Valorization of sugarcane bagasse ash: Producing glass-ceramic materials

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

Estudo da infiltração marginal em restaurações de resinas compostas para dentes posteriores: efeito de material, preparo cavitário e condicionamento do esmalte a nível cervical

Pós-graduação em Odontologia Restauradora - ICT

On observation of the downconversion mechanism in Er3+/Yb3+ co-doped tellurite glass using thermal and optical parameters

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fabrication of Yb3+/Er3+ codoped Bi2O3-WO3-TeO2 pedestal type waveguide for optical amplifiers

We report, for the first time to our knowledge, experimental results on pedestal waveguides produced with Yb3+/Er3+ codoped Bi2O3-WO3-TeO2 thin films deposited by RF Sputtering for photonic applications. Thin films were deposited using Ar/O-2 plasma at 5 mTorr pressure and RF power of 40 W on substrates of silicon wafers. The definition of the pedestal waveguide structure was made using conventional optical lithography followed by plasma etching. Propagation losses around 2.0 dB/cm and 2.5 dB/cm were obtained at 633 and 1050 nm, respectively, for waveguides in the 20-100 mu m width range. Single-mode propagation was measured for waveguides width up to 10 mu m and 12 mu m, at 633 nm and 1050 nm, respectively; for larger waveguides widths multi-mode propagation was obtained. Internal gain of 5.6 dB at 1530 nm, under 980 nm excitation, was measured for 1.5 cm waveguide length (similar to 3.7 dB/cm). The present results show the possibility of using Yb3+/Er3+ codoped Bi2O3-WO3-TeO2 pedestal waveguide for optical amplifiers. (C) 2014 Elsevier B.V. All rights reserved.

Electrical conductivity of Ag-Na ion exchanged soda-lime glass

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

Efeito da aplicação do fluido de corte na usinagem da superliga Nimonic 80A

The nickel alloys have a chemical composition with high tenor of alloy elements which are responsible for the material's mechanical and thermal properties, but also are the main causative of problems during the machining, making the process difficult. The objective of this work is the study of the machining by external cylindrical turning of the nickel based alloy Nimonic 80A, seeking the machining optimization of this alloy, seeking the best condition of lubricant fluid use, providing real increases of productivity without the need of investments in new production means. Besides, the results of this work should offer more detailed information regarding the behavior of this alloy in relation to machining by turning. The machining experiences were accomplished in a specimen of the nickel alloy, considering the machining parameters: cutting speed (75 and 90 m/min), cutting depth (0,8 mm) and feed rate (0,15 and 0,18 mm/v). The valuations were accomplished in a CNC lathe and tools with of hard metal inserts. After each stage of the turning the measures of the cutting length were accomplished, of the waste of the tools through a magnifying glass (8x) and the roughness of the specimen evaluated in each phase of the process, with the aid of a portable roughness meter. Through light optical microscopy it was possible to observe the wear of the cutting tools for each appraised condition. The roughness values, Ra and Ry, for the appraised conditions were always superiors to the theoretical values. After analysis of the results it was possible to end that, the best acting for this work strip tested it was obtained for ap=0,8mm: f=0,15mm/rev and VC=75m/min, what resulted in a larger cutting length (1811 m)

Preparação e caracterização de vidros contendo nanopartículas de Ag

This work consists of preparation and characterization of glasses containing transition noble metals and the study of optical properties of such materials. The glasses were prepared by quenching of the glass melt followed by heat treatment and polishing of the monoliths. The structural characterization of glasses was made using differential thermal analysis, X-ray, Raman and infrared spectroscopies, while the optical properties were studied by UV-Vis and M-Lines spectroscopies. Preliminary results have shown that the color of the glasses is dependent on both concentration of silver and the melting temperature of the melt. Controlled heat treatments have been used to induce the crystallization of Ag nanoparticles within the glass. The study of crystallization was accompanied by electron microscopy and UV-Vis spectroscopy. Data from electron diffraction, as well as chemical analysis, EDX, were obtained using a transmission electron microscope. EDX data have shown that the atomic percentage of Ag is higher on the nanoparticle. X-ray diffraction was used in order to characterize the composition of the crystals and cubic AgCl was identified as the main crystallized nanophase obtained after annealing

Vitrocerâmicas porosas via conformação e consolidação com amidos

The search for new methods of manufacture of glass-ceramics with controlled porosity and permeability is interesting of the industrial and commercial point of view, and a challenge of great complexity. Porous glass-ceramics produced by sintering and crystallization of glasses can find applications, for example, as filters, materials with bactericidal properties, bio-implants, as catalytic and enzymes supports, among others. An alternative and low cost method of ceramic manufacture reaching different levels of porosity, for diverse purposes, is the conformation assisted by addition of starch, known as consolidation with starch. The objective of this project is to study the process of conformation with starch for making porous glass-ceramics from a commercial glass in the system Na2O-CaO-SiO2, whose kinetics of sintering by viscous flow and surface crystallization are known. The method of conformation with starches is innovative for glass-ceramics and its development opens the way for obtaining a new class of materials. We found a possible route for the production of porous compacts of glass particles, from the powder preparation to the removal of starch. It was observed that a glass powder obtained by dry milling in a ball mill with alumina balls for 24 h, afterwards mixed with water in an eccentric ball mill for 2 h, without the addition of a deflocculant, and subsequently mixed with starch also in an eccentric ball mill for 5 min resulted in slurries stable against sedimentation

Vitrocerâmicas para blindagens balísticas

The use of ceramic materials in ballistic armor is considerable. Such materials can be very harder and lighter than metallic materials commonly used and it presents advantages to replace metallic materials when necessary toughness can be achieved. However, as SiC and Al2O3 ceramic, traditionally used for shielding, still have high manufacturing cost or low density do not have enough to shield applications such as aircraft. An alternative is the glass-ceramics, ceramics obtained by controlled crystallization of glasses, whose properties can be adjusted by choosing the chemical composition of glass, heat treatment of crystallization and special treatments such as ion exchange on the surface, resulting in increased mechanical strength . The objective of this project is to study the kinetics of crystallization of a glass composition based on cordierite (2MgO.2Al2O3.5SiO2), low density and high hardness, for the manufacture of glass-ceramics for ballistic tests. Shown in this report are results of heat treatment of crystallization and characterization by thermal analysis (DSC) glass obtained previously, indicating uneven distribution of crystals, and drying, weighing, mixing of raw materials and a new fusion of glass, the same composition

Propriedades físicas de vidros Sb2O3-P2O5

This work presents experimental results of some physical properties of antimony phosphate glasses with compositions (x) Sb2O3 - (1-x) P2O5 (x = 0.75, 0.85, 0.90). Mechanical, thermal, optical and electrical properties were investigated: density, elastic moduli (Young's moduli and Poisson's ratio), Vickers microhardness, coefficient of thermal expansion, glass transition temperature, refractive index and electrical conductivity (for x = 0.75). There was no evidence of electronic conductivity by bipolaron hopping. Measurements of energy dispersive spectroscopy (EDS) showed that volatilization of Sb2O3 takes place during the glass melting

Estudo das propriedades físicas em materiais vítreos do sistema 50B2O3 - 15CuO - 20Li2O - 15X (X= Na2O, K2O, RbCI e Cs2O)

The increasing demand for devices for solid state applications in many technological areas has resulted in a high demand for new materials. Among these material have the advantage of being manufactured with different chemical compositions, and may have physical properties equal to or higher than the corresponding crystalline material. The aim of this paper was to produce borate glass system 50B2O3 – 15CuO – 20Li2O – 15X (X = Na2O, K2O, RbCl e Cs2O) to analyze the influence of the atomic radius of alkali in the physical properties of this glass system. The glasses were synthesized by the process of melting and molding. The characteristic temperatures were determined by the technique of scanning calorimetry (DSC). The non-crystalline was determined by x-ray diffraction. In order to determine the molar volume a density measurement by using the Archimedes method was used. The structural characterization was carried out using the technique of infrared spectroscopy

White Light and Multicolor Emission Tuning in Triply Doped Yb3+/Tm3+/Er3+ Novel Fluoro-phosphate Transparent Glass-ceramics

New Yb3+, Er3+ and Tm3+ doped fluoro-phosphate glasses belonging to the system NaPO3–YF3–BaF2–CaF2 and containing up to 10 wt% of rare-earth ion fluorides were prepared and characterized by differential scanning calorimetry, absorption spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and homogeneous glass-ceramics have been reproducibly obtained with a view to manage the red, green and blue emission bands and generate white light. X-ray diffraction as well as electron microscopy techniques have confirmed the formation of fluorite-type cubic nanocrystals at the beginning of the crystallization process while complex nanocrystalline phases are formed after a longer heat-treatment. The prepared glass-ceramics exhibit high optical transparency even after 170 h of thermal treatment. An improvement of up-conversion emission intensity – from 10 to 160 times larger – was measured in the glass-ceramics when compared to the parent glass, suggesting an important incorporation of the rare-earth ions into the crystalline phase(s). The involved mechanisms and lifetime were described in detail as a function of heat-treatment time. Finally, a large range of designable color rendering (from orange to turquoise through white) can be observed in these materials by controlling the laser excitation power and the crystallization rate.

Tailoring the refractive index of Ge-S based glass for 3D embedded waveguides operating in the mid-IR region

The photosensitivity of GeSx binary glasses in response to irradiation to femtosecond pulses at 800 nm is investigated. Samples with three different molecular compositions were irradiated under different exposure conditions. The material response to laser exposure was characterized by both refractometry and micro-Raman spectroscopy. It is shown that the relative content of sulfur in the glass matrix influences the photo-induced refractive index modification. At low sulfur content, both positive and negative index changes can be obtained while at high sulfur content, only a positive index change can be reached. These changes were correlated with variations in the Raman response of exposed glass which were interpreted in terms of structural modifications of the glass network. Under optimized exposure conditions, waveguides with positive index changes of up to 7.8x10−3 and a controllable diameter from 14 to 25 μm can be obtained. Direct inscription of low insertion losses (IL = 3.1 – 3.9 dB) waveguides is demonstrated in a sample characterized by a S/Ge ratio of 4. The current results open a pathway towards the use of Ge-S binary glasses for the fabrication of integrated mid-infrared photonic components.

Proposta de melhoria do layout de um armazém de vidros automotivos

This work was based on a case study of improvement of the warehouse layout of a multinational automotive glass sector, located in the State of Sao Paulo. The aim was to propose a layout template to be more effective and besides optimizing production would also promote an increase in warehouse packaging capacity for metal containers containing glasses, thus reducing operating costs. To achieve the desired purpose, it was developed two layout proposals and to this end inventory management tools have been used, such as ABC curve and the Spaghetti Diagram, and other concepts of Packaging Engineering and Logistics. By the end of this work, it was obtained as a result, a project in which it was possible to rearrange the packages according the demand, and the developed changes became the most efficient layout both in storage capacity as well as in the internal drive

EStudo fundamental da interação de nanopartículas metálicas com íons terras raras em vidros e vitrocerâmicas para aplicações na região do infravermelho

Pós-graduação em Química - IQ