Comprehensive study of rheological and surface properties of the selected slag system in the context of its internal structure

Rheological (dynamic viscosity, flow curves) and surface properties (surface tension) of real slag system were experimentally investigated. Measurements of dynamic viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. The method of sessile drop was used for measurement of surface tension. Surface tension and dynamic viscosity were measured in the temperature interval from 1 200 to 1 600 °C. The structural characteristics of the selected samples were determined by X-ray diffraction (XRD). The samples for given analysis were prepared by quench cooling. Experimentally determined values of dynamic viscosity and surface tension were compared with the results of X-ray diffraction phase analysis.Web of Science55470069

Effect of CaO/ SiO2 ratio on viscosity and structure of slag

The objective of this work is experimental determination of temperature dependences of viscosity of the molten CaO - Al2O3 - SiO2 system and assessment of impact of CaO/SiO2 ratio on viscosity and structure of this system. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. Viscosity was measured in a rotational mode during heating at the rate of 3,3 °C/min in the temperature interval from 1 673 to 1 873 K. Viscosity in the molten oxide system is determined by the internal structure. Exact clarification of the change of structure of the oxide system caused by the increased content of CaO was performed by Fourier transform infrared spectroscopy.Web of Science54345845

Wetting of refractory ceramics with high-manganese and structural steel and description of interfacial interaction

This work aims to describe the interfacial interaction at the interface between refractory material and high-manganese (XT 720) and structural (11 523) steel using a wetting test up to 1600 degrees C. The contact angles were determined through the sessile drop method, and the results were put into context through degradation testing and the characterization of the interfacial interface by Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses, and Scanning Electron Microscopy (SEM). The lowest resistance to molten steel was observed for chamotte materials, while the highest was observed for materials based on electrofused corundum. High-manganese steel was strongly erosive to the materials tested, with the wetting angle decreasing significantly from 10 to 103 degrees with decreasing Al2O3 content (an increase of 2.4 to 59.4% corundum) in the refractories. Structural steel showed wetting angles from 103 to 127 degrees for identical refractories. These results were consistent with the average erosion depth for Mn steel (0.2-7.8 mm) and structural steel (0-2.4 mm).Web of Science1212art. no. 178

Effect of chemical composition and temperature on viscosity and structure of molten CaO-Al2O3-SiO2 system

The effects of the change of chemical composition and temperature on the viscosity of CaO-Al2O3-SiO2 oxide system with basicity from 0.78 to 1.63 were investigated in this paper. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1600. Viscosity was measured in a rotational mode during heating at the rate of 2.2 K/min in the temperature interval from 1673 to 1873 K. Viscosity is often sensitive to the structural changes in molten oxide systems, which implies that the analysis of viscosity is an effective way to understand the structure of molten oxide systems. Exact clarification of the change of structure of the oxide system caused by increased content of CaO was performed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD).Web of Science6042878287

Synthesis of vacant graphitic carbon nitride in argon atmosphere and its utilization for photocatalytic hydrogen generation

Graphitic carbon nitride (C3N4) was synthesised from melamine at 550 degrees C for 4 h in the argon atmosphere and then was reheated for 1-3 h at 500 degrees C in argon. Two band gaps of 2.04 eV and 2.47 eV were observed in all the synthetized materials. Based on the results of elemental and photoluminescence analyses, the lower band gap was found to be caused by the formation of vacancies. Specific surface areas of the synthetized materials were 15-18 m(2)g(-1) indicating that no thermal exfoliation occurred. The photocatalytic activity of these materials was tested for hydrogen generation. The best photocatalyst showed 3 times higher performance (1547 mu mol/g) than bulk C3N4 synthetized in the air (547 mu mol/g). This higher activity was explained by the presence of carbon (V-C) and nitrogen (V-N) vacancies grouped in their big complexes 2V(C) + 2V(N) (observed by positron annihilation spectroscopy). The effect of an inert gas on the synthesis of C3N4 was demonstrated using Graham ' s law of ammonia diffusion. This study showed that the synthesis of C3N4 from nitrogen-rich precursors in the argon atmosphere led to the formation of vacancy complexes beneficial for hydrogen generation, which was not referred so far.Web of Science121art. no. 1362

Impact of Ni on the thermophysical and thermodynamic properties of Fe–C–Ni based alloys

Three model alloys based on Fe-C-Ni were studied containing carbon between 0.338 and 0.382 wt. % and nickel between 1.084 and 4.478 wt. %. Phase transition temperatures, heat capacity, enthalpy change, heat of fusion, coefficient of thermal expansion, and density were experimentally and theoretically determined in the high-temperature area from 1000 degrees C to 1595 degrees C. A number of techniques, namely differential thermal analysis (DTA), differential scanning calorimetry (DSC), and dilatometry, were used in this study, and the heat of fusion was determined by two approaches, that is, from the DSC peak area and from the enthalpy change. The experimental data were compared and discussed with the calculation results obtained using SW IDS, JMatPro, and Thermo-Calc operating with the commercially available TCFE8 thermodynamic database. The obtained experimental results show that the liquidus temperature and the coefficient of thermal expansion decrease with increasing nickel content. On the contrary, the density and heat of fusion values derived from the DSC peak increase with increasing nickel content. Furthermore, an ambiguous influence of nickel on the change in solidus temperature, heat capacity, enthalpy change, and heat of fusion obtained from the enthalpy change was observed.Web of Science204332431

Matematické modelování difúzních dějů ve svarových spojích materiálů na bázi železa

Import 10/12/2008PrezenčníNeuvedenoNeuveden

Modely koncentrační závislosti difúzních koeficientů intersticiálních prvků v tuhých roztocích železa

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrství. Katedra (618) metalurgi

Characterization of chemical heterogeneity of the welded joint of two steels by modelling of diffusion processes

The paper deals with original methodology for characterization of chemical heterogeneity of welded joint by measurement of concentration profi les of substitution elements in three straight lines in a plane perpendicular to the weld interface. Three concentration profi les were evaluated by modelling of diff usion based on solution of the 2nd Fick’s law. Primary goal of evaluation consists in characterization of chemical heterogeneity in the narrow area on both sides of the welded joint on the basis of their mutual position. Experimental data are optimised by original adaptation of the Levenberg-Marquardt’s algorithm of non-linear regression. The paper deals with diff usion of nickel in the welded joint of two diff erent steels as an example of investigated elements.Web of Science52335835

Polyaniline as a precursor of multi-layer graphene: Microscopic and microspectroscopic study

Aluminosilicate-based nanocomposites containing multi-layer graphene were prepared from polyaniline/montmorillonite intercalate in two different forms: tablets and thin layers. Starting materials, polyaniline/montmorillonite powder and polyaniline/montmorillonite layers deposited on quartz glass, were prepared by in situ polymerization of aniline in presence of montmorillonite particles. Powder was compacted into tablets using pressure 400 MPa. Samples were calcined at 1300 degrees C in argon atmosphere and multi-layer graphene was formed from polyaniline in both cases as confirmed by Raman microspectroscopy. Changes in morphology and surface conductivity of uncalcined and calcined samples were observed using atomic force microscopy and conductive atomic force microscopy. Also the differences between surface and internal volume of tablets were studied. Conductive atomic force microscopy revealed that the most conductive areas can be found solely on the edges of aluminosilicate particles formed from montmorillonite during calcination process. Detailed observation of multi-layer graphene in these areas was performed using transmission electron microscopy.Web of Science19127747773