Neste trabalho, relatamos o emprego de gibbsita e de uma peneira molecular comercial para a retenção de íons cromo. Os estudos envolveram, além destes materiais, soluções com diferentes concentrações do íon e variações na concentração e na temperatura das soluções e, também, do tempo de contato entre essas e as fases estacionárias. Os resultados desses experimentos e dos posteriores processos de lixiviação do íon indicam que tanto a gibbsita quanto a peneira molecular são materiais que apresentam alta capacidade de retenção deste íon e, além disso, são altamente resistentes aos processos de lixiviação.

Herein we report the employment of the gibbsite and a commercial sieves on the retention of the chromium ions on different concentrations, temperatures and lay times. The results of those experiments plus those of the lixiviation processes show that both stationary phases present a high ratio of retention and resistance against leaching.

Nd16Co72-xRu xC11B boro-carbides have been prepared by arc melting and studied by X-ray diffraction and magnetization measurements. X-ray diffraction results confirm that all the prepared alloys possess the tetragonal 2:14:1 (P4(2)/mmm) hard magnetic phase. The observed decrease of the magnetization and Curie temperature indicate the development of antiferromagnetic spin correlations with the increase of the Ru content. The combined addition of B and C is favorable to the formation and stabilization of the tetragonal phase in these compounds. At lower Ru contents the Curie temperature is higher than in the corresponding Co-based boride in spite of larger cell volumes.

Uma das cargas mais utilizadas na fabricação de espumas flexíveis de poliuretano é o carbonato de cálcio (CaCO3) por ser não abrasivo, não tóxico e de fácil pigmentação. Contudo, é observado que o excesso de CaCO3 comercial usado nas indústrias causa deformações permanentes, o que prejudica a qualidade do produto final. No presente trabalho é proposto o estudo do efeito da concentração de CaCO3 comercial na fabricação de espumas flexíveis de poliuretano. Foram utilizadas diferentes concentrações de CaCO3 na síntese das espumas, as quais foram submetidas à análises térmica e morfológica, afim de verificar as alterações provocadas pela introdução progressiva da carga.

One filler often utilized in flexible polyurethane foams is calcium carbonate (CaCO3) because it is non-abrasiveness, non-toxicity and facilitated pigmentation. However, it is observed that the excess of commercial CaCO3 utilized in industry possibly causing permanent deformations and damaging the quality of the final product. The effect of different concentrations of commercial CaCO3, in flexible foams, was studied. Different concentrations of CaCO3 were used for the synthesis of flexible polyurethane foams, which were submitted to morphological and thermal analyses to verify the alterations provoked by the progressive introduction of this filler.

The Nd16Co76-xRu xC7B system has been investigated to assess the effect of boron-carbon combined addition on the ferromagnetic behavior of these intermetallic compounds. The results indicate that the addition of 1 at.% B favors the formation of the tetragonal magnetic phase 2:14:1 in these alloys. With the increase of the Ru concentration is observed an expansion of the lattice in the basal plane as well as a contraction along the c direction of the tetragonal unit cell. The Curie temperature decreases from 432 K at x = 6 to 421 K for x = 27, whereas the saturation magnetization has a steep decrease. The highest T C value has been verified for the alloy with the largest c parameter, despite its a parameter is the smallest one. In comparison to isotypic borides and pure carbides, a loss of coercivity and remanence is observed.

A mathematical model of a process for drying of Eucalyptus spp is presented. This model was based on fundamental heat and mass transfer equations and it was numerically solved using a segregated finite volume method. Software in the FORTRAN language was developed to solve the mathematical model. The kinetic parameters of drying for Eucalyptus spp were experimentally obtained by isothermal thermogravimetry (TG). The theoretical results generated using the mathematical model were validated by experimental data.