Flash Sintering of Composite Ceramic Materials and Structures

Ceramic materials are used in a wide range of applications including motion sensors, for energy storage in electric vehicles, dental replacement, hip and knee implants, cutting blades, and body and vehicle armour. They are exceptionally durable, even at high temperatures and in corrosive environments, and can be reused or recycled at the end of their life. However the high cost of manufacturing is a major barrier to the use of ceramic materials. Producing a dense strong ceramic material with minimal porosity requires heating to very high temperatures well over 1000 deg.C typically for many hours.

Recently scientists have discovered that the temperature and duration of the ceramic densification process (sintering) can be significantly reduced by passing an electric field through the ceramic during the heating process. This "flash sintering" process, so-called because the material densifies extremely rapidly within a few seconds and often with the simultaneous emission of light, has potential to significantly reduce energy use in industrial-scale ceramic manufacturing and reduce emissions of greenhouse gases from the process by up to 40%. The flash sintering technique may revolutionise the ceramic manufacturing industry by reducing the cost and environmental impact of producing ceramic materials.

In this research project a detailed investigation of the flash sintering method will be undertaken to establish the viability of this technique for use with a wide range of ceramic materials and particularly to understand the underlying mechanisms which cause the flash sintering effect. A flexible flash sintering facility will be established which can be used to flash sinter a wide range of ceramic materials. Composite materials with varying electrical conductivity will be flash sintered under different conditions. The results will used to understand the effect of both the material properties and the variables involved in the process (e.g. electric field strength, current, voltage, and temperature) on the observed flash sintering behaviour. Materials will be characterised by measuring their density, imaging using scanning electron microscopy and mapping the chemical composition, and using X-ray diffraction to determine any changes to the phase composition of the materials caused by the flash sintering process. New insights will be gained by flash sintering for the first time a structure made of layers of ceramic composite materials graded by composition and examining how the flash sintering behaviour changes compared to samples containing each individual composition. The results of this project will be used by our industrial project partners Lucideon and Morgan Advanced Materials in the industrial development and application of flash sintering technology.

The use of flash sintering of ceramic materials in the ceramic manufacturing industry is currently limited by a lack of understanding of the underlying driving forces for the process across a range of materials. By conducting this in-depth investigation of the effect of composition-based bulk property variations on the efficacy of flash sintering in composite ceramic materials and structures, this project will result in increased understanding of the underlying mechanisms of flash sintering in ceramic materials. As a result this project will facilitate future efforts to tailor the composition of ceramics to enable flash sintering, and so directly contribute to the wider use of flash sintering technology in ceramic manufacturing.

The UK ceramics industry employs 20,000 people directly and has sales of £2bn per year. Ceramics are also essential supporting technology for industries such as steel and glass production, petrochemicals, and renewable electricity production and distribution. The reduced costs enabled by flash sintering will result in greater use of ceramic materials and components. This project is supported by Lucideon, an SME at the leading edge of industrial-scale developments in flash sintering technology, and Morgan Advanced Materials, one of the largest ceramic manufacturing companies in the world. For both these companies, the research proposed in this project will lead to new insights directly relevant to their ceramic manufacturing business. In addition to engaging with the project partners, the research team will communicate their findings to other companies within the ceramic supply chain through presentations at UK and international conferences, using a project website to disseminate research findings, and through the High Value Catapult (of which the host department is a Centre) who will showcase the technology developed in this project.

The adoption of flash sintering by the ceramic manufacturing industry will also reduce CO2 emissions, necessary for the UK's greenhouse gas emission reduction goal for the 2015 Paris Climate Agreement. Energy use in the industry would also be significantly reduced, estimated at around 40% for tile manufacturing, for example, lowering the cost of producing ceramic materials. As applications requiring ceramic materials include healthcare (dental and joint replacement) and defence (body and vehicle armour), not only are there positive implications for the ceramic manufacturing industry but also for patients of the NHS and soldiers serving in the UK Armed Forces, as the reduced costs may enable more widespread availability of lifesaving ceramic implants and armour.

Involvement in this project will benefit the research team by gaining technical experience in the flash sintering process and through the experience of interacting with industrial and academic partners and collaborators, presenting at national and international conferences, and writing technical documents including journal articles to disseminate the research findings. The research in this project will also be incorporated into the applicant's teaching on the undergraduate Engineering course and the MSc in Manufacturing Systems Engineering at the University of Warwick. Individual projects and internships (at Warwick or with SMEs) will be offered on flash sintering topics, encouraging more students to consider a future career in ceramic manufacturing and related sectors. MSc students studying Manufacturing Systems Management and Supply Chain Management will be recruited for projects on the Life Cycle Analysis of ceramics manufacturing using flash sintering. In addition, bespoke Outreach activities on ceramic materials manufacturing will be developed and delivered by the project team at science festivals and local schools. These educational activities will result in a greater number of students graduating with knowledge and experience relevant to the ceramic manufacturing industry.