Optical Transitions from Hexavalent Chromium in Lithium-Borate Glasses

The melt-quenching technique was used to prepare a series of chromium-doped borate glasses with the composition xCr2O3 - (70-x) B2O3- 30 Li2O- (x = 0, 0.1, 0.2, 0.3 and 0.5 mol %). The low-doping level here employed allowed to unambiguously identify well-defined near-edge Cr6+ optical transitions, and to precisely determine the optical band gap of the borate glass host. Additional Cr3+ transitions were observed in the visible regime, rendering a strong modulation of the glass color, from colorless to dark greenish, with Cr content. Both Cr6+(after the charge transfer transformation into Cr5+) and Cr3+oxidation states and their variations with Cr doping were identified from electron spin resonance spectroscopy. All samples exhibit similar vibrational spectra dominated by BO3 and BO4 structural units, with the development of weak Cr6+ vibration with Cr doping. The present study provides structurally similar but optically active and tunable glass hosts suitable for various optical applications.

Mineral pigment studies on ancient ceramics and glass artifacts from commercial settlements on Danube border between Muntenia and Dobruja

We analyzed the compositions of mineral pigments for some ceramics and glass items excavated from the commercial settlements on Danube at the border between Ottoman Empire (Dobruja) and Romanian Principalities — Piua Petrii and Dinogetia–Garvan, using external milli-beam PIXE. The problem of mineral pigments used for Turkish ceramics (16th–17th centuries) is very important for the understanding of commercial routes of late medieval period. We determined the elemental compositions of green, red, brown and especially blue pigments. The most interesting case is the one of the Co-based blue pigments. The origin of the raw materials for these pigments in the 17th century could be the mining district of Schneeberg in Germany, characterized by the presence of Ni traces, our study revealing a possible trade route connection between Saxony and Ottoman Empire. As concerning glass samples, we analyzed fragments of Byzantine painted bracelets identifying manganese (mixed with iron) and copper for blue–black bulk-glass color, respectively for green bulk-glass color, a mixture of lead and tin for yellow painting and powders of gold and silver for some painted areas.

Holocene tephrochronology of the lower Río Cisnes valley, southern Chile

Sediment cores from lakes and bogs in the Río Cisnes valley contain tephra from explosive eruptions of volcanoes in the southern part of the Andean Southern Volcanic Zone (SSVZ). These tephra, which thicken and coarsen to the west, are attributed to eruptions from Melimoyu, Mentolat, Hudson, and potentially either Macá, Cay or one of the many minor eruptive centers (MEC) located both along the Liquiñe-Ofqui Fault Zone (LOFZ) and surrounding the major volcanoes. Correlation of the tephra between two new cores in the lower Río Cisnes valley, and amongst other cores previously described from the region, and source volcano identification for the tephra, has been done using lithostratigraphic data (tephra layer thickness and grain size), petrography (tephra glass color, vesicle morphology, and type and abundance of phenocryst phases), and by comparison of bulk tephra trace-element characteristics with previously published whole-rock and bulk tephra chemical analysis. Four tephras in these cores are attributed to eruptions of Mentolat, four to eruptions from Melimoyu, one possibly to Hudson, and six cannot be assigned to a specific source volcano. Some of these tephra correspond to pyroclastic tephra fall deposits previously observed in outcrop, including the MEL2 eruption of Melimoyu and the MEN1 eruption of Mentolat. However, others have not been previously observed and represent the products of newly identified small to medium sized eruptions from volcanoes of the SSVZ. These results provide new information concerning the frequency and magnitude of explosive eruption of SSVZ volcanoes and contribute to the evaluation of volcanic hazards in the region.

Redox Effects of Erbium Oxide Doped Industrial Soda-Lime Glasses by UV-VIS-NIR Study

Redox states of soda lime glass melts have been widely studied by using variations of oxidizing and colorizing agents. In physical decolorizing process, the clear white glassware can be obtained by controlling the suitable amount and type of both oxidizing and colorizing agents in the batch formula. Erbium oxide (Er2O3) is interested in this study since it provides beautiful pink color and enhances optical properties of the glass. The aim of present work is to decolorized glasses by adjusting the redox number and using Er2O3 as a doping agent. The industrial soda-lime glasses were melted at 1450 °C for 3 hours and quenched in the air. Sodium sulfate (Na2SO4), Sodium nitrate (NaNO3), Antimony trioxide (Sb2O3) and carbon were used as the oxidizing agents. The redox states were calculated and adjusted by using the Simpson’s redox number concept. The oxide compositions of the glass samples were measured by XRF. The color of glass samples was examined by using UV-VIS spectrophotometer. The results show that by doping Er2O3 in glasses, the brightness of glasses is improved, and the glass color is located in the white zone of the color space diagram. The optimum glasses should have the ratio of Fe2+/Fetotal less than 0.10, and the redox number should not exceed 15. By using various kinds of oxidizing agent, the glass has more clear white color than using Na2SO4 alone.

Holocene tephrochronology around Cochrane (~47° S), southern Chile

Two Holocene tephras encountered in outcrops, cores and trenches in bogs, and lake cores in the area around Cochrane, southern Chile, are identified (based on their age, tephra glass color and morphology, mineralogy, and both bulk and glass chemistry) as H1 derived from Hudson volcano, and MEN1 derived from Mentolat volcano. New AMS radiocarbon ages indicate systematic differences between those determined in lake cores (MEN1=7,689 and H1=8,440 cal yrs BP) and surface deposits (MEN1=7,471 and H1=7,891 cal yrs BP), with the lake cores being somewhat older. H1 tephra layers range from 8 to 18 cm thick, suggesting that both the area of the 10 cm isopach and the volume of this eruption were larger than previously suggested, but not greatly, and that the direction of maximum dispersion was more to the south. MEN1 tephra layers range from 1-4 cm in thickness, indicating that this was probably a reasonably large (>5 km3) eruption. Some of the lake cores also contain thin layers (<2 cm) of late Holocene H2 tephra and the recent H3 (1991 AD) tephra, both derived from the Hudson volcano. No tephra evidence has been observed for any late Pleistocene tephra, nor for the existence of the supposed Arenales volcano, proposed to be located west of Cochrane.

Eco-Friendly Glass Color Coating Process Using RF Magnetron Sputtering

Color glasses are fabricated with Titanium target by RF magnetron sputtering. The physical properties of the Ti thin films are investigated according to preparation conditions, such as argon and oxygen gas flow ratio, RF power and Working pressure. The results indicate that it is possible to deposits various Ti thin film’s of different colors on glass substrate, such as yellow, orange, brown, purple. The thickness according to the color was analyzed using Veeco's Stylus profiler (model: dektak 6M).