X.P. Zou

Controllable growth of single wall carbon nanotubes by pyrolizing acetylene on the floating iron catalysts

Single wall carbon nanotubes (SWNTs) without amorphous carbon coating were prepared by thermally decomposing acetylene (C2H2) at the temperature range 750–1200 °C in a floating iron catalyst system. The C2H2 partial pressure was controlled to make a carbon supply limiting growth of SWNTs. The higher reaction temperature above 1100 °C seemed not to favor the SWNT production due to the quick thermal decomposition of C2H2.

Large-scale synthesis of β-SiC nanorods in the arc-discharge

Single crystals of Tb2Fe17 have been grown by Czochralski method cold crucible system. Good-quality crystals can be obtained by using the relative low growth rate and stoichiometrical composition. The single crystalline sample shows a pure hexagonal Th2Ni17 structure with lattice parameters of n=0.8368 +/- 0.0005nm, c=0.8331 +/- 0.0003nm. No detectable traces of Th2Zn17 phase can be found. A new phase diagram has been given based on the DTA results. Tb2Fe17 compound shows a congruent melting point of 1316 degreesC with 89.5 at % Fe and an eutectic point at 1301 degreesC With 92.5 at % Fe, which is different From the peritectic reacting published in some previous reports (see Dariel et al., J. Lesscommon Met. 35 (1976) 91). The magnetic measurements revealed a small difference in the magneto-crystalline anisotropy which could be measured in good crystal samples. Some growth conditions, such as high rate and non-stoichiometrical starting material, caused second-phase defects. Those defects are difficult to be observed by metallography. but can be indirectly found by measuring the magnetization behavior, type II first-order magnetization process (FOMP). Our results indicate that some defects might affect the rotation path of the magnetic victors in the FOMP

Growth of amorphous silicon nanowires

We have grown vertically aligned amorphous silicon nanowires on Au-Pd co-deposition silicon oxide substrate by thermal chemical vapor deposition using SiH4 gas at 800 degreesC. The diameter of silicon nanowires is in the range 10-50 nm and the length is about 1 mum. Transmission electron microscopy (TEM) observations show that the grown silicon nanowires are of an amorphous state and some of nanowires appear to bifurcate in the vertically growth process. The effect of Hz gas etchings on the catalytic size and the effect of catalytic size on the formation of the vertical growth nanowires are discussed

Nanographite ribbons grown from a SiC arc-discharge in a hydrogen atmosphere

[3] Banhart F, Ajayan M. Self-compression and diamond forma[12] Vignal V, Morawski AW, Konno H, Inagaki M. Quantitative tion in carbon onions. Adv Mater 1997;9(3):261–3. assessment of pores in oxidized carbon spheres using scan[4] Kang ZC, Wang ZL. Mixed-valent oxide-catalytic carbonizaning tunneling microscopy. J Mater Res 1999;14(3):1102– tion for synthesis of monodispersed nano sized carbon 12. spheres. Philos Mag B 1996;73:905–29. [13] Inagaki M, Vignal V, Konno H, Morawski AW. Effect of [5] Wang ZL, Kang ZC. Pairing of pentagonal and heptagonal carbonization atmosphere and subsequent oxidation on pore carbon rings in the growth of nanosize carbon spheres structure of carbon spheres observed by scanning tunneling synthesized by a mixed-valent oxide-catalytic carbonization microscopy. J Mater Res 1999;14(7):3152–7. process. J Phys Chem 1996;100:17725–31. [14] Auer E, Freund A, Pietsch J, Tacke T. Carbon as support for [6] Kang ZC, Wang ZL. On accretion of nanosize carbon industrial precious metal catalysts. Appl Catal spheres. J Phys Chem 1996;100:5163–5. 1998;173:259–71. [7] Wang ZL, Kang ZC. Graphitic structure and surface chemi[15] Flandrois S, Simon B. Carbon materials for lithium-ion cal activity of nanosized carbon spheres. Carbon rechargeable batteries. Carbon 1999;37:165–80. 1997;35(3):419–26. [16] Serp Ph, Figueiredo JL, Bertrand P, Issi J-P. Surface treat[8] Sharon M, Mukhopadhyay K, Yase K, Ijima S, Ando Y, Zhao ments of vapor-grown carbon fibers produced on a substrate. X. Spongy carbon nanobeads – a new material. Carbon Carbon 1998;36(12):1791–9. 1998;36(5–6):507–11. [17] Serin V, Brydson R, Scott A, Kihn Y, Abidate O, Maquin B [9] Inagaki M, Washiyama M, Sakai M. Production of carbon et al. Evidence for the solubility of boron in graphite by spherules and their graphitization. Carbon 1988;26(2):169– electron energy loss spectroscopy. Carbon 2000;38:547–54. 72. [18] Stephan O, Ajayan PM, Colliex C, Cyrot-Lackmann F, [10] Kamegawa K, Yoshida H. Preparation and characterization of Sandre E. Curvature-induced bonding changes in carbon swelling porous carbon beads. Carbon 1997;35(5):631–9. nanotubes investigated by electron energy-loss spectrometry. [11] Wang YG, Chang YC, Ishida S, Korai Y, Mochida I. Phys Rev B 1996;53(2):13824. Stabilization and carbonization properties of mesocarbon microbeads (MCMB) prepared from a synthetic naphthalene isotropic pitch. Carbon 1999;37(6):969–76.

Catalytic synthesis of straight silicon nanowires over Fe containing silica gel substrates by chemical vapor deposition

We report a new method to synthesize very straight silicon nanowires using a porous iron/SiO2 gel as a template by thermal chemical vapor deposition at a temperature of about 500 degreesC. Scanning electron microscopy, transmission electron microscopy and Raman scattering spectroscopy were used to characterize the samples. The results show that a large amount of straight Si nanowires with diameters of about 30 nm and lengths of about 1 mum was obtained. High-resolution transmission electron microscopy observation shows that microtwin defects lie in the straight silicon nanowires. Raman scattering from the nanowires shows a larger line width (about 15 cm(-1)) and a down-shifted (about 9 cm(-1)) peak as compared to that of bulk crystalline silicon

Raman scattering and thermogravimetric analysis of iodine-doped multiwall carbon nanotubes

Iodine-doped multiwall carbon nanotubes ~I-MWNTs! were characterized by means of Raman scattering and thermogravimetric analysis. The results show that multiwall carbon nanotubes ~MWNTs! can be effectively doped by iodine and exchange electrons with iodine. Iodine atoms form charged polyiodide chains inside tubes of different inner diameter, which is similar to the iodine-doped single-wall carbon nanotubes ~I-SWNTs!, but can not intercalate into the graphene walls of MWNTs. The Raman scattering behavior of I-MWNTs exhibits some differences from that of I-SWNTs and the low-dimensional conductive hydrocarbon-iodine complex ‘‘peryleneiI 2.92 .’’

Growth of carbon nanofibers array under magnetic force by chemical vapor deposition

In this Letter, we report the growth of carbon nanofibers arrays by chemical vapor deposition in the presence of magnetic force. We find that when a magnet is applied carbon nanofibers arrays are grown and when the magnet is absent carbon nanotubes arrays are grown at the same experimental conditions. The nanofibers are worse in alignment and less in graphitization than those of the nanotubes grown at the same conditions. What is interesting is that two or three nanofibers can be connected together through a catalyst nanoparticle. These connections might be useful, especially in the fabrication of nanoelectronic devices.

Growth of carbon nanotube arrays using the existing array as a substrate and their Raman characterization

Abstract In this Letter, we report that after oxidation in air and reduction in hydrogen the existing carbon nanotube arrays can be used as a substrate to grow another nanotube array. The two arrays are connected through a thin catalyst layer. Micro-Raman study of these two nanotube arrays shows that they have different characteristic spectra. Besides the small shift in the peak frequencies of the two kinds of arrays in Micro-Raman spectra, we have observed changes in the relative intensities of D, G and D ′ lines and proposed the mechanism of this phenomenon.

Preparation of monodispersed multi-walled carbon nanotubes in chemical vapor deposition

Monodispersed multi-walled carbon nanotubes were prepared in a chemical vapor deposition (CVD) method by using monodispersed nanoparticles of Fe3O4 (1 nm) as the precursor of catalyst particles. High-resolution electron microscopy (HREM) revealed that over 50% of these carbon nanotubes synthesized at 600 degreesC and 180 Torr were quadruple walled nanotubes with mean outer diameter of 5.6 nm. At the same time, in the close tips of these carbon nanotubes, no catalyst particles were detected by HRTEM, which means that the catalyst particles were too small to be detected by HRTEM, even though they exit in the tips of carbon nanotubes in our experiments