If the test results are positive, it will be the first time in 25 years that a new coating mixture has been found on the basis of theoretical calculations.Werner Stamm and Arturo Flores Renteria, Power and Gas
The efficiency of a gas turbine can be increased by raising the combustion temperature. To withstand high temperatures, the blades are covered with a ceramic insulation layer. Werner Stamm and Arturo Flores Renteria, from Power and Gas, are employing a new research method to develop a thermal insulation layer that allows the blades to be used at even higher temperatures.
“Many researchers have spent years searching for a new composition of the thermal insulation layer of turbine blades so that they can withstand heat as high as the combustion temperature,” says Stamm. A look at the specific requirements the layer must fulfill demonstrates why this is such a difficult task: From a crystallographic point of view, the lattice structure of the ceramic material must be tetragonal so that it is neither too soft nor too brittle. The base compound nowadays consists primarily of zirconium oxide and yttrium oxide. This compound withstands temperatures of up to 1,200°C without any critical phase transformations occurring. Siemens wants to increase the efficiency of its gas turbines even further while keeping the costs for new developments at a bearable level. Stamm and Flores Renteria discussed this problem during one of their work meetings. They had the idea to first test new base compounds with the help of a special computer simulation before starting on the more complex lab experiments.
This is an entirely new approach to the problem – and there's a good reason for that: Calculating the interaction between a large number of atoms using quantum mechanics is such a complex matter that it far exceeds the capacity of today’s computers. Professor Jochen Schneider from the Chair of Materials Chemistry at RWTH Aachen University developed a model based on density functional theory that traces the behavior of a many-particle system by calculating the ground-state particle density. After initial talks with Professor Schneider, the three experts decided that they would become the first researchers ever to try out a computer simulation for this application.
Using the existing formula as a starting point, Stamm and Flores Renteria began making small adjustments. “Sometimes we replaced one element with another, at other times we changed the relation of the quantities,” Flores Renteria explains. They soon arrived at a formula that met the requirements in the simulation and had it patented. The next step is to carry out experiments in the lab, where they will find out whether the chemical composition will deliver in practice what it promises in theory.