Abstract: According to different experimental data the grain boundary diffusion the triple product (P) can change in opposite directions after alloying. In this paper the analysis of the effect of alloying for different systems is proposed. It was shown that in Al-based system (Cu diffusion in Al, Zn diffusion in Al) the P value increases with alloying while the solidus temperature according to the phase diagram decreases, in other systems no such tendency can be seen. Estimations based on the segregation factor value demonstrate that some structural effect must be proposed in addition to describe the experimental results.
Abstract: The questions of metallurgical processing of titanium-containing ores are considered. The ores and concentrates of the Kachkanarsky deposit of low-titanous and high-titanous are studied. The reducibility, durability, temperatures of a softening and melting of metallurgical iron ore raw materials are studied in vitro. Via X-ray the structural analysis are carried out. The calculations by means of mathematical models of pyrometallurgical processes are executed. Possibility of the processing of these ores according to schemes is shown: «blast furnace melting − converter melting» and «metallization – electric melting».
Abstract: Cermets with four different compositions of lanthanum and cerium oxide in Cu-Ni-Ag alloy as metallic matrix were fabricated by powder metallurgy and characterized by their structural and physical properties. It was detected the formation of intermetallic compounds as a consequence of diffusion processes. The powder metallurgy allowed to obtain samples with high electrical conductivities and interesting structural characteristics with potential technological applications.
Abstract: Despite the ever-growing worldwide interest in the use of lignocellulosic fibers as reinforcement in either thermoset or thermoplastic matrices, the use of these fibers to replace synthetic ones, is limited. The reasons for these limitations are associated with the vegetable fiber’s heterogeneity, lower compatibility to most polymers, inferior durability, flammability, poorer mechanical properties and higher moisture absorption when compared with synthetic fibers. Nevertheless, despite these drawbacks, vegetable fiber reinforced polymer composites are lighter in weight, more sustainable and can be used for non-structural products. Strategies to minimize these drawbacks include fiber and or matrix modification, the use of compatibilizers, fiber drying and the concomitant use of vegetable and synthetic fibers, for the production of hybrid composites, the latter being an unquestionable way to increment overall mechanical and thermal properties of these hybrid systems. Here we present data on the water sorption of polymer composites having thermoset and thermoplastic matrices as a function of vegetable fiber identity, content and hybridization with glass fibers. Our data indicates that, regardless if the matrix is a thermoset of a thermoplastic, water absorption tends to be relatively independent of vegetable fiber identity and to be significantly dependent of its content. Fiber drying prior to composite manufacturing and hybridization with glass fibers leads to lower overall water absorption and higher mechanical properties.
Abstract: School buildings energy efficiency is crucial but also environmental, aesthetics, acoustics, accessibility and comfort requirements will be valued. Focus will be on creating value for all the users involved not only in terms of economics, but also in terms of comfort, health, environment, academic success, etc...Various attempts to optimize school buildings design have been made throughout Europe. However, the in-use performance of these buildings revealed very different than the expected. It is crucial to minimize the gap between computer simulation and measured performance. Moreover, the maintenance and operation costs of the recently rehabilitated buildings revealed unaffordable for the limited school budgets. Therefore, cost-effective, high-performing, and minimally invasive solutions should be developed and monitored to ensure their performance during the service life and guaranteeing the full performance predicted at the design stage. This will be achieved by combining innovative construction with real performance information and users’ feedback.This work intends to present a short critical review of several works presented in literature.
Abstract: Controlled release fertilizer (CRF) has attracted a lot of interest because of its advantages for ecosystem in terms of enhancement of nutrient utilization and reducing nutrient loss from leaching and volatilization, etc. While a number of research studies on novel coating material to control the release of nutrients, modelling has a significant role in predicting release behaviour and determining good CRF design that matches the nutrient requirement from the plants. The present study proposes a solution to predict coating material parameters based on multi-diffusion model and preliminary experimental results using inverse simulation technique. In addition, the solution showed an advantage in prediction the release of nutrient, i.e., the reduction in experimental time which plays an important role in investigation novel coating material and designing of CRFs which are matched the nutrient uptake from plants. Hence, this solution reduces experimental cost and time to researchers, who investigated novel CRFs.
Abstract: In binary systems Kirkendall shift is a well-known phenomenon. We investigated nanoscale diffusion in the framework of a recently published continuum model [Erdélyi and Schmitz, Acta. Mater. 60 (2012) 1807]. In thin films the usual vacancy creation and annihilation mechanisms, leading to the Kirkendall shift on larger scales, cannot operate in the same way. On this length-scale the characteristic distances between vacancy sinks and sources can be comparable to the dimension of the sample, causing differences in the development of the Kirkendall effect. Our group recently reported results in simulating nanoscale Kirkendall shift. In present work we show how using conventional method for velocity reconstruction used in multifoil experiments can be misleading if the distribution of vacancy sinks and sources is not uniform.
Abstract: Heat pipe is well known device which is used to heat transfer phase-change of working fluid. Pulsating heat pipe (PHP) is special type of heat pipe which heat transfer by pulsating movement of working fluid. Article deals about operating activity and thermal performance measurement of this special heat pipe. Operating activity visualization of PHP was performed with PHP made from glass. The two types of PHPs were made. The first PHP has internal diameter of tube 1 mm, second PHP has internal diameter of tube 1.5 mm and both PHPs have eleven meanders. The working fluids used in PHP were water and Fluorinert FC-72. These fluids were chose for their different thermo-physical properties and the visualization observe formation of liquid and vapour phase working fluid during filling process and working operation.Next, the article describes thermal performance measurement of PHP depending on working fluid amount and heat source temperature. Measurement was performed with PHP made from copper tube with inner diameter 1.5 mm curved to the twenty one meanders and filled with water. The results give us image about formation and distribution of working fluid in pulsating heat pipe and about influence of working fluid amount on the heat transfer ability of pulsating heat pipe.
Abstract: Foam-type porous silicon carbide (SiC) ceramics without cracks and hollow struts were fabricated using the polymer replica method with polycarbosilane (PCS) and polyurethane (PU) foam as the starting materials. The synthesized porous SiC was analyzed using X-ray diffraction and scanning electron microscopy. The results revealed that a porous SiC ceramic structure was formed with a dense framework at a low temperature of 1200°C. During the heat-treatment process, the PCS experienced an organic–inorganic transformation and then converted to the SiC ceramics. It was determined that the organic–inorganic transformation of PCS, which was the stage of silicon oxycarbide formation, is affected by the curing condition. In this study, the optimum curing condition was determined to be an air atmosphere at 200°C for 7 h.
Abstract: A consistency between the Darken method and the Onsager representation for cross diffusion in multicomponent system is shown. The justification is made by defining new sets of forces and fluxes linearly interrelated by a symmetric matrix of phenomenological coefficients. For the first time, the system of the components having various molar volumes is treated in this way. It is shown that the transformation leaves the entropy production unchanged. As an example, the entropy production for interdiffusion in the ternary Co-Fe-Ni diffusion couple is calculated and compared with mixing entropy.