[en] The non-isothermal precipitation behaviors of Al–Mg–Si–Cu alloys with different Zn contents were investigated by differential scanning calorimetry (DSC) analysis, hardness measurement and high resolution transmission electron microscope characterization. The results show that Zn addition has a significant effect on the GP zone dissolution and precipitation of Al-Mg-Si-Cu alloys. And their activation energies change with the changes of Zn content and aging conditions. Precipitation kinetics can be improved by adding 0.5 wt% or 3.0 wt%Zn, while be suppressed after adding 1.5 wt%Zn. The Mg-Si precipitates (GP zones and β″) are still the main precipitates in the Al-Mg-Si-Cu alloys after heated up to 250 °C, and no Mg-Zn precipitates are observed in the Zn-added alloy due to the occurrence of Mg-Zn precipitates reversion. The measured age-hardening responses of the alloys are corresponding to the predicted results by the established precipitation kinetic equations. Additionally, a double-hump phenomenon of hardness appears in the artificial aging of pre-aged alloy with 3.0 wt% Zn addition, which resulted from the formation of pre-β″ and β″ precipitates. Finally, the precipitation mechanism of Al-Mg-Si-Cu alloys with different Zn contents was proposed based on the microstructure evolution and interaction forces between Mg, Si and Zn atoms.

[en] The acoustic properties are investigated of the Fibonacci Nb-Cu metallic superlattices from surface waves by means of light scattering. The measured velocities of surface waves do not show a dramatic difference between quasiperiodic superlattices and periodic superlattices. The velocity of Rayleigh surface is found to be 9 to 16% less than the theoretical value calculated from bulk elastic constants and densities. (author)

[en] The effects of ion implantation on the resistivity and structure of polycrystalline diamond films which were prepared by hot-filament chemical vapor deposition using methane as the reactant gas are reported. Ion implantation was carried out with 80 keV P⁺ ions at different temperatures. The depth profile of P⁺ in diamond measured by RBS is consistent with the results of TRIM calculation. After ion bombardment the resistivity of CVD diamond films decreases to a saturated value. The structural changes after ion irradiation were characterized by SEM and Raman spectra, and the conduction mechanism is also discussed. (Author)

[en] The authors present Raman scattering results on transverse acoustic phonons in metallic superlattice and have verified most expectations regarding acoustic phonon folding as in semiconductor superlattices. Raman folded peaks up to seventh order can be observed which agree closely with elastic continuum prediction in frequency. Owing to metal high optical absorption, phonon momentum nonconserving have caused increasing linewidth and disorder-activated transverse-acoustic mode scattering

[en] Graphical abstract: The SEM images of Li_2Ti_6O_1_3 nanobelts (a) and galvanostatic charge and discharge cycling performance of Li_2Ti_6O_1_3 nanobelts (b) at a constant current density of 12.5 mA g"−"1 in the voltage range between 1.0 and 3.0 V at 25 °C. - Highlights: • Li_2Ti_6O_1_3 nanobelts have been prepared via a self-template process for the first time. • The electrochemical properties of Na_2Ti_6O_1_3 and Li_2Ti_6O_1_3 nanobelts are investigated and compared. • The photocatalytic activities of nanobelts and counterpart bulks are investigated and compared. • The reversible discharge capacity of nanobelts is slightly less than that of counterpart bulks. - Abstract: Single-crystalline Li_2Ti_6O_1_3 nanobelts have been prepared from Na_2Ti_6O_1_3 nanobelts as the precursor templates via sodium/lithium ion-exchange in molten LiNO_3 at 400 °C for 10 h for the first time. Both Na_2Ti_6O_1_3 and Li_2Ti_6O_1_3 nanobelts are also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). Our experiments show that Na_2Ti_6O_1_3 and Li_2Ti_6O_1_3 nanobelts exhibit higher photocatalytic efficiency than their bulk counterparts for the degradation of Rhodamine B (RhB) under ultraviolet light (UV) irradiation. In comparison to Na_2Ti_6O_1_3 nanobelts, Li_2Ti_6O_1_3 nanobelts exhibit lower photocatalytic efficiency, which may result from the expansion of tunnel space in Li_2Ti_6O_1_3. However, the electrochemical Li insertion–extraction experiments reveal that the stable reversible discharge capacity of Li_2Ti_6O_1_3 nanobelts is higher than that of Na_2Ti_6O_1_3 nanobelts. Moreover, our results also indicate that the reversible discharge capacities of Na_2Ti_6O_1_3 and Li_2Ti_6O_1_3 nanobelts are slightly less than that of their bulk counterparts

[en] Highlights: • Relationships between adhesion work and the microstructures are quantitatively established in different wetting state. • Adhesion work of a water droplet is strangely larger than that of its frozen (namely, W_aw > W_ai, a challenging question). • Theoretical explanation for anti–icing and icephobicity of superhydrophobic surface. • Adhesion work of the frozen water droplet may be used for characterization of contact state. -- Abstract: Although surface microstructures is the key to superhydrophobicity, and possibly leads to significant icephobicity when a water droplet freezes on superhydrophobic surfaces (SHS), thermodynamic mechanisms responsible for the icephobicity and anti–icing still need to be further studied. For this reason, we established the relationships between some quantities, i.e., contact angle (CA) together hysteresis (CAH), adhesion work and the microstructures by a three–dimension (3–D) surface model, and theoretically explained the anti–icing and icephobicity from the SHS. Our theoretical and experimental study indicate, the adhesion work (W_ai) of a frozen water droplet to the SHS in composite wetting state (CWS) is apparently less than that in the non–composite wetting state (NCWS). Therefore it is necessary to create such CWS by designing surface micro/nanostructure. Further study also shows, the adhesion work (W_aw) of a water droplet to the SHS is larger than that (W_ai) of their frozen, thus implying decrease of the adhesion work after icing. This will improve on the understanding of the SHS for anti–icing and icephobicity.

[en] Quaternary Heusler alloy Ni₅₀Mn₈Fe₁₇Ga₂₅ ribbons have been prepared by the melt-spun method. The ribbons exhibit large negative magnetoresistance (MR){=[R(H)-R(0)]/R(0)} over a wide temperature region, particularly in the region during the martensitic phase transformation. The MR decreases significantly after annealing. The large MR is isotropic and is mainly attributed to the local magnetic disorders, magnetic clusters, and heterogeneity. The maximum MR at martensitic transformation may be due to the redistribution of electrons and the increase of phase boundary scattering. This feature adds a useful functionality to the already interesting Heusler alloys

[en] Abtract: The submicron chromium dioxide (CrO_2) thin films have been fabricated on poly-crystal stannic oxide (SnO_2) films by atmospheric pressure chemical vapor deposition method. At low temperature, the CrO_2 thin film has sharp increase in the MR at low fields. This should be mainly attributed to spin-dependent tunneling through grain boundaries between adjacent CrO_2 grains. At high temperature, the magnetoresistance (MR) of CrO_2 thin film has small value and shows linear dependence on applied magnetic field. The resistivity of CrO_2 thin film decreases significantly as temperature increases, which can be best described by the fluctuation-induced tunneling model below 220 K. The MR for the CrO_2 thin film on SnO_2 film also decreases rapidly with increasing temperature.

[en] MnCoGe-based materials exhibiting large magnetocaloric effect (MCE) are potential candidates for magnetic refrigerants. However, the poor mechanical properties and intrinsic brittleness restrict their applications. Here, we report the synthesis of epoxy-bonded Mn_0.98CoGe composites and the evolutions of their microstructure, mechanical properties, and MCE with varying epoxy content. The mechanical properties and machinability are remarkably improved with epoxy resin addition. Meanwhile, the magnetic entropy change (ΔS_M) remains nearly unchanged when the content of epoxy is <5 wt%. Their relative cooling powder and the thermal conductivity are comparable to those of typical magnetic refrigerants with giant MCE.

[en] Materials showing abrupt change of thermal conductivity are strongly desired for rapidly developing thermal regulation applications. Here, we report a sharp change of thermal conductivity (Δκ/κ₀) up to 200% within a temperature interval of ~ 40 K in hexagonal sulfides Ni_1-xFe_xS bonded with silver. Such Δκ/κ₀ values exceed those reported in other thermal regulation materials, e.g., VO₂ series (Δκ/κ₀1-_xFe_xS and thus improves machinability and thermal cycling stability, which is beneficial to the practical applications. Our work presents a new promising material for thermal management applications.