Papers by Keyword: Heterogeneous Structure

Abstract: The Harmonic Structure [1] is a novel design concept that facilitates the engineering of metallic materials to achieve enhanced mechanical performance. The Harmonic Structure is composed of soft, coarse-grained regions, designated as the Core, which are surrounded in three dimensions by an interconnected network of hard, ultra-fine grain regions, referred to as the Shell. The interaction in these core/shell regions produces a synergistic effect during plastic deformation, resulting in superior mechanical properties that are of great significance. The distinctive network configuration of the Harmonic Structure enhances the dislocation density within the coarse-grain regions in contact with the interface through stress partitioning, thereby accelerating the work hardening rate and consequently enhancing the strength. This phenomenon is referred to as Hetero Deformation Induced (HDI) strengthening [2]. The fabrication of HS material is achieved through the application of mechanical milling (MM) to the powder, which results in the formation of a deformed layer on the surface of the powder and the creation of bimodal structured particles. However, a notable constraint of the MM process is its extended time requirement to attain the desired bimodal structure. In contrast, the bi-modal milling (BiM) technique involves the controlled mechanical milling of coarse and fine powders in conjunction with each other, with the objective of forming a layer of fine powders of a specified thickness over the coarse particles. The most advantageous aspect of bi-modal milling (BiM) is not only its reduced processing time, but also its superior ability to control the thickness of the surface deformation layer.

Abstract: The liquid-solid fluidization bed is an effective method for removing hard ions from water. However, it is widely believed that the flow in the liquid-solid fluidization bed is homogeneous, which limits the transfer rates of heat, mass, momentum, and mixing. In this study, the results of the computational fluid dynamics (CFD) method showed significant heterogeneous particle–fluid patterns in the liquid-solid fluidization bed. On the other hand, simulations of the hydrodynamics behavior in the liquid-solid fluidized bed were first performed using different solid particle sizes, then particle classification, velocity distribution, and the vortical structures in the liquid-solid fluidized bed were assessed. In addition, a new model was proposed in this study to predict the flow behavior of the fluid-particle system used. The obtained results demonstrated the presence of the heterogeneous flow regime in the liquid-solid fluidized bed. The developed model for the onset of heterogeneous fluidization behavior revealed reasonable prediction results. Therefore, this model can be applied in future related studies on the hydrodynamics of the liquid-solid fluidized bed.

Abstract: 3D Printing can be considered as one of the most innovative manufacturing processes of our time. Part of the innovative potential of 3D Printing is associated with the production of geometrically complex parts in a relatively short time. In the present paper, a methodology for the production of parts with complex internal structure and intra-layer density variability (ILDV) is presented. The proposed methodology may be used to produce structures composed by two materials, such as functionally graded parts and composites. The variability of the internal structure and composition is captured through voxel modeling, where at each voxel a unique relative density value for each material is assigned. These relative density values are then translated to predefined extrusion paths, which the 3D printer follows for the construction of layers composed by one or two materials. Representative cases and examples of parts with ILDV are presented and discussed.

Abstract: New {[({[(Co₄₁Fe₃₉B₂₀)_X(SiO₂)_100X]/[(Co₄₁Fe₃₉B₂₀)_X(SiO₂)_100х+O₂]}₁₇₈ and {[(Co₄₅Fe₄₅Zr₁₀)_X(Al₂O₃)_100-X]/[(Co₄₅Fe₄₅Zr₁₀)_X(Al₂O₃)_100-X+O₂]}₃₀₀ multilayer heterogeneous structure has been obtained by ion-beam sputtering method. Magnetostatic and magnetodynamic properties and the structure of the nanocomposites have been investigated. It was shown that, the oxidized interlayer composite adding lead to suppression of perpendicular magnetic anisotropy component, and a change in the magnetic structure of the composites, which determines the change in the frequency dependence of the real (μ^/) and imaginary (μ^//) parts of the complex permeability.

Abstract: The technique was developed with the purpose of definition of parameters for surface layer uniformity after mechanical hardening. It was found that one of the most effective methods of surface plastic deformation that provide precise adjustment of uniformity level of surface layer hardening is presented by static-pulse treatment technique. This method helps to develop hardened surface layer 8 mm deep with virtually uniform or heterogeneous structure.

Abstract: New static-pulse treatment method was offered to increase contact pitting resistance of machinery parts. This method forms cold-worked layer with high hardness located deep in the part. The static-pulse treatment method is characterized by important feature that helps to form various levels of hardening uniformity of the surface layer. For the first time undertaken studies provided recommendations relating to uniformity of surface layer mechanical hardening, which increases contact pitting resistance of machinery parts made of 45, 40H, 35HGSA steel.

Abstract: Recently polycrystalline silicon (pc-Si) thin film transistors (TFT’s) have emerged as the devices of choice for many applications. The TFTs made of a thin un-doped polycrystalline silicon film deposited on a glass substrate by the Low Pressure Chemical Vapor Deposition technique LPCVD have limits in the technological process to the temperature < 600°C. The benefit of pc-Si is to make devices with large grain size. Unfortunately, according to the conditions during deposition, the pc-Si layers can consist of a random superposition of grains of different sizes, where grains boundaries parallels and perpendiculars appear. In this paper, the transfer characteristics IDS-VGS are simulated by solving a set of two-dimensional (2D) drift-diffusion equations together with the usual density of states (DOS: exponential band tails and Gaussian distribution of dangling bonds) localized at the grains boundaries. The impact of thickness of the active layer on the distribution of the electrostatic potential and the effect of density of intergranular traps states on the TFT’s transfer characteristics IDS-VGS have been also investigated.