Assessment of intensive grinding effects on alumina as refractory compound: Acceleration of γ to α phase transformation mechanism

Synthesis of plate‐like α ‐alumina crystals by solid state reaction of fir immersed with slurry mixture of gibbsite and non‐fluorine morphological modifiers

“…The activation energies of SM and FISM were determined from the fitted slope as 109.8 and 132.9 kJ/mol, respectively. Owing to the existence of liquid sintering mechanism during calcination of SM and FISM containing gibbsite and morphological modifiers, these values of E are lower than those reported in other literature (198–485 kJ/mol) [17, 22]. Significantly, the activation energy for FISM is higher than that for SM, indicating the difficulty of mass transformation during phase conversion in free structures after combustion of fir.…”

“…1 d ) in the micrometre scale involves surface diffusion over a large distance from α ‐alumina nucleation [16, 17]. Generally, the reconstructive transition upon heating results in a loss in specific volume because of the difference in theoretical density during polymorphic transformation, such as from θ with 3.6 g/cm 3 to α ‐alumina with 3.986 g/cm 3 ( γ to α ‐alumina via the meta‐stable δ and θ phases) [16, 17]. In comparison, finger‐grained α ‐alumina powders aggregate loosely for calcined fir immersed with gibbsite slurry (Fig.…”

“…The endothermic peak in 600–800°C with a slight mass loss is attributed to liquid formation for morphological modifiers. Based on the XRD results, an exothermic peak (denoted as T p ) around 990.9°C with no observance of weight loss is related to phase transformation from γ ‐alumina to α ‐alumina [12, 17]. For FISM, the broad exothermic peak at 480.9°C is due to the decomposition of fir reduces, which reduces the value of T p to 961.5°C as a result of the energy supply after the combustion of fir templates.…”

Geopolymers from lunar and Martian soil simulants

“…In order to test this hypothesis, the dust was milled to reduce the particle size and, at the same time, enhance reactivity by mechanical activation (Terzić et al 2014). A planetary mill Pulverisette 5 by Fritsch GmbH was used for 30 minutes at 200 rpm followed by a 125µm sieve to remove any larger particles left.…”

The fabrication of porous corundum spheres with core-shell structure for corundum-spinel castables

“…The α-Al 2 O 3 phase transformation occurs during the process of nucleation and growth [20]. Anja Terzić et al [21] reported that the transition of θ-Al 2 O 3 appeared at approximately 900°C and transformed completely into α-Al 2 O 3 at 1200°C.…”