Margarete Regina Freitas Gonçalves

Estimativa da deterioração da madeira de assoalho de prédio histórico por meio de ondas ultrassônicas

This study aimed to detect the external degree of decay of Araucaria angustifolia (Bert.) O. Kuntze wood used in flooring. The visual method through grades and the non-destructive method based on the propagation of ultrasound waves were applied. The comparison between the propagation velocity of ultrasonic waves on clear wood and decayed wood showed statistical difference at the 5% level. Moreover, the proportion of decay wood was inversely proportional to the velocity of propagation. The samples were evaluated only on their superficial faces, therefore additional studies to assess the influence of the wood internal defects in the ultrasonic velocity are necessary.

Evaluation of the influence of manufacture parameters during organoclay synthesis

Clays are raw materials composed mainly of minerals with diameter lower than 2 μm [1], composed of hydrous aluminum or magnesium silicate with other elements, such as lithium, iron and potassium, showing a lamellar structure composed of tetrahedral or octahedral sheets with thickness lower than 1 nm and average diameter of hundreds of nanometers [2]. Besides that, they are hydrophilic and responsible for the plasticity properties [1]. The isomorphic substitution, chemical bond breaking at the edge and replacement of hydrogen (H+) to hydroxyls (OH-) in clays generate a charge instability on its crystalline structure that induces the adsorption of ions in order to stabilize the structure. The quantification of the amount of ions exchanged in a clay is ruled by the cation exchange capacity (CEC) expressed in mEq per 100 g of clay. CEC allows a chemical modification of the clay [1], that may occur via a reaction of cations presents in an aqueous solution without the modification of the clays’ crystalline structure [1, 3]. A process named organophilization is one of the methods used to modify the clays’ structure. This procedure consists in the insertion of organic molecules in the clays’ structure, transforming the hydrophilic structure into a hydrophobic structure through the expansion of structural planes (d001) [1, 4-6]. In this process, the clay suffers an expansion of the mineral layers in water, followed by the addition of a surfactant. The expansion facilitates the intercalation of organic molecules between the layers. It is important to note that the final properties of the organoclay are dependent of the concentration and composition of the surfactant, as well as the stirring and rest time used in the synthesis [5, 7, 8]. Evaluation of the influence of manufacture parameters during organoclay synthesis

Análise comparativa entre radiação micro-ondas e aquecimento resistivo para sinterização do aço inox 316L reforçado com B4C

O aco inoxidavel 316L e utilizado em diversas areas da engenharia devido suas caracteristicas de alta resistencia a corrosao e bom acabamento superficial. Porem, sua aplicacao e limitada em funcao de sua baixa resistencia ao desgaste decorrente de sua baixa dureza. Uma forma de aumentar sua dureza e pela inclusao de particulas de um material mais duro em sua matriz. Este trabalho avalia a sinterizacao do aco inoxidavel 316L reforcando sua matriz pela inclusao de particulas de carbeto de boro -B 4 C. Foi realizada uma analise comparativa entre o forno micro-ondas e o forno resistivo do tipo tubular durante a sinterizacao deste material, quanto seu consumo de energia a fim de verificar qual processo e mais efetivo energeticamente. Para avaliacao da qualidade do sinterizado, foi realizada uma caracterizacao microestrutural a partir de microscopia optica e eletronica de varredura, bem como por difracao de raios-X e ensaio de microdureza Vickers. Concluiu-se que o consumo de energia com uso de forno tipo micro-ondas foi menor que o resistivo e tambem apresentou uma sinterizacao mais homogenea e uma dureza maior.

Nano and Micro Ceramic Membranes from Degradable Templates

The nano/microstructures with highly porous surface area have attracted tremendous attention, particularly the synthesis and tailoring of porous and hollow materials of high performance. In this paper, an easy method of cost-effective synthesis of hollow ceramic fiber membranes based on Hydroxyapatite, TiO2 and ZrO2 stabilized with Yttrium, is proposed by a single chemical route (polymeric precursor method) and a bio-template route (easy to degrade in thermal conditions). This article reports also the ZrTiO4 nanowires synthesis on a silicon (100) wafer in a single step deposition/thermal treatment. Template-directed membrane synthesis strategy was associated to the polymeric precursor route and spin-coating deposition technique. In this method, ZrTiO4 nanowire ceramic were synthesized by spin-coating thermal treatment technique using polycarbonate membrane as a template. According to the results, after heat-treatment by the template removal, the ZrTiO4 nanowire consists of uniformly deposited crystalline and porous nanoparticles that exhibited a higher surface area and a higher porosity. The polycrystalline nanowires were obtained at by thermal treatment with diameter in the range of 60-100 nm. Photoluminescence spectra were collected for fiber at room temperature. These characterizations demonstrate the morphology of structures formed, showing its hollow and porous conformation, suitable applications to advanced reinforced or device component material.

Wood under fresh water: Effect on the chemical properties and on decay resistance

This study aimed to evaluate the effect of waterlogging on the chemical properties and on decay resistance of two fast-growing eucalypt species. Samples of spotted gum and rose gum wood were placed underwater and taken out at different times: after 4, 8 and 12 months. Chemical properties were performed via wet chemical quantification (Tappi standards), monomeric sugars by HPLC, and qualitative evaluation of extractives by Py-GC/MS and ATR-IR spectroscopy; biological performance was investigated using Trametes versicolor and Gloeophyllum trabeum rot fungi. The results showed slight changes to the chemical properties of both wood species, with an increase in lignin represented by the reduction of sugars due to waterlogging. Both species showed higher susceptibility to Gloeophyllum trabeum mainly in the sapwood, with no influence on decay resistance due the waterlogging.