Surfactant-Assisted Dispersion of Carbon and Inorganic Nan tubes

Thathan Premkumar,신지용 한국고분자학회 2010 한국고분자학회 학술대회 연구논문 초록집 Vol.2010 No.4

A Systematic Study on the Dispersion of Single-Walled Carbon Nanotubes Using Surfactants

Thathan Premkumar,Kurt E Geckeler 한국고분자학회 2009 한국고분자학회 학술대회 연구논문 초록집 Vol.2009 No.10

Shape-tailoring of gold nanostructures: can a detergent act as the reducing or protecting agent?

Premkumar, Thathan,Kyungjae Lee,Geckeler, Kurt E. Royal Society of Chemistry 2011 Nanoscale Vol.3 No.4

<P>A commercially available detergent was found to be an effective reducing as well as stabilizing agent for the synthesis of differently shaped gold nanoparticles in an aqueous solution at an ambient condition and the as-prepared gold nanoparticles behave as an efficient catalyst for the reduction reaction of 4-nitrophenol at room temperature.</P> <P>Graphic Abstract</P><P>The synthesis of differently shaped gold nanoparticles can be performed in an aqueous solution at ambient conditions by using a commercial detergent that was found to be an effective reducing as well as stabilizing agent. In addition, the as-prepared gold nanoparticles were found to be able to act as an efficient catalyst for the reduction reaction of 4-nitrophenol at room temperature. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0nr00853b'> </P>

Novel Switching Table for Direct Torque Controlled Permanent Magnet Synchronous Motors to Reduce Torque Ripple

Arumugam, Sivaprakasam,Thathan, Manigandan The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6

The Direct Torque Control (DTC) technique for Permanent Magnet Synchronous Motors (PMSM) is receiving increased attention due to its simplicity and robust dynamic response when compared with other control techniques. The classical switching table based DTC results in large flux and torque ripples in the motors. Several studies have been reported in the literature on classical DTC. However, there are only limited studies that actually discuss or evaluate the classical DTC. This paper proposes, novel switching table / DTC methods for PMSMs to reduce torque ripples. In this paper, two DTC schemes are proposed. The six sector and twelve sector methodology is considered in DTC scheme I and DTC scheme II, respectively. In both DTC schemes a simple modification is made to the classical DTC structure. The two level inverter available in the classical DTC is eliminated by replacing it with a three level Neutral Point Clamped (NPC) inverter. To further improve the performance of the proposed DTC scheme I, the available 27 voltage vectors are allowed to form different groups of voltage vectors such as Large - Zero (LZ), Medium - Zero (MZ) and Small - Zero (SZ), where as in DTC scheme II, all of the voltage vectors are considered to form a switching table. Based on these groups, a novel switching table is proposed. The proposed DTC schemes are comparatively investigated with the classical DTC and existing literatures through theory analysis and computer simulations. The superiority of the proposed DTC method is also confirmed by experimental results. It can be observed that the proposed techniques can significantly reduces the torque ripples and improves the quality of current waveform when compared with traditional and existing methods.

A Facile Approach to Single-Wall Carbon Nanotube/Poly(allylamine) Nanocomposites

Kim, Jong-Boem,Premkumar, Thathan,Lee, Kyungjae,Geckeler, Kurt E. WILEY-VCH Verlag 2007 Macromolecular Rapid Communications Vol.28 No.3

<P>A facile approach to polymer nanocomposites with single-wall carbon nanotubes and cationic polymers is reported. The composite material was synthesized by producing carboxylic acid groups at the nanotube termini followed by a reaction with poly(allylamine) in water. Fourier transform infrared spectral and thermogravimetric analyses corroborate that the poly(allylamine) chains were wrapped on the surface of the carbon nanotubes. The scanning electron microscopic (SEM) image shows that the nanotubes were dispersed with little aggregation, thus, strongly suggesting that the poly(allylamine) chains have covered the single-wall carbon nanotubes, which was further evidenced by transmission electron microscopy. The composites are soluble in water, and this solubilization process opens up new opportunities in the solution chemistry on pristine nanotubes.</P><P> <img src='wiley_img/10221336-2007-28-3-MARC200600627-gra001.gif' alt='wiley_img/10221336-2007-28-3-MARC200600627-gra001'> </P>

Dispersion of Single-Walled Carbon Nanotubes by Using Surfactants: Are the Type and Concentration Important?

Shin, Ji-Yong,Premkumar, Thathan,Geckeler, Kurt E. WILEY-VCH Verlag 2008 Chemistry Vol.14 No.20

<B>Graphic Abstract</B> <P>Facile dispersion: A facile method to disperse SWNTs in water by using three different types of surfactants, such as neutral, cationic, and anionic, is described. Surprisingly, the surfactant Igepal (neutral) could disperse SWNTs well at a low minimum concentration compared with cetyltrimethylammonium bromide (cationic) or sodium dodecylsulfate (anionic). This is the first time the very efficient surfactant Igepal is introduced for the dispersion of SWNTs. <img src='wiley_img/09476539-2008-14-20-CHEM200800357-content.gif' alt='wiley_img/09476539-2008-14-20-CHEM200800357-content'> </P>

Fabrication of Silver Nanoparticles in Hydrogel Networks

Mohan, Y. Murali,Premkumar, Thathan,Lee, Kyungjae,Geckeler, Kurt E. WILEY-VCH Verlag 2006 Macromolecular rapid communications Vol.27 No.16

<P>Summary: This paper describes a simple and facile approach to fabricate well dispersed silver nanoparticles (AgNPs) in poly[N-isopropylacrylamide-co-(sodium acrylate)] hydrogels. The silver nanoparticles formed are spherical in shape with a narrow size distribution in the hydrogel networks in which the nanoparticles are stabilized by the polymer network. Uniformly dispersed silver nanoparticles were obtained with poly[N-isopropylacrylamide-co-[sodium acrylate)] hydrogels, whereas a poly(N-isopropylacrylamide)/poly(sodium acrylate) IPN gel showed aggregated nanoparticles. It is demonstrated that the hydrogel network structure determines the size and shape of the nanoparticles. These particles are more stable in the gel networks compared to other reduction methods. The hydrogel/silver nanohybrids were well characterized by XRD, UV-vis spectrometry, scanning electron microscopy and transmission electron microscopy.</P><P> <img src='wiley_img/10221336-2006-27-16-MARC200600297-gra001.gif' alt='wiley_img/10221336-2006-27-16-MARC200600297-gra001'> Graphic Schematic representation of the preparation of Ag nanoparticles in hydrogel networks. </P>

Nanocomposites of poly(L-lysine) and single-walled carbon nanotubes

Kim, Jong-Beom,Premkumar, Thathan,Giani, Olivia,Robin, Jean-Jaques,Schue, Francois,Geckeler, Kurt E John Wiley Sons, Ltd. 2008 Polymer international Vol.57 No.2

<P>BACKGROUND: Single-walled carbon nanotubes have inspired research owing to their promise in a broad range of applications. The dispersion of carbon nanotubes is of key importance for the utilization of this interesting material for various potential applications.</P><P>RESULTS: A novel and simple method was developed to fabricate polymer composites with single-walled carbon nanotubes based on a solid-state reaction, in which the nanotubes were reacted with poly(L-lysine) using high-speed vibration milling. Fourier transform infrared and UV-visible spectroscopy as well as thermogravimetry were employed to characterize the novel composites. The morphology and the dispersion of the carbon nanotubes were determined using scanning and transmission electron microscopy.</P><P>CONCLUSION: The resulting composites were dispersable in water and are expected to have great potential for both molecular-level studies and device applications of nanotubes. Copyright © 2007 Society of Chemical Industry</P>

Optimal Harmonic Stepped Waveform Technique for Solar Fed Cascaded Multilevel Inverter

Alexander, S.Albert,Thathan, Manigandan The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.1

In this paper, the Optimal Harmonic Stepped Waveform (OHSW) method is proposed in order to eliminate the selective harmonic orders available at the output of cascaded multilevel inverter (CMLI) fed by solar photovoltaic (SPV). This technique is used to solve the harmonic elimination equations based on stepped waveform analysis in order to obtain the optimal switching angles which in turn reduce the Total Harmonic Distortion (THD). The OHSW method considers the output voltage waveform as four equal symmetries in each half cycle. In the proposed method, a solar fed fifteen level cascaded multilevel is considered where the magnitude of six numbers of harmonic orders is reduced. A programmable pulse generator is developed to carry the switching angles directly to the semiconductor switches obtained as a result of OHSW analysis. Simulations are carried out in MATLAB/Simulink in which a separate model is developed for solar photovoltaic which serves as the input for cascaded multilevel inverter. A 3kWp solar plant with multilevel inverter system is implemented in hardware to show the effectiveness of the proposed system. Based on the observation the OHSW method provides the reduced THD thereby improving power quality in renewable energy applications.

Optimal Harmonic Stepped Waveform Technique for Solar Fed Cascaded Multilevel Inverter

S.Albert Alexander,Manigandan Thathan 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.1

In this paper, the Optimal Harmonic Stepped Waveform (OHSW) method is proposed in order to eliminate the selective harmonic orders available at the output of cascaded multilevel inverter (CMLI) fed by solar photovoltaic (SPV). This technique is used to solve the harmonic elimination equations based on stepped waveform analysis in order to obtain the optimal switching angles which in turn reduce the Total Harmonic Distortion (THD). The OHSW method considers the output voltage waveform as four equal symmetries in each half cycle. In the proposed method, a solar fed fifteen level cascaded multilevel is considered where the magnitude of six numbers of harmonic orders is reduced. A programmable pulse generator is developed to carry the switching angles directly to the semiconductor switches obtained as a result of OHSW analysis. Simulations are carried out in MATLAB/Simulink in which a separate model is developed for solar photovoltaic which serves as the input for cascaded multilevel inverter. A 3kWp solar plant with multilevel inverter system is implemented in hardware to show the effectiveness of the proposed system. Based on the observation the OHSW method provides the reduced THD thereby improving power quality in renewable energy applications.