Double-Walled Crabon Nanotubes ≥95%,OD:2-5nm, Length:5-15μm, Ni≤1ppm，>60%,ID:1-3nm,OD:2-4nm,Length:~50um，>60%,ID:1-3nm,OD: 2-4nm,Length:0.5-2 um，≥50%,OD:＜5nm,Length:＜50μm
