SYNTHESIS OF COPPER NANOPOWDER BY PULSE CURRENT ELECTROLYSIS METHOD AND NUMERICAL MODELING OF GRAIN SIZE

• Main Author: Wahyudi, Soleh
• Format: Dissertations
• Language: Indonesia
• Subjects: Pertambangan dan operasi berkaitan
• Online Access: https://digilib.itb.ac.id/gdl/view/54387
• Institution: Institut Teknologi Bandung

Copper is a metal that has excellent electrical and thermal conductivity and has catalytic and anti-microbial properties. In nanoscale powder, copper has been used for magnetic recording raw materials, conductive inks and pastes, sensors, catalysts, anti-septic and lubricating oils. Copper powder can be synthesized by electrolysis method and the resulted powder has a micron-scale particle size with a dendritic structure. Currently, the pulse current electrolysis (PCE) method has been developed by setting the time-On (ton) and time-Off (toff) of the electrolysis which changes periodically. The PCE method is able to reduce the powder particle size and dimension of the dendritic structure. In this study, the PCE method was developed and periodically modulated by ultrasonic scrapping to produce a nanoscale copper powder with a rounded particle shape. This study aims to investigate the effects of current density, copper concentration in the electrolyte, duty cycle, and PCE frequency on the particle size and morphology of the resulted copper powder. A numerical model was also developed for predicting grain size and mapping PCE operating conditions to obtain copper nanopowder. The grain size predicted by the numerical model was verified by experimental data. The mathematical equation used in the numerical model of grain size related with the mechanisms of nucleation and growth of copper during the PCE. The parameters that were simulated for predicting the grain size of copper powder are the concentration of copper in electrolyte, current density, duty cycle, and electrolysis time. The average grain size of copper powder was determined by an integral equation which was numerically solved by the multiple trapezoidal rules. The experimental works started with the measurement of cathodic polarization during copper deposition by potentiodynamic scan using a potentiostat to obtain the limiting current density (iL) under variation of copper concentration. The iv obtained limiting current densities ware used as references for the minimum applied current density (iapp) to meet the criteria for the formation of copper powder. The copper powder synthesis experiment using the PCE method was carried out with an electrolyte solution containing dissolved copper in sulfuric acid and carried out in an airtight electrolysis cell equipped with a scale burette to measure the volume of hydrogen gas generated from the cell reaction on the cathode surface. The anode used was a pure copper plate (99.99% Cu), while a titanium G1 plate was used as a cathode. The DC power supply used a pulse rectifier equipped with modulation control for powder scrapping. A series of copper powder synthesis experiments with PCE were carried out at room temperature (25-28 °C) and 1M H2SO4 under variations of copper concentration in the electrolyte, current density, duty cycle, pulse frequency and duration of electrolysis. The copper powder deposit was dried at 100±1°C in an inert atmosphere using argon gas. The data collected from the experiments were the weight of copper powder and the volume of hydrogen gas which were then used to calculate the current efficiency and energy consumption of the electrolysis. Characterization of copper powder were carried out which includes determining particle size using a Particle Size Analyzer (PSA), morphology and particle size using a Scanning Electron Microscope (SEM), powder composition using Energy Dispersive X-Ray Analysis (EDX), morphology and confirmation of nano-scale particle size using Transmission Electron Microscope (TEM) and identification of elements and compounds as well as powder crystallinity using X-Ray Diffraction (XRD). The results showed that the PCE method was able to produce copper nanopowder with a particle size of 40-90 nm and has a relatively rounded shape with a rounded index level of 0.91-0.98. These results were achieved at copper concentration of 0.03-0.04M, 1M H2SO4, 0.3-0.5 A/cm2 current density, 3-40 seconds electrolysis time, 5-10% of duty cycle, 100 Hz frequency, and electrolyte temperature of 25- 28°C.