Controlled growth of anodic aluminium oxide films with hexagonal array of nanometer-sized pores filled with textured copper nanowires

Anodic aluminium oxide (AAO) films exhibiting a homogeneous morphology of parallel pores perpendicular to the surface were prepared in a two-step anodization process and filled with copper by electrochemical deposition. The optimum growth conditions for the formation of freestanding AAO films with hexagonal compact array of cylindrical pores were studied by field emission scanning electron microscopy and small angle X-ray scattering. The results show well-defined periodic structures with uniform pores size distribution for films with pore diameters between 40 and 70 nm prepared using different voltages and temperatures during the second anodization step. X-ray photoelectron spectroscopy and X-ray diffraction analysis of AAO films filled with copper show the formation of nanowires with high structural order, exhibiting a preferential crystalline orientation along the (2 2 0) axis and only small fraction of copper oxides. The best results for textured Cu nanowires were obtained at a reduction potential of -300 mV. (C) 2009 Elsevier Ltd. All rights reserved.

Effect of cobalt(II) oxide and manganese(IV) oxide on sintering of tin(IV) oxide

Additions of 0.5 to 2.0 mol% of CoO or MnO2 onto SnO, promote densification of this oxide up to 99% of theoretical density. The temperature of the maximum shrinkage rate (TM) and the relative density in the maximum densification rate (p*) during constant sintering heating rate depend on the dopant concentration. Thus, dopant concentration controls the densifying and nondensifying mechanisms during sintering. The densification of SnO2 witih addition of CoO or MnO, is explained in terms of the creation of oxygen vacancies.

Sintering of tin oxide processed by slip casting

Sintering of SnO 2 compacts, obtained through slip casting, was studied by means of dilatometry, Hg porosimetry, scanning electron microscopy, and density measurement (Archimedes method). Sintering is strongly influenced by the green microstructure. Moreover, the sintering mechanisms are not dependent on the slurries' solid content up to 50% of solids in volume. Above this value, agglomerates are formed, leading to differential sintering inside and among the agglomerates. Another important point is the reduction of the temperature of maximum shrinkage rate when compared to tin oxide processed by isostatic pressing. This reduction is more accentuated when ammonium hydroxide is added to the suspension. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.

Rheological properties of tin oxide suspensions

The rheological properties of tin oxide slurries were studied experimentally and theoretically. The deflocculants used were ammonium polyacrilate (PAA) and the copolymer poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB-PVA-PVAc), in water and ethanol, respectively. The amount of deflocculant was optimized for different solid contents by means of viscosity measurements. In spite of the high stability of PVB-dispersed slurries, a high solid concentration was not obtained. On the other hand, a slurry with a 56.4 vol.% of solids was attained when PAA was used. A theoretical study of the adsorption of PAA in its dissociated (basic solution) and non-dissociated (acidic solution) forms on SnO 2 (110) is presented. This analysis was made by means of the PM3 method using a large cluster Sn 15O 28 for the surface model. The calculated adsorption energy is larger for the ionized PAA than for the non-ionized form, indicating that alkaline slurries favor PAA adsorption on the SnO 2 surface. © 2002 Elsevier Science Ltd. All rights reserved.

Effect of ceramic surface treatment on the microtensile bond strength between a resin cement and an alumina-based ceramic

Purpose: The objective of this study was to test the following hypothesis: the silica coating on ceramic surface increases the bond strength of resin cement to a ceramic. Materials and Methods: In-Ceram Alumina blocks were made and the ceramic surface was treated: G1 - sandblasting with 110-μm aluminum oxide particles; G2 - Rocatec System: tribochemicai silica coating (Rocatec-Pre powder + Rocatec-Plus powder + Rocatec-Sil); G3 - CoJet System: silica coating (CoJet-Sand) + ESPE-Sil. The ceramic blocks were cemented to composite blocks with Panavia F resin cement (under a load of 750 g/1 min). The cemented blocks were stored in distilled water at 37°C for 7 days and sectioned along the x and y axes with a diamond disk. Samples with an adhesive area of ca 0.8 mm 2 (n = 45) were obtained. The samples were attached to an adapted device for the microtensile test, which was performed in a universal testing machine (EMIC) at a crosshead speed of 1 mm/min. Results: The obtained results were submitted to ANOVA and Tukey's test. Mean values of tensile strength (MPa) and standard deviation values were: (G1) 16.8 ± 3.2; (G2) 30.6 ± 4.5; (G3) 33.0 ± 5.0. G2 and 63 presented greater tensile strength than G1. There was no significant difference between G2 and G3. All the failures took place at the ceramic/resin cement interface. Conclusion: The silica coating (Rocatec or CoJet systems) of the ceramic surface increased the bond strength between the Panavia F resin cement and alumina-based ceramic.

Effect of surface treatments on the resin bond to zirconium-based ceramic

Purpose: This study tested the hypothesis that the tribochemical silica coating on ceramic surfaces increases the bond strength of resin cement to a glass-infiltrated zirconium-based ceramic. Materials and Methods: Fifteen blocks of In-Ceram Zirconia from CEREC InLab (5 per group) and 15 composite blocks (Z-250) 5 mm x 5 mm x 4 mm were made. The ceramic surfaces were polished, and the blocks were divided into three groups: (1) airborne abrasion with 110-μm aluminum oxide particles; (2) Rocatec system, tribochemical silica coating; and (3) CoJet system, tribochemical silica coating. The ceramic blocks were cemented to the composite blocks using Panavia F according to the manufacturer's specifications. All samples were stored in 37°C distilled water for 7 days and later sectioned in two axes using a diamond disk under cooling to obtain specimens with a cross-sectional area of approximately 1 mm2 (n = 45). Each specimen was then attached with cyanoacrylate glue to an adapted device for the microtensile test, which was carried out on a universal testing machine. Results: The results were subjected to ANOVA and Tukey's test. Group 2 (23.0 ± 6.7 MPa) and group 3 (26.8 ± 7.4 MPa) showed greater bond strength than group 1 (15.1 ± 5.3 MPa). There was no significant difference between groups 2 and 3. All failures were in the adhesive zone. Conclusion: The hypothesis was confirmed - the tribochemical systems increased the bond strength between Panavia F and In-Ceram Zirconia.

Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic: The effect of surface conditioning

This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Thirty blocks (5×5×4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR, VITA) were fabricated according to the manufacturer's instructions and duplicated in resin composite. The specimens were polished and assigned to one of the following three treatment conditions (n=10): (1) Airborne particle abrasion with 110 μm Al2O3 particles + silanization, (2) Silica coating with 110 μm SiOx particles (Rocatec Pre and Plus, 3M ESPE) + silanization, (3) Silica coating with 30 μm SiOx particles (CoJet, 3M ESPE) + silanization. The ceramic-composite blocks were cemented with the resin cement (Panavia F) and stored at 37 °C in distilled water for 7 days prior to bond tests. The blocks were cut under coolant water to produce bar specimens with a bonding area of approximately 0.6 mm2. The bond strength tests were performed in a universal testing machine (cross-head speed: 1 mm/min). The mean bond strengths of the specimens of each block were statistically analyzed using ANOVA and Tukey's test (α≤0.05). Silica coating with silanization either using 110 μm SiOx or 30 μm SiOx particles increased the bond strength of the resin cement (24.6±2.7 MPa and 26.7±2.4 MPa, respectively) to the zirconia-based ceramic significantly compared to that of airborne particle abrasion with 110-μm Al2O3 (20.5±3.8 MPa) (ANOVA, P<0.05). Conditioning the INC-ZR ceramic surfaces with silica coating and silanization using either chairside or laboratory devices provided higher bond strengths of the resin cement than with airborne particle abrasion using 110 μm Al2O3. © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Fatigue resistance of the bond of a glass-infiltrated alumina ceramic to human dentin

Purpose: To evaluate the fatigue resistance of the bond between dentin and glass-infiltrated alumina ceramic, using different luting protocols. Materials and Methods: The null hypothesis is that the fatigue resistance varies with the luting strategy. Forty blocks of In-Ceram Alumina were prepared, and one surface of each block was abraded with 110-μm aluminum oxide particles. Then, the blocks were luted to flat dentin surfaces of 40 human third molars, using 4 different luting strategies (luting system [LS]/ceramic surface conditioning [CSC]) (n=10): (G1) [LS] RelyX-Unicem/[CSC] airborne abrasion with 110-μm Al2O3 particles; (G2) [LS] One-Step + Duo-Link (bis-GMA-based resin)/[CSC] etching with 4% hydrofluoric acid + silane agent; (G3) [LS] ED-Primer + Panavia F (MDP-based resin)/[CSC] Al2O 3; (G4) [LS] Scotchbond1+RelyX-ARC (bis-GMA-based resin)/[CSC] chairside tribochemical silica coating (air abrasion with 30-μm SiO x particles + silane). After 24 h of water storage at 37°C, the specimens were subjected to 106 fatigue cycles in shear with a sinusoidal load (0 to 21 N, 8 Hz frequency, 37°C water). A fatigue survivor score was given, considering the number of the fatigue cycles until fracture. The failure modes of failed specimens were observed in a SEM. Results: G3 (score = 5.9, 1 failure) and G4 (score = 6, no failures) were statistically similar (p = 0.33) and had significantly higher fatigue resistance than G1 (score = 3.9, 5 failures) and G2 (score = 3.7, 6 failures) (p < 0.03). SEM analysis of fractured specimens of G1 and G2 showed that almost all the failures were between ceramic and cement. Conclusion: The MDP-based resin cement + sandblasting with Al2O3 particles (G3) and bis-GMA-based resin cement + tribochemical silica coating (G4), both using the respective dentin bonding systems, were the best luting protocols for the alumina ceramic. The null hypothesis was confirmed.

Bond strength of a resin cement to high-alumina and zirconia-reinforced ceramics: The effect of surface conditioning

Purpose: The aim of this study was to evaluate the effect of two surface conditioning methods on the microtensile bond strength of a resin cement to three high-strength core ceramics: high alumina-based (In-Ceram Alumina, Procera AllCeram) and zirconia-reinforced alumina-based (In-Ceram Zirconia) ceramics. Materials and Methods: Ten blocks (5 ×6 × 8 mm) of In-Ceram Alumina (AL), In-Ceram Zirconia (ZR), and Procera (PR) ceramics were fabricated according to each manufacturer's instructions and duplicated in composite. The specimens were assigned to one of the two following treatment conditions: (1) airborne particle abrasion with 110-μm Al2O3 particles + silanization, (2) silica coating with 30 μm SiOx particles (CoJet, 3M ESPE) + silanization. Each ceramic block was duplicated in composite resin (W3D-Master, Wilcos, Petrópolis, RJ, Brazil) using a mold made out of silicon impression material. Composite resin layers were incrementally condensed into the mold to fill up the mold and each layer was light polymerized for 40 s. The composite blocks were bonded to the surface-conditioned ceramic blocks using a resin cement system (Panavia F, Kuraray, Okayama, Japan). One composite resin block was fabricated for each ceramic block. The ceramic-composite was stored at 37°C in distilled water for 7 days prior to bond tests. The blocks were cut under water cooling to produce bar specimens (n = 30) with a bonding area of approximately 0.6 mm2. The bond strength tests were performed in a universal testing machine (crosshead speed: 1 mm/min). Bond strength values were statistically analyzed using two-way ANOVA and Tukey's test (≤ 0.05). Results: Silica coating with silanization increased the bond strength significantly for all three high-strength ceramics (18.5 to 31.2 MPa) compared to that of airborne particle abrasion with 110-μm Al2O3 (12.7-17.3 MPa) (ANOVA, p < 0.05). PR exhibited the lowest bond strengths after both Al2O3 and silica coating (12.7 and 18.5 MPa, respectively). Conclusion: Conditioning the high-strength ceramic surfaces with silica coating and silanization provided higher bond strengths of the resin cement than with airborne particle abrasion with 110-μm Al2O3 and silanization.

Polishing methods of an alumina-reinforced feldspar ceramic

The purpose of this study was to test the hypothesis that mechanical polishing methods of ceramic surfaces allow similar superficial roughness to that of glazed surfaces. Twenty-five Vitadur Alpha ceramic discs (5 mm x 2 mm) were prepared according to the manufacturer's specifications. All specimens were glazed and randomly assigned to 5 groups (n=5), according to finishing and polishing protocols: G1: glazed (control); G2: diamond bur finishing; G3: G2 + silicon rubber tip polishing; G4: G3 + felt disc/diamond polishing paste; G5: G3 + felt disc impregnated with fine-particle diamond paste. Next, surface roughness means (Ra - μm) were calculated. Qualitative analysis was made by scanning electron microscopy. Surface roughness data were submitted to ANOVA and Tukey's test at 5% significance level. G1 and G4 were statistically similar (p>0.05). G2 presented the highest roughness means (p<0.05) followed by groups G3, G5, G4 and G1 in a decreasing order. The hypothesis was partially confirmed as only the mechanical polishing (G4) produced similar superficial roughness to that of surface glazing, although finishing and polishing are technically critical procedures.

Microtensile bond strength of a repair composite to leucite-reinforced feldspathic ceramic

The purpose of this study was to evaluate the microtensile bond strength of a repair composite resin to a leucite-reinforced feldspathic ceramic (Omega 900, VITA) submitted to two surface conditionings methods: 1) etching with hydrofluoric acid + silane application or 2) tribochemical silica coating. The null hypothesis is that both surface treatments can generate similar bond strengths. Ten ceramic blocks (6x6x6 mm) were fabricated and randomly assigned to 2 groups (n=5), according to the conditioning method: G1- 10% hydrofluoric acid application for 2 min plus rinsing and drying, followed by silane application for 30 s; G2- airborne particle abrasion with 30 μm silica oxide particles (CoJet-Sand) for 20 s using a chairside air-abrasion device (CoJet System), followed by silane application for 5 min. Single Bond adhesive system was applied to the surfaces and light cured (40 s). Z-250 composite resin was placed incrementally on the treated ceramic surface to build a 6x6x6 mm block. Bar specimens with an adhesive area of approximately 1 ± 0.1 mm2 were obtained from the composite-ceramic blocks (6 per block and 30 per group) for microtensile testing. No statistically significant difference was observed between G1 (10.19 ± 3.1 MPa) and G2 (10.17 ± 3.1 MPa) (p=0.982) (Student's t test; á = 0.05). The null hypothesis was, therefore, accepted. In conclusion, both surface conditioning methods provided similar microtensile bond strengths between the repair composite resin and the ceramic. Further studies using long-term aging procedures should be conducted.

Effect of ceramic surface treatment on the shear bond strength of a resin cement to different ceramic systems

This study evaluated three surface treatments and their effects on the shear bond strength between a resin cement and one of three ceramics. The ceramic surfaces were evaluated with scanning electron microscopy (SEM ) as well. Specimens were treated with 50 μm aluminum oxide airborne particles, 10% hydrofluoric acid etching, or a combination of the two. Using a matrix with a center hole (5.0 mm × 3.0 mm), the ceramic bonding areas were filled with resin cement following treatment. The specimens were submitted to thermal cycling (1,000 cycles) and the shear bond strength was tested (0.5 mm/minute). The failure mode and the effect of surface treatment were analyzed under SEM . Data were submitted to ANOVA and a Tukey test (α = 0.05). Duceram Plus and IPS Empress 2 composite specimens produced similar shear bond strength results (p > 0.05), regardless of the treatment method used. Hydrofluoric acid decreased the shear bond strength of In-Ceram Alumina specimens. For all materials, surface treatments changed the morphological surface. All treatments influenced the shear bond strength and failure mode of the ceramic/resin cement composites.

Broadband NIR emission in novel sol-gel Er3+-doped SiO 2-Nb2O5 glass ceramic planar waveguides for photonic applications

This paper reports on the sol-gel preparation and structural and optical characterization of new Er3+-doped SiO2-Nb 2O5 nanocomposite planar waveguides. Erbium-doped (100-x)SiO2-xNb2O5 waveguides were deposited on silica-on-silicon substrates and Si(1 0 0) by the dip-coating technique. The waveguides exhibited uniform refractive index distribution across the thickness, efficient light injection at 1538 nm, and low losses at 632 and 1538 nm. The band-gap values lied between 4.12 eV and 3.55 eV for W1-W5, respectively, showing an excellent transparency in the visible and near infrared region for the waveguides. Fourier Transform Infrared (FTIR) Spectroscopy analysis evidenced SiO2-Nb2O5 nanocomposite formation with controlled phase separation in the films. The HRTEM and XRD analyses revealed Nb2O5 orthorhombic T-phase nanocrystals dispersed in a silica-based host. Photoluminescence (PL) analysis showed a broad band emission at 1531 nm, assigned to the 4I13/2 → 4I15/2 transition of the Er3+ ions present in the nanocomposite, with a full-width at half medium of 48-68 nm, depending on the niobium content and annealing. Hence, these waveguides are excellent candidates for application in integrated optics, especially in EDWA and WDM devices. © 2012 Elsevier B.V. All rights reserved.

Dielectric behavior of epoxy/BaTiO3 composites using nanostructured ceramic fibers obtained by electrospinning

Composite materials made of epoxy resin and barium titanate (BT) electrospun nanostructured fibers were prepared. BT fibers were synthesized from a sol based on barium acetate, titanium isopropoxide, and poly(vinyl pyrrolidone). The fibers were heat-treated at different temperatures and characterized by X-ray diffraction, scanning electron microscopy (SEM), and Raman spectroscopy. Mats of BT fibers heat-treated at 800 C were embedded in epoxy resin into suitable molds. The composites were characterized by SEM, and dielectric measurements were performed by means of dielectric spectroscopy. The dielectric permittivity and dielectric modulus of epoxy resin/BT-fiber composites were measured for two types of samples: with the electrodes parallel and perpendicular to the BT fiber layers. Interestingly, composite samples with electrodes perpendicular to the fiber layers and a BT content as low as 2 vol % led to dielectric permittivities three times higher than that of pure epoxy resin. © 2013 American Chemical Society.

Optical properties of the MoO3-TiO2 particulate system and its use as a ceramic pigment

Mo-doped TiO2 powders were prepared using a dry mixture of TiO2 and MoO3 oxides with several compositions, followed by a calcination step at several temperatures. The resulting oxide system develops yellow and green tones. The XRD patterns showed only traces of MoO 3; however, EDS results, combined with TG/DTA data, confirmed the presence of molybdenum ions, suggesting that the changes in optical properties of the oxide system is due to the incorporation of Mo ions into the TiO 2 matrix, substituting Ti+4 with Mo+6 ions. The band gap decreased with increasing of MoO3 content; on the other hand, the band gap reached a maximum value at about 850°C to 910°C when plotted as a function of the calcination temperature. The glazes produced showed that the oxide system under study is a potential material for use as abinary ceramic pigment. Copyright © 2013 Taylor & Francis Group, LLC.