Epitaxial growth by monolayer restricted galvanic displacement

The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD) was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV) and scanning tunneling microscopy (STM) are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111), Cu on Ag(111), and Cu on Au(111) by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process

TiO2 nanoparticles supported on natural zeolite clinoptilolite from Serbia for removal of bisphenol A from aqueous solution

Bisphenol A (BPA) is a well-known emerging contaminant that pose a severe threat to human health due to its negative effect on the body’s endocrine systems. BPA is widely used in the production of polycarbonate plastic and epoxy resins and therefore often detected in different water environments. Since the conventional wastewater treatments for BPA removal haven’t been proven efficient it is important to find a green and efficient method for its complete elimination. Therefore, the aim of this work was to prepare a cost-effective hybrid photocatalyst based on TiO2 nanoparticles and natural zeolite clinoptilolite and study its photocatalytic performance toward BPA. The TiO2/clinoptilolite, containing 20 wt% of TiO2, was prepared using ultrasound assisted solid-state dispersion method and characterized using a multi-technique approach by combining X-ray powder diffraction, FTIR, UV Vis DRS spectroscopy, atomic force microscopy (AFM), BET measurements and laser diffraction. The study showed complete removal of BPA (5 mg/L) after 180 minutes of simulated solar irradiation using 2 g/L of hybrid photocatalyst, at pH = 6.4. The addition of H2O2 led to a faster BPA removal after 120 minutes of irradiation. When BPA removal was tested in bottled drinking water a lower removal of 60 % after 180 minutes of irradiation was observed because of the presence of bicarbonate ions and its scavenger effect toward hydroxyl radicals. The reused photocatalyst showed good photocatalytic activity in repeated cycles (e. i. 70 % of BPA was still successfully removed at the end of the 4th cycle)

The Effect of Sintering Temperature on Mesoporous Structure of WO3 Doped Tio(2) Powders

In this study, WO3 doped TiO2 powders were synthesized via sol-gel method combined with a hydrothermal process. The effect of sintering temperature on mesoporous structure and catalytic activities of these powders were investigated. The physical analysis via X-ray diffraction indicates that prepared samples are a mixture of anatase and rutile TiO2 phases. X-ray peak analysis is used to evaluate the crystallite size and lattice strain by the Williamson-Hall analysis. Considering all the reflections of the anatase phase the lattice strain ranging from c = 9.505 to c = 9.548 is calculated, suggesting that microstrain decreases when calcination temperature increases. N-2 adsorption-desorption analysis shows that the surface area and pore volume decrease with increasing temperature and that WOx-TiO2 powders primarily consist of mesopores. Sintering temperature induced a change in textural properties causing a systematic shift towards larger mesopores. Simultaneously, photoactivity in decolorization of methyl orange increases with increasing calcination temperature up to 700 degrees C, followed by significant decrease with its further increase

Morphology and fractal dimension of tio2 thin films

The influence of annealing temperature on the morphology and surface fractal dimension of titanium dioxide (TiO2) films prepared via the spray deposition process was investigated. Thin films with various morphologies were obtained at different temperatures and characterized by X-ray diffraction and atomic force microscopy (AFM). It was found that the crystalline structure of TiO2 films depends strongly on annealing temperature. At higher temperatures, the partial phase transformation of anatase-to-rutile was observed. The morphology and surface fractal dimensions were evaluated by image analysis methods based on AFM micrographs. The results indicate that the value of surface roughness (the standard deviation of the height values within the given area of AFM image) of TiO(2)films increases with increasing annealing temperature. Fractal analysis revealed that the value of the fractal dimension of the samples decreases slowly from 2.23 to 2.15 following the annealing process

Mechanical Properties of Electrolytically Produced Copper Coatings Reinforced with Pigment Particles

Copper from sulfate baths without and with added inorganic pigment particles based on strontium aluminate doped with europium and dysprosium (SrAl2O4: Eu2+, Dy3+) was electrodeposited on a brass cathode by a galvanostatic regime. Morphological, structural, and roughness analysis of the pigment particles, the pure (pigment-free) Cu coating, and the Cu coatings with incorporated pigment particles were performed using SEM, XRD, and AFM techniques, respectively. Hardness and creep resistance were considered for the examination of the mechanical properties of the Cu coatings, applying Chicot–Lesage (for hardness) and Sargent–Ashby (for creep resistance) mathematical models. The wettability of the Cu coatings was examined by the static sessile drop method by a measurement of the water contact angle. The incorporation of pigment particles in the Cu deposits did not significantly affect the morphology or texture of the coatings, while the roughness of the deposits rose with the rise in pigment particle concentrations. The hardness of the Cu coatings also increased with the increasing concentration of pigments and was greater than that obtained for the pigment-free Cu coating. The presence of the pigments caused a change in the wettability of the Cu coatings from hydrophilic (for the pigment-free Cu coating) to hydrophobic (for Cu coatings with incorporated particles) surface areas

Hardness and Wettability Characteristics of Electrolytically Produced Copper Composite Coatings Reinforced with Layered Double Oxide (Fe/Al LDO) Nanoparticles

The lab-made ferrite-aluminium layered double oxide (Fe/Al LDO) nanoparticles were used as reinforcement in the production of copper matrix composite coatings via the electrodeposition route in this study. The Cu coatings electrodeposited galvanostatically without and with low concentrations of Fe/Al LDO nanoparticles were characterized by SEM (morphology), AFM (topography and roughness), XRD (phase composition and texture), Vickers microindentation (hardness), and the static sessile drop method (wettability). All Cu coatings were fine-grained and microcrystalline with a (220) preferred orientation, with a tendency to increase the grain size, the roughness, and this degree of the preferred orientation with increasing the coating thickness. The cross-section analysis of coatings electrodeposited with Fe/Al LDO nanoparticles showed their uniform distribution throughout the coating. Hardness analysis of Cu coatings performed by application of the Chicot-Lesage (C-L) composite hardness model showed that Fe/Al LDO nanoparticles added to the electrolyte caused a change of the composite system from “soft film on hard cathode” into “hard film on soft cathode” type, confirming the successful incorporation of the nanoparticles in the coatings. The increase in roughness had a crucial effect on the wettability of the coatings, causing a change from hydrophilic reinforcement-free coatings to hydrophobic coatings obtained with incorporated Fe/Al LDO nanoparticles

Hardness and Wettability Characteristics of Electrolytically Produced Copper Composite Coatings Reinforced with Layered Double Oxide (Fe/Al LDO) Nanoparticles

The lab-made ferrite-aluminium layered double oxide (Fe/Al LDO) nanoparticles were used as reinforcement in the production of copper matrix composite coatings via the electrodeposition route in this study. The Cu coatings electrodeposited galvanostatically without and with low concentrations of Fe/Al LDO nanoparticles were characterized by SEM (morphology), AFM (topography and roughness), XRD (phase composition and texture), Vickers microindentation (hardness), and the static sessile drop method (wettability). All Cu coatings were fine-grained and microcrystalline with a (220) preferred orientation, with a tendency to increase the grain size, the roughness, and this degree of the preferred orientation with increasing the coating thickness. The cross-section analysis of coatings electrodeposited with Fe/Al LDO nanoparticles showed their uniform distribution throughout the coating. Hardness analysis of Cu coatings performed by application of the Chicot-Lesage (C-L) composite hardness model showed that Fe/Al LDO nanoparticles added to the electrolyte caused a change of the composite system from “soft film on hard cathode” into “hard film on soft cathode” type, confirming the successful incorporation of the nanoparticles in the coatings. The increase in roughness had a crucial effect on the wettability of the coatings, causing a change from hydrophilic reinforcement-free coatings to hydrophobic coatings obtained with incorporated Fe/Al LDO nanoparticles

ZnO Particles Modified MgAl Coatings with Improved Photocatalytic Activity Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy in Aluminate Electrolyte

MgAl and MgAl/ZnO coatings were prepared by plasma electrolytic oxidation (PEO) of AZ31 magnesium alloy in aluminate electrolyte (5 g/L NaAlO2) without and with addition of ZnO particles in various concentrations. The MgAl coating was partially crystallized and contained MgO and MgAl2O4 phases. The addition of ZnO particles to aluminate electrolyte had no significant effect on the surface morphology of formed coatings, while the Zn content increased with ZnO particle concentrations. X-ray diffraction confirmed the incorporation of ZnO particles in the coatings. The photodegradation of methyl orange (10 cm3 of 8 mg/L) was used to measure the photocatalytic activity (PA) of MgAl and MgAl/ZnO coatings. The PA of MgAl coating after 8 h of irradiation was around 58%, while the PA of MgAl/ZnO coatings formed in aluminate electrolyte with the addition of ZnO particles in concentrations of 4 g/L, 8 g/L, and 12 g/L were around 69%, 86%, and 97%, respectively

High photocatalytic activity of TiO2/Al2TiO5 coatings obtained by plasma electrolytic oxidation of titanium

In this work, it was shown that TiO2/Al2TiO5 coatings obtained by plasma electrolytic oxidation of titanium in alkaline electrolyte with added NaAlO2 show significantly better photocatalytic activity (PA) in degradation of methyl orange under simulated sunlight than anatase TiO2 coatings obtained in pure alkaline electrolyte. The TiO2/Al2TiO5 coating with the highest PA was obtained in alkaline electrolyte with the addition of 2.0 g/L NaAlO2, which has approximately 2.4 higher PA than anatase TiO2. Photoluminescence indicates that increased PA of TiO2/Al2TiO5 coatings is associated with increased number of oxygen vacancy and other defects

Photoluminescent and Photocatalytic Properties of Eu3+-Doped MgAl Oxide Coatings Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy

The synthesis of Eu3+-doped MgAl oxide coatings containing MgO and MgAl2O4 was accomplished through plasma electrolytic oxidation of AZ31 magnesium alloy in aluminate electrolyte with the addition of Eu2O3 particles in various concentrations. Their morphological, structural, and above all, photoluminescent (PL) and photocatalytic activity (PA) were thoroughly investigated. PL emission spectra of MgAl oxide coatings feature characteristic emission peaks, which are ascribed to f–f transitions of Eu3+ ions from excited level 5D0 to lower levels 7FJ. The charge transfer state of Eu3+ or direct excitation of the Eu3+ ground state 7F0 into higher levels of the 4f-manifold are both attributed to the PL peaks that appear in the excitation PL spectra of the obtained coatings. The fact that the transition 5D0 → 7F2 (electrical dipole transition) in Eu3+-doped MgAl oxide coatings is considerably stronger than the transition 5D0 → 7F1 (magnetic dipole transition) indicates that Eu3+ ions occupied sites with non-inversion symmetry. Because of oxygen vacancy formation, the Eu3+-doped MgAl oxide coatings had a higher PA in the degradation of methyl orange than the pure MgAl oxide coating. The highest PA was found in Eu3+-doped MgAl oxide coating formed in an aluminate electrolyte with 4 g/L of Eu2O3 particles. The PA, morphology, and phase of Eu3+-doped MgAl oxide coatings did not change after several consecutive runs, indicating outstanding stability of these photocatalysts