Mohd Asyadi Azam

Aligned carbon nanotube from catalytic chemical vapor deposition technique for energy storage device: a review

Carbon nanomaterial especially carbon nanotube (CNT) possesses remarkably significant achievements towards the development of sustainable energy storage applications. This article reviews aligned CNTs grown from chemical vapor deposition (CVD) technique as electrode material in batteries and electrochemical capacitors. As compared to the entangled CNTs, aligned or well-organized CNTs have advantages in specific surface area and ion accessibility in which more electrolyte ions can access to CNT surfaces for better charge storage performance. CVD known as the most popular technique to produce CNTs enables the use of various substrates and CNT can grow in a variety of forms, such as powder, films, aligned or entangled. Also, CVD is a simple and economic technique, and has good controllability of direction and CNT dimension. High purity of as-grown CNTs is also another beauty of the CVD technique. The current trend and performance of devices utilizing CNTs as electrode material is also extensively discussed.

Thermal Degradation of Single-Walled Carbon Nanotubes during Alcohol Catalytic Chemical Vapor Deposition Process

We have grown single-walled carbon nanotubes (SWCNTs) from Co catalyst thin films using the alcohol catalytic chemical vapor deposition (CVD) method for different CVD processing times. The structural properties of the SWCNTs grown have been investigated by Raman spectroscopy with various laser excitations. The growth progressed up to t ¼ 20 min, but the Raman intensity of SWCNTs decreased with increasing CVD processing time. The quality of as-grown SWCNTs also decreased with increasing CVD processing times, similar to the trend for Raman intensity. Raman intensity analysis in the radial breathing mode region shows a relatively wide distribution for SWCNTs grown for all CVD processing times, owing to the variations in growth and burning rates with SWCNT diameter. In this paper, we suggest that Co catalyst poisoning and SWCNT burning occur when the CVD processing time is more than 20 min. # 2010 The Japan Society of Applied Physics

X-Ray and Morphological Characterization of Al-O Thin Films Used for Vertically Aligned Single-Walled Carbon Nanotube Growth

Al oxide (Al-O) films used as catalyst-support layer for vertical growth of carbon nanotubes (CNTs) were characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission, and scanning electron microscopies (TEM and SEM). EB-deposited Al films (20 nm) were thermally-oxidized at 400 o C (10 min, static air) to produce the surface structure of Al-O. The Al-O was found amorphous and after the incorporation with Co catalyst, the grown CNTs were twisted together before vertically grown. The prepared Al-O surface is an electron-acceptor-dominated (oxygen-rich) surface where the formation of active catalyst could be enhanced to promote the vertically aligned CNT growth.

Fabrication and characterization of carbon nanotube field-effect transistors using ferromagnetic electrodes with different coercivities

We have succeeded in fabricating source and drain structures of carbon nanotube field-effect transistors (FETs) using ferromagnetic electrodes with different coercive fields. The electrodes were successfully bridged with single-walled carbon nanotubes (SWNTs) by a direct growth method. We investigated the magnetic properties of electrodes and FET characteristics. The magnetic properties of the electrodes survived the chemical vapor deposition process at up to 800 °C, and were found to be qualitatively preserved even at growth times of 20 and 30 min. In addition, the devices showed good field-effect modulation in conductivity. This device structure could be applied to carbon nanotube spintronics devices fabricated by a direct growth method.

A Sustainable Polymer Composite from Recycled Polypropylene Filled with Shrimp Shell Waste

This research explores the potential of using recycled polypropylene (PP) incorporated with shrimp shell waste to produce a sustainable polymer composite. In this study, the mechanical and physical properties of recycled polypropylene/shrimp shell (rPP/SS) composites prepared by melt compounding and compression molding techniques were evaluated. The effects of SS loading were investigated by using various compositions of rPP/SS composites, ranging from 0 to 8 wt.% SS that consists of two different sizes, i.e., fine and coarse SS. The composites were tested for their mechanical and physical properties using impact, tensile and water absorption tests. Furthermore, the morphology of the composites was examined by using a scanning electron microscope (SEM). Incorporation of SS was found to increase the Youngs modulus of the rPP, but the impact and tensile strength showed a decrease. However, we observed that both the impact and tensile strength improve with the further increase of the SS content. In other words, composites with high shrimp shell loading were observed to exhibit better tensile and impact properties compared to composites with low shrimp shell loading. Moreover, at 8 wt.% of SS, the value of tensile strength is comparable to that of neat rPP.

Electrochemical synthesis and characterization of poly(3-hexylthiophene)/single-walled carbon nanotube array hybrid materials

AbstractIn this study, we demonstrate that by directly employing single-walled carbon nanotube arrays (SWCNT-arrays)—grown on conductive substrates—as working electrodes, selective and uniform electrodeposition of a conducting polymer, namely poly(3-hexylthiophene), can be achieved on the surface of the nanotubes. The overall kinetic pattern of the electrodeposition was studied by separating the deposition charge from the one related to the redox transformation of the polymer film deposited during the precedent cycles. Both the structure and the electrochemical properties of the hybrid materials were studied as a function of the electrodeposition cycles, thus the amount of the formed polymer. The hybrids were characterized by electron microscopic (SEM, TEM) and vibrational spectroscopic (Raman spectroscopy) means. The obtained results were compared and contrasted with those gathered on macroscopic-sized multi-walled carbon nanotube array-based composites in our group recently. Overall, we conclude that electrochemical polymerization is an attractive tool to synthesize conducting polymer/SWCNT hybrid materials with controlled composition and morphology.n Graphical abstractHighy organized nanostructures of conduction polymer/SWCNT array hybrids were obtained via electrodeposition

Synthesis of Fe catalyst nanoparticles by solution process towards carbon nanotube growth

Abstract The iron catalyst nanoparticles were prepared on silicon wafers by solution process, which first spins coat the solution of iron (III) nitrate nonahydrate and colloidal solution, and then are heated to obtain the formation of iron nanoparticles. The effects of different spin speed and heat treatment parameters during the solution process were investigated. As a result, the smallest thickness of the Fe catalyst thin films is 78 nm, and the smallest Fe catalyst nanoparticles, i.e. 9·67 nm, were obtained at the highest spin speed of 8000 rev min−1 and 500°C. The uniformity of the thin films was also found to increase with increasing spin speed. The particle and thickness analysis was performed by means of field emission scanning electron microscopy.

Structural And Electronic Properties Of Transition-Metal Oxides Attached To A Single-Walled CNT As A Lithium-Ion Battery Electrode : A First-Principles Study

Single-walled carbon nanotubes (SWCNTs) and metal oxides (MOs), such as manganese(IV) oxide (MnO2), cobalt(II, III) oxide (Co3O4), and nickel(II) oxide (NiO) hybrid structures, have received great attention because of their promising application in lithium-ion batteries (LIBs). As electrode materials for LIBs, the structure of SWCNT/MOs provides high power density, good electrical conductivity, and excellent cyclic stability. In this work, first-principles calculations were used to investigate the structural and electronic properties of MOs attached to (5, 5) SWCNT and Li-ion adsorption to SWCNT/metal oxide composites as electrode materials in LIBs. Emphasis was placed on the synergistic effects of the composite on the electrochemical performance of LIBs in terms of adsorption capabilities and charge transfer of Li-ions attached to (5, 5) SWCNT and metal oxides. Also, Li adsorption energy on SWCNTs and three different metal oxides (NiO, MnO2, and Co3O4) and the accompanying changes in the electronic properties, such as band structure, density of states and charge distribution as a function of Li adsorption were calculated. On the basis of the calculation results, the top C atom was found to be the most stable position for the NiO and MnO2 attachment to SWCNT, while the Co3O4 molecule, the Co2+, was found to be the most stable attachment on SWCNT. The obtained results show that the addition of MOs to the SWCNT electrode enables an increase in specific surface area and improves the electronic conductivity and charge transfer of an LIB.

Electronic properties and gas adsorption behaviour of pristine, silicon-, and boron-doped (8, 0) single-walled carbon nanotube: A first principles study

Carbon nanotubes (CNTs) have received enormous attention due to their fascinating properties to be used in various applications including electronics, sensing, energy storage and conversion. The first principles calculations within density functional theory (DFT) have been carried out in order to investigate the structural, electronic and optical properties of un-doped and doped CNT nanostructures. O2, CO2, and CH3OH have been chosen as gas molecules to study the adsorption properties based on zigzag (8,0) SWCNTs. The results demonstrate that the adsorption of O2, CO2, and CH3OH gas molecules on pristine, Si-doped and B-doped SWCNTs are either physisorption or chemisorption. Moreover, the electronic properties indicating SWCNT shows significant improvement toward gas adsorption which provides the impact of selecting the best gas sensor materials towards detecting gas molecule. Therefore, these pristine, Si-, and B-doped SWCNTs can be considered to be very good potential candidates for sensing application.

Characterization of graphene growth using RF-PECVD on Cobalt films

We report graphene growth on polycrystalline Cobalt (Co) films by using induced coupled plasma RF-PECVD at 800°C temperature with 40 W plasma power. We also do the comparison by growing with and without plasma to observe the contribution of plasma in graphene growth on Cobalt films. Results show that the existence of plasma helps graphene formation meanwhile the existence of graphene is not observed with the absence of plasma. Plasma power is proven to generate high energy for decomposing methane forming radical carbon for the graphene growth mechanism. The as-grown graphene was characterized by using Raman Spectroscopy and Atomic force microscopy (AFM). The graphene was identified as multilayer from the Raman spectra. With the aid of plasma and proper optimization of the growth condition, the number of graphene layers can be tailored for low temperature substrate.