Confocal Laser Microscopic Analysis of Biofilm on Newer Feldspar Ceramic

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

Evaluation of thermal compatibility between core and veneer dental ceramics using shear bond strength test and contact angle measurement

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The modulational instability in deep water under the action of wind and dissipation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ferroelectric characteristics of SrBi4Ti4O15 thin films grown on Pt/Ti/SiO2/Si substrates by the soft chemical method

Ferroelectric SrBi4Ti4O15 thin films were successfully prepared on a Pt(111)/Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. X-ray diffraction patterns of the films indicate that they are polycrystalline in nature. Atomic force microscopy (AFM) analyses showed that the surface of these films is smooth, dense and crack-free with low surface roughness (6.4 nm). At room temperature and at a frequency of 1 MHz, the dielectric constant and the dissipation factor were, respectively, 150 and 0.022. The C-V characteristics of perovskite thin film prepared at low temperature show normal ferrolectric behaviour. The remanent polarization and coercive field for the films deposited were 5.4 mu C/cm(2) and 8 5 kV/cm, respectively. All the capacitors showed good polarization fatigue characteristics at least up to 1 x 10(10) bipolar pulse cycles indicating that SrBi4Ti4O15 thin films can be a promising material for use in nonvolatile memories. (c) 2005 Elsevier B.V. All rights reserved.

Influence of oxygen flow on crystallization and morphology of LiNbO3 thin films

Polymeric precursor solution (Pechini method) was used to deposit LiNbO3 thin films by spin-coating on (100) silicon substrates. X-ray diffraction data of thin films showed that the increase of oxygen flow promotes a preferred orientation of (001) LiNbO3 planes parallel to the substrate surface. Surface roughness and grain size, observed by atomic force microscopy, change also with oxygen flow.

Rugosidade e pigmentação superficial de materiais ionoméricos

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

Microstructural, dielectric and ferroelectric properties of calcium-modified lead titanate thin films derived by chemical processes

Ferroelectric Pb1-xCaxTiO3 (x = 0.24) thin films were formed on a Pt/Ti/SiO2/Si substrate by the polymeric precursor method using the dip-coating technique for their deposition. Characterization of the films bq X-ray diffraction showed a perovskite single phase with a tetragonal structure after annealing at 700 degreesC. Atomic force microscopy (AFM) analyses showed that the film had a smooth and crack-free surface with low surface roughness. In addition, the PCT thin film had a granular structure with an 80 nm grain size. The thickness of the films observed by the scanning electron microscopy (SEM) is 550 nm and there is a good adhesion between the film and substrate. For the electrical measurements metal-ferroelectric-metal of the type capacitors were obtained, where the thin films showed good dielectric and ferroelectric properties. The dielectric constant and dissipation factor at 1 kHz and measured at room temperature were found to be 457 and 0.03. respectively. The remanent polarization and coercive field for the: deposited films were P-r = 17 muC/cm(2) and E-c = 75 kV/cm, respectively. Moreover. The 550-nm-thick film showed a current density in the order of 10(-8) A/cm(2) at the applied voltage of 2 V. The high values of the thin film's dielectric properties are attributed to its excellent microstructural quality and the chemical homogeneity obtained by the polymeric precursor method. (C) 2001 Elsevier science Ltd. All rights reserved.

Different methods of finishing and polishing enamel

Statement of problem. Highly polished enamel surfaces arc recommended for axial tooth surfaces that will serve as guiding planes and be contacted by component parts of a removable partial denture. There is little evidence to support the assumption that this tooth modification will provide accurate adaptation of the framework and prevent build-up of plaque.Purpose. The aim of this investigation was to evaluate the surface roughness of the tooth enamel, prepared to serve as guiding planes, with different polishing systems.Material and methods. Four different methods (designated A, B, C, and D) for finishing and polishing the prepared enamel surfaces of 20 freshly extracted third molar teeth were studied. Each method involved 3, 4, or 5 different steps. The roughness of each specimen was measured at the start of each method before recontouring, after recontouring, and after each step of the 4 finishing and polishing procedures. The 4 experimental finishing methods were applied after recontouring the axial surfaces (buccal, lingual, and proxinial) of each tooth. Thus the 20 teeth (60 surfaces) were finished and polished by use of 1 of the experimental methods. Surface roughness was measured with a profilometer (mum); the readings of the unpolished enamel Surfaces were recorded as control measurements. Results were statistically analyzed with one-way analysis of variance followed by Tukey's test at the 95% level of confidence.Results. The highest roughness mean values (14.41 mum to 16.44 mum) were found when the diamond bur was used at a high speed for tooth preparation. A significant decrease in roughness values was observed with the diamond bur at a low speed (P<.05). Analysis of the roughness values revealed that all polishing methods produced surface roughness similar to that of the corresponding control teeth.Conclusion. Within the limitations of this study, all finishing procedures tested effectively promoted an enamel surface similar to the original unpolished enamel.

Doping of polyaniline by corona discharge

In the present article it is shown that a corona discharge can be employed to dope thin films of polyaniline (PANI) coated on poly(ethylene terephthalate) films, allowing the electrical conductivity to be tuned within the range 10(-10) to 0.3 S cm(-1). A study of the effect of different corona conditions, namely corona treatment for positive and negative polarities, air humidity, treatment time, corona current, and the geometry of the corona triode, on the electrical conductivity of the polyaniline is presented. The results indicate that the corona discharge leads to protonic doping of polyaniline similar to that which occurs in conventional protonic acid solution doping. Atomic force microscopic analysis shows that, as the PANI is exposed to the corona discharge, its globular morphology is disrupted leading to the appearance of droplet-like features and a significant decrease in the average height and surface roughness. Doping by corona discharge presents several advantages over the conventional solution method namely that it is a dry process which does not require use of chemicals reagents, and which is both rapid and avoids dopant migration. The latter can be important for applications of PANI in microelectronic devices. (C) 2000 American Institute of Physics. [S0021-8979(00)01608-X].

Microstructure and dielectric properties of (Ba,Sr)TiO3 thin film produced by the polymeric precursor method

BaxSr1-xTiO3 (x = 0.6) (BST) thin films were successfully prepared on a Pt(111)/TiO2/SiO2/Si(100) substrate by spin coating, using the polymeric precursor method. BST films with a perovskite single phase were obtained after heat treatment at 700 degrees C. The multilayer BST thin films had a granular structure will a grain size of approximately 60 nm. A 480-nm-thick film was obtained by carrying out five cycles of the spin-coating/heating process. Scanning electron microscopy and atomic force microscopy analyses showed that the thin films had a smooth, dense, crack-free surface with low surface roughness (3.6 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 748 and 0.042. The high dielectric constant value was due to the high microstructural quality and chemical homogeneity of the thin films obtained by the polymeric precursor method.

Preparation and properties of ferroelectric Pb1-xCaxTiO3 thin films produced by the polymeric precursor method

Pb1- xCaxTiO3 thin films with x = 0.24 composition were prepared by the polymeric precursor method on Pt/Ti/SiO2/Si substrates. The surface morphology and crystal structure, and the ferroelectric and dielectric properties of the films were investigated. X-ray diffraction patterns of the films revealed their polycrystalline nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness. The multilayer Pb1-xCaxTO3 thin films were granular in structure with a grain size of approximately 60-70 nm. The dielectric constant and dissipation factor were, respectively, 174 and 0.04 at a 1 kHz frequency. The 600-nm thick film showed a current density leakage in the order of 10(-7) A/cm(2) in an electric field of about 51 kV/cm. The C-V characteristics of perovskite thin films showed normal ferroelectric behavior. The remanent polarization and coercive field for the deposited films were 15 muC/cm(2) and 150 kV/cm, respectively. (C) 2001 Kluwer Academic Publishers.

Grazing incidence X-ray diffraction and atomic force microscopy analysis of BaBi2Ta2O9 thin films

Thin films of BaBi2Ta2O9 (BBT) composition were prepared through the metal organic decomposition method. The crystallinity, phase formation, crystallite size and morphology of the thin films were measured as a function of the type of substrate, stoichiometry of solution and process variables such as thickness and temperature. The thin films were investigated by grazing incidence X-ray diffractometry and atomic force microscopy (AFM) techniques. For the sample without excess of bismuth, diffraction peaks other than that of the BBT phase were observed. A well crystallized BBT single phase was observed for films prepared from a solution with 10% excess of bismuth, deposited on Si/Pt substrate, with a thickness up to 150 nm and sintered at temperatures of 700 degreesC. The thin BBT phase films heat-treated at 600 degreesC presented a diffraction pattern characteristic of samples with lower degree of crystallinity whereas for the thin films heat-treated at 800 degreesC, we observed the presence of other phases than the BBT. For the thin film deposited on the Sin+ substrate, we observe that the peaks corresponding to the BBT phase are broader than that observed on the samples deposited on the Pt and Si/Pt substrates. No variation of average crystallite size was observed as the excess of Bi increased from 10 to 20%. AFM images for the samples showed that the increasing the amount of bismuth promotes grain growth. The average surface roughness measured was in the range of 16-22 nm showing that the bismuth amount had no or little effect on the roughness of films. (C) 2002 Elsevier B.V. B.V. All rights reserved.

SrBi2Nb2O9 thin films deposited by dip coating using aqueous solution

A new approach for SrBi2Nb2O9 (SBN) thin films synthesis using aqueous solution was successfully experienced. The deposition solution was prepared from Sr-Bi-Nb mixed-citrate solution, requiring no special atmosphere and using common reagents. Films were deposited by dip coating onto Pt/Ti/SiO2/Si(100) substrates and hear treated at temperatures ranging from 300 to 700 degrees C. The process of formation and crystallization of SrBi2Nb2O9 thin films, prepared by the aqueous solution method have been studied with particular emphasis on the microstructure of crystallized films. Crystalline phases formation were followed by grazing incident X-ray diffraction (GIXRD), microstructure characterization was evaluated by scanning electron microscopy (SEM) and surface roughness were observed using atomic for ce microscopy (AFM). To reach the desired thickness, substrates were dipped in the deposition solution twice, forming double-layered films. The thickness of each layer ranged from 80 to 100 nm. (C) 1999 Elsevier B.V. Limited. All rights reserved.

Microstructural and ferroelectric properties of PbZr1-xTi(x)O(3) thin films prepared by the polymeric precursor method

The polymeric precursor method was employed in the preparation of PZT thin films on Pt(111)Ti/SiO2/Si(100) substrates. X-ray diffraction patterns revealed the polycrystalline nature of the PZT (53:47) thin films, which had a granular structure and a grain size of approximately 70 nm. A 350-nm thick film was obtained by running three cycles of the dip-coating/heating process. Atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness (= 2.0 nm). The PZT (53:47) thin films annealed at 700 degreesC showed a well-saturated hysteresis loop. The C-V curves of perovskite thin film displayed normal ferroelectric behavior, while the remanent polarization (2P(r)) and coercive field (E-e) of the film deposited and measured at room temperature were 40 muC/cm(2) and 110 kV/cm, respectively. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Electrodeposited thin mercury films on Pt-Ir alloy electrodes

Mercury thin films prepared by electrochemical deposition on Pt-Ir alloy and after partial removing of mercury at different temperatures were studied by means of an interferometric surface mapping microscope and by X-ray photoelectronic spectroscopy. Mercury film samples having mercury partially removed by anodic stripping at a potential more positive than the corresponding peak in the voltammogram were also studied using the same techniques. For blank samples the surface topographic studies showed well defined grain boundaries. Mercury film samples when heated up to different temperatures showed as material is removed and that the surface roughness decreases as the temperature increases. For samples heated up to 800 degrees C the surface roughness is approximately the same that for the blank. A model for the interphase of volumetric mercury electrodeposited on a Pt-Ir alloy has been proposed using samples both electrochemically and thermally removed of their Hg coatings. The model includes a layered three-region structure, containing at least two Pt-Hg intermetallics: PtHg4 and PtHg2. A substrate modified region, iridium rich, has also been detected. (C) 1999 Elsevier B.V. S.A. All rights reserved.