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The results of investigations of electrical breakdown mechanisms, and their influences on the time delay distributions are presented. The investigations are performed by analyzing the density distributions and probability plots of experimentally obtained time delay distributions for different relaxation times and overvoltages in gas tube filled with neon at 10 3 Pa (10 mbar). The time delay density distributions are fitted with Gaussian distributions for relaxation time smaller than 15 ms and exponential distributions for relaxation time greater than 150 ms, while in the region of relaxation time between 15ms and 150 ms with the Weibull distribution. Index Terms -Electrical breakdown, time delay density distributions, probability plots, electrical breakdown, neon. 202 Č. A. Maluckov and S. A. Mladenović: Breakdown in Low Pressure Ne Gas: Mechanisms and Statistical Analysis of Time Delay

This paper presents the investigation results of the electrochemical behavior of copper in 1 M Na2CO3 solution in the presence of potassium ethyl xanthate (KEtX) with different concentrations. Tests were conducted on copper samples obtained without deformation and with deformation of 83, 91 and 99 %. Samples were obtained by cold drawing of wire, which was previously obtained by dip-forming procedure. Corrosion behavior of cold deformed copper wire is characterized by its open circuit potential and behavior during anodic polarization. Experiments were carried out in aqueous solution 1 M Na2CO3 with added various amounts of KEtX between 0.008 g/l and 0.15 g/l. It was experimentally proved that the degree of deformation between 83 and 99 % does not have a large effect on the open circuit potential, as well as on the behavior of copper during anodic polarization in 1 M Na2CO3. Voltammograms show no significant differences between peak heights obtained for different electrodes. The first peak which occurs at potential of around -0.06 V vs. SCE corresponds to the formation of copper oxide Cu2O. The second wide peak is at potential of around 0.15 V vs. SCE and corresponds to the formation of CuO. Addition of potassium ethyl xanthate in alkaline 1 M Na2CO3 solution changes the mechanism of the process in anodic part, which is reflected in the change of shape of voltammograms. In presence of KEtX in concentration between 0.008 g/l and 0.15 g/l on voltammograms a sharp peak appears at potential of about -0.2 V vs. SCE and corresponds to the oxidation of xanthate. Current density, which determines the rate of the process which takes place at the electrode surface, yet in the presence of smallest amounts of KEtX (<0,08 g/l) is higher than in the absence of KEtX. It allows one to conclude that the processes of oxidation of copper accelerate in presence of potassium ethyl xanthate.

Research on the lead-free solders has attracted wide attention, mostly as the result of the implementation of the Directive on the Restriction of the Use of Hazardous Substances in Electrical and Electronic Equipment. The Sn-Zn solder alloys have been considered to be one of the most attractive lead-free solders due to its ability to easily replace Sn-Pb eutectic alloy without increasing the soldering temperature. Furthermore, the mechanical properties are comparable or even superior to those of Sn-Pb solder. However, other problems still persist. The solution to overcoming these drawbacks is to add a small amount of alloying elements (Bi, Ag, Cr, Cu, and Sb) to the Sn-Zn alloys. Microstructure, tensile strength, and hardness of the selected Sn-Zn-Bi ternary alloys have been investigated in this study. The SEM-EDS was used for the identification of co-existing phases in the samples. The specimens’ microstructures are composed of three phases: Sn-rich solid solution as the matrix, Bi-phase and Zn-rich phase. The Bi precipitates are formed around the Sn-dendrit grains as well as around the Zn-rich phase. The amount of Bi segregation increases with the increase of Bi content. The Sn-Zn-Bi alloys exhibit the high tensile strength and hardness, but the values of these mechanical properties decrease with the increase of Bi content, as well as the reduction of Zn content. The results presented in this paper may offer further knowledge of the effects various parameters have on the properties of lead-free Sn-Zn-Bi solders

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