Silvana B. Dimitrijević

Temperature effect on decorative gold coatings obtained from electrolyte based on mercaptotriazole – comparison with cyanide

Abstract The aim of this work was to investigate the effect of temperature on the thickness, surface roughness, visual appearance and morphology of electrochemically deposited gold decorative coatings obtained from conventional cyanide electrolyte (AUROCIN DPB) and electrolyte based on mercaptotriazole (Au-MT). Heating of cyanide electrolyte does not significantly affect the thickness (b) of gold coatings (at 20 °C b = 0.08 μm, at 30 °C b = 0.07 μm and at 40 °C b = 0.08 μm) and, for this reason, the decorative coating processes were carried out at room temperature. Temperature increase has a positive effect on thickness of decorative gold coatings obtained from electrolyte based on mercaptotriazole, but this effect is very small, so the heating of electrolyte is not recommended for this type of electrolyte (at 20 °C b = 0.08 μm, at 40 °C b = 0.12 μm and at 60 °C b = 0.13 μm). The best coating roughness profiles are obtained at a temperature of 20 °C for both types of electrolyte. The morphology of gold deposits, obtained from both electrolytes, was studied using scanning electron microscopy.

Pt-Rh Alloys: Investigation of Creep Rate and Rupture Time at High Temperatures

Abstract The results of experimental investigation of creep rate and rupture time of the alloys of Pt-Rh system are presented in this paper. Selected alloys with 7–40 wt.-% Rh content were examined using a universal device for tensile testing of materials at high temperatures, and monitoring structure changes of the samples by electron microscopy. Investigations were performed in the temperature range between 1200°C and 1700°C at a stress between 2 MPa and 15 MPa.

Experimental Investigation of Microstructure and Phase Transitions in Ag-Cu-Zn Brazing Alloys

Microstructure and phase transitions of selected brazing alloys from the Ag-Cu-Zn ternary system were investigated. Four ternary alloys with silver content in the compositional range from 25 to 60 wt.% were studied using x-ray diffraction (XRD) and scanning electron microscopy coupled with the energy-dispersive spectroscopy (SEM–EDS). Phase transitions of the investigated alloys were measured using differential scanning calorimetry (DSC). Experimentally obtained results were compared with the results of a thermodynamic calculation of the phase equilibria according to the CALPHAD method. The experiments confirmed the optimized thermodynamic parameters for the calculations from the thermodynamic assessment in literature. Phase compositions, liquidus and solidus temperatures were confirmed by the EDS and DTA methods. Additionally, the calculated solidification paths and predicted phase transformations were in agreement with the SEM images.

Design of anti-tarnish sterling silver Ag-Cu-Zn alloy and investigation of silicon addition influence on mechanical and corrosion characteristics

This paper presents investigations of the influence of silicon addition on the mechanical and corrosion characteristics of the sterling silver Ag-Cu-Zn alloys. The procedure for obtaining Ag-Cu-Zn-Si alloys in small ranges of composition was also presented. Vickers hardness tests and three electrochemical tests were performed on the samples in this study. Open circuit potential measurements, linear polarization resistance method, and potentiodynamic polarization tests were employed to determine corrosion characteristics of the alloys. The materials were tested in 0.9% NaCl solution, artificial sweat, 0.1 and 0.01 M sodium sulfide solutions. It was shown that addition of silicone increases hardness and generally improves sulfidation resistance and corrosion characteristics in near-neutral chloride solutions of the Ag-Cu-Zn alloys.

Investigation of solidification behavior of the Sn-rich ternary Sn–Bi–Zn alloys

Solidification properties and microstructure of six as-cast Sn –Bi –Zn alloys with 80 at.% of Sn and variable contents of Bi and Zn were experimentally investigated using the scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and differential scanning calorimetry (DSC). The experimentally obtained results were compared with predicted phase equilibria according to the calculation of phase diagram (CALPHAD) method and by the Scheil solidification simulation.

Characterization of the Ag43Cu37Zn20 alloy surface after potentiostatic polarization using LDI-TOF mass spectrometry

Abstract This work is the first to demonstrate the possibilities of direct analysis of the corrosion film formed on Ag43Cu37Zn20 alloy using laser desorption/ionization (LDI) on a commercial matrix-assisted LDI time of flight mass spectrometry (MS) instrument. In the LDI mass spectra measured from the water solution of the corrosion film, the ion species Zn+, Zn(H2O)+, AgH+, Cu2H+, Cu2O(OH)+, Cu3O(OH)+ (high intensity), and Cu(OH)(H2O)+, ZnCl(OH)(H2O)+, AgCl+, CuCl+ (low intensity) were identified. The LDI mass spectra of the propan-2-ol solution of the corrosion film contains the ions Zn5Cl(OH)3(H2O)11+, Zn5Cl2(OH)8(H2O)6+, and Zn5Cl2(OH)(H2O)14+. Mass spectra were observed at laser energies in the range of 1340–1860 arbitrary units in positive ion mode. Previously, Raman spectra and X-ray diffraction (XRD) analysis of the same anodic film have shown similar results as LDI MS – that the anodic film contains the mixture of Ag, Cu2O, CuCl, Zn5Cl2(OH)8·H2O, and β-Zn(OH)Cl. LDI MS could be a complementary method for XRD and Raman, as demonstrated in this investigation. The LDI MS method greatly reduces the analysis time and amount of the sample compared to traditional methods. For this reason, the LDI MS method can be a useful tool for the fast qualitative screening of corrosion films.

Effects of recrystallization annealing on mechanical properties of cold-rolled PdNi5 wires

The aim of this investigation was to determine the influence of the recrystallization temperature and recrystallization time on the microstructure and mechanical properties of the PdNi5 alloy subjected to cold deformation in the process of rolling at a constant deformation degree. The samples of PdNi5 alloy were recrystallization annealed within the temperature range of 200-1000oC and annealing time range of 20-45 min after cold rolling with deformation degree of 97%. The tensile test was carried out using universal material testing machine. The hardness was also measured on the combined device for measuring Vickers and Brinell hardness. Metallographic observations were performed on an optical microscope. The analysis of the results of investigations regarding the microstructural changes and corresponding mechanical properties of cold-rolled PdNi5 strips shows that annealing temperature of 500oC was sufficient to activate the energy for various recrystallization processes causing a change in the mechanical properties of cold-rolled PdNi5 strips. The annealing time, at constant annealing temperature, almost did not affect a recrystallization temperature and the mechanical properties of the cold-rolled PdNi5 strips.

Microhardness of decorative gold coatings obtained from gold complex based on mercaptotriazole: Comparison with cyanide

Abstract The aim of this work was to investigate the effects of current density, temperature, pH and concentration of ethylhexilsulfonate additive on the microhardness of electrochemically deposited gold decorative coatings obtained from a conventional cyanide electrolyte and gold complex based on mercaptotriazole. Mechanically and chemically prepared brass samples were first nickeled from acidic electrolyte. Nickel was a substrate deposit, and then decorative gold coatings were deposited from two types of electrolytes at different current densities and temperatures. Decorative gold coatings were deposited from auri-mercaptotrizole at different pH values and from electrolyte with and without the ethylhexilsulfonate additive. The microhardness of the gold coating was measured using the Knoop method. The highest values of microhardness were obtained at a current density of 1 A dm−2 at room temperature for both electrolytes. The microhardness of the gold coatings from cyanide electrolytes was HK = 740 MPa, and the coatings obtained from auri-mercaptotriazole HK = 660 MPa. This difference is not relevant for decorative purposes. The highest values of microhardness, HK = 660 MPa, were obtained at pH = 9 from the gold complex based on mercaptotriazole without the additive.

The influence of novel organic gold complex on photoresist layers of printed circuit boards

The goal of this paper was to study the influence of organic gold complex based on mercaptotriazole on photoresist layers used in manufacturing of printed circuit boards (PCBs). Investigations were performed by immersion the previously prepared boards in electrolytes with different pH values (pH=2, 4, 7, 9 and 12) at gold concentration of 2.5 g/dm3 and in gold complexes with different gold concentrations (1.5; 2.0; 2.5; 3.0 and 3.5 g/dm3) at pH value of pH=9. Investigations showed that photoresist layers on boards are the most resistant at optimal operating conditions, pH=9 and concentration of gold of 2.5 g/dm3.