TiO2 Powder Research Articles

Palladium-modified TiO2 Photocatalysts: Synthesis, Characterization, and Environmental Application

Sol-gel method was used to prepare palladium-modified TiO2 powder photocatalysts (Pd atomic percentage range of 0–1.00). The materials were characterized by X-ray diffraction, N2 physisorption, UV–Vis diffuse reflectance spectroscopy and transmission electron microscopy. Photocatalytic activity was tested for phenol degradation, with UV and visible lamps. The optimum palladium content was determined (0.10% atomic Pd), showing phenol degradation of 100% under UV irradiation (2 h) and 68% under visible irradiation (5 h). The presence of PdO particles was revealed on this material. Furthermore, the immobilization of this material on glass slides was studied by dip-coating method to overcome the limitations of the slurry mode. This film presented photocatalytic activity under UV and visible irradiation (5 h), reaching 80% and 23% of phenol degradation, respectively. This film is a promising alternative to degradation of pollutant using solar irradiation effectively.

The microstructure and photocatalytic properties of nitrogen-doped nano titanium dioxide loaded on porous ceramics

Nitrogen-doped nano TiO2 powder was prepared using the solvothermal method. The nano TiO2 powder was loaded on the porous ceramic carriers with a different aperture through the vacuum impregnation method using polyvinyl alcohol as a binder. The effects of deionized water content and carrier pore size on the microstructure and photocatalytic activity of nitrogen-doped nano TiO2 powder and supported TiO2 were investigated. The results show that, when introducing 25% deionized water, the nitrogen-doped nano TiO2 powder obtains a good crystallinity, small grain size, and high photocatalytic properties because of adequate hydrolysis of tetrabutyl titanate. The photocatalytic activity of nitrogen-doped nano TiO2 powder is improved by distorting the lattice and inhibiting grain growth. The nano TiO2 powder can be tightly loaded on the surface of the strut or hole-wall of porous ceramic carriers. The absorption and photocatalytic activity of supported TiO2 are demonstrably improved as the macropore provides the transmission channel, and the micropore realizes a good absorbing effect. The 20 PPI carrier with high porosity and suitable strength is beneficial to promote the photocatalytic property of supported TiO2. Moreover, the supported TiO2is easily recycled and reused.

Comparative Study on Lithium Recovery with Ion-Selective Adsorbents and Extractants: Results of Multi-Stage Screening Test with the Use of Brine Simulated Solutions with Increasing Complexity

Oil (and natural gas) field brines can be considered promising sources of lithium for the sustainable supply of a growing market. To date, many materials have been developed for direct lithium recovery from brines, but most often these materials have been tested under various conditions, what makes it impossible to compare them. The aim of this research is to provide knowledge that would enable the comparison and selection of effective sorbents for different types of brines. For this purpose, an eight-step experimental protocol was employed. The recovery tests started with a pure lithium solution (300 mg/kg), and then other salts were gradually added, resulting in a brine containing Li+ (220 mg/kg), Na+ (7.21 wt%), Ca2+ (3.0 wt%) and Mg2+ (1000 mg/kg). For selected cases, the effect of pH was also investigated. Fifty materials (including ion exchange resins, organophosphate extractants, mineral adsorbents) were examined, for which the distribution coefficient and lithium recovery were determined. Moreover, for the most promising materials, lithium over magnesium selectivity and lithium ion capacity were determined. Only γ-Al2O3, TiO2 and MnOx-based powders keep their effectiveness in ultra-high salinity ranges and in the presence of high concentrations of Ca2+ and Mg2+ in alkaline solution.

Structures of water on the surface of anatase TiO2 studied by diffuse reflectance near-infrared spectroscopy

Investigating the structures of water on metal oxides is helpful for understanding the mechanism of the adsorptions in the presence of water. In this work, the structures of adsorbed water molecules on anatase TiO2 (101) were studied by diffuse reflectance near-infrared spectroscopy (DR-NIRS). With resolution enhanced spectrum by continuous wavelet transform (CWT), the spectral features of adsorbed water at different sites were found. In the spectrum of dried TiO2 powder, there is only the spectral feature of the water adsorbed at 5-coordinated titanium atoms (Ti5c). With the increase of the adsorbed water, the spectral feature of the water at 2-coordinated oxygen atoms (O2c) emerges first, and then that of the water interacting with the adsorbed water can be observed. When adenosine triphosphate (ATP) was adsorbed on TiO2, the intensity of the peaks related to the adsorbed water decreases, indicating that the adsorbed water is replaced by ATP due to the strong affinity to Ti5c. Therefore, there is a clear correlation between the peak intensity of the adsorbed water and the adsorbed quantity of ATP. Water can be a NIR spectroscopic probe to detect the quantity of the adsorbed ATP. A partial least squares (PLS) model was established to predict the content of adsorbed ATP by the spectral peaks of water. The recoveries of validation samples are in the range of 92.00–114.96% with the relative standard deviations (RSDs) in a range of 2.13–5.82%.

Preparation and Electrochromic Study of Ce3+ Doped TiO2 Thin Films

Ce3+ doped TiO2 thin films were prepared on ITO conductive glass by sol-gel method and dip-coating method using tetrabutyltitanate and glacial acetic acid as raw materials and adding cerium nitrate into cerium. The Ce3+ doped TiO2 powder was characterized by XRD, TG-DTA and SEM. The electrochromic properties of the films were tested by electrochemical workstation. The films were tested by UV-Vis spectrophotometer. Results show that the concentration of doped Ce ions is 2%, and the electrochromic properties of the films are improved greatly. The more the doping is, the more significant the effect on the electrochromic properties of the films is.

Fabrication of aluminum titanate–glass composites with controlled thermal expansion and improved mechanical strength

Aluminum titanate–glass sintered composites with a controlled thermal expansion coefficient were successfully prepared by the solid-state reaction of Al2O3, TiO2, and soda-lime glass powders. The thermal expansion of the specimens monotonically increased from negative to positive when the glass addition was increased from 0 to 30 wt%, indicating that a zero-thermal-expansion material could be obtained at a glass addition of 5–7 wt%. Chemical reaction between glass and Al2TiO5 was not observed during sintering, and the glassy state of the raw soda-lime glass was maintained. The scanning electron microscopy–energy-dispersive X-ray spectroscopy results indicate that the glassy phase penetrates the grain boundaries of the sintered composites with a glass addition of 5 wt%, thereby increasing the thermal expansion coefficient and apparent density. For the composites with a glass content of >5 wt%, a glassy phase that possibly forms outside the grain boundary could increase the thermal expansion coefficient and decrease the density. The glassy phase at the grain boundary also effectively improved the mechanical bending strength.

Microscale spherical TiO2 powder prepared by hydrolysis of TiCl4 solution: Synthesis and kinetics

Hydrolysis of TiCl4 solution is capable of preparing microscale TiO2 particles. This research studied the synthesis of microscale spherical TiO2 powders and the hydrolysis kinetics. The effects of the flow field generated by different agitators and baffles in the crystallizer, the initial free acid concentration, the initial equivalent TiO2 concentration, and the temperature on the hydrolysis progress and powder morphology were systematically studied. The results show that the flow field in a crystallizer can significantly affect the morphology and particle size of the powders, and the axial flow can improve the sphericity of the powders. The increased free HCl and equivalent TiO2 concentrations in the pregnant solution inhibit the forward hydrolysis reaction, prolong the time to reach equilibrium, and reduce the yield. An appropriate temperature matching the compositions of the pregnant solution is crucial for the powder morphology and size. Powders with sizes ranging from around 5 μm–40 μm can be tuned under controlled flow field, solution compositions, and temperature conditions. In addition, the Cheng and Wunderlich modified Avrami equation was used for the crystallization kinetic modeling. The effects of the free HCl concentration, equivalent TiO2 concentration, and hydrolysis temperature are reflected in the reaction rate constant and active nuclei reduction index. Increasing the free HCl and equivalent TiO2 concentrations will reduce the reaction rate constant and accelerate the deactivation of the active nuclei, thus increasing the final powder size, while increasing the temperature will lead to the opposite results.

Preparation and characterization of Zr-containing silica residue purification loaded nano-TiO2 composite photocatalysts

ZSR-P loaded nano-TiO2 composite photocatalysts (TiO2/ZSR-P) have been prepared by the sol–gel method using the by-product Zr-containing silica residue (ZSR) as precursors during the production process of zirconium oxychloride, the structure and properties of TiO2/ZSR-P were characterized in this paper. The results showed that the TiO2/ZSR-P composite photocatalysts were characterized by the uniform loading of nano-TiO2 on the surface of amorphous SiO2 particles in ZSR-P. TiO2 and SiO2 were combined by forming -Ti-O-Si- bonds at the interface and the crystalline structure of TiO2 powders was identified a mixed phase of anatase and rutile, its loading amount was 17.14%, the particle size raged from 7 to 12 nm. The degradation rate of TiO2/ZSR-P to the concentration of 5 ppm and 10 ppm methyl orange solution reached 99.52% and 100% respectively after 140 min of ultraviolet irradiation, and it still maintained stable performance after repetitive-use of the catalyst for 4 times.

Features of Phase Formation in Al–TiO2 Powder Mixture Under Changing Temperature

Features of Phase Formation in Al–TiO2 Powder Mixture Under Changing Temperature

Effects of MgO and Fe2O3 additives on the microstructure and fracture properties of aluminium titanate flexible ceramics

Aluminium titanate (Al2TiO5, AT) flexible ceramics were prepared from Al2O3–TiO2 powder system with MgO and Fe2O3 as additives through solid-state method. The effects of addition level of MgO and Fe2O3 on phase compositions, sintering behavior, microstructure and fracture properties of AT flexible ceramics were systematically investigated. The experimental results show that the introduction of additives can promote the formation of AT and improve the densification by forming solid solution. The addition of MgO could effectively refine AT grains since the formed MgAl2O4 spinel grains could pin at the AT grain boundary and inhibit the growth of AT grains. Conversely, the addition of Fe2O3 could promote the AT grain growth. And the simultaneous addition of MgO and Fe2O3 is beneficial to develop elongated rod-like AT grains. With that, the improved fracture properties can be obtained. Due to pining effect of spinel and better densification, the flexural strength of modified AT flexible ceramics is about 34 times higher than that of virgin. In addition, thanks to the microcracked structure and high grain aspect ratio, events of crack deflection, crack branching, grains pull-out and grains bridging are more likely to occur, leading to an increase in the flexibility by about 133%.

Antibacterial Activity of ZnSe, ZnSe-TiO2 and TiO2 Particles Tailored by Lysozyme Loading and Visible Light Irradiation.

ZnSe, ZnSe-TiO2 microspheres and nanostructured TiO2 obtained by hydrothermal and sol-gel methods were tested against Staphylococcus aureus ATCC 25923 and Micrococcus lysodeikticus ATCC 4698 before and after lysozyme (Lys) loading. Morphological characterization of inorganic matrices and hybrid organic-inorganic complexes were performed by microscopy techniques (SEM, AFM and Dark Field Hyperspectral Microscopy). Light absorption properties of ZnSe, ZnSe-TiO2 and TiO2 powders were assessed by UV-visible spectroscopy and their ability to generate reactive oxygen species (•OH and O2•-) under visible light irradiation was investigated. Antibacterial activity of ZnSe, ZnSe-TiO2, TiO2, Lys/ZnSe, Lys/ZnSe-TiO2 and Lys/TiO2 samples under exposure to visible light irradiation (λ > 420 nm) was tested against Staphylococcus aureus and Micrococcus lysodeikticus and correlated with ROS photogeneration.

Photocatalytic Performance of Sn–Doped TiO2 Nanopowders for Photocatalytic Degradation of Methyl Orange Dye

The tin-doped TiO2 powders obtained by sol-gel and microwave-assisted sol-gel methods were investigated. The synthesis took place in a basic medium (pH 10, ammonium hydroxide, 25%) starting from tetrabutyl orthotitanate in its parental alcohol. In the case of the dopant, Tin(II) 2-ethylhexanoate as SnO2 precursor was used in the amount of 1, 2, or 4 mol % SnO2. Based on thermal analysis data, the powders were thermally treated in air, at 500 °C. The comparative investigation of the structure and morphology of the nanopowders annealed at 500 °C was performed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy with selected area electron diffraction (HRTEM/SAED), scanning transmission electron microscopy (STEM) coupled with EDX mapping, Fourier transmission infrared (FTIR), UV–Vis, Raman and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), and X-ray florescence spectroscopy (XRF). The obtained materials were tested for the photocatalytic removal of methyl orange dye from aqueous solutions. High degradation efficiencies (around 90%) were obtained by Sn doping after 3 h of UV light irradiation.

Design and preparation of resin matrix composite coating with good ablation resistance performance under high-energy laser irradiation

High-energy lasers can cause severe damage to conventional materials in an extremely short time. Highly reflective coatings are effective against damage, but they cannot withstand high laser power densities. In this study, a composite coating with two characteristics, namely, reflection and energy consumption, was designed and prepared. TiO2 and BN powders, as light reflective media, were introduced into a boron-modified phenolic resin (BPF) to prepare an anti-laser composite coating. The results show that the initial reflectivity of the composite coating can reach 78.8% at a wavelength of 1064 nm. After damage-free protection for 0.4 s, ablation occurred in the irradiation region. Owing to the formation of residual char, which is the pyrolysis product of BPF, the coating maintained its protective performance. When the composite coating was irradiated at 1000 W/cm2 for 10 s, the back-surface temperature was 186 °C, which indicates decent anti-laser performance. We also studied the role of BN by setting a control experiment. The high conductivity and energy consumption caused by the evaporation of B2O3, which is the oxidation product of BN, helped in improving the anti-laser performance. The residual char with high porosity and degree of graphitization proved to be effective to isolate laser energy. This study provides a new design for protection of conventional materials against laser damage.

A Sol-Gel/Solvothermal Synthetic Approach to Titania Nanoparticles for Raman Thermometry.

The accurate determination of the local temperature is one of the most important challenges in the field of nanotechnology and nanomedicine. For this purpose, different techniques and materials have been extensively studied in order to identify both the best-performing materials and the techniques with greatest sensitivity. In this study, the Raman technique was exploited for the determination of the local temperature as a non-contact technique and titania nanoparticles (NPs) were tested as nanothermometer Raman active material. Biocompatible titania NPs were synthesized following a combination of sol-gel and solvothermal green synthesis approaches, with the aim of obtaining pure anatase samples. In particular, the optimization of three different synthesis protocols allowed materials to be obtained with well-defined crystallite dimensions and good control over the final morphology and dispersibility. TiO2 powders were characterized by X-ray diffraction (XRD) analyses and room-temperature Raman measurements, to confirm that the synthesized samples were single-phase anatase titania, and using SEM measurements, which clearly showed the nanometric dimension of the NPs. Stokes and anti-Stokes Raman measurements were collected, with the excitation laser at 514.5 nm (CW Ar/Kr ion laser), in the temperature range of 293-323 K, a range of interest for biological applications. The power of the laser was carefully chosen in order to avoid possible heating due to the laser irradiation. The data support the possibility of evaluating the local temperature and show that TiO2 NPs possess high sensitivity and low uncertainty in the range of a few degrees as a Raman nanothermometer material.

Solution combustion synthesis of Mg-TiC@NiO nanocomposite and investigation on its metallurgical and biological properties

Using Nickel(II) Nitrate Hexahydrate as oxidant and glycine as fuel, a simple combustion technique and magnesiothermic reduction were used for the first time to synthesize Mg-TiC@NiO nanocomposite powders. Various characterization techniques, such as X-ray diffractometry, scanning electron microscopy, compression strength, and hardness study were used to investigate the effects of mechanical allying and combustion conditions on structural, microstructural, physical, and mechanical properties. The starting powder mixture (Mg, TiO2, and nanocarbon powders) was milled at room temperature using a high-energy planetary ball mill with a vial rotation speed of 360 rpm. The process was conducted using a milling container atmosphere of Argon for 20 h, 50 h, 60 h, and 70 h. After 60 h of milling, the desired phase of TiC along with Mg peaks appeared and no unreacted quantities of raw materials remained. The hardness of Mg-TiC metal matrix nanocomposite ball-milled for 60 h shows a 42.37% increase in hardness as compared to pure magnesium. The presence of TiC particles inhibits dislocation motion and increases the hardness of the Mg matrix composite. As a result of the solution combustion synthesis, a thin layer of nickel oxide was deposited on the synthesized Mg-TiC composite, which has a high resistance to corrosion in various aqueous and dry environments. In this study, the presence of the NiO layer has shown to have significant inhibitory against pathogenic bacterial strains which will demonstrate further in the manuscript. This thin layer of nickel oxide was found to be the best suitable for biomedical applications since it has substantial antibacterial characteristics.

Direct Interfacial Excitation from TiO2 to Cu(II) Nanoclusters Enables Cathodic Photoresponse for Hydrogen Evolution under Visible-Light Irradiation.

The titaniumdioxide(TiO2 )photocatalyst is only active under UV irradiation due to its wide-gap nature. A novel excitation pathway denoted as interfacial charge transfer (IFCT) has been reported to activate copper(II) oxide nanoclusters-loaded TiO2 powder (Cu(II)/TiO2 )under visible-light irradiation for only organic decomposition (downhill reaction) so far. Here, the photoelectrochemical study shows that the Cu(II)/TiO2 electrode exhibits a cathodic photoresponse under visible-light and UV irradiation. It originates from H2 evolution on the Cu(II)/TiO2 electrode, while O2 evolution takes place on the anodic side. Based on the concept of IFCT, a direct excitation of electrons from the valence band of TiO2 to Cu(II) clusters initiates the reaction. This is the first demonstration of a direct interfacial excitation-induced cathodic photoresponse for water splitting without any addition of a sacrificial agent. This study is expected to contribute to the development of abundant visible-light-active photocathode materials for fuel production (uphill reaction).

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.

Photocatalytic Degradation of Paracetamol under Simulated Sunlight by Four TiO2 Commercial Powders: An Insight into the Performance of Two Sub-Micrometric Anatase and Rutile Powders and a Nanometric Brookite Powder

The photocatalytic degradation of the emerging contaminant paracetamol in aqueous solution has been studied under 1 SUN (~1000 W m−2) in the presence of four commercial TiO2 powders, namely sub-micrometric anatase and rutile, and nanometric brookite and P25 (the popular anatase/rutile mixture used as a benchmark in most papers). The rutile powder showed low activity, whereas, interestingly, the anatase and the brookite powders outperformed P25 in terms of total paracetamol conversion to carboxylic acids, which, according to the literature, are the final products of its degradation. To explain such results, the physicochemical properties of the powders were studied by applying a multi-technique approach. Among the physicochemical properties usually affecting the photocatalytic performance of TiO2, the presence of some surface impurities likely deriving from K3PO4 (used as crystallization agent) was found to significantly affect the percentage of paracetamol degradation obtained with the sub-micrometric anatase powder. To confirm the role of phosphate, a sample of anatase, obtained by a lab synthesis procedure and having a “clean” surface, was used as a control, though characterized by nanometric particles and higher surface area. The sample was less active than the commercial anatase, but it was more active after impregnation with K3PO4. Conversely, the presence of Cl at the surface of the rutile did not sizably affect the (overall poor) photocatalytic activity of the powder. The remarkable photocatalytic activity of the brookite nanometric powder was ascribed to a combination of several physicochemical properties, including its band structure and nanoparticles size.

Production and Characterization of Photocatalytic PEO Coatings Containing TiO2 Powders Recovered from Wastes

In this work, the possibility of incorporating TiO2 titanium dioxide particles derived from the recycling process of photovoltaic panels into PEO coatings was investigated. These particles constitute the main filler of the polymer constituting the rear part of the panels, and are characterized by possessing photocatalytic properties. The particles were added in different quantities to the electrolyte (a basic solution containing sodium silicate). The incorporation into the PEO coating produced on an aluminum alloy 1050, and the possibility of conferring photocatalytic properties to the surface of the samples were studied. The different samples were first characterized by optical microscope analysis, SEM and XRD and from the point of view of corrosion resistance by means of potentiodynamic tests. The photocatalytic properties of the samples were evaluated by monitoring the degradation of aqueous solutions of methylene blue exposed to a UV lamp. The particles have been successfully incorporated into the coating, and their presence does not alter the corrosion properties, which are improved compared to the uncoated sample. The particles, initially composed of a mixture of rutile and anatase, are instead transformed into rutile after incorporation due to the locally very high temperatures that can occur during the PEO process. In the samples obtained with higher quantities of titanium dioxide particles (60 and 80 g/L), a significant photocatalytic effect is observed with a significant reduction of methylene blue.

Design and fabrication of self-suspending aluminum-plastic/semiconductor photocatalyst devices for solar energy conversion

The design and synthesis of self-suspending photocatalyst device with easy recyclability is important for practical application. Here, this work utilizes aluminum-plastic package waste as raw material to prepare an aluminum-plastic supported TiO2 (AP-TiO2) photocatalyst device through 3D printing design and surface deposition method. A series of characterizations were carried out to explore the structure, morphology and performance of the AP-TiO2 device. Under UV light illumination, the AP-TiO2-50 efficiently degrade 93.6% tetracycline hydrochloride (THC) after 4 hr, which increases by 8.3% compared with that of TiO2 powder suspension system with the same catalyst amount. Based on it, AP-ZnO, AP-CdS, AP-g-C3N4 and AP-Pt-TiO2 are also fabricated, and applied in photocatalytic degradation and hydrogen evolution, which all exhibit higher photoactivities than powder suspension systems. This work provides a new avenue for the fabrication of advanced recyclable photocatalyst device. Moreover, the work offers a novel sight for the high-value utilization of aluminum-plastic package waste, which has positive implications for environmental protection.