Abstract
In recent decades, talc and kaolinite have been widely used as raw materials for the ceramic industry. In this study, the final characteristics of kaolinitic clay mixed with 6 mass% of magnesite obtained in our previous work were compared with those obtained with mixtures of kaolin (kaolin BIP) and talc (as the source of magnesium oxide). However, different amounts of talc in the kaolin powder were studied, namely 10, 30, and 50 mass% of added talc (with respect to kaolin + talc). The tape casting process was used during this work in order to manufacture the green tapes in an aqueous system with 0.2 mass% of dispersant. Subsequently, the green tapes were heated to 1000 and 1100 °C with a dwelling time of 12 min. The green and sintering tapes were characterized using the following techniques: DTA/TG, X-ray diffraction, porosity, and flexural strength analyses. The results obtained from our previous work indicate that the specimen with 6 mass% of MgCO3 sintered at 1200 °C for 3 h exhibited the best performances, with high flexural strength and weak porosity value—117 MPa and 27%—respectively. As results from this study, the optimal mechanical and thermal properties of sintering tapes were obtained for the specimen with 10 mass% of added talc sintered at 1100 °C. Indeed, this specimen exhibited 50 MPa and 43% of stress to rupture and apparent porosity, respectively.
Highlights
Many traditional and advanced ceramic materials are made from clay [1,2,3,4]
The dehydration of the green tapes in the region between 70 and 120 ◦ C; The burning of organics used as binders and plasticizer in the range 150 to 400 ◦ C; The dehydroxylation of kaolinite between 400 and 650 ◦ C, characterized by an endothermic peak which appeared proportional to the kaolin content in the mixture; The dehydroxylation of talc in the range 850 to 1000 ◦ C, characterized by an endothermic peak very close to the exothermic peak associated to the structural reorganization of the metakaolinite
Considering these thermal analyses results, it appeared that above 1100 ◦ C, an important melting occurred within our kaolin–talc tapes; it was decided to conduct the heat treatments at 1000 and 1100 ◦ C in line with the characterization of apparent porosity and flexural strength
Summary
Many traditional and advanced ceramic materials are made from clay (or clay mixed with other materials) [1,2,3,4]. Kaolinite and talc are both phyllosilicate minerals which present considerable interest to produce several types of ceramic materials (traditional and advances ceramics) for having certain valuable properties [7,8,9,10,11]. Kaolinite has a 1:1 sheet structure with chemical formulae Al2 Si2 O5 (OH) (39.8 mass% Al2 O3 , 46.38 mass% SiO2 , and 13.9 mass% H2 O). It is a layered clay mineral consisting of the pilling up of two Minerals 2020, 10, 1080; doi:10.3390/min10121080 www.mdpi.com/journal/minerals
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