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Phosphorus-modified boehmite nanosheets were synthesized through equivalent-volume impregnation with NaHPO solutions, which was further calcined to form γ-alumina. The XRD and HR-TEM analyses indicated that the phosphorus modification had no significant effects on the framework of the boehmite nanosheets. The FTIR spectra suggested that the phosphorus groups replaced some -OH groups and formed P-O-Al bonds with the boehmite. The modified boehmite nanosheets impregnated at the P/Al molar ratio of 1% showed a α-phase transition temperature at 1298.3 °C, much higher than that of boehmite (1189.1 °C). The IEP of the phosphorus-modified γ-alumina prepared by 2 h calcination of phosphorus-modified boehmite (P/Al = 5%) at 600 °C was as low as 7.1. [ABSTRACT FROM AUTHOR]

Eu-doped boehmite nanofiber materials with different Eu concentrations were synthesized without any surfactant, and followed by a series of characterizations. It was found that the boehmite nanofibers became coarser with the increase of Eu concentration, which resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by thermogravimetry-differential scanning calorimetry. All materials showed the phase transition from γ-AlO to other forms. Yet the transition temperature was increased with the increase of Eu concentration. The Eu-doped boehmite nanofibers with the maximum Eu concentrations showed the best thermal stability. Photoluminescence spectra showed that the 2 mol% of doping concentration of Eu ions in Eu:AlO nanofiber was optimum. [ABSTRACT FROM AUTHOR]

Boehmite nanofiber materials with controlled particle size were synthesized without any surfactant by careful tuning of the hydrothermal temperatures, and followed by a series of characterizations. It was found that the boehmite nanofibers became shorter and coarser with the increase of temperature, and resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by in situ HT X-ray diffraction and thermogravimetry-differential scanning calorimetry. All materials showed the phase transition from γ-AlO to other forms. Yet the transition temperature was increased with the increase of hydrothermal temperature. The boehmite nanofibers with the largest diameter showed the best thermal stability. [ABSTRACT FROM AUTHOR]

NaP zeolites samples with different morphologies were successfully synthesized and their thermal behaviors were fully characterized by in situ HT-XRD, IR spectrum, and TG-DSC techniques. It was found that the cubic zeolite NaP phase underwent the same phase transitions, despite their different morphologies. During the whole heating process, they first underwent a minor phase transition into the tetragonal phase at 200 °C. Then they were gradually converted into the phillipsite phase between 400 and 700 °C. Finally, a very stable NaAlSiO nepheline phase formed when the calcination temperature reached 800 °C, which would be kept even after the sample was cooled to room temperature. Although samples with different morphologies had similar phase transitions, they did have different thermal stability as proved by the TG-DSC study. [ABSTRACT FROM AUTHOR]

The boehmite nanofibers were prepared by using NaAlO and Al(SO) as the starting materials without any surfactant. The phase transitions of the boehmite nanofibres against different temperature were studied and various phases were derived from well-crystallized boehmite nanofibers. All these phases had the same morphology even after high temperature calcination. In addition, the retention of specific surface area of the samples were very high because of the limited aggregation occurred in calcinations for each sample. For instance, the γ-AlO obtained at 500 °C had the specific surface area (208.56 m/g) with an average pore diameter of 6.0 nm. With the further increase of the calcination temperature, the nanofibers became shorter and coarsening, which resulted in the decrease of the specific surface area. It is worthwhile to notice that the BET surface areas (40.97 m/g) and the pore volume (0.27 cm/g) of the fibrous structures obtained after 1200 °C calcination are substantially higher than that of the non-fibrous alumina because of the morphology maintenance. [ABSTRACT FROM AUTHOR]