A simulation of air bearing surface materials with copper substrate for corrosion investigation
Corrosion defect is one of the important defects found in hard disk drive manufacturing. Fail to detect this defect might lead to fatal hard disk drive failure. In general, corrosion defect was found after the end of process. The fundamental methodology used to measure corrosion defect in head magnetic process of hard disk drive manufacturing is Electrochemical impedance spectroscopy (EIS). This method applies a low frequency voltage to a chemical cell in order to measure corrosion rate which is defined as a reaction of material in aqueous solution. The data obtained from EIS measurement method are complex and thus hard to analyze. Furthermore, EIS method is destructive materials measurement and the obtained results cannot well predict corrosion behavior of the system. However, head magnetic materials/slider is a stack of three materials in layers i.e. soft magnetic layer, diamond like carbon (DLC) layer, and photoresist layer respectively. These three stack layer of slider can be replaced by R-C equivalent circuit. Nyquist plot and Bode plot are used to observe the frequency response of the equivalent circuit. This observation can help in prediction of corrosion behavior before starting of mass fabrication or transferring to new materials. This work shows that the results obtained from an equivalent R-C circuit model of copper substrate coated with photoresist and the one obtained from EIS method are comparable. It should be noted that the parameters of R-C equivalent circuits are modified for corrosion behavior studying according to two different types of photoresists.
Macroporous polymer electrolytes based on PVDF/PEO-b-PMMA block copolymer blends for rechargeable lithium ion battery
Abstract A novel macroporous polymer electrolyte based on poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide)- block -poly(methyl methacrylate) (PEO -b- PMMA) block copolymers blends was prepared by a phase inversion technique. The crystallinity of the polymer matrix was found to decrease with increase of PEO -b- PMMA content, which was confirmed by DSC thermal analyses. The pore structure and connectivity could be improved with addition of PEO -b- PMMA in the polymer matrix. The resulting macroporous polymer electrolyte exhibited high ionic conductivity, 2.79 × 10 −3  S cm −1 at room temperature, and a good electrochemical stability up to 5.0 V (vs. Li/Li + ). These results showed that it is of great potential application in polymer lithium ion batteries.
Structure and performance of porous polymer electrolytes based on P(VDF-HFP) for lithium ion batteries
Abstract In order to develop polymer electrolyte for lithium ion batteries, highly porous P(VDF-HFP) membranes were prepared by using phase inversion method, then they were immerged in 1 mol kg −1 solution of LiClO 4 -EC/PC(1:1) to form porous polymer electrolytes. Conductivity of the polymer electrolytes was found to be as high as 10 −3  S cm −1 . Structures of the porous membranes were observed with SEM. Porous membranes with different structure, porosity and pore diameter were prepared by changing the processing conditions. There are two kinds of typical structure, one is honeycomb-like (type I), and the other is network-like (type II). Membrane structures were found to be important to the performance of the porous polymer electrolytes. Small pore diameter with narrow distribution is needed to prevent solution leakage and high porosity is needed to achieve high conductivity. The type II membranes can meet the requirements. The model lithium ion batteries made of the resulting porous polymer electrolytes have good cycleablity.