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Structural and optical properties of H2 diluted c-Si/a-SiO x core-shell silicon nanowire
Swain, B. S.,Swain, B. P.,Mahmood, K.,Yang, S. M.,Hwang, N. M. Springer Science + Business Media 2015 APPLIED PHYSICS A MATERIALS SCIENCE AND PROCESSING Vol.118 No.1
<P>We observed photoluminescence quenching in crystalline (c) Si/amorphous (a) SiO (x) core-shell silicon nanowires (Si-NWs). We observed that the photoluminescence (PL) intensity strongly depends on the stoichiometry of outer a-SiO (x) matrix, which was characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The PL showed a broad-range emission from 1.6 to 2.4 eV with the peak centered at 2.27 eV, which quenched as the oxygen content decreased from 60.5 to 54.6 at.%. Both transverse optic and longitudinal optic signatures of Si-O-Si were shifted to lower wavenumbers, which indicate the modification of chemical networks in core-shell Si-NWs. The minority carrier life time (tau) increased from 3.4 to 7.5 A mu s as the diameter of core Si increased from 22 to 78 nm, indicating the decrease of trap densities and alternation trap states. The reason for PL quenching is mostly attributed to the structural and stoichiometry changes in outer a-SiO (x) of c-Si/a-SiO (x) -NW.</P>
Modeling of Microwave Assisted Drying of Osmotically Pretreated Red Sweet Pepper (Capsicum annum L.)
Sachidananda Swain,D. V. K. Samuel,Lalit M. Bal,Abhijit Kar,G. P. Sahoo 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.4
Drying kinetics modeling and effective moisture diffusivity (Deff) of osmotically dehydrated pretreated red sweet pepper (Capsicum annum L.) during microwave assisted convective drying at power levels of 0.35, 0.70,1.05, and 1.4 W/g, air temperature of 30, 45, and 60oC, and constant air velocity of 1.5 m/s were investigated. The drying data were applied to 11 different semi-empirical mathematical models to characterize the drying kinetics and Page model provided a good agreement between experimental and predicted moisture ratio values with higher coefficient of determination (R2) and lower root mean square error (RSME) and residual sum of square (RSS). Deff decreased from 1.859×10−7 to 3.55×10−8 m2/s which is 102 to 103 times more than the previous investigations for food materials. Similarly, the activation energy decreased from 8.943 to 5.228 with decrease of drying temperature from 60 to 30oC which is due to the effect of pretreatment (osmotic dehydration). So, pretreatment can be used as criteria for faster drying thereby maintaining final product quality.
Dissolution kinetics of chromite overburden by using mineral acids
Gautam Roy Chaudhury,P. K. Swain,L. B. Sukla 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.6
different mineral acids were used to determine the kinetics of dissolution of Ni and Fe from chromiteas acid concentration, pulp density, temperature and particlesize. Both Fe and Ni dissolution followed 1st order irreversible kinetics. The activation energy was also measured. Uni-fied rate equations were established for Ni and Fe dissolution for two different mineral acids, HCl and H2SO4. The dis-solution reaction was observed to follow diffusion control-dense-constant size spherical particles.