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Title of Thesis

Study Of Physical Mechanisms Of Regenerative Sooting Discharges

Author(s)

Sohail Ahmad Janjua

Institute/University/Department Details
Department of Physics and Applied Mathematics / Pakistan Institute of Engineering and Applied Sciences (PIEAS) Nilore, Islamabad
Session
2008
Subject
Physics
Number of Pages
107
Keywords (Extracted from title, table of contents and abstract of thesis)
Sooting, Nanotubes, Regenerative, Physica, Mechanisms, Discharges, Dominate, Carbonaceous, Clusters, Conditions, Fullerene

Abstract
This thesis describes the experimental study of the sooting discharges in which a variety of carbon clusters is produced. The regenerative sooting discharges have been studied and their carbon cluster forming characteristics are compared with the non-regenerative sooting discharges. A large number of experimental arrangements have been used in which sublimation and sputtering processes were investigated in detail to understand the basic mechanisms for the formation of carbon clusters. The effects of experimental parameters on the clusters formed in the two types of carbonaceous discharges i.e. the non-regenerative and the regenerative sooting discharges are reported. Continuous as well as pulsed operations of the discharges have been studied. The carbon clusters are produced in carbonaceous environments where either the high temperature arc discharges sublime the graphite electrodes or the glow/arc discharges in the graphite hollow cathodes take place with sputtering being the dominant mechanism.
Regenerative soot is shown to have different characteristics and constituents compared with those in the non-regenerative soot. We have shown that small clusters dominate in the regenerative sooting discharges. The basic constituents of the two types of soot are also different; in the case of the regenerative soot C3 is the basic constituents while for the non-regenerative soot C2 seems to be an essential basic unit. Emission spectroscopy of the non-regenerative discharges indicates the predominance of diatomic carbon C2 in the continuous as well as the pulsed modes. C2 is the main sublimed species. Under these conditions cage closure leading to fullerenes and nanotubes is more likely.
Mass spectrometry with an ExB Wien velocity filter has been used to complement the results of emission spectroscopy in the case of the regenerative soot. The mass spectra from graphite hollow cathode duoplasmatron ion source clearly show that C3 is the major surviving specie along with other clusters C4 & C5 with lesser yields. The environment of the twin plasmas in the duoplasmatron ion source is such that higher clusters cannot survive and are fragmented into smaller clusters with C3 as the dominant end product.

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS
 

 

vii
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2 1 CLUSTERS FORMATION MECHANISMS IN CARBONACEOUS VAPOURS

1.1 Carbon Soot
1.2 Carbon Clusters Formation
1.3 Non-Regenerative Versus Regenerative Sooting Discharges
1.4 Non- Regenerative Sooting Discharges
1.5 Regenerative Sooting Discharges

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3 2 DIAGNOSTICS TECHNIQUES

2.1 Emission Spectroscopy
2.2 Mass Spectrometry
 

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4 3 NON-REGENERATIVE SOOTING DISCHARGES

3.1 Setup for Continuous Arc Discharge Between Graphite Electrodes
3.2 Results of Continuous Arc Discharge Between Graphite Electrodes
3.3 Setup for Pulsed Arc Discharge in Cylindrical Geometry
3.4 Results of Pulsed Arc Discharge in Cylindrical Geometry
3.5 Sublimation of Graphite
3.6 Setup for Continuous arc in Graphite Hollow Cathode
3.7 Results of Continuous Arc in Graphite Hollow Cathode
3.8 Setup for Pulsed arc with Wedge Shaped Graphite
3.9 Results of Pulsed Arc with Wedge Shaped Graphite
3.10 Setup for Continuous Spark Discharge
3.11 Results of Continuous Spark Discharge
3.12 Sputtering of Graphite

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5 4 REGENERATIVE SOOTING DISCHARGES

4.1 Setup for Graphite Hollow Cathode
4.2 Results of Graphite Hollow Cathode
4.3 Role of HeI
4.4 Role of CI
4.5 Setup for Twin Hollow Cylinders
4.6 Results of Twin Hollow Cylinders
4.7 Setup for Graphite Hollow Cathode duoplasmatron
4.8 Results of Graphite Hollow Cathode duoplasmatron
4.9 Setup for Graphite Hollow Cathode duoplasmatron in Dual Mode
4.10 Results of Graphite Hollow Cathode duoplasmatron in Dual Mode
4.11 Setup for Optimization of Quadrupole Electrostatic Lens
4.12 Results of Quadrupole Electrostatic Lens
4.13 Setup for Optimization of Beam Transport System
4.14 Results of Optimization of Beam Transport System

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6 5 CONCLUSION

5.1 The Non-Regenerative Sooting Discharges Based on Sublimation
5.2 The Non-Regenerative Sooting Discharges Based on Sputtering
5.3 The Regenerative Sooting Discharges Formed by Sputtering

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7 6 REFERENCES

 

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