Advanced Materials Research Vol. 620 (2013) pp 236-240 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.620.236
Hybrid Multiwalled Carbon Nanotubes/Minerals as Potential Fillers for Polymer Composites MUHAMMAD HELMI ABDUL KUDUS1,a, HAZIZAN MD. AKIL1,2,b and SITI SHUHADAH MD. SALEH1, 3,c 1
School of Materials and Minerals Resources Engineering, Engineering Campus, UniversitiSains Malaysia, 14300 NibongTebal, Pulau Pinang, Malaysia.
2
Cluster for Polymer Composite (CPC), Science and Engineering Research Center, Engineering Campus, UniversitiSains Malaysia, 14300 NibongTebal, Pulau Pinang, Malaysia. 3
School of Materials Engineering, Universiti Malaysia Perlis, 2600 Jejawi, Perlis, Malaysia. a
[email protected],
[email protected],
[email protected]
Keywords: MWCNT/mineral, hybrid compound, CVD
Abstract: Minerals are always used as filler material in polymer composite application purposely to reduce the price. In order to optimize the use of mineral fillers instead of price reduction, there were several approaches that have been done such as surface treatment, finding suitable coupling agent, and etc. The study on hybridization of minerals with carbon nanotubes (CNT) are rare to be found. CNT has received great attention from researchers due to their superior properties to be used in many applications. Hybridizing CNT with minerals proposes potential fillers for polymer composite. In this study, chemical vapor deposition (CVD) technique was used to synthesize the CNT-minerals hybrid compound. A mixture of CH4/N2 was used as the carbon source and nickel as the metal catalyst for the growth of CNT hybrid compound. Three different types of minerals were used namely talc, muscovite and CaCO3 are used to synthesize the MWCNT-talc, MWCNTmuscovite and MWCNT-CaCO3 hybrid compound. In short, the process involved precipitation of mineral filler with nickel salt. The process was followed by calcinations and reduction of the catalyst, and methane decomposition. The produced hybrid compounds were then analyzed. Introduction Polymer matrix composites (PMC) studies have become an interesting field in science and technology application nowadays. Due to their tailorable properties, PMC can be applied in various applications such as structural, electrical, mechanical, thermal, and tribological applications[1]. Some researchers tailored the PMC by their matrix, while the rest of them focus on the filler or reinforcement. The fillers and reinforcement for PMC are intriguing to be studied. The PMC is always classified by its filler/reinforcement. There are several types of PMC namely structural reinforced, fiber reinforced and particulate reinforced polymer composites intentionally fabricated to serve their applications respectively. For the particulate filler or reinforcement, there are several types of materials have been used. The earth minerals is one of particulate fillers that is widely used, especially for price reduction material in PMC fabrication[2]. Instead of using minerals filler as price reducer, there are some research works on the optimization of the mineral fillers, such as surface treatment, finding the suitable coupling agent, etc. in order to improve the use of the fillers[2, 3]. However, the optimization of the mineral fillers by hybridizing them with carbon nanotube (CNT) is rarely to be found. CNT is a kind of material that gains tremendous interest in its properties in various advanced applications[4]. The fibrous nanometer size CNT supposedly improves the minerals filler capability in PMC application. In this study, three hybrid CNT-mineral compounds had been synthesized via chemical vapor deposition (CVD), namely CNT-muscovite, CNT talc and CNT-CaCO3 hybrid compound, where all these hybrid compounds are potentially to be used in PMC application. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 202.170.51.237-18/10/12,04:40:53)
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Materials and Methodology MWCNT was directly deposited on different minerals, namely muscovite, talc and CaCO3 particles via chemical vapor deposition (CVD) by using nickel as the metal catalyst. The metal catalyst was attached on each mineral particles by precipitating nickel nitrate hexahydrate (Ni(NO3).H2O) and minerals powder in distilled water with the presence of sodium hydroxide, NaOH. After 24 hours, the precipitated catalyst paste was dried and calcined at 900oC for 10 hours. Then each catalyst namely Ni-muscovite (HYBRIDMUS), Ni-Talc (HYBRIDTALC) and Ni-CaCO3 (HYBRIDCA) were undergoing reduction process under the presence of hydrogen gas and followed by methane decomposition in a custom-made horizontal tube furnace similar to earlier reports from elsewhere[5], under the presence of methane and nitrogen atmosphere at 800oC for 30 minutes. The CVD synthesized HYBRIDMUS, HYBRIDTALC and HYBRIDCA were then characterized accordingly. The x-ray diffraction was used to analyze the presence of carbon (C), muscovite (KAl2 (AlSi3O10) (OH) 2), talc (Mg3Si4O10(OH)2) and calcium carbonate (CaCO3) in HYBRIDMUS, HYBRIDTALC and HYBRIDCA respectively. Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) were used to observe the CNT and minerals structure. Result and Discussion The hybrid MWCNT-minerals were successfully synthesized, namely HYBRIDMUS, HYBRIDTALC and HYBRIDCA via CVD, using complex nickel-minerals catalyst respectively. Methane gas was used as carbon feed in order to grow MWCNT on every mineral mentioned above. The HYBRIDMUS, HYBRIDTALC and HYBRIDCA would be used as filler in polymer composites. The XRD pattern which is shown in Fig. 1 shows the presence of carbon element after undergoing methane decomposition. Fig. 2 shows the SEM images of HYBRIDMUS, HYBRIDTALC and HYBRIDCA. The nanometer size wire-like structure is believed to be CNT, which had grown homogenously on each of the mineral surfaces. In order to confirm the wire-like structure to be CNT, higher resolution observation was used to observe the samples using HRTEM. Fig. 3(a)-(c) show the HRTEM images of HYBRIDMUS, HYBRIDTALC and HYBRIDCA respectively. The wire-like structures was confirmed to be multi-walled CNTs (MWCNT) which are shown in Fig. 3(d).
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Fig. 1: XRD pattern of (a) HYBRIDMUS, (b) HYBRIDCA, and (c) HYBRIDTALC
Fig. 2: SEM images of (a) HYBRIDMUS, (b) HYBRIDTALC and (c) HYBRIDCA This study would give some contributions to the polymer composite science and technological applications. The hybrid MWCNT-minerals would be potentially used as filler and reinforcement in polymer composite. The hybrid fillers should be an alternative solution to the fillers modification and treatment in order to obtain the compatibility between fillers and matrix, dispersion of the fillers in the matrix, and at the same time provide hybrid effects which are not shown by using single compound fillers. At the same time, this study had sparked a new idea to the researchers that MWCNT can be grown on minerals substrates. In current CNT research, CVD is a popular method of producing massive CNT where the supporting metal catalyst is usually used to catalyze the process. The supporting material that are widely used are alumina [6, 7], magnesia [8] , silica [9], etc. The earth minerals are rare to be found to be used as the support-material in catalytic CNT synthesis, CVD [10]. The earth minerals that were used in this study were muscovite, talc and CaCO3. All of these minerals possess the common supporting material elements such as alumina, silica and calcite ‘embedded’ within the minerals. This would simply explain the reason why minerals are capable to support the CNT growth.
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Fig. 3: HRTEM images of (a) HYBRIDMUS, (b) HYBRIDTALC, (c) HYBRIDCA and (d) multi-walled CNT
Conclusion The MWCNT has been successfully synthesized on the minerals surfaces. The synthesized MWCNT-minerals could be used in polymer composite as filler/reinforcement to improve some of the composites’ properties. These hybrid compounds can be potentially used as polymer composite reinforcement. At the same time, this study had proven that minerals are also suitable as a supporting material in catalytic CNT growth. Acknowledgement. Authors would like to thank USM (Short Term Grant: 60311010) for the financial assistance that has resulted in this article. Helps from Dr Mat Hussin (AMREC Kulim) on HRTEM analysis is also gratefully acknowledged.
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