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Researchers at North Carolina (NC) State University have developed a single-step laser-based method to synthesize hafnium carbide (HfC), significantly streamlining the production of this ultrahigh-temperature ceramics.
Published in American Ceramic Society (ACS) journal, the study was led by co-corresponding authors Tiegang Fang and Chengying Xu, both professors in NC State’s Department of Mechanical and Aerospace Engineering. HfC is one of the most thermally stable materials known, with a melting point above 3900 °C, high hardness, and strong resistance to oxidation and thermal shock.
These properties make it a critical material for aerospace and defense applications, particularly in thermal protection systems for hypersonic vehicles and re-entry modules. However, conventional synthesis methods are complex and energy-intensive, involving multiple stages such as crosslinking, furnace-based pyrolysis, and extensive post-processing. These steps not only prolong the production cycle but also constrain the material’s scalability and application flexibility.
The process introduced by the NC State team, known as selective laser reaction pyrolysis (SLRP), replaces traditional workflows with a single-step laser treatment. Using a carbon dioxide infrared laser from OMTech, the system heats a hafnium-based liquid precursor (SHP199 HFC from Starfire Systems) inside an argon-filled chamber.
“Our technique allows us to create ultra-high temperature ceramic structures and coatings in seconds or minutes, whereas conventional techniques take hours or days,” Xu says.
Temperatures exceeding 2000 °C are reached within seconds, triggering crosslinking and pyrolysis simultaneously. This rapid conversion enables the formation of HfC powders or coatings without the use of molds or high-temperature furnaces.
Evaluating additives for yield and purity
To examine how precursor composition affects energy absorption and material yield, the researchers introduced two additives. Dicumyl peroxide, a thermal activator, had minimal effect on laser energy reflectance but improved ceramic yield and preserved material purity.
Secondly, benzophenone, a photo-activator that initiates crosslinking under ultraviolet (UV) light, reduced energy reflection and enhanced heat absorption. However, it also led to trace hafnium oxide formation, likely due to reactions involving residual oxygen during UV exposure. The results show that thermal activation offers greater phase control, while photo-activation may require tighter environmental regulation.
Material characterization confirmed that HfC was successfully synthesized at target temperatures of 1700 °C, 1800 °C, and 2000 °C. X-ray diffraction identified a consistent cubic-phase structure in all samples produced without photo-activation.
Crystallite sizes remained near 39.8 nm, while scanning and transmission electron microscopy revealed well-formed grain structures, low porosity, and uniform elemental distribution. No oxygen contamination was observed in thermally activated samples, affirming the effectiveness of the inert atmosphere.
The researchers also demonstrated that the method could deposit HfC coatings onto carbon–carbon composite substrates, materials widely used in aerospace systems. A single coating layer reduced surface irregularities by filling fiber gaps.
A second layer altered surface roughness and geometry, resulting in a more complex profile. Profilometry and confocal imaging confirmed measurable changes in height and texture, indicating that surface properties can be tuned by adjusting deposition parameters.
When compared with traditional polymer-derived ceramic techniques, which require hours of heating and produce yields between 26–36 %, the laser-based method achieved up to 56 % ceramic yield in under ten minutes. The method’s ability to deliver rapid, localized heating while preserving material quality makes it well suited for scalable manufacturing, particularly in applications involving intricate geometries or thermally sensitive components.
“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,” says Xu.
Laser processing of ceramics
Lasers are being used in different ways across ceramic processing. Some methods focus on purity and speed, others on geometry and structural control, all aiming to move past conventional manufacturing limits.
Two years ago, ceramic 3D printing specialist Lithoz and the U.S. Department of Energy’s (DoE) Oak Ridge National Laboratory (ORNL) signed a Cooperative R&D Agreement to explore the use of Lithoz’s Laser-Induced Slipcasting (LIS) 3D printing to process non-oxide ceramics.
The project focused on high-refractive index ceramics like silicon carbide and silicon nitride, aiming to assess the scalability and performance of LIS for extreme temperature applications in aerospace, defense, and heat exchange systems. Using the CeraMax Vario V900 3D printer, the team leveraged laser slurry drying to produce complex, support-free ceramic parts. Plans included printing, debinding, and sintering oxide-ceramic materials, followed by rigorous testing to assess performance and demonstrate LIS as a scalable alternative to traditional ceramic molding techniques.
Elsewhere, Jiangnan University researchers developed a novel 3D printing technique that enabled the fabrication of complex ceramic structures without the need for support materials. The method combined direct ink writing (DIW) with near-infrared (NIR) light-induced photopolymerization, using a 980 nm laser to cure the ceramic slurry in situ as it was extruded.
This allowed multi-scale filaments, ranging from 0.41 mm to 3.5 mm in diameter, to solidify almost instantly, resulting in freestanding shapes like torsion springs and cantilevers. Compared to UV light, NIR offered significantly greater curing depth in a fraction of the time. The process also reduced post-processing, improved precision, and operated without heating or cooling, holding promise for applications in aerospace, energy, electronics, and biomedicine.
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Featured image shows photographic images of the experimental setup, displaying the front and top views of the environmental chamber used for laser-based HfC synthesis. Photo via NC State.
