SUOYI Alumina Ceramic Powder Mainstream Preparation Process

SUOYI Alumina Ceramic Powder Mainstream Preparation Process

The mainstream preparation processes for alumina ceramic powder are classified into four main categories based on raw material routes: industrial bauxite method, high-purity aluminum hydroxide calcination method, aluminum salt chemical precipitation method, and alkoxide hydrolysis method. The ceramic industry primarily uses the first two for mass production.

1. Bauxite Sintering Method (Common low-cost process for 85% and 95% ceramic powder)

1.1 Raw Materials: High-alumina bauxite + calcium carbonate, talc, quartz, and other sintering aids;

1.2 Process: Batching → Wet ball milling → Spray drying → High-temperature pre-firing (1250～1350℃) → Crushing and ultrafine grinding → Iron removal → Sieving of finished product;

1.3 Characteristics: Low cost, relatively high impurities, specifically for 85% and 95% ordinary industrial ceramic powder, not suitable for high-purity 99% ceramic powder.

2. Industrial Aluminum Hydroxide Calcination Method (Mainstream Process for 95% and 99% Ceramic Porcelain)

2.1 Calcination Phase Inversion Principle
Industrial aluminum hydroxide: γ-alumina (high activity, porous) → α-alumina (corundum phase, crystal form for ceramics).

2.2 Process Flow
High-purity aluminum hydroxide → Calcination to generate α-Al₂O₃ → Addition of ceramic additives such as MgO, SiO₂, and CaO → Wet sand milling for ultrafine processing → Iron removal → Spray granulation/dry powder dispersion → Graded discharge

- Low-temperature calcination: Activated alumina, used for refractory and adsorption applications;

- High-temperature calcination: α-phase corundum powder, core raw material for 95% and 99% ceramic powder;

- Advantages: Easy composition control, low iron and sodium impurities, good sintering stability.

3. High-purity aluminum salt chemical precipitation method (99.5% or higher high-purity ultrafine ceramic powder)

3.1 Raw materials: Aluminum sulfate/aluminum chloride + ammonium bicarbonate/ammonia water;

3.2 Process: Preparation of aluminum salt solution → Neutralization and precipitation of aluminum hydroxide → Washing and impurity removal (removal of sodium and sulfate ions) → Drying → High-temperature calcination → Ultrafine grinding;

3.3 Advantages: Purity can reach over 99.9%, fine particle size, and uniform particle size;

3.4 Applications: Ultrafine ceramic powder for electronic substrates, transparent alumina, and medical precision ceramics; production cost is relatively high.

4. Aluminum isopropoxide alkoxide hydrolysis method (nano-high-purity Alumina Powder, high-end special ceramics)

4.1 Aluminum alkoxides hydrolyze in water to generate aluminum hydroxide precursors;

4.2 Low-temperature calcination yields nano-α-Al₂O₃;

4.3 Mostly used for casting ultrathin substrates and advanced electronic ceramics; highest cost.

5. Post-processing and Modification of Porcelain Powder (Finished Product Finishing)
Regardless of the precursor powder formulation, the finished porcelain powder undergoes secondary processing as needed:

5.1 Dry/Wet Ultrafine Grinding: Controlling D50 to 0.3–3 μm;

5.2 Spray Granulation: Forming spherical particles suitable for dry pressing;

5.3 Iron Removal and Magnetic Separation: Removing fine iron powder to prevent black spots during firing;

5.4 Formula Premixing: Uniformly mixing additives and alumina, eliminating the need for ceramic factories to prepare their own materials.

- 85/Ordinary 95 Porcelain Powder: Bauxite formulation sintering method

- General 95/99 Industrial Porcelain Powder: High-temperature calcination of aluminum hydroxide + additive compounding

- High-purity 99.5+ Precision Porcelain Powder: Chemical precipitation method

- Nano High-end Special Porcelain: Alkyl salt hydrolysis method