An alkaline bath was developed for electroless deposition of Co – W – P thin films on a copper substrate. Effects of pH values, various concentrations of reducing agent, and different powers of ultrasonic on composition, microstructure, and magnetic properties of the films were investigated. It was found out that higher pH could improve cobalt atomic percentage and reduce amounts of phosphorus and tungsten in the film while larger amounts of NaH 2 PO 2 would decrease the cobalt content but increase the tungsten and phosphors content. The ultrasonic was introduced during the electroless deposition. Few effects of ultrasonic on the cobalt content were observed. X-ray diffraction showed that almost all of the deposited films were crystalline and contained hexagonal cobalt with a preferred crystallographic orientation (002). However, a typical amorphous Co – W – P film, which has smooth surface, and no crystallite with definite grains could be obtained when the concentration of NaH 2 PO 2 in the bath was over 1.2 mol/L. The films with rougher and agglomerate nodular structures would be formed in the bath with a higher pH value. Certain power (60 W, 40 kHz) of ultrasonic could smash the grains and led to the formation of a denser and smoother surface. Cracks appeared at the surface of the film when the ultrasonic power was 150 W. Vibration sample magnetometer results showed that the film with maximum magnetization (600 emu/g) and coercivity (1000 Oe) could be achieved when introducing ultrasonic (60 W, 40 kHz) during the deposition.
In this paper, a new environmental-friendly electrolyte containing sulfuric acid and tartaric acid has been used as the substitute of chromic acid for anodization. The work discussed the influence of anodizing voltages on the fatigue life of anodized Al 2024-T3 by performing fatigue tests with 0.1 stress ratio (R) at 320 MPa. Meanwhile the fatigue cycles to failure, yield strength, tensile strength and fracture surface of anodic films at different conditions were investigated. The results showed that the fatigue life of anodized and sealed specimens reduced a lot compared to aluminum alloy, which can be attributed to the crack sites initiated at the oxide layer. The fracture surface analyses also revealed that the number of crack initiation sites enlarged with the increase of anodizing voltage.
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