Figure 2
(a,b) Vickers hardness measurement for single–crystal δ– and γ–MoN. Indentations numbered with ′1′, ′2′, ′3′ and ′4′ correspond to applied loads of 0.245, 0.49, 0.98 and 1.96 N, respectively. The crystals in (a) were prepared by sintering of phase–pure δ–MoN powders at 8 GPa and 1800 °C for 60 min. The γ–MoN crystal in (b) was directly grown using ion–exchange reaction (see Fig. 1e). (c) Vickers hardness, Hv, of δ– and γ–MoN as a function of applied load. Also plotted are the reported Hv values for other hard nitrides including ZrN, NbN and HfN (ref. 4). (d) Hv vs volume per atom (i.e., normalized volume in terms of per atom) for γ–MoN, γ–ZrN (ref. 4) and γ–NbN (ref. 4) under a load of 0.49 N. (e) Bulk modulus, B0, vs volume per atom. The measured bulk moduli for δ– and γ–MoN are ~335 and ~307 GPa, respectively, based on compression experiments (Suppl Figures S6–S7). (f) Shear modulus, G, vs volume per atom.
