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- 저자 : Y. Malathi (검색결과 2 건)
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Purification of Multi Walled Carbon Nanotubes (Mwcnts) Synthesized by Arc Discharge Set Up
Y. Malathi,Balaji Padya,K.V.P. Prabhakar,P.K. Jain 한국탄소학회 2010 Carbon Letters Vol.11 No.3
Carbon nanotubes are unique tubular structures of nanometer diameter and large length/diameter ratio. The nanotubes may consist of one up to tens and hundreds of concentric shells of carbons with adjacent shells separation of ~0.34 nm. Multiwalled carbon nanotubes were synthesized by arc-discharge technique. MWCNTs were formed at the cathode deposit along with other carbonaceous materials like amorphous carbon, graphite etc. However, to get the best advantage of carbon nanotubes in various advanced applications, these undesired carbonaceous materials to be removed which is a challenging task. In the present study, various techniques were tried out for purifying MWCNTs such as physical filtration, chemical treatment and thermal annealing. SEM, FTIR, TGA and BET techniques were used to characterize the CNTs at various stages. Results shows that suitable chemical treatment followed by thermal annealing under controlled flow of oxygen gives the better route for purification of carbon nanotubes.
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Malathy Narayanasamy,Y. Sukhi 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.11
The starting time of a large-rated variable-speed pumped storage unit (PSU) operating in pumping mode is crucial in the power balancing scenario in a modern power system because it establishes the transition period from generation to pumping modes, and vice versa, which determines the power system stability. Doubly fed induction machines (DFIM) are preferred in large-rated variable-speed PSUs (> 100 MW) because they ensure variable-speed operation through partial-rated power converters. Initiating the DFIM in pumping mode is challenging, but it is overcome by utilizing rotor-side power converters. The start-up of DFIM is preferred through short-circuiting the stator windings and supplying power to the rotor windings via power converters. However, this task can be performed through either short-circuiting the rotor or stator windings. This work detailed the field-oriented vector control strategies of the rotor short-circuited method and compared the results with the conventional stator short-circuited method in a commercial 306 MVA DFIM-fed variable-speed PSU. Results demonstrate that short-circuiting the rotor windings reduces the starting time and power consumption by 27.5% and 27%, respectively, compared with the typical starting method. This reduced starting time is preferred by the grid authorities because it improves the power system stability. Furthermore, experimental results are validated in the laboratory with a scaled-down unit of 7.5 kW DFIM.
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