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This work studies the impact of silica nanoparticles on the dielectric properties of synthetic ester oil. A stable nanofluid is prepared by addition of surfactant. With addition of nanoparticles there is an increment in dielectric constant and decrement in dielectric loss constant. An attempt is made to understand the conduction mechanisms in uniform field and non-uniform electric field configuration by means of analysing the mobility of ions. Under uniform electric field stress (

Plastic wastes are necessary to recycle due to their disposal issues around the world. They can be recycled through various techniques i.e., mechanical reprocessing, mechanical recycling, chemical recycling and incineration. Most recycling techniques are expensive and end up in producing low-grade products excluding chemical recycling; it is an eco-friendly way to deal with plastic waste. Catalytic cracking is one of the chemical recycling methods, for converting waste plastics into liquid fuel same as commercial fuels. An experimental investigation of polystyrene catalytic cracking process was conducted with impregnated fly ash catalyst and 88.4% of liquid product yield was found as a maximum at optimum operating conditions 425 ̊C and 60 min. The liquid fuel quality was analyzed using FTIR spectra analysis, GC/MS analysis and Physico-chemical property analysis. The GC/MS analysis shows that the fly ash cracking of polystyrene leads to the production of gasoline fuels within the hydrocarbon range of C3-C24, and the aliphatic and aromatic functional compounds were detected using FTIR analysis. Moreover, the Aspen Hysys simulation of polystyrene catalytic cracking was conducted in a pyrolytic reactor at 425 ̊C and at the end of the simulation, 93.6% of liquid fuel yield was predicted. It was inferred that the simulation model for the catalytic cracking is substantial to fit the experimental data in terms of liquid fuel conversion

The tunable electrical conductivity in the conducting polymer is one of the significant advantages for focusing on these materials for flexible electronics and electrical applications. In this work, the polyaniline electrical conductivity is tuned by doping with different dopant materials, varying doping concentrations, and different morphologies. The experimental electrical conductivity results are correlated with the optical band gaps and their corresponding electronic transitions. Increasing the doping concentration from 0 to 1.0 M HCl increases electrical conductivity from 1.98 to 10.2 Scm−1. The observed five-fold increment is attributed to the increase in polarons in the polymer chain with doping. The polyaniline electrical conductivity is also tuned by making different morphologies. The measured electrical conductivity is larger for the polyaniline nanowhisker and nanofiber (~ 2 Scm−1) samples than the sample with highly entangled polymer chains (0.26 Scm−1). Moreover, it was found that the polyaniline nanofibers with ordered polymer chains show larger electrical conductivity (1.75 and 1.27 Scm−1) as compared with the disordered polymer chains (0.22 Scm−1).

Localized electric field strength in high-voltage (HV) equipment results in electrical discharges which radiate electromagnetic waves in ultrahigh frequency (UHF) range of 0.3-3 GHz. Due to the large antenna dimensions in UHF regime and lack of radome, existing UHF sensors have limited use in HV equipment for online partial discharge (PD) detection. In this work, we present the design and experimental verification of a UHF antenna with relatively small aperture and radome for PD detection. The proposed UHF sensor is a compact conical monopole with ground plane and protective radome. The monopole shape was optimized for broadband operation and directional radiation pattern using electromagnetic simulations. A cylindrical radome transparent to electromagnetic waves was designed without perturbing the radiation characteristics of the optimized UHF antenna. The 130 mm diameter fabricated sensor has directional radiation pattern, UHF bandwidth of 0.5 – 3 GHz and compact radome of 150 mm diameter. PD signals gathered for three defects in gas insulated test cells indicate better detection capability and sensitivity for the proposed UHF sensor than the reference sensor.The improved performance of the proposed sensor suggest that it could be used for PD detection in HV equipment such as gas insulated switch gear and transmission line.

The electrical and mechanical properties of the epoxy alumina nanocomposites depend on the uniform dispersion of the nanofiller in the epoxy matrix. Epoxy alumina nanocomposites were prepared using 1, 3, and 5 wt% of alumina nanofiller, and electrical and mechanical properties were analyzed using experimental and modelling studies. Water droplet initiated corona inception voltage (CIV) was identified using fluorescence fiber technique and by Ultra High Frequency (UHF) technique, under AC and DC voltages. The CIV formed due to water droplet have reduced drastically with increase in number of droplets and fluorescent fiber technique found to be more sensitive to identify water droplet initiated discharges. A micro mechanical model was proposed to analyse the combined effect of the interphase and agglomeration properties of the alumina nanoparticles on the tensile strength of epoxy alumina nanocomposites. Variation in ϕagg, Eagg, and E were analysed by adopting the non-parametric distribution of alumina nanoparticles and Young’s modulus increased with the increment in the alumina nanofiller dispersion level. The presence of aggregated particles exhibits a negative effect on the tensile properties of nanocomposites.

This article reports the thermal ageing of ester fluid‐impregnated pressboard material along with its performance evaluation using optical emission spectroscopy (OES) and classification using machine‐learning algorithms adopting laser‐induced breakdown spectroscopy (LIBS). The surface discharge analysis on ester‐impregnated pressboard (EIP) is studied using OES and the plasma temperature was evaluated based on the Cu I emission lines which were higher under the negative DC compared with the positive DC and AC voltages. The LIBS analysis was performed on the EIP material operated at different energy levels in order to acquire the optimal energy required to be used for its classification algorithm. The intensity ratio and electron density evaluated from LIBS studies correlated well with the plasma temperature. The lower limit of detection (LOD) calculated based on linear regression analysis for copper peak was around 3.5 times higher than the identification of carbon peak. The machine‐learning techniques like principal component analysis and neural network algorithm have been performed on the LIBS spectral dataset in order to classify the ageing of EIP material. Artificial neural network adopting LIBS provided a better classification accuracy on all the aged samples compared with principal component analysis which classified only for the samples aged at higher temperatures.

Silicone rubber nanocomposites were prepared using 1, 3, 5, and 10 wt% of alumina nanofiller. Corona inception voltage (CIV) due to water droplets was measured using fluorescence technique, and it has decreased for alumina-added silicone rubber nanocomposites and with corona-aged samples. The effect of the corona discharges on the surface morphology characteristics of the nanocomposites was analyzed by measuring contact angle, surface profile measurement using atomic force microscopy (AFM), and characterized by adopting multiresolution signal decomposition (MRSD) technique. The addition of the alumina nanofiller suppressed the surface roughness for the corona-aged nanocomposites and 5-wt% sample observed to have the lowest surface roughness values. Recovery of the surface roughness caused by corona discharges was analyzed at different time intervals, and it was observed that alumina nanoparticle-added silicone rubber showed an incremental reduction in the roughness recovery rate. The laser-induced breakdown spectroscopy (LIBS) technique was adopted to analyze the nanocomposites after the corona aging, and further plasma temperature was evaluated at different recovery times. The addition of an alumina nanofiller increased the plasma temperature, and 5-wt% samples have the lowest plasma temperature recovery rate after corona aging. The analysis of the study indicates that the corona-aged silicone rubber specimen surface properties recover in 8 h of resting time period.

Charge trap characteristics of epoxy spacer insulating material due to surface flashover are important for improving the stable operation of GIS. In this work, magnesium oxide (MgO) filled epoxy nanocomposite material is proposed as the spacer material and its performance is compared with pure epoxy. The surface properties of spacer materials were altered using surface flashovers generated due to standard lightning impulse (LI) and steep fronted lightning impulse (SFLI) having front time of 0.1 µs, using rod plane electrode setup. The impact of surface flashovers on charge trap characteristics were analysed through surface and space charge studies. The surface charge behaviour was estimated by surface potential decay and their trap characteristics, space charge accumulation was measured using pulsed electro acoustic technique. SFLI flashover voltage was lower compared to LI voltages and MgO filled epoxy nanocomposite had higher flashover voltage compared to pure epoxy. The space charge density of MgO filled epoxy nanocomposite was less compared to pure epoxy after treating with LI/SFLI flashover voltages. MgO filled epoxy nanocomposite had enhanced surface potential decay and reduced trap energy after surface flashover. Due to the superior insulating properties, MgO filled epoxy nanocomposite can be used as the spacer material in GIS components.

Zinc-air battery (ZAB) technology is a strong competitor in the automobile sector for powering automotive. Alas, there are a few issues that restrain them from being commercialized. One prominent issue which has not been discoursed thus far in alkaline ZAB is the impact of the type and content of the binder. The present work incorporates a study conducted to get insights on the impact of eleven different polymeric binders in the air electrode of an alkaline zinc-air battery. They include anion and cation conducting polymers, hydrophilic and hydrophobic polymers. The galvanostatic polarisation curves reveal a huge variation depending on the type of binder. Fumion ionomer, an anion conducting material, shows the highest current density of about 163 mA cm−2 at 0.6 V owing to the right proportion of hydrophilic-hydrophobic segments and ion-conducting nature. A specific capacity of 770 mA h g−1 was obtained when Fumion was employed as a binder with 1 mgPt cm−2. Eventually, the upshot of the experiment motivated us to try a home-made less commonly known anionic binder, functionalised-Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene, which performed on par with Nafion™ and Fumion at a practical operating voltage of ∼1.2 V.

Change in soil ionization surrounding a ground rod electrode after impulse voltage application with addition of water, acid rain and bentonite to different sized sand is examined. Impulse voltage and current responses in a rod-plane configuration show a characteristic change in sand ionization and breakdown with addition of water and gap length but no effect from voltage polarity. Soil ionization voltage (V 50 ) and time to ionization (t bd ) of sand are found to be increasing with increase in its grain size. Increase in water content in sand decreases the V 50 and t bd indicating increased ionization activity. Acid rain-sand mixture shows approximately the same V 50 as water mixed with sand, but a lower t bd due to increased ion concentration and new functional groups formation, as observed through FTIR patterns. Bentonite-sand mixture shows lower V 50 than sand, especially with large grain size due to filled voids. This is attributed to a decrease in permittivity and an increase in plasma temperature after addition of bentonite to sand, as verified by measurements. Modifications of the physico-chemical properties of sand and bentonite are also observed when the samples are subjected to successive impulse voltages; these changes are verified by XRD, FTIR, VSM, LIBS and DRS analyses.

The authors report the key findings from an experimental study that explored the use of activated bentonite for the reclamation of thermally aged ester‐based transformer nanofluids to improve their insulation performance. Bentonite activated with acid treatment caused an increase in the specific surface area and pore volume of bentonite compared to the bentonite sample before treatment, thus imparting an improved adsorption capability. Physico‐chemical diagnostic studies were carried out to characterise the activated bentonite. The insulation performance of the reclaimed natural ester and nano‐filled ester fluid samples was assessed by measuring the corona inception voltage and breakdown voltage of each fluid sample, apart form measuring the flow electrification current using the spinning disk method. The results revealed that the reclamation process improved the corona inception voltage, dissipation factor and the breakdown voltage of the base ester fluid sample due to attraction of carbon particles to activated bentonite, but no significant variation was observed with nanofluids due to the depletion of the electrical double layer. The flow electrification current of ester and ester nanofluids reduced after treatment with activated bentonite, may be attributed to the interaction between copper and bentonite that alters the double layer formation responsible for the separation of charges.

Vanadium redox flow batteries (VRFB) are emerging as the preferred energy storage solution for long-duration energy storage (LDES) and grid-scale load levelling. Herein we report a novel binder-free sandwich electrode architecture consisting of a thin layer (6−12 mg cm−2) of thermally activated graphite felt mat (TGFM) sandwiched between thin carbon papers (TCP-TGFM-TCP). This electrode architecture substantially reduced the polarization (I-V) resistance of the VRFB by 23 %, resulting in a current density increase from 340 mA cm−2 at 1 V for the thermally activated graphite felt (TGF) electrode to 470 mA cm−2 at 1 V, and an energy efficiency of 80 % at 100 mA cm−2 is realized.

Pulsed electric field therapy is a novel non-invasive approach for cancer therapy. It serves as a cell permeability enhancing agent for cancer treatment. Nanosecond, high-electrical field pulse power technology is used for delivering variable, controllable, intracellular electrical perturbations in several biological systems. Here, we investigated the effect of nanosecond (ns) electric pulse (nsEP) as a therapeutic tool for cancer. In in-vitro study, the breast cancer cells (MCF-7) were exposed with electric field of ~18kV/cm intensity, ~25ns duration, at 1.5Hz in a 2mm electroporation cuvette. Post exposure, observation shows a significant reduction in cell viability. It was evident that after treatment the viability of MCF-7 cancer cells at 630 pulses are remains ~38% only. The optical microscopic analysis of MCF-7 cells shows cell morphology changes after electrical pulse exposure. Moreover, we have also investigated a comparative study of the effect nano-second electrical pulses on MCF-7 cells and Chinese Hamster Ovary (CHO) cell line. The comparative study, demonstrated that the effect of nsEPF on MCF-7 is more destructive than on CHO cell line. The obtained results support that the pulse electrical field of nanosecond (ns) duration therapy would be a potential solution for cancer treatment. Keywords: Nanosecond Pulse Electric Field; Full Width at Half Maxima; Pulse Forming Line; Pulse Exposure; Viability

In this present research, the machinability studies of TiAlN/TiCN, TiCN/TiAlN coated and uncoated inserts were investigated on machining custom 450 alloy. The machining input parameters such as feed rate (f), cutting speed (V) and depth of cut (d) are set using orthogonal array. The machining output parameters such as surface roughness, tool wear and cutting forces were studied for its parametric contribution and it was analyzed using Analysis of Variance (ANOVA). Further, the tool wear obtained was studied using scanning electron microscopic images and energy dispersive spectroscopy analysis was conducted to check the addition of work material elements to the coated tool surface. The results show that, the feed rate is the most contributing factor in deciding resultant forces, surface roughness and tool wear respectively. TiAlN/TiCN coated carbide tool has obtained improved machinability, when compared to TiCN/TiAlN coated carbide and uncoated carbide inserts. To obtain one optimal level for all three responses of three types of tools, multi criteria decision making approach, named utility concept approach is selected. Based on the MCDM analysis, it is found that trial number 4 gives better experimental output of improved surface integrity, lower resultant force and less tool wear for all types of tools.

In the current study, hard turning of AISI H11 tool steel is done using TiAlN coated cutting tool. The workpiece is prepared by three different processing conditions (Solution treated, Heat treated, Cryogenic treated). The machining performance are studied by the input parameters; cutting speed (60, 90, 120 m/min) and feed rate (0.06, 0.12, 0.18 mm/rev) with a constant depth of cut of 0.5mm using Taguchi’s L9 design. The responses like, surface quality, wear on the tool, and forces generated for all three specimens are studied. The hardness of all three components is measured using Vicker’s micro-hardness tester. The experimental results proved that feed rate is the most influential parameter in deciding, surface roughness, cutting force and tool wear. The utility concept approach is applied and found, solution treated sample with 120 m/min of cutting speed and 0.06 mm/rev of feed rate produces optimal results in all three response criterion.

Life expectancy of a thermally aged oil impregnated pressboard (OIP) in the presence of corrosive dibenzyl disulphide (DBDS) is studied in this work using a fast estimation method based on level of diffusion of Cu contaminant. Data from laser induced breakdown spectroscopy (LIBS) is used as the degradation parameter. Thermogravimetric analysis (TGA) is used for rapid evaluation of life expectancy at various temperatures. Aged OIP material is tested for its surface flashover breakdown strength and its thermal stability is studied by TGA and differential scanning calorimetry. Thermal activation energy is estimated using Flynn-Wall-Ozawa method and is agreement with isothermally calculated values. Aging law is derived and found to be nearly first order based on which temperature dependent life expectancy law is formulated. LIBS data of OIP collected from a failed transformer is considered to be end-of-life condition. Estimated life expectancy values using proposed fast method are compared with traditional long-aging evaluation and are in good agreement. Increase in corrosive DBDS concentration and change in aging medium using proposed method and are found to have a significant impact on life expectancy of the OIP insulation.

Laser texturing has been carried out on the surface of the silicone nano‐micro composites to achieve super hydrophobic properties, and water droplet‐initiated Corona discharge studies were carried out. The Corona inception voltage (CIV) exhibits considerable enhancement with increase in the nano filler content under DC voltage compared with AC voltage. The corona inception voltage is high with the textured surface and is found to have direct correlation with contact angle of the composite specimen. The Corona inception voltage was measured using Ultra‐high frequency (UHF) and fluorescent fibre techniques. It is observed that the fluorescent fibre technique is more sensitive in identifying discharges. Frequency domain analysis of UHF signal shows a dominant frequency at 1 GHz and for fluorescent signal, the spectral content is in the range of DC to 10 MHz. The rise time and pulse width of the UHF signal increases with the increase in the nano filler in composite material. The energy content of UHF/fluorescent signal due to discharges shows similar trend with its increase in energy with variation in its magnitude of the signal formed. The pulse width of fluorescent signal formed due to water droplet‐initiated discharges under AC and DC voltage is almost the same, and with the textured specimen it is quite low than the non‐textured material.

Carbon fiber-reinforced polymer (CFRP) composites are increasingly replacing the metals and other composites in automotive and aerospace industries due to their excellent properties. These application components have required micro-holes on CFRP for joining different components. In the present work, micro-holes are fabricated on CFRP using CO2 laser for achieving the high-quality-dimensional precision and accurate hole. The input parameters such as laser power, cutting velocity and argon pressure were varied. The responses such as heat-affected zone, kerf width, kerf angle and aspect ratio were measured using video measurement system. Besides, analyses of variances, regression modeling and microstructural analysis were presented. Results showed that the cutting velocity is most influential factor that affecting the heat-affected zone and kerf width and followed by power.

Additive manufacturing (AM) is an expeditiously developing technology for the manufacturing of biomedical implants. It provides an excellent and broad opportunity for the bio-mimicry of desired complex profiles of bodily implants because of its customized fabrication, lower manufacturing time and cost. Metal AM of biomedical implants has increased many medical practitioner’s attention because of its increased fatigue strength and excellent corrosion resistance properties, patient-specific implants for a speedy recovery, and it is found to be a suitable alternative to amputation. But there are some issues related to metal AM that are desired dimensional accuracy, preferred surface quality, strength, etc. Based on the said shortcomings, the following properties are chosen for the present review article; mechanical and metallurgical behavior. The main objective is to review the above-stated properties for 3D printed biomedical implants manufactured through laser additive manufacturing (LAM), friction stir additive manufacturing (FS-AM), paste extruding deposition (PED) and selective laser melting (SLM) techniques and its future scope of AM processes.

Aqueous Zn-ion batteries have tremendous potential to penetrate the energy storage market, as an alternative to Li-ion batteries, given the high volumetric capacity of Zn (5853 mAh cm–3), cost-effe...

The micro-aluminium trihydrate (ATH) and nano-alumina fillers in the silicone rubber (SR) significantly improve the electrical, thermal and mechanical properties. ATH fillers improved the resistance to the corona ageing and water droplet-initiated erosion. Scanning electron microscopy (SEM) analysis was carried out to understand degradation condition caused due to corona ageing and damage caused due to water droplet-initiated discharges. The inclusion of these fillers significantly altered the surface and bulk charge distribution characteristics of the polymer. A right shift is observed in the trap distribution characteristics. The reduced electric field threshold limit for space charge formation is observed with composites, due to increment in impurities/agglomerations with respect to increment in filler concentration. Performance of composites subjected to polarity reversal is improved on inclusion of nano-filler in addition to micro-filler. The inclusion of fillers enhanced the thermal conductivity and improved significantly thermal stability of the SR composite.

The electrical, thermal and mechanical properties of epoxy nanocomposites and hybrid epoxy nanocomposites have been studied. Short term breakdown voltage studies, Surface discharge analysis, PRPD studies have been carried out and found that hybrid nanocomposites with 1.5 wt% clay in epoxy resin have high performance. Thermo gravimetric studies indicate that major weight loss of material occurs between 530 and 560°C. Tensile test, flexural test and impact test with epoxy nanocomposites and hybrid epoxy nanocomposites indicate hybrid epoxy nanocomposites have good mechanical strength. Laser Induced Breakdown Spectrometry (LIBS) studies indicate that Silica (Si), Calcium (Ca), Potassium (K) are present in fiber material and energy required to generate plume is high with hybrid nanocomposites.

Metal additive manufacturing (AM) processes are used to produce metal parts with greater design freedom and no material wastage from a CAD model, using powder or wire as feedstock with a layer by layer joining of materials by a high intensity energy source such as laser or electron beam. These processes include selective laser melting (SLM), electron beam melting (EBM) and wire arc additive manufacturing (WAAM) techniques which has wide usage in fabricating metal alloys such as aluminum and titanium for the aerospace and automotive applications. However, these AM parts show many limitations in the as built state like poor surface finish and high tensile residual stress, which will affect the mechanical properties and surface integrity because of the usage of high intensity energy-based melting for the fabrication of parts. This give rise to the need for post processing techniques such as heat treatment and additional machining and polishing operations such as shot peening (SP), laser shock peening (LSP), abrasive flow machining(AFM), friction stir processing (FSP) and hot isostatic pressing (HIP) to improve its surface finish, fatigue life and other material properties. This review paper aims to understand the defects of as built AM parts and focus on the post processing techniques employed by the researchers and its effects on the improvement of AM components.

3D printing of composites is one of the trending topics in the field of additive manufacturing. Several research papers on carbon fiber reinforced composites, used carbon fiber tows directly or sized carbon fibers as reinforcement for the composite, which is time consuming and not reliable as frequent clogging occurs. This paper presents a simple method by introducing the novel use of twisted carbon fiber filament and analyze its effect on the additive manufactured composites. The matrix material used is PLA. The commercially available 3D printers for printing continuous fibers, use double nozzle setups for printing the matrix and reinforcement separately in a layer by layer manner. However, there are no reports on the use of twisted continuous carbon fiber as filament and its effect on the printed parts. This paper uses twisted carbon fibers with single nozzle setup such that the material coming out of the nozzle will be ready to use CCF-PLA composite. Thus, the need of separate stacking of each layer of the matrix and fiber can be avoided. A separate path process planning has been done for printing the twisted carbon fibers in consideration of its continuity and the anisotropy. Standard mechanical tests are conducted, and the morphological study of the composite is done.

Cascade photoelectrocatalysis (PEC) is a possible method to improve the selectivity of solar-driven CO2 reduction (CO2R). This concept can be realized by coupling different CO2R catalysts to different subcells in a multijunction photovoltaic (PV) stack. Efficient implementation will require careful tuning of the photocurrents and design of the photovoltages provided by the subcells to the CO2R catalysts in such a way as to facilitate the target reaction. Here, we outline the design principles of the tandem PEC approach using two-step conversion of CO2 to ethylene in aqueous electrolyte, via a CO intermediate, as a model system. To perform this reaction, the first coupled PV-catalyst component should provide 4 electrons to reduce 2 molecules of CO2 to CO; the second component should provide 8 electrons to reduce 2 CO molecules to C2H4. Based on known CO2R catalysts, the overpotential required to produce CO can be less than that required to reduce it to ethylene, creating the opportunity for improved efficiency. Cascade PEC can be realized in a three-terminal tandem (3TT) configuration using III-V-semiconductor based subcells coupled to Au (produces CO intermediate) and Cu (converts CO to ethylene). The current to each catalyst can be controlled by the area of the subcell exposed to the electrolyte, and the photovoltage is determined by the materials selected and device configuration. Operating conditions are found by simulating the coupled system using the open-source circuit simulator SPICE (Simulation Program with Integrated Circuits Emphasis). We identify conditions under which a 3TT configuration can have a higher solar to chemical conversion efficiency compared to a two-terminal two-junction tandem (2T 2J) with the same absorbers and a Cu catalyst only. We also show that 3TT PEC devices can be less sensitive to variations in catalyst activity compared to 2T devices. Finally, we discuss the applications of cascade PEC to CO2 reduction, using different intermediates, and to other chemical networks.

This paper reports the experimental investigation of the corona discharge activity of punga oil under the influence of a local magnetic field and different voltage profiles (AC and DC voltages) using fluorescent fiber sensor as well as UHF sensor technique. The corona inception voltage (CIV) of punga oil is higher under negative DC voltage followed by positive DC and AC voltage, with a marginal reduction in its CIV magnitude observed on the impact of external magnetic field. The dominant frequency of the UHF signal obtained under AC voltage shifted towards lower frequency (0.6 GHz) with the influence of magnetic flux density to about 85 mT. The rise time, pulse width and energy content of the fluorescent signal formed due to corona activity under AC voltage is found to vary under high magnetic fields confirming the inception results. The fluorescent signals formed due to corona discharge under both AC and DC voltages have its dominant frequency at 1 MHz with no shift observed in the presence of magnetic field. Also, there is no variation in the phase resolved partial discharge (PRPD) pattern observed due to corona discharge (with and without magnetic field) signal using both UHF sensor and the fluorescent sensor. The fluorescent fiber-based technique provides a better accuracy on detecting the corona discharges in punga oil at an early stage compared to conventional UHF sensor. The breakdown voltage of punga oil under different voltage profiles with and without the effect of magnetic field follows normal distribution. The dielectric dissipation factor and electrostatic charging tendency (ECT) of punga oil is observed to be higher than the limit set for insulating fluids towards power transformer operation.

The proposed study compares the electrical, thermal and mechanical performances of thermally aged cellulose pressboard material impregnated in mineral oil, synthetic ester fluid and mixed oil. The electrical insulation characteristics of oil-impregnated pressboard (OIP) are studied by means of surface discharge inception voltage (SDIV) using an ultra-high frequency technique and surface potential measurement analysis. It indicates that OIP aged in mineral oil has higher surface potential due to higher charge trap density compared to that of the mixed oil and synthetic ester fluid. Mechanical and thermal characteristics of the aged OIP are studied by means of tensile strength measurement and thermo-gravimetric analysis, respectively. The change in the chemical composition of OIP is studied by means of laser-induced breakdown spectroscopy, which indicates lower plasma temperature with mineral oil-based OIP indicating higher degradation state. To further understand the microscopic structure of the thermally aged OIP in different oils, scanning electron microscopy and X-ray diffraction studies have been performed. The pressboard thermally aged in synthetic ester fluid and the mixed oil has better electrical, thermal and mechanical properties as compared with the pressboard aged in mineral oil.

Epoxy aluminium nitride (AlN) nanocomposites were prepared to understand the influence of thermal ageing on dielectric and space charge performance of the material. It is observed that the real relative permittivity values of epoxy AlN nanocomposites are higher than epoxy resin when wt% of AlN is >1 wt%. Also, the epoxy AlN nanocomposites depicted an increase in dielectric loss compared to the neat epoxy specimen. The space charge variations in the test specimens are analysed by adopting a pulse electro-acoustic technique. It is observed that the nanocomposites have lesser space charge in the bulk volume of insulating material compared with pure epoxy resin. Also, it is realised that the local electric field is less with nanocomposite material in both virgin and thermally aged specimens. The threshold electric field is observed to be lesser with epoxy resin compared to nanocomposites. Laser-induced breakdown spectroscopy (LIBS) analysis clearly indicates the reduction in plasma temperature with epoxy AlN nanocomposites compared to pure epoxy resin. Principle component analysis (PCA) has classified the nanocomposite materials having different filler concentrations from the pure epoxy resin, qualitatively based on their LIBS spectra. Thermally aged epoxy AlN nanocomposites are successfully classified from unaged nanocomposite specimens, using PCA.

Epoxy alumina nanocomposites were prepared to understand the space charge variations with ultra violet (UV)- and water-aged specimens. Addition of alumina nanofiller to epoxy resin had suppressed the space charge formation. A pulsed electroacoustic technique was employed to measure the space charge accumulation in epoxy–alumina nanocomposites. A marginal increase in space charge with enhanced electric field in the bulk volume of insulation was observed with UV- and water-aged nanocomposites. It was observed that 3 wt% sample showed better performance in all ageing conditions, which was confirmed through space charge studies and by the measurement of the dielectric parameters especially dielectric constant and tan(δ).

Decolorization of dye waste water is performed using a tubular electrochemical reactor. Stainless steel and oxide coated on titanium mesh acts as the cathode and anode respectively. Experiments were conducted in batch with recirculation mode. The effect of operating parameters such as current density, initial dye concentration, flow rate and supporting electrolyte concentration on decolorization of Acid red dye has been studied and the results were analysed using Taguchi method. A residence time distribution (RTD) study has been conducted in a tubular electrochemical reactor and an axial dispersion model has been developed to determine percentage decolorization. The model results are compared with experimental results and it was found that the model satisfactorily matches with the experimental results with high correlation coefficient.

The dielectric properties of 20% synthetic ester oil mixed with mineral oil were studied for its potential applications as an insulator in transformers. The corona inception voltage of mixed oil under AC and DC voltages was measured by the ultra-high frequency (UHF) technique. A statistical study of the breakdown voltage of mixed oil under AC, DC and standard lightning impulse voltages was carried out to obtain a database which would be useful for designing transformer insulation. Further, the mixture was subjected to continuous breakdown studies under AC voltage with lightning impulse voltages, at regular intervals and characterised through measurement of interfacial tension, flash point, ionic mobility as well as UV–vis spectroscopy and frequency-domain spectroscopy studies to understand the liquid's chemical stability. The results of the study have shown that the mixture was stable even after several breakdowns. The ionic mobility and polarisation current have increased, indicating higher losses in the oil. UHF signal energy analysis and phase-resolved partial discharge analysis have revealed a reduction in discharge activity with mixed oils.

Insulating liquids play an important role as insulating media in various high voltage applications and infrastructure installations. The dielectric strength of an insulating liquid depends on the experimental conditions (in case of laboratory testing) and/or the service conditions (in case of apparatuses in service). One of the main factors affecting the dielectric strength of insulating liquids is the so-called size effect, i.e. the effect of the size of the electrodes, of the size of the liquid volume under stress and of the gap spacing between the electrodes. All the aforementioned parameters are investigated in the context of the present short review.

Many industrial applications necessitate lightweight materials that possess better tribological behaviour. Whilst aluminium based nanocomposites are proposed owing to their lightness, their tribological characteristics must be improved which are dominantly influenced by the selection of reinforcements, manufacturing process and heat treatments. In this research, an aluminium hybrid nanocomposite is produced using a novel molten salt processing and subjected to different heat treatments. Their tribological behaviour is assessed under different operating conditions viz. load, sliding velocity and material condition of the pin. Regression models are formulated to predict the tribological behaviour of developed hybrid composite under different heat treatments. The most significant parameter and optimum level for each of these operating parameters are determined using analysis of variance, main and interaction plots and response surface methodology in the end. The integrated approach helps in deciding the optimum parameter setting for the development of nanocomposite with ameliorated tribological behaviour. Under the optimized conditions, the hybrid nanocomposite could able to reduce the wear resistance by about 63% and the coefficient of friction by 18.5% than unreinforced alloy.

Wire electrical discharge hybrid turning (WEDHT) is one of the unconventional machining process following thermo-electric material removal principle to machine cylindrical components at meso and micro scale with very high accuracy and precision. Thermal simulation and validation of Ti6Al4V alloy on temperature profile, crater formation, rate of material removal during WEDHT process was reported less by previous researchers and this creates path for framing the objective. The objective of the present study is to, numerically simulate and validate the material removal through crater formation and temperature generation in WEDHT process using COMSOL Multiphysics 5.2. The time-dependent and heat transfer in solid module is chosen with current, voltage and discharge ON time (TON) of 106, 109, 112 µs as the input parameters for modelling. With the same varying TON, varying wire feed rate of 3, 4, 5 m/min and varying servo feed of 5, 7, 9 mm/min, the validation experiments are performed to validate the crater formed. Based on the comparison plot, the numerically predicted and experimentally obtained data resulted in the error percentage of 41.6%, 21.2%, 15% for 106, 109 and 112 µs discharge ON time, respectively. The images of the crater formed on the work material are captured using scanning electron microscope and atomic force microscopy images. The results of the numerical and experimental study, proved that, high the TON, more would be material removal.

This study shows that TiO 2 nanofiller and cetyl trimethyl ammonium bromide (CTAB) surfactant in ester oil demonstrates higher corona inception voltage under AC and DC voltages. Flow electrification studies with nano fluid adopting the spinning disk method confirms that the streaming current increases with increasing pressboard thickness, disc diameter, oil temperature and spinning disk velocity. The study also indicates that nanofluids with surfactant have higher streaming currents than its effect without surfactant. It is found that the streaming currents could be suppressed by the addition of aromatic additive 1, 2, 3-benzotriazole (BTA). In addition, the permittivity of the nanofluid is not affected by adding surfactant or BTA but a marginal reduction occurs with increasing temperature. However, the loss tangent of the nanofluid with surfactant and BTA shows an increase with increasing temperature. The rheological studies indicate transition from laminar to turbulent flow in the case of nanofluids.

This paper reports the key findings from an experimental study carried out on thermally aged natural ester fluid impregnated pressboard (EOIP) material. The results show that the surface discharge inception voltage (SDIV) with thermally aged EOIP material is higher under negative DC voltage compared with positive DC and AC voltage. The SDIV increases with AC voltage frequency and a minimal reduction in voltage was observed under harmonic AC voltages with different total harmonic distortion (THD). The rate of change in voltage due to ripple content in DC voltage affects the SDIV of EOIP material, initiating discharges at lower voltages. The UHF signals radiated during the surface discharge process have a bandwidth in the range 0.9 to 2 GHz. Surface potential variation studies indicated the formation of high trap sites and trap density due to thermal aging. A reduction in the oxidation onset temperature and the activation energy of thermal decomposition were observed with thermally aged EOIP material. A pyrolysis study showed high composition of levoglucosan and acidic residue with the thermally aged specimen, which reduces its degree of polymerization. Impedance spectroscopic analysis indicates a non-Debye type of relaxation with thermally aged EOIP material. The mobility and charge transfer characteristics were also inferred from the modulus spectroscopy which showed less change for thermally aged pressboard material.

This work studies the impact of silica nanoparticles on the dielectric properties of synthetic ester oil. A stable nanofluid is prepared by addition of surfactant. With addition of nanoparticles there is an increment in dielectric constant and decrement in dielectric loss constant. An attempt is made to understand the conduction mechanisms in uniform field and non-uniform electric field configuration by means of analysing the mobility of ions. Under uniform electric field stress (

Antimony sulfide (Sb2S3) is a promising light-absorbing semiconductor for photovoltaic applications, though it remains vastly unexplored for photoelectrochemical water splitting. Sb2S3 was synthesized by a simple sulfurization of electrodeposited antimony metal at relatively low temperatures (240–300 °C) with elemental sulfur. Using a TiO2 buffer layer and a platinum co-catalyst, photocurrent densities up to ∼9 mA cm–2 were achieved at −0.4 V vs RHE in 1 M H2SO4 under one sun illumination. Using X-ray photoelectron spectroscopy band alignment studies and potential-dependent incident photon-to-current efficiency measurements, a conduction band offset of 0.7 eV was obtained for the Sb2S3/TiO2 junction as well as an unfavorable band bending at the heterointerface, which explains the low photovoltage that was observed (∼0.1 V). Upon inserting an In2S3 buffer layer, which offers a better band alignment, a 0.15 V increase in photovoltage was obtained. The excellent photoelectrochemical water splitting performance and the identification of the origin of the low photovoltage of the Sb2S3 photocathodes in this work pave the way for the further development of this promising earth-abundant light-absorbing semiconductor for solar fuel generation.

This article encompasses the design of compact ultra-wideband (UWB) bandpass filter with low insertion loss and high selectivity using circular open-circuited stubs (COSs). Low insertion loss from ...

A super compact parasitic patch loaded patch antenna with enhanced gain and super wide band is proposed in this study for 5G millimetre-wave (mm-wave) applications. The proposed antenna has hybrid geometry and is constructed using circular and two rectangular driven patches with two semi-circular parasitic patches fed by stepped impedance microstrip line. The two rectangular stubs are incorporated on driven patch to improve the voltage standing wave ratio (VSWR) bandwidth. The two semi-circular parasitic patches are added on the fundamental radiator (driven/main patch) to further enhance the bandwidth to cover the entire Ka-band spectrum for 5G mm-wave requirements and covers 24–40 GHz frequency spectrum with VSWR ≤2. This designed radiator is feasible to be placed inside the multilayered housing systems or can be integrated along with the electronic components existing on the printed circuit board. Furthermore, a four-element modified corporate feed array configuration is constructed and their enhanced gain performances are compared with proposed radiator (single element). Both the prototypes are fabricated and experimentally validated for impedance and radiation characteristics and it is observed that, the simulated and measured responses are in good arrangement. The presented radiating element finds its applications in future 5G mm-wave, 5G base station controlling networks and 5G wideband code division multiple access.

Silicone insulators are gaining its importance in the transmission and distribution of the power system networks. This study proposes a simple and high throughput way of fabrication of superhydroph...