35 research outputs found

    Selection of sugarcane families and parents by Reml/Blup.

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    Were evaluated 113 full-sib families obtained by unbalanced diallel matings in three experiments in an augmented block design (ABD) planted side by side in the same area. The individual and joint analyses of the experiments were performed by the Reml/Blup method. The use of the ABD without replication did not prove adequate in experiments of family selection owing to the low heritability estimate at the level of family means in comparison to the joint analysis of the three experiments. The results presented predominance of the additive effects for all evaluated traits: number of stalks, tons of stalks per hectare and mean stalk weight. The components of estimated means via Blup allowed the selection of families and superior parents

    Efeito da adição de polímero precursor cerâmico na sinterização de alumina

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    Foram estudados os efeitos da adição de polímero precursor na sinterização, microestrutura e dureza da alumina. O polímero inorgânico polifenilmetilvinilhidrogenosilsesquioxano (PPS) foi utilizado como aditivo em cerâmicas de alumina sinterizadas a 1650 ºC. Os materiais sinterizados foram caracterizados por dilatometria, determinando-se a densidade aparente por picnometria de hélio, pela análise de carbono total, por difração de raios X, por microscopia eletrônica de varredura, espectrometria de energia dispersiva de raios X e por análise de indentação Vickers para determinação de dureza e tenacidade a fratura. Foram obtidas fases heterogêneas de Si2Al4O4N4 nas amostras com PPS. Dentre as amostras analisadas, a que contém 5% de PPS apresentou dureza e tenacidade à fratura superiores à da alumina pura. A preparação de compósitos cerâmicos com pequenas quantidades de polímero precursor mostrou-se um processo adequado para cerâmicas à base de alumina, sendo uma rota simples de conformação com grande potencial para a obtenção de peças com geometria complexa

    Development of the microstructure of the silicon nitride based ceramics

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    Basic regularities of silicon nitride based materials microstructure formation and development in interrelation with processing conditions, type of sintering additives, and starting powders properties are discussed. Models of abnormal or exaggerated grain growth are critically reassessed. Results of several model experiments conducted in order to determine the most important factors directing the microstructure formation processes in RE-fluxed Si3N4 ceramics are reviewed. Existing data on the mechanisms governing the microstructure development of Si3N4-based ceramics are analyzed and several principles of microstructure tailoring are formulated
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