Research On Size Control Mechanism Of Copper Powder By Electrolysis Process

This article prepared ultra-fine copper powder by electrolysis process under ultrasonic emulsify condition and studied the mechanism of how current, anode character and content of organic addition agent oleic acid influence on the size of copper powder.We analyse phase by XRD, detect whether oleic acid coating the surface of copper powder by infrared spectrum equipment, test the size by Malven, and gain electrochemistry parameter by triple-electrode system on constant current condition.Current density changed by changing current. When current increase faster then the speed of increasing cathode area, current can increase, which lead to the increase of electrochemical polarization overvoltage. To increase current density can make Cu²⁺ change into Cu, however, it can also decrease Cu²⁺ content around cathode surface which increase concentration polarization overvoltage. To increase current density can make Cu atom diffusion to the growing point easy which also increase crystal overvoltage. While current ranging from 0.4A to 0.6A current density increased, the average cathode overvoltage increase from 0.258V to 0.552V, and make size of copper powder decrease from 338nm to 92nm. While current changing from 0.7A to 1.0A current density decreased, the average cathode overvoltage decrease from 0.481V to 0.340V, and make size of copper powder increase from 106nm to 254nm.To change different character anode will have different result. If using Cu as anode may not get Cu₂O. On the other hand, when using Ni as anode can get O₂ and H₂ during the process of electrodeposition which produces Cu₂O. But H₂ can be a dynamic force to stir the liquor around cathode surface which will decrease concentration polarization overvoltage and make Cu atom diffusion to the growing point easy which also increases crystal overvoltage. So the average cathode overvoltage is 0.398V when chosing Cu as anode, however, the average cathode overvoltage is 0.316V when chosing Ni as anode. The cathode overvoltage ranging from 0.293V to 0.395V when chosing Ni as anode which also lead to a reduction of size from 307nm to 47nm.To alter oleic acid content can get different size. When reducing oleic acid content make sorbing layer of organic mater on the cathode surface thin which reduce the rejection of Cu²⁺ discharging and reduce electrochemical polarization overvoltage. To reduce oleic acid content will reduces the possibility of H⁺ discharging which reduces the active of stiring the liquor around cathode surface and decrease concentration polarization overvoltage. To reduce oleic acid content will make sorbing layer of organic mater on the cathode surface thin which makes Cu atom diffusion to the growing point easy and also increases crystal overvoltage. In general, when oleic acid content changing from 15ml/L to 5ml/L, cathode overvoltage increases from 0.315V to 0.481V and makes average size decreases from 307nm to 106nm. But if there is no oleic acid in electrolyte, the activation energy of reaction system will be too high make the electrode reaction impossible.