Search Results

You are looking at 1 - 6 of 6 items for

  • Author: Roman Jedrzejewski x
Clear All Modify Search
Open access

Anna Steplewska, Roman Jedrzejewski and Ewa Borowiak-Palen

Preparation and characterization of catalyst mix Fe-Co/MgO for carbon nanotubes growth

Fe-Co/MgO is one of the most common catalyst mix applied to carbon nanotubes (CNTs) growth in chemical vapor deposition process. Therefore, here we present detailed study on the preparation and characterization of Fe-Co/MgO. The precursors of Fe and Co are iron (II) acetate and cobalt acetates, correspondingly. The molar ratio of the catalyst mix is Fe:Co:MgO=1:1:100. Initially, thermogravimetric analysis (TGA) of the mixture was performed. TGA analysis of it indicated the stepwise mass losses which pointed out the crucial thermal conditions for the changes in the elemental composition, morphology, crystallographic structure and vibrational properties. In current state of the art the lowest growth temperature for singlewalled carbon nanotubes is 550°C in CVD technique and here the characterization of the catalyst mix strongly suggest that this temperature can be decreased what would enhance the compatibility of CNT growth with current complementary metal-oxide-silicon (CMOS) technology for CNTs-based nanoelectronics. The morphology, crystallographic structure, elemental composition of the samples and its spectroscopic properties were performed via high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and Infrared spectroscopy (IR), respectively.

Open access

Zofia Lendzion-Bieluń and Roman Jędrzejewski

Taking advantage of differences in etching rates of crystallographic phases, forming an oxidized form of the fused iron catalyst, a content of promoters in main phases, magnetite and wustite, was determined. A calcium oxide content in magnetite and wustite was 0.54 wt% and 3.59 wt%, respectively. Aluminum oxide was found in the magnetite phase, and its content was 4.5 wt%. The third promoter, potassium oxide, was almost completely located outside these phases. XRD and ICP-OES instrumental methods were used in the investigations.

Open access

Joanna Piwowarczyk, Roman Jędrzejewski and Jolanta Baranowska

Abstract

The paper presents results of the investigation on the influence of deposition parameters, such as substrate temperature, total gas pressure and reactive gas composition on the structure, chemical composition and mechanical properties of aluminum oxynitride coatings obtained by pulsed laser deposition (PLD) method. Selection of process parameter ranges, which could be promising for aluminum oxynitride (ALON) coatings deposition, was the main objective of the work. Two series of experiments were carried out with varied pressure and temperature. It was found that from the chemical composition viewpoint, the most promising are atmospheres containing 20 % to 40 % oxygen. The nitrogen to oxygen ratios in the coatings can be controlled by increasing the total pressure or substrate temperature. However, increasing the pressure has a negative effect on the O + N:Al ratio, mechanical properties and quality of the coatings. The influence of temperature is much less drastic and more controllable. Increasing the deposition temperature is much more beneficial since it improves the mechanical properties and can compensate to some extent the negative effect of the total pressure. From the coating quality viewpoint, it is possible to establish an optimum temperature range for which the coatings are characterized by a compact structure and a limited number of droplets.

Open access

Roman Jedrzejewski, Zofia Lendzion-Bieluń and Walerian Arabczyk

Abstract

The iron catalyst precursor promoted with Al2O3, CaO, and Li2O was obtained applying the fusing method. Lithium oxide forms two phases in this iron catalyst: a chemical compound with iron oxide (Li2Fe3O4) and a solid solution with magnetite. The catalyst promoted with lithium oxide was not fully reduced at 773 K, while the catalyst containing potassium was easily reducible at the same conditions. After reduction at 873 K the activity of the catalyst promoted with lithium oxide was 41% higher per surface than the activity of the catalyst promoted with potassium oxide. The concentration of free active sites on the surface of the catalyst containing lithium oxide after full reduction was greater than the concentration of free active sites on the surface of the catalyst promoted with potassium oxide.

Open access

Agnieszka Wróblewska, Edyta Makuch, Małgorzata Dzięcioł, Roman Jędrzejewski, Paweł Kochmański, Agnieszka Kochmańska and Łukasz Kucharski

Abstract

This work presents the studies on the optimization the process of allyl alcohol epoxidation over the Ti-SBA-15 catalyst. The optimization was carried out in an aqueous medium, wherein water was introduced into the reaction medium with an oxidizing agent (30 wt% aqueous solution of hydrogen peroxide) and it was formed in the reaction medium during the processes. The main investigated technological parameters were: the temperature, the molar ratio of allyl alcohol/hydrogen peroxide, the catalyst content and the reaction time. The main functions the process were: the selectivity of transformation to glycidol in relation to allyl alcohol consumed, the selectivity of transformation to diglycidyl ether in relation to allyl alcohol consumed, the conversion of allyl alcohol and the selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed. The analysis of the layer drawings showed that in water solution it is best to conduct allyl alcohol epoxidation in direction of glycidol (selectivity of glycidol 54 mol%) at: the temperature of 10–17°C, the molar ratio of reactants 0.5–1.9, the catalyst content 2.9–4.0 wt%, the reaction time 2.7–3.0 h and in direction of diglycidyl ether (selectivity of diglycidyl ether 16 mol%) at: the temperature of 18–33°C, the molar ratio of reactants 0.9–1.65, the catalyst content 2.0–3.4 wt%, the reaction time 1.7–2.6 h. The presented method allows to obtain two very valuable intermediates for the organic industry.

Open access

Walerian Arabczyk, Urszula Narkiewicz, Zofia Lendzion-Bieluń, Dariusz Moszyński, Iwona Pełech, Ewa Ekiert, Marcin Podsiadły, Rafał Pelka, Roman Jędrzejewski, Izabela Moszyńska and Daniel Sibera

Utilization of spent iron catalyst for ammonia synthesis

Several methods of the utilization of spent iron catalyst for ammonia synthesis have been presented. The formation of iron nitrides of different stoichiometry by direct nitriding in ammonia in the range of temperatures between 350°C and 450°C has been shown. The preparation methods of carbon nanotubes and nanofibers where iron catalyst catalyse the decomposition of hydrocarbons have been described. The formation of magnetite embedded in a carbon material by direct oxidation of carburized iron catalyst has been also presented.