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Charpy toughness and microstructure of vibrated weld metal
Bogdan Pučko, Vladimir Gliha, 2006, izvirni znanstveni članek

Opis: Vibration during welding can be used to obtain certain changes in mechanical properties of weld metal. Research work on the influence of vibration on the secondary microstructure of welds and hence on the Charpy toughness was performed. Vibration during welding exhibits positive effects on the microstructure constituent formation. Multipass welding was simulated with reheating of the original single pass weld in order to obtain similar microstructure to multipass welds. Microstructures were examined with an optical microscope. Additionally, fractographic examination of the rupture of Charpy specimens was performed. Changes in the microstructure according to vibration were observed which affect toughness of the weld metal. Vibration during welding was rated more effective in the case of reheating the weld metal, which is the case in multipass welding.
Ključne besede: welding, welded joints, mechanical properties of metals, ferrite, vibration, microstructure, toughness, notched bar testing, weld metal
Objavljeno: 31.05.2012; Ogledov: 1427; Prenosov: 66
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Optical properties of plastically deformed copper
J. Trajić, Rebeka Rudolf, Ivan Anžel, M. Romčević, N. Lazarević, M. Mirić, Z. Lazarević, B. Hadžić, Nebojša Romčević, 2010, objavljeni znanstveni prispevek na konferenci

Opis: Pure copper (99.99), prepared in the sample of square cross-section (10 x 10 mm2) and length about 50 mm, was extremely plastically deformed with the repeated application of Equal Channel Angular Pressing (ECAP). ECAP was applied as an effective technique for producing bulk nano-scaled structures. Optical properties of the sample were investigated using Raman spectroscopy. Two types of lines: narrow (with width of 7 cm¡1) and wide ( 40 cm¡1) are registered. Existence of two types of lines indicates that in the specimen exists nano-sized crystal structures of both Cu and CuO related with three dimensional amorphous boundary spaces, which indicates that plastic deformation of the sample did not lead to total amorphisation of the specimen.
Ključne besede: plastically deformed copper, hydrometallurgical extraction of metals
Objavljeno: 31.05.2012; Ogledov: 1102; Prenosov: 58
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Ellipsometric measurements of plastically deformed copper
M. Mirić, Rebeka Rudolf, Ivan Anžel, B. Hadžić, M. Romčević, J. Trajić, Nebojša Romčević, 2009, objavljeni znanstveni prispevek na konferenci

Opis: Chemically pure copper (99.99) prepared in the sample of square cross-section (10 x 10 mm2) and length about 50 mm was extremely plastically deformed with the repeated application of equal channel angular pressing. Equal channel angular pressing was applied as an effective technique for producing bulk nanoscaled structures. It is well known that severe plastic deformation of metallic materials often leads to microstructure with ultrafine grains and cross-sections which remain about equal before and after deformation. Optical properties of the sample were studied using spectroscopic ellipsometry in UV-VIS range. The parameters of the sample like copper oxide and surface roughness overlayer were calculated using two-film model together with the Bruggeman effective medium approximation.
Ključne besede: hydrometallurgical extraction of metals, copper
Objavljeno: 31.05.2012; Ogledov: 947; Prenosov: 75
URL Povezava na celotno besedilo

Protection of copper and its alloys using corrosion inhibitor-literature review
Milorad V. Tomić, Miomir Pavlović, Milovan Jotanović, Regina Fuchs-Godec, 2010, izvirni znanstveni članek

Opis: A review of the literature dealing with the electrochemical corrosion of copper and its alloys with purpose to find the most suitable inhibitor for its protection has been done. According to their chemical composition of corrosion inhibitors are divided into inorganic and organic inhibitors. Inhibition of alloying metals are possible (such as the addition of arsenic alloy components in brass, preventing its unzincanization). The paper reviews the theoretical basis of application of inhibitors to protect metals from corrosion as well as an overview of current research application of inhibitorsto protect copper and copper alloys. Benzotriazole (BTA) is most often used corrosion inhibitor for copper and its alloys in acidic and alkaline solution, because of its high inhibition efficiency. The lowest concentration of inhibitor for protection of copper in various solutions was 0.05%, and for the protection of copper in contact with steel is 0.1%. On the surface of copper and brass BTA forms a protective Cu-BTA film. However, BTA is like many other synthesized organic inhibitors is very toxic and if used invery small concentrations. It turnedout that the AETD, AETDA and PTAT good corrosion inhibitors of copper mixed type with the efficiency of inhibition increases with concentration. Due to the adverse effects on the environment, health and other bodies in recent times the focus of researchis transferred to the inhibiting action of biological molecules or mixtures of natural compounds called "Green inhibitors".
Ključne besede: corrosion inhibitors, protection of metals, inorganic inhibitors, organic inhibitors, alloys elements, green inhibitors
Objavljeno: 31.05.2012; Ogledov: 1361; Prenosov: 67
URL Povezava na celotno besedilo

Sensing heavy metals using mesoporous-based optical chemical sensors
Špela Korent Urek, Nina Frančič, Matejka Turel, Aleksandra Lobnik, 2013, pregledni znanstveni članek

Opis: Heavymetal pollution is one of the more serious environmental problems; therefore, there is a constant demand for the development of new analytical tools for its monitoring. An optical chemical sensor represents a good alternative to classical instrumental methods.The mesoporous materials used in optical chemical sensorsʼ fabrications have properties such as high porosity, exceptional adsorption capacity, tuneable 3D shape, geometry, and morphology, which enable improved limit of detection, response time, and selectivity properties of optical sensors. In this review, we firstly present the properties of mesoporous materials, provide a brief description of sensing mechanisms, and briefly discuss the importance of continuous monitoring. Recent advances in those mesoporous silica-based optical sensors used for heavy metal detection have been reported and their advantages and limitations also discussed. This review covers publications that have appeared since 2008.
Ključne besede: heavy metals, magnetic properties, structural properties, heavy metal pollution
Objavljeno: 14.06.2017; Ogledov: 644; Prenosov: 161
.pdf Celotno besedilo (3,19 MB)
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Synthesis and structure of transition metal bisalkinylselenolato complexes
Rudolf Pietschnig, Carmen Moser, Stefan Spirk, Sven Schäfer, 2005, objavljeni znanstveni prispevek na konferenci

Opis: We synthesized closely related cis and trans platinum complexes of SeCC-n-C5H11 and elucidated their structures in solution and the crystalline state. In line with previous work we find exclusive coordination of the selenium atom of the ambident alkynylselenolate ligand and a preference for the obviously more stable trans isomer. In contrast to previous work we find auniform increase of all metal ligand bond lengths in the cis vs. the trans isomers. Moreover we studied the coordination of alkynykselenolate ligands to group 4 metals.
Ključne besede: analytical chemistry, isomers, stability, metals
Objavljeno: 22.06.2017; Ogledov: 255; Prenosov: 163
.pdf Celotno besedilo (614,73 KB)
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Determination of microstructural changes by severely plastically deformed copper-aluminum alloy
Nebojša Romčević, M. Gilić, Ivan Anžel, Rebeka Rudolf, Miodrag Mitrić, M. Romčević, B. Hadžić, D. Joksimović, Milica Petrović Damjanović, Matija Kos, 2014, izvirni znanstveni članek

Opis: Our work deals with the problem of producing a complex metal-ceramic composite using the processes of internal oxidation (IO) and severe plastic deformation. For this purpose, Cu-Al alloy with 0.4wt.% of Al was used. IO of sample serves in the first step of the processing as a means for attaining a fine dispersion of nanosized oxide particles in the metal matrix. Production technology continues with repeated application of severe plastic deformation (SPD) of the resulting metal matrix composite to produce the bulk nanoscaled structural material. SPD was carried out with equal channel angular pressing (ECAP), which allowed that the material could be subjected to an intense plastic strain through simple shear. Microstructural characteristics of one phase and multiphase material was studied on internally oxidized Cu with 0.4wt.% of Al sample composed of one phase copper-aluminum solid solution in the core and fine dispersed oxide particles in the same matrix in the mantle region. In this manner AFM, X-ray diffraction and Raman spectroscopy were used. Local structures in plastically deformed samples reflect presence of $Cu$, $CuO$, $Cu_2O$, $Cu_4O_3$ or $Al_2O_3$ structural characteristics, depending on type of sample.
Ključne besede: metals, oxides, atomic force microscopy, Raman spectroscopy, microstructure
Objavljeno: 08.08.2017; Ogledov: 348; Prenosov: 61
.pdf Celotno besedilo (596,63 KB)
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