Nirmal Kumar Roy

Bio: Nirmal Kumar Roy is an academic researcher from National Institute of Technology, Durgapur. The author has contributed to research in topics: Partial discharge & Transformer. The author has an hindex of 12, co-authored 55 publications receiving 409 citations. Previous affiliations of Nirmal Kumar Roy include Indian Institute of Technology Guwahati & Motilal Nehru National Institute of Technology Allahabad.

Growth of Carbon Dot-Decorated ZnO Nanorods on a Graphite-Coated Paper Substrate to Fabricate a Flexible and Self-Powered Schottky Diode for UV Detection.

Abstract: The fabrication of flexible as well as self-powered optoelectronic devices is a growing and challenging area of research Some scientists have reported the fabrication of either flexible or self-powered photodetectors recently However, most of the literature studies fail to report the fabrication of self-powered as well as flexible photodetectors This study reports the fabrication of self-powered, carbon dot (CD)-enhanced, flexible ZnO/graphite heterojunction-based UV detector where cellulose paper has been used as the substrate A detailed study on the crystallinity and the defects of the ZnO nanorods has been done with appropriate characterizations The CD-enhanced ZnO/graphite heterojunction showed Schottky characteristics The Schottky parameters such as the barrier height, ideality factor, and the series resistance have also been calculated using the Cheung-Cheung method The observed values of barrier height, ideality factor, and the series resistance are 074 eV, 374, and 503 kΩ, respectively The transient response at self-powered condition has been demonstrated The response time and the recovery time at self-powered condition have also been calculated with the help of the transient response, and those values are ∼2 and ∼32 s, respectively The responsivity and the specific detectivity of the fabricated UV detector have been calculated as 957 mA/W and 427×108 Jones, respectively, at 330 nm wavelength, which is quite comparable with literature-reported values, considering a self-powered photodetector

Mineral oil based high permittivity CaCu3Ti4O12 (CCTO) nanofluids for power transformer application

Abstract: Power transformer is the heart of the power transmission and distribution in an electrical system and its lifeblood is transformer's insulating oil that acts as an insulation of the transformer. The physical and electrical properties of insulating oil mainly depend on the constituents of insulating oil and the properties of oil can be optimized by introducing nanofluid. Mineral oil based CaCu3Ti4O12 (CCTO) nanofluids with various volume percent of CCTO (0 to 0.05 vol %) have been prepared under ultrasonication. These nanofluids (before ageing) were evaluated for the critical parameters such as AC breakdown voltage (BDV), loss tangent, dielectric permittivity, resistivity, acidity, interfacial tension, flash and fire point as per the procedure outlined in the ASTM and IEC standards. The nanofluids (NF-0 to NF-3) showed improvement in the AC breakdown voltage, tan delta, flash and fire properties. The AC breakdown voltage increased as the CCTO volume percent increase in the mineral oil. The nanofluids were also subjected to accelerated ageing and the critical parameters, evaluated on the aged nanofluids (ANF-0 to ANF-3), were compared with that of fresh nanofluids. The nanofluids do not show any significant change in the viscosity, however, influences on the electrical properties were observed. The improvement in electrical properties can be attributed to the formation of insulating boundaries in nanomaterial which acts as insulation barrier that hinders the breakdown mechanism.

Analysis of self-excited induction generators

Abstract: An analytical technique using the `Newton-Raphson' method is presented to identify the saturated magnetising reactance and the generated frequency of a self-excited induction generator for a given capacitance, speed and load. The technique is shown to be very efficient in analysing such systems under steady state. Computed results are compared with the experimentally obtained values on a laboratory machine, and a reasonable correlation has been observed. Effects of various system parameters on the steady-state performance have been studied, and the results presented provide guidelines for optimum design of such systems.

Review on Partial Discharge Detection Techniques Related to High Voltage Power Equipment Using Different Sensors

Abstract: When operating an equipment or a power system at the high voltage, problems associated with partial discharge (PD) can be tracked down to electromagnetic emission, acoustic emission or chemical reactions such as the formation of ozone and nitrous oxide gases. The high voltage equipment and high voltage installation owners have come to terms with the need for conditions monitoring the process of PD in the equipments such as power transformers, gas insulated substations (GIS), and cable installations. This paper reviews the available PD detection methods (involving high voltage equipment) such as electrical detection, chemical detection, acoustic detection, and optical detection. Advantages and disadvantages of each method have been explored and compared. The review suggests that optical detection techniques provide many advantages in the consideration of accuracy and suitability for the applications when compared to other techniques.

Self-powered UV photodetectors based on ZnO nanomaterials

Abstract: Self-powered photodetectors can work with low power consumption or even without any supply from external power sources, and they are recognized as one of the developing trends of next-generation optoelectronic devices. As one of the most-known n-type metal oxides applied in electronic devices, ZnO nanostructures and their heterostructures with other appropriate materials have been widely applied in the assembly of self-powered UV photodetectors. In this review, the recent research on different types of ZnO-based self-powered UV photodetectors is outlined. ZnO nanostructures with different dimensionalities adopted in these photodetectors are discussed in detail. The influences of specific effects, such as the piezo-phototronic effect, the pyro-phototronic effect, the photo-gating effect, and even their fusions, on modulating the self-powered photo-response of these photodetectors have also been demonstrated. The applications of these photodetectors in UV sensing, environmental recognition, wearable devices, functional devices, and light communication are displayed. Finally, possible opportunities and directions for the future developments of these photodetectors are proposed.

Current and future perspectives of carbon and graphene quantum dots: From synthesis to strategy for building optoelectronic and energy devices

Abstract: Carbon quantum dots (CQDs) and graphene quantum dots (GQDs) are new carbon-based nanomaterials with unique electronic, optical, and physicochemical properties. Both CQDs and GQDs have received attention in different material research fields such as optoelectronics, energy harvesting, chemical sensing, and biosensing. The combination of edge effects and/or zero-dimensional quantum-confined structures make them a promising alternative for applications like LED emitters, photodetectors, solar cells, water splitting, and optoelectronic devices. Despite the great potential for using these materials in energy harvesters, their potential in energy applications has not yet been reviewed thoroughly. In this review, we particularly focused on the role of edge effects and attached functional groups on flexible optoelectronic devices for energy harvesting applications. In addition, we also discussed the underlying challenges and future prospects for CQD/GQD-based devices with respect to their performance, sustainability, durability, and cost-effectiveness to efficiently realize their industrial scale-up.