Papers by Keyword: Nanostructured Ceramic

Abstract: It is well known that microstructure evolution during rapid solidification depends on the rate between undercooling and solidification velocity. Microstructural evolution in a nonequilibrium solidification process depends critically on the melt undercooling and growth (solidification) velocities of competing phases. One way of obtaining metastable structures is by Thermal Spray Technology. Metastable coatings can be produced starting from microstructured powders through Atmospheric Plasma Spray (APS) technique, followed by a quenching route. The initial powders are melted during the spraying and deposited over a substrate that is quenched with nitrogen feeders, producing metastable coatings. The obtained coatings were characterized using XRD, SEM, FESEM and TEM in the Thermal Spray Centre (CPT) of the University of Barcelona. The properties of such coatings were studied by hardness, obtaining promising results.

Abstract: Highly structure controlled ceramics were required for improving their properties. Here, we demonstrate such ceramics fabricated by novel colloidal processing; (i) dense nano-sized zirconia without pressure sintering, (ii) porous ceramics with controlled pore size by hetero-coagulated suspension of ceramics and polymer, and (iii) textured ceramics with feeble magnetic susceptibility by electrophoretic deposition in a high magnetic field.

Abstract: In this work, was proposed to produce nanosized α-Al2O3 powder from precipitation reactions, in order to reduce the alumina ceramics sintering temperature. For this an addition of nanosized powder in the commercial microsized powders was done. The nano and microsized powder particle mixtures were obtained by precipitation of nanosized aluminum hydroxide in microsized Al2O3 in liquid suspension. Several compositions of nano and microsized powders were carried out. These powder compositions were based on data of simulated particle packing. The nano and microsized powder mixtures was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric and differential thermal analysis (TGA and DTG). The powder mixtures were compacted by uniaxial (75MPa) and isostatic (300MPa) pressing, producing cylindrical samples. The powder compacted samples were sintered at 1400oC. Sintered ceramics were characterized by XRD and SEM. The results showed that the higher density of sintered ceramic was obtained for 65% of microsized powder and 35% of nanosized powder mixture. This composition of size of particles of the powder was in agreement with the theoretical simulation.