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Endohedral metallofullerenes have special structures, therefore we are interested in. High-temperature laser vaporization method and direct current arc discharge method, which are the two methods for preparing endohedral metallofullerenes. Here we study the preparation of endohedral metallofullerenes by direct current arc discharge method, which uses two graphite rods as electrode and vaporizes the one which infill metal complex in high temperature and low helium gas pressure environment. We study in some metal complexes such as Mo(C5Ph5)2, Fe(CO)9, Ag and Au. After reaction, we collect the soot produced in reaction and choose different solvents to separate the products from it with Soxhlet extraction.

The mass production of carbon nanotubes (CNTs) by a cost effective process is still a challenge for further research and application of CNTs. This research focussed on the deposition of CNTs on a continuously-fed carbon substrate via arc discharge at atmospheric pressure. In this work, modifications, control and optimization of the available arc-discharge reactor were conducted. New reactor support and new tape feeding mechanisms were added to the reactor for better temperature assessment, longer operating period and better control of the speed of the tape. The influence of inter-electrode gap, substrate velocity and arc current on the surface temperature were investigated. Multiwalled carbon nanotubes (MWNTs) were produced at lower currents (< 20 A) and at larger inter-electrode gaps. Further investigation shows that inter-electrode gap influenced both the arc characteristic and the anode surface temperature (Ts). Here, Ts was measured by an optical pyrometer. The inter-electrode gap was found to indirectly affect the formation of NTs. Anode surface temperature (Ts) varied with gap, reaching a minimum at an intermediate gap. Higher CNTs yield was found at this lowest Ts. This minimum Ts is consistent with the presence of a cloud of nanoparticles ejected by the heated graphite/carbon surfaces. These graphene fragments are thought to later fold and form nanotube “seeds” and then develop into multiwall nanotubes. This cloud of nanoparticles also may affect the electrical conductivity at the front of the anode. Simulation of the arc behaviour, i.e. temperature distributions and flow properties of the plasma, using a computer package Comsol Multiphysics 3.2, was stable only when the electrical conductivity of a dusty plasma near to the electrodes was included. Our experiments show that carbon nanotubes grew better at a Ts range of ~ 3650 K - 3700 K and at the tape speed of 3 mm/s. The results from our work also strongly suggested that tiny carbon crystallites are the main intermediates for CNT growth in an electric arc. The limiting factor for a solid state growth mechanism, therefore, is high temperature annealing of carbon or graphene fragments. Further work should aim to understand the growth mechanism of CNTs, produce comprehensive analysis on the arc plasma composition and also explore the possibility of producing CNTs at higher rates.

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Diamond has superior characteristics, such as high hardness, high isolation, and high breakdown voltage, but it is also difficult to manufacture for industrial application. Because diamond is a nonconductor, the usual electrical discharge machining (EDM) method cannot be used. Hence, this study uses the plating nickel to keep the diamond powder as the composite electroplated layer of nickel-diamond powder. The variation of the composite layer and the diamond particle erosion characteristic after arc discharge can be realized by single-arc discharge. By the result of experiment, it can be known that the erosion area will be enlarged when the diamond particle is near to central erosion area, because the diamond that has good heat stability makes plasma to spread. The erosion area will be decreased when the diamond particle is near to edge of erosion area, because it stops the melted nickel to spread. The surface of diamond particle is broken slightly that the particle become more spherical and has some nickel remain on it when pulse voltage is less than 300 volt or the diamond particle is near to edge of erosion area. The surface of diamond particle is broken seriously that the particle is cracked to pieces when pulse voltage is more than 300 volt or the diamond particle is near to central erosion area.

The trends of present design in electronic systems are towards high speed, small size, and lower voltage levels. The noise immunity of high speed digital circuit decreases. ESD problem becomes more and more important for electric products because of the triboelectricity caused by human body with synthetic material. In this thesis we introduce the phenomenon in real life ESD caused by a charged human body source. Then we provide a good measurement method of ESD which enhances the repetition that gives a reliable and accurate result. Finally we try to build the numerical model for the air and contact discharge simulation by FDTD to provide a good measurement validation.

Abstract The arc behavior during the closing and opening of electrical contacts not only influences the surface morphology, but also causes the erosion of contact material. The mechanical stresses, the molten bridge, and the arc cause this erosion. Consequently, the erosion mechanism is very complex. Therefore, to avoid the influences of mechanical stresses and numerous arc striking, static-gap experiments with a single arc discharge are conducted to investigate the effects of pulse voltage, gap distance, and arc duration on the erosion characteristics and mechanism of silver based contact materials. Moreover, this experimental result is verified by the finding of the dynamic testing of electrical contacts. The results of the erosion characteristics show that the arcing and non-arcing regions have been distinguished at the supply voltage from 32 V to 500 V and the gap distance from 0.2 mm to 40 mm. The empirical formula for the minimum pulse voltage at arc initiation in terms of gap distance is established. When the pulse voltage is smaller than 200 V, the erosion area increases with increasing gap distance due to the action of the metallic-phase arc. However, when the pulse voltage is greater than 200 V, with increasing gap distance, the erosion area increases to a maxim, and finally diminishes due to the increase in the amount of gaseous-phase arc. The results of the erosion mechanism show that the arcing region is classified into three erosion patterns, namely, the molten metal bridge (B), metallic-phase arc (M), and gaseous-phase arc (G). At the gap distance of 0.2 mm, the erosion pattern of anode silver is varied from B, through B+M, and, M, to M+G. According to the electron transfer across triangular potential barrier, the thermionic emission causes the erosion patterns of B, B+M, and M, and mixed thermionic and field emission results in the erosion pattern of M+G. When the pulse voltage is 500 V, with increasing gap distance, the splashing of metallic particles around the anode crater becomes more dispersed, shorter with more silver powder, and finally disappeared with a little silver powder due to the influence of the gaseous-phase arc. The results of the anti-weld ability show that when the pulse voltage is 500 V and the arc energy is grater than 14 J at the static-gap experiments, the critical gap distance to produce welding for Ag-Ni, Ag-CdO, and Ag-SnO2 is 3 mm, 8 mm, and 15 mm, respectively. This indicates Ag-Ni contact possesses the best anti-weld ability. On the other hand, the results of dynamic testing of electrical contacts show that at the arc energy less than 10 J, the anti-erosion, anti-weld ability, and the welding area are seen to increase with contact materials in the following order: Ag-CdO > Ag-SnO2 > Ag-Ni. However, when the arc energy is greater than 10 J, the anti-erosion, anti-weld ability, and the erosion area are seen to increase in the reverse order: Ag-SnO2 < Ag-CdO < Ag-Ni, which are in very good agreement with the results of static-gap experiments. Furthermore, the erosion surface of the silver-based contact materials can be observed and analyzed by using the X-ray diffraction method (XRD), differential thermal analysis (DTA), and gravitation thermal analyzer (GTA). Results show that when the arc energy is greater than 14 J, Ag-CdO and Ag-SnO2 have been decomposed into Ag-Cd and Ag-Sn alloys, respectively, which reduce their anti-weld ability. On the other hand, the welding trend has been reduced due to the dispersion of NiO on the surface of Ag-Ni contact. Consequently, the anti-erosion and anti-weld ability for the Ag-Ni contacts are better than those of the other Ag-MeO contact materials.

Carbon nanotubes have become one of the most important building blocks critical to nanotechnology. Carbon nanotubes have attracted the interests of many scientists since their discovery due to their remarkable properties and have been widely used for various applications. However, the bottle neck in nanotube research has been the lack of a cheap, continuous and fast nanotube production method. This study concerns a reactor where nanotubes are continuously deposited on a carbon substrate using arc discharge at atmospheric pressure. This process appears to be the first to employ an arc discharge as the method for continuous mass deposition of nanotubes on a substrate. This nanotube deposition method eliminates the generic multistep process of nanotube deposition on substrates for its use in many applications. The effect of various parameters influencing growth and morphology of nanotubes on the substrate in the arc reactor (inter-electrode gap, atmosphere composition, current density, flushing, substrate type and speed and catalyst) have been systematically explored to optimise nanotube growth. The field emission properties of the nanotube laden substrate are studied for use and applicability as electron emitters. The nanotube samples demonstrated superior emission properties, low turn-on field and excellent current stability when put into applications such as a luminescent tube and an ionisation sensor. Theoretical modelling of the behaviour of a single nanotube during field emission was performed using finite element analysis software (COMSOL 3.2) to understand the effect of nanotube length, diameter, and vacuum gap on an individual nanotube. The results reveal that resistive heating (temperature) limits the maximum current carried by an individual nanotube. Furthermore, a new growth model is introduced to explain the formation of nanotubes from graphene fragments and nanocrystallites, due to polarisation of carbon species near the electrode surface suggesting that carbon vapour is unlikely to be responsible for nanotube growth.

Carbon nano-onions (CNOs), concentrically multilayered fullerenes, are prepared by several different methods. We are studying the properties of two specific CNOs: A-CNOs and N-CNOs. A-CNOs are synthesized by underwater arc discharge, and N-CNOs are synthesized by high-temperature graphitization of commercial nanodiamond. In this study the synthesis of A-CNOs are optimized by designing an arc discharge aparatus to control the arc plasma. Moreover other synthesis parameters such as arc power, duty cycles, temperature, graphitic and metal impurities are controlled for optimum production of A-CNOs. Also, a very efficient purification method is developed to screen out A-CNOs from carboneseous and metal impurities. In general, A-CNOs are larger than N-CNOs (ca. 30 nm vs. 7 nm diameter). The high surface area, appropriate mesoporosity, high thermal stability and high electrical conductivity of CNOs make them a promising material for various applications. These hydrophobic materials are functionalized with organic groups on their outer layers to study their surface chemistry and to decorate with metal oxide nanoparticles. Both CNOs and CNO nanocomposites are investigated for application in electrochemical capacitors (ECs). The influences of pH, concentration and additives on the performance of the composites are studied. Electrochemical measurements demonstrate high specific capacitance and high cycling stability with high energy and power density of the composite materials in aqueous electrolyte.

Due to the explosive improvement of micro machining technology, many kinds of meso-scale products and parts are developed. There are two techniques, CMM (Coordinate Measuring Machine) and SPM (Scanning Probe Microscopy), commonly used to measure the profile of meso-scale products. However, both of these methods have their own strengths and weaknesses in that scale. The CMM can¡¦t be precise and accurate; while the SPM measurement system will be a time-consuming process. The micro scale CMM measurement system with micro spherical probes would be suitable for measuring meso-scale objects. In this study, equipments are built to fabricate the micro spherical probes. The glass optical fiber is selected as the material to fabricate the probes. The heating-pulling method and arc fusion method are selected as the fabrication process. The commercial equipments are available for fabricating micropipette and NSOM (Near-field Scanning Optical Microscopy) probes. However, most of these commercial equipments are expensive, and the heating area is too small to fit our study. In this study, the gas heater is used to replace the laser power as a heat source. A vertical pulling mechanism is developed to pull the optical fiber. Moreover, this study uses Taguchi method to reduce the number of experimental runs and find the suitable parameters for fabrication. The straight-circular-cone-type probe and the bent-circular-cone-type probe can be fabricated at the same time. The radius of the probe tip can be smaller than 0.5£gm for NSOM. In addition, the heating-pulling mechanism can reduce the diameter of optical fiber from £p125£gm to less than £p50£gm for different purposes. An arc discharge machine is also developed to melt the cleaved end-face of the prob. The heating-pulling mechanism and arc discharge machine developed in this study are successfully applied in fabricating different types of probe ends, £p20~125£gm hemispherical end-face and £p50~300£gm spherical end-face for example, for different applications.