CNTs和CNFs成长过程中催化剂的作用.ppt

1、Revealing the Role of Catalysts in CarbonNanotubes and Nanofibers by ScanningTransmission X-ray Microscopy,Directory,Abstract,we found that the catalyst may migrate with the growth of CNT (CNF) through the whole CNT (CNF) as tiny clusters or even atomic metal, which provides the direct evidence on t

2、he existence of the atomic metal for the ORR. Moreover, the catalyst nanoparticles at the tip of CNT (CNF) show a strong interaction with carbon as metal-carbon bonds, as revealed by the XANES spectra.,Synthesis of catalysts,流程图：,Si衬底,蒸发沉积Ti（80nm）,蒸发沉积Fe（Ni）催化剂（20nm）,电子束蒸镀法,退火，6000C，2mbar，NH3气流，3min

3、,催化剂薄膜变成纳米颗粒,等离子体增强化学气相沉积法生长碳纳米结构,7500C，混合气体NH3:C2H2为4:1，压强7 Torr，等离子体的功率210W，应用电压530V，生长周期15min,暴露之前冷却至室温,CNTs grown with Fe/Ti underlayer,(a) SEM and (b) TEM images of CNTs grown with 20 nm Fe/Ti underlayer.,CNTs grown with Fe/Ti underlayer,(c) Magnified TEM image of CNTs.,CNTs grown with Fe/Ti un

4、derlayer,(a) TEM image and (b) STXM map (at C K-edge) of CNTs,CNTs grown with Fe/Ti underlayer,(c) Normalized C K-edge XANES spectra of tube14 ，(d)Fe L-edge XANES spectra of tube14,CNFs grown with Ni/Ti underlayer,(a) SEM and (b) TEM images of CNFs grown with 20 nm Ni/Ti underlayer,CNFs grown with N

5、i/Ti underlayer,(a) TEM image and (b) STXM map (at C K-edge) of CNFs,CNFs grown with Ni/Ti underlayer,(c) Normalized CK-edge XANES spectra of fiber14, (d) Ni L-edge XANES spectra of fiber14,CNFs grown with Ni/Ti underlayer,Normalized Ni L-edge XANES spectra of fiber14,Summary,We have probed the elec

6、tronic structure of CNTs and CNFs grown with Fe and Ni as catalyst, respectively, by STXM.Thecatalyst clusters along the tube (fiber) were detected indicating a migration of the catalysts with the growth of CNTs (CNFs), which could help to explain the existence of atomic metal in CNT for the ORR. Different chemical states of the catalyst clusters are also observed in CNTs and CNFs. The STXM results reveal the distribution and chemical state of the growth catalysts in CNTs (CNFs)