No abstract

In the present work, electroactive grain boundaries of highly dense metal oxide SnO2-based polycrystalline varistors were determined by electrostatic force microscopy (EFM). The EFM technique was applied to identify electroactive grain boundaries and thus estimate the amount of active grain boundary, which, in the metal oxide SnO2-based varistor, was calculated at around 85%, i.e., much higher than that found in traditional metal oxide ZnO-based varistors. The mean potential barrier height value obtained from the EFM analysis was in complete agreement with the values calculated from the C-V measurements, together with a complex capacitance plane analysis that validates the methodology proposed here.

No abstract

A new method for high-resolution analyses of hair surface charge density under ambient conditions is presented in this paper. Electrostatic force microscopy (EFM) is used here to analyze changes in surface charge density in virgin hair, bleached hair, and hair treated with a cationic polymer. The atomic force microscopy technique is used concomitantly to analyze morphological changes in hair roughness and thickness. The EFM images depict exactly how the polymer is distributed on the surface of the hair fiber. The EFM's powerful analytical tools enabled us to evaluate the varying degrees of interaction between the hair fiber surface charge density and the cationic polymer. The surface charge density and the polymer's distribution in the hair fibers are presented in the light of EFM measurements.

O uso de microondas no processamento e obtenção de materiais tem adquirido nos últimos anos crescente interesse por parte de diversas áreas do conhecimento como a química e a engenharia de materiais. Neste sentido, aparatos especialmente projetados têm começado a ser descritos na literatura como reatores e câmaras de processamento a microondas visando aplicação na pesquisa e na indústria. Em particular o uso de fornos de microondas domésticos em atividades científicas tem se mostrado de interesse dado uma série de novas aplicações, simplicidade e baixo custo. O presente trabalho reporta um dispositivo desenvolvido a partir de um forno de microondas doméstico, capaz de efetuar sínteses e processamentos de sólidos mesmo quando os materiais envolvidos não possuem susceptibilidade as microondas. O novo dispositivo tem sido utilizado com sucesso na síntese de óxidos metálicos e, em especial na sinterização e ordenamento de redes cristalinas de filmes finos.

No abstract

No abstract

Ferroelectric SrBi 2 Nb 2 O 9 (SBN) thin films were prepared by the polymeric precursors method and deposited by spin coating onto Pt/Ti/SiO 2 /Si substrate and crystallized using a domestic microwave oven. It was studied the influence of the heat flux direction and the duration of the thermal treatment on the films crystallization. An element with high dielectric loss, a SiC susceptor, was used to absorb the microwave energy and transfers the heat to the film. Influence of the susceptor position to the sample crystallization was verified, the susceptor was placed or below the substrate or above the film. The SBN perovskite phase was observed after a thermal treatment at 700 8C for 10 min when the susceptor was placed below the substrate and for 30 min when the susceptor was placed above the film. Electrical measurements revealed that the film crystallized at 700 8C for 10 min, with the susceptor placed below the film, presented dielectric constant, dielectric loss, remanent polarization and coercive field of, 67, 0.011, 4.2 mC/cm 2 and 27.5 kV/cm, respectively. When the films were crystallized at 700 8C for 30 min, with the susceptor placed above the film, the dielectric constant was 115 and the dissipation factor was around of 0.033, remanent polarization and coercive field were 10.8 mC/cm 2 and 170 kV/cm, respectively.