Hardness, Young’s Modulus and Elastic Recovery in Magnetron Sputtered Amorphous AlMgB14 Films

We report optical and mechanical properties of hard aluminum magnesium boride films magnetron sputtered from a stoichiometric AlMgB14 ceramic target onto Corning® 1737 Glass and Si (100) wafers. High target sputtering rf-power and sufficiently short target-to-substrate distance appeared to be critical processing conditions. Amorphous AlMgB14 films demonstrate very strong indentation size effect (ISE): exceptionally high nanohardness H = 88 GPa and elastic Young’s modulus E* = 517 GPa at 26 nm of the diamond probe penetration depth and almost constant values, respectively, of about 35 GPa and 275 GPa starting at depths of about 2–3% of films’ thickness. For comparative analysis of elastic strain to failure index H/E*, resistance to plastic deformation ratio H3/E*2 and elastic recovery ratio We were obtained in nanoindentation tests performed in a wide range of loading forces from 0.5 to 40 mN. High authentic numerical values of H = 50 GPa and E* = 340 GPa correlate with as low as only 10% of total energy dissipating through the plastic deformations.

The MgB2-catalyzed growth of boron nitride nanotubes using B/MgO as a boron containing precursor

In this paper, magnesium boride (MgB2) was directly introduced as an efficient catalyst to grow boron nitride nanotubes with high quality and purity from a B/MgO/MgB2 precursor in a conventional horizontal tubular furnace.

Role of Mg-B-O Nanostructural Inhomogenities on the Performance of Superconducting MgB2

Auger and SEM studies show that with increasing of MgB2 manufacturing temperature from 600÷800 °C to 1050÷1100 °C the Mg-B-O nanolayers which are present in the MgB2 matrix transform into distinct dispersed Mg-B-O inclusions. On the other hand the sizes of inclusions of higher magnesium borides (MgBx, x=7 ÷ 25) which are also present in the MgB2 matrix. The tendency is observed in a wide range of synthesis pressures (0.1 MPa-2 GPa). The described structural transformations are accompanied by an increase in critical current density, jc, in low and medium magnetic fields and by transition from the grainboundary to the point pinning. The Ti addition results in a further increase in jc due to: Ti promotes the formation of higher magnesium boride inclusions and localization (or segregation) of oxygen in MgB2 matrix, and, hence, facilitates the formation of a homogeneous MgB2 matrix with lower oxygen content, but with an increased number of Mg-B-O and MgBx pinning centers. At low synthesis temperature Ti absorbs hydrogen forming titanium hydrides, thus preventing the formation of MgH2 and provides the material densification. The positive effect of Ti addition is connected with the high ability of Ti to absorb hydrogen, oxygen, and magnesium. The results of the critical current and AC loss study by transformer method using rings from MgB2 are discussed.