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Fusion Technology and Battery Systems

 

 

 

KOR_Krauss

A sustainable energy supply calls for the transition to environmentally friendly power generation and storage. Nuclear fusion will achieve this very well by fusion of two hydrogen isotopes deuterium and tritium to form helium and release of energy in the form of neutrons. Deuterium is extracted from sea water and the isotope tritium is produced by the power plant itself by transforming lithium into tritium and helium. For better handling lithium can be used in the power plant as eutectic lead-lithium alloy with 15.7 atomic% lithium, which stands in contact with structural steels. Essential for the life of such steel components will be the corrosive interaction of the flowing lead-lithium melt with the materials. The work area fusion technology analyzes the occurring phenomena and develops less corrosion-sensitive materials. Additionally, data are provided for modeling development and the optimization of system components.
In addition to power generation their efficient, safe and cost-effective storage will be an encouraging, trend-setting development area for mobile and stationary applications. In development of lithium-ion batteries compatibility analyses of electrode systems in novel electrolyte systems are in the foreground. The corrosion department supports these research fields by its long-term electrochemical know-how of the development work on fusion relevant materials and analysis of battery materials.

The development strategy in fusion technology and battery systems is focused on the main activities:

Fusion technology

  • Compatibility testing of structural materials in non-isothermically flowing lead-lithium-alloy.
  • Analyzing of corrosion phenomena, transport of corrosion products and precipitation formation in closed loops.
  • Model development and validation for future plant design and analyzes



Electro-chemical processes

  • Development of novel shaping methods by electro-chemical machining (ECM) of hard and brittle tungsten alloys
  • Electro-chemical plating of functional scales / barriers and high temperature brazing alloys
  • Development of coating processes for aluminum and refractory metals e.g. tungsten with barrier or filler metal function applying innovative electrolytes based on ionic liquids



Battery systems

  • Analyzing compatibility behavior of electrodes and current leads in modified novel electrolyte systems for optimization of lithium ion batteries

 

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Lead lithium liquid metal loop PICOLO

The corrosion behavior of ferritic-martensitic steels and the stability of anti-corrosion coatings are investigated in the liquid metal loop PICOLO. PICOLO is a non-isothermal loop with forced Pb-15.7 Li flow where the flow rate can be varied between a few mm / s and 1 m / s. Test temperatures are in the range of 480 to 550 ° C similar to operation temperature in the ITER fusion reactor. PICOLO is designed for exposure times above 10,000 hours and its test chamber can be simultaneously equipped with about twelve samples. Picolo is now regarded as a reference facility in the European Corrosion Research. All bare steels always show corrosion attack and the corrosion products are transported with the circulating melt and form precipitates at cooler area. The lead-lithium purification and analyses of the impurity impact on the corrosion behavior are in the focus of future investigations to ensure a reliable and safe operation of ITER or prototype systems.

 

Electro-Chemical-Machining (ECM)

ECM is meanwhile a well established mass processing method in steel machining and surface finishing of complex shaped geometries or processing of hardened steel dies. By nature, electro-chemical removal is a soft processing method which can not introduce structural defects as micro cracks into work pieces. However, an application in the field of tungsten is impossible due to passivation reactions in standard electrolytes as used in steel processing. This drawback was solved by development of a special two-component water-based electrolyte system. Fine-structured tungsten components e.g. heat exchanger plates can now be shaped applying DC currents with aspect ratios of 1:10.
 

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Brazing scales and functional barriers

Assembling of complex divertor components requires brazing joints with specially adjusted properties. For example in steel to tungsten joining a mismatch in the expansion coefficients by one order of magnitude has to be bridged. Often a direct wetting of the components (tungsten) by commercially available fillers is not given, thus functional intermediate layers have to be deposited to realize a metallurgical bonding and filler metals have to be adjusted.
Electro-chemical plating technology is a tool to deposit such layers and solders e.g. from aqueous electrolytes. Main advantages of this technique are the uniform and defect free wetting, good reproducibility and thickness control of deposited scales as well as multi element plating.
  Coatings

Corrosion-resistant protective layers and diffusion barriers are often needed to protect complex assemblies under critical environmental conditions. Often such scales can not be obtained by process reasons applying CVD or PVD. Electro-chemical coating provides an alternative however, resistant layers can often not be deposited from aqueous electrolytes. For example, aluminum coated steel after heat treatment has excellent corrosion resistance in contact with lead-lithium melt. To obtain such scales processes are under development for aluminum coating and deposition of other refractory from ionic liquids. Only this type of electrolyte can be operated near room temperature and does not cause oxidation of the deposited layers. The developed aluminum coating process shows a good scattering effect, a homogeneous layer structure and the scale properties are easily controllable by the process parameters deposition time and applied current density.
 

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In the current development of battery systems so-called lithium ion systems are in the interest for electrically powered cars. Their acceptance, however, requires e.g. higher storage capacity and extended life time. To achieve this, the current development is focused on novel electrodes and electrolyte systems. Compatibility is essential and initiated the research topic characterization of these new materials concerning their corrosion resistance in advanced electrolyte systems.

 

For further details please contact Dr. Wolfgang Krauss.