The objective of this work was to evaluate the mechanical properties of porous alumina ceramics, using the rice husk as a porogenic element. The rice husk was milled and graded in two granulometry, <65 μm and 65-150 μm, and added in a high purity calcined alumina in the proportion of 5, 15 and 30 wt%. The samples were pressed by uniaxial pressing and sintered at 1450 ºC for 1 h. Sintered density, total porosity, Young's modulus, modulus of rupture, and compressive strength were evaluated. Samples were also prepared without the addition of rice husk (RH) in order to compare the properties. Porous ceramics with total porosity ranging from 24% to 54% were produced, and with the composition of 5% RH 65-150 μm, a high porosity value was obtained for a lower loss in mechanical properties.
Em geral, o ensino de óptica no nível médio está concentrado na óptica geométrica. Apesar de ser um modelo de sucesso para explicar fenômenos como reflexão e refração da luz, ele não aborda satisfatoriamente a discussão sobre a natureza ondulatória da luz, além de não explicar fenômenos como difração e interferência. Neste trabalho propomos um experimento simples e de baixo custo para discutir a natureza ondulatória da luz e o limite em que a óptica geométrica é válida. A proposta constitui também um dispositivo para realização de medidas de objetos cuja dimensão seja da ordem do comprimento de onda da luz.
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