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In this work, the most suitable conditions were determined for shaping ceramic bodies of the MSnO3 system (M = Ba, Zn, Ca), using submicron particles of these perovskites synthesized by a chemical route. For this, the rheological behaviours of colloidal suspensions of the MSnO3 powders (M = Ba, Zn, Ca) were studied considering the effects of solid content and concentration of ammonium polyacrylate (APA). The results indicated that the optimal solids contents for stable suspensions in each system were 13.8 (BaSnO3), 19.4 (ZnSnO3), and 21.5 vol.% (CaSnO3). The suspensions containing BaSnO3 and ZnSnO3 showed large reductions in viscosity, approximately 87%, when APA (0.5-0.8wt.%) was added. In contrast, the CaSnO3 suspension did not show significant changes after addition of APA. Slip casting of the stable suspensions allowed formation of porous green bodies, which were subsequently sintered in the range 1000-1500 °C. Considering their potential use as gas sensors, a preliminary study of the sintered bodies showed high detection responses (Ra/Rg) toward 80 ppm reducing gas at operating temperature of 270 °C, especially ZnSnO3 to acetone and ethanol vapours, BaSnO3 to ethanol vapour and CaSnO3 to toluene vapour.

This work describes the obtaining of cobalt-doped tin oxide nanoparticles using the method of controlled precipitation. The synthesized powders were used to form stable slurry, using as solvent water and 64% in solids, adding the suspension 5% ammonium polyacrylate -- PAA as a deflocculant and tetraetil ortosilicato -- TEOS. With this slip, and using the colloidal method (slip casting), were obtained in green pieces to sintering to 1250 °C, 2 hours, presented a uniform porous microstructure and a 94% of theoretical density, to doping sample with 2% by weight of Co, very suitable microstructure considering these parts used as active material in devices gas sensors. [ABSTRACT FROM AUTHOR]

Tin oxide, SnO2, has a big technological importance. For its uses it is of great interest to optimize the sintering conditions to obtain an adequate densification, microstructure and mechanical properties, depending on the technological application. In this paper, ceramic powders of SnO2 obtained by controlled precipitation method were sintered. Powders were shaped to obtain "green" pieces using both pressing and by the casting method ("slip casting") for this. For the slip casting method was realized a careful study of SnO2 suspensions to obtain a stable slurry. For determine the effect of shaping methods on the densification of pieces, were obtained important information analyzing the results of curves of weight loss, shrinkage and densification, as temperature functions, of the different samples. Finally, the sintered pieces were characterized using SEM to know their microstructure. The shaped pieces using colloidal method showed the higher density values (ρ= 4,2 ± 0,2 g/cm3). These samples showed a uniform microstructure with very small pores. These characteristics would allow their use as membranes or gas sensors. [ABSTRACT FROM AUTHOR]

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The titanium dioxide, TiO2, is a material of technological importance for their physicochemical properties. Also is known that material properties depend of synthesis process used for their production, condition that is more demanding in new technologies, specifically in nanotechnology. In this work we used two methods of synthesis, sol-gel and polymeric precursor (Pechini), we realized a comparative analysis of the two processes. The synthesized powders were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (TEM and SEM). With the results we determined the effect of the synthesis methods on the characteristics of the final product. The powders obtained presented nanometric size and primary anatase crystalline phase, from a temperature up of 450°C. The presence of AcacH complexing, in the system, reduced the size of the agglomerates and modified their morphology. [ABSTRACT FROM AUTHOR]