Electrical conductivity of lyotropic phases of dodecylbenzenesulphonates with Li+, Na+, and K+ ions in water

The electrical conductivity of dodecylbenzenesulphonate (DoBS) ionic lyotropic liquid crystal of the systems: LiDoBS (dodecylbenzenesulphonic acid lithium salt)/water, NaDoBS (dodecylbenzenesulphonic acid sodium salt)/water, and KDoBS (dodecylbenzenesulphonic acid potassium salt)/water were investigated by impedance spectroscopy in the frequency range from 0.5 Hz to 0.5 MHz. The electrical conductivity of lyotropic LiDoBS was higher than that of isotropic phase. The electrical conductivity isotropic KDoBS and NaDoBS was higher than the conductivity of lyotropic ones. The temperature dependence of electrical conductivity was investigated in the systems LiDoBS/water and KDoBS/water for different phases. The activation energy of electrical conductivity is lowest for the normal hexagonal phase LiDoBS/water. Such systems based on anionic surfactants are of interest as the electrolyte for the supercapacitors.     

Metastable ionic cubic structure I clathrate hydrate formed with tetra-n-butylammonium bromide

1. Download : Download high-res image (143KB)
2. Download : Download full-size image

     

A facile approach to prepare water-soluble magnetic metal (oxide) frameworks based on Na,Ca alginate and maghemite

1. Download : Download high-res image (135KB)
2. Download : Download full-size image

     

Effect of eluant composition on the retention of water-soluble vitamins in reversed-phase high-performance liquid chromatography

The effects of the quantitative composition and pH of water-acetonitrile eluants and temperature on the retention of water-soluble vitamins in reversed-phase high-performance liquid chromatography were studied. The retention parameters of the analytes were calculated and the limits of the applicability of the main adsorption models of retention to the test chromatographic system were discussed.     

Characterisation of anodic oxide films on zirconium formed in sulphuric acid: XPS and corrosion resistance investigations

Present work describes investigations of a two-step process consisting of galvanostatic anodising in a 1 M H₂SO₄ solution at 100 mA cm⁻² up to the limiting voltages of 20, 60, 80, 100 and 120 V, directly after which potentiostatic regime was employed and the current was allowed to drop. The total treatment time (5 min) was held constant for all samples. The treatment was carried out to improve the corrosion resistance of zirconium in physiological conditions, which was determined by electrochemical evaluation in Ringer’s solution. XPS studies revealed that after anodising sulphur was incorporated into the oxide film in the form of sulphated zirconia. The maximum content of sulphate in the oxide layer was observed after anodising at 80 V. Anodising at higher voltages resulted in formation of coatings with decreasing amount of sulphur. It was found that there is a strong correlation between the sulphur content in the oxide layers and the measured corrosion current density. On the other hand, the pitting corrosion resistance seemed to be unaffected by the presence of S and it was improving with the increasing limiting voltage of the treatment.