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Item type:Publication, Designing Colloidal Silica-Bonded Porous Structures of In-situ Mullite for Thermal Insulation(Springer, 2020-09-01)Abstract: Colloidal silica (CS) is a promising raw material for refractory castable ceramics. It consists of stable suspensions of synthetic amorphous silica nanoparticles that behave simultaneously as liquid medium and binder for ceramic particles and as a porogenic agent and highly reactive source of silica to promote in-situ reactions. The setting mechanism of CS balances two opposite effects. Adding more CS to a suspension increases the bonding potential for gelling reactions and strengthening; on the other hand, it also introduces more water into the system, enhancing pore content. Such effects can be advantageously employed in the preparation of porous structures from aqueous suspensions and applied as high-temperature thermal insulators. The present study addresses the production of porous structures of in-situ mullite attained from aqueous suspensions of highly porous transition alumina particles bonded with colloidal silica. Different grades of CS and transition aluminas were combined to present suitable workability (flowability and gelling time) and to generate stoichiometric mullite or mullite-alumina porous structures after sintering. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Estrategias bioclimáticas para clima frío tropical de altura. Validación de prototipo de vivienda. Puno, Perú(University of Cuenca, 2021-01-27)Las condiciones de frío extremo en la región del altiplano peruano generan problemas recurrentes que afectan la salud y la economía de la población local. El limitado desempeño térmico de las viviendas sobre los 4200 m s.n.m., sumado a una economía de subsistencia y a la necesaria dispersión en el territorio debido a su actividad ganadera, agrava la situación de vulnerabilidad de la población. En el marco de un proyecto de transferencia tecnológica para la mejora térmica y constructiva de la vivienda altoandina, se diseñó, construyó y validó, junto con la población local, un prototipo bioclimático y sismorresistente en la localidad de Orduña, Puno, Perú. El presente documento se centra en las estrategias bioclimáticas pasivas implementadas en el prototipo, lográndose demostrar que es posible obtener confort térmico en dichas condiciones extremas a partir de la utilización casi exclusiva de materiales locales y naturales. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, De la “Quesana” tradicional a un sistema modular de paneles aislantes de Totora(Catholic University of Colombia, 2024-01-01)La “Totora” es una fibra natural disponible en el lago Titicaca, al sur del Perú, y de uso tradicional entre las comunidades circundantes. Actualmente existe un importante excedente, por lo que anualmente se quema una gran cantidad de totorales. Este estudio plantea el uso y la estandarización de la totora como material aislante térmico y de baja energía incorporada, para extender su uso a edificaciones en la fría región altoandina. Se realizó la exploración en campo de esta fibra natural y de cómo la trabajan las comunidades del lago, a través del intercambio tecnológico con pobladores locales. A partir de esta experiencia, y a través de pruebas básicas en gabinete, se desarrolló el panel doble cruzado y modular de totora. La transmisión térmica del panel se comprobó con pruebas de laboratorio. Se construyó un prototipo de vivienda con cerramiento de paneles de totora y estructura de madera, monitoreando su desempeño constructivo y térmico por tres meses. El resultado térmico fue mejor que el de una cabaña tradicional alto-andina. El panel de totora propuesto mantuvo su forma, rigidez y características aislantes, demostrando su potencial como material constructivo natural y de bajo impacto ambiental en su procesamiento. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Microstructure Evolution of Porous Calcium Hexaluminate Compacts During First Heating(Elsevier BV, 2023-11-23)Porous calcium hexaluminate (CaAl 12 O 19 or CA 6 ) structures show long-term stability at high temperatures, high refractoriness, low thermal conductivity , and excellent chemical resistance, thus being Taylor-made for thermal insulation . Previous works attained porous structures from in situ formation of CA 6 combining CaO and Al 2 O 3 sources in solid-state reactive sintering. Although the approach is time-and-energy-saving regarding the production of large parts of complex shapes, it faces considerable difficulties related to the expansive formation of calcium aluminates. To overcome such drawbacks, pre-formed porous CA 6 aggregates improve the system's dimensional stability before sintering. Despite the straightforward processing, few studies have investigated such materials systemically. This article addresses the combination of pre-formed porous CA 6 aggregates and organic and inorganic binders for the production of porous structures by two shaping processes, namely, uniaxial pressing and direct casting of aqueous suspensions. After drying, the samples' microstructure and physical properties evolution were investigated up to sintering (1100-1500 °C) through total porosity, Young's modulus , compression strength , pore diameter, and thermal conductivity measurements, dilatometric analyses, and scanning electron microscopy. Reference samples of coarse calcined alumina were tested under the same conditions to highlight the impacts of CA 6 particles' morphology. Compared to them, the CA 6 -containing samples showed almost no variation in total porosity and average pore size levels during thermal treatments, although their strength and rigidity increased significantly after sintering. Their microstructure remained practically unchanged after drying, showing clusters of large asymmetrical CA 6 crystals bonded to each other by their edges, and surrounding a large fraction of 1.8–2.2 μm pores. According to the results, although water content, processing method, and compacting levels are important parameters, particles' microstructure, ratio of intra-particle pores, and asymmetrical shape are key variables for the development of physical properties. Such characteristics strongly contributed to their densification resistance and lower thermal conductivity after exposure to high temperatures.