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  • 8/7/2019 Report Nikhil




    April 2010

    Performed atInternational Advanced Research Centre for Powder Metallurgyand New Materials (ARCI)

    Balapur PO, Hyderabad 500005, Andhra Pradesh, IndiaBy



    Mahatma Gandhi Institute of TechnologyJawaharlal Nehru Technological University, Hyderabad, India

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    Mr. P.K. Subramanian




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    This is to certify that the project titled EffectofBufferGasandCathodeshapeontheSynthesisof

    CarbonNanotubesusing Arc-Dischargemethod is a bonafide work done by RangaNikhilVinayakYellakara, bearing Roll no. 06261A1835during the academic year 2009-2010 as a part ofFinal year industrial project.

    The report of this project work is submitted to the department/college in the fulfillment of therequirements for the award of BachelorofTechnologyin Metallurgy andMaterialsTechnologyby Jawaharlal Nehru Technological University.

    P. K. SUBRAMANIANInternal GuideHead of the DepartmentMetallurgy and Materials Technology3

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    I would like to express the deepest gratitude to all those who had been instrumental in the successfulcompletion of my project work at International Advanced Research Centre for Powd

    er Metallurgyand New Materials (ARCI), Hyderabad, India.My heartfelt gratitude to Mr. K. V. Phani Prabhakar, Scientist D, ARCI, who continually andconvincingly conveyed a spirit of adventure in regard to project. Without his guidance and persistenthelp, this dissertation would not have been possible.I am deeply indebted to Dr. Pavan Kumar Jain, Team Leader, Scientist E, ARCI, without whosesupport I could not have accomplished the project.I would like to thank Mr. Balaji Padya, Scientist B, Mr. G. Venkata Ramana, Post Graduate

    Trainee, ARCI, for having shared their time and knowledge with me.I would also like to acknowledge Mr. Venkat Reddy and Mr. Subba Rao, Technicians, ARCI, forhelping me with the technical aspects.In addition, I would like to thank Dr. J. Viplava Kumar and Mr. P. K. Subramanian (Internal Guide),who introduced me to Metallurgy and Material Sciences, and whose enthusiasm forthe field haslasting effect.I would like to acknowledge Mr. K. Ramanjaneyulu, Mr. P. Venkata Ramana, Associate Professors,MGIT, Mr. Bhomik. K. Deogade, Mr. P. V. S. Lakshmi Narayana, Mrs. Jhansi Jadav and Mr. R. V.

    S. M. Ramakrishna, Assistant Professors, MGIT, who has always been a great source of inspirationand a driving force in all my endeavors.My sincere thanks to the department of Metallurgy and Materials Technology, Mahatma GandhiInstitute of Technology and the Jawaharlal Nehru Technological University, Hyderabad, for givingme the permission to do my project work in ARCI.I would like to give my special thanks to my parents, sister and friends whose love and supportenabled me to complete this work.Ranga Nikhil Vinayak Yellakara


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    Abstract 6

    .Introduction 7.Theory.8.CharacterizationTechniques.28.Experiment 31

    .ResultsandDiscussion.34.Conclusions 40References..41


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    We have investigated the effect of the buffer gas, its partial pressure and theshape of the cathode onthe synthesis of multi-walled carbon nanotubes using Arc-Discharge method. We ha

    ve synthesizedMWCNTs in two different gas atmospheres i.e. in helium and hydrogen at differentpartial pressures,separately. We observed that the time taken for the synthesis process drastically decreased inHydrogen atmosphere. Observations using field emission scanning electron microscopy indicatethe presence of MWCNTs in hydrogen atmosphere at 350 Torr in a large number compared to thatof helium atmosphere at 300 Torr. Characterization using Thermo Gravimetric Analysis (TGA)confirmed the SEM results. This suggests that hydrogen at 350 Torr partial press

    ure is muchfavorable for the synthesis of MWCNTs using arc-discharge method in order to gethigh yield ofMWCNTs.MWCNTs were also synthesized using a cup shaped cathode instead of a flat cathode in hydrogenatmosphere. FE-SEM analysis and TGA suggests that MWCNTs are more in the depositobtained onflat cathode compared to that on cup shaped cathode.


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    Since their discovery in 1991 by Iijima, carbon nanotubes have been of great interest, both from afundamental point of view and for future applications. The most eye-catching fea

    tures of thesestructures are their electronic, mechanical, optical and chemical characteristics, which open a way tofuture applications. These properties can even be measured on single nanotubes.For commercialapplication, large quantities of purified nanotubes are needed.Different types of carbon nanotubes can be produced in various ways. The most common techniquesused nowadays are: arc discharge, laser ablation, chemical vapour deposition, HiPCO and flamesynthesis. Purification of the tubes can be divided into a couple of main techniques: oxidation, acid

    treatment, annealing, sonication, filtering and fictionalization techniques. Economically feasiblelarge-scale production and purification techniques still have to be developed.Fundamental and practical nanotube researches have shown possible applications in the fields ofenergy storage, molecular electronics, nanomechanic devices, and composite materials. Realapplications are still under development.Arc discharge, which is one of main methods of preparing carbon nanotubes (CNTs), has beenexplored extensively since this process has a very high temperature (about 4000K) and it can yieldthe most highly graphitized tubes. For example, much work has been done to inves

    tigate the effect ofbuffer gas, arc current and electrode temperature on the quality and output of CNTs in arc discharge,and then optimal conditions for preparing high density and loosely entangled CNTs have beenobtained.MWCNTs synthesized by arc discharge always coexist with carbonaceous nanoparticles, possessundefined morphologies, and have wide size and shape distributions, which have become one ofmain obstacles to the applications of MWCNTs.Thermo Gravimetric Analysis (TGA) is commonly employed in research and testing to determinecharacteristics of materials such as MWCNTs, to determine degradation temperatures, absorbedmoisture content of materials, the level of inorganic and organic components inmaterials,decomposition points of explosives, and solvent residues. It is also often usedto estimate thecorrosion kinetics in high temperature oxidation.Microscopy techniques such as Field Emission Scanning Electron Microscopy (FE-SEM) are usedto produce real space magnified images of CNTs showing what it looks like. In general, microscopyinformation concerns surface crystallography, surface morphology and surface com



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    Before dealing with the experiment, it is very important to know what exactly are carbon nanotubes,their growth mechanism, their properties, and their applications for which MWCNT

    s are creating ahuge impact on the field of advanced materials. The name Carbon Nanotubes clearly indicates thattheir source material is carbon.


    Carbon is a Group 14 element and is distributed very widely in nature. Its atomic number is 6 andatomic weight is 12.0107 g/mol. It is a non-metallic solid which comes under p-block elements of

    the periodic table. It is a tetravalent compound having four valence electrons to form covalentchemical bonds. Carbons electronic configuration is 1s2 2s2 2p2.All forms of carbon are highly stable, requiring high temperature to react evenwith oxygen. Themost common oxidation state of carbon in inorganic compounds is +4, while +2 isfound in carbonmonoxide and other transition metal carbonyl complexes. It has an affinity for bonding with othersmall atoms, including other carbon atoms, and is capable of forming multiple stable covalent bondswith such atoms. As a result, carbon is known to form almost ten million different compounds, the

    large majority of all chemical compounds1. Carbon also has the highest melting and sublimationpoint of all elements2 under inert conditions.Carbon sublimes in a carbon arc which has a temperature of about 5800 K. Thus, irrespective of itsallotropic form, carbon remains solid at higher temperatures in the absence of oxygen than thehighest melting point metals such as tungsten or rhenium. Although thermodynamically prone tooxidation, carbon resists oxidation more effectively than elements such as ironand copper which areweaker reducing agents at room temperature.Hybridization in Carbon:Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for thequalitative description of atomic bonding properties. Hybridised orbitals are very useful in theexplanation of the shape of molecular orbitals for molecules. Three types of hybridized bonds arepossible for carbon. They are sp3, sp2 and sp. In Methane (CH4), in which 1 electron