How it Works: Particulate Filters and Ceramic Substrates
How it Works: Filters and Substrates
Take a breath in. Now, let it out. If you keep doing that for a whole day, you’ll breathe close to 3,000 gallons of air. That’s enough to fill a tanker truck! Now imagine doing that in a world where the air is filled with harsh gases and harmful particulates like soot. Suddenly, taking deep breaths becomes a lot less appealing.
That’s where Corning comes in. You can breathe easier knowing that Corning’s particulate filters and ceramic substrates help make the air cleaner, removing harsh gases and particulate matter from the vehicle exhaust of cars and trucks of all sizes before they become a part of the air around you.
Substrates and filters are key components of the emissions control system, which lives in the engine compartment and underneath trucks and cars, connecting the engine to the exhaust pipe. When an engine burns fuel, diesel, or gasoline, its exhaust carries harmful byproducts like hydrocarbons, nitrogen oxides, carbon monoxide, and particulates. As exhaust moves through the system, it passes through Corning’s substrates and filters -- this is where the magic happens.
Corning makes substrates and filters for gasoline and diesel vehicles of all sizes, from passenger cars to heavy-duty trucks, construction, and agricultural equipment. Diesel-powered vehicles use substrates to remediate gaseous pollutants and filters to remove particulate pollutants. Current gasoline-powered vehicles only use substrates to remediate gaseous pollutants, though future regulations will require particulate filters for gasoline exhaust, too.
Filters and substrates are created from high-temperature, low-expansion materials, which can withstand scorching temperatures and rapid temperature changes. They are made using an extrusion process to create thousands of parallel channels with porous walls, which eventually anchor catalysts. The extruded bodies are fired at high temperatures and then cut to a finished size.
With filters and substrates, one size does not fit all. Corning works with engine and vehicle manufacturers to understand their emissions control system needs and constraints, using different materials, sizes, and shapes to fit each system.
How Substrates Work
Both substrates and filters are filled with thousands of tiny, parallel channels, creating the look of a “honeycomb” – where exhaust can flow through. These channels provide a very large internal surface area allowing catalysts to have intimate contact with the exhaust gases. For substrates, the parallel channels remain open, while filters have alternately plugged channels, forcing the exhaust gas through the porous wall and capturing dangerous particulates on the inlet walls. When you look through a substrate, you can see straight through the tiny channels. Whereas when you look through a filter, you can’t see the other side, but instead see the plugged “checkerboard” pattern on the surface.
The other big difference between substrates and their filter partners is in functionality. The work a substrate does is largely invisible, a conversion of gases that allows the exhaust released out of vehicles to be breathable, while filters remove solids from engine exhaust.
The completed substrate is coated with a combination of high surface area catalytic materials that essentially turn it into a mini chemistry lab. At high temperatures, toxic gases such as nitrogen oxides and carbon monoxide in the exhaust come into contact with the catalysts and are converted into harmless nitrogen and water and less harmful carbon dioxide. Filters, which can also contain catalysts, capture particles on inlet walls as the exhaust gas is forced through them. These walls then periodically need to be cleaned. However, unlike your vacuum bag or your air filter, which are disposed of when full, these filters can often be cleaned in place using sophisticated “self-cleaning” engine controls that are not even noticeable.
While substrates and filters have done tremendous work in making cleaner air around the world, there is still room for innovation. Clean air regulations are becoming more stringent and vehicle technology is advancing to meet those needs, leaving Corning room to invent and grow. For example, substrates require a certain operating temperature to activate the catalysts, which means that they do not begin converting the toxic gases immediately. The exhaust has to heat up to activate the substrate, which can sometimes lead to high emission rates in the initial minutes after a car is started.
These emissions, called cold-start emissions, are often the most toxic moments of a drive, and Corning is working to solve this problem. Using new materials that reach active temperature more quickly, Corning developed FLORA™ substrates specifically designed to reduce cold-start emissions.
Substrates and filters have an enormous impact on our world. Corning filters remove 20 trillion soot particles from the air we breathe every second. It’s easy to overlook the work done by these products since they are hidden from sight under cars and trucks, but it’s hard to imagine a world without them. Corning is committed to clean air; we want everyone to breathe easy.