N. Rajeswara Rao; T. Venkatappa Rao; S.V.S. Ramana Reddy; B. Sanjeeva Rao
Abstract
Thermal, morphological and antioxidant properties of lignin irradiated with electron beam (EB) of doses 30, 60 and 90 kGy have been investigated by Electron spin resonance (ESR), Fourier transform infrared spectroscopy, Differential scanning calorimetry, Scanning electron microscope and Spectrophotometer ...
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Thermal, morphological and antioxidant properties of lignin irradiated with electron beam (EB) of doses 30, 60 and 90 kGy have been investigated by Electron spin resonance (ESR), Fourier transform infrared spectroscopy, Differential scanning calorimetry, Scanning electron microscope and Spectrophotometer techniques. ESR studies confirm the presence of poly-conjugated radicals in unirradiated lignin; whereas irradiated lignin posses both poly-conjugated and peroxy radicals. The peroxy radicals decay near the glass transition point on thermal heating while poly-conjugated radicals are stable even up to a temperature of 450K. Presence of conjugated structures is confirmed by the presence of 1604 cm -1 absorption band whose concentration increases following radiation dose. Up to a radiation dose of 60 kGy the fall in glass transition temperature (Tg) is very slow, while at 90 kGy Tg decreased abruptly. The decrease in Tg is assigned to be due to intermolecular chain interactions or plasticization effect. Granular structure of lignin is found to be effected by EB irradiation. Cracks were generated on lignin granules on EB irradiation. Due to increase in poly-conjugation, amorphous nature and granular cracks the antioxidant property is observed to increase. The current research trends in lignin materials include modification of lignin, fabrication of biodegradable thermoset/thermoplastic and use of lignin as stabilizers and dispersants.
S. Mohapatra; J. Ghatak;D.K. Avasthi; Y.K. Mishra
Abstract
Elongated Au nanoparticles (NPs) embedded in silica matrix were fabricated by 100 MeV Ag ion irradiation of 3 MeV Au ion implanted SiO2/Si(100) substrates, annealed at 1050 o C. Electron-beam-induced shape evolution of elongated Au NPs embedded in SiO2 has been studied by high resolution transmission ...
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Elongated Au nanoparticles (NPs) embedded in silica matrix were fabricated by 100 MeV Ag ion irradiation of 3 MeV Au ion implanted SiO2/Si(100) substrates, annealed at 1050 o C. Electron-beam-induced shape evolution of elongated Au NPs embedded in SiO2 has been studied by high resolution transmission electron microscopy. Electron beam irradiation resulted in a decrease in the aspect ratio of Au NPs from ~ 1.4 to 1 with increase in irradiation time. The observed ellipsoidal-to-spherical shape transition of Au NPs has been ascribed mainly to the cumulative effects of electron beam induced heating, softening of silica matrix and radiation enhanced diffusion of knock-on displaced O and Si atoms, resulting in local stress relaxation.
Y. K. Mishra; S. Mohapatra; D. K. Avasthi; N. P. Lalla; Ajay Gupta
Abstract
Au nanoparticles (NPs) embedded in silica matrix were synthesized by atom beam co-sputtering and investigated in detail by transmission electron microscopy (TEM). A study on electron beam induced tailoring of size of Au nanoparticles has been performed in an in-situ TEM experiment as a function of electron ...
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Au nanoparticles (NPs) embedded in silica matrix were synthesized by atom beam co-sputtering and investigated in detail by transmission electron microscopy (TEM). A study on electron beam induced tailoring of size of Au nanoparticles has been performed in an in-situ TEM experiment as a function of electron irradiation time. This study concludes that electron beam irradiation can result in a controlled growth of NPs in proportion to irradiation fluence. Analytical calculations for electron energy loss in Au NPs and fused silica have been performed, which indicate that the observed growth of Au NPs in present case is due to rise in temperature of Au NPs and surrounding silica.
