Researchers at North Carolina State University have developed a new laser-based technique for creating ceramics that can withstand extremely high temperatures. The method holds potential applications in nuclear power, spacecraft, and jet exhaust systems. It allows the creation of ceramic coatings, tiles, or complex three-dimensional structures.
“Sintering is the process by which raw materials – either powders or liquids – are converted into a ceramic material,” explained Cheryl Xu, co-corresponding author of the study and a professor of mechanical and aerospace engineering at NC State. “For this work, we focused on an ultra-high temperature ceramic called hafnium carbide (HfC). Traditionally, sintering HfC requires placing the raw materials in a furnace that can reach temperatures of at least 2,200 degrees Celsius – a process that is time-consuming and energy intensive.”
Xu emphasized the advantages of their new method: “Our technique is faster, easier and requires less energy.” This approach involves using a 120-watt laser on a liquid polymer precursor within an inert environment like a vacuum chamber or argon-filled chamber to create solid ceramics.
The new technique has two primary applications. First, it can apply ceramic coatings to underlying structures such as carbon composites used in hypersonic technologies. “Because the sintering process does not require exposing the entire structure to the heat of the furnace,” said Xu, “the new technique holds promise for allowing us to apply ultra-high temperature ceramic coatings to materials that may be damaged by sintering in a furnace.”
The second application involves additive manufacturing or 3D printing through laser sintering combined with stereolithography techniques. The laser converts liquid polymers into solid ceramics layer by layer based on digital designs.
“It’s actually a bit of an oversimplification to say that the laser is only sintering the liquid precursor,” noted Xu. “It is more accurate to say that the laser first converts the liquid polymer into a solid polymer and then converts the solid polymer into a ceramic. However, all of this happens very quickly – it’s essentially a one-step process.”
The research team successfully demonstrated their method’s capability in producing crystalline phase-pure HfC from liquid polymer precursors. “This is the first time we know of where someone was able to create HfC of this quality from a liquid polymer precursor,” Xu stated.
Additionally, they created high-quality HfC coatings for carbon-fiber reinforced carbon composites (C/C), showing strong adhesion and uniform coverage suitable for thermal protection and oxidation resistance.
“Our technique allows us to create ultra-high temperature ceramic structures and coatings in seconds or minutes,” Xu said. She added that their approach uses significantly less energy than conventional methods while achieving higher yields.
Xu concluded with optimism about future collaborations: “We are excited about this advance in ceramics and are open to working with public and private partners to transition this technology for use in practical applications.”
The study titled “Synthesis of Hafnium Carbide (HfC) via One-Step Selective Laser Reaction Pyrolysis from Liquid Polymer Precursor” appears in the Journal of the American Ceramic Society. Co-corresponding author Tiegang Fang also contributed alongside co-first authors Shalini Rajpoot and Kaushik Nonavinakere Vinod.
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