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GEO2 Technologies Introduces New Fiber-based SiC Substrate for Diesel Particulate Filters; Ceramic Fiber Technology Enables Significant Increase in Porosity

The GEO2 SiC substrate offers increased porosity compared to standard powder-derived SiC filters due to its microfiber-based microstructure. Click to enlarge. Source: GEO2

GEO2 Technologies Inc. has introduced a new ceramic fiber silicon carbide (SiC) substrate for diesel particulate filtering. The new SiC substrate achieves high porosity and high strength simultaneously while delivering lower back pressure and high trapping efficiency, according to the company.

Unlike other SiC products, GEO2 filters are based on a cross-linked microstructure (CLM) that increases maximum porosity to 67%—an increase of about 20% compared to other SiC filters—effectively reducing the size, weight and cost of emissions control systems.

Soot capture on the GEO2 filter. Click to enlarge. Source: GEO2.

The new GEO2SiC filter can remove 99.9% of pollutants from diesel exhaust while achieving better fuel economy, emissions control and enhanced engine performance.

SiC-based filters have become the mainstay of the diesel light-duty vehicle market. The filters support higher temperatures, and are more robust—and expensive—than other chemistries. The common manufacturing approach is to take ceramic powders, and extrude into them into a honeycomb. This process yields filters with porosity of around 40-50%.

Porosity is a key factor in a filter—higher porosity results in lighter weight, higher catalyst loads, and reduced back pressure. Increased back pressure due to emissions treatment equipment can cause increased emissions, increased fuel consumption, and can negatively affect engine performance.

GEO2’s breakthrough that led to the cross linked microstructure, says co-founder and vice president of product development Dr. Bilal Zuberi, was the development of a process to extrude ceramic fibers into the honeycomb filter shape.

Ceramic fibers typically look like cotton, Zuberi says, and cotton cannot be molded. The powder-based materials are like clay—add water, and it becomes moldable, and can be put through a die.

We figured out what kind of organics we can add to the fiber mix to change properties to become moldable. Once moldable, you create the shape. Then, because a ceramic product needs to be fired, during that time you burn out the organic materials. The choice of the organic and the burning cycle is key—otherwise the material just falls apart.

—Bilal Zuberi

Trying to deliver higher porosity with traditional materials can result in tradeoffs in strength and durability. The GEO2 substrate not only delivers significantly increases porosity, but maintains its strength.

In internal testing, GEO2 ran the new SiC materials through 1,000 regeneration cycles (most filters go for 200 cycles in their lifetimes in an light duty vehicle). Part of the strength and performance is driven by the chemistry of the SiC material, but part is because of the internal structure, says Zuberi. Where other materials get brittle fractures, the GEO2 materials dissipate the force throughout their structure.

GEO2’s business model calls for licensing the technology to established filter manufacturers. The company is also looking at other markets such as solutions for gasoline direct injection engines and fuel cells as well as gasification systems and fuels processing.



How does this perform in reducing nanometer range PM (smaller than 2.5 µm)?

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