Femtosecond laser writing of buried waveguides in erbium III-Doped oxyfluoride glasses and nano-glass-ceramics

Femtosecond-pulsed laser writing of waveguides, a few mm long, is demonstrated; waveguides were written orthogonally to the writing beam inside the bulk of ErIII-doped oxyfluoride glasses at a depth of 160 mum. The writing beam was 795 nm wavelength, 54 fs pulse duration and 11 MHz repetition rate. Tracks were written at pulse energies of 13.1 nJ to 26.1 nJ and sample translational velocity of 10 mmmiddot.s-1 to 28 mmmiddots-1. The influence of translational velocity and pulse energy on the cross-sectional shape and integrity of the written tracks is reported. Tracks tend to be narrower as the pulse energy is lowered or translational velocity decreased. Above 22.9 nJ, pulse energy, tracks tend to crack. The estimated refractive index profile of one track has a maximum increase of refractive index of 0.003 at the centre. These glasses normally form nano-glass-ceramics on heat treatment just above the glass transformation temperature (Tg). Here, a post-fs-writing heat-treatment just above Tg causes nano-ceramming of the glass sample and removes a light-guiding peripheral region of the fs-written tracks suggesting that this region may have been fs-modified by stress alone. Waveguiding at 651 nm and 973 nm wavelengths, and upconversion, are demonstrated in optimally written tracks.

Interaction of fluorescence of resin cements with glass ceramics

Poster presented at the 24th Annual Meeting of the Portuguese Dental Association, Lisbon, 12-14 November 2015.

Crystallization Kinetics and Electrical Relaxation of BaO-0.5Li(2)O-4.5B(2)O(3) Glasses

Transparent glasses in the composition BaO-0.5Li(2)O-4.5B(2)O(3) (BLBO) were fabricated via the conventional melt-quenching technique. X-ray powder diffraction combined with differential scanning calorimetric (DSC) studies carried out on the as-quenched samples confirmed their amorphous and glassy nature, respectively. The crystallization behavior of these glasses has been studied by isothermal and nonisothermal methods using DSC. Crystallization kinetic parameters were evaluated from the Johnson-Mehl-Avrami equation. The value of the Avrami exponent (n) was found to be 3.6 +/- 0.1, suggesting that the process involves three-dimensional bulk crystallization. The average value of activation energy associated with the crystallization of BLBO glasses was 317 +/- 10 kJ/mol. Transparent glass-ceramics were fabricated by controlled heat-treatment of the as-quenched glasses at 845 K/40 min. The dielectric constants for BLBO glasses and glass-ceramics in the 100 Hz-10 MHz frequency range were measured as a function of the temperature (300-925 K). The electrical relaxation and dc conductivity characteristics were rationalized using electric modulus formalism. The imaginary part of the electric modulus spectra was modeled using an approximate solution of the Kohlrausch-Williams-Watts relation. The temperature-dependent behavior of stretched exponent (beta) was discussed for the as-quenched and heat-treated BLBO glasses.

Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials

The advent of high optical quality transparent nano—structured glasses, the so-called transparent glass ceramics or vitroceramics disclosed the possibility of producing nano-sized photonic devices based on rare-earth doped up—converters. Transparent glass ceramics have been investigated as hosts for lanthanide ions envisioning the production of materials that are easy to shape and with high performance for photonic applications. Rare earth doped glasses have been extensively studied due to their potential applications in optical devices such as solid state lasers and optical fibers. Various photothermal and optical techniques have been successfully applied for the thermal and optical characterization of these rare earth doped materials. In the present thesis, the effective thermal parameters like thermal diffusivity and thermal effusivity of complex materials for various applications have been investigated using photothermal methods along with their optical characterization utilising the common optical absorption as well as fluorescence spectroscopic techniques. These sensitive optical procedures are also essential for exploiting these materials for further photonic applications.

Estudo estrutural e cristalização em vidros fluorogermanatos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vidros e vitrocerâmicas em sistemas oxifluoretos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudos estruturais em vidros e vitrocerâmicas contendo 'PBF IND.2'-'CDF IND.2

Pós-graduação em Química - IQ

Dielectric anomaly in strontium borate-bismuth vanadate glass nanocomposite

Transparent glass nanocomposites in the pseudo binary system (100 - x) SrB4O7 (SBO)-x Bi2VO5.5 (BiV) (0 less than or equal to n less than or equal to 70) were prepared by the splat quenching technique. The nano-crystallization of bismuth vanadate (BiV) in 50 SBO-50 BiV (in mol%) glass composite has been demonstrated. These were characterized for their structural, thermal and dielectric properties. As-quenched composites under study have been confirmed to be amorphous by X-ray powder diffraction (XRD) studies. The glass transition temperature (T-g) and crystallization temperatures (T-er) were determined using differential thermal analyses (DTA), High resolution transmission electron microscopic (HRTEM) studies carried out on heat-treated samples reveal the presence of spherical nanosize crystallites of Bi2VO5.5 (BiV) dispersed in the glassy matrix of SrB4O7 (SSO). The dielectric constant (epsilon (r)) and the dielectric loss (D) measurements were carried out on the as-quenched and heat-treated glass nanocomposite samples in the frequency range 100 Hz-10 MHz. The as-quenched and the heat-treated at two different temperatures (720 and 820 K) samples exhibited broad dielectric anomalies in the vicinity of the ferroelectric-to-paraelectric transition temperature of the parent BiV ceramics. The Curie-Weiss law was found to be valid at a temperature above the transition temperature, establishing the diffused nature of the transition. (C) 2001 Elsevier Science Ltd. All rights reserved.

Fabrication of Transparent BaNaB9O15 Glass-Microcrystal Composites

Transparent glasses in the BaO-Na2O-B2O3 (BNBO) system were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were confirmed by x-ray powder diffraction (XRD) and differential thermal analysis (DTA), respectively. Cyclic heat treatment of the as-quenched glasses yielded transparent glass-microcrystal composites. The volume fraction of the crystallites and their sizes could be easily controlled by this process. Heat-treated samples were highly transparent owing to the minimum mismatch between the refractive indices of the crystallites and the glass residual matrix. BNBO samples that were heat treated at 540A degrees C for 4 h for 10 cycles were found to be 60% to 70% transparent in the 500 nm to 900 nm wavelength range.

Influence of heat treatment on spectroscopic properties of Er3+ in multicomponent ZrF4-ZnF2-AlF3-YF3-MF2 (M = Ca, Sr, Ba) based glass

Er3+ doped multicomponent fluoride based glass was prepared. These precursor fluoride glass samples were then heated using different schedules. Crystalline phase particles were successfully precipitated in the multicomponent fluoride glass samples after heat treatment. The influence of heat treatment on the spectroscopic properties of Er3+ in multicomponent fluoride based glass samples were discussed. Small changes of the Judd-Ofelt parameters Omega(i) (i = 2,4,6) were found in multicomponent fluoride glass samples before and after heat treatment compared to oxyfluoride telluride glass. Preparation conditions used to produce transparent multicomponent fluoride glass ceramics doped with rare-earth ions are discussed. (c) 2007 Elsevier B.V. All rights reserved.

Flexural Strength of Glass-Infiltrated Zirconia/Alumina-Based Ceramics and Feldspathic Veneering Porcelains

Purpose: To compare the flexural strength of two glass-infiltrated high-strength ceramics and two veneering glass-ceramics.Materials and Methods: Four ceramic materials were tested: two glass-infiltrated high-strength ceramics used as framework in metal-free restorations [In-Ceram Zirconia IZ (Gr1) and In-Ceram Alumina IA (Gr2)], and two glass-ceramics used as veneering material in metal-free restorations [Vita VM7 (Gr3) and Vitadur-alpha (Gr4)]. Bar specimens (25 x 5 x 2 mm(3)) made from core ceramics, alumina, and zirconia/alumina composites were prepared and applied to a silicone mold, which rested on a base from a gypsum die material. The IZ and IA specimens were partially sintered in an In-Ceram furnace according to the firing cycle of each material, and then were infiltrated with a low-viscosity glass to yield bar specimens of high density and strength. The Vita VM7 and Vitadur-alpha specimens were made from veneering materials, by vibration of slurry porcelain powder and condensation into a two-part brass Teflon matrix (25 x 5 x 2 mm(3)). Excess water was removed with absorbent paper. The veneering ceramic specimens were then removed from the matrix and were fired as recommended by the manufacturer. Another ceramic application and sintering were performed to compensate the contraction of the feldspar ceramic. The bar specimens were then tested in a three-point bending test.Results: The core materials (Gr1: 436.1 +/- 54.8; Gr2: 419.4 +/- 83.8) presented significantly higher flexural strength (MPa) than the veneer ceramics (Gr3: 63.5 +/- 9.9; Gr4: 57.8 +/- 12.7).Conclusion: In-Ceram Alumina and Zirconia were similar statistically and more resistant than VM7 and Vitadur-alpha.

Thermal properties of 3BaO-3TiO(2)-B2O3 glasses

Transparent glasses in the system 3BaO-3TiO2-B2O3 (BTBO) were fabricated via the conventional melt-quenching technique. The as-quenched samples were confirmed to be non-crystalline by differential thermal analysis (DTA). Thermal parameters were evaluated using non-isothermal DTA experiments. The Kauzmann temperature was found to be 759 K based on heating-rate-dependent glass transition and crystallization temperatures. A theoretical relation for the temperature-dependent viscosity is proposed for these glasses and glass-ceramics.

Edge of Danger: electric light and the negotiation of public and private domestic space in Philip Johnson's Glass and Guest House

In the first half of the twentieth century the dematerializing of boundaries between enclosure and exposure problematized traditional expectations of the domestic environment. At the same time, as a space of escalating technological control, the modern domestic interior also offered new potential to redefine the meaning and means of habitation. The inherent tension between these opposing forces is particularly evident in the introduction of new electric lighting technology and applications into the modern domestic interior in the mid-twentieth century. Addressing this nexus of technology and domestic psychology, this article examines the critical role of electric lighting in regulating and framing both the public and private occupation of Philip Johnson's New Canaan estate. Exploring the dialectically paired transparent Glass House and opaque Guest House, this study illustrates how Johnson employed electric light to negotiate the visual environment of the estate as well as to help sustain a highly aestheticized domestic lifestyle. Contextualized within the existing literature, this analysis provides a more nuanced understanding of the New Canaan estate as an expression of Johnson's interests as a designer as well as a subversion of traditional suburban conventions.