Advanced Materials Research Vol. 1036

Abstract: The aim of the work is to employ the artificial neural networks for prediction of hardness of the alloyed copper like CuTi, CuFe, CuCr and CuNiSi. In this paper it has been presented an original trial of prediction of the required hardness of the alloyed copper like CuTi, CuFe, CuCr and CuNiSi. Artificial neural networks, can be applied for predicting the effect of the chemical composition, parameters of heat treatment and cold working deformation degree on the hardness. It has been assumed that the artificial neural networks can be used to assign the relationship between the chemical compositions of alloyed copper, temperature and time of solution heat treatment, degree of cold working deformation and temperature and time of ageing. In order to determine the relationship it has been necessary to work out a suitable calculation model. It has been proved that employment of genetic algorithm to selection of input neurons can be very useful tool to improve artificial neural network calculation results. The attempt to use the artificial neural networks for predicting the effect of the chemical composition and parameters of heat treatment and cold working deformation degree on the hardness succeeded, as the level of the obtained results was acceptable. Worked out model should be used for prediction of hardness only in particular groups of alloyed copper, mostly because of the discontinuous character of input data. The results of research make it possible to calculate with a certain admissible error the hardness value basing on combinations of concentrations of the particular elements, heat treatment parameters and cold working deformation degree.

Abstract: The paper presents different physical-chemical treatment applications for textile effluents (i.e. one-single or mixed treatment stages as coagulation-flocculation, homogenous advanced oxidation with hydrogen peroxide as Fenton-like processes, sorption applied for different textile wastewaters followed by sedimentation and/or filtration). The efficiencies of textile wastewater treatments in terms of effluent quality, treatment degree, and optimal operating parameters (i.e. pH, concentration of chemical reagents and materials used, temperature, operating regime, and time) are discussed, together with some restrictions and recommendations. These data concerning different effluent treatments are useful to the environmental management staff but also to all employees that adopted an environmental attitude (EA) in all them behaviour. The concern of solving inside environmental problems (mainly focused on quality of final effluent discharge in aquatic receptor and/or treated effluent recycling), and acting into an ethical, legal and viable manner is necessary and obligatory in the present condition of fresh water deficit, pollution increasing of natural surface water resources, and its variety and/or complexity.

Abstract: The paper presents results of investigations on a potential for utilisation of waste materials, containing silver powders, ceramics and polymer, for production of PTFE-matrix composites. The waste is a mix of Ag powders (10 – 15%), SiC and Al₂O₃ powders (20 – 50%) and polymeric powders (20 –50%). For composite production, high-temperature press moulding method was applied. Reinforcing materials and the matrix powder were mixed and subjected to the pressing process in a graphite mould at 350oC. Composite specimens containing 25% Ag, 50% Ag and 75% Ag were obtained. For the obtained composites, density, HB hardness and a friction coefficient were determined. The friction coefficient was evaluated in the “pin-on-block” test with the sliding distance of 2500 m and a load of 25 N with no lubrication. Wear of the composites was assessed based on a profilometry analysis. The obtained results suggest that the composites may be applied for manufacturing of components resistant to abrasive wear with a required, low friction coefficient.

Abstract: Corrosion of reinforcing steel in concrete leads to the premature failure of many structures exposed to harsh environments. Rust products form on the bar, expanding its volume and creating stress in the surrounding concrete. In this study we will present how metal acts into an aggressive environment and how we can adopt the best solutions to reduce the attack of corrosion. First we should understand how corrosion occurs. Corrosion occurs when two different metals, or metals in different environments, are electrically connected in a moist or damp concrete. This will occur when: steel reinforcement is in contact with an aluminium conduit; concrete pore water composition varies between adjacent or along reinforcing bars; where there is a variation in alloy composition between or along reinforcing bars; where there is a variation in residual/applied stress along or between reinforcing bars. Loss of alkalinity due to carbonation or chlorides, crack due to mechanical loading, stray currents, agents from atmospheric pollution, moisture pathways, low concrete tensile strength, electrical contact with dissimilar metals are some of the most important reasons of corrosion. Electro-chemical corrosion, which plays a subordinate role in air, is of greater significance in liquids. The extent of electro-chemical corrosion depends on the electrical conductivity of the liquid, which affects the protective influence of the zinc layer over greater or smaller areas. The pH value of the liquid is of most significance. The corrosion rate of zinc is normally low and stable in the pH range of 5,5—12,5, at temperatures between 0 and 20 °C. Corrosion outside this range is usually more rapid. Hard water, which contains lime and magnesium, is less aggressive than soft water. Together with carbon dioxide these substances form sparingly soluble carbonates on the zinc surface, protecting the zinc against further corrosion. Soft water often attacks zinc, since the absence of salts means that the protective layer cannot be formed. In some waters, polarity reversal can occur at about 70 °C so that the zinc coating becomes more electro-positive than the steel and pitting occurs. Oxygen, sulphates and chlorides counteract polarity reversal, which means that the problem may exist only in very clean water. Water temperature is of great significance to the rate of corrosion. Above approximately 55 °C, the layer-forming corrosion products acquire a coarse-grained structure and lose adhesion to the zinc surface. They are easily dislodged and expose new, fresh zinc for continued and rapid corrosion attack. The rate of corrosion reaches a maximum at about 70 °C, after which it declines so that at 100 °C it is about the same as at 50 °C. Keywords : composite materials, corrosion, reinforcement, water corrosion, reinforcement bars.

Abstract: Materials are the main substances that have an important effect on company development and require some simple or complex manufacturing technologies. The future use of recyclable materials will become an extremely important factor in all fields of activity. Therefore, "liquid wood", due to its biodegradability and mechanical properties superior to other plastics, could replace some plastic materials in the near future. The injected parts can be obtained using the same injection machines used for the injection of plastic materials. The technological injection parameters such as: injection pressure, injection time, cooling time, mold temperature, etc. are different. A new study of transport fenomena in liquid wood treated with the complex fluid is proposed considering that the complex fluid and agents moving in continuous and non-differentiable curves (fractal curves). Within this framework, the transport equations of mass, energy and impulse are obtained and the fundamental theorems of complex fluid are established at well. In the end, our model and the classical results are correlated.

Abstract: Nanostructured materials have gained a lot of importance in the latest technologies due to their amazing mechanical, thermal, and even nuclear properties. Either used as classic protective coatings or particle detectors, nanostructured materials require special synthesis methods, from physical or chemical vapour deposition, flame synthesis to plasma processing. The complex phenomena accompanying their synthesis required the deep study of the thermodynamic parameters of such systems, with special emphasis on a theoretical approach which is independent to the synthesis method and generally applicable. The complex mathematical description of such phenomena and the solution to the thermodynamic functions of the system, achieved in many cases by numerical methods, was often done by strong commercial codes. Despite the efforts, many of the predicted synthesis parameters did not match experimental determinations, and furthermore, conducted to confusing and even wrong results regarding especially the pressure and temperature range required to obtain the quality materials. The present work aims to draw a comparative computational analysis of nanostructured materials, indicating not only some commercial code results, but also the differences in softwares, methods, theoretical approach and conclusions. Both similarities and differences are underlined by the numerical and graphical solutions, as offered by various commercial codes, revealing strong and weak aspects in thermodynamic considerations. The output of such a computational thermodynamic analysis doesnt depend on the synthesis method, but on the assumptions done and the materials under evaluation, and presents a good concordance with many experimental data, either obtained during authors work or literature-reported. The study is useful when needing the synthesis parameters, such as temperature, system and component pressure, feedstock composition, the degree of freedom analysis, the Gibbs free energy, the driving force, the phase diagrams, the pressure-temperature or pressure-volume graph. Taking into account the balance between assumptions, accuracy, and effective nanostructured material, one has to choose the most suitable commercial code and approach in order to obtain the a-priori thermodynamic characterization of the system.

Abstract: In the present work an experimental investigation is carried out to evaluate the performance of helical coiled tube with the swirl flow device using Al₂O₃nanofluid.The effects of wire coil insert with different parameter on heat transfer and friction loss in the helical tube were examined with Dean number (De) ranging from 700 to 2000. The circular or square coil wire has different cross sections, insertedin the tube with different pitch. The wire coil with Al₂O₃ nanoparticles with a diameter of 80nm dispersed in distilled water with volume concentrations of (0.08,0.1, 0.2and 0.3 vol.% ) were used as the test fluid. The effects of Dean Number, volume concentration of suspended nanoparticles, and wire coil on heat characteristics were investigated. The results reveal that the use of tabulators leads to a considerable increase in heat transfer and friction loss over those of a smooth tube. The Nusselt number increases with increasing of Dean number and reduction in pitch of wire coil. The square type of wire coil provides slightly higher heat transfer than the circular under the same conditions. Results show that the optimum heat transfer is caused of P=15mm of wire coils. Adding nanoparticles to the base fluid causes a significant enhancement in heat transfer characteristics. The overall enhancement in heat transfer using two mechanisms simultaneously compared to using pure fluid within the smooth helical tube exceeds over 213.2% (180% spring enhancement +33.2%Al₂O₃). The optimum results were found to be P=15mm, φ=0. 3Al₂O₃ t=2mm square cross section and De=1889. Finally, empirical correlations are developed of predicting Nusselt number of the flow with and without nanofluid. Comparison between the present result in reference results show good agreement.

Abstract: High entropy alloys (HEAs) are a newly developed family of multi-component alloys composed of several major alloying elements, such as copper, nickel, aluminum, cobalt, chromium, iron, silicon, titanium, etc. The fact that HEA alloys is formed participation molar is approximately equal with at least five elements, entropy configuration is double that of binary systems, entitles us to call them "high entropy alloys'. Recent studies suggested that the refractory HEAs exhibited great promise for high temperature structural materials. This alloy can be processed and analyzed as an ordinary material AlNiMnZnCu high-entropy alloys are prepared by an induction furnace. The microstructure and properties of alloy samples were examined by SEM and testing machine for obtained materials. Mechanical tests were made with a INSTRON 3382 machine.

Abstract: This paper presents the microstructure and the mechanical properties of FeNiCrCuAl high entropy alloys. The microstructure and mechanical properties of the annealed FeNiCrCuAl high entropy alloys were investigated using scanning electron microscopy, and X-ray diffraction. High entropy alloys have been known as a new type of materials and have been defined as having five or more principal elements, each one having a concentration between 5 and 35 at.%. Previous researches show that HEAs can be processed to form simple solid solution structures instead of intermetallics and other complicated compounds. This phenomenon is commonly attributed to the high configurational entropy in the solid solution state of HEAs. Furthermore, HEAs have also exhibited interesting properties such as high hardness and high strength, good thermal stability outstanding wear and oxidation resistance which offer great potential for engineering applications. The HEA systems explored in the past decade show that metallic elements are the most commonly used, e.g. Al, Cr, Fe, Co, Ni, Cu,Ti, etc. A wide range of HEAs exhibit high hardness, high strength, distinctive electrical and magnetic properties, high-temperature softening resistance, as well as favorable combination of compression strength and ductility. This combination of properties and the particular structures of HEAs are attractive for a number of potential engineering applications.

Abstract: Composite materials are the most advanced class of materials invented and produced by humans in modern times as well as a challenge for the future in the field of scientific and technological performance. They are made up of at least two phases of different nature which are so combined to form a new material with a superior combination of properties. They are generally materials with unusual performances on the relationship between properties and specific gravity. Composites are multiphase materials with distinct and well-defined interface between the constituent phases ensuring a transfer of property but can lead to obtaining a product with exceptional performance from the starting material. In this paper we have focused research on Al-Mg alloys with magnesium and silicon carbide (SiC). Stabilized Aluminium Foams (SAF) are new class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They offer potential for lightweight structures, for energy absorption, and for thermal management; and some of them, at least, are cheap. Metal foams offer significant performance gains in light, stiff structures, for the efficient absorption of energy, for thermal management and perhaps for acoustic control and other, more specialized, applications. They are recyclable and nontoxic. They hold particular promise for market penetration in applications in which several of these features are exploited simultaneously. The paper presents some results related to the research of metallic foams based on AlMg10 metallic alloy obtained by melt bubbled C₄H₁₀ addition of SiC particles. Microsrtucture of these foams is analyzed by using (SEM) Scanning Electron Microscope, laying out the network of pores imbued into each others developed around SiC particles and other issues microstructural characteristics.