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Biomedical application of Hf for hard tissue repair may be expanded if it can be imparted with bone-bonding ability. Apatite formation in the body is required for artificial materials to bond to bone. We have shown that apatite can form on NaOH- and heat-treated Hf in simulated body fluid, although the degree of apatite formation is not high. In this study, we investigated apatite formation on surface-modified Hf metal in simulated body fluid. Hf substrates were soaked in NH4F solution or electrochemically polarized in H2SO4 or NH4F solution, followed by heating at 600°C. The sample soaked or cathodically polarized in NH4F solution had porous structure, and the anodically polarized sample had nanotube aggregates on its surface. F was incorporated into the sample polarized in NH4F solution, but not the sample merely soaked in the solution. NH4F was more effective than H2SO4 in facilitating apatite formation. Remarkably, the sample soaked in NH4F solution had the highest apatite-forming ability. Its porous structure was considered to play a dominant role in apatite formation. Furthermore, there was little correlation between surface energy and apatite formation. Notably, NH4F treatment is more effective than the previously reported NaOH and heat treatments in promoting apatite formation.

While self-propagating reactions in metallic multilayers have been known since the early 1990s, the vast majority of research has been conducted on binary systems comprising either elemental or alloyed layers. The properties of reaction and ignition in these samples are, for a given composition, mainly determined by the bilayer thickness as main design parameter. Here, we present how the stacking sequence is established as an additional design parameter when going from binary to ternary layered systems. The basis for this study is reactive Ru/Al multilayers which are extended to ternary samples by introducing a third element (Ni, Pt, or Hf) as a third, individual component. It is shown that exothermic solid state reactions at the layer interfaces and grain boundaries control the ignition temperature. Furthermore, the stacking sequence determines the specific volume density of phase boundaries and, thus, the magnitude of contribution of these reactions to the process of ignition. While the addition of hafnium is found to have little to no effect on ignition, nickel and platinum lower the ignition temperatures by up to 150 °C (Ni) and 230 °C (Pt), respectively. This can be attributed to the exothermic formation of Ni2Al9, amorphous a-(Al,Pt), and Pt2Al3 which are formed at temperatures significantly lower than that of RuAl6 which is the driving reaction for ignition in binary Ru/Al multilayers. [ABSTRACT FROM AUTHOR]

While the main application of resistive switching structures currently targets non-volatile memories, increasing interest is being focused on their logic applications. Resistive switches are suitable for Boolean logic, neuromorphic computing and for implementation of Zadeh fuzzy logic. In this work, we analyzed implementation of the resistive switching structures for logic application based on Zadeh fuzzy logic. Resistive switching structures based on hafnium oxide and tantalum oxide were connected in an anti-serial configuration (complementary resistive switch). The complementary resistive switches integrated into logic circuit for Min-Max function implementation were analyzed using quasi-static voltage sweeps. We have shown that the accuracy of the Min/Max function determination depends on the ratio of the high and low resistivity states of the single switches. Determination of the Min/Max values is relevant only above the threshold voltage of the resistive structures. Reproducibility of the Min/Max function constructed from the resistive switching structures was evaluated. In addition, pulsed reconfiguration of complementary resistive switch using 100 ns long pulses was demonstrated. [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]

In this work, a series of (x)Hf-β zeolite catalysts were prepared by a simple wet impregnation method and used as bifunctional catalysts with Lewis and Brønsted acid sites for synthesizing 5-hydroxymethylfurfural (5-HMF) from cellulose in H 2 O (NaCl) -THF biphasic system. Characterization analysis of (x)Hf-β zeolite catalysts with ICP-OES, N 2 adsorption-desorption isotherm, XRD, FTIR, SEM, NH 3 -TPD and Py-FTIR indicated that the catalysts possessed favorable pore structure, appropriate acid strength and acidity. A superior 86.3 % cellulose conversion and 53.4 % 5-HMF yield could be obtained at 200 °C for 4 h by using (5 %)Hf-β zeolite as the catalyst. In addition, the catalytic system provided a favorable 5-HMF yield from other carbohydrates, including glucose (85.1 %), sucrose (80.6 %), starch (65.1 %), maltose (65.0 %), dextran (59.9 %), and Moso bamboo (21.9 %). Nevertheless, the recyclability of (5 %)Hf-β zeolite catalyst was unsatisfactory and the 5-HMF yield showed a downtrend from 53.4 % to 24.4 % after 5 cycles. The catalyst has promising potential for converting biomass materials into high-value platform compounds. [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]

A composite anodic oxide film is formed by electrochemical treatment of an ultra‐thin Hf film superimposed on Ta, due to the growth of Ta2O5 columns through HfO2. The oxidation dynamic is governed by an electrical version of the Rayleigh–Taylor effect, the current preferring the more conductive path via Ta during anodization of the superimposed Hf film. Memristive devices obtained by patterning Pt top electrodes are investigated and their electrical behavior is reported. The effect of electrolyte species incorporation on the memristive behavior is analyzed by anodization in different solutions. The influence of citrate‐buffered (CB) and phosphate‐buffered (PB) electrolytes is studied, and the presence of P in the composite anodic oxides is evidenced in the latter case leading to early device failure. Composite memristors grown in citrate electrolytes show both unipolar and bipolar switching, high stability, very good retention, and endurance. The coexistence of both switching mechanisms is related to the special composite oxide nanostructuring. [ABSTRACT FROM AUTHOR]

The possibility of removing metallic (such as Zr, Fe, Cr, and Zn) impurities and non-metallic (such as [O] and C) impurities from technogenic hafnium through single and double refining in the conditions of electron beam melting (EBM) has been studied. The influence of thermodynamic and kinetic parameters on the degree of removal of these impurities from the base metal under vacuum conditions and within a temperature interval of 2500 K to 3100 K is defined. The relative volatility of metal impurities and the stability of the oxides and carbides present in the base metal are evaluated. The possibility for complete removal of Fe, Cr, Zn, [O], and C during EBM is shown. In the case of double refining, at a temperature of 2700 K for 20 min, the maximum degree of removal of Zr is 46.8%, the achieved highest hafnium purity is 99.004%, and the overall effectiveness of the refining of hafnium from impurities is 53%. There is a correlation between the degree of removal of Zr and the micro-hardness of the Hf ingots obtained after EBM. The weight losses vary in the ranges of 1.5–5.8% and 1–8% under the studied single and double refining processes, respectively. [ABSTRACT FROM AUTHOR]

The SiHfOC ceramic microspheres were synthesized from the polysilazane and hafnium(IV) acetylacetonate hybrid precursors through a combination of hydrothermal method and polymer‐derived ceramics (PDCs) method. The SiHfOC ceramic microspheres consist of β‐SiC, SiO2, and m‐HfO2 in an amorphous SiOC matrix and are in a spherical morphology with an average size of about 2 μm. Hafnium‐containing nanoparticles with ∼50‐nm size are not only uniformly distributed on the surface of the ceramic microspheres but also embedded in the SiHfOC ceramic microspheres, forming a unique mosaic structure. Pyrolyzing at 1000°C offers a possibility of an in situ formation of nanocrystal nuclei in the amorphous SiOC ceramic matrix, and the subsequent annealing at 1500°C helps the small nanocrystal nuclei grow and separate the amorphous SiHfOC into a multiphase SiOC network containing β‐SiC, SiO2, m‐HfO2 nanocrystalline and free C. This research provides a methodology for preparing multicomponent ceramic microspheres that can efficiently develop high‐performance PDCs modified by transition metal alkoxide. [ABSTRACT FROM AUTHOR]

It is important to improve the accuracy of rotor position estimation for the high-performance operation of position sensorless permanent magnet synchronous motor (PMSM) drives. To mitigate the position harmonic error caused by the nonideal factors in high-frequency signal injection based methods, an adaptive quasi-proportional-resonant rotor position observer (AQPRO) for sensorless PMSM drives is proposed in this article. The AQPRO can track the estimation error and generate the compensation value, which can realize online suppression for position error. By analyzing the stability and the influence of parameters of the proposed position observer on the suppression performance, a proportional-resonant gain self-tuning strategy is investigated to improve the suppression effect of the position harmonic error for different loads and speeds. The influence of self-tuning regulator parameters is modeled and analyzed in detail. The proposed method does not require offline detection and has a strong suppression ability for different harmonic error components. The effectiveness is verified by experiments on a 2.2-kW PMSM drive platform. [ABSTRACT FROM AUTHOR]

Traditional nonisolated multilevel inverters based on the buck–boost principle usually have some disadvantage such as necessary dead time or capacitor precharging. To overcome these, a new transformerless single-stage buck–boost voltage source inverter topology and its control method are proposed. In addition, the proposed topology has greater advantages in cost and loss. In this letter, the topological characteristics and working mode of the inverter are analyzed, and a modulation scheme that can ensure the balance of the output capacitor voltage is designed. Finally, a hardware experimental prototype is built, and the proposed scheme is experimentally verified based on DSP TMS320F28335 and FPGA XC6SLX9-2TQG144C digital controller. [ABSTRACT FROM AUTHOR]

The high-frequency (HF) signal injection method has been widely used in sensorless control for IPMSM drives. However, the audible noise caused by HF injection restricts the sensorless application. Moreover, the control bandwidth of systems based on sinusoidal multifrequency injection or variable-frequency injection for audible noise reduction is limited due to the need for filters. This article proposes a novel amplitude modulation multirandom frequency injection (AMMRI) method to improve control bandwidth and reduce audible noise. First, the detailed message signal modulation, error extraction, position tracking, and position estimation error compensation based on amplitude-modulated voltage signal are derived and analyzed. Because the filters for HF current and error extractions are removed, the control bandwidth is improved. Second, in order to reduce audible noise, the proposed AMMRI is derived by selecting the message signal according to equal-loudness contour. The proposed method improves the control bandwidth compared to conventional multifrequency injection and reduces audible noise compared to conventional square wave injection. Finally, experimental results verify the proposed method on a 1.5-kW IPMSM platform. [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]

In real world, a typical decision-making problem in the medical field can be seen as an uncertain hesitant fuzzy multiattribute decision-making problem when existing experiences of decision-makers are insufficient. A three-way decision model is an effective tool to deal with uncertain decision-making problems, which can realize the classification of objects. However, different psychological behaviors of decision-makers are likely to affect decision-making results in actual decision-making processes. In order to address this challenge, we first propose a regret-theory-based three-way decision model in hesitant fuzzy environments, which mainly combines regret theory with hesitant fuzzy sets to calculate the perceived utility value of objects. Second, since one of the core ingredients for regret theory is the regret–rejoice function, we put forward a new regret–rejoice function that preserves the original indecisive uncertainty in hesitant fuzzy environments. In addition, according to the inherent relationship of the used data, this article provides a three-way classification method based on the preference ranking organization method for enrichment evaluations I method. Finally, the practicability, rationality, and superiority of the proposed method are shown via the case analysis and comparative analysis in the medical field. [ABSTRACT FROM AUTHOR]

In this article, a novel design of a hierarchicalfuzzy system (HFS) based on a self-organized fuzzy partition and fuzzy autoencoder is proposed. The initial rule set of the system is empty, and all the fuzzy sets and fuzzy rules are generated by a self-organized fuzzy partition algorithm. By adopting an improved box plot data standardization method, the processed data can more accurately represent the distribution characteristics of the input data, which improve the accuracy and the rationality. A fuzzy autoencoder is used to train the HFS layer by layer, which can not only ensure the effectiveness of the fuzzy system's hidden layer variables but also provide interpretability. Compared with the traditional fuzzy logic system, the HFS reduces the total number of rules and the complexity. The proposed HFS is tested on three different regression datasets. The experimental results illustrate that the hierarchical self-organized fuzzy system still performs better in terms of regression accuracy indicators than the self-organized fuzzy system. [ABSTRACT FROM AUTHOR]

The current study was designed to calculate the dose enhancement factor (DEF) of iodine (I), gold (Au), bismuth (Bi), gadolinium (Gd), and hafnium (Hf) nanoparticles (NP)s by Monte Carlo (MC) modeling of an electronic brachytherapy source in resection cavities of breast tumors. The GEANT4 MC code was used for simulation of a phantom containing a water-filled balloon and a Xoft source (50 kVp) to irradiate the margins of a resected breast tumor. NPs with a diameter of 20 nm and concentrations from 1 to 5% w/w were simulated in a tumor margin with 5 mm thickness as well as a hypothetical breast model consisting of spherical island-like residual tumor-remnants. The DEFs for all NPs were calculated in both models. In the margin-loaded model, for the concentration of 1% w/w heavy atom, DEFs of 2.5, 2.3, 2.1, 2, and 1.7 were calculated for Bi, Au, I, Hf, and Gd NPs (descending order), which increased, almost linearly with concentration for all NPs. Moreover, normal tissue dose behind the NP-loaded margin declined significantly depending on NP type and concentration. When modeling residual tumor islands, DEF values were very close to the margin-loaded values except for Bi and I, where DEFs of 2.55 and 1.7 were seen, respectively. Considerable dose enhancements were obtained for the heavy atom NPs studied in the partial breast brachytherapy with a Xoft electronic source. In addition, normal tissue doses were lowered in the points beyond the NP-loaded margin. The findings revealed promising outcomes and the probability of improved tumor control for NP-aided brachytherapy with the Xoft electronic source. [ABSTRACT FROM AUTHOR]

Accurate rotor position estimation is important to ensure the high-performance operation of position sensorless permanent magnet synchronous motor (PMSM) drives. To suppress the estimated rotor position harmonic error (ERPHE) caused by inverter nonlinearities, flux spatial harmonics, and the current measurement error in high-frequency signal injection-based schemes, an adaptive iterative learning control-based online suppression method is proposed in this article. This method constructs a P-type iterative learning rotor position observer with the forgetting factor to obtain the tracking error and generate the compensation value in real time. The stability, the convergence, and the parameter sensitivity of this observer are analyzed in detail. To improve the suppression effect of the ERPHE for different loads and speeds, an iterative learning gain self-tuning strategy is investigated. The proposed method does not require the offline detection and the discrimination of harmonic frequencies, which has strong suppression ability for different harmonic error components. The effectiveness is verified by experiments on a 2.2-kW interior PMSM drive platform. [ABSTRACT FROM AUTHOR]

The separation of trace hafnium from bulk tungsten alloys is of interest for isotope harvesting at the National Superconducting Cyclotron Laboratory and the Facility for Rare Ion Beams because 172Hf, the parent of 172Lu, accumulates in tungsten alloy beam blockers at these facilities. In this work, a procedure for the separation of trace hafnium from a bulk tungsten alloy (454 g) was established using tracer isotopes (175Hf, 88Zr, 173Lu, and 88Y). The procedure employed dissolution in an HF–HNO3 solution followed by a calcium fluoride precipitation, and then extraction chromatography was used for more selective separation steps. Two stages of column separations using LN resin (HDEHP based) and TRU resin (CMPO based) were performed. Gamma-ray spectroscopy and mass spectrometry were used to analyze the final hafnium sample and follow the steps in the chemical processing. The final recovery of hafnium was high (90 ± 8)%, and the mass of tungsten and other transition metals was reduced to near background levels (as determined by ICP-MS of the blank acid solutions). Zirconium follows hafnium quantitatively in this procedure; there was no detectable 173Lu in the final hafnium sample. [ABSTRACT FROM AUTHOR]

A dinuclear hafnium complex containing the parent imido ligand [(PN)(PNC)Hf=NH{μ2‐K}]2 (2) (PN−=(N‐(2‐PiPr2‐4‐methylphenyl)‐2,4,6‐Me3C6H2; PNC2−=(N‐(2‐PiPr2‐4‐methylphenyl)‐2,4,6‐CH2Me2C6H2), was prepared by reduction of the bisazide trans‐[(PN)2Hf(N3)2] (1) with two equiv of KC8. Encapsulation of K+ in 2 with crown‐ether or cryptand affords the first discrete salt [K(encap)][(PN)(PNC)Hf≡NH] (encap=18‐crown‐6(THF)2, 3; 2,2,2‐Kryptofix, 4), featuring a terminal parent imide and possessing some of the shortest Hf−N bond lengths known to date. DFT calculations revealed formation of 2 to proceed via an extremely basic monomeric nitrido, [(PN)2Hf≡N]−(A), having a computed pKBH+ of ∼57 followed by heterolytic splitting of an inert 1,2‐CH bond of a benzylic methyl group across the Hf≡N triple bond in A. An electronic structure analysis reveals A to possess a covalent Hf≡N triple bond and of super‐basic character. We also showcase reactivity of the Hf≡NH bond with various electrophiles. [ABSTRACT FROM AUTHOR]

An increased interest in longitudinal neurodevelopment during the first few years after birth has emerged in recent years. Noninvasive magnetic resonance imaging (MRI) can provide crucial information about the development of brain structures in the early months of life. Despite the success of MRI collections and analysis for adults, it remains a challenge for researchers to collect high-quality multimodal MRIs from developing infant brains because of their irregular sleep pattern, limited attention, inability to follow instructions to stay still during scanning. In addition, there are limited analytic approaches available. These challenges often lead to a significant reduction of usable MRI scans and pose a problem for modeling neurodevelopmental trajectories. Researchers have explored solving this problem by synthesizing realistic MRIs to replace corrupted ones. Among synthesis methods, the convolutional neural network-based (CNN-based) generative adversarial networks (GANs) have demonstrated promising performance. In this study, we introduced a novel 3D MRI synthesis framework– pyramid transformer network (PTNet3D)– which relies on attention mechanisms through transformer and performer layers. We conducted extensive experiments on high-resolution Developing Human Connectome Project (dHCP) and longitudinal Baby Connectome Project (BCP) datasets. Compared with CNN-based GANs, PTNet3D consistently shows superior synthesis accuracy and superior generalization on two independent, large-scale infant brain MRI datasets. Notably, we demonstrate that PTNet3D synthesized more realistic scans than CNN-based models when the input is from multi-age subjects. Potential applications of PTNet3D include synthesizing corrupted or missing images. By replacing corrupted scans with synthesized ones, we observed significant improvement in infant whole brain segmentation. [ABSTRACT FROM AUTHOR]

Mono-substituted imidazolinX-2-iminato hafnium(IV) complexes (X = iPr, tBu, Mesityl, Dipp) were synthesized and fully characterized, including solid-state X-ray diffraction analysis. When the X group is small (iPr), a dimeric structure is obtained. In all the monomeric complexes, the Hf-N bond can be regarded as a double bond with similar electronic properties. The main difference among the monomeric complexes is the cone angle of the ligand, which induces varying steric hindrances around the metal center. When the monomeric complex of mono(bis(diisopropylphenyl)imidazolin-2-iminato) hafnium tribenzyl was reacted with three equivalents (equiv) of iPrOH, the benzyl groups were easily replaced, forming the corresponding tri-isopropoxide complex. However, when BnOH was used, dimeric complexes were obtained. When five equivalents of the corresponding alcohols (BnOH, iPrOH) were reacted with the monomeric complex, different dimeric complexes were obtained. Regardless of the high oxophilicity of the hafnium complexes, all complexes were active catalysts for the ring-opening polymerization (ROP) of ε-caprolactone. Dimeric complexes 5 and 6 were found to be the most active catalysts, enabling polymerization to occur in a living, immortal fashion, as well as the copolymerization of ε-caprolactone with rac-lactide, producing block copolymer PCL-b-LAC. The introduction of imidazolin-2-iminato ligands enables the tailoring of the oxophilicity of the complexes, allowing them to be active in catalytic processes with oxygen-containing substrates. [ABSTRACT FROM AUTHOR]

Hafnium carbide (HfC) and tantalum carbide (TaC), as potential ultra-high temperature ceramics (UHTCs), have attracted widespread attention due to their unique physical and chemical properties. Here, dense HfC and TaC ceramics are synthesized under high pressure and high temperature 15 GPa and 1700 °C, respectively. The sound velocities and elasticity behavior of sintered HfC and TaC under high pressure have been experimentally investigated by using ultrasonic interferometry and validated by first-principles study. The bulk and shear moduli with their pressure dependence have been determined as B 0 = 272.6(2.7) GPa, G 0 = 215.8(2.2) GPa, ∂ B / ∂ P = 3.44 (5) , and ∂ G / ∂ P = 1.74 (3) for HfC, B 0 = 355.9(3.6) GPa, G 0 = 236.6(2.4) GPa, ∂ B / ∂ P = 3.98 (5) , and ∂ G / ∂ P = 1.65 (2) for TaC. The Vickers hardness and fracture toughness of HfC and TaC are generated from empirical models. The present work provides deep insights into the engineering application of UHTCs HfC and TaC under high-pressure extreme conditions. [ABSTRACT FROM AUTHOR]

A circuit structure, topological family, and unipolar phase-shift SPWM master-slave power distribution energy management control strategy (EMCS) of the single-stage Buck type multi-input high-frequency (HF) link's inverters with multiwinding time-sharing power supply are proposed in this article, in order to reduce the power conversion stage, volume and weight, and increase conversion efficiency and reliability. The key technologies of this kind of inverter, such as circuit structure and topological family, EMCS, power supply mode (PSM), and steady-state principle characteristics, are deeply studied. The circuit structure is composed of multiple isolated HF inverting bridges, a HF transformer with multi-input single-output, a cycloconverter and an output LC filter. The EMCS is to generate the bipolar tristate multilevel SPWM waves by phase-shift between the right arm and the left arm of multiple HF inverting bridges; the cycloconverter demodulates it into the unipolar tristate multilevel SPWM wave, and performs zero voltage commutation. The experimental results of the designed and developed 1kVA multi-input inverter prototype have shown it has the advantages of single-stage power conversion, HF electrical isolation, high conversion efficiency, small volume and weight, high reliability, stable output voltage, multi-input source master-slave power distribution, and smooth switching of different PSMs. [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]

The results of the theoretical and experimental studies of the field-emission cells with the aspect ratio of several hundred units obtained on the basis of laser milling technology are presented. Hafnium, molybdenum, glassy carbon, and tungsten were used as a material for field emitters. Applicability of field-emission electron cells in electrooptical systems for electric vacuum devices including O-type devices with extended electron beam was demonstrated. [ABSTRACT FROM AUTHOR]

Tetrachlorides of zirconium- and hafnium form adducts (2, 3) with an intramolecular germylene phosphine Lewis pair. Two electron reduction treating the adducts with [MesNacnacMg]2 gives the low valent metal complexes (4, 5) featuring η6-Trip coordination at the Zr(II) and Hf(II) metal atom. Reduction of the M(II)-complexes gives the zerovalent metal complexes of zirconium (6) and hafnium (7), which have been structurally characterized. Two arene moieties and the germylene exhibit metal coordination. Puckered coordination of a P-phenyl unit was observed for both derivatives 6 and 7. Four electron reduction of a reaction mixture of metal tetrachloride with the germylene-phosphine Lewis pair also gives the zerovalent complexes in good yield. Carbonyl complexes were synthesized treating the reduced metal complexes with carbon monoxide. Dimethylbutadiene shows a reaction with an arene moiety and the coordinated germylene ligand of the zerovalent complexes. A cyclohexadienyl and a triorganogermate ligand are formed. For zirconium this reaction is reversible at room temperature., (© 2024 Wiley‐VCH GmbH.)

The superconducting properties of 85 nm thick hafnium thin films with a 5 nm thick titanium layer on top have been investigated for three different geometries, that is, a film covering the entire 7 × 7 mm 2 chip surface, bridges with a width of 200 μm and length up to 1800 μm, and bridges in the form of squares with sides from 100 to 1000 μm. The bridges were formed by a photolithographic lift-off process and are intended to be used as the main sensing element of a microcalorimeter based on a transition-edge sensor (TES) in experiments to determine the magnetic moment of neutrinos. Based on the measurements of the critical current, the critical temperature, and the width of the superconducting transition, we estimate the energy resolution δ E of the TES prototypes, showing that it is possible to fabricate microcalorimeters with δ E less than 1 eV using these films., (Copyright © 2024, Safonova et al.)

Hafnium-based ferroelectric memories are a promising approach to enhancing integrated circuit performance, offering advantages such as miniaturization, compatibility with CMOS technology, fast read and write speeds, non-volatility, and low power consumption. However, FeRAM (Ferroelectric Random Access Memory) still faces challenges related to endurance and retention susceptibility to process variations. Hence, testing and obtaining the core parameters of ferroelectric capacitors continuously is essential to investigate these phenomena and explore the potential solution. The traditional method for measuring ferroelectric capacitors has limitations in timing generation capability, introduces parasitic capacitance, and lacks accuracy for small-area capacitors. In this study, we analyzed the working principle of ferroelectric capacitors and designed a method to detect the remnant polarization, saturation polarization, and imprint offset of ferroelectric capacitors. Further, we further proposed a circuit implementation method. The proposed test circuit conquers these limitations and enables high-precision testing of ferroelectric capacitors, contributing to developing hafnium-based ferroelectric memories. The circuit includes a flip-readout circuit, a capacitance calibration circuit, and a voltage-to-time converter and time-to-digital converter (VTC&TDC) readout circuit. According to simulation results, the capacitance calibration circuit reduces the deviation of the capacitance by 84%, and the accuracy of the readout circuit is 5.91 bits, with a readout time of 150 ns and a power consumption of 1 mW. This circuit enables low-cost acquisition of array-level small-area ferroelectric capacitance data, which can guide subsequent device optimization and circuit design.

The intercalation of heteroatoms between graphene and metal substrates is a promising method for integrating epitaxial graphene with functional materials. Various elements and their oxides have been successfully intercalated into graphene/metal interfaces to form graphene-based heterostructures, showing potential applications in electronic devices. Here we theoretically investigate the hafnium intercalation between graphene and Ir(111). It is found that the penetration barrier of Hf atom is significantly large due to its large atomic radius, which suggests that hafnium intercalation should be carried out with low deposition doses of Hf atoms and high annealing temperatures. Our results show the different intercalation behaviors of a large-size atom and provide guidance for the integration of graphene and hafnium oxide in device applications. [ABSTRACT FROM AUTHOR]

As research into additives and intentionally introduced impurities in dielectric thin film for enhancing the resistive switching based random access memories (RRAM) continues to gain momentum, the aim of the study was to evaluate the effects of chemically presynthesised Ni nanoparticles (NPs) embedded in a dielectric layer to the overall structure and resistive switching properties. HfO2-based thin films embedded with Ni NPs were produced by atomic layer deposition (ALD) from tetrakis(ethylmethylamino)hafnium (TEMAH) and the O2 plasma ALD process onto a TiN/Si substrate. The Ni NPs were separately synthesised through a continuous flow chemistry process and dispersed on the dielectric layer between the two stages of preparing the HfO2 layer. The nanodevices' morphology and composition were analysed with physical characterisation methods and were found to be uniformly dispersed across the sample, within an amorphous HfO2 layer deposited around them. When comparing the resistive switching properties of otherwise identical samples with and without Ni NPs, the ILRS/IHRS ratio rose from around a 4 to 9 at 0.2 V reading voltage, the switching voltage dropped from ~2 V to ~1.5 V, and a distinct increase in the endurance characteristics could be seen with the addition of the nanoparticles. [ABSTRACT FROM AUTHOR]

Carbon fiber/phenolic (C/Ph) composites were modified with different weight ratios of hafnium diboride (HfB2) nanofibers to apperceive thermomechanical properties of C/Ph–Hf nanocomposites. Mechanical properties, thermal stability, and ablation resistance of C/Ph–Hf nanocomposites were found to be optimum when the weight percentage of HfB2 was equal to one. Maximum flexural strength and modulus were obtained with 118 MPa and 1.9 GPa for C/Ph–1%Hf nanocomposite, respectively. Increasing the proportion of HfB2, by delaying the temperature of thermal degradation of nanocomposites, enhanced the thermal stability and residual of C/Ph–Hf relative to C/Ph in both nitrogen and air environments. In the oxyacetylene flame test at 2500°C for 160 s, the optimum mass ablation rate of C/Ph–1%Hf nanocomposites was found to be 0.0150 g/s compared to 0.068 g/s for blank C/Ph, along with reducing the back surface temperature by 51%. The ablation mechanism of C/Ph–Hf nanocomposites after the oxyacetylene torch test was concluded from the derivations obtained from X‐ray diffraction, energy dispersion spectroscopy, and microstructure analyses. These clarified that the formation of high‐temperature species, such as HfO2, HfC, and B4C owing to oxidation of HfB2 and subsequent reaction products with char, resulted in an increased ablation resistance of the nanocomposites. [ABSTRACT FROM AUTHOR]

In this article, a method of simultaneous sensorless rotor position and torque estimation is proposed for interior permanent magnet synchronous machines at standstill and low speed. The proposed method estimates the torque using high-frequency inductances identified from the current variations due to high-frequency square wave voltage injections in the estimated dq-axes, which are simultaneously used for sensorless rotor position estimation. The proposed method is not dependent on the fundamental model and has taken the cross-coupling effect into consideration, allowing for low cost and fast torque estimation at standstill and low speed. Both simulations and experiments are carried out to verify the effectiveness of the proposed method. [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]

Variable speed drives (VSDs) for electric motors are a foundational component of global electrification, with electric motors consuming 45% of global electricity. Conventional three-phase buck–boost inverter topologies have substantial low-frequency current stresses in the buck–boost inductor, driving size, losses, and cost in VSD systems. In this letter, we propose a novel circuit topology for phase-modular three-phase buck–boost inverter systems based on the four-switch noninverting buck–boost concept, which we call the return path inductor Y-inverter (RPI-YI). By relocating the buck–boost inductors from the forward current path to the return path, the RPI-YI concept reduces the inductor rms and peak current stresses by up to $90 \%$ compared to a conventional topology, resulting in a potential magnetics volume reduction of $80 \%$. The RPI-YI concept, therefore, supports more compact, efficient realizations of modular buck–boost VSD systems. [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]

Currently, the conventional halide synthesis method of preparing hafnium alkoxides [Hf(OR)4, R is an alkyl] has problems of inefficiency, a heavy CO2 emission footprint, and substantial solid and gas waste, which severely hinders its wide deployment. Herein, we propose an electrodissolution-coupled Hf(OR)4 synthesis system using an alcohol solvent and Hf metal as feedstock for the efficient, low-carbon and waste-free electro-synthesis of Hf(OR)4. The electrochemical behavior of the tetraethylammonium-hydrogen sulfate (Et4NHSO4)-based EHS process is investigated by cyclic voltammetry, linear sweep voltammetry, Tafel, and electrochemical impedance spectroscopy, complemented with SEM observation. The anodic hafnium dissolution/corrosion occurs inside the passive film while the cathodic ethanol dehydrogenation occurs in a two-stage pathway. Tafel extrapolation and numerical fitting analysis acquires important kinetics parameters, such as corrosion current density, exchange current density, and apparent activation energy as well as solution, polarization and "Warburg" resistances, etc. This work can provide theoretical guidance for the efficient operation of EHS. [ABSTRACT FROM AUTHOR]

Environmental emissions and decreasing costs of renewable energy sources (i.e., photovoltaic (PV), wind, hydrogen (H2), etc.) are prompting a sharp increase in renewable energy penetration into the grid. Among various energy sources, H2 energy with its promising technical, economic, and environmental merits has demonstrated great potential for large deployment in distribution systems. This article proposes a multiobjective network-constrained framework for the day-ahead scheduling of hydrogen systems (HS), including hydrogen production from water electrolysis by electrolyzers, hydrogen storage, stationary fuel cells, and fueling of fuel cell electric vehicles (FCEVs). This framework includes various physical constraints to ensure reliable operation and considers integrated demand response and conservation voltage reduction, and reactive power support from HSs for realistic day-ahead scheduling. It also incorporates the cooperative operation of PV units and HSs to supply power for water electrolysis from stationary HSs equipped with onsite PVs. Moreover, conditional value-at-risk is applied to address the risk of PV output, FCEVs’ H2 demand, loads, and market price. The proposed model is formulated as a mixed-integer linear programming problem and validated by testing on a 33-node distribution test feeder. [ABSTRACT FROM AUTHOR]

Materials with ultralow lattice thermal conductivity have attracted considerable interest in thermoelectrics and thermal management. Here, we have studied the lattice thermal conductivities in the layered material, hafnium germanium tetratelluride HfGeTe4, by the first-principles calculations and revealed an ultralow out-of-plane lattice thermal conductivity of 0. 3   W ⋅ m − 1 ⋅ K − 1 at 300 K. HfGeTe4 also had a large anisotropy in its lattice thermal conductivities, and the κ x x / κ y y ratio reached as high as 10.4 at 300 K. By analyzing its phonon dispersion, group velocities, and lifetimes, we find that the ultralow lattice thermal conductivity of HfGeTe4 was mainly due to the small group velocities and short lifetimes of phonons, which was essentially caused by its heavy elements and complex layered crystal structure. Considering that HfGeTe4 is a semiconductor with a moderate band gap, HfGeTe4 would be a potential thermoelectric material. Our work sheds light on future studies on the thermoelectric properties of HfGeTe4. [ABSTRACT FROM AUTHOR]

Materials with ultralow lattice thermal conductivity have attracted considerable interest in thermoelectrics and thermal management. Here, we have studied the lattice thermal conductivities in the layered material, hafnium germanium tetratelluride HfGeTe4, by the first-principles calculations and revealed an ultralow out-of-plane lattice thermal conductivity of 0. 3   W ⋅ m − 1 ⋅ K − 1 at 300 K. HfGeTe4 also had a large anisotropy in its lattice thermal conductivities, and the κ x x / κ y y ratio reached as high as 10.4 at 300 K. By analyzing its phonon dispersion, group velocities, and lifetimes, we find that the ultralow lattice thermal conductivity of HfGeTe4 was mainly due to the small group velocities and short lifetimes of phonons, which was essentially caused by its heavy elements and complex layered crystal structure. Considering that HfGeTe4 is a semiconductor with a moderate band gap, HfGeTe4 would be a potential thermoelectric material. Our work sheds light on future studies on the thermoelectric properties of HfGeTe4. [ABSTRACT FROM AUTHOR]

The oxidation resistance of the hafnium carbonitride Hf(C,N), HfCN+10 wt% SiC and HfCN+20 wt% SiC ceramics were investigated using thermogravimetric analysis (TGA) and static oxidation experiments at 1200 °C. TGA data showed that in the 1400 °C temperature range weight gain of the Hf(C,N)-SiC ceramics almost halted, while the Hf(C,N) sample continued to oxidize. Experiments at 1200 °C and further microstructure investigations at the ceramic/oxide interfaces showed formation of a dense HfSiO 4 barrier layer with low oxygen diffusivity allowing increased oxidation resistance compared to the pure Hf(C,N). A possible formation mechanism for the protective layer and its influence on oxidation was suggested. Also, it was shown that addition of the SiC powder to the Hf(C,N) allows decreasing consolidation temperature by 200 °C without mechanical properties loss. Hf(C,N) with 20 wt% SiC showed a high fracture toughness (5.1 MPa∙m1/2), high hardness (20.2 GPa), and lower density compared to the Hf(C,N) ceramics. [ABSTRACT FROM AUTHOR]

A novel single-source precursor was synthesized to prepare HfC x N 1-x /SiC multiphase ceramics by using hafnium chloride (HfCl 4), diallylamine (DAA) and polycarbosilane (PCS). We conducted an investigation of the synthesis process, polymer-to-ceramic conversion, as well as the microstructure and phase evolution of HfC x N 1-x /SiC multiphase ceramics with different levels of SiC content. The results showed that the core-shell particles of HfC x N 1-x -carbon were embedded homogeneously in the β-SiC matrix which is beneficial for preventing grain growth and improving oxidation resistance. Based on data from oxidation tests, the ceramics improved the oxidation temperature and remained stable at a high temperature (1500 °C) with oxidation layer formation on the surface. Due to the highly cross-linked structure without oxygen, high ceramic yield, homogeneous composition and excellent oxidation resistance of the pyrolysis product, the as-prepared precursor is a promising material for making high-performance composite ceramics. [ABSTRACT FROM AUTHOR]

In this paper, we obtain coatings on substrates of polycrystalline aluminum oxide, single-crystal silicon, glass, and stainless steel at temperature not exceeding 100°C by ion-plasma sputtering of ultrafine particles of hafnium and cadmium. The structure study of the obtained coatings shows the existence of solid solutions in the concentration range of 5.8–64.1 at % Cd. In the concentration range of 0–50 at % Cd, the coating is represented by a phase of a solid solution of cadmium in α-Hf, while at a Cd concentration of more than 64 at %, cadmium begins to precipitate into a separate phase. The effect of the substrate material on the border of the field of existence of a solid solution of cadmium in hafnium is noted and an assumption about the effect of epitaxy on the border of the field of the existence of solid solutions of cadmium in hafnium is stated. [ABSTRACT FROM AUTHOR]