Nanostructural characterization of carbon nanotubes in laser-sintered polyamide 12 by 3D-TEM
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Mo Song Department of Materials, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
Hideyuki Murakami Surface Kinetics Group, High Temperature Materials Unit National Institute for Materials Science, Tsukuba 305-0047, Japan (Received 3 March 2014; accepted 30 May 2014)
Three-dimensional transmission electron microscopy (3D-TEM) is a powerful technology that provides 3D characterization of the internal details of a material. In this work, for the first time, 3D-TEM was used to characterize a laser-sintered polymer nanocomposite. The dispersion of carbon nanotubes (CNTs) in the laser-sintered polyamide 12 (PA12)-CNT nanocomposite parts was evaluated. At first, to prepare 3D-TEM samples at specific locations, a focused ion beam technique was used. Then, high quality two-dimensional (2D)-TEM images were achieved at various scanning angles for the PA12-CNT laser-sintered sample. After that, 3D-TEM images were reconstructed by combining all the 2D-TEM images. Results revealed that the CNTs were agglomerate-free in the PA12-CNT parts after laser sintering, which helps to explain previously reported improvement in mechanical properties of laser-sintered PA12-CNT parts. I. INTRODUCTION
Laser sintering, also referred to as selective laser sintering (SLS™), is one of the most established powderbased additive manufacturing processes. Laser sintering uses a pulse or continuous laser as a heating source to fuse and join powder materials into predefined geometries.1,2 Theoretically, almost any polymer available in powder form can be laser-sintered using optimized processing parameters. However, in reality very few polymers are currently available for laser sintering, which is partly due to the complex thermal behaviors of polymers during the laser sintering process.3 At present, polyamides 11 and 12 (PA11/PA12) are the most commonly used laser sintering materials, making up more than 95% of the current laser sintering materials market.4 Several other polymers such as polystyrene, polypropylene, polycarbonate, poly(ether-ether-ketone) have been supplied as laser sintering materials. However, currently available materials cannot completely meet the requirements of various functional applications.1,5 To enhance the properties (mechanical, thermal, electrical, etc.) of lasersintered parts, nanofillers have been introduced to make polymer nanocomposites (PNCs) in recent years.6–14 a)
Present address: Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075, Singapore. b) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.126 J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
http://journals.cambridge.org
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When comparing nanofillers with conventional fillers, one of the most important differences is the surfaceto-volume ratio. Nanofillers have an exceptionally high surface-to-volume ratio and the area at the interface between the matrix and reinforcement phase is much greater than conventional composite material
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