Reaction sintering of ZnO-Al2O3 mixtures

Effect of TiO2 doping on the characteristics of macroporous Al2O3/TiO2 membrane supports

“…As the sintering temperature increases, the disappearance of TiO 2 and formation of Al 2 TiO 5 accordingly increase the distance between Al 2 O 3 particles and result in an increase in pore size. 25 It should be noted that the pore size of the supports A95/5 and A85/15 sintered at 1500 • C is (slightly) smaller than that of those supports sintered at 1400 • C. This result can be attributed to the densification of a support consisting of Al 2 O 3 and Al 2 TiO 5 after the completion of reaction of Al 2 O 3 -TiO 2 composite at 1400 • C. Fig. 6 gives the pure water flux of the support as function of transmembrane pressure.…”

Spinel-based ceramic membranes coupling solid sludge recycling with oily wastewater treatment

“…The nucleation and subsequent growth of NiAl 2 O 4 crystals begin from the solid interface between nickel oxide and bauxite (both mullite and alumina) as two parent phases, where Ni and Al ions counter-diffused through spinel lattice to maintain continuous crystal growth. Three distinct stages can be identified for spinel NiAl 2 O 4 formation from NiO and calcined bauxite (with mullite and corundum as crystalline phases) (Leblud et al, 1981). The first stage occurred between 1000 °C and 1050 °C, the reaction between NiO and α-Al 2 O 3 (eq 3) was much more favored as compared to that between NiO and thermally more stable mullite (eq 4), which is further fully evidenced by the unchanged phase content of mullite with increasing temperature (Fig.…”

Binder effect on ZnAl2O4-containing high-alumina refractory castables

“…Besides that, ZnO addition affected the evolution of CaAl 12 O 19 grains from plate-like to equiaxed structures, which favored an easier development of the MA grains and improved the densification of the prepared specimens [22]. However, the in situ generation of ZnAl 2 O 4 , MgAl 2 O 4 and calcium aluminates in refractories is accompanied with a large volume expansion [24][25][26]. Li et al [6] stated that zinc carbonate or hydroxide could be used as alternative materials to suppress volume expansion and improve the ceramics' volume stability, as the decomposition of such compounds during the specimens first heating would give rise to micropores in the refractory structure, providing space to counter-balance the expansion related to the formation of spinel and calcium aluminate compounds at high temperatures.…”