Resources

Technical guides, selection tools, and answers to common questions about alumina products and applications.

Selection Guide

Match your application to the recommended product and grade. Contact us for custom formulations not covered here.

Application Product Recommended Grade Key Reason
Refractory castables (general) AF-C Calcined Alumina AF-C-1 / AF-C-2 Controlled particle size, good flow properties, consistent alpha phase
Refractory castables (low cement) AF-R Reactive Alumina AF-R-1 / AF-R-2 High green density, low water demand, bimodal packing
Refractory castables (extreme duty) AF-T Tabular Alumina AF-T-1 Best thermal shock resistance, dense aggregate, low porosity
Steel ladle linings AF-T Tabular Alumina AF-T-1 (K2–K4) Exceptional thermal shock resistance at ΔT > 1000°C
Slide gate plates AF-T Tabular Alumina AF-T-1 (K3/K4) High bulk density, low porosity, erosion-resistant
Technical ceramics (wear parts) AF-C Calcined Alumina AF-C-3 Fine D50 2–5 μm, high alpha, good sinterability
Electronic substrates AF-R Reactive Alumina AF-R-3 Ultra-fine D50 0.8–1.0 μm, high sintered density, low soda
Ballistic armor AF-R Reactive Alumina AF-R-2 / AF-R-3 High green density, bimodal packing, sintered density ≥ 3.87 g/cm³
Steel and stainless steel finishing AF-P Polishing Alumina AF-P-2 / AF-P-3 High alpha >97%, controlled D50 4–15 μm, balanced cut/polish
Metal surface lapping AF-P Polishing Alumina AF-P-3 / AF-P-4 Medium to high cut, stable PSD, consistent stock removal
Ceramic glazes AF-C Calcined Alumina AF-C-3 Fine particle size, consistent chemistry, good dispersion
Polishing compounds (solid bar) AF-P Polishing Alumina AF-P-1 / AF-P-2 Consistent batch quality, contamination-free, low Na₂O for sensitive alloys

Alumina Basics

Crystal Phases

Aluminum oxide (Al₂O₃) exists in several metastable transition phases (gamma, delta, theta) that convert irreversibly to alpha-alumina (corundum) upon heating above ~1100°C. Alpha is the only thermodynamically stable phase and is the form supplied in all commercial alumina products.

Key Properties

  • • Melting point: 2040–2072°C
  • • Hardness: 9 Mohs (second only to diamond)
  • • Density: 3.95–3.99 g/cm³ (theoretical)
  • • Thermal conductivity: ~30 W/(m·K) at 25°C
  • • Chemically inert, excellent dielectric properties

Production Routes

Bayer Process: Bauxite → Al(OH)₃ (gibbsite). This is the feedstock for all viseray products.

Calcination: Al(OH)₃ heated to 1100–1400°C → alpha-Al₂O₃ powder. Grinding and classification control particle size.

Sintering: Calcined alumina fired at ~1900°C → dense tabular alumina aggregates.

Electro-fusion: Calcined alumina melted in electric arc furnace at >2000°C → solidified, crushed, and graded into abrasive grits.

Packaging Guide

Paper Sacks

25 kg multi-wall paper sacks, stacked on 1000 kg pallets, stretch-wrapped. Standard for most powder products (AF-C, AF-R, AF-T fines, AF-P polishing grades). Moisture barrier liner included for reactive grades.

Big Bags (FIBC)

500 kg or 1000 kg flexible intermediate bulk containers with filling and discharge spouts. Standard for tabular alumina fractions and large-volume orders. UV-stabilized fabric for outdoor storage.

Bulk & Custom

Bulk tanker delivery for high-volume calcined alumina. Container liners for ocean freight of tabular alumina. Plastic drums for fine micro grits. Custom pallet configurations available.

Technical Data Sheets

Download detailed specifications, chemical composition, physical properties, and application notes for each product series.

AF-C Series

Calcined Alumina

Download PDF ↓

AF-R Series

Reactive Alumina

Download PDF ↓

AF-T Series

Tabular Alumina

Download PDF ↓

AF-P Series

Polishing Alumina

Download PDF ↓

Frequently Asked Questions

What is alpha-alumina (α-Al₂O₃)?
Alpha-alumina (corundum) is the most thermodynamically stable crystalline form of aluminum oxide. It has a hexagonal close-packed crystal structure and is the phase present in all viseray products. Alpha phase content determines high-temperature stability — higher alpha means less shrinkage during sintering or service at elevated temperatures.
What is BET surface area and why does it matter?
BET (Brunauer-Emmett-Teller) surface area, measured in m²/g, indicates the total surface area available per gram of powder. Higher BET means finer primary crystallites and higher reactivity/sinterability. For refractories, lower BET (0.5–2 m²/g) is preferred for reduced water demand. For advanced ceramics, higher BET (3–8 m²/g) enables lower sintering temperatures and higher final density.
What is D50 and how is it measured?
D50 is the median particle size — 50% of particles (by volume) are smaller than this value. It is measured by laser diffraction (Malvern or similar). D10 and D90 describe the width of the distribution: D10 is the 10th percentile, D90 the 90th. A narrow distribution (D90/D10 ratio < 5) gives more predictable packing and sintering behavior.
What is the difference between calcined, reactive, and tabular alumina?
Calcined alumina is produced by heating aluminum hydroxide to 1100–1400°C, yielding alpha-Al₂O₃ powder with D50 from 2 to 80 μm. Reactive alumina is ground finer (D50 0.8–2.5 μm) with higher BET for enhanced sintering. Tabular alumina is sintered at ~1900°C into dense, coarse aggregates (0–6 mm) — it is an aggregate product, not a powder, used primarily in refractory castables.
What is the difference between cut and polish in alumina polishing?
Cut is the ability to remove stock (material) from the workpiece. Polish is the ability to produce a smooth, glossy surface finish. These are opposing properties: high-cut grades have large primary crystals and hard agglomerates for aggressive stock removal but leave a matte finish; high-polish grades have fine primary crystals and soft agglomerates that break down quickly for buffing. The calcination degree determines primary crystal size: higher alpha-Al₂O₃ content = larger crystals = higher cut. ALTEO and viseray grade their polishing aluminas on a relative 1–10 cut/polish scale to help users match grades to their multi-stage polishing process.
What packaging options are available?
Standard packaging: 25 kg paper sacks on 1000 kg pallets (most powder products), 1000 kg big bags (all products), and plastic drums for fine micro grits. Bulk tanker delivery and container liners are available for large-volume orders. Moisture-barrier liners are standard for reactive alumina grades.
How do I request a sample or CoA?
Contact us at [email protected] with your target specification and application. We ship sample quantities (1–5 kg) within 5 business days. Every commercial shipment includes a Certificate of Analysis (CoA) with actual measured values for your batch.

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