Cerámicos Nanoestructurados. Síntesis, caracterización y aplicaciones

En este trabajo de revisión se consideran algunos aspectos del Proyecto “Materiales Nanoestructurados”, desarrollado desde hace más de diez años en la División Sensores de Gases del CINSO-CITEDEF-CONICET (actualmente, UNIDEF-MINDEF-CONICET). Al comienzo se definen los nanomateriales y se presentan algunas referencias de sus asombrosas propiedades. Luego, se mencionan diferentes métodos de síntesis, particularmente para el caso de las nanocerámicas semiconductoras y se informan técnicas empleadas para caracterizarlas. Finalmente, entre los numerosos usos de los óxidos metálicos nanosemiconductores, se describe su aplicación en sensores de gases resistivos. Cuando el material microcristalino convencional se reemplaza en la construcción del sensor por el mismo material pero nanocristalino se observa un notable aumento en la sensibilidad del dispositivo (30-37%) y un marcado decrecimiento de la temperatura de operación de más de doscientos grados (ºC).Fil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de Las Fuerzas Armadas. Centro de Investigaciones En Sólidos; Argentina. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin

Evaluation of different bovine muscles to be applied in freeze-drying for instant meal. Study of physicochemical and senescence parameters

The aim of the present research was to evaluate bovine muscles to be subjected to freeze-drying for an instant meal. Physicochemical and senescence parameters were evaluated. The experimental part was divided into two steps. In the first step, the Semitendinosus muscle was chosen to establish methodology and experimental conditions. Physicochemical, microstructure and senescence parameters were analysed. In the second step, economic bovine muscles such as Semimembranous and Spinalis dorsi were subjected to the same methodology and conditions as in the first step in order to compare them by analysing the same parameters. L* and a* values were statistically significant (P<0.05) for Semimembranous and Spinalis dorsi muscles, showing differences among condition effects and in muscles. Humidity and water activity showed among the muscles analysed that cooked and rehydrated samples did not exhibit differences. Microstructure of Semitendinosus and Semimembranous were not separated and fragmented as occurred with Spinalis dorsi after freeze-drying. Results allowed us to select among the muscles studied that Semimembranous was suitable and economic to be used in an instant meal.Instituto de Tecnología de AlimentosFil: Messina, Valeria Marisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; ArgentinaFil: Sancho, Ana María. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto Tecnología Alimentos; ArgentinaFil: Grigioni, Gabriela Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Filippini, S. Universidad Nacional de Luján; ArgentinaFil: Pazos, Adriana Alejandra Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; Argentina.Fil: Paschetta, Fernanda. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; ArgentinaFil: Chamorro, Verónica Celeste. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin

Applications of electronic nose based on MOX and QMB sensors

The electronic nose emerged in the mid 80´s due that the food industry needed quickerinstruments to be applied in food control for the characterization of smell, in order to complement thework done by human panels. But scientific researchers noticed that electronic nose could also be used in other fields, such as environmental contamination, health, defence, automotive industry, control of hazardous substances, etc. The aim of this research article is to explain how electronic nose work and to report the latest researches obtained with electronic nose in the Centre of Investigation of Solids (CINSO).Fil: Messina, Valeria Marisa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin

Transmission electron microscopy of the induced damage by argon implantation in (111) HgCdTe at room temperature

HgCdTe (MCT) is an important semiconductor material used for infrared photovoltaic detectors. Although ion implantation is a widely used technique in the manufacture of devices based on MCT to obtain n/p junctions, a detailed understanding of the n-type behavior of the unannealed damage region has not yet been established. In this work, n/p junctions were formed by Ar++ implantation on MCT (111) grown by the isothermal vapor phase epitaxy method. Structural damage after implantation for different implantation doses (10 13, 1014, 1015Ar++/cm2) was evaluated by transmission electron microscopy. At high doses, damage distribution exhibits a double region of defects. These were mainly vacancy dislocation loops and lines in the first region, whereas the second zone exhibited small dislocation loops. The observed n-type behavior after implantation was attributed to the generation and diffusion of Hg from the damaged region.Fil: Aguirre, Myriam H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Canepa, Horacio Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; Argentin

Monitoring odour of heated extra-virgin olive oils from Arbequina and Manzanilla cultivars using an electronic nose

It is known that fats and oils, when submitted to prolonged heat, are subjected to a series of chemical-physical modifications, generating changes in sensory and nutritional characteristics. The aim of the present research was to develop an accurate and repeatable method to predict appearance of undesired odour when extra-virgin olive oils from Arbequina and Manzanilla are submitted to heating processes, using an electronic nose. Among the metal oxide sensor response (electronic nose) an odour index was performed. Emissions of several volatile organic compounds released during the process were analysed by SPME-Gas chromatography. Linear discriminant analysis was applied on the sensor response; it was found that among eight sensors, four sensors were more specific for detecting release of volatile organic compounds during the heating process. The Mahalanobis distance method was adopted to create an odour index and was correlated with emissions of n-pentanal, n-hexanal, n-heptanal and n-nonanal. Data showed that the methodology accurately and rapidly predicted changes in odour pattern between cultivars.Fil: Messina, Valeria Marisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Sancho, Ana. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentin

Microstructural study of nanocrystalline pure and doped tin dioxide to be used for resistive gas sensors

Nanocrystalline pure and doped SnO2 have been intensively studied for a long time to build resistive gas sensors. However, it is still useful to synthesize nanopowders with the smallest crystallite size to build devices. A modified gel-combustion method and a novel reactive oxidation process are proposed for nanopowders synthesis and results are compared. Materials have been characterized by XRD, Scherrer equation to evaluate the crystallite size; BET absorption to determine specific area and HRTEM to observe the crystallites (evaluating their mean size and distribution); defects and effect of calcination treatments are also considered. Previous studies have shown that if nano-SnO2 replaces the conventional microcrystalline-SnO2 to build resistive gas sensors, sensitivity increases (>30%) and the operation temperature considerably decreases. A heating and measuring system has been designed for achieving low power consumption and uses pulsed heating operation. This method of electrical control and measurement is operated intermittently, with "heating" and "readout" cycles (readout: signal of sensitive film).Fil: Bianchetti, Mario Fidel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Arrieta, Cristian L.. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; ArgentinaFil: Walsoe, Noemi Elizabeth. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin

Grain Boundaries In Doped-Ceria Nanofilms Used As Electrolytes For It-Sofc Fuel Cells

Las cerámicas de ceria (CeO2), dopadas con Y2O3 (CYO) o con samaria Sm2O3 (CSO son consideradas como materiales promisorios para electrolitos sólidos de celdas de combustible de tipo SOFC- Solid Oxide Fuel Cells, debido a su alta conductividad por iones oxígeno. Los requerimientos necesarios para electrolitos de las pilas de combustible son: estabilidad química, alta conductividad, condiciones adecuadas de sinterizado, alta densidad y ausencia de porosidad abierta. En este trabajo, se utilizó CeO2 dopada con 10% molar de samaria, material ya estudiada en algunos aspectos por los autores, tratándoselo térmicamente por “fast-firing” durante un corto tiempo (3 min) a 850ºC y a 1450ºC para producir el sinterizado del material. En el DEINSO-CITEDEF se realiza una planificación completa de los efectos del “fast-firing” para comprender el comportamiento de estas cerámicas, estudiando: el crecimiento de grano; velocidad de sinterizado, cambios en las características de los bordes de grano, tamaño de cristalitas, densidad de poros, densificación e interacción de defectos. En este trabajo, se consideran especialmente, los efectos del “fast-firing” respecto de la estructura de los bordes de grano para contribuir a lograr electrolitos sólidos que exhiban mayor estabilidad y mejor calidad. La caracterización de las cerámicas fue realizada por técnicas de adsorción BET, DRX, SEM and HRTEM.Ceria (CeO2) ceramics as doped with Y2O3 (CYO) or with Sm2O3 (CSO) are considered promisingmaterials as electrolytes for SOFCs Solid Oxide Fuel Cells due to their high conductivity by oxygen ions.The necessary requirements for fuel cells electrolytes are chemical stability, high conductivity,convenient sintering conditions, high density and absence of open porosity. In this work, the alreadystudied materials in some aspects by the authors: doped CeO2 with molar 10% samaria, was thermallytreated by fast-firing for a short time (3 min) at 850oC and at 1450oC to produce the material sintering.A complete planning of the fast-firing effects to understand these ceramics defects behavior isperformed at DEINSO-CITEDEF, studying: the grain growth, sintering velocity, changes in the grainboundaries, crystallites size measurements, pores density, densification and defects interaction. In thiswork, the fast-firing effect on grain boundaries structure is considered.This study also contributes to synthesize solid electrolytes with higher chemical stability and improvedquality. The ceramics characterization was performed by BET adsorption techniques, XRD, SEM andHRTEM.Fil: Bianchetti, Mario Fidel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Otonicar, Mojca. Jozef Stefan Institute; EsloveniaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentin

Transmission electron microscopy of the induced damage by argon implantation in (111) HgCdTe at room temperature

HgCdTe (MCT) is an important semiconductor material used for infrared photovoltaic detectors. Although ion implantation is a widely used technique in the manufacture of devices based on MCT to obtain n/p junctions, a detailed understanding of the n-type behavior of the unannealed damage region has not yet been established. In this work, n/p junctions were formed by Ar++ implantation on MCT (111) grown by the isothermal vapor phase epitaxy method. Structural damage after implantation for different implantation doses (10 13, 1014, 1015Ar++/cm2) was evaluated by transmission electron microscopy. At high doses, damage distribution exhibits a double region of defects. These were mainly vacancy dislocation loops and lines in the first region, whereas the second zone exhibited small dislocation loops. The observed n-type behavior after implantation was attributed to the generation and diffusion of Hg from the damaged region.Fil: Aguirre, Myriam H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Canepa, Horacio Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; Argentin

Observation of CuPt and CuAu I-type ordered structure in HgCdTe grown by isothermal vapour phase epitaxy

Ordered structures, CuPt and CuAu I types in HgCdTe are reported for the first time. Hg1-xCdxTe thin crystals were grown by isothermal vapour phase epitaxy (ISOVPE) method on a CdTe substrate and they were observed by transmission electron microscopy (TEM) in planar view and cross-sectional geometries. Two variants of CuPt-type ordered structure were found in different microdomain sets on HgCdTe. Another superstructure observed was the CuAu I-type coexisting with CuPt domain structure.Fil: Aguirre, Myriam H.. Universidad Complutense de Madrid; EspañaFil: Canepa, Horacio Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentin