Nb Content Research Articles

Mineralogy, geochemistry, origin, and potential industrial applications of kaolin deposit from Hassi Abyad, Mauritania

The Hassi Abyad kaolin deposit is in the southern part of Mauritania, around 45 km east of the town of M'Bout. Hassi Abyad lies in the middle of the Mauritanides Shield, which consists of deformed and metamorphosed Precambrian and Paleozoic formations. Complementary geological, mineralogical, and geochemical studies have been carried out to help answer questions linked to the origin of these kaolin and to determine the potential suitability for different industrial applications. The mineralogical compositions showed that Hassi Abyad kaolin is mainly composed of kaolinite (61–96%) and other minerals such as chlorite, illite, muscovite, cronstedtite, quartz, rutile, magnetite, laumontite, and gibbsite. The average chemical composition of the kaolin samples is 35.84% Al₂O₃, 45.27% SiO₂, and 14.19% LOI. Other oxides occur in low concentrations (less than1%). The higher chemical indices of alteration CIA (99.5%) and CIW (99.6%) indicate that this kaolin deposit underwent a high degree of alteration during the process of kaolinization of the source rock. The absence of high temperature minerals such as pyrite, topaz and dickite, and the presence of high Ce + Y + La and Cr + Nb contents signifies that the development and evolution of this deposit are affiliated with supergene processes. This kaolin is derived from a lateritic material, proving that they are the source rock of this deposit. The geochemical and mineralogical characteristics indicate that Hassi Abyad kaolin is applicable in ceramics, paper, cosmetics, pharmaceutics, bricks making, and pottery.

Systematic trends in the substitution mechanisms of minor elements in cassiterite

A dataset of 4751 EPMA point analyses on cassiterite crystals from 18 localities spanning a range of different granite-related Sn-bearing mineral systems was investigated and compared with thermodynamic considerations from speciation and lattice strain models. The existence of previously inferred charge balanced coupled substitution mechanisms of Fe3+, Fe2+, Mn2+, Nb5+, Ta5+ and W6+ for Sn4+ are confirmed. The homo­valent substitution of Sn4+ by Ti4+ and Zr4+ is also confirmed, and the first evidence for homovalent substitution of Nb4+ and W4+ in natural cassiterite is presented. The preferred substitution mechanisms for Ti, Fe, Mn, Nb, Ta, W and Zr vary systematically as a function of the mineralising environment. Cassiterite precipitated from silicate liquid dominated systems (such as in pegmatites) primarily display a coupled Fe–(Nb,Ta) substitution mechanism with a 1:2 stoichiometry, whereas cassiterite precipitated in systems dominated by autometasomatic processes (such as greisens) more closely follow a 1:1 stoichiometry, as well as increased levels of Ti. Cassiterite precipitated solely from hydrothermal fluids (such as Sn–(W) quartz vein systems) exhibit the highest Ti concentrations, with lower contents of Fe–(Nb,Ta) coupled substitutions, instead displaying a switch to the incorporation of Fe3+ via FeO.OH stoichiometry. Hydrothermally precipitated cassiterite from skarn systems display the highest Fe3+ contents, and the lowest Nb, Ta and Ti contents. These systematic changes define a continuous trend in a Ti–(Fe + Mn)–(Nb,Ta) ternary diagram, allowing for classification of the primary source of alluvial cassiterite.

Multi-physics simulation of non-equilibrium solidification in Ti-Nb alloy during selective laser melting

This paper underscores the critical role of temperature distribution in the molten pool on the resulting solidification microstructure during selective laser melting (SLM) process. A powder-resolved computational fluid dynamics (CFD) model of Ti-Nb alloy is established to investigate heat transfer and fluid flow in the molten pool. When comparing the bulk model to the powder bed model, discrepancies in temperature gradient and cooling rate can reach up to 26.29 % and 18.32 %, respectively. Utilizing the powder bed CFD model, temperature gradient and cooling rate data at the molten pool boundary are integrated into the finite interface dissipation phase-field model. The simulation results illuminate the non-equilibrium solidification microstructure in the SLMed Ti-Nb alloy. Results indicate that the rapid solidification fosters a pronounced solute trapping effect, mitigating solute microsegregation. The microstructure manifests as cellular and dendritic structures, with Nb concentration in cellular cores and depletion in intercellular region. Predicted primary dendrite arm spacing (PDAS) or cell size range between 0.4 to 0.6 μm, consistent with experimental observations. In particular, the study reveals a transition from dendritic to cellular and from cellular to planar structures, with an accompanying analysis of the underlying mechanisms.

Chemical and boron isotopic compositions of tourmaline from the pegmatite in Ke'eryin rare metal orefield, Eastern Tibet: Implications for pegmatitic evolution

Pegmatites occur widely in the Ke'eryin rare metal orefield. The genesis and evolution of the Ke'eryin pegmatites are still in dispute, and morphological and geochemical studies on tourmalines from the Ke'eryin pegmatites are limited. In this study, in-situ analyses of major and trace elements and B isotope were conducted to uncover the origin of tourmaline and the evolution of related pegmatites. Three types of tourmaline from the Ke'eryin barren pegmatite were identified: elongated columnar or needle-columnar tourmaline (Tur-1 type), isolated, disseminated, irregular, and massive tourmaline (Tur-2 type), and long columnar tourmaline (Tur-3 type). Petrographically, the Tur-1 type crystallized at the early stage of pegmatitic crystallization sequence, the Tur-2 type possibly formed at the early- and/or syn-pegmatitic crystallization sequence, whereas the Tur-3 type likely formed at the relatively late crystallization sequence. Compositionally, most tourmalines belong to the alkali group with a few falling in the vacancy group. All the tourmalines show a schorl composition and are of magmatic origin. Chemical variations from the Tur-1 to Tur-3 tourmalines are controlled by magma fractionation and melt compositions rather than crystal chemical effects. Most tourmalines follow the (Na, Mg)(Xvac, Al)−1, (Mg, OH)(Al, O)−1, and (Ca, Mg2)(Xvac, Al2)−1 exchange vectors. The higher contents of Zn, Sn, Li, Be, Nb, and Ta and negative Eu anomalies in the Tur-3 type indicate that it was likely crystallized at a more evolved stage. In combination with textural evidence and tourmaline chemistry, we suggest that the Tur-1 and Tur-2 types were formed at the relatively earlier stage of pegmatite-forming magma and the Tur-3 type was likely formed closer to the end-stage of barren pegmatite crystallization. The B isotopic compositions are relatively homogeneous and display slightly higher in the Tur-3 type, which were likely caused by fractional crystallization during B-rich magma evolution. It can be inferred that the tourmaline in more evolved and/or Li-mineralized pegmatite with magma evolution should have higher Li, Be, Nb, Ta, and Sn contents, implying that tourmaline chemistry may be used as a potential exploration indicator for rare metal mineralization.

Zircon in tin granite as tracer for fluid metasomatism and Sn mineralization

Most tin deposits in the world are genetically related to tin granite and form during complex magmatic-hydrothermal processes. Zircon is a common accessory mineral in granite and related ore systems and can host a number of ore metals, such as Sn, W, Nb, Ta, U and Th, in its crystal lattice. However, whether metal enrichment/depletion can trace ore-forming processes is still unclear. Here, we report that the metal concentrations in various types of zircons from the Mopanshan tin granites in the southern Great Xing'an Range (Northern China) can be used as good indicators of fluid metasomatism and Sn mineralization. Two lithological zones are developed in the Mopanshan pluton, including porphyritic syenogranite (PG) in the center and fine-grained syenogranite (FG) at the margin. Zircons in the PG (PGZ-1, PGZ-2, and PGZ-3) are all magmatic in origin, while zircons in the FG can be categorized into magmatic zircons (FGZ-1 and FGZ-2) and metasomatic zircons (FGZ-3). The PGZ-1 and FGZ-1 grains are transparent prismatic crystals with bright oscillatory zonation, whereas the PGZ-2 grains are murky crystals with dark oscillatory zonation. PGZ-3 and FGZ-2 grains occur as overgrowths of previously formed zircon (PGZ-1, PGZ-2, and FGZ-1) or as brown individual crystals, showing dark and homogeneous cathodoluminescence (CL) textures. The metasomatic FGZ-3 grains are translucent-opaque porous crystals with vermicular CL zonation and commonly replace FGZ-2. The trace element compositions of magmatic zircons are completely melt controlled, providing a record of magmatic evolution as a constant decrease in Zr/Hf ratios and a gradual increase in Th, U, Nb, and Ta contents. Moreover, the structure of magmatic zircons transforms from a crystalline state to an amorphous state as a consequence of radioactive decay of U and Th. A coupled dissolution-reprecipitation process is proposed for the formation of metasomatic FGZ-3. The reactive fluid is the magmatic fluid that exsolved from the melt in the late magmatic stage. The magmatic fluid replaced biotite and rare earth phosphates (mainly monazite and apatite) enclosed within biotite, resulting in significant amounts of Nb, Ta, Sn, P, Al, Ca, Fe, and REEs, which subsequently reacted with the FGZ-2 zircons to leach Th, U, Y, and HREEs. Eventually, REEs, Y, Th, and U in the fluid combined with P to form monazite and xenotime, while the other elements partially precipitated with the crystallization of the FGZ-3 zircons. Although the alteration of biotite only released approximately 190 ppm of Sn into the fluid, this is still a significant Sn source for the Sn deposits surrounding the Mopanshan pluton, taking the granite size (∼50 km2) and the volume proportion of biotite (∼5%) into account. Furthermore, based on previous studies on tourmaline from the Mopanshan granite and regional geochemistry, it may be inferred that the addition of wall rock components may also play an important role in Sn mineralization.

First-principles study on the structure, mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C high-entropy carbide ceramics

High-entropy carbide ceramics (HECCs) have demonstrated extraordinary properties and broad application potential. However, the action mechanisms of metallic elements on the properties have not been understood in depth. In this study, the structural stability and the mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C HECCs across a broad composition spectrum were systematically analyzed based on the density functional theory and Debye–Grüneisen model. The crystal structure was constructed and validated through experimental testing. The mechanical properties such as elastic moduli, ductility, hardness, and Poisson's and Pugh's ratios were calculated. Furthermore, the temperature dependence of bulk moduli, thermal expansion coefficients, and heat capacities of the HECCs were investigated. To interpret the elastic and toughening mechanisms of non-equiatomic HECCs, the electronic structures were investigated. The results indicate that the HECCs with a single solid solution phase of the FCC rock-salt structure are thermodynamically stable. The HECCs containing higher Nb and Ta contents have greater strength and stiffness, and those containing higher Ti and Hf contents exhibit greater hardness and brittleness than the equiatomic HECC. In addition, non-equiatomic HECCs containing higher Nb and Ta contents have larger bulk moduli and lower linear thermal expansion coefficients, which can be attributed to the stronger covalent interaction among metallic elements and carbon. This study is expected to have an impact on designing ideal HECCs for high-temperature applications under extreme environments.

Experimental Investigation of the Impact of Niobium Additions on the Structural Characteristics and Properties of Ti-5Cr-xNb Alloys for Biomedical Applications.

In this study, a series of Ti-5Cr-xNb alloys with varying Nb content (ranging from 1 to 40 wt.%) were investigated to assess their suitability as implant materials. Comprehensive analyses were conducted, including phase analysis, microscopy examination, mechanical testing, and corrosion resistance evaluation. The results revealed significant structural alterations attributed to Nb addition, notably suppressing the formation of the ω phase and transitioning from α' + β + ω to single β phase structures. Moreover, the incorporation of Nb markedly improved the alloys' plastic deformation ability and reduced their elastic modulus. In particular, the Ti-5Cr-25Nb alloy demonstrated high values in corrosion potential and polarization resistance, signifying exceptional corrosion resistance. This alloy also displayed high bending strength (approximately 1500 MPa), a low elastic modulus (approximately 80 GPa), and outstanding elastic recovery and plastic deformation capabilities. These aggregate outcomes indicate the promising potential of the β-phase Ti-5Cr-25Nb alloy for applications in orthopedic and dental implants.

Corrosion behavior of Nb-doped FeCrAl alloy in 500°C steam

The corrosion behavior of Fe-13Cr-4Al-2.2Mo, a candidate cladding material for accident tolerant fuel, doped with varying concentrations of Nb (0, 0.5, 1.0, and 1.5 wt%), was investigated under conditions of 500°C/10.3 MPa superheated steam. Upon exposure, a triple-layer oxide film comprising outer, inner, and diffusion oxide layers was formed. The results indicate that the addition of Nb significantly enhances the corrosion resistance of this alloy by reducing the thickness and porosity of the oxide film. The enhanced volume diffusion rate of Al and Cr, facilitated by the solid solution Nb, along with the inhibited inward diffusion of oxidant ions along grain boundaries owing to Laves phase precipitates, contributed to the enhanced corrosion resistance of the Nb-doped Fe-13Cr-4Al-2.2Mo alloy.

Nb Doping and Alloying of 2D WS2 by Atomic Layer Deposition for 2D Transition Metal Dichalcogenide Transistors and HER Electrocatalysts.

We utilize plasma-enhanced atomic layer deposition to synthesize two-dimensional Nb-doped WS2 and NbxW1-xSy alloys to expand the range of properties and improve the performance of 2D transition metal dichalcogenides for electronics and catalysis. Using a supercycle deposition process, films are prepared with compositions spanning the range from WS2 to NbS3. While the W-rich films form crystalline disulfides, the Nb-rich films form amorphous trisulfides. Through tuning the composition of the films, the electrical resistivity is reduced by 4 orders of magnitude compared to pure ALD-grown WS2. To produce Nb-doped WS2 films, we developed a separate ABC-type supercycle process in which a W precursor pulse precedes the Nb precursor pulse, thereby reducing the minimum Nb content of the film by a factor of 3 while maintaining a uniform distribution of the Nb dopant. Initial results are presented on the electrical and electrocatalytic performances of the films. Promisingly, the NbxW1-xSy films of 10 nm thickness and composition x ≈ 0.08 are p-type semiconductors and have a low contact resistivity of (8 ± 1) × 102 Ω cm to Pd/Au contacts, demonstrating their potential use in contact engineering of 2D TMD transistors.

Association between trace element contents in normal human breast and age investigated using inductively coupled plasma mass spectrometry

The etiology of breast cancer remains largely unclear; however, it is well known that the incidence of this disease increases with age. In the presented work, for the first time, the age-related changes of Al, As, B, Ba, Bi, Cd, Ce, Cr, Cu, La, Li, Mg, Mn, Nb, Ni, Pb, Rb, Sb, Sn, Sr, Ti, W, and Zn content in the mammary gland of women aged 16-60 years was investigated. For this purpose, a method based on inductively coupled plasma mass spectrometry (ICP-MS) was employed, which makes it possible to determine the mass fractions of these trace elements in microsamples (mass from 10 mg) of breast tissue. With the help of this method, the material obtained during the autopsy of 38 practically healthy women aged 16-60 years who died suddenly was studied. Trace element mass fractions were determined in two age groups of women: 16-40 and 41-60 years old. Using the parametric Student's t-test and the non-parametric Wilcoxon-Mann-Whitney U-test to compare two age groups, as well as Pearson's correlation coefficients between age and trace elements mass fractions, it was found that the Cu, Mg, Rb, and Zn mass fractions in normal breast tissue decrease with age, while the As mass fraction increase. The phenomenon of the age-related changes of trace elements mass fractions in the normal mammary gland, discovered for the first time, requires further detailed study.

Triassic oceanic–continental transition of the Ganzi–Litang Ocean basin: Evidence from high-Mg andesites and Nb-enriched basalts in the Litang area, Eastern Tibet

Petrological evidence of the oceanic–continental transition of intra-oceanic arcs enables the identification and reconstruction of the transformation of ocean basins into continents. In this study, we present new elemental and Sr–Nd isotopic compositions and zircon U–Pb ages for Triassic andesites and basalts in the Litang area, Eastern Tibet. Andesites in Cunge and basalts in Juewu contain zircon grains with U–Pb ages of 246 ± 2 and 248 ± 2 Ma, respectively, indicating a Middle Triassic origin. Andesites in Cunge have high SiO2 contents (53.1–56.5 wt%), MgO contents (5.15–7.13 wt%), and Mg# values (54–61), similar to Sanukite-type high-Mg andesites. Basalts in Juewu have high TiO2 (1.43–1.80 wt%) and Nb (12.5–20.2 ppm) contents, and high Nb/U and (Nb/La)N values, typical of Nb-enriched basalts. The andesites and basalts were both characterized by low (87Sr/86Sr)i values (0.7033–0.7044) and positive εNd(t) values (+4.2–+4.8). Therefore, interactions between melt from the subducting slab and mantle wedge peridotite formed andesites in Cunge, whereas the partial melting of mantle peridotite metasomatized by an adakitic melt (produced by the melted slab) formed basalts in Juewu. The findings of this study indicate that the formation of the andesites and basalts in the Litang area were related to intra-oceanic subduction magmatism, which was the product of the westward subduction of the Ganzi–Litang Ocean basin in the Middle Triassic.

Fine tuning of Nb-incorporated TiO2 thin films by atomic layer deposition and application as efficient electron transport layer in perovskite solar cells

Access to finely tuned thin films that can act as electron transport layer (ETL) and adapt to the absorber composition and whole cell fabrication process is key to achieve efficient perovskite-based solar cells. In this study, the growth of mixed niobium-titanium oxide (Nb-TiO2) thin films by atomic layer deposition and its use to extract photogenerated electrons is reported. Films were obtained at 200 °C from titanium (IV) i-propoxide, (t-butylimido)tris(diethylamido)niobium(V), and water by introducing Nb2O5 growth cycle in a TiO2 matrix. Process parameters (order of precursor introduction, cycle ratio) were optimized; the growth mechanism and the effective Nb incorporation were investigated by an in situ quartz crystal microbalance and x-ray photoelectron spectroscopy. The composition, morphology, structural, and optoelectronic properties of the as-deposited films were determined using a variety of characterization techniques. As a result, a fine control of the film properties (between TiO2 and Nb2O5 ones) could be achieved by tuning Nb content. To allow a successful implementation in solar devices, a comprehensive annealing study under several conditions (temperatures, various atmospheres) was conducted leading to an evolution of the optical properties due to a morphological change. Ultimately, the incorporation of these 15 nm-thick films in mesoscopic perovskite solar cells as ETL shows an improvement of the cell performances and of their stability with increasing Nb content, in comparison of both TiO2 and Nb2O5 pure compounds, reaching power conversion efficiency up to 18.3% and a stability above 80% of its nominal value after 138 h under illumination.

Influence of Doping of Niobium Oxide on the Catalytic Activity of Pt/Al2O3 for CO Oxidation

Pt-based alumina catalysts doped with varying niobium contents (i.e., 0, 1.20, 2.84, and 4.73 wt%, denoted as Pt/Nb–Al2O3) were synthesized via stepwise impregnation for catalytic CO oxidation. The effective incorporation of Nb species without altering the fundamental properties of the Al2O3 support was confirmed by the characterization using XRD, Raman, and TEM. Pt metallic particles were uniformly deposited on the niobium-doped alumina (Nb–Al2O3) support. H2-TPR and CO–TPD analyses were performed to reveal the influence of niobium doping on catalyst reduction and CO adsorption properties. The results consistently demonstrate that the doping of niobium affects reducibility and alleviates the competitive adsorption between CO and O2 during the CO reaction. Particularly, when compared to both undoped and excessively doped Pt/Al2O3 catalysts, the catalyst featuring a 2.84 wt% Nb content on Pt1.4/Nb2.8–Al2O3 displayed the most promising catalytic performance, with a turnover frequency of 3.12 s−1 at 180 °C. This superior performance can be attributed to electron transfer at the Pt/NbOx interface.

Effect of Controlling Nb Content and Cooling Rate on the Microstructure, Precipitation Phases, and Mechanical Properties of Rebar.

Seismic anti-seismic rebar, as materials for supporting structures in large buildings, need to have excellent mechanical properties. By increasing the Nb content and controlling the cooling rate, the microstructure and precipitation behavior of the steel are adjusted to develop seismic anti-seismic rebar with excellent mechanical properties. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and a universal tensile testing machine were used to characterize the microstructure, precipitation phases, and mechanical properties of the experimental steels. The results show that the ferrite grain size, pearlite lamellae layer (ILS), and small-angle grain boundaries (LAGB) content of the high-Nb steels decreased to 6.39 μm, 0.12 μm, and 48.7%, respectively, as the Nb content was increased from 0.017 to 0.023 wt.% and the cooling rate was increased from 1 to 3 °C·s-1. The strength of the {332}<113>α texture is the highest in the high-Nb steels. The precipitated phase is (Nb, Ti, V)C with a diameter of ~50 nm, distributed on ferrite, and the matrix/precipitated phase mismatch is 8.16%, forming a semicommon-lattice interface between the two. The carbon diffusion coefficient model shows that increasing the Nb content can inhibit the diffusion of carbon atoms and reduce the ILS. The yield strength of the high-Nb steel is 556 MPa, and the tensile strength is 764 MPa.

Metallogenetic epoch and material source of Be-pegmatite differentiated from biotite granite in Mufushan complex

The Mufushan Complex (MFSC) is a significant rare metal mineralized in the central China district and is renowned for its marked economic value of rare metal deposits. While the main rare metal mineralization (RMM) stage in the MFSC relates to the magmatic event of two-mica monzogranite, the mineralization event related to biotite monzogranite remains unknown. To fill this gap, this study focuses on porphyritic biotite monzogranite and adjacent Be-rich pegmatite samples obtained from Changqing Pegmatite No. 1, which is situated in the southeastern part of the MFSC. We subjected these samples to zircon U–Pb dating and Hf isotope analysis using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and utilized an electron probe X-ray microanalyzer (EPMA) and LA–ICP–MS to examine the major and trace elements present in the muscovite samples. Our findings revealed precise chronological data for the geological history of Changqing, pinpointing the intrusion age of biotite monzogranite to 145.8 ± 1.1 Ma and the crystallization age of Be-rich pegmatite to 144.9 ± 1.1 Ma, firmly situating these events within the Late Jurassic to Early Cretaceous epoch. Regarding isotopic composition, zircon εHf (t) for granite ranged from −9.29 to −5.09, and their corresponding TDM2 ranged from 1788 to 1520 Ma. Similarly, zircon εHf (t) for pegmatite ranged from −7.89 to −5.47, and their corresponding TDM2 ranged from 1699 to 1544 Ma. These isotopic signatures strongly indicate a shared origin for the initial magma of granite and pegmatite. The partial melting of the thick Lengjiaxi Group tasedimentary strata serves as a material source for RMM. The transition from granite to pegmatite exhibits remarkable constancy in the primary components of muscovite. By examining its geochemical attributes, we observed synchronous decreases in FeO, MgO, SiO2, MnO, Be, Rb, and Cs, coupled with synchronous increases in Nb and Ta contents, along with Ta/Nb values. These findings strongly imply that the Changqing biotite monzogranite and Be-rich pegmatite originate from the continuous differentiation and evolution of a common magmatic source, establishing a clear genetic relationship between them. The MFSC has its origins in three distinct stages of magmatic activity and RMM spanning from 160 Ma to 120 Ma. Considering the distribution patterns of similar pegmatite veins, the metallogenic potential observed during the biotite granite stage may serve as an external indicator of marked mineralization within large batholiths.

Flame-retardant mechanism of TiAl alloy by frictional ignition method

TiAl is used as the preferred material for aero-engine low-pressure turbine blades, which is also faced with similar problems of “Titanium fire” under long-term high temperature service conditions. In this paper, the micro-combustion behavior of TiAl is discussed. It is found that the flame-retardant of the TiAl alloy has better performance compared to that of TC11, TA11. In this regard, the higher content of Al and Nb is identified as the primary reason for the superior flame-retardant performance for TiAl alloy. Moreover, the segregation serves as a transport channel for atoms and entraps oxygen atoms during the process of extended combustion. The three-stage combustion model before deflagration is presented. Furthermore, the flame-retardant mechanism before and after deflagration is explained, highlighting the main reason behind the formation of the final morphology of the alloy after combustion.

Effect of Nb addition on microstructure and mechanical properties of TiC/Ti-7.8Cr composites

The morphology of TiC is not difficult to control when the titanium matrix composites with high TiC content are prepared by the melting-casting method. TiC tends to grow into dendrites, increasing the brittleness of the Ti matrix composites. In this study, in-situ TiC-reinforced titanium matrix composites with varying Nb content were prepared by adding Nb. The effects of adding Nb on the microstructure evolution and mechanical properties of the composites were studied. The results show that with the increase of Nb content, the grain size of the composites decreased gradually from 276 μm to 122.8 μm, the primary TiC content decreased, and the eutectic TiC content increased. On the other hand, the orientation relationship between TiC (111)//β-Ti (110) and TiC [10 1‾]//β-Ti [1‾ 11] was studied by HTEM. The two-dimensional mismatch of TiC (111)//β-Ti (110) is only 9.06 %, which means that TiC can be used as a nucleation particle of β-Ti. Furthermore, there was a gradual increase in the Rockwell hardness of the composites as the Nb content was incrementally raised from 0 wt% to 1.5 wt%, with the highest recorded value being 47.4 HRC. Notably, when the Nb addition reached 1.0 wt%, the composite achieved its maximum tensile strength of 1352.9 MPa, signifying a 69 % enhancement compared to the absence of Nb. This is due to the combined effect of fine grain strengthening, solution strengthening, and second-phase strengthening in the composites. It introduces a novel approach to regulate the in-situ formation of TiC morphology during the preparation of titanium matrix composites through melting and casting.

Mineralogy and 40Ar-39Ar dating of the recently discovered tainiolite occurrences in the Kaerqiaer fluorite Belt, western Altyn Tagh Terrane

The Kaerqiaer Fluorite Belt (KFB) contains the Kaerqiaer, Xiaobaihegou, Kumutashi, Northern Layidan, and Gaijike fluorite deposits in the western Altyn Tagh Terrane of NW China. An occurrence of Li-bearing mica tainiolite (KLiMg2(Si4O10) F2) has been recently discovered, associated with fluorite-bearing alkali feldspar granite. The tainiolite is hosted by fluorite-calcite veins that contain assemblages of tainiolite-fluorite-calcite and apatite-bastnaesite-tainiolite-fluorite-calcite along the contact zone with alkali feldspar granite. The tainiolite occurs as euhedral crystals and has high concentrations in the veins. 40Ar-39Ar dating of the tainiolite from Xiaobaihegou yields an age of 421 ± 2 Ma, and single-crystal X-ray diffraction confirms the tainiolite has a monoclinic 1 M−type with a C2/m (#12) space group. Minor structural variations in the mica are attributed to the substitution of Li for Mg. EPMA and LA-ICP-MS analyses show that the tainiolite has high Li, Rb, Cs, Sn and Nb concentrations, and low Ta, total REE concentrations. The average Li2O content of the fluorite-tainiolite veins reaches 0.36 %, surpassing the economic cut-off grade. We suggest that the fluorite deposits formed from highly fractionated Li-F-P-rich residual melt evolved from the parental magmas of alkali feldspar granite. The tainiolite mineralisation may result from subsequent hydrothermal activities caused by the reactivation of regional faults under the extensional regime between the Middle Altyn and Eastern Kunlun terranes. The discovery of tainiolite occurrences made KFB a potential area for not only F but also Li resources.

Microstructural characterization and mechanical behaviors of Ti-xNb alloys (x = 34–44.at%) fabricated by spark plasma sintering: The role of sintering temperature and Nb content

Microstructural characterization and mechanical behaviors of Ti-xNb alloys (x = 34–44.at%) fabricated by spark plasma sintering: The role of sintering temperature and Nb content

Stabilization of γ-Fe2O3 nanoparticles to heat by doping Nb and its property studied by Mössbauer spectroscopy

Nb5+-doped γ-Fe2O3 was synthesized by sol–gel method followed by calcination at various temperatures from 200 to 700 °C, analyzed using Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS) and Mössbauer Spectroscopy. PXRD results show the formation of γ-Fe2O3 at 300 °C and it begins to transform to α-Fe2O3 at 350 °C for pure and 2 at.% Nb-doped samples. As the Nb doping increases (≥3.8 at.%), the transformation was suppressed up to 600 °C. TEM EDS confirms the incorporation of Nb to γ-Fe2O3 lattice in 9.1 at.% Nb sample calcined at 500 °C. At elevated temperature of 700 °C, γ-Fe2O3 went through full transformation to α-Fe2O3 by expelling large amount of Nb to the surface forming FeNbO4. TEM EDS confirms the compositional change during this process with reduced Nb content in α-Fe2O3 and Nb-rich nanoparticle on the surface of α-Fe2O3. Superparamagnetic properties were observed for Mössbauer spectra when the Nb doping increased, which is caused by decreased particle size. The slight increase in internal magnetic field also indicated the transformation from γ-Fe2O3 to α-Fe2O3. High Nb doping with 20 and 40 at.% shows the formation of FeNbO4 at lower temperature where limited or almost no Nb substitution in α-Fe2O3 was detected by EDS.