Nb Hf Research Articles

Multi-principal element grain boundaries: Stabilizing nanocrystalline grains with thick amorphous complexions

Amorphous complexions have recently been demonstrated to simultaneously enhance the ductility and stability of certain nanocrystalline alloys. In this study, three quinary alloys (Cu–Zr–Hf–Mo–Nb, Cu–Zr–Hf–Nb–Ti, and Cu–Zr–Hf–Mo–W) are studied to test the hypothesis that increasing the chemical complexity of the grain boundaries will result in thicker amorphous complexions and further stabilize a nanocrystalline microstructure. Significant boundary segregation of Zr, Nb, and Ti is observed in the Cu–Zr–Hf–Nb–Ti alloy, which creates a quaternary interfacial composition that limits average grain size to 63 nm even after 1 week at ~ 97% of the melting temperature. This high level of thermal stability is attributed to the complex grain boundary chemistry and amorphous structure resulting from multi-component segregation. High-resolution transmission electron microscopy reveals that the increased chemical complexity of the grain boundary region in the Cu–Zr–Hf–Nb–Ti alloy results in an average amorphous complexion thickness of 2.44 nm, approximately 44% and 32% thicker than amorphous complexions previously observed in Cu–Zr and Cu–Zr–Hf alloys.Graphical abstract

Experimental Investigation and Thermodynamic Description of the Fe–Hf–Nb System

Experimental Investigation and Thermodynamic Description of the Fe–Hf–Nb System

Design and properties of novel Ti–Zr–Hf–Nb–Ta high-entropy alloys for biomedical applications

The novel high-entropy alloys (HEAs) with compositions of (Ti1/3Zr1/3Hf1/3)15(Nb1/2Ta1/2)x (x = 3, 5) for biomedical applications have been designed and synthesized, using the cluster formula approach. The present HEAs have a single body-centered-cubic (BCC) solid-solution structure and possess prominent mechanical properties of high compressive yield strength (834–890 MPa) and microhardness (287–293 Hv), large plasticity (>45%) under compression, as well as low Young's moduli (56–68 GPa). Also, these HEAs exhibit good bio-corrosion resistance, as revealed by a low corrosion rate at the order of 10−4 mm/year and the low passive current densities of 10−2 – 10−1 A/m2, which are attributed to the formation of passive films consisting of Ti-, Zr-, Hf-, Nb-, and Ta- oxides. The high cell viability and proliferation of bone-forming MC3T3-E1 cells on the HEAs are comparable to those on the Ti–6Al–4V alloy, indicating their good biocompatibility. The present work demonstrates the great potential of these novel Ti–Zr–Hf–Nb–Ta HEAs for biomedical applications.

Specific Features of the Structure and Electrophysical Characteristics of Nitride Coatings Based on Ti–V–Zr–Nb–Hf High-Entropy Alloy

Specific Features of the Structure and Electrophysical Characteristics of Nitride Coatings Based on Ti–V–Zr–Nb–Hf High-Entropy Alloy

High-temperature-tolerable superconducting Nb-alloy and its application to Pb- and Cd-free superconducting joints between NbTi and Nb3Sn wires

For more than 30 years, Pb–Bi alloy and Wood's metal (50% Bi, 26.7% Pb, 13.3% Sn, and 10% Cd) have been used as representative superconducting solder intermedia to establish superconducting joints between NbTi and Nb3Sn wires in high-field nuclear magnetic resonance magnet systems. However, the use of Pb and Cd has been severely restricted by environmental regulations, such as the Restriction of Hazardous Substances Directive. Herein, a novel method of forming a superconducting joint between NbTi and Nb3Sn wires without Pb and Cd has been proposed. This approach is based on metallurgical bonding processes using a superconducting Nb-alloy intermedium, whose fine microstructure is maintained even after exposure to temperatures higher than 650 °C. Further, fine crystal defects become sources of magnetic flux pinning centers. Among transition elements close to Nb, Hf is considered the most suitable additive for realizing high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia. Utilizing the HTT characteristic of Nb–Hf, a superconducting joint between Nb3Sn filaments and one end of the Nb–Hf alloy core was created by forming a superconducting Nb3Sn layer at the interface through a chemical reaction. The other end of the Nb–Hf alloy core was cold-pressed with NbTi filaments, to connect their active new surfaces to each other in order to create a superconducting joint. Ultimately, a superconducting joint between NbTi and Nb3Sn wires was realized with a high critical magnetic field (Bc2) of more than 1 T. The formation of the superconducting joint was confirmed by current decay measurements. This method of forming a superconducting joint is promising for application in environmentally friendly nuclear magnetic resonance magnet systems.Graphical abstract

Effect of Scandium on the Microstructure of the Al–Cu–Mn–Mg–Hf–Nb Alloy

Effect of Scandium on the Microstructure of the Al–Cu–Mn–Mg–Hf–Nb Alloy

Design and development of Ti–Zr–Hf–Nb–Ta–Mo high-entropy alloys for metallic biomaterials

Applying empirical alloy parameters (including Mo equivalent), the predicted ground state diagram, and thermodynamic calculations, noble nonequiatomic Ti–Zr–Hf–Nb–Ta–Mo high-entropy alloys for metallic biomaterials (BioHEAs) were designed and newly developed. It is found that the Moeq and valence electron concentration (VEC) parameters are useful for alloy design involving BCC structure formation in bio medium-entropy alloys and BioHEAs. Finally, we find a Ti28.33Zr28.33Hf28.33Nb6.74Ta6.74Mo1.55 (at.%) BioHEA that exhibits biocompatibility comparable to that of CP–Ti, higher mechanical strength than CP–Ti, and an appreciable room-temperature tensile ductility. The current findings pave the way for new Ti–Zr–Hf–Nb–Ta–Mo BioHEAs development and are applicable for another BioHEA alloys system.

Origin of Carboniferous intra-oceanic arc granitoids from the eastern Pamir and implications for the Paleo-Tethyan ocean

The expanding and diminishing of the Paleo-Tethyan ocean recorded in the Pamir, and relationships between different segments of the Paleo-Tethyan suture from Pamir to Tibet are poorly constrained. Here we present new zircon U–Pb ages and geochemical data of the Waqia granitoid pluton from the eastern Pamir. Both the host granitoids and gabbroic to dioritic enclaves have similar zircon U–Pb ages of 323–318 Ma, being contemporaneous in origin. These rocks are metaluminous, calc-alkaline, tholeiitic series. They exhibit low K2O, low Sr/Y ratios, low REE contents with depleted to flat LREE patterns, slight enrichment in Rb, Ba, Zr, Hf, and negative Nb, Ta, P, and Ti anomalies. They have similar initial 87Sr/86Sr ratios of 0.7040 to 0.7045, positive εNd(t) (+4.63 to +5.02) and εHf(t) (+9.9 to +14.7) values. Detailed elemental and isotopic data indicate that these coeval rocks in the Waqia pluton were cognate and formed by hydrous partial melting of a juvenile mafic crust within an intra-oceanic arc setting. This study is the first to report reliable isotopic ages of the early Paleo-Tethyan subduction in the eastern Pamir. Further, the Tanymas-Mazha Paleo-Tethyan suture in the eastern Pamir should be the western extension of the Jinshanjiang Paleo-Tethyan suture in the central to eastern Tibetan plateau. An integration of published results leads us to conclude that closure of the Jinshanjiang Paleo-Tethyan ocean was diachronous along its 3000–4000 km length, with closure times of ca 240 Ma in the Pamir and ca 220 Ma in the Sanjiang region.

Novel Ti–Zr–Hf–Nb–Ta–Mo High-Entropy Alloys for Metallic Biomaterials

Noble nonequiatomic Ti–Zr–Hf–Nb–Ta–Mo high-entropy alloys (HEAs) for metallic biomaterials (BioHEAs) were designed and developed. Ti28.33Zr28.33Hf28.33Nb6.74Ta6.74Mo1.55 (at%) BioHEA exhibits biocompatibility that is comparable to that of commercial-purity Ti (CP–Ti), with higher mechanical strength than CP–Ti and appropriate room-temperature ductility available for tensile tests. The Moeq, as well as the VEC parameters, were useful for alloy design with body-centered cubic (BCC) structure formation in bio medium-entropy alloys and BioHEAs.

Martensitic Transformation in Quenched Hf–Nb Alloys

Martensitic Transformation in Quenched Hf–Nb Alloys

Strength design of Zr(x)Ti(x)Hf(x)Nb(x)Mo(x) alloys based on empirical electron theory of solids and molecules

In this paper, the valence electron structure parameters of Zr(x)Ti(x)Hf(x)Nb(x)Mo(x) alloys were calculated based on the empirical electron theory of solids and molecules (EET), and their performance through these parameters were predicted. Subsequently, the alloys with special valence electron structure parameters were prepared byarc melting. The hardness and high-temperature mechanical properties were analyzed to verify the prediction. Research shows that the influence of shared electron number nA on the strongest bond determines the strength of these alloys and the experiments are consistent with the theoretical prediction.

Electrochemical Oxidation of Hf–Nb Alloys as a Valuable Route to Prepare Mixed Oxides of Tailored Dielectric Properties

AbstractMetal oxides with high dielectric constant are extensively studied in the frame of substituting SiO2 as gate dielectric in nanoelectronic devices. Here, high‐k mixed HfO2/Nb2O5 oxides are prepared by a facile electrochemical route starting from sputtering‐deposited Hf–Nb alloys with several compositions. Transmission electron microscopy, grazing incidence X‐ray diffraction, and glow discharge optical emission spectroscopy are employed to study the oxide structures, disclosing a crystalline–amorphous transition of the electrochemically prepared oxides by increasing the Nb content. Photo‐electrochemical measurements allow the observation of optical transitions ascribed to localized states inside oxide bandgap induced by the presence of oxygen vacancies for Hf‐rich oxides. Impedance measurements, coupled with withstand voltage and leakage current estimates, provide a comprehensive view of the real dielectric properties of the oxides. The highest ε is estimated for the anodic oxide grown on Hf–39 at% Nb (i.e., 45) but thin film grown on Hf–57 at% Nb alloy shows the best dielectric properties, revealing high dielectric constant, high withstand voltage, and low leakage current. Promising equivalent oxide thickness (down to 0.38 nm) is estimated for the oxide thin layers. The electrochemical oxidation represents a valuable and reliable way to prepare high‐k thin oxide films with tailored and controlled dielectric properties.

Discovery of the Plagiogranites in the Diyanmiao Ophiolite, Southeastern Central Asian Orogenic Belt, Inner Mongolia, China and Its Tectonic Significance

AbstractIn this study, plagiogranites in the Diyanmiao ophiolite of the southeastern Central Asian Orogenic Belt (Altaids) were investigated for the first time. The plagiogranites are composed predominantly of albite and quartz, and occur as irregular intrusive veins in pillow basalts. The plagiogranites have high SiO2 (74.37–76.68wt%) and low Al2O3 (11.99–13.30wt%), and intensively high Na2O (4.52–5.49wt%) and low K2O (0.03–0.40wt%) resulting in high Na2O/K2O ratios (11.3–183). These rocks are classified as part of the low‐K tholeiitic series. The plagiogranites have low total rare earth element contents (ΣREE)(23.62–39.77ppm), small negative Eu anomalies (δEu=0.44–0.62), and flat to slightly LREE‐depleted chondrite‐normalized REE patterns ((La/Yb)N=0.68–0.76), similar to N‐MORB. The plagiogranites are also characterized by Th, U, Zr, and Hf enrichment, and Nb, P, and Ti depletion, have overall flat primitivemantle‐normalized trace element patterns. Field and petrological observations and geochemical data suggest that the plagiogranites in the Diyanmiao ophiolite are similar to fractionation‐type plagiogranites. Furthermore, the REE patterns of the plagiogranites are similar to those of the gabbros and pillow basalts in the ophiolite. In plots of SREE–SiO2, La–SiO2, and Yb–SiO2, the plagiogranites, pillow basalts, and gabbros show trends typical of crystal fractionation. As such, the plagiogranites are oceanic in origin, formed by crystal fractionation from basaltic magmas derived from depleted mantle, and are part of the Diyanmiao ophiolite. LA–ICP–MS U–Pb dating of zircons from the plagiogranites yielded ages of 328.6±2.1 and 327.1±2.1Ma, indicating an early Carboniferous age for the Diyanmiao ophiolite. These results provide petrological and geochronological evidence for the identification of the Erenhot–Hegenshan oceanic basin and Hegenshan suture of the Paleo‐Asian Ocean.

Geochronology and geochemistry of the Late Jurassic bimodal volcanic rocks from Hailisen area, central‐southern Great Xing'an Range, Northeast China

Zircon U–Pb dating and whole‐rock geochemical analysis have been studied on the Late Jurassic volcanic rocks in the Hailisen area, Northeastern China, with the aim of constraining the tectonic evolution of the central‐southern Great Xing'an Range during the Late Jurassic. The volcanic rocks mainly consist of andesite from the Tamulangou Formation, and rhyolite and minor dacite from the Manketouebo Formation. The results of inductively coupled plasma‐mass spectrometry Zircon U–Pb dating for two andesites and one dacite indicate that they formed in the Late Jurassic (161–150 Ma). The mafic rocks are characteristic of low TiO2 (1.01–1.04 wt.%) and P2O5 (0.23–0.31 wt.%) contents, and high Al2O3 (17.19–20.18 wt.%) and CaO (6.69–7.45 wt.%) contents, and belong to the low‐K tholeiitic series. These mafic rocks are also characterized by moderately enriched light rare earth element (LREE) patterns and high abundances of Th, U, Zr, and Hf but negative Nb, Ta, and Ti anomalies. The felsic rocks are enriched in alkalis, Th, U, and LREEs; depleted in Ba, Sr, Nb, Ta, and Ti; and exhibit moderately LREE‐enriched patterns. These features indicate that the mafic volcanic rocks were likely formed by the partial melting of a lithospheric mantle that was metasomatized by subduction‐derived components, but the felsic rocks could derived by partial melting of a crustal source. The Tamulangou and Manketouebo formations have compositions of typical bimodal volcanism, an extensional environment, similar to a post‐orogenic setting, which might be related to the closure of Mongol–Okhotsk Ocean.

Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar

Centimeter-size intrusions of gabbros and plagiogranites occur in mantle peridotites of the Myitkyina ophiolite, Myanmar. The gabbros mainly consist of plagioclase and clinopyroxene, whereas orthopyroxene occasionally occurs. The plagiogranites are mainly composed of plagioclase, quartz and amphibole, with small amount of accessory minerals, such as zircon, apatite and rutile. Plagioclase in the gabbros varies from andesine to anorthite (An37–91), whereas plagioclase in the plagiogranites is less calcic (An1–40). Clinopyroxene in the gabbros is pervasively altered to hornblende. The gabbros contain 42.97–52.88wt% SiO2, which show negative correlations with Al2O3, CaO and MgO, but positive correlations with Na2O, P2O5 and TiO2. Microtextural relations reveal the crystallization of clinopyroxene prior to plagioclase in the Myitkyina gabbros. This suggests that the gabbros were crystallized from hydrous melts, which is also supported by the occurrence of orthopyroxene and anorthitic plagioclase in some gabbros. The gabbros have slightly enriched Sr-Nd isotopes, with initial 87Sr/86Sr ratios of 0.703938–0.706609 and εNd(t) values of +2.4–+7.2, and relatively variable Hf isotopes, with εHf(t) values of +13.4–+24.9. A subduction component is required to explain the decoupled Nd-Hf isotopes of the gabbros. Binary mixing suggests that addition of ca 2% subducted sediments to a depleted mantle can account for the Nd-Hf decoupling. Therefore, both petrological and geochemical data of the gabbros support that the Myitkyina ophiolite was originated in a supra-subduction zone setting. The plagiogranites have compositions of tonalites and trondhjemites, containing 56.93–77.93wt% SiO2, 1.27–10.79wt% Na2O and 0.05–0.71wt% K2O. They are slightly enriched in LREE over HREE and display positive anomalies in Eu, Zr, Hf but negative Nb anomalies. Very low TiO2 contents (0.03–0.2wt%) of the plagiogranites suggest that they were not products of fractional crystallization of MORB but were generated by hydrous melting of gabbros. This process is also supported by the nearly constant contents of both La and Yb with increasing SiO2 of the plagiogranites. The Sr-Nd-Hf isotopes of the plagiogranites indicate the involvement of crustal component in their genesis. We proposed that the Myitkyina plagiogranites were generated by partial melting of the mafic protoliths in the subducted slab.

Variations of nanotubes on the Ti–Nb–Hf alloys with applied voltages

In this study, variations of nanotubes on the Ti–Nb–Hf alloys with applied voltages in dental applications were studied using different experimental techniques. Cone-shaped nanotubes were formed during the anodization of Ti–29Nb–xHf alloys by varying the applied DC voltage from 10 to 30V, and from 30 to 10V. The anodization time was 180min and the electrolyte was 1M H3PO4 with 0.8wt.% NaF. The morphology changes in anodized Ti–29Nb–xHf alloys were analyzed by optical microscopy, field emission scanning electron microscopy and X-ray diffractometer. The microstructures of the Ti–29Nb–xHf alloys changed from needle-like to an equiaxed structure, and with the increasing of Hf content, the β-phase gradually increased with a concomitant decrease in the α″-phase. Cone-shaped nanotubes were formed when the applied voltage was stepped up and the inversed cone-shape nanotube was formed on stepping down the applied voltage. The diameter, cross-section, length, and shape of the nanotube on the Ti–29Nb–xHf alloys can be controlled both by varying the applied voltage and the Hf content.

Changes in microstructure, solidification path and hydrogen permeability of Nb–Hf–Co alloy by adjusting Hf/Co ratio

The effect of Hf/Co ratio on microstructure, solidification path and hydrogen permeability of as-cast Nb40Hf30+xCo30−x and Nb35Hf32.5+xCo32.5−x (x = −2, 0, 2, 4) alloys is investigated. The above two series of alloys mainly consist of the primary BCC-(Nb, Hf) and the eutectic {BCC-(Nb, Hf) + Bf-HfCo} phases, while Nb40Hf34Co26 alloy additionally contains small fractions of the Hf2Co phase that results from a ternary eutectic reaction. Increase of Hf/Co ratio induces higher fraction of primary BCC-(Nb, Hf) and Hf2Co phases. Two kinds of solidification paths are found in this two series of alloys, particularly [L→BCC-(Nb,Hf)]→[L→BCC-(Nb,Hf) + Bf-HfCo] and [L→BCC-(Nb,Hf)]→[L→BCC-(Nb, Hf)+Bf-HfCo]→[L→BCC-(Nb, Hf) + Bf-HfCo + Hf2Co]. The permeability increases with increasing Hf/Co ratio and increasing volume fraction of the primary BCC-(Nb, Hf) phase. Nb40Hf32Co28 (x = 2) exhibits a high hydrogen permeability of 5.21 × 10−8 mol H2 m−1s−1Pa−1/2 at 673 K and excellent durability in hydrogen permeation (∼72 h), which becomes superior to that of the Nb40Hf30Co30 previously reported to be the best in the Nb–Hf–Co alloy series. The present work demonstrates that the hydrogen permeability of this alloy series can be optimized by appropriately adjusting the Hf/Co ratio for a given niobium content.

Effect of composing element on microstructure and mechanical properties in Mo–Nb–Hf–Zr–Ti multi-principle component alloys

A series of non-equiatomic Mo–Nb–Hf–Zr–Ti alloys are synthesized to investigate the effects of the concentration variation of each composing elements on the microstructure and mechanical properties. It is found that all studied alloys form single body-centered-cubic (BCC) phase only with the variation of the lattice parameter, which indicates that the concentration variation of each composing elements has no effect on the phase constitutes. All studied alloys exhibit typically dendritic and interdendritic structure while the concentration variation of each composing elements has different effects on the microsegregation. The concentration variation of Zr leads to the most serious microsegregation. Elements with a higher melting point such as Mo and Nb solidify preferentially and thus are enriched in the dendrites. Both the increase and decrease of the concentration of each composing element reduce the hardness and strength of non-equiatomic Mo–Nb–Hf–Zr–Ti alloys compared with the equiatomic MoNbHfZrTi alloy.

Study on the use of 3-aminopropyltriethoxysilane and 3-chloropropyltriethoxysilane to surface biochemical modification of a novel low elastic modulus Ti-Nb-Hf alloy.

A biocompatible new titanium alloy Ti-16Hf-25Nb with low elastic modulus (45 GPa) and the use of short bioadhesive peptides derived from the extracellular matrix have been studied. In terms of cell adhesion, a comparative study with mixtures of short peptides as RGD (Arg-Gly-Asp)/PHSRN (Pro-His-Ser-Arg-Asn) and RGD (Arg-Gly-Asp)/FHRRIKA (Phe-His-Arg-Arg-Ile-Lys-Ala) have been carried out with rat mesenchymal cells. The effect of these mixtures of short peptides have already been studied but there are no comparative studies between them. Despite the wide variety of silane precursors available for surface modification in pure titanium, the majority of studies have used aminosilanes, in particular 3-minopropyltriethoxysilane (APTES). Nevertheless, the 3-chloropropyltriethoxysilane (CPTES) is, recently, proposed by other authors. Unlike APTES, CPTES does not require an activation step and offers the potential to directly bind the nucleophilic groups present on the biomolecule (e.g., amines or thiols). Since the chemical surface composition of this new alloy could be different to that pure titanium, both organosilanes have been compared and characterized by means of a complete surface characterization using contact angle goniometry and X-ray photoelectron spectroscopy.

Morphology change of HA films on highly ordered nanotubular Ti–Nb–Hf alloys as a function of electrochemical deposition cycle

The aim of this study was to investigate the morphology change of HA films on highly ordered nanotubular Ti–Nb–Hf alloys as a function of electrochemical deposition cycle. The Ti–25Nb–xHf alloys were manufactured by vacuum arc-melting, heat treated for 12h at 1000°C, and water quenched. The HA deposition was carried out using a cyclic voltammetry method with a potential range from −1.5V to 0V (vs. SCE) in Ca(NO3)2·4 H2O+NH4H2PO4 at 80°C±1°C (number of cycles: 5, 10, 20, and 50). The morphology changes were observed by OM, FE-SEM, XRD, EDS and image analyses. The microstructures of the Ti–25Nb–xHf alloys were transformed from α″ phase to β phase, and from a needle-like structure to an equiaxed structure as the Hf content increased. The average length of the TiO2 nanotubes increased, and the nanotubes became more highly ordered, as the Hf content increased. The fraction of the alloy surface area covered by the nanotubes decreased from 81% to 73% with increased Hf content. The nucleation of HA was initiated, and the HA precipitates subsequently agglomerated, at the nanotube interspace area for a low number of deposition cycles. The HA precipitates on the nanotube-formed Ti–Nb–Hf alloy surfaces exhibited a needle-like particle morphology, which had different shapes and larger sizes with an increasing number of deposition cycles. Based upon a scratch test, the adhesion of the deposited layer to the titanium alloy was similar for all samples, and a critical load of approximately 6.0N was required to detach the layer. The HA-deposited surface after nanotube formation on the Ti–Nb–Hf alloys should provide improved cell proliferation at a higher rate than on the nanotubular and bulk titanium alloy surfaces.