Synthesis of Nitrogen Incorporated Carbon Nanotubes with Different Diameters by Catalytic Pyrolysis

CHEM. RES. CHINESE UNIVERSITIES 2011, 27(6), 903- -905Synthesis of Nitrogen Incorporated Carbon Nanotubes withDifferent Diameters by Catalytic Pyrolysis of ButylamineJIN Hai-ying, BING Nai-ci, WANG Ling-ling and WANG Li-jun°School of Urban Development and Environment Engineering, Shanghai Second Polyechnic Universiny,Shanghai 201209, P. R. ChinaAbstract Bamboo-like nitrogen-doped carbon(CN,) nanotubes were synthesized by chemical vapor deposition(CVD) at a high reaction temperature of 600- 900 °C. The butylamine and Fe/SBA-I5 molecular sieve have beenused as precursor and catalyst, respectively. Transmission electron microscopy(TEM) and high resolution transmis-sion electron microscopy(HRTEM) observations show that the outer diameter and wall thickness as well as the innerdiameter were increased with increasing reaction temperature in a temperature range of 600- -800。C. A synergismmechanism of the growth through bulk diffusion and the competitive growth through surface diffusion functionsduring the synthesis of CN, nanotubes was proposed.Keywords Carbon nanotube; Bamboo-like structure; Nitrogen-doped carbon; Multilayer structureArticle ID 1005-9040(2011)-06-903-031 Introductionfor different purposes, nitrogen doped carbon nanotubes withdifferent diameters and different wall thicknesses were synthe-Since the landmark discovery by ljjimna in 19910，carbonsized by CVD at a reaction temperature of 600~ -900 °C. Tonanotubes(CNTs) have attracted great research interests due toinvestigate the effect of the reaction temperature on the diame-their novel structure, uniquc properties, and wide potentialter, wall thickness and mesostructure of nitrogen doped carbonapplication. Most of the properties of CNTS are highly depen-nanotubes, X-ray diffraction(XRD), transmission electron mi-dent on their diameters, chiralit, structural defects2I, andcroscopy(TEM)，and high resolution transmission electronlength which can be controlled by regulating reaction condi-microscopy(HRTEM) images of the products were measured,tions. It is desirable or even essential to obtain the CNTs withdifferent properties for specific purposes, which is actually amesostructure change. A synergism mechanism of the growthcurrent big challenge in CNT studies- 0. Doping differentthrough bulk diffusion and the competitive growth throughelements is a promising method to tailor the specific propertiessurface diffusion via vapor-liquid-solid and through bulk-of CNTSl7.8]. The nitrogen-in-corporation could efficiently in-difusion was applied to explaining our experimental results.troduce chemically active sites into the CNTs. Hence, greatefforts have been devoted to the preparation of nitrogen-doped2 Experimentalcarbon(CN,) nanotubes, and many methods such as arc dis-As reported in previous papersl, about 0.5 g ofchargc, magnetron sputtering'. and chemical vapor deposi-Fe/SBA-15 catalyst powder was placed in the central part of ation(CVD) have been employed for the purpose. CVD methodis regarded as the most promising approach due to its low cost,horizontal quartz tube in the furmace. After the reaction cham-mild conditions, and possible large-scale production. Diferentber was evacuated and flushed with N2 several times to removeoxygen and moisture, the reactor was heated to the reactionkinds of precursors, including C- and N-containing moleculessuch as CqH,N(2I, CHgzCNl0, CyH;NI" and HOCN(CH3){"21 ortemperature, e.g.,. 600 °C at a rate of 20。C/min in N2. Butyla-the mixtures of C- or N-containing gaseous species such asmine was then switched into the systcm for about 120 min, byCH/N2{13) and CH2/NH:]l4-16] have been used for the synthe-the carrying gas of N2 at a flow rate of 20 mL/min passingsis of CNx nanotubes. Actually, controllable synthesis andthrough a butylamine saturator at room temperature. The feedstructural modulation of the carbon-based nanotubes will berate of butylamine was estimated to be about 10 mg/min. Afterpossible only when the growth mechanisms are well unders-that, the reactor was cooled in N2 and a dark sponge liktood, which strongly urges the understanding on this mecha-product was obtained. For comparison, CNTs were also synthe-sized at 700, 800 and 900 °C from butylamine precursor undernism from the theoretical point of view.In this work, to obtain the CNTs with specific propertiesthe same other conditions. The as-prepared products were中国煤化工*Corresponding author. E mail: Ljwang@edsspu.cnReceived April 6, 2011; accepted September 29, 2011.MHCNMHGSupported by the National Natural Science Foundation of China(No.21101 105), NSFC-Shenbua Group(No.51174274), the“Shu Guang" Project, China(No.09SGS4) and the Innovation Program of Shanghai Municipal Education Commission, China(No. 12ZZ195).No.6JIN Hai-ying et al.905nanotubes demonstrates an increasing tendency with reactiona higher reaction temperature.temperature increasing, which should result from the synthesismechanism of bulk diffusion and surface diffusion growth2).4 ConclusionsFrom Fig.3(A)- -(F), it is also learmed that as the reaction tem-In conclusion, a series of bambo-like CNx nanotubes hasperature is increased, the domains become straighter and lessbeen catalytically synthesized fom butylamine in a tempera-corrugated, which was resulted from the decrease of the totalture range of 600- -900 。C. The outer diameter and wall thick-nitrogen content in the CN, nanotubes'2. The total nitrogenness of CN, nanotubes increased with reaction temperaturecontent in the CN, nanotubes was obtained from EDX detec-increasing from 600- 900 。C. And a synergism mechanism oftion, which depends on the reaction temperature(ln). The totalcompetitive growth through surface diffusion via vapor-liquid-nitrogen atom content decreases from the highest value of 8.8%solid and growth through bulk diffusion was proposed. Wefor 1p=600 °C to the lowest one of 2.7% for (p=900 °C, andexpect that these results will contribute to the understanding ofincreases a lite to 4.4% for t4p=700 。C and 3.6% forthe formation and application of the CNx nanotube materials.14n=800 °C.As discussed previouly!2, at a low reaction temperature,Referencesconsiderable butylamine molecules were selectively dehydro-[I] lijima s, Nature, 1991, 354, 56genated on the catalyst surface, and CNx nanotubes were pro-[2] Hong C., Yong Y, Zheng H., Fu H. K, Yan W. M, Yi C, J. 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B. 2005, 109, 1683a 600 °C; b.700°C;c. 800 C; d 900 C.中国煤化工MYHCNM HG