Формирование состава и характеристик поверхности хромоникелевой стали 12Х18Н10Т при лазерном модифицировании в слое экспериментальной легирующей обмазки

The results of an experimental study of laser pulsed modification of the surface of stainless steel 12CR18NI10T in a layer of alloying compound made of graphite paste and nanodispersed titanium dioxide powder (anatase) and without coating are presented. A comparative analysis of the effect of the coating on the elemental and phase compositions, morphological characteristics and microhardness of the modified surface is carried out. It was found that as a result of the treatment, the processes of cementation and oxidation of the surface occur, which made it possible to obtain a mixture of iron carbide and high-strength oxides in the surface layer of steel. In the samples that underwent laser treatment in the coating layer, an increase in the intensity of the diffraction peaks of the graphite phase and the formation of iron oxides Fe3O4 and chromium Cr2O3 with the presence of titanium dioxide TiO2 were revealed, which created a mixed heterophase metal oxide structure with increased mechanical strength. An increase in the microhardness of the modified surface after laser pulsed scanning in the layer of the experimental alloying compound is established.

Population Balance Application in TiO2 Particle Deagglomeration Process Modeling

The deagglomeration of titanium-dioxide powder in water suspension performed in a stirring tank was investigated. Owing to the widespread applications of the deagglomeration process and titanium dioxide powder, new, more efficient devices and methods of predicting the process result are highly needed. A brief literature review of the application process, the device used, and process mechanism is presented herein. In the experiments, deagglomeration of the titanium dioxide suspension was performed. The change in particle size distribution in time was investigated for different impeller geometries and rotational speeds. The modification of impeller geometry allowed the improvement of the process of solid particle breakage. In the modelling part, numerical simulations of the chosen impeller geometries were performed using computational-fluid-dynamics (CFD) methods whereby the flow field, hydrodynamic stresses, and other useful parameters were calculated. Finally, based on the simulation results, the population-balance with a mechanistic model of suspension flow was developed. Model predictions of the change in particle size showed good agreement with the experimental data. Using the presented method in the process design allowed the prediction of the product size and the comparison of the efficiency of different impeller geometries.

Изменение характеристик поверхности стали 12Х18Н10Т при лазерном модифицировании в слое графитовой пасты, содержащей наночастицы диоксида титана

Experimental studies of laser modification of the surface of 12Cr18Ni10T stainless steel in a layer of graphite paste and nanodispersed titanium dioxide powder (anatase) were carried out. It was established that as a result of laser pulsed processing, a microheterogeneous modifying layer is formed on the surface of the samples. The surface is characterized by increased microhardness and microroughness parameters, which depend to a greater extent on the pulse voltage. In the diffusion layer of the experimental samples, the formation of fine particles with sizes ranging from 100 to 300 nm was revealed

ON PRODUCTION POSSIBILITY TITANIUM DIOXIDE POWDER SYNTHESIZED BY DYNAMIC PLAZMA METHOD

These days, environmental pollution problems are relevant, therefore, the problems associated with photocatalysis as a direction for the future development of alternative energy are solved by many world scientists. Titanium dioxide TiO2 is known to be a photocatalytic material with many unique properties. However, its use is limited due to its wide band gap and the high recombination rate of electron pairs. The method of direct plasma dynamic synthesis of dispersed titanium dioxide was proposed. It was established that the synthesized product consisted of two fractions which had different sizes: a coarse fraction with particle sizes from ~10 microns to ~100 microns and a fine one - from ~10 nm to ~1 micron. It was also revealed that fractions mainly consisted of two TiO2 crystalline modifications: anatase and rutile with tetragonal syngony.

Powder and Nanotubes Titania Modified by Dye Sensitization as Photocatalysts for the Organic Pollutants Elimination

In this study, titanium dioxide powder obtained by the sol-gel method and TiO2 nanotubes, were prepared. In order to increase the TiO2 photoactivity, the powders and nanotubes obtained were modified by dye sensitization treatment during the oxide synthesis. The sensitizers applied were Quinizarin (Q) and Zinc protoporphyrin (P). The materials synthesized were extensively characterized and it was found that the dye sensitization treatment leads to modify the optical and surface properties of Titania. It was also found that the effectiveness of the dye-sensitized catalysts in the phenol and methyl orange (MO) photodegradation strongly depends on the dye sensitizer employed. Thus, the highest degradation rate for MO was obtained over the conventional Q-TiO2 photocatalyst. In the case of the nanotubes series, the most effective photocatalyst in the MO degradation was based on TiO2-nanotubes sensitized with the dye protoporfirin (ZnP). Selected catalysts were also tested in the phenol and MO photodegradation under visible light and it was observed that these samples are also active under this radiation.