Investigation of oxidation process of mechanically activated ultrafine iron powders

The oxidation of mechanically activated ultrafine iron powders was studied using X-ray powder diffraction and thermogravimetric analyzes. The powders with average particles size of 100 nm were made by the electric explosion of wire, and were subjected to mechanical activation in planetary ball mill for 15 and 40 minutes. It was shown that a certain amount of FeO phase is formed during mechanical activation of ultrafine iron powders. According to thermogravimetric analysis, the oxidation process of non-milled ultrafine iron powders is a complex process and occurs in three stages. The preliminary mechanical activation of powders considerably changes the nature of the iron powders oxidation, leads to increasing in the temperature of oxidation onset and shifts the reaction to higher temperatures. For the milled powders, the oxidation is more simple process and occurs in a single step

Study of Sorption Properties of Aluminium Oxides and Hydroxides Powders Obtained by Electro-Impulse Methods

Experimental results of physicochemical and sorption properties of material samples obtained by electro-spark dispersion in water and by conductor electric explosion in argon are shown in the paper. Due to comparison of investigated samples sorption activity under static conditions, it was able to determine the most effective samples in the process of extraction of Cu{2+} ions from aqueous solutions

Microconstituents of the Modified Surface Layer of Austenitic Steel With Nanofibres of Aluminium Oxyhydroxide

In the paper the authors provide the results of experimental study of the effect caused by introduction of nanostructured fibres of aluminium oxyhydroxide into the surface layer of austenitic steel upon its microconstituents. The authors show that, due to introduction of given fibres dendrite size is reduced and equilibrium structure is formed

Assignment of Appropriate Conditions for Synthesizing Tungsten Nanopowder by Electric Explosion of Conductors

The paper provides the results of experimental research into properties of tungsten nanopowders synthesized by electric explosion of a conductor in argon at various energies, put into the conductor when exploding. The authors have studied how the conditions of synthesizing the tungsten nanopowder influence on the average size of particles

Ultradispersed Electro-explosive Iron Powders as Catalysts for Synthesis of Liquid Hydrocarbons of CO and H[2]

Catalytic activity of ultradispersed iron powders (UDIP) obtained by electric explosion of the conductor in media of nitrogen, carbon monoxide, and carbon dioxide in synthesis of liquid hydrocarbons by Fischer-Tropsch method was studied. It was shown that iron powder obtained in media of CO[2] has the highest specific surface area. A sample of powder was pelletized at pressure of 21 MPa during 30 seconds with use of 10 mass% polyvinyl alcohol as adhesive for experimentation in catalytic system. Catalyst fraction of 1-2 mm was selected for study. The experiments were carried out under conditions of 1 MPa, 300 mln/min of total reactants consumption, and varied values of temperature and reactants ratio. The maximal conversion level of CO was reached at 290°С and reactants ratio of H[2]:CO=2 in the initial mixture. It was shown that UDIP has high activity at lowered concentration of hydrogen in the initial mixture. The obtained mixture of liquid hydrocarbons is applicable for further refining for upgrading and improving of operating features

Microconstituents of the Modified Surface Layer of Austenitic Steel With Nanofibres of Aluminium Oxyhydroxide

In the paper the authors provide the results of experimental study of the effect caused by introduction of nanostructured fibres of aluminium oxyhydroxide into the surface layer of austenitic steel upon its microconstituents. The authors show that, due to introduction of given fibres dendrite size is reduced and equilibrium structure is formed

Water Purification with Natural Sorbents: Effect of Surface Modification with Nano-structured Particles

Modified nanostructured sorbents are widely used in water treatment processes. In this work, aluminum and iron particles prepared by electro-spark dispersion have been applied as modifiers. Zeolite samples from "Holinskoe" mineral deposit (Russia, Republic of Buryatia), with a size smaller than 0.1 mm, have been modified with aluminum and iron particles, using a sol-gel process. The properties of the modified materials have been determined by means of sorption test, when removing ions Pb{2+}, Fe{3+} and Cd{2+} from the model solutions in static conditions. Using the method of thermal desorption of nitrogen (BET) it has been shown that increasing the iron content in the samples of nanostructured modified sorbents does not affect the increase in specific surface area and pore volume of the samples. Ions concentrations have been analyzed by stripping voltammetry and photocolorimetry. As a result, modified sorbents revealed a high efficiency sorption of heavy metals

Investigation of Massive Catalyst based on Molybdenum Disulphide by Simultaneous Thermal Analysis and Mass Spectrometry Methods

The paper presents the results of experimental studies of massive sulfide catalysts by simultaneous thermal analysis and mass spectrometry. It is found that the STA/MS methods are quite informative for testing the catalyst systems based on MoS2 and are useful in identification of the reference features that could be used to predict their activity. It is also shown that the defect structure of molybdenum disulfide formed during mechanical activation is reflected on the DSC curves

Processing of heavy residual feedstock on Mo/Al[2]O[3]-catalytic systems obtained using polyoxomolybdate compounds

The urgency of creating new efficient catalysts for the processes of deepening oil refining rises on the background of stricter requirements for the quality of motor fuels, as well as the deterioration of the quality of crude oil for processing, and an increase in the number of distillates of secondary processes involved in the production of commodity petroleum products. In this work, alumina-catalytic systems were synthesized using polyoxomolybdate compounds. The morphology, structure and phase composition of the synthesized catalytic systems were studied using the following analysis methods: scanning electron microscopy, microelement analysis, X-ray phase analysis, X-ray diffraction, electron spectroscopy. It has been established that the Mo/AI[2]O[3] system is active in the process of thermal catalytic conversion of heavy residual raw materials

Comparative Study of Genotoxicity of Silver and Gold Nanoparticles Prepared by the Electric Spark Dispersion Method

Objective: There is plenty of information dedicated to nanomaterial toxicity, but it is often contradictory. This work presents results of the comparative investigation of silver and gold nanoparticles genotoxicity and genotoxic effect of water medium after the spark dispersion process. Material and methods: The nanoparticles were produced in water by the modified energy-efficient electric spark dispersion method. The comet assay, transmission electron microscopy, DLS spectroscopy and thermal desorption of nitrogen (BET method) were used for the investigation. Results: The silver nanoparticles showed a genotoxic effect which appeared at concentration of 0.03 mg/ml and above. The application of gold nanoparticles did not lead to a significant DNA damage at concentrations range of 0.01 - 0.03 mg/ml. However, a notable level of genotoxicity was observed at concentrations of gold nanoparticles about 0.1 mg/ml. Supernatant water medium (with trace of Au and Ag metals) following the spark dispersion process showed no genotoxic action. Conclusion: Accordingly, the testing of the nanoparticles produced by the electric spark dispersion in water revealed more expressed genotoxic effect of silver nanoparticles in comparison with the gold ones