Search

microcomposite catalyst based on zinc oxide microstructures and silicon was synthesized for heterogeneous catalysis. ZnO microstructures with elements 6 μm in diameter, 15 μm long, were grown on conductive silicon (001) substrates by the vapor phase method. Methyl orange (C14H14N3NaO3S) was selected as an organic dye for testing the photocatalytic and photoelectrocatalytic properties of ZnO microstructures. The sample was placed in an aqueous solution of methyl orange in order to perform a photocatalytic decomposition of the dye. DRT-125 quartz lamp with a radiation power of no more than 26 W was used as the radiation source in the wavelength range from 315 to 400 nm. The sample with the aqueous solution of dye in a standard 3.5 ml quartz quvet was irradiated with the lamp at a distance of 10 cm from it. In order to perform the photoelectrocatalytic decomposition of the dye in the aqueous solution, an electric field of 1.5 V was applied between ZnO/Si and Al electrodes, that were simultaneously irradiated with UV for 5 cycles lasting 20 minutes (100 minutes). The degradation kinetics of the dye was determined by changing its concentration, on the basis of the optical density measurement at the absorption maximum of the dye (465 nm) using a Specord M 40 spectrometer. During the photocatalysis, the concentration of the dye decreased by 41 % in 100 min, and during the photoelectrocatalysis, by 59 % in 100 min. First-order kinetics was used for the kinetic analysis of the catalytic reactions. The reactions rate constants were found to be k = 5.1·10-3 min-1 in the case of the photocatalysis, and k = 8.8 ·10-3 min-1 in the case of the photoelectrocatalysis. The increase in the efficiency of the dye decomposition in the latter case was associated with a more efficient redistribution of charge when voltage (1.5 V) was applied and with a higher amount of hydroxyl radicals on the surface of the catalyst. [ABSTRACT FROM AUTHOR]

The increasing scientific interest in Sn-based nanocomposite alloys with minor additions of oxides, metals and carbon in nanosized form is explained by the possible application of these materials as an alternative to commercial lead-free solders. As pointed out in recent literature reviews, the improved mechanical properties and reinforced microstructure of solder joints using nanocomposite Sn-Ag-Cu (SAC) alloys, compared to those without nanoinclusions, revealed new possibilities for the development of the currently used commercial lead-free solders. The main benefit of the nanosized additions is related to the suppression of the extensive growth of the Cu6Sn5 intermetallic compound (IMC) at the solder/Cu interface towards the solder side. This is achieved due to the spreading of nanoparticles over the IMC's surface, thereby suppressing the growth of Cu6Sn5 on the interface as well as in the bulk solder. In particular, the adsorbed nanoparticles on the IMC layer interface hinder the diffusion of Sn atoms from the bulk solder towards the interface and thereby suppress the IMC growth. Compared to the solid state, there is a limited number of papers dealing with experimental investigations of nanocomposite SAC solders in the liquid state after melting as well as in the semi-solid state. It has been shown that minor metal nanoadditions have an impact on the microstructure of solidified SAC solders, but practically without any significant change of the melting temperatures. The effect of small nanosized (up to 3 wt.%) nickel impurities on the electrical conductivity of Sn95.5Ag3.8Cu0.7 (SAC387) alloy has been investigated. It has been shown that the electrical conductivity gradually decreases with an increase in the impurity content of Ni. Conductivity, as a structure-sensitive transport characteristic of the liquid state of a substance, is important for modeling the processes of melting and solidification. The conductivity data provide additional information on the influence of admixtures on the structure and physicochemical properties of the metal matrix, which is important for understanding the microstructural transformations in a liquid state. Morphology of the samples was examined using REMMA-102-02 Scanning Electron Microscope- Analyzer (JCS SELMI, Sumy, Ukraine). [ABSTRACT FROM AUTHOR]

Wastewater treatment to remove organic impurities remains the most important task of water resources recovery facilities. A promising method of purification of water from the organic dyes is photocatalysis with semiconductor materials. The most known and popular photoactive materials are based on TiO2, WO3, Zn2SnO4 and ZnO. The catalysts based on ZnO are low cost, stable, non-toxic and do not require reactivation. A composite photocatalyst formed by a layer of ZnO nuclei with n-type electric conductivity covered with ZnO nanoflowers with n-type electric conductivity and porous silicon with p-type electric conductivity has been obtained. The photodegradation of dye in the presence of the composite photocatalysts based on the thin films and nanoflowers was investigated. The photocatalytic properties of ZnO materials were tested using the photocatalytic degradation of an aqueous solution of methyl orange dye serving as a model water contaminant. It has been found that the usage of nanoflowers leads to an improvement in the photocatalytic properties of the composites. An increase of about 30% in the efficiency of dye photodegradation, when a composite photocatalyst based on ZnO nanoflowers and porous silicon was used instead of a composite photocatalyst based on ZnO film and porous silicon, was found to be due to a larger effective surface area of ZnO nanoflowers. The morphology of the samples was examined using a scanning electron microscope-analyzer. [ABSTRACT FROM AUTHOR]

The increasing scientific interest in Sn-based nanocomposite alloys with minor additions of oxides, metals and carbon in nanosized form is explained by the possible application of these materials as an alternative to commercial lead-free solders. As pointed out in recent literature reviews, the improved mechanical properties and reinforced microstructure of solder joints using nanocomposite Sn-Ag-Cu (SAC) alloys, compared to those without nanoinclusions, revealed new possibilities for the development of the currently used commercial lead-free solders. The main benefit of the nanosized additions is related to the suppression of the extensive growth of the Cu6Sn5 intermetallic compound (IMC) at the solder/Cu interface towards the solder side. This is achieved due to the spreading of nanoparticles over the IMC's surface, thereby suppressing the growth of Cu6Sn5 on the interface as well as in the bulk solder. In particular, the adsorbed nanoparticles on the IMC layer interface hinder the diffusion of Sn atoms from the bulk solder towards the interface and thereby suppress the IMC growth. Compared to the solid state, there is a limited number of papers dealing with experimental investigations of nanocomposite SAC solders in the liquid state after melting as well as in the semi-solid state. It has been shown that minor metal nanoadditions have an impact on the microstructure of solidified SAC solders, but practically without any significant change of the melting temperatures. The effect of small nanosized (up to 3 wt.%) nickel impurities on the electrical conductivity of Sn95.5Ag3.8Cu0.7 (SAC387) alloy has been investigated. It has been shown that the electrical conductivity gradually decreases with an increase in the impurity content of Ni. Conductivity, as a structure-sensitive transport characteristic of the liquid state of a substance, is important for modeling the processes of melting and solidification. The conductivity data provide additional information on the influence of admixtures on the structure and physicochemical properties of the metal matrix, which is important for understanding the microstructural transformations in a liquid state. Morphology of the samples was examined using REMMA-102-02 Scanning Electron Microscope- Analyzer (JCS SELMI, Sumy, Ukraine). [ABSTRACT FROM AUTHOR]