Analysis of interfacial phenomena of aqueous solutions of polyethylene oxide and polyethylene glycol flowing in hydrophilic and hydrophobic capillary viscometers

Viscosities of aqueous solutions of five polyethylene oxide (PEO) samples with molar masses from 1.5 x 10(5) to 1.0 x 10(6) were carefully measured in a polytetrafluoroethylene (PTFE) capillary Ubbelohde viscometer in the concentration range from dilute down to extremely dilute concentration regions and compared with those of the same sample obtained from a glass capillary viscometer. At the same time, viscosities of aqueous solutions of three PEG samples in glass and paraffin-coated capillary viscosity were measured. The wall effects occurred in viscosity measurements for PEO and PEG aqueous solutions in different capillary viscometers were theoretically analyzed and discussed. It was found that different interfacial behaviors occurred in both hydrophobic and hydrophilic capillary viscometers respectively and the interfacial behaviors also exhibit molar mass dependence.

Several new phenomena in the formation of ring-banded spherulites of poly(epsilon-caprolactone) and poly(styrene-random-acrylonitrile) blends

Ring-banded spherulites in crystallization of poly(epsilon-caprolactone) and poly (styrene-random-acrylonitrile) blends were observed with polarizing optical microscopy and digital image analysis technique was applied directly to the image obtained by polarizing microscope, Several new interesting phenomena were found. One is that the ring-banded structure is still clearly seen after the analyzer was removed and this astonished phenomenon couldn't result from the general concept about formation mechanism of ring-banded spherulite - lamellae twisting, Another one is that there is a slight, dark line in the bright band when cross polars were added, which may be related to the formation process and mechanism of ring-banded spherulites in the blends of poly (epsilon-caprolactone) and poly (styrene-random-acrylonitrile).

Luminescence and energy transfer phenomena of several rare earth ions in the CaAl2B2O7

The luminescence properties of Ce3+, Gd3+, and Tb3+ have been investigated in the compound CaAl2B2O7. The single excitation band peaking at about 320 nm and single emission band peaking at about 384 nm for Ce3+, without the characteristic doublet, are attributed to the extensive crystal-field splitting of 4f ground state. The emission of Gd3+ consists of well-known sharp lines and two weak bands around 319.5 and 325 nm. These bands are due to the coupling of Gd3+ with BO33- groups. The green emission of Tb3+ is considerably sensitized by Ce3+. Energy transfer from Ce3+ to Tb3+ in CaAl2B2O7 is efficient. (C) 1997 Elsevier Science Ltd.

STUDIES ON INTERFACIAL PHENOMENA OF POLYCRYSTALLINE HG1-XCDXTE THIN-FILM ELECTRODE POLYSULFIDE REDOX SOLUTION

Electrode capacitance and photocurrent spectra of electrodeposited polycrystalline Hg1-xCdxTe thin films of varying (1-x) were measured in polysulfide redox solution, hence the flatband potentional PHI(fb) and the bandgap E(g) of Hg1-xCdxTe thin films obtained. It was of interest to find out that only the location of conduction band E(c) shifts negatively with increasing (1-x) while the valence band E(v), is almost constant. The experimental open circuit photovoltage V0 is smaller than theoretical value V(max) calculated through flatband potential PHI(fb), therefore there is a possibility of promoting the experimental open circuit photovoltage.

STUDY ON THE PHENOMENA OF LASER-EXCITED POPULATION-CHANGE ON RES-ONANTLY TRANSITIONAL LOWER LEVEL AND ITS APPLICATION

Ⅰ. INTRODUCTIONLaser-excited atomic fluorescence spectrometry in hollow cathode discharge(HCD) has been widely used in the research field of laser spectroscopy in recent years. Similar to traditional method, information obtained in the researches was direct line nonresonance fluorescence arising from the resonantly transitional upper level. Attention has not been sufficiently paid to the phenomenon of population change on the resonantly transitional lower level due to laser irradiation of plasma in HCD,...

Ethanol crossover phenomena and its influence on the performance of DEFC

In the present work, Nafion (R) membrane porosity changes were determined in aqueous ethanol solutions with different concentrations by weighing vacuum-dried and ethanol aqueous solution equilibrated membranes at room temperature. The ethanol crossover rate through Nafion (R)-115 membrane at different temperatures and different concentrations had been investigated in a fuel cell test apparatus by using membrane gets higher as ethanol solution gas chromatography analysis. The experimental results show that the swelling degree of Nafion (R) concentration increases. The ethanol crossover rate increases with ethanol concentration and temperature increment. The single direct ethanol fuel cell (DEFC) tests were carried out to investigate the effect of ethanol concentration on ethanol crossover and consequently, on the open circuit voltage and the cell performance of DEFC. It can be found that ethanol crossover presented a negative effect on the OCV and the cell performance of DEFC. It can also be found that an improved DEFC performance was obtained as temperature increased although the ethanol crossover rate increased with temperature increment. (c) 2005 Elsevier B.V. All rights reserved.