The Experts below are selected from a list of 108 Experts worldwide ranked by ideXlab platform

Sergio Neves Monteiro - One of the best experts on this subject based on the ideXlab platform.

  • Effect of the Fiber Equivalent Diameter on the Elastic Modulus of Eucalyptus Fibers
    Materials Science Forum, 2016
    Co-Authors: Anderson De Paula Barbosa, Frederico Muylaert Margem, Sergio Neves Monteiro, Caroline Gomes De Oliveira, Noan Tonini Simonassi
    Abstract:

    Environmental, economical, societal and technical advantages are today favoring natural lignocellulosic fibers over glass fiber. However, natural fibers are not as uniform in their dimension and properties as compared to synthetic ones. In recent works, it was found that the variation in strength could be correlated to the diameter for several lignocellulosic fibers, including that obtained from the eucalyptus wood. The present work investigated a possible correlation of the diameter with changes in the elastic modulus of eucalyptus wood fibers. Precise measurements of the equivalent diameter, conducted in a profile projector, were correlated with the elastic modulus by means of the Weibull Statistic analysis. The results showed that an inverse correlation with the diameter applies for the elastic modulus with a reasonable degree of precision. SEM observation of the eucalyptus fiber, both it its structure and fracture aspects, strongly indicates that defects and microfibrils participation could be responsible for the inverse correlation.

  • increase of flexural strength of red ceramic pieces incorporated with ornamental rock waste application of Weibull Statistic for determination of best firing temperature
    Characterization of Minerals Metals and Materials, 2015
    Co-Authors: Carla Bozzi Piazzarollo, Gustavo De Castro Xavier, Jonas Alexandre, A R G Azevedo, Sergio Neves Monteiro
    Abstract:

    Ceramic materials exhibit dispersion results after being subjected to various levels of stress, from the point of view of mechanical strength. With the focus on sustainable development and to improve the strength of these material, was incorporated ornamental rock waste into clay in up to 10% in mass to conform some samples, that was fired to 750°C, 850°C and 950°C and submitted to technological tests. This paper presents an analysis of the technological properties of the samples through the use of Weibull Statistic to determine which the best firing temperature for these red ceramic materials. The Weibull Modulus indicates a greater homogeneity for samples with 10R at 950°C.

  • Characterization of Minerals, Metals, and Materials 2015 - Increase of Flexural Strength of Red Ceramic Pieces Incorporated with Ornamental Rock Waste: Application of Weibull Statistic for Determination of Best Firing Temperature
    Characterization of Minerals Metals and Materials 2015, 2015
    Co-Authors: Carla Bozzi Piazzarollo, Gustavo De Castro Xavier, Jonas Alexandre, A R G Azevedo, Sergio Neves Monteiro
    Abstract:

    Ceramic materials exhibit dispersion results after being subjected to various levels of stress, from the point of view of mechanical strength. With the focus on sustainable development and to improve the strength of these material, was incorporated ornamental rock waste into clay in up to 10% in mass to conform some samples, that was fired to 750°C, 850°C and 950°C and submitted to technological tests. This paper presents an analysis of the technological properties of the samples through the use of Weibull Statistic to determine which the best firing temperature for these red ceramic materials. The Weibull Modulus indicates a greater homogeneity for samples with 10R at 950°C.

  • Correlation between the Diameter and the Density of Coir Fiber Using the Weibull Statistic Methodology
    Materials Science Forum, 2014
    Co-Authors: Sergio Neves Monteiro, Helvio Pessanha Guimarães Santafé Júnior, Lucas Barbosa De Souza Martins, Frederico Muylaert Margem, Michel Picanco Oliveira
    Abstract:

    Economical, technical and environmental advantages justify the substitution of glass fiber for lignocellulosic fibers in polymeric composites. However the uniformity of the glass fiber dimensions and composition contrast to the lignocellulosic fibers heterogeneity. In this work, a Statistical analysis of the correlation between the diameter and the density of coir fiber using the Weibull methodology was performed. The diameter was obtained by profile projector measurements, while the density used precise determinations of the fibers mass and volume. The results revealed an inverse dependence between the coir fiber diameter and its density.

  • Correlation between the Diameter and the Density of Coir Fiber Using the Weibull Statistic Methodology
    Materials Science Forum, 2014
    Co-Authors: Sergio Neves Monteiro, Helvio Pessanha Guimarães Santafé Júnior, Lucas Barbosa De Souza Martins, Frederico Muylaert Margem, Michel Picanco Oliveira
    Abstract:

    Economical, technical and environmental advantages justify the substitution of glass fiber for lignocellulosic fibers in polymeric composites. However the uniformity of the glass fiber dimensions and composition contrast to the lignocellulosic fibers heterogeneity. In this work, a Statistical analysis of the correlation between the diameter and the density of coir fiber using the Weibull methodology was performed. The diameter was obtained by profile projector measurements, while the density used precise determinations of the fibers mass and volume. The results revealed an inverse dependence between the coir fiber diameter and its density.

Carla Bozzi Piazzarollo - One of the best experts on this subject based on the ideXlab platform.

Claudinei Dos Santos - One of the best experts on this subject based on the ideXlab platform.

  • mechanical properties of lithium metasilicate after short term thermal treatments
    Journal of The Mechanical Behavior of Biomedical Materials, 2019
    Co-Authors: Bruno Galvao Simba, Marcos Valerio Ribeiro, Paulo Atsushi Suzuki, Manuel Fellipe Rodrigues Pais Alves, Kurt Strecker, Claudinei Dos Santos
    Abstract:

    Abstract Objectives The properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate (Li2Si2O5) and on the resulting mechanical properties has been investigated. Methods Lithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P–3B) testing assembly. Complementary Weibull Statistic were conducted as Statistical analysis. Results The results indicate a progressive reduction of the Li2SiO3 phase with increasing isothermal holding time at 820 °C until the conversion into Li2Si2O5, is completed for treatments longer than 7 min. A complete transformation of Li2SiO3 into Li2Si2O5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ± 0.17 GPa, 1.60 ± 0.03 MPa m1/2, 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li2Si2O5 grains and higher amount of residual amorphous phase. Conclusion In general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties.

  • Mechanical Behaviour of ZrO2-Bioglass Dental Ceramics under Cyclic Fatigue Loading
    Materials Science Forum, 2010
    Co-Authors: Luiz De Araujo Bicalho, R.c. Souza, Claudinei Dos Santos, Miguel Ribeiro Justino Barboza, Carlos Antonio Reis Pereira Baptista
    Abstract:

    The cyclic fatigue life of 3mol%Y2O3-stabilized ZrO2 (3Y-TZP) ceramics doped with bioactive glass has been investigated. Samples of 3Y-TZP containing 3 or 5wt% of bioglass were sintered at 1300oC for 120 minutes. Sintered samples were characterized by relative density, XRD and SEM analysis. Mechanical properties of hardness and fracture toughness were determined using Vickers indentation method and Modulus of Rupture was determined by four-point bending testing. Furthermore, the reliability of the samples was estimated using Weibull Statistic analysis. The cyclic fatigue life was estimated using four-point bending testing under frequency of 25Hz and stress ratio, R, of 0.1. Highly dense tetragonal ZrO2 samples were obtained after sintering and presented hardness of 10.5 and 11GPa, KIC of 6 and 7MPam1/2, bending strength of 320 and 450MPa and Weibull’ modulus of 6 and 7 for samples containing 5 or 3% of bioglass respectively. The fatigue behavior indicates that the increasing of stress level leads to decreasing of the number of cycles and the number of run-out specimens. Fatigue behavior was similar for the two compositions tested. Samples containing 3% of bioglass are more resistant (near 10%) to fatigue presenting cyclic fatigue life near to 250MPa while samples with 5% presented fatigue limit near to 220MPa.

Manuel Fellipe Rodrigues Pais Alves - One of the best experts on this subject based on the ideXlab platform.

  • mechanical properties of lithium metasilicate after short term thermal treatments
    Journal of The Mechanical Behavior of Biomedical Materials, 2019
    Co-Authors: Bruno Galvao Simba, Marcos Valerio Ribeiro, Paulo Atsushi Suzuki, Manuel Fellipe Rodrigues Pais Alves, Kurt Strecker, Claudinei Dos Santos
    Abstract:

    Abstract Objectives The properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate (Li2Si2O5) and on the resulting mechanical properties has been investigated. Methods Lithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P–3B) testing assembly. Complementary Weibull Statistic were conducted as Statistical analysis. Results The results indicate a progressive reduction of the Li2SiO3 phase with increasing isothermal holding time at 820 °C until the conversion into Li2Si2O5, is completed for treatments longer than 7 min. A complete transformation of Li2SiO3 into Li2Si2O5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ± 0.17 GPa, 1.60 ± 0.03 MPa m1/2, 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li2Si2O5 grains and higher amount of residual amorphous phase. Conclusion In general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties.

Lars Stenmark - One of the best experts on this subject based on the ideXlab platform.