Celio Costa - Academia.edu (original) (raw)
Papers by Celio Costa
Journal of The American Ceramic Society, 2004
A four-point flexure test, capable of simultaneously measuring load-point and beam-center displac... more A four-point flexure test, capable of simultaneously measuring load-point and beam-center displacements and permitting in situprofiling of the beam throughout the test, has been developed. Compressive and tensile strains in the outer fibers, together with the neutral axis displacement, were determined in real time for Si3N4-whisker-reinforced Si3N4-ceramic-matrix composites. Combining these data with the closed form solution of Chen and Chuang gave excellent correspondence between the creep exponents determined from flexure tests with those determined independently from tensile and compressive creep tests.
International Review of Psychiatry, 2008
Little is known in our own as well as in other cultures about the knowledge and prejudices mental... more Little is known in our own as well as in other cultures about the knowledge and prejudices mental health professionals have about mental illness and those affected. We therefore: 1) assessed mental health literacy and general attitudes towards people with mental illness in a sample of Brazilian mental health professionals; 2) compared the outcomes among the different professional groups; and 3) compared the data with a sample of Swiss mental health professionals. A questionnaire used to assess knowledge and attitudes towards the mentally ill among mental health professionals in Switzerland was translated into Portuguese. Mental health professionals were presented a case vignette describing a person suffering from a major depression as well as related treatment proposals. Furthermore, general attitudes towards people with mental illness were assessed. Both samples had equal scores for social acceptance. Brazilian mental health professionals displayed a more positive attitude towards community psychiatry whereas the Swiss sample showed more stigmatization and social distance, and a more positive attitude towards psychopharmacology. Recognition of the case vignette was significantly better in Brazil than in Switzerland (94.7% versus 71%). Mental health professionals in Brazil were more conservative/medically orientated in their treatment propositions whereas professionals from Switzerland also proposed social interventions and alternative treatment strategies. There are some major differences in attitudes towards people with mental illness between mental health professionals in Switzerland and Brazil. With respect to therapeutic interventions, the different healthcare systems as well as the cultural differences seem to have an impact.
Journal of Materials Engineering and Performance, 2006
In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densi... more In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densified via gas pressure sintering and hot pressing, respectively, were evaluated using the single-edge V-notched beam (SEVNB) fracture toughness technique. The mean value ofK IC for each material was 5.7 and 7.9 MPa·m1/2, respectively, and the toughness was influenced by the presence of the elongated Si3N4 grains in the microstructure. The notch radius was observed to have the same effect as a sharp crack when notch-root radius was smaller than 10 µm, which was considered to be a realK IC for these materials.
Materials Research-ibero-american Journal of Materials, 2006
This present work evaluates the influence of microstructure on the fracture toughness of two type... more This present work evaluates the influence of microstructure on the fracture toughness of two types of silicon nitride. The two microstructural types of silicon nitride were processed using the gas pressure sintering (GPS) and hot pressing (HP) pathways. The fracture toughness was measured using the Single Edge V-Notch Beam (SEVNB) and Chevron Notch Beam (CNB) methods. The results from both methods for the two forms were in close agreement (with a maximum variation of 5.8%); the KIc of the material processed by HP was 35% higher than that of GPS and the grain length had a direct influence on the fracture toughness.
Journal of Materials Engineering and Performance, 2006
In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densi... more In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densified via gas pressure sintering and hot pressing, respectively, were evaluated using the single-edge V-notched beam (SEVNB) fracture toughness technique. The mean value of K IC for each material was 5.7 and 7.9 MPa·m1/2, respectively, and the toughness was influenced by the presence of the elongated Si3N4 grains in the microstructure. The notch radius was observed to have the same effect as a sharp crack when notch-root radius was smaller than 10 µm, which was considered to be a real K IC for these materials.
Powder Technology, 2006
Silicon carbide powder (SiC) was comminuted in a planetary mill during time intervals of 0.5, 2, ... more Silicon carbide powder (SiC) was comminuted in a planetary mill during time intervals of 0.5, 2, 4 and 6 h. The wet milling media was ZrO 2 spheres in isopropyl alcohol. The powders were then characterized with respect to chemical composition, particle size distribution, surface area and density for each milling time. The average particle size was reduced from 1.8 μm to 0.4 μm in 30 min and the amount of ZrO 2 increased linearly with milling time. The result was a homogeneous combination of submicrometer and nanometric SiC + ZrO 2 powder, which possessed good sinterability in liquid phase and high fracture toughness.
Journal of The American Ceramic Society, 2004
A four-point flexure test, capable of simultaneously measuring load-point and beam-center displac... more A four-point flexure test, capable of simultaneously measuring load-point and beam-center displacements and permitting in situprofiling of the beam throughout the test, has been developed. Compressive and tensile strains in the outer fibers, together with the neutral axis displacement, were determined in real time for Si3N4-whisker-reinforced Si3N4-ceramic-matrix composites. Combining these data with the closed form solution of Chen and Chuang gave excellent correspondence between the creep exponents determined from flexure tests with those determined independently from tensile and compressive creep tests.
International Review of Psychiatry, 2008
Little is known in our own as well as in other cultures about the knowledge and prejudices mental... more Little is known in our own as well as in other cultures about the knowledge and prejudices mental health professionals have about mental illness and those affected. We therefore: 1) assessed mental health literacy and general attitudes towards people with mental illness in a sample of Brazilian mental health professionals; 2) compared the outcomes among the different professional groups; and 3) compared the data with a sample of Swiss mental health professionals. A questionnaire used to assess knowledge and attitudes towards the mentally ill among mental health professionals in Switzerland was translated into Portuguese. Mental health professionals were presented a case vignette describing a person suffering from a major depression as well as related treatment proposals. Furthermore, general attitudes towards people with mental illness were assessed. Both samples had equal scores for social acceptance. Brazilian mental health professionals displayed a more positive attitude towards community psychiatry whereas the Swiss sample showed more stigmatization and social distance, and a more positive attitude towards psychopharmacology. Recognition of the case vignette was significantly better in Brazil than in Switzerland (94.7% versus 71%). Mental health professionals in Brazil were more conservative/medically orientated in their treatment propositions whereas professionals from Switzerland also proposed social interventions and alternative treatment strategies. There are some major differences in attitudes towards people with mental illness between mental health professionals in Switzerland and Brazil. With respect to therapeutic interventions, the different healthcare systems as well as the cultural differences seem to have an impact.
Journal of Materials Engineering and Performance, 2006
In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densi... more In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densified via gas pressure sintering and hot pressing, respectively, were evaluated using the single-edge V-notched beam (SEVNB) fracture toughness technique. The mean value ofK IC for each material was 5.7 and 7.9 MPa·m1/2, respectively, and the toughness was influenced by the presence of the elongated Si3N4 grains in the microstructure. The notch radius was observed to have the same effect as a sharp crack when notch-root radius was smaller than 10 µm, which was considered to be a realK IC for these materials.
Materials Research-ibero-american Journal of Materials, 2006
This present work evaluates the influence of microstructure on the fracture toughness of two type... more This present work evaluates the influence of microstructure on the fracture toughness of two types of silicon nitride. The two microstructural types of silicon nitride were processed using the gas pressure sintering (GPS) and hot pressing (HP) pathways. The fracture toughness was measured using the Single Edge V-Notch Beam (SEVNB) and Chevron Notch Beam (CNB) methods. The results from both methods for the two forms were in close agreement (with a maximum variation of 5.8%); the KIc of the material processed by HP was 35% higher than that of GPS and the grain length had a direct influence on the fracture toughness.
Journal of Materials Engineering and Performance, 2006
In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densi... more In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densified via gas pressure sintering and hot pressing, respectively, were evaluated using the single-edge V-notched beam (SEVNB) fracture toughness technique. The mean value of K IC for each material was 5.7 and 7.9 MPa·m1/2, respectively, and the toughness was influenced by the presence of the elongated Si3N4 grains in the microstructure. The notch radius was observed to have the same effect as a sharp crack when notch-root radius was smaller than 10 µm, which was considered to be a real K IC for these materials.
Powder Technology, 2006
Silicon carbide powder (SiC) was comminuted in a planetary mill during time intervals of 0.5, 2, ... more Silicon carbide powder (SiC) was comminuted in a planetary mill during time intervals of 0.5, 2, 4 and 6 h. The wet milling media was ZrO 2 spheres in isopropyl alcohol. The powders were then characterized with respect to chemical composition, particle size distribution, surface area and density for each milling time. The average particle size was reduced from 1.8 μm to 0.4 μm in 30 min and the amount of ZrO 2 increased linearly with milling time. The result was a homogeneous combination of submicrometer and nanometric SiC + ZrO 2 powder, which possessed good sinterability in liquid phase and high fracture toughness.