Vacation travel was among the biggest stories of summer 2021, raising questions about air travel’s contribution to greenhouse gas emissions and climate change.

According to the Environmental and Energy Study Institute, 710 million tons of global carbon dioxide came from commercial aviation in 2013.

By 2017, that number reached 860 million tons, a 21% increase in four years. By 2018, it climbed to 905 million tons, 2.4% of total CO2 emissions.

Airplane manufacturers and their customers in government and industry have invested in the design of new aircraft engines that function at extremely high temperatures, which means the engines can generate more energy while burning less fuel.

However, the very high temperatures can be a problem for the materials used to make the engine.

Haydn Wadley, Edgar Starke Professor of Materials Science and Engineering at the University of Virginia School of Engineering and Applied Science, and Jeroen Deijkers, a postdoctoral research associate in Wadley’s group, found a way to greatly extend the life of the materials used in these jet engines.

Their paper, “A Duplex Bond Coat Approach to Environmental Barrier Coating Systems,” is published in the September 2021 issue of Acta Materialia.

“A jet engine gulps huge quantities of air, which, when compressed and mixed with hydrocarbon fuel and burned in a combustor, powers the plane’s propulsion system. The hotter the combustor, the more efficient the engine,” Wadley said.

Combustion in airplane engines now reaches or exceeds 1500 degrees centigrade, well above the melting temperatures of engine parts typically made of nickel and cobalt alloys.

Research has turned to ceramics that can withstand these temperatures, but they must contend with chemical reactions from the water vapor and unburnt oxygen in the extreme combustion environment.

Their solution uses an outer layer of ytterbium disilicate, a rare earth element that shares silicon’s and silicon carbide’s thermal expansion characteristics and is slow to transport oxygen and water vapor toward the silicon layer.

They first deposited the silicon bond coat and then placed a thin layer of hafnium oxide between the silicon and the ytterbium disilicate outer layer.

Deijkers, who is from the Netherlands, combined these early memories with his interest in serving in the Dutch Air Force, earning a bachelor’s and master’s degree in aerospace engineering from Delft University of Technology.

Over 260,000 kilometres of river could potentially be severed by planned hydroelectric developments according to McGill University researchers.

The Amazon, the Congo, and the Irrawaddy are just a few of the rivers at risk of losing their free-flowing status if the proposed construction of new hydropower dams takes place.

The study, led by World Wildlife Fund and published recently in Global Sustainability, showed that planned dams and reservoirs are leading contributors to the decline of free-flowing rivers around the world.

It also provides a comprehensive list of science-based solutions to minimize the impacts of hydropower development in rivers.

“We used a dataset of more than 3700 potential hydropower projects and calculated their impacts on rivers worldwide,” says Prof. Bernhard Lehner from McGill University’s Global HydroLab, who created the underpinning global river maps.

“It was sobering to learn that many of today’s remaining free-flowing rivers are at risk of being permanently transformed by new energy infrastructures.”