TiO2-based Oxide Research Articles

Enhanced Surface Properties of TiO2-Based Coatings via Stevia-Assisted Spark Suppression: Insights from Density Functional Theory Calculations

This study investigates the enhancement of surface properties in TiO2-based coatings on the Ti-6Al-4V alloy through micro-arc oxidation (MAO), employing stevia sugar as a novel additive. By incorporating stevia sugar into acetate–glycerophosphate–tetraethoxysilane solutions used in MAO treatment, the porous morphology of TiO2-based oxide layers is regulated. The incorporation of stevia moderates plasma discharge intensity, facilitating the formation of a uniform silicon-rich structure characterized by reduced porosity and pore size. This effect is attributed to the interaction between stevia and tetraethyl orthosilicate (TEOS), which modifies the TEOS hydrolysis process, thereby enhancing structural uniformity and stability while concurrently reducing plasma discharge intensity. Additionally, theoretical calculations offer a valuable understanding of the reactivity and interactions of stevia, TEOS, and their complex during the MAO process, laying the groundwork for further research and optimization in this promising field.

Synthesis of the Novel Nanocatalyst of Pt<sub>3</sub>Mo Nanoalloys on Ti<sub>0.8</sub>W<sub>0.2</sub>O<sub>2</sub> via Hydrothermal and Microwave-Assisted Polyol Process

Direct methanol fuel cell (DMFC) attracts much attention due to its high abundance, environmental friendliness, and convenient transportation and storage. In this study, a novel catalyst of Pt3Mo alloy nanoparticles (NPs) on non-carbon Ti0.8W0.2O2 support was synthesized by microwave-assisted polyol process. The characteristic of Pt3Mo NPS/Ti0.8W0.2O2 catalyst was determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), energy-dispersive X-ray (EDX), and Brunauer-Emmett-Teller (BET) method. Pt3Mo NPs had an average diameter of approximate 5.18 nm and were uniformly anchored on Ti0.8W0.2O2 surface. The ratio of Mo in the Pt3Mo alloy was consistent with the theoretical value, which supported the effectiveness of the synthesis method. In addition, Pt3Mo/Ti0.8W0.2O2 electrocatalysts exhibited higher CO-like tolerance in methanol oxidation reaction (MOR) than commercial electrocatalysts, excellent catalytic activity, and strong durability after 2000 cycles. The synergistic effect of Pt-Mo alloy, and the strong interaction between the bimetallic Pt-Mo alloy and the mesoporous Ti0.8W0.2O2 support, could weaken the Pt-CO bond. Besides, the high corrosion resistance and superior electrochemical durability of TiO2-based oxide also contribute to the excellent stability of Pt3Mo/Ti0.8W0.2O2 electrocatalyst in harsh electrochemical media. These results revealed that this material could be a potential catalyst in DMFC technology.

Influence of Alloy Elements on the Osteoconductivity of Anodized Ti-29Nb-13Ta-4.6Zr Alloy

Anodizing is expected to be an effective method to improve the osteoconductivity of the Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy because the bioactivity of anodized Ti is good. However, it is not known how the alloy elements influence the surface roughness, composition, hydrophilicity, and osteoconductivity of the anodized film on the Ti alloy. In this study, we investigated the effects of anodizing on the surface properties and the osteoconductivity of the anodized TNTZ alloy, focusing on the functions of the individual alloy elements. The anodized oxides of the Nb, Ta, and Zr metals were hydrophobic at all the voltages applied, in contrast to the anodized oxide of Ti. As well as pure Ti, a TiO2-based oxide film formed on TNTZ after anodizing. However, the oxide film also contained large amounts of Nb species and the molar Nb/Ti ratio in the TNTZ alloy was high, which makes the surface more hydrophobic than the anodized oxide on Ti. In vivo tests showed that the osteoconductivity of the TNTZ alloy was sensitive to both its surface roughness and hydrophilicity. When the TNTZ alloy was anodized, the process increased either the surface hydrophobicity or the surface roughness at the voltage used in this study. These changes in the surface properties did not improve its osteoconductivity.

Computer simulation of the energy gap in ZnO- and TiO2-based semiconductor photocatalysts

Ab initio calculations of the electronic structures of binary ZnO- and TiO2-based oxides are performed to search for optimum dopants for efficient absorption of the visible part of solar radiation. Light elements B, C, and N are chosen for anion substitution. Cation substitution is simulated by 3d elements (Cr, Mn, Fe, Co) and heavy metals (Sn, Sb, Pb, Bi). The electronic structures are calculated by the full-potential linearized augmented plane wave method using the modified Becke-Johnson exchange-correlation potential. Doping is simulated by calculating supercells Zn15D1O16, Zn16O15D1, Ti15D1O32, and Ti8O15D1, where one-sixteenth of the metal (Ti, Zn) or oxygen atoms is replaced by dopant atoms. Carbon and antimony are found to be most effective dopants for ZnO: they form an energy gap ΔE = 1.78 and 1.67 eV, respectively. For TiO2, nitrogen is the most effective dopant (ΔE = 1.76 eV).

TiO2 thin films prepared by sol – gel method

There is a growing awareness that titania (TiO2) and TiO2-based oxide systems are the most promising candidates for the development of photoelectrodes for photoelectrochemical cell (PEC) for solar-hydrogen production [1]. The PEC is equipped with a single photoelectrode (photoanode) and cathode, both of which are immersed in an aqueous electrolyte. In this work we present a sol-gel method to prepare TiO2 thin films on ITO using tetraisopropoxides of titanium, acetylacetone, 1-butanol and Tween 80 as surfactant. The films were deposited on ITO coated glass slides by spray pyrolysis. UV-VIS spectra and fluorescence measurements were made for the solutions and films. X-ray diffraction was used for structural investigations and the morphology of the film was studied by Scanning Electron Microscopy.

Novel High-Rate Lithium Intercalation Electrode Materials Prepared by LiOH Solution Treatment of TiO<sub>2</sub>/Carbon Composites

Anatase-type TiO2-based oxide gel /carbon composites were treated chemically with LiOH aqueous solution at 60 °C. The crystalline phase of treated powder was examined by powder x-ray diffraction using CuKα radiation. The main diffraction peaks may be detected as belonging to cubic LiTiO2. High-rate lithium intercalation properties of the samples were estimated in nonaqueous electrolyte including lithium ions. The composite electrodes exhibited high coulombic efficiency over 90% at first cycle and high capacities over 200 mAh g-1 after 200 cycle at large charge-discharge current density of 5.0 mA cm-2 (3.7 A g-1). The composite materials are one of the promising candidates as electrode materials for energy storage devices, such as hybrid capacitor, that require high-power operations.

Electrochemical impedance spectroscopy study of Ti–6Al–4V alloy in artificial saliva with fluoride and/or bovine albumin

To investigate the electrochemical mechanism of Ti-6Al-4V alloy in acidic artificial saliva with NaF and/or bovine albumin (BA). The electrochemical behavior of Ti-6Al-4V alloy was investigated using electrochemical impedance spectroscopy (EIS) measurements at the open circuit potentials. The electrolytes used included artificial saliva with 0-0.5% NaF, with 0.1% NaF+0.01-0.5% BA, and with 0.01-0.5% BA at pH 5 and 37 degrees C. One-way ANOVA was used to analyze the influence of NaF and BA concentration on the polarization resistance (Rp) obtained from the EIS data. Surface chemical analyses were performed with X-ray photoelectron spectroscopy. The impedance was mainly characterized by the resistance and capacitance of a protective TiO2-based passive film on Ti-6Al-4V alloy when NaF concentration was low (< or = 0.01%). When NaF concentration was higher than 0.1%, the impedance was characterized by two capacitive and one inductive effects, which were related to the metal's charge transfer reaction and the decayed TiO2-based oxide film (capacitive effects), and the relaxation of the adsorbed Ti-F complex compound (inductive effect). The addition of 0.01-0.5% BA in 0.1% NaF-containing artificial saliva significantly increased the impedance of Ti-6Al-4V alloy compared to that without BA addition (p < 0.001). The presence of BA in fluoride-free artificial saliva had no influence on the electrochemical impedance of Ti-6Al-4V alloy (p > 0.05). The EIS measurement technique is suitable for the study of the electrochemical behavior of dental alloy. The electrochemical mechanism of Ti-6Al-4V alloy in artificial saliva is related to the fluoride and bovine albumin concentration.

Electrochemical and surface characterization of a nickel–titanium alloy

For clinical implantation purposes of shape memory metals the nearly equiatomic nickel–titanium (NiTi) alloy is generally used. In this study, the corrosion properties and surface characteristics of this alloy were investigated and compared with two reference controls, AISI 316 LVM stainless steel and Ti6Al4V. The anodic polarization curves, performed in Hanks’ solution at 37°C, demonstrated a passive behaviour for the NiTi alloy. A more pronounced difference between the corrosion and breakdown potential, i.e. a better resistance to chemical breakdown of passivity was found for the NiTi alloy compared to AISI 316 LVM. X-ray electron spectroscopy (XPS) and scanning electron microscopy (SEM) were undertaken to study the elemental composition and structure of the surface films prior to, and after immersion in Hanks’ solution. The passive film on the NiTi alloy consists of a mainly TiO 2-based oxide with minimal amounts of nickel in the outermost surface layers. After immersion in Hanks’ solution the growth of a calcium-phosphate layer was observed. The passive diffusion of nickel from the NiTi alloy, measured by atomic absorption spectrophotometry reduced significantly in time from an initial release rate of 14.5×10 -7 μg cm -2 s -1 to a nickel release that could not detect anymore after 10 days. It is suggested that the good corrosion properties of the NiTi alloy and the related promising biological response, as reported in literature, may be ascribed to the presence of mainly a TiO 2-based surface layer and its specific properties, including the formation of a calcium-phosphate layer after exposure to a bioenvironment.