Ti Oxides Research Articles

Petrogenesis and metallogenesis of the Kawuliuke Fe-P-Ti oxide-rich intrusive complex in the Kuluketage Block, northeastern Tarim Craton

The Kawuliuke Fe-P-Ti oxide-rich intrusive complex is one of the largest layered mafic–ultramafic complexes associated with Fe-P-(Ti) oxide deposits in the Kuluketage Block, northeastern Tarim Craton, NW China. Here, based on new field observations, whole-rock trace element, radiometric dating analyses as well as Sr-Nd-Hf isotopes we propose a non-cogenetic origin of the parental magmas of the mafic–ultramafic rocks and syenite in the Kawuliuke intrusive complex (KIC), both of which formed synchronously at circa 808 Ma.Geochemical characteristics and Sr-Nd-Hf-S isotopes ((87Sr/86Sr)i = 0.70437–0.70560; εNd(t) = -2.60 to −7.15; εHf(t) = -1.3 to −10.0; δ34S = -2.98 ‰ to + 2.36 ‰), in combination with minerals composition and previous research, strongly indicate that the mafic–ultramafic rocks of the KIC formed via extensive crystal fractionation/cumulation of a tholeiitic magma, possibly derived from partial melting of an enriched subcontinental lithospheric mantle previously modified by slab-released fluids in a continental rift setting. The Kawuliuke syenite, meanwhile, is interpreted as generated by the emplacement of syenitic melts from the differentiation of newly coeval underplating basaltic magmas at depth based on lines of evidence from petrography, geochemical signatures and Sr-Nd-Hf isotopes. Our newly presented enriched Sr-Nd-Hf isotopic signatures, together with previous research, suggest that the enriched subcontinental lithospheric mantle could be metasomatized by asthenosphere mantle melts in different degrees. We further show the Kawuliuke clinopyroxenite-related apatite-rich oxide ores were the products of normal fractional crystallization/cumulation of H2O-Fe-P-Ti enriched residual magma in high oxygen fugacity condition, which experienced high differentiation. The tempo-spatial relationships of the KIC and other regional coeval mafic rocks jointly suggest that the KIC was most likely formed in response to the proposed mid-Neoproterozoic mantle plume in Tarim Craton, which likely induced partial malting of, and likely mixed with, the metasomatized subcontinental lithospheric mantle, to form the KIC with clinopyroxenite-related Fe-P-Ti oxide mineralization.

Breakdown of the anodized nanostructured anatase for photovoltaic devices: The effect of water content in the electrolyte on preparation of large surfaces of nanotubes

Many researchers are heavily involved in attempts to optimise the course of the electrochemical anodization for preparing nanostructured anatase thin-films. Particularly challenging is to prepare vertically aligned arrays of ordered nanotubes of anatase for application in the photovoltaic (PV) systems which require preparing larger homogeneous crack-free surfaces without the need for pre- or post-treatments. Having previously optimised the anodization cell geometry and electrical settings, here we focus on the electrolyte contribution during the anodization, specifically water content. It was elucidated that the water content can influence the equilibrium and the mechanisms behind several competing processes responsible for the formation of nanotubes (NT): (i) titania formation, (ii) NT formation over intermediate titanium hexafluoride, and (iii) etching of the mentioned phases. We employed broad structural, microstructural, electrochemical, and spectroscopic characterisation tools to shed more light on the development of the system with respect to water presence. Namely, water presence built up conductivity of the electrolyte, and consequently allowed faster oxidation of Ti and subsequently faster etching. Water content increase also facilitated the dissolution of the titanium hexafluoride which is the only water-soluble phase in the system. At moderate water content, the synergy of these processes facilitated: (I) forming the initial titania protective layer (titania prevented short circuits and thus eliminated the need for pre-deposition of protective layers), (II) growth of NT (upgraded the charge transfer), and (III) diminishing the residual nanoformations at the surface of residual titanium oxide or hydroxide phases (fewer nanoformations at surface and fewer residues increased charge transfer and apparent transparency and thus eliminated the need for post-treatment). The highest water content promoted excessive oxidation/etching where first NT with expanded tip were formed (crown-like NT), and then wormholes arose. Similarly, disproportioning in dissolution/oxidation/etching occurred at the lowest water contents resulted in less perfect NTs. The bottlenecks of the whole anodization process were identified proving the feasibility of the compositionally novel preparing procedure for obtaining perfect NT. Specifically for the solar cell application, 12% of water in the electrolyte will facilitate growth of the large-scale crack-free TNTs, with other parameters constant. In the course of the investigation, it was evidenced electrolyte can be utilised as a useful tool for controlling anatase to rutile occurrence and vertical distribution.

Understanding casting behaviour of low carbon high manganese steel through detailed characterization of mould powder and mould top slag

ABSTRACT This study focused on multistage characterization techniques in developing an understanding of the abnormal casting behaviour of low carbon high manganese (LCHMn) steel. In addition to raw mould powder used for casting LCHMn steel, mould top slag samples were also collected for normal and abnormal casting conditions. Raw mould powder and top slag samples were characterized using XRF, XRD, and SEM-EDS to determine chemical composition, crystallinity and morphology. The chemical composition results revealed deviation of normal and abnormal behaviours from the mould powder due to the pickup of oxides of Al, Mn, and Ti. The SEM analyses of raw mould powder showed different granular particle sizes while pores and glassy/crystalline structure were seen for normal and abnormal behaviour at casting. CaF2, CaSiO3, and Na2CaSi3O9 were revealed as the mineralogical phases. There was a modified crystalline phase present in the abnormal behaviours at casting due to pickup of other oxides.

Ceramic coatings by microarc oxidation of Ti and Al alloys

The influence of niobium carbide (NbC) incorporation on the structure and properties of the Microarc Oxidation (MAO) coatings prepared on Ti alloy and Al alloy was investigated in a solution composed of sodium hexametaphosphate, sodium tetraborate, sodium hydroxide, and sodium silicate. MAO was employed in the based solution with and without the addition of NbC particles. The phase composition and microstructure of the MAO coatings were evaluated using X-ray diffraction and scanning electron microscopy with an energy dispersive spectrometer. In addition, microhardness tester, tribometer, and electrochemical workstation were respectively used to carry out the microhardness, frictional property, and corrosion resistance of the coatings. The MAO coatings obtained on Ti alloy in the solution without NbC particles consisted mainly of Anatase and Rutile TiO2, and the oxide coatings on the Al alloy consisted primarily of γ-Al2O3. Adding NbC particles to the solution improved the forming speed and compactness of the MAO coatings on Ti and Al alloys, and NbC was detected in the coatings through X-ray diffraction. The NbC particles with high hardness and good chemical stability were evenly distributed in the MAO coatings. Therefore, the frictional property and corrosion resistance of the NbC-reinforced MAO coatings are markedly higher than the base oxide coatings on Ti and Al alloys.

Whole-rock geochemistry and mineral compositions of gabbroic rocks and the associated Fe–Ti (–V) oxide deposit in the Gonamsan intrusion, South Korea

The NS trending sill-like Gonamsan gabbroic intrusion in the central region of the Korean Peninsula intruded Neoproterozoic metasedimentary rocks composed of schists intercalated with gneisses, marbles, and quartzites. The intrusion has an east zone (EZ) composed of diorite–monzodiorite, diorite–gabbro, and oxide gabbro–monzodiorite, and a west zone (WZ) composed of quartz monzodiorite. These silicate rocks have similar primitive-mantle normalized trace elements and chondrite-normalized REE patterns, suggesting that they are co-magmatic. Plagioclase anorthite (An) contents (1.9–54.0), pyroxene MgO/ (MgO + FeO) (Mg#) (35.4–73.7), and olivine forsterite (Fo) values (14.5–20.9) show a wide range through the intrusive silicate suite, but each unit has narrow ranges, and reverse fractionation is absent. The Fe–Ti (–V) oxide mineralization only occurs in the EZ and is characterized by variations in morphology, size, mineral assemblages, and chemical compositions of the Fe–Ti oxide minerals. Stratiform Fe–Ti (–V) oxide mineralization interlayered with diorite–monzodiorite is restricted to metasedimentary host rocks in the central region of Gonamsan and comprises magnetite and ilmenite with lesser amount of olivine, tschermakite, apatite, spinel, pyroxene, and plagioclase. Lenticular mineralization occurs along the western margin of the diorite–gabbro and consists of magnetite and ilmenite with minor hornblende, apatite, chlorite, and spinel. Oxide gabbro interlayered with relatively thin monzodiorite bands forms cyclical units irregularly distributed throughout the EZ and consists of olivine and pyroxene with minor interstitial magnetite, ilmenite, and apatite. Magnetite is the principal Fe–Ti oxide mineral, and varies in chemical composition and microtextures in different ore zones. Overall, the compositions of magnetite from all mineralized zones fall in the compositional fields for magmatic Fe–Ti, V deposits defined by Dupuis and Beaudoin (2011). Magnetite from the stratiform Fe–Ti oxide mineralization is compositionally consistent with those from high-temperature silicate melts and displays complex ilmenite and spinel exsolution textures that resulted from re-equilibration of ulvöspinel–magnetite solid solution during cooling. In contrast, magnetite from the lenticular ore and oxide gabbro are compositionally consistent with being derived from evolved low-temperature melt. Based on the whole-rock geochemistry, mineral composition, and mineralization distribution, the Fe–Ti (–V) oxide mineralization in the Gonamsan intrusion seems to be related to Fe–Ti-rich melt formed from magmatic fractionation and migration along a relatively permeable zone, rather than other magmatic and post-magmatic processes.

High-entropy Sm2B2O7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) oxides with highly disordered B-site cations for ultralow thermal conductivity

• A family of high-entropy Sm2B2O7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) oxides with highly disordered cations on the B-sites has been synthesized by introducing large atomic-size mismatch, and mass and charge disorder at B-sites. • The high-entropy Sm2(Nb0.2Sn0.2Ti0.2Y0.2Zr0.2)2O7 and Sm2(Nb0.2Ta0.2Y0.2Yb0.2Zr0.2)2O7 exhibit ultralow thermal conductivity of 1.35 W•m−1•K−1 and 1.23 W•m−1•K−1, respectively. • The ultralow thermal conductivity of Sm2B2O7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) oxides can be attributed to the highly disorder on the B-sites including atomic-size mismatch, mass fluctuations and strain field fluctuations together with oxygen vacancies . • The high-entropy fluorite Sm2(Nb0.2Ta0.2Y0.2Yb0.2Zr0.2)2O7 also shows average thermal expansion coefficient of 10.2 °C−1 and high-temperature stability up to 1600 °C in air. Materials with ultralow thermal conductivity and good thermal stability are of great interest in numerous applications such as energy storage and conversion devices, and thermal insulation components. In this work, a family of high-entropy Sm 2 B 2 O 7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) oxides with highly disordered cations on the B-site has been synthesized by introducing large atomic-size mismatch, mass and charge disorder. Through tuning the composition, the high-entropy Sm 2 B 2 O 7 oxides can be engineered from pyrochlore to fluorite structure, accompanied with an order-disorder transition. The pyrochlore Sm 2 (Nb 0.2 Sn 0.2 Ti 0.2 Y 0.2 Zr 0.2 ) 2 O 7 and fluorite Sm 2 (Nb 0.2 Ta 0.2 Y 0.2 Yb 0.2 Zr 0.2 ) 2 O 7 exhibit low thermal conductivities of 1.35 W·m −1 ·K −1 and 1.23 W·m −1 ·K −1 , respectively, indicating their good thermal insulation. In addition, the high-entropy fluorite Sm 2 (Nb 0.2 Ta 0.2 Y 0.2 Yb 0.2 Zr 0.2 ) 2 O 7 also shows average thermal expansion coefficient of 10.2 × 10 −6 °C −1 and high-temperature stability even after thermal exposure at 1600 °C in air for 30 h. These results indicate that the high-entropy Sm 2 B 2 O 7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) can be promising candidates for thermal barrier coatings and thermally insulators.

Rainer Waser – A Pioneer of Fundamentals of Resistive Switching Memories

Rainer Waser – A Pioneer of Fundamentals of Resistive Switching Memories

Corrosion behaviors of Mo0.5NbTiVCr0.25 and Mo0.5NbTiV0.5Zr0.25 multi principal element alloys in high temperature borated and lithiated water

The corrosion behaviors of Mo0.5NbTiVCr0.25 and Mo0.5NbTiV0.5Zr0.25 multi principal element alloys were investigated in borated and lithiated water at 360 ℃. The two multi principal element alloys showed superior corrosion resistance than the M5 zirconium alloy due to the thinner inner oxide layer of the former, which may be related to composition of the inner oxides. The inner oxides primarily consisted of Ti and Nb elements, while the outer oxides primarily consisted of Ti, Nb and V elements. The corrosion behavior was dominated by the oxidation of Ti and Nb, and the corrosion process was explored.

The bifunctional role played by thiocyanate anions on the active dissolution and the passive film of titanium in hydrochloric acid

ABSTRACT The electrochemical behaviour of titanium dissolution and passivation in HCl was examined with and without the SCN− anions using potentiodynamic polarisation, electrochemical impedance spectroscopy, and current transients techniques. The nature of the Ti oxide film was characterised by utilising XPS and SEM tools. The corrosion current i corr, the critical passivation current i cc, and the passive current i pass values increased significantly when the HCl concentration, scan rate, and temperature were raised. On the contrary, the addition of SCN− anions decreases the i corr value, indicating that the Ti dissolution was inhibited as a result of SCN− adsorption on the Ti surface. The inhibition efficiency increased with increasing the concentration of SCN−. However, SCN− anions lead to destabilised passivity in the passive zone. The formation of the Ti oxide film is a diffusion-controlled operation, as shown by the i–t curves. According to the XPS measurements, the passive oxide coating consists mainly of TiO2 and less of Ti2O3.

In Vitro and Electrochemical Characterization of Laser-Cladded Ti-Nb-Ta Alloy for Biomedical Applications

Titanium (Ti) and its alloys are predominant choices for use as biomaterials in human implants. Research has shown the adverse effects of using commercial Ti alloy Ti-6Al-4V in the human body, and this presents a need for viable alternatives. In this study, Ti alloy Ti-17Nb-6Ta was manufactured by laser cladding—a prominent additive manufacturing (AM) technology. Laser cladded specimens were evaluated for their in vitro and electrochemical behavior. A human osteosarcoma cell line (MG-63 cells) was used for in vitro investigations. Cell proliferation was good in the physiological medium, and cells were alive when in contact with the laser cladded alloy, even after two to three weeks, indicating good cell viability and compatibility with this alloy. Electrochemical characterization was carried out in Ringer’s solution, and noticeably lower corrosion current density and corrosion rate values were observed. The lower amounts of these parameters indicated the passivation behavior due to multi-layer Ti, Nb, and Ta alloy oxide films. These oxide films also enhanced osseointegration. Thus, the Ti-17Nb-6Ta alloy can be an ideal biocompatible alternative to Ti-6Al-4V.

Optimisation of Anode Construction for PEM Water Electrolysis

Transformation of energy sector to carbon dioxide neutrality is one of the main goals of governments around the globe. This is closely connected with propagation of Hydrogen Economy scheme, where excess electric energy from renewable sources is stored in the form of hydrogen. Hydrogen is a valuable commodity and promising energy vector with numerous applications not only directly in industry, but also as a fuel for mobility sector. Water electrolyser with polymer electrolyte membrane (PEMWE) represents a key component for hydrogen production within Hydrogen Economy scheme. Among its principal advantages is use of water as a feed, option of operation at elevated pressure, flexibility of operation suitable for pairing with renewable electric sources and very high power to volume ratio, critical for delocalised hydrogen production.Despite these outstanding properties of PEMWE, several shortcomings still limit its application on industrial scale. The main constraint is a high loading of precious metals, especially on the anode, where IrO2 is the state-of-the-art catalyst and anode itself is a component most susceptible to degradation due to highly oxidative, acidic environment. In general, the anode consists of unsupported catalyst nanoparticles based on IrO2 and Ti porous transport layer (PTL), which is often coated with Pt, Au or Ir to prevent its passivation during electrolyser operation. The absence of catalyst support and microporous layer (MPL) on the top of Ti PTL decreases utilisation of catalyst, leading to the use of high catalyst loadings. Despite the significant progress in development of catalyst supports and Ti PTLs with gradient porosity in recent years, the issue of high Ir content and PTL without precious meatal coating passivation is still far from being solved. This presents a bottleneck for further PEMWE application.The goal of this work is to optimise anodic PTL for PEMWE in an efficient and economically feasible way, avoiding coating of PTL by precious metals and decreasing catalyst loading by its better utilisation. This was achieved by preparation of microporous layer on the top of commercially available PTLs, based on Ti felts and sintered Ti. From the materials potentially applicable for MPL, TiH2 was chosen due to its good electron conductivity and material compatibility with PTL. TiH2 is inherently thermodynamically unstable in presence of water and O2, forming non-stoichiometric Ti oxides with significantly lower electron conductivity. However, the rate of TiH2 oxidation at PEMWE operating conditions and impact of this process on cell Ohmic resistance was not yet investigated.MPL based on TiH2 powder was deposited on the surface of Ti PTLs by means of ultrasonically assisted spray deposition from ink. TiH2 was bonded in MPL by ionomer based on perfluorinated-sulfonated polymer. Stability of treated PTLs with and without MPL was investigated by single cell tests performed with in-house made membrane-electrode assembly in catalyst-coated membrane arrangement, consisting of commercial state-of-the-art materials at temperature of 80 °C and constant voltage of 2 V for 120 h. During single cell operation, its performance was periodically investigated by polarisation curves and impedance spectroscopy, performed at selected voltages. Impact of MPL of PEMWE performance is discussed in term of cell performance, Ohmic resistance and polarisation resistances.This study was supported by the Grant Agency of the Czech Republic under project no. GC20–06422J.

Microwave-ignited DC-plasma ejection from basalt: Powder-generation and lightning-like effects

A phenomenon of dusty plasma ejected from basalt is presented, in the form of a stable, long-lived fire-pillar, solely sustained by a direct-current (DC) supply. The plasma is emitted to the air atmosphere from a molten hotspot, initially created in the basalt rock by localized microwave-heating (LMH). After an LMH-to-DC transition, the plasma column is solely sustained as a fire-pillar of ∼2 cm diameter, ∼4-cm height using a DC supply of ∼0.2 kV, ∼5 A, steadily lasting for periods longer than 3 min. The dusty-plasma products, accumulated in a powder form, consist of micro- and nanoparticles of basalt's components, including oxides of Si, Na, Fe, P, K, Mg, and Ti. The experimental conditions for the DC sustainability of basalt's dusty-plasma column are analyzed by various theoretical estimates. A possible relevance of these laboratory observations is attributed to atmospheric fire-pillar-like effects, associated, for instance, with volcanic-, ball-lighting, and lunar dusty-plasma phenomena. A potential application, utilizing this effect of DC-sustained dusty-plasma columns, is proposed for the direct extraction of mineral powders from rocks.

The Northernmost Volcanoes in South America (Colombia, 5–6°N): The Potentially Active Samaná Monogenetic Volcanic Field

The northernmost volcanism in South America (5–6°N) is defined by the presence of several monogenetic volcanic edifices in Colombia, which have been grouped within the Samaná monogenetic volcanic field. Few volcanoes have been studied so far, but they are recognized as a cluster of volcanoes of intermediate-to-acid composition, formed by both explosive and effusive eruptions. This study aims to 1) characterize four more monogenetic volcanic edifices as part of the Samaná field, 2) highlight the potentially active volcanism in an area previously defined as non-volcanogenic, and 3) give insights into the magmatic evolution of the scarcely studied evolved monogenetic volcanism linked to subduction zones worldwide. To achieve these aims, this study uses petrography, mineral chemistry, whole-rock geochemistry, geochronological analyses, and geothermobarometric calculations. The analyses indicate that the field is formed by at least seven volcanoes with similar composition and that it is long-lived and potentially active. Mineralogically, the erupted products host plagioclase (An26–74) and amphibole (magnesio-hastingsite, tschermakite, and occasionally mangesio-hornblende) as the most abundant phases, although orthopyroxene (enstatite; Wo2–3, En70–76, Fs21–28) and clinopyroxene (diopside and augite; Wo44–45, En41–42, Fs13–15, and Wo42–44, En46–47, Fs10–11) also appear. Less abundant phases such as olivine (Fo81–88), biotite (magnesiobiotite), quartz, and Fe–Ti oxides (Usp4–89 Mag96–11, and Ilm61–92 Hem39–8) were also recognized. Chemically, the volcanoes are of andesitic-to-dacitic composition with calc-alkaline affinity and show similar behavior of LILE, HFSE, and REE, which is typical for magmatism in subduction environments. Ages yield a range between 1.32 ± 0.06 Ma (K/Ar) and 16,919 ± 220 years (14C). The results also indicate that the volcanoes share a common magmatic source that fed the individual eruptions and that the magma differentiation is mainly controlled by processes of fractional crystallization, although evidence of magma recharge processes or magma mixing and assimilation as a minor process are also recognized. Geothermobarometric calculations suggest that the different mineral phases are crystallized between 1,194 and 687 °C and a pressure between 0.88 and 0.19 GPa. This indicates that the aforementioned processes occurred not only at the main magmatic reservoir (∼33–21 km depth) but also at different stagnation zones at shallower levels of the crust (∼7–5 km). Taking this into account, it is shown that the magma evolution of this monogenetic field is more complex than individual batches of magma reaching the surface uninterrupted, as is normally described for monogenetic volcanic fields of more mafic compositions in other tectonic settings.

Modulation doping of the FeSe monolayer on SrTiO3

The discovery of higher-temperature superconductivity in FeSe monolayers on ${\mathrm{SrTiO}}_{3}$ substrates has sparked a surge of interest in the interface superconductivity. One point of agreement reached to date is that modulation doping by impurities in the substrate is critical for the enhanced superconductivity. Remarkably, the universal doping about 0.1 electrons per Fe, i.e., so-called ``magic'' doping, has been observed on a range of Ti oxide substrates, which concludes that there likely is some important interaction limiting the FeSe doping. Our study discovers that the polarization change at the interface Se because of the close proximity to the substrate from that in the free-standing FeSe film significantly amplifies the total potential difference at the interface above and beyond the work function difference for charge transfer. Additionally, the titanate substrate with a large number of free electrons basically serves as an ``infinite'' charge reservoir, which leads to the saturated FeSe doping with the complete removal of the interface potential gradient. Our work has developed the theory for modulation doping in the van der Waals materials/oxides heterostructure, providing a solution to the puzzle of magic doping in FeSe monolayers on titanates. The information also presents experimental pathways to accommodate a variable carrier density of FeSe monolayers via modulation doping.

Vanadium and Cobalt Occurrence in the Fe-Ti-V Oxide Deposits Related to Mesoproterozoic AMCG Complex in NE Poland

On the basis of geochemical whole-rock and mineralogical point analyses, the concentrations of V and Co were determined in magnetite-ilmenite oxide ores, associated with sulphides, at the Krzemianka and Udryn deposits in the Mesoproterozoic Suwałki Anorthosite Massif (SAM) in NE Poland. EPMA analyses showed that the main carrier of vanadium was magnetite (mean = 0.42 wt%) and, to a lesser extent, ilmenite (mean = 0.14 wt%) and minor Al-spinels (mean = 0.04 wt%). In turn, cobalt was found mainly in the form of isomorphic substitutions in magmatic sulphides such as pentlandite (mean = 4.41 wt% Co), pyrrhotite (mean = 0.16 wt%), and chalcopyrite (mean = 0.11 wt%). Moreover, Co-enrichments were also recognized in the secondary sulphides, such as pyrite and bravoite, replacing pyrrhotite (means = 1.6 and 2.7 wt% Co, respectively), and in the form of different thiospinels ((Fe, Ni) (Co, Ni)2S4), mainly siegenite (mean = 22.0 wt% Co), replacing pyrrhotite and pentlandite. Vanadium cations were substituted in Fe, Ti oxide minerals in place of Fe+3 cations, and in the case of cobalt, Fe+2 cations were substituted in sulphides and thiospinels. Vanadium and cobalt showed high Person’s correlation coefficients (r = 0.70), indicating their close spatial coexistence and a common source, which was parental anorthosite-norite magma of the SAM suites. The common magma genesis of magnetite-ilmenite and sulphide mineralization was also confirmed by the very similar shapes of the curves of REE content in the oxide-sulphide ores in relation to chondrite, in which negative Eu anomalies and positive Sm anomalies are clearly visible. Although the average contents of vanadium and cobalt were low (arithmetic means = 960 ppm, and 122 ppm, respectively), the resources of these metals were estimated to be large due to the enormous reserves of magnetite-ilmenite ores hosted by the SAM. However, the Fe-Ti-V ores associated with Fe, Ni, Co, and Cu sulphides were considered to be sub-economic because of their depth of occurrence (mainly 1.0 km below the surface level); their metal contents, which were usually too low; and additionally the fact that the location is in a highly environmentally protected landscape and lake area.

CO Oxidation over Pd Catalyst Supported on Porous TiO2 Prepared by Plasma Electrolytic Oxidation (PEO) of a Ti Metallic Carrier.

A porous TiO2 layer was prepared with the plasma electrolytic oxidation (PEO) of Ti. In a further step, Pd was deposited on the TiO2 surface layer using the adsorption method. The activity of the Pd/TiO2/Ti catalyst was investigated during the oxidation of CO to CO2 in a mixture of air with 5% CO. The structure of the catalytic active layer was studied using a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray diffraction (XRD). The PEO process provided a porous TiO2 layer with a uniform thickness in the range of 5–10 µm, which is desirable for the production of Pd-supported catalysts. A TOF-SIMS analysis showed the formation of Pd nanoparticles after the adsorption treatment. The conversion of CO to CO2 in all samples was achieved at 150–280 °C, depending on the concentration of Pd. The composition of Pd/ TiO2/Ti was determined using ICP-MS. The optimum concentration of Pd on the surface of the catalyst was approximately 0.14% wt. This concentration was obtained when a 0.4% PdCl2 solution was used in the adsorption process. Increasing the concentration of PdCl2 did not lead to a further improvement in the activity of Pd/ TiO2/Ti.

Styles of Fe–Ti–V ore deposits in the Neoproterozoic layered mafic-ultramafic intrusions, south Eastern Desert of Egypt: Evidence for fractional crystallization of V-rich melts

The Korab Kansi and Abu Ghalaga Neoproterozoic mafic-ultramafic intrusions in the South Eastern Desert (SED) of Egypt host economic Fe–Ti–V oxide deposits, ∼41 million tons for Abu Ghalaga ores. The Korab Kansi deposits are composed of titanomagnetite with subordinate ilmenite layers in dunites, gabbros and troctolites. The Abu Ghalaga ores consist of hemo-ilmenite and ilmenite with subordinate magnetite and titanomagnetite lenses in norites, gabbros and anorthosites. The difference in calculated oxygen fugacity (fO2: ∼ ΔFMQ–1.24 to −3.28 for Korab Kansi ores and +0.21 to −0.3 for Abu Ghalaga ores) during subsolidus re-equilibration is consistent with different dominant iron and titanium oxides, magnetite and hematite, respectively. Ilmenite in both deposits is enriched in Nb, Ta, Zr, Hf and V, but is poor in Cr and Ni relative to coexisting magnetite, which belongs to magmatic Fe–Ti–V deposits. The Korab Kansi and Abu Ghalaga ore deposits are rich in Ti, Fe, V, Nb, Ta and Hf with subordinate S, Cu, Ga and Zn at high fO2. The Abu Ghalaga gabbroic intrusion crystallized from ferrobasaltic magmas of tholeiitic affinity at lower temperature (∼1082 °C) and pressure (5.1 kbar) than the Korab Kansi intrusion (∼1180 °C, 8.3 kbar). The Korab Kansi ore deposits mainly formed by fractional crystallization of olivine followed by in situ crystallization of Fe–Ti oxides from ferropicritic/ferrobasaltic parent melts at the floor of the magma chamber. The Abu Ghalaga ores formed as a result of more advanced fractional crystallization of ferrobasaltic parent melts. The Abu Ghalaga Fe–Ti oxides in massive ores at the base of the intrusion grew in situ, whereas most ore lenses in the middle to the top of the intrusion precipitated from immiscible oxide melts that separated from the parental magma in association with floatation of plagioclase and sulfide crystals at a late magmatic stage. Both Fe–Ti ore deposits formed from similar mantle-derived magmas but Korab Kansi ores formed as early fractionates, whereas Abu Ghalaga ores formed late. The Korab Kansi ilmenite is rich in vanadium (up to 3.8 wt% V2O5) relative to that of other magmatic deposits. Its parental melt may have formed from locally Fe–Ti–V enriched part of the Neoproterozoic mantle due to interaction with upwelling asthenosphere or a mantle plume. Controlling factors for formation of economic SED Fe–Ti–V deposits were the V-rich ferropicritic/ferrobasaltic compositions of the parental magmas, and addition of H2O to cause high magma ƒO2.

High-entropy (Hf0.25Zr0.25Ti0.25Cr0.25)B2 ceramic incorporated SiC-Si composite coating to protect C/C composites against ablation above 2400 K

The ablation behavior and protection mechanism of high-entropy (Hf0.25Zr0.25Ti0.25Cr0.25)B2 ceramic incorporated SiC–Si (HETMB2-SiC-Si) composite coating on C/C composite were investigated under ultra-high temperature (up to 2404 K) dynamic ablation test using oxyacetylene torch (OAT). Thermodynamic computations, multicomponent oxide phase diagrams, schematic diagram of the oxidation protection effect of multi-component ceramics, as well as microstructure and composition evolution analyses were built and carried out. Compared with the monolithic or conventional solid-solution diborides incorporated SiC-based composite coatings, the HETMB2-SiC-Si composite coatings presented the minor mass and thickness changes after ablation for 60 s. The oxidation-dominated ablation procedure with good resistance to mechanical scouring mainly contains the selective oxidation of each elements in the coating materials, the phase separation of the Zr, Hf and Ti (group IVB) oxides, the selective melting of Si (group IVA) and Cr (group VIB) oxides, as well as the oxygen diffusion. This resulted in differentiated oxidation scale with enhanced high-temperature thermally-stable and defect-sealing ability under different ablation environments (regions). This work provides precious and insightful information for introducing high‐entropy materials to improve the heat resistance of high-temperature thermal protection systems applied in increasingly severe environments.

The eruptive chronology of the Carihuairazo volcano (Ecuador): Recurrent sector collapses of a Middle Pleistocene stratovolcano of the northern andes

The eruptive chronology of arc volcanoes consists of construction stages usually punctuated by large collapse events affecting the edifice. In this paper, we reconstruct the eruptive chronology of Carihuairazo volcano, a Middle Pleistocene edifice from the Ecuadorian segment of the Andean Northern Volcanic Zone. This study is based on extensive fieldwork on both the proximal flanks of the volcano and the medial-to-distal deposits of the nearby Ambato basin, as well as a large dataset of geochronological (40K-40Ar, 14C) and geochemical (major and trace element) data. The Basal Carihuairazo edifice is mainly composed of an andesitic lava flow succession dated at 230–200 ka. The resulting edifice suffered a first sector collapse that was responsible for a relatively large (4 ± 1 km3) debris avalanche deposit (DAD-1) that covers the entire Ambato basin. This event occurred between 206 ± 4 and 216 ± 5 ka. Then, Carihuairazo started a succession of construction (Intermediate and Terminal lava flow successions) and destruction stages lasting about 50 ky (i.e., from 200 to 150 ka), which are composed by thick block-and-ash flow deposits (L- and U-BAFD) and debris avalanche deposits (DAD-2). This volcanic succession is recorded in the Ambato basin, interlayered with several tephra fallout deposits (TFD-1 to −4) whose source is the neighbouring Huisla-Mulmul volcanic complex. The current morphology of Carihuairazo results from two additional sector collapses (DAD-3 and -4) that occurred during the past 40–50 ka, i.e., following a long period (at least 100 ka) without volcanic activity. We stress these debris avalanches were not related with magmatic activity. Samples from the Carihuairazo volcano defines a medium-K magmatic trend composed of andesites and dacites with a mineral assemblage of plagioclase, amphibole, ortho- and clino-pyroxene, and Fe–Ti oxides. The evolution of the Carihuairazo edifice, recorded in the medial-distal deposits of the Ambato basin, represents a unique example in the Ecuadorian arc of an edifice that experienced successive destruction and construction stages during a major part of its volcanic history.

Modulating the Oxidation State of Titanium via Dual Anions Substitution for Efficient N2 Electroreduction.

The electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable ammonia synthesis but remains significantly challenging due to the low yield and poor selectivity. Herein, a facile N and S dual anions substitution strategy is developed to tune the Ti oxidation states of TiO2 nanohybrid catalyst (NS-TiO2 /C), in which anatase TiO2 nanoplates with dense Ti3+ active sites are uniformly dispersed on porous carbon derived from 2D Ti3 C2 Tx nanosheets. The catalyst NS-TiO2 /C exhibits a superior ambient NRR efficiency with an NH3 yield rate of 19.97µg h-1 mg-1cat and Faradaic efficiency of 25.49% and is coupled with a remarkable 50 h long-term stability at -0.25V versus RHE. Both experimental and theoretical results reveal that the N and S dual-substitution effectively regulate the Ti oxidation state and electronical properties of the NS-TiO2 /C via simultaneously forming interstitial and substitutional TiS and TiN bonds in the anatase TiO2 lattice, inducing oxygen vacancies and dense Ti3+ active species as well as better electronic conductivity, which substantially facilitates N2 chemisorption and activation, and reduces the energy barrier of the rate-determining step, thereby essentially boosting NRR efficiency. This work provides a valuable approach to the rational design of advanced materials by modulating oxidation states for efficient electrocatalysis.