CNTs和CNFs成長過程中催化劑的作用.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,流程圖：,Si襯底,蒸發(fā)沉積Ti（80nm）,蒸發(fā)沉積Fe（Ni）催化劑（20nm）,電子束蒸鍍法,退火，6000C，2mbar，NH3氣流，3min

3、,催化劑薄膜變成納米顆粒,等離子體增強(qiáng)化學(xué)氣相沉積法生長碳納米結(jié)構(gòu),7500C，混合氣體NH3:C2H2為4:1，壓強(qiáng)7 Torr，等離子體的功率210W，應(yīng)用電壓530V，生長周期15min,暴露之前冷卻至室溫,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)