163 results on '"Sai Kiran"'
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2. Assessment of Pyrolytic Biochar as a Solar Absorber Material for Cost-Effective Water Evaporation Enhancement
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Gerardo Diaz and Sai Kiran Hota
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Materials science ,Evaporation rate ,Environmental engineering ,chemistry.chemical_element ,Pollution ,Photothermal conversion ,chemistry ,Biochar ,Environmental Chemistry ,Pyrolytic carbon ,Water desalination ,Solar desalination ,Waste Management and Disposal ,Carbon ,Solar absorber - Abstract
Enhancement of water evaporation using carbon-based solar absorbers has been gaining acceptance for its potential use in solar-driven water desalination. The evaporation rate can be increased by us...
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- 2021
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3. Microstructural Characterization of XH 67 Nickel-Based Superalloy Under Different Heat Treatment Conditions
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Venkata Sai Kiran Chakravadhanula, K. Jalaja, S. V. S. Narayana Murty, and Sushant K. Manwatkar
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Equiaxed crystals ,0209 industrial biotechnology ,Materials science ,Scanning electron microscope ,Alloy ,Metals and Alloys ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,Microstructure ,020501 mining & metallurgy ,Carbide ,Superalloy ,Nickel ,020901 industrial engineering & automation ,0205 materials engineering ,chemistry ,engineering ,Grain boundary - Abstract
XH 67 is a nickel-based superalloy, which is used in critical parts of modern aerospace engines. In the present study, XH 67 specimens in five different heat treatment conditions selected based on the processing and application have been investigated for their microstructures, morphology, and composition of the matrix and second-phase particles. Optical microscopic (OM) analysis revealed the presence of bi-model neck-lace type grains and equiaxed grains as a result of different heat treatment conditions. Scanning electron microscopy (SEM) and elemental composition analysis revealed precipitates and second-phase particles. Carbides such as Ti (N, C) and (W, Mo, Ti) C were observed having different sizes and shapes. Cr-rich carbide phases were found to be preferentially segregated along the grain boundaries. X-ray diffraction analysis was carried out for assessing the phases present in the alloy. X-ray diffraction analysis revealed the gamma matrix and the precipitate phase are crystallographically identical (coherent). Transmission electron microscopic (TEM) analysis of the specimens confirmed the presence of uniformly distributed spherical Ni3 (Al, Ti) precipitates which impart thermal stability to the superalloy. Presence of different types of carbides is also revealed by TEM analysis.
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- 2021
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4. A comparative analysis of surface roughness in robot spray painting using nano paint by Taguchi – fuzzy logic-neural network methods
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J. R. V. Sai Kiran, T Thushar, M. Uma, and Prabhu Sethuramalingam
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0209 industrial biotechnology ,Materials science ,Artificial neural network ,Mechanical Engineering ,Spray painting ,Mechanical engineering ,02 engineering and technology ,Fuzzy logic ,law.invention ,Taguchi methods ,020303 mechanical engineering & transports ,020901 industrial engineering & automation ,0203 mechanical engineering ,law ,Nano ,Surface roughness ,Robot ,Orthogonal array - Abstract
Taguchi L9 orthogonal array is used to conduct the IRB1410 robot spray painting experiments to investigate the surface characteristics of Cold Rolled close Annealed (CRCA) steel workpiece. The main...
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- 2020
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5. Enhancing solar water evaporation with activated carbon
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Gerardo Diaz and Sai Kiran Hota
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Materials science ,Mechanical Engineering ,Low-temperature thermal desalination ,Evaporation ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Absorbance ,Chemical engineering ,Mechanics of Materials ,Thermal ,Transmittance ,medicine ,General Materials Science ,Irradiation ,0210 nano-technology ,Dispersion (chemistry) ,Responsible Consumption and Production ,Activated carbon ,medicine.drug - Abstract
Fresh water production through sustainable approaches such as solar thermal sources is attracting widespread attention. One of the recently developed approaches aims at utilizing black particles to enhance evaporation and steam generation through efficient photo-thermal conversion process in direct solar thermal desalination systems. Activated carbon serves as one such material for meeting the objectives of freshwater production with negligible increments in cost of the overall system. A series of chemical and physical characterizations were performed to explore the possibility of using activated carbon as a stable carbon source. Optical characterization showed granular activated carbon to have 96.35% solar absorptance and its dispersion in water to have less than 1.5% transmittance (absorbance of 1.85) at 100 mg/L concentration. Outdoor experiments were performed at the University of California-Merced in the month of September (2019), with peak irradiation of 0.8 suns. The comparative measurements showed that the total evaporation enhancement was 38% and 100% for granular activated carbon and activated carbon dispersions, respectively, when compared to pure DI water.
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- 2020
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6. Crystallographic and Morphological Evidence of Solid–Solid Interfacial Energy Anisotropy in the Sn-Zn Eutectic System
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Sai Kiran Salapaka, Kamanio Chattopadhyay, Shanmukha Kiran Aramanda, Sumeet Khanna, and Abhik Choudhury
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010302 applied physics ,Materials science ,0211 other engineering and technologies ,Metals and Alloys ,02 engineering and technology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Rod ,Surface energy ,Crystal ,Crystallography ,Mechanics of Materials ,Phase (matter) ,0103 physical sciences ,Anisotropy ,021102 mining & metallurgy ,Eutectic system ,Directional solidification - Abstract
In this paper, we explore the morphological evolution during two-phase growth in the Sn-Zn eutectic system, which has a particularly low volume fraction of the minority Zn phase. The reason for this choice is its exotic nature, as even with such a low volume fraction, the reported morphology is “broken-lamellar,” in contrast to the usually expected hexagonal arrangement of Zn rods in the Sn matrix. Thus, the main objective of the study is to investigate the reasons behind this phenomenon. We begin by presenting experimental results detailing the morphology and crystallography of the eutectic microstructures under various combinations of thermal gradients and velocities in directional solidification conditions. Based on the crystallography and further specially designed experiments we find that the solid–solid interface between the Sn and Zn crystal is anisotropic. On the basis of the results, we propose a hypothesis that the presence of solid–solid interfacial energy anisotropy leads to the formation of predominantly broken-lamellar structures, even when the minority fraction is significantly low.
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- 2020
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7. Exotic colony formation in Sn-Te eutectic system
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Shanmukha Kiran Aramanda, Kamanio Chattopadhyay, Abhik Choudhury, Sumeet Khanna, and Sai Kiran Salapaka
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010302 applied physics ,Materials science ,Polymers and Plastics ,Metals and Alloys ,Intermetallic ,02 engineering and technology ,Cubic crystal system ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Crystal ,Chemical physics ,Impurity ,0103 physical sciences ,Ceramics and Composites ,0210 nano-technology ,Ternary operation ,Phase diagram ,Eutectic system - Abstract
Eutectics are self-organized composite materials that exhibit a wide variety of microstructural features. Besides intrinsic materials properties like interfacial energies or diffusivities as well as the nature of the phase diagrams, the process parameters such as magnitude and orientation of the temperature gradient as well as the velocity of the growth interface influence the evolution of the microstructure. Recently, we have observed the evolution of complex patterns due to addition of ternary impurities in the binary Sn-Te system that contains, in addition to (Te), an intermetallic SnTe phase with a cubic crystal structure. This paper examines in detail the origin of such a microstructure that arises due to a two-phase growth instability induced by impurity addition. The binary eutectics (Sn-Te) and ternary eutectics (Sn-Te with an impurity addition) are directionally solidified at different interfacial velocities in order to study the morphological evolution. The binary alloy exhibits a rod-like or an interconnected string of rods morphology while the addition of a third component leads to a diffusive instability (similar to a Mullins-Sekerka instability) that results in the formation of two-phase colonies. The onset of instability depends on both the growth velocity and impurity concentration while the growth direction of the cells is normal to the {0001} planes of (Te) and {111} planes of SnTe. Through the extensive use of multiple characterization techniques, we have explored the morphological characteristics and crystallography of these colonies. The colonies have a complex internal structure that bears a three-fold symmetry reminiscent of the trigonal symmetry of the (Te) crystal, arising possibly because of strong anisotropy in the solid-liquid interfacial energy or in the kinetics of growth. For the different impurity additions (Ag or Sb), the internal eutectic morphology of the colony, due to the addition of Ag is different from that observed for the addition of Sb. The latter leads to the formation of lamellae while a rod-like feature could be observed for impurities like Ag. The complex patterns exhibit a structural hierarchy that provides opportunities for designing novel materials.
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- 2020
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8. Dynamic Strain Aging and Embrittlement Behavior of IN718 During High-Temperature Deformation
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Sushant K. Manwatkar, S. V. S. Narayana Murty, P. Ramesh Narayanan, Venkata Sai Kiran Chakravadhanula, and K. Saravanan
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010302 applied physics ,Materials science ,Metallurgy ,Alloy ,0211 other engineering and technologies ,Metals and Alloys ,02 engineering and technology ,engineering.material ,Condensed Matter Physics ,01 natural sciences ,Superalloy ,Brittleness ,Mechanics of Materials ,0103 physical sciences ,Ultimate tensile strength ,engineering ,Grain boundary ,Deformation (engineering) ,Embrittlement ,Dynamic strain aging ,021102 mining & metallurgy - Abstract
The high-temperature deformation behavior of nickel-base superalloy IN718 was investigated in the solution-treated (ST) condition. High-temperature tensile tests were performed between 600 °C and 850 °C at strain rates of 1 × 10−3, 1 × 10−2, and 1 × 10−1 s−1. The deformation behavior of this material was analyzed using optical microscopy, scanning electron microscopy, and transmission electron microscopy. In the investigated temperature–strain rate regime, material undergoes partial precipitation, serrated yielding, and embrittlement. Serrated yielding was observed at 600 °C, 650 °C, and 700 °C and is attributed to dynamic strain aging. The appearance of serrated flow at high temperatures up to 700 °C in the ST condition can be attributed to the availability of excess Nb in the matrix. Beyond 700 °C, Nb concentration significantly decreases in the matrix due to the formation of Ni3Nb precipitate. Nb is responsible for the appearance and disappearance of serrations at high temperature. The alloy exhibits embrittlement phenomenon in the range of 750 °C to 850 °C when thermally exposed in air. The alloy shows a ductile mode of fracture when tested at 600 °C and 700 °C, whereas completely brittle fracture was observed at the 800 °C test temperature. Formation of brittle oxides at grain boundaries in the presence of atmospheric oxygen resulted in the embrittlement of the alloy at 750 °C to 850 °C. An oxidation-assisted intergranular cracking mechanism is responsible for embrittlement of this alloy, which was proved by scanning transmission electron microscopy-energy dispersive spectroscopy.
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- 2020
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9. Zirconium–Cerium and Zirconium–Lanthanum complexed polyvinyl alcohol films for efficient fluoride removal from aqueous solution
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Siva Kumar Belliraj, Anita Nehra, Sai Kiran M, Rajni Bhandari, and Chelli Sai Manohar
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Zirconium ,Aqueous solution ,Materials science ,Polymers and Plastics ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polyvinyl alcohol ,Surfaces, Coatings and Films ,Solvent ,chemistry.chemical_compound ,Cerium ,Adsorption ,020401 chemical engineering ,chemistry ,Lanthanum ,0204 chemical engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Fluoride ,Nuclear chemistry - Abstract
In the current work, user-friendly, biodegradable, Zirconium-Lanthanum (ZLPC) and Zirconium-Cerium (ZCPC) complexed Polyvinyl alcohol (PVA) films were solvent casted for effective defluoridation of water. The films were characterised using SEM coupled EDS, XPS, TGA, XRD and FT-IR. These films adsorbed 95−97% fluoride from water at pH 7, with 85% removal by ZLPC and 93% removal by ZCPC within the first 45 minutes of the adsorption process. A maximum adsorption capacity of 11.57 mg/g and 12.88 mg/g, corresponding to ZLPC and ZCPC respectively, was obtained using Langmuir adsorption isotherm. The films followed pseudo-second-order kinetics (R2≤0.99) in both the cases, which was further established by low values of chi-square and root mean square error (RMSE). The ICP-AES analysis confirmed no leaching of the metal ions from the polymer films into the treated water. The films were found to be stable in both acidic and basic medium. No interference to fluoride adsorption was detected even at 100 mg/L of Cl−, NO3− and SO42− while some interference was observed in the presence of PO43− and HCO3−. The change in Gibbs free energy for fluoride adsorption using the ab-initio method was found to be −330.05 kJ/mol, which indicated spontaneity of the process. This was further reinforced by the thermodynamic data obtained from adsorption studies. The films were reusable and showed ∼85% removal of fluoride even after the fifth regeneration cycle. Thus, these handy films have a scope to be developed into a prototype for defluoridation of ground water.
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- 2020
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10. Influence of optical constants in carbon-based dispersions for enhanced solar evaporation
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Gerardo Diaz and Sai Kiran Hota
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Materials science ,High-refractive-index polymer ,Attenuation ,Evaporation ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,010406 physical chemistry ,0104 chemical sciences ,chemistry ,Attenuation coefficient ,Physical and Theoretical Chemistry ,0210 nano-technology ,Absorption (electromagnetic radiation) ,Dispersion (chemistry) ,Carbon ,Refractive index - Abstract
Carbon-based nano- and microfluid dispersions show promise as effective media for solar-assisted desalination. They act as strong solar absorbers in the base fluid and increase its temperature by volumetrically heating the bulk of the fluid, leading to faster vapor generation. This radiative heating depends on the fraction of the solar radiation absorbed by the fluid dispersion system. This in turn depends on the optical constants, i.e., refractive index and attenuation (absorption) coefficient of the particles. Different carbon materials exhibit different values of the optical constants when exposed to the solar spectrum and so, the evaporation efficiency is different for different particles. An attempt is made to explore the influence of these optical constants on the evaporation rate and evaporation efficiency of water. The values chosen are within the upper and lower bounds of the refractive index ( $$1\le n \le 3$$ ) and attenuation coefficient ( $$0.001\le k \le 1$$ ), which are typical of carbon-based materials. It was found that the evaporation rate is higher for large attenuation coefficient for any refractive index. Also, at a relative refractive index of 1, the solar absorption coefficient is comparatively smaller than for other values, due to lower scattering efficiency. At high refractive index, the evaporation efficiency remained almost constant for volume fractions less than $$10^{-4}$$ (or 0.01%). In summary, water evaporation rate and evaporation efficiency are strongly influenced by the optical constants.
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- 2020
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11. Enhanced methane gas storage in the form of hydrates: role of the confined water molecules in silica powders
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Pinnelli S. R. Prasad, Burla Sai Kiran, and Kandadai Sowjanya
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Phase boundary ,Materials science ,business.industry ,General Chemical Engineering ,Kinetics ,Nucleation ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain size ,Methane ,0104 chemical sciences ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Chemical engineering ,Natural gas ,symbols ,0210 nano-technology ,Hydrate ,Raman spectroscopy ,business - Abstract
Methane hydrates are promising materials for storage and transportation of natural gas; however, the slow kinetics and inefficient water to hydrate conversions impede its broad scale utilisation. The purpose of the present study is to demonstrate rapid (2–3 h) and efficient methane hydrate conversions by utilising the water molecules confined in the intra- and inter-granular space of silica powders. All the experiments were conducted with amorphous silica (10 g) powders of 2–30 μm; 10–20 nm grain size, to mimic the hydrate formations in fine sand and clay dominated environments under moderate methane pressure (7–8 MPa). Encasing of methane molecules in hydrate cages was confirmed by Raman spectroscopic (ex situ) and thermodynamic phase boundary measurements. The present studies reveal that the water to hydrate conversion is relatively slower in 10–20 nm grain size silica, although the nucleation event is rapid in both silicas. The process of hydrate conversion is vastly diffusion-controlled, and this was distinctly observed during the hydrate growth in nanosize silica.
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- 2020
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12. A Review of Basics and Potential of Liquid Crystalline Nanoparticles as Drug Delivery Systems
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Dua Kamal, Singh Kamaldeep, Pradeep Kulkarni Mangesh, Kumar Rajesh, Sesha Sai Kiran Poluri, Tanwar Sagar, Satija Saurabh, and Singh Vrinderpal
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Materials science ,Liquid crystalline ,Drug delivery ,General Engineering ,Nanoparticle ,General Materials Science ,Nanotechnology - Abstract
Aim: For procuring the stable form of drug delivery, tremendous efforts have been made in developing new drug delivery vectors. One such approach that meets the desired stability standards is Liquid Crystalline Nanoparticles (LCNs). Background: The liquid crystals are the intermediate forms of solid and liquid materials, which hold high tolerance to bear the influences of physical parameters. The liquid crystals are employed in nanotechnology to find the best way to produce the intended action of customized targeting drug delivery. The structural alignment is another critical aspect to consider, as these can accommodate wholesome drug amounts. Methods: From the studies, it has been evident that distinct characteristics like the simplicity in structure, self-assembling properties, feasibility of production, efficacy in delivery with low toxic values, have addressed the excellency of LCNs. Conclusion: The current review focusses on key areas regarding the nature of liquid crystal, diverse forms, technologies used to transform them into the desired nanoparticles, and their applications as drug delivery carriers as well as theranostic agent.
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- 2021
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13. High Temperature Tensile Behavior of a Nickel-Based Superalloy 55Ni-17Cr-12Fe-9Mo-2Nb-1.5Al Used in Launch Vehicle Applications
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V. M. J. Sharma, P. Manikandan, S. V. S. Narayana Murty, Venkata Sai Kiran Chakravadhanula, M. Amruth, K. Saravanan, G. Sudarshan Rao, and P. Ramesh Narayanan
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010302 applied physics ,Materials science ,Mechanical Engineering ,Alloy ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Stress (mechanics) ,Superalloy ,Nickel ,chemistry ,Mechanics of Materials ,0103 physical sciences ,Ultimate tensile strength ,engineering ,Brazing ,General Materials Science ,Composite material ,0210 nano-technology ,Dynamic strain aging - Abstract
55Ni-17Cr-12Fe-9Mo-2Nb-1.5Al alloy is a nickel-based superalloy (Russian designation is XH55MбЮ or KhN55MBYu, XH55) without any equivalent in American/European alloy designation. It is used in cryogenic engine of satellite launch vehicles application in two different heat-treated conditions: (1) standard aged (STA) at 730 °C/15 h + 650 °C/10 h and (2) STA + BC (brazing cycle) treatment carried out in vacuum at 1030 °C with holding time of 30 min. Due to the braze cycle adopted for manufacturing, it is essential to study the deterioration in mechanical properties, if any. Hence, the present work is carried out to understand the material behavior in tensile mode (25, 425, 575, 700 and 900 °C) for XH55 alloy in STA condition and STA + BC conditions, compared with corresponding microstructural analysis, morphology and composition using microscopy at various length scales. The tensile stress–strain curve shows characteristic sudden drops in stress with respect to strain, attributed to dynamic strain aging at different temperatures for both STA and STA + BC conditions. In STA condition, the yield strength of the material decreased with increase in temperature. In STA + BC condition, the yield strength decreased up to 425 °C, increased up to 700 °C as the material was subjected to artificial aging during testing and finally decreased at 900 °C. Marginal deterioration in mechanical properties have been observed due to the braze cycle adopted against STA condition.
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- 2019
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14. Characterization of Glass/Jute Hybrid Fibre Reinforced Epoxy Composite for Axial Flow Fan Blade
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B. Venkata Sai Kiran, Koorapati Eshwara Prasad, Krishna Sai Vadapally, Sathola Anand, Venkata Sushma Chinta, and P. Ravinder Reddy
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Materials science ,Fracture toughness ,Flexural strength ,visual_art ,Ultimate tensile strength ,Composite number ,Glass fiber ,visual_art.visual_art_medium ,Shear strength ,Epoxy ,Fibre-reinforced plastic ,Composite material - Abstract
Traditionally axial flow fan blades were manufactured by using metal alloys, but with the increase in blade size the blades grew heavier resulting in more vibrations during its working. It is impossible to manufacture the metallic blades to close tolerances making it uneconomical. Due to this dimensional instability, the metallic impeller fan blades are instead fabricated with glass fiber reinforced plastics (GFRP). To reduce the after effects of GFRP blades on the environment necessitates the partial reinforcement of natural fibre. This paper deals with the characterization of GFRP blade material with partial Jute reinforcements i.e., glass to jute (95:5) weight percentage and estimating the properties like tensile strength, bending strength, shear strength, fracture toughness. The conventional GFRP blade material has 14 layers of glass fibers in various forms. By placing jute layer at various positions in GFRP blade material the mechanical strengths were estimated and compared with conventional one.
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- 2019
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15. Design and Analysis of Shock Absorber using ANSYS Workbench
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C. Sai Kiran
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Shock absorber ,Software ,Materials science ,business.industry ,Ansys software ,Workbench ,General Medicine ,Structural engineering ,Ride quality ,Impulse (physics) ,business - Abstract
In this paper, a shock absorber is designed and analyzed which is useful for damping shock impulse and dissipating kinetic energy. Shock absorber is a critical part of the suspension system, which is used to connect the vehicle to the wheels. The purpose of the work is to model a shock absorber which will be able to improve the ride quality by reducing the amplitude of disturbances caused by a bump road. Shock absorber is designed in CREO software. Analysis of shock absorber was performed by using ANSYS software and this analysis helps to predict the shock absorber failure when an external load acts on it.
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- 2019
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16. Escherichia Coli Fed Paper-Based Microfluidic Microbial Fuel Cell With MWCNT Composed Bucky Paper Bioelectrodes
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P. Sankar Ganesh, Prakash Rewatkar, Sanket Goel, Pichkari Sai Kiran, Dipankar Nath, and Balaji Krishnamurthy
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Paper ,Nanotube ,Microbial fuel cell ,Materials science ,Bioelectric Energy Sources ,Biomedical Engineering ,Analytical chemistry ,Energy-dispersive X-ray spectroscopy ,Pharmaceutical Science ,Medicine (miscellaneous) ,Bioengineering ,02 engineering and technology ,Electrochemistry ,Lab-On-A-Chip Devices ,Escherichia coli ,Electrical and Electronic Engineering ,Polarization (electrochemistry) ,Electrodes ,Nanotubes, Carbon ,Open-circuit voltage ,Equipment Design ,Microfluidic Analytical Techniques ,021001 nanoscience & nanotechnology ,Potentiostat ,Computer Science Applications ,Electrode ,0210 nano-technology ,Biotechnology - Abstract
This paper demonstrates a simple-in-struct- ure, cost-effective, and environment-friendly Microfluidic Paper-based Analytical Device for Microbial Biofuel Cell ( $\mu $ PAD-MBFC). It consists of a microchannel with biofuel cell (Escherichia.Coli) and an oxidant (aerated tap water) flowing co-parallelly over Multiwalled Carbon Nanotube (MWCNT)-based Bucky Paper (BP) electrodes using a self-capillary and co-laminar flow mechanism. The electrochemical studies, such as open circuit potential (OCP) and polarization were evaluated using a potentiostat. Various volumetric bacterial studies were also carried out to find out the best suitable optimal bacterial volume. Subsequently, the morphological and detailed element composition study of electrode surface was performed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. This well-designed portable $\mu $ PAD-MBFC yields a maximum power density of 4 $\mu \text{W}$ /cm2 ( $20~\mu \text{A}$ /cm2) at 0.405 V over $200~\mu \text{l}$ of culture and leveraging to its long-lasting potential to operate miniaturized microelectronics sensors and portable devices.
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- 2019
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17. Design and performance analysis of double cantilever type capacitive shunt RF MEMS switch
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K. Santhi Tarun, B. V. Sai Kiran, K. Srinivasa Rao, K. Girija Sravani, R. Prem Kumar, B. M. Siva Kumar, and D. Prathyusha
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010302 applied physics ,Cantilever ,Materials science ,business.industry ,HFSS ,Capacitive sensing ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Capacitance ,Electronic, Optical and Magnetic Materials ,RF switch ,Hardware and Architecture ,0103 physical sciences ,Scattering parameters ,Return loss ,Optoelectronics ,Insertion loss ,Electrical and Electronic Engineering ,0210 nano-technology ,business - Abstract
This paper presents a novel structure of capacitance shunt type RF switch for 5G applications. The proposed RF MEMS switch is having Cantilever type designed with optimized dimensions to operate in V-band applications. The electromechanical analysis is done by using the COMSOL tool. The actuation voltage of the proposed switch is 10.5 V with the air gap of 1 µm and gold as a beam material. The proposed switch with the meanders and perforations show the scattering parameters in HFSS software such as insertion loss (S12) of − 0.033 dB and return loss (S11) less than − 48 dB and the isolation (S21) calculated in off-state as − 62 dB at 50 GHz.
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- 2019
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18. Alignment‐ and metallic‐obstacle‐insensitive contactless power transmission system utilizing surface‐guided mode
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Franklin Bien, Jagannath Malik, Woojin Park, Sai Kiran Oruganti, Seoktae Seo, Bonyoung Lee, Haksun Kim, Seong-Kyu Song, and Nak-Young Ko
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Electromagnetic field ,Power transmission ,Materials science ,Acoustics ,020208 electrical & electronic engineering ,Impedance matching ,020206 networking & telecommunications ,02 engineering and technology ,Power (physics) ,Printed circuit board ,Electric field ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Antenna (radio) ,Sensitivity (electronics) - Abstract
A key limitation inherent in wireless power transmission (WPT) systems using coils is a high sensitivity to the alignment between the transmitting and receiving coils. Moreover, the physical separation of the transmitting and receiving coils or any metallic barrier between them can notably reduce the efficiency. To overcome these limitations, a practical WPT system that is insensitive to the alignment between coils and metallic obstacles is proposed. It uses a printed circuit board-type antenna fabricated by reducing the structure of an antenna used in previous research and is designed to resonate at the target frequency through impedance matching. The proposed system uses surface-guided-mode resonance at the metal–air interface and transmits uniform power within 1.3 m. In addition, the proposed system satisfies the electromagnetic field international standard that is the electric field and magnetic field reference values are 152.5 V/m and 0.4 A/m, respectively at 4 MHz.
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- 2019
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19. Wide wavelength photon harvesting in dye-sensitized solar cells utilizing cobalt complex redox electrolyte: Implication of surface passivation
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Shyam S. Pandey, Gaurav Kapil, Maryala Sai Kiran, Shuzi Hayase, and Anusha Pradhan
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Surface passivation ,Materials science ,Passivation ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,Dye-sensitized solar cells ,010402 general chemistry ,01 natural sciences ,Redox ,chemistry.chemical_compound ,Squaraine dyes ,Photocurrent ,Squaraine dye ,Renewable Energy, Sustainability and the Environment ,business.industry ,Cobalt electrolyte ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Dye-sensitized solar cell ,chemistry ,Energy transfer ,FRET ,Optoelectronics ,Photosensitization ,0210 nano-technology ,business ,Cobalt - Abstract
A combination of near infra-red (NIR) photon harvesting and cobalt electrolytes having deeper redox energy level are needed for the fabrication of high efficiency dye-sensitized solar cells (DSSCs). A logical molecular design of unsymmetrical squaraine dye (SQ-110) as a representative of NIR dyes has been demonstrated to function well in DSSC using cobalt complex redox electrolyte. Problem of mass transport limitations due to the bulky cobalt complex ions leading to relatively enhanced charge recombination was amicably solved by single as well as multiple compact metal oxide surface passivation on both of the transparent conducting oxide substrate as well as mesoporous TiO2. Complete absence of light absorption beyond 550 nm wavelength region by D-35 and utilization of a complementary light harvesting dye SQ-110 led to efficient wide wavelength photon harvesting. DSSC fabricated using a dye cocktail of D-35 and SQ-110 in 4:1 ratio resulted in to photoconversion efficiency (PCE) of 7.2%, which is much higher as compared to the constituent individual sensitizers D-35 (3.6%) and SQ-110 (1.9%). This synergistic enhancement in PCE by dye cocktail was associated with the mutual co-operation of respective dyes in terms controlling the dye aggregation and complementary photon harvesting. In this dye cocktail system, D-35 is involved in the prevention of dye aggregation, lower wavelength photon harvesting and energy transfer induced photocurrent enhancement.
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- 2019
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20. Third order nonlinear optical properties of β enhanced PVDF based nanocomposite thin films
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Pamarti Viswanath, Pranaya Vamsy Rambhatla, V. Sai Muthukumar, and Posam Sai Kiran
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010302 applied physics ,Diffraction ,Spin coating ,Nanotube ,Materials science ,Dielectric ,Condensed Matter Physics ,01 natural sciences ,Ferroelectricity ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Pyroelectricity ,0103 physical sciences ,Electrical and Electronic Engineering ,Composite material ,Thin film ,Refractive index - Abstract
PVDF based nanocomposite thin films have received great interest in energy harvesting, ferroelectric, pyroelectric and dielectric applications. In this novel study, we have exploited the electroactive β-phase (polar) formation in polyvinylidine fluoride–halloysite nanotube (PVDF–HNT) nanocomposite thin films fabricated by the spin coating technique for nonlinear optical applications. It was demonstrated that HNTs of different volume percentage loadings in the PVDF matrix were able to effectively nucleate PVDF in β (TTTT-all trans) conformation using X-ray diffraction and Infrared spectroscopy techniques. Closed aperture Z-scan measurements were performed for all the thin film samples with a CW laser as an excitation source at a wavelength of 632.8 nm. We observed a sign change in the nonlinear refractive index for PVDF. Nonlinear refractive index has a negative sign for pristine PVDF and a positive sign for HNT incorporated PVDF thin films. This anomalous behavior of change in the nonlinear refraction of PVDF is explained in our present work.
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- 2019
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21. Activated carbon dispersion as absorber for solar water evaporation: A parametric analysis
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Gerardo Diaz and Sai Kiran Hota
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Powdered activated carbon treatment ,Materials science ,Renewable Energy, Sustainability and the Environment ,020209 energy ,Analytical chemistry ,Evaporation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Desalination ,Volume fraction ,0202 electrical engineering, electronic engineering, information engineering ,medicine ,Particle ,General Materials Science ,0210 nano-technology ,Dispersion (chemistry) ,Absorption (electromagnetic radiation) ,Activated carbon ,medicine.drug - Abstract
Solar water evaporation has been a topic of interest in recent years due to its applications in desalination, power generation, and heating. As water is not a good absorber of light, seeding it with light-absorbing particles can enhance evaporation efficiency. Activated carbon (AC) is one such material with desirable absorption properties for this application. However, particle sizes in granular and powder activated carbon can vary significantly. In this work, AC particles of different sizes are analyzed and their effect on evaporation rate is studied. It is found that particle sizes less than or comparable to solar wavelength spectrum produce higher evaporation efficiencies under independent scattering conditions ( f v 0.6 % ). It is also found that the solar absorption coefficient reaches between 0.98 and 0.9 for a volume fraction as low as 0.01%. The evaporation efficiency is 57.3% and 38.2% higher than for pure water evaporation for size of 80 nm and 8 μm, respectively, for a volume fraction of 0.01%. A parametric analysis is performed to identify the respective effect on evaporation rate.
- Published
- 2019
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22. Evaluation of Porosity in Fusion Welded AA2014 Plates using X-Ray Radiography
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N. Nagendra Kumar, R. Akshay, and P. Durga Kishore | V. Sai Kiran
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X ray radiography ,Fusion ,Materials science ,law ,Welding ,Composite material ,Porosity ,law.invention - Published
- 2019
- Full Text
- View/download PDF
23. Effect of Test Temperature on Tensile Behavior of Ti-5Al-5V-2Mo-1Cr-1Fe (α+β) Titanium Alloy with Initial Microstructures in Hot Forged and Heat Treated Conditions
- Author
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Venkata Sai Kiran Chakravadhanula, R. K. Gupta, V. Anil Kumar, M.J.N.V. Prasad, S. V. S. N. Murty, and A. Gourav Rao
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010302 applied physics ,Materials science ,Metallurgy ,0211 other engineering and technologies ,Metals and Alloys ,Superplasticity ,02 engineering and technology ,Condensed Matter Physics ,01 natural sciences ,Solid solution strengthening ,Mechanics of Materials ,0103 physical sciences ,Ultimate tensile strength ,Dynamic recrystallization ,Deformation (engineering) ,Ductility ,021102 mining & metallurgy ,Hardenability ,Heat treating - Abstract
Ti-5Al-5V-2Mo-1Cr-1Fe (Ti-55211) is another popular (α+β)-Ti alloy which exhibits good hardenability and high strength due to the formation of α′ martensite. In the present study, this alloy in the as-forged and heat treated conditions was investigated to evaluate the tensile behavior as a function of test temperature (from room temperature to near its β transus). There was significant loss of ductility with a marginal improvement in tensile strength at room temperature upon heat treating the as-forged alloy near the β transus temperature. This is attributed to the solid solution strengthening, formation of α′ laths, change in shape and distribution of α phase during heat treatment. The alloy in both as-forged and heat treated conditions exhibited typical superplasticity characteristics with large elongations to failure (~ 200 to 230 pct) associated with high strain rate sensitivity values (0.2 to 0.4) at the testing temperature near its β transus. Microstructural investigation revealed that the morphology of the α-phase gets transformed from lamellar or acicular into equiaxed/globular with random deformation texture in both conditions during tensile deformation near β transus. It was found that the mode of deformation operating at temperature of 1123 K was found to be dynamic recrystallization (DRX) of α-phase, whereas dynamic recovery (DRV) of β-phase occurred at 1173 K.
- Published
- 2019
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24. Oxidation of 2D-WS2 nanosheets for generation of 2D-WS2/WO3 heterostructure and 2D and nanospherical WO3
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Joydip Joardar, Balaji Padya, L. Venkatesh, Venkata Sai Kiran Chakravadhanula, Ajoy Kumar Pandey, and Harish Kumar Adigilli
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Materials science ,General Physics and Astronomy ,Nanoparticle ,chemistry.chemical_element ,Heterojunction ,02 engineering and technology ,Continuous mode ,Tungsten ,Atmospheric temperature range ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Isothermal process ,0104 chemical sciences ,chemistry ,Chemical engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Monoclinic crystal system ,Nanosheet - Abstract
The oxidation behaviour of tungsten disulphide (WS2) nanosheet powder with an average thickness of about 10 nm was studied in the temperature range of 25–700 °C. The samples were subjected to exposure in air in a short continuous mode as well as extended isothermal holding. It was observed that WS2 nanosheets were stable below 350 °C in air for short exposure times. A two-dimensional WS2/WO3 heterostructure evolved at 350 °C on short exposures to the oxidising atmosphere. Complete oxidation of WS2 nanosheets was observed at a temperature of about 450 °C in the continuous heating mode and at 350 °C under isothermal holding for an extended exposure time. During oxidation, WS2 nanosheets were initially transformed to 2D-WO3 nanosheets with an average thickness of about 10 nm. Significant distortion in the monoclinic structure of 2D-WO3 was observed. At higher temperatures, the WO3 nanosheets disintegrated initially to rod-shaped WO3 particles, which were subsequently transformed to thermodynamically stable spherical shaped WO3 nanoparticles.
- Published
- 2019
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25. Mechanical and tribological studies of Boron Carbide reinforced Al7150 MMCs
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B. Jaswanth, G. B. Veeresh Kumar, S. Md Khalid, M. Sai Kiran, and B. Dileep
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Materials science ,Composite number ,Alloy ,Boron carbide ,engineering.material ,Tribology ,Carbide ,chemistry.chemical_compound ,chemistry ,Ultimate tensile strength ,engineering ,Composite material ,Reinforcement ,Tribometer - Abstract
The objective of current paper is to investigate mechanical, and tribological behavior of Al7150 matrix reinforced by Boron Carbide. Stir casting process, was used to make Al7150-Boron Carbide Metal Matrix Composites (MMCs). The incorporation of reinforcement in matrix ranged from 0 to 2 wt%, with 0.5 intervals. The collected composite samples were used in research studies including physical, mechanical and tribological experiments. The experiments were carried-out in harmony with ASTM Standards on Al7150 alloy & its composites. The test results show that as the reinforcing percentage increased, characteristics like hardness and tensile strength increase, while density decreases. The wear experiment was carried out using a tribometer with pin-on-disc setup, and obtained results show that composite possess a higher wear resistance.
- Published
- 2021
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26. Effect of Hybridization, Influence of Surface Modification on the Properties and Optimization of bio fiber Composites
- Author
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G. Venkatesha Prasanna, M. Nikhil, and A. Sai Kiran
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Morphology (linguistics) ,Materials science ,Flexural strength ,visual_art ,Ultimate tensile strength ,visual_art.visual_art_medium ,Vinyl ester ,Surface modification ,Epoxy ,Fiber ,Composite material ,Microstructure - Abstract
The target of the researcher and the work was to examine the tensile, flexural, and compressive properties of biofiber strengthened composites. The legitimacy and advantage of utilizing regular filaments was their effective accessibility, simple and safe dealing with, and biodegradable nature. While biofibers reveal commendable physical and mechanical properties, it shifts with the plant source, species, and geography. In the present work, bagasse–henequen filaments were utilized at the following fixations: 5, 10, 15, 20, 25, and 30 wt%. Untreated and soluble base-treated bagasse–henequen filaments were fortified in the epoxy/vinyl ester mix and composites have been created by hand lay-up strategy. The bagasse–henequen strands were salt-treated for 12 and 24 h in 10% NaOH. Composites were assessed as far as their microstructure and mechanical properties. 25% wt. filaments 24 h NaOH (soluble base)-treated composites have demonstrated prevalent and optimum values than untreated and 12-h-treated composites.
- Published
- 2020
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27. Comparative study of spin-coated and vapour deposited nickel oxides for detecting VOCs
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Christopher S. Blackman, James A. Covington, Jone Him Tsang, and Sai Kiran Ayyala
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Materials science ,Ethanol ,Nickel oxide ,Non-blocking I/O ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease ,01 natural sciences ,Toluene ,0104 chemical sciences ,Hexane ,chemistry.chemical_compound ,chemistry ,Acetone ,medicine ,Methanol ,0210 nano-technology ,Vapours ,Nuclear chemistry - Abstract
Nickel oxide (p-type) sensors are developed to detect volatile organic compounds (VOCs). In the presented work, NiO sensors are fabricated and tested towards acetone, ethanol, toluene, hexane, methanol, and n-propanol vapours between 5 to 25 parts-per-million concentrations, under both dry and humid conditions. NiO films are deposited onto alumina substrates using both spin-coating (SC) and vapour deposition (AACVD) methods. The measured thickness of the spin coated and AACVD NiO films are approximately comparable at 10.3 μm and 6.7 μm, respectively. Both SC and AACVD sensors showed a maximum response at 350°C. No significant influence of humidity was observed on sensor response and baseline resistance for either SC or AACVD sensors. The sensitivity is found to be highest for ethanol, acetone, and methanol vapours than the rest.
- Published
- 2020
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28. Investigation on Slurry Pot Erosion Wear Behaviour of AA5083 Aluminium Alloy
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B. Santhosh Kumar, K. Sasidhar Reddy, S. Baskaran, E. Sai Kiran Gowd, A. Sekhar Babu, R. Manoj Kumar, and B. Sasi Prasad
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Materials science ,Alloy ,Metallurgy ,technology, industry, and agriculture ,Material removal ,engineering.material ,law.invention ,Taguchi methods ,Optical microscope ,law ,visual_art ,engineering ,Erosion ,Aluminium alloy ,visual_art.visual_art_medium ,Slurry ,Orthogonal array - Abstract
In this study, the erosion wear behaviour of AA5083 aluminium alloy is investigated by slurry pot erosion method. Various sizes of silica sand particles are used to evaluate the erosion wear behaviour of AA5083 alloy by measuring the mass loss. By employing Taguchi L9 orthogonal array, experiments were conducted and optimum process parameters are identified by analysing results of erosion test. Based on the ANOVA, the significant contribution of input parameters is identified. The dominant material removal mechanisms are observed through an optical microscope images, and reasons are discussed in detail.
- Published
- 2020
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29. CFD Analysis of Automotive Radiators
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Swapnil Kumar, K. Sai Kiran, and Thundil Karuppa Raj Rajagopal
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Materials science ,business.industry ,Thermal ,Airflow ,Automotive industry ,Radiator (engine cooling) ,Mass flow rate ,Mechanical engineering ,Computational fluid dynamics ,Tube (container) ,business ,Thermal analysis - Abstract
This paper of ours deals with the automotive radiators. We have shown a computational fluid dynamics (CFD) modelling simulation of mass flow rate of air passing through an automotive radiator. Modelling has been done in Solidworks and exported to ANSYS for CFD analysis. In our paper, the main implication that we have drawn is that the heat which is been transferred by a radiator is a function of the airflow at different air velocity. We undertook this experiment on a single radiator of constant geometry on the basis of some parameters like the material of the radiator and the vehicle’s speed. The thermal analysis is done for different velocities of air mixture passing through different tube materials such as aluminium and stainless steel. The numerical results were compared and results obtained served as a good database for the future investigations.
- Published
- 2020
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30. Assessment of Normal Occular Volume Using Magnetic Resonance Imaging
- Author
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Surekha B, Rajendra T M, G Sai Kiran, and Naveen D
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Nuclear magnetic resonance ,Materials science ,medicine.diagnostic_test ,medicine ,Magnetic resonance imaging ,Volume (compression) - Published
- 2020
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31. Performance Evaluation of 10kV SiC-based Extreme Fast Charger for Electric Vehicles with Direct MV AC Grid Interconnection
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Vaibhav Uttam Pawaskar, G Veera Bharath, Ghanshyamsinh Gohil, Sai Kiran Voruganti, and Van Thuan Nguyen
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Interconnection ,Materials science ,business.product_category ,business.industry ,Electrical engineering ,Control reconfiguration ,Grid ,law.invention ,law ,MOSFET ,Electric vehicle ,Transformer ,business ,MATLAB ,computer ,Voltage ,computer.programming_language - Abstract
This paper evaluates the performance of a 10kV SiC MOSFET based direct Medium Voltage (MV) connected Extreme Fast Charger (XFC) for Electric Vehicle (EV) charging applications. Two-stage converter topology is considered, where the Active Front End (AFE) is directly connected to the 4.16kV MV grid. The MVDC output of the AFE is processed by the isolated DC-DC converter to achieve the output voltage that is compatible with the EV battery. Thanks to the reconfiguration capability, the proposed XFC can charge both 400V and 800V EVs without any significant performance degradation. The data collected through experimental characterization of the 10kV SiC MOSFETs is used for simulating the complete converter of MV-XFC and performing loss analysis through MV SiC modeling in PLECs software. Analytical transformer losses and multiobjective design optimization are obtained using MATLAB. Based on the outcome of the multiobjective design optimization, the converter design parameters are selected and the trade-off between the loss and volume of the proposed design has been evaluated.
- Published
- 2020
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32. Study and Optimisation of Process Parameter in Turning Of EN 45 - Spring Steel Material Under Dry And MQL Conditions
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Kosaraju Satynarayana, Kumkuma Rajkiran, and Kalemula Sai Kiran
- Subjects
lcsh:GE1-350 ,Materials science ,Depth of cut ,020208 electrical & electronic engineering ,Metallurgy ,02 engineering and technology ,Process variable ,010501 environmental sciences ,01 natural sciences ,Spring steel ,Taguchi methods ,Machining ,0202 electrical engineering, electronic engineering, information engineering ,Surface roughness ,Lubrication ,lcsh:Environmental sciences ,0105 earth and related environmental sciences - Abstract
Minimum quality lubrication has shown a noticeable changes with machining outcomes. MQL is one of updated technologies that have been prevailing in contributions towards production and environment enhancement. Present papers deals with the turning of EN 45 steel material which is commonly known to be spring material. En 45 one of the magnetic steel material with low manganese and high amount of carbons is turned under dry and MQL condition. DOE has been prepared with L9 taguchi. Machining factors of speed (75, 100, 125 m/min), feed (0.1, 0.2, 0.3 mm/rev) and depth of cut (0.3, 0.6, 0.9 mm). The surface roughness were optimized by considering the machining parameters of speed, feed, and depth of cut. For both the condition dry and MQL it was observed that speed at 125m/min, feed at 0.1 and depth of cut at 0.3mm was found optimum condition. The regression equation and mathematical model was generated using the experimental data. Furthermore the ANOVA analysis was performed and observed that in case of dry turning speed found to be most influencing parameter and in case of MQL turning Feed was found to be most influencing parameter.
- Published
- 2020
33. Experimental and Finite Element Analysis of Fracture Parameters of woven Glass/Epoxy Composite
- Author
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B. Venkata Sai Kiran, Venkata Sushma Chinta, P. Ravinder Reddy, and Koorapati Eshwara Prasad
- Subjects
Fracture toughness ,Materials science ,visual_art ,Composite number ,Glass fiber ,Fracture (geology) ,visual_art.visual_art_medium ,Fracture mechanics ,Epoxy ,Composite material ,Finite element method ,Corrosion - Abstract
In recent years, Composites are rapidly developing and replacing metals or alloys in numerous Engineering applications as automobiles, Marine Engineering, Aerospace, etc. Due to their properties like resistance to wear, corrosion, high stiffness and strength for reduced weight, superior fatigue characteristics, etc. This study, aimed to analyze the fracture toughness of glass fiber epoxy composite by analyzing the specimen in commercial finite element package in ANSYS environment and there by validating it through experiment. For the experimental process, the glass–epoxy composites plate has been fabricated by hand layup process considering epoxy resin as the matrix and woven roving as the reinforcement. The composite specimens are tested by performing a SENB (single edge notch bend) test to study the fracture toughness and the crack propagation of the glass fiber epoxy composite. The comparison showed good agreement.
- Published
- 2020
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- View/download PDF
34. Experimental investigation in machining EN18 using coated tool under dry and MQL condition
- Author
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Kumkuma Rajkiran, Kosaraju Satynarayana, and Kalemula Sai Kiran
- Subjects
lcsh:GE1-350 ,0209 industrial biotechnology ,020901 industrial engineering & automation ,Materials science ,Machining ,Metallurgy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,0210 nano-technology ,lcsh:Environmental sciences - Abstract
EN 18 is one of the versatile metal that exists its presences in all the industrial, transportation and building equipment’s. Machining of these material is done on large scale and consumes a whole lot of lubrication unit. Present paper discuss regarding the usage and substitutional to flood coolant systems by minimum quality lubrication ((MQL) systems for economical friendly green machining operation. Using three-factor parameters speed (50, 75, 100 m/min), feed (0.05, 0.1, 0.15 mm/rev) and depth of cut (0.4, 0.8, 1.2 mm) are varied and turned on the EN 18 steel. The experimental outcomes of surface roughness is discussed with comparison with dry machining and ST-CUT 54 MQL machining. It was observed that with MQL turning the roughness produce better compared to dry machining. The optimum condition was found to be cutting speed at 100m/min, feed at 0.05mm/rev and depth of cut at 0.4mm. The outcomes are useful for improved machining industrial practices.
- Published
- 2020
35. Effect of MoO3 additive on fabrication of mullite based porous ceramics
- Author
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Jyothi Mukthapuram, Sunipa Bhattacharyya, Amit Kumar Yadav, and Gandla Sai Kiran
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Materials science ,Flexural strength ,Aluminosilicate ,visual_art ,visual_art.visual_art_medium ,Kaolinite ,Mullite ,Ceramic ,Thermal treatment ,Composite material ,Porosity ,Microstructure - Abstract
Porous mullite is widely used ceramic material in the industries. It has a combination of properties of mullite like high thermal and chemical stability, low thermal expansion coefficient and high creep resistance along with merit of the presence of pores (lightweight, high surface area). In the current article, an attempt has been made to prepare stoichiometric porous mullite using china clay (kaolinite) and aluminum hydroxide [Al(OH)3]. The effect of the addition of MoO3 on the porosity, strength and microstructure of the prepared porous mullite was also studied. Kaolinite is the aluminosilicate ceramic consist of (Si2O5)2- and [Al2(OH)4]2+ molecular sheets which decompose thermally to produce mullite. Kaolinite is rich in silica which prevents it to form stoichiometric mullite. Therefore, external alumina source is required to maintain 72wt.% alumina and 28wt.% silica. Thermal treatment at different temperature 1300°C, 1400°C and 1500°C was studied to achieve a product with higher apparent porosity with moderate flexural strength. The prepared mullite ceramic was characterized by X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM) for the desired phase formation and to evaluate the morphology of the formed mullite grain. The1500°C sintered batch with 4wt.% additive shows apparent porosity of 36.11% and moderate flexural strength of 51.56 MPa. These results show the future perspective of the porous mullite in the field of catalyst support and adsorption.
- Published
- 2020
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36. SEM characterization of 3D printed ABS tensile specimens developed by fused deposition modelling
- Author
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Kaushik V. Prasad, B. Shashank, Ashutosh Pattnaik, B. Sandeep, Mitai Mallikarjuna, P. Sri Sai Kiran, and H. Adarsha
- Subjects
Materials science ,Scanning electron microscope ,Acrylonitrile butadiene styrene ,Stacking ,Fracture mechanics ,computer.file_format ,chemistry.chemical_compound ,chemistry ,Ultimate tensile strength ,Deposition (phase transition) ,Raster graphics ,Composite material ,computer ,Layer (electronics) - Abstract
The present paper investigates the effect of raster angle and layer thickness on the tensile strength of Acrylonitrile butadiene styrene (ABS) developed via fused deposition modelling. Three levels of raster angles (0°, 30°, 60°) and layer thickness (0.127, 0.178, 0.20 mm) were chosen while keeping the raster width constant as 0.40mm. Tensile tests reveal that load bearing capacity of the specimens increase when there is a finite angle between filaments and loading direction. Scanning Electron Micrographs (SEM) reveal that strong bonding between filaments and layers is necessary for good tensile strength apart from layer thickness. It is observed that micro-cracks and voids between filaments act as source of crack propagation leading to failure. Cooling of a layer is necessary before printing the next layer in order to prevent stacking defects.
- Published
- 2020
- Full Text
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37. Optimization of Process Parameters in MIG Welding of Two Dissimilar Materials
- Author
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J. Sree Hari, M. S. Amarnath Reddy, and K. Sai Kiran
- Subjects
Materials science ,Process (computing) ,Mechanical engineering ,Gas metal arc welding - Published
- 2018
- Full Text
- View/download PDF
38. Electrostatic self-assembly of LiFePO4 cathodes on a three-dimensional substrate for lithium ion batteries
- Author
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Lukas Pfaffmann, Andy Fiedler, Venkata Sai Kiran Chakravadhanula, Frieder Scheiba, Guiying Tian, Geethu Balachandran, Zijian Zhao, and Helmut Ehrenberg
- Subjects
Materials science ,Fabrication ,General Chemical Engineering ,Ionic bonding ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Polyelectrolyte ,Cathode ,0104 chemical sciences ,law.invention ,Carbon film ,Chemical engineering ,chemistry ,law ,Electrode ,Electrochemistry ,Lithium ,Self-assembly ,0210 nano-technology - Abstract
In this work, the electrostatic self-assembly of LiFePO4 particles coated with polyelectrolytes on a three-dimensional carbon substrate is described. This new fabrication method allows precise control of ionic and electronic conduction pathways as well as the interfaces between the different electrode components, thus enabling new strategies for tailored electrode designs. Further, it is shown that the polyelectrolytes used to build up the electrode by electrostatic self-assembly can be converted into a conductive matrix by a simple carbonization step. This leads to a firmly adhering carbon film on the surface of LiFePO4, which further improves electron transport. The three-dimensional composite cathode exhibits a high specific capacity even at high current rates as well as a long cycle life. The excellent electrochemical performance can be attributed to the improved three-dimensional structure of the electrode as well as to the obtained intrinsic carbon coating of LiFePO4 particles.
- Published
- 2018
- Full Text
- View/download PDF
39. Synthesis and Photophysical Characterization of Unsymmetrical Squaraine Dyes for Dye-Sensitized Solar Cells utilizing Cobalt Electrolytes
- Author
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Gaurav Kapil, Shyam S. Pandey, Anusha Pradhan, Maryala Sai Kiran, and Shuzi Hayase
- Subjects
Materials science ,cobalt electrolyte ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Redox ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,dye-sensitized solar cells ,surface passivation ,Alkyl ,chemistry.chemical_classification ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Dye-sensitized solar cell ,chemistry ,far-red sensitization ,0210 nano-technology ,Cobalt ,squaraine dyes - Abstract
Development of novel near-infrared (near-IR) dyes compatible with cobalt complex based redox shuttles for their utilization as sensitizer is inevitable for the fabrication of high-efficiency dye-sensitized solar cells (DSSCs). A series of newly designed unsymmetrical squaraine dyes as a model of near-IR sensitizer were synthesized and characterized for their application as far-red sensitizers of DSSCs utilizing Co(bpy)2+/3+ redox electrolyte. It was shown that logical molecular design led to not only energetic tunability of the sensitizers but also the possibility of good far-red photon harvesting up to 750 nm. One of the newly designed sensitizers, SQ-110, bearing two long alkyl substituents in combination with an electron donating methoxy group directly linked to the aromatic ring was par excellent in terms of its photoconversion efficiency among the dyes utilized in this work. DSSC fabricated using SQ-110 as sensitizer and Co(bpy)2+/3+ redox electrolyte furnished a photoconversion efficiency of 1.98% along with good photon harvesting mainly in the far-red wavelength region. It was further demonstrated that dye molecular structure plays a rather more prominent role than their energetics in controlling the overall device performance of the DSSCs.
- Published
- 2018
40. Experimental Study on Behaviour of Cruciform and Modified Cruciform Steel Section
- Author
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S.Kav ya, Pabbisetty Sai Kiran, M. Usha Rani, and J. Martina Jenifer
- Subjects
Materials science ,Cruciform ,business.industry ,Section (archaeology) ,Structural engineering ,business - Published
- 2018
- Full Text
- View/download PDF
41. Calculation of Contact Stresses during Titanium Alloy Cutting
- Author
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Ying Bin Guo, Jia Yu Zhang, Victor Kozlov, and Sai Kiran Sabavath
- Subjects
020303 mechanical engineering & transports ,Materials science ,0203 mechanical engineering ,Mechanics of Materials ,Mechanical Engineering ,Metallurgy ,Titanium alloy ,General Materials Science ,02 engineering and technology ,Tool wear ,021001 nanoscience & nanotechnology ,0210 nano-technology - Abstract
The paper presents data about distribution of contact stresses on a rake surface and flank-land of a cutter in free orthogonal turning of a disk made from a titanium alloy (Ti-6Al-2Mo-2Cr). On the cutting edge of the bar blade, there is a normal force Nρ, directed perpendicularly to a transient surface, with a large magnitude of specific linear force qN r= 182.6 N/mm, but the tangential force on the cutting edge Fρis equal to zero. On the rake surface, there are uniformly distributed shear contact stresses with very small magnitude of τ ≈ const ≈ 25 MPa, irrespective of feed rate, which speaks about plastic character of the contact on the rake surface. The greatest normal contact stress on the rake surface σmax≈ 1009 MPa, irrespective of feed rate. The greatest magnitude of normal contact stresses on the flank surface chamfer near the cutting edge σh max= 3400-2200 MPa confirms the hypothesis about recovery of a transient surface sag after separation of a formed element of a chip, and explains increased wear of the cutting tool on the flank surface at initial time. Normal σhand shear τhcontact stresses on the flank surface chamfer are essentially diminish with a distance from the cutting edge. It explains working ability of the cutting tool even at very large wear on the flank surface (hf> 3 mm). Our experimental data allows calculating the components of cutting force and contact stresses on the rake and flank surfaces of cutting tools during titanium alloy (Ti-6Al-2Mo-2Cr) machining.
- Published
- 2018
- Full Text
- View/download PDF
42. Research of Contact Stresses Distribution on Plunge-Cutting into a Steel Workpiece
- Author
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Victor Kozlov, Jia Yu Zhang, Sai Kiran Sabavath, and Ying Bin Guo
- Subjects
0209 industrial biotechnology ,020303 mechanical engineering & transports ,020901 industrial engineering & automation ,Materials science ,0203 mechanical engineering ,Distribution (number theory) ,Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Geotechnical engineering ,02 engineering and technology ,Tool wear - Abstract
The paper presents the distribution of contact stresses on the flank land of a cutter during steel turning (Fe-0.4C-1Cr) at the initial time of cutting. Plunge-cutting into a steel workpiece by the whole length of the cutting tool edge features almost twofold short-term increase of in cutting force components in comparison with stable cutting. Such increase is absent, if the feed rate exceeds 0.34 mm/rev and the cut depth exceeds 2 mm. This is explained by sagging of the cutting surface under the influence of the dead zone in the area of the cutting edge, which moves before the cutting tool and reduces the contact interaction of the flank surface chamfer with the workpiece. The contact stresses on the flank surface chamfer increase with the distance from the cutting edge, which is explained by recovered cutting surface sag, conditioned by the action of the dead zone in the cutting edge area. This increase accelerates with the reduction in the feed rate. Normal contact stresses increase more quickly on a flank-land at a distance from the cutting edge of more than 0.8 mm, which is explained by recovering of a transient surface sag, and explains the increase in the probability of cutting wedge destruction when the length of flank-land wear exceeds 1.2 mm.
- Published
- 2018
- Full Text
- View/download PDF
43. Propellant grade ultrafine aluminum powder by RF induction plasma
- Author
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Dibyendu Chakravarty, P. Sai Karthik, S.B. Chandrasekhar, P.V.V. Srinivas, Tata N. Rao, and Venkata Sai Kiran Chakravadhanula
- Subjects
Quenching ,Materials science ,Passivation ,Hydrogen ,General Chemical Engineering ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Volumetric flow rate ,Differential scanning calorimetry ,chemistry ,Mechanics of Materials ,Aluminium ,Particle size ,0210 nano-technology ,Forming gas - Abstract
A continuous process of synthesizing ultrafine aluminum powder (UFAP) having high yield rate using RF induction plasma is reported in the current work. The processing parameters (powder injection probe position; powder feed rate; flow rates of gases for plasma forming, quenching and passivation) were varied systematically to evaluate their influence on the size and distribution, and metallic Al content of the synthesized powder. The UFAP was characterized using X–ray diffraction and, scanning and transmission electron microscopes. The metallic aluminum content of UFAP was evaluated using hydrogen gas evolution technique and its thermal behavior was studied using simultaneous thermo–gravimetric and differential scanning calorimetry under static air. UFAP with an average particle size varying between 220 and 400 nm was obtained under different processing conditions and a maximum metallic Al content of 89.2% was obtained at a high powder feed rate. Among the parameters studied, increased powder feed rate, plasma forming gas flow rate and the position of the powder injection probe had a significant effect on the particle size, distribution and the metallic Al content of the synthesized UFAP.
- Published
- 2018
- Full Text
- View/download PDF
44. Artificial Composite Anode Comprising High-Capacity Silicon and Carbonaceous Nanostructures for Long Cycle Life Lithium-Ion Batteries
- Author
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Torsten Brezesinski, Christian Suchomski, Venkata Sai Kiran Chakravadhanula, Jürgen Janek, Ben Breitung, Artur Schneider, and Heino Sommer
- Subjects
Materials science ,Nanostructure ,Silicon ,Composite number ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Lithium-ion battery ,0104 chemical sciences ,Anode ,Ion ,Chemical engineering ,chemistry ,Electrochemistry ,Lithium ,Electrical and Electronic Engineering ,0210 nano-technology ,Carbon - Published
- 2018
- Full Text
- View/download PDF
45. Facile Synthesis of Corn Silk Derived Nanoporous Carbon for an Improved Supercapacitor Performance
- Author
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Tata N. Rao, Srinivasan Anandan, Chandra Shekhar Sharma, Tadepalli Mitravinda, Adduru Jyothirmayi, Katchala Nanaji, and Venkata Sai Kiran Chakravadhanula
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,01 natural sciences ,Materials Chemistry ,Electrochemistry ,medicine ,Supercapacitor ,Renewable Energy, Sustainability and the Environment ,Nanoporous ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Chemical engineering ,chemistry ,Electrode ,0210 nano-technology ,Mesoporous material ,Current density ,Carbon ,Activated carbon ,medicine.drug - Abstract
Efforts made in this current study focus on the development of a novel, simple, cost-effective yet efficient approach to synthesize nanoporous carbon material from corn silk biomass for supercapacitor applications. We have employed different activation approaches in order to obtain a higher surface area and large mesoporous volume fraction. The performance of corn silks derived nanoporous activated carbon materials for supercapacitor applications was evaluated in a symmetric two electrode configuration using aqueous/non-aqueous electrolytes at various current densities and scan rates. Electrochemical results indicated that the as-synthesized nanoporous carbon prepared by single step activation exhibits ideal supercapacitor performance ∼160 F/g (at 1 A/g current density) with excellent rate capability and cyclic stability. Further, it displayed a promising amount of energy that can be stored in a given mass ∼32.28 Wh/kg at the power density of 870.68 W/kg. Benchmark studies revealed that the nanoporous carbon developed in the current study is at par with the performance of the commercial carbon electrode. The superior performance of corn silks derived nanoporous carbon is attributed to high surface area pertaining to its unique mesoporous fiber-like morphology, which facilitates fast ionic and electronic diffusion of the electrolyte into and out of the pores during charging and discharging.
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- 2018
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46. Investigating the pore structure of the calcium silicate hydrate phase
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Erich A. Müller, Andreas Gerdes, Venkata Sai Kiran Chakravadhanula, Olivia Wenzel, Matthias Schwotzer, and Torsten Scherer
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Materials science ,Argon ,Scanning electron microscope ,Mechanical Engineering ,0211 other engineering and technologies ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Focused ion beam ,chemistry.chemical_compound ,Adsorption ,chemistry ,Chemical engineering ,Mechanics of Materials ,Transmission electron microscopy ,021105 building & construction ,Scanning transmission electron microscopy ,General Materials Science ,Calcium silicate hydrate ,Electron beam-induced deposition ,0210 nano-technology - Abstract
The physical properties of the calcium silicate hydrate phase (C-S-H) greatly impact material strength and durability of cement-based materials. However, despite its widespread use and influence on material stability, there is still debate concerning its nanostructure. In this paper, the pore structure of C-S-H was characterized by analyzing focused ion beam prepared lamellas from a model tricalcium silicate clinker cement paste using scanning transmission electron microscopy (STEM) performed with a scanning electron microscope (SEM) for measurements at 30 keV and a transmission electron microscope (TEM) operating at low primary electrons energy (80 keV). The composition was mapped in the SEM using energy-dispersive X-ray spectroscopy (EDX). These investigations were accompanied by argon adsorption measurements using non-local density functional theory (NLDFT) models to calculate the pore size distribution. Mercury intrusion porosimetry (MIP) was used to investigate macropores. The STEM investigations performed at 30 and 80 keV both reveal a sponge-like pore structure built up by 0.7–4.0 nm thin C-S-H foils. The pore sizes range between 2 and 10 nm with a dominance of 5 nm wide pores. These results are in line with the pore size distribution determined with argon adsorption, which predominantly found 4.6 nm wide pores. The similar pore width distributions in STEM and gas adsorption validates the gas adsorption measurements and points towards minimal electron beam damage occurring during observation and analysis.
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- 2017
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47. Microstructure and performance of cold sprayed Al-SiC composite coatings with high fraction of particulates
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S. Kumar, Shrikant V. Joshi, and Sai Kiran Reddy
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010302 applied physics ,Materials science ,Composite number ,Metallurgy ,Gas dynamic cold spray ,chemistry.chemical_element ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Surfaces, Coatings and Films ,chemistry ,Aluminium ,0103 physical sciences ,Materials Chemistry ,Deposition (phase transition) ,Wetting ,0210 nano-technology ,Thermal spraying ,Porosity - Abstract
Deposition of metal matrix composites (MMCs) through thermal spraying has traditionally presented problems associated with heterogeneity, porosity, and low wettability of particulates with matrix. Cold spray is a very rapid deposition process which is suitable for depositing a variety of ductile materials without any thermal degradation. Many researchers have attempted to deposit Al-SiC MMCs with 10–20% SiC using this technique. In the present study, three different powder compositions (FAl-23SiC, FAl-46SiC, FAl-71SiC) obtained by mixing Al and SiC powders were cold sprayed on aluminum substrates. The volume percentage and the average size of the SiC particulates in the cold sprayed coatings were estimated and found to be 23%, 47% and 52% for FAl-23SiC, FAl-46SiC and FAl-71SiC feedstocks, respectively. Effects of percentage and size of the SiC particulate retained in the composite coatings on the mechanical properties and the sliding wear performance were studied at different sliding conditions in the as-sprayed and heat treated conditions. The results were comprehensively analyzed and found to correlate well with the microstructure of the coatings.
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- 2017
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48. Interlayer-Expanded Vanadium Oxychloride as an Electrode Material for Magnesium-Based Batteries
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Venkata Sai Kiran Chakravadhanula, Maximilian Fichtner, Thomas Diemant, Zhirong Zhao-Karger, Ping Gao, Xiaoke Mu, Maxim Pfeifer, R. Juergen Behm, and Christian Bonatto Minella
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Materials science ,Electron energy loss spectroscopy ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Anode ,chemistry ,X-ray photoelectron spectroscopy ,Electrode ,Lithium ,Inductively coupled plasma ,Cyclic voltammetry ,0210 nano-technology - Abstract
Mg-based batteries, which use the Mg2+ shuttle, offer several advantages compared to the Li technology such as higher theoretical volumetric capacity (3833 mA h cm-3) of the Mg-metal anode, the possibility to be safely handled in air and dendrite-free electrodeposition. In this study, VOCl was employed as electrode material in a Mg-based battery. Since the cell delivered just 45 mA h g-1 in the first cycle, we tried to improve the delivered capacity by a preliminary cycling of the VOCl electrode with Li. The strategy is based on the ability of VOCl to expand its interlayer spacing upon intercalation of ions or molecules within them. In fact, a VOCl-electrode with expanded interlayer spacing should facilitate the intercalation of Mg2+, thus leading to higher specific capacities. The Li-pre-treatment was able to promote the specific capacity by a factor of four (170 mA h g-1) after the first discharge at 298 K. Over 130 mA h g-1 were retained at 5 mA g-1 after 70 cycles. The structural and electrochemical characterization were carried out by means of galvanostatic charge/discharge tests, cyclic voltammetry (CV) and ex-situ X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) as well as transmission electron microscopy (HR-TEM) coupled with energy dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the concentration of lithium in the electrode.
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- 2017
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49. A 47nW, 0.7-3.6V wide Supply Range, Resistor Based Temperature Sensor for IoT Applications
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Ashfakh Ali, Sai Kiran, Zia Abbas, and Arpan Jain
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Materials science ,business.industry ,Linearity ,Capacitance ,Line (electrical engineering) ,law.invention ,Power (physics) ,law ,Low-power electronics ,Optoelectronics ,Resistor ,business ,Sensitivity (electronics) ,Voltage - Abstract
A sub 1-V, ultra low power temperature sensor has been implemented in TSMC 180 nm. The architecture is digital friendly since it creates a pulse width modulated wave instead of voltage. It uses proportional to absolute temperature(PTAT) characteristics of resistance to generate PTAT delay. Temperature to delay conversion depends only on passive elements, thereby making the circuit insensitive to supply variations. Line sensitivity of 0.23 °C/V is achieved for a wide supply range of 0.7-3.6V. A non linearity error of less than 0.8 °C is measured for -55 to 125 °C using linear fit curve. This occupies an area of 0.82 mm 2 and consumes a power of 47 nW at 0.8 V supply.
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- 2019
- Full Text
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50. A hybrid organic-inorganic polariton LED
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Andrew J. Musser, Pavlos G. Lagoudakis, Harriet Coulthard, Jenny Clark, Alexis Askitopoulos, David G. Lidzey, Ifor D. W. Samuel, Kyriacos Georgiou, Rahul Jayaprakash, Graham A. Turnbull, David M. Coles, Sai Kiran Rajendran, EPSRC, University of St Andrews. School of Physics and Astronomy, University of St Andrews. Centre for Biophotonics, University of St Andrews. Condensed Matter Physics, and University of St Andrews. Sir James Mackenzie Institute for Early Diagnosis
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lcsh:Applied optics. Photonics ,Materials science ,Photon ,Exciton ,NDAS ,Polaritons ,Physics::Optics ,02 engineering and technology ,7. Clean energy ,01 natural sciences ,Article ,law.invention ,010309 optics ,Condensed Matter::Materials Science ,law ,0103 physical sciences ,OLED ,Polariton ,lcsh:QC350-467 ,Organic LEDs ,Quantum well ,QC ,Condensed Matter::Quantum Gases ,business.industry ,Condensed Matter::Other ,lcsh:TA1501-1820 ,021001 nanoscience & nanotechnology ,Optical microcavity ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Organic semiconductor ,Semiconductor ,QC Physics ,Inorganic LEDs ,Optoelectronics ,0210 nano-technology ,business ,lcsh:Optics. Light - Abstract
Polaritons are quasi-particles composed of a superposition of excitons and photons that can be created within a strongly coupled optical microcavity. Here, we describe a structure in which a strongly coupled microcavity containing an organic semiconductor is coupled to a second microcavity containing a series of weakly coupled inorganic quantum wells. We show that optical hybridisation occurs between the optical modes of the two cavities, creating a delocalised polaritonic state. By electrically injecting electron–hole pairs into the inorganic quantum-well system, we are able to transfer energy between the cavities and populate organic-exciton polaritons. Our approach represents a new strategy to create highly efficient devices for emerging ‘polaritonic’ technologies., Microcavities: Hybrid semiconductors team up for a quantum LED Researchers have optically connected organic semiconductors and inorganic thin films to produce a light-emitting diode powered by quasi-particles that are part light and part matter. Polaritons, which form when electron–hole pairs in a semiconductor interact with photons, can be energy efficient sources of coherent light. Rahul Jayaprakash from the University of Sheffield in the United Kingdom and co-workers have now developed a device that generates electron-hole pairs inside a reflective microcavity filled with gallium–indium–phosphorus thin films. Then, they coupled the chamber’s optical resonance to a second microcavity containing light-absorbing phthalocyanine dye molecules. Time-resolved spectroscopy revealed that energy transfer from the inorganic to the organic microcavity creates sufficient polaritons densities for a visible-light LED, thanks to a delocalized quantum state that forms over both chambers.
- Published
- 2019
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