Defect and Diffusion Forum Vols. 326-328

Abstract: Guest diffusion in nanoporous materials reveals a wide spectrum of phenomena associated with random mass transfer in condensed matter quite in general. Taking advantage of their potentials for monitoring mass transfer over microscopic dimensions, micro-imaging (by interference microscopy and IR spectroscopy) and pulsed field gradient (PFG) NMR are exploited for providing typical examples highlighting these options. Starting with the surprise provided by the application of these microscopic measuring techniques to nanoporous materials, namely discrepancies of up to five orders of magnitude in comparison with the so far well-established data, the review covers some of the most impressive further results, including the determination of sticking coefficients on the surfaces of these materials and the specification and detection of conditions where molecular mass transfer is accelerated rather than hampered by counter fluxes.

Abstract: The present work is focused on the preparation and the properties of Sn-Ag-nanoCu composite solder by two methods, i.e. ball milling and paste mixing. Copper nanoparticles were added at two different compositions, 0.7% and 3%, to Sn-3.5Ag solder powder and paste by ball milling and paste mixing, respectively. The composite solder was deposited on the Cu substrate and heated at 250°C for 60 seconds and allowed to cool at room temperature. The wetting ability was evaluated with the wetting angle of deposited composite solder on Cu substrate. The microstructure, morphology and hardness were examined for composite solder joints. It was found that the lowest melting point was achieved at 213.6°C for Sn-3.5Ag-3nanoCu produced by ball milling. The wetting angle deterioted as Cu nanoparticles were added into the Sn-3.5Ag solder paste by paste mixing. However, when Cu nanoparticles were added by 0.7% and 3.0% by ball milling, the wetting angle improved by 5% and 37%, respectively. The hardness of composite solder improved up to 32% when 3% Cu was added by ball milling.

Abstract: The metabolic secretions produced by the cells inside the human eye are accumulated simultaneously in all of its parts; subject only to their origin. However, the symptomatology is well characterized by the location of accumulation. Genetic factors are directly related to how the clumps of metabolic secretions occur and the form of accumulation is very specific to the movement of the eyes based on the activities performed by the patient, so any outcome is unpredictable. The outer retinal layers are avascular and are supplied by diffusion from the choriocapillatis. Abnormalities of retinal blood circulation and drainage of metabolic secretions are key indicators to retinal dysfunction and may point to perturbations of systemic circulation. The weakening of the cornea bending mechanism results in the loss of variation of intraocular pressure. Consequently, due to the increase of its work activities, the weakening of the forced convection mechanism of the metabolic secretions produced in the retina initiates the accumulation of these secretions without uniformity in the retina, causing gradual obstruction of its system of mass transport, nutrients and metabolic secretions. This accumulation is readily observed by pressing ones hands for several minutes on closed eyes, subsequently, there is the perception of light in one without a region of uniformity. This work analyzes the anatomic structure and biophysics, depicted in the scientific literature, along with the symptoms of the presbyopia treatment of the first author of this paper, to understand that the accumulation of metabolic secretions causes an agglutination and dehydration process by decanting that triggers the loss of flexibility of the fibrous coat, vascular coat (uveal tissue) and nervous coat (retina) and consequently the gradual obstruction of the system of mass transport in the retina, compromising its nutrition and obstructing the drainage of its metabolic secretion.

Abstract: Currently, one of the major technological challenges refers to issues related to the emission of gaseous pollutants, particularly those based on SO_x and NO_x. Generated mainly by the burning of fossil fuels, their reduction can be achieved by changes in the conditions of refining processes, capable of adapting the legal specifications of fuel sulphur and nitrogen, or by treatment of gases exhausted. If on the one hand the industries represent an essential portion of such gases, on the other hand the automotive vehicles contribute resolutely to complement another fraction of the emissions. The growing number of diesel-powered cars in Brazil, together with the existing environmental constraints in the country, requires greater control of the indices of gaseous mixtures mentioned above, which can be decreased through reducing agents based on technologies Reducing Agents Automotive Liquids (RAAL). By injection of an aqueous solution of urea on vehicular exhaust, it is possible for example, to catalytically reduce NO_x compounds to a mixture of N₂ and H₂O. Although this project is already in development, several challenges must be overcome, such as the catalyst deactivation by biuret (present in the solution of urea), more efficient engine design and development of fuels with lower levels of nitrogen. This work aims to study the removal of biuret by commercial adsorbents, as a way to adequate the RAAL to employment systems of diesel injection.

Abstract: Currently, the biggest concern of different industries is the disposal of waste generated. The liquid effluents in general have more elaborate studies realizing alternatives for their treatment by reducing their toxicity or changing specifications for a return to the process, an internal recycling or even studying alternatives for recycling outside. In the case of solid waste, there are many papers on reuse. In general, the studies involve alternatives to reduce the possible toxicity and subsequent disposal. In some cases, the studies dealt with the residue already involve their use as material for construction (bricks). This work aims to evaluate two types of waste, namely, the drilling mud to clay-based generated by the activity of exploration and exploitation of oil and solid waste generated in the production process and catalyst for fluid catalytic cracking plant. In both cases, is currently the destination for industrial landfills, and the generating unit has to bear all expenses related to material handling. Our purpose in studying this waste, will initially study the temperature profiles. The dry material being ground and with a pre-determined size will be tested for physical-chemical, such as X-ray fluorescence (XRF) to see the composition and ASAP to analyze the surface area and pore volume. With this material treated in bench tests will be performed to assess the capability of removing nitrogen and sulfur contaminants in lighter fractions of petroleum. Preliminary tests with the industrial base of sorbent clay and zeolite showed a good result. These tests serve as a basis for comparison with material obtained in the laboratory.

Abstract: The technique of electrochemical impedance spectroscopy (EIS) is widely used in laboratories and industries for materials evaluation. The aim of this investigation is to monitor the thickness of the anodized (oxide) aluminium sheets (samples) by using the EIS in a laboratory and a field study at a predetermined exposure duration in the field, i.e., 0, 1, 3, 6, 9, 12 months, in 0-10 % sulphuric acid. Four experimental stations were built out of KISR in order to monitor the thickness of the anodized (oxide) layer and the electrochemical parameters of anodized aluminium sheets by using the EIS. The zero state results at 0 exposure duration, indicating that as the concentration of the sulphuric acid increased from 0-10% H₂SO₄, the polarization resistance was observed to decrease from 3.15E+05 to 9.80E+03 Ohms, except at a concentration of 4% H₂SO₄, where the polarization resistance was observed to increase from 5.20E+03 to 2.90E+04 Ohms. On the contrary, the value of the solution resistance was observed to vary several times between 1.33E+04 to 1.53E+00 Ohms as a function of the increase of the sulphuric acid concentration from 0-10% H₂SO₄. In similar fashion to the polarization resistance, as the concentration of the sulphuric acid increased from 0-10% H₂SO₄, values of the alternating current impedance were found to vary several times between 1.94E+09 to 3.95E+05 Ohms, in a non-linear fashion. A similar behavior was observed on the values of the double layer capacitance as a function of the sulphuric acid increased, from 0-10% H₂SO₄, in which the values of the double layer capacitance was observed to change several times from 2.24E-09 to 2.53E-06 μF. The optimum thickness of the oxide film was detected (26.5 nm) at 8% H₂SO₄ of the sulphuric acid concentration. In order to determine the performance of the anodized aluminium-sheet in surrounding areas of Kuwait, a plan was arranged for such a field study. The field study consists of setting up four racks of sample panels in different locations in Kuwait. The racks were installed in the main field of Kuwait Institute for Scientific Research (KISR) in Shuwaikh area, in a residential area of South Sura area, in the main field of the Petroleum Research Department and Studies Center (PRSC) of Kuwait Institute for Scientific Research (KISR), in an industrial area of Ahmadi city, and in the main field of the fishery department of Kuwait Institute for Scientific Research (KISR) in a marine area of Salmia. The investigation planned to take a sheet each three months, for a 12 months duration, in order to determine the electrochemical parameters and the oxide film thickness of the sheets by the EIS technique in the field and to compare the data with those obtained in this report, at zero state.

Abstract: As the silicon melting point is very high (1414 °C), the temperature in the solid fraction, near the interface solid/liquid during solidification is also high and this can provoke a solute redistribution in the solidified portion. This phenomena is called back diffusion. So, it is important to estimate the potential of back diffusion during the solidification processes. This calculation is complex and there is commercial software, such as DICTRA, to do this in binary alloys. For zone melting, a simple method to predict the extension of the back diffusion is not available. In this study, it was developed a simple method to evaluate the back diffusion during zone melting, which does not require computational calculation.

Abstract: The treatment of rising damp in historical buildings walls is very complex. Moisture transfer in walls of old buildings, which are in direct contact with the ground, leads to a migration of soluble salts responsible for many building pathologies. The present work describes an extensive numerical analyse of rising damp phenomenon, using the software WUFI-2D, developed by Fraunhofer Institute for Building Physics. The results show that the numerical simulation describes very well the rising damp front for different boundary conditions and materials. The influence of the wall thickness, boundary conditions, composition of walls and material properties, such as, porosity and water absorption coefficient were analysed in detail.

Abstract: The treatment of rising damp in the walls of historical buildings is very complex, due to the thickness and heterogeneity of the walls. The techniques traditionally used for dealing with this problem (such as watertight barriers, injection of hydrofuge products, etc.) have sometimes proved ineffective, and that is why it is necessary to find a new approach. In recent years, the Building Physics Laboratory at the Faculty of Engineering, University of Porto has been conducting experimental research on the effectiveness of the wall base ventilation system, using natural or mechanical higro-regulate systems to reduce the level of the damp area. This experimental research and the simulations that were performed, clearly show that wall base ventilation is a system with potential. This paper presents the characterization of the hygro-regulated systems operation based on experimental studies developed in laboratory, which allowed the influence of the velocity of the air, condensation risk and the possibility of salt crystallization.