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Alkoxide precursors have been highlighted for depositing carbon-free films, but their use in Atomic Layer Deposition (ALD) often exhibits a non-saturated growth. This indicates no self-limiting growth due to the chain reaction of hydrolysis or ligand decomposition caused by β-hydride elimination. In the previous study, we demonstrated that self-limiting growth of ALD can be achieved using our newly developed precursor, hafnium cyclopentadienyl tris(N-ethoxy-2,2-dimethyl propanamido) [HfCp(edpa)3]. To elucidate the growth mechanism and the role of cyclopentadienyl (Cp) ligand in a heteroleptic alkoxide precursor, herein, we compare homoleptic and heteroleptic Hf precursors consisting of N-ethoxy-2,2-dimethyl propanamido (edpa) ligands with and without cyclopentadienyl ligand—hafnium tetrakis(N-ethoxy-2,2-dimethyl propanamido) [Hf(edpa)4] and HfCp(edpa)3. We also investigate the role of a Cp ligand in growth characteristics. By substituting an alkoxide ligand with a Cp ligand, we could modify the surface reaction during ALD, preventing undesired reactions. The last remaining edpa after Hf(edpa)4 adsorption can undergo a hydride elimination reaction, resulting in surface O–H generation. In contrast, Cp remains after the HfCp(edpa)3 adsorption. Accordingly, we observe proper ALD growth with self-limiting properties. Thus, a comparative study of different ligands of the precursors can provide critical clues to the design of alkoxide precursors for obtaining typical ALD growth with a saturation behavior. [ABSTRACT FROM AUTHOR]

Understanding the oxidation behavior of hafnium carbide is crucial to its application in extreme environments. In this work, the transition in high‐temperature oxidation kinetics regimes in hafnium carbide is explained based on phase equilibria considerations supported by observed changes in oxide scale microstructure evolution associated with different transformation pathways. Below, a composition‐dependent critical temperature and oxygen pressure, hafnium carbide first transforms to an amorphous material with nominal composition HfO2C followed by phase separation into carbon and hafnia domains. Subsequently, gaseous transport through a nanometric pore network formed by oxidative removal of phase‐separated carbon becomes rate‐limiting. Above this critical point, the oxidation sequence involves a direct transformation from hafnium carbide to hafnia and gaseous products, leading to dissimilar scale morphologies responsible for the reported transition from gaseous to solid‐state diffusion‐limited oxidation regimes at ultra‐high temperatures. [ABSTRACT FROM AUTHOR]

Ultra-high temperature ceramics (UHTCs) are refractory transition-metal carbides, nitrides, and borides with the highest melting temperatures known materials, making them prime candidates for applications in aerospace and hypersonic vehicles. Of the UHTCs, tantalum carbide (TaC) and hafnium carbide (HfC) feature the highest melting temperatures. We investigated the binderless consolidation of HfC/TaC powder blends using Field Assisted Sintering Technology (FAST). Powders consisting of 90/10, 50/50, and 10/90 vol% HfC:TaC were sintered to high densities (>94 %). Bulk and nanomechanical, chemical, and microstructural characterization revealed substantially greater strength, hardness, and stiffness for ternary alloys. Mechanical properties correlated with physiochemical analysis indicated trace oxygen phases, solid-solution strengthening, and nonstoichiometric carbon were the key mechanisms driving the peak property enhancement of the 50 vol% solid-solution sample, despite lower densities. This study provides insight into optimizing the compositional design of HfC-TaC alloys by balancing influences from solid solution strengthening and the thermodynamic effects of oxygen/carbon stoichiometry. [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 macroscopic Schmid's law and microscopic local strain accommodation mechanism have been widely used to determine the twin variants selection combinedly. In the present study, the selection of 10 1 ¯ 2 twin variants of pure Hf under uniaxial compression was studied with the combined use of electron backscatter diffraction (EBSD) technology and displacement gradient tensor. Results indicated that the initially formed 10 1 ¯ 2 twin variant in one grain adheres to the Schmid's law, and its appearance modifies the local stress state within the matrix and in neighboring grains. The formation of the following intragranular twin variants and twin pairs at grain boundaries (GBs) was affected by the modified local stress field. For example, the growth and even nucleation of one twin variant can be suppressed by the intragranular local stress induced by the appearance of its para-position twin; paired 10 1 ¯ 2 twins can be generated at GB if one of the twin variants is able to accommodate the local stress caused by twin impingement on GB in its neighboring grain. For the twin pairs at GBs, the value of misorientation angle between two neighboring grains determines whether the incoming twins can transfer across the GB or be blocked by the GB, and this threshold is 33° in the present study. [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]

Cr3+ ions doped broadband emission near‐infrared (NIR) phosphors are pertinent to widespread emerging applications and get rapid developed. However, it remains a challenge to simultaneously achieve highly efficient and broadband near‐infrared emission in Cr3+ ions doped phosphors. Herein, the Cr3+ ions firstly doped into organic–inorganic hafnium chlorine TEA2HfCl6 (TEA = Tetraethylammonium, C8H20N), which show broadband emission at a range of 700–1300 nm, a full width at half maximum (FWHM) of 164 nm, and a high photoluminescence quantum yield (PLQY) of 60%. The organic–inorganic metal halides show huge advantages than traditional inorganic phosphors, like high luminescence efficiency, low temperature solution synthesis progress, and low cost, which provide an efficiency strategy for lighting industry. Based on these advantages, a high power NIR light emitting diode (LED) is fabricated by TEA2HfCl6:Cr3+ with a high‐power 530 nm chip, which is used in food analysis, night vision, and biomedical imaging as a demonstration. This work indicates the feasibility of organic–inorganic metal halides as host materials for developing Cr3+ ions emitting phosphor toward multi‐optoelectronic applications. [ABSTRACT FROM AUTHOR]

Archean cratons are dominated by tonalite–trondhjemite–granodiorite (TTG) suites, the products of crustal differentiation that formed early continental crust. These rocks may have been primarily generated by partial melting of hydrated basaltic crust in a variety of settings including subduction zones or the deep lithosphere. Sources are mainly inferred from examination of TTGs alone, as potential source rocks are rarely exposed. In the southern Superior Province, Canada, the Kapuskasing Uplift exposes an important crustal cross-section with upper- to middle-crustal TTGs and lower-crustal metabasites, which show evidence of having produced trondhjemitic anatectic melt. Here, we test the hypothesis that these metabasites were the source of the Mesoarchean to Neoarchean TTGs in the Kapuskasing Uplift by combining phase equilibrium and melt trace element modelling with whole-rock and zircon Lu–Hf isotope analysis and geochronology (garnet Lu–Hf and zircon U–Pb) of metabasic samples. By comparison of the results with existing data from TTGs in the Kapuskasing Uplift, we determined that the metabasites are plausible source rocks for the TTGs. The Lu–Hf systematics of the metabasites and TTGs are the most robust evidence of a genetic connection. Modelling results support an increase in TTG source depth over time. New geochronological data constrain partial melting of metabasite and crystallization of anatectic melt between ca. 2685 Ma and ca. 2600 Ma, coeval with crystallization of only the youngest TTGs. Overall, these results indicate a complex history of intracrustal differentiation in the Kapuskasing Uplift, with partial melting of two isotopically distinct lower-crustal metabasic sources at different times and depths. [ABSTRACT FROM AUTHOR]

Scientific studies involving hafnium have grown significantly in recent years due to the potential applications that this metal has. These potential applications come from the properties of this element, which for many years since its discovery were neglected in research. Among the factors that contributed to this was the high cost of extracting its ores from nature. One of the properties is the solubility of this metal in concentrated sulfuric acid, reacting to form hafnium(IV) sulfate and hydrogen gas. This acid is one of the few that can dissolve this metal, since hafnium is highly resistant to corrosion. The present work reports a chemometrically planned study on the surface of hafnium metal during its dissolution in sulfuric acid at different temperatures (13 °C, 25 °C and 97 °C) and for different times (5 minutes, 60 minutes and 120 minutes). Samples of metallic hafnium were completely immersed in sulfuric acid, subsequently characterized by scanning electron microscopy and the mass variation of the samples was analyzed. The corrosion of hafnium occurs only after the rupture of the protective film of hafnium(IV) oxide of the material, this rupture being faster as the temperature increases. [ABSTRACT FROM AUTHOR]

The paper analyzes promising industrial processes for obtaining electrolytic hafnium powder. It is shown that extraction and iodide refining are the main processes used to purify hafnium from impurities, achieving both reactor-grade and high purity. The conducted studies have demonstrated the possibility of creating an alternative, more economical, and environmentally safe technology for hafnium recovery, compared to the current magnesium-thermal method. Production of reactor hafnium by electrolysis from molten electrolyte K2HfF6-KCl-KF is possible due to obtaining hafnium oxynitrate salt of nuclear purity and the creation of a hermetic electrolyzer. It is shown that the process of electrolysis leads to the accumulation of potassium fluoride in the electrolyte and requires its periodic draining with deterioration of technological indicators associated with increased recycling of the electrolyte. It was found that along with hafnium, metallic potassium is released on the cathode, which additionally worsens the technical and economic indicators of production. Sealing the electrolyzer makes it possible to create an overpressure of anode gas and determine its quantitative and chemical composition. Processing hafnium cathode sludge with potassium carbonate solution preserves the potassium cycle in the system and eliminates the effluents generated by ammonium carbonate. [ABSTRACT FROM AUTHOR]

The term "light yield" (LY) refers to the ability of scintillator materials to convert high‐energy radiation into visible light. A higher LY corresponds to improved energy and spatial resolution in detectors. The enhancement of scintillator material performance is a crucial aspect of their development. In this study, the Cs2TeCl6 (CTC) double perovskite microcrystals is synthesized, and the broadband yellow emission shows a high degree of matching with the Charge‐coupled Device (CCD). However, the LY of CTC is poor for practical applications in X‐ray imaging. The scintillation performance is significantly enhanced through hafnium alloying. The LY increased from ≈4167 to 38 523 photons/MeV, and the detection limit decreased from 948 to 258 nGy s−1. The underlying mechanism of Te4+ ions emission is systematically explored through density function theory (DFT) analysis, along with investigations into pressure‐dependent photoluminescence, temperature‐dependent photoluminescence, and low‐temperature thermoluminescence. Furthermore, a flexible X‐ray scintillator screen with an outstanding high spatial resolution of 15.9 lp mm−1 is successfully fabricated. This work not only represents a substantial advancement in the scintillation performance of Te4+ ions emission double perovskite microcrystals but also provides an effective strategy for the development of the next generation of halide scintillators. [ABSTRACT FROM AUTHOR]

This theoretical analysis provided the exact solution of a steady flow of Casson rheological fluid in fluid-particle suspension models through a divergent channel with consideration of porous medium, electric, and magnetic fields, and slip boundary conditions. The thermal transport analysis is also observed with the consideration of viscous dissipation and uniform heat source. The suitable transformation is used to reduce the partial differential equation into ordinary differential equations and obtain the exact solution by adopting the mathematical software MATHEMATICA 12.0. The momentum and thermal profiles are decreasing functions of the magnetic field parameter. The number of streamlines is increased and covers more parts of the channel for increasing the Darcy force and velocity slip parameters. The computational results of this study will help to understand the momentum and thermal analysis in the fluid-particle suspension model. The results of the current study are useful to increase the oil recovery system, in thermal transport energy, energy production, cooling and heating systems, etc. The current model can be useful in renewable energy to store thermal energy by using the hafnium nanoparticles. The present analysis is original and has not been submitted nor published before. [ABSTRACT FROM AUTHOR]

A stereoselective synthesis of new (6Z,10Z)-16-hydroxyhexadeca-6,10-dienoic and (7Z,11Z)-18-hydroxyoctadeca-7,11-dienoic acid that involved the Ti-catalyzed homocyclomagnesiation of the functionally substituted 1,2-dienes was developed. Subsequent intramolecular cyclization of the synthesized ω-hydroxyalkadienoic acids in the presence of catalytic amounts (2.5–10 mol.%) of hafnium(iv) triflate gave unsaturated macrocyclic lactones and diolides with pharmacophoric 1Z,5Z-diene moieties. [ABSTRACT FROM AUTHOR]

This study investigates the incorporation of hafnium (Hf) into polyurethane foams (PUs), an underexplored area in polymer materials research. The synthesis of Hf-containing PU foams was conducted, and their characterization was performed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), optical microscopy (OM), and dynamic mechanical analysis (DMA). The results revealed a significant increase in the stiffness of PU foams due to the potential formation of hafnium isocyanate. Quantitative values obtained through DMA tests demonstrated an approximate increase of 95.97% for PU Hf 0.5% and 342.72% for PU Hf 3%, compared to the sample without Hf. These data highlight the influence of hafnium on enhancing the mechanical properties of polyurethane foams.

The effects of Hafnium on the microstructure and tensile property of a Ni-based superalloy after solution heat treatment and long-term thermal exposure were investigated with field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD). The results revealed reveal that Hf intensified intensifies the element segregation and promoted promotes the precipitation of MC carbide and honeycomb-like Ni5Hf phase in the as-cast alloy. The solid solution strengthening and second phase (MC) strengthening effects are both enhanced in the alloy doping 0.5 wt% Hf after solution heat treatment. Therefore, the tensile yield strength at 700 °C of the alloy with 0.5 wt% Hf is higher than that in the Hf-free alloy. Otherwise, a large amount of the low melting point Ni5Hf phases appear in the alloy with 0.8 wt% Hf. Ni5Hf phase is prone to become the crack initiation, which decreases diminishes the yield strength in the alloy with 0.8 wt% Hf. The addition of 0.5 wt% Hf can inhibit the formation of needle-like δ phase at grain boundary due to the decrease of grain boundary energy and diffusion rate at grain boundary. Therefore, the 700 °C tensile strength and ductility increase simultaneously in the alloy with 0.5 wt% Hf after thermal exposure at 700 °C.

The study addresses the effect of 1580 and 1590 alloys cold rolled strip annealing practices on the alloys’ grain structure and mechanical properties. The 1590 alloy differs from the 1580 alloy by hafnium and erbium additions. Samples of such alloys were produced by casting into a steel mold. After that they were homogenized during 4 h at 440°С. Then the samples were hot rolled at 440°С, with further cold rolling to 2 mm, with the cumulative percentage reduction equal to 66%. The cold rolled strip was annealed at the temperature ranging from 330 to 440°С with 1 h soaking. The sizes and morphology of Al3Sc strengthening nanoparticles were examined in homogenized condition using transmission microscopy. The mechanical properties and grain structure were defined in cold rolled and annealed conditions. During homogenizing annealing in the 1590 alloy finer strengthening nanoparticles are formed compared to the 1580 alloy. Such features of the microstructure can be explained by the presence of erbium, promoting formation of additional Al3Sc-type nanoparticles nuclei, and hafnium, preventing their further growth. Non-recrystallized structure was identified in both alloys after cold rolling and final annealing. The 1590 alloy has better mechanical properties, regardless of the annealing temperature, which is explained by a larger portion and smaller size of strengthening nanoparticles.

The purpose of the work is to study the influence of hafnium additives on the mechanical properties and thermal stability of particles at elevated temperature during heat treatment of aluminum alloys with a high magnesium content. Two modifications of 1570 alloy were chosen for the study: without hafnium content and with its addition of 0.5 % by weight. Both alloys were subjected to homogenizing annealing at a temperature of 440 °C with different exposure modes, which ranged from 2 to 100 h. Microhardness was studied for various heat treatment modes, and the fine microstructure was studied as well using transmission microscopy. As a result, it was possible to identify that during annealing at a short exposure time (2–8 h), the alloy with the hafnium addition has higher microhardness values exceeding those of 1570 alloy by an average of 20 HV units. This is associated with the fact that in 1570 alloy with hafnium additives, during heat treatment, the number of precipitated particles increases while their average size decreases compared to the base alloy. At the same time, in 1570 alloy without hafnium content, when annealed at a temperature of 440 °C, there is no increase in microhardness. This is caused by the fact that in 1570 alloy without hafnium content, when cooled after casting, discontinuous decomposition occurs, which resulted in the fact that most of the scandium precipitates from the supersaturated solid solution in the form of dispersoids. This phenomenon is not observed in the alloy with hafnium additives, which indicates its ability to stop discontinuous decomposition during cooling the ingot after casting.

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 paper presents a method, implemented for the first time, for the thermal synthesis of hafnium carbide powder using a DC arc discharge initiated in the open-air atmosphere. Based on the results of the series of experiments, the dependences of the current strength of the power source and the time of thermal treatment on the phase composition of the resulting powder product were established. Required parameters have been determined to ensure the synthesis of a powder containing ~98 mass % of the cubic phase of hafnium carbide: heat treatment of the initial mixture containing the stoichiometric ratio of hafnium to carbon for 60 s at a current of 220 A. The size, shape, and substructure of particles of the synthesized carbide are characterized. The differential thermal analysis carried out in an oxidizing medium showed that the obtained hafnium carbide powder is oxidized most intensively at a temperature of ~700°C. [ABSTRACT FROM AUTHOR]

The process of obtaining hafnium diboride via the carbothermal reduction of hafnium oxide, which involves heat treatment in a vacuum furnace and a spark plasma sintering unit, was studied. When the charge was heat treated in a vacuum furnace, hafnium diboride powder characterized by the presence of secondary crystalline phases was obtained within a temperature range of 1500 – 1700°C. Monophase hafnium diboride powder having a fine-grained uniform structure was obtained using the spark plasma sintering method at a temperature of 1500°C. [ABSTRACT FROM AUTHOR]

High‐temperature plasmonics deals with optically active nanostructures that can withstand high temperatures. A conventional approach relying on standalone noble metal nanoparticles fails to deliver refractory plasmonic nanomaterials, and an alternative route envisions metal nitrides. The main challenge remains the development of advanced synthesis techniques and the insight into thermal stability under real‐life application conditions. Here, hafnium nitride nanoparticles (HfN NPs) can be produced by gas aggregation using reactive magnetron sputtering, a technique with a small environmental footprint are shown. As‐deposited NPs are of 10 nm mean size and consist of stoichiometric, crystalline fcc HfN. They are characterized by optical absorption below 500 nm caused by interband transitions and in the red/near‐infrared (NIR) region due to intraband transitions and localized surface plasmon resonance (LSPR). The optical response can be engineered by tuning the NP composition as predicted by finite‐difference time‐domain (FDTD) calculations. Going beyond the state‐of‐the‐art, the HfN NP thermal stability is focued under ultrahigh vacuum (UHV) and in air. During UHV annealing to 850 °C, the NPs retain their morphology, chemical and optical properties, which makes them attractive in space mission and other applications. During air annealing to 800 °C, HfN NPs remain stable until 250 °C, which sets a limit for air‐mediated use. [ABSTRACT FROM AUTHOR]

A high-pressure assisted precursor impregnation pyrolysis method (PIP) was used to prepare 3D PyC-C f /SiHfBOC composites. Its anti-ablation properties were tested in an oxygen-acetylene torch ablation environment exceeding 2000 °C. They revealed the ablation behavior and mechanism of SiHfBOC ceramics, carbon fiber, and the PyC interface layer. Under the action of Hf modification, a dense HfO 2 -SiO 2 oxide layer was formed in situ on the surface of 3D PyC C f /SiHfBOC composites, effectively preventing further ablation of the composite's matrix by high-temperature oxidation gases. During the ablation process of an oxyacetylene torch at 2000 °C, it still exhibits excellent anti-ablation properties (linear ablation rate of 1.10 × 10−4 mm s−1). This work enriches the system of hafnium containing ultra-high temperature ceramic precursors and their composites, which provides beneficial exploration for their application in the ultra-high temperature field. [ABSTRACT FROM AUTHOR]

For removal of the natural isobar 182W interference prior to ultra-trace 182Hf determination by accelerator mass spectrometry, an extraction chromatographic method for separation of Hf from W has been developed by using a newly synthesized tri-n-octylamine (TOA)/XAD-7 resin as the stationary phase and HCl-HF media as the mobile phase. Based on the TOA liquid-liquid extraction studies in HF and HCl-HF solutions at wide concentration range, a maximum separation factor of 8.6 × 103 for W/Hf was obtained in 8 M HCl-0.05 M HF solution. Subsequently, the macroporous organic polymer-based TOA/XAD-7 resin was prepared by vacuum impregnation technique and its morphology, chemical structure and composition were characterized by SEM, EDS, FT-IR, TG-DSC, and EA. The results showed the self-assembly TOA/XAD-7 resin uptakes about 50% of extractant and keeps intact binding characteristic for metal ions. Hence, this resin was employed to investigate the column chromatographic behavior of Hf and W with variable parameters of sample loading and column bed dimensions. As a result, a high yield of more than 99% for Hf and high decontamination factor of 3.2 × 105 for W were achieved under the optimal column condition. The strategy developed provides a simple and efficient alternative to sample preparation for 182Hf measurement. [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 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]

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]

Hafnium carbide (HfC) is a refractory compound known for its exceptional mechanical, thermal, and electrical properties. This compound has gained significant attention in materials science and engineering due to its high melting point, extreme hardness, and excellent thermal stability. This study presents crystal structure prediction via energy landscape explorations of pristine hafnium carbide supplemented by data mining. Apart from the well-known equilibrium rock salt phase, we predict eight new polymorphs of HfC. The predicted HfC phases appear in the energy landscape with known structure types such as the WC type, NiAs type, 5-5 type, sphalerite (ZnS) type, TlI type, and CsCl type; in addition, we predict two new structure types denoted as ortho_HfC and HfC_polytype, respectively. Moreover, we have investigated the structural characteristics and mechanical properties of hafnium carbide at the DFT level of computation, which opens diverse applications in various technological domains. [ABSTRACT FROM AUTHOR]

Hafnium disulfide (HfS2) monolayer is one of the most promising two-dimensional (2D) materials for future nanoscale electronic devices, and patterning it into quasi-one-dimensional HfS2 nanoribbons (HfS2NRs) enables multi-channel architectures for field-effect transistors (FETs). Electronic, transport and ballistic device characteristics are studied for sub-7 nm-wide and ~15 nm-long zigzag HfS2NR FETs using non-equilibrium Green's functions (NEGF) formalism with density functional theory (DFT) and maximally localized Wannier functions (MLWFs). We provide an in-depth analysis of quantum confinement effects on ON-state performance. We show that bandgap and hole transport mass are immune to downscaling effects, while the ON-state performance is boosted by up to 53% but only in n-type devices. Finally, we demonstrate that HfS2NR FETs can fulfill the industry requirements for future technology nodes, which makes them a promising solution for FET architectures based on multiple nanosheets or nanowires. [ABSTRACT FROM AUTHOR]

This work experimentally investigated the wake-up behaviors of hafnium oxide-based ferroelectric capacitors by manipulating the interval time between each characterization cycle. Both Positive-Up–Negative-Down (PUND) and Negative-Down–Positive-Up (NDPU) waveforms were used as the stress and measurement waveforms in the experiments. It was found that the imprint occurs as the total interval time increases to a several-seconds level. However, this only affects the remnant polarization (PR) of ferroelectric capacitors when stressed by NDPU waveforms, since the voltage amplitude saturates under the PUND stress conditions and does not influence the PR. The wake-up behavior has been proved to be caused by the defects redistribution during electrical cycling. Notably, when using PUND waveforms, the change in the interval time can result in different increase rates of PR, indicating the possibility of recovery during the intervals. This recovery leads to a slower wake-up when cycling with a longer interval time. Moreover, it is observed that this PR recovery could reach saturation after several seconds of the interval time. This comprehensive investigation of wake-up and imprint behaviors can provide new insights to evaluate and enhance the reliability of ferroelectric memories. [ABSTRACT FROM AUTHOR]

A hafnium‐based coordination vitrimer (Hf−CooAN‐10) has been prepared by carboxylate ligand exchange from [Hf6O4(OH)4(O2CMe)12]2 and poly‐((ethylhexyl methacylate)‐co‐(carboxyethyl acrylate)) (Mn = 14.4 kg mol−1, Đ = 2.2, 90 : 10 comonomer molar ratio), using a 10 % molar Hf loading with respect to the polymer maximum crosslinking capacity. The material shows high insoluble fraction and expected properties for a 3D network and has been reshaped three times at 50 °C under a 3‐ton pressure without significant property alteration. The Hf−CooAN‐10 thermomechanical and rheological properties are very similar to those previously reported for the analogous Zr−CooAN‐10. The associative nature of carboxylate exchange between the [Hf6O4(OH)4(O2CR)12] crosslinks and the polymer matrix free −COOH functions is suggested by parallel 1H NMR line‐broadening kinetic investigations of acetate exchange in the [Hf6O4(OH)4(O2CMe)12]2 precursor with free MeCOOH, the rate of which has a zero‐order dependence on [MeCOOH], and by DFT calculations on a [Hf(μ‐O2CMe)(O2CMe)2(OH)(H2O)]2 model. The results of these investigations, including the activation parameters for the exchange of both chelating and bridging ligands, are very similar to those of the previously investigated zirconium system and suggest partial acetate dissociation assisted by H‐bond formation with a (μ3‐OH) ligand as the rate‐determining step, followed by acid coordination and intramolecular proton transfer. [ABSTRACT FROM AUTHOR]

This article offers a comparative investigation for Newtonian and non‐Newtonian multiphase flows drifting through an inclined channel. A non‐Newtonian Jeffrey fluid is used as the base fluid. However, Hafnium particles and crystal particles are considered to form two different kinds of two‐phase suspensions. Each flow comes under the influence of an external and transversely applied magnetic force. The effects of gravitational force have also been taken into account which is the main source of the supercritical flow. Flow dynamics are modeled with the help of Navier–Stokes. A closed‐form solution is achieved by invoking the analytical technique subject to, no‐slip condition at the boundary of the channel. A detailed parametric study, regarding the contribution of pertinent variables, is carried out in the graphical section. Furthermore, the obtained analytical and visual results have been vetted numerically through different tables, as well. The findings reveal that non‐Newtonian biphase flows are more significant than Newtonian biphase flows. Similarly, Jeffrey fluid is much suitable for multiphase flows and Hafnium particle suspension with Jeffrey fluid is much better than the one obtained by the crystal‐Jeffrey suspension. Finally, Hafnium suspends well with non‐Newtonian fluid. Such alloys are more suitable for mechanical purposes, particularly for nuclear reactors as coolants. In addition to this, no comparative analysis between Newtonian and non‐Newtonian multiphase flows has so far been reported in the existing literature. [ABSTRACT FROM AUTHOR]

[Display omitted] The first bromide complex of the tetramercury anticrown, [(o , o '-C 6 F 4 C 6 F 4 Hg) 4 Br]− (PyH)+, was synthesized by the reaction of alkenyl bromide complex of hafnocene Cp 2 Hf(Br)–C(But)=C(H)–C≡CBut with cyclic tetrameric perfluoro- o , o '-biphenylenemercury (o , o '-C 6 F 4 C 6 F 4 Hg) 4. The structures of the obtained complex and initial alkenyl bromide complex were studied by the X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

he article discusses the Upper Jurassic Galice Formation in the Western Klamath Mountains, focusing on its formation within an intra-arc basin during the Nevadan orogeny, and how new detrital zircon U-Pb age analyses provide insights into its provenance and age range. Topics include the complex provenance of the Galice Formation, inferred sediment transport pathways, and implications for tectonic models of the Nevadan orogeny.

Copper alloys containing chromium and hafnium combine elevated mechanical strength and high electrical and thermal conductivity. For the simultaneous enhancement of both material properties, precipitation hardening is the utilized mechanism. Therefore, the aim is to analyze the influence of chromium and hafnium in binary and ternary low-alloyed copper alloys and to compare the precipitation processes during temperature exposure. Atom probe tomography (APT) and differential scanning calorimetry (DSC) measurements enable to understand the precipitation sequence in detail. CuCr0.7 starts to precipitate directly, whereas CuHf0.7 is highly influenced by prior diffusion facilitating cold rolling. Within the ternary alloy, hafnium atoms accumulate at the shell of mainly Cr-containing precipitates. Increasing the local hafnium concentration results in the formation of intermetallic CuHf precipitates at the sites of mainly Cr-containing precipitates. Indirect methods are utilized to investigate the materials' properties and show the impact of cold rolling prior to an aging treatment on binary alloys CuCr and CuHf. Finally, ternary alloys combine the benefits of facilitated precipitation processes and decelerated growing and coarsening, which classifies the alloys to be applicable for usage at elevated temperatures. [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.

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]

In this study, a chloride-assisted boro/carbothermal reduction method was employed to prepare HfB 2 whiskers, aiming to address the challenges associated with large-scale preparation of HfB 2 whiskers and the development of high-temperature resistant electromagnetic wave absorbing materials. When the precursors were mechanically stirred, the resulting mixture underwent calcination at 1450 °C for 3 h, leading to the formation of single-phase HfB 2 whiskers. The as-synthesized HfB 2 whiskers showed exceptional resistance to oxidation at temperatures up to 700 °C. The microwave absorption performance and mechanism of the HfB 2 whiskers/paraffin composite were also investigated. The results revealed that the composite achieved a minimum reflection loss of −41.29 dB when the HfB 2 whiskers content reached 80 wt%, while the widest effective absorption bandwidth of the composite reached 3.6 GHz when the HfB 2 whiskers content increased to 82.5 wt%. This work presents a novel candidate for high-temperature resistant materials used in absorbing electromagnetic wave. [ABSTRACT FROM AUTHOR]

The quest for lightweight, high-performance structural materials for demanding applications such as in the fields of automotive, aerospace, and other high-tech and military industries pushes the boundaries of material science. The present work aims to draw attention to a novel, sustainable manufacturing approach for the development of next-generation 7xxx series aluminum alloys that have higher strength by rejuvenating a sustainable compositional and thermomechanical processing strategy. Our innovative strategy integrates two key synergies: trace hafnium (Hf) addition for microstructural refinement, unique thermomechanical treatment involving cryorolling, and a short annealing method. Experimental results revealed that our base alloy exhibited a 33 µm grain size and impressive initial mechanical properties (334 MPa UTS, 150 HV). Adding 0.6 wt.% Hf and employing 50% cryorolling with short annealing led to a remarkable 10 µm grain size reduction and significant mechanical property leaps. The resulting alloy boasts a 452 MPa UTS and 174 HV, showcasing the synergistic advantageous effect of Hf and cryorolling plus annealing treatment. The developed alloys were compositional- and work hardening-dependent, leading to a rich mix of strengthening mechanisms. Optical and scanning electron microscopy reveal several intermetallic phases within the fcc matrix, wherein the Al3Hf phase plays a key role in strengthening by impeding dislocation movement. In addition to experimental results, a 12-full-factorial design experiment via ANOVA analysis was also utilized to validate the significant influence of Hf and cryorolling on properties with (p-values < 0.05). Among the different parameters, cryorolling plus annealing appeared as the most noteworthy factor, followed by the composition. Using the regression model, the ultimate tensile strength and hardness were predicted to be 626 MPa UTS and 192 HV for an alloy with 0.6 wt.% Hf and 85% cryorolling, which opens a new avenue for ultra-high-strength Al7xxx alloys. [ABSTRACT FROM AUTHOR]

This paper presents the results of thermodynamic calculation of adiabatic temperature and the equilibrium composition of products of HfO2 reduction with calcium depending on carbon and calcium content at different pressures. The formation of solid HfN–HfC solutions is identified with the formation of hafnium carbonitride. It is shown that adiabatic temperatures lie in a range of 2000–2900 K, and its elevation is limited by the melting of CaO at 2900 K. The introduction of carbon often reduces the adiabatic temperature, and a pressure rise leads to its increase. A connection is revealed between the composition of products and the type of temperature curves. The main reason why adiabatic temperature rises along with pressure is a displacement of equilibrium toward the formation of condensed phases and an increase in the fraction of HfN in the products. [ABSTRACT FROM AUTHOR]

2D semi‐metallic hafnium ditelluride material is used in several applications such as solar steam generation, gas sensing, and catalysis owing to its strong near‐infrared absorbance, high sensitivity, and distinctive electronic structure. The zero‐bandgap characteristics, along with the thermal and dynamic stability of 2D‐HfTe2, make it a desirable choice for developing long‐wavelength‐range photonics devices. Herein, the HfTe2‐nanosheets are prepared using the liquid‐phase exfoliation method, and their superior nonlinear optical properties are demonstrated by the obtained modulation depth of 11.9% (800 nm) and 6.35% (1560 nm), respectively. In addition, the observed transition from saturable to reverse saturable absorption indicates adaptability of the prepared material in nonlinear optics. By utilizing a side polished fiber‐based HfTe2‐saturable absorber (SA) inside an Er‐doped fiber laser cavity, a mode‐locked laser with 724 fs pulse width and 56.63 dB signal‐to‐noise ratio (SNR) is realized for the first time. The generated laser with this SA has the second lowest mode‐locking pump threshold (18.35 mW), among the other 2D material based‐SAs, thus paving the way for future laser development with improved efficiency and reduced thermal impact. Finally, employing this HfTe2‐SA, a highly stable single‐frequency fiber laser (SNR ≈ 74.56 dB; linewidth ≈ 1.268 kHz) is generated for the first time, indicating its promising ultranarrow photonic application. [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]

Hafnium, owing to its excellent mechanical characteristics, corrosion resistance, high temperature resistance, and remarkable nuclear attributes, is widely used in a variety of fields, including aerospace engineering, nuclear technology, and metallurgy. Nonetheless, the burgeoning nuclear industry has led to an increasing demand for hafnium of elevated purity, and the conventional thermal reduction method for producing hafnium metal is no longer sufficient to meet the market requirements. This review summarizes recent progresses on the extraction and purification technology of hafnium metal, with a specific focus on the electrolysis process, as a prospective alternative to the conventional Kroll process. The electrolysis process can be divided into two categories: molten salt electrolysis and electro-deoxidation. The principles, flow, current status, and obstacles of industrial application of these electrolysis processes are discussed in detail. The review conclusively offers recommendations and maps out the prospects for future research exploration on hafnium metal. [ABSTRACT FROM AUTHOR]

Hafnium is a promising element as contrast agent for diagnostic and therapeutic radiology. Currently there are no suitable hafnium drugs with renal excretion which can be used in radiology. In this work two new hafnium complexes with nitrilotriacetic acid (Hf-NTA) and 1,2-diaminocyclohexanetetraacetic acid (Hf-CDTA) were synthesized and studied for acute toxicity and biodistribution. Inorganic chemistry methods were used for Hf-NTA and Hf-CDTA synthesis. Acute toxicity was studied in female mice C57Bl/6. Median lethal dose (LD50) of Hf-CDTA was assessed as 408 ± 64 mg Hf/kg and of Hf-NTA less than 120 mg Hf/kg. Biodistribution and contrast properties studies of Hf-CDTA were performed in vivo using micro-CT in mice with transplanted subcutaneous mammary adenocarcinoma Ca755. CT imaging of mice intravenously injected with Hf-CDTA confirmed its renal excretion and contrast capability. CT imaging of tumor region with single intratumoral administration of Hf-CDTA showed promising hafnium concentration and retention in tumor for use in contrast-enhanced radiotherapy. Hf-CDTA showed acceptable toxicity and biodistribution in mice with subcutaneous tumors for biomedical application in radiology and radiotherapy. For diagnostic clinical application, the Hf-CDTA formulation must be improved to increase water solubility and decrease toxicity. Hf-NTA appeared to be unacceptably toxic for radiological application. [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]

In this work, diamond–SiC composite materials modified with hafnium have been obtained, and their thermal stability at 1200°C in air has been studied. The phase composition, microstructure, and physical and mechanical characteristics have been determined. A higher thermal stability of sintered Hf-modified materials has been demonstrated compared to a diamond–silicon carbide composite materials with no additives. [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]