ABSTRACT Currently, the presence of spurious microwave radiation is increasing in the environment, which has caused concern due to possible health problems in living beings and electromagnetic interference in electronic systems. To control this problem, studies in the materials area are taking place, aiming to attenuate the spurious radiation and meet requirements of good performance in broadband, low cost and low weight. The present work aimed to study Cu and Ni nanometric films with thicknesses of 65 and 200 nm, deposited on polyethylene terephthalate substrate by magnetron sputtering. Scanning electron microscopy with a field emission gun (FEG-SEM) showed that the films produced have different morphological textures, due to the parameters used in the sputtering process and also the free energy of metals. Impedance spectroscopy measurements showed that the films have low conductivity values, due to the metallic oxides formed on the film surfaces, confirmed by X-ray diffraction, and also to the presence of defects. Electromagnetic characterization (8.2 – 12.4 GHz) showed that the Cu and Ni thin films had low performance, except the Ni_200 nm film, which showed a total shielding efficiency of about 30% in broadband. This result is promising considering the nanometric thickness of the Ni film. Currently environment systems problem place broadband weight 6 20 FEGSEM FEG SEM (FEG-SEM textures metals values surfaces Xray X ray diffraction defects 8.2 82 8 2 (8. 124 12 4 12. GHz Ni200 Ni_20 30 8. (8 1 Ni20 Ni_2 3 ( Ni2 Ni_

Abstract Treatment of landfill leachate is an important environmental issue, especially in developing countries such as Brazil. Advanced oxidation processes (AOPs) have been considered interesting treatment alternatives. In this study, ZnO-TiO2 mixtures were incorporated into a paint polymer matrix and fixed onto supports. Paints were applied by overlapping coat layers on plates, resulting in high film thickness (600 ± 80 µm). Treatment of mature leachate by an AOP was conducted in a plug flow reactor connected to a stirred tank under solar irradiation. The objective was to evaluate the degradation of humic acid (HA) and fulvic acid + humins (FAH). The highest HA and FAH removal efficiencies were 62% ± 4.9% and 16% ± 4.2%, respectively. The kinetic model provided a coefficient of determination (R 2) of 0.974. Rate constants for HA and FAH removal were 2.96 and 1.03 × 10−3 min−1, respectively. Statistical models for HA and FAH degradation had R 2 values of 0.96 and 0.99, respectively. Both approaches indicated that HA degradation is greater at acidic pH and higher TiO2 concentrations. FAH degradation was favored by acidic pH and higher ZnO concentrations. Statistical models showed the same mean difference in conversion between replicate runs of HA and FAH, suggesting a uniform diffusion of fractions through catalysts. issue Brazil AOPs (AOPs alternatives study ZnOTiO2 ZnOTiO TiO ZnO-TiO supports plates 600 (60 8 µm. µm . µm) irradiation (HA FAH. (FAH) 62 49 4 9 4.9 16 42 4.2% respectively 0974 0 974 0.974 296 96 2.9 103 1 03 1.0 10 3 10− min1 min min−1 096 0.9 099 99 0.99 concentrations catalysts 60 (6 (FAH 6 4. 4.2 097 97 0.97 29 2. 1. min− 09 0. (

Resumo O tratamento de chorume de aterro é uma questão ambiental importante, especialmente em países em desenvolvimento como o Brasil. Os processos oxidativos avançados (POA) têm sido considerados interessantes alternativas de tratamento. Neste estudo, misturas de ZnO-TiO2 foram incorporadas a uma matriz polimérica de tinta e fixadas em suportes. As tintas foram aplicadas pela sobreposição de camadas de revestimento em placas, resultando em alta espessura de filme (600 ± 80 µm). O tratamento do lixiviado maduro por um POA foi conduzido em um reator de fluxo contínuo conectado a um tanque de agitação sob irradiação solar. O objetivo foi avaliar a degradação de ácido húmico (HA) e ácido fúlvico + huminas (FAH). As maiores eficiências de remoção de HA e FAH foram 62% ± 4,9% e 16% ± 4,2%, respectivamente. O modelo cinético forneceu um R2 de 0,974. As constantes de velocidade para remoção de HA e FAH foram 2,96 e 1,03 × 10−3 min−1, respectivamente. Os modelos estatísticos para degradação de HA e FAH tiveram valores de R2 de 0,96 e 0,99, respectivamente. Ambas as abordagens indicaram que a degradação do HA é maior em pH ácido e concentrações mais altas de TiO2. A degradação de FAH foi favorecida por pH ácido e maiores concentrações de ZnO. Os modelos estatísticos mostraram a mesma diferença significativa na conversão entre as execuções repetidas, sugerindo uma difusão uniforme das frações através dos catalisadores. importante Brasil (POA estudo ZnOTiO2 ZnOTiO ZnO TiO2 TiO ZnO-TiO suportes placas 600 (60 8 µm. µm . µm) solar (HA FAH. (FAH) 62 49 4 9 4,9 16 42 2 4,2% respectivamente R 0974 0 974 0,974 296 96 2,9 103 1 03 1,0 10 3 10− min1 min min−1 096 0,9 099 99 0,99 repetidas catalisadores 60 (6 (FAH 6 4, 4,2 097 97 0,97 29 2, 1, min− 09 0, (

Abstract: This paper has described the radar absorbing materials characterization and radar cross section measurements, in the frequencyrange of 8 to 12 GHz, using a very simple setup. Simple targets like sphere, cylinder, flatplate, and dihedral comer were characterized by measuring the backscattered radiation patterns when these targets were illuminated by monostatic microwave radiation. Measurements were carried out inside an anechoic chamber (9x5x4m3). Typical radar cross section patterns were obtained in different aspect angles, by rotating the targets around their vertical axes. The measured values and the theoretical previsions for each metallic target showed that the used setup guarantees a good precision of the obtained data. By recovering one of the targets, a cylinder, with a specific radar absorbing material developed at Materials Division of the Brazilian Aeronautics and Space lnstitute, it was possible to compare the obtained patterns and to discuss the influence of radar absorbing materiais on the observed radar cross section reduction patterns. The used methodology showed to be useful for attending aeronautical and telecommunication applications.

The use of polyamic acid (PAA) precursor as interphase in polymer composites is one of the many applications of polyimides (PIs). In this work, composites based on poly(ether-ether-ketone) (PEEK) and carbon fibers were prepared using two manufacturing techniques for thermoplastic composites: hot compression molding, and aqueous polymeric suspension prepregging using PIs as interphase. Two PAAs were synthesized and used as interphases: 3,3'-4,4'-benzophenonetetracarboxylic dianhydride/oxydianiline (BTDA/ODA) and pyromellitic dianhydride/oxydianiline (PMDA/ODA). The PAA/PI systems were analyzed by differential scanning calorimetry (DSC), thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Results from these analyses confirmed the synthesis of these compounds. Aqueous polymeric suspension prepregging was more efficient than hot compression molding when the PMDA/ODA PAA/PI interphase was used; also, the interlaminar shear strength of composites produced using this technique was 14.5% higher than the one produced using hot compression molding.

Resumo: Materiais Absorvedores de Radiação Eletromagnética (MARE) são compostos que absorvem a radiação eletromagnética incidente em determinadas faixas de frequências e a dissipam sob a forma de calor. Esses materiais são obtidos a partir do processamento adequado de matrizes poliméricas incorporadas com compostos que atuam como centros absorvedores da radiação incidente, na faixa de micro-ondas. Este trabalho mostra a avaliação eletromagnética de MARE processados pelo uso de uma hexaferrita de cálcio modificada pela incorporação dos íons CoTi e La. A substituição realizada pelos íons mencionados mostra, via análises de MAV, que a ferrita apresenta baixos valores de magnetização de saturação (123,65 Am2/kg) e de campo coercitivo (0,07 T), indicando o seu amolecimento. Amostras de MARE preparadas com diferentes concentrações desta hexaferrita (40 - 80% em massa) apresentam mudanças nos parâmetros complexos de permeabilidade e permissividade e no desempenho da atenuação da radiação incidente. Valores de atenuação da radiação incidente entre 40 e 98% são obtidos.

Abstract: Radar Absorbing Materials (RAM) are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg) and coercive field (0.07 T) indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w) show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.

Sized PAN-based carbon fibers were treated with hydrochloric and nitric acids, as well as argon and oxygen cold plasmas, and the changes on their surfaces evaluated. The physicochemical properties and morphological changes were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), tensile strength tests and Raman spectroscopy. The nitric acid treatment was found to cause the most significant chemical changes on the carbon fiber surface, introducing the largest number of chemical groups and augmenting the roughness. The oxygen plasma treatments caused ablation of the carbon fiber surface, removing carbon atoms such as CO and CO2 molecules. In addition, the argon plasma treatment eliminated defects on the fiber surface, reducing the size of critical flaws and thus increasing the fiber's tensile strength.