TiO₂/WO₃ nanofibers were prepared in a one-step process by electrospinning. Titanium(IV) bis(ammonium lactato)dihydroxide (TiBALDH) and ammonium metatungstate (AMT) were used as water-soluble Ti and W precursors, respectively. Polyvinylpyrrolidone (PVP) and varying ratios of TiBALDH and AMT were dissolved in a mixture of H₂O, EtOH and CH₃COOH. The as-spun fibers were then heated in air at 1 °C min⁻¹ until 600 °C to form TiO₂/WO₃ composite nanofibers. Fiber characterization was done using TG/DTA, SEM–EDX, FTIR, XRD, and Raman. The annealed composite nanofibers had a diameter range of 130–1940 nm, and the results showed a growth in the fiber diameter with an increasing amount of WO₃. The photocatalytic property of the fibers was also checked for methyl orange bleaching in visible and UV light. In visible light, the photocatalytic activity increased with an increase in the ratio of AMT, while 50% TiBALDH composite fibers showed the highest activity among the as-prepared fibers in UV light.

A new electrospinning process was developed for preparing TiO₂ nanofibers using a water-soluble Ti-precursor, [bis(kappa1O-hydroxo)(bis(kappa2O,O′-lactato)titanium(IV)] commonly known as titanium(IV) bis (ammonium lactato) dihydroxide (TiBALDH). The importance of the study is justified by the fact that Ti-precursors used for electrospinning, sol–gel, hydrothermal and other fiber synthesis processes are mostly non-water soluble. Accordingly, anatase TiO₂ nanofibers of diameter between 20 and 140 nm were synthesized by electrospinning and annealing. Polyvinylpyrrolidone (PVP) and different concentrations of TiBALDH were dissolved in a mixture of water, ethyl alcohol and acetic acid to optimize the electrospinning conditions. The thermal decomposition and fragmentation of PVP, TiBALDH and the fibers with 50% mass fraction of TiBALDH were studied by TGA-MS measurements. The fibers were then annealed at 1 °C min⁻¹ until 600 °C. The TiO₂ fibers were characterized using SEM–EDX, FTIR and XRD

A CFD model was performed with commercial software through the adoption of the finite volume method and a SIMPLE algorithm. SiO₂-P25 particles were added to water/ethylene glycol as a base fluid. The result is considered a new hybrid nanofluid (HN) for investigating heat transfer (HT). The volume concentrations were 0.5, 1.0, and 1.5%. The Reynolds number was in the range of 5000–17,000. The heat flux (HF) was 7955 W/m², and the wall temperature was 340.15 K. The numerical experiments were performed strictly following the rules that one should follow in HT experiments. This is important because many studies related to nanofluid HT overlook these details. The empirical correlations that contain the friction factor perform better with higher Reynolds numbers than the correlations based only on Reynolds and Prandtl numbers. When temperature differences are moderate, researchers may consider using constant properties to lower computational costs, as they may give results that are similar to temperature-dependent ones. Compared with previous research, our simulation results are in agreement with the experiments in real time.

In the literature data, several papers reported the synthesis by various chemical or physical methods of the SrCu₂O₂ (SCO) having possible applications in thermoelectric or completely electronic devices such as solar cells, liquid crystal displays and touch screen. A great challenge is represented by the formation of the pure SrCu₂O₂ (SCO), due to the high labiality of the Cu valence, depending on temperature. In the present paper, the thermal behavior of Sr–Cu–O gels obtained by sol–gel (SG) or microwave (MW)-assisted SG methods was studied in order to establish the appropriate thermal conditions for pure nanostructured SrCu₂O₂ preparation. As reagents, copper and strontium acetylacetonate in alcoholic media were used. The starting solutions were homogenized either by stirring for 2 h at room temperature or were exposed to MW for 5 min at 300 W and a frequency of 2.45 GHz. Both solutions were left to gel at room temperature. The obtained gels were investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, as well as by thermal analysis combined with evolved gas analysis (TG/DTA-MS) measurements in air, inert and reducing atmospheres. For both type of samples, a stepwise thermal decomposition of the gels was noticed in a large temperature range. In the case of samples obtained by microwave-assisted SG method, a higher number of thermal effects were registered assigned to a higher number of molecular species formed in the sample. The residues obtained by non-isothermal treatment up to 900 °C, of both type of samples, were investigated by X-ray diffraction. The results demonstrate the influence of the MW on the SG synthesis and on the thermal properties of the resulted gels. Based on the obtained results, the required thermal treatment of the gels in order to obtain convenient precursors powders for obtaining pure SrCu₂O₂ could be proposed.

Extending the absorption range of TiO₂ nanofibers to visible light is a great improvement of the photocatalytic property of TiO₂. In this study, TiO₂/WO₃/C/N nanofibers were prepared by electrospinning using precursors soluble in water then annealing in argon. Titanium(IV) bis(ammonium lactato)dihydroxide (TiBALDH) and ammonium metatungstate (AMT) were used as the precursor for TiO₂ and WO₃ respectively. Different volume ratios of the precursors were added to a solution of PVP before electrospinning. The fibers were studied by XPS, SEM-EDX, TEM, FTIR, XRD, Raman spectroscopy and UV–VIS diffuse reflectance spectroscopy (DRS). The photocatalytic degradation of methylene blue by the fibers in visible light was investigated. The fibers had anatase TiO₂ and monoclinic WO₃. Based on UV–VIS DRS and Kubelka-Munk function the fibers could absorb visible light. Moreover, 100% TiBALDH had an indirect band gap of 2.9 eV, and the band gap decreased with increase in AMT, i.e., for 0% TiBALDH, band gap was 2.4 eV. The fibers degraded methylene blue dye in visible light, and 90% TiBALDH had the highest photocatalytic activity, i.e., it degraded 40% of the dye after 240 min.