High-purity Zirconium Research Articles

Functional materials based on high-purity zirconium compounds for applications in alternative energy

The paper presents the results of experiments on obtaining functional materials (piezoceramics, catalysts, heat-resistant coatings) based on zirconium oxide. It is shown that zirconium oxynitrate, obtained in the process of extraction separation of zirconium and hafnium, has a low content of impurities determining the quality of products based on zirconium oxide. The method of homogeneous deposition of stoichiometric zirconium compounds with alloying additives provided homogeneous salt systems for functional ceramics. The high homogeneity of the material and its physicochemical and mechanical properties allowed to obtain powders at much lower temperatures than solid-phase synthesis, providing high-quality products at low energy consumption.

Resource-saving and environmental protection in nuclear-grade zirconium and hafnium production

The development of efficient and environmentally friendly technological processes for processing zircon concentrate is an urgent problem in the technology of producing reactor-pure zirconium and hafnium used in nuclear power. The review presents the environmental, technical and economic characteristics of zircon decomposition processes using existing industrial technologies and provides data on the environmental safety of each technology. It is shown that current industrial technologies do not meet the criteria of sustainable development and allow emissions of toxic reagents into the environment. New applications of particularly pure zirconium and hafnium compounds which have emerged in recent decades, with impurity content of 10-3–10-5%, require less corrosive reagents than chlorine and fluorine, new resource-saving processes and equipment. Today, technical zirconium oxide with a purity of 98% is the main industrial product of zircon processing, but it allows for losses of hafnium, scandium and silicon. This is equivalent to financial losses of over USD 150 million per year. Based on the analysis of promising halogen-free technologies, a new integrated zircon processing technology is proposed which allows producing scarce hafnium, scandium and silicon compounds along with reactor-pure zirconium and its high-purity chemical compounds. The chemicals consumed in the zircon processing process are utilized in the production of mineral fertilizers, eliminating environmental pollution. The use of the highly efficient refining extraction process in a nitric acid environment using centrifugal extractors with an available tributilphosphate extractant allows us to obtain reactor metals with a purity of 99.95%. The production of high-purity zirconium, hafnium, scandium and silicon oxides meets the demand for non-nuclear products, which expands the volume of integrated zircon processing and meets the growing market demand for new functional materials. The integrated approach to zircon processing can reduce the cost of zircon by producing by-products, recycling consumed reagents and eliminating non-recyclable solid and liquid waste. This will ensure environmental protection even with relatively small volumes of reactor-pure metal production.

Phase transitions in high-purity zirconium under dynamic compression

We present results from ramp compression experiments on high-purity Zr that show the $\ensuremath{\alpha}\ensuremath{\rightarrow}\ensuremath{\omega}, \ensuremath{\omega}\ensuremath{\rightarrow}\ensuremath{\beta}$, as well as reverse $\ensuremath{\beta}\ensuremath{\rightarrow}\ensuremath{\omega}$ phase transitions. Simulations with a multiphase equation of state and phenomenological kinetic model match the experimental wave profiles well. While the dynamic $\ensuremath{\alpha}\ensuremath{\rightarrow}\ensuremath{\omega}$ transition occurs $\ensuremath{\sim}9\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ above the equilibrium phase boundary, the $\ensuremath{\omega}\ensuremath{\rightarrow}\ensuremath{\beta}$ transition occurs within 0.9 GPa of equilibrium. We estimate that the dynamic compression path intersects the equilibrium $\ensuremath{\omega}\text{\ensuremath{-}}\ensuremath{\beta}$ line at $P=29.2\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, and $T=490\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The thermodynamic path in the interior of the sample lies $\ensuremath{\sim}100\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ above the isentrope at the point of the $\ensuremath{\omega}\ensuremath{\rightarrow}\ensuremath{\beta}$ transition. Approximately half of this dissipative temperature rise is due to plastic work, and half is due to the nonequilibrium $\ensuremath{\alpha}\ensuremath{\rightarrow}\ensuremath{\omega}$ transition. The inferred rate of the $\ensuremath{\alpha}\ensuremath{\rightarrow}\ensuremath{\omega}$ transition is several orders of magnitude higher than that measured in dynamic diamond anvil cell (DDAC) experiments in an overlapping pressure range. We discuss a model for the influence of shear stress on the nucleation rate. We find that the shear stress ${s}_{ji}$ has the same effect on the nucleation rate as a pressure increase $\ensuremath{\delta}P=c{\ensuremath{\epsilon}}_{ij}{s}_{ji}/(\mathrm{\ensuremath{\Delta}}V/V),$ where $c$ is a geometric constant $\ensuremath{\sim}1$ and ${\ensuremath{\epsilon}}_{ij}$ are the transformation shear strains. The small fractional volume change $\mathrm{\ensuremath{\Delta}}V/V\ensuremath{\approx}0.1$ at the $\ensuremath{\alpha}\ensuremath{\rightarrow}\ensuremath{\omega}$ transition amplifies the effect of shear stress, and we estimate that for this case $\ensuremath{\delta}P$ is in the range of several GPa. Correcting our transition rate to a hydrostatic rate brings it approximately into line with the DDAC results, suggesting that shear stress plays a significant role in the transformation rate.

A Novel Process for Production of High Purity Zirconium Oxy Chloride from Zircon Sand for Bio-Inert Ceramics

A Novel Process for Production of High Purity Zirconium Oxy Chloride from Zircon Sand for Bio-Inert Ceramics

Effect of Raw Material Purity on Structure and Properties of Metallic Glasses

Zirconium base metallic glasses [Zr0.73(Cu0.59Ni0.41)0.27]87Al13 was fabricated by industrial zirconium with low purity and high purity zirconium according to different quality ratios in order to study the effect of raw material purity on the structure and properties of metallic glasses. The results showed that the complete metallic glasses was failed to be fabricate with low purity zirconium. And the compression process was typical brittle fracture with low compressive strength and without plastic strain. The glasses forming ability of low purity zirconium metallic glass with different purity was significantly improved after the addition of yttrium element. The compression experiments showed that the compressive strength and plasticity of metallic glasses were improved, and the microhardness was also increased. It indicates that yttrium element can eliminate the adverse effect of impurity in low purity zirconium on the glasses forming ability of the alloy and improve the structural properties of the metallic glasses.

Tribological properties of ZrN coatings deposited by magnetron sputtering in reactive and non-reactive mode

Zirconium and zirconium nitride coatings were deposited via magnetron sputtering by using high-purity zirconium or zirconium nitride targets. As a particularity, the zirconium nitride coatings were deposited by using a ZrN target via non-reactive mode or by using a Zr target via reactive technique, in argon/nitrogen environment. Depending on the time deposition, coatings with different thicknesses (200, 500 and 1000 nm) have been obtained. Chemical and phase composition, thickness of the coating and morphology of the surfaces were investigated by highly sensitive X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The wear tests have been performed by High Frequency Reciprocating Rig (HFRR). The wear scar diameters decrease with an increase of coatings thickness, while the friction coefficient for the coatings with 500 nm thickness revealed the lowest values for friction coefficients, for all type of coatings

Experimental verification of a crystal plasticity-based simulation framework for predicting microstructure and geometric shape changes: Application to bending and Taylor impact testing of Zr

This paper is concerned with experimental verification of a recently developed multi-scale simulation framework for plastic deformation of metallic materials from quasi-static to impact deformation conditions. The framework is a visco-plastic self-consistent (VPSC) polycrystalline model embedded in an implicit finite element method (FE-VPSC) to provide a microstructure-sensitive constitutive response at each material point. Each material point of the FEM model is a polycrystalline aggregate with crystallographic deformation mechanisms operating at the single crystal scale with their evolving activity based on a dislocation density-based hardening law and texture. Four beams and three cylinders machined in different orientations from a textured plate of high-purity zirconium are tested quasi-statically in 4-point bending and at speeds of 100 m/s, 170 m/s and 243 m/s during Taylor impact tests, respectively. The variation in dimensional changes resulting from different sample orientations in the plate with respect to loading directions is measured for each sample. Moreover, texture and twinning characterization is performed using electron backscattered diffraction (EBSD). The deformation processes and underlying evolution of microstructure are successfully simulated using the FE-VPSC framework. In doing so, the model parameters are optimized and validated across a broad range of strain rates and temperatures. Simulation results in terms of geometrical changes and microstructural evolution are compared with the experimental measurements. The model predicts anisotropic material flow resulting from the hard-to-deform crystallographic directions, the development of gradients in texture and twinning through the geometries, tension–compression asymmetry, as well as the extent of plasticity under impact.

Zirconium Phase Transformation under Static High Pressure and ω-Zr Phase Stability at High Temperatures.

High-purity Zr has been observed to undergo a phase transformation from the α-phase to the hexagonal ω-phase under high pressure generated either statically or by shock loading. The transition pressure from α-Zr to ω-Zr at 300 K is 2.10 GPa. The main aim of this research was to determine the conditions of α-Zr in ω-Zr transformation and the state of stresses after the high-pressure pressing and sintering of zirconium powders. Commercially acquired zirconium powders of 99.9% and 98.8% purity were used in this study. Qualitative and quantitative phase analysis of the materials was carried out using X-ray diffraction. The materials were statically pressed and sintered using a Bridgman-type toroidal apparatus at under 4.0 and 7.8 GPa. After pressing, the transformation proceeded for the zirconium powder containing 98.8% purity (with hydrides admixture) but did not occur for the high-purity zirconium powders with 99.9% purity. The zirconium powders were sintered using the HPHT (High Pressure—High Temperature) method at temperatures of 1273 K and 1473 K. The transformation proceeded for both powders. The highest contribution of the ω-Zr phase was obtained in the zirconium (98.8% purity with the hydrides contents) sintered for 1 min at a temperature of 1473 K and a pressure of 7.8. The ω-phase content was 87 wt.%. The stress measurement was performed for the pressed and sintered materials using the sin2ψ X-ray diffraction method. The higher sintering temperature resulted in a decrease of the residual stresses in the ω-Zr phase for the sintered zirconium. The higher levels of stress limited the transformation of the α-Zr phase into the ω-Zr phase. Investigated materials characterized by higher compressive macrostresses were also typical of the greater stability of the ω-Zr phase at high temperatures.

The influence of powder characteristics on the sintering behaviour and impurity content of spark-plasma-sintered zirconium

At present, most zirconium products as well as its alloys are obtained by foundry methods. New technologies used to manufacture high-quality components, such as direct laser sintering or microwave sintering, require spherical powders of a narrow particle size distribution, as this affects the packing density and sintering mechanism. The powders also have to be chemically pure, as impurities such as H, O, C, N and S cause brittleness and problems with corrosion. Commercially procured, high purity zirconium powders from three different sources were characterised for their particle size and phase composition. Dilatometer studies have shown the effect of powder contamination at the beginning and at end of the sintering process. For powders of 99.9% purity, the start of sintering takes place at a temperature of about 700 °C. For powders of 98.8% purity, the sintering starts at 500 °C. In the studies presented in this paper, the SPS/FAST (Spark Plasma Sintering/Field Assisted Sintering Technique) method was chosen for densification processes. Sintered materials were characterised for their density using the Archimedes principle, relative density and Vickers hardness. A determination of the oxygen, nitrogen and hydrogen content in zirconium powders and sintered samples was carried out. The studies confirmed that SPS of zirconium powders in an argon atmosphere slightly decreases the content of oxygen and nitrogen. At 1000 °C, at pressure of 35 MPa, in argon, there is no decomposition of zirconium hydrides in sintered materials.

Vacuum activation assisted hydrogenation-dehydrogenation for preparing high-quality zirconium powder

ABSTRACTThe vacuum activation assisted hydrogenation-dehydrogenation (HDH) method was applied to fabricate the high-purity and ultrafine nuclear grade zirconium powders. An additional vacuum activation process was specially used prior to the hydrogenation to suppress the oxygen content and increase the hydrogen content. It was found that this extra process was not only efficient in shortening the length of the whole process, but also critical in improving the quality of Zr powders. The detailed investigations on the mechanism indicated that the merits could be both attributed to the removal of the oxygen sources on the sponge zirconium surface and the formation of micro-cracks on the ZrO2 film. By adjusting the parameters of the vacuum activation assisted HDH process, the oxygen content of the intermediate material ZrH2 was decreased down to 0.16 wt.%, while the hydrogen content was increased up to 2.14 wt.%, nearly approaching to the theoretical value. Based on this high-quality ZrH2 bulks, the Zr powders with oxygen content of 0.21 wt.% and D50 of ~2.9 μm could be fabricated after the ball-milling and dehydrogenation process. An efficient approach to produce high-quality Zr powders was systematically investigated in this paper to satisfy with the demand of the nuclear industry.

Dynamic reflectance changes in high-purity zirconium when it is shocked from the α to ω phase

Flash lamp-illuminated integrating spheres have been used to measure the dynamic reflectance at the interface between a shocked metal target and a window maintaining the shock stress. In conjunction with radiance measurements, this method was recently used to study the pressure versus temperature phase boundary of the beta phase to body-centered-tetragonal transition of tin at around 13 GPa and, in separate experiments, to show a relationship between the reflectance and the phase fraction. We have used this technique to measure the ratio, R, of the dynamic reflectance relative to the ambient value for a high-purity zirconium sample attached to a sapphire window to study the alpha to omega phase transition. Nine experiments cover the range of stress, σ, from 4 to 16 GPa at six wavelengths from 500 to 1550 nm. The two phases in zirconium differ in volume by <1%, so a phase change between them can be difficult to identify from anomalies in the particle velocity measured on the shock Hugoniot. The phase boundary is believed to cross the Hugoniot around 3 GPa, but dynamically it is observed at much higher stresses >6 GPa. Our results show that the relative reflectance decreases upon initial shock in the alpha state but increases as the material transforms to its omega state. The slope dR/dσ changes the sign around the phase transition. For shocks below 6 GPa, dR/dσ < 0, and for σ above 10 GPa, dR/dσ > 0. In the stress region between 6 and 10 GPa, dR/dσ varies somewhat, perhaps due to the band structure or because the transition is incomplete there.

Nano ZrO2 Synthesis by Extraction of Zr(IV) from ZrO(NO3)2 by PC88A, and Determination of Extraction Impurities by ICP-MS

High purity Zirconium (Zr) materials are essential in many components of nuclear reactors, especially fuel cladding tubes. Due to the matrix influence, determination of impurities in the Zr materials requires separation from the Zr matrix. Among extraction methods, solvent extraction is common and suitable for large-scale production. In this study, extraction capability of Zr(IV) by 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (PC88A) was examined by FT-IR and UV of ZrO(NO3)2 salt, PC88A-toluene solvent, and Zr-PC88A-toluene complex. ZrO2 (obtained from Institute for Technology of Radioactive and Rare Elements—ITRRE), after being separated from the Zr matrix, was determined for impurities using internal standard (indium, In) by 50% of PC88A dissolved in toluene. Separation of impurities from the Zr matrix underwent two stages. First, one cycle of extraction of the Zr matrix and impurities in 3 M HNO3 using 50% PC88A/toluene was conducted. Second, impurities were scrubbed by 4 M HNO3 in two cycles. Results revealed that approximately 74% of Zr(IV) was separated to the organic phase and 26% remained in the aqueous phase. Determination of impurities after separation from the Zr matrix by ICP-MS using internal standard in revealed that the recovery of impurities achieved 95–100%. With the mentioned amount of Zr, the effect of the Zr matrix on the determination of elements by ICP-MS is negligible. Levels of impurities have relative standard deviations (RSD) of less than 6.9% and recovery of 88.6–98.8%. Therefore, the determination of impurities has high reliability and accuracy. The back-extraction of Zr(IV) in organic phase by 1 M H2SO4 has stripped about 99.5% of the Zr matrix back to the aqueous phase. Following this, NH3 was added to the solution containing Zr after back-extraction to form Zr(OH)4 which was then desiccated to produce ZrO2. X-ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM and TEM) images showed that the new ZrO2 product has spherical nanostructure with diameters of less than 25 nm, which is suitable for applications for the treatment of colorants, metal ions in wastewater sources and manufacture of anti-corrosion steel. In addition, the energy dispersive X-ray (EDX) of the new ZrO2 product showed that it has high purity.

Fabrication of Carbon Encapsulated ZrC Nanoparticles by Electrical Explosion of Zr Wire in Ethanol

The method of electrical explosion of metal wire in organic liquid was adopted to prepare carbon encapsulated nanoparticles. In the medium of absolute ethyl alcohol, under the high-voltage pulse current (HVPC), the high purity zirconium wire became fusion, gasification, expansion and explosion, accompanied with separating of carbon out of ethanol and reaction of carbon and zirconium, and carbon encapsulated ZrC nanoparticles formed. The energy, voltage and current in the experiments were measured to analyze the influence of them on the products. The products were analyzed by X-ray diffraction technique (XRD), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results show that the carbon encapsulated ZrC nanoparticles are fabricated successfully. The diameter range is between 10~150 nm. For the voltage of 4, 8 and 12 kV, the average size of the products is 24.9, 41.4 and 43.9 nm, respectively. Finally, the procedure and mechanism of fabrication of the carbon encapsulated ZrC nanoparticles were discussed preliminarily.

Synthesis of sub-micro sized high purity zirconium diboride powder through carbothermal and borothermal reduction method

Sub-micro sized zirconium diboride (ZrB2) powders were successfully prepared via the boro/carbothermal reduction method using zirconium oxide and boron carbide as the primary raw materials. The prepared mixtures were thermally reacted at 1250°C for 1h. The optimized composition range containing the lowest oxide and carbide impurity, which was 0.14% of oxygen and 0.3% of carbon contents, was determined using crystallographic and elemental analysis. The particle size was reduced from 5µm to 245nm by the addition of B4C as a reductant within a composition range that maintained the highest purity. The morphology changed from faceted to angular hexagonal bar-like with a simultaneous growth in particle size. Changes in the particle structure were a result of the existing liquid B2O3 phase during the reaction. The 245-nm particles contained 12.1% oxygen content and 16.2% oxygen content for the 5-μm particle in the circumstance in which limited oxides could be produced.

Effect of zirconium purity on the glass-forming-ability and notch toughness of Cu43Zr43Al7Be7

The effect of substituting standard grade zirconium lump (99.8% excluding up to 4% hafnium) for high purity zirconium crystal bar (99.5%) in a Cu43Zr43Al7Be7 bulk metallic glass (BMG) is examined. The final hafnium content in the BMG specimens was found to range from 0 to 0.44at%. Introducing low purity zirconium significantly decreased the glass-forming-ability and reduced the notch toughness of the BMG. In contrast, when adding high purity hafnium to Cu43Zr43Al7Be7 made with high purity zirconium, no significant change in the glass-forming-ability or toughness was observed. This suggests that the introduction of low purity zirconium in BMGs creates a more complex response than a simple addition of hafnium. It is likely that other impurities in the material, such as oxygen, play a role in the complex crystallization kinetics and change in mechanical properties. The notch toughness was measured through four-point-bend tests, which showed a decrease in notch toughness from an average of ~53MPam1/2 for the high purity samples to an average of ~29MPam1/2 with full substitution of low purity zirconium. A similar decrease in glass-forming-ability and toughness is observed in commercially synthesized high purity Cu43Zr43Al7Be7. The large scale commercial process is expected to introduced some unintentional impurities, which decrease the properties of the BMG in the same way as the lower purity elements. Lastly, Weibull statistics are used to provide an analysis of variability in toughness for both ingots synthesized in a small laboratory arc-melter and those synthesized commercially.

Study of the Simultaneous Determination of Different Volatile Elements in High Purity Zirconium Dioxide by In situ Matrix Removal and ETV-ICP-MS

Study of the Simultaneous Determination of Different Volatile Elements in High Purity Zirconium Dioxide by In situ Matrix Removal and ETV-ICP-MS

Investigations of orientation and length scale effects on micromechanical responses in polycrystalline zirconium using spherical nanoindentation

Here we investigate the elastic and plastic anisotropy of hexagonal materials as a function of crystal orientation using a high-throughput approach (spherical nanoindentation). Using high purity zirconium as a specific example, we demonstrate the differences in indentation moduli, indentation yield strengths and indentation post-elastic hardening rates over multiple grain orientations. These results are validated against bulk single crystal measurements, as well as data from cubic materials. By varying the indenter size (radius), we are also able to demonstrate indentation size effects in hexagonal materials, including possible signatures of strain hardening due to twin formation in the nanoindentation stress–strain curves.

High-purity Zirconium under Niobium ion implantation: possibility of a dynamic precipitation?

High-purity (6N purity) Zirconium was subjected to different Niobium ion (Nb+) fluences in a particle accelerator. Grazing incidence X-ray diffraction confirmed subsurface phase transformation. While an approximate scaling was noted between Nb+ fluence and quantum of phase transformation, the sample subjected to the highest ion irradiation also showed significant subsurface shear residual stresses (τ13). Molecular dynamics simulations, considering momentum transfer, revealed a drop in τ13 beyond a critical displacements per atom or Nb+ fluence. High-resolution cross-sectional transmission electron microscopy (HRXTEM) confirmed formation of bcc (body-centred cubic) β phase and also linked τ13 with such transformation. HRXTEM revealed, at about 100 nm depth, presence of 10–15% β with 2–15 nm size. The β particles and the surrounding α also had significant microscopic shear strains. The dynamic nature of the Nb implantation is expected to create fluctuations in temperature, Nb concentration and relative lattice damage. Such fluctuation, on the other hand, is/was hypothesized to dynamically alter the critical nuclei size: a clear possibility of ‘dynamic precipitation’.

Thermoelectric Figures of Merit of Zn4Sb3 and Zrnisn-based Half-heusler Compounds Influenced by Mev Ion-beam Bombardments

Semiconducting β-Zn4Sb3 and ZrNiSn-based half-Heusler compound thin films with applications as thermoelectric (TE) materials were prepared using ion beam assisted deposition (IBAD). High-purity solid zinc (Zn) and antimony (Sb) were evaporated by electron beam to grow the β-Zn4Sb3 thin film while high-purity zirconium (Zr) powder and nickel (Ni) tin (Sn) powders were evaporated by electron beam to grow the ZrNiSn-based half-Heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardment for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardment. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam couldcause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ω-method (3rd harmonic) measurement system to measure the cross-plane thermal conductivity, the van der Pauw measurement system to measure the electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.

Automation of High-Purity Zirconium Production from Wastes and Recycled Materials on Industrial Equipment at the Chepetskii Mechanical Plant

Automation of High-Purity Zirconium Production from Wastes and Recycled Materials on Industrial Equipment at the Chepetskii Mechanical Plant