Zr Samples Research Articles

Compositional changes at the interface between thorium-doped uranium dioxide and zirconium due to high-temperature annealing

Compositional changes at the interface between thorium-doped uranium dioxide (U0.97Th0.03O2) and Zr before and after annealing at 1700 °C for 18 h were studied by X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. At room temperature, the U0.97Th0.03O2 pellet consisted of hyperstoichiometric UO2+x with UO2 and ThO2, and the Zr sample contained Zr with ZrO2. After annealing, the former contained stoichiometric UO2 with ThO2 and the latter consisted of ZrO2 along with ZrO2·2H2O.

Discontinuous dynamic recrystallization in α-Zr

This study attempts to identify the type of dynamic recrystallization (DRX) occurring in hot deformed zirconium. For this, samples of Zr were uniaxially compressed at 800 °C and 0.1 s−1 to varying strains. Microstructural characterization was done using electron back scatter diffraction (EBSD). The flow stress showed an initial hardening followed by softening to a steady state value. DRX grains were identified as those with a grain orientation spread of less than 2°. Fine recrystallized grains were observed along grain boundaries at low to intermediate strains (0.15 and 0.6). The grain size decreased with increasing strain up to a strain of 0.6, beyond which it showed no further decrease. The degree of misorientation of boundaries was used to distinguish between discontinuous and continuous dynamic recrystallization (dDRX and cDRX, respectively). Most recrystallized grains had their boundaries of very high misorientation (> 50°) suggesting that dDRX was prevalent. The evidence of cDRX was weak, although it cannot be ruled out at higher strains. It was concluded that Zr undergoes dDRX when deformed at 800 °C and 0.1 s−1.

High-intensity low energy titanium ion implantation into zirconium alloy

This research describes the possibility of ultra-high dose deep titanium ion implantation for surface modification of zirconium alloy Zr-1Nb. The developed method based on repetitively pulsed high intensity low energy titanium ion implantation was used to modify the surface layer. The DC vacuum arc source was used to produce metal plasma. Plasma immersion titanium ions extraction and their ballistic focusing in equipotential space of biased electrode were used to produce high intensity titanium ion beam with the amplitude of 0.5 A at the ion current density 120 and 170 mA/cm2. The solar eclipse effect was used to prevent vacuum arc titanium macroparticles from appearing in the implantation area of Zr sample. Titanium low energy (mean ion energy E = 3 keV) ions were implanted into zirconium alloy with the dose in the range of (5.4–9.56) × 1020 ion/cm2. The effect of ion current density, implantation dose on the phase composition, microstructure and distribution of elements was studied by X-ray diffraction, scanning electron microscopy and glow-discharge optical emission spectroscopy, respectively. The results show the appearance of Zr-Ti intermetallic phases of different stoichiometry after Ti implantation. The intermetallic phases are transformed from both Zr0.7Ti0.3 and Zr0.5Ti0.5 to single Zr0.6Ti0.4 phase with the increase in the implantation dose. The changes in phase composition are attributed to Ti dissolution in zirconium lattice accompanied by the lattice distortions and appearance of macrostrains in intermetallic phases. The depth of Ti penetration into the bulk of Zr increases from 6 to 13 μm with the implantation dose. The hardness and wear resistance of the Ti-implanted zirconium alloy were increased by 1.5 and 1.4 times, respectively. The higher current density (170 mA/cm2) leads to the increase in the grain size and surface roughness negatively affecting the tribological properties of the alloy.

Temperature evolution of microstructure of deformed submicrocrystalline Cu–Zr samples

Temperature evolution of microstructure of deformed submicrocrystalline Cu–Zr samples

Wear and corrosion properties of in-situ grown zirconium nitride layers for implant applications

Zirconium (Zr) and its alloys are considered as promising materials for implant applications due to their excellent biocompatibility. However, the poor tribological properties of Zr are limiting its widespread applications. Therefore, in this investigation thermal nitriding of laser processed Zr was carried out with an aim to improve its wear and corrosion properties for potential wear resistant implant applications. The influences of nitriding temperature and time on the nitride layer thickness, phase constituents, wear and corrosion properties of nitrided Zr layer were studied. The Zr samples were nitrided at 600°C and 800°C for 2 and 6h in flowing nitrogen. The results demonstrated that the nitriding temperature had relatively stronger influence on the nitride layer thickness, wettability, hardness and wear resistance than nitriding time. In general, the nitride layers found to contain ZrN and ZrO2 as major phases and Zr2N and Zr7O8N4 as minor phases. The nitride layer thickness increased from 5±0.7μm to 26±5μm with increase in the nitriding temperature and time. Nitriding also enhanced the wettability and passivity of Zr. The samples nitrided at 600°C for 2h resulted in noblest Ecorr of −130mV vs SCE with Icorr of 0.001μA/cm2 in Hank's balanced salt solution. Lowest in vitro wear rate of 4.4×10−7mm3/N·m was recorded, against Al2O3,when the samples were nitrided at 800°C for 6h, which is 93% lower than that of pure Zr. These results demonstrate that thermal nitriding of Zr can be used to increase the corrosion and wear resistance of Zr in physiological environment.

Nanoscale heterogeneity as remnant hexagonal-type local structures in shocked Cu-Pb and Zr

Extended X-ray absorption fine structure spectroscopy was used to determine the local structure in: (1) Zr that had undergone quasistatic elongation; (2) Zr that had undergone plastic deformation by shock at pressures above and below the ω-phase transformation; and (3) shocked Cu that contained a few percent of insoluble Pb. Below the transition pressure, Zr samples showed only general disorder as increases in the widths of the Zr-Zr pair distributions. Above this pressure, Zr that was a mixture of the original hcp and the high pressure ω-phase when measured by diffraction showed two sets of peaks in its distribution corresponding to these two phases. Some of the ones from the ω-phase were at distances substantially different from those calculated from the diffraction pattern, although they are still consistent with small domains exhibiting stacking faults associated with hexagonal-type structural components exhibiting variability in the [0001] basal plane spacing. A similar result, new pairs at just over 3 and 4 Å consistent with hexagonal-type stacking faults in addition to the original fcc structure, is found in shocked Cu despite the absence of a second diffraction pattern and peak pressures being far below those expected to induce an fcc to hcp transition. This result, therefore, demonstrates that the correlation between high strain rates and reduced stacking fault energy continues down to the length scale of atom pairs. These findings are significant as: (1) a microscopic description of the behavior of systems far from equilibrium; (2) a demonstration of the importance of strain rate at short length scales; and (3) a bridge between the abruptness of macroscopic pressure-induced phase transitions and the continuity of martensitic ones over their fluctuation region in terms of the inverse relationship between the length scale of the martensitic texture, manifested here as ordered lattice distortions and the lower pressure at which such texture first appears relative to the bulk transition pressure.

Síntesis e investigación del mono cristal BiSBTeSe dopado con Zr obtenido mediante el método de Bridgman

El lingote del mono cristal de BiSbTeSe dopado con Zr se sintetizó utilizando el método de Bridgman. La composición química se determinó mediante análisis con espectroscopía de dispersión de energía (EDS). Mediante difracción de rayos X (DRX) se demostró que el lingote de cristal obtenido es un mono cristal y confirmó que se trata de un compuesto del tipo Bi2Te3, con orientación del mono cristal (001). El punto de fusión se determinó por medidas dilatométricas. La movilidad, concentración, resistividad/conductividad, y el coeficiente de Hall del BiSbTeSe dopado con Zr, se determinaron utilizando un sistema de medición de efecto Hall basado en el método de Van der Pauw. El efecto Hall se midió a temperatura ambiente con una intensidad de campo magnético aplicada de 0,37 T a diferentes intensidades de corriente. 
 Las muestras de lingotes medidos se cortaron y se rompieron de diferentes regiones. Las muestras de lingotes utilizadas en las medidas fueron obtenbidas mediante corte y escisión en distintas zonas. Los resultados obtenidos utilizando un sistema de medición de efecto Hall (Ecopia, HMS-3000) en las distintas muestras, se compararon entre sí. Los resultados confirmaron que las propiedades eléctricas y de transporte del mono cristal dependen de la dirección del crecimiento del cristal. La movilidad se mejoró significativamente en comparación no solo con el valor teórico de Bi2Te3 sino también con los datos existentes en la literatura.

Determination of 1-keV to 1-MeV Neutron Flux by Radiative Capture (n, $\gamma $ ) on92,94 Zr Dosimeters

The purpose of this paper is to demonstrate 92,94Zr application in neutron reactor dosimetry. We aim to detect neutron flux in 1-keV to 1-MeV energy range by irradiating 92,94Zr samples under boron nitride (BN) filter. The presence of BN is needed in order to cut off thermal neutron contribution. This paper describes Zr irradiation and experimental results that were obtained by $\gamma $ spectrometry and accelerator mass spectrometry. In parallel, Zr irradiation is modeled with Monte Carlo-based code for neutron transport—TRIPOLI-4v10 developed by CEA (Saclay). Experimental values of 95Zr activity and 93Zr/92Zr ratio are compared to calculation results. Since crosssection values are necessary for the neutron flux determination, we present here the comparison between several nuclear data libraries for radiative capture on 92,94Zr. Uncertainties for calculation/experience (C/E) ratios are obtained combining both experimental and nuclear data ones. This paper shows the feasibility of 1-keV to 1-MeV neutron detection by using 92,94Zr (n, $\gamma $ ) reaction and introduces a postirradiation analysis for reactor dosimetry based on accelerator mass spectrometry. It also reveals that more precise evaluation of 92,94Zr (n, $\gamma $ ) cross section is required in order to improve C/E values.

High strain rate superplasticity in an Al–Mg–Sc–Zr alloy processed via simple rolling

The superplastic behavior of Al–Mg–Sc–Zr samples with standard gauge size (18mm by 6mm) were prepared using simple rolling and were tested in the temperature range from 450°C to 525°C at strain rates ranging from 1.67×10–3s−1 to 1×10–1s−1. With proper deformation parameters, the Al–Mg–Sc–Zr alloy has an elongation to failure much higher than 300% and the maximum elongation is 740%. The Microstructure and dislocation substructure investigation using optical microscopy (OM) and transmission electron microscopy (TEM) revealed a dynamic recrystallization in it. The grain size and activation energy on the deformation mechanisms of superplastic is discussed. Results also show that these nano-scale Al3(Sc1−xZrx) particles play an important role in the superplastic process. Al6FeMn particles were found to induce the formation and growth of cavities, which can lead to the fracture of specimens.

Slow positron beam studies of zirconium exposed to dry sliding

Slow positron beam studies of Zr samples exposed to dry sliding are reported. The observed increase of the annihilation line shape parameter indicates generation of vacancy clusters although an increase of the positron diffusion length suggests recovery process indicated by sliding. The increase of the number of positronium created on the worn surface in comparison to the non damaged surface was noticed.

Formation of Subsurface Zone Induced by Sliding Wear in Zirconium Studied by Positron Lifetime Spectroscopy

The zone below the surface in pure Zr exposed to dry sliding is the subject of studies using positron lifetime methods. New type of the defect depth profile is observed. The zone contains dislocations and vacancy clusters which occur only at a certain depth from the worn surface. The size of the vacancy clusters decreases with the depth increase. The total depth of the subsurface zone is about hundreds of micrometers and depends on the applied load. The estimated effective strain in the subsurface zone decreases exponentially with the depth increase. The similar kinds of defects and their depth profiles are observed also for the Zr samples exposed to sandblasting. This indicates the common origin of formation of the subsurface zone during dry sliding and sandblasting. Results of the theoretical calculations of the positron lifetime in vacancy clusters in Zr are also presented.

Microstructure, hardness and defect structure of the He irradiated ODS ferritic steel

In this paper, the microstructure, hardness and defect structure of the oxide dispersion strengthened Fe-16Cr-2W-0.5Ti-0.4Y2O3 (designated as ODS-16Cr) and Fe-16Cr-2W-0.5Ti-0.4Y2O3-4Al-1Zr (ODS-16Cr-Al/Zr) steels irradiated with different doses of He ions were investigated by means of TEM, nanoindentation and positron annihilation spectroscopy. In the both alloys, nano-scale bubbles appeared in the vicinity of the precipitates as well as the grain boundaries. High density dislocation networks were observed as well. Moreover, the hardness of the irradiated steels increased distinctly with increasing He implantation. The irradiation hardening in the ODS-16Cr-Al/Zr alloy is more prominent in comparison with the ODS-16Cr alloy. The positron annihilation results illustrated that concentration of vacancy clusters of ODS-16Cr-Al/Zr steel is higher in the near surface under the larger dose, which is one reason of stronger irradiation hardening below the surface of 300–400 nm. The higher concentration of vacancies or vacancy clusters in ODS-16Cr-Al/Zr samples can be attributed to the fact that the solute Al atoms can effectively trap interstitials, which suppresses the annihilation of interstitials with vacancies.

Growth and characterization of epitaxial Zr(0001) thin films on Al2O3(0001)

The authors report the growth of epitaxial Zr(0 0 0 1) thin films on Al2O3(0 0 0 1) substrates at a temperature of 700 °C via dc magnetron sputtering in an ultrahigh vacuum deposition system equipped with facilities for chemical vapor deposition, low-energy electron diffraction, and Auger electron spectroscopy. Zr layers with a nominal thickness of ∼220 nm are deposited at a rate of ∼0.06 nm/s in 10 mTorr Ar atmosphere. In situ Auger electron spectra of the as-deposited film surface reveal the presence of a Zr peak at 145 eV and Hf peak at 172 eV, the latter due to the presence of Hf impurities in the Zr sputter target. In situ low-energy electron diffraction patterns acquired from the Zr sample show sixfold symmetric spots with an in-plane lattice spacing of 0.31 ± 0.02 nm, characteristic of Zr(0 0 0 1)–(1 × 1) surface. Cross-sectional transmission electron microscopy images reveal columnar growth and the formation of a crystalline, 22 ± 8 nm thick, interfacial layer. Energy dispersive x-ray spectra obtained from this region reveal the presence of both Zr and Al. The authors attribute the formation of this interfacial layer to plasma-induced substrate decomposition during sputtering followed by interdiffusion of Al and Zr at the film–substrate interface. ω-2θ x-ray diffraction data show that the Zr layers are single-phase with hexagonal close-packed structure. Using high-resolution symmetric as well as asymmetric reciprocal space maps, the authors determined that the film is fully relaxed with in-plane and out-of-plane orientation lattice parameters of 0.324 and 0.516 nm, respectively, and identified epitaxial orientation relationships as Zr(0 0 0 4) ‖ Al2O3(0 0 0 12) and Zr(101¯0) ‖ Al2O3(112¯0).

Fibroblast response to initial attachment and proliferation on titanium and zirconium surfaces

Introduction: In recent decades, dental implants have become one of the best options for comprehensive dental restoration; their placement is a multidisciplinary task that requires a solid understanding of biological, periodontal, surgical and prosthetic principles. Objective: The aim of this study was to quantify in vitro the adhesion and proliferation of human gingival fibroblasts’ (HGF) response on titanium (Ti) and zirconia (Zr) surfaces. Methodology: Samples of Ti and Zr were observed under atomic force microscopy (AFM). HGFs were inoculated in each sample to determine adhesion and cell proliferation. The MTT reagent was mixed with DMEM and inoculated in each plate; formazan was dissolved with dimethyl sulfoxide and analyzed at 540 nm in a microplate spectrophotometer. The test was performed with three independent experiments. Data were analyzed with Kolmogorov-Smirnov tests (Lilliefors), Kruskal-Wallis tests and Mann-Whitney test comparisons. Results: Topography of the Zr plates showed greater roughness (Ra= 0.39μm) than Ti (Ra= 0.049μm). Quantification of HGF adhesion was significantly higher (p˂0.05) in Ti, while proliferation showed no statistically significant differences between the groups. Conclusion: It is noteworthy that, even though Ti initially showed increased cell adhesion on the surface, after 24 h Zr samples showed similar proliferation; this demonstrates that both surfaces have a comparable biological response.

Thermal stability of Cu-Cr-Zr alloy processed by equal-channel angular pressing

Thermal stability of a Cu-Cr-Zr alloy processed by equal-channel angular pressing up to16 passes was investigated using isochronal annealing ranging from 250 to 850°C for 1h. The microstructure, crystallographic texture and micro hardness of samples were characterized through electron back scatter diffraction and Vickers micro hardness measurements. The recrystallized grain size was stable between 250°C and 500°C then increased quickly. The achieved mean grain size, after 1, 4 and 16 ECAP passes, was around 5.5μm. A discontinuous mode of recrystallization was found to occur and a Particle Simulated Nucleation mechanism was evidenced. The evolution of the high angle grain boundary fraction increased notably after annealing above 550°C. The crystallographic texture after isochronal annealing was similar to that of ECAP simple shear, no change of the texture during annealing was observed but only slight intensity variations. Micro hardness of all Cu–Cr–Zr samples showed a hardening with two peaks at 400 and 500°C associated with precipitation of Cu cluster and Cu5Zr phase respectively, followed by a subsequent softening upon increasing the annealing temperature due to recrystallization.

Use of aluminum oxide as a permeation barrier for producing thin films on aluminum substrates

Aluminum has desirable characteristics of good thermal properties, good electrical characteristics, good optical properties, and the characteristic of being nonmagnetic and having a low atomic weight (26.98 g atoms), but because of its low melting point (660 °C) and ability as a reactive metal to alloy with most common metals in use, it has been ignored as a substrate material for use in processing thin films. The author developed a simple solution to this problem, by putting a permeation barrier of alumina (Al2O3) onto the surface of pure Al substrates by using a standard chemical oxidation process of the surface (i.e., anodization), before additional film deposition of reactive metals at temperatures up to 500 °C for 1-h, without the formation of alloys or intermetallic compounds to affect the good properties of Al substrates. The chromic acid anodization process used (MIL-A-8625) produced a film barrier of ∼(500–1000) nm of alumina. The fact that refractory Al2O3 can inhibit the reaction of metals with Al at temperatures below 500 °C suggests that Al is a satisfactory substrate if properly oxidized prior to film deposition. To prove this concept, thin film samples of Cr, Mo, Er, Sc, Ti, and Zr were prepared on anodized Al substrates and studied by x-ray diffraction, Rutherford ion back scattering, and Auger/argon sputter surface profile analysis to determine any film substrate interactions. In addition, a major purpose of our study was to determine if ErD2 thin films could be produced on Al substrates with fully hydrided Er films. Thus, a thin film of ErD2 on an anodized Al substrate was prepared and studied, with and without the alumina permeation barrier. Films for study were prepared on 1.27 cm diameter Al substrates with ∼500 nm of the metals studied after anodization. Substrates were weighed, cleaned, and vacuum fired at 500 °C prior to use. The Al substrates were deposited using standard electron beam cold crucible evaporation techniques, and after deposition the Er film was hydrided with D2 gas using a standard nonair exposure hydriding technique. All processing was conducted in an all metal ion pumped ultrahigh vacuum system. Results showed that e-beam deposition of films studied onto Al substrates could be successfully performed, if a permeation barrier of Al2O3 from 500 to 1000 nm was made prior to thin film deposition up to temperatures of 500 °C for 1-h. Hydrides also, could be produced with full gas/metal atomic ratios of ∼2.0 as evidenced by the ErD2 films produced. Thus, the use of a simple permeation barrier of Al2O3 on Al substrates prior to additional metal film deposition was proven to be a successful method of producing both thin metal films and hydride films of various types for many applications.

Surface, structural and tensile properties of proton beam irradiated zirconium

This paper reports the surface, structural and tensile properties of proton beam irradiated pure zirconium (99.8%). The Zr samples were irradiated by 3.5MeV protons using MC-50 cyclotron accelerator at different doses ranging from 1×1013 to 1×1016 protons/cm2. Both un-irradiated and irradiated samples were characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Universal Testing Machine (UTM). The average surface roughness of the specimens was determined by using Nanotech WSxM 5.0 develop 7.0 software. The FESEM results revealed the formation of bubbles, cracks and black spots on the samples’ surface at different doses whereas the XRD results indicated the presence of residual stresses in the irradiated specimens. Williamson–Hall analysis of the diffraction peaks was carried out to investigate changes in crystallite size and lattice strain in the irradiated specimens. The tensile properties such as the yield stress, ultimate tensile stress and percentage elongation exhibited a decreasing trend after irradiation in general, however, an inconsistent behavior was observed in their dependence on proton dose. The changes in tensile properties of Zr were associated with the production of radiation-induced defects including bubbles, cracks, precipitates and simultaneous recovery by the thermal energy generated with the increase of irradiation dose.

Femtosecond filament-laser ablation molecular isotopic spectrometry

A new remote sensing technology for real-time isotopic analysis is introduced: Femtosecond Filament-Induced Laser Ablation Molecular Isotopic Spectrometry (F2-LAMIS). The technique combines femtosecond (fs) laser filamentation and ablation-based molecular isotopic spectroscopy, thereby enabling isotopic analysis of samples at a distance, in ambient air and at ambient pressure conditions. Isotopic analysis of zirconium (Zr) samples by F2-LAMIS is demonstrated, and the molecular and atomic emission intensity, and properties of the filament-induced plasma generated at different filament propagation distances were investigated. Spectral fitting of F2-LAMIS spectra enabled semi-quantitative isotopic analysis without the use of calibration standards, which was independent of the filament propagation distance for the studied range. This technology provides new capabilities for direct isotopic ratio measurements at remote distances.

Nanomechanical Characterization of Temperature-Dependent Mechanical Properties of Ion-Irradiated Zirconium with Consideration of Microstructure and Surface Damage

Zirconium alloys for nuclear applications with different microstructures were produced by manufacturing processes such as chipping, rolling and annealing. The two Zr samples, rolled and rolled-annealed were subjected to different levels of irradiation, 1 keV and 100 eV, to study the effect of irradiation dosages. The effect of microstructure and irradiation on the mechanical properties (reduced modulus, hardness, indentation yield strength) was analyzed with nanoindentation experiments, which were carried out in the temperature range of 25°C to 450°C to investigate temperature dependence. An indentation size effect analysis was performed and the mechanical properties were also corrected for the oxidation effects at high temperatures. The irradiation-induced hardness was observed, with rolled samples exhibiting higher increase compared to rolled and annealed samples. The relevant material parameters of the Anand viscoplastic model were determined for Zr samples containing different level of irradiation to account for viscoplasticity at high temperatures. The effect of the microstructure and irradiation on the stress–strain curve along with the influence of temperature on the mechanisms of irradiation creep such as formation of vacancies and interstitials is presented. The yield strength of irradiated samples was found to be higher than the unirradiated samples which also showed a decreasing trend with the temperature.

Synthesis gas generation by chemical-looping selective oxidation of methane using Pr1−xZrxO2−δ oxygen carriers

The Pr1−xZrxO2−δ complex oxides (x = 0, 0.1, 0.3, 0.5, 0.7, and 0.9) prepared by precipitation method were characterized by X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), O2 temperature programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS) technologies. Chemical-looping selective oxidation of methane (CLSOM) process using a gas–solid reaction between methane and Pr–Zr complex oxides was investigated at 850 °C for the synthesis gas generation. Pr–Zr–O solid solution could be formed by incorporation of Zr4+ to Pr6O11 at a large proportion range (0.1–0.9). Oxygen mobility and thermal stability of Pr–Zr samples was obviously enhanced by the formation of Pr–Zr–O solid solution. Pr-rich Pr–Zr oxygen carriers showed high selectivity towards CO and H2 and high methane conversion. Synthesis gas with a suitable H2/CO ratio of 2.0 could be obtained over those samples. Pr0.7Zr0.3O2−δ performed satisfactory performance for the successive generation of synthesis gas in CLSOM process.