Ca3Co4O9 powders and ceramics were synthesized and sintered using microwave-assisted heating method.Another batch of powders was calcined by the conventional heating method and this powder was used to produce ceramics sintered by microwave sintering aiming to compare with those prepared by microwave method. The formation of the phases based on calcination method and time was assessed by X-ray diffractometry. The synthesis and sintering methods affected various properties of the ceramics, including grain size, density, phase amount, Seebeck coefficient, thermal conductivity and electrical conductivity. Microwave heating method reduced the time required for the powder synthesis and sintering of ceramics. Ceramics produced using powder obtained by the conventional method presented Figure of Merit (ZT) values of approximately 0.04. However, these values were reduced for the ceramics produced by microwave heating reaching a value of about 0.02. The evaluation of the thermoelectric properties of the Ca3Co4O9 ceramics suggests that the main issue to enhance the Figure of Merit of the CCO ceramics is related to density and Ca3Co4O9 phase amount present in the ceramics.

Surface treatments done in banana fibers (BFs) can generate significant superficial structural changes enabling the production of mechanically stronger composites. In this way, the objective of this study was to evaluate the physicochemical and mechanical properties of banana fibers of Prata specie from inner and outer leaf sheaths, when irradiated with UV light (λmax = 400 nm) during 7 (UV7) and 15 (UV15) days. Structural and microstructural characterizations for non- and irradiated fibers were performed by, FT-IR spectroscopy and Scanning Electron Microscopy (SEM), which showed the influence of UV irradiation on BFs surface and chemical structure. The Ea involved in the thermal degradation process of InNatura fiber (188.2 kJ.mol–1) was obtained using Differential Thermal Analysis (DTA/TG). The results obtained from mechanical characterization showed that the UV7 fibers presented significant improvement in tensile strength (89.77 MPa) and elastic modulus (238.94 MPa) as compared to tensile strength (69.99 MPa) and elastic modulus (87.40 MPa) of InNatura fibers. Statistical analysis using two-way ANOVA has showed that there were no differences between mechanical properties of BFs from inner to outer leaf sheaths. UV radiation has proved to be a clean method for BF surface treatment, which can improve the mechanical properties of composites based on these fibers.

Many researchers have been studying coconut fibers due to its being a natural and renewable source. Moreover, coconut waste is discarded in landfills, bringing environmental problems because this material, although natural, takes time to be degraded. The use of natural fibers such as coconut fibers has become industrially attractive because of its low cost, high availability and desired mechanical properties for some applications, such as panels, ceilings, and partition boards and automotive components. In this study, polymers with coconut fiber composites were made by injection processing and mechanically characterized by tensile and dynamic testing. The fiber content ranged from 0 to 30wt%. The results of Young's modulus obtained from both methods decreased with fiber load and were nearly identical up to 15wt% of fiber, about 1.1GPa, but the increase in fiber concentrations distinctly interferes with each method in the values obtained.

Although the hydrophobicity is usually an arduous parameter to be determined in the field, it has been pointed out as a good option to monitor aging of polymeric outdoor insulators. Concerning this purpose, digital image processing of photos taken from wet insulators has been the main technique nowadays. However, important challenges on this technique still remain to be overcome, such as; images from non-controlled illumination conditions can interfere on analyses and no existence of standard surfaces with different levels of hydrophobicity. In this paper, the photo image samples were digitally filtered to reduce the illumination influence, and hydrophobic surface samples were prepared from wetting silicon surfaces with solution of water-alcohol. Furthermore norevious studies triying to quantify and relate these properties in a mathematical function were found, that could be used in the field by the electrical companies. Based on such considerations, high quality images of countless hydrophobic surfaces were obtained and three different image processing methodologies, the fractal dimension and two Haralick textures descriptors, entropy and homogeneity, associated with several digital filters, were compared. The entropy parameter Haralick's descriptors filtered with the White Top-Hat filter presented the best result to classify the hydrophobicity.

Polypropylene matrix composites reinforced with treated coconut fibers were produced. Fibers chemically treated (alkalization-CCUV samples) or mechanically treated (ultrasonic shockwave-CMUV samples) were dried using UV radiation. The goal was to combine low cost and eco-friendly treatments to improve fiber-matrix adhesion. Composite samples containing up to 20 vol. (%) of untreated and treated coconut fibers were taken from boxes fabricated by injection molding. Water absorption and mechanical properties were investigated according to ASTM D570-98 and ASTM D638-03, respectively. Electrical characterizations were carried out to identify applications of these composites in the electrical sector. NBR 10296-Electrical Tracking Standard (specific to industry applications) and conductivity measurements were obtained applying 5 kV DC to the samples. CMUV samples containing 5 vol. (%) fiber presented superior tensile strength values (σ~28 MPa) compared to the untreated fibers composite (σ~22 MPa) or alkali treatment (σ~24 MPa). However, CMUV composites containing 10 vol. (%) fiber presented best results for the electrical tracking test and electrical resistivity (3 × 10(7) Ω.m). The results suggest that composites reinforced with mechanically treated coconut fibers are suitable for electrical applications.

This study proposes a new method to obtain hydrophobicity classification (HC) in high voltage polymer insulators. In the method mentioned, the HC was analyzed by fractal dimension (fd) and its processing time was evaluated having as a goal the application in mobile devices. Texture images were created from spraying solutions produced of mixtures of isopropyl alcohol and distilled water in proportions, which ranged from 0 to 100% volume of alcohol (%AIA). Based on these solutions, the contact angles of the drops were measured and the textures were used as patterns for fractal dimension calculations.