Synthesis and photoluminescence study of La1.8Eu0.2O3 coating on nanometric alpha-Al2O3

In this work the La1.8Eu0.2O3 coating on nanometric alpha-alumina, alpha-Al2O3@La1.8Eu0.2O3, was prepared for the first time by a soft chemical method. The powder was heat-treated at 100, 400, 800 and 1200 degrees C for 2 h. X-ray powder diffraction patterns (XRD), transmission electronic microscopy (TEM), emission and excitation spectra, as well as Eu3+, lifetime were used to characterize the material and to follow the changes in structure as the heating temperature increases. The Eu3+ luminescence data revealed the characteristic transitions D-5(0) --> F-7(J) (J = 0, 1 and 3) of Eu3+ at around 580, 591 and 613 nm, respectively, when the powders were excited by 393 nm. The red color of the samples changed to yellow when the powder was annealed at 1200 degrees C. The decrease in the (D-5(0) --> F-7(2))/(D-5(0) --> F-7(1)) ratio from around 5.0 for samples heated at lower temperatures to 3.1 for samples annealed at 1200 degrees C is consistent with a higher symmetry of the Eu3+ at higher temperature. The excitation spectra of the samples also confirms this change by the presence of a more intense and broad band at around 317 nm, instead of the presence of the characteristic peak at 393 mn, which corresponds to the F-7(0) --> L-5(6) transition of the Eu3+. The lifetimes of the D-5(0) --> F-7(2) transition of Eu3+ for the samples heat-treated at 100, 400, 800 and 1200 degrees C was evaluated as 0.57, 0.72, 0.43 and 0.31 ms, respectively. (C) 2006 Elsevier Ltd. All fights reserved.

Microstructure and corrosion resistance of inorganic-organic (ZrO2-PMMA) hybrid coating on stainless steel

Zirconia-polymethylmetacrylate hybrids prepared by a sol-gel method were deposited by dip-coating on stainless steel to improve the resistance against wet corrosion. The effect of the concentration of polymethylmetacrylate and the number of coating applications on the microstructure and corrosion performance of coated samples was investigated. The microstructural properties of samples was analyzed by scanning electron and atomic force microscopy, adhesion tests and profilemeter measurements. The electrochemical corrosion was evaluated through potentiodynamic polarization curves at room temperature. Results show that the sample prepared with 17 vol.% of polymethylmethacrylate has a maximum corrosion resistance, smaller roughness, are hermetic and adherent to the substrate. This film increases the life time of the stainless steel by a factor 30. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Poole-Frenkel effect in Er doped SnO2 thin films deposited by sol-gel-dip-coating

Electrical properties of Er-doped SnO2 thin films obtained by sol-gel-dip-coating technique were measured. When compared to undoped tin dioxide, rare-earth doped films present much higher resistivity, indicating that Er3+ presents an acceptor-like character into the matrix, which leads to a high degree of electric charge compensation. Current-voltage characteristics, measured above room temperature for Er-doped films, lead to non-linear behavior and two conduction regimes. In the lower electric field range the conduction is dominated by Schottky emission over the grain boundary potential barrier, which presents an average value of 0.85 eV. Increasing the applied bias, a second regime of conduction is observed, since the Poole-Frenkel coulombic barrier lowering becomes a significant effect. The obtained activation energy for ionization is 0.67 eV. (C) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure of SnO2 alcosols and films prepared by sol-gel dip coating

To obtain SnO2 films to be used for surface protection of fluoride glasses, a non-aqueous sol-gel route for the preparation was developed. An ethanolic SnO2 colloidal suspension was prepared by thermohydrolysis of SnCl4 solution at 70 degreesC. By using this procedure, redispersable powders with nanometer sized particles were obtained. Films were obtained by dip coating on glass and mica substrates. The structures of the ethanolic precursor suspension and films were compared to those of similar samples prepared by the classical aqueous sol-gel route. Comparative analyses performed by photon correlation spectroscopy demonstrated that the powders obtained by freeze-drying are fully redispersable either in aqueous or in alcoholic solutions at pH greater than or equal to 8. As prepared sols and redispersed colloidal suspensions have hydrodynamic radius distribution (2-14 nm) with an average size close to 7 nm. The variations in film structures with firing temperature were investigated by small-angle X-ray scattering and X-ray reflectometry. The experimental results show that the films have a two level porous structure composed of agglomerates of primary colloidal particles. The sintering of the primary particles leads to the densification of agglomerates and to the formation of inter-agglomerate spatially correlated pores. The volume fraction of intra-agglomerate pores is reduced from approximate to 50% to approximate to 30% by the precipitation of precursor salts partially hydrolyzed in ethanolic solution. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Influence of heat treatment on the optical properties of SnO2 : Sb thin films deposited by dip coating using aqueous solution

Antimony doped tin oxide thin films were deposited on glass by a chemical route derived from Pechini method. Particular emphasis was given to the microstructure of crystallized films. Crystalline phase formation was studied by grazing incident X-ray diffraction and by thermal analyses. Scanning electron microscopy was carried out for microstructure characterization, surface roughness was observed using scanning tunneling microscope and the optical transmittance measurements were performed in the wavelength range of 200-800 nm. (C) 2002 Kluwer Academic Publishers.

Transparent and conductive ZnO : Al thin films prepared by sol-gel dip-coating

Aluminum doped zinc oxide polycrystalline thin films (AZO) were prepared by sol-gel dip-coating process. The sol was prepared from an ethanolic solution of zinc acetate using lithium hydroxide or succinic acid as hydrolytic catalyst. The quantity of aluminum in the sol was varied from 1 to 10 mol%. The structural characteristics studied by X-ray diffractometry were complemented by resistivity measurements and UV-Vis-NIR spectroscopy. The films are transparent from the near ultraviolet to the near infrared, presenting an absorption cut-off at almost 290 nm, irrespective of the nature of the catalyst and doping level. The best conductors were obtained for the AZO films containing 3 mol% of aluminum, prepared under acidic and basic catalysis and sintered at 450 degreesC. Their optical band-gap of 4.4 eV calculated from the absorption cut-off is larger than the values for band-gap widening predicted by the standard model for polar semiconductors. These polycrystalline films are textured with preferential orientation of grains along the wurtzite c-axis or the (100) direction. (C) 2003 Elsevier Ltd. All rights reserved.

Deposition of controlled thickness ultrathin SnO2 : Sb films by spin-coating

The technological interest in transparent conductive oxide films (TCOs) has motivated several works in processing techniques, in order to obtain adequate routes to application. In this way, this work describes a new route to obtain antimony-doped tin oxide (ATO) films, based in colloidal dispersions of oxide nanocrystals. The nanoparticles were obtained by a hydrolisis method, using SnCl2 and SbCl3 in ethanolic solutions. The residual halides were removed by dyalisis, obtaining a limpid and transparent colloidal suspension. By this, the method offers the advantage of producing ultrathin films without organic contaminants. This route was employed to produce films with 5, 10, 14, and 18 mol% Sb doping, with thickness ranging from 40 to 70 nm. The physical characterization of the samples showed a uniform layer deposition, resulting in good packing density and high transmittance. A preliminar electrical study confirmed the low electrical resistivity even in the ultrathin films, in such level similar of reported data. The method described is similar in some aspects to layer-by-layer (LbL) techniques, allowing fine control of thickness and interesting properties for ultrathin films, however, with low cost when compared to similar routes.

Preparation of 9/65/35 PLZT thin films deposited by a dip-coating process

Crack-free polycrystalline PLZT (Pb,a)(Zr,Ti)O-3 thin films with the perovskite structure were prepared by dir-coating using the Pechinis process. Lead acetate, hydrated lanthanum carbonate, zirconium n-propoxide and titanium isopropoxide were used as raw materials. The viscosity of the solution was adjusted in the range of 20 to 56 cP and the films were deposited by a dip-coating process on silicon (100) as substrate. Solutions with ionic concentration of 0.1 and 0.2 M were used. Thin film deposition was accomplished by dipping the substrates in the solution with control of withdrawal speed from 5 to 20 mm/min. The thin films were thermally treated in two steps: at 300 degreesC amid 650 degreesC. The influence of withdrawal speed. viscosity, heating rate and ionic concentration on the morphology of PLZT thin film was discussed. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Hard tissue formation adjacent to implants of various size and configuration immediately placed into extraction sockets: an experimental study in dogs

ObjectivesTo evaluate the influence of implant size and configuration on osseointegration in implants immediately placed into extraction sockets.Material and methodsImplants were installed immediately into extraction sockets in the mandibles of six Labrador dogs. In the control sites, cylindrical transmucosal implants (3.3 mm diameter) were installed, while in the test sites, larger and conical (root formed, 5 mm diameter) implants were installed. After 4 months of healing, the resorptive patterns of the alveolar crest were evaluated histomorphometrically.ResultsWith one exception, all implants were integrated in mineralized bone, mainly composed of mature lamellar bone. The alveolar crest underwent resorption at the control as well as at the test implants. This resorption was more pronounced at the buccal aspects and significantly greater at the test (2.7 +/- 0.4 mm) than at the control implants (1.5 +/- 0.6 mm). However, the control implants were associated with residual defects that were deeper at the lingual than at the buccal aspects, while these defects were virtually absent at test implants.ConclusionsThe installment of root formed wide implants immediately into extraction sockets will not prevent the resorption of the alveolar crest. In contrast, this resorption is more marked both at the buccal and lingual aspects of root formed wide than at standard cylindrical implants.To cite this article:Caneva M, Salata LA, de Souza SS, Bressan E, Botticelli D, Lang NP. Hard tissue formation adjacent to implants of various size and configuration immediately placed into extraction sockets: an experimental study in dogs.Clin. Oral Impl. Res. 21, 2010; 885-895.doi: 10.1111/j.1600-0501.2010.01931.x.

Optimization of Radial Basis Function neural network employed for prediction of surface roughness in hard turning process using Taguchi's orthogonal arrays

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of implants with different sizes and configurations installed immediately into extraction sockets on peri-implant hard and soft tissues: an experimental study in dogs

Aim: To study the influence on the healing of soft and hard peri-implant tissues when implants of different sizes and configurations were installed into sockets immediately after tooth extraction.Material and methods: Transmucosal cylindrical implants, 3.3 mm in diameter in the control sites, and conical 5 mm in diameter in the test sites, were installed into the distal socket of the fourth mandibular premolars in dogs immediately after tooth extraction. After 4 months, the hard and soft tissue healing was evaluated histologically. Results: All implants were integrated in mineralized mature bone. Both at the test and control sites, the alveolar crest underwent resorption. The buccal bony surface at the implant test sites (conical; 3.8 mm) was more resorbed compared with the control sites (cylindrical; 1.6 mm). The soft tissue dimensions were similar in both groups. However, in relation to the implant shoulder, the peri-implant mucosa was located more apically at the test compared with the control sites.Conclusion: The present study confirmed that the distance between the implant surface and the outer contour of the buccal alveolar bony crest influenced the degree of resorption of the buccal bone plate. Consequently, in relation to the implant shoulder, the peri-implant mucosa will be established at a more apical level, if the distance between the implant surface and the outer contour of the alveolar crest is small.