Coatings and ceramics
Development of advanced ceramics and coatings for structural and functional applications.
Research activities in this area are concerned with the development, understanding and evaluation of advanced ceramics and coatings.
The core activities focus on:
- characterisation and evaluation
- application areas.
Materials looks at bulk structural and functional ceramics, as well as coatings and modified surface layers, while processing is concerned with synthesis and densification of bulk ceramics, chemical and physical vapour deposition, in-liquid and electrolytic plasma processing, and thermal spraying.
Characterisation and evaluation relates to crystal structure, microstructure examination and chemical microanalysis; protective and functional properties of coatings and surface layers; and dielectric, piezoelectric and thermoelectric property measurements.
Application areas include thermally and chemically-resistant barrier coatings; wear, erosion and corrosion-resistant coatings; energy harvesting and conversion; and sensors and actuators.
Below are a series of examples of the work completed by researchers in this field:
Researchers at The University of Manchester, in collaboration with Central South University (CSU), China, have created a new kind of ceramic coating that could revolutionise hypersonic travel for air, space and defence purposes.
Hypersonic travel means moving at Mach five or above, which is at least five times faster than the speed of sound. When moving at such velocity the heat generated by air and gas in the atmosphere is extremely hot and can have a serious impact on an aircraft or projectile's structural integrity. That is because the temperatures hitting the aircraft can reach anywhere from 2,000 to 3,000 °C.
Oxidation and ablation
The structural problems are primarily caused by processes called oxidation and ablation. This is when extremely hot air and gas remove surface layers from the metallic materials of the aircraft or object travelling at such high speeds. To combat the problem materials called ultra-high temperature ceramics (UHTCs) are needed in aero-engines and hypersonic vehicles such as rockets, re-entry spacecraft and defence projectiles.
But at present even conventional UHTCs can't currently satisfy the associated ablation requirements of travelling at such extreme speeds and temperatures. However, the researchers at The University of Manchester and the Royce Institute, in collaboration with the Central South University of China, have designed and fabricated a new carbide coating that is vastly superior in resisting temperatures up to 3,000 °C, when compared to existing UHTCs.
New types of piezoelectric ceramic materials are required for use in ultrasonic transducers operating in high temperature environments, for example to monitor liquid flow and integrity of hot steel pipework in power stations. Our research is focused on polycrystalline ceramics prepared by combining two perovskite-type ferroelectric compounds, bismuth ferrite (BF) and barium titanate (BT), abbreviated as BF-BT.
We have found that these BF-BT ceramics develop a core-shell type microstructure (A) during high temperature processing, comprising BF-rich core and BT-rich shell regions. By utilising high energy X-ray diffraction (B), conducted at the UK's Diamond synchrotron facility, we have demonstrated that the electromechanical performance of these materials (C) is primarily associated with ferroelectric polarisation switching in the grain shell regions. This effect induces a squeezing action on the magnetic grain cores, resulting in unique multi-functionality that can potentially be applied in novel magneto-electric devices.
- Ilkan Calisir
- David Hall
- Yizhe Li