No abstract

A porcelana de ossos - bone china - é uma cerâmica de corpo especial de grande dureza e translucidez exclusivamente fabricada na Inglaterra e em outras poucas partes do mundo, mas não no Brasil. Suas matérias-primas são compostas por aproximadamente metade de cinza de ossos, além de caulim e feldspato. O trabalho apresenta a obtenção e caracterização de cinza de ossos a partir de ossos bovinos com o objetivo da fabricação de porcelanas. No processo de preparação da cinza de ossos envolve o uso de autoclave, descarnagem manual, calcinação e moagem dos ossos. As condições de preparação foram estudadas em função das condições de calcinação, moagem e lavagem do osso. A calcinação foi estudada através de análises térmicas e difração de raios X de diferentes partes do animal. O pó obtido foi caracterizado por análises químicas, medida de granulometria por difração de laser, e microscopia eletrônica de varredura. Os resultados mostraram que a matéria-prima obtida neste trabalho possui propriedades similares das originalmente utilizadas nas indústrias inglesas com baixo teor de ferro e partículas coloidais e que podem ser calcinadas a temperaturas inferiores a 1000 °C.

Hydraulic fracturing is a very important technique to increase the productivity and recovery of oil reservoirs with low pressure or high depth. The hydraulic fracturing technique is a method of well stimulation in which liquid under high pressure is pumped down a well to fracture the reservoir rock adjacent to the wellbore. Propping agents are used to keep the fractures/cracks open. They can be made from the reject of mineral extraction processes when they present specifics characteristic. The aim of this paper is the evaluation of the use of industrial rejects to the development of ceramic synthetic proppants that are resistant to chemical corrosion and high mechanical strength in aqueous acid and salt water environment. In this study, industrial rejects from nickel sulfide ore flotation (grey mud - GM), red mud (RM) from Bayer process and black mud (BM) from Caron processing of nickel was used as raw material for the production of ceramic synthetic proppants. The material processing was performed through drying, milling, pressing, sintering and characterizing raw material. Several characterization techniques such as X-ray powder diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), high temperature dilatometry and compression strength test were performed after sintering to evaluate the technological potential of recycling these metallurgical and mineral rejects. Mechanical properties were improved after sample sintering. The results show that it is possible to manufacture ceramics of high strength and resistance to acidic/salt water environment as a result of processing minerals reject.

No abstract

Neste trabalho foram desenvolvidas formulações de plastisóis com diferentes quantidades de carbonato de cálcio natural. O carbonato de cálcio natural foi adicionado para substituição da resina virgem (na proporção que variou de zero a oitenta pcr de carbonato de cálcio) nos plastisóis com vinte pcr de poli(cloreto de vinila) reciclado. Com o objetivo de se analisar a possibilidade do uso destas pastas estudou-se a variação de viscosidade com o tempo; sendo que as pastas foram espalmadas e rotomoldadas para obtenção dos corpos de prova, os quais foram submetidos aos ensaios de dureza, resistência à tração e alongamento. As superfícies de fratura dos corpos de prova testados foram analisadas em um microscópio óptico e as temperaturas de gelificação e transição vítrea foram determinadas através de medidas viscoelásticas e DSC, respectivamente. Através do processo de rotomoldagem foram obtidas peças com vinte e quarenta pcr de carbonato de cálcio natural.

No abstract

This paper presents a comparison of traditional thermal and chemical reduction methods with more recent ionizing radiation reduction via gamma rays and electron beams (e-beams). For GO, all synthesis protocols were adapted to increase production scale and are a contribution of this work. The typical Raman D-band of the GO was prominent (ID/IG ratio increased sixfold). When comparing the GO reduction techniques, dramatic differences in efficiency and GO particle characteristics were observed. Although thermal and chemical reduction are effective reduction methods, as shown through the use of FTIR spectroscopy and the C/O ratio from EDS chemical analysis, the thermal process renders great weight losses, whereas chemical processing may involve the use of hazardous chemical compounds. On the other hand, comparing the gamma rays and e-beam for 80 kGy, the Raman spectra and chemical analysis suggested that the e-beam caused a greater GO reduction: C/O ratio from EDS of 5.4 and 4.1, respectively. In addition to being fast and effective, ionizing radiation reduction processes allow easier control of the reduction degree by adjusting the radiation dose. When the dose increased from 40 to 80 kGy, the Raman spectra and EDS showed that the ID/IG and C/O ratios increased by 15 and 116%, respectively.

The onset of fiber failure signals the commencement of catastrophic structural failure in fiber bundle systems, a process that is important in standalone bundles and in other material structures. In this work, we have demonstrated a technique by which the onset of fiber failure can accurately be identified by monitoring the electrical continuity and resistance of filaments and bundles during loading. The dual sensor/loading functionality of the fibers differs from most prior approaches wherein separate sensors were added to the load-bearing fiber array. Individual fiber failure and bundle onset failures in 50 fiber bundles were reliably and reproducibly detected.