Zn Phase Research Articles

Dynamic precipitation of Al–Zn alloy during rolling and accumulative roll bonding

In this study, cold rolling was performed on a binary Al–20 wt%Zn alloy and dynamic precipitation identified for the first time in Al alloys under cold rolling. Zn clusters formed after application of 0.6 strain, and the Zn phase precipitated upon further increasing strain. Both grain refinement and rolling-induced defects are considered to promote Zn precipitation. The hardness of Al–Zn alloy initially increased with strain up to a strain of 2.9 and then decreased with increasing rolling strain. Dynamic precipitation greatly affects the strengthening mechanism of the rolled Al–Zn alloy under various strains.

ZnO Nanoparticle Formation in <sup>64</sup>Zn<sup>+</sup> Ion Implanted Al<sub>2</sub>O<sub>3</sub>

ZnO nanoparticles (NPs) formed in (-1012) sapphire substrates have been studied. The NPs were formed by implantation of 64Zn+ ions followed by furnace annealing in oxygen atmosphere for 1h at elevated temperatures. The radiation defects and Zn implant profiles were investigated by Rutherford backscattering spectroscopy of He+ ions with energy of 1.7MeV with scattering angle of 160o at Van de Graff accelerator using the ion channeling technique (RBS/CT). The surface morphology was studied by atomic force microscopy (AFM) and scan electron microscopy in secondary emission mode (SEM-SE). The distribution of Zn implant profiles was analyzed by secondary ion mass-spectrometry (SIMS). Identification of the phase content of the materials was carried out by X-ray photoelectron spectroscopy (XPS). In as implanted samples, a near-surface amorphization layer was formed, and in this layer the surface voids were created. After annealing in temperature range of 600-900°C the ZnO phase was synthesized in sapphire substrate. After annealing at 900°C one can see the phase variation from ZnO/Zn phases at sample surface to metal Zn phase in sample body at a depth of 40nm. Annealing at temperatures above 900°C leads to disappearing of ZnO phase and creating of ZnAl2O4 phase.

Effect of GO phase in Zn(OH)2/GO composite on the extent of photocatalytic reactive adsorption of mustard gas surrogate

Composites of zinc hydroxide with various contents of graphite oxide (GO) were synthesized with a controlled precipitation rate. They were used at ambient conditions as adsorbents of a mustard gas surrogate, 2-chloroethyl ethyl sulfide (CEES). The samples’ surface features were characterized by various physical and chemical methods. The materials acted as photocatalysts upon light irradiation, degrading CEES to less- or no-toxic compounds. Exposure to visible light and the presence of GO in the composites improved the performance. The results indicated a paramount role of terminal OH groups as well as the porosity in the reactive adsorption process. The enhanced performance is linked to an increase in the degree of chemical and structural heterogeneity upon addition of GO. The surface characteristics strongly depend on the amount of the carbonaceous phase and 10wt% was found as an optimal content. The CEES degraded mainly to ethyl vinyl sulfide by dehydrohalogenation and to hydroxyethyl ethyl sulfide via a hydrolysis pathway. The irradiation under visible light led to further transformation to vinyl vinyl sulfide and methyl vinyl sulfide through radical's reaction. The presence of GO promotes the electrons transfer and oxygen activation.

Effects of alloying elements (Ca and Sr) on microstructure, mechanical property and in vitro corrosion behavior of biodegradable Zn–1.5Mg alloy

Zn, a promising biodegradable material, possesses excellent biocompatibility and biodegradability, however its low strength and hardness largely limit its application in biodegradable implants. The addition of alloying elements would generally be suggested as an effective method for improving the mechanical properties. In the current study, alloying with a minor amount of Ca or Sr in Zn–1.5Mg alloy, the ternary alloys were composed of the matrix Zn and precipitated phase (Mg2Zn11 and CaZn13 for Zn–1.5Mg–0.1Ca alloy, Mg2Zn11 and SrZn13 for Zn–1.5Mg–0.1Sr alloy, respectively). Besides, the grain size of ternary alloys became more homogeneous and smaller than that of Zn–1.5Mg alloy. Meanwhile, the effect of alloying elements on the mechanical properties and corrosion behavior of Zn–1.5Mg alloy were analyzed. The results showed that the ternary alloys exhibited much higher yield strength (YS), ultimate tensile strength (UTS) and elongation than those of Zn–1.5Mg alloy. The measured corrosion rates of the ternary alloys were slightly increased due to galvanic corrosion reaction. Besides, a model of the corrosion mechanism in the simulated body fluid was discussed here based on the results of the studied alloys.

Calphad-type assessment of the Sb–Sn–Zn ternary system

The ternary Sb–Sn–Zn phase diagram was investigated experimentally by scanning electron microscopy (SEM) and differential thermal analysis (DTA) of long-term annealed samples. The overall composition of each sample was measured by energy-dispersive X-ray spectroscopy (EDX). The experimental results, together with additional available literature data, were used to perform a CALPHAD-type thermodynamic assessment of this ternary system. Two calculated isothermal sections (250 and 350°C), an isopleth (x(Sn)=17.57%) and the Zn activity in liquid ternary Sb–Sn–Zn alloys at 550°C for the composition ratio Sn/Sb=1/3 and at 650°C for the ratio Sn/Sb=9 are presented with experimental points superimposed. The liquidus projection for the ternary Sb–Sn–Zn system is also presented. The agreement between calculated and experimental results is reasonable.

Unexpected observation of splitting of skyrmion phase in Zn doped Cu2OSeO3.

Polycrystalline (Cu1−xZnx)2OSeO3 (0 ≤ x ≤ 0.2) samples were synthesized using solid-state reaction and characterized by X-ray diffraction (XRD). The effect of Zn doping upon saturation magnetization (MS) indicates that the Zn favors to occupying Cu(II) square pyramidal crystallographic site. The AC susceptibility (χ′ac) was measured at various temperatures (χ′ac–T) and magnetic field strengths (χ′ac–H). The Zn doping concentration is found to affect greatly the M-T and χ′ac-T. The skyrmion phase has been inferred from the χ′ac-H data, and then indicated within the H-T phase diagrams for various Zn doping concentrations. The striking and unexpected observation is that the skyrmion phase region becomes split upon Zn doping concentration. Interestingly, second conical boundary accompanied by second skyrmion phase was also observed from dχ′ac/dH vs. H curves. Atomic site disorder created by the chemical doping modulates the delicate magnetic interactions via change in the Dzyaloshinskii-Moriya (DM) vector of distorted Cu(II) square pyramidal, thereby splitting of skyrmion phase might occur. These findings illustrate the potential of using chemical and atomic modification for tuning the temperature and field dependence of skyrmion phase of Cu2OSeO3.

Microstructure, mechanical properties and stress corrosion cracking of Al–Zn–Mg–Zr alloy sheet with trace amount of Sc

Microstructural and property evolution of the Al–Zn–Mg–0.10%Sc–0.10%Zr alloy sheet during its preparation were investigated in detail by means of optical microscopy (OM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Vickers micro-hardness test and room temperature tensile test. Stress corrosion cracking (SCC) behavior of the Al–Zn–Mg–0.10%Sc–0.10%Zr alloy under different heat treatments was studied using slow strain rate test. The results showed that serious dendritic segregation existed in as-cast condition. The suitable homogenization treatment for Al–Zn–Mg–0.10%Sc–0.10%Zr alloy was 470°C/24 h. After homogenization treatment, dissoluble Zn and Mg enriched non-equilibrium phases dissolved into α-Al matrix completely. The suitable solid solution-aging treatment for Al–Zn–Mg–0.10%Sc–0.10%Zr alloy was solution treated at 470 °C for 60 min, followed by water quenching and then aged at 120 °C for 24 h. Under this aging temper, the grain structures were composed of sub-grains, ηʹ phases and nanometer-sized, spherical Al3(Sc, Zr) particles. Grain boundary precipitates (GBPs) area fraction was found to be an important parameter to evaluate the SCC susceptibility. The improved corrosion resistance from increasing aging temperature or prolonging aging time was due to the discontinuous η precipitates along the grain boundary and the high area fraction of GBPs. The main strengthening mechanisms of Al–Zn–Mg–0.10%Sc–0.10%Zr alloy are precipitation strengthening derived from ηʹ precipitates, dispersion strengthening, sub-grain strengthening and grain refinement caused by coherent Al3(Sc, Zr) particles.

Precipitation behavior of 14H-LPSO structure in Mg–12Gd–2Er–1Zn–0.6Zr Alloy

The microstructures of as-cast and as-solution Mg–12Gd–2Er–1Zn–0.6Zr alloys were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and selected-area electron diffraction (SAED) in the present investigation. The results show that the primary eutectic phase Mg5(Gd, Er, Zn) and some flocculent features are found in the as-cast alloy; the SAED pattern indicates that these flocculent features are the dense areas of stacking faults. The 14H-LPSO structure precipitates in the temperature range of 673–793 K, and the volume fraction of 14H-LPSO structure increases with the extension of heating time; however, there is no precipitation of 14H-LPSO structure when the temperature reaches up to 803 K. In addition, the Mg5(Gd, Er, Zn) phase dissolves gradually along with the precipitation of 14H-LPSO structure.

Novel Porous Polymorphs of Zinc Cyanide with Rich Thermal and Mechanical Behavior

We investigate the feasibility of four-connected nets as hypothetical zinc cyanide polymorphs, as well as their thermal and mechanical properties, through quantum chemical calculations and molecular dynamics simulations. We confirm the metastability of the two porous phases recently discovered experimentally [Lapidus, S. H.; et al. J. Am. Chem. Soc. 2013, 135, 7621–7628], suggest the existence of seven novel porous phases of Zn(CN)2, and show that isotropic negative thermal expansion is a common occurrence among all members of this family of materials, with thermal expansion coefficients close to that of the dense dia-c phase. In constrast, we find a wide variety in the mechanical behavior of these porous structures with framework-dependent anisotropic compressibilities. All porous structures, however, show pressure-induced softening leading to a structural transition at modest pressure.

Synthesis, crystal structure, magnetic properties and ionic conductivity of NaMFe(MoO4)3 (M = Ni, Zn)

Two isostructural iron molybdates NaMFe(MoO4)3 (M = Ni, Zn) have been prepared as single crystals by flux method and as powder by soft combustion synthesis technique. Both compounds crystallize in triclinic system with the space group P \( \overline{1} \), Z = 2 and similar parameters : a = 6.812(1) A, b = 6.828(1) A, c = 11.567(3) A, α = 76.31(1)°, β = 77.05(1)° and γ = 87.44(2)° for NaNiFe(MoO4)3 and a = 6.820(1) A, b = 6.872(1) A, c = 11.636(1) A, α = 75.89(1)°, β = 75.66(2)° and γ = 87.71(2)° for NaZnFe(MoO4)3. Their structure, isostructural with that of β-NaFe2(MoO4)3, is built up from [M,Fe]2O10 units of edge-sharing [M,Fe]O6 octahedra (M = Ni or Zn), connected to each other through the common corners of MoO4 tetrahedra. The resulting anionic three-dimensional framework leads to the formation of channels along b axis, where the Na+ cations are located. The disordered distribution of iron and divalent element in the same site is confirmed by bond valence calculation. Magnetic susceptibility measurements reveal that the title compounds are antiferromagnetic with Neel temperature T N below 4.5 K. At high temperature, the susceptibility follows a Curie–Weiss law with θ = −19 and −18 K for Ni and Zn phases, respectively. Ionic conductivity results obtained by the impedance spectroscopy technique show that these materials are good ionic conductors with particularly low activation energies: 0.29 eV for NaNiFe(MoO4)3 and 0.36 eV for NaZnFe(MoO4)3 close to those of Na super-ionic conductor (NASICON)-type compounds with similar formula such as AZr2(PO4)3 (A = Na, Li).

Effects of bismuth addition and electrodeposition processing onZn-based coatings

Zn and Zn – Bi coatings were electroplated on mild steel substrate by direct and pulse current (PC) techniques. The effects of Bi and deposition method on the phase, microstructure and mechanical properties of Zn -based coatings have been studied. Results showed that the crystal orientation and microstructure of Zn – Bi coatings were different compared to the pure Zn coating. By adding a small amount of Bi solution into Zn electrolyte, the microhardness of Zn – Bi coatings was increased by two times, and the wear volume loss was also decreased. Finer grain size and smoother surface can be achieved by utilizing PC deposition, resulting in better mechanical properties compared to the direct current (DC) deposition.

The Structural, Anisotropic Magnetization, and Spectroscopic Study of Delafossite CuCr1−x M x O2 Systems

This work describes the chemical doping effect on the magnetic properties of p-type transparent semiconductor with delafossitetype oxides CuCr 0.95M0.05O2 (M = Ni, Cr, Ga, V, Fe, Mn, and Zn). The lattice parameters were found to vary according to Vegard’s law. Reflection broadening is observed, that is ascribed to local lattice distortion due to the ionic radius difference between Cr 3+ and M dopants Raman spectra at a room temperature of CuCr 0.95M0.05O2 displayed three intense modes which are identified as σ(A 1g) at 691 cm −1, σ(E g) at 444 cm −1 and σ(A g) at 207 cm −1 that matched with other delafossite structures. Magnetic susceptibility measurements show that the dominant interactions are antiferromagnetic (AFM) but that doping induces significant changes. A large ferromagnetic component arises in the Fe, V and Mn-substituted samples below ≈120 K. The Ni, Zn and Ga-substituted phases retain antiferromagnetic ordering at TN≈ 24 K. The main origin of the stabilization of the AFM state is probably the randomness induced by doping. The coupling between the local spins at the Cr sites and doped metal transition may enhance spin fluctuations at the Cr sites, which break the residual magnetic degeneracy as fluctuation-induced symmetry breaking in a highly magnetic degenerate groundstate manifold of some frustrated systems.

Effects of High Magnetic Fields on Microstructures and Thermoelectric Properties of Zn-Sb Alloy

Several samples of Zn-Sb alloys, composed with β-Zn4Sb3 and Zn phases, were prepared by solidification under high magnetic fields (HMFs). The microstructure evolution and thermoelectric (TE) properties of the alloys were then investigated. Zn phase precipitated as strip and presented reticulation structure in the samples without HMFs. When the HMFs were imposed, Zn became disperse and the strip of Zn became thinner and shorter. In addition, the c-axis of Zn crystals showed a tendency to orientate toward the direction perpendicular to the magnetic field direction. The samples prepared under HMFs had higher resistivity and Seebeck coefficient and lower thermal conductivity. When compared to the solidified samples without HMFs, the application of 8.8 T of HMF increased the maximum figure of merit 3.7 times. In addition, the relationship between microstructure and TE properties was also analyzed.

Phase equilibria and transformations in ternary Mg–Gd–Zn alloys

Phase equilibria and transformations in ternary Mg–Gd–Zn alloys were studied experimentally by investigating 22 samples with up to 40at.% Gd and 60at.% Zn. These results, combined with a critical review of literature data, were used to develop thermodynamic descriptions of the Gd–Zn and the Mg–Gd–Zn systems and to calculate the Mg–Gd–Zn phase diagram in the entire composition range. In the ternary system the hexagonal long-period stacking ordered structure 14H, the hexagonal phase H1, Gd11Mg24Zn64, and five solid solution phases with ternary compositions, GdMg5, GdMg3, GdMg2, Gd(Mg,Zn), and W are found to be stable, whereas the icosahedral phase I, GdMg3Zn6, and other hexagonal phases are metastable. In addition, a new stable phase Gd20Mg19Zn81 with a face-centered cubic structure is identified in the Mg–Gd–Zn system. Based on the thermodynamic description obtained in this work, the microstructures and phase transformations previously observed in the as-cast, solution heat treated and aged conditions are discussed. It is shown that the current thermodynamic predictions are in good accord with the experimental findings, suggesting the viability of such an approach for the microstructure design of Mg–Gd–Zn alloys.

Additives and thermal treatment influence on microstructure of nonferrous alloys

Although Zn alloys are a very widely used material, there is a need for investigations concerning the influence of thermal conditions on its microstructure and its properties, which makes it useful for the specific tasks it has to fulfil for mass-produced items manufactured by the metalworking industry, in the automotive industry, as well as in countless electronic components. One of the possibilities is to create finer microstructures and enhance their properties, to change their chemical composition by adding alloying additives, and inoculation using modifiers. So in this paper, investigation results are presented concerning the influence of chosen alloying additives, such as Sr, Ce and Ti–B on the measured and calculated thermal characteristics and microstructure of zinc alloys with the addition of aluminium and copper. Based on the results on the phase and chemical composition of the cast Zn–Al–Cu alloys, inoculated with Sr and Ti–B, no differences were detected in the phase composition of the investigated alloys, owing to changes in cooling rates, which were chosen for the sample cooling process. A small amount of added cerium caused the occurrence of new phases present in the microstructure. Modification of the Zn–Al–Cu alloy precipitates changes in the thermomorphology of the phase and the ‘tweed’ type changes in the microstructure. Moreover, the addition of cerium causes a decrease in the temperature at the beginning (T L) and the end of the solidification, as well as the occurrence of a multicomponent eutectic, which can be detected on the derivative curve.

Formation of interfacial compounds and the effects on stripping behaviors of a cold-sprayed Zn–Al coating on interstitial-free steel

By means of cold spray, a Zn–Al coating was successfully deposited on an interstitial-free (IF) steel sheet. The formation of interfacial compounds between the coating and the IF steel was studied during diffusion annealing at 400°C. And its correlations with the stripping behaviors of the coating were investigated by using a three-point bending method. The results showed that Fe–Zn and Fe–Al–Zn compounds begin to form at the coating/substrate interface after an annealing duration of 60min, and the stripping resistance increases slightly before that duration and then decreases significantly by further increasing annealing duration. The enhanced stripping resistance at the earlier stage might be due to the modifications of microstructure and deformation compatibility of the sprayed coating, while the decreased stripping resistance at the later stage is related to the high stress concentration at the interface of the formed brittle Fe–Al–Zn phase and the Zn–Al coating.

Liquidus Projection and Isothermal Section of the Ag-In-Zn Ternary System

This study experimentally determines the liquidus projection and phase equilibria isothermal section at 773.2 K (500°C) of the Ag-In-Zn ternary system. There are ten primary solidification phases of the Ag-In-Zn ternary system. In addition to the (Ag) (In) and (Zn) phases, there are seven binary compounds: β-(Ag3In), ζ-(Ag3In), γ-(Ag9In4), AgIn2, β-(AgZn), γ-(Ag5Zn8), and e-(AgZn3). No ternary compounds were found. Among all these phases, the γ-(Ag9In4) primary solidification phase has the largest compositional regime. Five invariant reactions, two Class I reactions, two Class II reactions, and one Class III reaction, are determined by thermal analysis in this study. The reactions with the lowest and highest reaction temperatures are Liquid = (In) + AgIn2 + γ-(Ag5Zn8) at 413.5 K (140.3°C) and Liquid + (Ag) + β-(AgZn) = ζ-(Ag3In) at 964.9 K (691.7°C), respectively. In the isothermal section at 773.2 K, there are six tie-triangles: (Ag) + ζ-(Ag3In) + β-(AgZn), ζ-(Ag3In) + γ-(Ag9In4) + β-(AgZn), ζ-(Ag3In) + γ-(Ag9In4) + Liquid, γ-(Ag9In4) + β-(AgZn) + Liquid, β-(AgZn) + γ -(Ag5Zn8) + Liquid, and γ-(Ag5Zn8) + e-(AgZn3) + Liquid.

Anti-Corrosion and Tribo-Mechanical Properties of Co-deposited Zn–SnO2 Composite Coating

Zn–SnO2 composite coatings were prepared by direct potential using electrolytic co-deposition technique from sulfate solution. The effect of Zn2+ and SnO2 concentrations in deposited bath on the mechanical properties and morphological characteristics of the composite coatings were examined. The characterizations of the sample were analyzed using scanning electron microscopy couple with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The electrochemical degradation behavior of the samples in 3.65 wt.% NaCl solution was studied using potentiodynamic polarization technique and characterized by high-resolution optical microscope. From all the fabricated composite coatings, obvious diffraction peaks were observed with Zn-7Sn-S-0.3V film with Zn2Sn7, Sn, Zn2Sn5 and Zn phases, confirming the presence and formation of Zn–SnO2 coating. The XRD pattern shows that the presences of SnO2 particle remarkably play a major role in the precipitation and orientation of the alloy matrix. From the SEM/EDS and AFM results, the deposits show that composite particle and proper bath composition have strong influence on the microstructure. An enhanced corrosion resistance was attained as a result of the induced particles.

Microstructure and Mechanical Properties of As-Cast and As-Extruded Mg-Gd-Er-Zn-Zr Alloy

The Microstructure and mechanical properties of as-cast and as-extruded Mg-12Gd-2Er-1Zn-0.6Zr alloy are investigated in the present paper. The microstructure is analyzed by OM, SEM and TEM with SAED, and the mechanical properties are valued by the room temperature tensile test. The result shows that the coarse Mg5(Gd, Er, Zn) phase in the as-cast alloy was broken during hot extrusion process, and it was distributed at the grain boundary along the extrusion direction. The enhancement in mechanical properties of the extruded alloy is mainly ascribed to the refinement of these grains. The sizes of dynamical recrystallized grains are homogeneously, which was about 7 μm. Stacking fault existed in the as-cast alloy, which has a little effect on the dynamic recrystallization because of its tiny thicknesses.

Nanophase ZnV2O4 as stable and high capacity Li insertion electrode for Li-ion battery

Spinel ZnV2O4 nanoparticles are synthesized by a hydrothermal method and its properties are characterized using XRD, SEM, TEM, and electrochemical test. The structural and morphological characterizations show that ZnV2O4 sample has high purity and well crystallization with crystal size less than 20 nm. The as prepared electrode shows stable capacity over 660 mAh g−1 in the voltage range of 0.01–3.0 V at 50 mA g−1. The reaction mechanism with lithium ion is also investigated through ex-XRD and -TEM. It shows that the pristine ZnV2O4 is transformed to isostructural spinel LixV2O4 (x close to 7.6) and metal Zn phase during the first lithiation process. Then the spinel LixV2O4 seems to perform a topotactic intercalation reaction mechanism and that the in-situ formed LixV2O4 can still keep its spinel matrix while allowing more than 5.7 lithium reversibly into/out over 50 cycles.