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São José dos Campos, Brazil

Ozcan M.,University of Zurich | Melo R.M.,Sao Paulo State University | Souza R.O.A.,Federal University of Paraiba | Machado J.P.B.,National Institute of Spatial Research | And 2 more authors.
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2013

This study evaluated the effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading. Disc-shaped zirconia specimens (Ø: 15mm, thickness: 1.2mm) (N=32) were submitted to one of the air-particle abrasion protocols (n=8 per group): (a) 50μm Al2O3 particles, (b) 110μm Al2O3 particles coated with silica (Rocatec Plus), (c) 30μm Al2O3 particles coated with silica (CoJet Sand) for 20s at 2.8bar pressure. Control group received no air-abrasion. All specimens were initially cyclic loaded (×20,000, 50N, 1Hz) in water at 37°C and then subjected to biaxial flexural strength testing where the conditioned surface was under tension. Zirconia surfaces were characterized and roughness was measured with 3D surface profilometer. Phase transformation from tetragonal to monoclinic was determined by Raman spectroscopy. The relative amount of transformed monoclinic zirconia (FM) and transformed zone depth (TZD) were measured using XRD. The data (MPa) were analyzed using ANOVA, Tukey's tests and Weibull modulus (m) were calculated for each group (95% CI). The biaxial flexural strength (MPa) of CoJet treated group (1266.3±158A) was not significantly different than that of Rocatec Plus group (1179±216.4A,B) but was significantly higher than the other groups (Control: 942.3±74.6C; 50μm Al2O3: 915.2±185.7B,C). Weibull modulus was higher for control (m=13.79) than those of other groups (m=4.95, m=5.64, m=9.13 for group a, b and c, respectively). Surface roughness (Ra) was the highest with 50μm Al2O3 (0.261μm) than those of other groups (0.15-0.195μm). After all air-abrasion protocols, FM increased (15.02%-19.25%) compared to control group (11.12%). TZD also showed increase after air-abrasion protocols (0.83-1.07μm) compared to control group (0.59μm). Air-abrasion protocols increased the roughness and monoclinic phase but in turn abrasion with 30μm Al2O3 particles coated with silica has increased the biaxial flexural strength of the tested zirconia. © 2013 Elsevier Ltd. Source


Libardi J.,Brazilian Technological Institute of Aeronautics | Grigorov K.G.,Brazilian Technological Institute of Aeronautics | Grigorov K.G.,Institute of Space Technology | Guerino M.,Brazilian Technological Institute of Aeronautics | And 6 more authors.
Chip in Curitiba 2013 - SBMicro 2013: 28th Symposium on Microelectronics Technology and Devices | Year: 2013

Titanium dioxide (TiO2) thin films were deposited on silicon p type (100) substrates by reactive magnetron sputtering technique at different oxygen partial pressures. The film structure was studied by X-Ray Diffraction (XRD), while the film composition was examined by Rutherford Backscattering Spectroscopy (RBS). Finally, Metal-Oxide Semiconductor (MOS) capacitors were manufactured and some important physical constants were analyzed as function of the oxygen content in the films. It was found that the films deposited at lower oxygen partial pressure exhibited better crystalline structure and higher dielectric constant. © 2013 IEEE. Source


Vogt N.D.,National Institute of Spatial Research | Pinedo-Vasquez M.,Columbia International University | Brondizio E.S.,Indiana University Bloomington | Almeida O.,Federal University of Para | Rivero S.,Federal University of Para
Society and Natural Resources | Year: 2015

The question of how smallholders of the Amazon estuary, locally known as cabolcos, have adapted their land use systems to produce resources during booms and busts is analyzed in this article. We draw upon more than 50 years of census data and more than 30 years of remotely sensed land-cover data to reconstruct these dynamics from World War II to the present. We found that smallholders are highly flexible in their land use decisions and livelihood strategies and that such flexibility has helped them to adapt their land-use systems to produce resources in demand during market booms and conserve forests. Smallholder mosaic landscapes contain forest fragments that enhance socioecological resilience to floods and other events produced by changes in the local hydro-climatic regimes due to sea-level rise and other climate-related changes. We argue that flexibility is a tool to reduce livelihood vulnerability by facilitating adaptation to global market and climate driven changes over the long term. © 2015, Copyright © Taylor & Francis Group, LLC. Source


Souza R.O.A.,Federal University of Paraiba | Valandro L.F.,Federal University of Santa Maria | Melo R.M.,Sao Paulo State University | Machado J.P.B.,National Institute of Spatial Research | And 2 more authors.
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2013

This study evaluated the effect of different air-particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 μm Al2O3 (2.5 bar); Gr3: 50 μm Al2O3 (3.5 bar); Gr4: 110 μm Al2O3(2.5 bar); Gr5: 110 μm Al2O3 (3.5 bar); Gr6: 30 μm SiO2 (2.5 bar) (CoJet); Gr7: 30 μm SiO2(3.5 bar); Gr8: 110 μm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 μm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t→m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 μm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1030±153, Controlaged: 1138±138; Experimentalnon-aged: 1307±184-1554±124; Experimentalaged: 1308±118-1451±135) in both non-aged and aged conditions, respectively. Surface roughness (Ra) was the highest with 110 μm Al2O3(0.84 μm. FM values ranged from 0% to 27.21%, higher value for the Rocatec Plus (110 μm SiO2) and 110 μm Al2O3 groups at 3.5 bar pressure. TZD ranged between 0 and 1.43 μm, with the highest values for Rocatec Plus and 110 μm Al2O3 groups at 3.5 bar pressure. © 2013 Elsevier Ltd. Source

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