Solution Of Zr Research Articles

Effect of hydrogen on the structural and phase state and the deformation behavior of the ultrafine-grained Zr–1Nb alloy

The formation of an ultrafine-grained structure with predominantly high-angle grain boundaries and an average grain size of grain–subgrain structure elements of 0.4μm in zirconium alloys was shown by electron microscopy and X-ray diffraction analysis. The formation of such structure was found to result in the significant increase of the ultimate and yield strengths in comparison with the initial fine-grained state. The strength characteristics of ultrafine-grained Zr–1Nb–0.22H alloy are higher than the corresponding characteristics of the Zr–1Nb alloy. The presence of hydrogen in the solid solution of the ultrafine-grained Zr–1Nb–0.22H alloy during tension at room temperature is found to prevent the development of plastic deformation localization on the meso- and macrolevels and to increase the effect of strain hardening and deformation of uniform extension. At elevated temperatures, the presence of hydrogen reduces the resistance to deformation localization on the macrolevel and the deformation to failure in tensile tests.

Synthesis of nanostructured La2Zr2O7 by a non-alkoxide sol–gel method: From gel to crystalline powders

Nanocrystalline La 2 Zr 2 O 7 powders of single prochlore phase were synthesized by a non-alkoxide sol–gel process. Homogeneous sol, free of precipitation, was prepared by addition of citric acid, polyethylene glycol and formamide to aqueous solutions of Zr 4+ and La 3+ inorganic salt precursors. We found that fluorite structure La 2 Zr 2 O 7 was crystallized at 1000 °C, and then transformed to pyrochlore structure at 1200 °C. With further increase in temperature, the crystalline degree of pyrochlore La 2 Zr 2 O 7 powders increased. The particle size of the as-prepared La 2 Zr 2 O 7 powders at 1200 °C was about 80–200 nm. With temperature increase, sintering of La 2 Zr 2 O 7 particles resulted in grain size growth. Mechanism of La 2 Zr 2 O 7 nano-particles as function of temperature during heat treatment was analyzed. The density of the powders sintered at 1600 °C was 96.0% of the theoretical value, and thermal conductivity ranged from 0.65 to 0.85 W·m −1 ·K −1 , which was much lower than that of 7YSZ.

Generation of gas-phase zirconium fluoroanions by electrospray of an ionic liquid.

New approaches for forming anions are sought that have strong abundance and no isobaric overlap, attributes that are compatible with the measurement of isotope ratios. Fluoroanions are particularly attractive because fluorine is monoisotopic, and thus will not have overlapping isobars with the isotope of interest. Since many elements do not have positive electron affinity values, they do not form stable negative atomic ions, and hence are not compatible with isotope ratio measurement using high sensitivity isotope ratio mass spectrometers such as accelerator mass spectrometers. Zirconium fluoroanions were prepared using the fluorinating ionic liquid (IL) 1-ethyl-3-methylimidazolium fluorohydrogenate, which was used to generate abundant [ZrF5](-) ions using electrospray ionization. The IL was dissolved in acetonitrile, combined with a dilute solution of either Zr(4+) or ZrO(2+), and then electrosprayed. Mass analysis and collision-induced dissociation experiments were conducted using a time-of-flight mass spectrometer. Cluster structures were predicted using density functional theory calculations. The fluorohydrogenate IL solutions generated abundant [ZrF5](-) ions starting from solutions of both Zr(4+) and ZrO(2+). The mass spectra also contained IL-bearing cluster ions, whose compositions indicated the presence of [ZrF6](2-) in solution, a conclusion supported by the structural calculations. Rinsing out the zirconium-IL solution with acetonitrile decreased the IL clusters, but enhanced [ZrF5](-), which was sorbed by the polymeric electrospray supply capillary, and then released upon rinsing. This reduced the ion background in the mass spectrum. The fluorohydrogenate-IL solutions are a facile way to form zirconium fluoroanions in the gas phase using electrospray. The approach has potential as a source of fluoroanions for isotope ratio measurements, which would enable high-sensitivity measurement of minor zirconium isotopes without overlapping isobars caused by the charge carrier (i.e., the monoisotopic fluorine atoms).

An n-body potential for a Zr–Nb system based on the embedded-atom method

A novel n-body potential for an Zr–Nb system was developed in the framework of the embedded-atom method. All the parameters of the constructed potential have been systematically evaluated by fitting to the ground state properties obtained from experimental measurements and first-principles calculations for pure elements and some alloys. It is shown that most of the static thermodynamics properties for Zr and Nb can be well reproduced by using the present potential. Some calculation results based on the present model are even closer to the experimental data than those based on previous potential models. The ground state properties of hypothetical Zr–Nb alloys were also calculated and found to be in agreement with first-principles calculations. Furthermore, the formation energies of random solid solutions of Zr–Nb with lattices of body centered cubic (bcc) and hexagonal close packed (hcp) type were calculated by fitting the energy–volume relations to Rose’s equation of state. These values were compared with those obtained by first-principles calculations based on special quasirandom structure models and the Miedema-ZSL-07 model (the improved Miedema model proposed by Zhang, Sheng and Liu in 2007). It is indicated that our n-body constructed potential for a Zr–Nb alloy provides an effective description for the interaction between the dissimilar ion interactions for hcp–bcc systems.

Densification and mechanical properties of hot-pressed ZrN ceramics doped with Zr or Ti

Abstract The densification of hot-pressed ZrN ceramics doped with Zr or Ti have been investigated at 1500–1700 °C. It is shown that either Zr or Ti additive can facilitate the densification process. ZrN with 20 mol% Zr or Ti (named ZNZ and ZNT) sintered at 1700 °C can achieve above 98% relative densities whereas densification temperature up to 2000 °C is necessary for pure ZrN. The densification improvements are attributed to solid solution of Zr or Ti into ZrN to form non-stoichiometric ZrN1−x or (Zr, Ti)N1−x. The microstructures and mechanical properties of ZNZ and ZNT samples have been examined. Large grain size and flat fracture surface existed in ZNT sample sintered at 1700 °C, which lead to poor toughness as low as 2.3 MPa m1/2. On the contrary, the fracture toughness of ZNZ sample sintered at 1700 °C was up to 5.9 MPa m1/2, attributed to fine and uniform grain size distribution.

Composites with transition metal oxides on aluminum and titanium and their activity in CO oxidation

Plasma electrolytic oxidation (PEO) technique and impregnation in nitrate solutions with next air calcinations have been used to obtain the composites with binary oxides of transition metals on aluminum and titanium. The general composite formula is as follows: CuO+MxOy/PEO-layer/Ti(Al), where MxOy is oxide of transition metal (Mn, Fe, Co, Ni). Solutions of Zr(SO4)2 and of Zr(SO4)2+Ce2(SO4)3 as well as of Na2SiO3+NaOH have been used for PEO treatment of titanium, with the last one being used for aluminum treatment alone. The composites have been investigated by XRD, XSA, SEM and XPS. Catalytic tests in oxidation of CO into CO2 showed that both metal substrate and PEO layer composition impact the composites' catalytic activity. The results were compared with the catalytic test data of aluminum coatings obtained by one-stage PEO technique with precursors of transition metal oxides being added directly into forming solutions.

Distribution of Additives in Single-Modified TiO2

ABSTRACTIn the present work the influence of different modifiers, calculated to B2O3, CeO2, Sb2O3, ZnO, and ZrO2, on their distribution in TiO2 is investigated. The phase composition and phase transformation of prepared rutile-TiO2 is determined by the selective leaching method, ICP-AES, XRD and FT-IR techniques. The addition of Sb2O3 to TiO2 has no influence on the anatase–rutile phase transformation, CeO2 and ZrO2 act as inhibitors of the TiO2 phase transformation and the addition of ZnO or B2O3 to TiO2 accelerates rutile formation. It is observed that boron is located in TiO2 in the form of soluble B2O3, zinc partly reacts with titanium forming co-phase TiZn2O4 and antimony addition to TiO2 presumably causing the formation of a co-phase of Sb with Ti. Cerium forms a separate phase, CeO2, and reacts partly with titanium, probably creating co-phase, CexTi(1-x)O2 (for example Ce0.8Ti0.2O2). Zirconium addition in TiO2 forms separate ZrO2 phase and solid solution of Zr with Ti.

Preparation and Characterization of Single-Modified TiO2 for Pigmentary Applications

In the present work the influence of different additives, calculated to ZrO2, ZnO, and B2O3, on the anatase–rutile phase transformation was investigated. The chemical composition of prepared titania samples was determined by the selective leaching method, powder X-ray diffraction analysis, and FT-IR measurements. The effect of small amounts of additives on the optical properties, photoactivity, and surface area of rutile-phased TiO2 for pigmentary applications was examined using spectrophotometer, SEM, and BET measurements. ZrO2 acted as an inhibitor of the TiO2 phase transformation and the addition of ZnO or B2O3 to TiO2 accelerated rutile formation at 750 °C. ZrO2 addition in TiO2 could form separate ZrO2 phase and solid solution of Zr with Ti. Zinc partly reacted with titanium forming cophase TiZn2O4. Boron was located in TiO2 in the form of soluble compound, B2O3. Almost all optical properties were lower for modified TiO2 in comparison with the corresponding unmodified sample. The SBET increased with ...

Sealing of pores in sol–gel-derived tritium permeation barrier coating by electrochemical technique

An electrolytic deposition technique was applied to seal open pores in sol–gel derived ZrO2 coating and to improve barrier effects against permeation of hydrogen isotopes. Disk-type specimens of type 430 ferritic stainless steel were first covered by thin ZrO2 films (50nm) with a conventional sol–gel technique. Then, pores in the ZrO2 film was sealed with ZrO2 or Al2O3 by cathodic processes in ethanol solution of Zr or Al nitrate and subsequent heat treatments in air. The permeation rate of hydrogen was measured at 300–600°C. The sol–gel derived ZrO2 coatings showed only limited barrier effects; the permeation reduction factor (PRF) was about 6–800. Nevertheless, the treatments by electrolytic deposition technique resulted in considerable improvement in the barrier effects, especially at high temperature region (>500°C), and the PRF increased to 100–1000.

EVOLUTION OF NANOSCALE Al3(ZrxEr1-x) PRECIPITATES IN Al-6Mg-0.7Mn-0.1Zr-0.3Er ALLOY ALLOY DURING ANNEALING

Erbium(Er)has attracted considerable attention as a substitute to scandium (Sc)for microalloying.The solid solution of Er and Zr decomposes to form a dispersion of secondary Al_3(Zr_xEr_(1-x))during annealing.This secondary Al_3(Zr_xEr_(1-x))precipitates improve strength, especially the elevated temperature strength.In the present paper we investigate the evolution of Al_3(Zr_xEr_(1-x))precipitate during annealing by transmission electron microscopy(TEM).The Al_3(Zr_xEr_(1-x))precipitates nucleate homogeneously at lower temperatures(280℃and 470℃).The transition from homogeneous to heterogeneous nucleation at higher aging temperature(510℃)is a natural consequence of the reduced driving force for nucleus formation as the temperature increases and the Er supersaturation in theα-Al matrix decreases.The change in morphology of the Al_3(Zr_xEr_(1-x)) precipitates from faceted to approximately spheroidal is associated with a change in the value of interfacial free energies.The diameter and the ratio of Zr/Er increase with increasing aging time at constant temperature.The coarsening of Al_3(Zr_xEr_(1-x))is dependent on the diffusivity of Er,Zr inα-Al.

N/Zr-codoped TiO 2 nanotube arrays: Fabrication, characterization, and enhanced photocatalytic activity

We firstly report an electrochemical approach to fabricating N/Zr-codoped TiO 2 nanotube arrays for photocatalytic applications. In this approach, TiO 2 nanotube arrays were first prepared by anodic oxidation using titanium anode and platinum cathode. Then the formed TiO 2 nanotube arrays and Pt were used as cathode and anode, respectively for subsequent formation of N/Zr-codoped TiO 2 nanotube arrays through an electrochemical process in the presence of a solution of Zr(NO 3) 4 and NH 4Cl. The morphology and composition of the N/Zr-codoped nanotube arrays were characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–vis diffusion reflection spectroscopy (UV–vis DRS). The photocatalytic activities of the N/Zr-codoped TiO 2 nanotube arrays were evaluated by the degradation of a model dye, rhodamine B. We show that the codoping with N and Zr elements significantly improves the photocatalytic efficiency of TiO 2 nanotube arrays under both UV and visible light irradiation. XPS analysis suggests that the N impurities are interstitially doped into the TiO 2 lattice, also enhancing the visible light sensitivity. Findings from this study suggest that through a simple codoping approach, TiO 2 nanotube arrays with enhanced photocatalytic activity can be fabricated, thereby opening a new pathway to construct nanostructured TiO 2-based composite materials for photocatalytic applications.

A novel method for processing of Bangladeshi zircon: Part II: Leaching of zircon-caustic fused mass by hydrochloric acid

A thorough investigation on the leaching and kinetics of extraction of Zr(IV) from a semi-crystalline zircon–NaOH fused material by hydrochloric acid has been carried out. The fused material was produced by mixing NaOH/zircon at a wt. ratio of 1.8 (mole ratio 9) at 973° K for 15 min. Conditioning was done by water washing, drying, grinding and sieving. The optimum conditions for dissolution of Zr(IV) were leaching by 4 M HCl under reflux for only 5 min with a solid to liquid ratio of 1.41:10 w(g)/v(mL). By applying staged leaching it was possible to obtain a solution containing up to 112 g/L Zr(IV). The rate of leaching was found to be directly proportional to [HCl] 2 and very dependent on the temperature. The rate constant at 382° K with a particle diameter of 48.5 ± 4.5 μm was determined to be 10 − 1.91 g dm 4/min mol 2 and the activation energy, E a, was 64.3 kJ/mol indicating chemical reaction control. Stirring had little effect on the rate of dissolution due to the high porosity of the conditioned fused material. However, the rate was inversely proportional to the radius of the particles used. The novelty of the process is the fast rate of dissolution of the caustic fused material to give a concentrated solution of Zr(IV).

Synthesis, microstructure and mechanical properties of (Zr,Ti)B 2-(Zr,Ti)N composites prepared by spark plasma sintering

(Zr,Ti)B 2-(Zr,Ti)N composites were fabricated by spark plasma sintering (SPS) using ZrB 2 and TiN powders as initial materials. The adopted TiN contents in the initial compositions were 0, 4, 9, and 18 wt%, respectively. During the sintering process, the reaction between ZrB 2 and TiN first produced TiB 2 and ZrN and then (Zr,Ti)B 2 and (Zr,Ti)N were formed through the solid solutions between ZrB 2 and TiB 2, and between ZrN and TiN, respectively. When using 18 wt% TiN, the solid solutions of (Zr,Ti)B 2 and (Zr,Ti)N finished at 1600 °C. Above 1900 °C, the solid solution of (Zr,Ti)N reached saturation in all the composites. With the increasing (Zr,Ti)N content in the composites, the finer microstructure was obtained due to the inhibiting effect of (Zr,Ti)N particles on the growth of (Zr,Ti)B 2 grains. The mechanical properties investigation showed that fracture toughness of composites increased with the increment of (Zr,Ti)N content.

Effect of Pulsed Electrical Field on Deposition of YSZ Thin Films in an Aqueous Solution

In this study we investigated YSZ thin film deposition from an aqueous solution by applying constant electrical field and the effect of a pulsed electrical field upon the growth condition of films. The precursor was an aqueous solution of Zr(NO2)3-2H2O, Y(NO3)3-6H2O, and 0.5 vol% NH3(aq). The thin film was deposited on the minus electrode side of the glass substrate, which was placed above the minus electrode with a gap distance of 48–530 μm. By applying the electrical field, the thin film was effectively deposited on glass substrates under an applied voltage of 2.5 V for 300 s at room temperature. The as-deposited film was amorphous, and a crystalline phase with a transparent and smooth surface can be obtained after annealing at 773 K for 3 h in air. When a pulse bias is applied to the electrical field, the film thickness, surface defects, and roughness were changed with the frequency. At 2 Hz, the film was fabricated effectively, and a thick film was obtained, but films with smoother and fewer defect surfaces were obtained in a range of about 10–100 Hz.

Microstructure and mechanical properties of Al–Zr nanocomposite materials

Three different processing routes were explored to develop Al–Zr nanocomposite alloys using mechanical alloying and spark plasma sintering methods. Depending on the route of milling adopted, the powder in the as-milled condition consisted of either a solid solution of Zr in Al or a mixture of Al-solid solution and Al 3Zr (L1 2) phases. The alloys after sintering consisted of Al and Al 3Zr (L1 2) with grain sizes of less than 100 nm. These nanocomposite alloys exhibited a high compressive strength of 1 GPa with 10% plasticity. The high strength observed in these alloys was explained on the basis of the retention of nanometer sized grains and also the fine dispersion of the L1 2 phase. On the other hand, the good amount of plasticity was explained to be due to excellent bonding between the powder particles and the presence of coarse Al grains in the matrix.

Properties of nanocrystalline and nanocomposite W xZr 1− x thin films deposited by co-sputtering

W x Zr 1− x thin films were deposited at room temperature on glass substrates by co-sputtering tungsten and zirconium targets in argon. The composition was found in the range 0 ≤ x ≤ 0.81. The grain size deduced from X-ray diffraction analysis ranged from 1.3 nm to 16 nm depending on the composition. The events in the resistivity, optical reflectivity and thickness evolutions were correlated with the X-ray diffraction analysis. Depending on the composition, the local organization can be attributed to a nanocrystalline solid solution of W in Zr, to a nanocomposite structure involving ZrW 2 nanograins embedded in an amorphous matrix, to ZrW 2 Laves phase nanograins and to a nanocrystalline solid solution of Zr in W. For 0 < x ≤ 0.72, the equivalent grain size is very small (less than 2 nm) and the evolution of the resistivity can be fitted by the estimated volume of the material perturbed by the grain boundaries.

Reactive Oxygen Species Scavenging Properties of ZrO 2 –CeO 2 Solid Solution Nanoparticles

The hypothesis that an increase in defects in cerium oxide (CeO(2)) nanoparticles induced by solid solutions with differences in valency and ionic radius of the solute will yield superior reactive oxygen species (ROS) scavengers at room temperature will be tested. Solid solutions of zirconium in CeO(2), that is, Ce(x)Zr(1-x)O(2) nanoparticles, were synthesized by a reverse micelle method. Their crystal structures, particle sizes and level of agglomeration were characterized. The nanoparticles' activities to scavenge ROS were tested in response to hydrogen peroxide at physiological levels and room temperature using an enzyme peroxidase-based assay. Solid solutions of Zr in CeO(2) nanoparticles enhanced ROS scavenging fourfold. The hypothesis is confirmed that more defects are formed and that the scavenging activities of Ce(x)Zr(1-x)O(2) correlate to the nanoparticles' oxygen-storage capacity. The antioxidant efficacy of CeO(2) nanoparticles can be enhanced by dissolving zirconium in the CeO(2) lattice. The Ce(x)Zr(1-x)O(2) nanoparticles act as an enhanced catalyst at room temperature that scavenges ROS. Increased efficacy will enable lower nanoparticle dosages to protect cells from ROS, thus increasing the therapeutic width of these compounds.

CHEMICAL VAPOR DEPOSITION OF ZrxHf1-xO2 THIN FILMS USING ANHYDROUS MIXED-METAL NITRATES PRECURSORS

ABSTRACT Hafnium-based dielectrics have been extensively investigated as a possible replacement for SiO2. A novel volatile anhydrous Zr/Hf mixed-metal nitrate precursor ZrxHf1-x(NO3)4(ZHN) was successfully synthesized. ZrxHf1-xO2 thin films were first prepared by the chemical vapor deposition (CVD) technique from the precursor of this mixed-metal nitrate. Differential scanning calorimetry (DSC) and infrared spectra (IR) measurements of ZHN indicated that ZHN may be mixture of single Hf(NO3)4 and a solid solution of Zr(NO3)4 and Hf(NO3)4. The ZrxHf1-xO2 thin films exhibit good dielectric properties with a moderate bandgap value of 5.6 eV and a value for k of 22. ZrxHf1-xO2 is, therefore, a promising candidate for gate-dielectric application, and the anhydrous mixed-metal nitrate can be a potential precursor for high-k materials derived from CVD.

Stress analysis of ceramic insulation coating on Cu/MgB2 wires for W&amp;R MgB2 coils

Ceramic insulation coatings were produced on Cu/MgB2 wires, which were fabricated by Hyper Tech Research Inc., using Continuous Tube Forming and Filling (CTFF) process, from the solution of Zr, and Y based organometalic compounds, solvent and chelating agent using reel-to-reel sol–gel technique for MgB2 coils. Y2O3–ZrO2/Cu/MgB2 wires were annealed at 700 ◦C for 30 min with 5.8 ◦C/min heating rate under 4% H2–Ar gas flow. Residual stresses were examined for Cu/MgB2 wire and YSZ coatings with varying thicknesses. It was observed that displacement values are independent from YSZ thicknesses and the maximum effective stress value is in the Cu region. The surface morphologies and microstructure of samples were characterized using SEM. SEM micrographs of the insulation coatings revealed cracks, pinholes and mosaic structure.

Microstructure and fracture toughness of TiC–ZrC–WC–Mo–Ni cermets

Abstract TiC-based cermets have advantages such as lower friction coefficient and higher oxidation resistance compared with WC-based cemented carbides. However, the brittleness is still an unavoidable limitation for their utilizations. Microstructure of TiC– x ZrC–15WC–14Mo–20Ni–1C cermets with different ZrC contents was studied by using X-ray diffractometry (XRD), scanning electron microscopy (SEM) in combination with energy dispersive spectrometer (EDS). The experimental results show that ZrC dissolved in the cermets and formed solid solutions of (Zr, Ti, Mo, W)C. The bright and gray coreless grains have been regarded as beneficial for the toughness of the cermets.