Chunling Qin

Chemical characteristics of the passive surface films formed on newly developed Cu–Zr–Ag–Al bulk metallic glasses

In this paper, we systematically demonstrate the corrosion behavior and surface characteristics of a newly developed Cu 36 Zr 48 Ag 8 Al 8 bulk metallic glass (BMG). The Cu 36 Zr 48 Ag 8 Al 8 BMG exhibits excellent corrosion resistance in acidic and alkaline solutions without Cl − ions. The alloy is spontaneously passivated with a markedly low current density in 1 N H 2 SO 4 solution. The formation of the bilayered passive film of the present alloy immersed in 1 N H 2 SO 4 solution, which is composed mostly of Zr 4+ cations in the exterior part and Zr 4+ - and Al 3+ -enriched cations in the inner part, could be responsible for the high corrosion resistance.

Enhancement of glass-forming ability and corrosion resistance of Zr-based Zr-Ni-Al bulk metallic glasses with minor addition of Nb

Cu-free Zr-based bulk metallic glasses (BMGs) with high glass-forming ability (GFA) have been discovered in the Zr-Ni-Al-Nb system. The GFA of Zr-Ni-Al alloys can be significantly enhanced by the minor addition of Nb, which increases the glass transition temperature, and lowers the melting and liquidus temperatures. The Zr-Ni-Al-Nb BMGs have critical sample diameters of 15–20 mm as verified by a copper mold casting. They exhibit excellent corrosion resistance in chloride-ion-containing solutions, which is considerably better than that of other known Zr-based BMGs with superhigh GFA. It was revealed that the formation of highly protective Zr-, Al-, and Nb-enriched surface film is responsible for the high corrosion resistance. The BMGs also possess high compressive yield strength of 1786–1847 MPa, large plastic strain of 1.6–3.2%, and a high Poisson’s ratio of 0.365–0.371.

Low temperature transport properties of Ce-Al metallic glasses

The low temperature transport properties of Ce75−xAl25+x (x = 0, 10, and 15 at. %) metallic glasses were investigated. Magnetic field and composition tuned magnetoresistances changing from negative to positive values were observed at low temperature. It was suggested that these peculiar phenomena were caused by the tunable competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida interaction in Ce-Al metallic glass with the variation in Ce content and magnetic field. Further magnetization and Ce-2p3d resonant inelastic x-ray scattering spectroscopy measurements supported this scenario. These Ce-Al metallic glasses could provide an interesting model system for the investigation of 4f electron behaviors in complex condensed matter with tunable transport properties.

Dealloying of Cu-Based Metallic Glasses in Acidic Solutions: Products and Energy Storage Applications

Dealloying, a famous ancient etching technique, was used to produce nanoporous metals decades ago. With the development of dealloying techniques and theories, various interesting dealloying products including nanoporous metals/alloys, metal oxides and composites, which exhibit excellent catalytic, optical and sensing performance, have been developed in recent years. As a result, the research on dealloying products is of great importance for developing new materials with superior physical and chemical properties. In this paper, typical dealloying products from Cu-based metallic glasses after dealloying in hydrofluoric acid and hydrochloric acid solutions are summarized. Several potential application fields of these dealloying products are discussed. A promising application of nanoporous Cu (NPC) and NPC-contained composites related to the energy storage field is introduced. It is expected that more promising dealloying products could be developed for practical energy storage applications.

Tailored Dealloying Products of Cu-based Metallic Glasses in Hydrochloric Acid Solutions

Free dealloying of Cu-Hf-Al metallic glasses in HCl electrolytes are studied in this paper. The results show that the electrolyte concentration and dealloying time strongly influence the type of dealloying products. A superficial dealloying happens in diluted HCl electrolytes while a complete dealloying occurs in concentrated HCl electrolytes. The results present that Cu 2 O microparticles with regular morphology can be tailored on glassy surfaces in 0.05 M HCl solution by controlling the dealloying time. Furthermore, the designable products of nanoporous Cu, Cu 2 O nanoplates and CuO microwires can be fabricated in 1.2 M HCl electrolyte with the dealloying time. Due to a big difference of examined Cu-Hf-Al alloys in the electrolyte concentration and dealloying time, one or mixed dealloying products (Cu, Cu 2 O and CuO), which depend on the progress of relative chemical reactions and the different dealloying route, will finally be produced.

Synthesis of Cu xO(x = 1,2)/amorphous compounds by dealloying and spontaneous oxidation method

CuxO(x = 1,2)/amorphous compounds have been successfully synthesized by chemical free dealloying and spontaneous oxidation method. Technological parameters, such as the acid concentration and dealloying time strongly influence the crystal type, size and morphology of coppery oxide. The further study shows that with the increase of HCl concentration, the surface coverage rate of Cu2O micro-flowers increases and the sizes of Cu2O micro-flowers get bigger. Moreover, it is observed that cracks are formed on the etched ribbon surface and plentiful Cu2O/CuO particles grow up from these crack walls if the dealloying time extends to long enough. Considering many fascinating properties of Cu2O/CuO particles and the amorphous alloy carrier, potential application fields of these amazing compounds will be developed in future.

Tunable Cu 2 O nanocrystals fabricated by free dealloying of amorphous ribbons

This work discovers that Cu2O nanocrystals with controllable structures can be synthesized on surfaces of nanoporous Cu and amorphous ribbons by free dealloying of Cu-based amorphous alloys in acidic solutions. Technological parameters, such as the acid, acid concentration, and dealloying time strongly influence the crystal size, structure and morphology of Cu2O. Cu2O nanocubes are fabricated on surfaces of nanoporous Cu in the hydrofluoric acid treated alloy, while various Cu2O particles are tailored on surfaces of amorphous alloys immersed in hydrochloric acid for different time. The increasing dealloying time and adsorbed oxygen improve the growth rates along the 〈1 0 0〉 direction of Cu2O crystals relative to that of the 〈1 1 1〉 direction, which is the key to change the shapes of Cu2O crystals. The understanding of morphology evolution of Cu2O nanocrystals in this work is helpful in tailoring Cu2O particles with designable shapes and controllable properties in application fields.

Glass formation, chemical properties and surface analysis of Cu-based bulk metallic glasses.

This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs). In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni) and Cu–Zr–Ag–Al–(Nb) bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS) analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

Direct preparation of nano-quasicrystals via a water-cooled wedge-shaped copper mould

We have successfully synthesized multicomponent Mg-based nano-quasicrystals (nano-QCs) through a simple route by using a water-cooled wedge-shaped copper mould. Nanoscale QCs are prepared directly on tip of wedge-shaped castings. The further study shows that nano-QCs in the Mg71Zn26Y2Cu1 alloy show well microhardness of greater than HV450. Electrochemical properties of three kinds of quasicrystal alloys are investigated in simulated seawater. The Mg71Zn26Y2Cu1 nano-QC alloy presents the best corrosion resistance in this study for the formation of well-distributed nano-QC phases (1-5 nm) and polygonal Mg2(Cu,Y) nanophases (40-50 nm).

Tension and stress relaxation behavior of a La-based bulk metallic glass

Tension and stress-relaxation behaviors of a La 62 Al 14 Cu 11.7 Ag 2.3 Ni 5 Co 5 bulk metallic glass (BMG) as a function of isothermal annealing time have been investigated. It is found that annealing at 373 K below the glass-transition temperature (423 K) of the BMG alloy causes an increase of special heat difference at the glass transition and density of the alloy, indicating a reduction of free volume in the BMG alloy with annealing time. Compared with the as-cast sample, the fracture strength, Vickers hardness, viscosity, Young’s modulus, and stress-relaxation stability of the annealed BMGs increase with annealing time, which is caused by the reduction of free volume in the annealed samples. Furthermore, a change of fracture morphology from a mixture of smooth and furrow zones in the as-cast sample to a mainly furrow zone in the sample annealed for 8 h was also observed. All samples exhibit brittle behavior during tension tests.