Solution Of Zr Research Articles

Magnetic properties of melt-quenched Ni-rich amorphous and bcc Zr–Ni alloys (abstract)

It has been demonstrated recently that the structure of melt-quenched Zr–Ni ribbons in the vicinity of 90 at. % Ni was strongly dependent on the quenching rate: at the highest quenching rate, the alloys Zr10Ni90 and Zr9Ni91 could be prepared with an amorphous structure whereas at lower quenching rates the Zr9Ni91 alloy was prepared as a solid solution of Zr in Ni with a body-centered cubic (bcc) structure. In a preliminary measurement we have established a Curie point (Tc) of 66 K for the a-Zr9Ni91 ribbon which was much smaller than the value Tc=235 K reported for an a-Zr10Ni90 ribbon. This discrepancy has motivated us to perform the present detailed magnetization study in the temperature range 5 to 300 K. It was also of interest to compare the Curie point of the amorphous and bcc phase with the same chemical composition. The real component χ′ of the AC susceptibility as well as the magnetization isotherms up to H=18.5 kOe have been investigated. The measurements of χ′ yielded T=41, 66, and 70 K for a-Zr10Ni90, a-Zr9Ni91, and bcc-Zr9Ni91 ribbons, respectively. The para-ferromagnetic transitions were found to be fairly sharp although in some of these samples several transitions differing by a few degrees only could be observed. In some of the samples, however, very faint magnetic transitions indicated by a small broad peak could also be detected around 250 K. This feature can be attributed to some residual phases of either an unknown Zr–Ni intermetallic compound or of Ni(Zr) solid solution precipitates. The close coincidence of this peak with the Curie temperature reported by Kaul suggests that his value (Tc=235 K) cannot be representative of the amorphous Zr–Ni matrix but it rather may originate from ferromagnetic precipitates. The magnetization isotherms for the amorphous and bcc-Zr9Ni91 alloy indicated the development of a significant magnetization around the Tc values deduced from χ′. The saturation magnetization at the lowest temperature amounted to about 7 emu/g in both structural modifications. This value is reasonable in view of the reduction of Tc with respect to pure fcc-Ni. The present Tc data indicate that the critical concentration for the onset of magnetic ordering in the Zr–Ni system should be slightly below 90 at. % Ni. It can be concluded from this study that the magnetic behavior of Zr–Ni alloys at about 90 at. % Ni content is characteristic for very weak itinerant ferromagnets and the results will be analyzed in this framework with the help of Arrott plots.

Metal-organic deposition of thin-film yttria-stabilized zirconia-titania

Mixed-conducting yttria-stabilized zirconia-titania (YZTi) has attractive applications in solid oxide fuel cells (SOFC's) and electrocatalysis, particularly when used as a thin film to reduce its electrical resistance. Thin films of yttria (12 mol %) stabilized zirconia-titania (8 mol %) have been prepared using metal-organic deposition (MOD) whereby metal-organic solutions of Zr-, Y-, and Ti-2-ethylhexanoates are spun onto suitable substrates. Variables affecting the film surface-morphology, chemistry, and crystal structure are examined using scanning electron microscopy (SEM), auger electron spectroscopy (AES), and x-ray diffraction (XRD), respectively. Uniform, pore-free films having a low carbon content (<1 at. %) are made by sintering on a hot plate at 530 °C. The effect of thermal cycling on the chemical compatibility and adherence is examined for YZTi films on yttria-stabilized zirconia substrates.

Thermal treatment of binary carbonaceous/ zirconia gels and formation of Zr(C,O,N) solid solutions

Binary organic—inorganic gels, in which a carbonaceous gel obtained from a coal tar pitch and a zirconia gel are combined, were prepared as precursors for carbothermal reduction with and without simultaneous nitridation to form Zr(C,O,N) solid solutions. Zirconium(IV) propoxide as the starting material for zirconia was hydrolyzed in the presence of acetylacetone in order to avoid undesirable precipitation. After pyrolysis at 800 °C, a precursor consisting of reactive carbon and nanometersized ZrO 2 was obtained. Its behavior on heat treatment was investigated by TG, X-ray analysis, and nitrogen adsorption. Microporosity was generated by crystallization of the zirconia constituent in the temperature range 800–1100 °C. The carbothermal conversion into Zr (C,O,N) begins under nitrogen at about 1100 °C and under argon at about 1200 °C; mesoporosity is additionally formed in both cases. The final products at 1500 or 1600 °C—solid solutions of cubic Zr(C,O) or Zr(C,O,N)—are assemblages of fine crystallites with grain sizes of l μm and less. The formation of these sub-micrometer crystallites may be explained by the high homogeneity and reactivity of the gel-derived carbon reactant. Nitrogen adsorption is shown to be a useful technique to follow the reduction reactions in gel precursors.

Synthesis of ZrF4BaF2LnF3 glasses (Ln = La, Ce, Pr, Nd or Eu) by combined processes of sol-gel and fluorination

Amorphous 60ZrO2·30BaO·10LnO1.5 gels (Ln = La, Ce, Pr, Nd or Eu) were prepared by sol-gel reactions from alkoxide solutions of Zr, Ba and Ln. The dried gels were fluorinated by Nf3. The combined processes of sol-gel and fluorination gave 60ZrF4·30BaF2·10LnF3 glasses. In the fluorination process the rates of reaction were substantially different with the Ln species, becoming slower in the order La, Ce, Pr, Nd and Eu. The IR absorption, Eu3+ emission and Eu3+ Mössbauer spectra of the obtained 60ZrF4·30BaF2·10EuF3 glass were almost the same as those of a 60ZrF4·30BaF2·10EuF3 glass prepared by a conventional melting method. Thermal characteristics of the 60ZrF4·30BaF2·10LnF3 glasses were also examined.

Untersuchungen der Hydroxylammonium-Fluorozirconate(IV)

Hydroxylammonium fluorozirconates have been investigated. Two new microcristalline phases have been isolated from aqueous solutions: (NH3OH)2ZrF6 (1) and (NH3OH)3ZrF7 (2). The crystals were prepared by slow evaporation of the solution of NH2OH, Zr, and HF. Different compositions of the crystals were achieved by varying the molar ratios of the components. They were characterized by thermal analysis, vibrational spectroscopy, and structure (single crystal x-ray methods). (NH3OH)2ZrF6 (1) crystallizes triclinic, P\(\overline 1 \) (No.: 2),a=7.400(2),b=7.609(2),c=7.887(2) A, α=57.29(3)°, β=62.16(3)°, γ=67.83(2)°. (NH3OH)3ZrF7 (2) crystallizes triclinic, P\(\overline 1 \) (No.: 2),a=7.128(1),b=7.989(1),c=8.888(1) A, α=109.72(1)°, β=91.01(1)°, γ=104.27(1)°.

Formation Mechanism of Fine Anisotropically-Shaped m-ZrO<sub>2</sub> Crystals in Thermal Hydrolysis of Sulfate Solution

A solution of dilute zirconium oxide sulfate was hydrothermally treated at 240°C for different times. Metastable pseudo-zirconium oxide sulfate (PZOS) was formed at first with a decrease in SO42- ion concentration and then monoclinic ZrO2 was formed with an increase in SO42- ion concentration as a result of dissolution of PZOS. Monoclinic ZrO2 particles had crystals with elongated c-axis: flaky single crystals and bundles of (100) twin crystals. It seemed that the formation of two crystal types depends on the difference of crystal nuclei formed by dissolution of PZOS. Monoclinic ZrO2 particles formed from solutions of low Zr and high H2SO4 at ZS(0.01/0.3), which indicates the mixed solution of 0.01mol/l zirconyl carbonate and 0.3mol/l H2SO4, and ZS(0.01/0.4) were like chestnut buries. It was thought that the morphology change of monoclinic ZrO2 formed hydrothermally was caused by formation and dissolution of metastable PZOS and ZOS, the type of Zr-O solute species, and nucleation and growth of monoclinic ZrO2, which were affected by the concentration of sulfuric acid in the solution.

Structural role of zirconium in SiO2–ZrO2gels: evidence from17O NMR

17 O MAS NMR has been applied to SiO2–ZrO2 mixed alkoxide derived gels. It demonstrates unambiguously that Zr–O–Si bonds are formed during gelling and that there is almost complete solid solution of Zr into the SiO2 network. Preliminary results on a ternary SiO2–TiO2–ZrO2 gel clearly indicate that Ti and Zr have different chemical behaviour in these systems.

Metastable Phase Selection and Partitioning for Zr(1−x)AlxO(2−x/2) Materials Synthesized with Liquid Precursors

Aqueous solutions of zirconium acetate and aluminum nitrate were spray pyrolyzed at 250°C and upquenched to different temperatures to yield metastable solid solutions of composition Zr(1−x)AlxO(2−x/2). An amorphous oxide forms first during pyrolysis which subsequently crystallizes as a single phase for x ≤ 0.57 (≤40 mol% Al2O3). The crystallization temperature increased with Al2O3 content. Electron diffraction, supported by Raman spectroscopy, indicates that the initial phase is tetragonal. At higher temperatures, the initial solid solation partitions to other metastable phases, viz., t‐ZrO2+γ‐Al2O3, prior to achieving their equilibrium phase assemblage, m‐ZrO2+α‐Al2O3. Partitioning yields a nanocomposite microstructure with grain sizes of 20–100 nm, compared to the 3 to 5 nm in the initial, single phase. Compositions containing 45 to 50 mol% Al2O3 concurrently crystallize and partition. The structure selected during crystallization and the partitioning phenomena are discussed in terms of diffusional constraints during crystallization, which are conceptually similar to those operating during rapid solidification.

Texture Variations in Sol-Gel Derived PZT Films on Substrates with Platinum Metallization

ABSTRACTMetalorganic precursor solutions of composition Zr : Ti = 0.53 : 0.47 were used to spin-cast PZT layers on sputtered Pt films. After annealing at temperatures of 550 °C - 800 °C, the PZT films of tetragonal perovskite structure reproducibly showed different textures and surface morphologies, depending on whether or not a Ti layer was used as an adhesion layer for the Pt film. The texture differences were found to be independent of annealing treatment. It is argued that the observed texture differences are caused by a change in Pt-PZT interface composition, resulting from the diffusion of Ti into the Pt film during annealing; X-ray diffraction of an annealed Pt/Ti/SiO2/Si film combination provided evidence for a compound Pt3Ti. Annealing at 850 °C caused severe diffusion of Ti from the metal layer into the PZT film, leading to a tetragonal PZT layer with lattice constants corresponding to a Zr : Ti ratio of 30 : 70.

Structure and strength of cast alloys of the system aluminum-nickel-zirconium

1. With concentrations 6\2-6.5% of Ni and up to 0.7\2-0.9% Zr in Al\t-Ni\t-Zr-alloys with real solidification rates it is possible to obtain a structure consisting of primary dendrites of \ga-Al (supersaturated solution of Zr in Al) and eutectic \ga-Al +NiAl3. 2. During decomposition of supersaturated solid solution there is strengthening of Al\t-Ni\t-Zr-alloys due to secondary precipitates of ZrAl3 phase. The greatest increase in hardness is achieved with a zirconium content of about 0.8% after aging at 400°C. 3. The fine structure of eutectic \ga-Al+NiAl3 promotes an increase in strength with retention of quite a high level of ductility for Al\t-Ni\t-Zr-alloys. Presence in the structure of eutectic provides good casting properties for alloys and a high solidus temperature. This makes it possible to develop on the basis of the composition Al\t-6% Ni\t-0.8% Zr new heat-resistant cast alloys capable of competing with granulated aluminum alloys of the system Al\t-Cr\t-Zr.

Microstructural analysis of LWR spent fuels at high burnup

The microstructural changes in commercial light-water reactor (LWR) fuels irradiated to average burnups near 50 MWd/kgM were studied by analytical transmission electron microscopy and Auger electron spectrometry. Several poorly understood aspects of the fuel behavior were examined, including (a) precipitation of the fission gases in dense, highly pressurized inclusions, (b) apparent solution of Cs, Ba, Zr, and Te in the UO 2 matrix, and (c) the “rim effect” involving restructuring of the enhanced burnup region at the fuel outer edges. Initial observations of the high-burnup rim showed an extremely fine-grained structure formed by recrystallization of the original UO 2. The restructuring is a burnup-induced instability of the UO 2, possibly driven by the stored energy of fission products in solution, and is expected to extend across LWR fuel pellets irradiated to higher burnups.

Preparation of Lead Zirconate Titanate Thin Film by Hydrothermal Method

A hydrothermal method for preparing thin films of crystalline PZT was developed by controlling the rates of nucleation and crystal growth. This method consisted of two steps of hydrothermal reaction. The first step (nucleation process) was that in which the TiO2 substrate reacted with the mixed solution of Pb and Zr to form PZT and/or PZ nuclei on the surface. Subsequently, the crystal growth of PZT was promoted as the next hydrothermal step (crystal growth process) by the reaction of the mixed solution of Pb, Zr and Ti. From the experimental results of PZT powder preparation, the conditions of the nucleation and crystal growth process were determined as at 150°C for 24 h and at 120°C for 48 h, respectively. It was verified that the thin films consisted of PZT polycrystals and showed ferroelectric properties.

Anomalous temperature dependence of the yield strength in IVa-VIII intermetallic compounds with B2 structure

The mechanical properties of the binary compound CoHf, and the pseudo-binary compounds CoTi-CoZr and CoTi-NiTi with B2 structure were measured as functions of testing temperature, composition and strain rate. In all of investigated compounds, the anomalous (positive) temperature dependence of the yield strength was observed at intermediate temperatures. The yield strength of CoHf compounds was dependent on composition through the contained second phase particles. Thepseudo-binary compounds CoTi-CoZr were strengthened by a mutual solid solution of Ti and Zr, due to the atomic size difference between two atoms. Thepseudo-binary compounds CoTi-NiTi were, by a mutual solid solution of Co and Ni, strengthened at low temperatures but softened at intermediate and high temperatures. A positive strain rate dependence of the yield strength was clearly found at high temperatures in CoHf compounds. Very high strain-hardening rates were observed at intermediate temperatures, usually accompanied by serrations on the stress-strain curves. Based on these results, it was proposed that the intermetallic compounds with B2 structure consisting of IVa and VIII transition metals universally exhibit the anomalous temperature dependence of the strength and therefore involve the similar deformation mechanism. Also, a possible deformation mechanism was considered in each temperature region.

Calcination characteristics of spray-dried PZT and related powders

Solid state reaction characteristics of powders prepared by spray drying the individual as well as mixed nitrate solutions of Pb, Zr and Ti have been studied using DTA-TGA and XRD techniques. It has been observed that the powder obtained by spray drying the composite nitrate solutions of Pb, Zr and Ti is a mixture of Pb(No 3 ) 2 , ZrO(NO 3 ) 2 and Ti(OH) 4 . Decomposition of Pb(NO 3 ) 2 into PbO is a two step process and an exothermic peak in the DTA curve has been observed for the conversion of Ti(OH) 4 to TiO 2 . Formation of PbTiO 3 takes place at a considerably lower temperature of 430 °C and interdiffusion of PbO, ZrO 2 and PbTiO 3 phases results in the formation of PZT solid solution.

Acylation of pyridine rings mediated by Group 4 metal aryl oxide compounds: high yield formation of .alpha.,.alpha.'-disubstituted-2,6-pyridinedimethoxide ligands

The room-temperature carbonylation of solutions of the dialkyl compounds Zr(OAr') 2 (R) 2 OAr')=2,6-di-tert-butylphenoxide; R=CH 3 , CH 2 Ph) in the presence of a suitable pyridine leads to the formation of a series of α,α'-disubstituted-2,6-pyridinedimethoxide compounds (Ar'O) 2 Zr[OCH(R)-pyr-CH(R)O] [R=CH 3 , CH 2 Ph; pyr=NC 5 H 3 , NC 5 H 2 -4-Ph; NC 5 H 2 -4-Me]. Spectroscopic studies, 1 H and 13 C NMR

Early stage of Al3Zr precipitation in a rapidly solidified Al-Cr-Zr alloy

Abstract Early stages of A13Zr precipitation have been studied in detail in the ternary Al-2.4 at.% Cr-1.1 at.% Zr alloy. A supersaturated solid solution of Zr in the asrapidly solidified state decomposes during subsequent heat treatment at 400°C. This decomposition leads to a homogeneous precipitation of very small Al3Zr (LI2) particles in the grain interior, but this homogeneous precipitation is not stable in the vicinity of mobile grain boundaries and is progressively consumed, giving rise to a fan-shaped precipitation of Al3Zr (Ll2), often coexisting with very small interlamellar particles of Al3Zr (LI2). All these precipitation modes are analysed in the light of the current theory of discontinuous reactions.

ChemInform Abstract: Crystal Structure of the Basic Zirconium Sulfate Zr(OH)2SO4.

AbstractThe title compound is obtained from an aqueous solution of Zr(SO4)2·4 H2O (autoclave, 240‐550 °C, 1 week).

ChemInform Abstract: Transition Metal Peroxofluoro Complexes. Part 6. Preparation, Vibrational Spectra, and Crystal Structure of (NH4)3Zr(O2)F5.

AbstractSingle crystals of the title compound are grown from an aqueous solution of Zr", H2O2, HF, and NH; at pH 6. The disordered crystal structure is determined (Fmäm, Z=4).

希薄Cu-Zr合金の内部酸化により形成されるジルコニア相とその析出形態

Dilute Cu-Zr alloys containing 0.39-1.95 mass%Zr were internally oxidized in the temperature range of 973-1323 K. The phases of dispersed oxides were identified by X-ray diffractometry, and the mean oxide particle sizes were measured by transmission electron microscopy. From X-ray diffractometry of the nitric-acid-treated insoluble residues, the oxide phases precipitated by internal oxidation were monoclinic and tetragonal ZrO2. The amount ratio of monoclinic ZrO2 to the total oxide was increased with the concentration of Zr at a constant internal oxidation temperature. In the case of alloys having the same concentration of Zr, the amount of monoclinic ZrO2 presented the minimum values at about 1223-1243 K. By transmission electron microscopy, it was revealed that large monoclinic ZrO2 particles were precipitated at grain boundaries of Cu and fine monoclinic and tetragonal ZrO2 particles were precipitated inside the Cu grains. The mean particle size of fine precipitates in Cu grains was increased with the distance from the surface. Any difference in the mean particle size of fine ZrO2 inside the Cu grains was not observed among the alloys having different concentrations of Zr, owing to the limitation of solution of Zr into Cu.

Glass preparation of the ZrO 2SiO 2 system by the sol-gel process from metal alkoxides

Glasses in the ZrO 2SiO 2 system containing up to 50 mol.% ZrO 2 were prepared by heating the gels made from the mixed solutions of Zr(OC 3H 7) 4 and partially prehydrolyzed Si(OC 2H 5) 4. The anionic network structure similar to that of glass was already formed in the gels. And it was observed that the properties of the gels were determined by the porosity in the gel rather than the gel constituting structure. Porous gels converted into the non-porous impervious glasses through three major reactions with increasing temperature: the removal of the adsorbed water, dehydration-condensation and sintering. Density, refractive index and hardness of the non-porous glasses increased with the increase of ZrO 2 content. Infrared spectra and molar refractivity showed that the Zr 4+ ion was incorporated in the interstices of the silica network structure.