Huameng Fu

Ultrafast degradation of azo dyes catalyzed by cobalt-based metallic glass

Reactivity and mass loss are considered mutually exclusive in conventional zero-valent metal (ZVM) technology to treat environmental contaminants. Here, we report the outstanding performance of Co-based metallic glass (MG) in degrading an aqueous solution of azo dye, thus eliminating this trade-off. Ball-milled Co-based MG powders completely degrade Acid Orange II at an ultrafast rate. The surface-area-normalized rate constant of Co-based MG powders was one order of magnitude higher than that of Co-based crystalline counterparts and three orders of magnitude higher than that of the widely studied Fe0 powders. The coordinatively unsaturated local structure in Co-based MG responds to the catalysis for degradation, resulting in very low mass loss. Wide applicability and good reusability were also present. Co-based MG is the most efficient material for azo dye degradation reported thus far, and will promote the practical application of MGs as functional materials.

In situ spherical B2 CuZr phase reinforced ZrCuNiAlNb bulk metallic glass matrix composite

In situ microlevel spherical B2 CuZr phase reinforced Zr(49.5)Cu(36.45)Ni(4.05)Al(9)Nb(1) bulk metallic glass matrix composite was prepared successfully by the copper mold casting method. It was found that mechanical properties of Zr(50.5)Cu(36.45)Ni(4.05)Al(9) alloy were improved largely due to the Nb addition. The room-temperature compressive fracture strength and plastic strain for Zr(49.5)Cu(36.45)Ni(4.05)Al(9)Nb(1) rod with a diameter of 5 mm reaches 2037 MPa and 8%, respectively. The improvements are attributed to the precipitation of the spherical B2 CuZr phase distributed uniformly in amorphous matrix, which effectively hampers the propagation of shear bands by deflecting them at the interface and by a multiplication mechanism.

A practical thermodynamic method to calculate the best glass-forming composition for bulk metallic glasses

Bulk metallic glasses are regarded as a new class of engineering materials because of their extraordinary high strength, great elasticity, and high corrosion and wear resistance. The selection of good glass-forming composition is the most important issue in BMG development. In this paper, a thermodynamic method, which combines element substitution and mixing enthalpy calculation, has been successfully developed to predict the optimum glass-forming compositions in Cu-Zr-Ti, Cu-Hf-Ti, Cu-Zr-Hf-Ti and Pd-Ni-P alloy systems. Alloy compositions with the largest glass-forming ability are always accompanied with the smallest enthalpy value for the alloy systems. The prediction results have been confirmed by experiments. It is concluded that the thermodynamic method provides a practical and effective tool to find the optimum glass forming composition.

Nanoindentation response of laser shock peened Ti-based bulk metallic glass

The effect of laser shock peening (LSP) on mechanical properties of Ti-based bulk metallic glass (BMG) was investigated under nanoindentation. Two regions were generated within the specimen after the LSP: (I) the extremely thick softened region (∼300 µm) in which amounts of shear bands and excess free volume were generated; (II) the middle region where the free volume increased but nearly no shear bands were induced. The hardness decreased with the increase of the indenter depth (h), exhibiting indentation size effect (ISE). The ISE increased with the increase of the measured distance away from the laser shocked tip, indicating that the ISE was inhibited by the shear bands and excess free volume was generated by the LSP.

A novel Si/Sn composite with entangled ribbon structure as anode materials for lithium ion battery.

A novel Si/Sn composite anode material with unique ribbon structure was synthesized by Mechanical Milling (MM) and the structural transformation was studied in the present work. The microstructure characterization shows that Si/Sn composite with idealized entangled ribbon structured can be obtained by milling the mixture of the starting materials, Si and Sn for 20 h. According to the calculated results based on the XRD data, the as-milled 20 h sample has the smallest avergae crystalline size. It is supposed that the flexible ribbon structure allows for accommodation of intrinsic damage, which significantly improves the fracture toughness of the composite. The charge and discharge tests of the as-milled 20 h sample have been performed with reference to Li+/Li at a current density of 400 mA g−1 in the voltage from 1.5 to 0.03 V (vs Li/Li+) and the result shows that the initial capacity is ∼1400 mA h g−1, with a retention of ∼1100 mA h g−1 reversible capacity after 50 cycles, which is possible serving as the promising anode material for the lithium ion battery application.

Multifarious Fracture Features of CuZrAlGd(Ag) Bulk Metallic Glasses

Multifarious fracture features, such as coarse rive-like, micro holes, rugged and flat fracture surface, were systematically investigated in the monolithic Cu46-xZr45Al7Gd2Agx (x=0, 0.5) bulk metallic glasses. The fracture planes presented different angles with the loading direction. These fracture features were completely different from the typical fracture characteristics of amorphous alloys, i.e. vein-pattern and fracturing approximately along the maximum shear stress plane. On the other hand, some tiny strips with about 50 nm intervals were also detected on the flat fracture plane. The preliminary discussions on the formation mechanisms of these exceptional features were presented.