Alumina (Aluminum Oxide)
Aluminum oxide (Al₂O₃, alumina, α-phase corundum) is the global oxide-ceramic workhorse — 140 million t/yr global supply, ~85% used as Bayer-process metallurgical-grade feedstock for primary aluminum electrolysis. Higher-spec grades serve technical ceramics, refractory shapes, polishing slurry, adsorbent / catalyst support, and LED-sapphire / Li-ion-battery-separator / IGBT-substrate applications.
Key Properties at a Glance
| Product Range | Metallurgical-grade (smelter feedstock) / Calcined (standard, low-soda, reactive, tabular) / Activated (adsorbent) / High-purity HPA (4N–5N) |
|---|---|
| Al₂O₃ Purity Range | ≥98.5% (metallurgical) → ≥99.999% (5N HPA) — 3 orders of magnitude span |
| Crystal Form | α-Al₂O₃ (corundum, calcined/HPA) / γ-Al₂O₃ + transition phases (activated) |
| Hardness | Mohs 9.0 / Knoop 1800–2100 HK (calcined α-phase) |
| BET Surface Area | 0.5–10 m²/g (calcined) / 60–80 m²/g (metallurgical) / 200–380 m²/g (activated) / 1–15 m²/g (HPA α-phase) |
| Particle Size Range | 50 nm (HPA sub-micron) → 110 μm (sandy metallurgical) → 30 μm (tabular calcined) |
| Price Range (CIF) | $400–600/t (metallurgical) → $20,000–80,000/t (HPA 4N–5N) — 150× span |
| Standards | GB/T 24487, 4983; ASTM E1019, E1086, C1042, D5095; ISO 1768, 8835-3, 16622; SEMI C2 (HPA) |
Range shown is category-wide; refer to individual grade COA for precise specs.
Featured Grades
Metallurgical-Grade Alumina (Smelter-Grade Alumina, SGA)
CAS 1344-28-1
Metallurgical-grade alumina (MGA or SGA — smelter-grade alumina) is the high-tonnage Bayer-process Al₂O₃ powder used as feedstock for primary aluminum electrolysis (Hall-Héroult process). Al₂O₃ content ≥98.5%, soda (Na₂O) 0.30–0.50%, with controlled particle size distribution (D50 80–110 μm, fines below 45 μm <12%) optimized for dry-scrubbing dissolution kinetics in the electrolytic cell. China is the world's largest MGA producer at 80+ million t/yr, with major capacity concentrated in Shanxi, Shandong, Henan (Sanmenxia), Guizhou, and Guangxi. Supplied bulk by rail/sea, 25 kg packaging is uncommon at this grade. Trade pricing follows the LME aluminum benchmark with a regional FOB adjustment.
Calcined Alumina (α-Al₂O₃ for Ceramics, Polishing, Refractory)
CAS 1344-28-1
Calcined alumina is metallurgical-grade Al₂O₃ further fired at 1100–1400°C to convert γ-Al₂O₃ into the thermodynamically stable α-phase corundum structure. The result is high-density hexagonal α-Al₂O₃ with low specific surface area (0.5–10 m²/g), ready for downstream sintering into technical-ceramic bodies, polishing applications, and high-purity refractory shapes. Calcined alumina splits into three sub-types by D50 controlled crystal size: standard calcined (D50 3–5 μm, ceramics filler), tabular alumina (sintered <30 μm crystals, refractory bricks), and reactive calcined (D50 0.5–2 μm, high-end ceramic sintering). Al₂O₃ purity 99.0–99.7%, soda (Na₂O) 0.05–0.30%.
Activated Alumina (Adsorbent, Desiccant, Catalyst Support)
CAS 1344-28-1
Activated alumina is a calcined-alumina precursor processed to retain a high-surface-area γ-Al₂O₃ / χ-Al₂O₃ / η-Al₂O₃ porous structure (BET 200–380 m²/g, pore volume 0.3–0.5 cm³/g) optimized for adsorption and catalyst-support applications. The hydroxyl-functional surface adsorbs polar molecules (H₂O, HCl, HF, organic peroxides) through Lewis-acid interaction — making it the workhorse desiccant for compressed-air systems, industrial gas drying, hydrogen-peroxide stabilization, fluoride removal from drinking water, and as catalyst support for Claus sulfur recovery and hydrocarbon reforming. Supplied in spherical bead (3–6 mm) or cylindrical pellet (3 × 6 mm) shapes; regenerable by heating to 200°C with dry air.