Zirconia-Porcelain Bonding: Effect of Multiple Firings on Microtensile Bond Strength

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of the Layering Technique on Bond Strength and Cohesive Resistance of a Porcelain-Zirconia System

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structure and catalytic properties of sulfated zirconia foams

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis by a chemical method and characterization of CaZrO3 powders: Potential application as humidity sensors

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of surface treatment on the bond strength between yttria partially stabilized zirconia ceramics and resin cement

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

EVALUATION OF ROUGHNESS, WETTABILITY, AND MORPHOLOGY OF AN YTTRIA-STABILIZED TETRAGONAL ZIRCONIA POLYCRYSTAL CERAMIC AFTER DIFFERENT AIRBORNE-PARTICLE ABRASION PROTOCOL

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Oxide surface modification: Synthesis and characterization of zirconia-coated alumina

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Long-range and short-range structures of cube-like shape SrTiO3 powders: microwave-assisted hydrothermal synthesis and photocatalytic activity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Microwave-assisted hydrothermal synthesis of NiO-Ce1-XEuxO2-δ powders for fuel cell catalytic anodes

CeO2-based materials doped with rare earth (TR +3) can be used as alternative to traditional NiO-YSZ anodes in solid oxide fuel cells as they have higher ionic conductivity and lower ohmic losses compared to YSZ. Moreover, they allow fuel cell operation at lower temperatures (500-800°C). In the anode composition, the concentration of NiO acting as catalyst in YSZ provides high electrical conductivity and high electrochemical activity of reactions, promoting internal reform in the cell. In this work, NiO - Ce1-xEuxO2-δ compounds (x = 0.1, 0.2 and 0.3) have been synthesized by microwave-assisted hydrothermal method. The materials were characterized by TG, XRD, TPR and SEM-FEG techniques. The refinement of data obtained by X-ray diffraction showed the presence of ceria doped with europium crystallized in a cubic phase with fluorite structure, in addition to the presence of NiO. The microwave-assisted hydrothermal method showed significant reduction in the average particle size and good mass control of phase compositions compared to other chemical synthesis techniques.

Parameters optimization of heat treatment for obtaining luminescent PZT powders

Low crystalline PZT powder samples were successfully synthesized using polymeric precursor method and slow decomposition steps. The polymeric resin precursor was thermal treated in a muffle type oven varying the temperature from 250 °C to 700 °C and the time from 3 to 24 hours in order to investigate the order/disorder mechanism toward the amorphous powders. Powder samples with low crystalline phases were obtained at lower temperatures and long time of thermal treatment, demonstrating a kinetic dependence for organic removal and a thermodynamic barrier for crystallization processes. Through XRD and FTIR spectroscopy characterizations the long time thermal treated samples showed to be composed of the solid solution of metal oxides in absent of organic matter, originating broad XRD peaks profiles and no carbonaceous bands in FTIR spectra. A Photoluminescence characterization showed that the peak emission is higher for disordered and homogeneous phases, which only can be reached through the long time of thermal treatment.

Influence of the preparation route on the structural, morphological and spectroscopic properties of SrTiO3 and SrTiO3:eu3+ powders

This research shows the influence of the synthesis route in the structural and morphological characteristics as well as in the luminescent properties of doped with europium and pure SrTiO3 (STO) powders prepared by microwave assisted hydrothermal synthesis, MWH, and by the polymeric precursor method, PPM. The XRD at room temperature of the STO powders nominally pure obtained by PPM at 700°C for 3 hours, as well as by the MWH at 190°C by 30 minutes present all the reflection peaks for the cubic perovskite structure (JCPDS-ICDD 35-734). The morphology varies according to the synthesis route. The particles of pure STO obtained by PPM presents morphology in the form of plates and the morphology of the particles synthesized by MWH is spherical with approximately 150 nm. The photoluminescent analysis shows for pure STO wide bands associated with the transition of charge transfer from the titanates group (TiO3)2- that are centered on 450 nm. In both preparation methods the emission bands obtained in the composites spectra were found to be asymmetric and low intense. However, in the case of the STO prepared by the PPM a bigger FWHM of the band can be observed. The excitation of the samples was done using a laser (Coherent Innova) with wavelength of 350 nm.

Photocatalytic decomposition of rhodamine-B using scandium and silver-modified TiO2 Powders

Semiconductor-mediated photocatalytic oxidation is an interesting method for water decontamination and a specially modified TiO2 is said to be a promising material. This study verified that the synthesis of 1wt%Ag modified-Sc0.01Ti0.99O1.995 powder samples prepared by Polymeric Precursor Method is capable of forming a mixture of anatase-rutile phase with high photocatalytic performance. This kind of material is found to have a lower bandgap compared to the TiO2-anatase commercial powders, which can be associated to an innovative hybrid modification. The simultaneous insertion of scandium in order to generate a p-type semiconductor and a metallic silver nanophase acting as an electron trapper demonstrated being capable of enhancing the degradation of rhodamine B compared to the commercial TiO2. In spite of the different thermal treatments or phase amounts, the hybrid modified powder samples showed higher photocatalytic activity than the commercial ones.

Clinical fractures of veneered zirconia single crowns

Crowns made from an yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) core with a porcelain veneer have shown high clinical failure rates. Manifestations of clinical failure in veneering ceramic ranges from a single chip to an extended fracture. Core failures are uncommon but usually are catastrophic. This article examines the possible causes of failure in zirconia systems and presents a case report involving the diagnosis and repair of three different types of failure in six 3Y-TZP/porcelain crowns.

Air abrasion before and/or after zirconia sintering: surface characterization, flexural strength, and resin cement bond strength

The purpose of this in vitro study was to evaluate the effect of air-abrasion/zirconia sintering order on the yttria partially stabilized tetragonal zirconia polycrystal (Y-TZP) surface characterization (roughness, morphology, and phase transformation), flexural strength (FS), and shear bond strength (SBS) to a resin cement. Y-TZP specimens were air abraded with 50-μm Al2O3 particles after (AS), before (BS), or before and after zirconia sintering (BAS). For roughness (Ra), 30 block specimens (12×12×3.0 mm; n=10) had their surfaces analyzed by a profilometer. Next, on the air-abraded surfaces of these specimens, composite resin discs (n=30) were bonded with RelyX ARC. The bonded specimens were stored for 24 hours in distilled water at 37°C before shear testing. Failure mode was determined with a stereomicroscope (20×). The surface morphology (n=2) was evaluated by SEM (500×). For the four-point flexural strength test (EMIC DL2000), 39 bar-shaped specimens (20×4.0×1.2 mm; n=13) were air abraded according to the three conditions proposed, and an additional group (nonabraded) was evaluated (n=13). The quantitative analysis of phase transformation (n=1) was completed with Rietveld refinement with X-ray diffraction data. Ra (μm) and SBS (MPa) data were analyzed by one-way analysis of variance (ANOVA) and the Tukey test (α=0.05). Pearson correlation analysis was used to determine if there was a correlation between roughness and SBS. For FS (MPa) data, one-way ANOVA and the Dunnett C-test (α=0.05) were used. The air-abrasion/zirconia sintering order influenced significantly (p<0.001) Ra, SBS, and FS. The BS and AS groups presented the highest (1.3 μm) and the lowest (0.7 μm) Ra. The highest SBS (7.0 MPa) was exhibited by the BAS group, followed by the AS group (5.4 MPa) and finally by the BS group (2.6 MPa). All groups presented 100% adhesive failure. A weak correlation (r=−0.45, p<0.05) was found between roughness and SBS. The air-abrasion/zirconia sintering order provided differences in the surface morphology. The nonabraded (926.8 MPa) and BS (816.3 MPa) groups exhibited statistically similar FS values but lower values than the AS (1249.1 MPa) and BAS (1181.4 MPa) groups, with no significant difference between them. The nonabraded, AS, BS, and BAS groups exhibited, respectively, percentages of monoclinic phase of 0.0 wt%, 12.2 wt%, 0.0 wt%, and 8.6 wt%. The rougher surface provided by the air-abrasion before zirconia sintering may have impaired the bonding with the resin cement. The morphological patterns were consistent with the surface roughness. Considering the short-term SBS and FS, the BAS group exhibited the best performance. Air abrasion, regardless of its performance order, provides tetragonal to monoclinic transformation, while sintering tends to zero the monoclinic phase content.

Effect of particle size on the flexural strength and phase transformation of an airborne-particle abraded yttria-stabilized tetragonal zirconia polycrystal ceramic.

Statement of problem Because airborne-particle abrasion is an efficient method of improving the bond at the zirconia-cement interface, understanding its effect on the strength of yttria-stabilized tetragonal zirconia polycrystal is important. Purpose The purpose of this study was to evaluate the effect of the particle size used for airborne-particle abrasion on the flexural strength and phase transformation of a commercially available yttria-stabilized tetragonal zirconia polycrystal ceramic. Material and Methods For both flexural strength (20.0 × 4.0 × 1.2 mm) (n=14) and phase transformation (14.0-mm diameter × 1.3-mm thickness) (n=4), the zirconia specimens were made from Lava, and their surfaces were treated in the following ways: as-sintered (control); with 50-μm aluminum oxide (Al2O3) particles; with 120-μm Al2O3 particles; with 250-μm Al2O3 particles; with 30-μm silica-modified Al2O3 particles (Cojet Sand); with 120-μm Al2O3 particles, followed by 110-μm silica-modified Al2O3 particles (Rocatec Plus); and with Rocatec Plus. The phase transformation (%) was assessed by x-ray diffraction analysis. The 3-point flexural strength test was conducted in artificial saliva at 37°C in a mechanical testing machine. The data were analyzed by 1-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05). Results Except for the Cojet Sand group, which exhibited statistically similar flexural strength to that of the as-sintered group and for the group abraded with 250-μm Al2O3 particles, which presented the lowest strength, airborne-particle abrasion with the other particle sizes provided the highest values, with no significant difference among them. The as-sintered specimens presented no monoclinic phase. The groups abraded with smaller particles (30 μm and 50 μm) and those treated with the larger ones (110 μm and/or 120 μm particles and 250 μm) exhibited percentages of monoclinic phase that varied from 4% to 5% and from 8.7% to 10%. Conclusions Except for abrasion with Cojet Sand, depending on the particle size, zirconia exhibited an increase or a decrease in its flexural strength. Airborne-particle abrasion promoted phase transformation (tetragonal to monoclinic), and the percentage of monoclinic phase varied according to the particle size.