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A spark discharge generator for scalable aerosol CVD synthesis of single-walled carbon nanotubes with tailored characteristics
摘要： We have designed and built an exhaust-free spark discharge generator for robust aerosol CVD synthesis of single-walled carbon nanotubes. The systematic study has shown the generator to provide a facile and repeatable route to precisely control the size of the catalyst particle and, therefore, carbon nanotube growth. Using a comprehensive set of methods (the analysis of differential mobility of the aerosol particles, optical spectroscopy, scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy) we have revealed the relation between the defectiveness, length, diameter distribution of carbon nanotubes and specific features of a generator such as electrode characteristics (breakdown voltage, composition, and current) as well as the nature of the surrounding media (carrier gas nature, flow rate). The design used has resulted in separation of the nanoparticle formation and carbon nanotube nucleation processes. This provides a mutual independence of the growth parameters and the diameter distribution of the single-walled carbon nanotubes enhancing the scalability of the process. For instance, the breakdown voltage has been shown to have nearly zero effect on diameter and length distribution of carbon nanotubes produced while strictly governing the yield. We focus here on producing specifically short carbon nanotubes (l < 500nm) of pronounced defectiveness for drug delivery and transistor applications.
关键词： single-walled carbon nanotubes,differential mobility analyzer,catalyst activation,spark-discharge generator,aerosol CVD,floating bed reactor
更新于2025-11-14 17:03:37
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Activation of carbon nanotube film by gas discharge breakdown
摘要： Carbon nanotubes (CNTs) is considered to be eminently suitable cold-cathode material. We found that exposure of CNT films to gas discharge breakdown generated in atmospheric argon gas causes significant morphology changes, which show many dispersed CNTs, on those surfaces. These indicate that the exposure of the CNT film to the gas discharge breakdown can be used as a method for improvement of the field emission property of the CNT film. In this study, field emission properties of the CNT film that was exposed to the gas discharge breakdown was investigated. Many crater-shaped holes whose circumferences were surrounded by many dispersed CNTs were found after the exposure of the CNT film to the discharge breakdown. We found that the CNT film after the exposure of the gas discharge breakdown gave better field emission properties than it before the exposure.
关键词： carbon nanotubes,field emission,gas discharge breakdown,spark discharge
更新于2025-09-23 15:21:21
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Time-resolved optical characterization of the interaction between a laser produced plasma and a spark discharge
摘要： The interaction between a nanosecond laser produced plasma and a unipolar high voltage discharge was analyzed using time-resolved spectroscopy, fast photography with narrow band interference filters and profilometry. Here the laser ablation fluence was varied in the 60–1000 J/cm2 range. The 600-kW electrical discharge was triggered by an ablation plasma on the aluminum target at time 700 ns in order to enhance the laser-induced breakdown spectroscopy (LIBS) emission. Most of the spectra were obtained from a spot 1 mm above the target and these were: time-integrated to gauge overall enhancement and time-resolved to investigate emission enhancement, temperature and density as a function of time. It was found that the time-and-space integrated LIBS signal was enhanced by up to one order of magnitude at the lowest laser fluence employed when compared with a conventional LIBS experiment. Also, that this emission increment could not be mainly attributed to an increased mass removal, but rather to an enhancement of plasma ionization degree as was observed by means of fast photography with filters. This causes longer plasma duration and more enhancement of ionic species than neutrals. It was also found that both the electronic density and the temperature increase when the spark discharge is applied, in comparison with the ablation plasma. Emission enhancement is inversely proportional to laser fluence due to the fact that for higher fluences, by the time the discharge is applied, the laser-produced plasma is already highly excited.
关键词： LIBS,Spark discharge,Optical emission spectroscopy,Plume dynamics,Fast photography
更新于2025-09-23 15:21:01
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Carbon multicharged ion generation from laser-spark ion source
摘要： Multicharged carbon ions are generated by using a laser-assisted spark-discharge ion source. A Q-switched Nd:YAG laser pulse (1064 nm, 7 ns, ≤ 4.5 × 109 W/cm2) focused onto the surface of a glassy carbon target results in its ablation. The spark-discharge (～1.2 J energy, ～1 μs duration) is initiated along the direction of the plume propagation between the target surface and a grounded mesh that is parallel to the target surface. Ions emitted from the laser-spark plasma are detected by their time-of-flight using a Faraday cup. The ion energy-to-charge ratio is analyzed by a three-mesh retarding field analyzer. In one set of experiments, the laser plasma is generated by target ablation using a 50 mJ laser pulse. In another set of experiments, ～1.2 J spark-discharge energy is coupled to the expanding plasma to increase the plasma density and temperature that results in the generation of carbon multicharged ions up to C6+. A delay-generator is used to control the time delay between the laser pulse and the thyratron trigger. Ion generation from a laser pulse when a high DC voltage is applied to the target is compared to that when a spark-discharge with an equivalent pulsed voltage is applied to the target. The laser-coupled spark-discharge (7 kV peak voltage, 810 A peak current) increases the maximum detected ion charge state from C4+ to C6+, accompanied by an increase in the ion yield by a factor of ～6 compared to applying 7.0 kV DC voltage to the target.
关键词： carbon multicharged ions,plasma,ion generation,spark-discharge,laser-spark ion source
更新于2025-09-19 17:13:59
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Fine-tuning of spark-discharge aerosol CVD reactor for single-walled carbon nanotube growth: the role of ex situ nucleation
摘要： We report a development of recently designed apparatus equipped with a spark discharge generator of catalytic nanoparticles for robust aerosol CVD synthesis of single-walled carbon nanotubes. We achieve a profound control over the diameter distribution and the defectiveness of carbon nanotubes produced. By providing a justified comparison of the apparatus with the most abundant aerosol CVD reactor utilizing ferrocene as a catalyst precursor, we reveal the role of the activation procedure: while spark-discharge generator provides aerosol of nanoparticles (ex situ route), the ferrocene vapor decomposes in the nanotube growth zone providing an in situ formation of the catalyst. With other parameters being equal, we reveal the differences in the nanotube growth (diameter and length distribution, yield, defectiveness) employing a comprehensive set of methods (the analysis of differential mobility of the aerosol particles, optical spectroscopy, scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy). We show the ex situ activation in the spark discharge reactor to provide a lower utilization degree of the nanoparticles due to over-coagulation. However, the same method provides an independence of the key performance parameters of the nanotubes opening a room for scaling the apparatus.
关键词： spark-discharge generator,differential mobility analyzer,aerosol CVD synthesis,catalyst activation,floating catalyst,single-walled carbon nanotubes
更新于2025-09-16 10:30:52
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Nanocarbon colloid produced by electro-spark discharge in ethanol for seeding the substrates in MPACVD synthesis of polycrystalline diamond films
摘要： We produced a nanocarbon colloid by electro-spark discharge as substrate seeding for microwave plasma-assisted chemical vapor deposition (MPACVD) synthesis of micro- and nano-crystalline diamond films and solid free-standing microcrystalline diamond plates. The colloid was produced by a specially designed device via a pulse electro-spark discharge in ethanol. The nanocrystalline diamond films and polycrystalline plates that were grown were examined by optical, SEM and TEM microscopies and Raman spectroscopy.
关键词： MPACVD,electro-spark discharge,nanocarbon colloid,polycrystalline diamond films
更新于2025-09-10 09:29:36
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The Advantages of Spark Discharge Generation for Manufacturing of Nanoparticles with Tailored Properties
摘要： The number of nanoparticle-based products on the market is expected to increase considerably during the coming decades. For this to happen a solid supply of high-quality nanoparticles is needed. For metal nanoparticles no large-scale manufacturing method exists today but production using spark discharge generation is believed to be one of the most suitable candidates. Spark discharge generation offers several advantages over other methods and the ?rst steps towards scaling up have already been taken. In this paper the spark discharge generator concept is presented and its advantages are discussed. Examples of nanoparticle materials and applications for the as-generated particles are reviewed.
关键词： Nanoparticles,spark discharge generation,aerosols
更新于2025-09-09 09:28:46