The features of vanadium-boride

The VB2 coatings were synthesized by pulsed magnetron co-sputtering on the substrates of Si( 100) ,glass and M2 tool steel,pre-deposited with Ti transition layers. The impact of the frequency of power-

supply on the
microstructures and mechanical properties of the VB2 coatings was investigated. The VB2 coatings were characterized with X-ray diffraction,scanning electron microscopy,atomic force microscopy and

conventional mechanical probes.
The results show that depending on the frequency,the VB2 coatings possess improved surface mechanical properties,such as higher hardness,better wear-resistance and lower friction coefficient. As the

frequency increased,the surfaces with big columnar-structured grains turned into amorphous-like surfaces with smaller grains and reduced roughness. Grown at 250 kHz,the < 100 > preferentially

oriented,smooth and compact VB2 coatings had a surface hardness of 43 GPa,and a wear-rate of 7. 8 × 10 - 16 m3 /N m,300 times lower than that of M2 tool steel.

Thermodiffusion coatings (V+B) on steel have been obtained by an initial saturation with V followed by B. The properties of the diffusion layers, namely microstructure, microhardness, and phase composition,

have been studied, and the influence of temperature and duration of treatment with V on steel on the thickness of the metallized layer and its phase composition has been determined. By increasing the

temperature and duration of treatment with V on steel to more than 1200°C and 11 h, diffusion layers ∼350 μm thick and structures with clearly defined sublayers (zones) are obtained. VC is formed in the surface

zone, which after boronizing turns into VB2.

Investigation on the reactivity of atomic clusters represents an important approach to discover new species to activate and transform methane, the most stable alkane molecule. While a few types of transition

metal species have been found to be capable of cleaving the C–H bond of methane, methane activation by the transition metal boride species has not been explored yet. This study reports that vanadium boride

cluster cations VBn+ (n = 3–6) can dehydrogenate methane under thermal collision conditions. The mechanistic details of the efficient reactions have been elucidated by quantum chemistry calculations on the

VB3+ reaction system. Compared to the non-polar bare B3 cluster, the B3 moiety in VB3+ can be polarized by the V+ cation and thus its reactivity toward methane can be much enhanced. This study provides new

insights into the rational design of boron-based catalysts for methane activation.

The features of vanadium-boride