In-plane microstructure of plasma-sprayed MgAl spinel and -mullite based protective coatings: An electron microscopy study

Acid Corrosion Behavior of Sol–Gel‐Prepared Mullite Ceramics With and Without Addition of Lanthanum

“…It is known that mullite crystals of polycrystalline ceramics and melt‐grown mullite crystals do not only differ in microstructure but also display deviating compositions. Mullite crystals of sintered ceramics typically have the stoichiometric Al–Si ratio of 75:25 (60 mol% of Al 2 O 3 and 40 mol% of SiO 2 ), whereas crystals of melt‐derived mullite are typically Al‐rich . In addition, corundum crystals located at sample surface give rise to a measured aluminum amount.…”

“…Mullite crystals of sintered ceramics typically have the stoichiometric Al-Si ratio of 75:25 (60 mol% of Al 2 O 3 and 40 mol% of SiO 2 ), whereas crystals of melt-derived mullite are typically Al-rich. 28 In addition, corundum crystals located at sample surface give rise to a measured aluminum amount. More importantly, corroded samples are almost completely depleted of lanthanum confirming corrosion of a lanthanumrich glassy phase prone to chemical attack, while the crystalline structure have better acid resistance.…”

Amorphous zones in flame sprayed alumina–titania–zirconia compounds

“…This consideration emerges because the amorphous content in HA-coatings has important and direct impact on the in-vitro-performance of the coating in such a way, that the bioactivity of amorphous HA phase is much higher than that of the crystalline HA phase [6]. Finally, lots of work conducted transmission electron microscopy (TEM) examinations where sometimes amorphous phase was detected but due to the high resolution of this analyzing technique they could not be localized within the lamellae [1,[17][18][19][20][21][22][23][24][25]. The degree of amorphization is dependent on the cooling speed.…”

Formation of mullite thin film via a sol-gel process with polyvinylpyrrolidone additive

“…There are several reports 4À7 mentioning the preparation of mullite thin film. The methods included dip coat-ing of a sol on silica substrate, 4 by spin coating to form an unsupported film, 5 spray pyrolyzing of a precursor on a SiC substrate, 6 or CVD on a SiC substrate. 7 There are some advantages of using sol-gel precursors to form thin film.…”