Independently controlling the number density and diameter of Fe nanoparticles (FeNPs) used as a catalyst for vertically aligned carbon nanotube (VA-CNT) growth is difficult by conventional methods. In this study, mixed solutions of FeNPs and palmitic acid (C16) used as filler molecules were prepared to prevent the thermal aggregation of FeNPs and control the number density of VA-CNTs. FeNPs mixed with C16 monolayer films were prepared on the water surface and deposited on SiO2/Si substrates by the Langmuir–Blodgett (LB) technique. VA-CNTs were synthesized by a thermal chemical vapor deposition method using acetylene gas. Furthermore, we studied the optimum hydrogen reduction temperature and time of FeNPs used as a catalyst to encourage VA-CNT growth. By controlling the ratio of FeNP catalyst to C16 as a filler molecule in the LB film and optimizing hydrogen reduction condition, we were able to control the number density and diameter of FeNPs independently.
Dry-etching durabilities of poly(2-vinylnaphthalene-co-methyl methacrylate), the blend of poly(2-vinylnaphthalene) and poly(methyl methacrylate) [PMMA], and poly(α-methylstyrene-co-methyl methacrylate) films were studied as a function of vinylnaphthalene or α-methylstyrene content against four types of dry etching: 1) O2 plasma etching ( O2 PE), 2) O2 reactive ion etching ( O2 RIE), 3) Ar+ sputter etching (Ar SE), and 4) Ar ion beam etching (Ar IBE). Since the etching depth increased linearly with etching time the two-component polymer films were regarded to be etched uniformly without selected removal of aliphatic monomer units. Substantial enhacement of the durability was observed by incorporating or blending small amounts of aromatic moiety into PMMA for physical etching (Ar SE, Ar IBE) and physical/chemical etching ( O2 RIE) as well as chemical etching ( O2 PE). O2 RIE is a synergetic process involving both physical bombardment and chemical reaction.
Vertically aligned carbon nanotubes (VA-CNTs) were studied as a new catalyst support for polymer electrolyte fuel cells (PEFCs). Controlling the number density and the diameter of VA-CNTs may be necessary to optimize PEFC performance. As the catalyst for CNT growth, we fabricated Fe or Fe3O4 nanoparticle (NP) films by the Langmuir–Blodgett (LB) technique. The catalyst Fe or Fe3O4 NPs were widely separated by mixing with filler molecules [palmitic acid (C16)]. The number density of VA-CNTs was controlled by varying the ratio of catalyst NPs to C16 filler molecules. The VA-CNTs were synthesized from the catalyst NP–C16 LB films by thermal chemical vapor deposition (CVD) using acetylene gas as the carbon source. The developing solvents used in the LB technique and the hydrogen reduction conditions of CVD were optimized to improve the VA-CNT growth rate. We demonstrate that the proposed method can independently control both the density and the diameter of VA-CNTs.
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