The work represents a thorough treatment of ultra-high temperature materials with melting points around or over 2500 °C. The second volume included physical (structural, thermal, electromagnetic, optical, mechanical and nuclear) and chemical (binary, ternary and multicomponent systems, solid-state diffusion, wettability, interaction with chemicals, gases and aqueous solutions) properties of refractory carbide materials: tantalum carbides (monocarbide TaC1–x and semicarbide a/b-Ta2±xC), hafnium monocarbide HfC1–x, niobium carbides (monocarbide NbC1–x and semicarbide a/b/c-Nb2±xC) and zirconium monocarbide ZrC1–x. It will be of interest to researchers, engineers, postgraduate, graduate and undergraduate students alike. The reader/user is provided with the full qualitative and quantitative assessment for the materials, which could be applied in various engineering devices and environmental conditions in the wide range from cryogenic to ultra-high temperatures, on the basis of the latest updates in the field of physics, chemistry, nanotechnology, materials science and engineering.

Ultra-High Temperature Materials II: Refractory Carbides I (Ta, Hf, NB and Zr Carbides)

Transition metal carbides and nitrides as oxygen reduction reaction catalyst or catalyst support in proton exchange membrane fuel cells (PEMFCs)

As a new member in two-dimensional materials family, transition metal carbides (TMCs) have many excellent properties, such as chemical stability, in-plane anisotropy, high conductivity and flexibility, and remarkable energy conversation efficiency, which predispose them for promising applications as transparent electrode, flexible electronics, broadband photodetectors and battery electrodes. However, up to now, their device applications are in the early stage, especially because their controllable synthesis is still a great challenge. This review systematically summarized the state-of-the-art research in this rapidly developing field with particular focus on structure, property, synthesis and applicability of TMCs. Finally, the current challenges and future perspectives are outlined for the application of 2D TMCs.

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Recent Progress in Emerging Two-Dimensional Transition Metal Carbides

Chromium carbide films with different phase contents were deposited at 126 ± 26 °C by industrial high rate reactive magnetron sputtering, using both direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). Film structure and properties were studied by SEM, XRD, TEM, XPS, NRA, Raman spectroscopy, nanoindentation, unlubricated reciprocating sliding experiments, and a laboratory setup to measure electrical contact resistance. The films consisted of amorphous a-CrCy, a nanocrystalline minority phase of metastable cubic nc-CrCx, and a hydrogenated graphite-like amorphous carbon matrix (a-C:H). The DCMS and HiPIMS processes yielded films with similar phase contents and microstructures, as well as similar functional properties. Low elastic modulus, down to 66 GPa, indicated good wear properties via a hardness/elastic modulus (H/E) ratio of 0.087. Unlubricated steady-state friction coefficients down to 0.13 were obtained for films with 69 at.% carbon, while the electrical contact resistance could be reduced by two orders of magnitude by addition of a-C:H phase to purely carbidic films. The present films are promising candidates for sliding electrical contact applications.

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Growth and characterization of chromium carbide films deposited by high rate reactive magnetron sputtering for electrical contact applications

NbCxN1−x layers were deposited on MgO(001) by reactive magnetron co-sputtering from Nb and graphite targets in 5 mTorr pure N2 at Ts = 600–1000 °C The anion-to-Nb ratio of 109 ± 005 is independent of Ts and indicates a nearly stoichiometric rock–salt structure Nb(N,C) solid solution In contrast, the C-to-N ratio increases from 020–059 for Ts = 600–1000 °C, which is attributed to a low C sticking probability at high N surface coverage at low Ts Layers grown at Ts ≥ 700 °C are epitaxial single-crystals with a cube-on-cube relationship to the substrate, (001)NbCN||(001)MgO and [100]NbCN||[100]MgO, as determined from X-ray diffraction θ–2θ and ϕ-scans Reciprocal space mapping on a NbC037N063 layer deposited at Ts = 1000 °C indicates an in-plane compressive strain of − 04% and a relaxed lattice constant of 4409 ± 0009 A The lattice constant of NbCxN1−x increases with x, consistent with a linear increase predicted by first-principles density functional calculations The calculated bulk modulus, 307 GPa for NbN and 300 GPa for NbC, is nearly independent of x Similarly, c11 increases slightly from 641 to 666 GPa, but c12 decreases considerably from 140 to 117 GPa, and c44 more than doubles from 78 to 171 GPa as x increases from 0 to 1, indicating a transition from ductile NbN to brittle NbC This also results in an increase in the predicted isotropic elastic modulus from 335 to 504 GPa, which is in good agreement with the measured 350 ± 12 GPa for NbCxN1−x(001) with x = 019–031 The hardness H = 22 ± 2 GPa of epitaxial NbCxN1−x layers is nearly independent of x = 019–037 and Ts = 700–1000 °C, but is reduced to H = 182 ± 08 GPa for the nanocrystalline layer deposited at Ts = 600 °C The electrical resistivity decreases strongly with increasing Ts

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G. Cheng

Papers

Reactive magnetron sputtering deposition and characterization of niobium carbide films