Oxide TiO2 Research Articles

Medium-entropy Zr–Nb–Ti alloys with low magnetic susceptibility, high yield strength, and low elastic modulus through spinodal decomposition for bone-implant applications

Medium-entropy Zr–Nb–Ti (ZNT) alloys are being extensively investigated as load-bearing implant materials because of their exceptional biocompatibility and corrosion resistance, and low magnetic susceptibility. Nevertheless, enhancing their yield strength while simultaneously decreasing their elastic modulus presents a formidable obstacle, significantly constraining their broader utilization as metallic biomaterials. In this study, three medium-entropy ZNT alloys, i.e., Zr45Nb45Ti10, Zr42.5Nb42.5Ti15, and Zr40Nb40Ti20 (denoted ZNT10, ZNT15, and ZNT20, respectively), were designed based on the miscibility gap in the ZNT phase diagram and prepared by annealing of cold-rolled ingots. Their microstructures, mechanical properties, wear resistance, corrosion resistance, magnetic susceptibility, and biocompatibility were systematically studied. Spinodal decomposition occurred in the cold-rolled ZNT10 and ZNTi15 after annealing at 650°C for 2 h and resulted in nanoscale Zr-rich β1 and (Nb, Ti)-rich β2 phases, which significantly improved their yield strength and reduced their elastic modulus. The wear resistance of the alloys decreased with an increase in Ti content. Dense ZrO2, Nb2O5, and TiO2 oxide layers were formed during the polarization process in Hanks’ solution, which enhanced the corrosion resistance of the alloys. These ZNT alloys exhibited significantly lower magnetic susceptibility than medical Ti alloys. The ZNT alloys showed a cell viability of more than 94 % toward MG-63 cells after culturing for 3 d. Overall, the spinodal ZNT15 showed the best combination of mechanical properties, wear resistance, corrosion resistance, low magnetic susceptibility, and sufficient biocompatibility among the three alloys. Statement of SignificanceThis work reports on medium-entropy Zr–Nb–Ti (ZNT) alloys with heterostructure. Spinodal decomposition significantly improved their mechanical strength and reduced the elastic modulus of the alloys. The wear resistance of the ZNT alloys decreased with an increase in Ti content. Dense ZrO2, Nb2O5, and TiO2 oxide layers were formed during the polarization process in Hanks’ solution, which enhanced the corrosion resistance of the alloys. The ZNT alloys exhibited significantly lower magnetic susceptibility than medical Ti alloys. The ZNT alloys showed a cell viability of more than 94% toward MG-63 cells after culturing for 3 d. The results demonstrate that spinodal ZNT alloys have enormous potential as bone-implant materials due to their outstanding overall mechanical properties, high corrosion resistance, wear resistance, low magnetic susceptibility, and sufficient biocompatibility.

Heterogeneous Catalytic Ozonation of Pharmaceuticals: Optimization of the Process by Response Surface Methodology.

Batch heterogeneous catalytic ozonation experiments were performed using commercial and synthesized nanoparticles as catalysts in aqueous ozone. The transferred ozone dose (TOD) ranged from 0 to 150 μM, and nanoparticles were added in concentrations between 0 and 1.5 g L-1, with all experiments conducted at 20 °C and a total volume of 240 mL. A Ce-doped TiO2 catalyst (1% molar ratio of Ce/Ti) was synthesized via the sol-gel method. Response surface methodology (RSM) was applied to identify the most significant factors affecting the removal of selected pharmaceuticals, with TOD emerging as the most critical variable. Higher TOD resulted in greater removal efficiencies. Furthermore, it was found that the commercially available metal oxides α-Al2O3, Mn2O3, TiO2, and CeO2, as well as the synthesized CeTiOx, did not increase the catalytic activity of ozone during the degradation of ibuprofen (IBF) and para-chlorobenzoic acid (pCBA). Carbamazepine (CBZ) and diclofenac (DCF) are compounds susceptible to ozone oxidation, thus their complete degradation at 150 μM transferred ozone dose was attained. The limited catalytic effect was attributed to the rapid consumption of ozone within the first minute of reaction, as well as the saturation of catalyst active sites by water molecules, which inhibited effective ozone adsorption and subsequent hydroxyl radical generation (●OH).

FT-IR detection of DMMP on TiO2-Modified porous silicon substrates

In this study, we present a new chemical sensor based on a functionalized porous silicon and sensitive to dimethyl methyl phosphonate (DMMP), a simulant of sarin gas, known as one of the most toxic warfare agents. The porous silicon was prepared by anodising a boron-doped p-Si (100) wafer. A metal oxide TiO2 layer was then deposited by thermal evaporation of Ti and oxidized under atmospheric conditions to form a TiO2 film which was used as a reactive coating. The characterization of the PSi and TiO2/PSi films was investigated using SEM, EDX and XPS spectroscopies. The results indicated that the TiO2 was well incorporated on the surface and slightly inside the porous silicon layer. FT-IR studies were then carried out before and after exposure to DMMP and the detection performance was compared with PSi. The results obtained showed that our surfaces have the ability to detect DMMP down to 0.5 ppm compared to uncoated PSi layer. We have also shown that a TFA pre-treatment of our TiO2 modified PSi, prior the exposure to DMMP, is crucial for increasing its sensitivity and that our sensor can be reused several times with a simple hexane cleaning step, a key criterion for routine applications.

Novel cytotoxicity of nano-coated orthodontic micro-implants: An in vitro study

Objectives: Many attempts have been made to modify the surface of orthodontic micro-implants and prevent the development of microbes by coating them with antimicrobial nanoparticles (NPs). The purpose of the present study was to evaluate the cytotoxicity of different NPs, namely, TiO2 and zinc oxide (ZnO) NPs, that are used to coat titanium orthodontic micro-implants. Material and Methods: Thirty orthodontic micro-implants were included in this study. Those were divided into three groups: control group without coating, TiO2-coated orthodontic micro-implants, and TiO2- and ZnO-coated orthodontic micro-implants. Scanning electron microscope, energy-dispersive spectroscopy (EDS), and cytotoxicity tests were applied for all groups. Results: The results of scanning electron microscopy and EDS showed effective deposition of the titanium oxide layer onto the micro-implants. The ZnO layer applied on the micro-implants exhibited superior physicochemical characteristics in comparison to the uncoated samples with no significant cytotoxicity. Conclusion: Both NPs showed biocompatibility with the oral tissues.

Surface Structure Formation in Plasma Cutting of Aluminum and Titanium Alloys Using Direct Current Straight and Reverse Polarity

Abstract The structural features and phase composition are examined in near-surface layers of specimens of Al-Mg, Al-Cu-Mg alloys and commercially pure titanium obtained by plasma cutting using direct current straight polarity (DCSP) and direct current reverse polarity (DCRP). It is found that the flows of molten metal ejected by the gas stream from the cut cavity during cutting form the fusion and heat-affected zones, whose structural morphology, phase composition, and thickness depend on both the selected material and the cutting mode. The fusion zone is thicker in specimens cut using DCRP than in those cut with DCSP. The thickness of the adjacent heat-affected zone is also the largest in the mode that provides a thicker fused layer. Aluminum alloy specimens cut in ambient air are characterized by the presence of oxygen in the near-surface layers. The lowest degree of oxidation is observed in Al-Mg alloy. Oxygen penetrates into the fused layer to a depth of 350–500 μm in Al-Cu-Mg and up to 200–250 μm in Al-Mg alloy. In titanium alloy, the thickness of oxide layers does not exceed 100–150 μm during straight polarity cutting and 200–250 μm during reverse polarity cutting. A thin brittle layer of TiO and TiO2 oxides is formed on the titanium alloy surface. It is shown that the generation of “water mist” around the plasma jet when cutting materials of all types with DCRP leads to a more intensive oxidation of metal, less thermal effect on the material, and reduced roughness of the cut face.

An innovative interlayer improving the interfacial connection of FeCoNiCrTi coating on copper surface

To improve the performance of copper surface, a FeCoNiCrTi high entropy alloy coating was first attempted to be prepared on copper substrate by plasma cladding. The obtained single-layer coating had a smooth and flat surface, but the interfacial connection was poor. Interfacial defect analysis results showed that the alloying elements dominated by Ti in the coating reacted with the CuO formed during the preheating process on copper surface. A large amount of TiO2 and other complex oxides were generated and distributed at the interface, which hindered the interfacial connection. After introducing a Ni60A interlayer, the interface reaction between FeCoNiCrTi alloy and copper oxide was avoided, and the inter-diffusion of elements was promoted, thus forming a good metallurgical bonding. Furthermore, due to the dilution effect of Ni60A interlayer, the performance of FeCoNiCrTi surface layer slightly decreased, but still far superior to the Ni60A coating. The microhardness of FeCoNiCrTi surface layer was about 10.7 times that of copper substrate. The wear loss of the developed coating is only 1/2 of that of the single Ni60A coating at 600 °C. This study has a great significance for extending the application of FeCoNiCrTi high entropy alloy coatings in surface strengthening on copper.

Study on fabrication of multi-phase reinforcement coatings on Ti6Al4V by laser cladding for enhanced tribological performance

In order to improve the wear resistance, the multi-phase reinforcements coating with high hardness were fabricated on the surface of Ti6Al4V by laser cladding. In this study, Cr3C2 and Ti6Al4V powders, along with continuous fiber laser cladding in a protective gas of N2 atmosphere, were used to prepare a stepwise-solidifying-point multiphase composite coating (TiC, TiN, and CrN) on the surface of Ti6Al4V. The results showed that the crack-free coating with a coating depth of 1.24 mm and a maximum hardness of 1155.52 HV can be prepared on laser power of 900 W. As the laser power increases from 900 W to 1400 W, the combined effect of the soft α-Ti phase and the in-situ synthesized hard TiN phase on hardness results in a decrease in the maximum surface hardness at 1400 `W. And the surface hardness of Ti6Al4V after laser cladding increased by 2.80–2.68 times, and the wear rate decreased by 0.74–0.86 times. Due to the soft phase α-Ti and in-situ synthesized TiC-TiN secondary dendrites serve as the hard phase, which also serve as the supporting skeleton of the oxide film, and the coatings is enriched with TiO2 oxide film. Additionally, the wear mechanisms of Ti6Al4V include abrasive wear, adhesive wear, and oxidation wear. In contrast, the coatings primarily exhibit abrasive wear and oxidation wear.

Synthesis of composite coatings based on Mg and Ti oxides by PEO for modulation of Mg corrosion resistance

In this study, the application of Plasma Electrolytic Oxidation (PEO) technique was investigated for fabricating composite coatings on magnesium (Mg) substrates aimed at modulating their corrosion resistance, an important characteristic for biodegradable orthopedic implants. The coatings were manufactured using an electrolytic solution containing MgO and TiO2 oxides, varying mass ratios, at currents of 30 mA and 200 mA. X-ray diffraction patterns confirmed the presence of TiO2 and MgO phases in the coatings, demonstrating the PEO capability to modulate the chemical composition by adjusting the mass ratio of oxides in the electrolytic solution. Microstructural analysis revealed decreased surface roughness with increasing TiO2 concentration. Corrosion tests indicated a significant improvement in corrosion resistance for all coatings compared to uncoated Mg substrate. In particularly, coatings with higher TiO2 concentrations, and those applied at a current density of 30 mA exhibited, enhanced corrosion resistance.

Effects of Thermal Exposure Temperature on Room-Temperature Tensile Properties of Ti65 Alloy.

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility.

The effects of multielement basicity on niobium-bearing phase reconstruction in low grade niobium rougher concentrate

The beneficiation and recovery of ores with complex nature, low abundance have become the main direction for the development of niobium resources. The niobium resources with large reserves in Bayan Obo have not been effectively developed due to their fine particles, low grade, and complex nature. A new method for the phase reconstruction of minerals through a reconstruction process was proposed. The reconstruction of Bayan Obo niobium-bearing rougher concentrate was realized by a high-temperature melting-cooling crystallization process. The impacts of multielement basicity on the reconstruction of niobium-bearing minerals were investigated by adjusting the composition of the slag in this study. The loparite ((Ca,Ce,Na)(Nb,Ti)O3) phase is formed in slag with a higher basicity. On the contrary, the calciobetafite (Ca2(Nb,Ti)2O7) is generated in slag with a lower basicity. Besides, the combined mass fractions of valuable TiO2, Nb2O5, and rare earth oxide (REO) in calciobetafite reaches 71.94% (only 56.83% in loparite). The formation mechanism of niobium-bearing phases under different basicities was also discussed. The results of this study can provide theoretical guidance for transforming the niobium-bearing phase and enriching valuable elements in the process of phase reconstruction.

Ultrasound-assisted water oxidation: unveiling the role of piezoelectric metal-oxide sonocatalysts for cancer treatment

Ultrasound radiation has been widely used in biomedical application for both diagnosis and therapy. Metal oxides nanoparticles (NPs), like ZnO or TiO2 NPs, have been widely demonstrated to act as excellent sonocatalysts and significantly enhance cavitation at their surface, making them optimal for sonodynamic cancer therapy. These NPs often possess semiconductive and piezoelectric properties that contribute to the complex phenomena occurring at the water-oxide interface during sonostimulation. Despite the great potential in applied sonocatalysis and water splitting, the complex mechanism that governs the phenomenon is still a research subject. This work investigates the role of piezoelectric ZnO micro- and nano-particles in ultrasound-assisted water oxidation. Three metal oxides presenting fundamental electronic and mechanical differences are evaluated in terms of ultrasound-triggered reactive oxygen species generation in aqueous media: electromechanically inert SiO2 NPs, semiconducting TiO2 NPs, piezoelectric and semiconducting ZnO micro- and nanoparticles with different surface areas and sizes. The presence of silver ions in the aqueous solution was further considered to impart a potential electron scavenging effects and better evaluate the oxygen generation performances of the different structures. Following sonoirradiation, the particles are optically and chemically analyzed to study the effect of sonostimulation at their surface. The production of gaseous molecular oxygen is measured, revealing the potential of piezoelectric particles to generate oxygen under hypoxic conditions typical of some cancer environments. Finally, the best candidates, i.e. ZnO nano and micro particles, were tested on osteosarcoma and glioblastoma cell lines to demonstrate their potential for cancer treatment.

Assessment of Photocatalytic Efficiency of Graphene Oxide–TiO2 Nanocomposite for Removal of Binary Mixtures of Organophosphorus Pesticides from Water

Assessment of Photocatalytic Efficiency of Graphene Oxide–TiO₂ Nanocomposite for Removal of Binary Mixtures of Organophosphorus Pesticides from Water

Functional Medium Entropy Alloys for Joint Replacement: An Atomistic Perspective of Material Deformation and a Correlation to Wear, Corrosion, and Biocompatibility

The present study adopts a muti-facet approach to design bio inspired concentrated alloys for potential application as articulating surfaces in joint replacements. A series of equiatomic, Nb rich and Ti rich TiMoNbZr based medium entropy alloys (MEAs) were processed via arc melting and their mechanical, in-vitro corrosion, wear, and in vitro and in vivo biocompatibility were investigated. Equiatomic MEA had primarily bcc with minor hcp phases where the single bcc was achieved with the addition of Nb. The single bcc Nb rich alloy resulted in 13% elongation, much higher than equiatomic or Ti rich alloy. All the MEAs showed comparatively higher yield strength due to the climb of edge dislocations which is the main rate limiting mechanism at 300 K, as evident molecular dynamics (MD) simulation. The locally fluctuating energy landscape promotes kinks on edge dislocation, and at local minima nanoscale segments gets pinned. Upon yielding the entangled kink leaves a trail of vacancies/interstitials and escapes via climb motion to render high yield strength. The higher corrosion and pitting resistance of Nb enriched alloys can be attributed to the stable ZrO2, Nb2O5, TiO2, and MoO3 oxides, high polarization resistance (106-105 Ωcm−2), and low defect densities (1016-1018). In vitro cell-materials interaction using MC3T3-E1 showed bioinert but cytocompatible nature of the MEAs. The wear rate of the MEAs was in the range of 7-9×10−5 mm3N−1m−1. The wear debris did not show any tissue necrosis when implanted in rabbit femur rather new bone regeneration can be seen around the particles. Statement of SignificanceIn the present work, a noble Nb enriched MEAs with superior mechanical, in vitro wear, corrosion and cytocompatibility properties was designed for articulating surfaces in joint replacement.•Single bcc in Nb enriched MEAs resulted in 13 % elongation with high hardness and yield strength.•Climb of entangled edge segment is the rate limiting mechanism in controlling high yield strength of MEAs at 300 K.•High polarization resistance (106-105 Ωcm−2), and low defect densities (1016-1018) attributes to ZrO2, Nb2O5, TiO2, and MoO3 oxides enriched passive film.•Wet sliding wear rate ranged in order 7-9×10−5 mm3N−1m−1. In-situ generated wear debris when implanted in rabbit femur did not show any tissue necrosis rather new bone regeneration was observed around debris.

High-temperature oxidation behavior of high entropy carbide (TaNbTiV)C in atmospheres with different oxygen contents

A high entropy carbide (TaNbTiV)C was fabricated via spark plasma sintering of high entropy powders that were prepared using a molten salt method. The as-fabricated high entropy carbide was then investigated for its high-temperature oxidation behavior at 850 °C, under atmospheres with three different oxygen contents (20 vol%, 40 vol%, and 60 vol%). After the high-temperature oxidation process, the main phases observed in all the specimens were incompletely oxidized phase (NbxTi1-x)CyO2-y and oxides (Nb0.5Ta0.5)2O5, TiO2, and Nb2O5. Importantly, the thickness of the oxide layer initially increased and then decreased as the oxygen content increased. When the oxygen content reached 40 vol%, the ceramic displayed severe oxidation behavior with observed thicker of the oxide layer, as well as numerous pores and cracks in the oxide layer. This work provides new insights into the oxidation behavior of high entropy carbides.

Corrosion and tribocorrosion resistance of superhydrophobic LPBF-NiTi alloys surface fabricated by nanosecond laser and ultrasonic fluorination

NiTi alloys have been extensively studied for their excellent super-elasticity (SE) and shape memory effects (SME). With the development of laser powder bed fusion (LPBF), it is possible to process the complex structure of NiTi alloy, which results in the mechanical properties of LPBF-NiTi alloys receiving great attention. However, the processing method is different from the traditional one, which not only has an impact on the mechanical properties but also seriously affects the anti-corrosion resistance and causes a substantial deterioration. In the research work of this paper, nanosecond laser processing was used to fabricate the bionic mastoid-shaped micro-nano structure on the LPBF-NiTi alloys. An efficient and convenient ultrasonic fluorination treatment was used to achieve the full surface coverage of FAS-17 in 10 min, and the superhydrophobic LPBF-NiTi alloy surface (CA ~ 157°) was successfully achieved. The constructed superhydrophobic LPBF-NiTi alloy surface exhibits excellent anti-corrosion resistance compared with the original surface, and the icorr from (4.42 ± 0.5) × 10−7 A·cm−2 reduced to (3.21 ± 0.5) × 10−9 A·cm−2. Meanwhile, the superhydrophobic surface showed outstanding stability in the 15-day immersion test n 3.5 wt% NaCl solution. And it is also stable after the tribocorrosion tests in 3.5 wt% NaCl solution at 1 N and 5 N pressures. The remarkable anti-corrosion resistance and stability of the superhydrophobic surface can be attributed to the micro-nano structure rich in the TiO2 oxide layer, the air layer formed by the superhydrophobic surface insulates the corrosive liquid and the stable hydrophobic agent film.

Exploring Nb[sbnd]Si based alloys with excellent fracture toughness and oxidation resistance

The main objective of this paper is to give a comprehensive discussion of the fracture toughness and oxidation resistance of Nb-16Si-20Ti-3Al-5Cr-xSn-yZr (x=0.5, 1.5; y=2, 4, 6) alloys, based on experimental evidence, phase formation and diffusion theory. Results demonstrate that the microstructure of Sn0.5Zr2 and Sn1.5Zr2 alloys consist of Nbss and α-Nb5Si3, and the other four alloys are composed of Nbss, α-Nb5Si3 and γ-Nb5Si3. At the same time, the area fraction of γ-Nb5Si3 increases with the increase of Zr content. The coarsening of silicides increases with the addition of Sn. The KQ value of the Sn0.5Zr4 alloy reaches the highest with the mean of 12.64 MPa·m1/2. After oxidation at 800 °C for 24 h, Sn0.5Zr4 alloy alloy did not undergo pest oxidation. Sn0.5Zr4 alloy forms a continuous and dense TiO2 oxide layer oxidized at 1200 °C, which makes it have the best high temperature oxidation resistance. Sn0.5Zr4 alloy has excellent fracture toughness, medium temperature and high temperature oxidation resistance.

Development of Hydrophilic Self-Cleaning and Ultraviolet-Shielding Coatings Incorporating Micro-Titanium Dioxide/Nano-Calcium Carbonate (µ-TiO<sub>2</sub>)/(Nano-CaCO<sub>3</sub>)

The dust accumulation and dirt particles always degrade the transparency of glass, later hampers its various applications such as photovoltaic panels, building glass, and car-windshield. In this study, the hydrophilic self-cleaning coatings have been developed by using the nanocalcium Carbonate particles (nanoCaCO3) and hydrophilic micro-titanium dioxide particles (µ-TiO2). The presence of oxide groups, CO-3 and TiO2- forms a strong attraction of glass to polar water molecules. At the weight ratio of 1: 1 in the CaCO3 to TiO2 mixture, it forms a great hydrophilic property in which the water contact angle (WCA) of coated glass has been recorded as low as 11.46 ±0.85°. The coated glass also showed high transparency in UV and Visible regions. The optical transmission of coated glass was above 89% at the wavelength of 300-400nm and above 97% at the wavelength of 400-800nm. Due to its hydrophilic property, the coated glass is capable of removing the dust particles away via the water stream. The hydrophilic coating spontaneously forms the water-thin film after contact with coated glass without the presence of UV light.

Sol-Gel Synthesis of TiO2 with Pectin and Their Efficiency in Solar Cells Sensitized by Quantum Dots.

In this study, titanium oxide TiO2 nanoparticles were produced using the sol-gel approach of green synthesis with pectin as the reducing agent. The synthetized TiO2 nanoparticles with pectin were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), visible light absorption (UV-Vis) and the BET method. The structure and morphology of the TiO2 powder were described with SEM, revealing uniform monodisperse grains with a distribution of 80% regarding sizes < 250 nm; the resulting crystal phase of synthetized TiO2 was identified as an anatase and rutile phase with a crystallinity size estimated between 27 and 40 nm. Also, the surface area was determined by nitrogen adsorption-desorption using the Brown-Emmet-Teller method, with a surface area calculated as 19.56 m2/g, typical of an IV type isotherm, indicating mesoporous NPs. UV-Vis spectra showed that sol-gel synthesis reduced the band gap from the 3.2 eV common value to 2.22 eV after estimating the optical band gap energy using the adsorption coefficient; this translates to a possible extended photo response to the visible region, improving photoactivity. In addition, the power conversion of the photoelectrode was compared based on similar assembly techniques of TiO2 electrode deposition. Quantum dot crystals were deposited ionically on the electrode surface, as two different paste formulations based on a pectin emulsifier were studied for layer deposition. The results confirm that the TiO2 paste with TiO2-synthesized powder maintained good connections between the nanocrystalline mesoporous grains and the deposited layers, with an efficiency of 1.23% with the transparent paste and 2.27% with the opaque paste. These results suggest that pectin could be used as a low-cost, functional sol-gel catalysis agent for the synthesis of controlled NPs of metal oxide. It demonstrates interesting optical properties, such as an increase in photo response, suggesting further applications to photocatalysts and biomedical features.

Synergistic Bactericidal Effect of Zn2+ Ions and Reactive Oxygen Species Generated in Response to Either UV or X-ray Irradiation of Zn-Doped Plasma Electrolytic Oxidation TiO2 Coatings.

Zn-containing TiO2-based coatings with Na, Ca, Si, and K additives were obtained by plasma electrolytic oxidation (PEO) of Ti in order to achieve an effective and broad bactericidal protection without compromising biocompatibility. A protocol has been developed for cleaning the coating surface from electrolyte residues, ensuring the preservation of the microstructure and composition of the surface layer. Using high-resolution transmission electron microscopy, three characteristic microstructural zones in the PEO-Zn coating are well documented: zone 1 with a TiO2-based nanocrystalline structure, zone 2 with an amorphous structure, and zone 3 around pores with an amorphous-nanocrystalline structure. The excellent cytocompatibility of PEO-Zn samples was confirmed by three different methods: monitoring the proliferation of MC3T3-E1 cells, assessing the viability of sheep osteoblast cells using calcein-AM staining and fluorescence microscopy, and incubation with spheroids based on primary osteoblast cells and mouse embryonic fibroblast NIH3T3 cells. The PEO-Zn coatings absorb >60% of the incident light over the UV and Vis-NIR spectral ranges. After 24 h, the PEO-Zn coatings completely inactivate four types of strains: Gram-positive Staphylococcus aureus CSA154 and ATCC29213 and Gram-negative Escherichia coli K261 and U20, and also prevent E. coli U20 and K261 biofilm formation. The superior antibacterial activity is associated with the synergistic effect of Zn2+ ions in safe concentration and reactive oxygen species (ROS) generated in response to either UV irradiation or soft short-term X-ray irradiation. The X-ray irradiation-induced ROS formation by a PEO coating is reported for the first time. The enhanced bactericidal activity after X-ray irradiation compared to UV illumination is attributed to the more intense ROS generation in the first few hours. The results obtained significantly expand the possibilities of using PEO coatings on the surfaces of titanium implants.

High Specific Surface Area TiO2 Aerogels Incorporated in situ with Co/Mn Oxides as Stable Electrochemical Capacitor Electrodes

Nanocomposite aerogels comprised of TiO2 and metal (Co and Mn) oxides are synthesized via an in situ sol–gel method in this study, and their structural, compositional and electrochemical properties are evaluated for possible applications as electrodes in energy storage devices. The inclusion of metallic oxides into TiO2 aerogels hinder the formation of titania crystalline phases, preserved particle sizes close to their original dimensions and yielded higher specific surface areas compared to pure TiO2 aerogels after heat treatment. High specific surface areas in aerogels positively affect the electrochemical properties, allowing a high electrochemical activity of the electrodes, in addition to intensifying the transport of ions and solvents through the mesoporous network of this material. Evaluation of the electrochemical properties of the aerogel‐based nanocomposites involves galvanostatic charge–discharge, cyclic voltammetry, and impedance spectroscopy. The nanocomposites exhibit enhanced electrochemical properties and stable performance within the range suitable for supercapacitor applications, as indicated by the Ragone chart. Notably, aerogels with higher incorporation of cobalt and manganese oxides in TiO2 aerogels exhibit significantly elevated specific surface areas, reaching 562 and 555 m2 g−1, respectively. These values are notably high for nanocomposites, underscoring the potential of these electroactive materials for electrochemical capacitors.