Application of TOF-SIMS Method in the Study of Wetting the Iron (111) Surface with Promoter Oxides.

In the present work, a simplified model of the Fe(111) surface's promoter-oxide system was investigated in order to experimentally verify the previously proposed and known models concerning the structure and chemical composition of the surfaces of iron nanocrystallites in the ammonia-synthesis catalyst. It was shown that efficient oxygen diffusion from metal oxides to the clean Fe(111) iron surface took place even at temperatures lower than 100 °C. The effective wetting of the iron surface by potassium oxide is possible when the surface is covered with oxygen at temperatures above 250 °C.

Oscillatory Mechanism of α-Fe(N) ↔ γ'-FeN Phase Transformations during Nanocrystalline Iron Nitriding.

The kinetics of nanocrystalline α-iron nitriding to γ'-iron nitride in an ammonia atmosphere was studied at 598-648 K and at atmospheric pressure. Oscillatory changes in nitriding reaction rates depending on nitrogen concentration in a solid sample were observed. This phenomenon was explained by a gradual change in the iron active surface coverage degree, with nitrogen resulting from a gradual change in the free enthalpy of nitrogen segregation.

Reaction Model Taking into Account the Catalyst Morphology and Its Active Specific Surface in the Process of Catalytic Ammonia Decomposition.

Iron catalysts for ammonia synthesis/nanocrystalline iron promoted with oxides of potassium, aluminum and calcium were characterized by studying the nitriding process with ammonia in kinetic area of the reaction at temperature of 475 °C. Using the equations proposed by Crank, it was found that the process rate is limited by diffusion through the interface, and the estimated value of the nitrogen diffusion coefficient through the boundary layer is 0.1 nm/s.

Removal of anionic dyes using magnetic Fe@graphite core-shell nanocomposite as an adsorbent from aqueous solutions.

In this study, magnetic Fe@graphite nanocomposite (Fe@G-N) with a core-shell structure was prepared by chemical vapor deposition CVD process for the adsorptive removal of anionic dyes from aqueous solutions. Fe@G-N was characterized by XRD, HRTEM, HAADF-STEM, FTIR, Raman spectroscopy, BET and zeta potential measurements, and then applied in adsorption of two kinds of anionic dyes, Acid Red 88 (AR88) and Direct Orange 26 (DO26). The effect of parameters like initial dye concentration (5-40mgL), pH solution (4-10) and temperature (20-60°C) on the adsorption process was studied.

Investigation of nitriding and reduction processes in a nanocrystalline iron-ammonia-hydrogen system at 350 °C.

In this paper, the series of phase transitions occurring during the gaseous nitriding of nanocrystalline iron was studied. The nitriding process of nanocrystalline iron and the reduction process of the obtained nanocrystalline iron nitrides were carried out at 350 °C in a tubular differential reactor equipped with systems for thermogravimetric measurements and analysis of gas phase composition. The samples were reduced with hydrogen at 500 °C in the above mentioned reactor.

Cobalt-based Catalysts for Ammonia Decomposition.

An effect of promoters such as calcium, aluminium, and potassium oxides and also addition of chromium and manganese on the structure of cobalt catalysts was examined. Studies of the catalytic ammonia decomposition over the cobalt catalysts are presented. The studies of the ammonia decomposition were carried out for various ammonia-hydrogen mixtures in which ammonia concentration varied in the range from 10% to 100%.

Studies of the kinetics of ammonia decomposition on promoted nanocrystalline iron using gas phases of different nitriding degree.

Promoted nanocrystalline iron was nitrided in a differential reactor equipped with systems that made it possible to conduct both thermogravimetric measurements and hydrogen concentration analyses in the reacting gas mixture. The nitriding process, particularly catalytic ammonia decomposition reaction, was investigated under an atmosphere of ammonia-hydrogen mixtures, under atmospheric pressure. Ammonia concentrations, and so nitriding potentials, were changed gradually from 0 to 100% at the inlet of reactor.

Kinetics of the oxidation of iron carbide dispersed in a carbon matrix with water vapor.

The reaction of iron carbide embedded in a carbon matrix with water vapor was studied in the temperature range 300-500 degrees C and the partial pressure of water vapor p(H(2)O) = 0.63-3.26 kPa.

Studies of the kinetics of two parallel reactions: ammonia decomposition and nitriding of iron catalyst.

The reaction of ammonia decomposition and nitriding reaction as an example of the parallel reactions were studied. A surface reaction was assumed as the rate limiting step. The experiments were carried out in the range of temperatures from 623 to 723 K.

Solid-gas reaction with adsorption as the rate limiting step.

The model of nucleation where adsorption of reactant is a rate-limiting step has been considered. Assuming the adsorption range model, a numerical simulation has been made. The dependency of bulk concentration and surface coverage versus time and thermogravimetric curves are presented.