Investigation On Chemical Polishing Of The Inner Surface Of The Nickel Capillary

Nickel capillary has important applications in the fields of chemical industry, microelectronics, medical treatment and so on, especially in transmission of CO2 laser instead of fragile quartz glass capillary for its features of high mechanical strength, good toughness and resistance to corrosion and rust. However, the large roughness of inner surface has greatly limited its wide applications. At present, it is very scarce about polishing metal capillaries’ inner surface in literature reports, so investigate how to polishing metal capillaries and develop some kinds of polishing slurrys which can polishing inner surface effectively have become increasingly urgent.This study designed a method of polishing metal capillaries’ inner surface with liquid peristaltic pump when combined the features of long and narrow of metal capillaries with chemical polishing. Then, they were discussed about the influence of slurry concentration, polishing time and liquid peristaltic pump flowrate on polishing quality, especially the influence of hydrochloric acid, sulfuric acid and phosphoric acid on polishing quality. Three kinds of polishing liquids were developed which can effectively polishing inner surface of nickel capillary, they used hydrochloric acid, sulfuric acid and phosphoric acid as their etchant respectively.The properties of the inner surface before and after polishing were characterized by profile meter, scanning electron microscope(SEM) and fiber transmission loss. The roughness was obtained by profile meter, the results showed as follows: the arithmetic average roughness was reduced to less than 0.650 μm when use hydrochloric acid polishing liquid to polishing inner surface, the arithmetic average roughness was reduced to less than 0.560 μm when use sulfuric acid polishing liquid to polishing inner surface, the arithmetic average roughness was reduced to less than 0.540 μm when use phosphoric acid polishing liquid to polishing inner surface. It was also found that the polished inner surface quality of nickel capillary was much better than before when use SEM technique to observe the inner surface morphology and had much lower fiber transmission loss when made it as hollow fiber to transmit CO2 laser.It was analyzed about the change of the inner surface quality in etching, polishing and coarsening processes of chemical polishing by lots of experiments. The factors influenced inner surface quality of nickel capillary were discussed in chemical polishing processes, it would be helpful for other metal capillaries’ polishing.