TiO2 Grains Research Articles

Grooved TiO2/ZrO2 ceramic fibers with thermal insulation and mechanical properties prepared by coaxial electrospinning

In this study, grooved TiO2/ZrO2 ceramic fibers were prepared via coaxial electrospinning, which exhibit enhanced thermal insulation and superior mechanical properties. The fibers were architected with a distinctive core-shell structure, comprising a TiO2 shell that serves as an effective radiation shield and a ZrO2 core that maintains mechanical robustness. The interdiffusion of Zr and Ti atoms at the interface facilitated a seamless transition between TiO2 and ZrO2, effectively inhibiting TiO2 grain coarsening and substantially enhancing the tensile strength of the fibers, exemplified by the 1.47 ± 0.08 MPa achieved in the TZ-5 sample. Through control of the injection rate during electrospinning, we optimized the fibrous morphology to attain a synergistic balance of strength, flexibility and thermal insulation. The fibers showcased exceptional thermal insulation properties with thermal conductivity values ranging from 0.0294 to 0.0278 W m−1 K−1 and an average infrared reflectance exceeding 87 %. Practical thermal insulation tests confirmed the superior insulation performance of the TiO2/ZrO2 fibrous membranes.

Adsorption Performance and Photocatalytic Activity of La-TiO2@kaolin Composites

Abstract La-TiO2@kaolin(LTK) composites were prepared via sol-gel method with kaolin, lanthanum nitrate and tetrabutyl titanate as raw materials. The samples were characterized by XRD, SEM/EDS, and UV-Vis. The visible light photocatalytic reduction activity and adsorption performance of samples for Cr(VI) were studied. The results showed that La doping can refine TiO2 grains, stabilize phase structure of anatase TiO2, and expand its absorption spectrum, thereby enhancing its photocatalytic reduction activity. Due to the composite of kaolin, the dispersion of TiO2 is improves and it is endowed with a large specific surface area lead to enhance its adsorption ability for Cr(VI). The adsorption equilibrium process of LTK for Cr(VI) conforms to the Langmuir equation model. The coupling effect of doping and composite modification improves the adsorption and visible light catalytic reduction activity of Cr(VI) over composite material samples. The adsorption-photocatalytic removal rate of LTK for Cr(VI) under visible light irradiation for 6 hours reached the highest of 96.5%. The apparent first-order kinetic constant of its photocatalytic reduction reaction was 2.6 times that of pure TiO2.

The Utilization of Rice Husk as Both the Silicon Source and Mesoporous Template for the Green Preparation of Mesoporous TiO2/SiO2 and Its Excellent Catalytic Performance in Oxidative Desulfurization.

In recent years, TiO2-based catalysts have received extensive attention from researchers for their excellent oxidative desulfurization (ODS) performances. In this paper, a series of mesoporous TiO2/SiO2 catalysts with different TiO2 loadings are prepared, using an incipient wetness impregnation method with agricultural waste rice husk as both the silicon source and mesoporous template and tetrabutyl titanate as the titanium source. The effect of different TiO2 loadings on the ODS performance of the samples is investigated, and the appropriate TiO2 loading is 2.5%. Compared with pure TiO2, the 2.5%TiO2/SiO2 sample exhibits high catalytic activity for oxidative desulfurization. This is, on the one hand, due to the high specific surface area and mesopore volume of the 2.5%TiO2/SiO2 sample. On the other hand, it is due to the uniform dispersion of TiO2 grains with an average diameter of 6.1 nm on the surface of the mesoporous SiO2 carrier, which greatly increases the active sites of the 2.5%TiO2/SiO2 sample, thus improving the catalytic activity of the sample. The recycling performances of the 2.5%TiO2/SiO2 sample are further investigated. The results show that, after fifteen cycles, the 2.5%TiO2/SiO2 sample still maintains high conversions of dibenzothiophene (99.8%) and 4,6-dimethyldibenzothiophene (99.7%) without deactivation. In addition, the 2.5%TiO2/SiO2 sample treated with TBHP aqueous solution is characterized by the technique of UV-Vis, and the Ti-peroxo (Ti-OOtBu) species, the active intermediate for the ODS of bulky organic sulfides, is successfully captured. Finally, a possible reaction mechanism for the ODS process over the 2.5%TiO2/SiO2 sample is proposed.

Efficient preparation and oxidation kinetics of Ti3AlC2 powder via coconut shell charcoal as carbon source

Ti3AlC2 powder was prepared via an efficient solid-liquid reaction in flowing argon using coconut shell charcoal as novel carbon source, and phase evolution, microstructure and oxidation behavior of Ti3AlC2 powder were investigated. The results show that coconut shell charcoal is dominated by amorphous carbon after carbonization with some turbostratic graphite-like structure, and large specific surface area of coconut shell charcoal gives its excellent reactivity. Ti3AlC2 powder prepared at 1400 °C for 1.5 h exhibits good crystallinity and typical nanolayered structure. Ti3AlC2 powder remains thermally stable in air below 552 °C, while oxidizing occurs rapidly between 900 and 1100 °C. The isothermal oxidation curves show a parabolic-like, indicating that the oxidation process is primarily controlled by a diffusion mechanism. The good oxidation resistance of Ti3AlC2 powder is attributed to the oxidized products of TiO2 and Al2O3 grains formed a connected and dense protective layer on the particle surface at elevated temperatures.

Investigating the growth behavior of titanium dioxide film prepared with direct current pulsed–magnetron sputtering technology

The direct current pulsed magnetron sputtering technology is employed to deposit TiO2 film onto the glass and Si(100) substrates. After annealing treatment, TiO2 film displays anatase (001) preferential orientation. The growth behavior of deposited and annealed TiO2 films is investigated. The results show that in the original stage, TiO2 film growth behavior is in Volmer–Weber mode, which is dominated by the diffusion effect. Considering the rivalry between TiO2 crystal nuclei, both crystallographic orientation and diffusion effects jointly dominate the film growth behavior in the rest stage. More importantly, the annealing treatment resulted in the coalescence of TiO2 crystal nuclei, as well as the growth of TiO2 crystal nuclei. Most importantly, after coalescence and growth of TiO2 nuclei, the anatase [001] crystal orientation of TiO2 grains remains the same as the normal direction of TiO2 film. Finally, after annealing treatment, TiO2 films comprise anatase (001) preferential orientation.

Mechanism of thermal exposure on the mechanical properties of microtextured Ti60 alloys

In this study, the mechanism of thermal exposure on the mechanical properties of two Ti60 alloys with different micro-texture regions (MTRs) was systematically investigated through macro- and microstructural characterization. It was found that when the alloy was exposed to prolonged thermal exposure at 600 °C for 100 h, the strength of the no-MTR samples increased significantly and the plasticity decreased sharply. In contrast, the MTR samples showed a sharp decrease in strength and plasticity due to the transmissibility of dislocation slip and crack propagation, resulting in the formation of a continuous brittle cleavage plane on the fracture. Meanwhile, the oxide film formed on the surface promotes the formation of early cracks and cleavage planes, and the oxide film serves as the location of surface crack nuclei and creates a notch effect leading to premature fracture of the alloy. It is further found that the oxide film is mainly composed of alternating nanocrystalline grains of Al2O3 and TiO2, and there is an oxygen-rich layer of Ti3O near the matrix, and these nano-oxides increased the brittleness of the oxide film. The strengthening and embrittlement mechanism of the alloy was revealed based on the deformation characteristics, i.e. the plasticity reduction was attributed to the formation of the oxide film and precipitation of the α2 phase on the surface, whereas the inhomogeneous distribution of the α2 phase in the interior led to the formation of microcracks in the interior. The precipitation of (Ti, Zr)6Si3 phase at grain boundaries hinders the dislocation motion and leads to a significant increase in the strength of No-MTR alloys. This study reveals the effects of interactions between MTRs, oxide films and precipitated phases on the thermal exposure properties of Ti60 alloys, providing theoretical support for the stability of titanium alloy properties at elevated temperatures.

Enhanced photocatalytic degradation of polylactide (PLA) through TiO2-based up-conversion nanoparticles

As a degradable polymer material, the regulation of the degradation rate of polylactide (PLA) under an actual light exposure environment is of significant importance for realizing its multifaceted applications. This study aims to enhance the photodegradation of PLA under irradiation with lower-energy wavelengths by using TiO2-based up-conversion nanoparticles (UCNPs). Two modification methods were employed: doping TiO2 with Yb3+/Er3+/Tm3+ ions integrated within the TiO2 lattice, and creating a composite photocatalyst by adhering Y2O3: Yb3+/Er3+/Tm3+ to the exterior of TiO2 grains. The study investigated the impact of these two different TiO2-based UCNPs on the photocatalytic degradation rate and mechanism of PLA under simulated sunlight irradiation. Research has found that the doped TiO2, due to its narrower bandgap and higher photon utilization efficiency during the up-conversion process, exhibited superior catalytic efficiency in catalyzing the photodegradation reactions of PLA compared to unmodified TiO2 and composite TiO2. This work proposes a novel strategy for preparing PLA composites with enhanced photodegradation speed provided by modified TiO2, efficient light energy utilization offered by the up-conversion process, and potential applications in more advanced packaging and agricultural fields.

The static corrosion behaviors of gelcasted MAX phases in contaminated lead-bismuth eutectic (LBE) at 600 °C with low oxygen

The deployment of gelcasted MAX phase ceramic components in nuclear reactors is critical due to their exceptional performance. This study explores the corrosion behaviors of three gelcasted MAX phase ceramics (Ti3AlC2, Ti2AlC, and Ti3SiC2) in liquid lead-bismuth eutectic (LBE) at 600 °C under low oxygen conditions. Unique corrosion layers formed on the samples: Ti₃AlC₂ developed an Al2O3 inner layer and TiO2 outer layer, Ti₂AlC showed TiO2 grains coated with FeCr2O4 spinel, and Ti3SiC2 exhibited a composite layer of TiO2, Fe3O4, SiO2, PbO, and TiO2. LBE caused slight matrix enrichment in Ti₃AlC₂ and Ti₂AlC samples. Corrosion resistance was ranked as Ti3SiC2 > Ti3AlC2 > Ti₂AlC. Additionally, a coupled corrosion phenomenon resembling electrolytic electrodeposition between MAX phase ceramics and stainless steel was observed in contaminated LBE. This research provides novel insights into the corrosion mechanisms of MAX phases, paving the way for their application in advanced nuclear systems.

In@CdS sensitized TiO2 nano-rod for enhanced photocatalytic and photoelectrochemical performance under visible light

Titanium dioxide (TiO2) nano-rod are synthesized by one step hydrothermal method while cadmium sulphide (CdS) and Indium (In) doped CdS quantum dots (QDs) are sensitized on the surface of TiO2 nano-rod by using successive ionic layer adsorption and reaction (SILAR) approach. Characterization of this material was done using XRD, XPS, FE-SEM, EDX, HR-TEM, Raman, UV-DRS, PL, EPR. XRD pattern attributed that the preferential orientation of TiO2 grains is along the (101) plane perpendicular to the FTO substrate. XRD pattern also reveals the sensitization of CdS QDs in form of hexagonal CdS QDs and doping of In into CdS QDs. FE-SEM analysis suggests that the TiO2 nano-rod are uniform, thick and grown vertically on the FTO plate. Detailed investigations of the ‘In’ sensitization in 2%In-CdS/TiO2 were carried out by HR-TEM studies. UV-DRS analysis shows decrease in the band gap energy as doping of In in CdS/TiO2 nano-rod increases. EPR analysis reveals the presence of oxygen vacancies due to sensitization of ‘In’ on CdS/TiO2 matrix. The photoelectrochemical and photocatalytic performance of In doped CdS QDs embellished on the surface of TiO2 nano-rod photoanode was investigated by varying the concentration of In. The photo electrochemical (PEC) and photocatalytic H2 generation performance under natural sunlight of as prepared photoanode are explored in terms of photocurrent density and amount of H2 generation. 2% In-CdS/TiO2/Pt/FTO nano-rod shows highest 22.12 ml/h/g of hydrogen generation and photocurrent density of 4.78 (mA/cm2).

A Fresh Perspective on the Impact of ZnTiO3 Coupling on the Microstructure and Photocatalytic Properties of TiO2 Fabricated at Varied Temperatures.

ZnTiO3/TiO2 composite photocatalysts were synthesized via the sol-gel technique, and the impact of varying heat treatment temperatures (470, 570, 670 °C) on their crystalline arrangement, surface morphology, elemental composition, chemical state, specific surface area, optical characteristics, and photocatalytic efficacy was systematically investigated. The outcomes revealed that, as the temperature ascends, pure TiO2 undergoes a transition from anatase to rutile, ultimately forming a hybrid crystal structure at 670 °C. The incorporation of ZnTiO3 engenders a reduction in the TiO2 grain dimensions and retards the anatase-to-rutile phase transition. Consequently, the specimens manifest a composite constitution of anatase and ZnTiO3. In contrast, for pure TiO2, the specimen subjected to 670 °C annealing demonstrates superior photocatalytic performance due to its amalgamated crystal arrangement. The degradation efficacy of methylene blue (MB) aqueous solution attains 91% within a 60-min interval, with a calculated first-order reaction rate constant of 0.039 min-1. Interestingly, the ZnTiO3/TiO2 composite photocatalysts exhibit diminished photocatalytic activity in comparison to pristine TiO2 across all three temperature variations. Elucidation of the photocatalytic mechanism underscores that ZnTiO3 coupling augments the generation of photogenerated charge carriers. Nonetheless, concurrently, it undermines the crystalline integrity of the composite, yielding an excess of amorphous constituents that impede the mobility of photoinduced carriers. This dual effect also fosters escalated recombination of photogenerated charges, culminating in diminished quantum efficiency and reduced photocatalytic performance.

In-situ X-ray diffraction study of the oxidation behavior of arc-evaporated TiAlSiN coatings with low Al contents

TiAlSiN hard coatings are commonly known to exhibit a high oxidation resistance, however, the influence of a varying Al content on the oxidation mechanism has not yet been examined in detail. Thus, in this work, the temperature dependent phase composition of two powdered TiAlSiN coatings with low Al contents (Ti37Al2Si7N54 and Ti33Al6Si7N54) was evaluated by in-situ X-ray diffraction (XRD) in ambient air up to 1200 °C and subsequent Rietveld refinement complemented by differential scanning calorimetry measurements. The in-situ XRD experiments revealed the formation of metastable anatase TiO2 during oxidation for both TiAlSiN coatings, however, the maximum wt% of this phase was found to be doubled for the coating with higher Al content from 9 to 21 wt% at ~1025 °C. Furthermore, the microstructure of the compact Ti33Al6Si7N54 coating oxidized at 950 and 1100 °C was investigated comprehensively by means of XRD, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. These microstructural investigations revealed the formation of a thin protective Al2O3 layer, which was broken by the growth of TiO2 grains after oxidizing at 950 °C, leading to fully enclosed Al2O3 grains within coarsened TiO2 grains at 1100 °C. The present work allows to close the literature gap concerning the changes in oxidation mechanism of TiAlSiN coatings when exclusively varying the Al content and further illuminates the microstructure of an oxidized TiAlSiN with low Al content in detail.

Effective Reinforcement of Visible Light Photocatalytic and Gas Sensing Characteristics of Nanocrystalline TiO2: Gd-Based Nb and Mo Dopants

Efficient compositions for the selective detection of ethanol gas and the removal of organic contaminants were realized by codoping of (Gd, Nb) and (Gd, Mo) ions into TiO2. TiO2, Ti0.96Gd0.01Nb0.03O2, and Ti0.96Gd0.01Mo0.03O2 samples were prepared by a coprecipitation method. For all compositions, a crystalline anatase phase of TiO2 was detected. Compared to pure TiO2, the absorption edges of Ti0.96Gd0.01Nb0.03O2 and Ti0.96Gd0.01Mo0.03O2 samples were red-shifted, further broadening towards visible light. The morphological studies demonstrate that the grains of TiO2 were more refined after (Gd, Nb) and (Gd, Mo) codoping. The photocatalytic efficiency of the Ti0.96Gd0.01Mo0.03O2 catalyst for degrading 20 mg/L reactive yellow 145, brilliant green, and amoxicillin was 98, 95, and 93% in 90 min, respectively. The reusability experiments indicate that the Ti0.96Gd0.01Mo0.03O2 catalyst had high stability during reuse. The high photocatalytic activity of the Ti0.96Gd0.01Mo0.03O2 catalyst was correlated to the broad visible-light absorption and effective separation of electron–hole pairs by Gd3+ and Mo6+ cations. The gas sensing characteristic is reflected by the high sensitivity of the Ti0.96Gd0.01Nb0.03O2 sensor to ethanol gas in the presence of different gases at 275 °C. The obtained results indicated that the (Gd, Mo) mixture could more effectively induce the photocatalytic properties of TiO2 while (Gd, Nb) dopants were the best for reinforcing its sensing characteristics.

Pseudo‐single crystal growth of the entropy‐stabilized compound CoTi2O5: Microstructural evolution and kinetics

AbstractThe solid‐state transformation behavior of cobalt dititanate (CoTi2O5) has been studied at different temperatures. The starting structure consisted of a duplex (1:1 molar) mixture of CoTiO3 and TiO2 grains. A seed layer of CoTi2O5 grains was incorporated at the upper surface of the green, precursor powder samples. Cobalt dititanate is a member of the pseudobrookite family (Cmcm, orthorhombic); it is an entropy‐stabilized compound, hence is stable only at elevated temperatures (T > 1140°C). It was observed that transformation initiated adjacent to the seed layer. First, a narrow layer of CoTi2O5 forms at the diphase boundaries, creating a 3‐D network that propagates at a constant velocity through the structure. The velocity of the reaction front follows an Arrhenius dependence on temperature. Both the rates of nucleation and growth increase with increasing temperature. At 1300°C, the velocity was estimated to be in excess of 10 mm/h. The progression of the reaction front was modelled based on a discontinuous template growth mechanism, with enhanced diffusion along the boundary between the product and reactant phases. The activation energy derived for boundary diffusion was 475 ± 69 kJ/mol. Behind the reaction front, the microstructure consists of a continuous matrix of CoTi2O5, with isolated remnant grains of CoTiO3 and TiO2. Further transformation occurs more slowly by solid‐state diffusion through the CoTi2O5 phase. Studies of the crystallographic orientation of the CoTi2O5 phase showed that it was pseudo‐ single crystal, with a preferred growth direction of [100]. The system exhibits novel features, which have not been reported previously for ceramic systems.

Optimizing physico-chemical properties of hierarchical ZnO/TiO2 nano-film by the novel heating method for photocatalytic degradation of antibiotics and dye

The design of semiconductor catalysts with excellent photocatalytic properties, stability, recyclability, and good separation for the treatment of polluted water is still challenging. In this paper, the ZnO/TiO2 nano-thin films were fabricated using the magnetron sputtering technique and then heating the underlying ZnO layer and the upper TiO2 layer for their respective optimal heating time, i. e. heating ZnO for 3 h and heating TiO2 for 2 h. The as-prepared films were characterized. The results show that the preferred growth of TiO2 grains along the [001] axis, relatively large specific surface area, and increased amounts of surface oxygen vacancies (OVs) were induced to the heterojunction catalysts through this optimized heating strategy, which boosts the photocatalytic activity of ZnO/TiO2 nano-film. The degradation experiment inndicates that the ciprofloxacin (CIP) removal efficiency can reach 97.3% in 2 h duration, which was higher than that of the samples annealed for the same periods. Meanwhile, the prepared ZnO/TiO2 photocatalytic film exhibited favorable stability of 95.5% degradation efficiency after the fourth run and general applicability for the photodegradation of various contantains, whih removed 99.5% of ofloxacin (OFX) and 77.6% of tetracycline (TC) in 2 h and 94.1% of Rhodamine B (RhB) in 1 h. This work is expected to yields a novel insight into the production of heterojunction photocatalysts with excellen ability for photocatalytic degradation of pollutants in the practical industry.

Role of niobium in the high-temperature oxidation of titanium

We compared the oxidation of Ti and Ti-2 at.% Nb at 800 °C in Ar-20% O2 and in sequential 16O2-18O2 atmospheres to clarify the role of niobium in the high-temperature oxidation of titanium. Niobium had no effect on the amount of oxygen dissolved in the metal or on oxygen diffusion in the metal. Instead, niobium enhanced oxidation resistance by segregating to TiO2 grain boundaries, where it likely slowed outward Ti diffusion. These findings spotlight doping of TiO2 grain boundaries as a strategy for improving the oxidation resistance of Ti alloys and, more generally, TiO2-forming alloys.

Photocatalytic and Magnetic Properties of TiO2 Micro- and Nano- Powders decorated by Magnetic Cocatalysts

In this paper, photocatalytic TiO2 micro- and nano-powders coated by Ni and Co nanoclusters were prepared by the original electroless deposition method. The magnetic properties of Ni and Co nanoclusters decorating TiO2 grains were studied by the magnetometry measurements of the temperature dependence of magnetization. Their optical spectroscopy measurements showed a significant increase in light absorption by Ni and Co coated TiO2 nanopowders. The photocatalytic properties of the obtained magnetic nanopowders were studied with Electron Paramagnetic Resonance spectroscopy as well.

Micro-Structure and Dielectric Properties of Ti3C2Tx MXene after Annealing Treatment under Inert Gases

At present, the rapid development of electronic devices such as batteries, sensors, capacitors and so on is creating a huge demand for lightweight materials with a designed structure and function. Ti3C2Tx MXene, a lightweight two-dimensional (2D) nanomaterial with excellent electronic properties, has been favored in this field. In this work, Ti3C2Tx MXene was annealed under an inert gas (N2, Ar and CO2) atmosphere to design the crystal structure and interface of the nanosheets, and then the modified nanosheets with specific changes in dielectric properties were obtained. Among them, the key temperature points (100 °C, 300 °C, 500 °C and 800 °C) in the thermogravimetric (TG) test under an air atmosphere were used as the annealing temperature. When annealing under an air atmosphere, with the increase in temperature, the Ti layer gradually oxidized and evaporated, and the original two-dimensional structure was partly destroyed with some of the C atoms reacting with O2 to form CO2. In the inert gas atmosphere, however, the 2D structure is preserved, except that the surface end groups and layer spacing are changed. In addition, some N element doping was introduced into the nanosheets after N2 atmosphere treatment, which changed the original lattice structure. After the Ar atmosphere treatment, some Ti atoms on the surface were oxidized in situ to form TiO2 grains with different crystal forms, which increased the interfacial area. The C-TiO2 structure of the nanosheets was more complete after treatment with the CO2 atmosphere. All the nanosheets after heat treatment with an inert gas atmosphere retained the characteristic morphology of 2D materials, and different changes in the micro-structure caused changes in dielectric properties, thereby meeting the needs of 2D nanomaterials Ti3C2Tx MXene in different scenarios.

Oxidation mechanism of sputter deposited model SiNx/TiN/SiNx coatings

TiSiN coatings are of high interest for the cutting industry, since they not only offer excellent mechanical properties, but also exhibit exceptional oxidation resistance. Although up to date several studies have been conducted on evaluating the oxidation resistance of nanocomposite TiSiN coatings, the influence of the shielding effect of the amorphous SiNx phase on the nanocrystalline TiN phase during oxidation has not yet been illuminated in detail. Therefore, the aim of this work is to provide insight into this shielding effect by using a three-layer SiNx/TiN/SiNx model system. Three different SiNx layer thicknesses of 150, 300 and 800 nm were investigated, while the TiN layer thickness was with 900 nm identical for all coatings. The results revealed that the amorphous SiNx efficiently shields TiN against oxidation up to temperatures exceeding 800 °C, whereby the exact oxidation onset temperature increased with increasing SiNx layer thickness. After reaching a critical temperature, both the TiN and amorphous SiNx phase were found to exhibit a porous structure, leading to oxidation of the TiN layer and growth of coarsened TiO2 grains, which eventually break the SiNx top layer. Furthermore, amorphous SiNx was shown to be significantly more resistant to oxidation compared to crystalline TiN, being still mainly non-oxidized after oxidation at 1200 °C for 30 min. The present study allows to gain insight into the underlying mechanisms of the shielding effect of amorphous SiNx on TiN using a model coating system, thus providing a deeper understanding of the oxidation behavior of TiSiN nanocomposite coatings.

Facile Preparation of Durable Superhydrophobic Coating by Liquid-Phase Deposition for Versatile Oil/Water Separation

Serious damage caused by oily wastewater makes the development of efficient superhydrophobic and superoleophilic materials for oil/water separation processes critical and urgent. Herein, durable superhydrophobic nanometer-scale TiO2 grains with low-surface-energy substance composite-modified materials were fabricated by using a cost-effective and facile synthesis method for the gravity-driven separation of oil/water mixtures under harsh conditions. Different substrates, such as sawdust, wheat straw, cotton, sponge and fabric, were applied for superhydrophobic surface preparation, and various low-surface-energy reagents could interact with deposited TiO2 nanoparticles, including cetylamine, dodecanethiol, stearic acid and HDTMS. The resultant materials showed superhydrophobic properties with a water contact angle (WCA) higher than 150.8°. The separation of various oil/water mixtures with high efficiency and purity was acquired by using the as-prepared sponge. More importantly, the coated sponge exhibited good resistance to various harsh environmental solutions. Moreover, its superhydrophobicity also remained even after 12 months of storage in air or 10 cycles of abrasion. The durable superhydrophobic coating prepared in this work could be practically used for the highly efficient separation of oil/water mixtures under various harsh conditions.

Hydrothermal TiO2 polymorphs in a pyrite stratiform deposit: Lessons from a mineralogical and geochemical multiproxy record

This paper presents results of mineralogical and geochemical study of TiO2 polymorphs that occur within two hydrothermal stratiform zones of the Wiśniówka area (south-central Poland). These two mineralized zones consist primarily of alternating pyritiferous and REE-bearing sedimentary quartzites, quartzitic sandstones and silty-clayey shales. Of the TiO2 phases, anatase is a predominant type (mean of 56%) with a lesser amount of rutile (30%) and mixed rutile-anatase phases (11%) as well as rare rutile-brookite (2%) and brookite (1%) as evidenced by laser Raman microspectrometry. TiO2 polymorphs typically form interstitial euhedral to anhedral or skeleton-like grains and aggregations averaging 30–50 μm in diameter occasionally attaining 110 μm. Extremely scarce pyritiferous microfossils are infilled with needle- and lath-like anatase. Under backscattered electron microscope images, TiO2 grains are generally homogenous, in places with tiny inclusions of zircon, monazite, niobium oxide and palladium telluride. In addition, some rutile grains show oscillatory zonation or zonal-brecciated and patchy patterns. Results derived from electron microprobe examinations show enrichments of most TiO2 phases in niobium (up to 4.98 wt%), zirconium (up to 0.58 wt%) and tantalum (up to 0.57 wt%) substituting titanium in the TiO2 crystal structure. The TiNb pair shows the highest correlation (r2 = 0.98). Concentrations of these and other elements vary substantially within individual anatase/rutile grains. The lack of other potential Ti-bearing rock-forming or oxide minerals (e.g., biotite, pyroxene, hornblende, titanite, ilmenite, titanomagnetite, titanohematite) in sedimentary siliciclastic rocks of the study area also indicates that anatase and rutile may have crystallized along with prevailing pyrite, xenotime, aluminum-phosphate-sulfate (APS) minerals and most monazite directly from hydrothermal fluids at relatively low temperatures, presumably around 200 °C (range of 150 to 300 °C). Among these ore minerals, only goyazite and mixed goyazite-gorceixite aggregations contain up to 20.07 wt% Ti and 24.09 wt% Ti, respectively. Mineral and microtextural relationships show that TiO2 polymorphs may have formed in two phases under reducing and subsequently oxidizing conditions of the Wiśniówka Late Cambrian depositional basin.