First, three prepared samples (one sample from the Fe only series, one sample from
the Fe + S1813 series and one sample from the Fe + S1813 + Plasma series) were loaded into the thermal furnace, and the growth process was conducted selleckchem for 10 min at 900°C in a CH4 + H2 + Ar gas mixture at atmospheric pressure after 40-min-long heating. A gas supply system (bottles and mass flow controllers) was used to maintain the desired flow rates (up to 1,000 sccm for He or Ar) in the reaction area (quarts tube). After the growth, the samples were cooled down slowly, together with the furnace. Next, other three prepared samples (one from each series) were loaded into the thermal furnace, and the carbon nanotube growth was conducted for 10 min at 750°C in a C2H4 + H2 + Ar gas mixture at atmospheric pressure. Finally, three samples from each series were treated for 10 min at 700°C in C2H2 + H2 + Ar. Note that all the samples were coated with Fe which is an efficient catalyst for carbon nanotube growth due to the high carbon solubility in Fe and ability to form iron carbides [30]. The process sequence diagrams for all the samples are shown in Figure 2a, and the three-dimensional representation of one of the targeted structure (carbon
MG-132 research buy nanotubes in the nanoporous membrane) is shown in Figure 2b. The process was repeated on several samples to confirm the reproducibility. With the process conditions kept constant, tuclazepam no significant variation in the results (nanotube size, system morphology, etc.) were found on the samples that have undergone the same process. Figure 2 Temperature/time dependencies and three-dimensional visualization of the targeted structure. (a) Temperature/time dependencies for three processes used for growing carbon nanotubes on alumina membranes. (b) Three-dimensional visualization of the targeted structure – carbon nanotubes partially embedded in the nanoporous alumina matrix (membrane). The ready samples were then examined using field-emission scanning electron microscope (FE-SEM, type Zeiss
Auriga, Carl Zeiss, Inc., Oberkochen, Germany) operated at electron beam energy of 1 to 5 keV with an InLens secondary electron detector. The structure of the nanotubes was studied by transmission electron microscopy (TEM) technique using a JOEL 2100 microscope (JEOL Ltd., Akishima-shi, Japan) operated at the electron beam energy of 200 keV. Micro-Raman spectroscopy was performed using a Renishaw inVia spectrometer (Renishaw PLC, Wotton-under-Edge, UK) with laser excitations of 514 and 633 nm and a spot size of approximately 1 μm2. Raman spectra from multiple spots were collected to perform the statistical analysis of the samples. Results and discussion The results of the above described experiments are summarized in Table 1, in line with the process reagents and temperatures. SEM image of the typical nanotube array grown in the nanoporous membrane is shown in Figure 1d.