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    Laser-induced graphite plasma kinetic spectroscopy under different ambient pressures
    (2015-04-01)
    Chaudhary, K.
    ;
    Rosalan, S.
    ;
    Aziz, M. S.
    ;
    Bohadoran, M.
    ;
    Ali, J.
    The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Ablation and excitation of the graphite material is performed by using an 1064nm Nd:YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emission. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.
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    Kinetic model for carbon species distribution in arc discharge plasma
    (2015-01-12)
    Roslan, M. S.
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    Chaudhary, K.
    ;
    Aziz, M. S.
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    Ali, J.
    ;
    Yupapin, P. P.
    In present work, numerical integration for density distribution of carbon species in arc discharge plasma is presented. The model incorporates two-body collision effects using continuity equation of density in conservation mass rate law. Plasma species in inter-electrode gap are accelerated by the electric field across the gap and produced high density plasma. Electrons with high energy in arc discharge plasma cause extended ionization, excitation, recombination, and dissociation process due to particle collision which leads to enrichment of density in spatial and temporal mode. The extrapolation of species dominant in arc discharge process is critical issue to predict carbon nanostructure production. A chemical kinetic models and distribution of carbon ions and neutrals species based on collision in thermal plasma condition is developed. The reaction process of carbon species are identified in the between electrodes region. The electron-ion recombination cross section is analyzed to understand the density evolution.
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    Formation of Multi-Walled carbon nanotubes and graphene in methane arc discharge plasma
    (2014-01-01)
    Chaudhary, K. T.
    ;
    Bahtti, K. A.
    ;
    Rafique, M. S.
    ;
    Jamil, H.
    ;
    Ali, J.
    The growth of multi-walled carbon nanotube (MWCNT) and carbon nano structures is investigated in methane (CH4) environment at low pressure using arc discharge process for arc currents 50, 70 and 90A. Plasma density and temperature areestimated by optical emission spectroscopy to determine the contribution of arc current and ambient environmenttowards the growth of MWCNT and nano structures. The grown samples at different arc currents are analyzed by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier Transform Infrared spectroscopy, thermogravitic analysis and x-ray diffraction. An improvement in structure quality in term of defects and increase growth of MWCNT is observed in CH4 ambient environmentwith increasein arc current. For arc current 90A, the well aligned and straight MWCNT along with graphene are detected.