IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Quantitation of sulfate solubility in borosilicate glasses using Raman spectroscopy

Abstract: Raman spectroscopy is used here as an innovative technique to investigate sulfate content in borosilicate glasses. Using Raman spectroscopy after having heated the material, the evolution of sulfate amounts can be followed as a function of temperature, time and chemical composition of the starting matrix. The accu- racy of this technique was verified using electron probe micro analysis (EPMA), on two systems of glasses (SiO2-B2O3-Na2O (SBNa) and SiO2-B2O3-BaO (SBBa)) in order to compare the effect of alkaline or alka- line-earth elements on sulfur speciation and incorporation. To quantitate sulfate content with Raman spectroscopy, the integrated intensity of the sulfate band at 990 cm � 1 was scaled to the sum of the inte- grated bands between 850 and 1250 cm � 1 , bands that are assigned to Q n silica units. Calibration curves were then determined for different samples. The determination of sulfate contents with Raman spectros- copy analysis is possible with an accuracy of approximately 0.1 wt% depending on the composition of the glass. It mainly allows us to follow sulfate removal during the elaboration process and to establish kinetic curves of sulfate release as a function of the viscosity of the borosilicate glass.

Reconstructing the architectural evolution of volcanic islands from combined K/Ar, morphologic, tectonic, and magnetic data: the Faial Island example (Azores)

Abstract: The morpho-structural evolution of oceanic islands results from competition between volcano growth and partial destruction by mass-wasting processes. We present here a multi-disciplinary study of the successive stages of development of Faial (Azores) during the last 1 Myr. Using high-resolution digital elevation model (DEM), and new K/Ar, tectonic, and magnetic data, we reconstruct the rapidly evolving topography at successive stages, in response to complex interactions between volcanic construction and mass wasting, including the development of a graben. We show that: (1) sub-aerial evolution of the island first involved the rapid growth of a large elongated volcano at ca. 0.85 Ma, followed by its partial destruction over half a million years; (2) beginning about 360 ka a new small edifice grew on the NE of the island, and was subsequently cut by normal faults responsible for initiation of the graben; (3) after an apparent pause of ca. 250 kyr, the large Central Volcano (CV) developed on the western side of the island at ca 120 ka, accumulating a thick pile of lava flows in less than 20 kyr, which were partly channelized within the graben; (4) the period between 120 ka and 40 ka is marked by widespread deformation at the island scale, including westward propagation of faulting and associated erosion of the graben walls, which produced sedimentary deposits; subsequent growth of the CV at 40 ka was then constrained within the graben, with lava flowing onto the sediments up to the eastern shore; (5) the island evolution during the Holocene involves basaltic volcanic activity along the main southern faults and pyroclastic eruptions associated with the formation of a caldera volcano-tectonic depression. We conclude that the whole evolution of Faial Island has been characterized by successive short volcanic pulses probably controlled by brief episodes of regional deformation. Each pulse has been separated by considerable periods of volcanic inactivity during which the Faial graben gradually developed. We propose that the volume loss associated with sudden magma extraction from a shallow reservoir in different episodes triggered incremental downward graben movement, as observed historically, when immediate vertical collapse of up to 2 m was observed along the western segments of the graben at the end of the Capelinhos eruptive crises (1957-58).

Presence of sulfite (SIV) in arc magmas: Implications for volcanic sulfur emissions

Abstract: [1] The outstanding production of sulfur dioxide at arc volcanoes is not satisfactorily explained by most of the geochemical models involving the magmatic redox conditions. It is commonly accepted that sulfur is transported mainly as sulfide (SII−) and/or sulfate (SVI) by mantle-derived melts, before being released as SO2 and/or H2S in volcanic emissions. We present the first experimental evidence that other S-species coexist in water-rich arc basalts, by using X-ray microspectroscopy of olivine-hosted melt inclusions. In particular, we propose a new model involving sulfite (SIV) as the intermediate species dissolved in basaltic melts which results in highly efficient partitioning of sulfur into volcanic gas emissions at the origin of excess sulphur degassing observed at arc basaltic volcanoes.

Raman response of network modifier cations in alumino-silicate glasses.

Abstract: Raman scattering is performed in three sets of aluminosilicate glasses with light cations and concentrations varying from peralcaline to peraluminate domain. The depolarized spectra highlight two cation modes below ∼400 cm(-1). Comparison with infrared data reveals very stringent selection rules providing as much additional information for a vibrational analysis. The latter suggests in-phase (network-coupled) and out-of-phase (network-decoupled) displacements of the cations relative to their adjacent negatively charged structures. The low frequency vibration involves all cations whatever their role in the glass, network modifiers or charge compensators. Very interestingly, the second mode originates mostly from cations at modifier's places, providing thereby a new support for structural and chemical analysis of silicate glasses using Raman scattering.