Coal fly ash with the addition of Al₂O₃ was recycled to produce mullite/alumina composites and the camphene-based freeze casting technique was processed to develop a controlled porous structure with improved mechanical strength. Many rod-shaped mullite crystals, formed by the mullitization of coal fly ash in the presence of enough silicate, melt. After sintering at 1300-1500 °C with the initial...

Microbial fuel cells (MFCs) made with different types of ceramic membranes were investigated to find a low-cost alternative to commercially available proton exchange membranes. The MFCs operated with fresh human urine as the fuel. Pyrophyllite and earthenware produced the best performance to reach power densities of 6.93 and 6.85 W m(-3), respectively, whereas mullite and alumina achieved power...

Weakly bonded particle mixtures of mullite and alumina are assessed as candidate matrixes for use in porous matrix ceramic composites. Conditions for the deflection of a matrix crack at a fiber-matrix interface are used to identify the combinations of modulus and toughness of the fibers and the matrix for which damage-tolerant behavior is expected to occur in the composite. Accordingly, the pre...

S U M M A R Y . The high-temperature transformation of andalusite (AI2SiOs) into 3/2-mullite (3AIzO32SiO2) plus vitreous silica (SiO2) has been studied within the temperature interval from 13oo to 16oo ~ by means of X-ray powder and single-crystal techniques and by infrared spectroscopy. Results are interpreted in terms of a topotactic transformation in which (oi I) and (oI i) planes of andalus...

Mullite and mullite/ZrO2-7wt.%Y2O3 coatings could be thought among the main protective layers for environment barrier coatings (EBCs) to protect Si-based substrates in future gas turbine engines. Considering that feedstock of the compound powder is not commercially available, two powder processing routes Spray Drying (SD) and Flame Spheroidization (FS) were implemented for both types of powders...

A strategy is proposed to reduce surface tensile stresses that develop in ceramic microlaminate structures. As a specific example, surface stresses, which can lead to unwanted edge cracking, appear within a thin alumina/mullite layer bounded by thicker alumina layers after fabrication at some elevated temperature and subsequent cooling. A stress analysis is performed using the finite element me...

Large whiskers of a new KAl9O14 polymorph with mullite-type structure were synthesized. The chemical composition of the crystals was confirmed by energy-dispersive X-ray spectroscopy, and the structure was determined using single-crystal X-ray diffraction. Nanosized twin domains and one-dimensional diffuse scattering were observed utilizing transmission electron microscopy. The compound crystal...

Abstract Porous mullite ceramics were prepared from mixtures of Egyptian kaolinite-clay and calcined α-alumina powder. The effects two methods compaction as well types binder investigated. influence sintering temperature on the physical properties, crystalline phase, compressive strength microstructure was studied. Mullite bodies processed by uniaxial pressing utilizing 15wt. % water at 1500°C ...

Mullite (3Al2O3.2SiO2) and 10 mol% silica added zirconia (10 SiO2 - 90 ZrO2) ceramic powders were synthesized by conventional processing route. The mixtures prepared mechanical alloying method using ball mill in acetone environment. To synthesize mullite, Al2O3 mixture was with stoichiometric proportions fired it the air at 1600 oC for 3 h. And composites 1300 2 Thus, mullite composite phases o...