Aluminum Oxide

Abstract

The article contains sections titled: 1. General Aspects 1.1. Aluminum Hydroxides 1.2. Aluminum Oxide Hydroxides 1.3. Aluminum Oxide, Corundum 1.4. The Al 2 O 3 ‐ H 2 O System 1.5. Thermal Decomposition of Aluminum Hydroxides 1.6. Aluminates and Related Compounds 2. Bauxite, the Principal Raw Material 2.1. Definition and Geology 2.2. Composition and Properties 2.3. Genesis of Bauxites 2.4. Major Bauxite Deposits 2.5. Economic Aspects 3. Bayer Process 3.1. History and Procedure 3.1.1. Bauxite Preparation 3.1.2. Digestion 3.1.3. Equipment 3.1.4. Residue Separation 3.1.5. Precipitation 3.1.6. Impurities 3.1.7. Calcination 3.1.8. Evaporation 3.1.9. Residue Disposal 3.1.10. Energy in the Process 3.2. Economic Aspects 4. Other Processes for Alumina Production 4.1. Raw Materials 4.2. Alkaline Processes 4.3. Acid Processes 5. Metallurgical Alumina 5.1. Alumina Properties Required for Smelting 5.2. Typical Specifications for Metallurgical Alumina 6. Industrial Alumina Chemicals 6.1. Aluminum Hydroxides 6.2. Adsorbent and Catalytic Aluminas 6.2.1. Preparation of Activated Aluminas 6.2.2. Adsorbent Applications 6.2.3. Catalytic Applications 7. Ceramic Uses of Alumina 7.1. Calcined Alumina 7.2. Fused Alumina 8. Toxicology and Industrial Hygiene

Surface area, crystal morphology and characterization of transition alumina powders from a new gibbsite precursor

“…EDS elemental microanalysis indicates the absence of iodine in the microcrystals that were examined. The hexagonal platy crystals are similar to those used for paper coating 9 and are completely different from the Bayer gibbsite agglomerates 7,8 . The DTA curve of Figure 3a shows an intense endothermic peak starting at 250 °C and with maximum intensity at 300-320 °C.…”

“…The value of the specific surface area of the pristine I-gibbsite crystals is 29 m 2 .g -1 (Figure 3), which is bigger than from Hydral aluminum hydroxide, having the same crystal shape (the values are 6-8 m 2 .g -1 and 12 m 2 .g -1 for the two types 9 ). The variation of the specific surface area of the I-gibbsite powder with firing temperatures between 200 and 1500 °C is shown in Figure 3b in comparison with Bayer gibbsite data from literature (Figure 3c) 18 .…”

“…Hsu 5 , reviewing the literature on aluminum hydroxides, reproduced TEM of hexagonal plates of microcrystals of gibbsite, from the aging of aluminum hydroxide, in water containing sodium and perchlorate ions, at room temperature 6 . McZura et al 7 and Misra 8 described, by TEM, very uniforms hexagonal platy microcrystals, about 1 µm in diameter, produced by a patented process from an "organic-free aluminate liquor" for use as coating pigment for paper 9 , in ALCOA Hydral Series. Sweegers et al 10 reviewed the morphology of gibbsite crystals grown from pure and impure aqueous sodium aluminate solutions and Adamo et al 11 in tartrate solutions.…”

Al3BC3 Powder: Processing and Synthetic Mechanism

“…1(a)) was due to the vaporization of moisture and the dehydration of the raw powders. The transition of Al(OH) 3 to AlO(OH) and Al 2 O 3 was reported to occur at 102° and 452°C, respectively 13 . Al 2 O 3 (<0.6 wt% was contained in aluminum) reacted with carbon and decomposed, e.g., as follows 14 : …”

Microgranules and Nanoparticles on Their Surfaces

“…Fine Al 2 O 3 powders, with a large specific surface, are widely used as catalysts, supports in catalysis, sorbents, and starting materials for the fabrication of ceramics [49,50]. The main method for the preparation of fine Al 2 O 3 particles, including aerogels and xerogels, is controlled hydrolysis of aluminum alkoxides [51].…”