Advanced Toughness for Industrial Applications
Zirconia Toughened Alumina (ZTA) ceramic components combine the hardness and strength of alumina with zirconia’s superior fracture toughness to deliver performance and longevity for industrial applications.
Stress-induced transformation of fine tetragonal zirconia particles embedded within an alumina matrix leads to ZTA materials with superior strength and toughness, suitable for use in various harsh environments.
Toughness
ZTA materials combine the hardness of alumina with zirconia’s toughness for unparalleled resistance to wear and abrasion. This effect is made possible through stress-induced transformation toughening: when stressed, zirconia particles transition from their metastable tetragonal phase into stable monoclinic form; volume expansion caused by this structural change helps close any cracks within an alumina matrix and increase toughness significantly.
ZTA contains zirconia platelets that nucleate into an alumina matrix during sintering, improving fracture toughness and strength while increasing fracture toughness, creating a material with greater flexural strength than Y-TZP and up to twice its cyclic fatigue strength. This combination of toughness from alumina combined with zirconia strength makes ZTA an excellent material choice for industrial applications requiring damage resistance.
Durability
Zirconia Toughened Alumina (ZTA) boasts outstanding flexural and compressive strengths, with low thermal expansion equivalent to that of alumina and outstanding wear resistance properties.
Zirconia toughened alumina is created by adding tetragonal zirconia grains via stress-induced transformation to a hard alumina matrix, encasing them into its structure while restricting their transformation to local areas instead of spreading throughout.
This mechanism makes alumina-zirconia composites far more durable than monolithic zirconia due to their resistance to water absorption through chemisorption; monolithic zirconia can absorb polar water molecules which lead to low temperature degradation and eventually breakdown after long term usage.
ZTA, on the other hand, is specifically engineered to facilitate this tetragonal-to-monoclinic transformation through structural features and chemical additives. CeramTec markets Biolox Delta ZTA as an example; this formulation contains yttria and strontium aluminate to facilitate toughening mechanisms within its zirconia phase and consequently has less risk of low temperature degradation while withstanding high temperature environments.
Corrosion Resistance
ZTA ceramics offer superior corrosion resistance over their alumina counterparts and can therefore be used in equipment subject to harsh environments. Furthermore, ZTA can withstand higher temperatures while offering greater chemical stability.
Garvie et al (1975) demonstrated that adding 10-20% unstabilized zirconia can greatly enhance toughness compared to alumina, through transformation toughening. This process occurs when finely dispersed tetragonal metastable precipitates change into monoclinic zirconia under stress causing volume expansion that compresses cracks and slows or stops their propagation.
This mechanism resembles that of deformation-induced stresses; however, in order to cause phase changes the stress field must be large enough; for cracks in ZTA specimens this energy comes from bending stresses at fracture sites.
Heat Resistance
Zirconia Toughened Alumina boasts an exceptionally high melting point and corrosion resistance, making it the ideal material for equipment frequently exposed to high temperatures. Furthermore, this variant has greater friction-resistance than standard alumina, helping reduce wear-and-tear on equipment exposed to higher levels of kinetic energy.
ZTA ceramics are created through stress-induced transformation of tetragonal zirconia particles into an alumina matrix, creating compressive stresses within them that prevent crack propagation, increasing both strength and toughness while providing thermal shock resistance without fracture or cracking. They boast excellent thermal shock resistance; resisting rapid changes in temperature without fracture or cracking under stress.
Zirconia-toughened alumina has many uses across multiple industries due to its vast set of properties. Mechanical engineering uses it for pump components and seals; semiconductor processing utilizes it due to its thermal stability and strength; aerospace, automotive and power industries utilize it as engine parts due to its resistance against corrosion and harsh chemicals; it can even withstand high flexural strengths for dental implants!