Oxide gas purification ‘cleans’ car exhaust of harmful pollutants

Improving exhaust gas cleaning in petrol or diesel cars is indeed crucial to reducing emissions, as switching to electric vehicles is a laborious process.

A research team has created an oxide based on cerium and zirconium that can improve the ability of ceramics to clean pollutants inside catalytic converters, the part of conventional cars that convert dangerous gases into less toxic pollutants.

Ceramics breathe oxygen at low temperatures

(Photo: Matt Boitor/Unsplash)

Found in nearly all gasoline and diesel vehicles, catalytic converters remove dangerous hydrocarbons, carbon monoxide, and nitrous oxide from exhaust gas and convert them into safer gases like nitrogen, carbon dioxide, and water vapor .

Harmful gases pass through the honeycomb structure, which is coated with catalysts for exhaust gas purification, according to Science Daily.

The purification process is largely dependent on ceramics with oxygen storage capacity (OSC). Precious metals in catalytic converters do not coarsen, which reduces their ability to purify gases, and they help remove harmful gases.

By manipulating its crystal structure, a research team at Tohoku University’s Graduate School of Engineering has created a cerium-zirconium-based (Ce-Zr) oxide with a good OSC at 400 ºC.

Even without the use of precious metal catalysts, the OSC at 400 ºC is 13.5 times that of common materials.

Transition metal doping in oxides produces two distinct effects. It accelerates oxygen diffusion by promoting the development of oxygen vacancies and promoting cationic ordering.

Iron doping reduces the cationic ordering temperature and enables Ce-Zr-based oxides with larger surface area. This increases their toughness and ability to remove harmful gases. Takamura and his team intend to test the substance in the future by loading palladium onto honeycomb scaffolds.

read more: Why are spent catalytic converters valuable?

Disadvantages of Ceramic Engines

Despite these advantages, ceramics are not necessarily the only materials used in aerospace design.Manufacturers are also finding that ceramics are difficult to process and price, according to metal processing.

In an article on manufacturing engineering, Don Graham, education and technical services manager at Seco Tools, points out that the same properties that increase strength and temperature resistance can make machining more challenging.

Graham points out that the challenge comes in the final machining or grinding stage, where the surface integrity of the ceramic can be compromised if the cut is wrong. Additionally, high material removal rates further increase the likelihood of damage.

According to Alexander Gorin and M., due to the brittleness, high hardness, creep resistance, and high strength of advanced ceramics, standard machining techniques such as turning, milling, and drilling suffer from cracks, brittle fractures, and edge chipping. Advanced Ceramics: Some Challenges and Solutions for Mohan Reddy’s Traditional Machining.

A piece of poorly machined ceramic will have much lower structural strength. If the sandwich composite is cut with jagged, uneven or twisted edges, the overall structure will lose a considerable degree of rigidity.

According to the Gorin/Reddy report, given the importance of strong, efficient cuts when machining ceramics, it is understandable why many mills spend up to 80% of their total cost on maintaining the structural integrity of their ceramic substrates.

Naturally, this can be problematic when trying to stick to a budget or allocate funds for other work-related expenses.

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