Synthesis and characterization of a titanium phosphate-tellurite glass for Faraday rotators

This work is focused on investigation of thermal, structural, optical, magnetic, and magneto-optical properties of novel titanium phosphate-tellurite glass applied as Faraday rotators. The glass belonging to the system 35Li₂O–10Al₂O₃–5TiO₂–45P₂O₅–5TeO₂ was prepared by a nonconventional wet route of raw materials processing, followed by melting-quenching-annealing steps. Some important physical properties of the investigated glass have been measured and calculated, providing knowledge related to glass compactness, electronic structure, glass forming capability, etc. XRD analysis evidenced an amorphous network structure of the investigated glass. The optical absorption in the Vis domain is mainly due to Ti³⁺ ions and Te₂ clusters formed during the glass melting process. A relatively low optical absorption is noticed over 600 nm that activates a significant Faraday magneto-optical effect. Photoluminescence bands in the blue, red, and infrared domains are observed, caused by Te₂ clusters formed during the glass melting process. The magnetization in dependency on applied magnetic field reveals a complex behavior of the glass, depending on temperature. Thus, it is found a ferromagnetic behavior up to 2000 Oe, a paramagnetic component up to 40 000 Oe, followed by a diamagnetic one over 40 000 Oe. Faraday rotation angle and Verdet constant values in the visible domain are correlated with the reduced TeO₂ content of the glass.     

Features of the mechanical properties of phosphate glasses doped with rare earth elements under indentation

The microstructure, as well as the mechanical and thermal properties, of phosphate glasses (PhGs) doped with rare earth elements (REEs), namely, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, and Yb, were studied in the present paper. The strength parameters of the PhGs and their dependence on the load value modification were estimated by the dynamic indentation method. Three specific stages were revealed in the deformation process, including nano-, submicro-, and microdeformation. The factors responsible for each stage were determined. It was shown that the strength properties (Young’s modulus and hardness) and the thermal characteristics (the lower and upper annealing temperature, the softening temperature, and the vitrification temperature) exhibit no evident relationship with the atomic mass and ionic radius of an REE. An assumption was made that the elastic and plastic properties of PhGs can be determined by the internal structure of the glasses.     

Preparation method and thermal properties of samarium and europium-doped alumino-phosphate glasses

The present work investigates alumino-phosphate glasses from Li₂O–BaO–Al₂O₃–La₂O₃–P₂O₅ system containing Sm³⁺ and Eu³⁺ ions, prepared by two different ways: a wet raw materials mixing route followed by evaporation and melt-quenching, and by remelting of shards. The linear thermal expansion coefficient measured by dilatometry is identical for both rare-earth-doped phosphate glasses. Comparatively to undoped phosphate glass the linear thermal expansion coefficient increases with 2 × 10⁻⁷ K⁻¹ when dopants are added. The characteristic temperatures very slowly decrease but can be considered constant with atomic weight, atomic number and f electrons number of the doping ions in the case of T_g (vitreous transition temperature) and T_sr (high annealing temperature) but slowly increase in the case of T_ir (low annealing temperature–strain point) and very slowly increase, being practically constant in the case of T_D (dilatometric softening temperature). Comparatively to undoped phosphate glass the characteristic temperatures of Sm and Eu-doped glasses present lower values. The higher values of electrical conductance for both doped glasses, comparatively to usual soda-lime-silicate glass, indicate a slightly reduced stability against water. The viscosity measurements, showed a quasi-linear variation with temperature the mean square deviation (R²) being ranged between 0.872% and 0.996%. The viscosity of doped glasses comparatively to the undoped one is lower at the same temperature. Thermogravimetric analysis did not show notable mass change for any of doped samples. DSC curves for both rare-earth-doped phosphate glasses, as bulk and powdered samples, showed T_g values in the range 435–450 °C. Bulk samples exhibited a very weak exothermic peak at about 685 °C, while powdered samples showed two weak exothermic peaks at about 555 °C and 685 °C due to devitrification of the glasses. Using designed melting and annealing programs, the doped glasses were improved regarding bubbles and cords content and strain elimination.     

Bismuth and lead oxides codoped boron phosphate glasses for Faraday rotators

New magneto-optical vitreous materials were obtained by melting-quenching technique comprising wet route raw materials preparation. The glass has the following composition in oxide mol. %: 10 Li₂O, 9 Al₂O₃, 5 ZnO, (35; 20; 50) B₂O₃, (35; 50; 20) P₂O₅, 3 Bi₂O₃, 3 PbO, phosphorus and boron oxide being the vitreous network formers. It was also prepared a similar reference glass composition but without Bi₂O₃ and PbO. Optical and structural characterization by ultraviolet-visible (UV–Vis), Fourier Transform Infrared (FTIR) and Raman Spectroscopy of the bulk glasses showed a transmission over 90%, metaphosphate structure of glass together with Q² boron oxide units and P–O?B bonds. The mechanical parameters, hardness (H), Young's modulus (E) and fracture toughness (K_IC) of boron phosphate glasses, evaluated by micro- and nanoindentation techniques, demonstrated mostly higher values in comparison with those for alumino-phosphate glasses due to mixed boro-phosphate network. Thermal behavior was investigated by Differential Scanning Calorimetry (DSC) putting in evidence the vitreous transition temperature which decreases with about 45 °C when Bi and Pb oxides were added and two crystallization effects. The diamagnetic character of a highly transparent Bi and Pb oxide co-doped boron phosphate glass was confirmed by ellipsometry, and the glass presented high magneto-optical properties at the top of the commercial bulk products.     

The surface morphology and strength properties of SiO2-P2O5-Nd2O3 glassy films

The surface morphology and microstructure of undoped and neodymium-doped silicate-phosphate films, as well as the strength characteristics (Young??s modulus and the hardness) of both the films and the SiO₂-P₂O₅-Nd₂O₃/SLG and SiO₂-P₂O₅/SLG composite structures, have been studied. A specific surface microstructure composed of the basic surface with imbedded round islands with a size of a few microns to a few tens of microns has been identified. The film??s microstructure has been shown to exhibit high stability over time after the long-term resting of these structures. It has been found that the films and the composite structures have fairly high strength properties.     

Physico-Chemical Characterisation of Lipids from <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> (L.) and <Emphasis Type="Italic">Rapana venosa</Emphasis> and their Healing Properties on Skin Burns

Black Sea molluscs and gastropods are the most studied organisms from the Romanian littoral zone. In particular, those from the Mytilidae species are of great interest because biochemical investigations have shown that they can be sources of biological active substances which can have different applications (e.g. food additives). We report here the extraction of lipids from two different species of molluscs (Mytilus galloprovincialis L., Mediterranean mussel) and gastropods (Rapana venosa, hard-shell clam). The extracts were evaluated in terms of antioxidant and composition properties and their healing properties were tested on skin burns in Wistar rats. Our studies proved that the two lipid extracts contained a relatively complex distribution of compounds, in terms of characteristic indices, polyunsaturated fatty acids (PUFA) and vitamins E and D. The presence of such compounds rendered the extracts very efficient in healing induced skin burns in Wistar rats. The histological analysis showed a reduction in the time of healing (12-13 and 13-15 days for the Mytilus galloprovincialis (L.) Rapana venosa extracts, respectively) compared to 20-22 for untreated animals, based on results from tissues and blood samples. Our investigations have been proved to be promising in terms of future potential applications of the extracts as skin-care products, cosmetics and/or pharmaceutical preparations owing to their dermorestitutive properties.     

Thermal properties of ecological phosphate and silicate glasses

The present work deals with ecological phosphate and silicate glasses that belong to the oxide systems: Li₂O-MgO-P₂O₅, Li₂O-CaO-P₂O₅, Li₂O-MgO-P₂O₅-Fe₂O₃; Li₂O-CaO-P₂O₅-Fe₂O₃ and SiO₂-R₂O-R′O (R = Na, K; R′ = Mg, Ca), the last system contains certain amounts of ZrO₂, ZnO, TiO₂. These ecological glasses do not contain toxic substances as BaO, PbO, As₂O₃, As₂O₅, fluorine, CdS, CdSe and they have applications as regards the retention and counteracting action of the harmful compounds resulted from the nuclear plants. The replacement of MgO by CaO leads to an insignificant increasing of the thermal expansion index and a slight decreasing of the characteristic temperatures, except the softening point where the effect is opposite. Adding of iron oxide in the phosphate glass composition causes the increasing of characteristic temperatures and the decreasing of thermal expansion index, both in MgO and CaO-containing phosphate glasses. The ecological silicate glasses are used as opal glasses free of fluorine as well as for lead-free crystal glass (CFP) where BaO and PbO are replaced by non-toxic oxides as K₂O, MgO, ZrO₂, and TiO₂. The paper presents different glass compositions and the technological parameters to prepare the ecological glass samples. Both ecological phosphate and silicate glasses have been characterized as regards the characteristic temperatures (vitreous transition point, low and high annealing points, softening point) and the thermal expansion coefficient. This study presents the changes of the thermal parameters when CaO replaces MgO in phosphate glass samples and the role of iron oxide in the vitreous network. In the case of silicate glasses, the viscosity and wetting angle dependency of temperature are presented. The elemental analysis of the ecological glasses was made by XPS (X-ray photoelectron spectroscopy) which also put in evidence the iron species from the vitreous network.