Calcined aluminum oxide powder, commonly known as alumina (Al₂O₃), is produced by heating aluminum hydroxide or other aluminum compounds at temperatures above 1,000 °C. This high-temperature treatment removes bound water and transforms the material into a crystalline form with superior hardness, thermal stability, and chemical inertness. As a result, calcined alumina serves as a cornerstone material in industries ranging from refractory linings to advanced ceramics.Get more news about Calcined Aluminum Oxide Powder,you can vist our website!
Production Process
The production of calcined alumina begins with the Bayer process, which refines bauxite ore into aluminum hydroxide. After purification, the hydroxide is subjected to controlled high-temperature calcination. Key steps include:
Drying at 100–200 °C to remove free moisture
Pre-heating at 400–600 °C to decompose organics
Calcination at 1,100–1,200 °C for phase transformation
Cooling under inert atmosphere to avoid moisture uptake
Precise temperature ramp rates and hold times determine the final phase composition, specific surface area, and particle morphology.
Material Properties
Calcined alumina exhibits a unique combination of properties:
Hardness: Mohs scale rating of 9, second only to diamond
Density: Typically 3.9–4.0 g/cm³ for α-phase alumina
Thermal Stability: Retains strength up to 1,800 °C
Chemical Resistance: Inert to most acids and alkalis
These characteristics stem from its tightly packed oxygen and aluminum lattice, which also imparts electrical insulation and excellent wear resistance.
Particle Characteristics Table
Below is a comparison of common grades of calcined alumina powder:
Grade Median Particle Size (µm) Surface Area (m²/g) Phase Purity (%) Typical Application
Coarse 40–80 0.5–1.0 95–97 Refractory castables
Standard 5–20 1.5–3.0 98–99 Ceramic substrates, abrasives
Fine 1–5 4.0–6.0 ≥99.5 Precision ceramics, polishing
Ultra-fine <1 8.0–12.0 ≥99.9 Electronic ceramics, catalysts
Key Industrial Applications
Calcined alumina powder finds its way into a spectrum of applications:
Refractories: High-temperature linings for furnaces and kilns
Ceramics: Substrates for electronic components, spark plugs, and cutting tools
Abrasives: Grinding wheels, sandpapers, and blast media
Catalysts and Supports: Substrate for petrochemical catalysts
Polishing Media: CMP (chemical-mechanical planarization) slurries for semiconductor wafers
Its versatility stems from the ability to tailor phase content and particle size to specific performance requirements.
Quality Control and Testing
Ensuring consistent performance requires rigorous quality control:
X-ray diffraction (XRD) to verify α-phase purity
Laser diffraction or BET analysis for particle sizing and surface area
Titration or ICP analysis for trace impurity levels (Si, Fe, Na, Ti)
Hardness and bulk density measurements
Manufacturers often adhere to ISO 9001 systems and industry-specific standards to guarantee batch-to-batch uniformity.
Environmental and Safety Considerations
While alumina is chemically inert, handling ultra-fine powders poses inhalation risks. Key safety measures include:
Local exhaust ventilation and high-efficiency particulate air (HEPA) filters
Personal protective equipment (PPE): respirators, gloves, and protective clothing
Dust suppression in bulk handling areas
From an environmental standpoint, energy consumption during calcination is significant. Advances in regenerative kilns and waste heat recovery systems help reduce the carbon footprint of production.
Future Trends and Innovations
Research continues to expand the horizons of calcined alumina powder:
Nano-engineered alumina with tailored morphologies for specialty catalysts
Surface-coated alumina for improved bonding in composites
Hybrid materials combining alumina with ceramics like silicon carbide for ultra-high-temperature applications
Digital control systems and machine-learning optimization of calcination recipes to lower energy use and improve yield
As new applications emerge, the demand for customized alumina grades with precise microstructures will only grow.
