Ti Oxides Research Articles

Visualization of cathode spot control using laser irradiation and oxide addition in wire arc additive manufacturing of titanium alloys

Arc instability is one of the most critical problems in gas-metal-arc (GMA) based wire arc additive manufacturing of titanium (Ti) alloys. It can result in a poor bead surface, surface oxidation, and spattering. In particular, the relocation of the cathode spot area is the main cause of big spatters because of the high thermal energy of the molten droplet at the molten pool surface. In this study, two cathode spot control techniques were applied using auxiliary laser heating and prelaid oxides, and the behaviors of the cathode spots and arc were visualized using high-speed photography. When the laser beam was irradiated in front of the GMA, a cathode spot was formed at the laser irradiation position, and the cathode jet did not interfere with the arc plasma and droplet transfer from the GMA. However, when the distance between the GMA and the laser irradiation position increased by more than 8 mm, multiple cathode spots were established, and spattering increased. The prelaid Ti oxide particles increased the metal deposition efficiency by establishing multiple and dispersed cathode spots rather than a concentrated cathode spot by droplet impingement. It was found that the volumetric transfer efficiencies (excluding spattering) for the laser-assisted control and Ti oxide powder were up to 99.87% and 91.2%, respectively.

Effect of Mold Flux Containing Ce2O3 on the Contents of Aluminum, Silicon, and Titanium in Incoloy825 Super Alloy

The effect of mold flux containing Ce2O3 on the contents of aluminum, silicon, and titanium in Incoloy825 super alloy was investigated based on the slag-steel interfacial chemical reaction experiment between mold flux and alloy. Firstly, the activity model of the CaO-SiO2-Al2O3-Na2O-MgO-CaF2-Ce2O3 slag system was established according to the ion and molecule coexistence theory (IMCT), and the calculation results show that with the increase of Ce2O3 content in the mold flux, the activity of Al2O3 decreases significantly and the activity of SiO2 decreases and gradually tends to 0. Secondly, thermodynamic calculations of the slag-steel interfacial chemical reaction revealed that the main chemical reaction in this study system is [Ti] + (SiO2) = [Si] + (TiO2). With the increase of Ce2O3 content in the mold flux, the slag-steel interfacial chemical reaction is weakened and the oxidation of Al and Ti in steel is inhibited. Finally, the results of slag-steel reaction experiment show that the increase rate of Al content increases from 1.03% to 10.31%, the increase rate of Si content decreases from 55.95% to 31.25%, and the oxidation rate of Ti content decreases from 33.27% to 20.00% when Ce2O3 content in the mold flux increases from 0% to 15% and the slag-steel reaction for 40 mins.

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric "Ti(I)" and "Ti(0)" Synthons Supported by Imidazolin-2-Iminato Ligands.

Reduction of the diamagnetic Ti(III)/Ti(III) dimer [Cl2Ti(μ-NImDipp)]2 (1) (NImDipp = [1,3-bis(Dipp)imidazolin-2-iminato]-, Dipp = C6H3-2,6-iPr2) with 4 and 6 equiv of KC8 generates the intramolecularly arene-masked, dinuclear titanium compounds [(μ-N-η6-ImDipp)Ti]2 (2) and {[(Et2O)2K](μ-N-μ-η6:η6-ImDipp)Ti}2 (3), respectively, in modest yields. The compounds have been structurally characterized by X-ray crystallographic analysis, and inspection of the bond metrics within the η6-coordinated aryl substituent of the bridging imidazolin-2-iminato ligand shows perturbation of the aromatic system most consistent with two-electron reduction of the ring. As such, 2 and 3 can be assigned respectively as possessing metal centers in formal Ti(III)/Ti(III) and Ti(II)/Ti(II) oxidation states. Exploration of their redox chemistry reveal the ability to reduce several substrate equivalents. For instance, treatment of 2 with excess C8H8 (COT) forms the novel COT-bridged complex [(ImDippN)(η8-COT)Ti](μ-η2:η3-COT)[Ti(η4-COT)(NImDipp)] (4) that dissociates in THF solutions to give mononuclear (ImDippN)Ti(η8-COT)(THF) (5). Addition of COT to 3 yields heterometallic [(ImDippN)(η4-COT)Ti(μ-η4:η5-COT)K(THF)(μ-η6:η4-COT)Ti(NImDipp)(μ-η4:η4-COT)K(THF)2]n (6). Compounds 4 and 5 are the products of the 4-electron oxidation of 2, while 6 stands as the 8-electron oxidation product of 3. Reduction of organozides was also explored. Low temperature reaction of 2 with 4 equiv of AdN3 gives the terminal and bridged imido complex [(ImDippN)Ti(═NAd)](μ-NAd)2[Ti(NImDipp)(N3Ad)] (7) that undergoes intermolecular C-H activation of toluene at room temperature to afford the amido compound [(ImDippN)Ti(NHAd)](μ-NAd)2[Ti(C6H4Me)(NImDipp)] (8-tol). These complexes are the 6-electron oxidation products of the reaction of 2 with AdN3. Furthermore, treatment of 3 with 4 equiv of AdN3 produces the thermally stable Ti(III)/Ti(III) terminal and bridged imido [K(18-crown-6)(THF)2]{[(ImDippN)Ti(NAd)](μ-NAd)2K[Ti(NImDipp)]} (10). Altogether, these reactions firmly establish 2 and 3 as unprecedented Ti(I)/Ti(I) and Ti(0)/Ti(0) synthons with the clear capacity to effect multielectron reductions ranging from 4 to 8 electrons.

Surface characteristics and in vitro biocompatibility of surface-modified titanium foils as a regenerative barrier membrane for guided bone regeneration.

This study evaluated surface characteristics and biocompatibility of surface-modified thin titanium (Ti) foils as a regenerative barrier membrane for future application in guided bone regeneration (GBR) surgery to augment atrophic alveolar bone. Anodic oxidation and post-heat treatment were performed to prepare various Ti foil samples. Then, the in vitro soft and hard tissue compatibility of the samples was evaluated by examining the cell responses using primary human gingival fibroblasts (HGFs) and MG63 human osteoblast-like cells. Investigated Ti foil samples showed marked differences in physicochemical surface properties. Additional 400°C heat treatment applied to the anodized Ti surface led to formation of an anatase titanium dioxide structure and well-organized nanoscale protrusions, and significantly increased surface wettability. Anodization and heat treatment enhanced the growth of HGFs and MG63 cells in Ti foil samples. Additional heat treatment for 10 and 30min further significantly improved the response of HGFs including spreading and proliferation, and upregulated the mRNA expression of cell adhesion- and maturation-related genes as well as the osteoblast differentiation of MG63 cells. Ti foil sample with thin oxide coating obtained by a 30min heat treatment exhibited poor clinical plasticity as a regenerative barrier membrane, which showed complete coating failure in the bending test. Our results indicate that anatase Ti oxide coating of a specific film thickness with nanoscale surface protrusion morphology and hydrophilic characteristics obtained by anodization and post-heat treatment would be an effective approach as a biocompatible Ti regenerative membrane for inducing better regeneration of both gingival tissue and bone.

Heterostructured MXene-derived oxides as superior photocatalysts for MB degradation

This work offers a simple and effective strategy to design a two-dimensional layer heterostructure of carbon/Ti-based oxide nanocomposites via a long-term oxidation process of MXene (Ti 3 C 2 T x ). Oxidation kinetics parameters concluded that MXene initially reacted with oxygen by forming the carbon layer and nanostructured Ti-based oxides with a homogeneous distribution, including TiOF 2 and TiO 2 , whereas the further oxidation process was governed by oxygen diffusion. It suggested that lower oxidation temperature and longer time (300 °C/1 h) facilitated to fabricate carbon-supported TiO 2 @TiOF 2 heterojunction nanocomposites with a unique 2D layer structure, which achieved a 90 % removal of methylene blue (MB) at 1 h under visible light illumination, owning to its large specific surface area, good electronic conductivity, narrowed band-gap, enhanced absorption in the visible range and high charge separation efficiency. Hence, the designed MXene-derived oxides were considered as promising candidates for wide-range responsive photocatalytic degradation of pollutants. ● Ti-based oxides with different architecture were constructed via isothermal oxidation treatment of MXene (Ti 3 C 2 T x ). ● Oxidation of Ti 3 C 2 T x was initially governed by the surface reaction, and then controlled by the oxygen diffusion process. ● Lower temperature and longer holding time was the optimal oxidation condition to construct 2D C/TiO 2 @TiOF 2 heterojunction.

The effect of Fe–Ti oxide separation on iron isotopic fractionation during basalt differentiation

The effect of Fe–Ti oxide separation on iron isotopic fractionation during basalt differentiation

Corrosion behavior of Ti60 alloy under continuous NaCl solution spraying at 600 °C

• The corrosion rate of Ti60 alloy in NaCL spray is lower than that under NaCL film. • A mixed corrosion including classical oxidation and active oxidation happened. • The mixed corrosion delayed active oxidation and formed dense Ti oxides scale, both of which decreased corrosion rate. The corrosion behavior of Ti60 alloy was investigated under continuous NaCl solution spraying at 600 °C. Results indicate that the corrosion rate of the Ti60 alloy is lower than that obtained with the solid NaCl deposit film in H 2 O + O 2 . The outer corrosion products are compact layers mainly containing Na 2 TiO 3 and nanocrystalline TiO 2 . The inner layer is mainly composed of Ti 2 O, TiO and SnO 2 . Ti 2 O has a lamellar structure, and TiO has a strip-shaped structure. A mixed corrosion mechanism including classic oxidation and active oxidation occurred under NaCl solution spraying environment: the first stage was controlled by the classic oxidation mechanism with the promotion by the active oxidation following parabolic curves, and the second stage was controlled by the active oxidation mechanism following a linear rise in the mass gain curve. The mixed corrosion mechanism between classic oxidation and active oxidation produced a relatively dense Ti oxides scale, which decreased the corrosion rate.

Polycyclic soils with Bt and Bw developed on mafic rocks in a forest cerrado transition environment in Roraima, northern Amazon, Brazil

In the extreme north of Brazil, in Roraima, there is an important set of mafic, volcanic or plutonic rocks, associated with the Juro-Cretaceous magmatism, and one of the most extensive areas is the Colônia do Taiano region, the first agricultural colony of Roraima. In addition to basalts, many diabases and diorites occur, forming an extensive patch of soils with good agricultural suitability, in the cerrado-forest transition. Two soil profiles developed from diabase were studied, after selecting the most representative pedons of the area. P1, an Argissolo Vermelho Eutrófico latossólico (Ultisol) and P2 an Argissolo Vermelho Eutrófico típico (Ultisol), were described and collected. Morphological, physical, chemical, mineralogical analyses, and extraction of Fe, Al, Ti and Si oxides by sulfuric attack were carried out; Fe2O3, Al2O3, TiO2, and SiO2, by plasma emission spectrometry; and Fe-DBC (dithionite-citrate-bicarbonate) and Fe ammonium oxalate. The soils presented a typical latosolic morphology at the base of the profile, with the top of the B horizon showing waxiness varying from moderate to abundant, thus revealing a polycyclic genesis of Bt superimposed on Bw, formed in a previous cycle. The SiO2 contents indicated a desilication process, and the low contents of trace elements and TiO2 showed mafic materials poor in magnetite, and reworking of the parent material by pediment in a drier climate. The Feo/Fed ratio proved to be atypical for the Amazon region, consistent with the mafic lithology.

Improvement of corrosion and wear resistance of novel Zr-Ti-Al-V alloy with high strength and toughness by thermal nitridation treatment

In this work, a thermal nitridation treatment was carried out on the new high-strength and toughness Zr-Ti-Al-V alloy. The composition, thickness, corrosion resistance, hardness and wear resistance of thermal nitridation film were systematically studied. From the extracted results, it was demonstrated that the thermal nitridation film was mainly composed of nitrides and oxides of Zr and Ti, while the presence of the Al2Zr compound phase was also found. The hot nitrided samples were better resistant to corrosion than the matrix in 3.5% NaCl solution. The hardness and wear resistance of the hot nitrided samples were also improved.

Atomic layer deposition of oxide coatings on porous metal and polymer structures fabricated by additive manufacturing methods (laser-based powder bed fusion, material extrusion, material jetting)

Complex porous 316 L stainless steel, Ti-6Al-4V, Ti-6Al-7Nb, ULTEM™ 1010 and MED610™ polymer structures were produced with additive manufacturing methods. The structures were surface functionalized by atomic layer deposition of titanium, zinc and zirconium oxide coatings with a thickness between 14 and 43 nm. Deep and narrow structures with aspect ratios >10 could be coated. Titanium oxide films are mostly amorphous when plasma-assisted deposition is used and contain nanocrystalline anatase when deposited by thermal atomic layer deposition. The deposited titanium oxide grains ranged in size from ∼20 to 60 nm. In interior parts of the fractured porous polymer model structures with pore sizes of 1–2 mm, both thermal and plasma-assisted titanium oxide thin films and partly delamination were detected. X-ray photoelectron spectroscopy analysis revealed almost stoichiometric composition and dominance of the Ti (IV) oxidation state at a 250 °C deposition temperature. Zinc oxide coatings in porous polymer model structures partly delaminate as well, while adhesion and homogeneity is higher for printed Ti-6Al-7Nb lattice structures with a 0.5-mm mesh size. Zirconium oxide coatings on Ti-6Al-4V lattice structures with a 0.8-mm mesh size are comparable to zinc oxide coatings but are mostly crystalline. This is attributed to the relatively high, 300 °C deposition temperature. The findings demonstrate potential but also limitations of combined additive manufacturing and atomic layer deposition for medicine and energy production applications. In addition, the results confirm previous studies that metallic and polymeric substrate materials and process conditions strongly influence the coating structure and composition, and individual development of each intended application is required.

Mn-Fe catalyzed microwave combustion-plasma hybrid synthesis of 2D chips-like Mn-Fe boosted TiO2 architecture self-assembled of nano-walled honeycomb-like super-macroporous: Green fuel generation

The productive 2D chips-like Mn-Fe boosted TiO2 as self-assembled nano-walled honeycomb-like super-macroporous was synthesized via the Mn-Fe catalyzed microwave combustion-plasma hybrid to generate biodiesel. The physicochemical property of Mn-Fe doped TiO2 (Mn = 2at% & Fe = 2at.%) were executed by X-ray diffraction, FESEM, BET-BJH, TEM, and TPD-NH3 analyses. Fe and Mn increased the rutile phase and widened pores. 2D surface analysis of plasma-treated catalyst displayed the chips-like framework constructed of nanosheets comprising super-macropores. Plasma destroyed crumbly walls between pores. Hence more acidic sites were exposed, and the diffusion of large feed molecules within pores was eased. The total pore volume was 0.058 and 0.111 cm3/g, and the mean pore diameter was 2.94 and 4.57 nm, based on BET-BJH results. Besides, conversion was 91.9 and 96.1 % and after six runs conversion loss was 2.17 and 0.21 % for MnFe(2:2)TiO2 (MWC) and MnFe(2:2)TiO2 (PMWC), respectively. Conversion loss in MnFe(2:2)TiO2 (MWC) was because of the formation of a composite between undoped Mn and Fe and Ti oxides. The plasma made the bond between the composite components stronger and inhibited the leaching of components, so plasma made leaching slight.

Unveiling the phase evolution and mechanical properties of Ni1.5Co1.5CrTix alloys with ultrafine/nano structure

Oxide dispersion strengthening (ODS) is an effective way to optimize mechanical performance, radiation tolerance and wear resistance in alloys. Therefore, in this research, lightweight and oxyphilic element Ti was utilized to induce oxides particles for in-situ fabricating ODS alloys. We investigated systematically the influence of Ti content on the phase evolution and mechanical behaviors of Ni1.5Co1.5CrTix (x = 0, 0.2, 0.4, molar ratio) multi-principal element alloys (MPEAs) fabricated by mechanically alloying and high-pressure sintering (HPS). The Ni1.5Co1.5CrTix powders presented BCC phase, FCC phase and few additional oxides. Following HPS, the BCC phase transformed to FCC phase in these MPEAs. Ni1.5Co1.5Cr MPEA was composed of FCC, Cr7C3 and Cr2O3 phases. As Ti content increased, Cr oxides or carbides gradually transformed into Ti oxides or carbides. The Ni1.5Co1.5CrTix (x = 0.2, 0.4) MPEAs after HPS displayed ultrafine grained FCC matrix and uniformly dispersed ultrafine/nano Cr-C or TiOC complex compounds. With Ti content increasing, the grain sizes of FCC matrix and precipitates had a tendency to decrease. Quantitative increment of precipitation-strengthening and fine-grain-strengthening clarifies the influence of Ti content on MPEAs. The investigations may provide key insights into tuning Ti content into the MPEAs for being available structural materials.

Integrating mineralogy, geochemistry and aeromagnetic data for detecting Fe–Ti ore deposits bearing layered mafic intrusion, Akab El-Negum, Eastern Desert, Egypt

This study delineated the Fe–Ti oxide deposit concurrencies on the layered mafic intrusion in Gabal Akab El-Negum (GAN), South Eastern Desert, Egypt, using aeromagnetic mapping and chemical analysis of the hosted mafic rocks and mineralogical studies. Aeromagnetic data was improved using the enhanced horizontal gradient amplitudeto detect the primary structures (edges/contacts/faults) that control the distribution of Fe–Ti ore deposit. GAN layered gabbros are differentiated into troctolite, olivine–, pyroxene–, and hornblende–gabbros. These mafic rocks primarily comprise plagioclase, olivine, pyroxene, and hornblende with Fe–Ti ores (magnetite and ilmenite). The significant variation in Mg# of clinopyroxene between 0.70 and 0.82 indicates the importance of fractional crystallization in developing layered mafic intrusion. Clinopyroxene and plagioclase thermometry yielded low temperatures similar to the fractionated primary basaltic magma. The pairs of magnetite–ilmenite minerals in gabbros provide equilibrium temperatures of 539.44–815.56, and high fO2, reflecting various cooling and subsolidus reequilibration phases of minerals. The enrichment of GAN gabbros in light rare–earth elements relative to heavy rare–earth elements indicates the interaction between the Fe–Ti rich mantle and the fractionated tholeiitic magmas in the back-arc setting, generating Fe–Ti oxide ores.

Implication of nuclear analytical techniques for the assessment of coal quality in terms of ash content

ABSTRACT The manuscript deals with the utilization of Neutron Activation Analysis (NAA), external (in air) Particle Induced Gamma-ray Emission (PIGE) and X-Ray Fluorescence (XRF) for comprehensive characterization of Indian coal in order to evaluate their quality in terms of ash contents. NAA was used involving short irradiation at Pneumatic Carrier Facility (PCF) at Dhruva reactor, India, for determination of Na, Mg, Al and K; whereas long irradiation at Apsara-U reactor was used for estimation of Fe and Ca. External PIGE was applied for quantification of low Z elements (Na, Mg, Al and Si). Method was validated using coal-based standard reference materials: NIST 1635a and 1633c. Comparative evaluation was also carried out using Energy Dispersive X-Ray Fluorescence (EDXRF) spectroscopy. Total concentration of Na, Mg, Al, Si, K, Ca, Ti and Fe oxides has been used as markers for identifying the quality of coal in terms of coal ash contents. Elements such as Sc, Cr, Co, Zn, Se, Cs, Ce, Sm, Hf, U and Th were determined at trace level using conventional NAA techniques after long irradiation at Apsara-U reactor. The coal with higher ash content was found to contain high concentration of trace elements and the better quality coal contains lower concentration of trace elements.

Facilitating Hydrogen Dissociation over Dilute Nanoporous Ti-Cu Catalysts.

The dissociation of H2 is an essential elementary step in many industrial chemical transformations, typically requiring precious metals. Here, we report a hierarchical nanoporous Cu catalyst doped with small amounts of Ti (npTiCu) that increases the rate of H2-D2 exchange by approximately one order of magnitude compared to the undoped nanoporous Cu (npCu) catalyst. The promotional effect of Ti was measured via steady-state H2-D2 exchange reaction experiments under atmospheric pressure flow conditions in the temperature range of 300-573 K. Pretreatment with flowing H2 is required for stable catalytic performance, and two temperatures, 523 and 673 K, were investigated. The experimentally determined H2-D2 exchange rate is 5-7 times greater for npTiCu vs the undoped Cu material under optimized pretreatment and reaction temperatures. The H2 pretreatment leads to full reduction of Cu oxide and partial reduction of surface Ti oxide species present in the as-prepared catalyst as demonstrated using in situ ambient pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The apparent activation energies and pre-exponential factors measured for H2-D2 exchange are substantially different for Ti-doped vs undoped npCu catalysts. Density functional theory calculations suggest that isolated, metallic Ti atoms on the surface of the Cu host can act as the active surface sites for hydrogen recombination. The increase in the rate of exchange above that of pure Cu is caused primarily by a shift in the rate-determining step from dissociative adsorption on Cu to H/D atom recombination on Ti-doped Cu, with the corresponding decrease in activation entropy that it produces.

Soil formation and properties along a sedimentary lithosequence in the ecotonal Cerrados of Mato Grosso, Brazil

Despite numerous studies on the Cerrado savannas core areas in Brazil, soils located in its transition with Amazonia and other biomes are still poorly known, although these areas are currently undergoing massive agricultural expansion. Here, we describe a lithosequence of three soils developed from sedimentary rocks along a cuesta in Mato Grosso, namely a clayey Ferralsol (65–70% clay), an Arenosol and an Alisol (both 77–95% sand). All soils were nutrient-poor and acidic, but exchangeable aluminum was generally low except for the very high values in B horizons of the Alisol. Clay mineralogy varied widely: the Ferralsol is dominated by gibbsite and has highly crystalline kaolinite, Fe and Ti oxides. Conversely, the Arenosol has poorly crystalline kaolinite and no gibbsite, and in the Alisol clays were mostly an interstratified complex between poorly-crystalline kaolinite and a 2:1-type mineral, especially in B horizons, rich in exchangeable Al and gibbsite. Coarse biotite and fine-grained micas within the Alisol matrix were visible in thin sections, and were the likely source of the interstratified phase and the excess Al in the exchange complex. Clay coatings indicative of illuviation were evident, and also Mn oxides and Fe nodules apparently disintegrating, suggesting a limited drainage in Bt horizons of this Alisol. Although the three soils have in common their development from pre-weathered sedimentary parent materials, warm humid climate and similar native vegetation, the lithosequence showed contrasting soil formative processes, composition and land surface age. These contrasts suggest a considerable pedological diversity instead of the often assumed, homogeneously extremely-weathered soil, which can have implications for soil genesis, management and ecological functions in the humid tropics.

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.