Science and Engineering of Materials II

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Authors: Teck Hock Lim, Geok Bee Teh, Richard David Tilley
Abstract: Nanoscale alpha zinc phosphide (α-Zn3P2) particles are a class of promising opto-electronic materials which have attracted worldwide attention. The synthetic protocols pertaining to α-Zn3P2 nanoparticles have been largely based on the use of costly, pyrophoric and toxic phosphines precursors. We reported here the results of our investigation into the viability of fabricating crystalline α-Zn3P2 nanoparticles using phosphorous pentabromide (PBr5) as precursor via an air-stable solid hydrogen phosphide (PH)x intermediate. HRTEM analysis revealed the best sample as spherical crystalline α-Zn3P2 nanoparticles with diameter found to be 5.8±2.1 nm. These particles exhibited photoluminescence centered at 470 nm (2.6 eV), blue-shifted by 1.2 eV from the 1.4 eV of bulk α-Zn3P2.
Authors: Shazia Shukrullah, Norani Muti Mohamed, Maizatul Shima Shaharun, Muhammad Yasar
Abstract: This study investigated the effect of catalyst amount on chemical vapour deposition (CVD) growth of multi-walled carbon nanotubes (MWCNTs) with and without hydrogen feed. The ferrocene weight was varied from 100 mg to 200 mg for CNTs growth over Si/SiO2/Al2O3 substrate. Very few CNTs were seen in micrographs of the samples produced in the absence of the hydrogen feed. Most of the carbon atoms precipitated into amorphous carbon due to existence of inactive catalyst particles. However, CNT structures grown with hydrogen feed were more distinct; the nanotubes were thinner, straight and highly crystalline. MWCNTs arrays/forest length was also increased from 120 µm to 850 µm with hydrogen feed. An increase in catalyst weight significantly affected the diameter, crystallinity, alignment and growth of nanotubes. The lowest inner-shell spacing of 0.348 nm was obtained with 150 mg of ferrocene, which is an indication of growth of relatively pure CNTs. Under the optimum conditions, the areal density of the ferrocene particles was sufficiently increased to get required alignment and crystallinity of MWCNTs.
Authors: Amal Izzati Ismadi, Ku Ahmad Ku Zarina, Norazrina, Kin Yuen Leong, Raja Nor Othman
Abstract: Graphene was introduced in the epoxy matrix for the enhancement of thermal conductivity properties. Dispersion is a crucial step in nanocomposite processing. Therefore, it is important to tackle the issues and homogenously dispersed the graphene in the epoxy matrix. In this paper, we varied the stirring speed in order to understand its effects on enhancing the thermal conductivity values of the composites. Results show that the thermal conductivity increases up to 17.5% with the 1.5% weight loading of graphene that was stirred at 1500 rpm stirring speed. The experiment results are then compared to theoretical calculation by Maxwell model. Study implied that Maxwell model can predict the thermal conductivity of composites because it applies only for small volume fraction of filler. As the filler loading used in this study only up to 1.5 wt. %, Maxwell model was suitable to be used.
Authors: Mohd Junaedy Osman, Wan Md Zin Wan Yunus, Keat Khim Ong, Noor Azilah Mohd Kasim, Siti Hasnawati Jamal, Mansor Ahmad, Nor Azowa Ibrahim
Abstract: Modification of multi-walled carbon nanotube (MWCNT) plays an important role to produce MWCNT crossbreeds that may be useful for exploration of new materials. In this report, characterization of dimethyl dioctadecylammonium bromide (DDOAB) modified multi-walled carbon nanotube (Mo-MWCNT) using Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) is described. FTIR shows the presence of both aliphatic (CH stretching and CH bending) and ammonium (CN stretching) groups from DDOAB and the existence of C=C aromatic functional group from the structure of MWCNT in Mo-MWCNT spectra. This result was supported by TGA result which suggests that there are weight losses due to the degradation of DDOAB (between 250 °C to 500 °C) in the product. In addition, XRD pattern remain after modification suggesting attachment of MWCNT and DDOAB occurs at the surface of MWCNT.
Authors: Mohd Zuhri Shaiful Azni, Ho Kee Tan, Pei Ling Low, Nisha Kumari Devaraj, Boon Hoong Ong, Teck Yong Tou
Abstract: α-Fe2O3 thermoelectric thin films were electrodeposited onto copper substrates using chloride-based electrolytes by means of potentiostatic electrodeposition. The influence of several electrodeposition parameters on the surface morphology, elemental composition and electrical conductivity of the deposited films was studied and analyzed. The deposits formed porous, wire-like morphology, with the smallest width measured to be ~60 nm. The wires tend to aggregate to form clusters, in addition to multi-layered growth of the wires. Between the parameters studied, electrolyte concentration and deposition time parameters have higher influences on the electrical conductivity of the deposited films, with the increment up to two fold higher. Deposition potential parameter offered the lowest capability to improve on the electrical conductivity in addition to the non-uniform distribution of the measured electrical conductivities. The tunable electrical conductivity is favorable for improving the performance of α-Fe2O3 films for thermoelectric applications.
Authors: Mustaffa Ali Azhar Taib, G. Kawamura, Atsunori Matsuda, Mariatti Jaafar, Khairunisak Abdul Razak, Zainovia Lockman
Abstract: The present study employs NaOH as an oxygen source in fluorinated ethylene glycol (EG) electrolyte for the formation of titanium dioxide nanotube arrays (TiO2 NTs) by anodic process. The nanotube formed were 125 nm in diameter with length of ~ 7 µm after 30 min of anodization. They were then annealed to study the effect of annealing temperature on the photocurrent generated by the TiO2 NTs. It is found that TiO2 NTs annealed at 400 °C has the highest photocurrent (0.716 mA cm-2 at 0.5 V vs Ag/AgCl). This is attributed to the crystallinity (mostly anatase) of the TiO2 NTs as well as the nanotubular structure which retains at this temperature but not at higher temperature.
Authors: Solehah Fahdil, Siti Hajar Khalid, Azmi Mohamad Yusof, Marina Mokhtar, Ahmad Nazib Alias, Intan Syaffinazzilla Zaine
Abstract: Electrophoretic deposition (EPD) is a technique that uses electric field to deposit particles onto a conductive substrate. In this study, EPD technique has been utilized for fabrication of acid functionalized multi-walled carbon nanotubes (f-MWCNTs) and polyaniline (PANi) or denoted as (f-MWCNTs-PANi) nanocomposite film. The nanocomposite was prepared using ex-situ synthesis. This study revealed that the f-MWCNTs and protonated PANi in dimethyl formamide (DMF) can be well dispersed with addition of magnesium nitrate hexahydrate, Mg (NO3)2.6H2O. The fabricated films were characterized by Fourier Transform-Infrared Spectroscopy (FT-IR) and X-Ray Photoelectron Spectroscopy (XPS). Their surface morphologies were characterized by Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM). FT-IR results indicate the presence of carboxyl groups in f-MWCNTs spectrum. The presence of PANi was detected in the spectrum of f-MWCNTs-PANi nanocomposite. These results were further supported by FESEM and TEM results that show the morphology of f-MWCNTs and PANi coating around their sidewalls. The use of Mg (NO3)2.6H2O as dispersant for f-MWCNTs and protonated PANi allowed efficient EPD of their nanocomposite film fabrication. The fabricated f-MWCNTs-PANi composite thin film has future application in the development of supercapacitor device.
Authors: Chun Wey Low Andrew, Vahid Damideh, Sor Heoh Saw, Chin Seong Lim
Abstract: This paper reports the deposition of carbon nanomaterials on silicon substrate using a dense plasma focus device. The film property is studied using a field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX). The first test was deposited using 1, 3, 5, and 7 focus shots while the second test was carried out using 1 focus shot at 2, 3, 4, 5 and 7 Torr. Both tests were conducted with neon as filling gas at 7 Torr at distance of 8cm from the anode tip. In the first test, FESEM images exhibit a non-homogenous, non-uniformed and largely agglomerated carbon deposition at all films as pressure of filling gas increases. The EDX mapping confirms that carbon content in substrate increases from 10% to 30% as number of shot increases, and there is more carbon content detected in the centre position than the off-centre position. There is also a decrease in carbon content 35% to 25% as pressure of gas increases.
Authors: Khairul Anuar Wahid, M.A.S.M. Haniff, M. Ismahadi, Ishak Abdul Azid
Abstract: This paper reports a method to enhance the electro-activity on screen printing carbon electrode (SPCE) for electrochemical sensor platform application. The method to forming uniform gold nanoparticles on reduced graphene oxide and SPCE (Au-Nps/rGO/SPCE) based on plasma-enhanced CVD process has been investigated. The results demonstrated that the Au-NPs with high density and uniform sizes were successfully introduced via CVD process where the average size and thickness are 15.9+10nm and 2.18+0.4nm respectively. A high ID/IG ratio for Au-NPs/rGO is 1.01 which 44% higher compared to GO ID/IG ratio was observed in the Raman spectrum suggesting more defective sites on the surface of Au NPS/rGO. The redox performance of Au-NPs/rGO/SPCE has also been measured and compared with rGO/SPCE and the results shown that rGO decorated with Au-NPs has a highest redox current. The peak currents of Au-NPs/rGO are significantly increased compared to the bare SPCE with increment from 0.05mA to 0.14mA. This result is proportional with the effective surface area for SPCE that has been decorated with Au-NPs/rGO where the effective area is increased from 0.126cm2 to 0.166cm2. The peak potential at 0.01V which was found to shift up to 0.4V as the scan rate increases suggested that reaction is electrochemically reversible.
Authors: Maisara Azad Mat Akhir, Khairudin Mohamed, Sheikh Abdul Rezan, Hooi Ling Lee, Siti Suhaila M. Izah
Abstract: This paper studies the chemical vapor deposition (CVD) synthesis conditions for tin oxide (SnO2) nanowires (NWs) by using statistical design of experiment (DOE). The influences of synthesis parameters (growth temperature, deposition time and flow rate of argon) on SnO2 NWs diameter were studied. From perturbation analysis with DOE, it was found that temperature gave the most significant effect to the diameter of SnO2 NWs via CVD method followed by flowrate of argon and deposition time. Furthermore, based on the cube graph, the smallest SnO2 NWs (~18 nm) can be obtained at temperature of 850 °C with argon flow rate of 100 sccm using a deposition time of 60 min. On the other hand, the largest SnO2 NWs (~248 nm) can be produced at 900 °C.

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