In light of ecological considerations and the growing shortage of raw materials, non-polluting automobiles are becoming the focus of increased attention. In particular, electric automobiles are moving into the limelight. But before electric automobiles can compete effectively with their combustion-powered counterparts, a number of scientific challenges must be overcome by developing new technologies. Scientists across different disciplines are tackling these hurdles and researching new methods for lightweight construction, energy storage and the components of the automotive electronics systems. The Steinbeis Research Center Material Engineering Center Saarland (MECS) is researching high-resolution methods for inspecting localized damage to electrical systems.
One of the challenges the automotive industry currently faces is controlling and switching electricity in automotive electronics systems. Hybrid and electric automobiles must be able to handle large amounts of energy at high densities, which is only possible with a battery of several hundred volts instead of the conventional 12 volts. This high voltage places the vehicle's power cables, plugs and switch contacts under an extreme load, which existing automobile components are unable to withstand. This is particularly problematic as automotive relays are often crucial safety components responsible for establishing electrical insulation in emergencies (by physically separating the switch contacts) to prevent electrical hazards. In the long term, the industry's challenge is to miniaturize these switch components, allowing a lightweight design.
During each switching operation, as in the case of a switching relay, an arc is generated as the result of a brief, sudden plasma discharge. These arcs have a temperature of around 6000 °C and thus cause irreversible local damage to the material and the specially optimized microstructure of the switch contacts – creating an electric discharge crater.
The components most affected by this are the contact materials responsible for establishing electrical contact. Together with factors like corrosion, mechanical stress and wear, these discharge bolts lead to irreversible failure of the switching devices in the long term.
To investigate this problem, the Steinbeis Research Center Material Engineering Center Saarland (MECS) in Saarbrücken, Germany, is using new high-resolution examination methods and novel materials. Researchers there are using state-of-the-art analytical equipment with the aim of understanding the causes of these damage processes in order to develop special high-performance materials ideally suited to high-voltage conditions. In partnership with the Department of Functional Materials at Saarland University, the team will conduct precise 3D structural and quantitative analyses of the materials in the nanometer range. As a comparison, the diameter of a human hair is around 50,000 nanometers.
The most promising examination methods are 3D nanotomography and the use of a 3D atom probe, which delivers images at an atomic level. These methods are similar to computed tomography in medicine. Instead of looking at the materials piece by piece, nanotomography uses a focused ion beam to break down the sample under investigation into slices mere nanometers in width. The 3D atom probe can even separate individual atoms to analyze their chemical properties and original position in the material. The resulting 3D breakdowns of the individual sections or atoms can then be recombined using modern computing methods to give an exact 3D model of the material. The extremely high resolution offered by tomography combined with its different types of contrast make it possible to analyze the chemical composition of the material, its precise crystalline structure and the orientation of the crystals, and display these visually.
This new 3D insight into the material, its microstructure, nanostructure and even atomic structure allows a completely new approach to the analysis of damage mechanisms and to material production. This method also makes it possible to simulate and calculate the locally dominant properties of the materials (rigidity, electrical and thermal conductivity) using the “authentic” material data obtained via microstructural tomography. This allows scientists to take a new, three-dimensional, quantitative approach to a variety of challenges in materials engineering.
Christian Selzner
Univ. Prof. Dr.-Ing. Frank Mücklich
Steinbeis Research Center Material Engineering Center Saarland (MECS) (Saarbrücken)
su1294@stw.de