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Hard magnetic property enhancement of melt spun Co88Hf12 ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH)max) of 2.6 MGOe and intrinsic coercivity (iHc) of 1.5 kOe for B-free Co88Hf12 ribbons to (BH)max = 7.7 MGOe and iHc = 3.1 kOe for Co85Hf12B3 ribbons but also improve the Curie temperature (TC) of 7:1 phase. The (BH)max value achieved in Co85Hf12B3 ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher than that of Co11Hf2B ribbons spun at 16 m/s [M. A. McGuire, O. Rios, N. J. Ghimire, and M. Koehler, Appl. Phys. Lett. 101, 202401 (2012)]. The structural analysis confirms that B enters the orthorhombic Co7Hf (7:1) crystal structure as interstitial atoms, forming Co7HfBx, in the as-spun state. Yet B may diffuse out from the 7:1 phase after post-annealing, leading to the reduction of Curie temperature and the magnetic properties. The uniformly refined microstructure with B-doping results in high remanence (Br) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co7HfBx phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co7Hf-based ribbons.

The pattern of micropore with various diameters (0, 0.5, 1.5 and 5 μm) on the surface of single crystal silicon was obtained through laser treatment and then the graphite-like carbon (GLC) film was deposited on these substrates through magnetron sputtering technology. The effect of micropore diameter on tribological performance of GLC film under air and aqueous environments was systematically investigated. The results indicated that the micropore diameter and test environment greatly affected the tribological behavior of GLC film. The friction coefficient (COF) and wear loss of GLC film were significantly improved in aqueous environment compared with in air. This was attributed to the formation of aqueous molecular film, which could obstruct the immediate contact between GLC film and counterpart. Meanwhile, the anti-wear ability of GLC film in aqueous environment strengthened firstly and then weakened as the micropore diameter increased. When the micropore diameter was 1.5 μm, the GLC film displayed the lowest wear rate of 0.32×10 −8 mm 3 Nm −1 in aqueous environment, which was 67.65%, 46.08% and 26.67% lower than the micropore diameters of 0, 0.5 and 5 μm, respectively. This was due to the synergistic effect of surface roughness and lubricant (graphitized particles and aqueous medium) captured by micropores.

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