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Number of results: 5
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Abstract

The article presents the method to assess the diffusion coefficient D in the sub-layer of intermetallic phases formed during hot-dip

galvanizing “Armco” iron and ductile cast iron EN-GJS-500-7. Hot-dip galvanizing is one of the most popular forms of long-term

protection of Fe-C alloys against corrosion. The process for producing a protective layer of sufficient quality is closely related to diffusion

of atoms of zinc and iron. The simulation consist in performed a hot-dip galvanizing in laboratory condition above Fe-C alloys, in the

Department of Engineering of Cast Alloys and Composites. Galvanizing time ranged from 15 to 300 seconds. Then metallographic

specimens were prepared, intermetallic layers were measured and diffusion coefficient (D) were calculated. It was found that the diffusion

coefficient obtained during hot-dip galvanizing “Armco” iron and zinc is about two orders of magnitude less than the coefficient obtained

on ductile cast iron EN-GJS-500-7.

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Authors and Affiliations

D. Kopyciński
E. Guzik
A. Szczęsny
D. Siekaniec
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Abstract

The paper presents research on the influence of grain size of selected coals and their structural parameters on the diffusion coefficient and methane sorption isotherms. Two coals from Polish hard coal mines, differing in the coal rank, were tested. Sorption isotherms for methane were determined. An unconventional sequence of pressures 0→0.1→0→0.5→0→1.5 MPa was employed to assess the speed of achieving sorption equilibrium at different pressures. The studies of CH4 accumulation kinetics were performed on various grain classes of the tested coals. Both the sorption capacity of coal and the diffusion coefficient proved to be highly sensitive to the experimental methodology. Critical measurement parameters in terms of determining the diffusion coefficient concerning the assumptions of the Crank model were indicated. The influence of the equivalent radius of coal grain on the process kinetics was demonstrated. The stepwise pressure increase factor was examined in the context of minimising the impact of sorption isotherm non-linearity on the results. The importance of the width of the grain class of coals was determined to reduce their maceral inhomogeneities. These factors are the most common reason that makes it difficult to quantitatively compare diffusion coefficient values.
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Authors and Affiliations

Katarzyna Kozieł
1
ORCID: ORCID
Aleksandra Gajda
1
ORCID: ORCID
Marta Skiba
1
ORCID: ORCID
Norbert Skoczylas
2
ORCID: ORCID
Anna Pajdak
1
ORCID: ORCID

  1. Strata Mechanics Research Institute of the Polish Academy of Sciences, 27 Reymonta Str., 30-059 Kraków, Poland
  2. AGH University of Kraków, Facu lty of Geology, Geoph ysics and Environmental Protection,al. Mick iewicza 30, 30-059 Kraków, Poland
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Abstract

In this paper a method of analyzing air pollution data in an optional automatic measuring station, allowing for identification of the directions of the pollution inflow has been presented. The method is based on four parameters provided by the measuring station: pollution concentration, wind direction, wind speed and fluctuation of the wind directions. For the description of the wind direction fluctuation in 30-minutes' periods a coefficient of relative turbulent diffusion rr(3, 30) was used, which is defined as a deviation of 3-minutes' wind vectors from the 30-minutes' vector. The presented method was applied for identification of the inflow directions of SO2 and NO2 using the measuring data from a telemetric system OPSIS at the Institute for Ecology of Industrial Areas in Katowice-Załęże.
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Authors and Affiliations

Czesław Kliś
Mieczysław Żeglin
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Abstract

In the paper critical role of including the right material parameters, as input values for computer modelling, is stressed. The presented model of diffusion, based on chemical potential gradient, in order to perform calculations, requires a parameter called mobility, which can be calculated using the diffusion coefficient. When analysing the diffusion problem, it is a common practice to assume the diffusion coefficient to be a constant within the range of temperature and chemical composition considered. By doing so the calculations are considerably simplified at the cost of the accuracy of the results. In order to make a reasoned decision, whether this simplification is desirable for particular systems and conditions, its impact on the accuracy of calculations needs to be assessed. The paper presents such evaluation by comparing results of modelling with a constant value of diffusion coefficient to results where the dependency of Di on temperature, chemical composition or both are added. The results show how a given deviation of diffusivity is correlated with the change in the final results. Simulations were performed in a single dimension for the FCC phase in Fe-C, Fe-Si and Fe-Mn systems. Different initial compositions and temperature profiles were used.
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Bibliography

[1] Lambers, J.V. & Sumner, A.C. (2016). Explorations in Numerical Analysis. World Scientific Publishing.
[2] Nishibata, T., Kohtake, T. & Kajihara, M. (2020). Kinetic analysis of uphill diffusion of carbon in austenite phase of low-carbon steels. Materials Transactions. 61(5), 909-918. DOI: 10.2320/matertrans.MT-M2019255.
[3] Wróbel, M., & Burbelko, A. (2022). A diffusion model of binary systems controlled by chemical potential gradient. Journal of Casting & Materials Engineering. 6(2), 39-44. DOI: 10.7494/jcme.2022.6.2.39.
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[13] Nohara, K. & Hirano, K. (1973). Self-diffusion and Interdiffusion in γ solid solutions of the iron-manganese system. Journal of the Japan Institute of Metals. 37(1), 51-61. https://doi.org/10.2320/jinstmet1952.37.1_51
[14] Gegner, J. (2006). Concentration- and temperature-dependent diffusion coefficient of carbon in FCC iron mathematically derived from literature data. In the 4th Int Conf Mathematical Modeling and Computer Simulation of Materials Technologies, Ariel, College of Judea and Samaria.
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Authors and Affiliations

M. Wróbel
1
ORCID: ORCID
A. Burbelko
1
ORCID: ORCID

  1. AGH University of Science and Technology, Faculty of Foundry Engineering, al. A. Mickiewicza 30, 30-059 Krakow, Poland
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Abstract

Atmospheric gases and chemical impurities can be stored and chemically transformed in the tropospheric ice. Impurities are rejected during freezing of the ice to the grain boundaries, free ice surfaces or inclusions. Surface snow and tropospheric ice, however, may be exposed to high temperatures and, eventually, the gases and chemical impurities can be released into the environment. It is important to study the surface structure and transport mechanisms at temperatures near the melting point because the location of impurities and their interactions with water molecules in the ice are not yet sufficiently explained. In this work, the evolution of a scratch on the bicrystalline ice surface was studied at −5 ℃. The surface transport mechanisms near the melting point were studied and, as a consequence, the surface structure could be determined. An ice sample was kept immersed in ultra-pure silicone oil to prevent evaporation and, thus, isolate the effect of surface diffusion. The ice sample was made with water with chemical conditions similar to the water of polar ice sheets. Photographs of the scratch were taken periodically, for approximately 50 hours, using a photographic camera coupled to an optical microscope. From these images, the evolution of the width of the scratch was studied and the surface diffusion was the dominant transport mechanism in the experiment. Finally, the ice surface self-diffusion coefficient at −5 ℃ was determined and it was very similar to the super-cooled water diffusion coefficient. A liquid-like behavior of ice surfaces near the melting point was found and it could have a strong influence on the reaction rates with atmospheric gases.
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Bibliography

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Authors and Affiliations

Guillermo Aguirre Varela
1 2
ORCID: ORCID
Carlos L. Di Prinzio
1 2
ORCID: ORCID
Damián Stoler
1
ORCID: ORCID

  1. FAMAF, Universidad Nacional de Córdoba, Medina Allende and Haya de la Torre, 5000 Ciudad Universitaria, Córdoba, Argentina
  2. IFEG-CONICET, Universidad Nacional de Córdoba, Medina Allende and Haya de la Torre, 5000 Ciudad Universitaria, Córdoba, Argentina

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