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Neste trabalho foi estudada resistência de cadinhos de SnO2 dopados com 1%mol de ZnO frente a corrosão na fusão de vidro contendo metais pesados. Os cadinhos foram obtidos através do processo de colagem de barbotina, e a sinterização foi realizada até a temperatura de 1400ºC por 4 horas. Os vidros foram fundidos uma única vez por 1 hora, sendo que o vidro de composição 50B2O3-50PbO à 700 ºC, o de composição 60B2O3-40BaO à 1150 ºC e o de composição 66,67B2O3-33,33PbO à 700 ºC, sendo resfriados no interior dos cadinhos. Estes cadinhos foram então preparados e analisados por MEV-EDS.In this work it was studied resistance of crucibles of SnO2 doped with 1%mol of ZnO when they are submitted to thermal treatment for melting glass with heavy metals. The crucibles were obtained through the slip casting process, and the sintering temperature was 1400ºC by 4 hours. The glass composition of 50B2O3-50PbO, 60B2O3-40BaO and 66,67B2O3-33,33PbO was melted at 700ºC, 1150ºC and 700ºC respectively. All these glasses compositions were melted only one time for 1h and chilled inside the crucibles. These crucibles were analyzed by SEM-EDS.

Crack-free polycrystalline PLZT (Pb,La)(Zr,Ti)O 3 thin films with the perovskite structure were prepared by dip-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°C and 650°C. The influence of withdrawal speed, viscosity, heating rate and ionic concentration on the morphology of PLZT thin film was discussed.

Lead lanthanum zirconate titanate (PLZT) thin films with stoichiometry (9/65/35) were prepared by a dip-coating process using a polymeric organic solution. The solution viscosity was adjusted in the range of 15–56 cP. Silicon (100) substrates were previously cleaned and then immersed in the solution. The withdrawal speed of substrate from the solution was adjusted within a range of 5–20 mm/min. The coated substrates were thermally treated in the 450–700°C temperature range. Surface roughness and crystallization of these films are strongly dependent on the annealing conditions. Infrared and X-ray diffraction data for PLZT powders heat-treated at 650°C for 3 h show that the material is free of carbonate phases and crystalline.

PLZT thin films were prepared by a dip-coating process using Pechini’s method. The PLZT solution was obtained from the mixture of the cation solutions. The viscosity of the solution was adjusted in the range of 20–40 cP, while the ionic concentration was adjusted in the range of 0.1 and 0.2 M. PLZT solutions were deposited on Si (1 0 0) substrate with withdrawal speed at 5 mm/min. The coated substrates were thermally treated with heating rate of 1°C/min up to 300 and 5°C/min up to 650°C in order to obtain homogeneous and crack free films. The influence of viscosity and ionic concentration on crystallization and morphology of PLZT (9/65/35) thin film will be discussed.

Laboratorio Interdisciplinar de Cerâmica, Instituto de Quimica UNESP, CEP 14800-900 Araraquara SP

This study consisted of an investigation of the influence of powder preparation on the phase and chemical compositions and microstructure of 9.5/65/35 PLZT materials sintered in an oxygen atmosphere. The powders with the formula Pb 0.905 La 0.095 (Zr 0.65 Ti 0.35 ) 0.976 O 3 +3.5 wt.% PbO were prepared by the polymeric organometallic precursor method (the Pechini method and the partial oxalate procedure). Phase composition was determined by X-ray diffraction of powder and EDS analysis, while grain size was determined based on the micrograph obtained from SEM.

Two series of lead zirconate titanate (PZT) ceramics with composition Zr/Ti ≈ 53/47 have been prepared by the organic solution route. The effects on the electrical properties of calcination temperature in one series and of sintering time period in the other were examined. Dielectric constant, electrical conductivity and impedance spectroscopy results differed from one series to the other, probably due to differences in structure of the precursor powders, as seen by X-ray diffraction. Tetragonal and rhombohedral phases predominate in the powders used, respectively, in the calcined and sintered series. Physical and electrical behavior of ceramics prepared from predominantly rhombohedral powder suggests the evaporation of PbO. The presence of two semi-circles in impedance plots leads to the association of the low frequency semi-circle to the presence of PbO, which, apparently, was not eliminated from ceramics prepared from predominantly tetragonal powder.

The 9.5/65/35 PLZT was prepared from the polymeric precursors (the Pechini and partial oxalate process) and by sintering in two stages in an oxygen atmosphere. After thermal treatment at 400°C, the powders were calcinated and sintered at 1200°C with slow heating and cooling rates. The second stage of sintering consisted of hot pressing at the same temperature in oxygen atmosphere. After calcination of PLZT powders obtained by both methods, as well as after sintering of PLZT obtained by Pechini process, the paraelectric cubic phase was formed. After sintering of PLZT obtained by partial oxalate procedure, small tetragonality of crystal structure was observed. After hot pressing PLZT was pseudocubic. SEM microstructural analyses were carried out of the sintering and hot pressed samples and indicated the small grain size less than 2 μm.

The partial oxalate method, with the columbite route, associated with the Pechini method, was used to obtain a very fine ceramic powder at low temperature. Using this route it was possible to obtain a very reactive powder and to synthesize a lead magnesium niobate (PMN) powder with up to 100% of perovskite phase at a lower temperatures than the PbO melting point. The influence of the BaTiO 3 and PbTiO 3 seeds in the phase formation, along with time and temperature during the PMN calcination, was also investigated. The amount of 2% of BaTiO 3 seeds promoted PMN powder formation with 100% of perovskite phase and a very narrow particle size distribution.

The PLZT powders with the formula Pb 0.905 La 0.095 (Zr 0.65 Ti 0.35 ) 0.976 O 3 + 3.5 wt.% PhO were prepared by the organometallic precursor method (Pechini and partial oxalate processes). The microstructure of sintered 9.5/65/35 PLZT ceramics obtained from a partial oxalate procedure shows that the outstanding feature of this microstructure is its fairly uniform grains of about 1.8 μm. The microstructure of sintered PLZT ceramics obtained by the Pechini process consists of uniform small randomly-oriented grains tightly bonded together in the central part of the sample with a grain size of about 1.2 μm. Cubic and elongated grains are formed at the sample's border. The microstructures of hot pressed PLZT ceramics obtained from both processes are dense and rather uniform. After a double stage of hot pressing (2 plus 20 h) the microstructure of PLZT is fully dense uniform and homogeneous with a grain size of approximately 2.5 μm.

The Pechini method as well as the simultaneous addition of seeds particles and dopant solutions of BaTiO3 (BT) and PbTiO3 (PT) were used to prepare the perovskite phase 0.88 PZN–0.07 BT–0.05 PT. To study the influence of seed particle frequency on the synthesis of the PZN ceramic, two ranges of seed particle size were used: the range from 30 to 100 nm, termed small seed particles (frequency of 1015 particles/cm3); and the range from 100 to 900 nm, termed large seed particles (frequency of 1013 particles/cm3). The crystalline nuclei size influenced the calcining process, the sintering process and the microstructure. Samples prepared with lower seed frequency displayed more amount of pyroclore phase, need higher temperatures for sintering and showed a more heterogeneous microstructure with poor dielectric properties.

A 9.5/65/35 PLZT ceramic with a Pb 0.905 La 0.095 (Zr 0.65 Ti 0.35 ) 0.976 O 3 +3.5 w% PbO formula was prepared using the Pechini method for powder preparation and two-step sintering in an oxygen atmosphere. The first step consisted of sintering at 1200°C for 4 h with slow heating and cooling rates. The second step consisted of hot pressing at 1200°C for 4 h, with slow heating and cooling rates and pressing pressures of 20 MPa (initial pressure) and 40 MPa (at sintering temperature). Investigations were made of the powder phase formation and powder morphology, i.e. the structure of sintered and hot-pressed PLZT ceramics. SEM microstructural analyses were carried out on the sintering and hot-pressing processes.

The crystal structure of the Aurivillius compound Bi2BaTa2O9 prepared via the chemical route was determined by direct methods using EXPO97, and refined using the Rietveld method with conventional X-ray diffraction data. The structure was found to be tetragonal (space group I4/mmm, number 139) and Z=2, isomorphic of the Bi2BaNb2O9 reported by Blake and co-workers in the literature (1997). Two refinements were performed using the two asymmetry functions of DBWS-9807 (release 20/May/99). The unit cell for each case are: a=3.932 22(6) Å, c=25.5053(6) Å (RA) and a=3.932 50(7) Å, c=25.5069(6) Å (RCF). The differences for atom positions, interatomic distances and angles are in the range of one standard deviation. Final agreements factors are: Rwp=7.97%, S=1.84, RBragg=4.28%(RA), Rwp=7.98%, S=1.84, RBragg=4.30%(RCF). The occupancies of Ba and Bi in site 2b were refined but constrained to have their summation equal to 1.00. The same constraints were applied to the Ba and Bi of the 4e site. The results show that on site 2b there are 70% of Ba and 30% of Bi and on the site 4e there are 82% of Bi and 18% of Ba. The charge equilibrium is maintained for one standard deviation of the site occupancies.© 2000 International Centre for Diffraction Data.

Pechini’s method was used to prepare lead titanate zirconate with Zr/Ti ratio equal to 53/47. X-ray diffraction data revealed the presence of a rhombohedral phase, rich in zirconium, due to difference in carbonate stabilities, in PZT ceramics calcined at 600°C. Infrared spectroscopy presented COO- bonds in the 1400 cm -1 region, which disappeared after calcining at 700°C. Seeds with rhombohedral (PZT 57/43) or tetragonal structure (PZT 45/55) were added to the precursor. The microstructure was differentially influenced by the nature of seed particles. Rhombohedral nuclei promoted preferential crystallization of lead zirconate. This heterogeneity directly reflected on values of k p and d 33 .

This work presents the preparation and characterization of PZT ceramic obtained by the polymeric precursor method (PPM). The influence of the synthesis method on the grain size and the morphology are also object of study. The fabrication and characterization of composite films with 0-3 connectivity, immersing nanoparticles of PZT into the non-polar poly(vinylidene fluoride) - PVDF as the polymer matrix were presented. For comparison there are results obtained with composite samples made of ceramic particles unrecovered and recovered with a conducting polymer, the polyaniline (PAni).

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.

PbMg{sub 1/3}Nb{sub 2/3}O{sub 3} (PMN) prepared by organic solution of citrates was analyzed by Rietveld method to determine the influence of seeds and dopants on the perovskite and pyrochlore phase formation. In was observed that pyrochlore phase formation increases with an increase in calcination time when no additives are included during the preparation. It was also observed that a greater amount of perovskite phase appeared in doped or seeded samples. The fraction of perovskite phase increased from 88 mol{percent} in pure sample to {approximately}95 mol{percent} in doped and seeded samples calcined at 800{degree}C for 1 h. It is clear that the addition of dopants or seeds during PMN preparation can enhance the formation of perovskite phase. {copyright} {ital 1996 Materials Research Society.}

Made available in DSpace on 2013-08-12T18:48:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-01 Made available in DSpace on 2013-09-30T18:33:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:45:54Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T13:45:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The present work seeks to evaluate the biocompatibility of experimental glass ionomer cements (GIC) prepared from niobium-calcium fluoro-alumino-silicate glass powder and two commercial GICs. The GICs were implanted into the subcutaneous connective tissue of sixty rats. The rats were sacrificed during four varying time periods: 7, 15, 30, and 60 days and histopathological examinations were then performed. The Kruskal-Wallis test was performed to evaluate any significant differences between the materials. Additionally, multiple comparisons of the mean rank were also carried out using the Dunn test (p

Walter Katsumi Sakamoto1, Gilberto de Campos Fuzari Jr1, Maria Aparecida Zaghete2 and Ricardo Luiz Barros de Freitas3 1Faculdade de Engenharia, UNESP – Univ. Estadual Paulista – Campus de Ilha Solteira, Depto de Fisica e Quimica, Grupo de Polimeros, 2Instituto de Quimica, Universidade Estadual Paulista – UNESP, 3Faculdade de Engenharia, UNESP – Univ. Estadual Paulista – Campus de Ilha Solteira, Departamento de Engenharia Eletrica Brazil

A tubular furnace specifically designed for growing nanostructured materials is presented in this work. The configuration allows an accurate control of evaporation temperature, substrate temperature, total pressure, oxygen partial pressure, volumetric flow and source-substrate distance, with the possibility of performing both downstream and upstream depositions. In order to illustrate the versatility of the equipment, the furnace was used for growing semiconducting oxide nanostructures under different deposition conditions. Highly crystalline indium oxide nanowires with different morphologies were synthesized by evaporating mixtures of indium oxide and graphite powders with different mass ratios at temperatures between 900 oC and 1050 oC. The nanostructured layers were deposited onto oxidized silicon substrates with patterned gold catalyst in the temperature range from 600 oC to 900 oC. Gas sensors based on these nanowires exhibited enhanced sensitivity towards oxygen, with good response and recovery times.

Zinc oxide nanorods in the form of powder or nanostructured films were synthesized by the hydrothermal method using aqueous solutions. Once the synthesis time was completed, the reaction vessel was naturally cooled or submitted to a quenching process. X-ray diffraction, Scanning Electron Microscopy and Transmission Electron Microscopy techniques were employed to characterize the crystallinity, morphology and dimensions of the nanorods as well as their growth direction. Suspensions of powder material were spin-coated over oxidized silicon substrates in order to obtain nanostructured layers. Photodetectors based on in-situ grown and spin-coated films were prepared in order to evaluate the influences of cooling rate and device configuration on the UV sensing characteristics. Spincoated layers showed an excellent performance (current change by more than four orders of magnitude), better than nanorods grown directly on the substrate during the hydrothermal process. For both configurations, the sensitive layers built from quenched samples exhibited enhanced UV photoresponses when compared to the naturally cooled ones. Fil: Savu, Raluca. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Parra, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina Fil: Jancar, Bostjan. Jozef Stefan Institute; Eslovenia Fil: Zaghete, María Aparecida. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Joanni, Ednan. Centro de Tecnologia da Informação Renato Archer; Brasil

This study investigated the response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT) membrane. Osteoblastic cells were cultured in osteogenic conditions either on P(VDF-TrFE)/BT or polytetrafluoroethylene (PTFE) for up to 14 days. At 7 and 14 days, the mRNA expression of Runt-related transcription factor 2 (RUNX2), Type I collagen (COL I), Osteopontin (OPN), Alkaline phosphatase (ALP), Bone sialoprotein (BSP), and Osteocalcin (OC), key markers of the osteoblastic phenotype, and of Bcl2-associated X protein (Bax), B-cell CLL/lymphoma 2 (Bcl-2), and Survivin (SUR), associated with the control of the apoptotic cell death, was assayed by real-time PCR. In situ ALP activity was qualitatively evaluated by means of Fast red staining. Surface characterization was also qualitatively and quantitatively assayed in terms of topography, roughness, and wettability. Cells grown on P(VDF-TrFE)/BT exhibited a significantly higher mRNA expression for all markers compared to the ones on PTFE, except for Bcl-2, which was not detected for both groups. Additionally, Fast red staining was noticeably stronger in cultures on P(VDF-TrFE)/BT at 7 and 14 days. At micron- and submicron scale, SEM images and roughness analysis revealed that PTFE and P(VDF-TrFE)/BT exhibited a smooth topography and a similar roughness, respectively. PTFE membrane displayed higher contact angles compared with P(VDF-TrFE)/BT, as indicated by wettability assay. The novel P(VDF-TrFE)/BT membrane supports the acquisition of the osteoblastic phenotype in vitro, while up-regulating the expression of apoptotic markers. Further in vivo experiments should be carried out to confirm the capacity of P(VDF-TrFE)/BT membrane in promoting bone formation in guided bone regeneration.

Made available in DSpace on 2013-08-28T14:08:58Z (GMT). No. of bitstreams: 1 WOS000289369900001.pdf: 2722494 bytes, checksum: d92b2ce7c5d6e033222f227bdb821164 (MD5) Made available in DSpace on 2013-09-30T19:08:27Z (GMT). No. of bitstreams: 2 WOS000289369900001.pdf: 2722494 bytes, checksum: d92b2ce7c5d6e033222f227bdb821164 (MD5) WOS000289369900001.pdf.txt: 34007 bytes, checksum: 313945202ac33031ff745adcd7c1952b (MD5) Previous issue date: 2010-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:18:48Z No. of bitstreams: 2 WOS000289369900001.pdf: 2722494 bytes, checksum: d92b2ce7c5d6e033222f227bdb821164 (MD5) WOS000289369900001.pdf.txt: 34007 bytes, checksum: 313945202ac33031ff745adcd7c1952b (MD5) Made available in DSpace on 2014-05-20T14:18:48Z (GMT). No. of bitstreams: 2 WOS000289369900001.pdf: 2722494 bytes, checksum: d92b2ce7c5d6e033222f227bdb821164 (MD5) WOS000289369900001.pdf.txt: 34007 bytes, checksum: 313945202ac33031ff745adcd7c1952b (MD5) Previous issue date: 2010-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) CaBi(4)Ti(4)O(15) (CBTi144) thin films were grown on Pt/Ti/SiO(2)/Si substrates using a soft chemical solution and spin-coating method. Structure and morphology of the films were characterized by the X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman analysis, X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). The films present a single phase of layered-structured perovskite with polar axis orient. The a/b-axis orientation of the ferroelectric film is considered to be associated with the preferred orientation of the Pt bottom electrode. XPS measurements were employed to understand the nature of defects on the retention behavior of CBTi144 films. We have observed that the main source of retention-free characteristic of the capacitors is the oxygen environment in the CBTi144 lattice. Univ Fed Itajuba Unifei, BR-35900373 Bairro Amazonas Itabira, MG, Brazil Univ Estadual Paulista, Inst Quim, Dept Quim Fis, Lab Interdisciplinar Ceram, BR-14801970 Araraquara, SP, Brazil Univ Estadual Paulista, Inst Quim, Dept Quim Fis, Lab Interdisciplinar Ceram, BR-14801970 Araraquara, SP, Brazil

Made available in DSpace on 2022-04-29T08:45:01Z (GMT). No. of bitstreams: 0 Previous issue date: 1992-01-01 Lead zirconate titanate (PZT) with several Zr/Ti ratios was prepared by the organic solution of citrates of the respective cations. The Rietveld method was applied to perform quantitative analysis of the coexisting phases. The ratio of tetragonal/rhombohedral phases increased with calcination temperature. For the composition where Zr/Ti = 53/47, the tetragonal quantity varied from 25% to 35% for temperatures ranging from 600° to 800°C. For the powder with Zr/Ti = 57/43, only the rhombohedral phase was observed after calcination at 700°C. For the powder with Zr/Ti = 49/51, only the tetragonal phase was observed after calcination at 800°C. The amount of tetragonal phase was controlled in Zr/Ti = 55/45 by seeding the powder with the tetragonal phase of PZT. Copyright © 1992, Wiley Blackwell. All rights reserved Instituto de Química University of São Paulo State, São Paulo, Araraquara, 14800 Faculdade Ciências e Tecnologia University of São Paulo State, P. Prudente, São Paulo, 19060 Departamento de Química—Federal University of São Carlos, São Carlos, São Paulo, 13560 Instituto de Física e Química São Carlo University of São Paulo, São Carlos, São Paulo, 13560

The hydrothermal method was employed in order to obtain zinc oxide nanorods directly on Si/SiO2/Ti/Zn substrates forming brush-like layers. In the final stages of synthesis, the reaction vessel was naturally cooled or submitted to a quenching process. X-ray diffraction results showed that all the nanostructures grew [0001] oriented perpendicular to the substrate. The influence of the cooling process over the morphology and dimensions of the nanorods was studied by Scanning Electron Microscopy. High Resolution Transmission Electron Microscopy images of the quenched samples showed that the ZnO crystal surfaces exhibit a thin layered coating surrounding the crystal with a high degree of defects, as confirmed by Raman spectroscopy results. Photodetectors made from these samples exhibited enhanced UV photoresponses when compared to the ones based on naturally cooled nanorods. Fil: Savu, Raluca. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Parra, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Joanni, Ednan. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Jančar, Boštjan. Jozef Stefan Institute; Eslovenia Fil: Eliziário, Sayonara A.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: De Camargo, Rorivaldo. Universidade Federal do São Carlos; Brasil Fil: Bueno, Paulo R.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Varela, José A.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Longo, Elson. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Zaghete, Maria A.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:47Z No. of bitstreams: 1 S0100-40422009000500028.pdf: 422513 bytes, checksum: 431fdbc5a53051f0c02e078d92bfd83a (MD5) Made available in DSpace on 2013-08-22T18:48:47Z (GMT). No. of bitstreams: 1 S0100-40422009000500028.pdf: 422513 bytes, checksum: 431fdbc5a53051f0c02e078d92bfd83a (MD5) Previous issue date: 2009-01-01 Made available in DSpace on 2013-09-30T19:38:49Z (GMT). No. of bitstreams: 2 S0100-40422009000500028.pdf: 422513 bytes, checksum: 431fdbc5a53051f0c02e078d92bfd83a (MD5) S0100-40422009000500028.pdf.txt: 17975 bytes, checksum: c306d6c7c306784d68c1e2f29f01f5f4 (MD5) Previous issue date: 2009-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:17:30Z No. of bitstreams: 2 S0100-40422009000500028.pdf: 422513 bytes, checksum: 431fdbc5a53051f0c02e078d92bfd83a (MD5) S0100-40422009000500028.pdf.txt: 17975 bytes, checksum: c306d6c7c306784d68c1e2f29f01f5f4 (MD5) Made available in DSpace on 2014-05-20T14:17:30Z (GMT). No. of bitstreams: 2 S0100-40422009000500028.pdf: 422513 bytes, checksum: 431fdbc5a53051f0c02e078d92bfd83a (MD5) S0100-40422009000500028.pdf.txt: 17975 bytes, checksum: c306d6c7c306784d68c1e2f29f01f5f4 (MD5) Previous issue date: 2009-01-01 Glass ionomer cements (GICs) are products of the acid-base setting reaction between an finely fluoro-alumino silicate glass powder and poly(acrylic acid) in aqueous solution. The sol gel method is an adequate route of preparation of the glasses used to obtain the GICs. The objective of this paper was to compare two powders: a commercial and an experimental and to investigate the structural changes during hardening of the cements by FTIR and Al MAS NMR. These analyses showed that the experimental glass powder reacted with organic acid to form the GICs and it is a promising material to manufacture dental cements. Universidade Estadual Paulista Instituto de Química de Araraquara Universidade Federal de Itajubá Instituto de Ciências Exatas Universidade Estadual Paulista Instituto de Química de Araraquara

The aim of this paper is to compare the fluoride-releasing and mechanical properties of an experimental luting glass ionomer cement, which has a modified composition and a commercial luting cement. The experimental powder was obtained by sol-gel process and then, it was used to prepare the experimental cements. The properties of cement pastes, such as setting time and working time, microhardness and diametral tensile strength were determined. Fluoride release from GICs was evaluated at time intervals of 1, 7, 14, 21 and 28 days in deionized water. Atomic force microscopy (AFM) analyses showed that the surface of the experimental cements is more homogeneous than commercial GICs. The mechanical properties and the measure of liberation of fluoride of the two cements were influenced by ratio powder:liquid and chemical composition of the precursor powders. Experimental cements released less fluoride than commercial cements. However, this liberation was more constant during the analyzed period. Thus, the results obtained in this study indicated that the composition of the experimental powder modified by the niobium can lead the formation of the polysalt matrix with good mechanical properties. In other words, we can say that experimental powder offered considerable promise for exploitation in dental field.

Objectives The purpose of this paper is to modify the conventional calcium fluoro-alumino-silicate glass, which is used in the formation of glass ionomer cements (CIGs) by the niobium addition and to study the properties of GICs obtained. Materials and methods Sol–gel process was used to prepare the powder at lower temperature than fusion method. Glass–ceramic powder obtained in this way was used to prepare the GICs. The properties such as working and setting times, microhardness and diametral tensile strength were evaluated for the experimental GICs and a commercial luting cement. Results The ideal powder:liquid (P:L) ratio determined to prepare the experimental GICs was equal to 1:1. The cements prepared using this ratio showed working and setting times similar to the commercial GICs. In mechanical tests it was observed that microhardness and diametral tensile strength of the experimental GICs decreased significantly with the reduction of P:L ratio. On the other hand, the results obtained in microhardness tests indicated that the presence of niobium was a positive factor. Significance The chemical process allows the development of glass–ceramic powder at 600 °C which is the goal of the present paper. It was concluded that GICs containing niobium might be used in dental applications and these results encourage further researches on other compositions.

This study was aimed at investigating the in vitro biocompatibility of a novel membrane of the composite poly(vinylidene-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT). Osteoblastic cells were obtained from human alveolar bone fragments and cultured under standard osteogenic condition until subconfluence. First passaged cells were cultured on P(VDF-TrFE)/BT and expanded polytetrafluoroethylene (e-PTFE--control) membranes in 24-well plates. Cell adhesion and spreading were evaluated at 30 min, and 4 and 24 h. For proliferation assay, cells were cultured for 1, 7, and 10 days. Cell viability was detected by trypan blue at 7 and 10 days. Total protein content and alkaline phosphatase (ALP) activity were measured at 7, 14, and 21 days. Cultures were stained with Alizarin red at 21 days, for detection of mineralized matrix. Data were compared by ANOVA and Student t test. Cell attachment (p = 0.001), cell number (p = 0.001), and ALP activity (p = 0.0001) were greater on P(VDF-TrFE)/BT. Additionally, doubling time was greater on P(VDF-TrFE)/BT (p = 0.03), indicating a decreased proliferation rate. Bone-like nodule formation took place only on P(VDF-TrFE)/BT. The present results showed that both membranes are biocompatible. However, P(VDF-TrFE)/BT presented a better in vitro biocompatibility and allowed bone-like nodule formation. Therefore, P(VDF-TrFE)/BT could be an alternative membrane to be used in guided tissue regeneration.

Made available in DSpace on 2021-07-14T10:47:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-12. Added 1 bitstream(s) on 2021-07-14T11:38:24Z : No. of bitstreams: 1 S1516-14392003000400005.pdf: 774654 bytes, checksum: 869e79186f8c48977ec98d9de8fccbf8 (MD5) This paper reports a study of the influence of Cr concentration and preparation method in the electrical conductivity and microstructure of SnO2-based powders doped with Mn and Nb, prepared by an organic route (Pechini method) and a mixture of oxides. All the samples were compacted into discs and sintered at 1300 °C for 3h, resulting in ceramics with relative density varying between 81 and 99%. The powders were morphologically characterized by X-ray diffraction and their specific surface area was determined by N2 adsorption/desorption isotherms. Electrical conductivity characterization indicated that the conductivity decreases as Cr concentration increases, probably due to Cr segregation at grain boundaries, which reduces grain size, increasing the number of resistive boundaries, thus limiting the passage of current. Universidade Estadual Paulista, Instituto de Química Universidade Estadual Paulista, Instituto de Química

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T19:02:37Z No. of bitstreams: 0 Made available in DSpace on 2013-08-22T19:02:37Z (GMT). No. of bitstreams: 0 Previous issue date: 1999-12-01 Made available in DSpace on 2013-09-30T20:03:41Z (GMT). No. of bitstreams: 0 Previous issue date: 1999-12-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:17:29Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T14:17:29Z (GMT). No. of bitstreams: 0 Previous issue date: 1999-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) O Niobato de Chumbo e Magnésio (PMN) é um material que possui propriedades ferroelétricas de relaxação. Essa propriedade pode ser acentuada ou alterada mediante a adição de dopantes. Neste trabalho foi demonstrado como a adição dos íons Ba2+/Ti4+ e Pb2+/Ti4+, ou somente o íon K+, altera as características do precursor columbita obtido pelo método Pechini e da cerâmica PMN. Através da análise dos resultados obtidos por DRX e IV, constatou-se que a dopagem com os pares de íons Ba2+/Ti4+ e Pb2+/Ti4+ leva à retenção de maior quantidade de matéria orgânica nos carvões precursores e à formação de fases secundárias. Quando adiciona-se somente o íon K+, o comportamento do precursor columbita é similar ao puro. No entanto, seus efeitos positivos podem ser verificados na cerâmica PMN, como o aumento no tamanho de grão e a elevação em Tm. Lead Magnesium Niobate (PMN) is a ferroelectric with relaxation properties. These properties can be improved or modified by doping. In this work is showed that Ba2+/Ti4+ andPb2+/Ti4+ ions or only K+ ion change the characteristics of columbite precursor prepared by Pechini s method. The results obtained by XRD and FT-IR show that there is more retention of organic matter in the Ba2+/Ti4+ andPb2+/Ti4+-MN doped precursors than in the pure one. It was also possible to show that K+-MN doped powders exhibit characteristics similar to pure MN powder, but in the PMN ceramic there is positive effects. The size grain and Tm increase when K+ ion is used on the PMN synthesis. Universidade Estadual Paulista Universidade Estadual Paulista

Submitted by NATALIA JACOMACI (natalia.jacomaci@unesp.br) on 2019-09-20T19:37:36Z No. of bitstreams: 1 TESE final biblioteca.pdf: 5642308 bytes, checksum: 65c5600861dbb31ce986de063d6f703f (MD5) Approved for entry into archive by Valeria Aparecida Moreira Novelli (valeria.novelli@unesp.br) on 2019-09-24T19:46:02Z (GMT) No. of bitstreams: 1 jacomaci_n_dr_araiq_par.pdf: 1195676 bytes, checksum: f5e465e87d16c4496f0cdb4c41b89e77 (MD5) Made available in DSpace on 2019-09-24T19:46:02Z (GMT). No. of bitstreams: 1 jacomaci_n_dr_araiq_par.pdf: 1195676 bytes, checksum: f5e465e87d16c4496f0cdb4c41b89e77 (MD5) Previous issue date: 2019-08-27 Outra Esta pesquisa desenvolveu a síntese e caracterização de heteroestrutura a base de alfa tungstato de prata, α-Ag2WO4 , e oxido de zinco ZnO. Os compostos individuais e a heteroestrutura foram obtidas por síntese hidrotérmica em forno micro-ondas em duas etapas: na 1° etapa foram obtidasnanocristais anisotrópicos de α-Ag2WO4 e de ZnO; na 2°etapa foi obtida a Heteroestrutura α-Ag2WO4/Ag/ZnO. As amostras puras e a heteroestrutura foram analisadas por difração de Raios X (DRX) e os dados foram tratados por método de refinamento de Rietveld. A avaliação do modelo estrutural, parametros de rede, volume de cela únitária, angulos e distâncias de ligação, quantidade de fases foram obtidas através de refinamento refinamento. A morfologia das amostras puras foram analisadas por microscopia eletrônica de varredura de alta resolução e a heteroestrutura bem como as regiões interfaciais foram analisadas por microscopia eletronica de varredura com elétrons retroespalhado e microscopia eletrônica de transmissão de alta magnificação, em que obteve-se a formação de 3 regiões interfaciais formando heteroestrutra tipo II o α-Ag2WO4/ZnO e heteroestrutura decorada com nanopartículas de prata o Ag/ α-Ag2WO4 e Ag/ZnO. As medidas de espectroscopia de refletância difusa permitiram determinar a energia de band gap óptico cujos valores encontrados foram 3,11 eV para o α-Ag2WO4, 3,28 eV para o ZnO e 3,21 eV para a heteroestrutura α-Ag2WO4/Ag/ZnO que permitiu estimar as posições relativas da (BV) e (BC). Os resultados observados para as medidas de espectroscopia de fotoluminescência possibilitaram observar menor intensidade de emissão da heteroestrutura, devido a recombinação eletrônica entre os clusters [AgOy] e [WO6] com [ZnO4]. A fotodescoloração da Rodamina B, aumentou significativamente para a heteroestrutura obtendo 93% de fotodescoloração em 90 minutos. This research developed of the synthesis and characterization of heterostructure alpha-silver tungstate-based heterostructure, α-Ag2WO4 and ZnO zinc oxide. The pure and heterostructured samples were obtained by hydrothermal in the microwave oven in two stages: in the first stage were obtained anisotropic nanocrystals of α-Ag2WO4 and ZnO were destroyed; In the second stage, the α- α-Ag2WO4/Ag/ZnO heterostructure was used. The pure and heterostructure sample were analyzed by X-ray diffraction (XRD) and the data were analyzed by Rietveld refinement method. Structural model evaluation, lattice parameters, single cell volume, angles and bonding distances, number of phases were obtained by refinement. The morphology of the pure samples was analyzed by high resolution scanning electron microscopy and the heterostructure was analyzed by backscattered electron scanning electron microscopy and high magnification transmission electron microscopy, which obtained the formation of 3 interfacial regions: α -Ag2WO4/ZnO and Ag/α-Ag2WO4 and Ag/ZnO decorated with silver nanoparticles. The diffuse reflectance spectroscopy measurements allowed the determination of the optical band gap energy whose values were 3.11 eV for α-Ag2WO4, 3.28 eV for ZnO and 3.21 eV for α-Ag2WO4/Ag/ ZnO heterostructure which allowed estimating the relative positions of (VB) and (CB). The results observed for the photoluminescence spectroscopy measurements made it possible to observe lower intensity of the heterostructure emission, due to the electronic recombination between the clusters [AgOy] and [WO6] with [ZnO4]. A photodiscoloration of Rhodamine B, increased to a heterostructure obtaining 93% photodiscoloration in 90 minutes. CAPES

A hepatite C é uma doença caracterizada pela inflamação do fígado, decorrente da infecção viral pelo VHC, e uma das maiores epidemias virais da humanidade. Atualmente o diagnóstico e tratamento da doença possui um elevado custo para o sistema público de saúde, sendo a principal causa de transplante de fígado em todo o mundo. Por este motivo, é incentivado o desenvolvimento de diagnósticos para a detecção nas fases iniciais da infecção, que possam auxiliar no tratamento e até mesmo na cura da doença. Os biossensores baseados em métodos eletroquímicos de detecção vem se destacando na área de diagnóstico devido às suas características de maior estabilidade e sensibilidade, e um baixo custo de fabricação e miniaturização. O presente trabalho relata o desenvolvimento de uma plataforma laboratorial portátil com biossensores eletroquímicos amperométricos. Aproveitando o conhecimento prévio de técnicas de fabricação (silkscreen, sputtering e placa de circuito impresso), otimizou-se o projeto e respectivo fabrico de biossensores específicos para aplicação nesta plataforma laboratorial. No âmbito do desenvolvimento deste projeto, o interesse foi definir os processos mais adequados à produção em larga escala de biossensores e validar a plataforma em comparação com equipamentos comerciais para a sua aplicação em um teste imunodiagnóstico da infecção pelo vírus da hepatite C. Os resultados obtidos mostraram que a técnica de placa de circuito impresso apresentou melhores vantagens em comparação com as técnicas de sputtering e silkscreen além de permitir uma fácil integração com a plataforma laboratorial portátil. A plataforma de laboratório portátil desenvolvida inclui uma unidade microcontrolada responsável pelo controle e transferência de dados das reações eletroquímicas, um módulo Bluetooth para transmissão de dados para dispositivos móveis e uma interface potenciostática. O sistema desenvolvido mostrou-se adequado para uso em testes eletroquímicos e aplicação no imunodiagnóstico da hepatite C. Hepatitis C is a disease characterized by inflammation of the liver resulting from viral infection by HCV and one of the largest viral epidemics in mankind. Currently the diagnosis and treatment of the disease has a high cost for the public health system, being the main cause of liver transplantation worldwide. For this reason, it is encouraged the development of diagnostics for detection in the early stages of infection, which may aid in the treatment and even cure of the disease. Biosensors based on electrochemical detection methods have been prominent in the diagnostic area due to their characteristics of greater stability and sensitivity, and a low manufacturing and miniaturization cost. The present work reports the development of a portable laboratory platform with electrochemical amperometric biosensors. Taking advantage of the prior knowledge of manufacturing techniques (silkscreen, sputtering and printed circuit board), the design and respective manufacture of specific biosensors for application in this laboratory platform was optimized. In the development of this project, the interest was to define the most appropriate processes for the large-scale production of biosensors and to validate the platform in comparison with commercial equipment for its application in an immunodiagnostic test of the hepatitis C virus infection. The results obtained showed that the printed circuit board technique presented better advantages compared to the sputtering and silkscreen techniques in addition to allowing easy integration with the portable laboratory platform. The portable laboratory platform developed includes a microcontroller unit responsible for controlling and transferring electrochemical reactions data, a Bluetooth module for data transmission to mobile devices and a potentiostatic interface. The developed system proved to be suitable for use in electrochemical tests and immunodiagnostic application of hepatitis C.

Submitted by GLAUCO MEIRELES MASCARENHAS MORANDI LUSTOSA null (glauco.morandi@gmail.com) on 2017-09-29T17:45:43Z No. of bitstreams: 1 Tese Doutorado - Glauco Meireles vfinal.pdf: 3510906 bytes, checksum: f9c0e27e1271ff4e2d7b2d20d17ab492 (MD5) Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-10-04T18:29:33Z (GMT) No. of bitstreams: 1 lustosa_gmmm_dr_araiq_par.pdf: 828083 bytes, checksum: 6debdca69bb76e5205632227fd03be72 (MD5) Made available in DSpace on 2017-10-04T18:29:33Z (GMT). No. of bitstreams: 1 lustosa_gmmm_dr_araiq_par.pdf: 828083 bytes, checksum: 6debdca69bb76e5205632227fd03be72 (MD5) Previous issue date: 2017-08-24 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) O objetivo deste projeto foi sintetizar dois sistemas à base de dióxido de estanho (SnO2), sendo um dopado com zinco e nióbio e outro dopado com cobalto e nióbio, respectivamente (Zn,Nb)-SnO2 e (Co,Nb)-SnO2, e realizar as devidas caracterizações a fim de verificar o potencial destes sistemas para aplicações como varistor, sensor de gás e fotocatalisador. Para síntese dos sistemas dopados foi usado o método dos precursores poliméricos (MPP) a partir da mistura estequiométrica dos reagentes, seguida por complexação, polimerização e calcinação e posterior submissão a etapa de moagem para promover a desaglomeração e redução do tamanho das partículas. As nanopartículas foram depositadas em substrato de Si (100)/SiO2 (10000 A°)/Ti (200 A°)/Pt (1500 A°) para estudo da propriedade varistora, em substrato de alumina com eletrodos interdigitais para análise da propriedade sensora de gás quando na presença de monóxido de carbono (CO). A obtenção dos filmes ocorreu através da técnica de deposição por eletroforese (EPD), com as seguintes condições: 20 mg do pó suspenso em 20 mL de isopropanol, a qual foi aplicada tensão de 2 kV, por diferentes tempos. Para o estudo fotocatalítico o pó foi disperso na solução objeto de estudo, e manteve-se agitação, aeração e irradiação com luz ultravioleta (9 W e 11 W) para promover a excitação eletrônica e a geração dos sítios ativos de oxirredução (par elétron-buraco, e-/h+). O tempo máximo de reação foi de 120 minutos. Para o estudo da atividade como sensor de gás os filmes de (Zn,Nb)-SnO2 foram tratados termicamente a 600 °C por 10 minutos e os filmes de (Co,Nb)-SNO2 a 500 °C por 10 minutos. Esta etapa visou dar resistência mecânica aos filmes sem o crescimento de grãos, mantendo a presença dos poros para aumento da área superficial para adsorção do gás. Os filmes avaliados quanto as propriedades varistoras foram sinterizados a 1000 °C por 40 minutos e 900°C por 30 minutos, para as composições, (Zn,Nb)-SnO2 e (Co,Nb)-SNO2 respectivamente. Após a sinterização os filmes para avaliação da propriedade varistora foram modificados através da deposição de ions Cr3+ por eletroforese, seguido de tratamento térmico de 15 minutos na mesma temperatura em que foram sinterizados. Os ions Cr+3 atuam diretamente na região do contorno de grão influenciando a formação da barreira de potencial. A introdução dos íons cromo, após a sinterização, visa controlar sua difusão por tratamento térmico, com o intuito de promover o aumento do coeficiente de não-linearidade (α) e a resistividade do contorno de grão, características necessárias a um varistor. Ambos os sistemas à base de SnO2 apresentaram respostas para as propriedades de interesse, sendo que o melhor resultado de atividade fotocatalítica, na descoloração da solução aquosa de rodamina B, de aproximadamente 80% de eficiência foi para (Zn,Nb)-SnO2 em 90 minutos de análise. Por sua vez, o sistema (Co,Nb)-SnO2 apresentou melhor resposta sensora e varistora, sendo que para sensor de gás o filme apresentou resposta de 2,6 no sistema self-heating e para a propriedade varistor o filme sinterizado com atmosfera rica em O2 apresentou melhores resultados com coeficiente de não-linearidade (α) entre 11,4 e 15,1; tensão de ruptura (220 V < VR < 242 V) e corrente de fuga (IF ~10-8 A/cm²), valores estes que indicam um potencial para aplicação como varistor de baixa tensão utilizado em dispositivos eletrônicos. The objective of this project was to synthesize two tin dioxide (SnO2) systems, one doped with zinc and niobium and one doped with cobalt and niobium, respectively (Zn, Nb)-SnO2 and (Co, Nb)-SnO2, and conduce the appropriate characterizations to verify the potential use of these systems for applications such as varistor, gas sensor and photocatalyst. The polymer precursors (MPP) method was used for the synthesis SnO2-based systems, this method involves the stoichiometric mixture of the reactants, followed by complexation, polymerization and calcination and subsequent submission to the grinding stage to promote the deagglomeration and reduction of the particle size. The nanoparticles were deposited onto Si (100)/SiO2 (10000 A°)/Ti (200 A°)/Pt (1500 A°) substrate for the study of the varistor property and for analysis of the gas sensor property (when in the presence of carbon monoxide - CO) deposited in substrate of alumina with interdigital electrodes. The films were obtained by electrophoresis deposition technique (EPD), with the following conditions: 20 mg of the powder suspended in 20 mL of isopropanol, which was applied at 2 kV voltage, for different times. For the photocatalytic study, the powder was dispersed into the solution under study, and stirring, aeration and submitted to irradiation with ultraviolet light (9 W and 11 W) to promote the electronic excitation and the generation of active oxidation sites (electron- hole, e- / h+ ). The maximum reaction time was 120 minutes. For the study of the gas sensor activity the (Zn, Nb)-SnO2 films were heat treated at 600 °C for 10 minutes and the (Co, Nb)-SnO2 films at 500 °C for 10 minutes. This stage aimed to promote mechanical resistance to the films avoiding the grain growth, maintaining the presence of the pores to increase the surface area for adsorption of the gas. The films analyzed for the varistor properties were sintered at 1000 °C for 40 minutes and 900 °C for 30 minutes for the compositions, (Zn, Nb)-SnO2 and (Co, Nb)-SnO2 respectively. After sintering, the films for evaluation of varistor properties were modified by the deposition of Cr3+ ions by electrophoresis, followed by a 15 minute heat treatment at the same temperature at which they were sintered. The Cr+3 ions act directly in the region of the grain boundary influencing the formation of the potential barrier. The introduction of the chromium ions, after sintering, aims to control their diffusion by heat treatment, in order to promote the increase of the coefficient of nonlinearity (α) and resistivity of the grain boundary, characteristics necessary to a varistor. Both SnO2-based systems presented responses to the properties of interest, and the best result of photocatalytic activity, in the discoloration of the aqueous solution of rhodamine B, of approximately 80% efficiency was for (Zn, Nb)-SnO2 in 90 minutes of analysis. On the other hand, the system (Co, Nb)-SnO2 presented better sensor and varistor response, and for gas sensor the film presented a response of 2.6 in the self-heating system and for the varistor property the sintered film with rich atmosphere in O2 presented better results with coefficient of nonlinearity (α) between 11.4 and 15.1; (VR

A classe de óxidos contendo nióbio (Nb) ou tântalo (Ta) e possuindo estrutura AB2O6 (A = Mg, Zn, Ca e B = Nb, Ta) do tipo columbita ou trirutilo, tem sido investigada devido a sua potencialidade para ressonadores na freqüência de microondas (GHz), os quais podem ser usados em sistemas de comunicação móvel e satélite, tais como telefones celulares e sistemas de comunicação pessoal. Preparamos corpos cerâmicos densos pelo método convencional de mistura de óxidos e reação no estado sólido. A rota de processamento e condições ótimas de sinterização foram desenvolvidas para as cerâmicas de MgTa2O6 (MT), ZnTa2O6 (ZT), MgNb2O6 (MN) e ZnNb2O6 (ZN). Temperaturas de sinterização a 1300°C para os niobatos e 1400°C para os tantalatos, para tempos de patamar de 8 horas, promoveram alta densificação atingindo-se densidades relativas maiores que 98% em todos os casos. Na caracterização dielétrica das cerâmicas de ZT e MT, por meio de medidas de impedância nas faixas de freqüência de 24MHz a 1,5GHz, determinamos as constantes dielétricas com valores de ε´=32 para o MT e ε´=36,5 para o ZT; resultados similares aos melhores existentes na literatura. Na fase monocristalina, estes materiais possuem potencialidades para aplicação em geração, transmissão, detecção e conversão de sinais ópticos em uma larga faixa de comprimentos de onda e níveis de potência. Fibras de CaTa2O6 puderam ser eficientemente obtidas pela técnica de Laser Heated Pedestal Growth (LHPG) e a dopagem desses compostos com íons terras raras de Nd3+ e Er3+foi uma alternativa para a obtenção de um material laser ativo. O estudo de fibras dos compostos do tipo ATa2O6 como meio laser ativo, não tem sido devidamente explorado. Resultados de espectroscopia óptica com fibras de CaTa2O6 dopadas com íon de Nd+3revelaram ser um novo material laser ativo para ser bombeado com laser de diodo. The c1ass of oxides containing the elements niobium or tantalum with AB2O6 (A= Mg e Zn; B= Nb e Ta) structure of the type columbite or trirutilo, has been investigated due to their potentialities for applications in dielectric resonators at microwave frequencies (GHz), which can be used for mobile and satellite communications, as in cell phones and personal communication systems. We have prepared dense ceramic bodies by conventional method of oxides mixture followed by solid state reaction. The experimental route and sintering conditions were developed for the MgTa2O6 (MT), ZnTa2O6 (ZT), MgNb2O6 (MN) and ZnNb2O6 (ZN) ceramics. It was observed that sintering under temperatures of 1300°C for the niobates, and 1400°C for the tantalates, for 8 hours, promoted densities higher than 98% for all ceramic bodies. Impedance spectroscopy was used for the dielectric characterization of MT and ZT ceramics in the frequency range of 24MHz to 1.5GHz and the values of dielectric constant are ε´=32 and ε´ =36.5 respectively. These results are comparable to the best results found in the literature. Moreover, it is also shown that while in the single crystal form, these materials might be used for the generation, transmission, detection, and conversion of optical signals, over a broad range of wavelengths and power levels. Undoped or doped (Nd3+ or Er3+) CaTa2O6 (CT) single crystal fibers were efficiently obtained by the laser−heated pedestal growth (LHPG) technique. The doped samples were characterized from the structural and spectroscopic points of view, aiming to investigate them as potential candidates for compact laser active media, which can be pumped by low cost diode lasers. Although the study of ATa2O6 single crystal fibers for this purpose hasn\'t been much explored yet, the results obtained for CaTa2O6: Nd+3 fibers are very promising.

A síntese de nano partículas e a sua caracterização tem sido a grande mola propulsora do desenvolvimento de materiais nano-estruturados. Pouca atenção tem sido dedicada aos fenômenos físico-químicos relacionados às enormes superfícies intrínsecas destes materiais. Dentre eles, o titanato de bário ocupa uma posição de destaque devido ao seu grande potencial na geração de produtos de alta tecnologia. Neste estudo o BaTiO3 foi sintetizado pelo método Pechini que proporciona a geração de nanopartículas de grande uniformidade química. Contudo, o uso de cátions que formam carbonatos de alta estabilidade pode inviabilizar o uso do método. Os pós de titanato de bário preparados apresentaram elevada área de superfície específica, mas formação de fases parasitas de carbonato de bário e em algumas estequiometrias de ortotitanato de bário e carbonatos adsorvidos à superfície do titanato de bário. O estudo sistemático da química de superfície e da estrutura cristalina do material permitiu a proposta de um método de lixiviação em meio ácido onde as fases parasitas foram eliminadas e um material nanométrico de grande potencial de aplicação foi obtido com as seguintes características: fase com simetria tetragonal predominante ~95% (apesar da coexistência de fase cúbica ~5%); tamanho de cristalito ou partícula primária de 44 nm; área de superfície específica igual a 13,4 m2/g e D(BET) de 74 nm; está isento de contaminação de carbonatos ou outra fase; relação estequiométrica de Ba/Ti = 0,96 -> Ba0,98Ti1,02O3. The synthesis and characterization of Nanoparticles has been a great topic for nanostructured materials developments. The Relationship between Physicochemical phenomena and large surface area has had a little attention. The barium titanate has a great potential of high-tech products generation. In this work, the BaTiO3 was prepared by polymeric precursor method because this method generates a great chemical uniformity in nanoparticles. However, cations that form carbonates of high-stability may compromise this method use. The barium titanate powder was prepared and showed high specific surface area, but this powder has barium carbonate and ortotitanato contamination. The systematic surface chemistry and crystal structure study suggest an acid leaching method to contaminant phases eliminated. A nanomaterial of great potential for application was obtained with the following characteristics: tetragonal phase predominant ~95% (cubic phase coexist ~5%); crystallite size of 44 nm; surface area of 13,4 m2/g and Particle size (estimated BET) of 74 nm; carbonate free; Ba/Ti = 0,96 -> Ba0,98Ti1,02O3.

Este trabalho descreve um estudo sistemático da influência da adição do átomo de lantânio na estrutura da fase Bi4Ti3O12 (BIT) e do átomo érbio na fase Bi3,25La0,75Ti3O12 (BLT075) no que tange seu processo de síntese e suas propriedades estruturais, microestruturais e elétricas. Cerâmicas de composição nominal Bi4-xLaxTi3O12 (BLTx) com 0 x 2 mol % e Bi3,25La0,75Ti3O12 (BLT075) com substituição no sítio do La3+ (BLExT) e no sítio do Ti4+ (BLTEx) com 0 x 0,06 mol %, foram preparadas através do método de síntese por reação do estado sólido. Os dados de difração de raios X (DRX) das amostras BLTx mostram a formação de uma solução sólida para todas as amostras, exceto para amostra contendo 2 mol% de La3+. Verificou-se que a adição de La3+ leva a um aumento da temperatura de sinterização e diminui o tamanho médio dos grãos, alterando sua morfologia de grão na forma de placas para uma forma mais esférica. Quanto às propriedades dielétricas, amostras BLTx com x 1 mol% apresentam um comportamento característico de um ferroelétrico normal, enquanto que quando x > 1 mol%, observa-se um pequeno deslocamento da temperatura de máximo da permissividade dielétrica (Tm) com a freqüência, indicando a existência de um comportamento típico de materiais ferroelétricos relaxores. Os resultados de espectroscopia Raman sugerem que os íons La3+ tendem a ocupar preferencialmente o sítio do Bi3+ das camadas peroviskitas quando x < 1,0 mol %, enquanto que quando x >1,0 mol %, o processo de incorporação também ocorre no sítio do Bi3+ nas camadas de Bi2O2. De acordo com a analise dos espectros XANES e XPS, a estrutura local e eletrônica dos átomos de Ti, Bi e La, não são afetadas de forma significativa pela adição de lantânio.Em relação às amostras dos sistemas BLExT e BLTEx, os dados de DRX mostram somente a presença de fases secundárias nas composições x= 0,04 e 0,06 mol% do sistema no BLTEx. A sinterização à 1115oC possibilitou obter amostras apresentando uma densidade relativa superior a da amostra não dopada BLT075. A adição de Er3+ causa mudanças na morfologia, diminuindo o tamanho médio dos grãos no sistema BLExT e aumentando no sistema BLTEx. Através de medidas elétricas, foi observado um decréscimo no valor Tm em ambos os casos. Quando x > 0,02 mol%, o comportamento de Tm é dominado pelo limite de solubilidade para o sistema BLExT. De acordo com os dados de XAS, a estrutura local e eletrônica dos átomos de Ti e Er não são afetadas de forma significativa pela adição de érbio. This work describes a systematic study of the influence of the lanthanum atom addition in the Bi4Ti3O12 (BIT) phase and the erbium atom addition in the Bi3,25La0,75Ti3O12 (BLT075) phase in terms of their synthesis process and its structural, microstructural and electrical properties. Ceramics of nominal composition Bi4-xLaxTi3O12 (BLTx) with 0 x 2 mol% and Bi3,25La0, 75Ti3O12 (BLT075) with Er3+ replacing the La3+ atoms (BLExT) and replacing Ti4+ atoms (BLTEx) with 0 x 0, 06 mol%, were prepared by the solid state reaction method. X-ray diffraction (XRD) data of BLTx samples shows the formation of a solid solution for all samples, except for sample containing 2 mol% of La3+. It was found that the addition of La3+ leads to an increase in the sintering temperature, a decrease in the average size of grains and a modification on the grain from plates to a more spherical morphology. The dielectric properties of BLTx samples with x 1 mol% show a behavior characteristic of a normal ferroelectric whereas when x> 1 mol%, there is a small displacement of the temperature of maximum dielectric permittivity (Tm) with the frequency, indicating the existence of a typical behavior of a relaxor ferroelectric material. The Raman spectroscopy results suggest that La3+ ions tend to preferentially occupy the Bi3+ site in the peroviskite layer when x 1.0 mol%, the process of incorporation occurred also in the Bi3+ site of the Bi2O2 layer. According to the analysis of XANES and XPS spectra, the local structure of atoms and electronic structure of Ti, Bi and La atoms of BLTx samples are not affected significantly by the addition of lanthanum. For samples of BLExT and BLTEx systems, the XRD data shows only the presence of a secondary phase in the x = 0.04 and 0.06 mol% compositions of the BLTEx system. The sintering at 1115 °C allowed to obtain samples presenting a relative high density than the sample BLT075 undoped sample. The addition of Er3+ induces significative changes in grain morphology by decreasing the average size of grains in the BLExT system and by increasing the BLTEx system. Through electrical measurements, it was observed a decrease in the Tm value in both cases. In the BLExT system, when x> 0.02 mol%, the behavior of Tm is dominated by the solubility limit. According to the XAS data, the local and electronic structure of Ti and Er atoms are not affected significantly by the addition of erbium.

Made available in DSpace on 2015-07-13T12:10:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-20. Added 1 bitstream(s) on 2015-07-13T12:24:07Z : No. of bitstreams: 1 000835959_20170320.pdf: 339379 bytes, checksum: a5b2b1af9195b68012c616f718fe6b2c (MD5) Bitstreams deleted on 2017-03-24T12:04:45Z: 000835959_20170320.pdf,. Added 1 bitstream(s) on 2017-03-24T12:05:38Z : No. of bitstreams: 1 000835959.pdf: 7570828 bytes, checksum: 5ab972a5285c1f8bb3b327316f5a58af (MD5) O principal objetivo deste trabalho foi a otimização do processo para a obtenção de partículas lead-free de NaNbO3, visando a aplicação das mesmas em compósitos flexíveis com propriedades piezoelétrica e fotoluminescência. Por meio da síntese hidrotérmica assistida por micro-ondas, foram obtidas partículas na forma de fibras de Na2Nb2O6.H2O (uma fase metaestável decorrente da cristalização do NaNbO3) e cubos de NaNbO3. Realizando tratamento térmico das fibras de Na2Nb2O6.H2O as mesmas foram convertidas a NaNbO3 mantendo a morfologia anisotrópica do Na2Nb2O6.H2O. Após realizadas as devidas caracterizações, foram escolhidas as partículas de NaNbO3, tanto na forma de fibras como na forma de cubos, com as melhores caracteristicas, a fim de serem incorporadas ao polímero PVDF para a formação dos compósitos. Sabendo-se das boas propriedades apresentadas por materiais obtidos à partir de partículas anisotrópicas, e da influência nas características dos compósitos devido a inclusão de um polímero condutor em sua composição, as fibras de NaNbO3 foram recobertas parcialmente com o polímero PAni na sua forma condutora. À partir de prenssagem a quente, utilizando diferentes frações volumétricas de NaNbO3 imersas na matriz polimérica de PVDF, foram obtidos compósitos com NaNbO3 na forma de cubos, NaNbO3 na forma de fibras e NaNbO3 na forma de fibras recobertas com PAni. Os resultados mostraram que o aumento da fração volumétrica de NaNbO3 aumenta a eficiência das propriedades elétricas dos materiais, porém diminui a flexibilidade. A anisotropia das partículas de NaNbO3 influenciou positivamente nas propriedades elétricas e ópticas dos compósitos, uma vez que os compósitos obtidos com as fibras de NaNbO3 apresentaram respostas piezoelétrica e fotoluminescente melhores do que às apresentadas pelos compósitos obtidos à partir do NaNbO3 na forma de cubos. A inclusão... The main goal of this research was improved the process for obtaining of NaNbO3 lead-free particles, in order to use the particles in flexible composites with piezoelectric and photoluminescence properties. By microwave-assisted hydrothermal synthesis, Na2Nb2O6.H2O fiber-like particles (a metaestable phase resulting from crystallization of NaNbO3) and NaNbO3 cubic-like particles were obtained. By thermal treatment, the Na2Nb2O6.H2O fiber-like particles were converted to NaNbO3 fiber-like particles, maintaining the anisotropic morphology of the Na2Nb2O6.H2O. After the characterization, the NaNbO3 fiber-like particles and cubic-like particles wich presented the best characteristics were chosen to be combined with PVDF to make composites. Knowing of good properties of materials obtained from anisotropic particles, and their influence in composites characteristics, a conductor polymer was inclused in composite composition. For this, the NaNbO3 fiber like particles were partially covered by PAni polymer in the state conductive. Using different volume fraction of NaNbO3 particles immersed in PVDF polimeric matrix, the composites were obtained by hot press. The results showed that the increasing of vome fraction of NaNbO3 improve the electric properties of materials, but reduced the flexibility. The anisotropic of the particles influenced positively in the electric and optical properties of composites. The composites obtained from NaNbO3 fiber-like presented better propperties tha composites obtained from NaNbO3 cubic-like particles. The PAni presence in the composites improved the electric properties, but reduced the photoluminescence emission. The composites obtained from anisotropic NaNbO3 without PAni were the materials that showed simultaneously the best combination of piezoelectric and photoluminescence properties. These composites can be used in piezophotonic devices.

Made available in DSpace on 2014-11-10T11:09:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-01-14Bitstream added on 2014-11-10T11:57:25Z : No. of bitstreams: 1 000774915_20150228.pdf: 817618 bytes, checksum: 24cc6ba731989fdd1bdd5461735b376a (MD5) Bitstreams deleted on 2015-03-03T12:45:19Z: 000774915_20150228.pdf,Bitstream added on 2015-03-03T12:45:56Z : No. of bitstreams: 1 000774915.pdf: 2837940 bytes, checksum: 3b0281f8b4bc331d209a2b8aad1d6af7 (MD5) No presente trabalho foi estudada a obtenção de nanopartículas do sistema (98,95)SnO2(1,0)ZnO(0,05)Nb2O5 através do Método Pechini (método dos precursores poliméricos) e a preparação de filmes varistores destas partículas. O pó obtido foi caracterizado por Difração de Raios X, Microscopia eletrônica de Varredura e adsorção de N2. Os filmes das nanopartículas foram obtidos por deposição em substrato de Si (100)/TiO2 (10.000 A°)/Ti (200 A°)/Pt (1500 A°), com espessura 356-406 nm, através da técnica de eletroforese, utilizando suspensão etílica estável deste pó. Os filmes foram sinterizados em forno microondas por temperaturas de até 1000 °C e patamar de até 40 minutos visando à formação e o crescimento dos grãos. Após a sinterização e caracterização por MEV_FEG, foi depositada uma película de íons Cr3+ através da eletroforese na superfície dos filmes e submetidos aos tratamentos térmicos de 900 e 1000 °C por 5, 10 e 15 minutos para fins de difusão dos cátions nos contornos de grãos. O Cr+3 é responsável pelo aumento do coeficiente de não-linearidade no sistema varistor a base de SnO2, característica principal desejada na obtenção de varistores. Esta adição permite controlar, através da difusão por tratamento térmico, a resistividade, a tensão de ruptura e coeficiente de não linearidade em filmes cerâmicos à base de SnO2 visando a aplicação como varistores. Após deposição dos íons de Cr3+ e do tratamento térmico, os filmes foram caracterizados eletricamente através da análise em corrente contínua, para a determinação das curvas V vs I (tensão aplicada em função da corrente elétrica) e das curvas ln(J/T²) vs E1/2, e caracterização em corrente alternada (espectroscopia de impedância). A partir das curvas V vs I foi possível obter valores do coeficiente de não-linearidade, campo elétrico de ruptura e corrente de fuga. Os parâmetros da barreira de potencial formada... The present work was studied obtaining nanoparticles of the system (98,95)SnO2(1,0)ZnO(0,05)Nb2O5 by Pechini method (polymeric precursor method) and the preparation of varistors films of these particles. The powder obtained was characterized by X-Ray Diffraction, Scanning electron microscopy and N2 adsorption. The films of nanoparticles were obtained by deposition on Si (100)/TiO2 (10.000 A°)/Ti (200 A°)/Pt (1500 A°) substrate with 356-406 of thickness, by electrophoretic technique, using stable suspension of this powder. The films were sintered in the microwave oven for temperatures up to 1000 °C and time up to 40 minutes, in order to form and growth of grains. After sintering and characterization SEM, was deposited a layer of Cr3+ ions by electrophoresis on the surface of the film and submitted to heat treatment of 900 and 1000 ° C for 5, 10 and 15 minutes for purposes of diffusion of cations in the grain boundaries. The Cr+3 is responsible for increasing the coefficient of nonlinearity in varistor system based on SnO2, main characteristic required to obtain varistors. This addition allows to control, through the diffusion by heat treatment, the resistivity, breakdown voltage and nonlinearity coefficient in ceramic films based on SnO2 order to use as varistors. After deposition of ions Cr3+ and heat treatment, the films were electrically characterized by analyzing a direct current to the determination of curves V vs I (voltage applied as a function of electrical current) and curves ln(J/T²) vs E1/2, and characterization alternating current (impedance spectroscopy). From the V vs I curves was possible to obtain the coefficient of nonlinearity, breakdown voltage and leakage current. The parameters of the potential barrier formed at grain boundary region were calculated after analysis of the curves ln(J/T²) vs E1/2 obtained by the V vs I measurements as a function of temperature. The films showed nonlinear coefficient (α)...

Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-03-23Bitstream added on 2014-06-13T20:14:12Z : No. of bitstreams: 1 oliveira_ca_me_araiq.pdf: 3394061 bytes, checksum: cc62df1dfb4c9b02698f2eaba1b551fc (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Materiais eletrocerâmicos possuem diversas aplicações, tais como: capacitor de multicamadas, transdutores, sensor piroelétrico e dispositivos eletro-ópticos. Nos últimos anos, tem ocorrido uma crescente demanda por eletrocerâmicas de melhor desempenho e funcionalidade acelerando o desenvolvimento de técnicas de síntese e visando a produção de pós com partículas bem definidas em tamanho, forma e cristalinidade. O método dos precursores poliméricos e a síntese hidrotérmica, tem se destacado entre as demais técnicas, pois são consideradas ideais para a preparação destas partículas. Baseado neste contexto, este projeto teve como objetivo utilizar o método dos precursores poliméricos e a síntese hidrotérmica assistida por microondas para preparar pós com estrutura perovskitas, como o titanato zirconato de chumbo Pb(Zrx,Ti1-x)O3, com tamanho de partículas controlado, boa cristalinidade e estabilidade química. A cerâmica foi associada a um polímero para formar um compósito na forma de filmes. O polímero usado foi fluoreto de polivinideno, PVDF, já conhecido na literatura. Foram controlados o tamanho das partículas cerâmicas e a espessura dos filmes compósitos visando estabelecer um ótimo para as propriedades piezoelétricas e piroelétricas. A polarização tornou-se mais efetiva com a inclusão do polímero condutor a polianilina (PAni). A condutividade foi controlada pelos processos de protonação, desprotonação e reprotonação. Os resultados mostraram que é possível obter filmes compósitos e a melhor proporção foi de 30/70 v/v (cerâmica/polímero) garantindo boas propriedades eletrocerâmicas e ainda a flexibilidade proporcionada pelo polímero. Para a formação do compósito, PZT-PAni-rp/PVDF, a melhor condição encontrada foi para os filmes... Electroceramic materials have many applications such as multilayer capacitor, transducer, pyroelectric sensor and electro-optical devices. In recent years, there has been a growing demand for electroceramics with better performance and functionality, accelerating the development of synthesis techniques and focusing on the production of powders with well-defined particle size, shape and crystallinity. The polymeric precursor method developed by Pechini and hydrothermal synthesis have stood out among the other techniques and they are considered ideal for the preparation of these particles. Based on this context, this project aimed to use the polymeric precursor method and hydrothermal synthesis assisted by microwave to prepare powders with perovskite structure, such as lead zirconate titanate Pb (Zrx, Ti1-x) O3, with controlled particle size, good crystallinity and chemical stability. The ceramic was associated with a polymer to form a composite in the form of films. The used polymer was polyvinylidene fluoride, PVDF, already known in the literature. We controlled the size of the ceramic particles and the thickness of the composite films to establish the best for the pyroelectric and piezoelectric properties. The polarization has become more effective with the inclusion of the conducting polymer polyaniline (PAni). The conductivity was controlled by the processes of protonation, deprotonation - reprotonation. The results showed that is possible to obtain composite films and the best ratio was 30/70 v / v (ceramic / polymer) electroceramics ensuring good properties and also the flexibility offered by the polymer. To formation the composite PZT-PAni-rp/PVDF, was the best condition found for the films that the PZT was obtained by the method of the polymeric precursor to larger particle sizes and rounded morphology... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-18Bitstream added on 2014-06-13T19:17:20Z : No. of bitstreams: 1 teixeira_gf_me_araiq.pdf: 3060049 bytes, checksum: 1e07eb9c5f9e559d8f613ee18e23f273 (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Neste trabalho foram obtidos pós de Titanato Zirconato de Chumbo (PZT) com razão Zr/Ti igual 52/48 puro com diferentes concentrações de precursor (0,31 molL-1, 0,16 molL-1 e 0,08 molL-1) e pós com adição de Álcool Polivinílico (PVA) que atua como agente de cristalização. Para a preparação dos pós foi utilizada a síntese hidrotérmica assistida por micro-ondas, este método dentre outras vantagens permite obter materiais cristalinos em menores tempos de síntese a baixas temperaturas. Os pós de PZT puro e com PVA foram obtidos em diferentes tempos de síntese a temperatura de 180°C. As amostras foram caracterizadas por Difratometria de Raios X (DRX), Espectroscopia Raman, Microscopia Eletrônica de Varredura de alta resolução (MEV-FEG), Espectroscopia de Fotoluminescência (FL) e Espectroscopia na região do Ultra-Violeta Visível (UV-Vis). Os resultados de DRX indicaram a obtenção de PZT puro e PZT/PVA com estrutura cristalina tetragonal e romboédrica à partir de 1hora de síntese, independente da concentração dos precursores. As partículas possuem forma semelhante a cubos ou folhas que formam mesoestruturas para PZT puro e PZT/PVA. O band gap de energia calculado à partir dos dados de UV-Vis indicaram valores no intervalo de 2,7 eV a 3,1 eV. As bandas de emissão fotoluminescente seguem o modelo da banda larga com máximo de emissão predominante na região verde do espectro eletromagnético Pure powders of Lead Zirconate Titanate (PZT) with ratio Zr/Ti equal 52/48 with different concentrations of precursor (0.31 mol L-1, 0.16 mol L-1 and 0.08 mol L-1) and PZT powders with addition of Polyvinyl Alcohol (PVA) which acts as an agent of crystallization was obtained using hydrothermal synthesis assisted by microwaves. Among other advantages this method allows to obtain crystalline materials synthesis time decreases and low temperatures. The powders of pure PZT and PZT/PVA were obtained by different times of the synthesis at temperature 180°C. The samples were submitted to characterizations by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy high resolution (SEM-FEG), photoluminescence spectroscopy (PL), Ultra-Violet Visible (UV-Vis) spectroscopy. The XRD results indicate that pure PZT and PZT/PVA present a tetragonal and rhombohedral structure since one hour of synthesis, independent of precursors concentration. The shape of particles resembles cubes or sheets that form mesostructure for pure PZT and PZT/PVA. The band gap energy calculated from UV-Vis data indicated values in the range of 2.7 eV to 3.1 eV. The photoluminescent emission bands follow the model of broadband with maximum emission predominant in the green region of the electromagnetic spectrum

Made available in DSpace on 2014-06-11T19:23:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-28Bitstream added on 2014-06-13T19:28:56Z : No. of bitstreams: 1 nunez_l_me_araiq.pdf: 4805192 bytes, checksum: 64ff00eb729fd417b5e185bf3c523ca2 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Materiais com potencial para aplicação como sensores de gás tem sido estudados desde meados dos anos 70. Conhecer o comportamento destes materiais é de fundamental importância para o sucesso de pesquisas nesta área. No presente trabalho foram sintetizadas amostras de dióxido de titânio puro e dopado com os seguintes metais: alumínio, lantânio, cobre ou tungstênio utilizando os métodos Pechini e sol gel. As amostras foram obtidas na forma de pó e filmes finos por ambos os métodos. Na preparação dos pós foram usadas duas rotas de processamento para ambos. No método Pechini variou-se a temperatura de calcinação e a concentração do dopante, no método sol gel variou-se a concentração do dopante e o procedimento, inserindo tratamento hidrotermal assistido por micro-ondas. Os pós obtidos apresentam tamanhos de partículas nanométricos com áreas superficiais entre 8 e 190 m2/g, valores de energia do band gap óptico entre 2,58 a 3,47 eV. Na preparação dos filmes a partir de solução Pechini variou-se a razão de aquecimento, durante o tratamento térmico, a concentração dos dopantes e presença de polietilenoglicol na solução. Na preparação dos nos filmes obtidos a partir de sol gel variou-se a concentração dos dopantes. Todos os filmes foram depositados sobre substrato de silício recoberto com uma camada de 300nm de oxido de silício, utilizando o processo spin-coating. Obteve-se indicativo de resposta sensora a O2 nos filmes dopados com lantânio, cobre ou tungstênio, obtidos a partir de solução Pechini, e para o filme dopado com alumínio a partir de método sol gel. Materials with potential applications as gas sensor have been studied since the mid seventies. The success of researchers in this area is strongly dependent on the knowledge of the behavior of these materials. In the present work, both pure and aluminum-, lanthanum-, copper- or tungsten-doped titanium dioxide samples were synthesized by the Pechini and sol gel methods. Samples were obtained as powders and thin films. Powders were prepared by two routes in each of the processes. Sintering temperature and dopant concentration were varied in the Pechini method, whereas the dopant concentration and synthesis process were varied in the sol gel method, in which the microwave-assisted hydrothermal synthesis was implemented. The powders presented nanometric particles with specific surface areas between 8 and 190 m2/g, optical band-gap energies among 2.58 and 3.47 eV. Films were deposited by means of spin-coating technique onto silicon substrates covered with a 300 nm silicon oxide layer. Films doped with La, Cu and W obtained by the Pechini method, and films doped with Al obtained by the sol gel method, showed response towards O2.

Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-29Bitstream added on 2014-06-13T19:42:35Z : No. of bitstreams: 1 mourafilho_f_dr_araiq.pdf: 4051444 bytes, checksum: 71d39c1867370b918549d208eba537f8 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) O objetivo central deste trabalho foi obter cerâmicas de Ba(Ti1-xZrx)O3 puras e modificadas com íons vanádio (V5+) ou tungstênio (W6+) pelo método convencional de mistura de óxidos com elevada permissividade dielétrica. A fase pura foi obtida controlandose a temperatura de sinterização e quantidade de aditivos. Inicialmente, preparou-se e caracterizou-se as cerâmicas de Ba(Ti1-xZrx)O3, com x variando de 0,05 até 0,15. A composição com uma única transição de fase ferroelétrica-paraelétrica foi a escolhida para substituição com vanádio e tungstênio. Investigou-se a influência dos íons vanádio e tungstênio nas propriedades estruturais, morfológicas e elétricas das cerâmicas BZT10 sinterizadas, entre 1200oC e 1350oC com isoterma de 4 horas. A adição dos íons V5+ ou íons W6+ substituindo Ti4+ ou Zr4+, na rede da cerâmica BZT10, promoveu a densificação deslocando significativamente os valores da temperatura de sinterização do BZT10 puro de 1550oC para 1200oC. As propriedades elétricas foram avaliadas para as cerâmicas monofásicas de BZT10 modificada com íons V5+ ou W6+ e sinterizadas a 1350oC, 1200oC, respectivamente. Os valores otimizados para as cerâmica BZT10:2V e BZT10:2W indicam permissividades dielétricas da ordem (ε) 15160 e 6420 a 10 kHz, polarização de 8,50 e 3,10μC/cm2 com 4,194x1017 e 1,474x1017 (spins/g), respectivamente. Os resultados obtidos para a cerâmica BZT10:2V indicam potencial aplicação em memórias FeRaM, enquanto os resultados obtidos para cerâmica BZT10:2W apresentam comportamento relaxor e transição de fase difusa, com potencial aplicação em memórias DRAM. The main objective of this work was to obtain pure Ba(Ti1-xZrx)O3 and modified with vanadium and tungsten with high permittivity by the mixture oxide method. Single phase was obtained by controlling the temperature and amount of additive. In a first step, Ba(Ti1-xZrx)O3 ceramics with x varying from 0,05 to 0,15 were prepared and characterized. The ceramics with only one phase transition ferroelectric-paraelectric was chosen for modification with vanadium and tungsten. The influence of vanadium and tungsten in the structural, morphological and electrical properties of BZT ceramics sintered from 1200oC to 1350oC for 4 hours was investigated. The addition of V5+ or W6+ exchanging Ti4+ or Zr4+ in the BZT10 lattice, promotes the densification, changing the sintering temperature of pure BZT from 1550oC to 1200oC. BZT:2V and BZT:2W ceramics have dielectric permittivity of (ε) 15160 and 6420 at 10 kHz, remnant polarization equal to 8.50 and 3.10μC/cm2 with spins quantity equal to 4.194x1017 and 1.474x1017 (spins/g), respectively. BZT:2V ceramics have potential applications for FeRAM memory while BZT10:2W ceramics present relaxor behavior with a diffuse phase transition, being potential application in DRAM memory.