New macro-porous ceramics and glass filters from capillary suspensions
Researchers at the Karlsruhe Institute of Technology (KIT) have developed a novel, simple and potentially cost-saving production process for macro-porous ceramics. The process is based on the use of the capillary effect in a three phase suspension of nano- to micro-sized solid particulates. In this manner, it is possible to fabricate ceramics and polymer foams with macro-pores of diameter of 50 nm or greater and narrow pore size distribution.
Porous ceramics can be used in numerous different applications. For example they are used as filters in the food industry, in exhaust gas and sewage water treatment, as a gas diffusion coating in fuel cell technology, as insulation or building material, in chemical processes as catalyst support or electrode material and even in medical technology as scaffold for biological materials.
The most frequent industrial production processes, depending on the desired pore size respectively overall porosity (open or closed), include the demanding replication technique, the sacrificial template method, or the slurry foaming method.
Researchers at the Karlsruhe Institute of Technology (KIT) have developed a novel, simple and potentially cost-saving production process for macro-porous ceramics allowing for a specific selection of pore size ranging from 0.5 µm to 20 µm with a porosity of minimum 60 %.
The process is based on the use of the capillary effect in a three phase suspension of nano- to micro-sized solid particulates. The two liquid phases of such a capillary suspension have opposite polarities and thus are not miscible. Depending on the relative volume of these fluid phases, the solid-liquid-liquid system will exhibit either a fluid or a pasty consistency (see Figure 1). More general stabilizing tasks in dispersed systems can therefore also be tackled by means of capillary suspension.
- Universal applicability (oxides, such as metal oxides or glass)
- Controlled pore size
- Variation in pore size distribution from narrow to broader is possible (see Figure 4)
- Ability to control porosity, e.g. completely open pores
- Parts can be easily manufactured using typical forming processes (screen printing, injection molding etc.)
- Parts with complicated geometry or sophisticated structures can also be produced
- Commercial potential relative to conventional processes: simple, efficient and less cost-intensive
- No toxic pyrolysis gases are produced
- Process can be combined with traditional processes for highly porous material
- Organic liquid bulk phase can be recycled
Production of highly porous ceramics for:
- Filter material
- Catalyst support structure
- Electrode material
- Scaffolds for medical applications
- Support for other materials (light weight construction)