ZAŠTITA MATERIJALA 2011 52(3) 145-151 Scientific paper [PDF]
A. HRUSSANOVA*, I. KRASTEV*, A. ZIELONKA**
*“Rostislav Kaischew” Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
** Institute of Precious Metals and Metal Chemistry, 73525 Schwäbisch Gmünd, Germany
Effect of electrolyte composition on the electrodeposition of Cu-Sb alloys from methanesulfonate-tartrate electrolytes
Abstract: The electrochemical processes of deposition and dissolution of Cu and Sb separately or together from acid methanesulfonate-tartrate electrolytes are investigated by cyclic voltammetric technique. The influence of different parameters of the electrodeposition process, such as current density, temperature, electrolyte composition and acidity on the antimony content, phase composition and morphology of the coatings is shown. The increase in current density leads to an increase in the antimony content in the alloy, as well as to an increase in the deposition rate of the alloy. The antimony content decreases with the rise in temperature, as expected. The increase in D(-)-tartaric acid concentration in the electrolyte leads to a slight increase in antimony content. The possibility of deposition of compact bright Cu-Sb coatings with up to 52 wt.% Sb and compressive internal stress from the investigated electrolytes is shown. At high antimony content the deposition of multiphase heterogeneous coatings with ordered spatial distribution of the different alloy phases on the cathodic surface can be observed. The phenomena and the observed structures are very similar to those observed during electrodeposition of some other silver alloys, such as Ag-Sn, Ag-Sb, Ag-Bi and Ag-In.
ZAŠTITA MATERIJALA 2011 52(3) 153-158 Scientific paper [PDF]
U. Č. LAČNJEVAC, V. D. JOVIĆ, B. M. JOVIĆ
Institute for Multidisciplinary Research, Kneza Višeslava 1a, 11030 Belgrade, Serbia
Electrodeposition and characterization of Ni–Sn alloy coatings as cathode material for hydrogen evolution reaction in alkaline solutions
NEBOJŠA D. NIKOLIĆ1, GORAN BRANKOVIĆ2, MIOMIR G. PAVLOVIĆ1
1ICTM – Institute of Electrochemistry, University of Belgrade, Njegoševa 12, Belgrade, Serbia
2Institute for Multidisciplinary Research, Kneza Višeslava 1a, Belgrade, Serbia
Comparison of morphology of powder particles obtained by the constant and periodically changing regimes of electrolysis
Abstract: Morphologies of copper powder particles obtained by both potentiostatic and pulsating overpotential (PO) regimes of electrolysis were analyzed using the technique of scanning electron microscopy (SEM). The parameters of square waves PO were selected to enable a comparison of the obtained particles with those obtained in the potentiostatic regime from solutions of different CuSO4 and H2SO4 concentrations. It is shown that more solutions of different CuSO4 and H2SO4 concentrations can be replaced by the one solution if the appropriate PC parameters are applied, what can be of high technological significance.
ZAŠTITA MATERIJALA 2011 52(3) 163-172 Scientific paper [PDF]
S. RAJENDRAN1,2, V. SRIBHARATHY1, A. KRISHNAVENI3, J. JEYASUNDARI4, J. SATHIYABAMA1, T.S. MUTHUMEGALA1, M. MANIVANNAN5
1Corrosion Research Centre, GTN Arts College, Dindigul – 624 005, India
2Department of Physical Sciences, Servite College of Education for Women, Thogaimalai – 621 313, India
3Department of Che-mistry, Yadava College, Madurai, India
4Department of Chemistry, SVN College, Madurai, India
5Department of Chemistry, Chettinad College of Engineering, Karur, India
Inhibition effect of self assembled films formed by adipic acid molecules on carbon steel surface
Abstract: Well-ordered SAMs using adipic acid were formed on the oxide of iron carbon steel surface by immersion method. This leads to ordered, robust monolayers bound to the surface in a tetra dentate manner. Monolayer formation takes place when carbon steel is immersed in an aqueous solution containing 60 ppm of Cl– and 50 ppm of adipic acid for 5 minutes, and rinsing the physisorbed molecules in distilled water and heating in a hot air oven. The adipic acid monolayers on iron oxide steel carbon can withstand rinsing with water, concentrated acid and base exposure. Additionally, these monolayers are stable over the course of at least one week. The formation of monolayers were confirmed by AFM study and FTIR spectra. The SAMs were tested by polarization and EIS electrochemical analysis. The results of this study show that adipic acid monolayers adsorbed on metal surface can reduce electrochemical activity on the surface, often the first step in corrosion.
ZAŠTITA MATERIJALA 2011 52(3) 173-180 Scientific paper[PDF]
NADEŽDA M. TALIJAN
Electrical contact materials based on silver
Abstract: Composite electrical contact materials based on silver and oxides of different metals have been used for many years in different types of electrical devices for making and breaking of electrical circuit. Ag-CdO materials have been most commonly used over the years as the materials for electrical contacts and other electrical components due to their excellent electrical and mechanical properties, mainly for small and medium-current loads. Recent investigations have led to the development and implementation of new environmentally friendly electrical contact materials in which the toxic CdO is replaced by less harmful metal oxides, while maintaining the good final properties. It was found that the Ag-SnO2 composite material meets most of the required properties. Results of experimental investigations of different technological procedures for obtaining various types of silver based electrical contact materials are presented in this paper through defined technological phases with optimized process parameters. The structural, mechanical and electrical characteristics of the investigated and realized contact materials are presented as well. The examples of materials applications are given and illustrated.
ZAŠTITA MATERIJALA 2011 52(3) 181-188 Scientific paper [PDF]
M.V. TOMIĆ1, LJ.J. PAVLOVIĆ2, M.G. PAVLOVIĆ1, V. MIĆIĆ1, B. ĐUKIĆ1
1University of Eastern Sarajevo, Faculty of Technology Zvornik, Republic of Srpska
2Univesrity of Belgrade, ICTM – Centre for Electrochemistry, Belgrade, Serbia
Catalytic effect of sulphuric acid in the process of deposition of chromium coatings
Abstract: This paper analyzes the catalytic effect of sulphuric acid on current efficiency, the coating thickness and the rate of deposition of electrochemical chromium coatings. According to the properties of chrome, there are three types of chrome coatings: decorative, hard and porous. The quantitative composition of baths and working conditions are the factors which determine which type of a coating will be obtained. The cathodes are made of copper electrolitical plates (99.99%), which are submitted to mechanical smoothing and chemical preparation. Electrochemical chromium coatings were deposited galvanostaticaly from bath I (250 g/dm3 CrO3 + 2.0 g/dm3 H2SO4), are then deposited on the cathodes prepared in this way, also from bath II (250 g/dm3 CrO3 + 2.5 g/dm3 H2SO4), and from bath III (250 g/dm3 CrO3 + 3.0 g/dm3 H2SO4), at current densities of 10 A/dm2, 15 A/dm2 and 30 A/dm2. Deposition was performed for 5, 10 and 15 minutes intervals in all three baths and for all three current densities. The difference in samples mass before and after electrochemical deposition was measured on the analytical scale. Cathodic current efficiency, the coating thickness and deposition rate increase with the increase of acid concentration, current density and deposition time. The average deposition rates are approximately the same for baths II and III, for the same deposition time, at the same current densities. This shows that the increase of the concentration of sulphuric acid above 2.5 g/dm3 is not justifiable. The ratio of these parametres, according to the quantity of the sulphuric acid used is the best for bath II, which makes deposition of electrochemical chrome coatings from this bath most profitable, from the aspect of current efficiency, deposition rate, coatings quality and chemicals consumption of bath.
ZAŠTITA MATERIJALA 2011 52(3) 189-193 Scientific paper [PDF]
ZORICA LOPIČIĆ1, MIRJANA STOJANOVIĆ1, ČASLAV LAČNJEVAC2, JELENA MILOJKOVIĆ1, MARIJA MIHAJLOVIĆ1, TATJANA ŠOŠTARIĆ1
1Institute for Technology of Nuclear and Other Mineral raw materials, 86 F. d’Esperey St., Belgrade, Serbia
2University of Belgrade, Faculty of Agriculture, 6 Nemanjina St., Belgrade, Serbia
The copper biosorption using unmodified agricultural waste materials
Abstract: The rapid increase in global industrial activities has lead to the serious environmental pollution that requires systematic and sustainable approach in order to protect environment and biodiversity. Special concern is accented on heavy metal pollution because of their high toxicity, persistence and bioaccumulation tendency. The conventional methods for their removing are often either too expensive or create a large quantities of toxic sludge, so the other technologies, cheaper and more effective should be employed. Biosorption is one of the recently employed promising technologies that use biomaterials as sorbents for different type of pollution. Thanks to their active surface groups, biosorbents pose wider operational spectrum than mono functional ion exchangers. Agricultural waste materials have proved to be highly efficient, low cost and renewable source of biomass that can be exploited for heavy metal remediation, which leads to increase of their life cycle and also solve their disposal problem. The purpose of this paper is investigation of possible application of wasted untreated biomass from ”Vino Župa” Company as potential biosorbent that can be used for copper removal from water solutions. For this purpose, several type of biomass have been examined and the preliminary results presented in this paper have showed that this wasted untreated materials can bee used as promising and cheap adsorbents for copper removal from water solutions, but also that further physical and chemical modifications should be done in order to increase their biosorption capacity.
ZAŠTITA MATERIJALA 2011 52(3) 195-200 Originalni naučni rad [PDF]
MUSTAFA MEMIĆ, RANKA LUČIĆ
Univerzitet u Sarajevu, Prirodnomatematički fakultet, Sarajevo, BiH
Određivanje fosfora u čelicima, indirektno, mjerenjem koncentracije bizmuta odnosno molibdena u bizmut fosfomolibdatnom kompleksu metodom AAS
Izvod: Pored poželjnih elemenata u čeliku se u većim ili manjim količinama nalaze i nepoželjani elementi kakav je fosfor. Pri sadržaju fosfora od 0,2 % i na niskim temperaturama žilavost čelika praktično pada na nulu. Iz tih razloga poznavanje sadržaja fosfora u čeliku je od izuzetne važnosti. Fosfor u čelicima najčešće je određivan spektrofotometrijski kao fosfomolibdat u redukovanom ili neredukovanom obliku. Iako je puno korištena, ova metoda ima svojih nedostataka, tako da se nastoji iznaći nove metode za određivanje fosfora u čeliku. AAS se nameće kao dobro rješenje, međutim direktna metoda ne može biti primjenjena za određivanje fosfora, zbog rezonantnih linija koje se nalaze u UV području na talasnim dužinama: 177,5; 178,3 i 178,8 nm. U ovom radu, za određivanje fosfora razvijena je indirektna metoda-AAS, bazirana na formiranju bizmut-fosfomolibdatnog kompleksa, i njegovoj ekstrakciji sa metil-izobutil ketonom. Bizmut, odnosno molibden koji se u ovom kompleksu nalaze u poznatom stehiometrijskom odnosu sa fosforom određivani su AAS.
ZAŠTITA MATERIJALA 2011 52(3) 201-206 Originalni naučni rad [PDF]
VESNA ALAR, IVAN STOJANVIĆ, IVANA MIHALIC
Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, Zagreb, Hrvatska
Zaštita ugljičnog čelika vodorazrjedivim premazima
ZAŠTITA MATERIJALA 2011 52(3) 207-212 Stručni rad [PDF]
ŽELJKO STOJANOVIĆ , MILAN TOPLIČEVIĆ
Tehnički fakultet »Mihailo Pupin«, Đure Đakovića bb, Zrenjanin
Razvoj i primena postupka boriranja u funkciji produženja radnog veka mašinskih delova
Izvod: Autori su u radu pokušali da sistematizuju znanja i prikažu važnost upotrebe boriranja kao termodifuzionog postupka na uvećanje veka trajanja mašinskih elemenata, u zavisnosti od konstrukcije, odnosno tipa i radnih uslova. U radu su opisane osnovne zakonitosti za postupak boriranja koji se primenjuje prvenstveno u cilju povećanja otpornosti prema abrazivnom mehanizmu trošenja. Pored napred navedenog, autori su ukazali na sadašnje stanje i perspektive razvoja postupka boriranja, navodeći pri tom karakteristične primere njegove primene na sadašnjem nivou znanja. Autori su takođe ukazali na veliku razliku između naučnog istraživanja i industrijske prakse, što je posebno izraženo u inostranstvu, gde se radi toga organizovano podupiru i iniciraju projekti dopunskog obrazovanja o razvoju inženjerstva površina. Time se podupire primena, ne samo boriranja, već i ostalih postupaka modifikovanja, čijom se upotrebom postižu višestruka povećanja postojanosti i trajnosti metalnih mašinskih elemenata, što doprinosi značajnom povećanju kvaliteta tretiranog dela i ekonomičnosti proizvodnje. Dobijeni rezultati ukazuju na celishodnost proizvodnje boriranih elemenata, koji nisu jako dinamički napregnuti i koji tokom rada ne trpe naprezanje na istezanje, za primenu u uslovima koji zahtevaju ekstremnu otpornost na habanje.
ZAŠTITA MATERIJALA 2011 52(3) 213-217 Stručni rad [PDF]
IVAN KRSTIC1, M. STANISAVLJEVIC2, V. LAZAREVIC3, LJ. TAKIC4
1Fakultet zaštite na radu u Nišu
2Visoka tehnička škola strukovnih studija Požarevac
3Zavod za preventivnu medicinsku zaštitu u Nišu
4Tehnološki fakultet u Leskovcu
Redizajniranje tretmana otpadnih voda tehnološkog procesa galvanizacije
Izvod: Tehnološki proces galvanizacije, prema kvalitativno-kvantitativnim karakteristikama, predstavlja jedan od najkompleksnijih zagađivača otpadnih voda. Veliki broj zagađujućih materija (joni metala, cijanidi, kiseline, baze, masti i ulja, organski rastvarači, površinski aktivne materije, fosfati i dr.), koji se nalaze u galvanskim otpadnim vodama, prečišćavaju se konvencionalnim metodama (hemijska oksidacija i redukcija, neutralizacija, taloženje, koagulacija i flokulacija). Uvođenje nekonvencional-nih sistema za prečišćavanje otpadnih voda (elektohemijska oksidacija i redukcija, jonska izmena, kao i membranski procesi, reverzna osmoza, ultrafiltracija i elektrodijaliza) osnovni je preduslov za re-dizajn tehnološkog sistema, a sve u cilju ostvarivanja apsolutnih tehnologija. To podrazumeva de-toksikaciju cijanida, regeneraciju teških metala i njihovo vraćanje u tehnološki proces proizvodnje i recirkulaciju vode koja se ponovo koristi za ispiranje metalnih delova u galvanizaciji.
