A comparative study on the thermal stability, textural, and structural properties of mesostructured γ-Al2O3 granules in the presence of La, Sn, and B additives

Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

“…The specimens exhibited unimodal pore size distributions, predominantly corresponding to inter-particle pores [74], with peaks observed at 1.765 µm, 1.872 µm, 2.419 µm, and 2.777 µm for the specimens heat-treated at 900 °C, 1000 °C, 1100 °C, and 1200 °C, respectively. The pore size increased with the temperature, a finding consistent with those in similar reports on γ-Al2O3 [3,16,78], TiO2/γ-Al2O3 [25], and N-doped TiO2/γ-Al2O3 granules [26] processed through the oil-drop [3,16] and hydrocarbon-ammonia routes [25,26,78]. This phenomenon can be attributed to the enhanced viscous flow of the melt The specimens exhibited unimodal pore size distributions, predominantly corresponding to inter-particle pores [74], with peaks observed at 1.765 µm, 1.872 µm, 2.419 µm, and 2.777 µm for the specimens heat-treated at 900 • C, 1000 • C, 1100 • C, and 1200 • C, respectively.…”

“…This phenomenon can be attributed to the enhanced viscous flow of the melt The specimens exhibited unimodal pore size distributions, predominantly corresponding to inter-particle pores [74], with peaks observed at 1.765 µm, 1.872 µm, 2.419 µm, and 2.777 µm for the specimens heat-treated at 900 • C, 1000 • C, 1100 • C, and 1200 • C, respectively. The pore size increased with the temperature, a finding consistent with those in similar reports on γ-Al 2 O 3 [3,16,78], TiO 2 /γ-Al 2 O 3 [25], and N-doped TiO 2 /γ-Al 2 O 3 granules [26] processed through the oil-drop [3,16] and hydrocarbon-ammonia routes [25,26,78]. This phenomenon can be attributed to the enhanced viscous flow of the melt phase, facilitated by the capillarity effect.…”

La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

“…When structural changes to the starting alumina are avoided, the doped product will have properties (e.g., pore size distributions) similar to the alumina from which it was obtained. 96 Apart from impregnation, 22,27,28,32,33,51,52,55,61,69,73,77,78,81,85, 89,100,104−112 other doping methods include deposition by precipitation, 78,107 hydrothermal treatment, 91 coprecipitation, 26,83,113 sol−gel synthesis, 34,52,53,58,63,64,66,76,79,93,98,106,114 combustion synthesis, 8 nitrate decomposition, 76 and other solvent-free or solid-state reactions. 16,52,76,94 However, it appears to be difficult to achieve an adequate dispersion of lanthanum on alumina by solid-state reactions.…”

“…In the past, many studies have aimed at improving the thermal stability of aluminas by using new preparation methods or through the addition of dopants. ,,− Such additives exert an influence on the kinetics of sintering and phase transformation . Ca 2+ , Sr 2+ , Ba 2+ , Sn 4+ , Y 3+ , Zr 4+ , La 3+ , Er 3+ , Th 4+ , and other rare earth (RE) ions inhibit the transformation of t-aluminas into the α-phase; Mg 2+ , Ga 3+ , and In 3+ have the opposite effect. − , ,, , − , , − The cation size seems to have a major influence on the effectiveness of dopants. , Figure shows the specific surface areas at 1200 °C for an alumina powder doped with various elements. The corresponding surface area of the undoped alumina was 8–12 m 2 /g, while those of the modified aluminas are ≥40 m 2 /g …”

“…Apart from impregnation, , , ,, , ,, , ,, , , , , , ​ , ​ , ​ − other doping methods include deposition by precipitation, , hydrothermal treatment, coprecipitation, ,, sol–gel synthesis, , , , , , , , , ,, , , combustion synthesis, nitrate decomposition, and other solvent-free or solid-state reactions. , , , However, it appears to be difficult to achieve an adequate dispersion of lanthanum on alumina by solid-state reactions. E.g., Huang et al observed no stabilizing effect (at 1200 °C) for samples prepared by calcination of mechanically mixed boehmite and LaAlO 3 or La 2 O 3 .…”