Theoretical and Experimental Study of Copper Electrodeposition in a Modified Hull Cell

The primary current distribution and the resistance of a modified Hull cell are calculated by using conformal mapping technique coupled with numerical evaluation of the resulting integral equations. An approximate analytical expression for the primary current distribution of a modified Hull cell is presented. The primary current distribution along the cathode surface is noticed varying in controlled manner as a function of position on the substrate. The current distributions (primary, secondary, and tertiary) in the cell have also been calculated at different applied average current densities (2, 4.1, and 8.2 mA cm−2) through numerical simulation by using finite element based software. The numerical simulation result of the primary current distribution is then compared with the analytical solution and a good match is found. Experimentally, single Cu metal electrodeposition is carried out at different applied average current densities (2, 4.1, and 8.2 mA cm−2) in a modified Hull. The current distribution (primary, secondary, and tertiary) results obtained from the numerical simulation are compared with the experimental results and a satisfactory match is found. Surface morphology of the Cu deposits is examined using scanning electron microscopy (SEM)

Friction Stir Welding (FSW) Studies of Dissimilar Al-Based Alloys Using Different Pin Profiles

The feasibility of friction stir welding (FSW) of Al 5083 and Al 6082 sheets using different pin profiles: straight cylindrical (Cy), threaded cylindrical (Th), triangular (Tr) and square (Sq) are studied, as cylindrical and threaded cylindrical generate regular stirring action whereas, triangular and square pin profiles produce pulsating stirring action in the flowing material due to their flat faces. Further in-depth investigations are made to understand the effects of these tool pin profiles on microstructures, hardness, crystallographic texture and tensile strength of the welded specimens. All specimens showed minimum hardness values in their heat affected zone in the AA 6082 side and they fractured as well in this region during the tensile tests. Having comparable microstructures and hardness values in all the specimens, only the threaded cylindrical joined specimen showed the lowest tensile strength due to the presence of maximum tensile direction texture component in its heat affected zone

Friction Stir Welding of Aluminum 6082 with Mild Steel and Its Joint Analyses

Energy-saving and reduction in CO2 emission are the two important challenging issues that must be resolved in the coming future. Introducing aluminum components in a standard steel car body or in the hulls of ship brings the reduction in weight of vehicles, thereby reducing the emission. In this research study, Aluminum 6082 alloy and mild steel were tried to join together (weld) by an eco-friendly and energy efficient technology named as Friction Stir Welding (FSW), which is far advantageous than the conventional fusion welding especially in the case of joining dissimilar materials. As this is a solid state welding process, most of the defects occurring in the molten state of the material could be completely eliminated. Also, welding takes place at low temperature (below the melting point of the material) due to which there is less chance of intermetallics formation at the heat affected region that will eventually degrade the mechanical properties of the weld

Improved Photoelectrochemical Performance Of Cu(In,Ga)Se2 Thin Films Prepared By Pulsed Electrodeposition

Solar cells based on polycrystalline Cu(In,Ga)Se2 absorber layers have yielded the highest conversion efficiency among all the thin-film technologies. CIGS thin-films possess large optical absorption coefficient (≈105 cm-1) and a suitable bandgap of ≈ 1.20 eV for an ideal stoichiometry of CuIn0.7Ga0.3Se2. In the present study, Direct Current (DC) and Pulsed Current (PC) electrodeposition techniques are employed to obtain the near ideal stoichiometric CIGS thin-films on a Mo foil using a two electrode system at a constant potential. Deposited films are annealed at 550 °C under Ar atmosphere. Characterization of the annealed CIGS films is performed using SEM-energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, and photoelectrochemistry to study the morphology, stoichiometry, phase constitution, and the photoelectrochemical response. PC deposition offered suitable manipulation of various parameters, which has helped in obtaining a better quality stoichiometric single phase chalcopyrite structured CIGS thin films with the elimination of unwanted secondary phases like Cu2-xSe. An improved photoelectrochemical performance, characteristic of a p-type semiconductor, is observed for the PC deposited CIGS film

Photoelectrochemistry of Cu(In,Ga)Se2 thin-films fabricated by sequential pulsed electrodeposition

A novel approach for the fabrication of compact stoichiometric copper indium gallium selenium (CIGS) thin-films is reported. It uses a solution of CuCl2, GaCl3 and H2SeO3, pH adjusted with HCl with LiCl as additive employing a high purity graphite plate anode and Mo sputtered glass cathode during a simplified sequential pulsed current electrodeposition which avoids impurities from the use of a reference electrode during deposition and a separate selenization step. A Cu-Ga-Se film is optimally deposited by optimizing the deposition voltage, followed by deposition of In from InCl3 solution, and then annealing of the Cu-Ga-Se/In thin-film in an Argon atmosphere at 550 °C. A single phase chalcopyrite CIGS forms with a compact morphology and well-controlled composition of individual elements. The flat-band potential and carrier density of CIGS thin-films are −0.15 V and 2.6 × 1016 cm−3, respectively, as determined by Mott–Schottky studies. The photoelectrochemical performance of CIGS films shows a photocurrent density of −0.8 mA cm−2 at −0.4 V vs. SCE, an eight fold increment compared to our previous reported value. This simplified preparation using pulse plating gives superior quality CIGS films which are promising for application in thin-film solar cells and photoelectrochemical cells

CuIn1-xGaxSe2 thin-film absorber layers for solar photovoltaics fabricated by two-stage pulsed current electrodeposition

Single phase polycrystalline Copper Indium Gallium Diselenide (CIGS) thin-films for solar photovoltaic applications were fabricated by an economical two-stage method of Pulsed Current (PC) electrodeposition. Cu, Ga and Se were first co-deposited onto a Mo foil followed by deposition of In. The as-deposited films were annealed in Argon atmosphere at 550 C for 30 min and were further characterized to study their morphology, phase constitution, and optical absorption. The results revealed that the films have a compact morphology and are comprised of a crystalline chalcopyrite single phase CIGS. The bandgap of the CIGS films was found to be 1.27 eV from absorption studies. The photoelectrochemical studies revealed the p-type nature of CIGS films with improved photocurrent over that obtained for one-stage PC electrodeposited CIGS thin-film

Pulsed electrodeposition of Cuinse2 thin films with morphology for solar cell applications

Copper indium diselenide (CuInSe2) films have been prepared by pulse electrodeposition technique on Molybdenum substrate followed by post-deposition annealing at 550°C. Optimization of pulse parameters by varying the pulse duration (duty cycle) in order to achieve high quality films has been reported. Appropriate manipulation of pulse parameters has resulted in a novel flake-like crystallite morphology and better control over the composition of individual elements. The CIS thin films were comprehensively characterized using SEM-EDS, FIB, XRD and UV-DRS to study their morphology, phase constitution, etc. and PEC (photoelectrochemistry) measurements were also carried out to ascertain the photoelectrochemical performance of the CIS absorber layer. The bandgap of the CIS films was determined to be 1.02 eV. The flake like crystallite morphology observed in CIS thin films under the optimized processing conditions was found to yield enhanced cathodic photoresponse under solar simulated light with a photocurrent density of 20 μA/cm2 (observed at a potential of -0.6 V vs. SCE). The films exhibited a photoresponse typical of a p-type semiconducto

Inkjet printed CuIn(1-X)GaXSe2 thin film by controlled selenium distribution for improved power conversion efficiency in chalcopyrite solar cells

Selenium (Se) vapor pressure is a key factor during the selenization of CuIn1-XGaX (CIG) film to obtain a high-quality CuIn1-XGaXSe2 (CIGS) absorber layer. To investigate the effect of Se vapor distribution on the grain growth of inkjet printed precursor film, two geometries of graphite box (square and circular) are used. The results revealed that selenization in the round graphite box give rise to uniform surface coverage and suppressed fine-grained layer due to adequate and uniform distribution of Se vapor. In contrast, film selenized in a square graphite box exhibits high strain and low crystallinity with a thick fine-grained layer. Probable Se vapor distribution inside the graphite box based on internal geometrical constraint and its impact on crystal phase and microstructure is discussed. Finally, CIGS devices fabricated using films selenized in a round graphite box demonstrates higher power-conversion efficiency of 5.2%, owing to high light absorption and efficient carrier separation. Based on J-V and EQE results, probable losses and recombination in the devices are examined and discussed. © 2021 The Author(s

Texture studies of hot compressed near alpha titanium alloy (IMI 834) at 1000°C with different strain rates

IMI 834 Titanium alloy is a near alpha (hcp) titanium alloy used for high temperature applications with the service temperature up to 600°C. Generally, this alloy is widely used in gas turbine engine applications such as low pressure compressor discs. For these applications, good fatigue and creep properties are required, which have been noticed better in a bimodal microstructure, containing 15-20% volume fraction of primary alpha grains (αp) and remaining bcc beta (β) grains transformed secondary alpha laths (αs). The bimodal microstructure is achieved during processing of IMI 834 in the high temperature α+β region. The major issue of bimodal IMI 834 during utilization is its poor dwell fatigue life time caused by textured macrozones. Textured macrozone is the spatial accumulation of similar oriented grains in the microstructure generated during hot processing in the high temperature α+β region. Textured macrozone can be mitigated by controlling the hot deformation with certain strain rate under stable plastic conditions having β grains undergoing dynamic recrystallization. Hence, a comprehensive study is required to understand the deformation behavior of α and β grains at different strain rates in that region. Hot compression tests up to 5°% strain of the samples are performed with five different strain rates i.e. 10-3 s-1, 10-2 s-1, 10-1 s-1, 1 s-1 and 10 s-1 at 1000°C using Gleeble 3800. The resultant bimodal microstructure and the texture studies of primary alpha grains (αp) and secondary alpha laths (αs) are carried out using scanning electron microscopy (SEM)-electron back scattered diffraction (EBSD) method