In situ XAFS study on chemical states of Co and Ir nanoparticles under conventional growth condition of single-walled carbon nanotube via alcohol catalytic chemical vapor deposition

Single-walled carbon nanotube growth from Ni catalyst particles under conventional growth conditions by alcohol catalytic chemical vapor deposition: in situ X-ray absorption fine structure study

“…2(d) of Ref. 25. It should be noted that, in contrast with Ir catalysts, Ni catalysts were not completely metallic, but a small portion of them were carbonized; the ratio of coordination number for carbon atoms around Ni atoms was estimated to be 4.9%.…”

“…The preparation method for Ni catalysts for in situ XAFS analysis was the same as those reported in our previous study. 25) Ni catalyst particles supported on boron nitride (BN) powders were used for in situ XAFS analysis because BN exhibits high X-ray transmittance and is suitable for XAFS analysis in the transmission mode. Ni nitrate was stirred in deionized (DI) water, then the BN nanoslurry (average BN particle size ∼50 nm; MARUKA, SL-170-20-OG, Japan) and BN microparticles (BN particle size 55-60 μm; Kojundo Chemical Laboratory Co. Ltd, BB103PB, Japan) were added.…”

“…Detailed information on the CVD reactor and the setup were provided in our previous paper. 25) After evacuating the CVD reactor to < 2 Pa using a scroll pump, a carrier gas comprising Ar (vol97%)/H 2 (vol3%) was introduced into the reactor. The time sequences of the temperature and gas flow are summarized in Fig.…”

“…The details of data acquisition and the analytical procedure were also described in our previous article. 25) Furthermore, using structural information on standard phases from the "Materials Project" web interface, 29) curve-fitting analysis was performed for the first coordination spheres in the RSF to estimate structural parameters such as the coordination number and the bond distance.…”

“…Very recently, we also performed in situ XAFS analysis for a platinum group element catalyst, Ir, during SWCNT growth by ACCVD. 25) In contrast to Co, Ir catalysts remained metallic during the ethanol irradiation at 900 °C, although Ir is an efficient catalyst for SWCNT growth. 26,27) This suggests that the behavior of metal catalysts with low carbon solubility is different from Fe and Co catalysts, and the VLS model does not hold for SWCNT growth from such a catalyst.…”