Authors

Electrowinning of Nickel from Ammonical Sulphate Bath and Effect of Acetone
on Morphology of Nickel Deposit and its Correlation with Kinetic Parameters
abstract, article page 3 - 8 pdf - 870 kB

The Influence of Mechanical Activation of Chalcopyrite on the Selective Leaching
of Copper by Sulphuric Acid abstract, article page 9 - 12 pdf - 612 kB

D. K. Borikar, S. S. Umare, S. G. Viswanath - Electrowinning of Nickel from Ammonical Sulphate Bath and Effect of Acetone on Morphology of Nickel Deposit and its Correlation with Kinetic Parameters

     The electrodeposition of nickel from nickel sulphate bath was studied in ammonia medium. The electrolytic conditions for nickel deposition was optimized at room temperature. The effect of acetone on current efficiency, morphology, stability and particle size of deposited nickel powder was studied. The effect of organic additive Tribenzyl ammonium chloride (TBAC) on the morphology of nickel powder was also studied. The kinetics of electrodeposition was studied and the results were utilized in developing mathematical model. During electrodeposition the current efficiency was found to increase with increase in acetone concentration up to 15% V/V in bath solution. On further increase of acetone concentration in bath solution current efficiency decreases. The stability of the electrowon deposited nickel powder was found to be in the range of 85 to 89 %. Powder morphology was found to be dentritic, porous and irregular. The morphology was also found to be underdeveloped dentritic to rounded aggregate as the concentration of organic additive TBAC increases. The average particle size of the deposited powder was found to be decreasing as the concentration of the acetone increases. The average size of the particle is in the range of 13-16 µm. pdf - 870 kB

M. Achimovičová, P. Baláž, J. Briančin - The Influence of Mechanical Activation of Chalcopyrite on the Selective Leaching of Copper by Sulphuric Acid

     In this paper chalcopyrite, CuFeS₂, has been selective leached by H₂SO₄ as leaching agent (170 g/dm3) in procedure of hydrometallurgical production of copper. Mechanical activation of the chalcopyrite resulted in mechanochemical surface oxidation as well as in the mineral surface and bulk disordering. Furthermore, the formation of agglomerates during grinding was also occured. Surface changes of the samples using infrared spectroscopy and scanning electron microscopy methods were investigated before and after leaching. The leaching rate, specific surface area, structural disorder as well as copper extraction increased with the mechanical activation of mineral. pdf - 612 kB

S. Bockus, A. Dobrovolskis - Effect of Melting Techniques on Ductile Iron castings Properties

     The study was designed to investigate the effects of the charge, melting conditions, nodularizing and inoculation on the ductile iron castings properties. Results showed that the temperature and holding time of the melt in an induction furnace and the intensity of spheroidizing effect on the carbon and residual magnesium contents in the ductile iron castings. The same grade of ductile iron may be obtained using different chemical compositions. The castings of ductile iron will be ferritic as-cast only when large amount of pig iron in the charge and in addition some-steps inoculating treatment are used. pdf - 538 kB

A. Ševčík, J. Macurák, J. Ševčíková - High Temperature Mechanical Properties of the As-Cast Low Carbon Steels and Their Prediction

    High temperature properties of as-cast material, as reduction of area and strength, were tested in a temperature interval from 850 °C up to the melting temperature on measuring equipment provided with high frequency heating. The software for prediction of the high temperature plasticity development based on physical metallurgical and regression analyses was elaborated for the cast state of low carbon steels. The program was verified by using experimentally estimated values. pdf - 574 kB

G. Kugler, R. Turk, T. Večko-Pirtovšek, M. Terčelj - Wear Beahaviour of Nitrided Microstructures of AlSl H13 Dies for Hot Extrusion of Aluminium

    Nitriding of bearing surfaces on dies (tools, AISI H13) for hot extrusion of aluminium is technologically a very sensitive process with regard to achieving a constant quality of the nitrided layers. This study was based on the analysis of microstructure on dies with intentionally prepared deep and narrow gaps which were nitrided by various manufacturers of equipment for gas and ionic nitriding. The manufacturers chose their own nitriding parameters in order to achieve an optimal wear resistant microstructure. The microstructures obtained showed differences with regard to the presence or absence of a compound layer (white layer), its thickness and its e/g' phase ratio (XRD), nitriding depth and microhardness profile. The measured nitriding depths and the maximum microhardness values on nitrided surface layers were quite similar on dies of the same manufacturer, while for different manufacturers these values differed. Differences with regards to compound layer characteristics were also found on the same die. The die samples with these various nitrided microstructures were then laboratory tested for wear resistance using equipment that provides simulation of the tribological conditions during hot extrusion of aluminium. The wear testing results show differences in behaviour of the nitrided samples. The differences in the actual structures, microstructures, hardness, etc. explain the high level of scattering in die life in actual industrial applications. pdf - 1311 kB

    The paper deals with the classification of steel sheets for automotives industry on the basis of strength and structural characteristics. Experimental works were aimed to obtain the best possible strengthening parameters as well as work hardening and solid solution ferrite hardening, which are the result of thermal activation of interstitial carbon atoms during paint-baking of auto body. Hardening process coming from interstitial atoms is realized as two-step process. The first step is BH (bake hardening) effect achieved by interaction of interstitial atoms with dislocations. The Cottrels atmosphere is obtained. The second step of BH effect is to produced the hardening from precipitation of the carbon atoms in e-carbides, or formation of Fe₃₂C₄ carbides. WH (work hardening) effect is obtained as dislocation hardening from plastic deformations during sheet deep drawing. Experimental works were aimed at as to achieve such plastic material properties after cold rolling, annealing and skin-pass rolling, which would be able to classify the material ZStE220BH into the drawing categories at the level of DQ – DDQ. As resulting from the experimental results, the optimal treatment conditions for the maximal sum (WH+BH) = 86 MPa are as follows: total cold rolling deformation e_cold = 65 %, annealing temperature T_anneal. = 700 °C. pdf - 879 kB

M. Buršák, I. Mamuzić - The Influence of the Loading Rate on the Mechanical Properties of Drawing Steel Sheet

    The paper analyzes the influence of the loading rate in the interval from 1 to 1000 mm/min on the mechanical properties of drawing steel sheet H260LAD with the gauge of 1 mm, used for the manufacture of automotive parts, under tension and bending conditions. It describes the aspects of material characteristics under tension and bending conditions, while bending tests were made on notched specimens (a modified impact bending test). The paper presents knowledge that using a modified notch toughness test it is possible to achieve the pressability (formability) characteristics corresponding to dynamic strain rates even under the static loading. pdf - 514 kB

D. Ćubela - The Research of Technological Parameters Influence on the Process of Nitinol fabrication and Plastic Deformation

    Titanium and nickel alloy, with 48 - 55 at. % Ni (rest Ti), named Nitinol has property of thermal and mechanical memory and its properties and application depends strongly on a fabrication processes. Nitinol was produced in semi-industrial conditions. Testing results of the quality of the obtained alloy are related to technological parameters of the production and processing. The aim of this work is to give an answer to the question which technological parameters are most influential and possible for the quality control what kind of corrections regarding literature instructions are needed for successful production of Nitinol for given conditions. pdf - 1232 kB

E. Weiss, S. Majkuthová - Discounted Cash Flow (DCF) Assessment Method and its Use in Assessment of a Producer Company

    The present day theory and practice of assessment of enterprises is characterized by the existence of many different methods of assessment. One of its reasons is that the requirements for assessing of enterprises have considerably changed during the recent years. At the same time, the advancement in the science on enterprises has led to development of new assessing concepts and methods. pdf - 869 kB