Nonmetal Systems Research Articles

Hydrogen-Doping-Induced Metal-Like Ultrahigh Free-Carrier Concentration in Metal-Oxide Material for Giant and Tunable Plasmon Resonance.

The practical utilization of plasmon-based technology relies on the ability to find high-performance plasmonic materials other than noble metals. A key scientific challenge is to significantly increase the intrinsically low concentration of free carriers in metal-oxide materials. Here, a novel electron-proton co-doping strategy is developed to achieve uniform hydrogen doping in metal-oxide MoO3 at mild conditions, which creates a metal-like ultrahigh free-carrier concentration approaching that of noble metals (1021 cm-3 in H1.68 MoO3 versus 1022 cm-3 in Au/Ag). This bestows giant and tunable plasmonic resonances in the visible region to this originally semiconductive material. Using ultrafast spectroscopy characterizations and first-principle simulations, the formation of a quasi-metallic energy band structure that leads to long-lived and strong plasmonic field is revealed. As verified by the surface-enhanced Raman spectra (SERS) of rhodamine 6G molecules on Hx MoO3 , the SERS enhancement factor reaches as high as 1.1 × 107 with a detection limit at concentration as low as 1 × 10-9 mol L-1 , representing the best among the hitherto reported non-metal systems. The findings not only provide a set of metal-like semiconductor materials with merits of low cost, tunable electronic structure, and plasmonic resonance, but also a general strategy to induce tunable ultrahigh free-carrier concentration in non-metal systems.

Insignificant influence of the matrix on the melting of incoherently embedded tin and zinc nanoparticles

For studying the melting point depression of metals, isolated metallic nanoparticles embedded in a matrix are usually prepared by mechanical milling. Al is the main available matrix material. In this work, to explore possible alternative matrices for further investigation of melting, mechanically milled metal–nonmetal systems are developed, namely Sn–LiF, Zn–LiF and Zn–Al2O3. The outcome indicates that different matrices do not have a significantly different influence on the melting of Sn and Zn. Theoretical analyses of both the thermodynamics and kinetics of surface-induced melting may support this experimental finding.

Phase diagram and thermal properties of organic analogues of nonmetal–nonmetal systems

The solid–liquid phase equilibrium data on three binary organic systems, namely 4-hydroxy benzaldehyde (HB)–2-methyl-4-nitro aniline (MNA), 3-hydroxy-4-methoxybenzaldehyde (HMB)–2-chloro-4-nitroaniline (CNA) and 4-aminobenzophenone (ABP)–m-nitrobenzoic acid (NBA), determined by the thaw-melt method, show the formation of a eutectic at 0.60 mol fraction of HB, 0.48 mol fraction of HMB and 0.51 mol fraction of ABP. These systems are organic analogue of nonmetal–nonmetal system. The values of enthalpy of fusion of eutectics and parent components were determined by the DSC method. Using the heat of fusion values, entropy of fusion, heat of mixing, excess thermodynamic functions and Jackson’s roughness parameter were calculated. The negative values of enthalpy of mixing in each case suggest the associative interaction between the molecules of the eutectic melt. The positive value of excess free energy for HB–MNA system indicates the associative interaction between like molecules, while the negative values of excess free energy for HMB–CNA and ABP–NBA indicate the associative interaction between unlike molecules.

Activation of dihydrogen by non-metal systems

This feature article reviews advances in the metal-free activation of hydrogen and the utilization of these and related systems in catalytic hydrogenations.

Hot Spots from Dislocation Pile-up Avalanches

AbstractThe model of localized adiabatic heating associated with release of a dislocation pile-up avalanche is described and re-evaluated. The model supplies a fundamental explanation of shear banding behavior in metal and non-metal systems. Now, a dislocation dynamics description is provided for more realistic assessment of the hot spot heating, for both straight dislocation pile-ups and circular loop pile-ups. Such a localized heating effect was overestimated in the earlier work, in part, to show the dramatic enhancement of the work rate, and the corresponding temperature build-up, potentially occurring in the initial pile-up release, say, at achievement of the critical dislocation mechanics-based stress intensity for cleavage. Proposed applications are to potentially brittle metal, ionic, and energetic material systems.

Sticking of solids in liquids

Under small buoyancy forces, it was observed that solids stick together for varying times before separating, with the time interval depending on the buoyancy force, contact area, separation distance, and liquid viscosity. The effect was observed for both metal and nonmetal systems. The time dependence is accounted for quantitatively on the basis of a fluid mechanics analysis given by Landau and Lifshitz.

Investigations of the effects of ultrasound on some metal and nonmetal systems

The effects of power ultrasound on four metal-nonmetal powdered systems: copper-sulphur iron-sulphur, zinc-sulphur and magnesium-sulphur in various solvents, such as hexane and carbon disulphide, are briefly examined here. For each system, a sonication time of 30 min was affected. The sonicated products are analysed by X-ray diffraction, X-ray fluorescence and atomic absorption spectrophotometry to determine their qualitative and quantitative compositions and the percentage yields of the products obtained are then compared and discussed.

Mass transfer in liquid metals

AbstractThe rate of mass transfer was measured for solid metal shapes dissolving into mercury at room temperature. Sherwood numbers for horizontal tin, cadmium, zinc, and lead cylinders dissolving by natural convection agreed with Nusselt numbers for heat transfer in nonmetallic liquids at the same Rayleigh (Grashof × Prandtl) numbers. Dissolving of zinc tubes by mercury flowing turbulently within them agreed with heat transfer to nonmetals in tubes. Dissolving of random beds of lead spheres by mercury flowing through the bed agreed with similar nonmetal systems. It is concluded that mass transfer processes in liquid metals follow substantially the correlations for other fluids in heat or mass transfer, which with moderate safey factors may thus be used for at least preliminary design purposes.