Ta Content Research Articles

Basic and Associated Granitoid Magmatism and Geodynamic Evolution of the Altai Accretion–Collision System (Eastern Kazakhstan)

Abstract —The paper summarizes the results of study of the geologic position, composition, and age of basic igneous associations in Eastern Kazakhstan during the late Paleozoic (Carboniferous–Permian). At that time, the Altai accretion–collision system was developed here, which resulted from the interaction of the Siberian and Kazakhstan paleocontinents. The performed studies made it possible to establish three major stages of basic magmatism, corresponding to different stages of evolution of the collision system: early Carboniferous, late Carboniferous, and early Permian. The chemical composition of ultrabasic-basic associations changed, with a successive increase in the contents of K2O, P2O5, TiO2, LREE, Rb, Ba, Zr, Hf, Nb, and Ta. The variations in magma compositions were determined by different compositions of mantle sources (harzburgites, spinel lherzolites, and garnet lherzolites) and different degrees of their melting. The early Permian ultrabasic-basic associations are the most enriched in TiO2 and incompatible components (P2O5, Zr, Hf, Nb, and Ta), which indicates the involvement of relatively enriched mantle sources in the partial melting. All manifestations of mantle magmatism were accompanied by subsynchronous crustal magmatism (granitoid intrusions or silicic volcanics). The major crustal magmatism was manifested in the early Permian; the area of its occurrence was dozens of times larger than the area of Carboniferous crustal magmatism. Possible geodynamic scenarios for magmatism are considered for each stage. The early Carboniferous (C1s) magmatism of the early orogeny stage was manifested locally and was the result of the detachment of the subducting lithosphere (slab) beneath the margin of the Kazakhstan continent. The middle Carboniferous (C2m) magmatism of the late orogeny stage was manifested throughout the area; it was caused by the activation of shear–extension motions along large faults and the orogen collapse. The early Permian magmatism was the result of the interaction of the Tarim mantle plume with the lithosphere, which comprised three stages: initial interaction, maximum interaction, and relaxation. This magmatism in the study area was caused by a combination of thermal disturbance in the upper mantle and the lithosphere extension processes.

Petrogenesis of Ta-Nb mineralization related Early Cretaceous Lingshan granite complex, Jiangxi Province, southeast China: Constraints from geochronology, whole-rock and in-situ mineral geochemistry, and Nd-Hf isotopic compositions

The Lingshan granite complex, located in the northeast part of the Qin-Hang Belt, Jiangxi Province, southeast China, has produced the largest Ta-Nb deposits in China, i.e., the Huangshan Nb-Ta and Songshugang Ta-Nb-(W-Sn) deposits. This complex is spatially a ring-like multiphase batholith, and comprises a series of granitic rocks from the central to marginal units. Mafic microgranular enclaves (MMEs) occur only in the central unit. Geochronologic results show that the magmatic activities at Lingshan district took place at Early Cretaceous, with similar emplacement ages (133–134 Ma) between the central and marginal units. The Lingshan granites are metaluminous to weakly peraluminous (most A/CNK < 1.1), and display typical A-type affinity. However, the whole-rock REE contents and Zr/Hf and (La/Yb)N ratios exhibit an abnormal increase from the central to marginal units. The Li, Rb and Cs elements of biotite as well as the Zr/Hf ratios of zircon do not exhibit a continuous enrichment trend from the central towards marginal granites. All these features suggest that the generation of Lingshan granites is more complex than the fractional crystallization from a single parental magma. Alternatively, a crystal mush model could be applied to better interpret the geochemical and isotopic contrasts between different granite phases. The marginal granites were likely formed by later crystallization events after the rejuvenation and extraction from the crystal mush reservoirs, while the central granites were formed from the residual crystal-rich mush with a relatively low terminal porosity. Moreover, the Nb and Ta contents of biotite exhibit a gradual enrichment with increasing fluorine contents in the marginal granites. The enrichment of lithium and fluorine in the granitic melt can significantly promote the proportion of non-bridging oxygens (NBOs) for coordinating Nb and Ta in the melt, further enhancing the solubility of columbite and tantalite, and eventually causing the Nb and Ta elements either incorporate into the mineral lattice of micas in the early marginal granites or form columbite-group minerals in the pegmatite/altered granite. In summary, we propose that the Ta-Nb enrichment event in the Lingshan district is spatially and genetically related to the extensive fractionation evolution from central to marginal units.

Tunable optical and plasmonic response of Au nanoparticles embedded in Ta-doped TiO2 transparent conducting films

Localized surface plasmon resonances (LSPRs) are fascinating optical phenomena occurring in metal nanostructures, like gold nanoparticles (NPs). Plasmonic excitation can be tailored efficiently in the visible range by acting on size, shape, and NP surroundings, whereas carrier density is fixed, thus restricting the LSPR modulation. Transparent conductive oxides (TCOs), on the other hand, are gaining increasing interest for their transparency, charge carrier tunability, and plasmonic features in the infrared. The combination of these two materials into a metal-TCO nanocomposite can give access to unique electrical and optical characteristics, to be tailored in view of the desired optoelectronic application. In this paper, Au NPs and Ta-doped ${\mathrm{TiO}}_{2}$ TCO films have been merged with the aim to master the Au plasmon resonance by acting on the dielectric properties of the surrounding TCO. Morphology, structure, and electrical properties have been investigated as well to understand the optical response of the nanosystems. The role of the embedding geometry has been explored, revealing that the largest LSPR shift (550--760 nm) occurs when the NPs are sandwiched in the middle of the film and not at the bottom of the film (substrate-film interface). Ta doping in the TCO has been varied (5--10% at. and bare ${\mathrm{TiO}}_{2}$) to induce a permittivity change of the matrix. As a result, Au LSPR is clearly blueshifted when decreasing the dielectric permittivity at higher Ta content in the sandwich configuration. Despite the nonoptimal electrical performance caused by defectivity of the films, Au-$\mathrm{Ta}:\mathrm{Ti}{\mathrm{O}}_{2}$ multifunctional nanocomposites are promising candidates for their optical behavior as highly tunable plasmonic conductive metamaterials for advanced light management.

Improving tensile property and thermal stability of the Cu-Ta alloy by alloying with Cr

The wide applications of Cu-10Ta (at%) composite are limited due to the high cost of Ta element (24 wt%). In the present research, Cu-0.6Ta-0.6Cr and Cu-0.6Ta alloys with low Ta content were fabricated by mechanical alloying and spark plasma sintering. The results indicate that the thermal stability and tensile strength of Cu-0.6Ta-0.6Cr alloy are significantly increased by the addition of Cr. The microstructure characterizations reveal that the performance enhancement of Cu-0.6Ta-0.6Cr alloy is ascribed to the transformation of nanoparticles in the matrix from Ta to more stable Cr2Ta Laves and the refinement effects of these nanoparticles from 19.4 nm to 14.1 nm. This work provides a potential for the wide applications of Cu-Ta alloy with low Ta by alloying with Cr at elevated temperatures.

A new class of alumina-forming superalloy for 3D printing

A new class of crack-resistant nickel-based superalloy containing high γ′ fraction is studied for the laser-powder bed fusion (L-PBF) process. The effects of the (Nb+Ta)/Al ratio is emphasized, a strategy that is shown to confer excellent low-temperature strength whilst maintaining oxidation resistance at high temperatures via stable alumina scale formation. The processability of the new alloys is characterized with respect to defect assessment by micro-focus X-ray computed tomography; use is made of a prototype turbine blade geometry and the heritage alloy CM247LC as a benchmark. In all cases, some processing-related porosity is present in thin wall sections such as the trailing edge, but this can be avoided by judicious processing. The cracking seen in CM247LC – in solid-state, liquation and solidification forms – is avoided. A novel sub-solvus heat treatment strategy is proposed which takes advantage of AM not requiring solutioning; super-solvus heat treatment is inappropriate since it embrittles the material by deterioration of the texture and coarsening of grain boundary carbides. The tensile strength of the new superalloy is greatest when the Nb+Ta content is highest and exceeds that of CM247LC up to ∼900°C. The oxidation resistance is best when Al content is highest, and oxidation-assisted cracking resistance maximized when the (Nb+Ta)/Al ratio is balanced. In all cases these are equivalent or superior to that of CM247LC. Nevertheless, the creep resistance of the new alloys is somewhat inferior to that of CM247LC for which the γ′, C, and B contents are higher; this implies a processing/property trade-off which requires further clarification.

Titanite U-Pb dating and geochemical constraints on the Paleozoic magmatic-metamorphic events and Nb-Ta mineralization in the Yushishan deposit, South Qilian, NW China

Titanite, as one significant petrogenetic tracer, occurs in the ore-bearing alkaline unit (syenite and aegirine-augite syenite dikes) and in the barren calc-alkaline unit (monzodiorite) and metamorphosed strata (called as leptynite) in the recently found large Yushishan Nb-Ta deposit from South Qilian, NW China. Most titanite grains in the alkaline unit display obvious shape-preferred orientation and zonation, coexisting with allanite, zircon and alkali feldspar. Some titanite grains from the alkaline unit have been partially or completely altered into fine-grained euxenite and/or Nb-rich rutile, but retained their original crystal shapes. Although some titanite grains in the igneous rocks show obvious core-rim textures, both of them yield almost the same U-Pb ages. Combined with U-Pb dating of zircon from these different rock units, the complex magmatic-metamorphic events in the Yushishan district can be subdivided into two different periods: the first one occurring in the Neoproterozoic (ca. 834–790 Ma, zircon U-Pb ages) that are related to the regional volcanism and metamorphic activities and the formation of leptynite during the metamorphism, while the second one occurring in the early Paleozoic (ca. 490–470 Ma, titanite and zircon U-Pb ages) that are related to the formation of granitic intrusions and subsequent metamorphic process and Nb-Ta mineralization. Geochemically, titanite from these igneous rocks is consistent with the typical features of igneous titanite, such as high Fe and REE contents, and negative Eu anomalies. The zoned titanite in both alkaline (mainly syenite) and calc-alkaline units uniformly displays a core-to-rim decreasing trend for the Fe, REE, Nb and Ta contents and Th/U ratios, corresponding to a secular variation from the magmatic to metamorphic evolution. Titanite from the leptynite is interpreted to be of metamorphic origin, with low Fe and REE contents, weakly positively sloping REE patterns, along with positive Eu anomalies. It is suggested that the titanite can be used as an indicator of metal fertility and ore potential for the host rocks/fluids. The high Nb and Ta features in titanite from the alkaline unit suggest a genetic relationship between the alkaline granitic magmatism and Nb-Ta mineralization in the Yushishan deposit. In addition, the high and variable Nb and Ta contents in titanite from the leptynites reveal an inherited signature of the metamorphic fluids. Considering the absence of titanite in the ore-bearing leptynites, we speculate that titanites with high and variable Nb and Ta contents of titanite in the barren leptynites have the potential to provide abundant metals for the precipitation of Nb-Ta-bearing minerals to form economic orebodies.

Garnet and scheelite chemistry of the Weijia tungsten deposit, South China: Implications for fluid evolution and W skarn mineralization in F-rich ore system

Fluid evolution is an essential subject in the studies of hydrothermal ore-forming processes. Garnet and scheelite prevail in W-bearing skarn deposits and record plentiful information on W skarn mineralization. In-situ LA-ICP-MS trace element analyses have been carried out on the garnet and scheelite from the F-rich Weijia W deposit in South China to constrain the processes of fluid evolution and W skarn mineralization. The Weijia W deposit mainly consists of calcic and magnesian skarns and was formed through six stages of alteration and mineralization. Two stages of fluid exsolution are recognized in the magmatic-hydrothermal system. The earlier exsolved fluids are Cl-rich with rightward-sloping REE patterns and result in pre-ore skarnization. The later exsolved fluids are F-rich with relatively flat REE patterns and are responsible for W mineralization. The pre-ore garnets are LREE-enriched and HREE-depleted whereas the syn-ore garnets are LREE-depleted and HREE-enriched with lower δEu values than the former, denoting a transition from wall rock-controlled to magmatic fluid-dominated fluid-rock interaction. Combined with the skarn occurrences, mineral assemblages, and garnet textures, it is revealed that the mechanism of skarn formation shifts from more diffusive metasomatism under lower water/rock ratios to more advective metasomatism at higher water/rock ratios. The advective metasomatism with a high flux of ore-forming fluids is hydrodynamically favorable for the consequent W mineralization. The earliest-formed scheelite is akin to the host granite porphyry in REE patterns and can reflect the features of initial mineralizing fluids. It has high ΣREE (1255–5059 ppm), Y (616–1416 ppm), Nb (585–2629 ppm), Ta (14–248 ppm), Mn (up to 1977 ppm) and low Mo (mostly < 1000 ppm) contents, indicating that the primary F-rich magmatic fluids are reduced and enriched in REEs, Y, Nb, and Ta. The contents of ΣREE, Y, Nb, and Ta in scheelite are decreasing with the evolution of the F-rich mineralizing fluids. The latest-formed scheelites have distinctly lower ΣREE (2.9–140 ppm), Y (0.01–4.1 ppm), Nb (1.7–77 ppm), and Ta (0.04–0.19 ppm) contents and higher (La/Yb)N ratios and δEu values. They show 1:1 positive correlation of EuN vs. EuN* and have high Mo (up to 129466 ppm) and low Mn (as low as 3.4 ppm) contents, implying involvement of meteoric waters in the evolved ore-forming fluids and an oxidizing condition. Fluid-rock interaction, mineral precipitation, and fluid mixing largely control the process of fluid evolution. Fluorine consumption due to the formation of fluorite and the other F-rich minerals is vital for the compositional evolution of F-rich mineralizing fluids. The decrease of F concentration in fluids will depress the solubilities of REEs, Y, Nb, and Ta and enhance the LREE/HREE fractionation. Greisenization and skarnization induced the neutralization of the acidic W-bearing fluids and the liberation of Ca from the granite porphyry and carbonate strata and then triggered the scheelite precipitation. The carbonate strata contain abundant Ca and the granite porphyry is poor in Ca, and thus the economic W mineralization dominantly occurs in the skarns.

Influence of multilayer architecture on microstructure and fracture properties of arc evaporated TiAlTaN coatings

The incorporation of a fourth element in Ti1-xAlxN, like Ta, and a multilayer architecture are possible concepts to further enhance the coating performance in cutting applications. In the present study, both concepts are combined, focusing on the investigation of the microstructure and the fracture properties of two Ti1-x-yAlxTayN single layer coatings (Ti0.55Al0.44Ta0.01N and Ti0.33Al0.54Ta0.13N) and two corresponding multilayer coatings with the same bilayer thickness but an inverse layer sequence with different layer thicknesses. Energy dispersive X-Ray spectroscopy was utilized to determine the average composition of the coatings, confirming that the Al and Ta contents increase from single layer Ti0.55Al0.44Ta0.01N via the two multilayers to single layer Ti0.33Al0.54Ta0.13N. The residual stress and microstructure were studied using X-ray diffraction and scanning electron microscopy revealing higher compressive stress and grain refinement with higher Al and Ta content, which provoked an increasing hardness as evidenced by nanoindentation experiments. In contrast, the contribution of the multilayer architecture to the hardness increase is only minor. Additionally, micromechanical bending tests revealed a trend of higher fracture stress with increasing Al and Ta content. The fracture toughness was constant for all coatings as different toughening mechanisms occur.

Determination of Phase Equilibria among δ-Fe, γ-Fe and Fe2M Phases in Fe-Cr-M (M: Hf, Ta) Ternary Systems

Phase equilibria among δ-Fe, γ-Fe, and Fe2M phases in the Fe-Cr-M (M: Hf, Ta) ternary systems were determined using bulk alloys heat-treated at high temperatures. The final goal of this study is to develop novel ferritic heat resistant steels strengthened by precipitation of Fe2M phase on the eutectoid type reaction path: δ → γ + Fe2M. The phases present in heat-treated samples were identified by microstructural characterization and X-ray diffraction pattern analysis. The chemical compositions of the phases were analyzed by energy dispersive spectroscopy. A pseudo-eutectoid trough (δ → γ + Fe2M) exists at ~1220 °C at a Hf content of 0.1% and at ~1130 °C at a Ta content of 0.6% on the vertical section at a Cr content of 9.5% in each ternary system, respectively. A thermodynamic calculation with a database that reflects reported binary phase diagrams and the present study indicates that an increase in the Cr content decreases the temperature and the Hf/Ta contents of the pseudo-eutectoid troughs. The determined phase equilibria suggest that the supersaturation of Hf/Ta for the formation of γ phase is higher in the Hf doped system than in the Ta doped system, which is probably an origin of a much slower kinetics of precipitation on the eutectoid path in the latter system.

Durability-enhanced monolithic inorganic electrochromic devices with tantalum-doped nickel oxide as a counter electrode

Nickel oxide (NiO) is a well-known electrochromic (EC) material with anodic coloration. However, NiO degrades significantly upon cycling with Li + /H + -conducting electrolytes. Doping with various additives is the most effective method to enhance the cycling stability of NiO films. In this study, films of tantalum-doped nickel oxide, denoted as Ni 1- x Ta x oxide, were deposited onto indium tin oxide (ITO)-coated glass substrates by reactive DC magnetron co-sputtering from Ni and Ta metal targets for use as counter electrodes in monolithic inorganic EC devices (ECDs). The influence of the Ta content on the composition, structure, optical properties and EC properties of NiO was investigated. It was found that the microstructure of the Ni 1- x Ta x oxide films was closely related to the EC performance and cycling stability. With moderate optical modulation, the cycling stability and optical transmittance of the Ni 1- x Ta x oxide film with x = 0.274 were increased. All-solid-state inorganic ECDs were fabricated with the configuration ITO/WO 3 /Ta 2 O 5 /Ni 1- x Ta x oxide/ITO/glass. The full ECDs showed different EC behaviors compared to those of the Ni 1- x Ta x oxide single layers, which was attributed to the different counter electrode/ion conductor interfaces of the solid–solid and solid–liquid interfaces, respectively. The ECD fabricated with the Ni 1- x Ta x oxide film with x = 0.065 showed stable transmittance modulation up to 1000 cycles. We propose a degradation mechanism for monolithic all-solid-state inorganic ECDs based on the observed degradation in the EC performance, which can pave the way for highly durable ECDs for various optoelectronic devices. • Ta-doped Ni oxides were prepared by reactive DC magnetron co-sputtering with Ta content between 0.065 and 0.490. • A Ta content of 0.274 led to the most stable cycling stability with moderate optical modulation. • Ni 1- x Ta x oxide with x = 0.065 is an excellent electrochromic material for highly reliable electrochromic devices.

Trace‐element composition of zircon in Kofu and Tanzawa granitoids, Japan: Quantitative indicator of sediment incorporated in parent magma

AbstractZircon is one of the most important minerals in geochronologic research. Isotopic ratios and trace elements in zircons are expected to reflect those of their parent magmas. Many geochemical researchers have proposed various discrimination diagrams for zircon to indicate tectonic setting and to identify source rock. Because most detrital zircons accumulated at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. In our research, we focused on sediment involvement during granitoid formation and tried to identify trace‐element compositions in zircon that are sensitive to variation in sediment incorporation. To accomplish this, we examined trace‐element compositions of both the granitoids and the included zircons in the Kofu granitic complex and the Tanzawa tonalitic plutons in Japan. Among the high‐field‐strength elements (Th, U, Ta, Nb, Hf, and rare earth elements), only Nb and Ta concentrations in the granitoids increased as the rate of sediment contribution increased. However, the zircon did not show such trends in Nb and Ta content. Zircon Y and P contents exhibited a positive correlation, indicating that xenotime substitution occurs to some extent. Because P exists as pentavalent ions in igneous systems, its presence likely affects the concentrations of pentads in zircon. When we divided the Nb and Ta contents by the P content, it became clear that zircon Nb/P and Ta/P ratios increase depending on sediment involvement. While some exceptions exist, we found that zircon Yb/Gd ratios also respond to sediment involvement. Our data further demonstrated that zircons in granitoids with significant sediment incorporation are characterized by low Ce/P contents, which is partly attributable to monazite crystallization before zircon saturation. This study demonstrates that combining these element ratios is useful for indicating sediment incorporation.

NEW TYPES OF BASIC ROCKS IN THE KORSUN-NOVOMYRHOROD ANORTHOSITE-RAPAKIVI GRANITE PLUTON AS AN INDICATOR OF ITS PETROGENESIS

Two species types of basic rocks contrasting in chemical and mineral composition were investigated within the Korsun-Novomyrhorod anorthosite-rapakivigranite pluton (KNP) of the Proterozoic age. In comparison to more typical basic rocks of KNP, the investigated rocks are presented by the extremely Fe-rich fayalite gabbroids and the most MgO enriched biotite gabbronorite. The first of them occupy a deeper level of the Horodishche massif in the central part of KNP. According to a high-Fe association of minerals and reduced or low An content in plagioclase they may represent the crystallization of a highly evolved basic melt (after anorthosite and gabbronorites separation), which were crystallized under abyssal conditions and low oxygen fugacity. Preliminary geochemical data indicate that trace elements concentration and negligible negative Eu-anomalies (0.72-0.95) are similar to most distributed basic rocks but unlike the last it is slightly differed by decreasing La/Yb and enriched in Sc (up to 118 ppm). Thus, we suppose those rocks might be crystallized as a result of mixing highly differentiated (iron and alkali enriched) melt with the early generation of anorthitic plagioclase, with subsequent dissolution of the last. Enrichment in iron of the mafic minerals and increasing of alkalinity of plagioclase in the basic rocks is consistent with the appearance of ferrodioritic melts as a product of prolonged crystalline differentiation of the initial melt. In contrast to fayalitic gabbroids, the pyroxene-biotite gabbronorites from the border zone in according to increased Mg# of the mafic minerals and rocks are obviously the least differentiated varieties of the anorthosite-gabbronorite series. The regularities in chemical composition in such type of rocks are consistent with the liquid line of dissent for basic rocks in KNP, which implies their crystallization at an earlier stage of magma ascending. By composition, such melt can be formed at an intermediate stage from slightly differentiated melt. This is indicated by enrichment in Sr (453-881 ppm) and Ba (910-930 ppm), Eu/Eu* (0.85-1.10), increased content MgO (up to 8 wt. %), Cr and V (59-193 and 169-350 ppm respectively). At the same time these rocks are enriched in Zr and Hf (378-478 and 10.3-12.02 ppm respectively), highly enriched in Rb (169-192 ppm), with moderate Nb and Ta content (14.6-18.1 and 0.91-2.84 ppm respectively) that point out to interaction and partial assimilation by crust material. Summarizing geological data of the deep drill-holes, it is possible to reveal a general direction of the mafic minerals evolution in the basic rocks and the evidences of cryptic layering. The last are quite clearly manifested both in the large gabbro-anorthosite massifs and individual intrusive bodies. We suppose that the evolution trend of mafic mineral composition are consistent with the tholeiitic trend differentiation of the primary melt with gradual increasing of iron content (under low oxygen fugacity) during differentiation and ascending in the upper crust. According to this interpretation of the inner structure of gabbro-anorthositic massifs, on the modern erosional level of KNP are often exposed the fragments of the upper (or lateral) layered series (Fe-enriched), less often the drill-holes reach up to the heads of the lower layered series.

Mineralogy and geochemistry of pitchblende in the Changjiang U ore field, Guangdong Province, South China: Implications for its mineralization

The Changjiang U ore field developed typical granite-related U mineralization in the Zhuguangshan complex, China. Pitchblende is the most important ore mineral in these mineralizations. In this study, the mineralogy and geochemistry of pitchblende were investigated by electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) to identify the genesis of the Changjiang U ore field. Pitchblende exhibits colloidal, fragmented, spherulitic and fine-grained crystals in U ores. Its geochemical compositions are similar to those of other granite-related U deposits in South China, which have elevated contents of U, Sr, As and W; low contents of Pb, Th, Zr, Nb, Ta, Hf, Co, Ni and rare earth elements (REEs); and variable amounts of Ca, Si, Bi, Y, V and Zn. These geochemical signatures suggest that mineralization occurred through hydrothermal genesis and that the hosting Youdong and Changjiang granites acted as the dominant U sources. The uraninite in these granites might be the major U source mineral. Uranium mineralization occurred under the following conditions: low temperature (<250°C), low oxygen fugacity (log fO2=-29.5 - -25.5), weakly acidic (pH=5.3-5.9), high CO32- and F- contents and a silicon-saturated solution. Rapid changes in the physicochemical conditions of the ore-forming fluid are responsible for the precipitation of pitchblende. Combined with previous studies, we propose that U-rich granites, Cretaceous-Tertiary crustal extensions, regional faults and hydrothermal alterations were the critical factors for U formation in the Changjiang ore field.

Effects of Ta and Ti Content on Microstructure and Properties of Multicomponent Co-Ni-Based Superalloys

Effects of Ta and Ti Content on Microstructure and Properties of Multicomponent Co-Ni-Based Superalloys

Tantalum-Titanium Oxynitride Thin Films Deposited by DC Reactive Magnetron Co-Sputtering: Mechanical, Optical, and Electrical Characterization

The possibility to tune the elemental composition and structure of binary Me oxynitride-type compounds (Me1Me2ON) could lead to attractive properties for several applications. For this work, tantalum-titanium oxynitride (TaTiON) thin films were deposited by DC reactive magnetron co-sputtering, with a –50 V bias voltage applied to the substrate holder and a constant substrate temperature of 100 °C. To increase or to decrease in a controlled manner, the Ti and Ta content in the co-sputtered films, the Ti and Ta target currents were varied between 0.00 and 1.00 A, in 0.25 A steps, while keeping the sum of the currents applied to the two targets at 1.00 A. The reactive gases flow, consisting of a nitrogen and oxygen gas mixture with a constant N2/O2 ratio (85%/15%), was also kept constant. The single-metal oxynitrides (TaON and TiON) showed a low degree of crystallinity, while all the other co-sputtered films revealed themselves to be essentially amorphous. These two films also exhibited higher adhesion to the metallic substrate. The TaON film showed the highest hardness value (14.8 GPa) and the TiON film a much lower one (8.8 GPa), while the co-sputtered coatings exhibited intermediary values. One of the most interesting findings was the significant increase in the O content when the Ti concentration surpassed the Ta one. This significantly influenced the optical characteristic of the films, but also their electrical properties. The sheet resistivity of the co-sputtered films is strongly dependent on the O/(Ta + Ti) atomic ratio.

Super-hardening and localized plastic deformation behaviors in ZrB2 –TaВ2 ceramics

A systematic study of the Zr-Ta-B system was performed using thermodynamic and ab initio modeling, nanoindentation, and high-resolution TEM and XRD experiments. The phase diagram (convex hull) of the Zr-Ta-B system was constructed at 0 K, and phase stability, lattice parameters, and mechanical properties of ZrB2-TaB2 solid solutions were ascertained in silico. Dense ceramics were manufactured by the combination of combustion synthesis and hot pressing techniques. As opposed to theoretically predicted complete solubility in the ZrB2-TaB2 solid solution series, the highest experimentally attained Ta content in the ZrB2-based solution was 25–27 at%, suggesting that at higher Ta contents a non-equilibrium phase composition is formed during combustion synthesis and inherited during hot pressing. Single-phase ZrB2-TaB2 solid solutions displayed a super-hardness up to 70 GPa and coefficient of elastic recovery as high as 99.7%, which surpasses wurtzite and cubic boron nitride and rivals polycrystalline diamonds. In the non-equilibrium samples with multiple solid solutions, a “pop-in” (localized plastic deformation) effect was discovered and attributed to the formation of shearing bands, microtwins, and dislocation loops. The composition-dependent switching between super-hardened and locally plastic mechanical behavior allows the creation of a new generation of ultra-high temperature ceramic composites.

Magmatic–hydrothermal zircons in syenite: A record of Nb[sbnd]Ta mineralization processes in the Emeishan large igneous province, SW China

Zircon is a common accessory mineral in igneous rocks and can provide a record of radiation damage and hydrothermal alteration through changes in oxygen isotopic values, crystal structures, and geochemical and petrographic characteristics. Syenites with NbTa mineralization have been discovered recently in the Panxi region, which is part of the ca. 260 Ma Emeishan large igneous province in SW China. Four types of zircon were identified in samples of altered syenite from the Baicao and Luku deposits in the Panxi region. Type I zircons are fresh, similar to magmatic zircons from the Baima syenite. Type II zircons crystallized later than those of Type I and underwent weak hydrothermal alteration. Type III zircons were strongly affected by ore-forming fluids. Type IV zircons were precipitated from ore-forming fluids and occur as dipyramidal zircons or rims on Type III zircons. Type III zircons have higher Th, Hf, rare earth element (REE), Y, Pb, Nb, and Ta contents (24,261, 11978, 5597, 9080, 476, 1511, and 160 ppm, respectively) than Type I zircons (267, 918, 1344, 16.2, 5.66, and 2.16 ppm, respectively), Type II zircons (570, 8768, 1808, 3122, 42.7, 42.3, and 15.9 ppm, respectively), and Type IV zircons (2115, 9304, 3123, 5580, 61.5, 153, and 19.4 ppm, respectively). The measure DɑT is used to quantify the radiation damage undergone by zircon. A comparison of DɑT values, trace-element contents, and Raman characteristic peaks of the four types of zircon shows that chemical incorporation of trace elements into the zircon lattice has a greater impact than radiation damage on lattice distortion. Radiation damage and fluid alteration has affected the UPb isotopic system of the Type III zircons, meaning that the UPb ages of these zircons are unreliable. Similarly, UPb ages for the Type II and Type IV zircons are unreliable, due to their high U and high common Pb contents, respectively. Therefore, only the ages of Type I zircons are robust. UPb dating of Type I zircons yielded similar ages for mineralized and unaltered syenites (257 ± 0.8 and 259 ± 0.7 Ma, respectively). The NbTa mineralization of the Baicao and Luku deposits can be divided into four stages on the basis of the morphologies, element contents, and oxygen isotope values of the four types of zircon. Type I zircons represent the initial magmatic state of the syenites (stage I); Type II zircons represent the gradual evolution of magma and initial hydrothermal fluid activity (stage II); Type III zircons represent a fluid stage in which NbTa was enriched in large quantities but without mineralization (stage III); and Type IV zircons represent the mineralization stage, during which pyrochlores crystallized (stage IV). The geochemical characteristics of the Type III and IV zircons suggest that highly evolved ore-forming fluids became gradually more enriched in F, Ca, REE, Y, Th, Zr, Hf, Nb, Ta, and Pb. Furthermore, the lower δ18O values of Type II, III, and IV zircons compared with those of Type I show that meteoric water was added to the ore-forming fluid. Our findings may be more widely applicable to the development of other syenite-related deposits and their hydrothermal systems.

Tin isotopes via fs-LA-MC-ICP-MS analysis record complex fluid evolution in single cassiterite crystals

Abstract Tin isotope geochemistry of cassiterite may allow for reconstructing the fluid evolution of tin ore deposits. Here, we present cathodoluminescence (CL) imaging, trace element, and in situ Sn isotope compositions of two cassiterite crystals from an early and a relatively late stage of ore formation of the Xiling vein-style Sn deposit, southeastern China, by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS). Our results show that the early-stage cassiterite from a high-temperature feldspar-stable hydrothermal environment has core, mantle, and rim zones with a systematic decrease in δ124/117Sn3161A (relative to the Sn standard NIST 3161 A) from +0.38 ± 0.06‰ in the crystal core to –0.12 ± 0.06‰ (2 SE) in the mantle zone. This isotopic evolution, also paralleled by a decrease in Ta content by two orders of magnitude, suggests a fluid batch evolving toward isotopically lighter Sn. The very rim zone of this crystal has an intermediate tin isotope composition at about +0.05‰ δ124/117Sn3161A, combined with elevated Ta, suggestive of a second fluid batch. The late-stage cassiterite crystal from a muscovite-stable hydrothermal environment has a core with an evolved Sn isotope composition at about –0.15‰ δ124/117Sn3161A combined with low Ta, and a rim with heavier Sn isotope compositions up to +0.30 ± 0.08‰ δ124/117Sn3161A and higher Ta contents. As for the early-stage crystal, two different fluid batches must be involved in the formation of this crystal. Our pilot study highlights the advantage of spatially resolved analysis compared to conventional, solution Sn-isotope analysis of bulk cassiterite crystals. The Sn isotope variations at the microscale reveal the complexity of cassiterite crystal growth by a combination of closed- and open-system fluid evolution and isotope fractionation.

Tin enrichment in a highly fractionated A-type granite: Origin and mineralization potential of the Dayishan granite batholith in the Shi–Hang magmatic zone, South China

A-type granite intrusions in the southern Shi–Hang magmatic zone, South China, contain several world-class W–Sn deposits. The Dayishan granite batholith is located in the north of the southern Shi–Hang magmatic zone, and contains potential Sn mineralization. The batholith contains three intrusive phases, which are the Guankou, Tangshipu, and Nibantian phases. The Guankou phase consists mainly of biotite–K-feldspar granite (G1). The Tangshipu phase consists of three secondary units, which are coarse-grained biotite monzogranite (G2) that cut monzogranite (G3) and fine-grained two-mica monzogranite (G4). The Nibantian phase consists of coarse-grained two-mica monzogranite (G5). Zircon U–Pb dating indicates that the G1 to G4 granites were emplaced at ca. 160 Ma and the G5 granites formed at ca. 144 Ma. All the granites are silica-rich (SiO2 = 69.24–77.02 wt%) A2 sub-type granites, among which G1 granites are metaluminous and G2 to G5 granites are peraluminous. High εNd(t) (−6.9 to − 5.2) and zircon εHf(t) (−6.2 to − 1.9) values suggest that the parental magma was probably derived by partial melting of lower crust, which was induced by input of mantle-derived basaltic magmas. Oxygen fugacity determinations show that the G2 to G5 granitic magmas were reduced, but the G1 granitic magmas were relatively oxidized.From the G1 to G4 granites, Ba, Th, Nd, Zr, Hf, and rare earth element contents decrease, while Rb and Ta contents increase, indicative of extensive fractional crystallization of K-feldspar, plagioclase, and accessory minerals. This suggests that the G1 granites represent the least fractionated magmas, while the G2 to G4 granites are the highly fractionated products of the G1 granitic magma, with the G4 granites being the most fractionated. The G5 granites were formed during a later magmatic activity, though they show similar geochemical features with the G2 and G3 granites.Due to this continuous fractionation process, Sn was efficiently and progressively enriched in the G2 to G4 granites, as indicated by the good correlations between Sn contents and TiO2 contents, Eu/Eu*, Rb/Sr, Rb/Ba, K/Rb, Zr/Hf, Nb/Ta, and Y/Ho ratios, and TE1,3 values. Furthermore, the G2 to G4 granites crystallized at the magmatic–hydrothermal transition. These data indicate that the G2 to G4 granites underwent Sn mineralization, but the G4 granites are the best target for exploration. The G5 granites might also have Sn mineralization potential considering the similar geochemical features with G2 and G3 granites. Given the reduced nature of the magmas, the potential economic mineralization types are greisen and skarn.

Direct determination of a topmost atomic layer of (100) surfaces on (La0.3Sr0.7)(Al0.65Ta0.35)O3 single crystals annealed in air by high‐resolution scanning transmission electron microscopy

Herein, we investigated the surface of an (La0.3Sr0.7)(Al0.65Ta0.35)O3 (LSAT) single crystal via scanning transmission electron microscopy (STEM) after annealing in air. We found amorphous mounds and atomically flat surfaces formed on the surface of the (100) LSAT single crystal subsequent to heat treatment. These surface mounds mainly constituted SrO, including ~50 at.% Al. The atomically flat surface showed a B‐site termination determined by the direct surface observation at the atomic scale through HAADF‐STEM. The atomic arrangements on the surface were accommodated by surface‐mound formation and La evaporation. Consequently, the ordered structure disappeared because of the increase in the Ta content at the terminated B‐site layer.