(a) Cross section and (b) high-magnification top-view SEM images of CNTs grown for 10 min at 650 °C in atmospheric pressure on 1 nm Ni film subject to OP. (d) High- and (e) low-magnification top-view SEM images of CNTs grown at same conditions, except for RP. [(c) and (e)] HRTEM images of these tubes.
(Color online) [(a) and (d)] AFM topography of SiO2-supported 0.5 nm Ni film pretreated for 5 min at 650 °C in atmospheric pressure, under reducing or oxidizing environments, respectively. [(b) and (e)] XPS Ni 2p 3/2 core level lines of (a) and (d) nanoparticles, respectively. [(c) and (f)] Schematic representation of OP and RP nanoparticles, respectively.
[(a)–(c)] Schematic representations of possible metal silicate structures: metal cation incorporation into silicate framework, polymeric silicate, and surface silicate, respectively. (d) Typical phase diagram of a ternary M–O–Si system. (e) M–O–Si phase diagram for RP.
AFM topography of SiO2-supported 1 nm Ni film receiving pretreatment at 750 °C in atmospheric pressure for 5, 15, and 60 min, [(a)–(c)] under oxidizing atmospheres and [(d)–(f)] under reducing atmospheres, respectively.
(Color online) Schematic representation of SiO2-supported metals restructuring into nanoparticles under OP or RP and its influence on posttreatment/CNT growth.
(Color online) (a) SEM image of CNTs grown on OP films for 1 min at 700 °C by supplying C2H2, then stopped for 15 min, and restarted for another 10 min at 550 °C. (b) Schematic of this growth process for OP films.
(Color online) (a) XPS Fe 2p 3/2 core level lines of SiO2-supported 1 nm Fe film subject to Ar pretreatment for 15 min at 670 °C and atmospheric pressure. (b) CNTs grown on nanoparticles characterized in (a) by the addition of H2 and C2H2.
Species detected by XPS after RP or OP.
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