Composite Ceramics has prized the regime of material science with overwhelming advancements. Zirconia toughened Alumina and Alumina toughened Zirconia are two composite ceramics that offer goodness of Zirconia and Alumina. The article given below lists out all the major differences between Zirconia Toughened Alumina and Alumina Toughened Zirconia as ceramic.
Zirconia and Aluminum Oxide: An Overview
Alumina and Zirconia are the two most common ceramic used in engineering. Alumina is known for its good thermal conductivity and holds excellent hardness. Zirconia is known for its excellent toughness and thermal resistance. The toughness and thermal resistance of Zirconia offers mechanical resilience obtained at high temperature and higher stress.
Zirconia and Zirconia ceramic Properties (ZrO2)
Zirconium Oxide sometime known as Zirconia is generally found in white crystalline form known as Baddeleyite. It is one among the most studied ceramic and has monoclinic form. Zirconia also exhibits transition into tetragonal and cubic form at higher operating temperature. Zirconia undergoes stabilization when added with different compounds such as Yttria, this will retard the changes in forms.
The main uses of Zirconia are in the manufacturing of hard ceramics as they form refractory material, abrasives and enamels. They also form dental elements due to its biocompatible nature. Stabilized Zirconia are often used in oxygen sensors and fuel cells. They have high ionic conductivity and is successfully employed in electro ceramics
The properties of ceramic zirconia are listed here
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PROPERTIES |
UNITS |
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Zirconia Density |
5.7 g/cc |
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Zirconia Hardness |
13 G Pa |
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Zirconia thermal conductivity |
3 W/Mk |
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Zirconia Coefficient of thermal Expansion |
10 X 10-6 (1/C) |
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Zirconia Shock Resistance |
250 degC |
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Flexural Strength |
1000 MPa |
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Compressive Strength |
2000 MPa |
Alumina Ceramic and Alumina Ceramic Properties (Al2O3)
rAlumina or Aluminum Oxide is also called as Aloxide and Alundum. Aluminum oxide is one among the best electrical insulator offering higher thermal conductivity. It is generally Insoluble in water and is commonly found in Crystalline form known as Corundum. It offers excellent biocompatibility and inertness which makes them ideal for medical devices.
Alumina exhibits high hardness, wear resistance and resistance to lower erosion situations. High temperature resistance, Thermal stability and good thermal conductivity are other additive benefits of using Alumina Ceramic. Alumina ceramic is often suitable for high temperature application such as thermocouple in reactors or heating systems.
The properties of ceramic Alumina are listed here:
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PROPERTIES |
UNITS |
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Alumina Density |
3.72 g/cc |
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Alumina Hardness |
1100 Kg/mm2 |
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Alumina thermal conductivity |
25 W/Mk |
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Alumina Coefficient of thermal Expansion |
8.2 X 10-6 (1/C) |
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Alumina Specific Heat Capacity |
880 J/KgK |
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Flexural Strength |
345 MPa |
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Compressive Strength |
2100 MPa |
Zirconia Vs Aluminum Oxide
The below given table highlights a comparison between the two elements used in ZTA and ATZ.
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Property |
Alumina |
Zirconia |
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Chemical Composition |
(Al2O3) |
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Thermal Properties |
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Mechanical Properties |
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|
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Chemical Resistance |
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Economics |
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Zirconia Toughened Alumina (Al2O3-ZrO2)
Zirconia toughened Alumina as the name suggests is a combination of Zirconia and Alumina. Zirconia is the oxide of Zircon that is present in 1/5th or 1/10th in the material Zirconia Toughened Alumina. ZTA products are generally durable and stronger than Alumina and incur a cost lesser than Pure zirconia metal.
Zirconia Alumina is basically used in applications where structural merits are expected since they impart stability, hardness and wear resistance. Zirconia Alumina has many material advantages that include a working temperature of 1500 degC. Zirconia Alumina has higher fracture toughness, excellent bending strength and has an increased tolerance to ageing because of hydrothermal aspects. They are sintered and hot isostatic pressed to ensure Zirconia Alumina brings reliability to the applications they are subjected to.
Properties of Zirconia Toughened Alumina
The properties of Zirconia toughened Alumina has a significant contribution to the nature and functionality of the material. The mechanical strength of Zirconia Alumina is a result of the metastable tetragonal phase of the grains that are formed. The common specimen of the ZTA formed will have a percent of 10 – 20 percent of ZrO2. The percent of ZrO2 is the deciding factor when it comes to using the ZTA in variety of applications.
ZTA is priced in between Alumina and Zirconia as the geometry is considered in between Alumina and Zirconia Ceramic. Hence the cost of Zirconia Alumina is very much lower than that of Pure Zirconia and Alumina. The strength of the composite is increased by a process called as Stress induced transformation for toughening the composite.
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PROPERTIES |
VALUE |
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Density |
4.1 – 4.38 g/cm3 |
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Hardness |
1750 – 2100 Knoop |
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Elasticity |
45 – 49 x106 Psi |
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Thermal Expansion |
8.1 x10-6 1/c |
|
Poisson’s Ratio |
0.26 |
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Flexural Strength |
130 KSi |
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Thermal Conductivity |
20 – 21 W/Mk |
|
Compressive Strength |
2500 – 3000 MPa |
|
Vickers Hardness |
16 – 21.5 GPa |
|
Dielectric Strength |
16 KV/mm |
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Volume Resistivity |
>1016 Ohm-cm |
Applications of Zirconia Toughened Alumina
The applications of Zirconia Toughened Alumina are given for reference below:
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Threads, Wire gauges and Metal rollers for industrial use
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Extrusion dies made up of Metal
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Material for valve and valve seats for durable application in the industry.
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Used for making abrasion resistant Nozzles
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Used for making pumping elements that can be employed in ultra-high-pressure applications
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Used as the make material for ball valves and seats in the line conveying abrasive fluids or high flow materials.
Alumina Toughened Zirconia
Alumina Toughened Zirconia (ATZ) is a ceramic compositive with impeccable hardness, strength, wear and tear resistance and corrosion resistance. ATZ is majorly formed by conventional isostatic Pressing to increase is the reliability on the mechanical properties of the material. Alumina Toughened Zirconia is generally damage tolerant than that of Zirconia. Alumina Zirconia is generally included in a set of composites known as AZ composites.
Properties of Alumina Toughened Zirconia
Alumina toughened Zirconia functions at an operating temperature of 1500 degC. It has high wear resistance, chemical inertness and extreme fracture toughness. It offers higher strength when compared to pure zirconia.
|
PROPERTIES |
VALUE |
|
Density |
5.5 g/cm3 |
|
Hardness |
14 GPa |
|
Elasticity |
45 – 49 x106 Psi |
|
Poisson’s Ratio |
0.23 |
|
Flexural Strength |
1800 KSi |
|
Thermal Conductivity |
6 W/Mk |
|
Compressive Strength |
2500 MPa |
|
Youngs Modulus |
340 GPa |
|
Dielectric Strength |
25 KV/mm |
|
Volume Resistivity |
>1016 Ohm-cm |
Properties of Alumina Zirconia
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Alumina Zirconia is used in high pressure equipment such as valves and valve seats
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Alumina Zirconia is used as metal forming rollers and guides
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They are used in shaft bearings and bushing material.
Zirconia Toughened Alumina Vs Alumina Toughened Zirconia
Zirconia Alumina and Alumina zirconia are composite ceramic made up of Zirconia and Alumina. Zirconia Imparts the property of partial stabilization at its tetragonal phase and Alumina imparts moderate toughness. The combination of Alumina and Zirconia helps in retaining properties of higher hardness and good strength. It also imparts the resistance to degradation at low temperature.
In Zirconia Alumina Ceramic, Zirconia makes the toughening phase and the matrix phase are made up by Alumina. The Zirconia Alumina is made by adding un-stabilized zirconia to Alumina to impart properties of higher fracture toughness. This is the result of the interaction between the crack front and the second phase. Zirconia Toughened Alumina is used in applications such as Arthroplasty due to its enhanced properties.
Alumina Toughened Zirconia, on the other hand has Alumina as the toughening phase and Zirconia in the matrix phase. The composite is generally manufactured by adding Alumina to Zirconia to obtain a ceramic material that has high toughness. The Ceramic Alumina Zirconia is more durable than that of Pure Zirconia.
Benefits of Zirconia Alumina and Alumina Zirconia
The high Strength and fracture toughness of Alumina Zirconia makes it suitable for applications such as dental implants. They are also suited as orthopedic implants due to its superior biocompatibility
Alumina Zirconia or Zirconia Alumina both can be prepared in nano or microscale. The percent of Zirconia and Alumina is adjusted accordingly depending upon the demand and the application. The composite such as Alumina Zirconia or Zirconia Alumina are more advantageous than stabilized zirconia. They offer variety of properties when compared with Partially stabilized Zirconia and Yttrium Stabilized Zirconia.
Alumina Zirconia and Zirconia Alumina resists degradation at lower temperature of operation. They also offer higher strength and high fracture toughness. The fatigue strength of these ceramic composites is much better stabilized Zirconia or Yttrium Toughened Zirconia.
Bottom Line
Alumina Toughened Zirconia and Zirconia Toughened Alumina are two among the best composite ceramic with lot many benefits. The combination of the two different ceramic imparts superior properties in the final composite formed. However, the switching of phases has helped in bringing different set of properties to the ceramic formed.