Clay Culture: Are Kilns Obsolete? Faye Oney

Appears in the June/July/August 2017 issue of Ceramics Monthly.

Environmentally-friendly method of manufacturing ceramics may reduce companies carbon footprint, and render kilns obsolete for some applications and products.

The way your toilet is manufactured may soon undergo a metamorphosis. Researchers from the university ETH Zurich have developed a new way to manufacture ceramic products—such as bricks, porcelain, and cement—that saves energy and lowers the carbon footprint of the process.

André Studart, professor of complex materials, and Florian Bouville, a post-doctoral student working on Studart’s team, have devised a room-temperature cold sintering method that uses hydraulics to produce ceramic materials that have proven to be stronger than concrete.

Traditional manufacturers have to fire materials at temperatures in excess of 1832°F (1000°C) to create ceramic objects. For instance, ceramic tiles are often fired in tunnel kilns that operate at 2372°F (1300°C). That sucks up a lot of energy that could be harnessed to power, say, communities in a third-world country instead.

The Process

Starting with calcium carbonate nanopowder, Studart and Bouville simply added a little water and compacted the materials under extremely high pressure with a hydraulic press. The entire process takes only an hour to turn out a small one-inch piece of ceramic material.

The duo explained in an article on ETH Zurich’s website that the process they’ve developed can be compared to the similar process of sedimentary rock formation in nature. “Our work is the first evidence that a piece of ceramic material can be manufactured at room temperature in such a short amount of time and with relatively low pressure,” Studart says in the article.

This revolutionary process has several positive implications for the industry. The finished product can tolerate ten times more force than concrete, according to the scientists. The cold sintering process is more energy-efficient, as no high temperatures are required. Carbon could possibly be captured from the atmosphere, stored in a carbon sink, and “recycled” to produce the nanopowder. The process contributes to overall reduction of CO₂ in the atmosphere.

Although Studart and Bouville used small samples in their experiments, the benefits to the ceramics industry need to happen at scale. Producing larger pieces will require stronger hydraulics that can generate higher pressure and greater force. However, the researchers say it would be feasible to create ceramic samples the size of bathroom tiles.

Densification without heat as the primary driving force could have a huge impact on our understanding of sintering mechanisms. Pennsylvania State University researcher, Clive Randall, has also made some interesting discoveries in cold sintering, by employing high pressures at low temperatures.

As the cement industry looks to adopt sustainable alternatives in the manufacturing process, Studart’s and Bouville’s research could provide alternative materials to answer some of the environmental challenges. Along similar lines, Richard Riman at Rutgers, the State University of New Jersey, also is working on low-temperature, sustainable manufacturing and has shown that CO₂ incorporated into concrete not only captures the CO₂, but improves the end product.

The end result of research such as the ETH Zurich work, along with Riman’s and Randall’s work could lead to entirely new ways of thinking about manufacturing of ceramics, and could also disrupt the massive trillion-dollar concrete industry.

The paper, published in Nature Communications, is “Geologically-inspired strong bulk ceramics made with water at room temperature” (DOI: 10.1038/ncomms14655).

the author Faye Oney, is the content marketing specialist/editor for our sister publication, the Ceramic Bulletin, and the Ceramic Tech Today blog at the American Ceramic Society. She is a 20-year marketing and communications veteran, specializing in writing and social media strategy. She holds a master’s degree in marketing and communications from Franklin University, Columbus, Ohio.