Shaobai Sang

Microstructural Evolution and Oxidation Resistance of Multi-walled Carbon Nanotubes in the Presence of Silicon Powder at High Temperatures

The microstructural evolution and oxidation resistance of multi-walled carbon nanotubes (MWCNTs) by directly heating silicon powder and MWCNTs in a coke bed from 1000 to 1500 C are investigated with the aid of X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and thermogravimetry-differential scanning calorimetry (TG-DSC). The results showed that the morphology and microstructure of MWCNTs did not change much after being treated from 1000 C to 1200 C. An obvious SiC coating was formed on the surface of MWCNTs from 1300 to 1400 C. Up to 1500 C, nearly all the MWCNTs transformed into SiC nanowires. The oxidation resistance of the treated MWCNTs was improved compared with as-received ones. Non-isothermal kinetics showed that the oxidation activation energy of the treated MWCNTs reached 208 kJ/mol, much higher than 164 kJ/mol of as-received ones.

Effects of catalysts state on the synthesis of MWCNTs modified expanded graphite through microwave-assisted pyrolysis of ethanol

Abstract Multi-walled carbon nanotubes (MWCNTs) were prepared through microwave-assisted pyrolysis of ethanol to enhance the electron transfer of expanded graphite (EG). Three kinds of Fe-containing catalyst precursors (ferric nitrate, citric acid-enhanced ferric nitrate and ferrocene) were designated in the present work to investigate the influences of catalyst states on the formation of MWCNT. The cyclic voltammograms and electrochemical impedance of the prepared specimens were characterized. Furthermore, the microstructures of catalyst-loaded EG before and after microwave treatment were investigated by means of SEM and TEM. The results show that the growth of MWCNT under microwave treatment is determined by the state of catalyst and only nanoscaled Fe-containing catalysts favor the formation of MWCNT. The ferric nitrate tends to grow up into submicron Fe2O3 particles, which impedes the growth of MWCNT. In comparison, citric acid enhances the dispersion of ferric nitrate, allowing the growth of MWCNT. Ferrocene possesses dual functions, namely it assures well distribution of nanoscaled catalysts and is also responsible for the growth of first generation of MWCNT. With the growth of MWCNT on EG, the anodic peak current densities and charge transfer resistance of the MWCNT modified EG outperform those of pure EG remarkably.

Erratum to: Preparation of MgO-SnO2-TiO2 Materials and Their Corrosion in Na3AlF6-AlF3-K3AlF6 Bath

YIBIAO XU, Ph.D. Student, YAWEI LI and JIANHONG YANG, Professors, SHAOBAI SANG and QINGWEI QIN, Associate Professors, and BO REN, Postgraduate Student, are with The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science & Technology, Wuhan 430081, P.R. China. Contact e-mail: liyawei@wust.edu.cn The online version of the original article can be found under doi: 10.1007/s11663-015-0295-0. Article published online March 12, 2015.