NbCNbN

NbCNbN is a term used in materials science to describe niobium-based carbonitride systems that combine carbon and nitrogen with niobium. It can refer to (i) a solid solution Nb(C,N) in which carbon and nitrogen share the anion sublattice within NbC/NbN-type lattices, and (ii) nanolaminate or multilayer coatings consisting of alternating NbC and NbN layers. In either case, NbCNbN coatings are studied for their potential to combine hardness, thermal stability, and wear resistance, making them candidates for protective coatings in demanding environments.

Structure and composition: NbC and NbN crystallize in the rock-salt (NaCl) structure. In Nb(C,N), carbon and nitrogen occupy the same sublattice, with the Nb lattice constant varying with the C:N ratio. In multilayer NbC/NbN, layer thickness, interface quality, and residual stresses influence properties. The choice between a single-phase carbonitride and a laminated structure can dictate hardness, toughness, and thermal behavior.

Synthesis: Common synthesis methods include physical vapor deposition (PVD) techniques such as magnetron sputtering and arc evaporation, sometimes with co-sputtering of Nb, C, and N sources. Chemical vapor deposition (CVD) and plasma-enhanced methods are also used. The C:N ratio is tuned during deposition, and post-deposition annealing can improve phase formation and bonding between layers or within the solid solution.

Properties and applications: Hardness values for NbC/NbN systems typically reach tens of gigapascals, with Nb(C,N) coatings showing high hardness, good thermal stability, and oxidation resistance. Nanolaminate structures can exhibit enhanced toughness and damage tolerance due to the laminated architecture. Applications include protective coatings for cutting tools, wear-resistant surfaces, diffusion barriers in microelectronics, and protective seals in high-temperature equipment.

See also NbC, NbN, carbonitride, hard coatings, nanolaminates.