The Ni@PA66 double-layer nanotubes have better magnetic property than Ni nanotubes as indicated by the data shown in Table 1andFig. 4.
The magnetic properties of Ni nanotubes were degraded due to the easily oxidation of Ni under ambient condi-tions.
However, the PA66 nanotubes efficiently protected Ni from oxidation and improved the stability of the Ni nanotubes in air.