Preparation of TiO2–MoO3 composite nanofibers by water-based electrospinning process and their application in photocatalysis

Coupling TiO2 nanofibers with other semiconductor metal oxides can effectively extend the light absorbability of TiO2 to the visible range of the electromagnetic spectrum. This study demonstrates the synthesis of TiO2–MoO3 composite nanofibers via electrospinning using Ti and Mo water-soluble precursors. Aqueous solutions of these precursors were added to a PVP solution in N–N dimethylformamide. The mixture was electrospun, followed by annealing in air at 600 °C obtaining oxide nanofibers. The fibers were characterized via thermogravimetry and differential thermal analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. The diameter of the TiO2–MoO3 fibers was between 90 and 110 nm after annealing, Furthermore, methylene blue dye was used to investigate the photocatalytic activity of the fibers in visible light. TiO2–MoO3 fibers showed the best photocalaytic activity with a rate constant of 0.0018 min−1 while pure TiO2 and MoO3 nanofibers had 0.0009 min−1 and 0.0008 min−1 respectively

Influence of the Microwaves on the Sol-Gel Syntheses and on the Properties of the Resulting Oxide Nanostructures

Among the chemical methods in the liquid phase, the sol–gel technique is a versatile and efficient method for pure or doped metal oxide films or powders preparation, showing some advantages over other preparation techniques (high homogeneity, the possibility to introducing dopants in large amount, low processing temperature and control over the stoichiometry). Combining the sol–gel (SG)method with the effect of ultrasounds(US) or microwaves (MW) leads to improving the sol–gel procedure. The microwave-assisted sol–gel method is most frequently used for obtaining nanocrystalline, monodispersed oxide nanoparticles, or to transform amorphous gels into well-crystallized nanopowders. Less studied is the influence of the microwaves on the sol–gel reactions in solutions. The benefit of using microwave-assisted sol–gel preparation highly depends on the reagents used and on the composition of the studied systems. In the present chapter, results on the influence of the microwaves on the chemical reactions that take place during the sol–gel synthesis and on the properties of the resulted samples are discussed

Preparation of TiO2/WO3/C/N Composite Nanofibers by Electrospinning Using Precursors Soluble in Water and Their Photocatalytic Activity in Visible Light

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

Modelling the relationship between malaria prevalence as a measure of transmission and mortality across age groups

Parasite prevalence has been used widely as a measure of malaria transmission, especially in malaria endemic areas. However, its contribution and relationship to malaria mortality across different age groups has not been well investigated. Previous studies in a health and demographic surveillance systems (HDSS) platform in western Kenya quantified the contribution of incidence and entomological inoculation rates (EIR) to mortality. The study assessed the relationship between outcomes of malaria parasitaemia surveys and mortality across age groups.; Parasitological data from annual cross-sectional surveys from the Kisumu HDSS between 2007 and 2015 were used to determine malaria parasite prevalence (PP) and clinical malaria (parasites plus reported fever within 24 h or temperature above 37.5 °C). Household surveys and verbal autopsy (VA) were used to obtain data on all-cause and malaria-specific mortality. Bayesian negative binomial geo-statistical regression models were used to investigate the association of PP/clinical malaria with mortality across different age groups. Estimates based on yearly data were compared with those from aggregated data over 4 to 5-year periods, which is the typical period that mortality data are available from national demographic and health surveys.; Using 5-year aggregated data, associations were established between parasite prevalence and malaria-specific mortality in the whole population (RR; malaria; = 1.66; 95% Bayesian Credible Intervals: 1.07-2.54) and children 1-4 years (RR; malaria; = 2.29; 1.17-4.29). While clinical malaria was associated with both all-cause and malaria-specific mortality in combined ages (RR; all-cause; = 1.32; 1.01-1.74); (RR; malaria; = 2.50; 1.27-4.81), children 1-4 years (RR; all-cause; = 1.89; 1.00-3.51); (RR; malaria; = 3.37; 1.23-8.93) and in older children 5-14 years (RR; all-cause; = 3.94; 1.34-11.10); (RR; malaria; = 7.56; 1.20-39.54), no association was found among neonates, adults (15-59 years) and the elderly (60+ years). Distance to health facilities, socioeconomic status, elevation and survey year were important factors for all-cause and malaria-specific mortality.; Malaria parasitaemia from cross-sectional surveys was associated with mortality across age groups over 4 to 5 year periods with clinical malaria more strongly associated with mortality than parasite prevalence. This effect was stronger in children 5-14 years compared to other age-groups. Further analyses of data from other HDSS sites or similar platforms would be useful in investigating the relationship between malaria and mortality across different endemicity levels

A CFD Study on Heat Transfer Performance of SiO2-TiO2 Nanofluids under Turbulent Flow

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