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TiO2 thin films with different surface structure have been prepared from alkoxide solutions by the sol-gel method using different cationic precursors and heat treatment techniques. The effect of using titanium isopropoxide as well as titanium butoxide as a titanium source on the surface structure and photocatalytic activity of the resultant thin films was studied. Significant differences in the rate of hydrolysis and condensation reactions during the sol-gel synthesis were observed for these titanium precursors. This had a direct influence on the morphology of the as-prepared TiO2 films. Higher quality oxide coatings were obtained from titanium isopropoxide. They were characterized by a smaller grain size, improved surface roughness and uniform coverage of the glass substrate. A beneficial effect of calcination process after each sol application cycle in contrast to single step calcination after all dip-coating cycles was observed. Photocatalytic degradation tests showed that methyl orange was decolorized in the presence of all prepared TiO2 films by exposing their aqueous solutions to UV light (λ = 254 nm). The highest photocatalytic activity had the TiO2 layer produced using titanium isopropoxide.

Barium titanate is a ferroelectric perovskite with unique electric properties, therefore, it is widely applied in the fabrication of inorganic coatings or thin films, capacitors, or in the production of devices for energy storage and conversion. This paper describes the mechanochemical synthesis of BaTiO3 from BaO and TiO2 using a ball mill. XRD analysis allowed concluding that barium titanate was formed after 90 min of mechanochemical grinding. It was also proved by spectroscopic analysis and the band corresponding to Ti&ndash, O vibrations on obtained Fourier Transform Infrared (FT-IR) spectra. The specific surface area of obtained powder was 25.275 m2/g. Next, formed perovskite was dispersed in an acrylic poly(ethylene glycol) (superabsorbent polymer suspension, SAP) suspension prepared using microwave radiation. Final suspensions differed in the concentration of SAP applied. It was proven that the increase of SAP concentration does not affect the acidity of the suspension, but it does increase its dynamic viscosity. A sample with 83 wt.% of SAP reached a value of approximately 140 mPa∙s. Dispersions with higher values of SAP mass fraction exhibited lower sedimentation rates. Molecules such as SAP may adsorb to the surface of particles and thus prevent their agglomeration and make them well monodispersed. Based on the performed experiments, it can be concluded that acrylic poly(ethylene glycol) suspension is a suitable fluid that may stabilize barium titanate dispersions.

The results of a photocatalytic process performed in a new type of inclined, three-phase fluidised bed reactor with a periodic photocatalyst film are presented. These phases were fly ash cenospheres coated with TiO2, an aqueous solution of methylene blue and an air stream passing from the bottom of the photoreactor. The cenospheres have a density lower than water and could thus form a catalytic film on a top irradiated window. The formed surface film is stable but is easy to break and be reproduced in a cyclic air-sparged process. Mixing was performed in either a cyclic or a continuous manner. From an operational point of view, the best variant of mixing was a 10 s air-sparge/10 s break with a 50% duty cycle, because it provided the same discolouration efficiency and reduced energy demand by 50% in comparison with the continuous mixing. Due to film formation, the proposed catalytic reactor enables a substantial reduction in the energy required for mixing while maintaining the desired degree of discolouration.

The paper presents a simple way to improve the photocatalytic properties of titanium dioxide using mechanochemical method. The TiO2 (Anatase) powders was subjected to high-energy ball milling in dry environment and in methanol. It has been shown that it is possible to induce the phase transformation from Anatase to Rutile and produce a material with a higher photocatalytic activity in the UV light. Physicochemical characteristics of the products were based on the following methods and techniques: X-ray powder diffraction (XRD), IR and UV-Vis (DR) spectroscopy, measurements of specific surface area (BET). The photocatalytic activity of the powders was measured in the decomposition reaction of methyl orange in water.

In this paper we studied calcium titanate (CaTiO 3 ) nanopowders obtained via a mechanochemical method assisted by microwave irradiation from calcium oxide and titanium dioxide, as well as its suspensions with addition of acrylic-poly(ethylene glycol) suspensions (SAP) obtained using microwave irradiation as a stabilizing agent. Experiments carried out using X-ray diffraction technique confirmed success of mechanochemical synthesis assisted by microwave irradiation and scanning electron microscopy images allowed to determine the structure as well as dimensions of CaTiO 3 nanopowders. Suspensions of CaTiO 3 and SAP were examined and the results showed relationships between the SAP concentration and both viscosity and stability. Both viscosity and stability are significantly increased upon addition of SAP and the dependency is nearly linear for higher SAP concentrations. Based on the results, we conclude that addition of SAP allows to successfully stabilize CaTiO 3 nanopowders and the stabilizing effect can be explained by both electrostatic and steric forces.

The study shows the advisability of using a mechanochemical synthesis method, based on a high-energy planetary ball milling, to a modification of barium titanate by a vanadium doping. This method improves useful properties of BaTi0:95V0:05O3 as a capacitor material. It has a high value of electric permittivity ɛ′ in the wide range of temperature and low dielectric losses ɛ″ as well as a low electrical conductivity.

This paper presents mechanochemical synthesis as an alternative to the traditional high-temperature synthesis of advanced electrotechnical ceramic materials with a perovskite-type structure. The reaction conditions for high-energy ball milling, e.g. reaction environment, energy of milling and additives to BaTiO3 such as metallic iron or zirconia from the exfoliation of the milling vessel and grinding media are discussed.

Mechanochemical synthesis has been successfully employed to prepare a Cu3Fe4(VO4)6 powder. The formation of designed compound (in α-polymorphic form) is due to the reactions of copper, iron and vanadium oxide precursors which were activated by high-energy ball milling (Activator 2S, Novosibirsk, Russia) for 8 h instead of heat energy required in the conventional multi-stage high-temperature process during 80 h forming β-polymorphic form. Catalytic properties of Cu3Fe4(VO4)6 compound, which has been prepared by two different mentioned above techniques, tested in the methanol steam reforming reaction are satisfactory and closely the same. However, α-, as well as, β-polymorphic forms of Cu3Fe4(VO4)6 are structural unstable during steam reforming of methanol and form a metallic copper beside V2O3 and iron oxides, which probably catalyze simultaneously undesired methanation reaction. The real chemical mechanism is still not clear.

Mechanochemical synthesis has been successfully employed to prepare Cu0–Al2O3 composite powders. The formation of the designed compound is due to the self-propagating reaction of CuO and Al0 powders by high-energy ball milling using a planetary ball mill (Pulverissette 6, Fritsch GmbH). The products were characterized by means of nitrogen adsorption (BET surface area), X-ray diffraction, scanning electron microscopy and temperature-programmed reduction of hydrogen. The catalytic properties of the prepared materials were tested in the methanol steam reforming (SRM) process. The results show that the Cu0–Al2O3 system is active towards hydrogen in SRM. Hydrogen yields are satisfactory; however, methanol conversion to CO as a by-product is observed.