Preparation of La<Subscript>2</Subscript>NiMnO<Subscript>6</Subscript> thin films on Pt/TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si substrates by pulsed laser deposition

Double perovskite La₂NiMnO₆ thin films were prepared on Pt/TiO₂/SiO₂/Si substrates by the pulsed laser deposition process, and the crystal structure and microstructures were investigated. The temperature and the oxygen pressure played the primary roles dominating the crystallization behavior and the morphology of La₂NiMnO₆ thin films. The well crystallized La₂NiMnO₆ thin films could be obtained at 873 and 923 K under all oxygen pressures investigated here, and the fine morphology was obtained under the oxygen pressures equal to or higher than 50 and 100 Pa, respectively, while phase constitution was significantly affected by the oxygen pressure for La₂NiMnO₆ thin films prepared at 1,023 K where the higher oxygen pressure led to the appearance of some secondary phase.     

Electrical and optical properties of TiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript>:Fe thin films

TiO₂ and TiO₂:Fe thin films have been grown by electron beam evaporation and the influence of doping and heat treatment on their electrical and optical properties has been studied.     

Changes in dewetting behavior of SiO<Subscript>2</Subscript> films on TiO<Subscript>2</Subscript> substrates due to film thickness and crucible choice

The TiO₂/SiO₂ materials system has had renewed interest in recent years due to its photoelectric and photocatalytic properties, and serves as an ideal model system for liquid-phase sintering studies (LPS). In this study, glass SiO₂ films of three different nanoscale thicknesses were deposited onto (001) rutile TiO₂ substrates. The resulting dewet patterns of the glass were found to change depending on the initial film thickness when subjected to identical annealing conditions. In addition, changing the crucible type from Pt to Al₂O₃, caused films of the same thickness to undergo different convection mechanisms and thus developing very different surface patterns. It is proposed that Marangoni convection drove pattern formation when a Pt crucible was used, while the Rayleigh instability was responsible for dewetting when an Al₂O₃ crucible was used.     

Thin films of SiO<Subscript>2</Subscript> and hydroxyapatite on titanium deposited by spray pyrolysis

Wet spray pyrolysis of fine, well-dispersed a SiO₂ sol was used for the deposition of thin films of silicon dioxide. The sol was obtained by hydrothermal precipitation of silicon acid from a solution at pH = 10. The morphology, roughness, phase composition, chemical homogeneity and the mechanism of the films were investigated by SEM, EDS and IR spectroscopy. The obtained results show a complete covering of the titanium substrate with SiO₂ after 3 h of deposition. It was observed that the film thickness increased from 3 to 19 μm, the roughness of the film decreased from 12 to 3 μm, while the morphology of the deposit changed considerably. A hydroxyapatite film was prepared on the so-obtained SiO₂ thin film by spray pyrolysis deposition and its morphology and phase composition were investigated.     

Effect of annealing on leakage current characteristics of Pt/Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>TiO<Subscript>3</Subscript>/Pt thin-film capacitors

The effect of annealing on leakage current characteristics of Pt/Ba_0.6Sr_0.4TiO₃/Pt ferroelectric thin-film capacitors was investigated at the temperature range from 273 K to 393 K. The results show that the depletion layer width of the as-deposited BST film is about 3–5 times greater than that of the annealed film. For as-deposited samples, the Schottky barrier height increases with increasing temperature and voltage. However, for annealed samples, the Schottky barrier height linearly decreases with increasing voltage and is almost independent upon temperature.     

Electrochemical corrosion behaviors of titanium covered by various TiO<Subscript>2</Subscript> nanotube films in artificial saliva

TiO₂ nanotube films obtained by anodization have shown great promise as biomaterials. In the present work, we report on the corrosion behaviors of titanium (Ti) with various TiO₂ nanotubes prepared by using controlled anodization procedures. Special emphasis is put on the impact of film morphologies on the corrosion resistance of the Ti substrate. The corrosion behaviors of Ti with different nanotube films were studied in artificial saliva using open-circuit potential measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. Ti covered by TiO₂ nanotube films showed the markedly enhanced corrosion resistance properties compared to bare Ti. The existence of the compact oxide layer formed in a fluoride-free electrolyte was found to be beneficial for improving corrosion resistance properties. Besides, the TiO₂ nanotube films obtained by two-step anodization had better corrosion resistance than those obtained by single-step anodization, though they used the identical anodization parameters.     

Preparation of K<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript>/TiO<Subscript>2</Subscript> bio-ceramic on titanium substrate by micro-arc oxidation

K₂Ti₆O₁₃/TiO₂ bio-ceramic coatings are prepared successfully by micro-arc oxidation on titanium substrate in pure KOH electrolyte solution. The coating is prepared at various applied current density (150–500 mA/cm²) and in KOH electrolyte with different concentrations (0.5–1.2 mol/L). The composition and surface morphologies of coatings are strongly dependent on the applied current density and the electrolyte concentration. On the condition of lower current density and electrolyte concentration, K₂Ti₆O₁₃ phase almost cannot be formed. The phase is mainly composed of rutile and K₂Ti₆O₁₃ with increasing current density and electrolyte concentration. The surface morphologies are composed of whiskers and porous structures. The ability of K₂Ti₆O₁₃/TiO₂ bio-ceramic films inducing apatite deposition is evaluated by soaking it in biological model fluids. The results show the K₂Ti₆O₁₃/TiO₂ bio-ceramic coatings possess excellent capability of inducing bone-like apatite to deposit.     

IR protection property and color performance of TiO<Subscript>2</Subscript>/Cu/TiO<Subscript>2</Subscript> coated polyester fabrics

Both humans and objects can emit infrared (IR) wavelengths which generate thermal emissions that can be detected with an IR camera. Therefore, highly IR reflective materials have been the subject of interest recently, for example, in achieving IR stealth. In this work, IR reflective coatings on polyester fabric in the form of a titanium dioxide/copper/titanium dioxide (TiO₂/Cu/TiO₂; TCT) sandwich-like structure are fabricated by using magnetron sputtering. The coated fabric samples are then examined by using an energy dispersive X-ray detector, a scanning electron microscope and an X-ray diffractometer. The reflection of IR wavelengths which range from 8 to 14 µm of the TCT coated fabric is evaluated. The bending stiffness, and mechanical and adhesion strengths of the coated fabric samples are also investigated. The results show that the TCT sandwich-like structure on the polyester fabric sputtered for 30 min with Cu which results in a Cu film of 200 nm in thickness is observed to have the maximum reflection of IR wavelengths. The color of the TCT coated polyester fabric samples sputtered for 5, 10, 20, and 30 min with Cu is green, yellow, brown and purple, respectively. The TCT coated fabric therefore has potential applications as IR protection textiles for military purposes.     

Synthesis and characterization of nanocrystalline TiO<Subscript>2</Subscript> thin films

Nanocrystalline thin films of TiO₂ have been synthesized by sol gel spin coating technique Thin films of TiO₂ annealed at 700 °C were characterized by X-ray diffraction(XRD), Atomic Force Microscopy, High resolution TEM and Scanning Electron Microscopy (SEM), The XRD shows formation of tetragonal anatase and rutile phases with lattice parameters a = 3.7837 Å and c = 9.5087 Å. The surface morphology of the TiO₂ films showed that the nanoparticles are fine with an average grain size of about 60 nm. Optical studies revealed a high absorption coefficient (10⁴ cm^?1) with a direct band gap of 3.24 eV. The films are of the n type conduction with room temperature electrical conductivity of 10^?6 (Ω cm)^?1.     

TiO<Subscript>2</Subscript> crystalline structure and electrochemical performance in two-ply yarn CNT/TiO<Subscript>2</Subscript> asymmetric supercapacitors

Solid-state flexible energy storage devices play a crucial role in the development of wearable electronic textiles. In this study, we fabricated flexible asymmetric two-ply yarn supercapacitors from carbon nanotube yarns and surface-oxidized titanium filament. The crystalline structure of the TiO₂ surface layer can be adjusted to amorphous, anatase and rutile states by altering the annealing temperature. The titanium filament with a rutile TiO₂ surface layer produced at high annealing temperature showed far superior electrochemical performance over the filaments with amorphous and anatase TiO₂ surface layers. The as-prepared asymmetric two-ply yarn supercapacitors in aqueous gel electrolyte can achieve a durable operating voltage up to 1.4 V, with a maximum energy density of 11.7 Wh kg^?1 and a maximum power density of 2060 W kg^?1. The asymmetric two-ply yarn supercapacitors exhibited excellent flexibility and cycling stability over 1200 cycles at straight, twisted and bent states.     

Effect of substitution of titanium by magnesium and niobium on structure and piezoelectric properties in (Bi<Subscript>1/2</Subscript>Na<Subscript>1/2</Subscript>)TiO<Subscript>3</Subscript> ceramics

To develop new (Bi_1/2Na_1/2)TiO₃-based ceramics with excellent piezoelectric properties, the similarities and the differences between PZT and (Bi_1/2Na_1/2)TiO₃ ceramics were analysed. Based on the analysis, a new (Bi_1/2Na_1/2)TiO₃-based piezoelectric ceramic of B-site substitution of complex ions (Mg_1/3Nb_2/3)⁴⁺ for Ti⁴⁺ was prepared by a conventional ceramic technique, and effect of complex ions (Mg_1/3Nb_2/3)⁴⁺ addition on the microstructure, dielectric and piezoelectric properties was investigated. The results show that all compositions are mono-perovskite phase and the grain size increases with increasing content of (Mg_1/3Nb_2/3)⁴⁺. The piezoelectric constant, d ₃₃, first increases and then decreases, and electromechanical coupling factor, k _p, varies insignificantly with increasing content of (Mg_1/3Nb_2/3)⁴⁺.     

Effect of V<Subscript>2</Subscript>O<Subscript>5</Subscript> content on the optical,structural and electrochromic properties of TiO<Subscript>2</Subscript> and ZrO<Subscript>2</Subscript> thin films

Vanadium oxide (V₂O₅) mixed titanium oxide (TiO₂) and zirconium oxide (ZrO₂) thin films were fabricated on glass substrates (corning 2947) and on indium tin oxide (ITO) coated glass substrates by sol gel spin coating process. Their optical, structural and electrochromic properties were investigated. The results were compared with pure TiO₂ and ZrO₂ thin films. Mixture of V₂O₅ with both types of film reduces the transmittance at the higher wavelengths. The refractive index of the V₂O₅ mixed TiO₂ and ZrO₂ films increases when compared with pure TiO₂ and ZrO₂ films. AFM images demonstrate no significant topographical changes for V₂O₅ mixed TiO₂ whereas for V₂O₅ mixed ZrO₂ films a topographical change is observed. V₂O₅ mixed TiO₂ showed slight increase in their charge capacity.     

Pb/S/1,2-ethanedithiol composite thin films for efficient solid-state quantum-dot sensitized TiO<Subscript>2</Subscript> nanorod array solar cells

The Pb/S/1,2-ethanedithiol composite thin films were successfully deposited on TiO₂ nanorod arrays by spin-coating step-by-step 5 mmol dm^?3 Pb(NO₃)₂, Na₂S and 1% 1,2-ethanedithiol solution and their chemical compositions can be easily adjusted by changing the concentration of Na₂S solution from 5 to 3.5 mmol dm^?3 and 2 mmol dm^?3. The average crystal sizes of Pb/S/1,2-ethanedithiol quantum-dots decreased from 7.9 to 7.1 nm and 6.5 nm with the decrease of the concentration of Na₂S solution and the chemical bonding of Pb²⁺ and S in EDT was chelation of the penta-heterocycle in Pb/S/1,2-ethanedithiol composite thin films. All solid-state Pb/S/1,2-ethanedithiol composite thin film sensitized TiO₂ nanorod array solar cells using 5, 3.5, 2 mmol dm^?3 Na₂S solution exhibited the photoelectric conversion efficiency of 2.68, 3.41 and 4.51% under the illumination of simulated AM 1.5 sunlight (100 mA cm^?2).     

SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> fibers from titanium-modified polycarbosilane

We developed a process for preparing SiO₂/TiO₂ fibers by means of precursor transformation method. After mixing PCS and titanium alkoxide, continuous SiO₂/TiO₂ fibers were fabricated by the thermal decomposition of titanium-modified PCS (PTC) precursor. The tensile strength and diameter of SiO₂/TiO₂ fibers are 2.0 GPa, 13 μm, respectively. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) measurements, the microstructure of the SiO₂/TiO₂ fibers is described as anatase–TiO₂ nanocrystallites with the mean size of ~10 nm embedded in an amorphous silica continuous phase.     

Fabrication of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> double layer thin films with self-cleaning and photocatalytic properties

Transparent antireflective SiO₂/TiO₂ double layer thin films were prepared using a sol–gel method and deposited on glass substrate by spin coating technique. Thin films were characterized using XRD, FE-SEM, AFM, UV–Vis spectroscopy and water contact angle measurements. XRD analysis reveals that the existence of pure anatase phase TiO₂ crystallites in the thin films. FE-SEM analysis confirms the homogeneous dispersion of TiO₂ on SiO₂ layer. Water contact angle on the thin films was measured by a contact angle analyzer under UV light irradiation. The photocatalytic performance of the TiO₂ and SiO₂/TiO₂ thin films was studied by the degradation of methylene blue under UV irradiation. The effect of an intermediate SiO₂ layer on the photocatalytic performance of TiO₂ thin films was examined. SiO₂/TiO₂ double layer thin films showed enhanced photocatalytic activity towards methylene blue dye.     

Growth of ultrathin Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> films on quartz substrates

Niobium oxide films have been grown by reactive rf sputtering in a vacuum system and characterized by absorption spectroscopy and X-ray diffraction. The thickness of the (optically transparent) films has been determined as a function of sputtering time by examining interference effects in a plane-parallel layer. The average deposition rate is determined to be 7.4 ± 0.3 Å/min (95% confidence interval).     

Fabrication and properties of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> composites

Composites in the form of precipitated powders, hybrid xerogels, and SiO₂ core/TiO₂ shell particles have been produced via hydrolysis of precursors (alkoxides and inorganic derivatives of titanium and silicon) and have been characterized by differential thermal analysis, X-ray diffraction, adsorption measurements, and macroelectrophoresis. The results demonstrate that heat treatment of the composites leads to crystallization of the titanium-containing component and, accordingly, reduces their specific surface area. Hydrothermal treatment enables the fabrication of materials in which TiO₂ nanocrystals are evenly distributed over an amorphous SiO₂ matrix.     

Photoinduced properties of nanocrystalline TiO<Subscript>2</Subscript> sol-gel derived thin films

In this paper, nanostructure TiO₂ thin films were deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction and Fourier transform infrared spectroscopy were used to determine film behaviour. The super-hydrophilicity was assessed by contact angle measurement. Photocatalytic properties of these films were evaluated by degradation of methylene blue under UV irradiation. The XRD pattern of TiO₂ powder samples confirmed the presence of polycrystalline anatase phase with a crystal size of 17 nm. The results indicated that UV light irradiation had significant effect on super-hydrophilic and photocatalytic properties of TiO₂ thin films.     

Structural investigations on lead-free Bi<Subscript>1/2</Subscript>Na<Subscript>1/2</Subscript>TiO<Subscript>3</Subscript>-based piezoceramics

In this study, recent results from our electron, X-ray, and neutron-diffraction experiments with emphasis on the binary Bi_1/2Na_1/2TiO₃-BaTiO₃ (BNT–BT) and ternary Bi_1/2Na_1/2TiO₃–BaTiO₃–K_0.5Na_0.5NbO₃ (BNT–BT–KNN) system are presented and contrasted with literature. The experimental results clearly revealed a phase coexistence on the nanoscale level. A systematic study of superlattice reflections in conjunction with microstructural characteristics showed that the BNT-based systems have specific properties in common, which, however, strongly depend on composition. In situ transmission electron microscopy (TEM) electric field experiments unequivocally demonstrated the evolution of lamellar domains. Combining in situ TEM results with published in situ neutron-diffraction experiments, we proposed an electric field-induced phase transition that results in the giant unipolar and bipolar strain observed in specific compositions of the ternary system.