Zirconia Toughened Alumina – Enhanced Strength for Industrial Excellence
Zirconia Toughened Alumina (ZTA) is an exceptional ceramic, distinguished by high toughness and fracture resistance due to yttria stabilized zirconia particles dispersed through an alumina matrix.
This material can withstand rapid temperature changes without cracking or breaking, resists chemical corrosion and offers excellent thermal shock resistance.
Excellent Corrosion Resistance
ZTA ceramics offer an ideal balance between strength and value, being stronger than alumina products but less costly than pure zirconia. Their mechanical properties – fracture toughness, flexural strength and hardness as well as thermal shock resistance – make them suitable for making industrial tools like cutting wheels.
ZTA achieves its superior properties due to the addition of yttria stabilized zirconia (YSZ) particles within an alumina matrix. When dispersed evenly throughout, YSZ helps optimise both hardness-fracture toughness and tensile strength of both elements resulting in exceptional wear resistance, chemical inertness at room temperature and hot hardness/rapture strength properties for an exceptional ceramic material.
ZTA products’ mechanical properties depend heavily on their processing routes for producing powders, including heat treatments, calcination methods, drying techniques and sintering processes as well as tailored shaping with additives added during production. All these factors have an immediate effect on their strength, elasticity and hardness properties.
Excellent Thermal Shock Resistance
ZTA ceramics offer excellent thermal shock resistance, making them an excellent choice for aerospace applications that demand high levels of strength, toughness, and chemical inertness. When dispersed uniformly within an alumina matrix YSZ can be optimized. One such transformation-toughened zirconia-alumina ceramic that we offer is BIOLOX delta which can be found used for orthopedais load-bearing components like hip replacements.
Stress-induced transformation from metastable tetragonal to monoclinic structure of YSZ produces volume expansion and shear strain that counter crack propagation, increasing fracture toughness while simultaneously improving flexural strength. Performance of such an alumina-YSZ transformation-toughened ceramic is dependent upon processing conditions as well as on its stoichiometry of constituent oxides in the sintering process.
Poorly controlled sintering conditions may result in low flexural strength and poor homogeneity of an alumina-YSZ matrix, potentially due to air entrapment or particle agglomeration. By adding additives such as yttria or magnesium oxides, one may reduce tetragonal to monoclinic transformation temperature and enhance zirconia’s sintering properties.
Excellent Wear Resistance
ZTA not only excels in terms of thermal shock resistance and corrosion resistance, but is also highly wear resistant due to its tetragonal-monclinic phase transformation encasing mechanism. Furthermore, in vitro studies have revealed that ZTA components are less prone to hydrothermal degradation – something of major significance in hip replacement femoral head and cup ceramics (such as BIOLOX delta produced by CeramTec).
Simulated wear tests performed on ZTA components made of alumina-zirconia composite materials have produced impressive results in terms of wear resistance, flexural strength and hardness. ZTA samples exposed to multiple cycles in the hip simulator showed minimal degradation with significantly lower surface roughness than monolithic zirconia components.
ZTA components have proven suitable for demanding applications in automotive manufacturing (hot and cold forming tooling, can-closure rollers and capstans); energy industry (bearings, orifice inserts and vortex finders); food processing (homogenizing pump parts); and energy industry. Their mechanical properties depend on many variables: preparation routes used to prepare powders; drying methods employed during calcination; shaping techniques adopted during sintering techniques; tailored shaping; additives added and particle size distribution among others.
Excellent Strength
ZTA ceramics use stress-induced transformation to integrate zirconia into an alumina matrix, increasing strength and durability over time. This makes ZTA an excellent ceramic solution for industrial applications requiring toughness, high corrosion resistance, thermal shock tolerance and thermal shock tolerance.
Under strain, tetragonal metastable precipitates in cubic alumina undergo an abrupt transformation into monoclinic particles which increase its fracture toughness by creating compressive surface layers that adhere to cracks within its matrix.
Transformation toughening is a phenomenon known as fracture toughening, wherein increased fracture toughness of alumina results in shorter crack length, less crack blunting, and improved interactions with preexisting microcracks. This allows hard-on-hard and hard-on-soft bearing combinations which are used in modern medical-grade ceramics such as hip replacements. Furthermore, Yttrium stabilized zirconia implants known as y-TZP provide protection from wear over time.