Virginia Burghelea

Feldspar Porcelain with High Mechanical Strength

There were studied three compositions, according to the masses vitrified between 1150° and 1250°C, placed in the leucite – mullite – silica subsystem. The reference sample (a mullite type one) was obtained from English kaolin and aplite (provided from “Philip’s Ravine”, Romania) and the other two (mullite – cristobalite type) were made from reference samples mixed with Romanian Uricani’s quartz (in proportions of 7.5% and 15%). It was used two different quartz grain size (a fine one and a coarse one). The samples were prepared through classical ceramic technology, by thermal treatment between 1150-1300°C with 2 hour soaking time. Through X rays diffraction analysis was confirmed the existence of theoretical mineralogical compounds: silica, mullite and orthose. The compressive strengths of samples thermally treated at 1250°C, 2h were between 98 and 183 MPa range. The highest value was observed for sample with 7.5% fine quartz (<100μm).

Synthesis and Characterisation of Cordierite - Mullite Composites

According to classic ceramic technology was prepared stoichiometric cordierite from illite, magnesium oxide and calcined alumina. The sinter was characterised granulometric, by DTA&TG analysis and textural by optical microscopy in the transmitted light. From cordierite sinter (1300 o C – 2h) and electromelted mullite were synthesised three composite compositions by thermal treatment at 1300-1350 o C2 h. Sintering characteristics, bending strength and texture were determined.