Search Results (8)

The interrelationships between the topological features, such as surface roughness deduced from atomic force microscopy (AFM), and wettability properties expressed by the contact angle of a water droplet on the surface of nanostructured wide bandgap oxide films prepared by spray pyrolysis are investigated for a wide range of compositions. A direct relationship between the surface roughness and the value of the contact angle was found for nanocomposite (In₂O₃)_1−x(MgO)_x, (In_1−xGa_x)₂O₃, and Zn_1−xMg_xO films, for which both the surface roughness and the contact angle increase with the increasing x-value. On the other hand, in ITO films doped with Ga, it was found that the surface roughness increases by increasing the Ga doping, while the contact angle decreases. Both the surface roughness and the contact angle proved to increase in Ga₂O₃ films when they were alloyed with Al₂O₃, similar to other nanocomposite films. An inverse relationship was revealed for a nanocomposite formed from Ga₂O₃ and SnO₂. The contact angle for a (Ga₂O₃)_0.75(SnO₂)_0.25 film was larger as compared to that of the Ga₂O₃ film, while the surface roughness was lower, similar to ITO films. The highest value of the contact angle equal to 128° was found for a (In₂O₃)_1−x(MgO)_x film with an x-value of 0.8, and the largest RMS roughness of 20 nm was showed by a Ga_1.75Al_0.25O₃ film. The optical properties of the prepared films were also analyzed from optical absorption spectroscopy, demonstrating their bandgap variation in the range of (4 to 4.85) eV, corresponding to the middle ultraviolet spectral range. Full article

The nano-architecture of titanium oxide is a key element of a wide range of applications, mainly optical and catalytic activities. Therefore, the current study focuses on engineering and designing three interesting nanostructures of titanium oxides: nanoplates, nanotubes, and nanoparticle-supported nanolayers. The nanoplates of titanium oxides were prepared and confirmed by TEM images, X-ray diffraction, and EDX analysis. These nanoplates have an anatase phase, with the distance across the corners in the range of 15 nm. These nanoplates were modified and developed through a rolling process with sodium doping to generate the Na-doped TiO₂ nanotubes. These nanotubes were observed by TEM images and X-ray diffraction. In addition, the doping process of titanium oxides with sodium was confirmed by EDX analysis. A novel nano-architecture of titanium oxide was designed by supporting titanium oxide nanoparticles over Zn/Al nanolayers. The optical properties and activity of titanium oxides with the different morphologies indicated that titanium oxides became a highly photo-active photocatalyst after conversion to nanotubes. This finding was observed through the reduction in the band gap energy to 2.7 eV. Additionally, after 37 min of exposure to UV light, the titanium oxide nanotubes totally broke down and transformed the green dye of NGB into carbon dioxide and water. Furthermore, the kinetic analysis verified that the green dyes’ degradation was expedited by the high activity of nanotubes. Ultimately, based on these findings, it was possible to design an efficient photocatalyst for water purification by converting nanoplates into nanotubes, doping titanium sites with sodium ions, and creating new active sites for titanium oxides through defect-induced super radical formation. Full article

In this study, a low-sophistication low-cost spray pyrolysis system built by undergraduate students is used to grow aluminum-doped zinc oxide thin films (ZnO:Al). The pyrolysis system was able to grow polycrystalline ZnO:Al with a hexagonal wurtzite structure preferentially oriented on the c-axis, corresponding to a hexagonal wurtzite structure, and exceptional reproducibility. The ZnO:Al films were studied as transparent conductive oxides (TCOs). Our best ZnO:Al TCO are found to exhibit an 80% average transmittance in the visible range of the electromagnetic spectrum, a sheet resistance of 32 Ω/□, and an optical bandgap of 3.38 eV. After an extensive optical and nanostructural characterization, we determined that the TCOs used are only 4% less efficient than the best ZnO:Al TCOs reported in the literature. This latter, without neglecting that literature-ZnO:Al TCOs, have been grown by sophisticated deposition techniques such as magnetron sputtering. Consequently, we estimate that our ZnO:Al TCOs can be considered an authentic alternative to high-performance aluminum-doped zinc oxide or indium tin oxide TCOs grown through more sophisticated equipment. Full article

This study synthesized pristine and aluminum (Al)-doped zinc oxide (Al:ZnO) nanostructures through a simplistic low-temperature ultrasonicated solution immersion method. Al:ZnO nanostructures were synthesized as a sensing material using different immersion times varying from two to five hours. The Al:ZnO nanostructured-based flexible humidity sensor was fabricated by employing cellulose filter paper as a substrate and transparent paper glue as a binder through a simplistic brush printing technique. XRD, FESEM, HRTEM, EDS, XPS, a two-probe I–V measurement system, and a humidity measurement system were employed to investigate the structural, morphological, chemical, electrical, and humidity-sensing properties of the pristine ZnO and Al:ZnO nanostructures. The structural and morphological analysis confirmed that Al cations successfully occupied the Zn lattice or integrated into interstitial sites of the ZnO lattice matrix. Humidity-sensing performance analysis indicated that the resistance of the Al:ZnO nanostructure samples decreased almost linearly as the humidity level increased, leading to better sensitivity and sensing response. The Al:ZnO-4 h nanostructured-based flexible humidity sensor had a maximum sensing response and demonstrated the highest sensitivity towards humidity changes, which was noticeably superior to the other tested samples. Finally, this study explained the Al:ZnO nanostructures-based flexible humidity sensor sensing mechanism in terms of chemical adsorption, physical adsorption, and capillary condensation mechanisms. Full article

The Al- and Cu-doped ZnO nanostructured films in this study were deposited using a sputtering technique. Investigations based on X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Hall effect measurements, and optical transmission spectroscopy was performed to analyze the structural, electrical, and optical characteristics of the prepared Al–ZnO and Cu–ZnO nanostructured films. The analyses show that doping results in enhanced conductivity as well as improved mobility in Al–ZnO and Cu–ZnO films in comparison to pure ZnO films. The Al- and Cu-doped ZnO films exhibited low resistivity (2.9 × 10⁻⁴ Ω cm for Al–ZnO and 1.7 × 10⁻⁴ Ω cm for Cu–ZnO) along with an average transmittance of around 80% in the visible spectrum. Moreover, the optical bandgaps of undoped ZnO, Al–ZnO, and Cu–ZnO nanostructures were observed as 3.3, 3.28, and 3.24 eV, respectively. Finally, solar cells were assembled by employing ZnO nanostructured thin films as photoelectrodes, resulting in efficiencies of 0.492% and 0.559% for Al–ZnO- and Cu–ZnO-based solar cells, respectively. Full article

Al-free and Al-doped V₂O₅ nanostructures were synthesized by a thermal-chemical vapor deposition (CVD) process on Si(100) at 850 °C under 1.2 × 10⁻¹ Torr via a vapor-solid (V-S) mechanism. X-ray diffraction (XRD), Raman, and high-resolution transmission electron microscopy (HRTEM) confirmed a typical orthorhombic V₂O₅ with the growth direction along [110]-direction of both nanostructures. Metallic Al, rather than Al³⁺-ion, was detected by X-ray photoelectron spectroscopy (XPS), affected the V₂O₅ crystallinity. The photoluminescence intensity of V₂O₅ nanostructure at 1.77 and 1.94 eV decreased with the increasing Al-dopant by about 61.6% and 59.9%, attributing to the metallic Al intercalated between the V₂O₅-layers and/or filled in the oxygen vacancies, which behaved as electron sinks. Thus the Al-doped V₂O₅ nanostructure shows the potential applications in smart windows and the electrodic material in a Li-ion battery. Full article

This paper describes the microstructure and properties of titanium-based composites obtained as a result of a reactive spark plasma sintering of a mixture of titanium and nanostructured (Ti,Mo)C-type carbide in a carbon shell. Composites with different ceramic addition mass percentage (10 and 20 wt %) were produced. Effect of content of elemental carbon covering nc-(Ti,Mo)C reinforcing phase particles on the microstructure, mechanical, tribological, and corrosion properties of the titanium-based composites was investigated. The microstructural evolution, mechanical properties, and tribological behavior of the Ti + (Ti,Mo)C/C composites were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction analysis (EBSD), X-ray photoelectron spectroscopy (XPS), 3D confocal laser scanning microscopy, nanoindentation, and ball-on-disk wear test. Moreover, corrosion resistance in a 3.5 wt % NaCl solution at RT were also investigated. It was found that the carbon content affected the tested properties. With the increase of carbon content from ca. 3 to 40 wt % in the (Ti,Mo)C/C reinforcing phase, an increase in the Young’s modulus, hardness, and fracture toughness of spark plasma sintered composites was observed. The results of abrasive and corrosive resistance tests were presented and compared with experimental data obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase. Moreover, it was found that an increase in the percentage of carbon increased the resistance to abrasive wear and to electrochemical corrosion of composites, measured by the relatively lower values of the friction coefficient and volume of wear and higher values of resistance polarization. This resistance results from the fact that a stable of TiO₂ layer doped with MoO₃ is formed on the surface of the composites. The results of experimental studies on the composites were compared with those obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase. Full article

In this paper, ZnO and Co²⁺/Mg²⁺-doped ZnO thin films on TiAlV alloy substrates were obtained. The films were deposited by spin coating of sol-gel precursor solutions and thermally treated at 600 °C for 2 h, in air and slow cooled. The doping ions concentration was 1.0 mol%. The study’s aim was to obtain implantable metallic materials with improved biocompatibility and antibacterial qualities. The characteristics of the thin films were assessed from the point of view of microstructure, morphology, wetting properties, antibacterial activity and biological response in the presence of amniotic fluid stem cells (AFSC). The results proved that all deposited samples were nanostructured, suggesting a very good antibacterial effect and proving to be suitable supports for cellular adhesion and proliferation. All properties also depended on the doping ion nature. Full article