Obtenção e caracterização de dióxido de estanho nanoestruturado pelo método de síntese contínua por combustão em solução

Continuous Synthesis by Solution Combustion was employed in this work aiming to obtain tin dioxide nanostructured. Basically, a precursor solution is prepared and then be atomized and sprayed into the flame, where its combustion occurs, leading to the formation of particles. This is a recent technique that shows an enormous potential in oxides deposition, mainly by the low cost of equipment and precursors employed. The tin dioxide (SnO2) nanostructured has been widely used in various applications, especially as gas sensors and varistors. In the case of sensors based on semiconducting ceramics, where surface reactions are responsible for the detection of gases, the importance of surface area and particle size is even greater. The preference for a nanostructured material is based on its significant increase in surface area compared to conventional microcrystalline powders and small particle size, which may benefit certain properties such as high electrical conductivity, high thermal stability, mechanical and chemical. In this work, were employed as precursor solution tin chloride dehydrate diluted in anhydrous ethyl alcohol. Were utilized molar ratio chloride/solvent of 0,75 with the purpose of investigate its influence in the microstructure of produced powder. The solution precursor flux was 3 mL/min. Analysis with X-ray diffraction appointed that a solution precursor with molar ratio chloride/solvent of 0,75 leads to crystalline powder with single phase and all peaks are attributed to phase SnO2. Parameters as distance from the flame with atomizer distance from the capture system with the pilot, molar ratio and solution flux doesn t affect the presence of tin dioxide in the produced powder. In the characterization of the obtained powder techniques were used as thermogravimetric (TGA) and thermodiferential analysis (DTA), particle size by laser diffraction (GDL), crystallographic analysis by X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and electrical conductivity analysis. The techniques used revealed that the SnO2 exhibits behavior of a semiconductor material, and a potentially promising material for application as varistor and sensor systems for gas

influência da adição de diferentes sais em pastas de cimento portland para cimentação de poços de petróleo

One of the great challenges at present time related with the materials area concerns of products and processes for use in petroleum industry, more precisely related to the Pre-salt area. Progresses were reached in the last years allowing the drilling of the salt layer, with the time reduction for drilling and larger success at the end. For the oil wells companies the preponderant factor is the technology, however, in spite of the progress, a series of challenges is still susceptible to solutions and one of them refers to the slurries preparation for cementing in those areas. Inside of this context, this study had for objective to analyze the influence of the salts NaCl, KCl, CaSO4 and MgSO4 in strength and chemical structure of the hydrated products. As methodology, they were prepared and analyzed cement slurries with varied concentrations of these salts that are commonly found in the saline formations. The salts concentrations used in formulations of the slurries were of 5%, 15% and 30%. The slurries were formulated with specific weight of 15,8 lb / gal and the cement used was Class G. Strength tests were accomplished in samples cured by 24 hours and 28 days. Also were realized crystallographic characterization (XRD) and morphologic (SEM). In agreement with the presented results, it is observed that the largest resistance values are attributed to the slurries with concentration of 15%. There was reduction of the strength values of the slurries formulated with concentration of 30%. Through the characterization microstructural it was possible to note the salts influence in the main cement hydrated products

Light-driven transport of plasmonic nanoparticles on demand

Laser traps provide contactless manipulation of plasmonic nanoparticles (NPs) boosting the development of numerous applications in science and technology. The known trapping configurations allow immobilizing and moving single NPs or assembling them, but they are not suitable for massive optical transport of NPs along arbitrary trajectories. Here, we address this challenging problem and demonstrate that it can be handled by exploiting phase gradients forces to both confine and propel the NPs. The developed optical manipulation tool allows for programmable transport routing of NPs to around, surround or impact on objects in the host environment. An additional advantage is that the proposed confinement mechanism works for off-resonant but also resonant NPs paving the way for transport with simultaneous heating, which is of interest for targeted drug delivery and nanolithography. These findings are highly relevant to many technological applications including micro/nano-fabrication, micro-robotics and biomedicine.

Spectral self-action of THz emission from ionizing two-color laser pulses in gases

The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields. We show that produced THz signals interact with free electron trajectories and thus significantly influence further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action contributes to the observed strong spectral broadening of the generated THz field. We show that diffraction of the generated THz radiation is the limiting factor for the co-propagating low frequency amplitudes and thus for the self-action mechanism in 2D and 3D geometries.

Evading Vacuum Noise: Wigner Projections or Husimi Samples?

The accuracy in determining the quantum state of a system depends on the type of measurement performed. Homodyne and heterodyne detection are the two main schemes in continuous-variable quantum information. The former leads to a direct reconstruction of the Wigner function of the state, whereas the latter samples its Husimi Q function. We experimentally demonstrate that heterodyne detection outperforms homodyne detection for almost all Gaussian states, the details of which depend on the squeezing strength and thermal noise.

Protein disulfide isomerase as a target for besnoitiosis therapy : molecular characterization and studies of its role in infection and host immune response

Tese de Doutoramento em Ciências Veterinárias na especialidade de Sanidade Animal

Síntesis, caracterización, propiedades eléctricas y electroquímicas de Na₃V₂-xAlx(PO₄)2F₃ (x=0,0.02, 0.05, 0.1) como cátodos para su aplicación en baterías de ion-litio

Propósito y Método del Estudio: La demanda de baterías recargables ha aumentado de manera significativa cada año durante la última década impulsada por las necesidades vinculadas con el desarrollo tecnológico (portabilidad, alto desempeño de dispositivos electrónicos, vehículos eléctricos). La batería ión-litio es el dispositivo de mayor consumo, está diseñado para el almacenamiento y conversión de energía eléctrica basado en electrodos de intercalación. En la actualidad los esfuerzos están dirigidos a la mejora y/o remplazo de los componentes actuales de las baterías: ánodo, cátodo (LiCoO2) y electrolito, por materiales que tengan más altos rendimientos en términos de energía, potencia, costo, confiabilidad, tiempo de vida y seguridad. En este trabajo de investigación se prepararon y caracterizaron cuatro compuestos Na3V2-xAlx(PO4)2F3 (x= 0, 0.02, 0.05, 0.1) como materiales catódicos para baterías ión-litio. Estos materiales se obtuvieron mediante el método Pechini. La caracterización morfológica y microestructural se llevó a cabo por Microscopia Electrónica de Barrido de Emisión de Campo (FESEM), el análisis textural por Fisisorción de N2 por la técnica BET; la composición química y cristalográfica se determinó por Espectroscopia de Emisión de Plasma de Acoplamiento Inductivo (ICP-OES), Espectroscopia de Energía Dispersiva de Rayos X (EDXS) y Difracción de Rayos X (XRD), mientras que por Espectroscopia de Impedancia Electroquímica (EIS) se realizó la caracterización eléctrica; por último la aplicación de los materiales como cátodos en baterías ión-litio se evaluó mediante pruebas Galvanostáticas de carga/descarga. Contribuciones y Conclusiones: Se establecieron las condiciones de síntesis para los materiales Na3V2-xAlx(PO4)2F3 x= 0, 0.02, 0.05 y 0.1 vía método Pechini. El dopaje de la fase Na3V2-xAlx(PO4)2F3 se llevó a cabo con éxito hasta x=0.1 moles de aluminio, dado que se conservó la estructura cristalina tetragonal del Na3V2(PO4)2F3 (JCPDS 01-089-8485). Los materiales obtenidos tienen una microestructura formada por partículas de forma granular de tamaño nanométrico (40-100nm), esto se atribuye al efecto del carbono residual en la muestra (en promedio 8% en peso) ya que inhibe el crecimiento de partícula, además que permite mejorar el contacto entre las partículas lo que beneficia a la conductividad electrónica del material. Los materiales obtenidos tienen en promedio un tamaño de poro de 20 nm, con un área superficial del orden 30 m2/g. La fase con 0.05 moles de aluminio presentó el mejor resultado bajo las condiciones de estudio. Conjuga dos de las características básicas de una batería, presenta una alta capacidad de carga/descarga (123/101 mAh/g a un voltaje de celda de 4.4 V vs Li) y una buena capacidad de retención (82%), en comparación al material sin dopar (128/63 mAh/g y 49% de retención). Por lo anterior, el dopaje de la fase Na3V2(PO4)2F3 con Al, logró la estabilización de la estructura frente a los procesos de ciclado. Por lo cual es un material prometedor para su aplicación como cátodos en baterías ión-litio o ión-sodio.

Construção de um aparato experimental para monitoramento in situ da deposição de filmes finos de titânio por magnetron sputtering

The technique of surface coating using magnetron sputtering is one of the most widely used in the surface engineering, for its versatility in obtaining different films as well as in the micro / nanometric thickness control. Among the various process parameters, those related to the active species of the plasma are of the most fundamental importance in the mechanism and kinetics of deposition. In order to identify the active species of the plasma, parameters such as gas flow, pressure and density of electric power were varied during titanium coating on glass substrate. By flowing argon gas of 10, 20, 30, 40 and 50 sccm (cubic centimeters per minute) for each gas flow a sequential scan of the electric current of 0.10, 0.20, 0.30, 0.40 , 0.50 A. The maximum value of 0.50 A was chosen based both on literature data and on limitations of the equipment. The monitoring of plasma species present during the deposition was carried out in situ by the technique of optical emission spectroscopy (OES) through the spectrometer Ocean Optics USB2000 Series. For this purpose, an apparatus was developed to adapt the OES inside the plasma reactor to stay positioned closest to the target. The radiations emitted by the species were detected by an optical fiber placed behind the glass substrate and their intensities as a function of wavelength were, displayed on a monitor screen. The acquisition time for each condition of the plain parameters was related to the minima of spectral lines intensities due to the film formed on the substrate. The intensities of different emission lines of argon and titanium were then analyzed as a function of time, to determine the active species and estimate the thickness of the deposited films. After the deposition, the coated glasses thin films were characterized by optical transmittance through an infrared laser. It was found that the thickness and deposition rate determined by in situ analysis were consistent with the results obtained by laser transmittance

Elaboración de un plan de negocios para la implementación de una óptica con consultorio optométrico en la localidad de Suba, Bogotá

Tesis (Optometra). -- Universidad de La Salle, Facultad de Ciencias de La Salud. Programa de Optometria, 2014

Interacción de la óptica geométrica con el ojo y sus defectos refractivos

Tesis (Optometra). -- Universidad de La Salle, Facultad de Ciencias de La Salud. Programa de Optometria, 2014

Subwavelength Index Engineering for SOI Waveguides

Photonic structures with a sub-wavelength pitch, small enough to suppress diffraction, can behave as equivalent homogenous materials that can be engineered to exhibit a specific refractive index and dispersion. Here we discuss the design of a variety of integrated photonic devices, ranging from grating couplers to multimode interference couplers, for which the use of sub-wavelength structures enables unique characteristics. We will place special emphasis on the design and experimental demonstration of multi-mode interference couplers with an unprecedented bandwidth beyond 200nm at telecom wavelengths.

Athanasii Kircheri Fuldensis Buchonii... Ars magna lucis et umbrae, in decem libros digesta. Quibus admirandae lucis et umbrae in mundo, atque adeò vniuersa natura, vires effectusq. vti noua, uti varia nouorum reconditiorumq. speciminum exhibitione, ad varios mortalium vsus, panduntur...

En port. grab. xil. de sol con lema: "Sicuti tenebrae eius ita & lumen eius. Psal. 138"

Solderjet bumping technique used to manufacture a compact and robust green solid-state laser

Solder-joining using metallic solder alloys is an alternative to adhesive bonding. Laser-based soldering processes are especially well suited for the joining of optical components made of fragile and brittle materials such as glasses, ceramics and optical crystals due to a localized and minimized input of thermal energy. The Solderjet Bumping technique is used to assemble a miniaturized laser resonator in order to obtain higher robustness, wider thermal conductivity performance, higher vacuum and radiation compatibility, and better heat and long term stability compared with identical glued devices. The resulting assembled compact and robust green diode-pumped solid-state laser is part of the future Raman Laser Spectrometer designed for the Exomars European Space Agency (ESA) space mission 2018.