Niobium

Tin slag a waste product of tin smelting contains many
important metals such as niobium, tantalum, manganese, iron,
aluminum, titanium, etc. Niobium metal which is one of the
important metals found in tin slag has successfully been
extracted using leaching and electrothermal method. The tin slag
was crushed and ground to very fine particle sizes of nanometer
level using laboratory ball mill, piston and mortar. The particles
were sieved and 150nm and 180nm particle sizes range were
used for this experiment. The samples were subjected to two
leaching processes using hydrochloric acid and sodium
hydroxide. The residues from the leaching processes were
subjected to carbonchlorination at 300oC to produce Niobium
oxide. The purity of Niobium metal extracted was calculated to
up to 95% which means that tin slag from Nigerian Tin Smelting
Company is a good source of high quality Niobium metal.

The carbonatite of Mabounié (Gabon), first described in 1988 [1], is a complex igneous intrusion
approximately 2.3 km in diameter hosted in Paleoproterozoic fenitized gneisses and migmatites.
Numerous mineralogical and geochemical studies were conducted in the twenty years following its
discovery ([2-4], BRGM, pers. comm.) that led to the discovery of a polymetallic lateritic ore deposit
above the intrusion. In the present work, new petrographic studies are reported on fresh drill core samples
obtained within the framework of the Maboumine project.
The carbonatite is heterogeneous sövite, crosscut by a few dikes of rauhaugite (dolomite-rich
carbonatite). The mineralogy varies strongly along magmatic bedding, schlieren patches and
hydrothermally recrystallized areas [4]. Apatite-sövite and phlogopite-sövite are common and intermixed
with each other, and contain a variable amount of Ti-rich magnetite (in some cases, up to 40 vol.% of the
rock). Other accessory minerals include rare-earth carbonates, ilmenite, pyrochlore, zircon, baddeleyite,
calzirtite and zirconolite.
In the lateritic profile developed above the carbonatite suite, the lowermost horizon consists of
massive phosphates and is characterized by the dissoluion of carbonates; it is followed by “ribbon”
laterites characterized by the breakdown of apatite, and finally by an iron-oxide-rich horizon at the
surface of the deposit. Even though pyrochlore is affected by different processes and its composition
changes slightly across the profile [3], this mineral remains the main carrier of rare metals (Nb, Ta) and
rare earth elements, which are concentrated upward mainly in the “ribbon” ore.

Niobium pentoxide (Nb2O5) was added to cobalt spinel ferrite (CoFe2O4) powders for the first time, at varying amounts of 0, 5, 10 and 15 wt%. The purpose was to evaluate the effect of niobia on the crystalline phases, microstructure and complex electromagnetic behaviour (complex permittivity and permeability between 300 MHz and 10 GHz) of CoFe2O4. The samples were prepared by conventional ceramic methods and sintered at 1475 °C, as potential applications are as aerospace materials (radomes) which have to survive at such temperatures upon re-entry. The only crystalline phase observed in all samples was CoFe2O4 , but microstructural evaluation showed that a non-crystalline, niobium-rich intergranular region was formed between the grains with niobium addition, and this apparent liquid/glassy phase aided sintering as considerable grain growth was also observed. It was shown by Raman spectroscopy that this niobium-rich amorphous intergranular phase was FeNbO4. The electromagnetic measurements of complex permittivity (ε*) and permeability (μ*) measurements indicated a steady decrease in both permittivity and permeability with increasing niobium oxide addition, although the values for each sample were relatively stable between 300 MHz and 10 GHz. The real permittivity, ε′, decreased from ~ 12 in the pure CoFe2O4 to ~ 5.5 with increasing addition, while its imaginary part assumed values very close to zero. At the same time, the real permeability, μ′, decreased from ~ 1.4 to ~ 1.1, and a similar effect can be observed in the permeability curves. The results of the complex measurements also allowed us to obtain reflectivity graphs representing the energy loss of the incident electromagnetic wave when crossing the layer of the evaluated composition. The graphs are presented in the frequency domain, and indicate that the reflection loss increases with the addition of niobia.

This paper describes a rapid method of 94Nb
pre-concentration, separation and purification by using
cation and anion exchange resins. The method is suitable
for analyzing highly contaminated radioactive waste samples
in a relatively short time and high decontamination
factors. The use and effectiveness of the method was successfully
tested by analysis of samples from nuclear reactor
parts such as control rod drive shaft, shielding cassettes,
neutron in-core measurement channels (KNI), pressure
vessel construction material and fuel cassette construction
material samples.

During the evolution of the Earth, distinct geochemical reservoirs with different Nb/Ta ratios have developed. Archean granitoids of the tonalite–trondhjemite–granodiorite (TTG) suite, which represent the Earth’s early continental crust, show larger Nb/Ta variations than any other Earth reservoir. This implies that significant Nb–Ta fractionation must have occurred during early crust formation, while the underlying mechanism behind is still unclear. Here, we present a new model on how Nb may be fractionated from Ta during partial melting of subducted oceanic crust. Our data show that Nb/Ta ratios in melts derived from rutile- and titanite-bearing eclogite are largely controlled by the modal relative abundances of rutile and titanite in the source. High modal ratios of titanite over rutile generate melts with very high Nb/Ta (>60), whereas low modal titanite/rutile produces melts with much lower Nb/Ta (≤30). Very low Nb/Ta (<16) occur when all Ti-phases are consumed at very high degrees of melting. As the modal ratio of titanite to rutile is a function of pressure, the Nb/Ta of melts is a function of melting depth. Our new model helps to explain the extreme variation of Nb/Ta observed in many TTGs and thus how Nb and Ta were fractionated during the early evolution of the Earth. Furthermore, the model also indicates that simple one-stage melting models for mafic crust are not sufficient to explain the formation of TTGs.

The demand for reliable coating on medical implants is ever growing. In this research, enhanced performance of medical implants was achieved by a CrN/NbN coating, utilising nanoscale multilayer/superlattice structure. The advantages of the novel high power impulse magnetron sputtering technology, namely, its unique highly ionised plasma, were exploited to deposit dense and strongly adherent coatings on CoCr implants. Transmission electron microscopy analysis revealed coating superlattice structure with bi-layer thickness of 3.5 nm. CrN/NbN deposited on CoCr samples showed exceptionally high adhesion, critical load values of LC2 = 50 N in scratch adhesion tests. Nanoindentation tests showed high hardness of 34 GPa and Young&#39;s modulus of 447 GPa. Low coefficient of friction (μ) 0.49 and coating wear coefficient (K C) = 4.94 × 10(-16) m(3) N(-1) m(-1) were recorded in dry sliding tests. Metal ion release studies showed a reduction in Co, Cr and Mo release at physiological and eleva...

Auger electron (AES), electron energy loss (EELS) and X-ray photoelectron spectroscopy (XPS) were used to identify the reaction products at the fibre-matrix interface in SiC nicalon fibre-LAS (Li2O, Al2O3, SiO2) or LAS + Nb2O5 glass matrix composites. Chemical bonding of the different elements was investigated by AES using sputter-depth profiling on fibres extracted from two matrices by etching in hydrofluoric acid. The chemistry of the silicium was studied by EELS in nicalon-LAS + Nb2O5 composite cross-sections. XPS was performed on fibres extracted from the nicalon-LAS + Nb2O5 composite to confirm EELS and AES results. These investigations show that in both composites the reaction scale at the fibre-matrix interface consists of a carbon layer next to the matrix and of a silicate phase rich in oxygen which contains carbon, probably in the form of a silicon oxycarbide, and which is located between the carbon layer and the fibre core.

The aim of this study was to develop binary and ternary titanium (Ti) alloys containing zirconium (Zr) and niobium (Nb) and to characterize them in terms of microstructural, mechanical, chemical, electrochemical, and biological properties. The experimental alloys - (in wt%) Ti-5Zr, Ti-10Zr, Ti-35Nb-5Zr, and Ti-35Nb-10Zr - were fabricated from pure metals. Commercially pure titanium (cpTi) and Ti-6Al-4V were used as controls. Microstructural analysis was performed by means of X-ray diffraction and scanning electron microscopy. Vickers microhardness, elastic modulus, dispersive energy spectroscopy, X-ray excited photoelectron spectroscopy, atomic force microscopy, surface roughness, and surface free energy were evaluated. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). The albumin adsorption was measured by the bicinchoninic acid method. Data were evaluated through one-way ANOVA and the Tukey test (α=0.05). The alloying elements proved to modify ...

Betafite of composition [(Ca,U)2(Ti,Nb,Ta)2O7] was prepared via a solid state synthesis route. The synthesis was shown to be sensitive to initial reactant ratios, the atmosphere used (oxidising, neutral, reducing) and time. The optimum conditions for the synthesis of betafite were found to be heating the reactants required at 1150°C for 48 h under an inert gas atmosphere. XRD characterisation revealed that the synthesised betafite contained minor impurities. EPMA analysis of a sectioned surface showed very small regions of Ca-free betafite on grain boundaries as well as minor rutile impurities. Some heterogeneity between the Nb:Ta ratio was observed by quantitative EPMA but was generally within the nomenclature requirements stated for betafite. SEM analysis revealed the synthesised betafite was comprised mostly of hexaoctohedral crystals of ∼ 3 μm in diameter. XPS analysis of the sample showed that the uranium in the synthesised betafite was predominately present in the U(5+) oxidat...

LN photonic wires of cross-section dimensions down to 1 x 0.73 microm2 were fabricated by Ar milling of a single-crystalline LiNbO3 (LN) film bonded to a SiO2/LiNbO3 substrate. Mode intensity distributions, propagation losses, and group indices of refraction were measured at 1.55 microm wavelength and compared with simulation results. Moreover, effective mode indices and end face reflectivities were numerically evaluated. The waveguide of 1 microm top width is the smallest LN photonic wire reported to date; it has a mode size of approximately 0.4 microm2 (0.5 microm2) only and propagation losses of 9.9 dB/cm (12.9 dB/cm) for qTM (qTE) polarization.

This work describes the effect of Nb supersaturation in austenite on the suppression of static recrystallization of austenite during an isothermal holding period following hot deformation. The investigation involved three carbon structural steels with varying Nb concentration at constant C (0.20 pct) and N (0.007 pct) levels. The isothermal double-hit deformation technique led to the determination of T5 pct and T95 pct (recrystallization-stop and full recrystallization temperatures, respectively) as a function of a true strain and interpass time. The results indicate that the T5 pct increases with increasing Nb supersaturation in austenite at a rate of 40 °C per 0.006 pct Nb supersaturation for a true stain ε=0.40. At each respective T5 pct, all tested steels exhibited an Nb supersaturation ratio ≥ 7.5 in austenite. A high, localized strain-induced precipitation of Nb(CN) was observed at the austenite subgrain boundaries in the unrecrystallized microstructure. This translated into h...

Human chorionic gonadotropin (hCG) is a peptide hormone, whose one of the structural subunits is identical to that of thyroid-stimulating hormone (TSH). As a consequence, the receptors of TSH also act as receptor for hCG hormone. Keeping in mind this interesting property of hCG we have studied the complex formation ability of various no-carrier-added β-emitting isotopes of 61Cu (3.3 h), 62Zn (9.2 h), 90Nb (14.60 h) and 99Mo (66.02 h) with hCG molecule. Stability of the hCG–M (M=metal ions) complexes was investigated by dialysis with respect to triple distilled water and ringer lactate solution, which has the same composition as extracellular fluid.

Povidone-iodine and various bactericidal agents used in dental procedures may affect the corrosion response of an implant/prosthesis in the oral environment. The effect of various concentrations of povidone–iodine (PI) on the corrosion behavior of a low modulus beta titanium alloy, Ti-45Nb, has been investigated in normal saline solution. The open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements have been used to assess the electrochemical response of the alloy surface on PI addition so as to effectively predict the prosthetic treatment outcome. As the concentration of PI is increased, the corrosion rate decreases, suggested by decreased Rp values. Povidone–iodine acts as an anodic inhibitor by adsorbing on the anodic sites of the alloy. Addition of PI to a simulated body fluid such as normal saline leads to a decrease in corrosion rate of Ti-45Nb alloy.

This study evaluates the radiopacity and cytotoxicity of Portland cements containing a radiopacifier of bismuth oxide (Bi2O3) with yttria-stabilized zirconia (YSZ) dopant. Various radiopacifier powders of Bi2O3 with 0%, 15%, 30%, and 100% YSZ dopant were prepared by solid-state reaction at 700°C for 12 hours and characterized by x-ray diffraction. Portland cement/radiopacifier/calcium sulfate (75/20/5) were mixed and set by deionized water. Changes in radiopacity and in vitro cell viability of the hydrated cements were assessed. An average of 6 measured equivalent thickness of aluminum (N = 6) capable of producing similar radiographic density was recorded. The cytotoxicity of each material was determined in MC3T3 E1 cell-based methyl-thiazol-tetrazolium assay. The x-ray diffraction patterns of YSZ doped Bi2O3 are different from those of pure Bi2O3 and YSZ. The cement-containing radiopacifier of Bi2O3/YSZ (85/15) presented significantly greater radiopacity (P &lt; .05) compared with ...

Niobium (Nb) K-edge and tantalum (Ta) LIII-edge XANES spectra were acquired at the part-per-million concentration level in silicate glasses quenched from chondritic melts equilibrated at 5 GPa and under moderately to highly reducing conditions (IW-1, IW-4.5, IW-7.9). Standard materials have also been analyzed for Nb and Ta, and the data were used to construct the calibration curves of E0 (threshold energy) vs. valence. Under moderately reducing conditions our results are consistent with niobium and tantalum being mainly pentavalent in the silicate melts as also suggested by previous studies. We do not exclude that at IW-1, a small fraction of Nb and Ta could be reduced, leading to a mean formal valence slightly lower than five. At IW-4.5, Ta is mainly in the form Ta3+, and at IW-7.9, Ta appears to be Ta1+, whereas Nb is divalent (Nb2+). The possibility for Nb and Ta to be present in reduced forms has implications for the behavior of the two elements during the processes of differentiation on planetary bodies formed in the reduced parts of the early Solar System. Element partitioning is a function of size and valence, and our results show that high field strength elements could be reduced, which could change their chemical affinity. This may also be important for the Earth and Moon formation and early differentiation, as exemplified by the “Nb paradox.”