A reaction rate maximum occurs around 250 °C in the bleaching of chemically discolored sodium bet... more A reaction rate maximum occurs around 250 °C in the bleaching of chemically discolored sodium beta alurninas. It is determined that the bleaching rate depends on the diffusion rate of oxygen interstitials in the conduction planes of sodium beta alumina. The reaction rate maximum indicates that an irreversible transition occurs from a high mobility to a low mobility oxygen interstitial around 300 °C. It is proposed that this transition is one in which a free oxygen interstitial is transformed into a Roth-type interstitial. lOn leave from the Institut National Polytechnique de Grenoble-France
Optics for Arts, Architecture, and Archaeology VII
This paper investigates optical coherence tomography (OCT) as an advanced, non-invasive method fo... more This paper investigates optical coherence tomography (OCT) as an advanced, non-invasive method for 2D and 3D imaging of the surface and subsurface morphology of glass cultural heritage. The OCT system used is a commercial ThorLabs Ganymede II spectral domain-Fourier domain system with a 930 nm center wavelength, axial resolution of 4-6 μm, and lateral resolution of 8 μm. Results from model alkali silicate glass artificially aged at 90°C and 90% RH allow distinction of real features from artifacts produced by the highly reflective glass, and serve as a basis for interpretation of deterioration phenomena. Analytical results from historical glass artifacts are focused on a group of musical glass flutes created in Paris by Claude Laurent between 1807 and 1848. OCT images are compared to results of destructive analysis of the same samples and objects by scanning electron microscopy with backscattered electron imaging of cross-sections, as well as non-invasive light microscopy and NIR fiber optic reflectance spectrometry, the latter of which yields complementary molecular information in terms of water vibrations in hydrated glass.
h i g h l i g h t s " Tc, an environmental risk for nuclear waste storage, is commonly model... more h i g h l i g h t s " Tc, an environmental risk for nuclear waste storage, is commonly modeled using Re. " Tc and Re valences can diverge in original and hydrothermally altered glasses. " Tc and Re spatial distributions can diverge in hydrothermally altered glasses. " Re can be an unreliable surrogate for Tc in situations where redox is important. " Using Re as a surrogate for Tc in waste glasses can provide misleading results. a b s t r a c t Technetium (99 Tc) is a significant environmental risk factor to consider for nuclear waste disposal repos-itories. Rhenium (Re), in the same column of the periodic table as Tc, is often used as a non-radioactive surrogate for Tc. Six waste glasses containing both Tc and Re were synthesized under a variety of redox conditions to produce different distributions of Tc and Re oxidation states. These glasses were exposed to vapor hydration tests (VHT) at 200 °C for 23 to 30 days; and the Tc and Re oxidation state, coordina...
A range of compositions of high-zirconia borosilicate glasses were formulated and their structure... more A range of compositions of high-zirconia borosilicate glasses were formulated and their structures investigated by a combination of techniques. These compositions have potential applications for high-level nuclear waste storage in combination with advanced reprocessing methods. Raman and Zr EXAFS data were collected for a series of glasses spanning a range of zirconia concentrations. The Raman spectra indicate that Zr acts as a silicate network modifier, where the silicate tetrahedral network depolymerizes as the zirconia content increases. Zr EXAFS analysis indicates that Zr is found in octahedral sites, and to a minor extent, sevencoordinated sites. As the zirconia content increases, the fraction of seven-coordinated Zr-sites increases; this may be the cause of ZrO2 baddeleyite crystallization that was observed in some Zr-rich glasses investigated.
The corrosion of the glass-contact refractory Monofrax K-3 in two sodium-rich aluminosilicate mel... more The corrosion of the glass-contact refractory Monofrax K-3 in two sodium-rich aluminosilicate melts has been studied at 1208 and 1283°C using a modified ASTM procedure with constant agitation of the melt by air bubbling. The results for the monolithic refractory indicate a fast initial stage involving phase dissolution and transformation and a later “passivated” stage in which the surface of the refractory has been substantially modified. The composition of the stable spinel phase in the altered layer on monolithic coupons of K-3 is almost identical to the equilibrium composition bracketed by the dissolution of powdered K-3 into under-saturated melts on the one hand, and by crystallization of spinels from supersaturated melts on the other. The temperature and melt shear viscosity were found to have significant effects on the rates of K-3 dissolution and transformation.
ABSTRACT Glasses were prepared by systematic additions of P2O5, BaO, and PbO to glasses consistin... more ABSTRACT Glasses were prepared by systematic additions of P2O5, BaO, and PbO to glasses consisting of Al2O3-B2O3-(BaO)-CaO-Fe2O3-K2O-MgO-Na2O-(PbO)-(P2O5)-SiO2, and their chemical durability was examined by the EPA TCLP test. The addition of about 1 mol% P2O5 to a glass containing 5 mol% PbO increases the normalized lead leach rate (NLLR) by about 40 relative%, but increasing P2O5 to 2 mol% decreases the NLLR to about the NLLR obtained without P2O5. A similar, but more dramatic, behavior with changes in the NLLR of about 300 relative% is obtained by sequential combined additions of 1 mol% each of P2O5 and BaO to a glass containing 1 mol% PbO.
... the samples of interest for all three elements. Silica-rich glasses consist of a polymerized ... more ... the samples of interest for all three elements. Silica-rich glasses consist of a polymerized network dominated by silicate tetrahedra as well as network modifying cations, such as Na. Al can play dual roles in silicate structures ...
We report the growth, structural characterization, and magnetic properties of ferromagnetic Fe0.8... more We report the growth, structural characterization, and magnetic properties of ferromagnetic Fe0.8Ga0.2 nanowires that are grown on quartz substrates by electrospinning. Electrospun nanowires are annealed in ultrahigh purity argon-hydrogen gas mixture. Uniform, continuous, high aspect ratio FeGa nanowires with diameters in the range of 50-500 nm and lengths of up to 500 mum are grown. Hysteresis loops were measured with
A reaction rate maximum occurs around 250 °C in the bleaching of chemically discolored sodium bet... more A reaction rate maximum occurs around 250 °C in the bleaching of chemically discolored sodium beta alurninas. It is determined that the bleaching rate depends on the diffusion rate of oxygen interstitials in the conduction planes of sodium beta alumina. The reaction rate maximum indicates that an irreversible transition occurs from a high mobility to a low mobility oxygen interstitial around 300 °C. It is proposed that this transition is one in which a free oxygen interstitial is transformed into a Roth-type interstitial. lOn leave from the Institut National Polytechnique de Grenoble-France
Optics for Arts, Architecture, and Archaeology VII
This paper investigates optical coherence tomography (OCT) as an advanced, non-invasive method fo... more This paper investigates optical coherence tomography (OCT) as an advanced, non-invasive method for 2D and 3D imaging of the surface and subsurface morphology of glass cultural heritage. The OCT system used is a commercial ThorLabs Ganymede II spectral domain-Fourier domain system with a 930 nm center wavelength, axial resolution of 4-6 μm, and lateral resolution of 8 μm. Results from model alkali silicate glass artificially aged at 90°C and 90% RH allow distinction of real features from artifacts produced by the highly reflective glass, and serve as a basis for interpretation of deterioration phenomena. Analytical results from historical glass artifacts are focused on a group of musical glass flutes created in Paris by Claude Laurent between 1807 and 1848. OCT images are compared to results of destructive analysis of the same samples and objects by scanning electron microscopy with backscattered electron imaging of cross-sections, as well as non-invasive light microscopy and NIR fiber optic reflectance spectrometry, the latter of which yields complementary molecular information in terms of water vibrations in hydrated glass.
h i g h l i g h t s " Tc, an environmental risk for nuclear waste storage, is commonly model... more h i g h l i g h t s " Tc, an environmental risk for nuclear waste storage, is commonly modeled using Re. " Tc and Re valences can diverge in original and hydrothermally altered glasses. " Tc and Re spatial distributions can diverge in hydrothermally altered glasses. " Re can be an unreliable surrogate for Tc in situations where redox is important. " Using Re as a surrogate for Tc in waste glasses can provide misleading results. a b s t r a c t Technetium (99 Tc) is a significant environmental risk factor to consider for nuclear waste disposal repos-itories. Rhenium (Re), in the same column of the periodic table as Tc, is often used as a non-radioactive surrogate for Tc. Six waste glasses containing both Tc and Re were synthesized under a variety of redox conditions to produce different distributions of Tc and Re oxidation states. These glasses were exposed to vapor hydration tests (VHT) at 200 °C for 23 to 30 days; and the Tc and Re oxidation state, coordina...
A range of compositions of high-zirconia borosilicate glasses were formulated and their structure... more A range of compositions of high-zirconia borosilicate glasses were formulated and their structures investigated by a combination of techniques. These compositions have potential applications for high-level nuclear waste storage in combination with advanced reprocessing methods. Raman and Zr EXAFS data were collected for a series of glasses spanning a range of zirconia concentrations. The Raman spectra indicate that Zr acts as a silicate network modifier, where the silicate tetrahedral network depolymerizes as the zirconia content increases. Zr EXAFS analysis indicates that Zr is found in octahedral sites, and to a minor extent, sevencoordinated sites. As the zirconia content increases, the fraction of seven-coordinated Zr-sites increases; this may be the cause of ZrO2 baddeleyite crystallization that was observed in some Zr-rich glasses investigated.
The corrosion of the glass-contact refractory Monofrax K-3 in two sodium-rich aluminosilicate mel... more The corrosion of the glass-contact refractory Monofrax K-3 in two sodium-rich aluminosilicate melts has been studied at 1208 and 1283°C using a modified ASTM procedure with constant agitation of the melt by air bubbling. The results for the monolithic refractory indicate a fast initial stage involving phase dissolution and transformation and a later “passivated” stage in which the surface of the refractory has been substantially modified. The composition of the stable spinel phase in the altered layer on monolithic coupons of K-3 is almost identical to the equilibrium composition bracketed by the dissolution of powdered K-3 into under-saturated melts on the one hand, and by crystallization of spinels from supersaturated melts on the other. The temperature and melt shear viscosity were found to have significant effects on the rates of K-3 dissolution and transformation.
ABSTRACT Glasses were prepared by systematic additions of P2O5, BaO, and PbO to glasses consistin... more ABSTRACT Glasses were prepared by systematic additions of P2O5, BaO, and PbO to glasses consisting of Al2O3-B2O3-(BaO)-CaO-Fe2O3-K2O-MgO-Na2O-(PbO)-(P2O5)-SiO2, and their chemical durability was examined by the EPA TCLP test. The addition of about 1 mol% P2O5 to a glass containing 5 mol% PbO increases the normalized lead leach rate (NLLR) by about 40 relative%, but increasing P2O5 to 2 mol% decreases the NLLR to about the NLLR obtained without P2O5. A similar, but more dramatic, behavior with changes in the NLLR of about 300 relative% is obtained by sequential combined additions of 1 mol% each of P2O5 and BaO to a glass containing 1 mol% PbO.
... the samples of interest for all three elements. Silica-rich glasses consist of a polymerized ... more ... the samples of interest for all three elements. Silica-rich glasses consist of a polymerized network dominated by silicate tetrahedra as well as network modifying cations, such as Na. Al can play dual roles in silicate structures ...
We report the growth, structural characterization, and magnetic properties of ferromagnetic Fe0.8... more We report the growth, structural characterization, and magnetic properties of ferromagnetic Fe0.8Ga0.2 nanowires that are grown on quartz substrates by electrospinning. Electrospun nanowires are annealed in ultrahigh purity argon-hydrogen gas mixture. Uniform, continuous, high aspect ratio FeGa nanowires with diameters in the range of 50-500 nm and lengths of up to 500 mum are grown. Hysteresis loops were measured with
Uploads
Papers by Andrew Buechele