Niobium Diboride Research Articles

Production and evaluation of the polyester composites containing pyrite and niobium diboride for radiation protection

The presented study focused on investigating the radiation shielding properties of polyester/pyrite/niobium diboride (FeSNbB) composites. Various gamma-ray shielding parameters were evaluated with help of a HPGe detector system. Theoretical and simulation results are further evaluated by WinXCOM, GEANT4 and FLUKA codes, and the obtained results are compared with experimental values in the energy region 59.5 keV–1332.5 keV. The prepared samples are additionally evaluated using kerma relative to air values and Exposure build-up factors. Then, for the evaluation of neutron radiation shielding, effective removal cross sections for fast neutrons were determined for FeSNbB composites. Electron attenuation efficiency (AE%) for the produced composites was assessed across the energy spectrum of 4 MeV–18 MeV, utilizing experimental data from a Linac machine and theoretical predictions from Eclipse TPS. The results were found to be compatible with each other. FeSNbB50 has the best shielding properties among the studied composites.

A preparation of niobium diboride (NbB2) via molten salt method: Impact of boron concentration on the structural and electrochemical performance

In this work, niobium diboride (NbB2) nanoparticles were successfully synthesized using a simple and facile molten salt method and examined as electrodes for supercapacitors. The synthesized nanoparticles were characterized using SEM, HRTEM, XRD, XPS, and BET techniques. Also, the electrochemical performance of various NbB2 nanoparticles depending on the various amorphous boron concentrations was systematically investigated using both a neutral (1 M Na2SO4) and a basic (6 M KOH) electrolyte. Electrochemical analysis revealed that the obtained sample denoted as the NbB2–8 exhibited the best electrochemical performance (159.6 F/g at 10 mV/s) in Na2SO4 electrolyte compared to that of the KOH electrolyte (69.6 F/g at 10 mV/s). Such a result can be owing to the size and mobility of ions in the electrolyte. Overall, this work could pave the way for other metal borides’ versatility and potential in energy storage.

Multi-Objective Optimization of Novel Aluminum Welding Fillers Reinforced with Niobium Diboride Nanoparticles

New and innovative technologies have expanded the quality and applications of aluminum welding in the maritime, aerospace, and automotive industries. One such technology is the addition of nanoparticles to aluminum matrices, resulting in improved strength, operating temperature, and stiffness. Furthermore, researchers continue to assess pertinent factors that improve the microstructure and mechanical characteristics of aluminum welding by enabling the optimization of the manufacturing process. Hence, this research explores alternatives, namely cost-effective aluminum welding fillers reinforced with niobium diboride nanoparticles. The goal has been to improve weld quality by employing multi-objective optimization, attained through a central composite design with a response surface model. The model considered three factors: the amount (weight percent) of nanoparticles, melt stirring speed, and melt stirring time. Filler hardness and porosity percentage served as response variables. The optimal parameters for manufacturing this novel filler for the processing conditions studied are 2% nanoparticles present in a melt stirred at 750 rpm for 35.2 s. The resulting filler possessed a 687.4 MPA Brinell hardness and low porosity, i.e., 3.9%. Overall, the results prove that the proposed experimental design successfully identified the optimal processing factors for manufacturing novel nanoparticle-reinforced fillers with improved mechanical properties for potential innovative applications across diverse industries.

Niobium boride (NbB2): Salt-templated synthesis, pseudocapacitive electrode and lithium-ion capacitor applications

Lithium-ion capacitors (LICs), which combine great power and energy density, have become promising energy storage and have been well studied recently. Developing novel battery-type anode materials is the key to mitigating the kinetic mismatch between the anode and cathode electrodes. In this paper, niobium diboride (NbB2) nanoparticles are synthesized via a salt-templated method and proposed for the first time as the anodes for LICs. NbB2 is a layered two-dimensional material similar to graphite, which is favorable to the intercalation and deintercalation of Li+. The NbB2 with high conductivity delivers outstanding long cycling stability (254.1 mAh g−1 after 800 cycles at 0.1 A g−1) and great rate capability. Moreover, a high-performance LIC is assembled employing the prepared NbB2 as anode and commercialized activated carbon (AC) as cathode, which can display an energy density of 68.76 Wh kg−1, a power density of 7.02 kW kg−1, and a capacity retention ratio of 98% after 10,000 cycles. The work presents the great potential of transition metal borides as electrode materials and accelerates the development of LICs.

Niobium Boronizing: Influence of the Treatment Temperature and Time

Abstract The application of niobium borides to components such as lamination cylinders, hightemperature devices, and medical equipment shows their importance and versatility in engineering. To improve niobium’s mechanical resistance and possible oxidation resistance at temperature, this research applied boronizing to pure niobium, carried out with double pack cementation. Boronizing at 950°C and 1,100°C was carried out for 1 and 4 h. Ekabor commercial pack mixture with a nominal chemical composition of 90 % silicon carbide, 5 % boron carbide, and 5 % potassium tetrafluoroborate was used with and without 10 percent by weight (wt%) silicon addition. Scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction analyses and microhardness tests were used to characterize the treated samples. A continuous high-hardness 2,394-HV0.1 (23.5 GPa) niobium diboride layer was formed at the surface of the niobium substrate. A maximum layer thickness of 53.6 ± 2.9 µm was measured after 4 h at 1,100°C, whereas after 1 h at 950°C, no visible layer was identified with the applied characterization techniques, suggesting a threshold in this temperature. Adding 10 wt% silicon to the pack mixture impacted the kinetics of the diffusion process, which resulted in an increase in layer thickness of 72.6 ± 10.1 µm after processing for 1 h at 1,100°C, but cracks formed in the processed surface.

Synergistic effect of Fe/Co-doping and electric field in Niobium Diboride for boosting hydrogen production

A primary concern towards achieving a robust and sustainable water-splitting strategy consists in the development and designing of non-precious hydrogen evolution electrocatalysts capable of operating at relatively high current densities. In the present density functional theory (DFT) based study, we explored and identified α-NbB2-based catalysts consisting of Borophene as graphene-like noble metal-free networks in Niobium-metal based networks, as promising catalysts for the hydrogen-evolution reaction (HER). Our results unveiled that Fe/Co covalent doping in α-NbB2{001} surface provides high-efficiency HER activity sites, namely, TNb-sites in Nb-terminated Fe/Co-NbB2{001} surface with the lowest ΔGH∗ Gibbs free energy value of about 0.264/0.278 eV, which further drops to a very optimal value in the range of ΔGH∗≤± 0.10 eV upon the implementation of an external electric field. Furthermore, it was also revealed that in contrast to the extensively used Pt-based surface catalysts, both α-NbB2 and Fe/Co-NbB2 catalysts can sustain consistently high catalytic activity for HER over a very large hydrogen coverage and thus ensure a large density of effective catalytic free sites.

Topological tailoring-induced Dirac cone in ultrathin niobium diboride nanosheets for electrocatalytic sulfur reduction reaction

Two-dimensional topological Dirac materials with novel electronic structures have attracted increasing attention in materials science, where the Weyl fermions can emerge in topological insulating multilayers with unusual quantum transport properties. However, their practical catalytic performance is seldom reported. Here, we design ultrathin niobium diboride (NbB2) nanosheets by utilizing topological electronic states to power catalytic activity. In the lithium-sulfur batteries, the stable topological surface states of NbB2 with high carrier mobility are a recipe for high-activity catalysts to spur the sluggish electrocatalytic sulfur reduction reaction, which originates from the Dirac cone electronic structure. Most remarkably, it delivers stable capacities with 1500 cycles under the 3.6 mA/cm2 (3 C), which is far superior to most electrode catalysts. The proposed functional Weyl and/or Dirac materials would have broad applications in other related fields such as the hydrogen evolution reaction, nitrogen reduction reaction, and energy conversion.

Studies on synthesis and densification of niobium diboride using carbothermic reduction and hot pressing

Niobium Diboride (NbB2) is a candidate refractory metal boride material for high - temperature structural applications as well as a neutron absorber material in the fourth-generation nuclear reactors. In the present investigation, the feasibility study on the synthesis of high purity NbB2 was carried out by reduction of Nb2O5 using B4C and C as reducing agents. The process parameters such as the feed composition, temperatures etc. were optimised to carry out the reduction in a vacuum atmosphere. The production of NbB2 powder was scaled up to a kilogram scale by using this method. The synthesized and mechanically milled powder was characterized using XRD, chemical analysis and laser particle size analyser. Single - phase NbB2 powder was produced successfully under optimum conditions. The milled synthesized powder was having an average particle size of 3.1 μm with oxygen and carbon contents of <0.5% each. Pellets with a high density of 93% of theoretical value were prepared by hot pressing at 1800 °C, after carrying out the detailed densification studies. Hardness and elastic modulus of hot press NbB2 were determined by using the nano-indentation technique and values found to be 27.9 GPa and 705 GPa respectively. Flexural strength of hot pressed NbB2 obtained from a three-point bend test was found to be 339 MPa.

Niobium Diboride Nanoparticles Accelerating Polysulfide Conversion and Directing Li2S Nucleation Enabled High Areal Capacity Lithium-Sulfur Batteries.

The shuttle effect of polysulfides and Li2S sluggish nucleation are the major problems hampering the further development of lithium-sulfur batteries. The reasonable design for sulfur host materials with catalytic function has been an effective strategy for promoting polysulfide conversion. Compared with other types of transition metal compounds, transition metal borides with high conductivity and catalytic capability are more suitable as sulfur host materials. Herein, a niobium diboride (NbB2) nanoparticle with abundant and high-efficiency catalytic sites has been synthesized by facile solid-phase reaction. The NbB2 with both high conductivity and catalytic nature could regulate 3D-nucleation and growth of Li2S, decrease the reaction energy barrier, and accelerate the transformation of polysulfides. Thus, the NbB2 cathode could retain a high capacity of 1014 mAh g-1 after 100 cycles. In addition, the high initial specific capacities of 703/609 mAh g-1 are also achieved at 5 C/10 C and could run for 1000/1300 cycles within a low decay rate of 0.057%/0.051%. Even with a high sulfur loading up to 16.5 mg cm-2, an initial areal capacity of 17 mAh cm-2 could be achieved at 0.1 C. This work demonstrates a successful method for enhancing the kinetics of polysulfide conversion and directing Li2S nucleation.

Formation of Niobium Diboride Nanoparticles by the Reaction of Niobium Pentachloride with Sodium Borohydride in Ionic Melts of Alkali Metal Halides

Formation of Niobium Diboride Nanoparticles by the Reaction of Niobium Pentachloride with Sodium Borohydride in Ionic Melts of Alkali Metal Halides

Studies on Synthesis and Densification of Niobium Diboride Using Carbothermic Reduction and Hot Pressing

Studies on Synthesis and Densification of Niobium Diboride Using Carbothermic Reduction and Hot Pressing

Comparative investigation of the properties of graphene nanoplatelet reinforced titanium diboride and niobium diboride ceramics

In this study, the effect of GNP concentration on the mechanical properties of spark plasma sintered TiB2 and NbB2 ceramics was investigated. GNP reinforced TiB2 and NbB2 specimens were aimed to produce with nearly full densification. Herein, SEM investigations, Raman analysis, and oxidation behavior of the samples were reported. GNP addition into the TiB2 and NbB2 matrices showed a different effect on various properties of the composites. GNP loading tends to enhance densification by removing native oxides of both TiB2 and NbB2 matrices. GNPs were more effective in the oxygen removal mechanism for TiB2 composites than NbB2. The highest relative density was obtained for TiB2-GNP and NbB2-GNP composites as 98.6% with 7 vol% and 5 vol% GNP additions, respectively. The Vickers microhardness decreased with increasing GNPs loading for both matrices. NbB2-GNP composites possessed higher fracture toughness and better oxidation resistance than TiB2-GNP composites.

Synthesis of Niobium Diboride Nanoparticles by the Reaction of Amorphous Boron with Niobium in KCl and Na2B4O7 Ionic Melts

Close to spherical nanosized niobium diboride particles with an average diameter of 65 nm were synthesized by the reaction of amorphous boron with niobium powder at 1073 K in an argon atmosphere in KCl and Na2B4O7 ionic melts (autoclave, argon pressure of 4 MPa, 32 h).

Fracture and property relationships in the double diboride ceramic composites by spark plasma sintering of TiB2 and NbB2

AbstractBulk titanium diboride–niobium diboride ceramic composites were consolidated by spark plasma sintering (SPS) at 1950°C. SPS resulted in dense specimens with a density exceeding 98% of the theoretical density and a multimodal grain size ranging from 1 to 10 μm. During the SPS consolidation, the pressure was applied and released at 1950 and 1250°C, respectively. This allowed obtaining a two‐phase composite consisting of TiB2 and NbB2. For these ceramics composites, we evaluated the flexural strength and fracture toughness and room and elevated temperatures. Room‐temperature strength of thus produced bulks was between 300 and 330 MPa, at 1200°C or 1600°C an increase in strength up to 400 MPa was observed. Microstructure after flexure at elevated temperatures revealed the appearance of the needle‐shape subgrains of NbB2, an evidence for ongoing plastic deformation. TiB2–NbB2 composites had elastic loading stress curves at 1600°C, and at 1800°C fractured in the plastic manner, and strength was ranged from 300 to 450 MPa. These data were compared with a specimen where a (Ti,Nb)B2 solid solution was formed during SPS to explain the behavior of TiB2–NbB2 ceramic composites at elevated temperatures.

Chemical Synthesis of Niobium Diboride Nanosheets by a Solid-State Reaction Route

A new process was developed to synthesize niobium diboride (NbB2) nanosheets with the dimension of about 500 nm and thickness of about 10 nm by using metal niobium, iodine and sodium borohydride as starting materials in an stainless steel autoclave at 700°C. Iodine was used to facilitate the exothermic reaction between metal niobium and sodium borohydride and the formation of NbB2. X-ray powder diffraction pattern indicated that the obtained product is hexagonal phase NbB2 with the calculated lattice constants a = 110 A and c = 3.2929 A. The obtained product was also studied by thermogravimetric analysis. It had good oxidation resistance below 400°C in air.

Critical role of ZrO2 on densification and microstructure development in spark plasma sintered NbB2

The present work reports the densification and microstructure development in niobium diboride (NbB2) containing ZrO2, consolidated using four stage spark plasma sintering with final holding at 1750°C for 2 min. The adopted processing approach enables to obtain fully dense (99.6% ρth) NbB2-ZrO2 ceramic with good mechanical properties. The sintered microstructure is characterized by the uniform dispersion of intragranular ZrO2 particles within the NbB2 grains. Fine scale microstructure analysis using high resolution transmission electron microscopy (HRTEM) together with HAADF (high angle annular dark field) technique reveals the dispersion of t-ZrO2 or o-ZrO2 and the defect structure including edge dislocations and asymmetric twins in o-ZrO2. An attempt has been made to rationalize the enhanced densification in terms of quantitative analysis of ‘constriction resistance’ induced localized heating and defect structure. The evaluation of basic mechanical properties revealed that a combination of high hardness (∼22 GPa) together with moderate indentation toughness (∼5.2 MPa m1/2) can be achieved with solid state sintered NbB2 containing ZrO2. The present study, for the first time, conclusively establishes the role of zirconia in obtaining dense NbB2 with good mechanical property combination at relatively lower sintering temperature of 1750 °C.

Facile in-situ synthesis of NbB2 nanoparticles at low temperature

Niobium diboride (NbB2) nanoparticles have been successfully synthesized at 800 °C in a single step from niobium penta-oxide (Nb2O5), magnesium (Mg) and borax (Na2B4O7·10H2O) in an autoclave. The synthesis temperature and holding time have been optimized to obtain single phase NbB2. The phase determination, thermal stability and morphological features of synthesized samples have been analyzed by X-ray diffraction (XRD), thermal gravimetric-differential scanning calorimetry (TG-DSC) and electron microscopic technique respectively. Williamson-Hall (W-H) analysis has also been done to observe the effects of synthesis parameters (temperature and holding time) on crystal distortion. With the help of XRD, microstructural features and thermodynamic calculations, formation mechanism for the synthesized samples has been predicted.

High‐temperature strength and plastic deformation behavior of niobium diboride consolidated by spark plasma sintering

AbstractBulk niobium diboride ceramics were consolidated by spark plasma sintering (SPS) at 1900°C. SPS resulted in dense specimens with a density of 98% of the theoretical density and a mean grain size of 6 μm. During the SPS consolidation, the hexagonal boron nitride (h‐BN) was formed from B2O3 on the powder particle surface and residual adsorbed nitrogen in the raw diboride powder. The room‐temperature strength of these NbB2 bulks was 420 MPa. The flexural strength of the NbB2 ceramics remained unchanged up to 1600°C. At 1700°C an increase in strength to 450 MPa was observed, which was accompanied by the disappearance of the secondary h‐BN phase. Finally, at 1800°C signs of plastic deformation were observed. Fractographic analysis revealed a number of etching pits and steplike surfaces suggestive of high‐temperature deformation. The temperature dependence of the flexural strength of NbB2 bulks prepared by SPS was compared with data for monolithic TiB2, HfB2 and ZrB2. Our analysis suggested that the thermal stresses accumulated during SPS consolidation may lead to additional strengthening at elevated temperatures.

Investigation on mechanochemical behavior of Al/Mg–B2O3–Nb system reactive mixtures to synthesize niobium diboride

Aluminum and magnesium were used in the M–B2O3–Nb (M=Al, Mg) system to synthesize niobium diboride (NbB2) via a mechanochemical process. The phase transformation and structural evaluation were investigated by means of X-ray diffractometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential thermal analysis techniques (DTA). Unlike thermodynamic possibility and DTA results, negligible aluminothermic reaction was occurred in the system and AlNb2 intermediate phase was formed during milling. On the other hand, nanostructure NbB2 was mechanosynthesized by the magnesiothermic reduction after 2.4h of milling and the type of reactions was mechanically induced self-sustaining reaction (MSR). DTA results revealed that Mg3(BO3)2 was largely formed during the thermal process, while the quantity of this by-product extremely decreased during the mechanochemical synthesis and completely eliminated after 5h of milling. Scanning and transmission electron microscopy observations confirmed that the range of particle size was within 100nm.

Self-assembled synthesis of hollow Nb3O7F nanomaterials based on Kirkendall effect and its photocatalytic properties

Hollow niobium oxide fluoride was successfully synthesised by a facile hydrothermal approach in the hydrofluoric acid/hydrogen peroxide solution without any template. By selecting hydrogen peroxide as oxygen source which could ceaselessly release oxygen gas, niobium diboride could be oxidised and corroded to form niobium oxide fluoride nanomaterials in situ. The hollow structure may result from Kirkendall effect. Significantly, the method may provide a direct route to synthesise some novel oxide nanomaterials using non-oxide ceramic as raw materials. The photodegratation experiments show that niobium oxide fluoride catalysts have better photocatalytic properties than commercial P25 TiO2 catalysts, indicating that this kind of hierarchical nanomaterials could be a promising candidate as a photodegradation material.