Papers by Author: Arturo Domínguez-Rodríguez

Abstract: Boron carbide-based ceramics will be probably the most promising materials during the next decades due to their excellent mechanical properties combined with its chemical stability and low-density. Boron carbide itself is a very challenging system because of its complicated but highly-symmetrical crystallographic structure. Room-temperature mechanical properties of pure boron carbide have deserved considerable attention due to its remarkable hardness and resistance to shock-impact; however, its high-temperature plasticity with unsual ductility remains unexplored. The high-temperature creep of pure B₄C polycrystals and the microsturctural observation were performed to find the mechanism of deformation in this material.

Abstract: This lecture will outline the past, present and future of research in ceramics. The concept of “ceramic material” has evolved along the time and it hás broadened remarkably for the last decades from traditional clay-based materials to new systems: the term includes now high-performant capacitors, superconductors, highly-efficient oxides, carbides and nitrides of transition metals. The search of new materials has made that their processing and characterization become more technically sophisticated and it has encouraged the development of new techniques and more accurate scientific instruments, altogether providing a wider updated database. The landscape for ceramics research has changed dramatically for the past 15 years, and research in this field is now in a crossroad: in this lecture the emerging areas in ceramic science will be discussed, based upon a workshop held in March 2012 in USA on this regard.

Abstract: Single wall carbon nanotube reinforced yttria stabilized zirconia ceramic materials have been obtained by means of spark plasma sintering technique. Single wall carbon nanotubes were treated in an acid solution before mixing with zirconia powders to obtain a uniform distribution of both powders. This method allows obtaining ceramic materials with a grain size between 200 nanometers and 1 micron and with a grain size distribution which depends on processing conditions. This new route opens a new perspective for new ceramic composites tailoring with enhanced mechanical properties as structural materials

Abstract: The creep behavior of a TiCxN1-x-Co-Mo2C cermet has been investigated at temperatures between 1100-1200°C in an inert atmosphere to assess the one step mechanically induced self-sustaining reaction synthesis and pressureless sintering process, and the influence of the Mo2C additive in the high temperature mechanical properties of this cermet. The samples deform plastically at the chosen temperatures, and values of the stress exponent (n=1.70.6) and activation energy (Q= 4.30.5 eV) have been estimated from uniaxial compression tests. No significant grain growth has been detected after deformation. The reproducibility of the creep tests compared to other compositions indicates that the Mo2C addition contributes to increase notably the resistance to high temperature oxidation of the samples, so that the plastic behavior is not affected by oxidation when deformation experiments are performed in an inert atmosphere.

Abstract: Additive-free -SiC powders were sintered by means of Spark Plasma Sintering System. Experiments were performed in the temperature range from 1650°C to 2200°C, 3 to 10 min holding time and pressure from 50 until 150 MPa. In order to favour sinterization, the starting powder was mechanically activated: defect concentration was increased by centrifugal ball milling. Applied temperature, holding time and/or pressure were varied to analyze their effect on the densification and grain growth kinetics. The full sinterization of the material was obtained for temperatures as high as 1900°C and over. The relative density of the obtained material was high, up to 97.0  0.6 % the theoretical density for 2200°C sintering temperature. An intense grain growth took place while sintering. The final microstructure exhibited a grain size distribution range from 1.0 to 2.5 m, depending on the sintering conditions. Such grain growth strongly depends on the sintering time, not so much on the sintering temperature.

Abstract: Ceria-zirconia ceramic alloys with the following molar composition: 0.12CeO2-0.88ZrO2 have been sintered by high-temperature annealing. Monolithic specimens haven been crept in compression at high temperatures. Creep experiments have been rationalized to an empirical constitutive equation which is consistent with a classical Ashby-Verrall creep regime. This result has been assessed through microstructural characterization of as-received and post-mortem specimens. A pure Ashby-Verrall creep is contrary to the conventional mechanism controlling creep in other zirconia alloys. A discussion on the explanation for such mechanism is outlined.

Abstract: Commercial porcelain ceramic tiles have been irradiated with a laser to evaluate the thermal effects on their surface and in their tribological behavior. Different irradiation patterns were followed, varying the density of points where the laser was focused, from 25 to 150 dots per inch. Hardness and toughness were evaluated using Vickers indentations. Tribological behavior was studied using a ball-on-flat apparatus with alumina balls. An increase in the wear rate was observed in the higher irradiated samples, which can be correlated to a decrease in their toughness. A mechanism of severe wear by fracture propagation and material pullout is proposed to explain the experimental data and the observed corresponding microstucture.

Abstract: In this review paper, the macro and microcharacteristics of superplasticity will be analyzed. Based on the macroscopic features of the superplasticity, the joining of ceramics as a new application will be analyzed with special emphasis in the fabrication of functional gradient ceramics materials. Finally, the new trends as high strain rate superplasticity (HSRS) or superplasticity at low homologous temperature will be discussed.