Uses for advanced ceramics
Advanced ceramics have an amazing range of properties and uses. They can be designed and engineered to solve just about any problem or challenge we face.
O-Sialon research at IRL
In this video, Dr Ian Brown explains how his materials research team at IRL developed an oxygen-rich sialon called O-Sialon. The excellent thermal shock resistance properties allied to high oxidation resistance have resulted in this advanced ceramic being used to fabricate refractories for use in the aluminium industry.
The discovery of electricity, early advances in chemistry, the invention of the automobile and the artificial production of certain types of gemstones all played a role in the development of advanced ceramics.
Advanced ceramics enhance our lives by their constant usefulness. They play a critical role in electronics, telecommunications, manufacturing, transportation, medicine, defence and space exploration.
Defining ceramics
Dr Ian Brown, a senior research scientist with Industrial Research Limited, explains how the term ‘ceramics’ now has a more expansive meaning. Traditional ceramics are clay-based, but high-performance or advanced ceramics are being developed from a far wider range of inorganic non-metal materials. Advanced ceramics have the properties of high strength, high hardness, high durability and high toughness.
Sialons and the New Zealand connection
Sialons – based on the elements silicon (Si), aluminium (Al), oxygen (O) and nitrogen (N) – are a new family of ceramic materials.
The presence of nitrogen in the chemical structure of the ceramic is what makes the difference in terms of the properties the sialons show. Some have high thermal resistance, some have extreme hardness and others have extreme toughness.
Researchers like Ian Brown working at Industrial Research Limited (IRL) in Wellington have developed oxygen-enriched sialons called O-Sialons. These are made by combining clay, silica sand and silicon metal to create a plastic mix that can be shaped to order.
O-Sialon production
This interactive shows the process of creating an advanced ceramic, O-Sialon, in the laboratory.
O-Sialons have excellent thermal shock resistance and can withstand rapid heating to high temperatures followed by rapid cooling over many cycles with little structural damage. These properties have led to its use in the construction of pipes, tubes and conduits to contain and channel non-ferrous molten metals like aluminium and its alloys.
Boron carbide and body armour
The high degree of hardness of some advanced ceramics is put to use in the design of body armour used by soldiers and police officers.
One type of body armour uses the extremely hard ceramic known as boron carbide (B4C).
The ceramic is bonded onto a plate of fibreglass. When a bullet strikes the ceramic plate, the bullet shatters into little pieces. The ceramic also shatters near where the bullet hits but the fibreglass backing catches the fragments of bullet and ceramic.
The person wearing the armour may receive bruising, but at least the bullet did not penetrate and potentially kill the wearer.
Alumina and electronics
The largest market for advanced ceramics is in the electronics industry.
Ceramics can display a range of electrical properties from insulators to resistors to semiconductors.
The large ceramic insulators that hold the high-voltage electrical transmission wires are made of alumina (Al2O3).
Ceramic insulators like alumina are also very good heat conductors.
Ceramic insulators like alumina are also very good heat conductors. They can be used as backing material or mounting brackets to which other electrical components are attached, for example, the electronic systems in a modern car are mounted on alumina.
When the electronics unit is working, it generates heat and the alumina backing conducts the heat away. This allows the electronic systems to function efficiently.
Ceramic high-temperature superconductors
Researchers based at Industrial Research Limited in Wellington have developed a superconducting ceramic known as BSCCO (pronounced ‘bisco’) based on the elements bismuth, strontium, calcium, copper and oxygen.
High-temperature superconductivity wire
Scientists at IRL in Wellington have developed a high-temperature superconducting ceramic that can be fabricated into a wire. This wire is now in commercial production with American Superconductor Corporation.
This ceramic is splatter-coated onto a nickel/tungsten alloy tape. On reducing the temperature of the ceramic to -170°C (liquid nitrogen boils at -196°C), the electrical resistance drops to close to 0. Not only does it increase the capacity of the ceramic to carry much higher electric currents but also it does so with very low energy losses.
The tape can then be used in the production of high-field electromagnets such as those used in hospital imaging devices like PET and MRI scanners. By moving from expensive liquid helium to cheaper liquid nitrogen as the coolant, considerable running cost savings can be made.
Superconductors and high-temperature superconductors
In this video, Dr Nick Strickland, a research scientist at IRL, describes the shift that has occurred in the superconductor field from using metal and alloy superconductors that need to be cooled to 4 K to new ceramic superconductors that operate at higher temperatures.
Ceramic magnets
Ceramic materials can also be magnetic. Magnetic ceramics are widely used. Some types can be permanently magnetised, and these find use in motors for electric toothbrushes and knives, speakers, all of the motors that power the accessories in a car such as electric windows, windscreen wipers and household magnets. A common type of ceramic magnet is composed of strontium and iron oxides.
Other types can be magnetised and demagnetised readily, and these are used in television, radio, communication systems and electronic ignition systems.
Household magnet applications can be found in the:
garden – lawn mower, trimmers
workshop – electric drill, circular saw
garage – door opener, freezer, car
laundry – clothes dryer, washing machine
kitchen – microwave, dishwasher, fridge
office – computer, printer, telephone
lounge – TV, DVD player, sound system
bathroom – electric shaver, hair dryer.
Ceramics and the space shuttle
The friction of the atmosphere on the space shuttle during ascent into space and on re-entry generates very high temperatures on its outer surfaces. To protect the space shuttle, the outer surface is covered with more than 27,000 ceramic tiles that act as a thermal barrier.
Suburban homes
Ceramic magnets are used in many of the household appliances found in a typical suburban home.
The tiles are made of silica fibres that have been bonded together to form an open mesh structure. As a result, they are very lightweight and have excellent thermal insulation properties. The tiles vary in thickness, and each is given a code number so that, if one is lost on a mission, an exact replacement can be produced and fitted in the correct place.
Professor Susan Krumdieck from the University of Canterbury is helping to develop new materials for possible future hypersonic vehicles.
Nature of science
The world we live in is understandable. As the breadth of our knowledge expands, so does the depth of our understanding. Advances in ceramics serve to illustrate this point.
Related content
Explore what are ceramics and then find out more about how oxides and nitrides are used in the formation of advanced ceramics. The article Temperature – the highs and lows helps explain the importance of temperature in creating advanced ceramic materials.
Activity ideas
Try these activities with your students:
Sialons – Ian Brown video clips: watch videos of Dr Ian Brown talking about sialons and then answer a series of graded questions related to the content.
Investigating temperature: view the interactive Temperature – the hot and the cold and participate in a class discussion.
Liquid nitrogen demonstrations: observe a teacher demonstrating changes in the properties of common substances when cooled with liquid nitrogen.
