Niobium Metal Research Articles

Niobium doping effect on electrical and optical properties of ZnO nanorods produced by ultrasonic spray pyrolysis

Niobium metal doped ZnO nanorods were fabricated on a glass substrate using an ultrasonic spray pyrolysis system in two steps. The structural, morphological, and optical properties of the produced samples were investigated via an x-ray diffractometer (XRD), a field emission scanning electron microscopy (FE-SEM) combined with energy dispersive x-ray spectroscopy (EDX), and a spectrophotometer, respectively. The XRD patterns were indexed in the hexagonal (wurtzite) unit cell type for all the ZnO samples. In addition, according to the XRD peaks, the crystals grew in the c-axis (002) direction. The morphological features of the obtained thin films were examined. From the SEM micrographs, it was observed that ZnO thin films doped with Nb had a nanorod structure in the c-axis direction. The presence of Nb ions in the samples was proved via EDX analysis. The electrical conductivity values of the pristine and 10 % mol Nb-doped ZnO samples were 3.16 x 10−9 and 3.98 x 10−7 (ohm−1.cm−1) at 25 °C; and 7.08 x 10−7 and 5.01 x 10−5 (ohm−1.cm−1) at 300 °C, respectively. The optical transmittances of the samples were measured at wavelengths of 350–1000 nm. It was observed that the produced films had high optical transparency. The average optical transmittance value of the samples was 90 %.

Nitrogen doped carbon dots as a photocatalyst based on biomass. A life cycle assessment

The effectiveness of various transition metal phosphate-based acid catalysts, including vanadium and niobium, in the hydrothermal synthesis of carbon dots (CDs), has been assessed. Two sources of carbohydrates were employed for this: commercial xylose and liquor of xylose produced by processing olive pits. Catalysts were identified using the NH3-TPD, DTA/TG, XRD, and XPS techniques. The reaction was conducted for 4 h at a temperature of 180 °C. The existence of such nanoparticles, regardless of the carbohydrate source, was confirmed by an analysis of the features and characteristics of CDs nanoparticles. N-doped CDs with increased fluorescence were also created at the same time using a similar hydrothermal technique, and their photocatalytic activity was investigated. A Life Cycle Assessment (LCA) was conducted for both syntheses with the goal of comparing the environmental effects of the synthesis from commercial xylose to the synthesis from biomass. It was revealed that, although energy is the primary driver of both synthesis pathways' effect categories, the fundamental variations that seem to determine their relative sustainability are connected to the nature of the carbon precursor. Regarding the latter, it is determined that electricity has the greatest environmental impact.

PROSPECTS AND PROBLEMS OF DEVELOPMENT OF THE RAW MATERIAL BASE OF SUFFICIENT STRATEGIC TYPES OF SOLID MINERAL RESOURCES OF SIBERIA

The analysis of the state of the mineral resource base of strategic types of solid minerals in Russia in general and in Siberia in particular has been carried out. Particular attention is paid to the prospects for the development of the resource base of lithium, rare earth metals, ordinary and impact diamonds in Siberia. The characteristics of a number of deposits and options for their development were assessed, taking into account the quality of ores, geographical location, the state of the infrastructure and the level of development of technologies for ore dressing and obtaining end products. The prospects for the development of the raw material base of niobium and rare earth metals within the Tomtor massif and the territory of the Udzha uplift as a whole are assessed. Summary results of long-term regional field and laboratory studies of the distribution and compositional variations of Cr-pyrope garnet, the most informative of the set of indicator minerals for determining the potential diamond content of kimberlites, selected from uneven-aged intermediate reservoirs of the Siberian Platform, are presented. Based on these results, areas within the platform were identified with signs of the presence of new fields of potentially diamond-bearing kimberlites of the Middle Paleozoic age. A mineralogical description and assessment of the technological characteristics of impact diamonds from the Popigai astrobleme and from the ejection zone in its frame is given. The prospects of creating a new large area of the extractive industry on the raw material base of strategic materials in the territory of the Lena-Khatanga interfluve are substantiated

Interfacial structures evolution at hetero interfaces in SiCf/SiC | Nb | SiCf/SiC sandwich cladding structure

The appropriate hetero interfacial structure between metal and ceramics is a challenging topic in materials science. In this paper, a sandwich hybrid cladding structure made of SiCf/SiC composite and refractory metal niobium (Nb) is designed for application in a lead-cooled fast reactor. A diffusion reactive interfacial layer composed of β-SiC | NbC | Nb5Si4C | α-Nb5Si3 | β-Nb2C | Nb between SiCf/SiC composite and Nb is experimentally validated after heat treatment in a simulating reactor environment. Moreover, Kirkendall voids are found at the interface between Nb5Si4C and Nb5Si3 sublayers when the annealing temperature is higher than 1500 °C. Lastly, the formation mechanisms of interfacial structures are revealed based on thermodynamics and kinetics, meanwhile the diffusion coefficients k at 1500 °C and activation energy are calculated to be 2.81 × 10−14 m2/s and 270 kJ/mol, respectively. This work provides a practical strategy for developing hybrid composites of metal/ceramic matrix composites.

High-temperature irradiation-resistant thermocouple instability model for in-pile reactor use

This article presents an instability model for the high-temperature irradiation-resistant thermocouple (HTIR-TC). Here the term instability defines the superposition of both drift and inhomogeneity of TC thermoelements occurring simultaneously. The HTIR-TC is an advanced thermocouple (TC) that uses the refractory metals niobium and molybdenum as sensing thermoelements for generating electromotive force (EMF) in a field of neutrons and at temperatures upward of 1,600°C. In the Advanced Gas Reactor (AGR) 5/6/7 tests conducted at Idaho National Laboratory’s Advanced Test Reactor (ATR), the HTIR-TCs showed low to moderate instability throughout the life of the test. The instability model reveals that HTIR-TCs can, when the operating temperature of the reactor fuel is normal, maintain performance throughout an 18-month refueling cycle typical of nuclear power plants, reflecting an instability of less than ±1%. The HTIR-TC is also qualified for incorporation into a test fixture during the testing of new fuels.

Solvent- and Co-Catalyst-Free Cycloaddition of Carbon Dioxide and Epoxides Catalyzed by Recyclable Bifunctional Niobium Complexes.

CO2, as a cheap and abundant renewable C1 resource, can be used to synthesize high value-added chemicals. In this paper, a series of bifunctional metallic niobium complexes were synthesized and their structures were characterized by IR, NMR and elemental analysis. All of these complexes have been proved to be efficient catalysts for the coupling reaction of CO2 and epoxides to obtain cyclic carbonates under solvent- and co-catalyst-free conditions. By using CO2 and propylene oxide as a model reaction, the optimal reaction conditions were systematically screened as: 100 °C, 1 MPa, 2 h, ratio of catalyst to alkylene oxide 1:100. Under the optimal reaction conditions, the bifunctional niobium catalysts can efficiently catalyze the coupling reaction with high yield and excellent selectivity (maximum yield of >99% at high pressure and 96.8% at atmospheric pressure). Moreover, this series of catalysts can also catalyze the coupling reaction at atmospheric pressure and most of them showed high conversion of epoxide. The catalysts have good substrate suitability and are also applicable to a variety of epoxides including diepoxides and good catalytic performances were achieved for producing the corresponding cyclic carbonates in most cases. Furthermore, the catalysts can be easily recovered by simple filtration and reused for at least five times without obvious loss of catalytic activity and selectivity. Kinetic studies were carried out preliminarily for the bifunctional niobium complexes with different halogen ions (3a(Cl-), 3b(Br-), 3c(I-)) and the formation activation energies (Ea) of cyclic carbonates were obtained. The order of apparent activation energy Ea is 3a (96.2 kJ/mol) > 3b (68.2 kJ/mol) > 3c (37.4 kJ/mol). Finally, a possible reaction mechanism is proposed.

Doping with Niobium Nanoparticles as an Approach to Increase the Power Conversion Efficiency of P3HT:PCBM Polymer Solar Cells.

Metal additive processing in polymer: fullerene bulk heterojunction systems is recognized as a viable way for improving polymer photovoltage performance. In this study, the effect of niobium (Nb) metal nanoparticles at concentrations of 2, 4, 6, and 8 mg/mL on poly(3-hexylthiophene-2,5-diyl) (P3HT)-6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends was analyzed. The effect of Nb volume concentration on polymer crystallinity, optical properties, and surface structure of P3HT and PCBM, as well as the enhancement of the performance of P3HT:PC61BM solar cells, are investigated. Absorption of the P3HT:PC61BM mix is seen to have a high intensity and a red shift at 500 nm. The reduction in PL intensity with increasing Nb doping concentrations indicates an increase in PL quenching, suggesting that the domain size of P3HT or conjugation length increases. With a high Nb concentration, crystallinity, material composition, surface roughness, and phase separation are enhanced. Nb enhances PCBM's solubility in P3HT and decreases the size of amorphous P3HT domains. Based on the J-V characteristics and the optoelectronic study of the thin films, the improvement results from a decreased recombination current, changes in morphology and crystallinity, and an increase in the effective exciton lifespan. At high doping concentrations of Nb nanoparticles, the development of the short-circuit current (JSC) is associated with alterations in the crystalline structure of P3HT. The highest-performing glass/ITO/PEDOT:PSS/P3HT:PCBM:Nb/MoO3/Au structures have short-circuit current densities (JSC) of 16.86 mA/cm2, open-circuit voltages (VOC) of 466 mV, fill factors (FF) of 65.73%, and power conversion efficiency (µ) of 5.16%.

PHASE FORMATION DURING ALUMINOTHERMAL REDUCTION OF Ti, Nb, Gd (Y) FROM OXIDES

Alloys based on titanium and aluminum with additions of niobium and rare-earth metals have unique mechanical and heat-resistant properties, and also it likely that such alloys would have increased corrosion resistance. The method of thermodynamic modeling using the HSC program was used to study a system with aluminum consumption varying in the range from 0 to 100% of the mass of the initial charge. The features of phase formation in Al–[50TiO2–5Nb2O5–1Y2O3 (Gd2O3)] systems have been studied. The calculation of the heat balance of the process at 1600°C and 44% of Al was – 0.196 MJ per 1 kg of charge, which indicates the possibility of its occurrence with only the aluminothermic reactions. The reduction of titanium and niobium can proceed by reactions through the formation of their oxides of lower valency – TiO, NbO2, NbO. The aluminothermic reduction of gadolinium is thermodynamically possible only at temperatures below 1200°C. The reduction of yttrium through the interaction of Y2O3 with aluminum with the formation of AlY, Al2Y3 AlY2 compounds for the range of 1000–1800°C is thermodynamically impossible. The results of thermodynamic modeling of interactions correlated well with the data of differential thermal and X-ray phase analysis using STA 449 F3 Jupiter (NETZSCH) synchronous thermal analysis and XRD-7000 diffractometer (Shimadzu) with automatic program control, respectively. It was found that the process enters the active phase after the appearance of liquid aluminum and, apparently, is accompanied by exothermic effects with the formation of double and triple intermetallic compounds of aluminum with rare (Nb, Ti) and rare earth (Gd, Y) metals. Transformation of titanium dioxide and niobium pentoxide in the process of transformations is likely carried out through successive and parallel stages of formation of simple and complex oxides with low oxidation states. At the initial stages of the interaction of aluminum with oxides, niobium and titanium aluminides are mainly formed. At subsequent stages, the formation of more complex compounds is observed. At temperatures above 1300°C, ternary intermetallic compounds Al43Nb4Gd6, Ti4Al20Gd and Ti4Al3Y6, Al3Ti, Al0.23Nb0.07Ti0.7 are formed. Gadolinium and yttrium tend to form complex intermetallic compounds in such systems.

Freestanding Foils of NbSe2 and Carbon Nanotubes for Efficient Electromagnetic Shielding

The presence of electromagnetic radiation is becoming an ongoing topic due to possible interference issues as well as potential health risks. Therefore, the development of electromagnetic interference (EMI) shielding materials is of utmost importance. Herein, a composite material for EMI shielding based on metallic niobium diselenide (NbSe2) and single-walled carbon nanotubes (CNTs) with a low loading of 3 wt % is reported. The NbSe2 + 3CNTs composite was prepared using a high shear-force homogenizer followed by vacuum filtration to obtain a freestanding foil with a thickness of 219 ± 22 μm. The EMI shielding effectiveness (SE) of the NbSe2 + 3CNTs composite was also compared with its building blocks. The EMI SEs at 12.4 GHz were 31.4, 48.5, and 62.7 dB for pure NbSe2, pure CNTs, and the NbSe2 + 3CNTs composite, respectively. Such excellent performance of our composite material is attributed to a synergistic effect between the NbSe2 and CNTs, where the CNTs not only increase the conductivity of the composite but also form an interconnecting network between the NbSe2 sheets, thus forming a 3D network with abundant sites for EM wave attenuation. It is the first study on the EMI shielding performance of a TMD other than MoS2-based material.

Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting

We present the photoelectrochemical (PEC) water-splitting properties of pristine and reduced graphene oxide (rGO)-coated GaN nanocolumns (NCs) on flexible niobium (Nb) metal foils. The structural, optical, and electronic structure analyses of rGO-coated GaN-NCs on Nb foils revealed the formation of a rGO/GaN-NCs hybrid structure. Further, the valence-band studies of pure GaN-NCs shows valence-band maxima at ∼3.0 eV below the Fermi level, which decreased to ∼2.8 eV for rGO/GaN-NCs. The PEC measurement performed on pristine GaN-NCs under standard (1 Sun) conditions shows an effective photocatalytic nature with a photocurrent density of ∼60 μA/cm2 at 0.8 V (vs Ag/AgCl) in a 1 M oxalic acid electrolyte, which increases to ∼110 μA/cm2 for rGO/GaN-NCs. The efficient PEC characteristics of rGO/GaN-NCs are attributed to the effective charge separation/transport of photogenerated carriers. Furthermore, transient photocurrent measurement reveals that hybrid and pristine GaN-NCs on flexible metal foil have a fast and stable photoresponse in an aqueous solution. The development of a hybrid nitride nanostructure-based PEC device on flexible metal foils paves the way toward developing scalable PEC devices for hydrogen production applications.

Identifying the Interfacial Polarization in Non‐stoichiometric Lead‐Free Perovskites by Defect Engineering

AbstractRecent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead‐free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A‐site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect‐driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering.

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.

Phonon Dominated Thermal Transport in Metallic Niobium Diselenide from First Principles Calculations.

Niobium diselenide (NbSe2) is a layered transition metal dichalcogenide material which possesses unique electrical and superconducting properties for future nanodevices. While the superconducting, electrical, and bulk thermal transport properties of NbSe2 have been widely studied, the in-plane thermal transport property of NbSe2, which is important for potential thermoelectric applications, has not been thoroughly investigated. In this report, we study the lattice in-plane thermal transport of 2D NbSe2 by solving the phonon Boltzmann transport equation with the help of the first principles calculation. The thermal conductivity obtained at room temperature is 12.3 W/mK. A detailed analysis shows that the transverse acoustic phonon dominates the lattice thermal transport, and an anomalously small portion of electron contribution to the total thermal conductivity is observed for this metallic phase. The results agree well with experimental measurements and provide detailed mode-by-mode thermal conductivity contribution from different phonon modes. This study can provide useful information for integrating NbSe2 in nanodevices where both electrical and thermal properties are critical, showing great potential for integrating monolayer NbSe2 to thermoelectric devices.

Особенности дефектной структуры и фотолюминесценция номинально чистых кристаллов LiNbO3, выращенных из шихты, содержащей бор

Features of the defect structure of nominally pure LiNbO3:В crystals were investigated by X-ray diffraction analysis and photoluminescence. Crystals were grown by the Czochralski from a mixture of congruent composition charge containing 0.08 and 0.12 wt. % boron. At this, the concentration of boron in crystals is at the level of trace amounts of metallic impurities and is ~ 10–4 wt%. MeO6 oxygen-octahedral clusters are responsible for the ferroelectric and nonlinear optical properties of the crystal. It has been found that in LiNbO3:B crystals, the lengths of O–O, Me–O, and Me–Me (Me–Li, Nb) bonds in clusters, the arrangement of Me cations, vacancies, and NbLi point defects along the polar axis differ significantly from those for nominally pure congruent crystal. NbLi defects and transition metals are deep electron traps responsible for the photorefraction effect. The photoluminescence spectra showed that the concentration of defects and metals in the investigated LiNbO3:B crystals is lower than in the congruent crystal. these differences can be due to both a change in the properties of the boron-containing melt and the localization of trace amounts of boron in the O4 tetrahedral gaps of the LiNbO3 crystal structure. In the first case, reactive boron binds cations of niobium and transition metals in the melt into stable complexes.

Decrease in the Starting Temperature of the Reaction for Fabricating Carbides of Refractory Metals When Using Carbon Nanoparticles as Precursors

Metal matrix composites with a matrix of refractory metals (niobium, tungsten) and reinforcing nanodiamond particles were prepared for studying the possibility of decreasing the starting temperature of carbide synthesis. The size of primary nanodiamond particles was 4–6 nm, but they were combined in large-sized agglomerates. Mechanical alloying was used for producing the composites by crushing agglomerates and distributing nanodiamonds evenly in the metal matrix. The initial and fabricated materials were investigated by X-ray diffraction, differential scanning calorimetry, and transmission and scanning electron microscopy. Thermal processing leads to the reaction for carbide synthesis. Studies have found that the usage of carbon nanoparticles (nanodiamonds) as precursors for fabricating carbides of refractory metals leads to a dramatic decrease in the synthesis temperature in comparison with macro-precursors: lower than 200 °C for tungsten and lower than 350 °C for niobium.

Fabrication of niobium metal organic frameworks anchored carbon nanofiber hybrid film for simultaneous detection of xanthine, hypoxanthine and uric acid

Early determination of abnormal levels of uric acid (UA), xanthine (XA), and hypoxanthine (HXA) in the body fluid and food stuff could be useful in preventing various diseases. In this paper, we have fabricated a self-standing hybrid film based on niobium (benzene 1,3,5-tricarboxylic acid) MOFs (Nb(BTC)MOFs) and carbon nanofibers (CNFs) and explored as an enzyme-free electrochemical sensor for simultaneous determination of these analytes in phosphate buffer (pH = 7). As-developed hybrid film has a high specific surface area that permits faster transport of analyte molecules across the electrode-electrolyte interfaces, whereas a large number of active oxygen functionalities in MOF matrix could promote the sensitivity of the hybrid sensor. The Nb(BTC)MOF@CNF modified glassy carbon electrode (GCE) sensor demonstrated excellent electrochemical responses to these purine derivatives. The diffusion-controlled electrooxidation reactions of these three analytes were noticed. The hybrid sensor exhibited a wide linear range of 5 to 2000 µM along with a low LOD of 70 nM, 76 nM, and 68 nM for UA, XA, and HXA, respectively. The present interference-free sensor showed high selectivity and good storage stability (40 days). Finally, the sensing performances of the Nb(BTC)MOF@CNF/GCE toward UA, XA, and HXA in real samples were found to comparable to those of high-performance liquid chromatography (HPLC) results.

Модифікація поверхні базальтових волокон та вуглецевих матеріалів для покращення їх змочування легкоплавкими розплавами

The effect of metal coatings and coverings on wetting of substrates by In, Sn, Pb in vacuum 1—2•10-3 Pa in the temperature range 400—700 C was studied by the sessile drop method using the capillary purification method of melt. Substrates of hot-polished basalt material, MPG-6 graphite, composite materials based on high-modulus carbon fibers, tapes and fabrics used. Vanadium, niobium, copper and nickel metals were chosen for the coatings, which were sprayed on the materials by electron beam evaporation of metals in vacuum, and titanium, nickel powders for the coatings were used. The nature of the wetting angle dependence on the film thickness is a linear decrease in the angle with increasing film thickness. Studies have shown the possibility of using double films V—Cu, V—Ni for the manufacture of composite materials from basalt fibers.Wetting the vanadium and niobium coatings on surface of the basalt material at by lead, tin and indium improves with increasing film thickness and experimental temperature. The nature of the contact angle–coating thickness dependences for all studied systems is the same: the angle value decreases linearly with increasing film thickness from the angle wetting of the basalt surface to the wetting angle of the compact metal film (V, Nb). The coating thickness, when the contact angle wetting for all adhesive-active metals with high oxygen affinity does not change, is close, and for vanadium is 200•10-10 m, for niobium about 100•10-10 m. Studies have shown the possibility of using double V—Cu and Nb—Cu films for the manufacture of composite materials from basalt fibers and matrix metal. Keywords: contact angle wetting, metal coatings and covering, basalt and carbon materials, low-melting metals.

First principles study of the electronic and optical properties of high‐valence transition metal‐doped anatase titanium dioxide

AbstractThe formation energies and electronic and optical properties of anatase titanium dioxide doped with high‐valence transition metals (niobium, tantalum, tungsten, and molybdenum) were studied through first‐principles calculations based on density functional theory. The results showed that the doped titanium dioxide systems exhibited a typical n‐type metallic characteristic and high transmittance within the visible light spectrum. The high‐valence transition metal‐doped anatase titanium dioxide films should be formed under oxygen‐rich conditions and the niobium‐doped anatase titanium dioxide film is easier to synthesize and more stable than the other three films. Moreover, the band gaps of the doped titanium dioxide systems decrease due to the hybridization of transition metal d, tantalum 3d and oxygen 2p states. Niobium‐ and tantalum‐doped titanium dioxide have lower effective mass and higher electron mobility than tungsten‐ and molybdenum‐doped titanium dioxide, hence are more suitable for transparent conductive oxide materials.

Dissimilar micro beam welding of titanium to Nitinol and stainless steel using biocompatible filler materials for medical applications

In the present investigation, thin sheet geometries of commercially pure titanium (cp, grade 4) are butt-welded to AISI 316L stainless steel as well as Nitinol by means of micro electron beam welding using filler materials. In order to avoid mixing of the base materials, the refractory metals tantalum, niobium and hafnium are applied as intermediate layers. Owing to the biocompatibility of these filler materials, the final products are suitable for medical technology applications. In combination with low energy inputs and precise beam alignments, it is demonstrated that high-quality and crack-free joints can be produced using micro electron beam welding. The welded joints are analysed using nanoindentation to identify critical weld areas, e.g. high concentrations of intermetallic compounds, and to evaluate the compatibility of the base and filler materials. To correlate the hardness mappings with the microstructural evolution of the welds, an exemplary joint is analysed by means of electron backscatter diffraction and energy dispersive X-ray spectroscopy with special emphasis on intermixing and the formation of intermetallic compounds. Based on the generated hardness mappings as well as the ultimate tensile strengths of the joints, it will be concluded which filler material provides the most promising results for the given material combinations.

Oxidation behaviour and its effect on fracture toughness of Niobium metal

Niobium metal was studied for its oxidation behaviour at different temperatures (800, 1000 & 1200 °C) and time (1, 3 & 5 h). The study revealed that Nb underwent oxidation forming pro-active Nb oxides with initial formation of meta-stable Nb12O29 which forms as an oxidisation resistant layer. However, formation of Nb2O5 from a meta-sable Nb12O29 did not act as protective layer as it exposed underneath to further oxidation leading to cracks. The oxidation kinetics of Nb shown a linear behaviour and the devised mathematical model using Deal Grove determined the thickness of oxide layers. The un-protectiveness of Nb2O5 was verified by the Vickers hardness (8.06 ± 0.4 GPa) and indentation fracture toughness (28.14 ± 0.4 MPa.m1/2) of material which decreased with increase in oxidation temperature.