This study evaluated the shear bond strength between dual‐cured resin luting cement and pure zirconium (99.9%) and industrially manufactured yttrium‐oxide‐partially‐stabilized zirconia ceramic, and the effect of MDP (10‐methacryloyloxydecyl dihydrogen phosphate) primer (MP) and zirconate coupler (ZC) on bond strength. Two different‐shaped pure zirconium and zirconia ceramic specimens were untreated or treated with various primers, including different concentrations of MP containing phosphoric acid ester monomer (MDP) in ethanol, ZC containing a zirconate coupling agent in ethanol, or a mixture of MP and ZC. The specimens were then cemented together with dual‐cured resin luting cement (Clapearl DC). Half of the specimens were stored in water at 37°C for 24 h and the other half were thermocycled 10,000 times before shear bond strength testing. The bond strengths of resin luting cement to both the zirconium and zirconia ceramic were enhanced by the application of most MPs, ZCs, and the mixtures of MP and ZC. For the group (MP2.0+ZC1.0) containing 2.0 wt % MP and 1.0 wt % ZC, no significant difference was observed between in shear bond strength before and after thermal cycling for both zirconium and zirconia ceramic (p > 0.05). For the other primers, statistically significant differences in shear bond strength before and after thermal cycling were observed (p < 0.05). The application of the mixture of MP and ZC (MP2.0+ZC1.0) was effective for bonding between zirconia ceramic and dual‐cured resin luting cement. This primer may be clinically useful as an adhesive primer for zirconia ceramic restoration. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006

This study evaluated the effect of alumina-blasting and three commercial adhesive primers on the shear bond strength of a dual-cured resin luting agent to zirconia ceramics. Two different-sized zirconia ceramic specimens were treated with or without alumina-blasting and then treated with one of three adhesive primers. Subsequently, specimens were cemented together with Linkmax HV（GC） . Half of the specimens were stored in water at 37℃ for 24 hours and the other half thermocycled 10,000 times before shear bond strength testing. For groups treated with either alumina-blasting or primer, shear bond strength significantly decreased after thermal cycling. For groups treated with both alumina-blasting and one of the three primers, there were no significant differences in shear bond strength before and after thermal cycling（p＜0.05） . It was thus concluded that the application of each of the three adhesive primers following alumina-blasting was effective for strong bonding of resin luting agent to zirconia ceramics.

Three-point bending tests were performed after 24 h storage at 37°C. Two different-shaped zirconia ceramic specimens with or without sandblasting with alumina were treated with each primer. The specimens were then cemented together with each resin luting agent. Half of the specimens were stored in water at 37°C for 24 h and the other half were thermocycled 5,000 times. Results: VLII revealed statistically higher Knoop hardness and flexural modulus than NRC for each thickness of ceramic. No significant differences in flexural strength were observed between VLII and NRC for each ceramic spacer.Reduction of the mechanical properties with increase of ceramic thickness varied for each property. However, these properties were similar between the two materials. Blasting with alumina was significantly effective for increasing shear bond strength of both resin luting agents before and after thermal cycling.The use of New Ceramic Primer showed the highest shear bond strength and maintained bond durability after 5,000 thermocycles. Conclusion: Mechanical properties of NRC dual-cured resin luting agent appear adequate for ceramic 3 restorations.

The photoelectrochemical behavior of electrochemically etched Si cathodes contacting a nonaqueous redox electrolyte is described. The electrochemically etched Si electrodes exhibit higher energy conversion efficiencies than Si electrodes chemically treated in HF solution. The porous Si layer formed during electrochemical etching plays an important role in suppressing surface recombination and stabilizing the Si electrodes against photocorrosion.

We report on the results of our investigation of using porous Si to enhance the performance of crystalline silicon photovoltaic solar cells. Possible approaches include using the porous Si for (1) surface texturing to enhance light trapping, (2) front or back surface fields because of its wider bandgap, and (3) photon color conversion of blue light to longer wavelengths that have higher quantum efficiency in a Si solar cell. In our surface texturing study, a porous-Si-covered single-crystal Si wafer showed an integrated reflectance of only 1.4% at 500-nm wavelength compared to about 40% for a polished Si surface. For our solar cell study, we used a point-contact cell structure with diffused p+ and n+ point contacts on the back of the cell. This cell structure allows us to form the porous Si on the front surface after both the junction formation and the evaporation and alloying of metal contacts.

Abstract:The purpose of this study was to determine the flexural strength and flexural fatigue strength of a machinable composite (GN-I) and three hybrid composites (Artglass, Estenia, and Gradia). Specimens (2×2×25 mm) were polymerized in a laboratory-photo-curing unit and then immersed in water at 37°C for 24 h, 6 months, and 1 year. After each immersion period, flexural strengths (4-PFS) were measured at a cross-head speed of 1 mm/min in 4-point bending (span = 20 mm; distance between inside loading points = 10 mm).The cyclic fatigue test was performed at 2.0 Hz on a fatigue tester. The staircase method was employed for flexural fatigue strength (FFS) using a 5,000 cyclic load limitation, 5 MPa stress increment, and 20 specimens for each material. Both 4-PFS and FFS of the machinable composite after all immersion periods were significantly greater than those of the three hybrid composites. The FFS results followed the same pattern as those of the 4-PFS.The Estenia material exhibited the highest 4-PFS and FFS after 24-h-immersion among three hybrid composites, whereas after 1-year-immersion, all three composites showed almost identical 4-PFS and FFS statistically. A strong correlation was observed between 4-PFS and FFS of the machinable composite and three hybrid resin composites.

We report a treatment that enhances and stabilizes the photoluminescence (PL) from porous Si films. Films prepared by anodization in a 50% HF/ethanol solution were annealed at 450 °C in vacuum, exposed to air, and then exposed to a remote-hydrogen plasma. Infrared absorption spectroscopy revealed that the concentration of oxygen, rather than hydrogen, was increased by the processing steps, and that silicon dihydride species had been eliminated from the surface. The PL from a treated film was initially ∼30 times more intense than from the as-etched films. The PL intensity increased with illumination time in air until a steady-state intensity was reached.

Hydrogen-bombardment-induced structural changes in single-crystal silicon were studied using ellipsometry and transmission electron microscopy techniques. Hydrogen ion energies ranged from 400 to 1900 eV and the total dose was about 5×1019 ions/cm2. Various degrees of damage and phase mixtures in the layers were identified. It was concluded that ellipsometry can be used effectively as a nondestructive characterizational tool for analyzing bombardment-induced microstructural changes in this material.