Scientists' new stardust recipe could strengthen materials on Earth

In a new study, the researchers detail their analysis of a type of presolar stardust grain with a core of titanium carbide with a shell of graphite. Titanium carbide, a combination of titanium and carbon, is an incredibly durable ceramic-like material that is nearly as hard as diamond.

The scientists set out to figure out how these carbon-coated cores sometimes clump together into larger grains made up of hundreds of the single cores.

Testing the material on Earth is challenging because the grains wouldn't have had to deal with gravity during their formation. In June 2019, in order to overcome this obstacle, scientists launched a sounding rocket from Esrange Space Center in Kiruna, a Swedish town north of the Arctic circle.

Sounding rockets don't fly to orbit. Instead, they launch to high altitudes to analyze the atmosphere and test instruments as well as scientific payloads.

In this case, the rocket flew to an altitude of 240 km (150 miles), allowing it to experience microgravity. It took with it a payload of dust grains and instruments that could record their composition during the flight. Using this method, the scientists were able to record the effects of microgravity on dust grains over a period of six and a half minutes. The grains were recovered roughly 46 miles from the rocket's launch site and were sent to Japan where they were analyzed by scientists at the University of Hokkaido.

Stardust recipe could lead to stronger materials on Earth

Using the microgravity analysis, as well as follow-up experiments on Earth, the scientists were able to compile a recipe for a titanium carbide dust grain. In their paper, they detail how the recipe is made up of a core of carbon atoms in graphite form that are sprinkled with titanium. These cores are then fused together in large quantities and covered in graphite.

The new discovery not only sheds new light on the early universe, it could also have a very practical application here on Earth. The scientists believe the recipe could help engineers and manufacturers to develop stronger materials on Earth. In fact, the development of nanoparticles is very similar to the process that creates titanium carbide stardust.

Nanoparticles have been used for years to strengthen plastics and asphalts and even to deliver drugs into the human body. However, they are typically developed using a liquid solution that creates a lot of waste. The scientists believe their stardust-inspired method could develop similar materials without that waste. As the researchers point out, stardust-strengthened construction tools could even one day help manufacture spacecraft that send humans out to explore the distant cosmos.

The scientists detailed their findings, including the titanium carbide dust grain recipe, in a paper in Science Advances.

Abstract:

Just as the shapes of snowflakes provide us with information on the temperature and humidity of the upper atmosphere, the characteristics of presolar grains in meteorites place limits on their formation environment in a stellar outflow. However, even in the case of well-characterized presolar grains consisting of a titanium carbide core and a graphitic carbon mantle, it is not possible to delimit their formation environment. Here, we have demonstrated the formation of core-mantle grains in gravitational and microgravity environments and have found that core-mantle grains are formed by a nonclassical nucleation pathway involving the three steps: (i) primary nucleation of carbon at a substantially high supersaturation, (ii) heterogeneous condensation of titanium carbide on the carbon, and (iii) fusion of nuclei. We argue that the characteristics of not only core-mantle grains but also other presolar and solar grains might be accurately explained by considering a nonclassical nucleation pathway.