Papers by Keyword: Diffusion Processes

Abstract: In wafer-based silicon solar cell technology cleaning of silicon surfaces has so far been treated without much interest – the cheapest, simple solution, which means mostly rinsing with or dipping into diluted acids (HCl, HF), was the best. Whatever worked was rarely further investigated. Hence, not much work has been published in the field of contamination control and cleaning process optimization and development. With solar cell efficiencies increasing and processes becoming more and more sensitive, the interest in quality control and optimization of cleaning processes is rising.

Abstract: Assessing the vulnerability of critical infrastructure objects is of major concern when dealing with the process of dependability and risk management. Special attention is paid to the objects of higher interest, such as nuclear power plants. In spite of the protection of these objects, there is still a certain level of a potential threat. The aim of the paper is to describe a possible way of attacking on the object in order to get into a particular part of it. Several characteristics of an adversary ́s attempt were obtained. For this reason as well as for modelling adversary ́s behaviour diffusion processes have been used.

Abstract: This paper deals with the possibility of applying controlled diffusion processes in the remelting of steel surface layers using the electric arc of non-consumable electrode in the environment enriched with selected elements. The objective was to achieve an increased wear resistance. Boron was used in experiments as an alloying element. An assumption was stated in the experiment design that environment dissociation and ionisation can be achieved using electric arc, allowing diffusion processes initiation in the surface layer of remelted steel. Conditions for hard and stable structures formation with required properties should be achieved by surface layers enriching. Steel grade STN 41 5230 was used in experiments. Hardness and relative abrasive wear resistance values were measured on samples after remelting, being crucial as for required properties of surface layers. Not only hardness values were measured in the remelted layer but also their course inwards the material up to reaching the depth of base material not affected by heat. The metallographic analysis of remelted samples was made as well. A significant increase of parameters observed in the boron remelting environment was found. The dependency of the environment effect on the change of properties and boron content in the remelting environment was observed.

Abstract: This paper highlights the role played by diffusion processes to achieve a better characterization of structure and dynamics in atomic-scale studies of materials. Two classes of examples are presented. In the first, we take advantage of diffusion coefficients to assess the performances of different exchange-correlation functionals employed within the framework of density functional theory. By calculating the diffusion coefficients one is able to make a choice on the functional best suited to describe a prototypical disordered system, liquid GeSe2. In the second class of examples, we rely on classical molecular dynamics to describe diffusion mechanism on nanostructured substrates. The migration of a Co adatom on a stepped Pt(111) surface is analyzed in detail and correlated to the value of the different diffusion barriers. The diffusion behavior of Au adatoms on the reconstructed Au(111) substrate is described in terms of diffusion isotropy and anisotropy, by comparison with the case of Co/Au(111). Taken altogether, these studies exemplify the close link between diffusion properties, a realistic description of materials and the current level of performances of atomic-scale simulations methods.