Processing of Nanostructured Ceramics

The appeal of nanocrystalline ceramics arises from their potential to offer unusual physical and mechanical properties, which, depending on the material, can include superplasticity at elevated temperatures, optical transparency for normally opaque materials and a range of other electrical, optical and magnetic properties as well as potentially higher strengths, toughnesses and hardness.Although some commercial nanopowders are now produced in relatively large quantities, consolidation into dense nanostructured components by industrially-viable routes is needed to take full advantage of the potential offered. If this can be achieved there is the potential to use the materials for a very wide range of applications. Advanced ceramics are the active material in many electronics devices, fuel cells, magnets, sensors and biomaterials, as well as a very wide range of structural components. This means that they are used in almost every type of industry, including power generation, aerospace, transportation and military applications as well as in the manufacture of other materials. Such applications are vital to maintaining global competitiveness, decreasing energy consumption and minimising pollution. Their estimated world market was >$20B in 2000, with an annual growth rate of 7.2%. Of this, the electronics sector was ~65% of the market, the rest falling into the chemical processing, coatings and advanced structural mechanics sectors.The primary objective of this research proposal is to develop a number of recent developments at Loughborough Univ. that have been achieved under previous EPSRC grants. Specifically:* Whilst it is now possible to slip cast very homogeneous and high density compacts from nanosuspensions, there is currently a major problem with drying those made from high solids content suspensions (which yield the best bodies) - it can take several days even using a humidity drier. The structure of these bodies need understanding as a function of the processing conditions used, particularly the solids content of the suspension. This then gives us a chance to control the situation and perhaps improve it so that drying times can be much faster without sacrificing the properties of the body.* Similarly, it is now possible to dry press homogeneous and high density compacts from powders that have been formed by spray-freeze drying the nanosuspensions (the same process used to make instant coffee granules). Once again, however, the high solids content suspensions (which yield the highest densities) provide problems, this time with hard agglomerates that don't crush. Very similar work needs performing as above to allow us to understand why this is happening and what can be done about it.* Both types of compact need firing in furnaces to produce fully dense ceramics whilst retaining an extremely fine, sub 100 nm, average grain size. Whilst this can now also be done using a novel pressureless (and hence low cost) process, the understanding of how this process works is still not perfect and we also need to scale up to make larger components.* Finally, as we near the point where we can exploit these developments commercially, we really need to develop a better understanding of industry's requirements. Just how close are we to developing process routes that they can use on their factory floors? Which ceramic systems are they most interested in? Which companies are really ready to embrace the new 'nanotechnology' and which are keen to sit on the sidelines for a bit longer yet. These issues, and others, will all be addressed in the final task of the programme.