N.A. Asli

Variety of Bio-Hydrocarbon Precursors for the Synthesis of Carbon Nanotubes

In this work, we have synthesized carbon nanotubes (CNT) using different bio-hydrocarbon precursors namely palm, olive, coconut, corn and sesame oils. Prior to the synthesis process, thermogravimetric analysis (TGA) characterization was performed on the carbon precursors to facilitate the optimization procedures of CNT and reach maximum yield and higher quality CNT. The CNT arrays were deposited on a silicon substrate by thermal catalytic decomposition of the precursor using 5.33 wt% ferrocene. The synthesis was carried out at 750 °C for 60 min under argon ambient. The samples were characterized using field emission scanning electron microscopy, micro-Raman spectroscopy and TGA analysis. The difference in oil density resulted in different quality and tube diameter of CNT produced. Among all, the CNT synthesized from coconut oil can be considered as the best bio-hydrocarbon precursor for higher quality (ID/IG ~0.62) and good purity (81.95 %) CNT.

Synthesis and nucleation-growth mechanism of almost catalyst-free carbon nanotubes grown from Fe-filled sphere-like graphene-shell surface

This finding focuses on the optimization of synthesis time for the transformation of Fe-filled spherical-like graphene shell (GS) to almost catalyst-free carbon nanotube (CNT) structure using two-stage catalytic chemical vapor deposition apparatus. The camphor oil and ferrocene were used as carbon precursor and catalyst respectively, following the variety growth of graphene-family nanomaterials for 2, 4, 6, 8, 10, 30, and 60 min at 800°C synthesis temperature. The graphene-family nanomaterial properties were characterized using field emission scanning electron microscope, high resolution transmission electron microscope, micro-Raman spectrometer, thermogravimetric, and carbon-hydrogen-nitrogen-sulfur/oxygen (CHNS/O) analyzer. The result of field emission scanning electron microscopy analysis reveals that the CNTs were observed with high aspect ratio at 60-min synthesis time. The dependence of integrated intensity ratio of D-band and G-band (ID/IG) presented that ID/IG ratio sharply decreases with longer synthesis time. At higher synthesis time, thermogravimetric and CHNS/O analysis of CNT can obviously improve with decreases of non-carbonaceous material and transition metal catalyst. The nucleation-growth model of Fe-filled spherical-like GS to almost catalyst-free CNT has been highlighted to explain the change in growth mode.

Effect of the ratio of catalyst to carbon source on the growth of vertically aligned carbon nanotubes on nanostructured porous silicon templates

BackgroundThe effect of the ratio of catalyst to carbon source on the growth of vertically aligned carbon nanotubes (VACNTs) has been studied.ResultsDense VACNTs were successfully synthesised on optimised nanostructured porous silicon templates using modified floated carbon source-catalyst in a two-stage hot filament thermal chemical vapour deposition system with different amounts of ferrocene as the catalyst at 800°C. The surface morphologies of the VACNTs were analysed using field emission scanning electron microscopy, and the crystallinity of the nanotubes was observed using micro-Raman spectroscopy.ConclusionsThese data revealed that the amount of catalyst used significantly affected the diameter, crystallinity and growth rate of the synthesised nanotubes. The average diameter of the nanotubes ranged from ≈ 9 to 30 nm with lengths of ≈ 110 μm when 0.5 g ferrocene was used.

Effect of iron and cobalt catalysts on the growth of carbon nanotubes from palm oil precursor

Catalysts which are typically a transition metal is mandatory and plays an important role in the production of CNT. In this work, the effect of iron (Fe) and cobalt (Co) nitrate catalyst on the growth of carbon nanotubes (CNT) were systematically studied. Green bio-hydrocarbon precursor namely palm oil was used as a precursor. The synthesis was done using thermal chemical vapour deposition method at temperature of 750°C for 15 min synthesis time. The Fe and Co solution were spin-coated separately on silicon substrate at speed of 3000 rev.min-1. The CNT characteristics were analyzed using field emission scanning electron microscopy and micro-Raman spectroscopy. The experimental results revealed that CNT properties were strongly affected by the catalyst type. CNT catalyzed by Co yields large diameter, crooked tube and lower quality, whereas CNT produced by Fe catalyst results in the smallest diameter and reasonably good graphitization. As a conclusion, Fe was considered as the optimum catalyst for better CNT structure and crystallinity. This was due to efficient, uniform and stable Fe catalytic activity as compared to Co catalyst in producing CNT.

Novel Method: Coral Like Structure of Align Carbon Nanotubes (A-CNTs) on Porous Silicon Template (PSiT) without Catalyst; Green Approach

Align Carbon Nanotubes (A-CNTs) is very promising materials and offer attractive applications especially in opto-emission devices and nanoelectronic. Normally CNTs prepared by catalytic chemical vapor deposition using various types of template such as alumina, quartz, silicon and glass template. In this paper, Novel method was introduced to prepare A-CNTs which is combination between immersion and evaporation method. The align CNTs were successfully growth on Porous Silicon template (PSiT) without catalyst. Camphor oil is used as precursor and evaporation temperature is at 800 °C. The PSiT was prepared by photo-electrochemical anodization method. The surface morphology of PSiT layer and A-CNTs were studied using Field Emission Scanning Electron Microscope (FESEM).While Raman spectroscopy will be carried out to study the degree of crystallinity or graphitization of A-CNTs. The growth mechanism will be discussed in this paper. Stubby A-CNTs was successfully growth with 30 nm diameter and 250 nm length on PSiT without metal catalytic process. Meanwhile, this novel technique was found that PSiT is an ideal template for growing A-CNTs without metal catalyst assisted. This novel technique was capable to obtained carbon nanotubes without metal catalyst assisted and improves their purity of product with low cost.

Relation of Anodisation Parameter for Nanocrystallite Size of Porous Silicon Template Studied by Micro-Raman Spectroscopy

Nanostructured porous silicon templates (NPSiT) were prepared by photo-electrochemical anodization of p-type crystalline silicon in HF electrolyte at different etching time. Two set anodisation parameter were observed, anodisation time nd current density applied. For set one, five samples were prepared with etching time varied from 10 to 50 minutes at 20 mA/cm2 of current density. For set two, five samples were prepared with current density varied from 5 to 40 mA/cm2 for 30 minutes. The effects of these anodisation parameter on NPSiT were observed based on nanocrystallite size. These studied was demonstrated by Raman spectroscopy. It was found that NPSiT sample with large pore diameter, which is smaller nanocrystallites size of Si between pore.

Diameter controlled of carbon nanotubes synthesized on nanoporous silicon support

Carbon nanotubes (CNTs) have been successfully synthesized on nanoporous silicon template (NPSiT) using botanical source, camphor oil. Diameter of CNTs synthesized was controlled by pore size of NPSiT prepared by photo-electrochemical anodization method. The diameter of CNTs grown on different NPSiT corresponded to the pore diameter of NPSiT. FESEM images showed self-organized bundles of fiber-like structures of CNTs with diameter of around 20nm which were successfully grown directly on nanoporous silicon while raman spectra obtained ratio of ID/IG at 0.67.

Raman and photoluminescence spectroscopy studies on porous silicon nanostructures

In this work, the study of photoluminescence (PL) and Raman spectroscopy of porous silicon nanostructures (NPSi) have been carried out. The samples were prepared by photo-electrochemical anodization method using p-type silicon wafer based. Photoluminescence measurement of NPSi shows increase of PL intensity and blue shift with increasing of etching time. The varies etching time from 20 min to 40 min produced PL emission at a range of 550–800 nm which is in the range of visible PL band [Fig. 1]. While Raman Spectroscopy measurement shows the spectra were symmetry and broaden when etching time increase from 20 min to 40 min [Fig. 2]. It may due to lattice mismatch strain and part of distortion [1] when porous layer form with increasing the etching time. The photon energy and full half width maximum (FWHM) measurement were carried out to study the optical properties of NPSi which can be used to study the quantum confinement effect.

Anodisation Time-Related Nanocrystallite Size of Porous Silicon Template Studied by Raman Spectroscopy, Photoluminescence and Fourier Transforms Infrared Spectroscopy

Nanostructured Porous Silicon templates (NPSiT) were prepared by photo-electrochemical anodization of p-type crystalline silicon in HF electrolyte at different etching time. Five samples were prepared with etching time varied from 10 to 50 minutes at 20 mA/cm2 of current density. The effects of etching time on NPSiT were observed based on nanocrystallite size, photon energy and surface distribution. These studied was demonstrated by Raman spectroscopy, photoluminescence (PL) and Fourier transforms infrared spectroscopy (FTIR). It was found that NPSiT sample with large pore diameter, which is smaller nanocrystallites size of Si between pore. The optical properties of NPSiT were investigated by photoluminescence (PL) and PL peak broadening and shifting towards higher energy can be observed with increasing etching time. The optimum etching time with respect to PL intensity was obtained at 30 minutes, for which uniform pores and a shift of the PL maximum to a higher energy of 1.9 eV is observed.

Effect of Electrolyte Volume Ratio on Electroluminescence of Porous Silicon Nanostructures (PSiNs) Intensity

For this experiment, the main purpose of this experiment is to determine the electroluminescence of PSiNs samples with optimum electrolyte volume ratio of photo-electrochemical anodisation. PSiNs samples were prepared by photo-electrochemical anodisation by using p-type silicon substrate. For the formation of PSiNs on the silicon surface, a fixed current density (J=20 mA/cm2) and 30 minutes etching time were applied for the various electrolyte volume ratio. Volume ratio of hydrofluoric acid 48% (HF48%) and absolute ethanol (C2H5OH), HF48%:C2H5OH was used for sample A (3:1), sample B (2:1), sample C (1:1), sample D (1:2) and sample E (1:3). The light emission can be observed at visible range. The effective electroluminescence was observed for sample C. Porous silicon nanostructures light–emitting diode (PSiNs-LED) has high-potential device for future flat screen display and can be high in demand.