Wet-Chemical Shaping Techniques

Wet-chemical shaping methods are mainly taken to mean techniques in which suspensions, pastes, or slips based on powder particles are processed into components, structures, or coatings. Techniques which process sols are also included in this category.
IEK-1 has a wide range of thick- and thin-film techniques permitting the manufacture of planar as well as three-dimensional, dense or porous structures.
In addition to these facilities, methods for characterizing the liquid precursors and the layers and components are available. They include particle size analysis, BET surfaces, rheological properties, topography, as well as light, confocal, and scanning electron microscopy, and X-ray diffractometry.
After manufacturing the structures or coating them, various drying and sintering techniques are available (furnaces up to 2000 °C, air, vacuum, inert gases).

Powder injection moulding

Two-component injection moulding: Arburg 370U 2K allrounder 700-100-100; processing of two injection moulding materials in one facility by applying an appropriate tool with two cavities.

Hot isostatic pressing

Manufacturer: EPSI, max. temperature: 2000 °C, max. pressure: 350 MPa, max. dimensions: Ø = 150 mm, h = 400 mm, pressure gases: Ar, N₂, Ar/O₂ (20 vol % O₂), heating elements: graphite, molybdenum, Kanthal

Tape casting and micro-tape castin

Tape-casting device, complete facility

Tape-casting facility; laser measurements of layer thickness on green tape

By means of tape casting, extensive two-dimensional continuous structures of various casting thicknesses can be manufactured, depending on the facility used. Sintering thicknesses range between 5 µm and 1000 µm. With this method, substrates for high-temperature fuel cells (SOFCs) and gas separation membranes can be manufactured.
Facilities: SAMA technical facility; micro tape casting facility (currently on order)

Screen printing

By means of screen printing, ceramic and metallic layers of 10–100 µm thickness can be applied to porous or dense substrates.
The method is currently employed to manufacture the functional layers of solid oxide fuel cells (anode, electrolyte, cathode) and intermediate layers (mesoporous layers) for membrane technology.

Ekra screen printer

Detail of Ekra screen printer

Roll coating

Roll coating entails coating continuously planar components with a paste by means of a roller. Layer thicknesses between 10 µm and 100 µm are achievable. Applications can be found in solid oxide fuel cells (SOFCs) and gas separation membranes.

Facility: Mathis Reverse Roll Coater

Wet powder spraying

With the wet powder spraying technique (WPS), planar, spherical, and three-dimensional, structured (but not undercut) components can be coated. Through the WPS technique, coating thicknesses of 5 µm to approx. 150 µm can be achieved (multilayer coating). Currently, the metallic interconnects, for example, of solid oxide fuel cells are coated with protection and bond coats by WPS.

Facility: a WPS cabin for components of up to 1 m length (in-house construction)

Facility: a WPS cabin for larger formats

Inkjet printing

Process: PixDro Direct Inkjet Printer LP50

Inkjet printing is realized by applying a layer of a suspension, a solution, or a sol onto a substrate by means of a print head with a large number of nozzles.

Equipment: Direct ink jet printer LP50 manufactured by PixDro

Vacuum slip casting

Vacuum slip casting device for components of up to 300 x 300 mm²

Vacuum slip casting is based on a filtering process, which means that planar, porous substrates can be coated with a suspension. The solvent is sucked through the porous substrate by a negative pressure applied to the other side, while the powder particles form a filter cake on the substrate. The functional layer is then produced by means of a sintering process. Typical layer thicknesses are 5–20 µm. Facilities: several devices constructed in-house for various substrate sizes of up to 200 x 200 mm².

Spin and dip coating

Spin coating involves coating planar structures with a sol or a suspension by rotating the component that is to be coated. Attainable layer thicknesses are usually 2 µm or less. During dip coating, the component is either dipped into a suspension or a sol vertically, or by a circular movement. This method is suitable mainly for micrometre-thin layers.

Vertical dip coating device

Warm pressing

Warm pressing device for components of up to 350 x 350 mm²

Warm pressing at IEK-1 is used for compacting and shaping powders coated with a binder. Pressures for warm pressing are in the region of 1 MPa, and temperatures around 100 °C. Planar, relatively thick components can be produced, which can be used as substrates. The substrate thickness ranges from 1 mm to 4 mm. The method is used to produce substrates for solid oxide fuel cells and membranes. Facility: Device constructed in-house for component sizes of up to 350 x 350 mm².