Tuning of nanomaterials by high pressure annealing

One of the foundations of our modern world are highly functional materials. The importance of the control of the materials humans use is reflected in the fact that several historical periods refer to the use of the materials discovered and used: the stone age, bronze age, etc. Important in the development of materials and their applications is the control over the material to adapt it for use. The same is true for modern materials, but even today a large part of the material production consists of the base manufacturing (alloying, mixing,), modifying the initial structure (casting, forging, ) and a final adjustment step (quenching, annealing, ). For the latter, especially metals, often heat treatments are applied. There the factors adjusted for influencing the properties of the final substance are the annealing time, temperature and heating/cooling speeds. They need to be carefully chosen to adjust properties like strength and deformability as needed. In the last decades science gave mankind a new class of materials: nanostructured materials. As their name suggests, they have structures in the nanometer range (several hundreds of atom sizes). This results in unconventional properties and is very promising for applications. One way to produce bulk nanostructured materials is sever plastic deformation. It can be seen as forging on steroids deforming the initial sample to insane amounts while keeping a hydrostatic pressure in the sample. The process has already produced interesting results, for example for thermoeletric materials. These produce electric energy directly from heat, which allows to take the excess heat generated in nearly any process/machine and recover part of this, usually lost, energy. This increases the efficiency and ultimately benefiting the environment. How much of the heat is turned into electricity depends on the material and its structure. Nanostructuring of one type of thermoeletrica resulted the highest conversion rate so far allowing for application. Yet the efficiency can still be improved by rearranging the internals. Furthermore the thermal stability could be increased to widen the temperature range for application which also improves the amount of energy recovery. For both a proper heat treatment is a valid option. This project researches a new option for tempering, using also hydrostatic pressure to influence the processes during annealing. This gives one more control parameter ultimately increasing the possibilities to alter and use the material. A pilot study successful showed that this method will help keeping the nanostructure and thus its advanced properties. But before this can put to use first the fundamentals need to be determined in simple materials, our task for now. Yet we already know that the method has a real potential in further advancing the ability to create materials that will improve the world we live in.