The effects of the post-annealing time on the growth mechanism of Bi2Sr2Ca1Cu2O8+∂ thin films produced on MgO (100) single crystal substrates by pulsed laser deposition (PLD)

Bi₂Sr₂Ca₁Cu₂O_8+∂ thin films were deposited on MgO (100) substrates by pulsed laser deposition (PLD). The effects of post-annealing time on the phase formation, the structural and superconducting properties of the films have been investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature dependent resistivity (R–T), atomic force microscopy (AFM), and DC magnetization measurements. The films deposited at 600 °C were post-annealed in an atmosphere of a gas mixture of Ar (93%) and O₂ (7%), at 860 °C for 10, 30, and 60 min. All films have demonstrated a mainly single phase of 2212 with a high crystallinity (FWHM≈0.159°) and c-axis oriented. The critical temperature, T_C, of the films annealed for 10, 30, and 60 min were obtained as 77, 78, and 78 K, respectively. The highest critical current density, J_C, was calculated as 3.34×10⁷ A/cm² for the film annealed at 860 °C for 30 min at 10 K.     

Residence time distribution analysis and optimization of photocatalysis of phenazopyridine using immobilized TiO2 nanoparticles in a rectangular photoreactor

Optimization of photocatalytic degradation of phenazopyridine (PhP) under UV light irradiation using immobilized TiO₂ nanoparticles was studied. The effect of operational parameters was investigated using response surface methodology (RSM). Maximum removal efficiency was achieved at the optimum conditions: initial drug concentration of 10 mg/L, UV light intensity of 47 W/m², flow rate of 200 mL/min, and reaction time of 150 min. The residence time distribution (RTD) analysis was studied to find the effect of flow rate on the drug removal efficiency. The tracer (PhP) pulse injection response was studied with UV–vis measurements and was used to prepare RTD curves.     

Hydrothermal processing and in situ surface modification of metal oxide nanomaterials

In situ surface modification of TiO₂ and ZnO metal oxide particles has been carried out under hydrothermal conditions within a wide range of temperature and pressure (T = 150–400 °C; P = up to 20 MPa). The influence of the surfactant and selective doping with active metal ions on the crystal size, morphology, and photocatalytic activity of TiO₂ and ZnO particles has been carried out. A systematic characterization of the product has been carried out using powder XRD, FTIR, TGA, SEM/TEM, and UV–vis spectroscopy. Similarly the photocatalytic activity in these metal oxides varies with the size, shape and dopant metals.     

Sulfonated-polysulfone membrane surface modification by employing methacrylic acid through UV-grafting: Optimization through response surface methodology approach

Membrane surface modification through UV-grafting method was studied and optimized using response surface methodology (RSM) approach. Sulfonated-polysulfone (SPS) membrane was modified through grafting process by employing methacrylic acid (MAA) monomer solution under the exposure of UV light. The parameters used were the concentration of MAA in the range of 0–6 wt% and UV activation time of 0–50 min. The optimized parameters from RSM were 2.61 wt% of MAA and 21.10 min of UV activation time. The optimized water permeability obtained was 8.75 L m⁻² h⁻¹ bar⁻¹, while the rejection percentages for humic acid, NaCl and MgSO₄ solution were 95.0%, 65.7% and 48.3%, respectively.     

Evaluating the photocatalytic activity of Pt/TNT film catalyst

TiO₂ nanotubes (TNT) were prepared by a hydrothermal method from the commercially available TiO₂-P25. Five types of TNT were produced at different temperatures (120 °C, 130 °C, and 150 °C) and by using different reaction times (12 h, 24 h, and 30 h). The photocatalytic reactor that was used is a film catalytic reactor, in which the height of the catalyst is 1.0 mm. The BET and FESEM analysis results showed that TNT130-24 (130 °C, 24 h) and TNT150-12 (150 °C, 12 h) possessed well-formed tubular structures with a high specific surface area (282.9–316.7 m² g⁻¹) and large pore volumes (0.62–0.70 cm³ g⁻¹). However, TNT120-30 (120 °C, 30 h) presented the best photocatalytic activity upon CO removal due to the synergistic effect of TiO₂ nanotubes and TiO₂ particles. After the TNT catalysts were modified with Pt particles, the removal efficiency was in the order of Pt/TNT120-30>Pt/TNT130-24>Pt/P25. Pt/TNT120-30 showed 99% removal efficiency in a continuous photoreactor with a high space velocity of 1.79×10⁴ h⁻¹. The results of the TEM and DRS analyses confirmed that the Pt particles enhanced the photocatalytic reaction, which was attributed to the well-dispersed nature of the 1 nm nanoscaled Pt particles on the surfaces of the TNT catalysts, and narrowed the band gap from 3.22 eV to 3.01 eV.     

Preparation of Cu2O/exfoliated graphite composites with high visible light photocatalytic performance and stability

Cu₂O/exfoliated graphite composites (Cu₂O/EG (1 wt%), Cu₂O/EG (4 wt%), Cu₂O/EG (7 wt%), Cu₂O/EG (10 wt%), and Cu₂O/EG (15 wt%)) were prepared by the precipitation method. The photocatalytic activity of the material was evaluated using the decolorization of methyl orange (MO) solution as model reaction. Results showed that Cu₂O deposited on the worm-like flakes of EG in the form of nanocrystals. The EG provided a three-dimensional environment for photocatalytic reaction and endowed a high adsorption capacity for the sample. Under optimal conditions, the decolorization efficiencies of MO for 60 min reached 96.7%. Recycling of the catalyst showed Cu₂O/EG composites (10 wt%) to possess high photocatalytic efficiency even when repeatedly used for five times.     

A hybrid photocatalytic and enzymatic process using glucose oxidase immobilized on TiO2/polyurethane for removal of a dye

A rectangular recycling photo-bioreactor using glucose oxidase (GOx) immobilized on TiO₂/polyurethane (PU) was developed as a novel coupling of photodegradation and enzymatic process. This method was tested for removal of Acid Orange 7 (AO7), as a model pollutant. High efficiency of decolorization (>99%) was achieved after 22 min using the GOx/TiO₂/PU photo-biocatalyst. Roles of various processes including photodegradation (TiO₂/PU), enzymatic process (GOx/PU) and a coupling of photocatalytic–enzymatic (GOx/TiO₂/PU) process were investigated in the presence and absence of UV light. All the experiments were performed in a circulation photoreactor equipped with a 6 W UV lamp with rate of 5 mL/min.     

A novel TiO2 − xNx/BN composite photocatalyst: Synthesis,characterization and enhanced photocatalytic activity for Rhodamine B degradation under visible light

A novel TiO_2 − xN_x/BN composite photocatalyst was prepared via a facile method using melamine–boron acid adducts (M·2B) and tetrabutyl titanate as reactants. The morphological results confirmed that nitrogen-doped TiO₂ nanoparticles were uniformly coated on the surface of porous BN fibers. A red shift of absorption edge from 400 nm (pure TiO₂) to 520 nm (TiO_2 − xN_x/BN composites) was observed in their UV–Vis light absorption spectra. The TiO_2 − xN_x/BN photocatalysts exhibited enhanced photocatalytic activity for the degradation of Rhodamine B (RhB) and the highest photocatalytic degradation efficiency reached 97.8% under visible light irradiation for 40 min. The mechanism of enhanced photocatalytic activity was finally proposed.     

Environmental remediation of cyanide solutions by photocatalytic oxidation using Au/CdS nanoparticles

CdS nanoparticles were prepared by a hydrothermal method, and Au was deposited onto the surface of CdS via a photoassisted deposition method. The resulting samples were characterised by X-ray diffraction, ultraviolet and visible spectroscopy, photoluminescence emission spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and surface area measurements. The catalytic performance of the samples in the photocatalytic oxidation of cyanide under visible light was determined. The UV–vis analysis indicated that a red shift occurred after Au was loaded onto CdS nanoparticles. The maximum photocatalytic oxidation efficiency was 100%, which was obtained using 0.2 wt% Au/CdS after a reaction time of 40 min.     

Effect of PI film surface on printing of Pd(II) catalytic ink for electroless copper plating in the printed electronics

Pd(II) catalytic ink was synthesized by the hydrolysis of PdCl₂, followed by treatment with a small amount of stabilizing agent. The Pd(II) ink has excellent storage stability and the same low viscosity and surface tension as water. Polyimide film was used as a substrate for inkjet printing of the Pd(II) ink, while various characteristic changes of the printing were observed according to the contact angle on the substrate surface. The contact angle was affected by the concentration of KOH solution, and a surface condition suitable for composing Copper circuit was obtained by printing Pd(II) catalyst ink and electroless plating when it was treated in 1 M KOH solution for 10 min. The physical properties of Pd(II) ink were analyzed using a surface tension meter, viscometer, pH meter and UV–visible spectrophotometer, whereas the surface properties of polyimide film were analyzed using a contact angle instrument, FTIR-ATR, video microscope, XPS, FESEM and AFM. The physical properties of Pd(0) particles were analyzed by XPS and AFM, while the characteristics of electroless copper plating were analyzed by video microscope and XPS.     

N-doping TiO2 thin film prepared by heat treatment in electric field

A visible-light-active TiO_2−xN_x photocatalyst was synthesized in electric field. The N-doping TiO₂ film had a thickness of about 70–80 nm. The results of the photocatalytic experiments showed that the vis-activity rose largely. XPS and XRD analysis implied that the doping N substituted the oxygen-deficient in TiO₂ film. The Einstein shift in optical absorption spectrum of the N-doped film was also observed by the UV–VIS with a cut wave length of about 550 nm. Based on the experiment, it could be concluded that the N doping is effective to narrow the gap and enhance the photocatalysis.     

Application of TiO2/perlite photocatalysis for degradation of ammonia in wastewater

The purpose of this study was removal of ammonia by a new photocatalytic process from synthetic wastewater under UV irradiation. TiO₂ was used as the photocatalyst and immobilized on perlite granules as a supporter. The prepared catalysts were characterized by SEM and FTIR analysis showed that TiO₂/perlite catalyst has mesoporous structures and uniform coating of TiO₂ on support. Also, the optimum efficiency of photocatalytical degradation of ammonia was obtained at pH 11 for UV intensity irradiation with 125 W lamp. About 68% degradation of ammonia in wastewater was achieved after 180 min of irradiation by using the optimized reaction conditions.     

Zn2 +-assisted synthesis of concave Cu2O crystals and enhanced photocatalytic properties

The effects of Zn^2 + on the structure Cu₂O crystals and photocatalytic decoloration of methylene orange (MO) were studied. Samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), and Ultraviolet–Visible Spectroscopic (UV–VIS). The results indicated that Zn^2 + ions can transform the surface curvature of Cu₂O microcrystals from convex to concave. Tests of photodecoloration showed that the concave trisoctahedron Cu₂O microcrystals exhibited higher catalytic activity than those of octahedra Cu₂O and convex Cu₂O for MO under visible light.     

High temperature erosion behavior of spark plasma sintered ZrB2-SiC composites

Damage of structural components of hypersonic vehicles by atmospheric particles demands thorough understanding on their wear behavior. In the present work, dense ZrB₂-SiC (10, 20, and 30 vol%) composites are prepared by spark plasma sintering at 55 MPa in two stages: 1400 °C for 6 min followed by 1600 °C for 2 min. With increase in SiC content, microstructures of sintered composites reveal strongly bonded ZrB₂ grains with SiC particles. A combination of maximum hardness of 23 GPa, elastic modulus of 398 GPa and fracture toughness of 5.4 MPa m^1/2 are obtained for the composite containing 30 vol% SiC particles. It is found that cracks are bridged or deflected by SiC particles in the composites. When the composites are subjected to SiC particle erosion at 800 °C, a 14% decrease in erosion rate is obtained with increase in SiC content from 10 to 30 vol%. The formation of large extent of boro-silicate rich viscous surface on eroded surfaces is attributed to reduced fracture or removal of ZrB₂ grains of the composites with increased SiC content.     

Hydrogen production from glycerol steam reforming over molybdena–alumina catalysts

The glycerol steam reforming was investigated on alumina supported molybdena catalysts (with 2, 5 and 12 wt.%) prepared by the sol–gel method and gel combustion. The catalysts were characterized by XRD, BET, UV–VIS, DRIFT, SEM and TEM. The catalytic performances were studied at 400–500 °C, steam to glycerol molar ratio between 9:1 and 20:1 and feed flow rate 0.04–0.08 ml/min. The conversion is directly proportional to molybdena loading, while the hydrogen selectivity has reached greater value on catalyst with 2% MoO₃. The optimum ratio steam to glycerol for reforming is 15:1 and for decomposition in syngas 9:1 and the ratio 20:1 favors water gas shift reaction.     

Effect of milling time and pH on the dispersibility of lead zirconate titanate in aqueous media for inkjet printing

Micrometre-sized Pb(Zr_0.53Ti_0.47)O₃ (PZT) powder was dispersed in water, stabilized with the ammonium polyacrylate (PAANH₄) and milled to reduce the particle size. The influence of the pH, the amount of PAANH₄, and the milling time on the zeta potential, the PZT particle size and the particle size distribution was studied. The agglomeration took place regardless the milling time at pH 3. The suspension, containing 5 vol.% of PZT and 5 wt.% of PAANH₄, milled at pH 10 for 240 min, was stable and contained particles with a narrow, log-normal particle size distribution with the median size of 160 nm. The dissociated carboxyl groups from the PAANH₄ interacted with the PZT particles as evidenced by Fourier transform infrared spectroscopy and electrosterically stabilized the particles in water at pH 10. The PZT particle size and the stability of the suspension fitted the requirements for the ink, suitable for ink-jet printing.     

Spectrophotometric studies of photo-induced degradation of Tertrodirect Light Blue (TLB) using a nanostructure zinc zirconate composite

Zinc zirconate nanopowder (ZZN) photocatalyst was prepared by sol–gel method using zinc acetate and zirconium acetylacetonate as precursors. The optimal calcination temperature was 800 °C and ZnZrO₃ phase was formed. The structural and morphology properties of the nanocomposite were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDAX) and ultraviolet visible diffuse reflectance (UV-DRS). The SEM observation for ZZN showed the average grain size of 26 nm. UV–vis diffuse reflectance spectra (DRS) of the nanocomposite showed an absorption edge at 355 nm. The catalytic activity of ZZN was investigated by degradation of Tertrodirect Light Blue (TLB) dye in water using UV–vis spectroscopy (UV–vis) with an initial concentration of 20 mg/L dye. The influence of the catalyst concentration, time of irradiation and pH on photodegradation of dye was investigated. The results showed that degradation of TLB dye can be conducted in the photocatalytic process. Accordingly, a degradation of more than 97% of dye was achieved by applying the optimal operational parameters with 30 mg/L of catalyst, pH 9 at 1 h irradiation.     

Photocatalytic degradation of methyl tert-butyl ether (MTBE) by Fe-TiO2 nanoparticles

Nowadays, since the underground waters are known as the main source for supplying the drinking water, their pollution to the organic contaminants such as methyl tert-butyl ether (MTBE) is a very significant issue. Therefore, in this study, photocatalytic degradation of MTBE was investigated in the aqueous soloution of Fe-TiO₂ nanoparticale under UV irradiation (wavelenght 254 nm) in a batch reactor. The Fe-TiO₂ mixed oxides were prepared by sol–gel impregnation method. The samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and BET specfic surface area. Then, the effect of various operational parameters namely pH, catalyst loading, molar ratio of [H₂O₂]₀/[MTBE]₀ and UV light intensity on degradation of aqueous MTBE were evaluated in a batch reactor. The optimal condition to achieve the best degradation for the initial concentration of 75 ppm MTBE was found at pH 7, catalyst concentration 2 g/L, molar ratio of [H₂O₂]₀/[MTBE]₀ 4, and UV irradiation 24 W. Total degradation of MTBE with initial concentration of 75 ppm was reached in optimal condition after 70 min. In addition, investigations were also carried out to determine the appropriate kinetics of MTBE degradation using UV/Fe-TiO₂/H₂O₂ process in optimal condition.     

Sol–gel preparation of titania multilayer membrane for photocatalytic applications

The main goal of the present study is to prepare a titania membrane with high permeability and photocatalytic activity for environmental applications. In this investigation a mesoporous titania multilayer membrane on alumina substrate is successfully fabricated via the sol–gel processing method. The prepared titania polymeric sol for the membrane top layer has an average particle size of 11.7 nm with a narrow distribution. The resulting TiO₂ multilayer membrane exhibits homogeneity with no cracks or pinholes, small pore size (4 nm), large specific surface area (83 m²/g), and small crystallite size (10.3 nm).The permeability and photocatalytic properties of the titania membrane were measured. The photoactivity of the titania membrane was examined to be 41.9% after 9 h UV irradiation based on methyl orange degradation. This measurement indicates high photocatalytic activity per unit mass of the catalyst. Through multilayer coating procedure, the photocatalytic activity of the membrane improved by 60% without sacrificing the membrane permeation. The prepared TiO₂ photocatalytic membrane has a great potential in developing high efficient water treatment and reuse systems due to its multifunctional capability such as decomposition of organic pollutants and physical separation of contaminants.     

Supercritical anti-solvent micronization of chromatography purified marigold lutein using hexane and ethyl acetate solvent mixture

This work aims to study supercritical anti-solvent micronization of marigold derived purified lutein that was dissolved in the mixture of hexane and ethyl acetate (70:30 v/v), the solvent used as the mobile phase for chromatographic purification. The results show significant effect of pressure on the morphology of micronized lutein particles. The increase in lutein initial concentration from 1.5 mg/ml to 3.2 mg/ml and the increase in SC-CO₂ flow rate from 15 ml/min to 25 ml/min show no significant effects on the morphology of lutein particles. However, the reduction of mean particle size from about 2 μm to 0.8 μm was observed by increasing SC-CO₂ flow rate. The X-ray diffraction patterns of the micronized lutein particles show apparent amorphous nature, while the Fourier transform infrared spectroscopy results show that no chemical structural changes occurred. Moreover, the solubility of the micronized lutein particles in aqueous solution was found to increase significantly from being almost insoluble to having approximately 20% solubility