Bone china is known for its technical and aesthetical quality with distinguishable whiteness, brightness and high mechanical strength. In this work, the use of waste glass was investigated in a bone china composition. This makes the production of this porcelain even more interesting from the environmental point of view, since most of its raw materials are from recyclable sources. Potash feldspar was partially replaced by waste glass, and the technical and slip rheological properties, phase development and microstructure after firing of the ceramic bodies were evaluated. The results revealed that waste glass provides a reduction in firing temperature and large plateau for firing while maintaining the quality of the final porcelain, including thermal expansion and mechanical strength.
The utilization of wollastonite as a flux in bone china was investigated in this work. Ceramic industry is always looking to optimize the use of fluxes as a way of reducing energy costs associated with firing. Wollastonite is added in ceramic formulations as an auxiliary flux and allows fast firing production. However, its use in bone china has not been tested before. In the present work, two formulations were prepared, comparing the traditional formulation to another in which the conventional flux (potash feldspar) was partially replaced by wollastonite. The firing behavior, technical properties, microstructure, and phase development were analyzed. A slip with wollastonite was also developed to analyze its rheology. Wollastonite body achieved a reduction of firing temperature, a large plateau for firing, and optimal slip stabilization for casting pieces.
The use of a waste from mineral processing, a spodumene-bearing rock, was investigated as a flux for bone china composition, partially replacing feldspar. The effect of lithium oxide in bone china body was favorable for reducing firing temperature. The presence of Li 2 O reacting with other oxides and silicates formed a liquid phase of lower viscosity, which was favorable for densification through viscous flow sintering, and to a higher mechanical strength. It was obtained a large plateau for firing, without deformation on firing (pyroplastic deformation) of parts; which is not an easy task to be achieved in bone china processing. Rheological and casting properties were also investigated. Microstructures of the fired bodies were discussed. They correlated well with the final properties of the parts.
ResumoA crescente preocupação ambiental trouxe grande interesse na reutilização e reciclagem de materiais. Dentro desse contexto, está o propósito do presente trabalho de estudar a utilização de um resíduo de embalagens de vidro em porcelana de ossos. Especificamente, foi analisado o comportamento reológico de formulações de porcelana de ossos, nas quais o fundente feldspato foi parcialmente substituído por vidro reciclado. Avaliou-se a reologia em relação ao comportamento da viscosidade e da tensão de cisalhamento em função da taxa de cisalhamento, e da viscosidade em função da concentração de dispersante, considerando-se a especificidade de cada matéria-prima. As peças coladas foram avaliadas em relação à facilidade de desmoldagem, tempo de formação de parede e qualidade visual do colado. Obteve-se uma barbotina com o vidro com estabilidade e comportamento reológico próximo da de feldspato. Palavras-chave: porcelana de ossos, colagem, reologia, vidro reciclado. AbstractThe growing environmental concern brought great interest in recycling of materials. This paper shows the use of waste glass in bone china, and the analysis of the rheological behavior of bone china compositions, in which the feldspar flux was partially replaced by recycled glass. We evaluated slip viscosity, shear stress, shear rate, and viscosity in function of dispersant addition, considering the specificity of each raw material. The casting pieces were analyzed for ease of demoulding, wall-forming time and visual quality of the parts. The slip with glass showed stability and rheological behavior similar to the feldspar slip.
O titânio quando mantido em temperatura e atmosfera ambiente, produz uma fina e aderente camada de óxido (TiO2) tornando resistente à corrosão. Por essa característica, a anodização do titânio vem sendo estudada para aplicações biomédicas. Apesar de possuírem excelente biocompatibilidade, as próteses de titânio podem gerar infecções associadas ao implante. Estudos mostram que aliando nanocargas de prata (AgNPs) ao titânio, a atividade antimicrobiana do material é ampliada, o que reduz a taxa de infecções. O objetivo do trabalho foi identificar o processo mais adequado para incorporação de nanocargas de prata em titânio anodizado. Para tanto, amostras de titânio foram (i) anodizadas em ácido cítrico contendo nitrato de prata (AgNO3), (ii) anodizadas em ácido cítrico e posteriormente imersas em solução de extrato vegetal + AgNO3 e (iii) anodizadas em H2SO4 + H2O2 e seladas em solução contendo extrato vegetal + AgNO3. Análises morfológicas por Microscopia Eletrônica de Varredura (MEV) e análises químicas semiquantitativas por Espectroscopia De Energia Dispersiva (EDS) foram realizadas para verificar a eficácia de incorporação das nanocargas de cada método. Os resultados mostraram que é possível incorporar AgNPs ao óxido de titânio por meio do processo (i) anodização em ácido cítrico + AgNO3 e (iii) anodização em H2SO4 + H2O2 e selagem em solução contendo extrato vegetal + AgNO3. Além disso, testes de polarização potenciodinâmica e de citotoxicidade foram realizados somente nas amostras do processo (iii) e mostraram que a incorporação de prata melhora o desempenho anticorrosivo do titânio e favorece o efeito antimicrobiano da superfície em bactérias.
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