Calcined Aluminum Oxide vs. Fused Aluminum Oxide

Attribute	Calcined Aluminum Oxide	Fused Aluminum Oxide
Production Method	Calcination of aluminum oxide	Fusion of aluminum oxide
Hardness	High	Very high
Purity	High	High
Particle Shape	Irregular	Sharp-edged
Color	White	Dark gray

Introduction

Aluminum oxide, also known as alumina, is a versatile material used in a variety of applications, including abrasives, refractories, ceramics, and catalysts. Two common forms of aluminum oxide are calcined aluminum oxide and fused aluminum oxide. While both materials share some similarities, they also have distinct attributes that make them suitable for different purposes.

Production Process

Calcined aluminum oxide is produced by heating aluminum hydroxide to high temperatures, causing it to lose water molecules and undergo a phase transformation. This process results in a material with high purity and controlled particle size distribution. Fused aluminum oxide, on the other hand, is produced by melting alumina in an electric arc furnace and then cooling it down rapidly to form a solid material. This process leads to a material with high hardness and toughness.

Physical Properties

Calcined aluminum oxide typically has a higher purity level compared to fused aluminum oxide, making it suitable for applications where contamination is a concern. It also has a lower density and higher porosity, which can be advantageous in certain applications, such as catalyst supports. Fused aluminum oxide, on the other hand, has higher hardness and toughness, making it ideal for abrasive applications where wear resistance is crucial.

Particle Size and Shape

Calcined aluminum oxide is available in a wide range of particle sizes, from fine powders to coarse aggregates, depending on the specific application requirements. The particles are typically angular in shape, which can provide better cutting action in abrasive applications. Fused aluminum oxide, on the other hand, has a more uniform particle size distribution and a blocky shape, which can result in a more consistent finish in abrasive applications.

Chemical Composition

Calcined aluminum oxide is primarily composed of alpha alumina crystals, which are stable at high temperatures and resistant to thermal shock. This makes it suitable for use in refractory applications where high temperature resistance is required. Fused aluminum oxide, on the other hand, contains a mixture of alpha and beta alumina crystals, which can provide a balance of hardness and toughness in abrasive applications.

Applications

• Calcined aluminum oxide is commonly used as a raw material in the production of ceramics, where its high purity and controlled particle size distribution are beneficial.
• Fused aluminum oxide is widely used in abrasive applications, such as grinding wheels, sandpaper, and cutting tools, where its high hardness and toughness are essential.
• Calcined aluminum oxide is also used as a catalyst support in the petrochemical industry, where its high surface area and porosity can enhance catalytic activity.
• Fused aluminum oxide is used in refractory applications, such as lining for furnaces and kilns, where its high temperature resistance is critical.

Conclusion

While both calcined aluminum oxide and fused aluminum oxide are forms of alumina, they have distinct attributes that make them suitable for different applications. Calcined aluminum oxide is known for its high purity and controlled particle size distribution, making it ideal for ceramics and catalyst supports. Fused aluminum oxide, on the other hand, is valued for its high hardness and toughness, making it essential for abrasive applications. Understanding the differences between these two materials can help in selecting the right material for a specific application.