Because K is very active in air, so that it is possible to autoignite.
B.
The widely-investigated metal species for the catalytic growth of carbon nanotubes include Fe, Co, Ni.
C.
The specific suce area of the material is up to 3000 m2/g, the pore volume is as high as 2 cm3/g.
D.
The conventional synthesis requires tedious multistep procedures and prolonged synthetic time, and the resulting bimetallics usually disperse unevenly and show poor stability.