The formation process and mechanism of passive film on Cu with two different grain sizes in solutions with different Cl-concentrations were studied by electrochemical methods and Mott-Schottky theory.The carrier density in the passive film formed at two oxidation potentials(0.2 V,0.4 V) in the solutions with different Cl-concentrations was calculated.The results indicated that under different conditions,the Mott-Schottky plots of the oxide films on the surface of Cu were linear with a negative slop and showed the behavior of P-type semiconductor.The majority carriers in the passive film were holes.With the increase of the grain size of Cu and the increase of anodic passivation potential,the acceptor density(NA) in the passive film formed on the surface of Cu reduced.When the concentration of Cl-in the medium solution increased,the acceptor density(NA) in the passive film increased.
This research puts forward the structure model of knowledge-based decision support system (DSS), which includes knowledge base, reasoning machine, model base, method base and database.With the six-layer structure of data management process, the knowledge-based DSS adopts distributed resource organization and task allocation strategy for cloud computing to optimize data processing.Besides, we design development tools of human resource management (HRM) expert system for knowledge base and reasoning machine and construct a comprehensive DSS for HRM, which includes knowledge base, model base, method base and various management modules.The applications in enterprises, business and education are also shown here.
Under the low temperature conditions,phosphate coating on the surface of mild steel by the addition of nano-SiO_2 in phosphating solution was prepared in this paper.The influence of nano-SiO_2 on structure and performance of phosphate coating was investigated by SEM,XRD,EDS,thickness, surface roughness and corrosion electrochemical testing.The results show that although nano-SiO_2is not main component of phosphate coating,but the coating thickness decreases with increasing the concentration of nano-SiO_2,nano-SiO_2 can reduce the crystal size of coating and increase the density and corrosion resistance of coating.When the nano-SiO_2 concentration is 2 g/L,the best corrosion resistance of phosphate coating is obtained in 3.5%NaCI solution.The corrosion current of phosphating sample was 0.231μA/cm~2 in 5%NaCI solution.
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