RESUMONeste trabalho, a técnica de viscosimetria foi utilizada para avaliar as características reológicas de suspensões preparadas com precursor vitrocerâmico do sistema LZSA (Li 2 O-ZrO 2 -SiO 2 -Al 2 O 3 ). A partir da caracterização reológica, foi possível estabelecer condições composicionais adequadas de fração de sólidos, dispersante e monômeros orgânicos. A quantidade de agente espumante para produção de espumas vitrocerâmicas por gelcasting foi determinada pela variação volumétrica após agitação. As espumas resultantes foram submetidas a tratamentos térmicos no intervalo de temperatura compreendido entre 200 e 500°C/60 min, para degradação da matéria orgânica e a 950°C/60 min para sinterização e cristalização. Com os corpos cerâmicos porosos foram realizadas medidas de retração térmica, densidade aparente, análise microestrutural e resistência mecânica. A adequação das características reológicas do precursor LZSA por gelcasting permitiu a produção de espumas com elevada porosidade (> 90%) aberta e interconectada com boa estabilidade térmica e com resistência mecânica compatível com cerâmicas porosas. Palavras-chave: reologia, gelcasting, espumas vitrocerâmicas. ABSTRACTIn this work the viscosimetry technique was used to evaluate the rheological characteristics of ceramic suspensions prepared with a LZSA (Li 2 O-ZrO 2 -SiO 2 -Al 2 O 3 ) glass. From the rheological characterization it was possible to establish optimized conditions of solid fraction, dispersant, organic monomers and foaming agent for the production of glass-ceramic foams by gelcasting. The resulting foams were subjected to heattreatments at 200-500°C/60 min, for degradation of organics and at 950°C/60 min for sintering and crystallization. With the obtained porous ceramic bodies linear thermal shrinkage, apparent density and mechanical strength measurements as well as microstructural analysis were performed. The adaptation of the rheological characteristics of the LZSA parent glass powder with the gelcasting processing technique allowed the production of ceramic foams with high open and interconnected porosity (>90%) with good thermal stability and with mechanical strength suitable for the production of porous ceramics.
Rheological behaviour of Al 2 O 3 and CuO suspensions was characterised in order to fabricate Al 2 O 3 /Cu foams as an alternative way to produce foams with better mechanical properties than common Al 2 O 3 foams. Different quantities of raw materials were combined to select the formulations for the ceramic-metal foams. Foams were produced by a double impregnation process, followed by a thermal cycle and a reduction cycle. In this work, materials were characterised trough zeta potential, SEM and optical dilatometry. Foams microstructure and compressive strength were evaluated. Final structures had a compressive resistance of 0.44 ± 0.14 MPa.
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