LUIS ANTONIO GENOVA

LUIS ANTONIO GENOVA

(Fonte: Lattes)

Resumo

Graduate at Materials Engineering from Universidade Federal de São Carlos (1984), working for six years in ceramic industries. Master's and Ph.D. at Nuclear Engineering from Universidade de São Paulo. Has experience in Material Engineering, focusing on Ceramics, acting on the following subjects: processing, sintering, ceramic microsphere, porous ceramic, ceramic machining, adsorption, photocatalisys. (Text obtained from the Currículo Lattes on November 12th 2021)

Possui graduação em Engenharia de Materiais pela Universidade Federal de São Carlos (1984), com atuação por seis anos em indústrias cerâmicas. Possui mestrado e doutorado pela Universidade de São Paulo (2003). Atualmente é tecnologista senior do Instituto de Pesquisas Energéticas e Nucleares. Tem experiência na área de Engenharia de Materiais, com ênfase em Cerâmicos, atuando principalmente nos seguintes temas: processamento, sinterização, microesferas cerâmicas, cerâmicas porosas, usinagem cerâmica, adsorção, fotocatálise. (Texto extraído do Currículo Lattes em 12 nov. 2021)

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Microstructural, mechanical, and optical characterization of an experimental aging-resistant zirconia-toughened alumina (ZTA) composite
2020 - LOPES, A.C.O.; COELHO, P.G.; WITEK, L.; BENALCAZAR JALKH, E.B.; GENOVA, L.A.; MONTEIRO, K.N.; CESAR, P.F.; LISBOA-FILHO, P.N.; BERGAMO, E.T.G.; RAMALHO, I.S.; CAMPOS, T.M.B.; BONFANTE, E.A.
Objective. To evaluate the effect of aging on the microstructural, mechanical, and optical properties of an experimental zirconia-toughened alumina composite with 80%Al2O3 and 20%ZrO2 (ZTA Zpex) compared to a translucent zirconia (Zpex) and Alumina. Methods. Disc-shaped specimens were obtained by uniaxial and isostatic pressing the synthesized powders (n = 70/material). After sintering and polishing, half of the specimens underwent aging (20 h, 134 °C, 2.2 bar). Crystalline content and microstructure were evaluated using X-ray diffraction and scanning electron microscopy, respectively. Specimens underwent biaxial flexural strength testing to determine the characteristic stress, Weibull modulus, and reliability. Translucency parameter (TP) and Contrast ratio (CR) were calculated to characterize optical properties. Results. ZTA Zpex demonstrated a compact surface with a uniform dispersion of zirconia particles within the alumina matrix, and typical alumina and zirconia crystalline content. ZTA Zpex and alumina exhibited higher CR and lower TP than Zpex. ZTA Zpex and Zpex showed significantly higher characteristic stress relative to alumina. While aging did not affect optical and mechanical properties of ZTA Zpex and alumina, Zpex demonstrated a significant increase in translucency, as well as a in characteristic stress. Alumina reliability was significantly lower than others at 300 MPa, ZTA Zpex and Zpex reliability decreased at 800 MPa, except for aged Zpex. Significance. While aging did not affect the mechanical nor the optical properties of ZTA Zpex and alumina, it did alter both properties of Zpex. The results encourage further investigations to engineer ZTA as a framework material for long span fixed dental prostheses specially where darkened substrates, such as titanium implant abutments or endodontically treated teeth, demand masking.
Aging resistant ZTA composite for dental applications
2020 - JALKH, ERNESTO B.B.; MONTEIRO, KELLI N.; CESAR, PAULO F.; GENOVA, LUIS A.; BERGAMO, EDMARA T.P.; LOPES, ADOLFO C. de O.; LIMA, ERICK; LISBOA-FILHO, PAULO N.; CAMPOS, TIAGO M.B.; WITEK, LUKASZ; COELHO, PAULO G.; BORGES, ANA F.S.; BONFANTE, ESTEVAM A.
Objective. To synthesize a zirconia toughened alumina (ZTA) composite with 70% aluminareinforced by 30% zirconia for dental applications and to characterize its microstructureand optical properties for comparison with the isolated counterpart materials and a first-generation 3Y-TZP.Methods. Disc-shaped specimens were divided in four groups (n = 70/material): (1) 3YSB-E(first generation 3Y-TZP), (2) Zpex (second generation 3Y-TZP), (3) alumina, and (4) ZTA-Zpex70/30. After synthesis, ceramic powders were pressed, and green-body samples sinteredfollowing a predetermined protocol. Specimens were polished to obtain a mirror surfacefinish. Apparent density was measured by Archimedes principle. X-ray diffraction (XRD)and scanning electron microscope (SEM) were used to characterize the crystalline contentand microstructure. Reflectance tests were performed to determine the contrast-ratio (CR)and translucency-parameter (TP). Mechanical properties were assessed by biaxial flexuralstrength (BFS) test. All analyses were conducted before and after artificial aging (20 h, 134◦C, 2.2 bar). Optical parameters were evaluated through repeated-measures analysis of variance and Tukey tests (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results. High density values (95–99%) were found for all ceramic materials and SEM images exhibited a dense microstructure. While XRD patterns revealed the preservation of crys- talline content in the ZTA composite, an increase in the monoclinic peak was observed for pure zirconias after aging. Significantly higher CR and lower TP values were observed for the ZTA composite, followed by alumina, 3YSB-E, and Zpex. The highest characteristic stress was recorded for 3YSB-E, followed by intermediate values between ZTA and Zpex, and the lowest for alumina. Aging affected the optical and mechanical properties of both zirconias, while remained stable for ZTA composite and alumina. Significance. The synthesis of experimental 70−30% ZTA composite was successful and its relevance for dental applications relies on its higher masking ability, aging resistance, and strength similar to zirconia.
Nanomechanical and microstructural characterization of a zirconiatoughened alumina composite after aging
2019 - LOPES, A.C.O.; COELHO, P.G.; WITEK, L.; BENALCAZAR JALKH, E.B.; GENOVA, L.A.; MONTEIRO, K.N.; CESAR, P.F.; LISBOA FILHO, P.N.; BERGAMO, E.T.P.; RAMALHO, I.S.; BONFANTE, E.A.
This study's objective was to mechanically characterize and validate the synthesis method of a polycrystalline composite comprised of 80% alumina reinforced with 20% translucent zirconia (zirconia-toughened alumina, ZTA) and compare to an experimental translucent zirconia. Experimental ZTA (ZTA ZPEX 80/20) and translucent Y-TZP (ZPEX) green-state disc-shaped specimens were obtained via uniaxial/isostatic ceramic powder pressing technique. The discs were sintered using a predefined protocol after both sides of the discs were polished. The specimens were subjected to nanoindentation testing to acquire their elastic modulus (E) and hardness (H) before and after a simulated low temperature degradation (LTD) challenge. Subsequently, the fabricated discs had their 3D surface topographical (Sa/Sq) parameters assessed via interferometry before and after exposure to a simulated LTD aging protocol. The specimens were evaluated using X-ray diffraction (XRD) to assess the tetragonal-monoclinic phase transformation and via scanning electron microscopy (SEM) to evaluate the homogeneity of the surfaces and distribution of the grains. The apparent density was measured using Archimedes’ principle. All of the data were statistically evaluated through repeated measures ANOVA following post-hoc comparisons using the Tukey test (p < 0.05). The XRD patterns indicated a higher increase in the monoclinic peak for ZPEX compared to ZTA ZPEX 80/20 aged. LTD aging did not have an effect on the surface roughness (Sa/Sq) for both groups (p > 0.05). A significant decrease in the E values after the aging protocol was observed for both groups (p < 0.01). While ZTA ZPEX 80/ 20 did not show statistically significant differences in the hardness values after the aging protocol (p=0.36), ZPEX demonstrated a significant decrease in the H values (p=0.03). For ZTA ZPEX 80/20, simulated LTD aging did not affect the tested properties, except for the E values. Although artificial aging did not affect the surface roughness of ZPEX, the E and H values significantly decreased after aging.
Effect of temperature and heating rate on the sintering performance of SiC-Al2O3-Dy2O3 and SiC-Al2O3-Yb2O3 systems
2017 - RIBEIRO, S.; GENOVA, L.A.; RIBEIRO, G.C.; OLIVEIRA, M.R.; BRESSIANI, A.H.A.
Samples of SiC+10 vol%(Al2O3+Dy2O3) and SiC+10 vol%(Al2O3+Yb2O3) mixtures were obtained by cold isostatic pressing and sintered for one hour in a dilatometer at 1800 °C and 1900 °C, applying heating rates of 10, 20 and 30 °C/min. The results of the complete sintering cycle indicated that the heating rates do not significantly influence the shrinkage, but that temperature and total sintering time may be relevant factors. The compacts sintered at 1900 °C shrank on average 9% more than those sintered at 1800 °C, and it was found that the sintering time can be reduced by 40–50% at faster heating rates. The maximum shrinkage rates occurred at temperatures lower than those of the sintering thresholds for the two mixtures, two temperatures and three heating rates. It was also found that after formation of the liquid, the mechanisms of particle rearrangement and solution-precipitation were not as fast as reported in the literature, even at high heating rates, for example 30 °C/ min, but they are responsible for much of the shrinkage occurring throughout the sintering cycle.
Effect of heating rate on the shrinkage and microstructure of liquid phase sintered SiC ceramics
2016 - RIBEIRO, S.; GENOVA, L.A.; RIBEIRO, G.C.; OLIVEIRA, M.R.; BRESSIANI, A.H.A.
This paper describes a study of shrinkage behavior in the liquid phase sintering of silicon carbide, SiC, using eutectic mixtures of Al2O3+Dy2O3 and Al2O3+Yb2O3 as liquid-forming additives. A volume fraction 10% of these mixtures was added to the SiC and homogenized in an attrition mill. Sintering was performed in a horizontal dilatometer at 1800 °C for 60 min, applying heating rates of 10, 20 and 30 °C/min. The results indicate that these heating rates affected neither shrinkage nor microstructure, from the standpoint of the complete sintering cycle. However, significant differences occurred during the non-isothermal sintering stage, leading to very different shrinkage results as a function of the heating rate. Higher heating rates produced lower shrinkage, and the work of final shrinkage occurred during the isothermal stage.