Mao Fa Wang

High-Quality Single-Walled Carbon Nanotubes Synthesized by Floating Catalyst Chemical Vapor Depostion

High-quality single-walled carbon nanotubes (SWNTs) are a key aspect in the emerging field nanotechnology. Although many approaches have been developed, the research on the synthesis of SWNTs is still needed. In this study, we report the synthesis of high-quality SWNTs by floating catalyst chemical vapor deposition, which employs ferrocene as the catalyst precursors. We obtained massive deposits at low temperature region. The deposits were characterized by scanning electron microscopy, transmission electron microscopy, and visual laser Raman spectroscopy. The Raman spectrum obtained from raw deposits shows clear radial breathing mode at the range from 180cm-1 to 300cm-1 and high-intensity graphite mode at 1577.7cm-1 with a shoulder at 1550.5cm-1, and almost no detectable peak around at 1545cm-1, which is induced by defects, is observed. These results indicate that the deposits are high-quality SWNTs.

Carbon Nanofibers Synthesized by Ethanol Catalytic Chemical Vapor Deposition

. Carbon nanofibers have been attracted many attentions for their potential applications in nanocomposites and electromagnetic wave-absorbing materials due to their remarkable mechanical, electrical and other properties. Ethanol as carbon source possesses low toxicity, easier storage and transportation. In this paper, we report ethanol catalytic chemical vapor deposition (ECCVD) for synthesizing carbon nanofibers. We utilized ferrocene as catalyst precursor and use ethanol as carbon source to synthesize carbon nanofibers by ethanol chemical vapor deposition. The deposits were characterized by employed scanning electron microscopy, transmission electron microscope and Raman spectroscopy.

Preparation of Silica Nano-Rods by CVD

The straight silica nano-rods with a diameter of about 200nm and smooth surface were synthesized by chemical vapor deposition method at 1300°C. The as-synthesized samples were characterized by means of scanning electron microscopy, energy dispersive x-ray, and transmission electron microscopy. The results show that as-synthesized silica nano-rods have a uniform size, well-defined shape, and smooth surface. However, the morphologies and microstructures of silica nano-rods are affected by synthesis conditions, such as the concentration of the SiOx and the the deposition temperature. On the basis of these experimental results, a possible growth mechanism of silica nano-rods in this process is proposed.

Synthesis of Mono-Sized Silica Nanoparticles by Combustion Technique

A simple combustion technique is presented for the preparation of mono-sized silica nanoparticles by employing tetraethyl orthosilicates as precursor. The as-grown white powders were characterized by means of scanning electron microscopy. The results showed the size of silica nanoparticles were relative to the unique synthesis conditions. According to the observation and analysis of the scanning electron microscopy images, the possible growth mechanism of silica nanoparticles in this process is proposed.

Synthesis of Carbon Nanofibers by Ethanol Catalytic Combustion Technique

In this paper, we report a simple growth of carbon nanofibers by means of the combustion of ethyl alcohol. In our experiment, copper plate was employed as substrate, iron nitrate and iron chloride as catalyst precursor and ethanol as carbon source. The as-grown carbon nanofibers were characterized by employing scanning electron microscopy, transmission electron microscopy, high-resolution field-emission transmission electron microscopy and Reinshaw optical confocal Raman spectroscopy. Our results suggested that it would tend to form relatively uniform nanofibers when the catalyst precursor was iron nitrate, however, to form some helical structure nanofibers when the catalyst precursor was iron chloride. The sample using iron chloride as the catalyst precursor has a higher graphitization degree than that using iron nitrate as the catalyst precursor.

Synthesis of Straight Y-Shaped Silica Nanorods

The straight Y-shaped silica nanorods have been synthesized on Si wafer by thermal chemical evaporation of mixed powders of silica and graphite at 1300°C and condensation on Si substrate without assistance of any catalyst. The synthesized samples were characterized by means of scanning electron microscopy, transmission electron microscopy. The results suggested that the straight Y-shaped silica nanorods have uniform diameter about 50-200nm and neat smooth surface. The growth of such silica nanorods may be a result of the fluctuation of external conditions causing a change in the growth direction of silica nanorods developed.

Influence of Carbon Sources and Catalytic Precursors on the Products Prepared by Catalytic Combustion

It is very important to study the effects of various factors on synthesis of carbon nanofibers for controlled synthesis, which plays a significant role in realizing desired nanostructures or nanodevices for applications. In this report, we employed different carbon source and different catalyst precursor solution, respectively, and studied the effects of those on carbon nanofibers that were synthesized by catalytic combustion process. We have characterized the as-grown carbon nanofibers by employing scanning electron microscopy (SEM) for deep understanding.

Catalytic combustion synthesis of carbon nanofibers

The catalytic combustion technique was used to synthesize carbon nanotubes and carbon nanofibers. In this paper, we report that carbon nanofibers were synthesized by ethanol catalytic combustion technique. The as-grown products were characterized by means of scanning electron microscopy, transmission electron microscopy, Raman spectroscopy. The results showed that the products have a mass of carbon nanofibers. However, morphology and microstructure of carbon nanofibers are affected by synthesis conditions, such as stability of flames and sampling time, sampling temperature etc. Different Influence factors were depicted in detail. Ethanol catalytic combustion technique offer a simple method to synthesize carbon nanotubes and carbon nanofibers, it also has some advantages, such as flexible synthesis conditions, simple setup, and environment-friendly.

Raman Spectroscopic Characterization of Carbon Nanofibers Obtained by Using Metal Chloride as Catalyst Precursor

Carbon nanofibers have been obtained by the interaction of ethanol with metal chloride over copper plate. Different metal chloride was used as the catalyst precursor. The products were characterized by the Raman spectroscopy for the degree of graphitization. The relative intensities and the amount of amorphous carbon were estimated. The results indicate that the catalyst precursor has effects on the degree of graphitization of carbon nanofibers.

The Effects of Size of Catalysts on the Morphology of Carbon Fibers

A simple method was reported for synthesis of carbon nanofibers. Ethanol burner was employed as the setup. Different morphological carbon nanofibers were synthesized by the decomposition of ethanol. As-grown carbon nanofibers were characterized. The results indicate that depending on the size of catalyst, carbon deposits with different morphologies were produced.