Low-temperature Ti-containing 3:2 and 2:1 mullite nanocrystals from single-phase gels

Microstructure and oxidation behavior of sol–gel mullite coating on SiC-coated carbon/carbon composites

“…The main phases in the as-prepared coating are mullite and cristobalite. These form when the monophasic mullite precursors crystallize into an Al 2 O 3 -rich pseudo-tetragonal mullite at about 1253 K. Then the Al 2 O 3 -rich mullite gradually transforms into 3:2 orthorhombic mullite by reaction with the silica phase upon being further heated above 1573 K. The latter transformation step is slow because the diffusion rate is limited [26][27][28]. In addition, no peak of SiC or Si is found, indicating that a dense mullite outer coating with enough thickness has formed.…”

Preparation and characterization of diphasic sol-gel derived unsupported mullite membranes

“…After the addition was completed, the reaction mixture was heated to 60°C for 3 h under constant stirring in a glove box. The standard silica sol molar TEOS:HNO 3 overnight dried at a relative humidity (R.H.) of 60% (Binder-KBF 115, Constant Climate Chamber) unsupported membranes were heat treated in the 600-900°C range for 1 h with a heating rate of 5°C/min (Carbolite-CWF 1300).…”

“…The particle size distribution obtained from DLS measurements is based on intensity of light scattered and it is possible to convert size distributions into volume/number based distributions by using Mie theory [20]. Although, there is a direct relation between the diameter (D) and the number, volume fraction is proportional to D 3 . In general, measured particle sizes are in the order of intensity [ volume [ number.…”

“…It is the only stable binary phase in contact with a liquid at high temperatures in the Al 2 O 3 -SiO 2 system [2]. It is assumed that stable mullites exist in the range of compositions between 3Al 2 O 3 Á2SiO 2 (3:2) and 2Al 2 O 3 ÁSiO 2 (2:1) [3]. Sol-gel processing has been used during the last decade for mullite preparation with chemically homogeneous microstructures [4][5][6][7][8][9].…”

Evaluation of the Influence of MgO and La2O3 on the Fast Sintering of Mullite

“…The role of sintering additives has been attributed to the formation of liquid phase and to a reduction in viscosity of the glassy (or liquid) phase or to a reduction in mullite formation temperature in gel-derived powders, thereby leading to higher mobility of diffusing species [7][8][9][10][11] . Reports in the literature on studies involving mullite have focused on the nucleation of gel-derived mullites and doped mullites 5,7,[12][13][14][15][16] and on the conventional sintering of mullite compacts [17][18][19][20] . Few researches have investigated the fast sintering behavior of mullite bodies [21][22][23][24][25] , and even fewer studies 26,27 have sought to ascertain the influence of additives on the rapid sintering of mullite.…”