bulletin cover story Corning DuraTrap® GC gasoline particulate filter (foreground) and a Corning FLORA® low-mass substrate for catalytic converters (background). Smog begone! How development of ceramic automotive catalytic substrates and filters Credit: Corning Incorporated. eep in the heart of your car’s helped reduce Dexhaust system—withstanding temperatures of more than 1,800 degrees Fahrenheit and staying tough over hundreds of air pollution thousands of miles of bumpy roads—a highly engineered ceramic material is an important part of helping to prevent harmful emissions from escaping into the air you breathe. By keeping the air cleaner, these same ceramic products help save as many as 160,000 lives each year and help to prevent just By Douglas M. Beall and Willard A. Cutler as many cases of heart disease and asthma.1 From 1975 through today, light and heavy-duty vehicle emis- sions dropped by an astounding 99%. Ceramic-based mobile Ceramic-based mobile emissions control products have emissions control products prevented more than 4 billion tons of prevented billions of tons of hydrocarbons, nitrogen oxides, hydrocarbons, 4 billion tons of nitrogen oxides (NOx), and 40 bil- lion tons of carbon monoxide from entering the atmosphere. carbon monoxide, and particulates from entering the atmo- The clean-air movement brought economic benefits as well. sphere—and researchers continue to innovate to make these Emissions-related technologies represent about $37 billion in products even better. annual economic activity, with a significant portion of the indus- try involving ceramic-based components.2 Capsule summary A DIRTY PROBLEM CERAMIC SOLUTION INNOVATION AHEAD By the mid-1900s, health hazards associated In the 1970s, Corning scientists invented a Most emissions in a typical drive cycle are with poor air quality had come into stark view. substrate for catalytic convertors based on produced in the first minutes of operation, Governments set new federal air pollution cordierite and also a ceramic-based wall-flow so the remaining frontier of a zero-emission regulations that presented both a technologi- particulate filter for diesel engines. Nowadays, internal combustion vehicle is tackling this first cal challenge and business opportunity for ceramic substrates and filters are the keystone minute of operation. industry manufacturers. of mobile pollution control ecosystems. 24 www.ceramics.org | American Ceramic Society Bulletin, Vol. 99, No. 3 Innovations in ceramics will continue began its first attempt to legislate a solu- Control Act of 1965, and the Air Quality to be needed for at least the next couple tion with the Air Pollution Control Act Act of 1967 all lacked the teeth to make a of decades. Consumers throughout the of 1955, which focused on research and difference in the deadly problem. world, not only in areas with untreated information, leaving the states to devise But in 1970, sweeping new federal mobile pollution sources, are demanding ways to deal with polluters. A few states, regulations required clean-air compliance better air quality. Areas of focus that con- notably California, had a plan to combat from every segment of industry. The new tinue to drive ceramic innovations include the issue. Environmental Protection Agency (EPA) (1) Ensuring that real-world emissions The U.S. government made several was formed with the mandate to enforce are as low as emissions on the certifica- more attempts to regulate sources of air the regulations. tion test; pollution. However, the Clean Air Act of The Clean Air Act of 1970 estab- (2) Gaseous emission limits reduc- 1963, the Motor Vehicle Air Pollution lished air-quality standards that strictly ing, particularly NOx emissions, while supporting the reduction of greenhouse Clean Air Act of 1970 extreme benefits thanks to this legislation. gases; and For example, a 2011 EPA study2 estimated When it comes to clean air in the United (3) Reducing the last remaining bursts the central benefits exceed costs by a factor States, one of the most important pieces of of gaseous and particulate emissions of more than 30 to one, largely due to reduc- legislation that made it possible is the Clean tions in premature mortality associated with from internal combustions engines, the Air Act (CAA) of 1970. reductions in ambient particulate matter. emissions that occur during the first Prior to CAA 1970, there were a few federal minute or two of vehicle operation—an However, the gains in clean air made thanks acts involving air pollution.1 The first was the event that can happen several times dur- to CAA 1970 and its amendments may be Air Pollution Control Act of 1955, which pro- challenged in the future. The Trump admin- ing a drive with hybrid vehicles. vided funds for federal research on air pollu- istration has pursued the rollback of almost tion. This was followed by CAA 1963, which 100 environmental rules, 58 of which are now A growing dirty problem established a federal program within the U.S. completed. Of these completed rollbacks, 16 By the late-1940s, industrial activity in Public Health Service and authorized research involve air pollution and emissions rules.3 the United States had grown for nearly a into techniques for monitoring and control- ling air pollution. In 1967, the Air Quality Act Recent studies also show air quality improve- century. Little attention was paid to the ment is leveling off. A 2018 report4 by the consequences of smoke and pollutants was enacted to expand federal government activities, including conducting the first-ever U.S. PIRG Education Fund and Environment from coal-burning factories. Suburbs extensive ambient monitoring studies and America Research & Policy Center found were growing. More and more fami- stationary source inspections. 2018 had more days of pollution than each of lies could afford cars. With city traffic the previous five years, a finding supported crowding new highways, unprecedented However, CAA 1970 marked a major shift in by studies by the American Lung Association5 the federal government’s role in air pol- and Carnegie Mellon University.6 levels of harmful chemicals flowed into lution control by substantially expanding the air, especially in major population the government’s enforcement authority.1 References: centers—both in the U.S. and in other It authorized development of comprehen- 1United States Environmental Protection Agency. “Evolution developed countries. sive federal and state regulations to limit of the Clean Air Act.” Accessed 28 Feb. 2020. https:// www.epa.gov/clean-air-act-overview/evolution-clean- The health hazards associated with emissions from both stationary (industrial) air-act poor air quality came into stark global sources and mobile sources. In particular, it 2United States Environmental Protection Agency. “Benefits view in London in late 1952, when air- established four major regulatory programs and Costs of the Clean Air Act 1990-2020, the Second affecting stationary sources: Prospective Study.” Accessed 28 Feb. 2020. https://www. borne pollutants, mostly arising from the epa.gov/clean-air-act-overview/benefits-and-costs-clean- use of coal, mixed with fog to form a thick • National Ambient Air Quality Standards air-act-1990-2020-second-prospective-study blanket of smog over the city. Historical (NAAQS) 3N. Popovich, L. Albeck-Ripka, and K. Pierre-Louis (21 Dec. accounts vary on the details, but most • State Implementation Plans (SIPs) 2019). “95 environmental rules being rolled back under Trump,” The New York Times. https://www.nytimes.com/ agree between 4,000 and 6,000 people • New Source Performance Standards interactive/2019/climate/trump-environment-rollbacks. died over the course of five days from the (NSPS) html choking effects of the Great Smog.3,4 • National Emission Standards for Hazard- 4E. Ridlington, G. Weissman, and M. Folger (Winter 2020). The following year, New York City ous Air Pollutants (NESHAPs) “Trouble in the air: Millions of Americans breathed polluted air in 2018.” U.S. PIRG Education Fund. Accessed 28 Feb. was covered with a toxic mix of sulfur In 1977 and 1990, two sets of major amend- 2020. https://uspirgedfund.org/sites/pirg/files/reports/ dioxide and carbon monoxide that blan- ments were added to CAA 1970.1 The 1977 EnvironmentAmerica_TroubleintheAir_scrn.pdf keted the city. During one week, accord- amendments focused on ensuring attainment 5American Lung Association. “The state of the air 2019.” and maintenance of NAAQS by establishing Accessed 28 Feb. 2020. https://www.lung.org/our-initia- ing to reports, as many as 260 deaths tives/healthy-air/sota/key-findings/ major permit review requirements; the 1990 were attributed to the smog. More 6 amendments substantially increased the fed- K. Clay and N. Z. Muller (October 2019). “Recent deadly smog crises would hit both New increases in air pollution: Evidence and implications for York and London again over the follow- eral government’s authority and responsibility. mortality.” NBER, Working Paper No. 26381. https://www. nber.org/papers/w26381 n ing decades.5 To date, several in-depth benefit-cost analy- With the public health effects of air ses of the CAA Amendments performed by pollution now beyond dispute, the U.S. the Environmental Protection Agency all show American Ceramic Society Bulletin, Vol. 99, No.3 | www.ceramics.org 25 Smog begone! How development of ceramic automotive catalytic substrates and . a) b) c) d) Schematic of laboratory scale production Figure 1. Numerous pathways to fabricating porous ceramic substrates were tried before settling on extruded honeycombs. (a) Alternate layers of flat and crimped paper infused with glass- Credit: Beall and Cutler ceramic (CERCOR material); (b) layers of cordierite glass-ceramic sheets with small “nubbins” to increase the surface area and permit exhaust flow; (c) open, layered structure similar to ribbon candy formed by buckling a hot glass stream and later ceraming the part; and (d) glass tubing fused together, then ceramed, looking like a packet of hollow cigarettes.