Small Amount Of Zr Research Articles

Comprehensive Study of Zr-Doped Ni-Rich Cathode Materials Upon Lithiation and Co-Precipitation Synthesis Steps.

Ni-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC811, x = 0.1 and y = 0.1) are considered promising cathode materials in lithium-ion batteries (LiBs) due to their high energy density. However, those suffer a severe capacity loss upon cycling at high delithiated states. The loss of performance over time can be retarded by Zr doping. Herein, a small amount of Zr is added to NMC811 material via two alternative pathways: during the formation of the transition metal (TM) hydroxide precursor at the co-precipitation step (0.1%-Zr-cp) and during the lithiation at the solid-state synthesis step (0.1%-Zr-ss). In this work, the crystallographic Zr uptake in both 0.1%-Zr-ss and 0.1%-Zr-cp is determined and quantified through synchrotron X-ray diffraction and X-ray absorption spectroscopy. We prove that the inclusion of Zr in the TM site for 0.1%-Zr-cp leads to an improvement of both specific capacity (156 vs 149 mAh/g) and capacity retention (85 vs 82%) upon 100 cycles compared to 0.1%-Zr-ss where the Zr does not diffuse into the active material and forms only an extra phase separated from the NMC811 particles.

Magnetron Sputtering as a Microstructural Screening Tool for Laser Additive Manufacturing: Study on Ni Superalloys

In this work, magnetron sputtering coupled with a heat treatment is demonstrated as a route to obtain surrogate microstructures comparable to those achieved by laser‐based additive manufacturing (AM) for Ni superalloys. Furthermore, this technique is shown to be a novel and efficient way of screening elemental additions with high compositional resolution for AM, without the need for designing and characterizing custom‐atomized powders. Herein, Inconel 718 films are sputtered from both arc‐melted and AM targets to capture any compositional changes and to develop a comprehensive methodology. Films are characterized via electron microscopy techniques to establish similarities between sputtered plus heat‐treated films and bulk AM Inconel 718 microstructures reported in literature. Since Inconel 718 is susceptible to high‐temperature S embrittlement, films were then co‐sputtered with small amounts of Zr or Hf, which are found to facilitate sulfur segregation via nano secondary ion mass spectrometry analysis. Overall, this work highlights how magnetron sputtering plus heat treatment can be leveraged to rapidly screen novel AM microstructures, thereby accelerating the development and deployment of AM materials.

Strength and stability through variable micro segregation behaviour of Ta and Zr solutes at intermetallic interfaces in Al-Cu alloys

A small amount of Zr and Ta are added to aluminium-copper (Al-Cu) alloys, and the evolution of strengthening phases with multi-step heat-treatment and their stability after prolonged thermal exposure at 250 °C has been studied. The L12 ordered (Al,Cu)3(Zr,Ta) precipitates were formed in the Al-matrix, followed by preferential nucleation of Cu-rich θ"/θ' plates on the L12/matrix interfaces. Transmission electron microscopy and atom probe tomography studies established the segregation of Zr and Ta at θ' plate/matrix in the aged alloys. It is shown that Zr segregates at coherent broad interfaces of θ' plate and inhibits the growth of these interfaces. Segregation of Ta primarily occurs at the growing θ' plate interface in the lengthening direction (semi-coherent interface) along with Zr and restricts the lengthening of the plate. The restricted growth triggers sympathetic nucleation of newer plates at the plate edges to sustain the growth process. A yield strength of ∼475 MPa at room temperature is recorded due to the presence of ordered precipitates and the growth restriction of θ' plate. Segregation of slow diffusing elements (Zr and Ta) also enhances the thermal stability of the microstructure.

Interface characteristic of Zr-based metallic glass and copper by laser pulse welding

The crystallization behavior of amorphous alloys during welding is more complex than that of traditional metals. In this paper, the Zr-based amorphous alloy and copper crystals were welded by pulsed laser butt welding method, the crystallization behavior of the amorphous alloy/crystalline metal welding interface is deeply studied. The results show that Zr2Cu and Zr2Ni crystal phases appear at the interface between Zr based amorphous alloy and copper, and a Cu rich region is formed at the amorphous side of the interface. A small amount of Zr, Ni, Ti diffuses to the Cu side, forming ZrO2, TiO2, CuO and other oxides on the surface of the sample. These oxides will cause changes in the voltage potential at the interface.

Improvement of Curie temperature and magnetic entropy change of a Fe88Zr8B4 metallic glass by minor Nd substitution

A small amount of Zr in the Fe88Zr8B4 metallic glass (MG) was replaced by Nd and the fully amorphous Fe88Zr8-xNdxB4 (x = 2, 4) ribbons were successfully fabricated. The influences of Nd substitution on the glass formability, Curie temperature and magnetic entropy change (−ΔSm) of a Fe88Zr8B4 MG were investigated. It was found that the minor Nd substitution not only results in the improved glass formability, but also enhances the −ΔSm peak to ∼ 3.65 J/(kg×K) at 314 K for x = 2, and to ∼ 4.10 J/(kg×K) at 335 K for x = 4 under 5 T. The mechanisms for the weak spin-glass-like behavior and the improvement of −ΔSm induced by minor Nd substitution were investigated.

Experimental and theoretical characterization of Al3Sc precipitates in Al–Mg–Si–Cu–Sc–Zr alloys

Abstract The structure of Al3Sc precipitates in Al –Mg– Si–Cu – Sc –Zr alloys annealed at 450 °C was investigated using transmission electron microscopy and energy-dispersive X-ray spectroscopy. The Al3Sc particles contain mainly Sc and small amounts of Zr, Si, and Cu. The addition of Zr limits the size of the Al3Sc precipitates to about 10– 30 nm, and these precipitates are coherent with the matrix. Density functional energy calculations showed that exceptionally small energies are required to dissolve Zr and Cu in Sc and Al sublattices, respectively. On the contrary, Cu, Mg, and Si are difficult to be dissolved in the Sc sublattice.

First Principles Density Functional Theory Prediction of the Crystal Structure and the Elastic Properties of Mo2ZrB2 and Mo2HfB2

The Molybdenum rich ternary alloys Mo-M-B (M = Zr, Hf) contain, next to the Mo solid solution (bcc Mo with small amounts of Zr or Hf as substitutional atoms), the binary borides Mo2B, MB and MB2. Recently, it was found that there is also ternary Mo2MB2, but the crystal structure and further properties are currently unknown. Density functional theory (DFT) calculations were used not only to predict the crystal structure of the Mo2MB2 phases, but also to estimate the isotropic and anisotropic elastic properties like bulk, shear and Young’s modulus, as well as the Vickers hardness of these new borides. Several known crystal structures that fulfill the criterion of the chemical composition were investigated, and the AlMn2B2 type structure seems to be the most stable crystal structure for Mo2HfB2 and Mo2ZrB2 as there are no signs of electronic or dynamic instability. Regarding the elastic properties, it was found that Mo2HfB2 shows higher elastic moduli and is less elastically anisotropic than Mo2ZrB2.

Dense ZrB<sub>2</sub>-MoSi<sub>2</sub> Composite Coating Fabricated by a New Multi-Chamber Detonation Accelerator on Carbon/Carbon Composites

A new multi-chamber detonation accelerator (MCDS) was applied to fabricate ZrB2–MoSi2 composite coating containing 20 mol.% of MoSi2 on carbon/carbon composites. Phase composition and microstructure of the coating were characterized by X-ray diffraction and scanning electron microscopy. The ZrB2–20MoSi2 coating displayed compact and lamellar microstructure with porosity lower than 1%, where SiO2 phase was uniformly distributed in the ZrO2 matrix. The coating was well-adhered with carbon/carbon composites. Silica, m-ZrO2, and small amount of Zr(MoO4)2 were formed.

STRUCTURAL, FERROELECTRIC AND ENERGY-STORAGE PROPERTIES OF LEAD-FREE Zr-DOPED Bi0.5(Na0.80K0.20)0.5TiO3 FILMS

Perovskite-type lead-free Bi[Formula: see text](Na[Formula: see text]K[Formula: see text](Ti[Formula: see text]Zrx)O3 (BNKT-[Formula: see text]Zr) ferroelectric films (with [Formula: see text] from 0.00 to 0.05) were synthesized on Pt/Ti/SiO2/Si substrates via chemical solution deposition. The influence of Zr[Formula: see text] concentration on the microstructures, ferroelectric and energy-storage properties of the prepared films was investigated in detail. It showed that the BNKT-[Formula: see text]Zr films possessed rhombohedral and tetragonal symmetries in morphotropic phase boundary when a small amount of Zr[Formula: see text] was added. Ferroelectric and energy-storage properties of the films investigated at an applied electric field of 600[Formula: see text]kV/cm were significantly enhanced with appropriate Zr[Formula: see text] concentration. The remnant polarization ([Formula: see text]), maximum polarization ([Formula: see text]) and [Formula: see text]–[Formula: see text] values at [Formula: see text] reached the highest values of 18.1[Formula: see text][Formula: see text]C/cm2, 42.0[Formula: see text][Formula: see text]C/cm2 and 24.0[Formula: see text][Formula: see text]C/cm2, respectively. Thanks to the strong enhancement in [Formula: see text] and the large [Formula: see text]–[Formula: see text] value, the highest recoverable energy-storage density gets the value of 4.6[Formula: see text]J/cm3 for the 2[Formula: see text]mol.% Zr[Formula: see text]-doped BNKT film. These obtained results indicate that the appropriate Zr[Formula: see text]-doped BNKT films have many application potentials in the advanced capacitors.

Formation of High-Oxidation-Resistant NiAl Surface Layer by Simultaneous Electrodeposition of Al and Zr in Molten Salt

A coating layer consisting of Zr-containing NiAl was prepared by the simultaneous electrodeposition of Al and Zr using a molten salt as the medium. In particular, the morphology and chemical composition of the coating layer were investigated based on the influence of the ZrF4 concentration of the bath and the electrodeposition potential. Furthermore, in the surface layer consisting of the NiAl phase, the Zr concentration was measured by ICP analysis of the solution in which the surface layer was dissolved. For the prepared samples, the cyclic oxidation resistance was evaluated in air at 1423 K. For the Ni sample after the electrodeposition in a NaCl–KCl–3.5 mol%AlF3 bath without ZrF4 at − 1.5 V, a surface layer consisting of Ni2Al3 was formed. On the other hand, when the simultaneous electrodeposition of Al and Zr was carried out in a NaCl–KCl–3.5 mol%AlF3 salt containing 0.05 mol%ZrF4 at − 1.3 V and the molten salt containing 0.1 mol%ZrF4 at − 1.3 ~ − 1.5 V, the formation of a surface layer consisting of NiAl was observed. In particular, by the simultaneous electrodeposition in the molten salt containing 0.1 mol% ZrF4 at − 1.5 V, a thick surface layer consisting of NiAl (about 40 μm) was formed. Furthermore, the detailed analysis of the Zr concentration in the surface layer revealed that the Zr content in the layer was 0.05 at%. Cyclic oxidation tests revealed that a mass loss was observed for the samples coated with the NiAl layer formed by the electrodeposition of only Al. However, for the sample coated with the NiAl layer containing a small amount of Zr, no decrease in the mass due to exfoliation of the oxide was observed. After the cyclic oxidation tests, a scale consisting of α-Al2O3 with good adhesion to the substrate metal was formed on the samples coated with the NiAl layer containing a small amount of Zr. This scale included ZrO2 particles.

Effect of Zr Addition on the Microstructure and Mechanical Properties of CoCrFeNiMn High-Entropy Alloy Synthesized by Spark Plasma Sintering.

As a classic high-entropy alloy system, CoCrFeNiMn is widely investigated. In the present work, we used ZrH2 powders and atomized CoCrFeNiMn powders as raw materials to prepare CoCrFeNiMnZrx (x = 0, 0.2, 0.5, 0.8, 1.0) alloys by mechanical alloying (MA), followed by spark plasma sintering (SPS). During the MA process, a small amount of Zr (x ≤ 0.5) can be completely dissolved into CoCrFeNiMn matrix, when the Zr content is above 0.5, the ZrH2 is excessive. After SPS, CoCrFeNiMn alloy is still as single face-centered cubic (FCC) solid solution, and CoCrFeNiMnZrx (x ≥ 0.2) alloys have two distinct microstructural domains, one is a single FCC phase without Zr, the other is a Zr-rich microstructure composed of FCC phase, B2 phase, Zr2Ni7, and σ phase. The multi-phase microstructures can be attributed to the large lattice strain and negative enthalpy of mixing, caused by the addition of Zr. It is worth noting that two types of nanoprecipitates (body-centered cubic (BCC) phase and Zr2Ni7) are precipitated in the Zr-rich region. These can significantly increase the yield strength of the alloys.

Effects of Zirconium Doping Into a Monoclinic Scheelite BiVO4 Crystal on Its Structural, Photocatalytic, and Photoelectrochemical Properties.

Effects of zirconium (Zr) doping into BiVO4 powder on its structural properties and photocatalytic activity for O2 evolution were examined. The formation of BiVO4 powder crystallized in a monoclinic scheelite structure (ms-BiVO4) was achieved when the sample was doped with a relatively small amount of Zr. The photocatalytic activity of Zr-doped ms-BiVO4 powder was much higher than that of non-doped ms-BiVO4. However, further doping caused a reduction of photocatalytic activity for O2 evolution due to the occurrence of structural alterations into tetragonal scheelite and tetragonal zircon structures. Similar effects of Zr doping were also observed for the photoelectrochemical (PEC) system based on BiVO4 thin films doped with various amounts of Zr. Thus, Zr doping was confirmed to be effective for improvements of photocatalytic and PEC functions of BiVO4 for water oxidation.

Overview of As(V) adsorption on Zr-functionalized activated carbon for aqueous streams remediation

The present work introduces a simple methodology of carbon modification with zirconium, using an organic complexing ligand, as efficient media for selective As(V) removal. It is hypothesized that the incorporation of Zr-nanoparticles improves the attraction of anionic species such as arsenates (HAsO42−/H2AsO4−) making the material highly selective. The effects of pH (3–11) and temperature (15, 25 and 35 °C) were studied. Furthermore, potentiometric titrations, the effect of competing anions, thermodynamics, and adsorption kinetics were evaluated in order to clarify the rate-controlling process and the adsorption mechanism for arsenic removal. Results demonstrated that OH and COOH groups play an important role during the arsenic adsorption process; a small amount of Zr(IV) species (0.77%) increased the adsorption capacity of activated carbon in about a 43%. Thermodynamic analysis showed the spontaneous exothermic nature of the adsorption process was favored at lower temperatures. The presence of anions, such as chloride, sulfate, carbonate, nitrate and phosphate, did not affect the adsorption capacity, while kinetic studies demonstrated that the arsenic adsorption process in Zr-modified activated carbon is not exclusively controlled by intraparticle diffusion.

Influence of Zr doping on solubility of Xe in UO2: A first-principle study

As a major fuel of the light-water reactors, UO2 has excellent properties such as high melting point, good radiation resistance, corrosion resistance, compatibility with cladding materials, and strong ability to tolerate fission gas. The Zr atoms are inevitably introduced into UO2 lattice during the operation of a nuclear reactor, which can affect the solubility of Xe in the UO2. In this paper, we calculate the formation energy of vacancy defect and the binding energy of Xe in vacancy of Zr doped UO2. The calculations presented here are based on density functional first-principle and projector augmented-wave method. A plane-wave basis set with a cutoff energy of 400 eV is used. The generalized gradient approximation refined by Perdew, Burke and Ernxerhof is employed for determining the exchange and correlation energy. Hubbard U term is used for considering the f-electron localization. Brillouin zone is set to be within 555 k point mesh generated by the Monkhorst-Pack scheme. The self-consistent convergence of total energy is 110-4 eV/atom. The calculations are performed in a 222 supercell. In order to verify the calculating process, the formation energies of U and O point defects are compared with those in the literature. Then the influence of Zr doping in the UO2 on the solubility of Xe in the UO2 is studied. The results show that the ability to form the vacancy defects is different in the U-rich and O-rich environment of UO2. The vacancy defects in UO2 are more likely to form in O-rich UO2. The Zr doping will lead to the increasing of the formation energies of defects in both cases. The Zr doping will also change the binding energy of Xe in void. For all the systems studied, only the binding energy of Xe adsorbed to the void consisting of four point defects increases, while the rest decrease. The solution energy, equaling the sum of the binding energy of Xe and the vacancy formation energy, will increase after doping Zr, because the decrement in binding energy is generally less than the increment in vacancy formation energy. In summary, the presence of Zr will weaken the solubility of Xe in UO2, which is mainly due to the hindering of vacancy defects from forming. This result has a certain value in studying the dissolution of fission product Xe after a small amount of Zr has entered into the UO2 fuel in nuclear reactor.

β-Phase thermal degradation in Zr-added Cu–Zn–Al shape memory alloy

Small amounts of Zr, as a grain refiner, were added to the β Cu–Zn–Al shape memory alloy. The resulting microstructure was polycrystalline, with Zr-rich precipitates preferentially located in the grain boundary. An alloy of similar composition, without addition of Zr, was studied for comparison. The martensitic transformation and the stability of β-phase were studied by differential scanning calorimetry and optical microscopy. The activation energy of phase decomposition, within the β-phase metastability range, was determined by the Kissinger–Akahira–Sunose method, and values of 121 kJ mol−1 for Cu–Zn–Al(Zr) and 110 kJ mol−1 for Cu–Zn–Al were obtained. Furthermore, it was observed that the Zr-rich particles, responsible for controlling the grain size, were unstable during the heat treatments at temperatures within the β-phase stability range. The dissolution of precipitates leads to a gradual decrease in the volume fraction of the sample that transforms to martensite. Finally, after prolonged aging the martensitic transformation disappeared.

Effect of the Al–Zr–Y master alloy composition on the modifying effect in the Al–4% Cu alloy

The results of modifying the Al–4% Cu alloy with test Al–1.04% Zr–0.70% Y and Al–1.23% Zr–0.39% Y master alloys are reported; the Zr-to-Y atomic-percentage ratio in the alloys is 1.41 and 3.08, respectively. The effect of small amounts of Zr and Y (from 0.1 to 0.3%) added in the form of test ternary master alloys of different compositions and binary Al–Zr and Al–Y master alloys on the grain refinement in the Al–4% Cu alloy has been studied. The structure of the initial alloy is characterized by pronounced directional solidification of the α phase. As the Zr + Y content increases, the columnar-crystal zone decreases and the equiaxed-crystal zone increases; at a (Zr + Y) content of 0.326%, only equiaxed crystals ~200 μm in size are present in an ingot. When Zr and Y are added with binary master alloys, the macrostructure of the modified Al–4% Cu alloys indicates that columnar crystals grow until their contact at the center of the ingot, and their growth is independent of the amount of added Zr and Y.

MELCOR 2.1 analysis of melt behavior in a BWR lower head during LOCA and SBO accident

Melt behavior in reactor pressure vessel (RPV) lower head is important for estimating melt leakage to reactor cavity (pedestal), molten core concrete interaction (MCCI) and radioactivity release to the environment. In order to expand universal knowledge of severe accident research on boiling water reactors (BWRs), the melt behavior in BWR lower head and leakage paths during hypothetical loss-of-coolant accident (LOCA) and station blackout (SBO) accident were analyzed with MELCOR 2.1. The instrument guide tube (IGT) failure, a potential lower head failure mechanism, was modeled in MELCOR code. When IGTs failure was not considered the lower head failed through creep rupture, resulting in the discharge of all the debris into the reactor cavity. Otherwise, the debris discharged out through the openings at the IGT locations, but a part of debris still remained in the lower plenum as solid state. The pressure vessel wall did not suffer from creep rupture after IGTs failure. The timing of events in SBO accidents were delayed compared with LOCAs, and the oxidation degree of core debris was higher in SBO accidents. In each case, only SS (stainless steel) and a small amount of Zr (zircaloy) were present in molten state in the lower plenum. Most of the discharged debris was in solid state.

Effect of Zirconium on Boron Removal in Electromagnetic Solidification Refinement of Silicon from Si-Al Melt

This work investigates the removal of B in Si by the addition of Zr in the electromagnetic solidification refinement of silicon-aluminum melts. As Zr has a strong affinity for B and can form the thermodynamically stable compound of ZrB2, the B content of lower-grade Si is expected to be effectively removed by adding a small amount of Zr to the Si-55 at% Al melt. The results show that Zr is strongly responsible for the decrease in B content of refined Si. The removal fraction of B significantly increased from 60.2% to 97.3% by adding a small amount of Zr (0 to 3500 ppmw). In addition, the removal fraction of Zr from Si was found to be as high as 98.6%; however, its residual content in the refined Si was significantly larger than its solid solubility in Si, possibly due to the non-equilibrium solidification occurring during the refining process.

Role of Zr and Sc addition in controlling the microstructure and tensile properties of aluminum–copper based alloys

The present work was carried out on eight alloys containing Al–2%Cu–1.5%Si–0.5%Fe–0.6%Mn-0.4%Mg–0.07%Ti, with small amounts of Zr, Sc or both. Tensile test bars were produced using low pressure die casting. All bars were solution heat-treated, followed by artificial aging. The as-cast microconstituents were determined using electron probe microanalyzer equipped with both electron dispersive x-ray and wavelength dispersive spectroscopic systems. The results show that in addition to the currently observed Fe-and Cu-based intermetallics, several Zr- and Sc-containing intermetallics were also formed during solidification (of the present alloys). Neither the Sc/Zr nor the Sc/Al ratio is constant, and both ratios may vary from one particle to another. The presence of Zr or Sc has a significant grain refining effect, equivalent to that obtained from the addition of a Ti-based grain refiner. The main influence of a Zr or Sc addition on the tensile properties of the base alloy appears during aging, and before the onset of softening. Although the addition of Zr or Sc improves the alloy tensile properties, Sc is less effective compared to Zr. Also, a Sc content beyond 0.15% results in no further improvement in the alloy strength.

Effect of Ti on the properties of (KxNa1−x)NbO3 based lead-free ceramics

The effect of modifying lead-free alkaline niobate based piezoelectric ceramics with different amounts of Ti has been investigated. Thermal studies using a dilatometer show that increasing Ti amount leads to decreasing sintering temperature by approximately 11.7°C for every 1mol% of the dopant added. Chemical analysis on the ceramics reveals that the measured amounts of the alkali elements are slightly lower while small amounts of Zr were introduced to the ceramic through the milling process. Microstructural analysis shows that that the average grain size decreases with increasing dopant amount and that new, smaller sized grains are formed in the presence of Ti. Two-phase orthorhombic–tetragonal diffraction patterns are observed using synchrotron X-ray diffraction while the analysis using Rietveld refinement shows that the fraction of the tetragonal phase in the two-phase patterns increase with increasing Ti content. The dielectric, piezoelectric coefficient values and ferroelectric properties of the ceramics decrease with increasing Ti amount. The current density values in the samples increase by up to 5 orders of magnitude when more than 0.5mol% of the dopant is added.