Zircon–zirconia (ZrSiO4–ZrO2) dense ceramic composites by spark plasma sintering (original) (raw)
Related papers
Dense zircon (ZrSiO 4) ceramics by high energy ball milling and spark plasma sintering
Ceramics International
The addition of sintering additives has always been detrimental to the mechanical properties of sintered ceramics; therefore, methods to reduce or, as in this case, eliminate sintering additives are usually relevant. In this paper, dense zircon ceramics were obtained starting from mechanically activated powder compacted by spark plasma sintering without employing sintering additives.
Densification and characterization of spark plasma sintered ZrC–ZrO2 composites
Materials Science and Engineering: A, 2014
ZrC based composites alloyed by nanosized tetragonal 3 mol% yttria stabilized zirconia were produced with spark plasma sintering to 498% of the theoretical density by sintering at 1900 1C under pressure of 50 MPa for 10 min. The volume fraction of stabilized zirconia varied from 25 to 40 vol% in the precursor powder blend. Room temperature hardness and modulus of elasticity of the compacts were in the range reported earlier for similar materials densified by pressureless sintering, while indentation fracture toughness was around 7 MPa m 1/2 . Structural analysis indicated formation of oxycarbides of various stoichiometries.
Sintering properties of zirconia-based ceramic composite
Materials Research Innovations, 2014
This study examines the effects of different ZrB 2 content on various mechanical properties and electrical conductivity of ZrB 2 /Y-TZP composite. Composites with ZrB 2 content of up to 20 wt-% were particularly beneficial at the lower sintering temperature range by achieving greater densification and better hardness than Y-TZP monolith. In contrast to the trends estimated from rule of mixture, the increment of ZrB 2 content did not result in any significant improvement in the elastic modulus and hardness of the zirconia composites. Nevertheless, all composites showed tremendous improvement in fracture toughness compared with monolithic Y-TZP and thus, suggested that other toughening mechanisms were operative besides transformation toughening of zirconia. Incorporation of ZrB 2 up to mass fraction of 20 wt-% into Y-TZP generally did not affect the tetragonal phase stability of zirconia. Significant reduction of electrical resistivity of the composites was achieved with ZrB 2 content of 20 wt-% and sintering temperature of 1400°C.
Journal of Materials Science, 2008
Ce- and/or Y-doped zirconia nanopowders having average particle sizes ranging 12–18 nm have been synthesized by a technique based on mechanochemical processing (MCP). Despite their small particle size, the powders had excellent compactibility with green densities exceeding 50% achieved under a moderate uniaxial pressure of 150 MPa. Nearly fully dense ceramics having grain sizes of around 100 nm were successfully produced from these powders by spark plasma sintering (SPS) at temperatures of 1,050–1,150 °C for 5 min under pressures of 50–80 MPa; these temperatures and pressures are considerably lower than those required for achieving near full density with conventional nanopowders. Hardness and fracture-toughness measurements showed that the ceramics prepared by SPS had superior mechanical properties to those prepared by conventional pressureless sintering. It is argued that the high sinterability of the MCP nanopowders is ascribed to their ability to form uniform powder compacts under relatively low pressure, and that that ability in turn originates in two features of the MCP powders: absence of hard agglomeration and pseudo-spherical particle morphology.
Densification and properties of zirconia prepared by three different sintering techniques
Ceramics International, 2007
Densification of nanocrystalline yttria stabilized zirconia (YSZ) powder with 8 mol% Y 2 O 3 , prepared by a glycine/nitrate smoldering combustion method, was investigated by spark plasma sintering, hot pressing and conventional sintering. The spark plasma sintering technique was shown to be superior to the other methods giving dense materials (!96%) with uniform morphology at lower temperatures and shorter sintering time. The grain size of the materials was 0.21, 0.37 and 12 mm after spark plasma sintering, hot pressing and conventional sintering, respectively. Total electrical conductivity of the materials showed no clear correlation with the grain size, but the activation energy for spark plasma sintered materials was slightly higher than for materials prepared by the two other densification methods. The hardness, measured by the Vickers indentation method, was found to be independent on grain size while fracture toughness, derived by the indentation method, was slightly decreasing with increasing grain size. #
Science of Sintering, 2012
Pure Zircon and Zircon: Alumina (ZrSiO 4: α-Al 2 O 3 ) composite powders were subjected to densification studies employing spark plasma sintering (SPS). Physico chemical and microstructural properties of the samples were evaluated and compared with that of conventionally sintered (CRH-Constant Ramp and Hold) compacts. Density measurements and microstructural evaluation revealed a low temperature densification of Zircon: Alumina at temperatures as low as 1300°C by SPS. Increase of temperature to 1350°C had shown negligible changes in density and on further heating the sample melts at 1400°C as a result of excessive formation of liquid phase. However, pure zircon could not be densified in the absence of alumina under SPS conditions. It is evident that addition of alumina enhances partial low temperature decomposition of zircon under the influence of plasma generated during SPS. Mullite formed as a result of this insitu reaction between alumina and silica acts as a bonding phase as revealed by the X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Electron disperse scanning (EDS) analysis.
Dense zircon (ZrSiO4) ceramics by a simple milling-sintering route
Science of Sintering, 2018
In this work, a simple milling sintering route (pressure less) to process dense zircon ceramics from fine (D50 0.8 ?m) zircon powders is explored. Particularly, the milling time effect (0-120 min) and the maximum sintering temperature (1400-1600?C) were studied. The sintering grade developed microstructure and Vickers hardness (Hv) were evaluated and correlated. The dissociation of silicate into (monoclinic and tetragonal) zirconia and silica was evaluated by X-ray diffraction followed by the Rietveld method; it was found to be below 10 wt% in all the studied ranges. The sintering was enhanced by the milling pretreatment. No sintering additives were incorporated. Dense zircon (porosity below 1%) ceramics were obtained by a simple milling-sintering route of this high refractory powder at 100-200?C below the sintering temperature used with conventional processing routes to obtain equivalent final properties. The Vickers hardness reached: 9.0 GPa.
Low-Temperature Processing and Mechanical Properties of Zirconia and Zirconia-Alumina Nanoceramics
Journal of the American Ceramic Society, 2003
The 1.5-to 3-mol%-Y 2 O 3 -stabilized tetragonal ZrO 2 (Y-TZP) and Al 2 O 3 /Y-TZP nanocomposite ceramics with 1 to 5 wt% of alumina were produced by a colloidal technique and lowtemperature sintering. The influence of the ceramic processing conditions, resulting density, microstructure, and the alumina content on the hardness and toughness were determined. The densification of the zirconia (Y-TZP) ceramic at low temperatures was possible only when a highly uniform packing of the nanoaggregates was achieved in the green compacts. The bulk nanostructured 3-mol%-yttria-stabilized zirconia ceramic with an average grain size of 112 nm was shown to reach a hardness of 12.2 GPa and a fracture toughness of 9.3 MPa⅐m 1/2 . The addition of alumina allowed the sintering process to be intensified. A nanograined bulk alumina/zirconia composite ceramic with an average grain size of 94 nm was obtained, and the hardness increased to 16.2 GPa. Nanograined tetragonal zirconia ceramics with a reduced yttria-stabilizer content were shown to reach fracture toughnesses between 12.6 -14.8 MPa⅐m 1/2 (2Y-TZP) and 11.9 -13.9 MPa⅐m 1/2 (1.5Y-TZP).
Carbon, 2012
It is demonstrated that 0.1 wt% of multi-walled carbon nanotubes (MWCNTs) or singlewalled carbon nanotubes (SWCNTs) added to zirconia toughened alumina (ZTA) composites is enough to obtain high hardness and fracture toughness at indentation loads of 1, 5, and 10 kg. ZTA composites with 0.01 and 0.1 wt% of MWCNTs or SWCNTs were densified by spark plasma sintering (SPS) at 1520°C resulting in a higher hardness and comparable fracture toughness to the ZTA matrix material. The observed toughening mechanisms include crack deflection, pullout of CNTs as well as bridged cracks leading to improved fracture toughness without evidence of transformation toughening of the ZrO 2 phase. Scanning electron microscopy showed that MWCNTs rupture by a sword-in-sheath mechanism in the tensile direction contributing to an additional increase in fracture toughness.