Papers by Author: Carlos Kuranaga

Abstract: The polymeric precursor route based on the Pechini process was used to prepare a mixture of nano and microcrystalline powders. The zirconia powder was stabilized with 3 mol% of yttria. Powder characteristics were evaluated by the BET technique determined the specific area and the BJH method supplied the pore size distribution. The X-ray diffraction results and SEM observations were carried out to characterize both the powder mixture and the microstructures of the ceramic bodies. The sintering behavior shown in this work was studied by dilatometric experiment, being considered the shrinkage rate and densification of the microstructure.

Abstract: Due to the necessity of the automation and control of processes in agriculture, as well as to the crescent interest for the environmental monitoring, efforts have been demanded in the development of more versatile, reliable sensors and sensor systems with smaller cost [1-2]. In this sense, the search of new materials, the modeling study of sensor and the development of new measurement techniques and processing of signs have been orientating the progress in this area [3-4]. In this work, the results of the characterization analyses of sensor elements of ZrO2-TiO2 porous ceramic for application as soil humidity sensor, are shown and discussed. These ceramics were obtained from the mechanical mixture of ZrO2- TiO2 powders and sintered at 1000, 1100 and 1200 oC, for obtaining different porosities. The characterization of the ceramic was carried out using measurements of B.E.T.; nitrogen and mercury porosimetry; scanning electronic microscopy and X-ray diffraction. The porous ceramic characterization as soil humidity sensor element was accomplished through capacitance and impedance measurements using a RLC bridge. The ceramic sensor elements were immersed in the selected and previously characterized soils, the humidities of which were defined in accordance with Atterberg limits, more exactly liquid limit. The results obtained for specific surface area, distribution curves of pore size, microstructure, crystalline phases and sensibility to the soil humidity showed that the ZrO2-TiO2 porous ceramic sintered at 1100 oC presents a great potential to be applied as sensor element for soil humidity monitoring.

Abstract: The humidity sensing behavior of a ceramic oxide based on the ZnO-TiO2-Ta2O5 system was analyzed. Samples were uniaxially pressed and sintered at temperature range from 1000 to 1200oC. Electrical impedance and capacitance measurements were realized in different values of relative humidity (from 11 to 100%). The microstructures of the sintered samples were characterized by X-ray diffractions and SEM observations. Mercury porosimetry analyses were carried out to determine the open porosity and the surface area was measured by using the BET nitrogen method. The obtained results were correlated and discussed.