Directionally solidified fabrication in planar geometry of Al2O3-Er3Al5O12 eutectic composite for thermophotovoltaic devices

In this work Al2O3-Er3Al5O12 eutectic composite was manufactured in planar geometry departing from eutectic particles both produced by directional solidification using a CO2 laser system at rates of 180 and 720 mm/h. Microstructure and mechanical properties were investigated as a function of the growth rate. Homogeneous and interpenetrated microstructure was found with phase size strongly dependent on the growth rate, decreasing when the processing rate was increased. Thermal emission of eutectic composites was studied in function of thermal excitation by using CO2 laser radiation as a heating source. An intense narrow emission band at 1.55 µm matching with the sensitive region of the InGaAs photoconverter and a low emission band at 1 µm were obtained. Features of thermal emission bands were correlated with collecting angle, microstructure and laser power, and compared to those obtained from departing eutectic particles

Superplastic deformation of directionally solidified nanofibrillar Al2O3-Y3Al5O12-Zr O2 eutectics

Nanofibrillar Al2O3–Y3Al5O12–ZrO2 eutectic rods were manufactured by directional solidification from the melt at high growth rates in an inert atmosphere using the laser-heated floating zone method. Under conditions of cooperative growth, the ternary eutectic presented a homogeneous microstructure, formed by bundles of single-crystal c-oriented Al2O3 and Y3Al5O12 (YAG) whiskers of ˜100 nm in width with smaller Y2O3-doped ZrO2 (YSZ) whiskers between them. Owing to the anisotropic fibrillar microstructure, Al2O3–YAG–YSZ ternary eutectics present high strength and toughness at ambient temperature while they exhibit superplastic behavior at 1600 K and above. Careful examination of the deformed samples by transmission electron microscopy did not show any evidence of dislocation activity and superplastic deformation was attributed to mass-transport by diffusion within the nanometric domains. This combination of high strength and toughness at ambient temperature together with the ability to support large deformations without failure above 1600 K is unique and shows a large potential to develop new structural materials for very high temperature structural applications

Laser processing of ceramic materials for electrochemical and high temperature energy applications

The laser is a powerful tool for materials processing, incorporated already in many industrial processes and laboratory procedures. In this work, we are concerned with laser processing applied to research and development of ceramics for electrochemical cells and other high temperature oxide ceramics for energy applications. Solidification of single crystals or composites of relevant oxides can be performed by the laser assisted floating zone method, providing samples for structural, mechanical or functional fundamental research, as well as knowledge about its manufacture by melt processes. Selective laser melting of these ceramic oxides is a very promising technology, at the research level. Successful examples of surface laser melting of oxide eutectic composites are presented. The technologies of subtractive laser processing of ceramics (cutting, drilling, structuring, cleaning, etc.) are more developed, and the research is directed towards the optimization of mechanisms, increase of resolution and efficiency and the investigation of the effects of the laser treatment on the functional performance. Different laser processes of SOC (solid oxide cell) components are shown to decrease the ohmic, concentration and activation losses. The manuscript describes the state-of-the art of the technologies as applied to oxide and composite materials present in solid oxide electrochemical devices (SOFC, SOEC, and batteries) and selective emitters for thermophotovoltaics, with emphasis on the last achievements by the authors team. El láser es una potente herramienta para el procesamiento de materiales, incorporada ya en muchos procesos industriales y procedimientos de laboratorio. En este trabajo nos ocupamos del procesamiento láser aplicado a la investigación y desarrollo de cerámicas para celdas electroquímicas y otras cerámicas de óxido de alta temperatura para aplicaciones energéticas. La solidificación de monocristales o composites de óxidos relevantes se puede realizar mediante el método de zona flotante asistida por láser, proporcionando muestras para investigación básica estructural, de propiedades mecánicas o funcionales, así como conocimiento sobre su fabricación mediante procesos de fusión. La fusión selectiva por láser de estos óxidos cerámicos es una tecnología muy prometedora, cuyo desarrollo es todavía incipiente. Se presentan ejemplos exitosos de fusión por láser de superficie de compuestos eutécticos de óxidos. Las tecnologías sustractivas de procesamiento de cerámicas con láser (corte, taladrado, estructuración, limpieza, etc.) están más desarrolladas, y la investigación se dirige hacia la optimización de procedimientos, aumento de resolución y eficiencia y la investigación de los efectos del tratamiento láser sobre el rendimiento funcional. Diferentes procesos láser de los componentes de celda de óxido sólido disminuyen las pérdidas óhmicas, de concentración y de activación. El manuscrito describe el estado actual de las tecnologías aplicadas a óxidos y materiales compuestos presentes en dispositivos electroquímicos de óxidos sólidos (SOFC, SOEC y baterías) y emisores selectivos para aplicaciones termofotovoltaicas, con énfasis en los últimos logros del equipo

Directionally solidified fabrication in planar geometry of Al_2O_3-Er_3Al_5O_12 eutectic composite for thermophotovoltaic devices

In this work Al2O3-Er3Al5O12 eutectic composite was manufactured in planar geometry departing from eutectic particles both produced by directional solidification using a CO2 laser system at rates of 180 and 720 mm/h. Microstructure and mechanical properties were investigated as a function of the growth rate. Homogeneous and interpenetrated microstructure was found with phase size strongly dependent on the growth rate, decreasing when the processing rate was increased. Thermal emission of eutectic composites was studied in function of thermal excitation by using CO2 laser radiation as a heating source. An intense narrow emission band at 1.55 µm matching with the sensitive region of the InGaAs photoconverter and a low emission band at 1 µm were obtained. Features of thermal emission bands were correlated with collecting angle, microstructure and laser power, and compared to those obtained from departing eutectic particles