Physics

The contact angle (Θ) of molten Sn and Sn-Ag alloys (0.5, 1.5, 3.5, 6 wt.% Ag) on Cu substrates have been studied by using sessile drop method at various temperatures (230, 250, 275 and 300 • C). Experimental results showed that additions of Ag to Sn resulted in a continuous decrease in the Θ up to 3.5 wt.% above which the Θ value was increased. Increasing alloy temperature also decreased the Θ proportionally. Experimental results revealed that a correlation between the Θ, alloy composition and the alloy temperature exists which yielded an empirical model to predict the Θ at a given Ag content and temperature for a given Sn-Ag alloy. The empirical model predicts the Θ reasonably well with the present work and the other published works.

In this work, the radionuclide activity concentrations of 226 Ra, 232 Th and 40 K in surface soils and radon levels in dwellings of Karabük, Turkey were determined in order to evaluate the environmental radioactivity. Concentrations of 226 Ra, 232 Th and 40 K radionuclides were determined using gamma spectrometry with using HPGe detector. The etch track detectors (CR-39) were used to determine the distribution of radon concentrations. The average activity concentrations for 226 Ra, 232 Th and 40 K were found as 21.0, 23.5 and 363.5 Bq kg-1 , respectively. The calculated average annual effective dose equivalent from the outdoor terrestrial gamma radiation from 226 Ra, 232 Th and 40 K is 53.5 lSv y-1. The average radon concentration and annual effective dose equivalent of 222 Rn in Karabük dwellings were obtained 131.6 Bqm-3 and 3.32 mSv y-1 , respectively. The evaluated data were compared with the data obtained from different countries.

Radon concentration for the summer seasons of 2020 was measured in 12 buildings of Karabük University / Karabük governorate / Turkey using the passive technique. Solid state nuclear track detectors (CR-39) were used for calculating the track of alpha particles emitted from the decay of radon. The results of 222 Rn concentration for ground and underground showed that the lowest value was 8.547 Bq/m 3 in Literature Faculty (LF) building, and the highest value was 83.498 Bq/m 3 in Foreign Language High School (LHS) building. All radon concentrations are within the acceptable concentrations for natural exposure by International Committee of Radiation Protection [ICRP, 2009]. Annual effective dose (AED), lung cancer cases per year per million person (CPPP), potential alpha energy concentration (PAEC), the dose rate for soft tissues, the dose rate for the lungs and the effective dose equivalent rate have a range of 0.216-2.107 mSv/y, 0.634x10-2-6.19x10-2 per million person, 1.04-10.155 mWL, 0.043-0.417 nGy/h, 0.342-3.340 nGy/h and 1.538-15.030 nGy/h respectively, which are all below the recommended limits by the international agencies [UNSCEAR & ICRP].

This work investigates the effect of bismuth (Bi) addition, 1 wt% Bi, on wettability of the Sn-3.0Ag-0.5Cu (SAC305) ternary Pb-free solder alloy. Adding Bi to SAC305 decreased the contact angles (h) of the Sn-2.0Ag-0.5Cu-1.0Bi (SAC-1Bi) quaternary Pb-free solder alloy, which were measured by using of the sessile drop method at various temperatures (250, 280 and 310°C) on Cu substrate in argon (Ar) atmosphere. Microstructures, inter-metallic phases and melting temperatures were analyzed by optical microscope, scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry, and effects of the amount of Bi on microstructure were investigated. The experimental results exhibited that when the addition of Bi was 1 wt%, changing in melting temperature of SAC-1Bi solder was insignificant, but the wetting angles (h) of the solder alloy decreased which were measured by using of the sessile drop method at various temperatures. The lowest h was obtained as 35.6°for SAC-1Bi alloy at 310°C.

The improvement in the hardness of Sn-3.0Ag-0.5Cu solder alloy reinforced with 1.0 wt. % TiO2 nanoparticles was evaluated by nanoindentation. A specific indentation array was performed on four different horizontal cross sections of the composite solder with different heights and diameters, in order to verify the mixing homogeneity of TiO2 nanoparticles within the Sn-3.0Ag-0.5Cu solder paste during the ball milling process. The phase analysis indicated successful blending of the Sn-3.0Ag-0.5Cu with the TiO2 nanoparticles. According the scanning electron microscopy micrographs, presence of the TiO2 nanoparticles reduced the size of the Cu6Sn5 and Ag3Sn intermetallic compound phases. Incorporation of the 1.0 wt. % TiO2 nanoparticles improved the hardness values up to 26.2 % than that of pure SAC305. The hardness values increased gradually from the top cross sections towards adjacent to the solder/substrate interface. The mechanism of the hardness improvement attained by the TiO2 nanoparticles addition were also investigated on the horizontal cross sections of the samples.

Purpose This paper aims to invastigate of the wetting and interfacial properties of Sn-(3-x)Ag-0.5Cu-(x)Bi (x = 0.5, 1 and 2 in Wt.%) Pb-free solder alloys at various temperatures ( 250, 280 and 310°C) on Cu substrate in Ar atmosphere. Design/methodology/approach In this study, new Sn-(3-x)Ag-0.5Cu-xBi systems, low Ag content quaternary lead-free solder alloys, were produced by adding 0.5, 1 and 2% Bi to the near-eutectic SAC305 alloy. The wetting angles of three new alloys, Sn-2.5Ag-0.5Cu-0.5 Bi(SAC-0.5 Bi), Sn-2Ag-0.5Cu-1Bi(SAC-1Bi) and Sn-1Ag-0.5Cu-2Bi(SAC-2Bi) were measured by sessile drop technique on the Cu substrate in argon atmosphere. Findings In accordance with the interfacial analyses, intermetallic compounds of Cu3Sn, Cu6Sn5, and Ag3Sn were detected at the SAC-Bi/Cu interface. The results of wetting tests show that the addition of 1 Wt.% Bi improves the wetting properties of the Sn-3Ag-0.5Cu solder. The lowest wetting angle (θ) was obtained as 35,34° for Sn-2Ag-0.5Cu-1Bi...

This study reports the investigation on indium addition into Sn-3Ag-0.5Cu (SAC305) ternary Pb-free solder alloy to evole its varied performances. The effects of indium addition on wettability of the solder alloy was studied. The experimental results exhibited that when the addition of indium was 1.0 wt.%, the change in melting temperature of Sn-2Ag-0.5Cu-1In (SAC-1In) solder was negligible, but the contact angles (θ) of the solder alloy decreased which were measured by using of the sessile drop method at various temperatures (250, 280 and 310 °C) on Cu substrate in Ar atmosphere. Inter-metallic phases, microstructures, and melting temperatures of alloy was characterized by X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM + EDX), and differential scanning calorimeter (DSC), and effects of the amount of In on microstructure were investigated. The lowest θ was obtained as 35,55° at 310 °C. The formation of intermetallic compounds (IMC's) between the Pb-free solder alloy and the Cu substrate was observed. As a result, the studies show that the wetting capability of Sn-2Ag-0.5Cu-1In quaternary solder alloy is better than Sn-3Ag-0.5Cu ternary alloy.

The aim of this study is to investigate the corrosion behavior of potentiodynamic polarization indium added Sn-3Ag-0.5Cu alloy in 1M HCl solution. SEM and EDX analyses were examined the properties of the alloy samples. Polarization analyses showed by the addition of 0.5, 1, and 2 wt.% indium to the SAC305 solder alloy does not lead to notably different corrosion potentials. The pseudo-passivation region is observed instead of a true passivation region that currents are nearly constant. By the scanning interval, this pseudo-passive region does not have a reactivation point. On the other hand, corrosion rates follow a pattern in which 0.5% wt of indium substitution of silver causes the corrosion rate to decrease. However, with further silver replacement by indium, the rate of corrosion increases. According to the results of microstructure analysis, the formation of corrosion products and the existence of voids and porous structures limit their stability.

In this work, the effect of Cu content on the microstructures, mechanical properties and electrical conductivity of Nb-V added microalloyed powder metallurgy (PM) steels were investigated. Microalloyed steel samples were pressed at 750 MPa and sintered at 1400 o C in argon atmosphere for 1 h. The grain size and phase distribution of the microalloy steels were determined by optical microscope. The precipitates and fracture surface of samples were analyzed with the help of SEM and EDS analyses. Tensile test, hardness test and electrical conductivity measurement were carried out for the Nb-V added microalloyed steel with different Cu content. Results indicated that 10 wt.% Cu added PM microalloyed steel showed the highest values in yield strength (YS) and ultimate tensile strength (UTS). However, when the amount of Cu content increased from 10 to 15 wt.%, YS and UTS decreased. Elongation also tends to decrease with increasing Cu content. Although the electrical conductivity in general increased with the addition of Cu, a decrease in some conductivity was observed in the addition of 15 wt.% Cu.

In the present study, wetting behaviors of Sn-9Zn-xAl ternary lead-free solder alloys produced by the addition of Al in various amounts binary Sn-9Zn eutectic lead-free solder alloy (wt%) were investigated. Contact angles of alloys were measured by using of the sessile drop method. Microstructures, inter-metallic phases, and melting temperatures of alloys were characterized by optic microscope and scanning electron microscope and energy dispersive X-ray spectroscopy, X-ray diffraction, and differential scanning calorimeter, and effects of the amount of Al on microstructure were investigated. As a result, the studies show that Al-rich areas were found on microstructure of Sn-9Zn-xAl alloys. The lowest melting temperature for Sn-9Zn-0.5Al and Sn-9Zn-0.7Al alloys was determined as 200.9 • C. It was determined that wetting capability of Sn-9Zn-xAl alloys failed because of oxidation.

The wetting behavior and interfacial properties of molten SAC300, SAC305 and SAC0307 (Sn-Ag-Cu) Pb-free solder alloys were investigated by sessile drop technique at various temperatures (250, 280 and 310°C) on Cu substrate in Ar atmosphere, as well as its dependence on time. The contact angles of the Pb-free solder alloys on Cu substrate do not decrease sharply with increasing temperature but change with time. The contact angles were measured for SAC305, SAC300 and SAC0307 alloys and the lowest θ was obtained as 41.90°for SAC305 alloy at 310°C. The melting temperatures were examined which for SAC305 Pb-free alloy is lower than those for SAC300, SAC0307 Pb-free alloys. The formation of intermetallic compounds (IMC) between the Pbfree solder alloys and the Cu substrate was observed.

Original scientific paper This study aims to investigate the effects of bismuth addition on the corrosion behaviour of Sn-3.0Ag-0.5Cu (SAC 305) solder alloy in 1M HCl acid solution under potentiodynamic polarization. After electrochemical tests, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to examine and characterize the properties of the samples. Polarization studies indicate that the addition of 0.5, 1, and 2 wt.% Bi in the SAC305 solder alloy does not significantly change the corrosion potentials. Instead of a true passivation region, a pseudo-passivation region is observed in which currents are nearly constant (though high). This pseudo-passive region does not include a reactivation point within the scanning interval. On the other hand, the corrosion rates follow a pattern in which 1 wt.% bismuth replacement of silver causes a decrement in corrosion rate. However, the corrosion rate increases with the further replacement of silver with bismuth. Microstructure analysis reveals the existence of gaps and porosities which introduce limits on the formation and stability of protective passive corrosion products.

In this study, effect of melting temperatures of Sn-3Ag (SAC300), Sn-3Ag-0.5Cu (SAC305) and Sn-0.3Ag-0.7Cu (SAC0307) ternary Pb-free solder alloys on wettability were investigated. The sessile drop technique was used in order to evaluate the contact angles of Pb-free solder alloys on Cu substrate at predetermined temperatures (250, 280 and 310 ℃). The melting temperatures of alloys were examined by differential scanning calorimeter (DSC) that SAC305 Pb-free alloy has lower than those of SAC300 and SAC0307 alloys. The best wettability was found for SAC305 and this was followed by SAC300 and SAC0307. The lowest value of contact angle for SAC305 was 41.90° at 310 ℃ on Cu substrate.

The purpose of this project is to investigate the wetting behaviors of Sn3−xAg0.5CuxIn (SAC-In) (x = 0.5 wt%, 1 wt%, and 2 wt%) alloys at various temperatures (250 • C, 280 • C, and 310 • C) on copper (Cu) substrate in argon (Ar) atmosphere. The contact angles (θ) of alloys were gaged by sessile drop technique. The alloys' microstructures were examined by scanning electron microscopy/energy dispersive spectroscopy. Intermetallic compounds of Cu3Sn, Cu6Sn5, and Ag3Sn were observed at the interface of SAC-In/Cu. The results of wetting tests represent that the addition of 1 wt% In improves the wetting properties of the Sn-3 wt%Ag-0.5 wt%Cu (SAC305) alloy. The lowest θ was obtained as 35.55 • for Sn-2 wt%Ag-0.5 wt%Cu-1 wt%In alloy at 310 • C.