An Innovative Process for Synthesis of Carbon-Base Nanostructured Materials Using a Solid-State Route
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An Innovative Process for Synthesis of Carbon-Base Nanostructured Materials Using a Solid-State Route I. Estrada-Guel1, 2, A. Okonkwo1, Z. Tang3, A. M. Guloy3, F.C. Robles-Hernandez1 Department of Mechanical Engineering Technology, University of Houston, Houston, TX 77204 USA. 2 Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No. 120, C.P. 31136, Chihuahua, Chih, Mexico. 3 Department of Chemistry, and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA.
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ABSTRACT This work shows a cost effective process to prepare carbon-carbon nanostructured composites using mechanical milling (MM) and a new manufacturing method based on rapid induction sintering. Here we use commercially and cost effective amorphous sources of carbon. The nature of the raw carbon is characterized by means of XRD and Raman, and after MM and sintering we observe a clear evolution of the phases of carbon in situ into more complex structures, including but not limited to graphene, graphitic carbon, and nanodiamond. The raw soot transforms in situ into graphitic particles after 1 hour of MM. Further milling (10 hours) induces the formation of nano-diamond particles. Milling times between 1 and 10 h are ideal to prepare intermediate phases between graphene and nanodiamond. In other words MM is capable of inducing the formation of nearly amorphous carbon soot into complex structures that are ideal for structural composite materials. The sintering process is a novel method involving a “pressureless” process and rapid induction heating. Furthermore, the carbon nanostructures that are produced during milling serve as seeds to grow larger particles that can easily reach micrometric sizes. This process achieved high densification as that proposed in commercial methods such as Spark Plasma Sintering. INTRODUCTION Carbon soot was used in this work due to its abundance, high purity, and it is a by product of incomplete combustion of fuels (coal, petroleum coke, charred wood, etc.). Theoretically, soot is considered the second largest cause of global warming [1] . On the other hand, mechanical milling (MM) is a solid-state method for powder processing with the potential to enhance in situ reactions of powders. The main steps in MM are cold welding and fracturing followed by rewelding of powder particles during collisions between the powders and the media (e.g. balls and mill) causing interdiffusion [2, 3]. The MM can drive chemical reactions; however, the technique is mainly applied to obtain amorphous or nanocrystalline materials and supersaturated solid solutions [4]. Throughout the years, MM has proved to be a very convenient and effective way to produce nanoparticles [5] with improved physical and mechanical properties[2]. Additionally, MM is cost effective, simple and yield from grams to mega grams depending on the facility[6]. In the present work we induce mechanochemical effects that influences directly the crystallinity, crystallite size, lattice strai
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