Sunday, December 11, 2011

Zirconia Toughened Alumina

Zirconia aluminia (or zirconia toughened alumina), a combination of zirconium oxide and aluminum oxide, is part of a class of composite ceramics called AZ composites. Noted for their mechanical properties, AZ composites are commonly used in structural applications, as cutting tools, and in many medical applications. Additionally, AZ composites feature high strength, fracture toughness, elasticity, hardness, and wear resistance. Zirconia toughened alumina (ZTA), in particular, offers several key properties.

Zirconia Toughened Alumina (ZTA)

Zirconia toughened aluminum typically consists of alumina with a 10 to 20 percent zirconia concentration, which enhances the strength of the alumina. To achieve the increase in the composite’s strength, a process known as stress induced transformation toughening takes place. Stress induced transformation toughening results in uniform internal strain, which causes the zirconia structure to crack, and the zirconia particles to switch phases. Because of this phase switch, the amount of zirconia particles increases and creates stresses within the alumina’s structure. These stresses effectively heal the crack and block further cracking—the added zirconia doubles the composite’s strength and enhances toughness between two and four times.

Properties of ZTA

With increased strength and toughness as a result of stress induced transformation toughenening, ZTA also exhibits other notable properties. ZTA has good thermal traits, allowing the material to withstand high temperature applications without experiencing degradation. Additionally, ZTA has very good mechanical properties, and increased wear resistance when compared with alumina. ZTA also offers high corrosion-resistance.

Applications of ZTA

Because of ZTA’s diverse range of properties, it can be used in an array of applications. In the medical industry, ZTA serves as a ceramic that can be used in joint replacement and rehabilitation, where its wear-resistance helps create high-performance implants. Additionally, ZTA is often used in other load-bearing applications, as its high-strength and corrosion-resistance enable the material to withstand heavy loads without succumbing to degradation.

Cutting tools can also be manufactured from ZTA, which can then be used in metal-cutting applications. In order to produce effective cutting tools, ZTA must be manufactured through sintering and grinding, with the grinding process playing a key role in determining the surface characteristics of the blade.

Other applications of ZTA include pump components, such as seals, brushings and impellers, where the material’s corrosion-resistance is an important attribute. Valve seats and certain engine components can also be manufactured from ZTA, as can labware, industrial crucibles, and refractory tubes. Abrasive applications, such as sandblasting, also employ ZTA.

No comments:

Post a Comment