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Phenylene-salalens-sequential tetradentate dianionic {ONNO}-type ligands that include an ortho-phenylene group bridging between an imine and amine internal donors bound to phenol arms with a broad variety of substitution patterns are described. Zirconium and hafnium complexes of the type [{ONNO}M(O-tBu) 2 ] were formed as single diastereomers, which, according to crystallographic structures, featured the fac(around the amine)-mer(around the imine) wrapping mode. The reactivity and stereoselectivity in rac-lactide (rac-LA) polymerizations were found to depend on the substitution pattern: complexes featuring small groups on the imine-side phenol and bulky groups on the amine-side phenol exhibited the favorable combination of high activity and high isoselectivity (P m ≤0.91). Isotactic stereoblock copolymers of high molecular weights were prepared. The polymers crystallized in the stereocomplex phase according to thermal (differential scanning calorimetry) and crystallographic analysis., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Zirconium and hafnium have opposite nuclear properties and are used very differently in the nuclear industry. However, hafnium is a common metal impurity in zirconium, and the chemical properties of the two are very similar except for nuclear properties, and it is difficult to separate and detect them. At present, the detection of hafnium content in zirconium is usually achieved by using an inductively coupled plasma (ICP) spectrometer, but ICP equipment is expensive, and the detection cost is high. Therefore, it is necessary to develop a simple and low-cost method for the determination of hafnium content in zirconium. Based on this, this paper takes the spectrophotometric method as a starting point. Through a series of experiments on the influence of pH and concentrations of the color-developing agent xylenol orange sodium salt on the absorbance of zirconium and hafnium ions, the appropriate variables are selected to detect the content of hafnium in zirconium. Finally, according to the measured absorbance and total ion concentration, by comparing the working curve of zirconium and hafnium ions, the content of hafnium in zirconium is calculated based on the lever principle. [ABSTRACT FROM AUTHOR]

A simple method was developed for the determination of REEs, Zr, Hf, Th and U in ultramafic rocks by inductively coupled plasma‐mass spectrometry with a combination of RE and UTEVA extraction resins for their separation and pre‐concentration. Ultramafic rocks were digested with HNO3‐HF‐HClO4 and finally turned into 11 mol l−1 HCl solutions together with H3BO3 to remove insoluble fluorides. The removal of matrix elements was achieved during the loading procedure. Following this, REEs on RE resin, and Zr, Hf, Th and U on UTEVA resin were eluted with 10 ml of 0.24 mol l−1 HCl, with recoveries better than 94.4%. This method was validated using reference materials JP‐1, DTS‐2B, OKUM, UB‐N, MUH‐1 and DZΣ‐2, and the measurement results for target analytes were comparable to literature values, indicating its applicability to the determination of REEs, Zr, Hf, Th and U at ultra‐trace level in ultramafic rocks. [ABSTRACT FROM AUTHOR]

The effect of doping with scandium, zirconium, and hafnium on the thermal stability of high-strength wrought Al-Zn-Mg-Cu (of 7XXX series) alloys at 80°С for 100 hours is investigated. The study is performed on rods produced by a two-stage hot extrusion of 1500 g ingots. As shown, the doping with scandium and zirconium has improved the hardness and strength characteristics due to the occurrence of two ensembles of dispersed precipitates: intermetallics η′-phase (MgZn2) and Al3(Sc1-xZrx) particles coherently bonded with the aluminium matrix. As proved, in the 7XXX alloy, which is additionally doped with the (Sc + Zr + Hf) complex, the composition of nanosize precipitates based on Al3Sc intermetallic compound includes zirconium and hafnium. The alloying of the base alloy with the complex (Sc + Zr + Hf) stabilizes the structural state of the alloy and, after holding at 80°С, no significant changes in the size and distribution of strengthening particles are observed. This makes it possible to obtain high strength characteristics of Al-Zn-Mg-Cu alloys with a high level of plasticity at long-term holding at 80°С. [ABSTRACT FROM AUTHOR]

We revisited the synthesis of zirconium(IV) and hafnium(IV) alkoxides, namely the metal isopropoxide isopropanol complex (M(OiPr)4·iPrOH, M = Zr, Hf) and the metal sec- and tert-butoxide (M(OsBu)4 and M(OtBu)4, M = Zr, Hf). We optimized the most convenient synthesis methods and compared the products with commercial sources. En route to the metal sec- and tert-butoxides, we synthesized the metal diethylamido complex (M(NEt2)4, M = Zr, Hf). [ABSTRACT FROM AUTHOR]

Nuclear-grade zirconium and hafnium play an essential role in the nuclear industry. It is difficult to separate and purify zirconium and hafnium because of the similar properties caused by lanthanide shrinkage and the preferential extraction of hafnium is challenging. In this work, a new extractant, di(p-tert-butylphenyl)phosphate (DTBPPA), was synthesized, and its separation performance of zirconium and hafnium in the sulfuric acid system was evaluated. Under identical extraction conditions, DTBPPA shows excellent preferential extraction properties for hafnium compared to current commercial extractants, such as D2EHPA and PC88A. The highest SFHf/Zr value is up to 16.3. A crystal of the hafnium extracted species was grown to study the extraction mechanism and the principle of preferential extraction of hafnium. It was found that the crystal growth of zirconium-extracted species was difficult under the same conditions. Hafnium extracted species crystals reveal a six-coordinated hafnium ion bound to six extractant molecules. The electron withdrawing effect of the aromatic substituents results in a low electron density of O atoms in the P–O group of the new extractant, and the extractant coordination group shows the characteristics of a soft base. This matches the soft acid properties of hafnium ions. DTBPPA shows a solid ability to identify hafnium ions, thus achieving preferential separation of hafnium from zirconium and hafnium mixtures. [ABSTRACT FROM AUTHOR]

The extraction of zirconium (Zr) and hafnium (Hf) in methyl isobutyl ketone (MIBK)—thiocyanic acid (HSCN) system has been widely used in the production of nuclear-grade zirconium and hafnium in industry, while the extraction mechanism was not adequately studied. In this study, the extraction and stripping equilibrium of Zr and Hf in the MIBK-HSCN system was studied. The results showed that elevated HCl concentration can increase the distribution ratio of SCN− and decrease that of Zr/Hf in organic phase. In the stripping process, HCl concentration and the Organic/Aqueous (O/A) phase ratio played important roles. The mechanism of the extraction reaction was discussed by considering the stoichiometric relationship of possible reaction equations and corresponding equilibrium constants. The results indicated that SCN− could be extracted into MIBK as HSCN·MIBK. Meanwhile, SCN− could also be extracted into MIBK by complexing with metal (Zr or Hf). The molar ratios of MIBK to the complexes of Zr and Hf have been found to be 5.34 and 5.03, respectively. With the increase in the initial concentration of HCl in the aqueous phase, the complexation molar ratios of SCN− to Zr and Hf increased first and then decreased, and so do the extraction equilibrium constants, which might be due to the extraction competition of HSCN and metal complexes. [ABSTRACT FROM AUTHOR]

The comparative corrosion resistance and electrochemical behavior in acidic, alkaline, and neutral media of both pure metals and the Ni–Re alloys doped with zirconium, hafnium, tungsten, and palladium were investigated. A positive effect of zirconium on the corrosion resistance of the Ni–Re alloy in all studied media was demonstrated. It is shown that the Ni–Re alloy doped with hafnium also improves corrosion resistance and compensates its reduction at introduction to a tungsten alloy. It is shown that the Ni–Re alloy doped with zirconium together with palladium has the maximum corrosion resistance. [ABSTRACT FROM AUTHOR]

The morphology of titanium, zirconium, and hafnium nanofilms deposited onto zirconia after annealing in vacuum at 1400, 1500, and 1600°C was studied. Nanofilms show a tendency to fragmentation; for titanium it begins at 1400°C, for zirconium and hafnium at 1500°C. At further heating, titanium nanofilm coagulates, while zirconium and hafnium nanofilms interact with the oxygen of the substrate. Tendencies for the formation of swellings on films prior to fragmentation and a certain role of grain boundaries in the cases of titanium and hafnium were noted. [ABSTRACT FROM AUTHOR]

Spent nuclear fuel contains heavy element fission products that must be separated for effective reprocessing for a safe and sustainable nuclear fuel cycle. 93Zr and 99Tc are high‐yield fission products that co‐transport in liquid‐liquid extraction processes. Here we seek atomic‐level information of this co‐extraction process, as well as fundamental knowledge about ZrIV (and HfIV) aqueous speciation in the presence of topology‐directing ligands such as pertechnetate (TcO4−) and non‐radioactive surrogate perrhenate (ReO4−). In this context, we show that the flat tetrameric oxyhydroxyl‐cluster [MIV4(OH)8(H2O)16]8+ (and related polymers) is dissociated by perrhenate/pertechnetate to yield isostructural dimers, M2(OH)2(XO4−)6(H2O)6 ⋅ 3H2O (M=Zr/HfIV; X=Re/TcVII), elucidated by single‐crystal X‐ray diffraction. We used these model compounds to understand the pervasive 93Zr‐99Tc coextraction with further speciation studies in water, nitric acid, and tetrabutylphosphate (TBP) ‐kerosene; where the latter two media are relevant to nuclear fuel reprocessing. SAXS (small angle X‐ray scattering), compositional evaluation, and where experimentally feasible, ESI‐MS (electrospray ionization mass spectrometry) showed that perrhenate/pertechnetate influence Zr/HfIV‐speciation in water. In Zr‐XO4 solvent extraction studies to simulate fuel reprocessing, we provide evidence that TcO4− enhances extraction of ZrIV, and compositional analysis of the extracted metal‐complexes (Zr‐ReO4 study) is consistent with the crystallized ZrIV2(OH)2(ReVIIO4−)6(H2O)6⋅dimer. [ABSTRACT FROM AUTHOR]

Zirconium and hafnium behave nearly identically in most geological processes due to their identical nominal ionic charge and similar radius. Some of the most pronounced exceptions from this rule are observed in fluoride-rich aqueous systems, suggesting that aqueous fluoride complexation may be involved in Zr/Hf fractionation. To understand the mechanisms causing this phenomenon, we investigated complexation of Zr4+ and Hf4+ in fluoride-rich (1.0 mol/kg HF) aqueous solutions at 40 MPa and 100–400 °C, using synchrotron X-ray absorption spectroscopy (X-ray absorption near edge structure and extended X-ray absorption fine structure) combined with classical and ab initio molecular dynamics simulations. The dominant experimentally observed complexes are [Zr(F,OH) 4 ·2H 2 O]0 and [Hf(F,OH) 4 ·2H 2 O]0, respectively. The first coordination shell comprises a distorted octahedron, with fluoride and hydroxide ligands at a similar mean radial distance (1.9–2.0 Å) from the central cation, and H 2 O ligands at a slightly greater distance (>2.1 Å). With increasing temperature, the H 2 O ligands move further out, causing first an increasing distortion of the octahedron and subsequently a partial transition to less hydrated complexes as a certain fraction of the H 2 O molecules move to the second shell at > 3 Å. As a consequence, the radial distance of the F- and OH– anions from the central cation, as well as the overall average radial distance of the first shell decreases due to decreased steric repulsion from the H 2 O ligands. Both experiments and simulations agree in that Hf forms slightly shorter bonds to its nearest neighbors than Zr. The results suggest two hypotheses for the mechanism of Zr/Hf fractionation during precipitation of minerals from fluoride-rich hydrothermal solutions: 1) The heavy twin (Hf) prefers the lower coordination (shorter bonds) and is thus less likely to enter into the higher coordination found in the solids. This mechanism would be analogous to equilibrium isotope fractionation. 2) The change of Hf into a higher coordination environment (e.g., from solution to solid) is slower because it forms stronger ligand-bonds than Zr. This would be analogous to reactive kinetic isotope fractionation. In either case mass dependent fractionation qualitatively matches the observations but mass independent effects on bond strength may also be significant. Quantitative investigations of these effects are needed and may also shed light on the currently still somewhat enigmatic fractionation behavior of Zr isotopes. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and reactivity of several group 4 metal complexes featuring a central anionic pyrrole moiety connected via CH2 linkers to two phosphine donors is described. Treatment of [P(NH)P-iPr] with [MCl4(THF)2] (M = Zr, Hf) in the presence of base yields the dimeric complexes [M(PNPiPr)(μ-Cl)(Cl)2]2 featuring two bridging chloride ligands. These complexes react with sodium cyclopentadienyl and SiMe3I to give the mononuclear complexes [M(PNPiPr)(η5-Cp)(Cl)2] and [M(PNPiPr)(I)3], respectively. The latter react with MeMgBr to form the trialkyl complexes [M(PNPiPr)(Me)3]. Upon treatment of [Ti(NMe2)4] with [P(NH)P-iPr] a complex with the general formula [Ti(PNPiPr)(NMe2)3] is obtained. DFT calculations revealed that the most stable species is [Ti(κ1N- PNPiPr)(NMe2)3] featuring a κ1N-bound PNP ligand. When [P(NH)P-iPr] is reacted with [Ti(NMe2)4] in CH2Cl2 complex [Ti(PNPiPr)(Cl)2(NMe2)] is formed. Treatment of a solution of [P(NH)P-iPr] and [Zr(NMe2)4] with SiMe3Br affords the anionic seven-coordinate tetrabromo complex [Zr(PNPiPr)(Br)4][H2NMe2]. The corresponding hafnium complex [Hf(PNPiPr)(Br)4][H2NEt2] is obtained in similar fashion by utilizing [Hf(NEt2)4] as metal precursor. All complexes are characterized by means of NMR spectroscopy. Representative complexes were also characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in metallocene catalysis due to the development of cyclopentadienyl (Cp) ligands by numerous researchers. Furthermore, various ligand combinations have been realized in the last 20 years for the development of post‐metallocene catalysts. Although ligands containing a Cp have been widely reported, only a few reports exist ligands based on other carbon‐only π‐electron moieties. Herein, we focused on the zirconium and hafnium with the 10π‐electron cyclooctatetraenyl (Cot) dianion as an ancillary ligand and investigated the olefin‐polymerization ability of these complexes. Thus, we performed ethylene and ethylene‐1‐octene (co)polymerization using dMAO, MMAO, and Ph3C[B(C6F5)4]/iBu3Al as cocatalysts and confirmed that completion of the polymerization reaction; the catalytic system except dMAO exhibited activities for olefin polymerization to give linear polyethylene or ethylene‐1‐octene copolymer. Furthermore, the zirconium complexes bearing trimethylsilyl‐substituted Cot ligand exhibited enhanced activities for ethylene polymerization compared with an unsubstituted CotZr catalyst. [ABSTRACT FROM AUTHOR]

This article presents the results of a study of the properties of three diffusion-hardening solders based on low-melting gallium alloys and copper-tin alloy powder after the introduction of inert metal powders of titanium, zirconium, and hafnium in an amount of 5% each, which is an additive of 15 wt.%. After heat treatment at low temperatures (125°C) in within 24 hours, and after high-temperature treatment (600°C) for 6 hours, the microhardness of the obtained composite diffusion-hardening solders was evaluated. Relatively long-term heat treatment at low temperatures does not lead the composition to achieve equilibrium states, possible physico-chemical transformations do not fully occur in them, which shows an increase in the hardness of samples after high-temperature treatment. X-ray phase analysis has determined the phases formed as a result of diffusion hardening, forming micro- and nanoscale intermetallic compounds, and the metal tin released in the form of nanoscale secretions in the intergrain space. Metal filler powders, inert at low temperature to exposure, but well wetted with gallium at high temperatures, interact with it, forming nanoscale intermetallic compounds, additionally strengthening composite solders.

Zr/Hf separation has always been a great challenge. Although the methyl isobutyl ketone (MIBK)-thiocyanic acid (HSCN) extraction system selectively extracts Hf over Zr and can realize Zr/Hf separation, it has the following disadvantages: it has a strong smell; it is easy to burn; and there is large loss of extractant during extraction due to the low boiling point (115.7 °C), low flashing point (13 °C), and high solubility of MIBK in water (1.7 % at 25 °C). In this study, Zr/Hf separation performance by MIBK homologues — of which one side of C = O is isopentyl, isohexyl, n-pentyl, n-hexyl or n-heptyl, while the other side are all methyl — were studied and compared with MIBK. Effects of HSCN pre-extraction, HCl concentration, NH4SCN concentration on Zr, Hf extraction and separation performance were investigated. Relationships between methyl alkyl ketone structure and their Zr/Hf separation performance were revealed. A new Zr/Hf separation system MNPK (methyl n-pentyl ketone)-HSCN was found. MNPK has a higher boiling point (151 °C), a higher flashing point (47 °C) and a lower solubility in water (0.43 % at 20 °C) than MIBK. Compared to MIBK, it is safer, more friendly operation environments and less extractant loss during extraction. MNPK has as fast extraction kinetics as MIBK. It also has good anti-emulsification performance. Its maximum βHf/Zr can reach to 12.61. The loaded Zr and Hf in MNPK have very similar stripping behaviors with those loaded in MIBK by HCl and H2SO4 solutions, respectively. MNPK is the most possible candidate to replace MIBK from HSCN media in Zr/Hf separation industry.

In this paper, we examine the purity level and impurity composition of the titanium, zirconium, and hafnium samples at the Exhibition–Collection of Extrapure Substances and present estimates of the average and total concentrations of elemental impurities in the purest samples. We examine the impurity composition of the array of the group 4 elements and contributions of particular groups of impurities and discuss the purity level of the group 4 elements and their compounds manufactured in Russia and abroad. [ABSTRACT FROM AUTHOR]

Ceramics and ceramic matrix composites (CMCs) produced by melt infiltration have emerged as commercially important components in advanced friction (e.g., brake rotors), propulsion (e.g., turbine engine and rocket motor parts), and optical (e.g., mirrors) applications. The use of alloyed silicon infiltrants provides an attractive means to adjust composite composition, structure, and properties via relatively straightforward processing changes. In the present work, the effects of alloying silicon with hafnium or zirconium on the phase evolution in the reactions between C and Si alloys are investigated. A diffusion couple configuration is used to study reactions in Si(l) + C, Si0.90Zr0.10(l) + C, and Si0.90Hf0.10(l) + C systems at 1450 °C. The Si0.90Zr0.10(l) − C system was found to evolve in a similar manner as the Si(l) − C system, forming SiC at the diffusion couple interface. This Zr-containing system was determined to form an additional mixed Zr, Si, C phase that causes a slight decrease in the overall rate of SiC when compared to Si–C system. The Si0.90Hf0.10(l) − C system exhibited behavior distinct from the phase evolution witnessed in the reaction of carbon with pure Si or Zr-containing Si alloys. Initial SiC formation at the interface in the Si0.90Hf0.10(l) − C system is found to enrich the Hf content of the melt enough to promote the formation of a HfC layer at the Si0.90Hf0.10(l) − C interface. This HfC layer then acts as a barrier that hinders further SiC growth, resulting in significantly reduced SiC formation kinetics when compared to the Si(l) − C and Si0.90Zr0.10(l) − C systems. The results of this fundamental study pose clear indications for the generation of SiC-based ceramic composites with refractory-containing Si-based melts. [ABSTRACT FROM AUTHOR]

Ten previously studied garnet pyroxenites and one eclogite from orogenic peridotites in the Western Gneiss Region of Norway were analysed for whole-rock major and trace and mineral trace elements to characterise the evolutionary stages of the East Greenland sub-cratonic mantle. A continuous range of whole-rock MgO contents (17–30 wt.%) correlates inversely with Na 2 O , Al 2 O 3 , and CaO contents. In contrast, rare earth element (REE) compositions allow the samples to be devided into two types. Type I samples have relatively flat primitive mantle (PM) normalised REE patterns (0.4 - 6.8 times PM values) with minor fractionation of middle–heavy REEs. Type II samples are simlar to type I samples but have higher light REE contents (6.1–57 times PM values) that reflect metasomatic enrichment. Whole-rock Zr contents (1– 27 μ g g - 1 ) and Zr/Hf ratios (17–39) are positively correlated. Type I samples have low Zr/Hf ratios that mostly differ from type II samples, indicating that metasomatism modified the initially sub-chondritic Zr/Hf ratios. Garnet Zr–Zr/Hf–Y–Ti systematics suggest that metasomatic enrichment transformed the type I samples into type II samples, consistent with processes observed in other cratonic areas (e.g., the northern East European Platform and the Kaapvaal Craton). The formation of type I pyroxenite in dunite from a melt at ∼ 100 km depth implies the sub-chondritic Zr/Hf ratios were inherited from that melt. Such melts are thought to form by melting of garnet-bearing, melt-depleted mantle, which is consistent with models for recycling of Archaean palaeo-oceanic crust throughout the mantle prior to the formation of the sub-cratonic lithosphere beneath East Greenland. [ABSTRACT FROM AUTHOR]

Tetrakis-(4-tritylphenoxy)phthalocyaninates of tin(IV), zirconium(IV), and hafnium(IV) were synthesize by the reactions of 4-tritylphenoxyphthalonitrile with SnCl2, ZrCl4, and HfCl4 catalyzed by ammonium molybdate in the presence of urea. The structures of the complexes were characterized by spectral methods, including mass spectrometry, 1H NMR, vibrational and electronic spectroscopy. The resulting complexes form J-type dimeric associates in chloroform at concentrations up to ~1.5×10–6 M and lower, are not associated in a mixture of toluene and pyridine up to concentrations of ~3×10–5 M and higher, and show catalytic activity in the electroreduction of molecular oxygen. Zirconium and hafnium complexes showed the greatest activity. Tin and zirconium complexes are thermally stable in an inert atmosphere up to 200°C. [ABSTRACT FROM AUTHOR]

A new Zr/Hf separation system was developed with a novel unsymmetrical dialkylphosphinic acid extractant (n-octyl)(2,4,4'-trimethylpentyl)phosphinic acid (INET-1). It selectively extracts Hf over Zr, and shows much better Zr/Hf separation efficiency than organophosphorous acid Cyanex 272. The Zr and Hf extraction reactions at acidities of < 2 mol/L H2SO4 and > 5.5 mol/L H2SO4 are revealed, respectively. An organic phase with 10 mmol/L INET-1 can load > 290 mg/L of Hf at 1 mol/L H2SO4. Acidic H2SO4 solutions with concentration of 3.0–4.5 mol/L is a good Zr scrubbing agent. [ABSTRACT FROM AUTHOR]

Pd+Zr and Pd+Hf co-doped aluminide coatings were deposited on the nickel superalloy Mar-M247 by palladium electroplating followed by zirconization-aluminization or hafnization-aluminization processes. Both coatings consisted of two zones, the outer and the interdiffusion zone consisting of the β-(Ni,Pd)Al phase. Hafnium and zirconium formed inclusions deposited at the edge of the zones and near the surface (only in the Zr+Pd modified coating). The oxidation resistance of the aluminide coating co-doped with Pd+Zr was significantly better than the one co-doped with Pd+Hf. The hafnium content in the Pd+Hf co-doped coating could exceed the limit.

Nanostructured single-phase hafnium-zirconium carbonitride powders were synthesized using a simple and fast mechanochemical synthesis approach. The critical milling duration, after which a (Hf,Zr)(C,N) solid solution formation inside a jar occurred via mechanically induced self-sustained reaction (MSR), was 10 min. After 30 min of treatment, a solid-gas reaction was completed, and as a result, a homogeneous (Hf,Zr)(C,N) powder consisting of 10–500 nm submicron particles was obtained. The phase and structure evolution of the powders after different treatment durations allowed for the establishment of possible reaction mechanisms, which included the formation of Hf/Zr/C-layered composite particles, their interaction via MSR, and further grinding and nitridization. Spark plasma sintering (SPS) was used to produce bulk hafnium-zirconium carbonitride ceramics from nanostructured powder. The sample had higher values of relative density, hardness, and fracture toughness than those for binary compounds of a similar composition. [ABSTRACT FROM AUTHOR]

The thermal stability of a bimetallic wire made of three novel aluminum alloys Al–0.25 wt % Zr with different Sc and Hf contents has been investigated. A wire made of pure aluminum A99 and Al‒0.25 wt % Zr alloy was studied as an object of comparison. Alloys were obtained by injection molding in vacuum. Cast samples were subjected to severe plastic deformation and annealing, which ensured the formation of a uniform microstructure and the release of stabilizing Al3(Zr,Sc,Hf) nanoparticles. The wire 0.26 mm in diameter was obtained by joint deformation of an aluminum alloy with a copper shell by rolling in rolls. The effect of annealing for 30 min in the temperature range from 200 to 500°C on the parameters of the microstructure and mechanical properties (microhardness, ultimate strength, ductility, specific electrical resistivity) of the wire was studied. The wire has high strength and increased thermal stability. After annealing at a temperature of 500°C, a homogeneous fine-grained structure with a grain size of 3–5 μm was formed in the wire; increased hardness and ultimate strength of the samples was observed owing to the separation of Al3(Zr,Sc,Hf) particles. There is an intense diffusion of copper from the shell into the surface layers of the aluminum alloy, which can lead to embrittlement of the wire. [ABSTRACT FROM AUTHOR]

The extraction of zirconium (Zr) and hafnium (Hf) in methyl isobutyl ketone (MIBK)—thiocyanic acid (HSCN) system has been widely used in the production of nuclear-grade zirconium and hafnium in industry, while the extraction mechanism was not adequately studied. In this study, the extraction and stripping equilibrium of Zr and Hf in the MIBK-HSCN system was studied. The results showed that elevated HCl concentration can increase the distribution ratio of SCN− and decrease that of Zr/Hf in organic phase. In the stripping process, HCl concentration and the Organic/Aqueous (O/A) phase ratio played important roles. The mechanism of the extraction reaction was discussed by considering the stoichiometric relationship of possible reaction equations and corresponding equilibrium constants. The results indicated that SCN− could be extracted into MIBK as HSCN·MIBK. Meanwhile, SCN− could also be extracted into MIBK by complexing with metal (Zr or Hf). The molar ratios of MIBK to the complexes of Zr and Hf have been found to be 5.34 and 5.03, respectively. With the increase in the initial concentration of HCl in the aqueous phase, the complexation molar ratios of SCN− to Zr and Hf increased first and then decreased, and so do the extraction equilibrium constants, which might be due to the extraction competition of HSCN and metal complexes.

[Display omitted] The reactions of the five-membered metallacyclocumulene complexes Cp 2 M[η4ButC 4 But] (M = Zr, Hf) with an equimolar amount of HCl in dioxane at 20 °C result in linear complexes Cp 2 M(Cl)–C(But)=CH–C CBut, whereas the reaction with an excess of HCl affords Cp 2 MCl 2 and trans -ButCH=CH–C CBut. The reaction of the latter hydrocarbon with an equivalent amount of the bis(trimethylsilyl)acetylene complex of zirconocene Cp 2 Zr(Me 3 SiC 2 SiMe 3)(Py) leads to bis(trimethylsilyl)acetylene and a five-membered zircona-cycloallene complex. This complex can also be obtained in 'one-pot' via the reactions of five-membered zircona-cyclocumulene with two equivalents of HCl and subsequent treatment with magnesium in THF. [ABSTRACT FROM AUTHOR]

The article presents the results of obtaining an aluminum electrical wire with a diameter of 0.5 mm from alloys of the Al–Zr-Hf system used in aircraft. Alloys of three compositions were cast in the form of a billet with a diameter of 12 mm using the method of electromagnetic crystallization. Next, the rheological characteristics of billets from experimental alloys were studied. The obtained data were used to simulate the process of combined rolling-extrusion when obtaining a rod with a diameter of 5 mm from a billet with a diameter of 12 mm using the Deform 3D program. A comparison of the experimental forces and forces during the simulation is made for the forces acting on the rolls and the die of the CRE-200 unit. At the next stage, experimental studies were carried out to obtain rods based on simulation data. The obtained rods with a diameter of 5 mm were subjected to drawing or sectional rolling with drawing and intermediate annealing to obtain a wire with a diameter of 0.5 mm. At all stages, the mechanical (ultimate tensile strength, yield strength, elongation to failure and area reduction) and electrophysical properties (electrical resistivity) of the obtained deformed semi-finished products were studied.

The isostructural compounds caesium decasodium tetrazirconium nonaarsenate, CsNa10Zr4(AsO4)9, and caesium decasodium tetrahafnium nonaarsenate, CsNa10Hf4(AsO4)9, arose as unexpected single-crystal products from the reactions of Na2CO3, MO2 (M = Zr, Hf) and As2O5 in a eutectic flux of NaCl and CsCl. They consist of MO6 octahedra and AsO4 tetrahedra sharing vertices to generate three-dimensional polyhedral networks encapsulating the caesium and sodium ions. The MO6 groups share all their vertices with adjacent As atoms but the As atoms have one or two `terminal' O atoms not bonded to Zr or Hf. The Cs+ ion adopts a squashed octahedral geometry and the coordination polyhedra of the partially occupied sodium ions are variously trigonal bipyramidal, tetrahedral, square pyramidal and trigonal pyramidal. Site symmetries: Cs \overline{3}; M 3; As 1 and 2; O 1; Na 1, 2 and 3. The M = Zr crystal was refined as an obverse/reverse rhombohedral twin.

[Display omitted] • A magnetic MOF-derived porous carbon (C(Zn/Co-ZIF)) was successfully prepared. • Porous carbon was first used as an excellent matrix of extraction agents (P507). • C(Zn/Co-ZIF)@P507 showed brilliant performance for the separation of Zr(IV) and Hf(IV). • Abundant Co-N x active sites of C(Zn/Co-ZIF) leaded to strong interaction with P507. • The strong host–guest interaction resulted in the good adsorption and separation performance. Extractant-based solid phase extraction exhibit practical application potential for efficient separation of Zr(IV) and Hf(IV), where the key is to regulate the host–guest interaction between the guest extraction agents and the host matrices to obtain high performance. However, the current research on the host matrices of extraction agents is insufficient. Leveraging the tunability of metal–organic frameworks (MOFs), we successfully prepared a magnetic MOF-derived porous carbon (C(Zn/Co-ZIF)) with a high specific surface area and Co-N x active sites as an excellent matrix. This was achieved by deliberately controlling the pore volume and microenvironment through a mixed precursor strategy and high-temperature pyrolysis method. Furthermore, as an excellent extractant for the separation of Zr(IV) and Hf(IV) in solvent extraction, 2-ethylhexyl phosphonic acid mono-(2-ethylhexyl) ester (P507) was carefully selected to modify C(Zn/Co-ZIF) to obtain C(Zn/Co-ZIF)@P507 by impregnation. Impressively, the maximum adsorption capacities of C(Zn/Co-ZIF)@P507 for Zr(IV) and Hf(IV) were up to be 0.58 and 0.39 mmol/g, respectively, while exhibiting excellent separation coefficient. Further mechanism studies indicated that the combination of high specific surface area and abundant Co-N x active sites of C(Zn/Co-ZIF) leaded to strong interaction with P507, resulting in the excellent adsorption and separation performance of Zr(IV) and Hf(IV) based on the coordination between phosphinic groups of P507 and Zr(IV)/Hf(IV). [ABSTRACT FROM AUTHOR]

An important chemical impurity in the composition of zirconium-based materials for nuclear power engineering is hafnium, the content of which should not exceed 0.05 and 0.01% for Russian and foreign alloy grades, respectively. Since the chemical properties of hafnium are similar to those of zirconium, determination of this element using classical methods of analytical chemistry is a challenging problem. Among the physical methods, the X-ray fluorescence method is the most expressive, which is important under conditions of continuous production. The X-ray fluorescence method for measuring the content of hafnium in zirconium-containing material has been tested by the example of potassium fluorozirconate, a precursor for obtaining alloys. Using various combinations of crystal analyzers, detectors, and collimators of a wave-dispersive spectrometer, the ratios of the intensities of the Hf and Zr analytical lines in the second order of reflection have been refined, and the degree of decrease in the fluorescence intensity of those lines has been determined. The X-ray fluorescence spectra of hafnium lines in potassium fluorozirconate have been studied for the content characteristic of nuclear-pure zirconium. The possibilities of recording the intensity of the Hf analytical lines and methods for eliminating the interference from the Zr lines in the second order of reflection are considered. The metrological characteristics of the determination of Hf using selected analytical lines have been calculated. It is shown that the error is the smallest and the detection limit is the lowest (0.001%) if the HfLβ1 line is used with certain settings of the wave-dispersive spectrometer (the X-ray tube operating mode, a combination of a crystal analyzer, a detector, and a collimator, and the amplitude discriminator settings). The proposed method of hafnium determination is applicable to the materials with a constant content of zirconium. [ABSTRACT FROM AUTHOR]

We performed density functional theory (DFT) calculations on binary and ternary oxo/fluoro crystals of the geochemical twin pair zirconium and hafnium to evaluate and compare their stabilities. This is the first DFT study on bulk ZrF4 or HfF4, as well as on a hypothetical ZrOF2 or HfOF2 bulk crystal. For α-MO2, β-MF4 and MOF2, we have found significantly higher cohesive energies for the respective hafnium species. This suggests a considerable gap in affinity toward fluorine and oxygen between the twin pair in the solid state. In agreement with experimental findings, this gap is slightly more pronounced for fluorine. This study is also the first to evaluate the theoretical, endothermic mono-hydroxylation of the respective fluorides or oxyfluorides to model the difference in affinity toward fluoride versus hydroxide. For these, we could also find a slight energetic preference for the hafnium compound. [ABSTRACT FROM AUTHOR]

In this study, we experimentally and theoretically demonstrated a universal pathway of hysteresis evolution in polarization switching cycling in both antiferroelectric (AFE) and ferroelectric (FE) Hf xZr $_{\text {1-x}}\text{O}\,\,_{{2}}$ (HZO) thin films. AFE films can achieve sufficient remnant polarization and high endurance by engineering the evolution process of double hysteresis merge. Based on this, we propose a new strategy for realizing high-endurance AFE films in non-volatile memory devices. Additionally, a record high endurance >10 12 on 6 nm AFE HZO under full polarization switching conditions at 4.5 MV/cm and 1 MHz is achieved to demonstrate the potential of this strategy. [ABSTRACT FROM AUTHOR]

The HfxZryO2 with high Zr content is demonstrated to form the anti-ferroelectric tetragonal phase (AFE t-phase). The peak dielectric constant (47) of Hf0.2Zr0.8O2 is achieved. By taking advantage of the high dielectric constant, the Hf0.2Zr0.8O2 is used in the gate stack on the high mobility Ge0.98Si0.02 channel to significantly enhance the drive current. Stacked two Ge0.98Si0.02 gate-all-around nanowires can have high ION per perimeter of $740~\mu \text{A}/\mu $ m at $\mathrm{V}_{\mathrm{OV}}= \mathrm{V}_{\mathrm{DS}}= 0.5\text{V}$. The thermal budget is as low as 450 °C. [ABSTRACT FROM AUTHOR]

Adsorption behaviour of 95Zr(IV), 181Hf(IV) and 95Nb(V) radionuclides onto bentonite is investigated in this study. Optimization of parameters is governed by conducting the adsorption experiments at different pHs, contact time, adsorbent mass and temperature. Distribution coefficient values of 21,388, 19,869 and 12,866 mL/g for 95Zr(IV), 181Hf(IV) and 95Nb(V) radionuclides, respectively, are achieved at pH 2.5. Contact time of 120 min was sufficient to reach equilibrium and the Lagergren kinetic model was appropriate to describe the kinetic data of zirconium. Of the studied adsorption isotherms, Redlich–Peterson was the best model to fit the adsorption equilibrium data of zirconium onto bentonite. The maximum adsorption capacity of bentonite toward zirconium is found to be 63.35 mg/g. The obtained values of enthalpy change and free energy change showed that adsorption of radionuclides onto bentonite was endothermic and spontaneous processes. Bentonite succeeded to efficiently remove the studied radionuclides even in presence of high concentrations of foreign ions. Bentonite succeeded to adsorb 95Zr(IV), 181Hf(IV) and 95Nb(V) radionuclides from radioactive process wastewater with distribution coefficient values of 10,422, 15,453 and 9774 mL/g, respectively. [ABSTRACT FROM AUTHOR]

The article presents the results of obtaining an aluminum electrical wire with a diameter of 0.5 mm from alloys of the AleZr-Hf system used in aircraft. Alloys of three compositions were cast in the form of a billet with a diameter of 12 mm using the method of electromagnetic crystallization. Next, the rheological characteristics of billets from experimental alloys were studied. The obtained data were used to simulate the process of combined rolling-extrusion when obtaining a rod with a diameter of 5 mm from a billet with a diameter of 12 mm using the Deform 3D program. A comparison of the experimental forces and forces during the simulation is made for the forces acting on the rolls and the die of the CRE- 200 unit. At the next stage, experimental studies were carried out to obtain rods based on simulation data. The obtained rods with a diameter of 5 mm were subjected to drawing or sectional rolling with drawing and intermediate annealing to obtain a wire with a diameter of 0.5 mm. At all stages, the mechanical (ultimate tensile strength, yield strength, elongation to failure and area reduction) and electrophysical properties (electrical resistivity) of the obtained deformed semi-finished products were studied. [ABSTRACT FROM AUTHOR]

Antiferroelectric random access memory (AFERAM) is one of the newest alternative non-volatile memory technologies to emerge in recent years. ZrO2-based antiferroelectric films are exceptionally well-suited for memory applications with very high cycling endurance (>1010) and low operating voltages (< 2 V). Lightly alloying ZrO2 with HfO2 is performed to assess AFERAM device performance with back-end-of-line compatible thin film Zr1−xHfxO2 (x $\le0.13$) capacitors. The transition fields associated with antiferroelectric behavior are reduced with more Hf incorporation, yielding a larger magnitude switching polarization and memory window. Cycling endurance beyond 1010 cycles is conducted on thin film capacitors where wake-up in AFERAM first leads to an increase, then a decrease in the memory window at a cumulative cycle number found to be dependent on the amount of Hf-incorporation. Hf-incorporation into ZrO2 is demonstrated to be a feasible way to improve the memory window in ZrO2-based AFERAM. [ABSTRACT FROM AUTHOR]

The selective chemical conversion of biomass components to useful bioproducts may contribute to a renewable resource-based economy. The selective production of target bioproducts may be accomplished using heterogeneous catalysts operating under relatively moderate reaction conditions. In this work, carbohydrate biomass derived α-angelica lactone (AnL) and levulinic acid (LA) were converted to the versatile bioproduct γ-valerolactone (GVL), in the presence of nanohybrid catalysts (M-FDCA) and the microcrystalline metal-organic framework CAU-28, all of which were synthesized from bio-based 2,5-furandicarboxylic acid (FDCA) and a metal (M = Zr or Hf) precursor. The nanohybrids were prepared in a simple fast (FT) fashion, and, for comparison, via a conventional solvothermal (S) procedure. The M-FDCA catalysts stood on a higher footing than CAU-28 in the conversion of AnL and LA to GVL. The superior results for the M-FDCA catalysts may be partly due to their higher ratio S ext :S BET and nano-features, which may advantageously enhance active sites accessibility. In particular, the Hf-FDCA catalysts were stable and performed superiorly to the Zr-FDCA ones. Experimental mechanistic studies shed light on the multifunctional behavior of the hybrid catalysts in the one-pot conversion of AnL-to-GVL, which involved acid and reduction chemistry. [Display omitted] • Fast synthesis of biobased 2,5-furandicarboxylic acid (FDCA), Zr and Hf nanohybrids. • Catalyst benchmarking with microcrystalline metal-organic framework CAU-28. • Hf-FDCA best-performing in one-pot conversion of angelica lactone to γ-valerolactone. • Catalyst multifunctionality associated with -COOH of the linker and metal sites. • Hf-FDCA also best performing for levulinic acid to γ-valerolactone in 2-butanol. [ABSTRACT FROM AUTHOR]

The isostructural compounds caesium decasodium tetrazirconium nonaarsenate, CsNa10Zr4(AsO4)9, and caesium decasodium tetrahafnium nonaarsenate, CsNa10Hf4(AsO4)9, arose as unexpected single-crystal products from the reactions of Na2CO3, MO2 (M = Zr, Hf) and As2O5 in a eutectic flux of NaCl and CsCl. They consist of MO6 octahedra and AsO4 tetrahedra sharing vertices to generate three-dimensional polyhedral networks encapsulating the caesium and sodium ions. TheMO6 groups share all their vertices with adjacent As atoms but the As atoms have one or two 'terminal' O atoms not bonded to Zr or Hf. The Cs+ ion adopts a squashed octahedral geometry and the coordination polyhedra of the partially occupied sodium ions are variously trigonal bipyramidal, tetrahedral, square pyramidal and trigonal pyramidal. Site symmetries: Cs 3; M 3; As 1 and 2; O 1; Na 1, 2 and 3. The M = Zr crystal was refined as an obverse/reverse rhombohedral twin. [ABSTRACT FROM AUTHOR]

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• Two kinds of novel dialkylphosphinic acid modified Merrifield resins were synthesized. • They both selectively extract Hf over Zr in H 2 SO 4 media. • Their adsorption and separation performance for Zr and Hf were investigated. • The adsorption mechanisms were studied. • DFT calculations were carried out. Deep separation of Zr and Hf has always been a great challenging due to their very similar physicochemical properties. In this study, we established a method to synthesize two novel extraction chromatographic resins which graft dialkylphosphinic acid groups through amide group. The dialkylphosphinic acid modified resins were characterized by FT-IR, EA, SEM-EDS, XPS, and BET. Their adsorption and separation behaviors for Zr and Hf were investigated, and the adsorption mechanism was studied. The Zr and Hf adsorption onto Mer-CON-POOH-272 and Mer-CON-POOH-HYY2 both fit pseudo-second order model and Langmuir isotherm model. Mer-CON-POOH-HYY2 has stronger affinity to Zr and Hf than Mer-CON-POOH-272. Mer-CON-POOH-272 has a theoretical maximum loading capacity of 5.663 mg·g−1 Zr and 11.111 mg·g−1 Hf, while Mer-CON-POOH-HYY2 has a higher theoretical maximum loading capacity of 8.376 mg·g−1 Zr and 13.157 mg·g−1 Hf. Dialkylphosphinic acids are the functional groups of Mer-CON-POOH-272 and Mer-CON-POOH-HYY2 that interact with Zr and Hf during adsorption. They adsorb Zr and Hf through cation exchange mechanism, which can be expressed as M(SO 4) 3 2– + 2HL ⇌ M(SO 4)L 2 +. 2H+ + 2SO 4 2-. With increasing H 2 SO 4 concentration, the Zr and Hf extraction percentages and their separation efficiency reduce. The DFT calculation reveals that the adsorption process is accompanied by charge transfer. Adsorption occurs mainly at P = O and P-O positions. The affinity of the two resins for Hf is higher than that of Zr, which is the reason why the resin preferentially adsorbs Hf. [ABSTRACT FROM AUTHOR]

First-principles evolutionary simulations are used to systematically predict stable compounds in the Zr-O system at pressures up to 120 GPa. Zr-O compounds and Hf-O compounds share many similarities, but four new phases Cmmm-Zr3O, R3c-Zr3O2, Pmma-ZrO, and Fe2P-type ZrO2 (P62m) appear in the Zr-O system: the latter two phases appear in the Hf-O system at higher pressure. OII ZrO2 (Pnma) transforms into Fe2P-type ZrO2 at 102 GPa. Meanwhile, Fe2P-type ZrO2 and P62m-ZrO have similar structures based on ω-Zr. However, the calculated Vickers hardness of Fe2P-type ZrO2 (5.6 GPa) is inferior to that of P62m-ZrO (14.1 GPa). The hardness of P62m-ZrO (14.1 GPa) is lower than that of P62m-HfO (16.1 GPa) and P62m-TiO (16.6 GPa). On the whole, Zr-O compounds exhibit lower hardnesses and bulk moduli than Hf-O compounds. [ABSTRACT FROM AUTHOR]

Flexible energy-storage capacitor has attrac- ted great interest on account of the rapid development of the combination of intelligent systems and flexible electronics. In this work, we fabricated flexible energy-storage capacitors by depositing HfxZr1-xO2 thin films on polyimide (PI) substrates using atomic layer deposition (ALD). The flexible capacitors exhibit high energy storage density (ESD $\approx 35.4$ J/cm3) and efficiency ($\eta \approx 69.3$ %). Furthermore, ESD and $\eta $ remained stable even bending 5000 cycles with a radius of 2 mm. This work provide reference for the development of high-performance flexible HfO2-based energy storage devices. [ABSTRACT FROM AUTHOR]