Mullite–SiC nanocomposites are synthesized by introducing surface modified sol–gel mullite coated SiC particles in the matrix and densification and associated microstructural features of such precursor are reported. Nanosize SiC (average size 180 nm) surface was first provided with a mullite precursor coating which was characterized by the X-ray analysis and TEM. An average coating thickness of...

Microwave sintering possesses unique attributes and has the potential to be development as a new technique for controlling microstructure and to improve the properties of advanced ceramics. Because microwave radiation penetrates most ceramics, uniform volumetric heating is possible. Thermal gradients, which are produced during conventional sintering because of conductive and radioactive heat tr...

Introduction (Al,Ge)-mullite of the composition 3 Alz03 . 2GeOz is well known from the structural point of view (Durovic and Fejdi, 1976). There exists a clase relationship to the corresponding silicon-mullite 3Alz03 . 2 SiOz. In contrast to the (Al, Si)-mullites it was not possible so far to grow (Al, Ge)mullites with a more extended solid solution range. Recently the synthesis of an (Al, Ge)-...

A simple, processable precursor to mullite can be synthesized in quantities of 100 g in a few hours by direct reaction of silica, aluminum hydroxide, and triethanolamine in ethylene glycol. To delineate a processing window whereby precursor shapes can be transformed into mullite, the chemical and phase microstructural evolution of this precursor on pyrolysis to selected temperatures in air is f...

Recent studies have shown that the mullitization of diphasic aluminosilicate matrices comprising transitional alumina and amorphous silica occurs via a nucleation and growth process. Nucleation is preceded by a temperature-dependent incubation period. Following this incubation period, rapid nucleation of mullite occurs, producing about 1.8 X 10" nuclei/cm3, which remains constant throughout the...

Polished plane-parallel sections (1 mm in thickness) of fused mullite (2Al 2 O 3 · 1SiO 2) were exposed to a slowly flowing (≈ 100 ml/min) water vapor containing atmosphere (H 2 O/O 2 = 20/80) at a temperature of 1670 °C for 1.5, 3, 6 and 12h, respectively. The water vapor experiments on fused mullite were carried out together with experiments on mullite single crystals reported earlier [1]. Al...

Coal fly ash (CFA) generated by coal-based thermal power plants is mainly composed of some oxides having high crystallinity, like quartz and mullite. In this study, the effect of CFA crystallinity toward lead adsorption capacity was investigated. To get solid with various crystallinity, the solution of sodium hydroxide (NaOH) of 1-7 M was used to treat CFA at various temperature and reflux time...

Dense, uniform, and adherent chemically vapor-deposited mullite coatings were deposited on SiC substrates using the AlCl3–SiCl4–H2–CO2 system. Typical coating morphology consisted of a thin interfacial layer of g–Al2O3 nanocrystallites embedded within a vitreous SiO2-based matrix. When a critical Al/Si ratio of 3.2 ± 0.29 was reached within this nanocrystalline layer, mullite crystals nucleated...

Clinoptilolite is a natural zeolite used for the abatement of ammonium in the treatment of urban wastewater. By considering that mullite was obtained through thermal treatment of NH4-exchanged synthetic zeolites, this work aimed to evaluate if this phase can be obtained from NH4-clinoptilolite. A material containing about 90 wt % of clinoptilolite, prepared using a Sardinian zeolite-rich rock, ...