High Zirconium Research Articles

Zirconium Phosphate with a High Surface Area as a Water-Tolerant Solid Acid

High surface area zirconium phosphate in an amorphous phase exhibits high activities for water-related reactions such as hydrolysis of ethyl acetate and esterification of acetic acid with ethanol. The zirconium phosphate is insoluble during the reaction, is recoverable by simple filtration, and can be reused at least five times without any treatment.

Is Cu60Ti10Zr30 a bulk glass-forming alloy?

The microstructures of Cu60Ti10Zr30 alloys fabricated by using two different methods, (rods of 2.5 mm in diameter prepared by a copper-mold casting method, and ribbons of about 0.03 mm in thickness prepared by the melt-spinning method), have been investigated by transmission electron microscopy and high-resolution transmission electron microscopy. Surprisingly, we found that the alloy in both geometries contains cubic nanometer-sized crystals of about 5–7 nm in diameter with a lattice parameter of 0.45 nm for ribbons and 7–15 nm in diameter with a lattice parameter of 0.42 nm for rods. Nanocrystals with a significant volume fraction are randomly distributed in the amorphous matrix. The copper element is enriched in nanocrystals while a slightly high zirconium content is found in the matrix. We classify that the Cu60Ti10Zr30 alloy prepared by both of the aforementioned methods is a nanocomposite: Nanocrystals embedded in an amorphous matrix.

Effects of electrochemical hydrogenation of Zr-based alloys with high glass-forming ability

Zr–(Ti)–Cu–Al–Ni metallic glasses exhibit a high thermal stability corresponding to a wide undercooled liquid region. Depending on their composition, the formation of metastable intermediate phases, e.g. a quasicrystalline phase is possible. The combination of early and late transition metals makes these alloys very interesting regarding their interaction with hydrogen. Amorphous Zr55Cu30Al10Ni5, Zr65Cu17.5Al7.5Ni10 and Zr59Ti3Cu20Al10Ni8 ribbons were prepared by melt spinning and their microstructure and thermal behaviour was checked by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The cathodic reactivity of alloy samples at different microstructural states and after pre-etching in 1 vol.-% HF was investigated in 0.1 M NaOH by applying potentiodynamic polarisation techniques. Galvanostatically hydrogenated samples were characterised by XRD, DSC, TEM and thermal desorption analysis (TDA). For amorphous Zr59Ti3Cu20Al10Ni8 samples an increase in electrochemical surface capacity by two orders of magnitude is observed after pre-etching. Compared to the quasicrystalline and crystalline alloy, the hydrogen reduction takes place at significantly lower overpotentials. Zr-based alloys cathodically absorb hydrogen up to H/M=1.65 while keeping the amorphous structure. Already small amounts of hydrogen cause a significant decrease of the thermal stability and changes in the crystallisation sequence. The hydrogen desorption is a two-stage process: (T<623 K) hydrogen desorption from high interstitial-site energy levels and (T>623 K) zirconium hydride formation and subsequent transformation under hydrogen effusion. Hydrogen suppresses the oxygen-triggered formation of metastable phases upon heating and supports primary copper segregation. At very high H/M ratios, severe zirconium hydride formation causes the crystallisation of new compounds.

Reconstruction of the inhalation dose in the 30-km zone after the Chernobyl accident.

Due to lack of measurements of activity concentrations in air, the assessment of the inhalation dose of the population evacuated from the 30-km zone after the Chernobyl accident is not possible from continuous filter measurements. Since the evaluation of the inhalation dose in each settlement of the zone is of great interest for epidemiological purposes, an approach was chosen that utilizes the available data on ground deposition of 137Cs, a recently performed best estimate of the radionuclide vector and its spatial distribution as well as the radionuclide dependent deposition velocity. The derived inhalation dose values in the 30-km zone range between 3 mSv to 150 mSv effective dose for adults depending on the distance to the reactor site and the day of evacuation. For 1-y-old infants the values range between 10 to 700 mSv. In Chernobyl town, an effective inhalation dose of 25 mSv until evacuation day was assessed. Thyroid doses due to inhalation ranged from 0.02 to 1 Sv for adults, for 1-y-old infants from 0.02 to 6 Sv. The inhalation dose in each settlement of the 30-km zone is approximately 8-13 times higher than the external exposure in each settlement if evacuation of the settlement occurred at an early stage. For settlements with evacuation at a later stage (day 10 or later) the inhalation dose was about 50-70% higher than the external dose. The dominant contribution to the effective inhalation dose comes from 131I (about 40%) and tellurium and rubidium isotopes (about 20-30%). Despite high zirconium and cerium ground depositions, zirconium and cerium isotopes contribute rather little to the inhalation dose which is mainly due to the great particle sizes to which they are attached. The relative contribution of short-lived radionuclides is, despite higher activities than at greater distances, less than 5%.

Preparation of antiferroelectric PbZrxTi1−xO3 thin films on LaSrMnO3-coated steel substrates

Antiferroelectric lead zirconate titanate (PZT) thin films have been prepared by chemical solution deposition using oxide powders. The films were processed onto steel substrates coated with a conducting oxide layer of LaSrMnO3. Homogeneous and uniform films up to 3.4 μm thick and with polarization saturation values up to 35 μC/cm2 have been obtained. The compositional transition from the ferroelectric to the antiferroelectric phase at the high zirconium side of the PZT phase diagram was studied by x-ray diffraction and hysteresis loop measurements as a function of the Zr/Ti ratio. Film thickness and annealing temperature dependencies are reported.

Mechanical response of zirconium—II. Experimental and finite element analysis of bent beams

In a companion paper [ Acta mater. 2001, 49(15), 3085–3096] we develop a polycrystal constitutive law that incorporates the deformation mechanisms operating in high purity zirconium (Zr) at liquid nitrogen (LN) and room temperature (RT). In this paper we present results of 4-point bending tests performed on beams of highly textured zirconium. These tests have been performed at LN and RT, in two orthogonal bending planes, and up to a strain of approximately 20% in the outermost fibers of the beams. A novel experimental technique, dot-matrix deposition and mapping (DMDM), has been developed and employed to analyze the distribution of local plastic strain and macroscopic deformation in the deformed beams. Automated electron backscatter diffraction (EBSD) pattern analysis has been used to evaluate the textures just below the outermost tensile and compressive surfaces and at the neutral plane. Experimental results compare very well with the predictions of finite element (FE) simulations obtained using the constitutive law developed in Part I. Specifically, we compare local deformation, macroscopic deformation and local texture in the beam. We show that the contribution of twinning to deformation results in different qualitative responses in the compressive and tensile fibers of the bent beam. Our results indicate the necessity of using a constitutive description that accounts for the anisotropy of the aggregate and for its evolution with deformation.

Importance of amorphous-to-crystalline transitions for ionic transport and oxygen generation in anodic films

Abstract Barrier-type anodic oxide films, with relatively uniform distributions of Al3+ and Zr4+ ions, have been formed on sputter-deposited, non-equilibrium Zr—Al alloys, containing 5, 15 and 43at.%Al, in 0.01 M ammonium pentaborate electrolyte at 293 K. The films formed on the last two alloys are primarily amorphous, with transport numbers of cations of about 0.18 and 0.25 respectively, i.e., increasing with increase in aluminium content. Thus, as for other amorphous anodic oxides, both cation and anion transport contribute significantly to film growth. However, nanocrystals, suggested to be based on cubic ZrO2, are formed near the alloy-film interface in the amorphous oxide matrix. in association with bubbles due to generation of oxygen gas in the vicinity of the alloy—film interface. Increase in the zirconium content to 95at.% leads to the formation of a relatively uniform, crystalline anodic film with a monoclinic ZrO2 structure; film growth now proceeds predominantly due to migration of anions, similar to films formed on high purity zirconium

Crystal structure of a hyperzirconium analogue of eudialyte

X-ray diffraction study of a new representative of the eudialyte family (R = 4.5%, 2347 independent reflections) provided the establishment of a number of characteristic features of its structure associated with a high zirconium content and some other characteristics of the composition. The deficiency of Ca is compensated with Mn, Fe, rare-earth elements, Sr, and Na. The excessive Zr atoms are located in octahedra participating in the formation of a new type of a TiZr3 cluster.

1096.ジルコニウム合金の均一腐食および水素吸収に及ぼす析出物の電気化学的役割,(II)

Substantial roles of precipitates such as Zr-Fe-Cr type intermetallic compounds on uniform corrosion and hydrogen pickup of zirconium alloys in pure water autoclave tests were investigated from an electrochemical point of view. In the previous paper, corrosion mechanism was elucidated by the anodic protection-precipitates degradation model. This paper describes the roles on hydrogen pickup. 633 K pure water autoclave test was performed on high purity zirconium, Zr-0.2Fe, Zr-0.2Cr, and Zr-0.1Fe-0.1 Cr alloys. Hydrogen analysis after the corrosion test showed that hydrogen pickup ratio of Zr-0.2Fe alloy was about 80%. It was much higher than about 30% of pure Zr and about 10% of both Zr-0.2Cr and Zr-0.1Fe-0.1Cr alloys. Larger hydrogen content was introduced into Zr-0.2Fe alloy than the other ones by the cathodic hydrogen charging under coulomic equivalence. The precipitates at metal-oxide interface could act not only as cathodic sites in the anodic protection mechanism but also 'windows' for hydrogen ingress.

Transmission Electron Microscopy of Corrosion of Stainless Steel-Zirconium Metal Waste Forms

Abstract Stainless steel-zirconium (SS-Zr) alloys have been developed as waste forms to immobilize and retain fission products generated during the electrometallurgical treatment of spent nuclear fuel. The baseline waste form is a stainless steel-15 wt.% zirconium (SS-15Zr) alloy, which is prepared by melting appropriate amount of Type 316 stainless steel (SS316) and high purity zirconium. As zirconium has very low solubility in iron, the addition of zirconium to SS316 results in the formation of ZrFe2 -type Laves intermetallic phases. The corrosion behavior of stainless steel has been widely studied; however, the corrosion behavior of the Zr-based-intermetallic has not been previously investigated. In this paper, we present a microstructural characterization of the corrosion layer formed on the Zr-intermetallic phase using energy-filtering transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDS). Specimens of SS-15Zr alloy, crushed to 75 to 150 μm sizes, were immersed in 90°C deionized water for a period of two years.

Identification and Stability of the Nitrogenous Species in Zirconium Phosphate Oxynitride Catalysts

A new family of basic phosphate oxynitride catalysts, ZrPON, has been synthesized by nitridation of high specific surface area zirconium phosphate precursor under ammonia flow. The identification study of the different nitrogenous species has been realized by the combination of XPS and DRIFTS analysis. The presence of NH4+, NH3, −NH2 and −NH− groups has been evidenced on the solid surface while nitride N3- anions replaced bulk oxygen O2- species. The evolution of the concentration of the various species allows us to propose a mechanism for the nitridation of the precursor powder. The thermal stability of the ZrPON oxynitrides has also been studied by TPD−MS and DRIFTS. Nitrogen is removed from the ZrPON powder by a three-step desorption process depending on the temperature range considered. At low temperature (<200 °C), weakly physisorbed species are desorbed from the surface. In the 200−400 °C range, ammonia adsorbed on the Lewis acid sites is removed, and at higher temperature, terminal amino groups are attacked by gaseous water coming from hydroxyls condensation which results in the appearance of new hydroxyls bonded to phosphorus atoms.

Determination of Rare Earth Impurities in High Purity Zirconium Dioxide by Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spectrometry Using 1-Phenyl-3-Methyl-4-Benzoyl-5-Pyrazone as Extractant and Chemical Modifier

ABSTRACT A novel method has been developed for the determination of trace La, Eu and Y in high purity ZrO2 by electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazone (PMBP) as extractant and chemical modifier. The matrix was quantitatively separated from the selected elements in 6M HNO3 medium by extraction with 0.1M PMBP in chloroform. The vaporization behaviors, effect factors and analytical characteristics of above selected elements were investigated in detail. Under the optimized conditions, the detection limits were 8.0, 0.9 and 1.0ng ml−1 for La, Eu and Y with the relative standard deviations of 3.3, 3.4 and 4.0% (n=7, c=0.5 μg ml−1), respectively. The proposed method has been applied to determine trace impurities in ZrO2.

Influence of the nitridation parameters on the stoichiometry, structure and specific surface area of zirconium phosphate oxynitride catalysts

Oxygen can be exchanged by nitrogen atom in high surface specific and amorphous zirconium phosphate solids thank to nitridation process. Various nitridation parameters influence the O/N substitution. A minimum temperature of 550°C is required for efficient nitridation whereas temperature higher than 850 and 1300°C induces reduction of phosphorus and zirconium atoms respectively. In intermediate temperature range, O/N exchange increases with temperature as well as with time of nitridation. In these conditions, the ZrPON solids obtained are X-ray amorphous and a slight decrease of precursor specific surface area is observed (110–210 m2 g-1).

Hybrid polydimethylsiloxane-zirconium oxo nanocomposites. Part 1 Characterization of the matrix and the siloxane-zirconium oxo interface

Hybrid materials made from polydimethylsiloxane and zirconium oxo species have been synthesized. They exhibit a high degree of homogeneity and dispersion for Zr/Si molar ratios ranging between 0.2 and 0.9. These hybrid materials show good mechanical integrity and transparency. They have been characterized by 29 Si, 17 O and 13 C MAS-NMR as well as FTIR, SAXS and dynamic mechanical analysis (DMA). These polydimethylsiloxane/zirconium oxopolymers are hybrids which consist of amorphous zirconium oxo domains of about one to two nanometers in diameter. The mean corrrelation distance between the zirconium–oxo domains decreases from about 6 to 2 nm when the Zr/Si ratio increases. The siloxane species (chains and loops) have an average chain length that decreases from approximatively 15-20 silicon atoms to 3 silicon atoms with increasing zirconium content. The interface between siloxane and zirconium oxo domains is composed primarily of Zr-O-Si(CH 3 ) 2 bonds and hydrogen bonds, their relative proportion being a function of the zirconium content. The curing of these hybrid materials at 140°C completes consolidation of the hybrid network, without affecting the overall characteristics of the organic-inorganic interface. Curing at 200°C induces the loss of small silicic species and the increase of cross-linking points in the siloxane regions. For samples with a high zirconium content (Zr/Si=0.9) curing at 200°C also induces an increase in the number of the Zr-O-Si interface bonds.

The kinetics of solid nucleation in zirconium

The framework of classical nucleation theory coupled with statistical analysis was used to evaluate nucleation data from zirconium undercooling experiments. Bulk samples of high purity zirconium were processed in a containerless, high vacuum environment using electrostatic levitation at Space Systems/Loral in order to obtain sets of nucleation temperature data. The relationships between undercooling and initial material purity have been investigated. The nucleation rate equation parameters, preexponential factor and work of cluster formation, were determined using a statistical analysis technique. The mean undercooling values ranged from 326 to 348 K for material purities between 99.8 and 99.995%, respectively. The range of values for the preexponential factors, 10 32–10 43, and the activation energies, 64–88 kT, for the classical nucleation rate equation also scaled with the purity levels.

A Study of the Structure of Vanadium Oxide Dispersed on Zirconia

Raman and UV−vis diffuse reflectance spectroscopy were used to characterize the structure of vanadia dispersed on high surface area zirconium oxide. Two-dimensional vanadia species with tetrahedral coordination appear on the surface of the ZrO2 and expand in size with increasing V loading. Crystalline V2O5 appears when the vanadia loading exceeds an apparent surface density of 7.0 V atoms/nm2, and ZrV2O7 is formed as a consequence of zirconia migration into the V2O5 crystallites. A model for the structure of two-dimensional vanadia overlayer is proposed based on the experimental data and information taken from the literature. Vanadia is found to absorb the light scattered by the support, and this gives rise to a reduction in the intensity of the Raman bands for zirconia as the surface loading of vanadia increases. Partial reduction of the dispersed vanadia increases the absorbance of the vanadia and alters the profile of absorbance versus frequency in such a manner as to increase the intensity of the Raman bands for zirconia relative to those for vanadia. Examination of Raman spectra taken after repeated reduction−oxidation cycles suggests that reduction occurs via removal of oxygen from the vanadia monolayer without agglomeration or reorganization of the surface species.

Local damage of HT-materials by laser irradiation in the SEM

By using a pulsed Nd:YAG laser the high temperature materials zirconium oxide, fine grain graphite and silicon nitride were rapidly irradiated (heating thermal shock) and their damage behavior was investigated. The laser beam parameters at sample surface were detected by a laser beam analyzing system and correlated with the local damage mechanisms of the materials as erosion, crack formation and solid-solid phase transformation. For the investigations image analysis, localized x-ray analysis, and the ion beam slope cutting technique were applied. The temperature field in the material was simulated by using temperature dependent material parameters for different laser beam parameters. The results illustrate both the strong influence of the temporal and spatial laser energy profile and the materials properties to the material damage.

Spectral Broadening of the 3463 å Line in a Zirconium Plasma Generated by Laser Irradiation

In a vacuum chamber a plasma is produced by shining a pulsed Nitrogen laser, 20 mJ and 20 ns (Nordstrom, 1995), focused in an area of 0.1 mm2 over a high purity polycrystalline Zirconium surface. This is accomplished by an optical system coupled to a monochromator, with a 0.1 A resolution power, by detecting the visible and ultraviolet radiation for Zr I and Zr II. For the transition a2 H4.5 → y2 G3.50, measurements are performed at different distances with respect to the impact area, to determine the Doppler and Stark effects dependence on the laser fluency (J/cm2). The Zr II ions velocity is determined in order to estimate the Doppler broadening effect in the fitting of the Voigt profile for the spectral line studied. These measurements are performed in a shoot to shoot way.

Raman spectroscopy investigation of the phase transition sequence in lanthanum-modified high zirconium -content lead zirconate titanate ceramics

Abstract The phase-transition sequence in lanthanum-modified lead zirconate titanate ceramics with between 0 and 4 at.% lanthanum and a Zr/Ti ratio of 92/8, (PLZT 100×/92/8), has been investigated using Raman spectroscopy and dielectric measurements. An antiferroelectric (AFE)-two ferroelectric (FR(LT)) and (FR(HT)) and paraelectric (Pc) phase sequence was confirmed for x 1%, the coexistence of antiferroelectric (AFE) and ferroelectric (FR(HT)) phases has been observed in the Raman spectra of these ceramics near 200 K.

ChemInform Abstract: Preparation and Characterization of Mesoporous, High Surface Area Zirconium(IV) Oxides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.