Comparison of drying procedures for the preparation of alumina powders with the system Al-alkoxide/tertiary butanol/water

Abstract

Abstract. Two series of alumina gel precursors, obtained from AI sec-butylate, ASB, or AI tert-butylate, ATB, dissolved in tertiary butanol, TB, have been dried according to five procedures, in order to compare their efficiency and the consequences they may have on the structure of the final product. They consist of lyophilization (or freezedrying), evacuation at room temperature (with or without ageing of the gel), drying in an oven at atmospheric pressure, or under hypercritical conditions. Chemical analysis, X-Ray diffraction and spectroscopic characterizations (FTIR and laser Raman) allow the identification of the phases present. The temperature of the drying step, as well as the nature of the alkoxide percursor, considerably affect the final dried products.

Characterization of Modified and Polymer Coated Alumina Surfaces by Infrared Spectroscopy

“…DRIFT spectra of Al HT and Al CHT are shown in Figure 3 and the bands assignment are illustrated in Table 4. From this data we can conclude that the -OH band at 3334 and 3504 cm −1 in Al and Al C respectively, was shifted and split into two bands at 3309 and, 3114 cm −1 in Al HT and Al CHT ; this is in agreement with the data reported by Ponthieu et al [20], who attributed this to the formation of crystalline boehmite. The intensity of band at 1060 cm −1 which is assigned to cluster of Al 3+ and O 2− ions on the surface of alumina was increased.…”

A new route to aerogels: Monolithic silica cryogels

“…Nevertheless, a significant amount of work has been carried out in the field of cryogels [15], from pioneering work on silica cryogels [16,17], to carbon [18,19], alumina [20] and zirconia [21] cryogels. The resultant cryogels usually have high surface area and porosity, but, as mentioned above, they are obtained as powders [22] or thin layers [15]. Only very recently, in the frame of ice-templated hydrogels [23], Nishihara and co-workers have been successful to produce small monoliths of micro-honeycomb titania-silica cryogels [24], and new work on obtaining silica cryogels from alcogels has also been published [25].…”

Silica-doped alumina cryogels with high thermal stability

“…Despite the simplicity, low cost, and harmless conditions of preparation, relatively few number of papers has dealt with the thermal stability of cryogels so far [9]. Ponthieu et al prepared pure alumina cryogels from aluminium alkoxides, and reported the marked thermal stability after firing at high temperatures [9][10][11]. For the industrial applications, it is expected that the thermal stability be further enhanced by the addition of doping elements to achieve the performance as high as that of aerogels, ensuring their commercial usage.…”