Preparation of micro-coiled carbon fibres by metal powder-activated pyrolysis of acetylene containing a small amount of sulphur compounds

Growth and Properties of Carbon Microcoils and Nanocoils

“…The reaction temperature used to synthesize b-DHCFs is usually between 700 and 850 °C with CVD and depends on the catalyst chemical composition [15]. Like the wide reaction temperature range, choice of catalyst can also vary broadly.…”

“…Like the wide reaction temperature range, choice of catalyst can also vary broadly. For example, Motojima et al [15] demonstrated that many types of metal powder catalysts such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, and Ni could be used to grow b-DHCFs, which Motojima et al [15] referred to as CMCs. Each of these metal catalysts has a different optimum reaction temperature and amount of sulfur additive gas during CVD.…”

“…Using Ni, the average external coil diameter was found to be 5 μm and the length of coil after two hours was between 5 and 8 mm [20]. Although Fe has been used as catalyst for the synthesis of carbon nanofibers and nanotubes, Fe powder with sulfur additive gas was not able to synthesize double helical CMCs [15]. Although hydrogen sulfide (H2S) gas or thiophene (C4H4S) has usually been used to synthesize double helical CMCs, they can be obtained without these additives using MoS2 catalyst.…”

“…This led to a proposed growth mechanism for double helical filaments [14]. In addition, the Motojima research group established a method to synthesize bidirectionally grown double helical carbon filaments or carbon microcoils (CMCs) that were several micrometers in diameter by adding sulfur compound [15]. The Nakayama research group developed tip grown single helical carbon filaments or carbon nanocoils (CNCs) with diameters in the range of several tens to several hundred nanometers using iron-tin based catalysts [6].…”

“…The amount of sulfur or phosphorus additive, the compositions and flow rate of gases and reaction temperature all strongly influence the growth of double helical structures [4,15]. Chemical vapor deposition (CVD) has been the most popular technique used to synthesize b-DHCFs; but other methods have been explored as well, including laser-induced thermal decomposition.…”