Photothermal microscopy applied to the characterization of nuclear fuel pellets

The photothermal photodeflection technique is shown to provide information on the homogeneity of fuel pellets, pore distribution, clustering detection of pure urania and gadolinea and to provide a two-dimensional mapping of the thermal diffusivity correlated to the composition of the interdiffused Gadolinium and Uranium oxide. Histograms of the thermal diffusivity distribution become a reliable quantitative way of quantifying the degree of homogeneity and the width of the histogram can be used as a direct measure of the homogeneity. These quantitative measures of the homogeneity of the samples at microscopic levels provides a protocol that can be used as a reliable specification and quality control method for nuclear fuels, substituting with a single test a battery of expensive, time consuming and operator dependent techniques.Fil: Zaldivar Escola, Facundo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martinez, Oscar Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; ArgentinaFil: Kempf, R.. Comisión Nacional de Energía Atómica; Argentin

Microscopía fototérmica

Las técnicas fototérmicas se basan en la absorción de un haz de luz modulado para generar ondas térmicas. Debido a este aumento de temperatura se producen diferentes procesos térmicos: expansión térmica, cambio de la reflectividad y cambio del índice de refracción. En materiales complejos como cerámicos, películas delgadas y compuestos es de sumo interés poder predecir y entender su comportamiento para la caracterización y desarrollo de nuevos materiales y procesos de fabricación industrial. Para ello es necesario conocer tanto los parámetros físicos como las propiedades de cada uno de los constituyentes a escalas microscópicas. Estas técnicas pertenecen al grupo de ensayos no destructivos dado que al no haber contacto no se alteran las propiedades de las muestras analizadas. En base a la experiencia del grupo en el área se presentan nuevos desarrollos tecnológicos consistentes en microscopios fototérmicos a medida de las aplicaciones, que permiten responder a demandas de distintos sectores.The photothermal techniques rely in the absorption of a modulated light beam to generate thermal waves. The temperature rise induces different thermal processes: thermal expansion, reflectivity change and changes in the refractive index. In complex materials such as ceramics, thin films and composites it is of great interest to be able to predict and understand their behavior for the characterization and development of new materials and industrial manufacturing processes. For this it is necessary to know both the physical parameters and the properties of each of the constituents at microscopic scales. These techniques belong to the group of non-destructive tests given that, when there is no contact, the properties of the samples analyzed are not altered. Based on the group’s experience in the area, new technological developments are presented, consisting of photothermal microscopes tailored to the applications that allow responding to the demands of different sectors.Fil: Zaldivar Escola, Facundo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jan, Luis Emiliano. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; ArgentinaFil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; Argentin

Characterization of Sintered Mixed Oxides by Photothermal Microscopy

A new photothermal microscopy device is presented and used to map the thermal diffusivity of mixed oxides. The particular cases of UO2 + 10 %Gd2O3 andUO2 +7.5%Dy2O3 are discussed, showing how to determine the homogeneity of theprepared samples, distinguish interdiffused oxides from mixed oxides, recognize and characterize clusters, and determine the relative abundance of different species and its spatial distribution. Histograms can be generated that provide a quantitative determination of the homogeneity. Adding an independent determination of the thermal diffusivity as a function of the composition made in bulk material allows the conversion of the diffusivity map into a concentration map, providing direct quantitative determination of the homogeneity and spatial distribution in concentration units. The new device can be added as an accessory to an optical microscope entering through a standard C mount camera port. Two semiconductor lasers within the viewing spectroscopic window of any microscope (650 nm wavelength for the pump and 785 nm for the probe) that were coupled to a single-mode fiber were used, and the reflected signal was collected using the same fiber. With this construction, the resulting equipment was robust and reliable.Fil: Zaldivar Escola, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; ArgentinaFil: Kempf, Rodolfo. Comisión Nacional de Energía Atómica; ArgentinaFil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; ArgentinaFil: Martínez, Oscar Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentin

Characterization of absorptance homogeneity in thin-film coatings for high-power lasers by thermal lensing microscopy

A focus error method photothermal microscope was designed for the characterization of absorptance homogeneity in thin-film coatings for high-power lasers. The technique relies on the detection of the thermal lens induced by the local absorption of a light power focused laser. The detailed design of the instrument is presented. The resolution of the system is better than 0.1 ppm and allows the realization of spatial sweeps and even measurements of the evolution of absorption as a function of time with a spatial resolution of 1 μm. These capabilities allow the location of defects and their characterization.Fil: Zaldivar Escola, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Martinez, Oscar Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Rocca, Jorge J.. State University of Colorado - Fort Collins; Estados UnidosFil: Menoni, Carmen. State University of Colorado - Fort Collins; Estados Unido

Influence of nodule count on residual stresses and distortion in thin wall ductile iron plates of different matrices

Surface characteristics of thin wall ductile iron (TWDI) parts, such as residual stresses, distortion and dimensional changes produced during casting and heat treatment, are relevant variables when it comes to production processes design. This work focuses on the effect of nodule count on residual stresses (RS) and of TWDI plates distortion. As-cast, ferritised and austempered samples were employed. The role played by two typical austempering temperatures (280 and 360 °C) and three significantly different nodule counts (265, 1200 and 1700 nodules (nod)/mm2) are discussed by establishing microstructural changes, i.e., microstructure fineness, retained austenite volume fraction (Vγ%), and austenite carbon content (Cγ%). Besides, residual stresses profiles below the surface and dimensional changes are determined. Results show that all samples display compressive RS on the surface and neighbouring layers. Samples with high nodule count austempered at 280 °C lead to higher compressive RS and distortion as well as to an increase in the RS field below the surface. As-cast and ferritised plates exhibit noticeably lower compressive RS values.Fil: Sosa, Amadeo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Echeverría, María Dolores. Universidad Nacional de Mar del Plata; ArgentinaFil: Moncada, Osvaldo Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Mingolo, Nelida. Comisión Nacional de Energía Atómica; ArgentinaFil: Sikora, Jorge Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Photothermal microscopy characterization of multiphoton annealing of defects in thin-film coatings for high-power lasers

A focus error method photothermal microscope was designed for the simultaneous annealing and characterization ofdefects in thin film multilayer coatings for high power lasers. The technique relies in the detection of the thermal lensinduced by the local absorption of a light power focused laser. A 10W CW laser at 1.06mm wavelength was used as apump and a HeNe laser at 632.8nm as a probe. A 4 quadrant detector and specifically designed astigmatic optic is usedto determine the defocusing of the transmitted probe beam at the modulation frequency of the pump. The instrumentscans the surface and detects the evolution of the absorptance with time with sensitivity below 0.1ppm. The pump beamfocus determines the spatial resolution of the instrument and the probe beam size, much larger than the pump, has tomatch the modulation frequency that yields a thermal diffusion distance of the order of the probe beam in onemodulation period. The detailed design of the instrument will be presented showing the design parameters that should beconsidered for an adequate sensitivity. The sensitivity of the system is better than 0.1ppm and allows the realization ofspatial sweeps and even measurements of the evolution of absorption as a function of time. These capabilities allow thelocation of defects and their characterization.Fil: Zaldivar Escola, Facundo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Martinez, Oscar Eduardo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rocca, Jorge J.. State University of Colorado - Fort Collins; Estados UnidosFil: Menoni, Carmen. State University of Colorado - Fort Collins; Estados Unido

Enhanced energy deposition efficiency of glow discharge electron beams for metal surface treatment

The energy deposition efficiency and focal spot dynamics of electron beams produced by pulsed cold-cathode high-voltage glow discharges for metal surface treatment are investigated for two different cathode geometries. A concave cathode geometry in which the focusing is dominated by the convergence of the electric field lines in the cathode fall region is compared with a flat cathode in which the focusing is exclusively caused by the self-generated magnetic field. Results of the treatment of AISI 4140 carbon steel samples show that the concave cathode geometry significantly increases the efficiency, reduces the threshold power necessary for melting, and is less sensitive to variations in the discharge parameters and sample position. The results of numerical modeling indicate that the observed increase in efficiency is caused by the longer persistence of the focal spot on the sample. The model can be used to predict the discharge parameters required for a desired treatment.Fil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Cesa, Yanina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Martínez, Oscar Eduardo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Etcheverry, Javier Ignacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rocca, Jorge J.. State University of Colorado - Fort Collins; Estados Unido

Absorptance homogeneity and its relaxation in thin films by photothermal microscopy

A photothermal microscope for absorptance homogeneity analysis is described. Absorptance maps with micrometer resolution and high sensitivity are obtained. Changes in absorptance are due to laser annealing of defects via one and two-photon processes.Fil: Zaldivar Escola, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; ArgentinaFil: Mingolo, Nelida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Haces Dirigidos; ArgentinaFil: Martinez, Oscar Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Rocca, Jorge J.. State University of Colorado - Fort Collins; Estados UnidosFil: Menoni, Carmen S.. State University of Colorado - Fort Collins; Estados UnidosOptical Interference Coatings ConferenceSanta Ana PuebloEstados UnidosOptical Society of Americ