‘Fuzzy fibres’ may help gen-next rockets stand extreme heat

Scientists, including those of Indian origin, have developed “fuzzy fibres” that act like Velcro and could stand up to the heat and pressure of next-generation rocket engines. The fibres made of  silicon carbide strengthen composites used in advanced rocket engines that have to withstand temperatures up to 1,600 degrees Celsius. Ceramic composites in rockets now being developed use silicon carbide fibres to strengthen the material, but they can crack or become brittle when exposed to oxygen. The researchers from Rice University in the US embedded silicon carbide nanotubes and nanowires into the surface of NASA’s fibres. The exposed parts of the fibres are curly and act like the hooks and loops that make Velcro so valuable – but on the nanoscale. The result creates very strong interlocking connections where the fibres tangle; this not only makes the composite less prone to cracking but also seals it to prevent oxygen from changing the fibre’s chemical composition. The researchers grew hooks and loops on nanotubes by first bathing silicon carbide fibre in an iron catalyst and then using water-assisted chemical vapour deposition to embed a carpet of carbon nanotubes directly into the surface. These become the template for the final product. The fibres were then heated in silicon nanopowder at high temperature, which converts the carbon nanotubes to silicon carbide ‘fuzz’. The researchers, including Mr Pulickel Ajayan from Rice University, hope their fuzzy fibres will upgrade the strong, light and heat-resistant silicon carbide fibres that, when put in ceramic composites, are being tested for robust nozzles and other parts in rocket engines. “The silicon carbide fibre they already use is stable to 1,600 degree Celsius,” said Mr Chandra Sekhar Tiwary, a postdoctoral associate at Rice University in the US. “So we are confident that attaching silicon carbide nanotubes and wires to add strength will make it even more cutting-edge,” he said. The new materials should also make entire turbo engines significantly lighter, said graduate student Amelia Hart. “Before they used silicon carbide composites, many engine parts were made of nickel superalloys that had to incorporate a cooling system, which added weight to the whole thing,” Hart said. “By switching to ceramic matrix composites, they could take out the cooling system and go to higher temperatures,” she said. “Our material will allow the creation of larger, longer-lasting turbo jet engines that go to higher temperatures than ever before,” she added. The research was published in the journal Applied Materials and Interfaces.

Source: http://www.deccanherald.com/

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