Electrochemical and Spectroscopic Study of Benzotriazole Films Formed on Copper, Copper-zinc Alloys and Zinc in Chloride Solution

The formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys at open circuit potential in aerated, near neutral 0.5 M NaCl solution containing benzotriazole (BTA) was studied using potentiodynamic measurements, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The addition of benzotriazole affects the dissolution of the materials investigated. Benzotriazole, generally known as an inhibitor of copper corrosion, is also shown to be an efficient inhibitor for copper-zinc alloys and zinc metal. The effectiveness of inhibition depending on the type of materials was compared. X-ray photoelectron spectroscopic results showed that the surface layer formed on alloys in BTA-inhibited solution comprised both oxide and polymer components. The formation of Cu2O/Cu(I)-BTA on copper, mixed oxides/Zn(II)-BTA and Cu(I)-BTA on copper-zinc alloys and ZnO/Zn(II)-BTA polymer surface film on zinc provides an effective barrier against corrosion on materials investigated in chloride solution

Zasliševanje arhitekture [Interrogating Architecture]

Teresa Stoppani is an Italian architect who grew up in the Venezia-Giulia, not far from the Slovene border. After studying in Venice and Florence she continued her career of teaching and research in Great Britain. Her work is focused on architectural history, contemporary architecture and in particular on the role of critical theory in architecture today. She recently participated in the symposium On Power in Architecture, organised by the Igor Zabel Association and Mateja Kurir and held at Museum of Architecture and Design in Ljubljana, where she presented a paper on Manfredo Tafuri. Teresa has recently become Professor of Research in Architecture at London South Bank University, moving there from Leeds Beckett University. The area where London South Bank University is situated is highly typical of the processes currently underway in London and especially south of the Thames. Once a relatively destitute area of the capital, it is now quickly transforming into one of the most expensive areas of the metropolis. Foreign investors, CEOs and students often live a stone’s throw from social housing tenants unsure of how long they will still be permitted to stay and when their estates will be redeveloped by private investors. A very suitable background for our discussion on criticality, gentrification and the understanding of the role of the architect today

Nanošenje električnom iskrom za popravak alata

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined.Nanošenje električnom iskrom postupak je za navarivanje tvrdih metalnih slitina, npr. karbida i stelita, na površinu novih ili starih elemenata strojeva. U tom postupku visoka struja provodi se kroz oscilirajuću elektrodu i supstrat na vrlo kratko vrijeme. U članku opisan je postupak i određeni su debljina nanesenog sloja, kemijski sastav, stupanj miješanja i hrapavost sloja

Mechanochemical synthesis of NaNbO3, KNbO3 and K0.5Na0.5NbO3

Mechanochemical synthesis of the K0.5Na0.5NbO3 solid solution (KNN) is studied. In order to explore the mechanochemical interactions between the constituents in the Na2CO3 - K2CO3 - Nb2O5 system, NaNbO3 and KNbO3 as the boundary compositions of the KNN solid solution are also studied. It has been shown that NaNbO3 can be prepared by a single-step mechanochemical synthesis, while in the case of K2CO3 and Nb2O5, and Na2CO3, K2CO3 and Nb2O5 mixtures, only amorphisation occurs even after prolonged milling

Procjena mikrostrukture alatnog čelika za hladni rad nakon pretaljivanja pulsirajućim laserom

The aim of this study is the investigation of micro-structural behaviour of a Mat. No. 1.2379 (EN-X160CrMoV121; AISI D2) cold work tool steel after remelting with a precise pulsed Nd:YAG laser. The investigated steel is one of the most hard to weld tool steels, due to large amount of alloying elements. The analysis was done on single spots remelted with specific laser pulse shape and parameters, assuring crack-less solidification. Re-solidifi ed areas were investigated with microscopy, hardness measurements, X-ray spectroscopy and diffraction method. Laser treatment causes rapid solidification leading into a formation of a fine dendritic microstructures containing high amount of retained austenite causing a significant decrease of hardness.Namjena ove studije je ispitivanje ponašanja mikro strukture alatnoga čelika za rad na hladno Mat. No.1.2379 (ENX160CrMoV121; AISI D2) po pretaljivanju s preciznim pulsiranim Nd:YAG laserom. Zbog velike količine legirnih elemenata istraživani materijal spada u grupu vrlo teško zavarljivih alatnih čelika. Analiza je provedena na pojedinim pretaljenim točkama korištenjem specifi čnog oblika i parametara laserskog impulsa koji osiguravaju skrućivanje bez pukotina. Pretaljena područja su ispitivana mikroskopom, mjerenjem mikro tvrdoće, rendgenskom spektroskopijom i defrakcijskom metodom. Tretman laserom uzrokvao je brzo skrućivanje koja dovodi do formiranja fi ne dendritičke strukture s velikim udjelom zaostalog austenita što uzrokuje bitno smanjivanje tvrdoće

Electrospark deposition for die repair

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined

Influence of the Deep Cryogenic Treatment on AISI 52100 and AISI D3 Steel’s Corrosion Resistance

The effect of deep cryogenic treatment (DCT) on corrosion resistance of steels AISI 52100 and AISI D3 is investigated and compared with conventional heat-treated counterparts. DCT’s influence on microstructural changes is subsequently correlated to the corrosion resistance. DCT is confirmed to reduce the formation of corrosion products on steels’ surface, retard the corrosion products development and propagation. DCT reduces surface cracking, which is considered to be related to modified residual stress state of the material. DCT’s influence on each steel results from the altered microstructure and alloying element concentration that depends on steel matrix and type. This study presents DCT as an effective method for corrosion resistance alteration of steels

Lasersko reparaturno zavarivanje alata s različitim oblicima impulsa

Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.Reparaturno zavarivanje alatnih čelika za rad na hladno konvencionalnim metodama je vrlo teško zbog pukotina nastalih tokom pretaljivanja i navarivanja i općenito vrši se uz predgrijavanje. U posljednje vrijeme se kao alternativna metoda koristi reparaturno zavarivanje upotrebom laserske tehnologije. Ovaj rad predstavlja utjecaj različitih oblika impulsa na zavarivanje alatnih čelika s pulsnim laserom Nd:YAG. Reparaturno zavarivanje testirano je na alatnom čeliku AISI D2, termički obrađenim na tvrdoću 56 HRc, poslije čega je provedena analiza mikrostrukture i traženje defekata skeniranjem elektronskim mikroskopom. Rezultati testiranja sugeriraju da je moguće izvesti dobre zavare bez predgrijavanja pravilnim izborom parametara zavarivanja i odgovarajućeg oblika impulsa

Lasersko reparaturno zavarivanje alata s različitim oblicima impulsa

Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.Reparaturno zavarivanje alatnih čelika za rad na hladno konvencionalnim metodama je vrlo teško zbog pukotina nastalih tokom pretaljivanja i navarivanja i općenito vrši se uz predgrijavanje. U posljednje vrijeme se kao alternativna metoda koristi reparaturno zavarivanje upotrebom laserske tehnologije. Ovaj rad predstavlja utjecaj različitih oblika impulsa na zavarivanje alatnih čelika s pulsnim laserom Nd:YAG. Reparaturno zavarivanje testirano je na alatnom čeliku AISI D2, termički obrađenim na tvrdoću 56 HRc, poslije čega je provedena analiza mikrostrukture i traženje defekata skeniranjem elektronskim mikroskopom. Rezultati testiranja sugeriraju da je moguće izvesti dobre zavare bez predgrijavanja pravilnim izborom parametara zavarivanja i odgovarajućeg oblika impulsa