Saúde & Segurança Ocupacional: reflexões sobre os riscos potenciais e o manuseio seguro dos nanomateriais

Every day the nanotechnology, that refers to a field whose theme is the control of matter on an atomic and molecular scale working with nanometric structures (<100 nm), is more present in the development of products and industrial processes. The particle manipulation of nanometric structures has created opportunities in the development of new products and materials. However, synthesis, handling, storage, stabilization and the incorporation of these materials, with nanometric dimensions, demand a new perspective of analysis and evaluation of old manufacturing processes, procedures and industrial devices, in order to guarantee collective and individual protection to workers and society. With the increasing of scale and production of nanoestrutuctured materials, a big part of labour community starts to be in contact with different nanomaterials (forms and ways). In this work the main aspects and involved risks of manufacture, storage, synthesis, stabilization and incorporation of nanomaterials on new products are evaluated in order to reduce, decrease and eliminate chemical, physical and biological risks for the employees. A bibliographic review was conducted about risk, safety and nanotechnology based on available English literature focusing safety and environmental agencies from different countries such as USA, Canada, EU (France, UK, Germany, Denmark), Australia and Japan.A cada dia a nanotecnologia, que pode ser definida como um campo multidisciplinar da ciência e da tecnologia que trabalha com estruturas de dimensões nanométricas, tipicamente <100 nanômetros (nm), está mais presente no desenvolvimento de novos produtos e processos industriais. A manipulação de partículas nanométricas tem aberto inúmeras oportunidades de desenvolvimento de novos produtos e materiais. Porém, a síntese, manuseio, estocagem, estabilização e a incorporação de materiais com dimensões nanométricas exigem uma nova análise e avaliação dos processos, procedimentos e dispositivos industriais de forma a garantir proteção coletiva e individual ao trabalhador e à sociedade, uma vez que, com o aumento de escala e de volume de produção dos materiais nanoestruturados, uma parcela cada vez maior da cadeia laboral passa a estar exposta aos nanomateriais em suas diversas formas e meios. Neste trabalho é apresentada uma revisão acerca de tópicos relacionados com o desenvolvimento da nanotecnologia abordando questões de riscos e de segurança ocupacional, em especial, os principais aspectos envolvidos quando do manuseio, estocagem, síntese, estabilização e incorporação de nanomateriais, visando à redução, minimização e eliminação dos riscos envolvidos nessas atividades, com o objetivo de garantir de forma plena a integridade física e a saúde do trabalhador

An analysis of Brazilian sugarcane bagasse ash behavior under thermal gasification.

Background: Ashes from sugarcane were analyzed by X-ray fluorescence, ash content, X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). FactSage 6.4 database software was used to estimate viscosity at high temperatures (900 - 1550°C) of them. Results: The results showed that although ashes from sugarcane bagasse contain silica, most of its SiO2 is from soil contamination. Higher and lower silica samples treated at 1350°C for 20 minutes showed that the fine portion of fraction of the ashes melted at this temperature. Conclusions: The melting phase could act as sticking flux for the coarse silica particles on the gasifier bottom wall, which could compromise the gasification process

Investigation of sustainable porous carbon as radar absorbing material

Radar Absorbing Materials (RAMs) are composite materials able to attenuate an incident electromagnetic wave. Usually, RAMs are made of a polymeric matrix and an electromagnetic absorbent filler, such as silicon carbide or carbon black. Several materials have been investigated as potential fillers, aiming to improve the Reflection Loss (RL) and absorption bandwidth broadening. In this paper, a composite made with silicone rubber and biochar was investigated as a sustainable porous carbon made with biomass waste. Five different composites were characterized, composed of 1 - 5 wt.% of biochar in the silicone rubber. Although the RL of pure biochar composites is not significant, it was demonstrated here how a biochar composite can improve the RL of a RAM material when it is applied as a double-layer structure. While the RL of a ferrite-based RAM with 2.0 mm thickness reaches -28 dB, a combination of this RAM with biochar composite reaches ~ -60 dB with the same thickness. The double-layer structure with 2.3 mm thickness can have an absorption bandwidth of 2.95 GHz over the X-band frequency range, and a structure with 2.6 mm thickness can reach a RL of ~-76 dB. This demonstrates a sustainable, cheaper, and lighter material application (i.e., biochar), which is successfully used in the development of high-efficient electromagnetic shield or sensors.Keywords: Biochar, permittivity, RAM, sustainability, reflectivity.

Caracterização de concretos refratários utilizados em unidades de craqueamento catalítico fluido (FCC)

Sendo um dos setores mais rentáveis em uma refinaria, a unidade de craqueamento catalítico fluido (FCC) basicamente converte produtos de baixo valor comercial em produtos de maior valor agregado, como a gasolina

Preparation of zirconium, titanium, and magnesium diborides by metallothermic reduction

Ceramic compositions based on carbides, nitrides, and borides are widely used as a result of their exceptional resistance to wear, creep at high temperature, thermal shock, and oxidation. In order to provide these properties, it is necessary to prepare a starting powder material structure characterized by uniformity and high specific surface. Zirconium, titanium, and magnesium diborides are prepared in this work by metallothermic reduction. The materials obtained are analyzed by x-ray diffraction (XRD), laser granulometry, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Thermodynamic calculations are carried out using FactSage® thermochemical software and databases. It is observed that a significant part of the specimens obtained in this work have a high MgO content in their structure. Apotential field of application of these materials could be as antioxidants in periclase-carbon refractories since this industrial application does not require magnesium oxide removal. It is clearly established that magnesium, zirconium, and titanium diborides exhibit good stability in reducing atmospheresFAPES

Synthesis and characterization of sol-gel derived ZrB2-ZrC compounds

In this work ZrB2-ZrC compounds were prepared by sol-gel process. These materials were examined by X-ray diffraction\ud (XRD), thermogravimetric (TG) analysis, laser granulometry, scanning electron microscopy (SEM), energy dispersive\ud spectroscopy (EDS), and nitrogen adsorption tests. Thermodynamic calculations were carried out using the FactSage®\ud thermochemical software and databases. XRD revealed that ZrB2 and ZrC are the major phases present in the materials\ud obtained in this study. It was observed that the relative amount of ZrB2 and ZrC in these samples can be tailored by controlling\ud the concentration of H3BO3 in the starting solution. On one hand, laser granulometry and SEM tests revealed that the ZrB2-\ud ZrC compounds prepared in this work show a coarse particle size distribution. On the other hand, they exhibited remarkable\ud specific surface areas (about 150 m2/g).\ud Key words: Sol-gel, ZrB2-ZrC compounds, Structural characterizationCNPqCAPESMagnesita Refratários S.A

Estudo do comportamento reológico de nanocompósitos poliméricos reforçados com nanotubos de carbono

A utilização de nanotubos de carbono como reforços em matrizes poliméricas é cada vez mais recorrente em virtude da melhora nas propriedades mecânicas e elétricas dos materiais poliméricos. Neste trabalho foram estudados nanocompósitos de Poli(metacrilato de metila) com adição de 0,5%, 1,0% e 2,0% em massa de nanotubos de carbono comerciais. A morfologia dos compósitos foi caracterizada por análises microscópicas (microscopia óptica e microscopia eletrônica de varredura) e ensaios reológicos, utilizando um reômetro de deformação controlada Anton Paar, modelo MCR 501. As análises microscópicas indicaram a presença regiões com dispersão da carga na matriz em escalas micro e nano. Os resultados reológicos indicaram que, à medida que a concentração de NTC aumenta, maior o aumento nos valores de viscosidade complexa da fase matriz, a baixas frequências, e que os nanocompósitos não apresentaram predominância de microestrutura finaCNP

Estudo reológico de nanocompostitos reforçados com óxido de grafite

Os grandes avanços nas áreas de eletrônica e de biomédica proporcionaram ao Òxido de\ud Grafite, um destaque mundial pelas suas promissoras aplicações na síntese do Grafeno. Oriundo de uma fonte abundante e de baixo custo, o Grafite é a sua única matéria, sendo, um material de fácil obtenção e altamente acessível no mercado.CNPqDEpartamento de Engenharia Metalúrgica e Materiai

Microstructural, thermochemistry and mechanical evaluation of self-reducing pellets using electric arc furnace (EAF) dust containing zinc for Waelz process

<div><p>ABSTRACT The increment of recycling of steel using electric arc furnace and the tendency to coat of steel products with zinc, in order to prevent corrosion, has increased the proportion of galvanized scrap used worldwide in the recent years. Approximately 10 to 20 Kg/t of cast steel is generated in casting arcs. These collected dusts electric arc furnace (EAF dust) contains iron, zinc, lead, and cadmium. Mainly in the form of oxides and their wastes are considered hazardous typically in countries such as Brazil, U.S., Japan and Germany. It is estimated that from the total of 7.5 million metric tons of EAF dust generated worldwide only 45% is recycled. With Waelz process, the EAF dust can be treated to recover zinc by means of reduction-volatilization-oxidation reactions occurring within the rotary kiln. In this work the thermodynamics of the Waelz process is studied to optimize the recovery of volatiles especially zinc. Kinetic parameters were evaluated trough series of ten experiments, comprise the major process factors such as type of reductants (charcoal and petroleum coke), time (20 – 120 minutes) and temperature (450 - 1150°C). The mechanical behavior of the pellets was evaluated by compressive cold strength and drop tests. Characterization was performed using scanning electron microscopy, microanalysis EDS, X-ray diffraction, X-ray fluorescence, granulometric analysis by laser diffraction, as well as measurements of moisture, bulk density and percentage of volatiles, fixed carbon and ash. The small pellets (10mm) with charcoal used as a reductant, presented a higher compression and higher recovery of volatiles than those with petroleum coke.</p></div

Desenvolvimento de propantes cerâmicos sintéticos de alta resistência à compressão e ao meio salino/ácido a partir de rejeitos do processamento mineral e metalúrgico

Os propantes são usualmente materiais esférico e arredondados com dimensões que variam entre 4, 00 e 0,07 mm de diâmetro, podem ser naturais como a areia, ou materiais cerâmicos sintéticos como os propantes a base de bauxita calcinada apresentando resistência mecânica ao esmagamento entre 40 e 50 MPa