Effect of Space Charge Density and High Voltage Breakdown of Surface Modified Alumina Reinforced Epoxy Composites

Chakraborty, Himel,Sinha, Arijit,Chabri, Sumit,Bhowmik, Nandagopal The Korean Institute of Electrical and Electronic 2013 Transactions on Electrical and Electronic Material Vol.14 No.3

The incorporation of 90 nm alumina particles into an epoxy matrix to form a composite microstructure is described in present study. It is shown that the use of ultrafine particles results in a substantial change in the behavior of the composite, which can be traced to the mitigation of internal charges when a comparison is made with conventional $Al_2O_3$ fillers. A variety of diagnostic techniques have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that, when the size of the inclusions becomes small enough, they act cooperatively with the host structure and cease to exhibit interfacial properties. It is postulated that the $Al_2O_3$ particles are surrounded by high charge concentrations. Since $Al_2O_3$ particles have very high specific areas, these regions allow limited charge percolation through $Al_2O_3$ filled dielectrics. The practical consequences of this have also been explored in terms of the electric strength exhibited. It would appear that there was a window in which real advantages accumulated from the nano-formulated material. An optimum filler loading of about 0.5 wt.% was indicated.

Electromagnetic Interference Reflectivity of Nanostructured Manganese Ferrite Reinforced Polypyrrole Composites

Chakraborty, Himel,Chabri, Sumit,Bhowmik, Nandagopal The Korean Institute of Electrical and Electronic 2013 Transactions on Electrical and Electronic Material Vol.14 No.6

Nano-size manganese ferrite reinforced conductive polypyrrole composites reveal a core-shell structure by in situ polymerization, in the presence of dodecyl benzene sulfonic acid as the surfactant and dopant, and iron chloride as the oxidant. The structure and magnetic properties of manganese ferrite nano-fillers were measured, by using X-ray diffraction and vibrating sample magnetometer. The morphology, microstructure, and conductivity of the composite were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and four-wire technique. The microwave-absorbing properties of composites reinforcement dispersed in resin coating with the coating thickness of 1.2 nm were investigated, by using vector network analyzers, in the frequency range of 8~12 GHz. A reflection loss of -8 dB was observed at 10.5 GHz.

Effect of Space Charge Density and High Voltage Breakdown of Surface Modified Alumina Reinforced Epoxy Composites

Himel Chakraborty,Arijit Sinha,Sumit Chabri,Nandagopal Bhowmik 한국전기전자재료학회 2013 Transactions on Electrical and Electronic Material Vol.14 No.3

The incorporation of 90 nm alumina particles into an epoxy matrix to form a composite microstructure is described in present study. It is shown that the use of ultrafine particles results in a substantial change in the behavior of the composite, which can be traced to the mitigation of internal charges when a comparison is made with conventional Al2O3 fillers. A variety of diagnostic techniques have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that,when the size of the inclusions becomes small enough, they act cooperatively with the host structure and cease to exhibit interfacial properties. It is postulated that the Al2O3 particles are surrounded by high charge concentrations. Since Al2O3 particles have very high specific areas, these regions allow limited charge percolation through Al2O3 filled dielectrics. The practical consequences of this have also been explored in terms of the electric strength exhibited. It would appear that there was a window in which real advantages accumulated from the nano-formulated material. An optimum filler loading of about 0.5 wt.% was indicated.

Electromagnetic Interference Reflectivity of Nanostructured Manganese Ferrite Reinforced Polypyrrole Composites

Himel Chakraborty,Sumit Chabri,Nandagopal Bhowmik 한국전기전자재료학회 2013 Transactions on Electrical and Electronic Material Vol.14 No.6

Nano-size manganese ferrite reinforced conductive polypyrrole composites reveal a core-shell structure by in situ polymerization, in the presence of dodecyl benzene sulfonic acid as the surfactant and dopant, and iron chloride as the oxidant. The structure and magnetic properties of manganese ferrite nano-fillers were measured, by using X-ray diffraction and vibrating sample magnetometer. The morphology, microstructure, and conductivity of the composite were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and four-wire technique. The microwave-absorbing properties of composites reinforcement dispersed in resin coating with the coating thickness of 1.2 nm were investigated, by using vector network analyzers, in the frequency range of 8~12 GHz. A reflection loss of -8 dB was observed at 10.5 GHz.

Durability Study of Silica Fume-mortar exposed to the Combined Sulfate and Chloride-rich Solution

조병완,sumit chakraborty,이승태,이윤성 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1

The present article investigates the mechanism behind the sulfate attack of the Ordinary Portland Cement (OPC) and the Silica Fume (SF) based mortar exposed to the combined sulfate and chloride-rich solution. In this study, the control mortar sample was fabricated using OPC. Additionally, the silica fume based mortar composites were fabricated using SF replacing the 5, 10, and 15% of OPC. The 28 days cured control and silica fume based mortar samples were exposed to a sodium sulfate (5%) solution and a mixture of sodium sulfate (5%) and sodium chloride (3.5%) solution for 510 days to examine the deterioration of mortar samples by the sulfate attack. The results reveal that a less extent of deterioration takes place in the silica fume based mortar as compared to that of the OPC mortar exposed to both solutions. The retarded deterioration of silica fume based mortar is primarily governed by the formation of a less extent of expansive ettringite and gypsum due to the consumption of portlandite in producing secondary Calcium Silicate Hydrate (CSH). Based on the analytical analyses, a model has been proposed to explain the overall performances of the silica fume based cement mortar composites exposed to different aggressive environments.

Investigation on the Effectiveness of Aqueous Carbonated Lime in Producing an Alternative Cementitious Material

Byung-Wan Jo,Sumit Chakraborty,Ji Sun Choi,Jun Ho Jo 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.1

With the aim to reduce the atmospheric CO₂, utilization of the carbonated lime produced from the aqueous carbonation reaction for the synthesis of a cementitious material would be a promising approach. The present investigation deals with the aqueous carbonation of slaked lime, followed by hydrothermal synthesis of a cementitious material utilizing the carbonated lime, silica fume, and hydrated alumina. In this study, the aqueous carbonation reaction was performed under four different conditions. The TGA, FESEM, and XRD analysis of the carbonated product obtained from the four different reaction conditions was performed to evaluate the efficacy of the reaction conditions used for the production of the carbonated lime. Additionally, the performance of the cementitious material was verified analyzing the physical characteristics, mechanical property and setting time. Based on the results, it is demonstrated that the material produced by the hydrothermal method possesses the cementing ability. Additionally, it is revealed that the mortar prepared using the alternative cementitious material yields 33.8 ± 1.3 MPa compressive strength. Finally, a plausible reaction scheme has been proposed to explain the overall performances of the aqueous carbonation as well as the hydrothermal synthesis of the cementitious material.

Effectiveness of the Top-Down Nanotechnology in the Production of Ultrafine Cement (<b>~</b>220 nm)

Jo, Byung-Wan,Chakraborty, Sumit,Kim, Ki Heon,Lee, Yun Sung Hindawi Limited 2014 Journal of nanomaterials Vol.2014 No.-

<P>The present investigation is dealing with the communition of the cement particle to the ultrafine level (~220 nm) utilizing the bead milling process, which is considered as a top-down nanotechnology. During the grinding of the cement particle, the effect of various parameters such as grinding time (1–6 h) and grinding agent (methanol and ethanol) on the production of the ultrafine cement has also been investigated. Performance of newly produced ultrafine cement is elucidated by the chemical composition, particle size distribution, and SEM and XRD analyses. Based on the particle size distribution of the newly produced ultrafine cement, it was assessed that the size of the cement particle decreases efficiently with increase in grinding time. Additionally, it is optimized that the bead milling process is able to produce 90% of the cement particle<350 nm and 50% of the cement particle<220 nm, respectively, after 6.3 h milling without affecting the chemical phases. Production of the ultrafine cement utilizing this method will promote the construction industries towards the development of smart and sustainable construction materials.</P>

Synthesis of a Cementitious Material Nanocement Using Bottom-Up Nanotechnology Concept: An Alternative Approach to Avoid CO₂Emission during Production of Cement

Jo, Byung Wan,Chakraborty, Sumit,Yoon, Kwang Won Hindawi Limited 2014 Journal of nanomaterials Vol.2014 No.-

<P>The world’s increasing need is to develop smart and sustainable construction material, which will generate minimal climate changing gas during their production. The bottom-up nanotechnology has established itself as a promising alternative technique for the production of the cementitious material. The present investigation deals with the chemical synthesis of cementitious material using nanosilica, sodium aluminate, sodium hydroxide, and calcium nitrate as reacting phases. The characteristic properties of the chemically synthesized nanocement were verified by the chemical composition analysis, setting time measurement, particle size distribution, fineness analysis, and SEM and XRD analyses. Finally, the performance of the nanocement was ensured by the fabrication and characterization of the nanocement based mortar. Comparing the results with the commercially available cement product, it is demonstrated that the chemically synthesized nanocement not only shows better physical and mechanical performance, but also brings several encouraging impacts to the society, including the reduction of CO2emission and the development of sustainable construction material. A plausible reaction scheme has been proposed to explain the synthesis and the overall performances of the nanocement.</P>

Prediction of the failure stress of hydrogen-rich water based cement mortar using the Weibull distribution model

Byung-Wan Jo,Sumit Chakraborty,Muhammad Ali Sikandar,Yun Sung Lee 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.5

The paper presents the compressive strength distribution pattern of the hydrogen-rich water based cement mortar. In this study, themortar samples were fabricated using different concentrations of hydrogen-rich water (0.2-0.5 ppm). The performance of hydrogenrichwater was evaluated measuring the setting time and the compressive strength of the mortar samples. Subsequently, the strengthdata were statistically analyzed using the Weibull distribution model in the 37% and the 95% confidence level (survival probability). Analyzing the results, it is anticipated that the use of hydrogen-rich water for the fabrication of mortar leads to set the cement quicklyand yields comparatively greater compressive strength than that of the control mortar prepared using normal water. Based on theWeibull distribution analysis, it is predicted that the mortar prepared using 0.5 ppm hydrogen-rich water would not break under 31.46MPa compressive stresses in 95% cases. Finally, based on the scanning electron microscopy in conjugation with the X-ray diffractionand thermogravimetry analysis, a plausible model has been proposed to explain the overall performances of the hydrogen-rich waterbasedmortar.

Diagnosis of Bronchobiliary Fistula—Utility of 99 m Tc-Mebrofenin Scan and SPECT/CT

Nishikant Damle,Manas Sahoo,Chandrasekhar Bal,Madhavi Tripathi,Parthasarthi Chakraborty,Saurabh Arora,Sumit Malapure,Santosh Gupta,Praveen Kumar 대한핵의학회 2013 핵의학 분자영상 Vol.47 No.2