Materials Science Forum Vol. 958

Abstract: This paper discusses an environmentally-friendly destination for the residual ashes resulting from the firing of biomass (wood wastes) at the Engie Brasil Cogeneration Power Plant located in Lages, Santa Catarina, Brazil. The study proposes reusing the residue as a substitution for crushed stones in the production of concrete. Environmental, physical, and chemical analyses were performed for characterization of the ashes. Specimens prepared with ash and subjected to testing presented a compressive strength of around 18.63 Mpa (2700 psi), which is in compliance with the ACI-213R and ASTM C330-5 specifications. With pretreatment and proper mixing ratios, biomass ashes may be employed as an aggregate in the manufacture of lightweight structural concrete.

Abstract: Graphene oxide (GO) can be partially reduced to graphene-like sheets by removing the oxygen-containing groups and recovering the conjugated structure. In this work, the thermal reduction of GO powder has been carried out using back pumping vacuum pressures and investigated employing X-ray diffraction analysis. The experimental results of estimating the number of graphene layers on the reduced powder at various temperatures (200 – 1000 °C) have been reported. Electrical changes have been produced in a graphene oxide with the vacuum reduction process. This study has shown that the ideal processing temperature for reducing graphene oxide nanomaterial was about 400 °C. It has also been shown that at 600 °C the number of layers in the reduced nanomaterial increased. The internal series equivalent resistance (ESR) has been improved substantially with the vacuum thermal treatment even at temperatures above 400 °C. ESR was reduced from 95.0 to about 13.8 Ω cm² with this processing. These results showed that the process can be applied to the reduction of graphene oxide to produce supercapacitor nanomaterials. The advantage of employing this method is that the processing is a straightforward and low cost thermal treatment that might be used for large amount of nanocomposite material.

Abstract: Million tons of ornamental stones residues are produced every year. Most of this residue is disposed without any kind of processing or treatment. Moreover, disposal occurs without a prospective of reuse or recycling. The incorporation into ceramics is a possible alternative for part of this residue. Clay-based ceramics have high capacity of incorporation of industrial residues. This work aimed to conduct a microstructural characterization of clay-based ceramics with incorporation of granite residues in the composition of the ceramic matrix. Specimens were produced with the addition of 0, 10, 20 and 30 wt. % of granite residues. The specimens were prepared by uniaxial pressing and sintered at temperatures of 1050 and 1200°C. For the microstructural analysis were carried out by scanning electron microscopy and X-ray diffraction. The results indicated that the incorporated ceramics sintered at 1200oC presented higher densification and lower porosity as compared with those sintered at 1050oC.

Abstract: Ornamental stones processing produces large amounts of wastes, which without treatment, are disposed in deposits, constituting the major environmental problem in this sector in Brazil. There is a great variety of rocks and different technologies in the ornamental stones processing. Rock block sawing can be performed using multi-blade gangsaw, the conventional technology, or multiwire gangsaw, latest technology which uses only diamond wire and water to cut blocks. In recent years there has been a great change in the use of ornamental stones sawing technologies, where currently almost 50% of the sawed materials are processed by the multi wire technology. The ornamental stones wastes have compounds that can collaborate in the processing of the ceramic. Due to the great variety of Brazilian ornamental stones and technologies in addition to the growth of de sector in recent years, there is a need for new studies regard to the characterization and environmental classification of waste, for a better management and application. Therefore, the objective of this work was the characterization and environmental classification of ornamental stones wastes aiming their use in red ceramics. The wastes were characterized with the determination of its chemical composition and mineralogical analysis, particle size, morphological analysis and environmental, the latter by means of the leaching and solubilization tests, for subsequent classification. The wastes are composed mainly of SiO₂, Al₂O₃, alkaline oxides, earth alkaline oxides and iron, and those which were submitted to the leaching and solubilization tests are classified as non-inert.

Abstract: The ceramic fibers can be obtained from different techniques. Due to the technological development, searches are performed to improve the existing fibers. Thus, recent studies have enabled the development of an unprecedented synthesis route for the production of nanofibers, the Solution Blow Spinning (SBS). In this context, the present work proposes to develop silica nanofibers doped with silver by the SBS method, evaluating parameters such as: silver content and acidification of solutions. The fibers were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results of XRD showed that the samples with 4% silver that were not acidified showed the most defined and intense characteristic peaks. The SEM showed the formation of fibers with diameters in the nanometer range independent of acidification or not of the solutions, with reduction of the agglomerates in the samples with 2% silver.