What is the Difference Between Zirconia and Aluminum Oxide?

Zirconia and aluminum oxide are two common types of abrasives used in sanding materials. They have different properties and are suited for different applications. Here are the main differences between the two:

1. Composition: Zirconia is a crystallized version of aluminum oxide and is considered a coarser material. Zirconia alumina is the result of aluminum oxide and zirconium dioxide.
2. Hardness: Zirconia is more rigid than aluminum oxide and can withstand incredibly strong loads. It has a Mohs hardness of 6.5, making it harder than aluminum oxide but softer than corundum and hardened steel.
3. Lifespan: Zirconia usually lasts longer than aluminum oxide due to its solid structure and ability to self-sharpen with repeated use.
4. Color: Zirconia comes in a green or blue color, while aluminum oxide typically has a pink or white color.
5. Application: Zirconia is best suited for grinding down medium-to-coarse materials and is often used in foundry or casting due to its heat-resistant properties. It performs best in high-pressure environments and is ideal for working with hard materials like metals and high-pressure jobs that require a lot of heat. In contrast, aluminum oxide is suitable for softer materials like wood, painted wood, and delicate surfaces.
6. Sanding: While aluminum oxide can be used for both wet and dry sanding, zirconia is best used for wet sanding. Zirconia is not recommended for polishing surfaces due to its density.

In summary, zirconia is more rigid, long-lasting, and suitable for harder materials and high-pressure jobs, while aluminum oxide is more versatile and suitable for softer materials and delicate surfaces. The choice between the two depends on the specific application and the materials being worked on.

Comparative Table: Zirconia vs Aluminum Oxide

Here is a table comparing the differences between zirconia and aluminum oxide:

Some notable differences between zirconia and aluminum oxide include:

• Hardness: Zirconia is harder than aluminum oxide, with a Knoop hardness ranging from 1210 to 1300, while aluminum oxide has a Knoop hardness ranging from 960 to 1660.
• Density: Zirconia has a higher density (5.7 - 6.0 g/cm³) compared to aluminum oxide (3.4 - 4.1 g/cm³).
• Compressive Strength: Zirconia has a higher compressive strength (1260 - 3080 MPa) than aluminum oxide (1920 - 2750 MPa).
• Flexural Strength: Zirconia has a higher flexural strength (630 - 970 MPa) than aluminum oxide (260 - 430 MPa).
• Tensile Strength: Zirconia has a higher tensile strength (410 - 450 MPa) than aluminum oxide (210 - 290 MPa).
• Maximum Temperature: Zirconia can withstand higher temperatures than aluminum oxide, with a maximum temperature of 500°C.

In terms of applications, zirconia is often used in foundries and casting due to its heat-resistant properties and is suitable for grinding down medium-to-coarse materials. Aluminum oxide is commonly used for large-scale metal and woodworking applications, such as sandpaper for finishing and grinding various materials.