Carbon Nanotube Growth on Different Types of Tool Steel Substrates
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1057-II05-19
CARBON NANOTUBE GROWTH ON DIFFERENT TYPES OF TOOL STEEL SUBSTRATES Gulfem Ipek Nasuf, and Max Yen Materials Technology Center, Southern Illinois University Carbondale, Carbondale, IL, 62901 ABSTRACT This paper investigates the effectiveness of different pretreatment methods applied on M50, M35, and W4 type of tool steel substrates for direct growth of carbon nanotubes. The pretreatments explored include treatment with sand paper polishing, nitric acid (HNO3) etching, and high temperature hydrogen gas treatment. Furthermore, in order to establish a correlation between the steel surface average roughness value and the carbon nanotube growth, surface topography of steel substrates created by mechanical polishing were measured before actual growth process. Grown carbon nanostructures were shown by SEM and TEM to be multi-walled carbon nanotubes (MWCNTs) and vapor grown carbon nanofibers (VGCFs). It was found that under the same pretreatment conditions, even when the same roughness values were achieved and the same thermal chemical vapor deposition conditions were applied, grown nanostructures on different types of tool steel substrates showed dissimilarity. INTRODUCTION Recently, research and development on fabrication and characterization of carbon nanotubes (CNTs) has been extensively pursued due to their excellent mechanical properties with unique electrical and thermal characteristics [1]. Superior properties of carbon nanotubes enable them to be applied in a wide range of applications, such as gas storage devices [2], scanning probe tips [3], robust and lightweight composites [4], and electronic nanodevices [5]. Direct growth of carbon nanotubes onto a metallic substrate is important in achieving a strong mechanical bonding between substrate and carbon nanotubes. In order to grow nanotubes directly from a suitable steel surface, pretreatment of the substrate steel surface is necessary. Results obtained by Reedy et al. [6], clarify the direct relationship of surface roughness with carbon nanotube growth. So far various pretreatments have been applied on metallic substrate surfaces to obtain the necessary roughness on the surface, such as hydrofluoric acid (HF) etching, hydrogen plasma treatment [7], and high temperature oxidation [8]. However, the objective of this paper is to show the effects of same the pretreatment methods on carbon nanotube growth over different types of tool steel substrates. EXPERIMENT In this work, molybdenum high speed tool steel (M50, M35) and water-hardening tool steel (W4) with a thickness of 0.64 cm and diameter of 0.64 cm were used as a substrate for the direct growth of carbon nanotubes by thermal chemical vapor deposition. Chemical composition of catalyst metals inside these steel substrates is given in Table 1 [9]. Substrate surfaces were prepared by mechanical polishing using both 280 and 1200 grit SiC papers and samples were then placed in an ultrasonic acetone cleaning bath for 10 minutes, and dried using nitrogen gas. After mechanical polishing of each type of steel
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