycnometry. For the determination of Φb, the bulk volume must be calculated as a function of temperature. This is done via a program constructed in MATLAB which takes an image of a pellet profile at a given temperature and calculates the volume of said pellet. The quenched density measured by pycnometry must be converted to the density at heat treatment temperature. This is done by taking into account the volume change due to thermal expansion/contraction.
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kinetic model for quartz and spinel dissolution during melting of high level waste Glass Batch
Journal of Nuclear Materials, 2013Co-Authors: Richard Pokorný, Pavel R Hrma, Michael J Schweiger, Jarrett A Rice, Jarrod V CrumAbstract:The dissolution of quartz particles and the growth and dissolution of crystalline phases during the conversion of Batch to Glass potentially affects both the Glass melting process and product quality. Crystals of spinel exiting the cold cap to molten Glass below can be troublesome during the vitrification of iron-containing high-level wastes. To estimate the distribution of quartz and spinel fractions within the cold cap, we used kinetic models that relate fractions of these phases to temperature and heating rate. Fitting the model equations to data showed that the heating rate, apart from affecting quartz and spinel behavior directly, also affects them indirectly via concurrent processes, such as the formation and motion of bubbles. Because of these indirect effects, it was necessary to allow one kinetic parameter (the pre-exponential factor) to vary with the heating rate. The resulting kinetic equations are sufficiently simple for the detailed modeling of Batch-to-Glass conversion as it occurs in Glass melters. The estimated fractions and sizes of quartz and spinel particles as they leave the cold cap, determined in this study, will provide the source terms needed for modeling the behavior of these solid particles within the flow of molten Glass in the melter.
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melting of Glass Batch model for multiple overlapping gas evolving reactions
Thermochimica Acta, 2012Co-Authors: Richard Pokorný, Pavel R Hrma, David A PierceAbstract:In this study, we present a model for the kinetics of multiple overlapping reactions. Mathematical representation of the kinetics of gas-evolving reactions is crucial for the modeling of the feed-to-Glass conversion in a waste-Glass melter. The model simulates multiple gas-evolving reactions that occur during heating of a high-alumina high-level waste melter feed. To obtain satisfactory kinetic parameters, we employed Kissinger's method combined with least-squares analysis. The power-law kinetics with variable reaction order sufficed for obtaining excellent agreement with measured thermogravimetric analysis data.
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effect of alumina source on the rate of melting demonstrated with nuclear waste Glass Batch
International Journal of Applied Glass Science, 2012Co-Authors: David A Pierce, Pavel R Hrma, Jose Marcial, Brian J Riley, Michael J SchweigerAbstract:The selection of raw materials affects the rate of Batch-to-Glass conversion. In all-electric melters, foam under the Batch blanket limits the heat flux from the molten Glass, thus slowing the rate of melting. Our study, in which we compare the melting behaviors of three Batches formulated to vitrify high-alumina high-level waste, shows that a slowly dissolving refractory component can cause excessive foaming. Faster melting Batches with gibbsite [Al(OH)3] or boehmite [AlO(OH)] as an alumina source produced substantially less foaming than a Batch with corundum (Al2O3). Although gibbsite and boehmite dissolved below 500°C, corundum was still present in the Batch up to 900°C; hence, the Glass-forming melt lacked alumina in the Batch with corundum. The low viscosity of that Batch caused the open pores to close prematurely at 660°C, trapping gases and expanding to foam. This would explain the literature-reported slow melting rate of a Batch with corundum, as compared to Batches with gibbsite and boehmite.
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dissolution retardation of solid silica during Glass Batch melting
Journal of Non-crystalline Solids, 2011Co-Authors: Pavel R Hrma, Jose MarcialAbstract:Abstract During Glass-Batch melting, solid silica (quartz) usually dissolves last. The measured rate of dissolution, while the temperature was increasing at a constant rate, was compared with the hypothetical diffusion-controlled volume flux from regularly distributed particles through concentration layers of a uniform thickness. The actual rate was up to two orders of magnitude lower than that of the “ideal” case, revealing a progressive inhibition of silica dissolution. As a measure of this retarded dissolution, we introduced a retardation factor defined as a ratio of the actual and “ideal” dissolution rates measured as the volume flux at the melt-particle interface. The severe inhibition of silica dissolution has been attributed to the irregular spatial distribution of silica particles that is associated with the formation of nearly saturated melt on a portion of their surfaces. Irregular shapes and unequal sizes of particles also contribute to their extended lifetime.
Leena Hupa - One of the best experts on this subject based on the ideXlab platform.
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effect of the Glass melting condition on the processing of phosphate based Glass ceramics with persistent luminescence properties
Optical Materials, 2016Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Laeticia Petit, Jorma Holsa, M Gaussiran, Leena HupaAbstract:Abstract In this paper, we discuss the impact of the temperature and the duration of the melting on the persistent luminescence properties of phosphate Glasses within the P 2 O 5 –Na 2 O–CaO and P 2 O 5 –Na 2 O–SrO systems prepared using a standard melting process in normal atmosphere by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. Glasses with persistent luminescence properties can be successfully prepared if the melting conditions are carefully controlled.
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new alternative route for the preparation of phosphate Glasses with persistent luminescence properties
Journal of The European Ceramic Society, 2015Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Lucas C V Rodrigues, Laeticia Petit, Jorma Holsa, Leena HupaAbstract:Abstract In this paper, we investigate a new alternative route for the preparation of phosphate Glasses with persistent luminescence properties. Phosphate Glasses within the P 2 O 5 Na 2 O CaO and P 2 O 5 Na 2 O SrO systems were prepared by a standard melting process in air by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. We found that all the investigated Glasses show persistent luminescence. It is clearly shown that conventional melting in air of Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in phosphate Glass Batch can be a new technique to prepare phosphate Glasses with persistent luminescence properties.
Jorma Holsa - One of the best experts on this subject based on the ideXlab platform.
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effect of the Glass melting condition on the processing of phosphate based Glass ceramics with persistent luminescence properties
Optical Materials, 2016Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Laeticia Petit, Jorma Holsa, M Gaussiran, Leena HupaAbstract:Abstract In this paper, we discuss the impact of the temperature and the duration of the melting on the persistent luminescence properties of phosphate Glasses within the P 2 O 5 –Na 2 O–CaO and P 2 O 5 –Na 2 O–SrO systems prepared using a standard melting process in normal atmosphere by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. Glasses with persistent luminescence properties can be successfully prepared if the melting conditions are carefully controlled.
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new alternative route for the preparation of phosphate Glasses with persistent luminescence properties
Journal of The European Ceramic Society, 2015Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Lucas C V Rodrigues, Laeticia Petit, Jorma Holsa, Leena HupaAbstract:Abstract In this paper, we investigate a new alternative route for the preparation of phosphate Glasses with persistent luminescence properties. Phosphate Glasses within the P 2 O 5 Na 2 O CaO and P 2 O 5 Na 2 O SrO systems were prepared by a standard melting process in air by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. We found that all the investigated Glasses show persistent luminescence. It is clearly shown that conventional melting in air of Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in phosphate Glass Batch can be a new technique to prepare phosphate Glasses with persistent luminescence properties.
P Gluchowski - One of the best experts on this subject based on the ideXlab platform.
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effect of the Glass melting condition on the processing of phosphate based Glass ceramics with persistent luminescence properties
Optical Materials, 2016Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Laeticia Petit, Jorma Holsa, M Gaussiran, Leena HupaAbstract:Abstract In this paper, we discuss the impact of the temperature and the duration of the melting on the persistent luminescence properties of phosphate Glasses within the P 2 O 5 –Na 2 O–CaO and P 2 O 5 –Na 2 O–SrO systems prepared using a standard melting process in normal atmosphere by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. Glasses with persistent luminescence properties can be successfully prepared if the melting conditions are carefully controlled.
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new alternative route for the preparation of phosphate Glasses with persistent luminescence properties
Journal of The European Ceramic Society, 2015Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Lucas C V Rodrigues, Laeticia Petit, Jorma Holsa, Leena HupaAbstract:Abstract In this paper, we investigate a new alternative route for the preparation of phosphate Glasses with persistent luminescence properties. Phosphate Glasses within the P 2 O 5 Na 2 O CaO and P 2 O 5 Na 2 O SrO systems were prepared by a standard melting process in air by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. We found that all the investigated Glasses show persistent luminescence. It is clearly shown that conventional melting in air of Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in phosphate Glass Batch can be a new technique to prepare phosphate Glasses with persistent luminescence properties.
Jonathan Massera - One of the best experts on this subject based on the ideXlab platform.
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effect of the Glass melting condition on the processing of phosphate based Glass ceramics with persistent luminescence properties
Optical Materials, 2016Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Laeticia Petit, Jorma Holsa, M Gaussiran, Leena HupaAbstract:Abstract In this paper, we discuss the impact of the temperature and the duration of the melting on the persistent luminescence properties of phosphate Glasses within the P 2 O 5 –Na 2 O–CaO and P 2 O 5 –Na 2 O–SrO systems prepared using a standard melting process in normal atmosphere by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. Glasses with persistent luminescence properties can be successfully prepared if the melting conditions are carefully controlled.
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new alternative route for the preparation of phosphate Glasses with persistent luminescence properties
Journal of The European Ceramic Society, 2015Co-Authors: Jonathan Massera, P Gluchowski, Mika Lastusaari, Lucas C V Rodrigues, Laeticia Petit, Jorma Holsa, Leena HupaAbstract:Abstract In this paper, we investigate a new alternative route for the preparation of phosphate Glasses with persistent luminescence properties. Phosphate Glasses within the P 2 O 5 Na 2 O CaO and P 2 O 5 Na 2 O SrO systems were prepared by a standard melting process in air by adding Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in the Glass Batch before melting. We found that all the investigated Glasses show persistent luminescence. It is clearly shown that conventional melting in air of Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ microparticles in phosphate Glass Batch can be a new technique to prepare phosphate Glasses with persistent luminescence properties.