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Bucharest, Romania

Elisa M.,Romanian National Institute for Optoelectronics | Iordanescu R.,Romanian National Institute for Optoelectronics | Sava B.A.,National Institute of Glass | Aldica G.,National Institute of Materials Physics Bucharest | And 8 more authors.
Journal of Materials Science | Year: 2011

The article reports the preparation and complex characterization of iron-containing phosphate glasses considered to be ecological materials, as they contain nontoxic compounds related to environment. The oxide system Li 2O-MgO-(CaO)-Al2O3-P2O 5-(FeO/Fe2O3) was investigated in respect to its structural changes caused by MgO replacement with CaO and by the iron addition. UV-vis-NIR (ultraviolet-visible-near infrared) spectroscopy as well as thermo-gravimetric (TG) measurements, differential thermo-analysis (DTA), X-ray diffraction (XRD) analysis, electronic paramagnetic resonance (EPR), and Mossbauer (nuclear gamma resonance) spectroscopy have been used to investigate redox states and coordination symmetry of iron, together with vitreous network changes during the heat treatment up to 1000 °C. UV-vis-NIR transmission spectroscopy revealed no structural modifications when MgO was substituted by CaO, but noteworthy absorption bands attributed to Fe2+/Fe3+ species. TG analysis made in the 20-1000 °C range shows low weight loss accompanied by several thermal effects, as evidenced by DTA. XRD patterns for the glass samples heat treated at about 700 °C revealed the presence of different phosphate crystalline phases containing Mg, Al, and Fe ions. EPR spectroscopy revealed the presence of paramagnetic Fe3+ ions and the change of the first coordination symmetry, when the samples are heated below the vitreous transition temperature. Mossbauer spectroscopy has evidenced two paramagnetic species, Fe2+ and Fe3+, both in octahedral coordination symmetry and a clustering process supported by only Fe3+ ions. © Springer Science+Business Media, LLC 2010. Source


Elisa M.,Romanian National Institute for Optoelectronics | Vasiliu I.C.,Romanian National Institute for Optoelectronics | Sava B.A.,National Institute of Glass | Nastase F.,University of Bucharest | And 5 more authors.
Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B | Year: 2010

This work is focused on obtaining and characterizing Of SiO 2-P2O5-Nd2O3 sol-gel thin films. Structural and morphological information were obtained by Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The preparation of sol-gel films started with tetraethoxysilane (TEOS) as precursor for SiO 2, triethylphosphate (TEP) as precursor for P2O 5 and NdCl3 as precursor for Nd2O3. The thin films were obtained by spin coating at three rotation speeds: 2000, 3500 and 5000 rpm. The deposition of the films was undertaken one day after the preparation of the precursor sols and the drying of the obtained layers took place in air, at room temperature (RT). FTIR spectra recorded in the 400-4000 cm-1 range revealed optical phonons characteristic of Si-O-Si, P-O-P, Si-O-P and OH bonds. Raman spectra collected in the 100-4000 cm-1 range provided evidence of stretching, bending and mixed vibration modes specific to the silicophosphate network as well as to Nd-O bonds. AFM analysis revealed that Nd-doped silicophosphate films were relatively uniform in thickness and chemically homogeneous, these features depending on the spinning rate of the substrate. SEM investigations made on films obtained for three spinning speeds indicated the presence of randomly distributed small units and round micro-units. Source


Ursu L.D.,National Institute of Glass | Diaconu A.,National Institute of Glass | Alexandru Sava B.,National Institute of Glass | Volceanov A.,Polytechnic University of Bucharest
UPB Scientific Bulletin, Series B: Chemistry and Materials Science | Year: 2011

The paper presents a study of the industrial waste incorporating in glass (the borosilicate glass cullet and sludge that contain heavy metals, mainly copper) in order to obtain decorative colored glasses. The samples properties such as thermal expansion coefficient and characteristic temperatures obtained from thermal expansion diagrams, UV-VIS-NIR transmission, hydrolytic stability, wetting angle and viscosity are investigated. Waste reusing in glass leads to reduction of raw materials amount in glass obtaining. Source


Elisa M.,Romanian National Institute for Optoelectronics | Sava B.A.,National Institute of Glass | Iordanescu R.,Romanian National Institute for Optoelectronics | Feraru I.,Romanian National Institute for Optoelectronics | And 9 more authors.
Optoelectronics and Advanced Materials, Rapid Communications | Year: 2010

The paper reports a study on lithium phosphate glasses, containing calcium or magnesium and ferric/ferrous oxides. Iron oxides provide high chemical stability against water and enhance the glass capacity to embed different chemical compounds. The wet synthesis method provides an enhanced homogeneity of the glass batch and improves the optical quality of the glass samples. FTIR and Raman spectroscopy revealed the network former role of P2O5 as well as the modifier/former role of iron. The vibration mode shifted at 1250 cm-1 is attributed to the iron that enters into the phosphate network, forming Fe-O-P bonds instead of P-O-P bonds. Source

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