Search results for " zirconia"
showing 10 items of 139 documents
Effect of different sintering process on flexural strength of translucency monolithic zirconia
2018
Background Sintering process is responsible for the strength of zirconia restoration. This study evaluated the effect of different sintering temperatures and sintered-holding times on flexural strength of translucency monolithic zirconia. Material and Methods One hundred and thirty five zirconia bar specimens (width-length-thickness = 10×20×1.5 mm) were prepared from yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic and randomly divided into nine groups to be sintered at different temperatures [decreasing- (SD, 1350°C), regular- (SR, 1450°C), and increasing- (SI, 1550°C) sintering temperature] and different sintered-holding times [shortening- (HS, 60 min), regular- (HR, …
Wear in Antagonist Teeth Produced by Monolithic Zirconia Crowns: A Systematic Review and Meta-Analysis
2020
Background: The aim of this systematic review and meta-analysis was to determine the wear sustained in the natural antagonist tooth in cases of full-coverage fixed-base prosthetic restorations or monolithic zirconia tooth-supported crowns, as well as to determine the wear in the restoration itself, both in the short- and medium-term and considering the factors that may influence wear. Material and methods: A systematic literature review and meta-analysis, based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations, of clinical studies that evaluated wear in antagonist teeth in relation to fixed-prosthesis monolithic zirconia crowns. A total of 5 data…
X-ray Absorption under Operating Conditions for Solid-Oxide Fuel Cells Electrocatalysts: The Case of LSCF/YSZ
2019
We describe a novel electrochemical cell for X-ray absorption spectroscopy (XAS) experiments during electrical polarization suitable for high-temperature materials such as those used in solid oxide fuel cells. A half-cell LSCF/YSZ was then investigated under cathodic and anodic conditions (850 °
Luminescence properties of zirconia nanocrystals prepared by solar physical vapor deposition
2014
Abstract Zirconia nanocrystals have attracted considerable interest as biolabels, which can be used as probes for medical imaging and biosensor applications. However, zirconia particle agglomeration forms a major limitation to its use for biolabeling. In this backdrop, for the first time, well-separated zirconia nanocrystals were obtained in a Heliotron reactor (PROMES CNRS, France) via the solar physical vapor deposition (SPVD) method. As the raw material target for solar evaporation, zirconia nanopowders obtained via the sol–gel process were used. The luminescence and upconversion luminescence properties of the Sol Gel nanopowders were compared with those of the SPVD nanocrystals. Erbium …
Effect of internal noise on the relaxation time of an yttria stabilized zirconia-based memristor
2022
The effects of temperature on the switching kinetics of an yttrium-stabilized zirconia-based memristor from a low-resistance state to a high-resistance state have been experimentally investigated. It was found that the memristor relaxation time depends on the temperature in a non-monotonous way, with a maximum observed at the temperature close to 55 °C. This nonmonotonic behavior is a signature of the noise-enhanced stability phenomenon observed in all physical and complex systems characterized by metastable states.
Effect of thermocycling with or without 1 year of water storage on retentive strengths of luting cements for zirconia crowns
2015
Abstract Statement of problem Bond stability between zirconia crowns and luting cement and between cement and dentin is a main concern; however, only limited evidence is available as to its longevity. Purpose The purpose of this in vitro study was to measure the retentive strengths of 7 self-adhesive cements (RelyX Unicem Aplicap, RelyX Unicem Clicker, RelyX Unicem 2 Automix, iCEM, Maxcem Elite, Bifix SE, SpeedCem), 2 adhesive cements with self-etch primers (Panavia 21, SEcure), 1 glass ionomer cement (Ketac Cem), 1 resin-modified glass ionomer cement (Meron Plus), and 1 zinc phosphate cement for luting zirconia crowns (LAVA) to extracted teeth after thermocycling with or without 1 year of …
Effects of redox treatments on the structural composition of a ceria–zirconia oxide for application in the three-way catalysis
2003
Abstract The influence of calcination and redox cycles on the structural modification and redox properties of a ceria–zirconia mixed oxide of nominal composition Ce 0.6 Zr 0.4 O 2 were investigated by XRD and Rietveld refinement, by BET measurement, TPR and OSC analyses. The material is characterized by high total OSC and retains this property after several redox and calcination cycles up to 1273 K, despite the loss of porosity and the decrease of surface area. The Rietveld analysis of the diffractograms allowed to establish that at least two solid solutions are present in the as-prepared sample: a cubic phase, space group Fm-3m, richer in cerium compared to the nominal composition, a tetra…
Spatiotemporal dynamics in the oxidation of groups IV?V metals: study of zirconium
1997
Abstract This paper focus on the mechanism of zirconium oxidation at 850 °C by X-ray diffraction (XRD) and the interactions between chemical (oxide growth, phase proportion) and physical processes (oxide scale texture, mechanical stresses). The structural gradients in the oxide scale composed of monoclinic ZrO 2 (higher proportion) and tetragonal ZrO 2 were revealed by XRD at variable incidence. The spatial evolution of the monoclinic zirconia texture through the oxide scale was shown and quantified. Relaxation of the oxide compressive stresses was observed for different oxidation times and correlated to kinetic breakaway evidenced by other methods. A structural mechanism of the oxide forma…
V-containing ZrO2 inorganic yellow nano-pigments
2015
In this work we report new results on the preparation, characterization and color properties of the inorganic yellow nano-pigmenting system based on monoclinic V–ZrO2 solid solution nanoparticles. The series of solid solution nanopowders were obtained by a polyol technique where the precipitates, obtained after heating at 180 °C ethylene glycol solutions of vanadyl acetonate and zirconium n-propoxide, were annealed at different temperatures up to 1300 °C for a short duration, in order to improve their crystallinity and control the crystalline form of the final nanoparticles. On annealing at around 450 °C highly crystalline tetragonal V-containing zirconia particles were developed, which tra…
MOCVD deposition of YSZ on stainless steels
2003
Abstract Yttria stabilized zirconia was deposited on stainless steel using the metal–organic chemical vapor deposition (MOCVD) technique, from β-diketonate precursors. The variation of the evaporation temperatures of yttrium and zirconium precursor allowed to control the level of Y within the film. Over the temperature range 125–150 °C, the Y content increased from 2.5 to 17.6 at.%. X-ray diffraction (XRD) analyses evidenced tetragonal phase of zirconia when the Y content was below 8 at.%, and cubic phase for higher concentration. Sputtered neutral mass spectrometry (SNMS) profiles confirmed that the control and stability of Y precursor temperature were of major importance to guarantee the …