Materials

New Titanium-Making Process Could Result in Lighter Aircraft

A new process could extend the use of titanium for lightweight, more fuel-efficient airplanes.

Air transportation is a fast-growing source of carbon dioxide emissions, and lighter planes would produce less pollution.

A new process for producing titanium—a metal that’s increasingly used in aircraft to reduce weight and fuel consumption—is significantly cheaper and less energy-intensive than conventional methods. The technique could lead to titanium being used to reduce the weight of cars, helping automakers meet tightening fuel economy regulations.

Titanium normally takes a significant amount of energy to make. The conventional method, called the Kroll process, involves multiple steps requiring very high temperatures. The new process, being developed by SRI International, takes fewer steps, uses less energy, and produces titanium powder, rather than ingots. The powder can be pressed and fused into something that’s very close to the shape of the final product, which reduces the amount of machining required.

SRI’s process uses plasma arcs to facilitate reactions between molecules of hydrogen and titanium chloride, a chemical produced from titanium ore. “Arcs, like lightning bolts, crack the hydrogen, producing atomic hydrogen that can readily react,” says Barbara Heydorn, senior director of the Energy Center at SRI. The reactions produce titanium vapor that quickly solidifies and forms titanium powder.

Carbon emissions limits in Europe have led to increased use of titanium in aircraft. The possibility of similar regulations being introduced in the United States and concerns over volatile fuel prices are also boosting the use of titanium in planes. The lightweight, corrosion-resistant material is ideal for certain engine parts, including fan blades. It also serves as a critical structural material in newer aircraft that use carbon composite materials, since the aluminum ordinarily used in aircraft structures is incompatible with carbon composites (see “Additive Manufacturing Is Reshaping Aviation”).

SRI has so far demonstrated a small-scale version of the process for producing pure titanium. It’s currently working on a two-stage process to improve yields and lower costs before attempting to scale it up.

SRI could face major challenges to bringing the new process to market. Introducing a new metals process is particularly difficult, says Donald Sadoway, a professor of materials chemistry at MIT. Large investments are required to make cost-efficient processing plants, he says, and it can be hard to get funding for new technologies because they face “the widely held belief that the metals industry is mature and that the optimum processes have been discovered.”

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