Mixture Of TiO2 Research Articles

Reduction and Diffusion of Cr-Oxide Layers into P25, BaLa4Ti4O15, and Al:SrTiO3 Particles upon High-Temperature Annealing.

Chromium oxide (Cr2O3) is a beneficial metal oxide used to prevent the backward reaction in photocatalytic water splitting. The present work investigates the stability, oxidation state, and the bulk and surface electronic structure of Cr-oxide photodeposited onto P25, BaLa4Ti4O15, and Al:SrTiO3 particles as a function of the annealing process. The oxidation state of the Cr-oxide layer as deposited is found to be Cr2O3 on the surface of P25 and Al:SrTiO3 particles and Cr(OH)3 on BaLa4Ti4O15. After annealing at 600 °C, for P25 (a mixture of rutile and anatase TiO2), the Cr2O3 layer diffuses into the anatase phase but remains at the surface of the rutile phase. For BaLa4Ti4O15, Cr(OH)3 converts to Cr2O3 upon annealing and diffuses slightly into the particles. However, for Al:SrTiO3, the Cr2O3 remains stable at the surface of the particles. The diffusion here is due to the strong metal-support interaction effect. In addition, some of the Cr2O3 on the P25, BaLa4Ti4O15, and Al:SrTiO3 particles is reduced to metallic Cr after annealing. The effect of Cr2O3 formation and diffusion into the bulk on the surface and bulk band gaps is investigated with electronic spectroscopy, electron diffraction, DRS, and high-resolution imaging. The implications of the stability and diffusion of Cr2O3 for photocatalytic water splitting are discussed.

A Laser-Induced Graphene-Titanium(IV) Oxide Composite for Adsorption Enhanced Photodegradation of Methyl Orange

Numerous treatment methods such as biological digestion, chemical oxidation, and coagulation have been used to treat organic micropollutants. However, such wastewater treatment methods can be either inefficient, expensive, or environmentally unsound. Here, we embedded TiO2 nanoparticles in laser-induced graphene (LIG) and obtained a highly efficient photocatalyst composite with pollutant adsorption properties. TiO2 was added to LIG and lased to form a mixture of rutile and anatase TiO2 with a decreased band gap (2.90 ± 0.06 eV). The LIG/TiO2 composite adsorption and photodegradation properties were tested in solutions of a model pollutant, methyl orange (MO), and compared to the individual and mixed components. The adsorption capacity of the LIG/TiO2 composite was 92 mg/g using 80 mg/L MO, and together the adsorption and photocatalytic degradation resulted in 92.8% MO removal in 10 min. Adsorption enhanced photodegradation, and a synergy factor of 2.57 was seen. Understanding how LIG can modify metal oxide catalysts and how adsorption can enhance photocatalysis might lead to more effective pollutant removal and offer alternative treatment methods for polluted water.

Synthesis of novel Zr-rich 312-type solid-solution MAX phase in the Zr-Ti-Si-C system

A novel 312-type MAX-phase solid solution series in the Zr-Ti-Si-C system has been synthesized by the vacuum carbosilicothermic reduction method using mixtures of TiO2, ZrO2, SiC, and Si powders as starting materials. The upper limit for Zr content in metal sublattice of the synthesized (Zr,Ti)3SiC2 MAX phase solid solutions was found to be as much as approximately 66 at%, closely corresponding to a hypothetical quaternary Zr2TiSiC2 MAX phase. A wide miscibility gap inside the interval of Zr content in metal sublattice ranging between 22 at% and 55 at% was found. Crystal structure of the synthesized MAX-phase solid solutions was studied by HR-STEM/HAADF and XRD Rietveld analyses. The lattice constants were determined to be linearly correlated with Zr content as predicted by Vegard's law. A significant inhomogeneity in distribution of metal atoms similar to that of out-of-plane ordered quaternary MAX phases has been established for both Ti-rich and Zr-rich MAX-phase solid solutions.

Sustainable and energy-efficient photocatalytic degradation of textile dye assisted by ecofriendly synthesized silver nanoparticles

In this study, we have touched on two goals of sustainable development, namely, the provision of clean water and sanitation and clean energy at acceptable prices, hoping for good health for all ages. A green economical method was used to prepare silver nanoparticles from chitosan biopolymer. AgNPs were fully characterized using UV–Vis, FTIR, XRD, HR-TEM, and EDX analysis. Different concentrations (0.02–0.18 g/L) of the nanoparticles were integrated into a mixture of heterogeneous nano photocatalysts TiO2 and ZnO (1:1 weight ratio) under UV irradiation for the photocatalytic degradation of Acid Red 37 textile dye to obtain clean water. The kinetic description of the performed photocatalytic process was presented assuming a pseudo-first-order reaction. The data revealed that increasing the concentration of AgNPs in the catalytic mixture showed a high apparent rate constant (kapp) accompanied by an increase in the apparent quantum yield (%Qapp), followed by dye destruction after a very short time (t0.5 = 3 min). Since the photocatalytic degradation process consumes electrical energy, the electrical energy per order (EE/O) was calculated, showing a low value of 20 kWh/m3/order, using 0.18 g/L AgNPs, indicating that the elicited photocatalytic degradation method is a sustainable one for the mineralization of the targeted dye.

Characterization and Growth of TiO2/ZnO on PTFE Substrates at Different Volumetric Ratios Using Chemical Bath Deposition

Developing non-toxic, semiconductor-doped heterojunction materials for optoelectronic applications on the surface of a flexible substrate is a viable strategy for meeting the world’s energy needs without introducing any environmental issues. In this paper, Ti:TiO2/ZnO nanocomposites were prepared by heat treatment and utilized as an active layer in UV photodetectors. First, a ZnO seed layer was deposited by radio frequency (RF) sputtering on polytetrafluoroethylene (PTFE) substrates. Then, TiO2/ZnO thin films (TFs) were successfully grown by combining volumetric mixtures of TiO2 and ZnO at the ratios of 1:7, 1:3, 3:5, and 1:1 via the chemical bath deposition (CBD) method. The morphological, elemental, and topographical analyses of the grown TFs were investigated through SESEM, EDX, and AFM spectroscopy, respectively. XRD patterns illustrated the presence of the unified (002) peak of the Ti/ZnO hexagonal wurtzite structure in all prepared samples, with intensities indicating a very strong preferential crystallinity with increasing TiO2 ratios. Enhanced diffuse reflectance curves were obtained by UV–Vis spectroscopy, with allowed indirect energy bandgaps ranging from 3.17 eV to 3.23 eV. FTIR characterization revealed wider phonon vibration ranges indicating the presence of Ti–O and Zn–O bonds. Metal–semiconductor–metal (MSM) UV photodetectors were fabricated by thermally evaporating Ag electrodes on the grown nanocomposites. The volumetric ratio of TiO2/ZnO impacted the photodetector performance, where the responsivity, photosensitivity, gain, detectivity, rise time, and decay time of 0.495 AW−1, 247.14%, 3.47, 3.68 × 108 jones, 0.63 s, and 0.99 s, respectively, were recorded at a ratio of 1:1 (TiO2:ZnO). Based on the results, the heterostructure nanocomposites grown on PTFE substrates are believed to be highly promising TF for flexible electronics.

Mechanochemical Synthesis of TiO2-CeO2 Mixed Oxides Utilized as a Screen-Printed Sensing Material for Oxygen Sensor.

TiO2 and CeO2 are well known as oxygen sensing materials. Despite high sensitivity, the actual utilization of these materials in gas detection remains limited. Research conducted over the last two decades has revealed synergistic effects of TiO2-CeO2 mixed oxides that have the potential to improve some aspects of oxygen monitoring. However, there are no studies on the sensing properties of the TiO2-CeO2 obtained by mechanochemical treatment. We have tested the applicability of the mechanochemically treated TiO2-CeO2 for oxygen detection and presented the results in this study. The sensing layers are prepared as a porous structure by screen printing a thick film on a commercial substrate. The obtained structures were exposed to various O2 concentrations. The results of electrical measurements showed that TiO2-CeO2 films have a significantly lower resistance than pure oxide films. Mixtures of composition TiO2:CeO2 = 0.8:0.2, ground for 100 min, have the lowest electrical resistance among the tested materials. Mixtures of composition TiO2:CeO2 = 0.5:0.5 and ground for 100 min proved to be the most sensitive. The operating temperature can be as low as 320 °C, which places this sensor in the class of semiconductor sensors working at relatively lower temperatures.

Fabrication of U-Ti alloy through direct electro-reduction from U3O8 and TiO2 mixtures in LiCl molten salt

U-Ti alloys have attracted much attention for its excellent mechanical performance and corrosion resistance. The conventional method to fabricate U-Ti alloy by melting U and Ti metals shows great disadvantages in high energy consumption, excessive impurity content, low security and compositional segregation. Hereby, direct electro-reduction method was employed to fabricate U-Ti alloy from U3O8 and TiO2 mixtures in LiCl molten salt. The co-reduction route and process were also analyzed in detail, which are helpful to comprehend the effects of alloying elements on electro-reduction of uranium oxides, further promoting the application of this technique on nuclear fuel recycling.

Comparison of titanium dioxide nanoparticles and silver nanoparticles for flexural strength once incorporated in heat-cure acrylic denture base resin: An in vitro Study.

Polymethylmethacrylate (PMMA) resin is the most by and large used denture base material. Denture fractures are sequential to the flexure or impacting forces. Different nanoparticles such as titanium dioxide and silver nanoparticles have been used to improve its antimicrobial properties. There are limited data on their effect on flexural strength. The aim of the study was to assess the effect of silver nanoparticles and titanium dioxide nanoparticles addition on flexural strength of PMMA resins. One hundred and thirty specimens divided into four groups: Control Group A, TiO2-reinforced Group B, silver nanoparticles reinforced Group C, and mixture of TiO2 and silver nanoparticle reinforced Group D. Each reinforced group further divided based on concentrations -0.5%, 1%, 2%, and 3%. Rectangular metal models of the American Dental Association (ADA)- specified dimensions: 65 mm × 10 mm × 3 mm were used to form a mold space for the fabrication of specimens. Three-point bend test was used to determine the flexural strength of the samples after immersion in distilled water for 2 weeks. The data collected were subjected to analysis of variance followed by post hoc Tukey's test. The comparison of the mean flexural strengths showed a statistically significant gradual decrease on increasing the concentrations of nanoparticles. Maximal flexural strength was seen in the control group and least with 3% Ag + TiO2 Nps. The modified specimen also showed color changes. In an in vitro environment, addition of TiO2 and silver decreases the flexural strength of the PMMA. It also causes visible color changes.

Adsorption and photocatalytic degradation of 2-chlorophenol in water: Evaluating the performance of TiO2/activated carbon vs. using a mixture of TiO2 and activated carbon

The work reported here compared between two photocatalytic degradation strategies of 2-chlorophenol (2-CP). The first strategy utilized titanium dioxide (TiO2) immobilized on activated carbons (AC) to produce TiO2/AC photocatalysts of various TiO2 loadings. Various immobilization techniques were used: chemical vapour deposition (CVD), direct air hydrolysis (DAH), high-temperature impregnation (HTI). In the first strategy, characterization, adsorption and photocatalytic degradation of 2-CP using TiO2/AC revealed that: 1) deposition of anatase TiO2 occurred in the micro pores of AC; 2) adsorption capacity decreased with increasing anatase TiO2 loading on TiO2/AC; 3) adsorption kinetics followed pseudo first order kinetics where 40 % of 2-CP was adsorbed; 4) photocatalytic degradation caused removal of all 2-CP and 80 % of total organic carbon (TOC), while no chloride ion (Cl−) was produced. In the second strategy, naked TiO2 (anatase) and mixtures of (anatase and AC) were involved to investigate the effect of presence of AC on degradation ability of anatase TiO2 towards 2-CP. The results showed that: 1) naked TiO2 (anatase) caused better degradation of 2-CP than TiO2/AC (Cl− was liberated; complete degradation of 2-CP occurred; some TOC remained in the suspension); 2) presence of AC with anatase TiO2 in the reaction mixture negatively affected Cl− production, but positively affected 2-CP and TOC disappearance; 3) when all 2-CP was adsorbed on AC, production of Cl− was inhibited but continued at a reduced rate. This might indicat that both dissolved and adsorbed 2-CP contributed to the degradation process.

Inserted hydrogen promotes oxidation catalysis of mixed Ru0.3Ti0.7O2 as exemplified with total propane oxidation and the HCl oxidation reaction

The solid solution of a reducible oxide with a (non or) less reducible oxide may open the way to incorporate substantial amounts of hydrogen by the simple exposure to H2 at elevated temperatures, as exemplified by the mixture of RuO2 and TiO2.

TWO-LEVEL MODEL OF COMPOSITE SYNTHESIS ON A SUBSTRATE FROM A POWDER MIXTURE OF TIO2 AND AL. 1. MODEL DESCRIPTION AND SIMPLE EXAMPLES

Modern 3D-technologies are of considerable interest due to the possibility of direct creation of products from composite materials, which are formed directly by laser action. This article presents a thermo-kinetic model of laser treatment of a powder layer on a substrate, taking into account the evolution of the composition. The model variant on a macrolevel is convenient for a detailed investigation of accompanying phenomena when varying technological parameters. Two variants of composition evolution are considered. In the formal-kinetic approach, taking into account successive parallel stages, kinetic equations are described in which the reaction rate depends on the temperature according to the Arrhenius law, and on the concentrations according to the law of active masses. In the second version, the evolution of composition is described on the mesolevel basis. Thermal processes are calculated in the macro problem and diffusion-kinetic ones in mesosystems. Melting in a mixture of powders is described on the macro scale by introducing a melting temperature interval and a fraction of the liquid phase. If, in the first variant, the mathematical model remains one-dimensional. In the second variant, the model becomes two-dimensional. Examples of calculations illustrating features of different subtasks and their possibilities for TiO2-Al system are presented.

Thermosolutal Marangoni Convection for Hybrid Nanofluid Models: An Analytical Approach

The present study investigates the effect of mass transpiration on heat absorption/generation, thermal radiation and chemical reaction in the magnetohydrodynamics (MHD) Darcy–Forchheimer flow of a Newtonian fluid at the thermosolutal Marangoni boundary over a porous medium. The fluid region consists of H2O as the base fluid and fractions of TiO2–Ag nanoparticles. The mathematical approach given here employs the similarity transformation, in order to transform the leading partial differential equation (PDE) into a set of nonlinear ordinary differential equations (ODEs). The derived equations are solved analytically by using Cardon’s method and the confluent hypergeometric function. The solutions are further graphically analyzed, taking into account parameters such as mass transpiration, chemical reaction coefficient, thermal radiation, Schmidt number, Marangoni number, and inverse Darcy number. According to our findings, adding TiO2–Ag nanoparticles into conventional fluids can greatly enhance heat transfer. In addition, the mixture of TiO2–Ag with H2O gives higher heat energy compared to the mixture of only TiO2 with H2O.

Photochromism of TiO2 Nanoparticles Doped with Molybdenum Ions: Neutral Color Change from Colorless to Black via Gray.

Transition metal oxide nanoparticles have been extensively studied for the development of smart windows which are expected to be a promising technology to save energy in buildings. However, most of them turn blue under UV irradiation. Since the blue coloration affects the color of objects through the windows, the development of materials with a neutral color which hardly disturbs the view is more beneficial. In this work, we prepared a colorless-transparent TiO2 colloidal solution containing Mo6+ ions (Mo-TiO2), which turns black via gray in a nitrogen atmosphere under UV irradiation. An absorption peak was observed at 535 nm, which increased with an increase in the UV irradiation time and reached a constant value (Absmax). The Absmax value increased linearly with an increase in the Mo doping amount. We demonstrated that the photochromic behavior of the Mo-TiO2 nanoparticles is completely different from that of pure MoO3 or the mixture of MoO3 and TiO2. In addition, we performed a kinetic study to elucidate the mechanism and found that the coloration rate at the initial stage decreased with an increase in Mo doping amount. Based on the kinetic analysis, the following results are obtained: a color center is formed at a deeper energy level than the Mo dopant level; the number of the color center depends on the Mo doping amount, and the color center traps the photogenerated electrons more rapidly when it is isolated. The black color was bleached by purging the air in the solution. In particular, the gray state which is observed as a transient color is promising for the development of smart windows to shield the sunlight while allowing a clear and undistorted view.

Novel surface carbon–oxygen-groups grafted TiO2 for selective catalytic reduction of NOx by NH3 at low temperature

Activated coke (AC) with has excellent low-temperature NH3-SCR denitration performance due to its abundant surface-active functional groups including carbon species, while it is easy to burn during industrial application. Herein, a novel surface carbon–oxygen-groups grafted TiO2 was constructed by calcining the solid mixture of polyethylene glycol (PEG) and TiO2. The prepared 0.4PEG/0.6Ti catalyst shows good NH3-SCR denitration activity, and its NOx conversion was up to 80 % above 210 °C, while the pure AC exhibited poor activity. Characterization results suggest that the superior catalytic activity of 0.4PEG/0.6Ti catalyst is mainly attributed to the formation of lactone and carboxyl groups, which can promote the adsorption and activation of NO and NH3 species. Furthermore, NH3 as the reactant can also inhibit the decomposition of carbonyl groups due to over-oxidation, thus 0.4PEG/0.6Ti catalyst has good long-term stability. The reaction mechanism study reveals that the NH3-SCR reactions over catalysts follow the E-R and L-H mechanisms. Finally, the desulfurization-regeneration-denitration test (imitated activated coke simultaneous desulfurization and denitrification process) was carried out, and the results confirm that the prepared PEG/Ti catalyst could be regenerated for denitration after desulfurization. We expect that this work can provide some guidance for the design of low-temperature denitration catalysts.

Synthesis and spectroscopic properties of aluminum oxynitride doped with 3d-metal ions: The case of γ-AlON:Ti

Polycrystalline samples of γ-aluminum oxynitride (Al5O6N) doped with titanium ions have been prepared via high temperature annealing of mixtures of AlN, Al2O3 and TiO2. Electronic structure and spectroscopic properties of AlON:Tin+ were studied for the wide range of Tin+ concentrations varying from 0.05 to 5.0 at% vs. aluminum. The solubility limit of Tin+ ions in Al5O6N can be estimated at the level of 0.2–0.5 at% and an excess of Tin+ forms TiN phase. Following the XPS data, titanium exists in three different coordination environments including [TiO6], [TiOxN6–x] and [TiN6]. The optical gap evaluated from the diffuse reflectance spectra is consistent with the earlier defined for γ-AlON and shows the tendency to decrease at higher titanium content. Pulsed cathodoluminescence spectra show several bands originating from intrinsic and impurity defects. The titanium doping of γ-AlON results in overall reducing of optical and luminescence properties.

Photodegradation of Reactive Blue 4 Using Suspension of Anatase-Titanium Dioxide and Corn Cob

Textile dyeing often employs reactive dyes. The dye wastewater contains hazardous materials and is toxic to humans and the environment. Photodegradation using a semiconductor photocatalyst is a promising alternative approach for water purification and wastewater treatment. However, the photocatalyst’s low adsorption ability is a problem in the photocatalysis process. To compensate for this shortcoming, photocatalyst content must be combined with an adsorbent. Raw corn cob and titanium dioxide (TiO2) were used in this photocatalysis. Due to a synergistic impact, raw corn cob’s ability to adsorb and titanium dioxide’s ability to photodegrade organic pollutants from water bodies is expected to boost the removal performance. The degradation of Reactive Blue 4 (RB4) as a targeted dye was carried out in this research using a suspended mixture of commercial anatase TiO2 and raw corn cob under UV light. The effect of initial pH solution, initial dye concentration and contact time, TiO2-corn cob dosages, and the influence of other pollutants were investigated as factors influencing photodegradation-adsorption of RB4. The high removal rate of RB4 was obtained at a low pH of 2 and RB4 concentration of 40 ppm. The increased dose of TiO2-corn cob improved the RB4 dye removal performance. In conclusion, combining photodegradation and adsorption systems as a hybrid treatment method resulted in a synergistic increase in the efficiency of RB4 removal.

Femtosecond large-area fabrication of multi-phase titanium oxide LIPSS on thin films

The effect of the laser beam scanning velocity and overlap on the large-area fabrication of Laser-Induced Periodic Surface Structures (LIPSS), on 400 nm thickness titanium films, is investigated. The experiments were performed in ambient air with well below ablation threshold laser fluence by using a femtosecond laser at a wavelength of 1030 nm with a pulse duration of 270 fs, operating at a repetition rate of 20 kHz.For this purpose, single-line experiments were performed to study the LIPSS formation process as a function of fs-laser-beam scanning velocity. Based on these results, the fabrication of large-area LIPSS pattern was investigated by unidirectional scanning of the fs-laser beam across the sample surface using different lateral spacing. The results show the formation of LSFL and TLIPSS, with different orientation with respect to the polarization of the incident radiation. The analysis of the chemical composition, by microRaman spectroscopy, indicates the formation of a mixture of TiO2 (anatase phase) and Ti2O3 (rutile phase) for high scanning velocities and TiO2 (rutile phase) for low scanning velocities. The chemical composition, spatial period, and depth of the LIPSS show a clear dependence with the laser-beam scanning velocity and overlap.

Niobium addition improves the corrosion resistance of TiHfZrNbx high-entropy alloys in Hanks’ solution

High-strength TiHfZrNbx high-entropy alloys could become the ideal materials for small-diameter endovascular stents once their corrosion resistance in the physiological milieu is confirmed. This work aims at evaluating the corrosion resistance of a TiHfZrNbx high-entropy-alloys family in Hanks’ solution at 37 °C and revealing the influence of niobium on the mechanisms of dissolution and passivation. The alloys were subjected to a series of static and dynamic electrochemical tests and surface characterization, employing the static/dynamic/cyclic polarizations, impedance spectroscopy, XPS, AFM, and SEM. Results confirm a higher corrosion resistance of the alloys compared to that of CP-Ti and Ti6Al4V. The addition of niobium considerably improves the microstructural homogeneity that ensures a low dissolution rate and a greater resistance of the film due to the lower concentration of point defects. The passive film behaves as an n-type semiconductor and is composed of a mixture of TiO2, Nb2O5, ZrO2, and HfO2 oxides, with the presence of metallic hydroxides on the outermost layer. A detailed description of the niobium influence on the mechanisms of the dissolution and passivation is presented in this work.

Photocatalytic abatement of formaldehyde under visible light irradiation via bamboo carbon/TiO2 modified by plasma at low temperature

A new catalyst modified by plasma was investigated to substantively improve the photoactivity of TiO2 for formaldehyde abatement. Pure anatase TiO2 mechanically mixed with biochar was fabricated by H2 plasma (denoted as C/TiO2) under low temperatures (<397 K). C/TiO2 exhibited a high and long-lasting activity and remove approximately 73.7% of formaldehyde within 3 h under a simulated visible light irradiation; this is much higher the corresponding values using untreated TiO2 and untreated mixtures (denoted as un-C/TiO2). It is concluded that, following H2 plasma treatment, the addition of 5% biochar to the catalyst had the best removal efficiency due to increased meso/microporous structures, a decreasing bandgap and diminishing recombination rate of electron–hole pairs. During the process, the surface active-oxygen groups including –OH increased from 19% to 24%. These results also reveal that the catalyst could be etched by high-energy electrons in order to gain better surface properties for formaldehyde degradation. This new plasma-assisted catalyst has enhanced visible light photoactivity and a boosted capture ability and could thus have promising applications to volatile organic compounds.

Visible-Light-Active Black TiO2 Nanoparticles with Efficient Photocatalytic Performance for Degradation of Pharmaceuticals.

Special attention has recently been paid to surface-defective titanium dioxide and black TiO2 with advanced optical, electrical, and photocatalytic properties. Synthesis of these materials for photodegradation and mineralization of persistent organic pollutants in water, especially under visible radiation, presents interest from scientific and application points of view. Chemical reduction by heating a TiO2 and NaBH4 mixture at 350 °C successfully introduced Ti3+ defects and oxygen vacancies at the surface of TiO2, with an increase in the photocatalytic degradation of amoxicillin—an antibiotic that is present in wastewater due to its intense use in human and animal medicine. Three TiO2 samples were prepared at different annealing temperatures to control the ratio between anatase and rutile and were subjected to chemical reduction. Electron paramagnetic resonance investigations showed that the formation of surface Ti3+ defects in a high concentration occurred mainly in the anatase sample annealed at 400 °C, contributing to the bandgap reduction from 3.32 eV to 2.92 eV. The reduced band gap enhances visible light absorption and the efficiency of photocatalysis. The nanoparticles of ~90 m2/g specific surface area and 12 nm average size exhibit ~100% efficiency in the degradation of amoxicillin under simulated solar irradiation compared with pristine TiO2. Mineralization of amoxicillin and by-products was over 75% after 48 h irradiation for the anatase sample, where the Ti3+ defects were present in a higher concentration at the catalyst’s surface.