Nanoporous silicon carbide created at only 800°C through liquid metal dealloying
Researchers at Tohoku University have developed a method to produce crystalline nanoporous silicon carbide (SiC) at just 800°C (1,472°F), a significantly lower temperature than conventional techniques typically require for nanostructured SiC. The study, published in the journal Scripta Materialia, describes the formation of β-SiC with a distinctive three-dimensional porous architecture made of interconnected nanoscale plates.
Silicon carbide is a ceramic material valued for its heat resistance and chemical stability, making it suitable for applications in electronics, catalysts and energy-related technologies. However, SiC generally demands high-temperature processing, and simultaneously forming and controlling porous structures at the nanometer scale has remained a challenge.
The research team, led by the Institute for Materials Research (IMR) at Tohoku University, used liquid metal dealloying (LMD) to address this issue. The technique involves immersing a solid precursor containing multiple elements in a molten metal, which selectively removes a specific element.
In this study, the researchers used Mn5SiC, a compound with a layered crystal structure, as the precursor and immersed it in molten bismuth. Manganese was selectively dissolved into the molten metal while the remaining silicon-carbon framework reorganized to form crystalline β-SiC.
„LMD is a method that has been previously applied mainly to metals, intermetallic compounds and semimetals, but our research expands the scope to strongly covalently bonded ceramics,” said Hidemi Kato, a professor at the Institute for Materials Research at Tohoku University. „We think this approach could provide an exciting new strategy for designing nanoporous ceramics.”
First-principles calculations indicated that the structural rearrangement of the remaining silicon-carbon framework into β-SiC is energetically favorable. The researchers also suggest that the layered crystal structure of the precursor may have influenced the formation of the nanoplate architecture. Further studies will be needed to clarify how the precursor structure is related to the growth and crystallographic orientation of the nanoplates.
The study demonstrates that crystalline nanoporous β-SiC can be formed at relatively low temperatures while simultaneously creating a three-dimensional nanoscale porous architecture, offering a new route for making and structurally controlling covalently bonded ceramics under milder thermal conditions than conventional methods.
