Defect and Diffusion Forum Vols. 312-315

Abstract: The article is devoted to an estimation of phase transformations of silicates magnesium at heating in the temperatures range from 0°C to 1100°С. The object of study is a silicates of magnesium containing oxide nickel ore. Differentially-thermal (NETZSCH 449 C - Jupiter), weights – spectrometer (QMS 403 C Aёolos), high-temperature X-ray diffraction, electron-probe microanalysis (JSM - 5900 LV) and chemical analysis methods have been used in the study. The temperature ranges of existence Mg6[(OH)8Si4O10] and Mg2Si2O6 are obtained. Parameters of an elementary cell of the above minerals and their changes with temperature and features of nickel distribution in magnesium silicates with various ration MgO/SiO2 are defined in this work.

Abstract: Heat and mass transfer in fluid flows traditionally is examined in terms of temperature and concentration fields and heat/mass-transfer coefficients at fluid-solid interfaces. However, heat/mass transfer may alternatively be considered as the transport of a passive scalar by the total advective-diffusive flux in a way analogous to the transport of fluid by the flow field. This Lagrangian approach facilitates heat/mass-transfer visualisation in a similar manner as flow visualisation and has great potential for transport problems in which insight into (interaction between) the scalar fluxes throughout the entire configuration is essential. This ansatz furthermore admits investigation of heat and mass transfer by well-established geometrical methods from laminar-mixing studies, which offers promising new research capabilities. The Lagrangian approach is introduced and demonstrated by way of representative examples.

Abstract: It has been found that the dispersion of phases in copper-nickel sulfide-metal alloys influences their electrochemical properties. X-ray diffraction and optical and electron microscopy have been used to study structural characteristics of the samples prepared by crystallization of sulfide melts at different rates of 10÷103 K/s. High-rate cooling of a converter matte leads to the formation of nonequilibrium sulfide phases and a metallic component dissolved in these phases. The electrochemical oxidation of copper-nickel sulfide alloys has been studied by voltammetry with a linear potential sweep. The data point to a reduction of the limiting oxidation currents of the sulfide alloys prepared by high-rate cooling. The compositions of the intermediate phases and solid products of the electrochemical oxidation, which form the passivating layer, have been determined. The electrolysis of dispersed sulfide alloys allows performing the process at low densities of the current and, thus, the diffusion limitations have been removed.

Abstract: We analyzed the hydrodynamics of the flow into an axis-symmetrical combustion chamber with a central bluff body. Using an axis-symmetrical turbulent flow model we determined the extent of the recirculation region behind the bluff body as well as the location and intensity of maximum kinetic energy as a function of the cone angle of the chamber wall. We showed that by shortening the convergent conical section of the chamber we obtain a compact recirculation with higher turbulence intensity, with positive influence on gas mixing. We used the software FLUENT 6.3 for the numerical simulation of the gas flow inside the combustion chamber. The simplified geometry of the two types of combustion chambers was built using the pre-processor GAMBIT 2.4. Two structured meshes were obtained for the domains of numerical analysis with approximately 170,000 cells each. For modelling the turbulence of the flow we used three different turbulence models which were implemented in FLUENT 6.3.

Abstract: The diffusion study in the V-Si system is reviewed. We show that the indirect method used previously to determine the diffusion parameters draws unnecessary error. Rather the method developed by Wagner should be used to calculate the diffusion parameters directly from the composition profile.

Abstract: This work demonstrates the need for updated review of the mechanism of mass transport in the human cornea, to understand the deterioration of visual acuity and plan your recovery. It is the conclusion of a work for ten years for recovery of presbyopia of the first author, through exercise the extra-ocular and ciliary muscles. It is shown that intraocular pressure varies according to the direction of the visual axis and that this variation is part of the mechanism of forced convection for the transport of nutrients and drainage of secretions metabolic in cornea. In both eyes, seven pressure measurements are proposed at intervals of one hour, with the non-contact tonometer: The first measurement in the initial condition; The second measurement after relaxation of the eyes; The following measurement after an activity with the attachment point near of the two eyes; The last four are proposed out after two activities, in the limit of the direction of the right border and, also, in the limit of the direction of the left border of the field of binocular vision, considering the two alternatives near and far from the eyes. The oblique muscles contraction causes a reduction in the anterior chamber volume and, consequently, the intraocular pressure increases, however, when the oblique muscles relax the opposite occurs. It is considered that, after an hour, the intraocular pressure reaches dynamic equilibrium. To measure the pressure, the equilibrium condition of the anterior chamber volume is changed, the system undergoes a new transient dynamic. There should be no change in intraocular pressure equilibrium during one day, unless because of an external factor. To collect the data, it is proposed to use the system eye of the first author who has good binocular vision.

Abstract: In this work we report on the structural, mechanical and magnetic properties of mechanically alloyed Fe40Co60 powders. Alloying formation, grain size, lattice parameter and internal strain were investigated using X-Ray Diffraction (XRD) measurements. The morphological aspect of the nanostructured powders was analysed by means of the Scanning Electron Microscopy (SEM). Compacted pastilles with circular shape have been under Vickers test of micro Hardness and magnetic measurements of Hysterisis loops. Discussed results according to milling time show that after 60 h milling the grain refinement is about 15.59 nm with internal strain of around 0.5809 %. The micro hardness increases with the decrease of the grain size and the hysterisis loop at 60 h milling is enhanced in term of decreased coercivity.

Abstract: Fabrics are needed further treatment after dyeing to restore their original mechanical properties by suitable drying/shrinkage process because of wetted and elongated fabrics cannot be used for clothes making. Heating up the dyed fabrics at suitable temperature can restore their original shapes and geometries by releasing the internal stress introduced by dyeing process. Thus, heat setting is a commonly used post-treatment process to stabilize fabric geometrical dimensions and prevent further shrinkage. Hot air jet impingement [1] and moist heat are conventional drying methods for different applications. Despite the well establishments of these drying technologies, most of the applications are for materials like clay and paper, and few on the study of textile materials. In fact that most of the developed heat setting machines used in textile industry are only designed by empirical models and lack of theoretical bases. This situation will obstruct further improvement of the drying technology. In this paper, a theoretical basis heat transfer model is developed for a precise description of a heated air flowing process for heat setting machine design. In the machine design, a better airflow circulation strategy for an efficient drying is addressed. Equations for heat and mass transfer in moist porous materials and theories on thermo- and fluid-dynamics are used to support the machine design. Outcomes from the research are to develop a heat transfer model that provides more precise and effective calculation for heat setting machine design that unavailable from the developed machine prototypes.

Abstract: We have considered the diffusion of particles in a dynamically disordered medium in the framework of a simple lattice-gas model of a reconstructive surface. Using kinetic Monte Carlo simulations we have investigated the diffusion of particles over the host lattice with moving atoms. The dynamic lattice reconstruction increases substantially the particle diffusion coefficient and changes its activation energy.

Abstract: Simulation systems used for many years in foundry industry such as MAGMASOFT, NovaFlow&Solid and ProCAST, contain thermo-mechanical modules permitting the estimation of mechanical stresses and hot tears appearing in casting during its cooling. It is also known that these modules are rarely used because of the very limited thermo-mechanical database especially for ceramic materials such as foundry sand moulds. These technologies – castings pouring in non-permanent sand moulds, particularly iron alloys are most often applied in foundry. In our study the method of evaluating the algorithms quality applied in thermo-mechanical phenomena models based on parameters sensitivity testing from the proper database of the simulation system was used [1]. The comparative analyses of both experimental and virtual results were realized (by stress estimation). The methodology of experimental research was similar to that described where gray cast iron castings of stress bars (grid) were casted in sand mould bonded by organic resins.