Papers by Keyword: Intermixing

Abstract: A deep understanding on the intermixing of components in hybrid yarn or composite structures is decisive in order to develop hybrid structures with desired properties. This paper presents the development of a versatile procedure for the determination of the degree of fiber mixing in yarns and composites based on microscopy images auto-segmented by a neural network. The procedure is based on the quantification of blend irregularity values and blend homogeneity. For this purpose, functions of spatial point patterns analysis have been used to investigate the blend uniformity of yarn and composite cross sectional areas. The results show that the trained neural network model for segmentation of images has an accuracy of 92 %, indicating that the method is capable of accurately assessing the location of fibers in hybrid struc-tures. The results of the spatial point patterns analysis reveals a correlation between the blend value and the properties of yarns and composites. The proposed method provides a fast and reliable way to evaluate the hybrid structures, which could be used as a tool for quality control and process optimization.

Abstract: The paper deals with investigation into segregation behavior of selected elements in longitudinal cut of continuous steel slab, in the breakout area. The breakout occurred after a flying change of tundish in order to begin casting of another steel grade. Altogether 11 samples were taken from the part of a solidified slab. Concentrations of selected elements (Al, Si, P, S, Cr, Mn, Ni and Mo) were measured in these samples using scanning electron microscope and energy dispersive spectroscopy. Using the original mathematical models the basic micro-segregation characteristics and the parameter of macro-heterogeneity were further determined for each analyzed element. Then a quantitative measurement of inclusions ("micro-purity") in the samples was performed using a metallographic microscope. Then method of differential thermal analysis was used for the measurements of temperatures of phase transformations. The following main results were found: - magnitude of micro-segregation of the analyzed elements in the measured sections of 1000 μm is approximately the same in all the analyzed samples, - chemical macro-heterogeneity is very high across the analyzed slab section, - very uneven mixing of melts of both steels was probably one of the main causes of formation of the breakout.

Abstract: The mixing situation of Co atoms implanting onto Cu(001) substrate is investigated with regard to incident energy and substrate temperature by molecular dynamics. The results indicate that higher substrate temperature and/or incident energy will result in higher intermixing between the incident atoms and the substrate atoms. Furthermore, the value of the first peak of the radial distribution function (RDF) becomes lower and wider for the Co-Cu system as the substrate temperature and/or incident energy are increased.

Abstract: Nano-scale spatial wavelength engineering of quantum nanostructures using nitrogen ion-implantation induced intermixing has been developed for tuning the bandgap of quantum-well, quantum-dash-in-well, and quantum-dot nanostructures. High performance bandgap-tuned quantum-well and quantum-dash lasers fabricated using this technique has been demonstrated.

Abstract: The adsorption of Au on clean Si(001) surface is investigated by the local density approximation using first-principles pseudopotentials. We found that the adsorption energy of Au on ideal Si(001)-(1×1) surface is lower than that on reconstructed Si(001)-(2×1) surface, suggesting that adsorbed Au atoms chemically react with the surface Si atoms and break Si-Si dimer bonds of the substrate. Furthermore, the intermixing of Au and Si is also considered and the calculation suggests that intermixing will not take place at low temperature. But due to the small energy barrier for Au atoms to diffuse into Si substrate, we can conclude that the Au-Si alloy is easily formed at relatively high temperature. This result should be one of the reasons of the lack of consensus on the issue of intermixing of Au and Si.

Abstract: The local acceleration effects, which are peculiar phenomena during atomic scale deposition process, were investigated byMolecular Dynamics (MD) simulation. The values of local acceleration were distributed widely for various surface orientations. Deposited atoms were accelerated along the potential energy surface, and accelerated values were evidently dependent on the local configuration of the surface. In contrast, the local acceleration became negligibly small for clusters consisting of many atoms.

Abstract: Pulse loading of diffusion couples leads to the formation of the broad metastable solid solutions. Under higher temperatures, combined with high deformation rates, intermetallics also can form. Possible mechanisms of this phenomenon are discussed. Formation of nanostructure under uniaxial compression/decompression (observed in MD simulations) seems to be one of the possibilities.

Abstract: We will discuss the stress release phenomena, structural relaxation and interdiffusion processes during annealing. The [Co(4nm)/Ta(4nm)]38 multilayers were prepared by dc magnetron sputtering on Si substrate. The multilayers were annealed at various temperatures (523 - 673K) in vacuum (under 10-5 torr) furnace. The effective interdiffusion coefficients were determined from the slope of the best straight line fit of the first peak intensity versus annealing time [d ln(I(t)/I(0)) /dt] by X-ray diffraction (XRD) low angle measurements. The drastic decrease of the relative intensity in the initial stage shown due to the structural relaxation was excluded in the calculation of effective interdiffusion coefficients. The temperature dependence of interdiffusion in the range of 523 - 673K is described by D = 3.2×10-19 exp(-0.51±0.11 eV/kT) m2s-1.