Evolution Of Zn Research Articles

Phase-transition tailored nanoporous zinc metal electrodes for rechargeable alkaline zinc-nickel oxide hydroxide and zinc-air batteries

Secondary alkaline Zn batteries are cost-effective, safe, and energy-dense devices, but they are limited in rechargeability. Their short cycle life is caused by the transition between metallic Zn and ZnO, whose differences in electronic conductivity, chemical reactivity, and morphology undermine uniform electrochemical reactions and electrode structural stability. To circumvent these issues, here we propose an electrode design with bi-continuous metallic zinc nanoporous structures capable of stabilizing the electrochemical transition between metallic Zn and ZnO. In particular, via in situ optical microscopy and electrochemical impedance measurements, we demonstrate the kinetics-controlled structural evolution of Zn and ZnO. We also tested the electrochemical energy storage performance of the nanoporous zinc electrodes in alkaline zinc-nickel oxide hydroxide (NiOOH) and zinc-air (using Pt/C/IrO2-based air-electrodes) coin cell configurations. The Zn | |NiOOH cell delivers an areal capacity of 30 mAh/cm2 at 60% depth of discharging for 160 cycles, and the Zn | |Pt/C/IrO2 air cell demonstrates 80-hour stable operation in lean electrolyte condition.

Microstructure evolution of as-extruded Zn–0.62Mn alloys during room temperature compression

The microstructure evolution of Zn–0.62Mn alloys during the room temperature compression with different strains was investigated by scanning electron microscope and X-ray diffraction. The results showed that with the increasing compression strains, the refined dynamic recrystallization grains increase gradually, and some grains rotate. It can also be found that the compression strain promotes the transformation from small-angle grain boundary to large-angle grain boundary. The highest basal textural can be obtained after the room-temperature compression with 80% strain. These results indicate that the microstructure evolution of as-extruded Zn–0.62Mn alloys during the room-temperature compression can be attributed to the grain refinement, grain boundary variation and texture changes.

In situ calorimetric investigation of ZnO transformation from flower-like nanostructures to microrod

The evolution of Zn ( OH ) 4 2 − solution during hydrothermal processing was studied using in situ calorimetry and the solid products were characterized by X-ray diffraction, scanning electron microscopy. It was shown that the formation of flower-like ZnO nanostructures exhibited first endothermic and then exothermic processes, of which the associated heat effect was measured as being −50.45 ± 0.01 J mol −1. Flower-like ZnO nanostructures and ZnO microrod may be selectively formed simply based on the hydrothermal reaction temperatures. The mechanism for the flower-like ZnO nanostructures and ZnO microrod has been suggested.

Atmosphere effects on the formation and evolution of Zn and ZnO nanoparticles in Zn ion implanted SiO 2

Metallic Zn nanoparticles (NPs) have been fabricated in the near surface region of SiO 2 by implantation of Zn ions at energy of 45 keV up to 5.0 × 10 16 ions/cm 2. Such NPs were then subjected to the furnace annealing in different atmospheres. Various techniques, such as ultraviolet–visible spectroscopy (UV–vis), grazing incidence X-ray diffraction spectroscopy (GXRD), photoluminescence spectroscopy (PL), were employed to characterize the formation and evolution of the Zn and ZnO NPs, and also their related optical properties. Our results clearly show that the evolution of Zn NPs depends strongly on the annealing atmosphere. ZnO NPs have been effectively formed with preferred (0 0 2) and (1 0 3) orientations when the samples were annealed in a flow of nitrogen gas or sequentially annealed in nitrogen and oxygen ambient. The PL measurements give the evidence that ZnO NPs with high-quality could be formed when the samples were sequentially annealed in the flows of nitrogen and oxygen gases.

Growth and microstructure for visible emission and surface optical phonon mode of Zn–ZnO nanostructure

The Zn–ZnO nanostructured thin films were prepared in carbon matrix using a cost-effective vacuum-carbon arc method. On increasing graphitization with ZnO, the grazing incidence X-ray diffraction pattern showed that the intensity of the ZnO peak increases, whereas that of the Zn peak decreases. X-ray line profile analysis and transmission electron microscopy were employed to investigate the microstructural evolution of Zn–ZnO nanostructure during vacuum arc processing. A growth mechanism is proposed for the Zn–ZnO nanostructure when reaction with carbon-containing gas inside the reactor wall takes place. Detailed studies of photoluminescence bands clearly exhibit the intensity variation of violet and blue-green bands on increasing graphitization ratio. Using the dielectric continuum approach, surface optical phonon modes of the Zn–ZnO nanostructure were studied for different synthesized samples.

Effect of zinc metal addition on microstructural evolution of Zn 0.22 Cd 0.78 S$ phosphors studied by transmission electron microscopy

The effect of zinc powder addition on the microstructural evolution of fine Zn0.22Cd0.78S:Ag$, Cl phosphor particles was investigated in relation to the luminescent property of phosphors. The phosphor microstructures were analyzed by high-resolution transmission electron microscopy (HRTEM) using the ultramicrotome technique for specimen preparation. The phosphor baking process at 480 °C for 30 min in air results in significant damage to the surface structure of the phosphors due to the decomposition and oxidation of the phosphor itself. The addition of zinc metal powders into the Zn0.22Cd0.78S$ phosphors suppresses the oxidization and decomposition of phosphors by oxidizing zinc metal during the baking process in air. The oxidation of the zinc powders during baking provides the baking furnace with less oxidizing atmosphere for phosphor particles. The structure of phosphors, especially at the surface region, is much less degraded compared to the phosphors baked with no zinc metal addition. © 2000 Kluwer Academic Publishers

Synergistic interactions in trimetallic bonding: A comparison of the [formula omitted] ( NM = Cu, AgorAu) systems

The properties of Ag-Zn alloy films on Ru(001) have been examined using thermal desorption spectroscopy and photoemission. The results were compared to those previously reported for Cu-Zn and Au-Zn alloys on Ru(001). For the Zn-noble-metal alloys, the mechanism of decomposition was always the same: evolution of Zn into gas phase, with the noble metal remaining solid. In thick alloys with a low concentration of Zn, the decomposition temperature of Ag-Zn (600 K) was lower than that of Cu-Zn (640 K) or Au-Zn (670 K). Alloy formation induced only small shifts ( −0.2 to −0.3 eV) in the position of the Zn 2p, 3s and 3d levels. In contrast, the core and valence levels of the noble metals showed large shifts toward higher binding energy. For small amounts of Cu, Ag and Au dissolved in Zn multilayers, the shifts in the noble-metal core levels follow the sequence: Ag(3d 5 2 ) , 0.72 eV < Cu(2p 3 2 ) , 0.85 eV < Au(4f 7 2 ) , 1.40 eV. These shifts reflect a nd → ( n + l) s, p rehybridization in the valence levels of the noble metal induced by the formation of bonds with Zn. Two-dimensional (2D) alloys of Zn and a noble metal in contact with Ru(001), θ Zn + θ NM ⩽1, show Zn-Ru and Zn-NM bonds more stable than the corresponding bonds in Zn Ru(001) or thick three-dimensional (3D) alloys. This phenomenon is caused by synergistic interactions that involve the Ru-Zn, Ru-NM and Zn-NM bonds. The strength of these interactions depends on the ability of the noble metal to form strong metal-metal bonds: Ag < Cu < Au. The supported 2D alloys show noble-metal core levels shifted toward lower binding energy with respect to those of thick 3D alloys. These shifts and the large thermal stability of the supported 2D alloys can be attributed to a cooperative charge transfer from Ru to Zn to the noble metal.

The electrochemical oxidation of zinc studied by ellipsometry

In neutral solution, an oxide-free zinc surface can be prepared at −1.4 V vs. SCE. The electrochemical oxidation of this surface is found to proceed by the formation of a monolayer film that passivates the surface initially. This film is retained in the transpassive region, suggesting that evolution of Zn(II) ions proceeds via a place exchange mechanism. Reduction of Zn(II) ions from solution is the reverse of this mechanism, and only after reduction of the Zn-O monolayer below −1.2 V does electrodeposition of zinc lead to a roughened surface.