Sol‐Gel Processing

Influence of the Obtaining Method on the Properties of Amorphous Aluminum Compounds

“…The exothermic effect on the DSC curves is due to phase transformation low-temperature Al2O3 to high-temperature oxide without changing the mass (Figure 2a-f, Table 2), according to the following scheme [20]: Al2O3 amorph → γ-Al2O3 → θ-Al2O3 → α-Al2O3. The amorphous alumina (Al2O3 amorph ) is formed due to thermal decomposition of X-ray amorphous aluminum hydroxide and basic aluminum salts [7]. The obtained from PB γ-Al2O3 is transformed to high-temperature alumina without a visible exothermic effect on the S1 DSC curve [1,4,7,12,22] (Figure 2a,b).…”

“…The amorphous alumina (Al2O3 amorph ) is formed due to thermal decomposition of X-ray amorphous aluminum hydroxide and basic aluminum salts [7]. The obtained from PB γ-Al2O3 is transformed to high-temperature alumina without a visible exothermic effect on the S1 DSC curve [1,4,7,12,22] (Figure 2a,b). The exothermic effect on the DSC curves is due to phase transformation low-temperature Al 2 O 3 to high-temperature oxide without changing the mass (Figure 2a-f, Table 2), according to the following scheme [20]:…”

“…is formed due to thermal decomposition of X-ray amorphous aluminum hydroxide and basic aluminum salts [7]. The obtained from PB γ-Al 2 O 3 is transformed to high-temperature alumina without a visible exothermic effect on the S1 DSC curve [1,4,7,12,22] (Figure 2a,b). Hereby, the method of the precipitation from a solution of aluminum nitrate with ammonia at pH = 6.0 without stabilization and aging (sample S1) allows for obtaining a complex amorphous compound in the form of a phase mixture that consists of amorphous aluminum hydroxide, basic aluminum salt, and poorly crystallized pseudoboehmite.…”

“…Gamma-alumina (γ-Al 2 O 3 ) is widely used in the petrochemical industry as a catalyst, catalyst carrier, and adsorbent. γ-Al 2 O 3 is formed during the thermal decomposition of the boehmite [1], obtained from the sol-gel method from bayerite [2], bauxite [3], salts and salt-like aluminum compound [4][5][6], amorphous aluminum oxide, and hydroxide [5,7]. Depending on the nature and characteristics of the precursor, it is possible to regulate the physicochemical properties of γ-alumina.…”

“…There are several ways to obtain the amorphous aluminum compounds: a calcination of the aluminum salts [7], the hydrolysis of the aluminum alcoholates [15], and the precipitation from Al-containing solutions by the base [7,16]. As a result, various non-crystalline aluminum compounds are formed differing in a phase composition and the physicochemical properties of surface.…”