Formation Of Metal Atoms Research Articles

Low-Current Discharge in a Flow of Atmospheric-Pressure Argon Under the Formation of Metal Atoms: Electric and Optical Characteristics

Low-Current Discharge in a Flow of Atmospheric-Pressure Argon Under the Formation of Metal Atoms: Electric and Optical Characteristics

The Electronic Theory of Reduction and the Extraction of Metals from Ore

None of the existing approaches to the extraction of metals from ore can completely explain the practical findings. This suggests that reduction occurs by more than one pathway. The solid-phase reduction of metals by carbon in complex and lean iron ores from different sources and also in individual oxides of silicon, chromium, and aluminum is investigated. The electrical characteristics of ores and individual oxides are studied in order to refine theoretical concepts regarding reduction. In all cases, the reduction of metals is found to involve the conversion of the oxide’s crystal lattice into the crystal lattice of the metal. On the basis of quantum mechanics and solid-state physics and chemistry, new fundamental principles are identified in the electronic theory of the reduction of metals. Reduction consists in electron exchange between the reducing agent and the metal cations in the oxide. As a result, anionic vacancies with free electrons are formed at the oxide surface. Depending on the concentration of the cations to be reduced, the conversion of the ionic bond of the oxide’s cations to the metallic bond of the metal’s cations involves the coalescence of charged anionic vacancies at the surface of the oxide or at greater depth. This process does not require motion of the cations over considerable distances or the formation of metal atoms; the thermodynamic constraints associated with the formation of new-phase nuclei do not apply. This theory is able to explain all the known experimental results regarding the solid-phase reduction of metals in oxides: the formation of continuous metallic shells at the surface of pieces of rich iron ore; the deposition of metal particles within lean and complex ores; and the formation and sublimation of suboxides. In the deposition of metallic phase within the complex oxide, there is no direct contact between the metal and reducing agent; therefore, in the reduction of iron in complex or lean ores by carbon, no sulfur or carbon is transferred to the metallic phase from the reducing agent. In the reduction of such ore, fuel coal may be used as the reducing agent. The product is a metal–oxide composite containing pure iron and valuable oxides of magnesium, titanium, and vanadium.

Vaporization Thermodynamics of Polymeric Cadmium Pivalate

The vaporization of cadmium pivalate CdPiv2 with a polymeric structure was studied by the Knudsen effusion mass spectrometry of the gas phase. The sublimation of this complex was found to be congruent and to be accompanied by thermal dissociation with the formation of metal atoms and organic compounds due to its polymeric character. The standard enthalpies of vaporization were found, and the standard formation enthalpy of condensed cadmium pivalate was calculated. Highly volatile cadmium compounds could be synthesized via the introduction of additional ligands able to saturate the coordination sphere of the central atom.

Facile synthesis of bimetallic nanoparticles by femtosecond laser irradiation method

Bimetallic Pt–Au and Fe–Pt nanoparticles are successfully fabricated by high-intensity laser irradiation of aqueous solution without any chemical reducing agent. The mechanism of the formation of bimetallic nanoalloys by laser irradiation of the solution without using any reducing agent was mainly attributed to the optically induced decomposition of water molecule. When an intense femtosecond laser field is focused in an aqueous solution containing metal ions, the free electrons will be produced by the dissociation of water molecules, these free electrons and hydrogen radicals contained in the plasma might be caught by H+ or OH− ions to form the bubbles of H2 and O2 gases or they can be trapped by metal ions, resulting in the formation of metal atoms during the femtosecond laser irradiation process. The average size of the bimetallic nanoparticles increases with irradiation time. This technique is simple and ‘green’ process without using any chemicals except for metal salt and dispersing agent.

Kinetics, Mechanism and Intermediates of Some Radiation‐Induced Reactions in Aqueous Solutions

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Estimation of partial pressure of oxygen inside the graphite furnace used for atomic absorption spectrometry

The spontaneity of metal atom formation from metal oxides, both in the condensed phase, via thermal decomposition or reduction by carbon in a graphite furnace, depends on the instantaneous partial pressure of oxygen inside the furnace. Since the partial pressure of the gaseous carbon species is very low, the reaction between carbon and oxygen is determined by heterogeneous, gas-solid reaction. The factors affecting the instantaneous partial pressure of oxygen inside a pulse-heated graphite furnace have been studied by computer simulation. The results suggest that the instantaneous oxygen partial pressure inside the furnace is determined by the initial amount of oxygen and the heating rate of the furnace. The effect of oxygen on the shift of the analyte atomic absorption pulse is also discussed.