Fig nbsp illustrates the surface morphology and

The thermal and chemical stability and lubricant properties of h-BN are closely associated with its crystalline degree. XRD was performed on all of the samples, and the results are shown in Fig. 3. Many signals were observed in all 4 patterns, and part of them can be attributed to titanium contained in the Ti-6242 alloy (JCPDS file 089-3073) and/or the MLN 8237 compounds (TiN, JCPDS file 087-0633 and TiB2, JCPDS file 089-3923). Our previous work demonstrated that during the annealing process via infrared irradiation, reactions occur between BN and Ti at the interface, leading to a new interphase composed of TiN and TiB2 that is several microns thick [8]. This interphase enhanced the coating/substrate adhesion thus increasing the sample life-time. H-BN crystallinity is generally characterized by peaks at 26.7° for (002) and 41.8° and 43.2° for (10) crystallographic planes [19]. Peaks at 42° to 45° could not be clearly distinguished from those of the substrate and interphase for samples deposited on Ti-6242 alloy. Therefore it is reasonable to focus our analysis on the signal at 2θ ≈ 26.7°. The XRD pattern recorded on LiBN0 sample presents a broadened peak shifted at 2θ = 25.1°, meaning that the average crystalline area is small, according to the Scherrer's equation (see Table 1). Moreover, the lattice parameter, d, can be obtained using the Bragg's law. The calculated value, d = 0.36 nm, is more important than the h-BN's theoretical one (0.33 nm) revealing a disorder arrangement. Moreover, we can see that the full width at half maximum, FWHM, of this peak becomes narrower and shifted toward the theoretical position of crystallographic planes at 26.7° with the increase of the Li3N ratio in the initial mixture. This variation means that under the same thermal treatment process, Li3N with an h-BN coating becomes remarkably more crystallized. In addition, the degree of crystallinity increased with the promoter ratio in the pre-mixture. Table 1 records the measurement values for the (002) diffraction plane position, its FWHM, the interlayer lattice, d002, and the calculated values for crystalline dimension, L002, obtained by using Scherrer's equation  [20].