Scientists have identified materials that can withstand temperatures of nearly 4,000 degrees Celsius, an advance that may pave the way for improved heat resistant shielding for the faster-than-ever hypersonic space vehicles.
Researchers from Imperial College London in the UK discovered that the melting point of hafnium carbide is the highest ever recorded for a material.
Tantalum carbide (TaC) and hafnium carbide (HfC) are refractory ceramics, meaning they are extraordinarily resistant to heat.
Their ability to withstand extremely harsh environments means that refractory ceramics could be used in thermal protection systems on high-speed vehicles and as fuel cladding in the super-heated environments of nuclear reactors.
However, there has not been the technology available to test the melting point of TaC and HfC in the lab to determine how truly extreme an environment they could function in.
The researchers developed a new extreme heating technique using lasers to test the heat tolerance of TaC and HfC.
They used the laser-heating techniques to find the point at which TaC and HfC melted, both separately and as mixed compositions of both.
They found that the mixed compound (Ta0.8Hf0.20C) was consistent with previous research, melting at 3,905 degrees
Celsius, but the two compounds on their own exceeded previous recorded melting points. The compound TaC melted at 3,768 degrees Celsius, and HfC melted at 3,958 degrees Celsius.
The findings may pave the way for the next generation of hypersonic vehicles, meaning spacecraft could become faster than ever.
"The friction involved when travelling above Mach 5 - hypersonic speeds - creates very high temperatures," said Omar Cedillos-Barraza, currently an Associate Professor at the University of Texas.
"So far, TaC and HfC have not been potential candidates for hypersonic aircraft, but our new findings show that they can withstand even more heat than we previously thought – more than any other compound known to man," said Cedillos-Barraza, who carried out the research as a PhD student at Imperial College London.
"This means that they could be useful materials for new types of spacecraft that can fly through the atmosphere like a plane, before reaching hypersonic speeds to shoot out into space," he said.
"These materials may enable spacecraft to withstand the extreme heat generated from leaving and re-entering the atmosphere," he added.
Examples of potential uses for TaC and HfC could be in nose caps for spacecraft, and as the edges of external instruments that have to withstand the most friction during flight.
Currently, vehicles going over Mach 5 speeds do not carry people, but Cedillos-Barraza suggests it may be possible in the future.
