Advances in the Creation of Filled Nanotubes and Novel Nanowires

Abstract

Soon after the identification of carbon nanotubes, produced by arc-discharge techniques, the possibility of introducing metals into the inner core of the tubes was considered (Figure 1). This idea followed logically from the successful observation of fullerenes containing endohedral metals. The introduction of metals or metal carbides and oxides into multiwalled nanotubes [usually 2–70 nm outside diameter (OD), <60 microns in length] may significantly alter their conducting, electronic, and mechanical properties, arising from the internal framework within these structures. Early theoretical work predicted that all carbon open nanotubes could behave as “molecular straws.” In this context, Ajayan and lijima were the first to introduce Pb by heating the metal with open-ended nanotubes (sometimes in the presence of oxygen). Capillarity, wetting, and surface tension play an important role in the process; other elements such as Bi, Cs, S, and Se were also introduced into nanotubes in this way. Generally, the filling of open nanotubes by capillary action is confined to low surface-tension substances. Alternative methods of encapsulating other materials within nanotubes have now been developed, including chemical treatment, arc discharge, catalyzed hydrocarbon pyrolysis, and electrochemical techniques. In addition, carbon nanotubes can be used as reactive templates to generate novel metal carbide and nitride nanorods. These developments represent only the tip of the iceberg, because numerous noncarbon materials (e.g., Si, SiOx, SiC, MoS2, WS2, etc.) are able to form novel nanowires and fullerene-like morphologies. This review discusses methods for generating these fascinating structures and evaluates their possible applications in materials science and engineering.

Structural transformations in carbon nanoparticles induced by electron irradiation

“…M e t a l -c a r b o n n a n o p a r t i c l e s . The encapsulation of crystalline metals in graphitic shells, either in nanotubes or in onions, is a subject of considerable interest [21]. Among techniques such as coevaporation of carbon together with metals at high temperature, irradiation of metal-carbon composites has shown to produce metal crystals that are completely encapsulated by graphitic shells [22].…”

On the synthesis and magnetic properties of multiwall carbon nanotube–superparamagnetic iron oxide nanoparticle nanocomposites

“…The filling of CNTs was accepted as an ingenious idea right from the early days of CNT research [9][10][11][12][13][14], and attempts at complete filling of CNTs are an ongoing research activity, rewarded with only partial success [15]. The confined existence of particles inside CNTs might introduce interesting new properties which have not been seen in these systems previously [16].…”

Single step process for the synthesis of carbon nanotubes and metal/alloy-filled multiwalled carbon nanotubes

“…Filling carbon nanotubes (CNTs) has prompted significant progress in preparation of novel materials with potential control over their intrinsic mechanical and physical properties [1][2][3]. The confined environments of nanotubes permit the formation of unique encapsulated low dimensional structures with unusual properties compared with the bulk with possible applications as nano-catalysts, electronic devices and magnetic tapes [4,5].…”

“…In most previous reports, certain organometallic compounds containing Fe, Co and Ni have been used for the production of CNT encapsulated binary alloy nanowires [14,15]. We have previously reported a simple and cost effective method to synthesize MWNTs in large yield and good purity by catalytic decomposition of acetylene using certain Zr based AB 2 and Mischmetal (Mm) based AB 2 /AB 5 alloy hydride catalysts, prepared through hydrogen decrepitation technique [16][17][18]. These alloy hydride particles are catalytically very active, due to the presence of transition metals such as Fe, Co or Ni and are free from being oxidized due to their novel preparation technique.…”