Atualmente os efeitos estudados pelos campos da Nanociência e da Nanotecnologia (N&N) influenciam o cotidiano do ser humano. No entanto, há ainda dificuldade por parte dos sistemas escolares em abordar esta temática, principalmente no nível de Educação Básica. Neste artigo, tecem-se considerações sobre uma metodologia de ensino de N&N baseada na aplicação de um minicurso a alunos do Ensino Médio, conjuntamente com uma variação do método de Aprendizagem Cooperativa Jigsaw, na qual se utilizou um texto de divulgação científica como eixo da atividade. Obteve-se que a junção das referidas atividades possibilitou que os alunos relacionassem e compreendessem os diferentes conceitos atrelados a N&N, formando e ampliando sua base conceitual de maneira cooperativa entre os sujeitos envolvidos no proceso.

In our days, the effects which are studied in the fields of Nanoscience and Nanotechnology (N&N) have influence on the daily lives of human beings. However, school systems still have difficulties addressing these subjects, especially at the level of basic education. In this article, a teaching methodology of N & N is discussed; it is based on the application of a short course to high school students, along with a variation of the method of Cooperative Learning Jigsaw, in which we use a scientific text as a focus for the activity. It was found that the combination of these activities enabled students to understand and correlate the different concepts related to N&N, as well as form and expand their conceptual bases in a cooperative way.

The present study reports the results of thick films (20-130 µm) produced through electrophoretic deposition of BaTi0.85Zr0.15O3 (BTZ) nanometric powders synthesized by the Pechini's method. The BTZ powderscalcined at 600°C/2h presented a single crystalline phase with an average particle size of ~20nm. To thick films deposition, a stable suspension of acetylacetone (Acac) and ethanol (EtOH)was prepared and the powder was deposited on platinum substrates. The viscosity of BTZ powders suspensions as a function of operational pH (OpH)was measured and the reactions between nanoparticles and the media were discussed. A milling process was used to deagglomerate the powders and it had a great influence in the suspension stability and deposition of thick films. Dense and crack-free thick films were obtained after sintering at 1220 °C/1h. The dielectric properties results, comparable with those of bulk BTZ ceramics, suggested potential applications of the EPD process for the deposition of ferroelectric/piezoelectric thick films.

Ba0.77Ca0.23TiO3 ceramics were produced in this work starting from nanopowders synthesized via a polymeric precursor method. By adjusting the pH values of the precursor solutions above 7, it was possible to prepare powders weakly aggregated and with a smaller particle size, both facts which traduced into an enhanced nanopowders' sintering process at comparatively lower temperatures. Irrespective of the initial pH value, highly-dense and second phase-free ceramics were obtained following optimal sintering parameters (temperature and time) extracted from dilatometric and density measurements. By considering these and other sintering conditions, moreover, polycrystalline materials with an average grain size varying from 0.35 to 8 mm were produced, the grain growth process involving liquid phase-assisted sintering for heat treatments achieved at 1320 °C. The study of grain size effects on the ferroelectric properties of these materials was conducted, the results being discussed in the light of previous debates, including grain size-dependent degree of tetragonal distortion in such materials, as verified in this work.

Development of the positive temperature coefficient of resistivity (PTCR) in Er3+ and Ca2+ co-doped ferroelectric BaTiO3 was studied in this work, with Er3+ being used to act as a donor doping. Irrespective of all the materials showing high densities after sintering at 1200 to 1300 ºC, these revealed insulator at the lowest sintering temperature, changing to semiconducting and PTCR-type materials only when the sintering temperature was further increased. Observations from X-ray diffraction help correlating this effect with phase development in this formulated (Ba,Ca,Er)TiO3 system, considering the formation of initially two separated major (Ba,Ca)TiO3- and minor (Ca,Er)TiO3-based compounds, as a consequence of cation size-induced stress energy effects. Thus, appearance and enhancement here of the semiconducting and PTCR responses towards higher sintering temperatures particularly involve the incorporation of Er3+ into the major phase, rendering finally possible the generation and "percolative-like" migration of electrons throughout the whole material.

O objetivo do estudo foi avaliar a deposição de óxido de alumínio no campo operatório do cirurgião-dentista durante a utilização do sistema de abrasão a ar em consultório odontológico, bem como a efetividade da sucção de alta potência na captação desse pó. Por meio de um dispositivo para a coleta das partículas nos locais correspondentes às posições e distâncias de trabalho do profissional, dentes artificiais foram abrasionados. O sistema de sucção empregado para aspiração das partículas foi o de alta potência com sugador de saliva convencional e sugador com abertura ampliada por funil. A mensuração das partículas foi determinada pela quantidade em massa de óxido de alumínio depositada em placas de Petri. Os resultados obtidos por meio de estatística descritiva gráfica revelaram que a maior quantidade de pó se encontrava a 20 cm do operador e na posição de trabalho 9h, quando foi utilizado o sugador de saliva convencional. Uma vez comprovado que a sucção não é totalmente eficiente na aspiração do pó de óxido de alumínio, reforça-se a importância da proteção individual apropriada para o emprego seguro do sistema de abrasão a ar para pacientes e, principalmente, para os profissionais que trabalham com este tipo de tecnologia.

This study aimed at evaluating not only the amount of aluminum oxide particles deposited in a dental office while a dentist is using a pressurized air abrasion system, but also how effectively high-power suction is able to remove the dust resulting from that process. Artificial teeth were abraded through a device, which collected the particles laid down on the operation site, exactly at the same distance kept by the dentist from the patient's mouth. A high-powered suction system was employed to absorb the particles with both, a conventional and a funnel-shaped saliva ejector. The amount of particles was determined by the aluminum oxide mass deposited in Petri plates. Results obtained and showed by means of statistic graphics, revealed that the greatest amount of abrasive particles was deposited at a distance of 20 cm from the center of the phantom head, at the 9 o'clock operating position, using a conventional saliva ejector. Once the experiment confirmed that suction does not totally remove the aluminum oxide particles from the premises, it is extremely important that dentists and their patients are protected by the correct PPE during an air-abrasion process.

Bi4Ge3O12 (bismuth germanate - BGO) single crystals were produced by the Czochralski technique and their electrical and dielectric properties were investigated by impedance spectroscopy. The isothermal ac measurements were performed for temperatures from room temperature up to 750 °C, but only the data taken above 500 °C presented a complete semicircle in the complex impedance diagrams. Experimental data were fitted to a parallel RC equivalent circuit, and the electrical conductivity was obtained from the resistivity values. Conductivity values from 5.4 × 10(9) to 4.3 × 10-7 S/cm were found in the temperature range of 500 to 750 °C. This electrical conductivity is thermally activated, following the Arrhenius law with an apparent activation energy of (1.41 ± 0.04) eV. The dielectric properties of BGO single crystal were also studied for the same temperature interval. Permittivity values of 20 ± 2 for frequencies higher than 10³ Hz and a low-frequency dispersion were observed. Both electric and dielectric behavior of BGO are typical of systems in which the conduction mechanism dominates the dielectric response.