بررسي رشد دندريتي در حسگرهاي خوردگي و روش هاي كنترل آن

چكيده انگليسي :

Dendritic Growth in Corrosion Sensors and it s Control Hassan Eslami Dashbelagh h eslamy@ma iut ac ir Date of Submission January 4 2010 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Dr Ahmad Saatchi Prof E mail asaatchi@cc iut ac ir Dr Seyyed Mahmood Monirvaghefi Assoc Prof E mail vagh mah@cc iut ac ir Avisor Dr Keyvan Raeissi Assoc Prof E mail k raeissi@cc iut ac ir Abstract Galvanic corrosion sensors commonly used for monitoring of atmospheric corrosion Newly developed thin film sensor consists of two copper electrodes mounted on a polymeric or composite substrate Two copper electrodes act as a cathode and anode This sensor is a type of electrical circuits One of the problems with these corrosion sensors is dendrite formation around cathode which creates a short circuit between the electrodes and the sensor is no longer usable Dendrite formation is due to the moisture adsorption and anodic dissolution Dendritic growth has been a known process in failure of microelectronic devices In this research samples were prepared to evaluation of this phenomena corrosion sensors by using potentiodynamic polarization potentiostatic and cyclic Voltammetry tests and scanning electron microscopy Important parameters are the amount of potential difference applied electric field between two electrodes existence of sharp edges surface roughness and the rate of copper dissolution affected by pH and contaminations It is recognized that surface properties of substrate such as texture and morphology has an important role on the rate of nucleation in electrodeposition process According to the similarity of dendritic growth to electrodeposition the effect of electrodeposition of copper on cathode electrode from acidic sulfate bath investigated in this research Direct current without additive and with KCl addition and also pulsed current were used for electrodeposition In DC plating process with increasing current density deposits become coarser and evolution of 220 observed By using 5 10 4 mol lit KCl additive intensity of 222 planes at current density of 5 mA cm2 and 111 planes at current density of 50 mA cm2 increased In the higher amount of KCl 9 10 4 mol lit preferential texture of deposits were 220 By using pulsed current 5 mA cm2 deposit has a random orientation In high pick current densities at pulsed electrodeposition excessive growth of planes observed in SEM images that led to increase in surface roughness KCl addition led to formation of smooth deposits that has a very low specific electrical resistance Dendritic growth behavior of coated samples evaluated by using electrochemical techniques In was observed that using KCl additive and pulsed electrodeposition at low current densities results in increase of short circuit time bye three to five times Because of coarser morphology samples coated at high current densities have not a higher short circuit time than uncoated sample Morphology and texture of deposits have a main role in short circuit time The effect of morphology is much higher than texture These effects related to the decrease in surface energy Evolutiom of random orientation has a positive effect on increasing the short circuit time while increasing of 222 and 311 planes have a negative effect It is in correspondence with decreasing surface energy of crystallographic planes by decreasing indexes Reduction in surface energy results in an increase of nucleation rate By nucleation of extra dendrites excessive growth of large dendrites inhibited and the amount of electricity requisite for short circuit increases Increase of nucleation rate in voltammetry and potentiostatic test was observed by scanning electron microscopy Keywords Copper dendritic growth corrosion sensors electrodeposition electrical circuits

اسلامي داشبلاغ، حسن

بررسي رشد دندريتي در حسگرهاي خوردگي و روش هاي كنترل آن

مس , رسوب دهي الكتريكي , مدارهاي الكتريكي