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The ultra-low thermal expansion coefficient α makes the Fe-Ni Invar alloys useful in various applications. Their low strength and low Curie temperature Tc are, however, limiting factors. Interestingly, some Fe-based bulk metallic glasses (BMGs), with inherent high strength, exhibit the clear Invar effect. In particular, the (Fe71.2B24Y4.8)96Nb4 BMG has the lowest α among Fe-based BMGs, but it unfortunately also has the lowest Tc. In this work, silicon was added into this alloy with the aim to elevate Tc while maintaining a low α. It was found that when silicon partially substituted boron, Tc did not increase significantly but α did, which is not ideal. On the other hand, when silicon partially substituted yttrium and niobium and especially niobium, Tc increased significantly while α did not, which is close to the ideal scenario. When 3% of niobium was substituted by silicon, Tc reached the maximum value of 296 °C while α remained a low value of 7.4 × 10−6/°C. Comparing to the Fe-Ni Invar alloy, although this BMG has an inferior α, it has much higher Tc (+115 °C) and strength (∼9 times), presenting a potential for application as a new Invar material with moderate (low) thermal expansion, high operating temperature, and high strength. [ABSTRACT FROM AUTHOR]

The prospect of creating ferroelectric or high permittivity nanomaterials provides motivation for investigating complex transition metal oxides of the form Ba(Ti, MV)O3, where M = Nb or Ta. Solid state processing typically produces mixtures of crystalline phases, rarely beyond minimally doped Nb/Ta. Using a modified sol-gel method, we prepared single phase nanocrystals of Ba(Ti, M)O3. Compositional and elemental analysis puts the empirical formulas close to BaTi0.5Nb0.5O3−δ and BaTi0.5Ta0.5O3−δ. For both materials, a reversible temperature dependent phase transition (non-centrosymmetric to symmetric) is observed in the Raman spectrum in the region 533–583 K (260–310 °C); for Ba(Ti, Nb)O3, the onset is at 543 K (270 °C); and for Ba(Ti, Ta)O3, the onset is at 533 K (260 °C), which are comparable with 390–393 K (117–120 °C) for bulk BaTiO3. The crystal structure was resolved by examination of the powder x-ray diffraction and atomic pair distribution function (PDF) analysis of synchrotron total scattering data. It was postulated whether the structure adopted at the nanoscale was single or double perovskite. Double perovskites (A2B′B″O6) are characterized by the type and extent of cation ordering, which gives rise to higher symmetry crystal structures. PDF analysis was used to examine all likely candidate structures and to look for evidence of higher symmetry. The feasible phase space that evolves includes the ordered double perovskite structure Ba2(Ti, MV)O6 (M = Nb, Ta) Fm-3m, a disordered cubic structure, as a suitable high temperature analog, Ba(Ti, MV)O3Pm-3m, and an orthorhombic Ba(Ti, MV)O3Amm2, a room temperature structure that presents an unusually high level of lattice displacement, possibly due to octahedral tilting, and indication of a highly polarized crystal. [ABSTRACT FROM AUTHOR]

We generalize a native Nb 2 O 5 dissolution model [G. Ciovati, Appl. Phys. Lett. 89, 022507 (2006)] to sequential overlayer dissolutions, multilayer dissolution, and realistic temperature profiles, which may be applicable to other materials. The model is applied to secondary ion mass spectrometry depth profile measurements for varying temperature profiles and two-step oxide dissolution in Nb and found to agree well. In the context of the Meissner screening response due to impurity profiles on the length scale of the London penetration depth, the shallow diffusion of O impurities results in a substantial decrease in the peak supercurrent density near the surface. In this framework, oxide dissolution and oxygen diffusion can account for a rise in peak supportable magnetic field in SRF cavities with baking time and a suppression after the optimal baking time is reached, in good agreement with peak-field baking temperatures and times as well as recent quench field measurements. [ABSTRACT FROM AUTHOR]

We report measurements of the Meissner screening profile in a Nb (300 nm)/ Al 2 O 3 thin film using 8 Li β -detected nuclear magnetic resonance (β -NMR). The NMR probe 8 Li was ion-implanted into the Nb film at energies ≤ 20 keV, corresponding to mean stopping depths comparable to Nb 's magnetic penetration depth λ. 8 Li 's strong dipole–dipole coupling with the host 93 Nb nuclei provided a "cross-relaxation" channel that dominated in low magnetic fields, which conferred indirect sensitivity to the local magnetic field via the spin-lattice relaxation (SLR) rate 1 / T 1. From a fit of the 1 / T 1 data to a model accounting for its dependence on temperature, magnetic field, and 8 Li + implantation energy, we obtained a magnetic penetration depth λ 0 = 51.5(22) nm, consistent with a relatively short carrier mean-free-path ℓ = 18.7(29) nm typical of similarly prepared Nb films. The results presented here constitute an important step toward using 8 Li β -NMR to characterize bulk Nb samples with engineered surfaces, which are often used in the fabrication of particle accelerators. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Extractive Metallurgy) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Materials with low‐dimensional (1D–2D) structures hold significant promise for electronic and optoelectronic applications owing to their distinctive structural features and inherent properties. These characteristics render them of substantial interest across various scientific domains, particularly in applications related to energy storage, such as supercapacitors and lithium‐ion batteries. Due to their high surface‐to‐volume ratios and unique geometric properties, low‐dimensional materials have attracted considerable attention in developing advanced broadband photodetectors (PDs) with enhanced performance capabilities. In this study, for the first time, the study reports self‐powered broadband PDs based on vertical‐core‐shell niobium diselenide (NbSe2)‐ZnO nanorods (ZNRs), which are produced using a hydrothermal method. Remarkably, the NbSe2(3 ml) doped ZNRs‐based device exhibits outstanding responsivity of 0.62, 23.21, 5.35, 1.11, 0.30 AW−1, detectivity of 2.15 × 1010, 4.10 × 1011, 1.62 × 1011, 8.83 × 1010, 1.42 × 1011 Jones, and high sensitivity of 8.74 × 104%, 5.78 × 105%, 2.71 × 105%, 2.79 × 105%, 1.43 × 105% at wavelengths of 365, 456, 532, 632, and 850 nm, respectively, at zero bias. The NbSe2(3ml)‐ZNRs device showed a rapid response and fall times of 37 ms and 40 ms, enabled by NbSe2 superconductivity. The concept introduced in this study is strongly believed to possess significant potential and can be extensively applied in developing next‐generation integrated optoelectronic, clean energy technology, and photodetection devices based on 1D/2D nanostructures. [ABSTRACT FROM AUTHOR]

Anodic Nb–Ti oxide crossbar memristor arrays are successfully produced on Si substrates. Their use as pH sensors is tested by analyzing their current–voltage (I–U) sweeps in Ringer´s solutions with different pH values. A gradual evolution of the memristive hysteretic curve is observed upon pH variation. A sensor calibration showing a linear trend with least square error close to 1 is performed and the performance of the pH sensing is assessed. The limit of detection (LOD), limit of quantification (LOQ), and the sensitivity (S) are determined. The calculated LOD is 0.4 pH, and the LOQ is 1.2 pH. The S is calculated as 0.5 pH corresponding to a concentration of c(OH−) = 3.5 mM. The reproducibility and repeatability of the measurements are calculated as 3.8% and 1.4%, respectively. An X‐ray photoelectron spectroscopy survey allows the study of the oxide composition providing information about its pH‐sensing mechanism. It is found that the OH− species diffused into the mixed anodic oxide are responsible for the pH‐induced high‐ to low‐resistance state changes. A conduction mechanism analysis is carried out and Schottky emission is identified as predominant. [ABSTRACT FROM AUTHOR]

A metal‐rich niobium oxyiodide was prepared by soft reduction of NbI4. The structure of the new compound Nb4OI10 was determined by single‐crystal X‐ray diffraction and contains a rectangular Nb4(μ4‐O) cluster that is interconnected into layers by iodide ligands. The local structure of the Nb4OI10 cluster bears a close relationship to a defect Nb6I11 structure. The two‐dimensional van der Waals material ∞2[ ${{}_{{\rm \infty }}{}^{2}[}$ Nb4OI8I4/2] is a small band‐gap semiconductor (<1 eV), as analysed by electrical conductivity measurements, photoresponse, experimental band gap determination, and band structure calculation. [ABSTRACT FROM AUTHOR]

The recrystallization behavior of ferrite single phase in ultrahigh‐strength low‐alloy (UHSLA) steels, with different titanium concentrations (1000, 1500, and 2000 ppm) is presented. Utilizing detailed dilatometer tests, we identified disparities between the observed austenite onset temperatures and those predicted using the JMatPro 13 program and ThermoCalc. This study accentuates the combined effects of titanium, niobium, and reduced manganese levels on the initiation of the ferrite‐to‐austenite transformation. The Hall–Petch relationship was used to draw a correlation between titanium concentration, yield strength, and grain size. Moreover, we explored the recrystallization kinetics of these steels using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, pinpointing titanium's crucial role in modulating the recrystallization dynamics. These findings have significant implications for advancements in steel manufacturing, enhancing the quality and performance of UHSLA steels in industrial applications. [ABSTRACT FROM AUTHOR]

Carbonatites are the primary geological sources for rare earth elements (REEs) and niobium (Nb). This study applies machine learning techniques to generate national-scale prospectivity models and support mineral exploration targeting of Canadian carbonatite-hosted REE +/− Nb deposits. Extreme target feature label imbalance, diverse geological settings hosting these deposits throughout Canada, selecting negative labels, and issues regarding the interpretability of some machine learning models are major challenges impeding data-driven prospectivity modeling of carbonatite-hosted REE +/− Nb deposits. A multi-stage framework, exploiting global hierarchical tessellation model systems, data-space similarity measures, ensemble modeling, and Shapley additive explanations was coupled with convolutional neural networks (CNN) and random forest to meet the objectives of this work. A risk–return analysis was further implemented to assist with model interpretation and visualization. Multiple models were compared in terms of their predictive ability and their capability of reducing the search space for mineral exploration. The best-performing model, derived using a CNN that incorporates public geoscience datasets, exhibits an area under the curve for receiver operating characteristics plot of 0.96 for the testing labels, reducing the search area by 80%, while predicting all known carbonatite-hosted REE +/− Nb occurrences. The framework used in our study allows for an explicit definition of input vectors and provides a clear interpretation of outcomes generated by prospectivity models. [ABSTRACT FROM AUTHOR]

The niobium-based nanocomposite (Nb-CP), inspired by MOF-based synthesis, was developed utilizing the ligands 4-benzenedicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic acid (BTC). This material was decorated with bimetallic nanoparticles (Ni 2 /Pt 8 NPs-Nb-CP) and applied for the first time for hydrogen evolution from sodium borohydride (NaBH 4). Characterization results indicated successful synthesis. The FT-IR analysis revealed the presence of functional groups such as -C-H, –C O, and -O-H from ligands in the composite. Thermogravimetric analysis confirmed the thermal stability of the niobium composite (Nb-CP). Through X-ray diffraction (XRD), peaks associated with sodium niobate were detected. Additionally, the material was functionalized with bimetallic Ni/Pt nanoparticles, whose presence was also identified by XRD. The cubic morphology of the material was observed, with the decoration of bimetallic nanoparticles (Ni 2 /Pt 8 NPs-Nb-CP) with an average size of 7.80 ± 0.10 nm, uniformly distributed in Nb-CP. The catalytic performance of the material was evaluated in hydrogen evolution from NaBH 4. Various reaction parameters were investigated, such as nanoparticle composition, variation in NaBH 4 concentration, catalyst dose, NaOH concentration, and temperature. Remarkably, the material exhibited a hydrogen generation rate (HGR) of 1782 mL min−1 g−1 cat and an activation energy of 23.1 kJ mol−1. Furthermore, it demonstrated efficiency close to 100% over 16 consecutive reaction cycles, indicating its promising stability and reusability. This study highlights the potential of Ni 2 /Pt 8 NPs-Nb-CP as an efficient and durable catalyst for hydrogen production through borohydride hydrolysis, providing insights into the design and application of advanced heterogeneous catalytic materials. [Display omitted] • Ni/Pt nanoparticles were decorated in a novel niobium-based composite. • The material synthesis was inspired by Metal Organic Framework (MOF) synthesis. • The material was employed in NaBH 4 hydrolysis, yielding an HGR of 1782 mL min−1 g−1 cat. • H 2 evolution exhibits an activation energy of 23.1 kJ mol−1. • The material was reused in up to 16 cycles. [ABSTRACT FROM AUTHOR]

Background: Our previous study found that the addition of pentavalent cations like niobium (Nb) to yttria-stabilized zirconia increased fracture toughness but also raised the coefficient of thermal expansion (CTE), and opacity also increased undesirably. A new surface treatment is required to boost fracture toughness without altering CTE or translucency. Methods: The surfaces of pre-sintered 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 4.2 mol% yttria-stabilized partially stabilized zirconia (4.2Y-PSZ) were treated with a Nb sol solution containing Nb2O5 nanoparticles. After drying and sintering, a high-Nb-content surface layer formed with a depth of approximately 1 mm. Results: The Nb content in this surface layer matched that of a bulk material with 1 mol% Nb2O5. The tetragonality of the surface zirconia increased, enhancing the surface fracture toughness without changing the CTE or translucency. Conclusions: Adding Nb near the surface improved the fracture toughness without affecting the CTE or translucency. This method could strengthen zirconia prostheses, allowing more reliable dental restorations. [ABSTRACT FROM AUTHOR]

Niobium films are a key component in modern two-dimensional superconducting qubits, yet their contribution to the total qubit decay rate is not fully understood. The presence of different layers of materials and interfaces makes it difficult to identify the dominant loss channels in present two-dimensional qubit designs. In this paper, we present the study that directly correlates measurements of RF losses in such films to material parameters by investigating a high-power impulse magnetron sputtered (HiPIMS) film atop a three-dimensional niobium superconducting radio frequency (SRF) resonator. By using a 3D SRF structure, we are able to isolate the niobium film loss from other contributions. Our findings indicate that microwave dissipation in the HiPIMS-prepared niobium films, within the quantum regime, resembles that of record-high intrinsic quality factor of bulk niobium SRF cavities, with lifetimes extending into seconds. Microstructure and impurity level of the niobium film do not significantly affect the losses. These results set the scale of microwave losses in niobium films and show that niobium losses do not dominate the observed coherence times in present two-dimensional superconducting qubit designs, instead highlighting the dominant role of the dielectric oxide in limiting the performance. We can also set a bound for when niobium film losses will become a limitation for qubit lifetimes. [ABSTRACT FROM AUTHOR]

[Display omitted] Inversion symmetry broken 3R phase transition metal dichalcogenides (TMDs) show fascinating prospects in spintronics, valleytronics, and nonlinear optics. However, the controlled synthesis of 3R phase TMDs is still a great challenge. In this work, two-dimensional 3R-NbSe 2 single crystals up to 0.2 mm were synthesized for the first time through chemical vapor deposition method by designing a space-confined system. The crystal size and morphology can be controlled by the location of the stacked substrates and the amount of the Nb 2 O 5 precursor. Scanning transmission electron microscopy and Raman measurements reveal the NbSe 2 exhibits a pure 3R stacking mode with relatively weak interlayer van der Waals interactions. Importantly, 3R-NbSe 2 shows obvious second harmonic generation signal which intensity intensified as thickness increases. Density functional theory calculations and optical absorption demonstrate the coexistence of metallic and semiconducting optical properties of 3R-NbSe 2. We designed a NbSe 2 /WS 2 /NbSe 2 photodetector utilizing the metallicity of 3R-NbSe 2 , which shows good performance especially an ultrafast response (6–7 μs, 0.5 ms − 7.9 s for Au electrodes in literature). The proposed strategy and findings are of great significance for the growth of many other 3R-TMDs and applications of nonlinear optical and ultrafast devices. [ABSTRACT FROM AUTHOR]

The integration of niobium (Nb) into emerging superconducting circuits can enhance their performance and function. However, growth of high purity Nb can be challenging due to its high reactivity with oxygen. Here, we examine the role of residual oxygen inside the growth chamber in transforming the structural, chemical, and superconducting properties of Nb films. We demonstrate that an increase in unintentional oxygen impurities lowers the superconducting critical temperature of Nb. This evolution coincides with the reduction of Nb crystal domains, which are separated by highly disordered oxygen-rich regions. Moreover, chemical analysis reveals the formation of niobium monoxide within the film during growth. These findings provide a comprehensive picture of how residual oxygen in the growth chamber can affect the properties of the Nb films. This study contributes to the materials science and engineering knowledge of superconducting Nb growth. [ABSTRACT FROM AUTHOR]

Recently, the inverted CsPbI3 perovskite solar cells (PSCs) have attracted extensive attentions due to their potential to combine with silicon solar cells for tandem devices with theoretical power conversion efficiency (PCE) of 44%. However, the reported self‐assembled molecules (SAMs) as hole selected layer for inverted PSCs have poor wettability and serious agglomeration, which greatly limits the efficiency and stability of PSCs. To address above problem, niobium pentachloride (NCL) is applied to prevent SAMs agglomeration for a homogenous SAMs film with a hydrophilic surface. The optimized SAMs surface facilitates the deposition of the cesium lead triiodide (CsPbI3)film with an enhanced referred orientation, suppressed defects, and released stress. Consequently, the NCL‐treated CsPbI3 PSCs achieved a champion PCE of 21.24%, which is the highest PCE value for inverted all‐inorganic PSCs. The optimized device maintained 97.61% initial PCE after 1000 h storage in air, and 92.27% initial PCE after 1000 h tracking at the maximum power point (MPP). [ABSTRACT FROM AUTHOR]

Bioactive glasses are renowned for their applications in dentistry, serving as restorative materials, dental adhesives, intracanal medicaments, and agents for enamel remineralization. Niobium pentoxide (Nb 2 O 5) is employed in dental adhesive resins and orthodontic adhesives, offering radio-pacifying properties essential for dental materials. Samarium oxide (Sm 2 O 3) emerges as a potential additive in aesthetic restorative dental ceramics and resins, enhancing the natural fluorescence of teeth. In this study Nb 2 O 5 and Sm 2 O 3 -doped (1, 3, and 5 wt%) 13–93 bioactive glass particles were synthesized via the sol-gel method, tailored for dental implementations. We conducted a comprehensive analysis of the physical, structural, and optical properties of the resultant glass powders. Additionally, their in vitro bioactivity and ionizing radiation shielding characteristics were rigorously evaluated. The results indicate that Sm3+ ions preserve the amorphous nature of the silicate glasses, while Nb5+ incorporation leads to the crystallization of the T-Nb 2 O 5 phase. Bioactivity assays across three physiological fluids—simulated body fluid, α-minimum essential medium, and phosphate-buffered saline, demonstrated the ability of doped glasses to facilitate hydroxyapatite layer formation, with the most pronounced bioactivity observed in phosphate-buffered saline immersed samples. Furthermore, radiation shielding simulations reveal that the addition of Nb 2 O 5 and Sm 2 O 3 enhances the ionizing radiation attenuation capabilities of the glasses, a property that holds significant promise for protecting against radiation in dental radiology. It can be concluded that the dual functionality of Nb5+ and Sm3+-doped bioactive glasses, which may revolutionize restorative dental practices and offer improved protection in radiological applications. [ABSTRACT FROM AUTHOR]

Na0.44MnO2 with tunnel structure is considered a promising low‐cost cathode material for sodium‐ion batteries. However, the sluggish Na+ transport kinetics and low initial Coulombic efficiency restrict its practical applications in rechargeable sodium‐ion batteries. Herein, a manganese‐based tunnel‐structured cathode with high rate capability and high initial Coulombic efficiency is prepared by niobium doping and sodium compensation. Via materials characterizations and theoretical calculations, it is demonstrated that a proper amount of niobium doping in tunnel structure can effectively improve its structural stability and charge transport kinetics, resulting in outstanding rate capability (76.6% capacity retained from 0.5 to 30 C) and superior cycling performance (82.3% capacity retention after 800 cycles at 5 C) for the optimized Nb‐doped Na0.44MnO2 cathode (Na0.44Mn0.98Nb0.02O2). Furthermore, NaCrO2 is added into the Na0.44Mn0.98Nb0.02O2 cathode as a self‐sacrificing sodium compensation additive, and a high initial Coulombic efficiency close to 100% is achieved for the composite cathode. This work establishes a facile strategy to design advanced manganese‐based cathode materials for large‐scale energy storage applications. [ABSTRACT FROM AUTHOR]

Presently, the main trend in thin-sheet steel production, including the high-strength automobile steel, is to reduce production costs while retaining essential properties and quality. A considerable part of the cost of high-strength steel comes from alloying with expensive chemical elements such as vanadium and niobium. Simply reducing the content of these elements in finished products would compromise the mechanical properties of rolled products, leading to inferior quality and defects. This work, based on statistical analysis for steel grade S355MC, demonstrated the potential to reduce alloying while maintaining the required yield strength by adjusting the hot rolling conditions. It was also revealed that, in addition to the concentration of chemical elements and the hot rolling mode, the thickness of the finished product affects the tensile strength. Therefore, the analysis was performed exclusively on products with a thickness of 4 mm. The study resulted in a regression equation that illustrates the dependence of yield strength on vanadium content and hot rolling parameters. [ABSTRACT FROM AUTHOR]

The paper presents the results of processing niobium-containing fluoride cinders to obtain niobium concentrate from them. The material composition of the cinder was studied by chemical and X-ray methods. X-ray phase analysis showed the presence of ammonium aluminium fluoride, ammonium iron fluoride, ammonium titanium fluoride, as well as niobium-containing sodium niobium fluoride. Leaching of the fluoride cinder was carried out with ammonia water at temperatures of 60 - 80°C until a precipitate was formed at pH = 9 with vigorous stirring at 300 rpm, for 90 min. Nitric acid purification of the sludge was performed with a nitric acid solution within 4 - 10 %, at 60°C, with a S:L ratio of 1:5 and an agitation time of 120 min. 8 % HNO3 was chosen as the optimum concentration of nitric acid. After washing the obtained cake was calcined at 500°C for 120 min. The niobium concentrate containing 57.5 % Nb2O5 was obtained according to the study results. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Powder metallurgy was used to create porous TiMoCuAgV HEA (VHEA) and TiMoCuAgNb HEA (NbHEA) using 0, 10, and 20 wt.% from ammonium hydrogen carbonates (AHCs) as a space holding material. Samples were mixed with AHCs as a foaming agent. All samples were compacted at 400 MPa and sintered at 1250oC. X-ray diffraction, scanning electron microscopy, and energy dispersive analyses were performed for phase identification, microstructure observation, and elemental composition, respectively. Fabricated HEAs density values were estimated according to Archimedes' principle. Also, hardness and Young's modulus were determined. The addition of vanadium (V) was shown to exceed that of niobium (Nb) in increasing the HEA Young's modulus without AHCs. The corrosion characteristics of the prepared HEAs in corrosive media were estimated by the weight loss (WL) method, indicating good improvement by adding either V or Nb. The findings showed that the 10-NbHEAs in SBF had the highest improvement values, where the CR value was 0.94 mm/y lower than other investigated media. Additionally, 10-VHEAs in a simulated body fluid solution (SBF) and hydroxyapatite (HA) corroded more rapidly than 10-NbHEAs. After the corrosion test, the surface morphology showed a protective layer for 10-NbHEAs in SBF media. Also, the surface morphology is well-defined as smooth and uniform in HA media for 10-NbHEAs and 20-NbHEAs, which agrees with WL and corrosion rate values. Generally, VHEAs have higher corrosion resistance than NbHEAs. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Pekinensis is the property of Editorial Office of Acta Scientiarum Naturalium Universitatis Pekinensis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A structural crossover from non-ergodic to ergodic phase in niobium doped (Na0.41K0.09Bi0.5)TiO3, i.e., (Na0.41K0.09Bi0.50)1−x/2(Ti1−xNbx)O3 was investigated using high resolution x-ray diffraction and Raman spectroscopy. The diffraction studies reveal the co-existence of cubic (Pm3m), rhombohedral (R3c), and tetragonal (P4bm) phases for lower concentrations of niobium, i.e., for x ≤ 0.005 and the emergence of the pseudo-cubic (Pm3m) structure for higher niobium contents (for x ≥ 0.0075). On the other hand, Raman spectroscopy reveals the augmentation of the tetragonal phase with niobium content. These observations advocate the crossover from the non-ergodic to ergodic phase with niobium content. The presence of the pseudo-cubic phase (Pm3m), especially for x ≥ 0.0075, does not indicate the existence of the long-range cubic phase; rather, it models the contribution of nano-regions with the tetragonal symmetry as indicated in the Raman measurements. It further suggests that, with the incorporation of niobium, the size polar nano-regions diminish that leads to the crossover from the non-ergodic to ergodic phase. [ABSTRACT FROM AUTHOR]

A structural crossover from non-ergodic to ergodic phase in niobium doped (Na0.41K0.09Bi0.5)TiO3, i.e., (Na0.41K0.09Bi0.50)1−x/2(Ti1−xNbx)O3 was investigated using high resolution x-ray diffraction and Raman spectroscopy. The diffraction studies reveal the co-existence of cubic (Pm3m), rhombohedral (R3c), and tetragonal (P4bm) phases for lower concentrations of niobium, i.e., for x ≤ 0.005 and the emergence of the pseudo-cubic (Pm3m) structure for higher niobium contents (for x ≥ 0.0075). On the other hand, Raman spectroscopy reveals the augmentation of the tetragonal phase with niobium content. These observations advocate the crossover from the non-ergodic to ergodic phase with niobium content. The presence of the pseudo-cubic phase (Pm3m), especially for x ≥ 0.0075, does not indicate the existence of the long-range cubic phase; rather, it models the contribution of nano-regions with the tetragonal symmetry as indicated in the Raman measurements. It further suggests that, with the incorporation of niobium, the size polar nano-regions diminish that leads to the crossover from the non-ergodic to ergodic phase. [ABSTRACT FROM AUTHOR]

The conventional theory of superconductivity holds that Cooper pairs form due to electron–phonon coupling; however, this description may not be adequate to describe certain unconventional superconductors such as cuprates and iron chalcogenides. In these unconventional superconductors, it has been proposed that spin fluctuations may be responsible for the formation of Cooper pairs. In this study, we explore spin interactions in the transition metal, dichalcogenide niobium disulfide, induced through proximity effects by fabricating antiferromagnet/NbS2 heterostructures. We tested three different 2D antiferromagnetic materials, each with different spin textures: anganese phosphorus trisulfide, manganese phosphorus triselenide, and chromium trichloride. Our results showed a substantial reduction in the critical temperature in the case of NbS2/MnPSe3. We hypothesize that this could be due to spin fluctuations in MnPSe3 inducing proximity effects in NbS2. [ABSTRACT FROM AUTHOR]

In the temperature range of (823–1023) K, we investigated the permeation behavior of deuterium in niobium under a pressure of (1–20) kPa and observed gradual changes in permeability and diffusivity during the permeation cycles. Notably, as the permeation cycles increased, the permeability curve exhibited an abnormal-to-normal transformation phenomenon. Increasing deuterium pressure at this stage could restore the permeability to its abnormal state. By comparing the permeation cycles of niobium foils with different oxidation degrees at 1023 K, we found that surface oxide thickness did not affect the abnormal phenomenon but reduced the diffusion coefficient of deuterium during initial permeation. Additionally, we observed that the permeation flux was proportional to the square root of pressure, indicating that diffusion still controlled permeation. After the deuterium loading, the abnormal phenomenon of the 1st permeation disappeared, and the diffusivity of deuterium in niobium decreased. The results suggested that the abnormal phenomena in 1st permeation were primarily caused by the irreversible defects resulting from the interaction between niobium and deuterium in the bulk phase and were not related to the surface effect. The pressure, concentration, and temperature of deuterium in the bulk phase accelerated the interaction between niobium and deuterium and promoted the transition of deuterium in niobium to abnormal permeation. These research findings hold significant implications for the application of niobium as a hydrogen isotope separation and purification material. [ABSTRACT FROM AUTHOR]

This article presents the results of a study on composite coatings based on high-entropy FeCoNiCrCuNb alloys with varying niobium content obtained through high-speed laser cladding. The primary objective of the research is to investigate the influence of composition on the structure, mechanical characteristics, and behaviour of the coatings. Microstructure analyses were performed using scanning electron microscopy and energy-dispersive spectroscopy analysis. The microhardness, shear strength, and coefficient of friction of the composite coatings were examined. It was demonstrated that the microstructure of the coatings is characterized by fine grains and the presence of columnar crystals. An increase in copper content leads to a transition to the face-centred cubic phase with elevated niobium content, influencing the mechanical characteristics. It was revealed that niobium-containing composite coatings exhibit improved mechanical properties and wear resistance. The incorporation of niobium synergistically affects the mechanical characteristics of the alloys. The obtained results hold practical applicability in the field of engineering, particularly where wear resistance and strength are of paramount importance.

This is an article in the field of mineral analysis and testing. A rapid method for the simultaneous determination of Nb, Ta, Li and Be in Nb Ta ore by alkali fusion inductively coupled plasma mass spectrometry was established. The mixed alkali of sodium peroxide and sodium hydroxide=1:1 is used to decompose the sample. During extraction, niobium, tantalum and other elements are completely precipitated and separated from the liquid. The content of niobium, tantalum, lithium and beryllium in the sample is determined by inductively coupled plasma mass spectrometer after conversion and precipitation with 25 mL of 10% sulfuric acid+10% hydrogen peroxide solution. This method is used to determine the national first-class reference materials GBW 07153, GBW 07155 and GBW 07185. The measured values of each element are basically consistent with the certified values, with a relative error of 0.50%～4.77% and a relative standard deviation (n=6) of -0.009%～0.008%. It is applicable to the determination of niobium and tantalum in niobium tantalum concentrates, refractory or complex samples, and has been applied in production practice.

Wettability is recognized as an important property of implant surfaces for ensuring improved biological responses. However, limited information exists on how bone grafting procedures including materials influence the hydrophilic behavior of implant surfaces. This in vitro study aimed to investigate the influence of two bovine grafting materials after hydration on the wettability of four different disk surfaces: commercially pure titanium (CP-Ti), titanium–zirconium dioxide (TiZrO2-Cerid®), zirconia (SDS®), and niobium. Wettability tests were performed on each of the four implant surfaces with a solution of 0.9% sodium chloride after mixture with W-boneTM (Group A) or Bio-Oss® (Group B) or 0.9% sodium chloride alone (Group C). In total, 360 contact angle measurements were completed with n = 30 per group. Statistical analysis was performed using a one-way analysis with variance (ANOVA) test with a significant mean difference at the 0.05 level. For pure titanium, Group A demonstrated increased hydrophilicity compared to Group B. Both TiZrO2 and zirconia showed significant differences for Groups A, B and C, exhibiting a decrease in hydrophilicity after the use of bovine grafting materials compared to titanium surfaces. Niobium remained consistently hydrophobic. In summary, this study revealed that bovine grafting materials may diminish the hydrophilicity of zirconia surfaces and exert varied effects on titanium and niobium. These findings contribute to the understanding of implant surface interactions with grafting materials, offering insights for optimizing biological responses in implantology. [ABSTRACT FROM AUTHOR]

The nitrogen doping (N‐doping) treatment for niobium superconducting radio‐frequency (SRF) cavities is one of the key enabling technologies that support the development of more efficient future large accelerators. However, the N‐doping results have diverged due to a complex chemical profile under the nitrogen‐doped surface. Particularly, under industrial‐scale production conditions, it is difficult to understand the underlying mechanism thus hindering performance improvement. Herein, a combination of spatially resolved and surface‐sensitive approaches is employed to establish the detailed near‐surface phase composition of thermally processed niobium. The results show that intermediate phase segregations, particularly the nanometric carbon‐rich phase, can impede the nitridation process and limit the interactions between nitrogen and the niobium sub‐surface. In comparison, the removal of the carbon‐rich layer at the Nb surface leads to enhanced nitrogen binding at the Nb surface. Combining the RF test results, it is shown that the complex uniformity and grain boundary penetrations of impurity elements have a direct correlation with the mid‐field quench behavior in the N‐doped Nb cavities. Therefore, proper control of the nanometric intermediate phase formation in discrete thermal steps is critical in improving the ultimate performance and production yield of the Nb cavities. [ABSTRACT FROM AUTHOR]

The phase transformation and nucleation growth behavior of niobium mineral phase in Bayan Obo mine under high temperature melting state were studied. The effects of different temperature mechanism, basicity (CaO/SiO2) and slag modifiers such as NaF, CaF2 and P2 Os on phase transformation and nucleation growth were emphatically investigated. The results show that the melting temperature above 1 400 °C and the crystallization temperature below 1 300 °C are the key to the phase conversion of high grade niobium ore. Control alkalinity between 1. 0 and 1. 3 is beneficial to the formation of single high grade niobium phase and the growth of grain. The addition of about 2% NaF or 2% 一 5 % CaF2 can improve the grade of Nb2O5 and grain coarsening of niobium rich phase. Although P2O5 is conducive to the transformation of niobium into a single high grade niobium mineral phase, excessive P2O5 will lead to sharp refinement of niobium phase grains. [ABSTRACT FROM AUTHOR]

Copper/diamond composite materials prepared via powder metallurgy were used to study the influence of different contents of the active element Nb on the modification mechanism of the copper interface and the thermal conductivity of the copper/diamond compositematerial were characterized by XRD,SEM, EDS, and thermal conductivity coefficient tester. The results showed that with the addition of Nb content, a carbide interface layer could be formed during the sintering process, and the defects at the interface between copper and diamond gradually decreased, and the interface bonding gradually improved. When the content was 1 %, the thermal conductivity of the composite material reached 370. 3 W/(m ♦ K), which was 1. 34 times higher than that of the pure copper/diamond composite material However, when the content exceeded 1 %, the thickness of the niobium carbide intermediate layer increased. Due to the low thermal conductivity of niobium carbide itself, the thermal conductivity of the composite material decreased. [ABSTRACT FROM AUTHOR]

Water pollution has emerged as a significant worldwide issue, with organic pollutants being a key contributor. Titanium dioxide (TiO2) has demonstrated promising photocatalytic performance in removing organic pollutants under ultraviolet (UV) irradiation. However, the wide band gap (3.2 eV) of TiO2 results in low absorption capacity of visible light, hindering its overall efficiency in degrading organic pollutants. To address the limitation, this research aimed to synthesize visible light-driven TiO2 photocatalyst with different polymorphs (anatase and rutile) and investigate the effect of various doping combination (Nb, B and Nb,B) and concentrations (0.25, 0.50, 0.75 and 1.00 mol%) on the photodegradation efficiency towards methylene blue (MB) dye solution. Anatase phase was obtained when TiO2-based nanopowders were calcined at 400 °C, while the rutile phase was formed at 900 °C based on XRD analyses. Additionally, the morphology analyses revealed that the particle size of anatase is much smaller than that of rutile. The presence of dopants further reduced the particle size of both anatase and rutile phases. Based on UV-Vis absorbance spectra analyses, the anatase Nb,B-TiO2 with 0.50 mol% of dopant concentration exhibited the best photocatalytic performance towards MB. Moreover, the anatse phase of 0.50 mol% Nb,B-TiO2 showed the narrowest band gap of 2.74 eV compared to the TiO2 (3.4 eV), representing a reduction of 19.41 %, according to UV-Vis analyses. These outcomes suggest the potential application of anatase phase of 0.50 mol% Nb,B-TiO2 in treating organic pollutants in wastewater under visible light conditions in future. [ABSTRACT FROM AUTHOR]

The strategy of carbon neutrality is reshaping the global landscape of resource flow and recycling. As the final sink of geological minerals, the proliferated anthropogenic minerals, also called secondary resources, play an increasingly important role in resource supply enrichment. Niobium is a critical metal that lacks full concern for its sustainability. The fundamental principle of niobium circularity is to recycle and maintain the material as close to the manufacturing process as possible. Here we estimate the niobium-containing applications lost at their end-of-life, underscoring the imperative to minimize such disposal. Additionally, we elucidate the extraction processes for scrap and alloy quantities throughout the industry's lifecycle. Drawing from anticipated waste generated by the majority of niobium applications, a forecast indicates a potential loss of approximately 168 kt by 2090 in the absence of recycling. Contrastingly, with a recycling efficiency of 90% for niobium, the projected loss diminishes to approximately 16 kt. We delve into the significance of niobium's circular economy and explore various aspects that demand further investigation for a seamless transition from linear to circular practices. [ABSTRACT FROM AUTHOR]

A high‐performance aluminum‐ion supercapacitor is fabricated using 2D few‐layered Nb2CTx MXene, as an active electrode material and Al2(SO4)3 electrolyte for efficient energy storage. Nb2CTx MXene has been synthesized from Nb2AlC MAX phase using HF. Nb2CTx MXene coated on carbon cloth (Nb@CC) displays a capacitance of 307 F g−1 with 90% coulombic efficiency. The specific capacitance of Nb@CC in Al2(SO4)3 electrolyte is exceptionally high compared to those (≤32.2 F g−1) in H2SO4, Na2SO4, and MgSO4 electrolytes. Both symmetric and asymmetric aluminum ion supercapacitors are fabricated with Nb@CC electrode. The Nb@CC//Nb@CC symmetric device exhibits a capacitance of 122 F g−1 with a high energy density (Ed) of 33.2 Wh kg−1 at 1.41 kW kg−1 power density (Pd). An asymmetric supercapacitor device (ASC), Nb@CC//CNT@CC, with carbon nanotube (CNT@CC) cathode delivers a maximum Ed of 24.7 Wh kg−1 at 3.41 kW kg−1 Pd and excellent stability with 90% capacitance retention after 4000 cycles. A remarkably high Pd of 34 kW kg−1 is maintained with 13.2 Wh kg−1 Ed, and the rate capability is 53% for a 10‐fold increase in current density. These results offer the feasibility of efficient aqueous supercapacitors with Al‐ion as guest species, presenting new possibilities for supercapacitors. [ABSTRACT FROM AUTHOR]

The conventional practice of heat-resistant nickel-alloys' brazing involves the utilization of industrial Ni-Cr-(B, Si)-based filler metals. However, employing filler metals within this system results in the formation of brittle compounds, specifically, silicides and borides of nickel, chromium, and other elements. These brittle phases have the potential to diminish the mechanical characteristics of brazed assemblies. This study investigates the feasibility of developing multicomponent high-entropy filler metals for brazing Nibased alloys (specifically, heat-resistant ones) without including boron and silicon in their composition. Utilizing computational methods and the updated Hume-Rothery rules, we identified a promising NiCoCrAl-(Ti, Nb) system. Various thermodynamic parameters are computed, and corresponding dependences on the alloying-components' content are established. The alloying limits of experimental alloys are determined, aligning with the criteria established for high-entropy alloys (HEA). Melting temperatures are calculated, and the liquidus-surface area of the NiCoCrAl-(Ti, Nb) system is delineated. Based on the research findings, it is determined that this alloy possesses a dendritic structure with some amount of eutectic component, and its melting temperature below 1220°C makes it suitable for brazing heatresistant nickel alloys. [ABSTRACT FROM AUTHOR]

Nb has the highest superconducting transition temperature among elemental materials, which makes it a realistic choice for superconducting junctions. However, self-organized oxide structures on its surface impede the preparation of well-defined interface. Once the oxide structure is clarified, this oxidized surface may be used as an interface. Atomic force microscopy can distinguish different elements among ionic crystals depending on the charge state of the scanning probes. We applied this method to the oxide surfaces of Nb(110) for structural analysis and observed Nb and O atoms independently as well as simultaneously. A structural model was constructed based on the density functional theory. Additionally, the density of states and the Bader charge were analyzed. [ABSTRACT FROM AUTHOR]

Press-hardened steel (PHS) with a tensile strength of 1.8 GPa exhibits significant potential for lightweight applications in automobile industry. Nevertheless, H embrittlement (HE) remains a serious concern in the practical applications of PHS. Nb alloying can improve the HE property of PHS by introducing extensive nanosized niobium carbides (10–20 nm in diameter), which are irreversible H traps in the steel matrix, into PHS. Interestingly, herein, we discovered that even without the formation of a large amount of nanosized niobium carbides, Nb alloying was beneficial for improving the HE property of a 1.8 GPa press-hardened PHS. The addition of Nb to this PHS resulted in complex submicron-sized (Nb,Ti)(C,N) precipitates rather than nanosized NbC precipitates. These submicron-sized (Nb,Ti)(C,N) precipitates effectively refined the prior austenite grain (PAG) size, leading to a higher density of low-angle grain boundaries, which reduced the H diffusion rate and also acted as H traps. Consequently, the average amount of H at the PAG boundary was substantially low, thereby improving the resistance to HE. [ABSTRACT FROM AUTHOR]

This study aims to develop of a novel electrochemical method for the detection of the antiviral drug favipiravir (FAV). For this purpose, a sensitive electrochemical sensor with niobium (Nb) nanoparticles supported on zirconium oxide‐carbon nanotubes (ZrO2‐(CNT)MW) was constructed on a glassy carbon electrode (GCE). The proposed electrochemical sensor (Nb@ZrO2‐(CNT)MW/GCE) exhibited excellent repeatability, high stability and high sensitivity for FAV owing to the impact of Nb on ZrO2‐(CNT)MW composite. The oxidation potential (Ep) of FAV was occurred at 1.2 V, 1.12 V, 1.03 V and 1 V at GCE, (CNT)MW/GCE, ZrO2‐(CNT)MW/GCE and Nb@ZrO2‐(CNT)MW/GCE, respectively. Interestlingly, the gradual shift clearly indicates that Nb@ZrO2‐(CNT)MW/GCE can exhibit high catalytic activity towards FAV. The proposed electrode has also good selectivity towards FAV. The Nb@ZrO2‐(CNT)MW/GCE system exhibited a linear working range of 5 nM–300 nM with a limit of detection (LOD) of 1.8 nM (based on 3sb/m) for FAV. The Nb@ZrO2‐(CNT)MW/GCE system was successfully applied for the detection of FAV in pharmaceuticals and biological fluids. The experimental results demonstrated that Nb@ZrO2‐(CNT)MW/GCE can be an ideal sensing platform for the sensitive detection of FAV. [ABSTRACT FROM AUTHOR]

Airbridges are extensively employed in superconducting quantum circuits to suppress parasitic slotline modes in coplanar waveguide and minimize crosstalk between control lines. Here, we introduce a fabrication technique for airbridges, leveraging niobium as the bridge layer and aluminum as the sacrificial layer to preclude the introduction of lossy dielectrics or residues upon release. Additionally, we utilize a triangular evaporation method to significantly bolster the structural integrity of the airbridges. Our experimental evaluation, focused on resonators equipped with these airbridges, reveals that the resultant additional loss per bridge is minimal, quantified at (5.0 ± 2.8) × 10 − 9 in the single-photon regime and (6.3 ± 0.9) × 10 − 9 at high drive powers. This advancement underscores the potential of niobium airbridges in facilitating the development of large-scale and high-performance superconducting quantum circuits. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) stands out as one of the most extensively studied electrocatalytic reactions in literature. Herein, niobium has been tested for the first time for the catalysis of the HER in the form of nanometer-thick-films. The deposition of 5, 10, and 50 nm-thick Nb thin films onto both smooth and porous silicon substrates, the latter ones with mesopores with mean diameters of 13 nm and 7 nm, respectively, has been successfully achieved using magnetron sputtering, a highly precise and controllable technique allowing a very efficient deposition of Nb films. After the sputtering deposition, the samples were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) analyses which confirmed the purity and uniformity of the Nb coating on all samples. Electrochemical tests revealed top-notch performance, with almost negligible onset potentials (es. 80 mV vs. RHE) and low Tafel slopes (es. 30 mV/dec), thereby paving the way for the future development of cutting-edge devices. • Niobium tested for the first time towards HER in the form of nanometer-thick-films. • Deposition of 5, 10, and 50 nm-thick Nb films on smooth and porous Si substrates. • Highly precise efficient and controllable deposition through magnetron sputtering. • Negligible overpotentials and low Tafel slopes. • Paving the way for H 2 production in a single, integrated Si-based device. [ABSTRACT FROM AUTHOR]

The effect of niobium modification on refinement of primary austenite, shrinkage characteristic, and solidification behavior of medium-carbon cast steel melted in a medium-frequency induction furnace is studied. It is established that the modification with 0.1 wt.% niobium increases the fluidity of the steel liquid, enhances the feeding capacity of the cast steel, turns the dispersed shrinkage porosity into concentrated shrinkage cavity, changes the coarse dendrites to fine ones, even in equiaxed grain structures, and dwindles the primary austenite grain size greatly. Using electron microscopy and energy-dispersive analysis, it is discovered that niobium combines with carbon to form solid phase particles of NbC. These particles are chemically stable at high melting temperatures and facilitate the primary austenite nucleation effectively by non-spontaneous nucleating. A model of matching between the crystal lattices γ-Fe and NbC is suggested. The mechanism of NbC heterogeneous nucleation consists in that the primary austenite grows on {111}γ-Fe along to the closest-packed plane {111}NbC in crystal orientation ⟨ 011 ⟩ γ - Fe ‖ ⟨ 112 ⟩ NbC , and the mismatch δ ⟨ 111 ⟩ NbC ⟨ 111 ⟩ γ - Fe of the crystal planes is only 9.79%. [ABSTRACT FROM AUTHOR]

The behavior of reaction powder mixtures of stoichiometric compositions calculated for the synthesis of higher niobium nitride and silicide in the temperature range 800–1400°С in vacuum according to the reactions 4Nb + Si3N4 and 3Nb + 2Si3N4, respectively, has been investigated. The decomposition of Si3N4 is accompanied by the formation of lower nitride and lower silicide phases of niobium. The content of the silicide phase increases with heat treatment temperature, and, at 1400°С, NbSi2 forms. The nitride phase remains practically unchanged up to 1300°С and disappears at 1400°С. On the basis of the established regularities, we have developed synthesis methods for Si3N4–NbN and Si3N4–NbSi2 powders, which include the introduction of excess Si3N4 with respect to the stoichiometric composition. The combined two‐stage technological cycle of synthesis of Si3N4–NbN involves vacuum annealing at 1000°С and subsequent nitriding at 1300°С. The synthesis method for NbSi2–Si3N4 assumes the in situ successive formation of niobium silicide phases up to 1400°С. The synthesized Si3N4–15NbN and NbSi2–14Si3N4 powders consist of multiphase agglomerates with a mean size of 5.5 and 8.8 µm, respectively, and a nanodisperse fraction with a mean particle size of 200 nm. [ABSTRACT FROM AUTHOR]

Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon steel, specifically A333 Grade 6, in a naphthenic acid solution. Various weight percentages of niobium were incorporated, and the resulting properties were observed. It was noted that the addition of 2% niobium in low-carbon steel exhibited the least mass loss and a lower corrosion rate after a 12 h immersion in naphthenic acid. Microstructural analysis using scanning electron microscopy (SEM) revealed small white particles, indicating the presence of oil sediment residue, along with corrosion pits. Following the addition of 2% niobium, the occurrence of corrosion pits markedly decreased, and only minor voids were observed. Additionally, the chemical composition analysis using energy-dispersive X-Ray analysis (EDX) showed that the black spot exhibited the highest percentage of carbon, resembling high corrosion attack. Meanwhile, the whitish regions with low carbon content indicated the lowest corrosion attack. The results demonstrated that the addition of 2% niobium yielded optimal properties for justifying corrosion effects. Therefore, low-carbon steel with a 2% niobium addition can be regarded as a superior corrosion-resistant material for offshore platform pipeline applications. [ABSTRACT FROM AUTHOR]

This paper systematically investigates the structure, stability, and electronic properties of niobium carbide clusters, NbmCn (m = 5, 6; n = 1–7), using density functional theory. Nb5C2 and Nb5C6 possess higher dissociation energies and second-order difference energies, indicating that they have higher thermodynamic stability. Moreover, ab initio molecular dynamics (AIMD) simulations are used to demonstrate the thermal stability of these structures. The analysis of the density of states indicates that the molecular orbitals of NbmCn (m = 5, 6; n = 1–7) are primarily contributed by niobium atoms, with carbon atoms having a smaller contribution. The composition of the frontier molecular orbitals reveals that niobium atoms contribute approximately 73.1% to 99.8% to NbmCn clusters, while carbon atoms contribute about 0.2% to 26.9%. [ABSTRACT FROM AUTHOR]

This article investigates the influence of niobium addition on the microstructure and properties of Ni–Cr cast iron. In situ observations and analysis of phase precipitation during solidification are conducted through a high‐temperature laser scanning confocal microscope and Thermo‐Calc software. The refining mechanism of the microstructure and the enhancement of wear resistance by NbC are explored. The results indicate that with an increase in Nb content, the precipitation temperature of NbC particles gradually rises. When the niobium content exceeds 0.2%, NbC becomes the first precipitated phase during the solidification of the liquid phase. NbC particles can serve as heterogeneous nucleus for austenite, refining the grain structure of Ni–Cr cast iron. The existence of NbC particles within the grain impedes the elongation of martensite and bainite bundles while providing additional nucleation sites to accelerate the phase transformation. The grain refinement and the obstructive influence of NbC particles collectively induce a more disordered bainitic structure. Moreover, the exceptional hardness of NbC particles effectively safeguards the matrix from abrasion, consequently enhancing the wear resistance of Ni–Cr cast iron. [ABSTRACT FROM AUTHOR]

The extraction of 1.09 × 10−2 Zr(IV) and 1.07 × 10−3 Nb(V) from their admixture solution was done using a phosphonic acid derivative (Ionquest 801 = IQ-801/kerosene). The calculated extraction constants for Zr(IV) and Nb(V) were found to be 17.1 × 103 M−3 and 1.1 × 103 M−1, respectively. The suggested extraction conditions were found to be (time =15–30 min, Organic: Aqueous ratio = 1, [HNO3] = 3 M, [IQ-801] = 0.015–0.02, and T = 25 ± 1. The calculated loading capacities per mole of IQ-801 were found to be 0.8 moles of Zr(IV) and 9 × 10−2 moles of Nb(V). According to McCabe-Thiele diagrams, 0.02 M IQ-801 can completely extract 1 × 10−2 M Zr(IV) and 1 × 10−3 M Nb(V) in just 2 stages. In the stripping process, about 99% Zr(IV) was stripped by stripping precipitation with 0.1 M oxalic acid and 1 M NaF, which also provides the best conditions for the separation of Nb(V) from Zr(IV). The highest separation was obtained using citric acid concentrations ranging from 0.25 to 4 M, oxalic acid concentrations ranging from 0.05 to 1 M, and sulfuric acid concentrations ranging from 1.5 to 3 M. A flow chart outlining the proposed technique steps for separating Zr(IV) and Nb(V) from an HNO3 solution using IQ-801 was suggested. [ABSTRACT FROM AUTHOR]

The article presents the estimation of temperature and emissivities of niobium and 100c6 steel around their melting points using techniques based on the minimization of the least squares norm or on Bayesian inference. Two models were considered for the spectral emissivity, including a linear variation with respect to the wavelength and independent spectral values. The measured data used for the solution of the parameter estimation problem were radiative fluxes collected from a five-wavelength pyrometer. The experimental apparatus used in this work was designed for the characterization of metal samples with sizes of few millimeters at high temperatures, combining aerodynamic levitation and laser heating. The use of the linear spectral emissivity model provided quite consistent results with the ordinary least squares estimator and with stochastic simulations using the Metropolis-Hastings algorithm. Similarly, the model of independent spectral emissivities resulted in accurate emissivities, but it required an informative prior for temperature, such as the known melting point of the metal sample. Therefore, whatever the inverse method used, a priori supplementary information in terms of emissivities or temperatures are needed due to the temperature-emissivity correlation and the unknow emissivity behavior. [ABSTRACT FROM AUTHOR]