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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Stability of fatigued and aged ZTA compared to 3Y-TZP and Al2O3 ceramic systems
2022 - BENALCAZAR JALKH, ERNESTO B.; BERGAMO, EDMARA T.P.; CAMPOS, TIAGO M.B.; ARAUJO-JUNIOR, EVERARDO N.S. de; LOPES, ADOLFO C.O.; TEBCHERANI, SERGIO M.; YAMAGUCHI, SATOSHI; GENOVA, LUIS A.; GIERTHMUEHLEN, PETRA C.; WITEK, LUKASZ; COELHO, PAULO G.; BONFANTE, ESTEVAM A.
To evaluate the effect of fatigue and aging on the crystalline content and reliability of a zirconia-toughened-alumina (ZTA) composite compared to its individual counterpart materials (3Y-TZP and Al2O3). Thirty-six disc-shaped specimens per group were obtained to comply with ISO 6872:2015. Crystalline content, microstructure and reliability of experimental groups were evaluated in four stages: 1) immediate; 2) aged; 3) fatigued; 4) aged + fatigue. Aging was performed in autoclave and Step-Stress-Accelerated-Life-Testing (SSALT) was performed using three stress profiles. Weibull statistics were used to determine Weibull parameters and life-expectancy. A significant increase in monoclinic phase in 3Y-TZP was observed after aging (19.31%), fatigue (17.88%) and aging + fatigue (55.81%), while ZTA evidenced minimal variation among all conditions (<5.69%). 3Y-TZP presented higher reliability than ZTA at 300 and 500 MPa, and ZTA outperformed Al2O3 at the same stress missions. None of the ceramics yielded acceptable reliability at 800 MPa. A higher characteristic strength was observed for 3Y-TZP, followed by ZTA and Al2O3. While after aging ZTA and Al2O3 remained stable, 3Y-TZP exhibited a significant increase in the characteristic stress. Aging did not affect the reliability of ZTA and Al2O3. 3Y-TZP demonstrated an increase in monoclinic content and characteristic strength after aging.
Nanoscale physico-mechanical properties of an aging resistant ZTA composite
2021 - BENALCAZAR JALKH, E.B.; COELHO, P.G.; WITEK, L.; BERGAMO, E.T.P.; LOPES, A.C.O.; MONTEIRO, K.N.; CESAR, P.F.; GENOVA, L.A.; LISBOA-FILHO, P.N.; ABREU, J.L.B.; CAMPOS, T.M.B.; CANTEENWALA, A.; BONFANTE, E.A.
Objective: To characterize the effects of aging on the nanomechanical properties and 3D surface topographical parameters of an experimental Zirconia Toughened Alumina (ZTA) composite compared to its respective individual counterpart materials. Methods: Disk-shaped specimens comprised of three material groups were processed: 1) ZTA 70/30 (70% alumina reinforced with 30% second-generation 3Y-TZP); 2) Zpex (Second-generation 3Y-TZP), and; 3) Al2O3 (High purity Alumina) (n = 10/material, 12 × 1 mm). After synthesis, ceramic powders were pressed, the green-body samples were sintered and polished. Nanoindentation testing was performed to record elastic modulus (E) and hardness (H). Interferometry was utilized to assess 3D surface roughness parameters (Sa, Sq), while X-ray diffraction (XRD) and scanning electron microscope (SEM) assessed the crystalline content and microstructure. All tests were performed before and after simulated aging (134°C, 2.2 bar, 20 h). Statistical analyses were performed using linear mixed-model and least square difference pos-hoc tests (α = 5%). Results: XRD spectra indicated increase of monoclinic peaks for Zpex (~18%) relative to ZTA 70/30 (~2.5%) after aging. Additionally, aging did not affect the surface roughness parameters of ZTA 70/30 and Al2O3, although a significant increase in Sa was recorded for Zpex following aging (~90 nm) (p < 0.001). Al2O3 yielded the highest H and E values (H:21 GPa, E: 254 GPa), followed by ZTA 70/30 (H: 13 GPa, E: 214 GPa) and Zpex (H:11 GPa, E: 167 GPa), all significantly different (p < 0.03). Conclusion: ZTA 70/30 and Al2O3 presented high hydrothermal stability with respect to all evaluated variables, where artificial aging significantly increased the monoclinic content and surface roughness of Zpex.
Aging resistance of an experimental zirconia-toughened alumina composite for large span dental prostheses
2020 - BENALCAZAR JALKH, E.B.; BERGAMO, E.T.P.; MONTEIRO, K.N.; CESAR, P.F.; GENOVA, L.A.; LOPES, A.C.O.; LISBOA FILHO, P.N.; COELHO, P.G.; SANTOS, C.F.; BORTOLIN, F.; PIZA, M.M.T.; BONFANTE, E.A.
Purpose: To synthesize a zirconia-toughened alumina (ZTA) composite with 85% alumina matrix reinforced by 15% zirconia and to characterize its optical and mechanical properties before and after artificial aging, to be compared with a conventional dental zirconia (3Y-TZP). Material and methods: After syntheses, ZTA and 3Y-TZP powders were uniaxially and isostatically pressed. Greenbody samples were sintered and polished to obtain 80 disc-shaped specimens per group (12 x 1 mm, ISO 6872:2015). The crystalline content and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical properties were determined by the calculation of contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength test (BFS). All analyses were conducted before and after artificial aging (20h, 134 °C, 0.22 MPa). Optical parameters and microhardness differences were evaluated through repeated-measures analysis of variance (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results: The synthesis of the experimental ZTA composite was successful, with 98% of theoretical density, as shown in the SEM images. XRD patterns revealed typical zirconia and alumina crystalline phases. ZTA optical properties parameters showed no effect of aging, with a high CR and low TP values denoting a high maskingability. 3Y-TZP presented lower masking-ability and aging significantly affected its optical properties. ZTA Vickers hardness, fracture toughness and Weibull parameters, including characteristic stress and Weibull modulus were not influenced by aging, while 3Y-TZP presented a significant decrease in characteristic stress and increase in fracture toughness after aging. The ZTA probability of survival for missions of 300 and 500 MPa was estimated at ~99% validating its use for 3-unit posterior fixed dental prostheses (FDP), and no different from conventional 3Y-TZP. At high-stress mission (800 MPa) a significant decrease in probability of survival was observed for aged 3Y-TZP (84%) and for immediate and aged ZTA (73 and 82% respectively). Conclusion: The ZTA composite presented a dense microstructure, with preservation of the crystalline content, optical and mechanical properties after artificial aging, which encourages future research to validate its potential use for large span FDP.