Codes associated with circulant graphs and permutation decoding

Binary codes that can be obtained from designs associated with circulant graphs G(n, S) are studied. The parameters of the codes and the information sets are obtained. PD-sets for full-error correction are found for certain values of n.     

Ionic conductivity enhancement in the solid polymer electrolyte PEO9LiTf by nanosilica filler from rice husk ash

Rice husk ash is a cheap raw material available in abundance in rice-growing countries. It contains around 85–90 % amorphous silica. Rice husk ash, when subjected to a simple chemical precipitation method, will produce nanosilica which can be used for many industrial and technological applications. In this work, we have successfully synthesized nano-sized silica from local rice husk ash and prepared the nanocomposite solid polymer electrolyte, PEO₉LiTf:SiO₂. The resulting electrolyte has been characterized by X-ray diffraction, differential scanning calorimetry, atomic force microscopy, Fourier transform infrared spectroscopy, and complex impedance spectroscopy. The electrolyte shows about a 12-fold increase in ionic conductivity at room temperature due to the silica filler. In the nanocomposite electrolyte, nanosilica particles obtained from rice husk ash behaved very similarly to the commercial grade nanosilica and had a size distribution in the 25- to 40-nm range. As already suggested by us and by others, the O^2? and OH^? surface groups in the filler surface interact with the Li⁺ ions and provide hopping sites for migrating Li⁺ ions through transient H bonding, creating additional high-conducting pathways. This would contribute to a substantial conductivity enhancement through increased ionic mobility. An additional contribution to conductivity enhancement, particularly at temperatures below 60 °C, appears to come from the increased fraction of the amorphous phase, as evidenced from the reduced crystallite melting temperature and the reduced enthalpy of melting due to the presence of the filler.     

Effect of plasticizers (EC or PC) on the ionic conductivity and thermal properties of the (PEO)9LiTf: Al2O3 nanocomposite polymer electrolyte system

A new plasticized nanocomposite polymer electrolyte based on poly (ethylene oxide) (PEO)-LiTf dispersed with ceramic filler (Al₂O₃) and plasticized with propylene carbonate (PC), ethylene carbonate (EC), and a mixture of EC and PC (EC+PC) have been studied for their ionic conductivity and thermal properties. The incorporation of plasticizers alone will yield polymer electrolytes with enhanced conductivity but with poor mechanical properties. However, mechanical properties can be improved by incorporating ceramic fillers to the plasticized system. Nanocomposite solid polymer electrolyte films (200–600 μm) were prepared by common solvent-casting method. In present work, we have shown the ionic conductivity can be substantially enhanced by using the combined effect of the plasticizers as well as the inert filler. It was revealed that the incorporating 15 wt.% Al₂O₃ filler in to PEO: LiTf polymer electrolyte significantly enhanced the ionic conductivity [σ _RT (max)?=?7.8?×?10^?6 S cm^?1]. It was interesting to observe that the addition of PC, EC, and mixture of EC and PC to the PEO: LiTf: 15 wt.% Al₂O₃ CPE showed further conductivity enhancement. The conductivity enhancement with EC is higher than PC. However, mixture of plasticizer (EC+PC) showed maximum conductivity enhancement in the temperature range interest, giving the value [σ _RT (max)?=?1.2?×?10^?4 S cm^?1]. It is suggested that the addition of PC, EC, or a mixture of EC and PC leads to a lowering of glass transition temperature and increasing the amorphous phase of PEO and the fraction of PEO-Li⁺ complex, corresponding to conductivity enhancement. Al₂O₃ filler would contribute to conductivity enhancement by transient hydrogen bonding of migrating ionic species with O–OH groups at the filler grain surface. The differential scanning calorimetry thermograms points towards the decrease of T _g , crystallite melting temperature, and melting enthalpy of PEO: LiTf: Al₂O₃ CPE after introducing plasticizers. The reduction of crystallinity and the increase in the amorphous phase content of the electrolyte, caused by the filler, also contributes to the observed conductivity enhancement.