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Spinning Process of Chitosan Fiber with Low Concentration of Formic Acid Solution and its Characteristics
Full text linkThe wet spinning of chitosan fiber was carried out using 7% chitosan concentration, 4% aqueous formic acid as a solvent for chitosan and 6M of aqueous CaCl2.2H2O as a coagulation system. A better method for preparation of chitosan spinning solution was investigated by studying the effect of reaction time on incubation of spinning solution in open air. The shear viscosity of chitosan solution (22.63 ~ 23.09 Pa.s) was found to be stabilize the spinning of chitosan fiber in this study. The characteristics of different chitosan fibers were determined by FT-IR and 1HNMR spectroscopies, XRD diffraction, scanning electron microscopy and mechanical properties. All the fibers were observed with high tenacity (dTex). The strength of fiber and water retention of chitosan fiber (%) was significantly increased with increasing the incubation time of spinning solution in open air
Comparative Study on Electrical and Dielectric Properties of Sintered Nano and Micro Silicon Nitride Ceramics
Full text linkIn the present work we have studied the electrical conductivity, dielectric constant and dielectric loss of Sintered Silicon Nitride ceramics. In this study it was found that the grain size has great impact on electrical conductivity and dielectric properties of Sintered Silicon Nitride Ceramics. The result shows more efficiency of electrical and dielectric properties with nano sized grains. The sintering was performed in a programmable furnace at 950 K. The dc conductivity measured in the temperature range 300 K to 900 K. At higher temperature (T > 800 K), the dc conductivity increases exponentially with temperature for both of the investigated samples. Dielectric constant and loss are measured in the temperature range 300 K to 900 K with frequency range 1 KHz to 1 MHz. To confirm the grain size, the samples are characterized by the Scanning Electron Microscope (SEM). These types of samples can be used as a high temperature semi-conducting material
Existence and Stability of the Libration Points in the Circular Restricted Three Body Problem with Variable Masses
Full text linkWe have investigated the existence and stability of the libration points in the circular restricted three body problem with the variation of all the masses (primaries and infinitesimal body) with time. We have used the Meshcherskii transformation for finding the autonomized equations of motion and found at most nine libration points. We have drawn the zero velocity curves and Poincare surface of sections for the different values of parameter k. Finally, we have checked the stability and found that all the libration points are unstable
Synthesis and Structural Investigation of Nano-Sized Cadmium Ferrite
Full text linkThis report presents the synthesis of cadmium ferrite (CdFe2O4) by Oxalate co-precipitation and its subsequent characterization by using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. XRD results confirm the single cubic spinel phase formation with lattice parameter 8.7561Ao. An infrared spectroscopy study shows the presence of main two absorption bands indicating the presence of tetrahedral and octahedral group complexes, respectively, within the spinel lattice. We also report strain (y), hopping length (LA and LB) and dislocation density (rD) of ferrite sample
Variations in Optical Properties of ZnS/Cu/ZnS Nanostructures Due to Thickness Change of ZnS Cap Layer
Full text linkNanostructures of ZnS/Cu/ZnS were deposited on glass substrate using physical vapor deposition technique. The thickness of the first and last ZnS layers was altered, while the thickness of the embedded Cu layer was fixed at 50 nm. The produced nanostructures were of good quality. Spectrophotometric measurements were carried out on the nanostructures to investigate the optical properties. The transmission and reflectivity spectra were recorded and studied in detail. ZnS was selected due to its high refractive index, ease of deposition, and low cost. The copper layer was used because of its low absorption in the visible part of the spectrum and its thermal stability. The ZnS layer was found not only to anti-reflective the Cu layer, but also to stabilize the nanostructure, improve its adherence on glass substrate, and increase the film thermal resistance up to 240 °C. Furthermore, all the samples exhibit good thermal stability up to 240 °C upon annealing for two hours