Influence of reaction time and synthesis temperature on the physical properties of ZnO nanoparticles synthesized by the hydrothermal method

Influence of synthesis temperature and reaction time on the structural and optical properties of ZnO nanoparticles synthesized by the hydrothermal method was investigated using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray, Fourier transform infra-red spectroscopy, and UV–visible and fluorescence spectroscopy. The XRD pattern and HR-TEM images confirmed the presence of crystalline hexagonal wurtzite ZnO nanoparticles with average crystallite size in the range 30–40 nm. Their energy gap determined by fluorescence was found to depend on the synthesis temperature and reaction time with values in the range 2.90–3.78 eV. Thermal analysis, thermogravimetric and the differential scanning calorimetry were used to study the thermal reactions and weight loss with heat of the prepared ZnO nanoparticles

Test Report for High Speed Alternator of MANIK Engine

The high speed alternator for ‘Manik’ Engine that is being developed by GTRE was tested at the rated speed of 53000 rpm with AC electrical loading upto 5 kW. This indigenous alternator is one of the most critical parts of the engine. A test rig is designed and developed with suitable air turbine drive at Propulsion Division, NAL-CSIR to map the electrical characteristics of the AC alternator and to assess DC power output of rectifier unit. An air turbine drive was designed to develop 20 kW power at 53000 rpm to drive the alternator. A lubrication system with an in-built reservoir tank is designed to provide cooling to the stator core and to lubricate the alternator bearings. The rig is instrumented with pressure, temperature and flow transducers for compressed air and the lubrication oil. Several vibration pick-ups are mounted on the test stand and the alternator to monitor the vibration signatures. The alternator was initially run up to 53000 rpm in increments without electrical load. The vibration levels were monitored at every incremental speed and resonant frequencies were identified. The alternator was accelerated quickly while passing through the resonant speeds in subsequent runs. The electrical load was applied after crossing 45000 rpm in increments using the DC load bank. After applying full load, the alternator was taken to full speed. The alternator produced 4.8 kW AC power and the DC power after rectification unit was measured to be 4 kW. The alternator and the test rig performed well and all the objectives were met. Successful testing of this alternator gave the confidence to integrate this indigenously developed alternator to the engine

Design and Development of Test Rig for High Speed Alternator

This report briefly presents the design and development aspects of the test rig to evaluate the performance of high speed alternators with power rating of 5 kW at rated speed of 55000 rpm. Major part of the report covers detailed mechanical design of the drive turbine and the other rig systems. The test rig is designed and developed at Propulsion Division, NAL-CSIR to map the electrical characteristics of the AC alternator to be used in a Small Turbo Fan Engine (STFE) which is being developed by Gas Turbine Research Establishment. An air turbine drive was designed to develop 20 kW power at 53000 rpm to drive the alternator. A parabolic solid disc configuration is arrived at to keep the stress minimum. Cyclic symmetry stress analysis is carried out on the sector model (1/27th) carved out from the blisk. The air turbine shaft is designed to be inserted in to the bore of the alternator hallow shaft and is to be fastened at the other end with a lock nut. The rotor-dynamic analysis is carried out for the rotor in overhang configuration with bearing support stiffness ranging from 17.5 to 175 MN/m and critical speeds of the rotor-bearing system is predicted. A lubrication system with an in-built reservoir tank is designed to provide cooling to the stator core and to lubricate the alternator bearings. Special fixtures are designed to insert and extract the air-turbine shaft into and from the alternator rotor respectively to ensure that the alternator bearings are not unduly loaded during assembly and dis-assembly procedures. The rig is instrumented with pressure, temperature and flow transducers for compressed air and the lubrication oil in addition to speed and vibration pick-ups. As the rotational speed of the rig is extremely high, several safety measures are considered and implemented

Bearing Failure Investigation of Turbomachinery Test Rig

This paper presents the investigation of bearing failure in a compressor test rig which has been satisfactorily in operation. Two pair of single row angular contact ball bearings, each pair in tandem, and the pairs in turn in back to back support the rotor shaft to meet compressor thrust and to provide moderate stiffness for smooth operation. Since being experimental rig, it is reassembled several times involving bearing replacements on each occasion. Recently one bearing on one side pair is found severely damaged and the other bearing of the pair with minor damage. The bearing with minor damage supported the rotor and this evaded the initial diagnostics until the time of severe damage. Initial investigation revealed that the primary cause of failure is washed off by the secondary failure. A thorough, systematic investigation with the help of fishbone approach is carried in order to find out the root cause of the failure and also to decide on new rig. This investigation revealed lack of preload as the major cause and bearing seat clearance as minor problem. New procedure is adopted to ensure proper preload and the rig is back in operation

Paleo–Mesoarchean sedimentary record in the Dharwar Craton, India: Implications for Archean ocean oxygenation

The early Archean oceans were marked by significant redox changes which have subsequently shaped the Earth’s biosphere. Archean chemical sediments of banded Iron and Manganese formations provide important geochemical proxies for these historical shifts in the redox conditions and to trace the ancient sedimentation patterns and protoliths. In this study, we investigate the proto-ore of the Archean Mn-formations of the Sandur, Chitradurga and Shimoga greenstone belts of Dharwar Craton of southern Peninsular India, which is geochemically characterised as quartz arenites, Mn-arenites, Fe-arenites, Mn-argillites and Fe-argillites. The geochemical systematics suggest their deposition in shallow to deeper shelf in the Archean proto-ocean. The detrital zircon U-Pb systematics of Mn arenites and argillites indicate their maximum depositional age of 3230 ± 52 Ma representing the oldest onset of sedimentation during the Paleo–Mesoarchean timeframe in the Chitradurga Group of Dharwar Supergroup. The detrital influx proxies suggest variations in sedimentation rates associated with the Archean transgressive–regressive cycles and fluctuating hydrodynamic conditions, together reflecting an increasing trend in the contributions of recycled sediment from Sandur to Chitradurga and Shimoga greenstone belts. The available detrital zircon ages of the Mn arenites and argillites from these greenstone belts indicate a ∼ 600 Ma prolonged period of Mn deposition for which high-T hydrothermal fluids from Archean mid-oceanic ridges supplied the manganese. The trace element compositions of the concordant detrital zircons suggest 3.3–3.1 Ga Dharwar basement TTG/granitoid source which is corroborated by the zircon crystallization temperatures of 690–820 °C. The source-normalised α-dose rates of the detrital zircons signify greater degrees of sediment transport and multi-cycle nature which correspond to the earliest episode of crustal growth in the Indian sub-continent associated with the Mesoarchean Ur supercontinent. The clastic-chemogenic sedimentation attained through concomitant detrital sediment–seawater-metalliferous hydrothermal fluid mixing at an epicontinental passive margin resulted in the deposition of Mn-arenites and argillites closer to the higher Eh shore, while the Fe-rich sediments formed at a relatively deeper shelf characterised by comparatively lower Eh and more alkaline conditions. The comprehensive geochemical and geochronological data of the Archean Mn arenite-argillite sequences reveal the significance of regional episodes of ocean oxygenation at the shallow shelves of Archean oceans prior to great oxygenation event (GOE) that was mediated by the prolific growth of ancient microbiota which transformed the Earth to a more habitable planet

Indigenous Development (Phase-I) of High speed Alternator with Rectifier Unit

The main objective was design and development of an alternator to generate 4.5 kW power at 30000 rpm along with uncontrolled rectifier unit. The configuration chosen was to use permanent magnetic material for field excitation and the stator made up of silicon steel material. The objective was to evolve a methodology to design the alternator. Analytical calculation and the magnetic field analysis of the alternator were carried out. An air turbine drive was designed for testing the alternator. The demonstration of the alternator performance up to designed speed and power was carried out successfully

Color Stability of Provisional Restorative Materials - A Tabular Review

Temporary prosthodontic materials used for temporization for crown and bridges to protect the vital tooth or teeth from hypersensitivity. Most commonly used temporization materials are Polymethylmethacrylate (PMMA), Bis-acryl composite resin, Light polymerized composite resin, and CAD/CAM provisional restorative material. In this review we have made an attempt to discuss the advantages and disadvantages of temporary prosthetic materials in a tabular format