| 1. |
- Druenert, F., et al.
(författare)
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Copper-based opaque red glasses - Understanding the colouring mechanism of copper nanoparticles in archaeological glass samples
- 2018
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 76, s. 375-381
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Tidskriftsartikel (refereegranskat)abstract
- Red opaque glasses of two different sites in central Germany, a medieval glassworks in Glashutten, Taunus Mountains, and an early modern glassworks in Wieda, Harz Mountains, were analysed with regard to their optical appearance. By scanning electron microscopy and X-ray diffraction, metallic copper nanoparticles were identified as a conspicuous constituent in these glasses. In addition, similar opaque red glasses were reproduced in the laboratory in order to better understand the manufacturing process. Detailed analysis of the optical scattering was conducted in order to evaluate the role of Cu-0 nanoparticles in the colouring mechanism relative to other possible reasons of colouration. We find clear differences between the possible contributions of Cu2O (cuprite) particles and metallic copper (Cu-0) nanoparticles. Through simulated backscattering spectra we were able to calculate an average copper particle radius in the archaeological glass samples resulting in a value of up to 95 nm, which matches well the results of SEM investigation (minimum 65 nm). Using the methods we applied in this study, it becomes possible to reconstruct various processing conditions as they were applied in medieval manufacture of these particular materials. (C) 2018 Elsevier B.V. All rights reserved.
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| 2. |
- Efthimiopoulos, I., et al.
(författare)
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Femtosecond laser-induced transformations in ultra-low expansion glass : Microstructure and local density variations by vibrational spectroscopy
- 2018
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 123:23
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Tidskriftsartikel (refereegranskat)abstract
- We report X-ray diffraction, resonance Raman, and infrared (IR) results on pristine ultra-low expansion (ULE) glass, a binary titanosilicate glass with 5.67 mol. % TiO2. ULE processing by femtosecond (fs) laser radiation leads to nanograting writing and photo-darkening for imaging and data storage. We investigate here the vibrational/structural changes induced by fs laser irradiation of ULE at 515 nm. Optical imaging revealed the formation of micro-cavities, and Raman mapping showed molecular oxygen trapped in such cavities of laser-irradiated ULE glass. While titanium in the pristine glass was found predominantly in tetrahedral Ti4+ sites highly dispersed in the silicate matrix, Raman and IR reflectance spectroscopy on laser-irradiated ULE indicated the formation of Ti3+ sites; Ti3+ octahedral sites are formed in the shells of cavities and aggregate in amorphous Ti2O3-type clusters, while the glass around and below cavities contains Ti3+ tetrahedral sites dispersed in the silicate network. Laser-processed ULE glass was found to also exhibit local restructuring of the silicate matrix. Shifts of the strong IR band at about 1080-1100 cm(-1) were translated into changes of the average Si-O-Si bond angle in the laser-transformed areas and found to reflect local density variations; the average local density increases relative to silica glass up to about 8% in the shells of micro-cavities and decreases by about 0.5% in the surrounding material. Chemical processes were proposed to account for photo-darkening and the local structural transformation effect in the probed areas of the fs laser-processed ULE glasses. Published by AIP Publishing.
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