Specific Surface Resistance Research Articles

Interaction between hydrophobic and superhydrophobic materials with aqueous media

Interactions between hydrophobic materials and aqueous media was studied using the analysis of specific surface resistance. Methods for measuring surface resistance are developed for both samples exposed in vapors and those in direct contact with liquid. As a result of the measurements performed, it is confirmed that water molecules penetrate the matrix of the material under prolonged contact with hydrophobic and superhydrophobic materials with aqueous media. The processes of formation on the surface of hydrophobic and superhydrophobic materials of the wetting/adsorption films are observed and the method of estimation their thickness is suggested.

Effect of microstructures on electrochemical behavior of La 0.8Sr 0.2MnO 3 deposited by suspension plasma spraying

Suspension plasma spraying (SPS) was employed to prepare La 0.8Sr 0.2MnO 3 (LSM) cathode for solid oxide fuel cell (SOFC). LSM powder in the nanometer size range synthesized by the glycine–nitrate processing (GNP) was used as precursor. The surface morphology and microstructure of the LSM deposits were characterized by scanning electron microscopy and x-ray diffraction. The influence of spray distance on SPS LSM microstructure was examined. The electrochemical behavior was analyzed through the impedance spectroscopy. The fine starting particles resulted in a fine microstructure of SPS LSM deposit. The results showed that the microstructure of SPS LSM cathode exhibits significant influence on the cathode polarization. The improved melting degree of LSM particles during spray deposition leads to reduction of the cathode polarization. The specific surface resistance of 0.45 Ω cm 2 was obtained at 950 °C for SPS LSM cathode deposited at a spraying distance of 70 mm.

Strain Sensing with Nanoscale Carbon Fiber – Epoxy Composites

To study the electrical behavior of nanoscale carbon fibers (NCF)/epoxy nanocomposites under mechanical load, NCF/epoxy materials were produced using different mechanical dispersion methods like pearl mill and three roll mill. Various preliminary mechanical tests with simultaneous resistance measurements have been conducted. The influence of the filler content, the dispersion quality and the filler geometry on the electrical properties of NCF/epoxy composites was investigated as a function of the mechanical loading. The strain sensitivity strongly depended on the filler content and the filler geometry. In cyclic loading tests at low strains the resistance showed a reversible and linear behaviour. At higher strains irreversible resistance changes were observed. In addition, the specific surface resistance corresponded even during unloading with the highest strain level applied so far. This indicates the potential of NCFs/epoxy nanocomposites to monitor the loading history of a sample.

Adsorption mechanism of surfactants on nonwoven fabrics

AbstractFor improved surface properties, nonwoven fabrics of polypropylene and poly(ethylene terephthalate) were treated with several kinds of surfactants, including anionic, cationic, and nonionic types. The adsorption isotherms of the anionic, cationic, and nonionic surfactants on the nonwoven fabrics were different. The adsorption isotherm of the cationic surfactant (dodecyl dimethylbenzyl/ammonium chloride) exhibited a maximum. The adsorption isotherm of the anionic surfactant (sodium dodecylbenzene sulfonate) was in the shape of the fifth Brunauer adsorption isotherm, and that of the nonionic surfactant (alkylphenol/ethylene oxide condensate) was similar to the fourth Brunauer adsorption isotherm. The time of the adsorption equilibrium was constant for the same types of adsorbate and adsorbent, and it was not related to the initial concentration. The specific surface resistance of the nonwoven fabrics decreased substantially after the adsorption of ionic surfactants. The nonwoven fabrics with the surfactants were characterized with scanning electron microscopy and X‐ray photoelectron spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3210–3215, 2003

Functionalized coating materials based on inorganic-organic polymers

ORMOCER®s (ORMOCER® Trademark of Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.) as inorganic-organic polymers synthesized by a two-step sol-gel processing method can be applied as thin transparent coatings on various substrates (polymers, metals, ceramics). The curing of ORMOCER®s is performed thermally (at temperatures below 200°C) or by UV-radiation. Their high abrasion resistance and good chemical stability led to several actual industrial applications. Beside mechanical protection functions (e.g. for sensitive polymer substrates) additional functionalities of ORMOCER® surfaces are investigated to find new application areas. This paper presents two additional surface functions of abrasion resistant ORMOCER® coatings: Antiadhesive and antistatic properties. Incorporation of perfluorinated alkoxysilane compounds via sol-gel processing decreases the surface energy of the cured layer. Water as well as non-polar substances lose their adhesion to the surface, wetting is reduced, solutions are drained off and particles can be removed easily.By addition of polar and/or ionic compounds bearing hydrolyzable alkoxysilyl groups a scratch resistant antistatic coating for polycarbonate was developed. Compared to the uncoated substrate, the specific surface resistance was decreased from 1015 to 108 Ω. Electrostatic charging is decreased and attraction of particles inhibited or reduced. The coatings are abrasion resistant and show very good adhesion even in a wet climate.

Electroadsorption of Ni2+ ions in an electrodialysis chamber containing granulated ion-exchange resin

Electrochemical processes taking place in an electrodialysis chamber packed with the granulated ion-exchange resin, when a dilute solution of a heavy metal salt is flowing through it, have been studied. The influence of the quantity of electricity transferred through such a system on the value of surface electrical resistance of the electrodialysis chamber and the limiting current value was experimentally determined. A mechanism for current transfer in such a system is presented. It allows for some unusual relationships between process parameters: current-voltage curves, the limiting current, the specific surface resistance, the quantity of transferred electricity and the solution flow rate.

Testing of biological aerated filter (BAF) media

The cost of filter media contributes a significant proportion of the initial capital outlay in wastewater treatment by biological aerated filters (BAFs). Media characteristics also affect day to day running costs such as those involved in backwashing. To allow an informed choice relating to filter media and their prospective uses a number of standards have been produced, most recently the British Effluent and Water Association (BEWA) standard. The aim of this study was to investigate a number of granular media using the BEWA standard in order to determine their suitability for BAFs. All the media samples investigated appear suitable for use as BAF media with one in particular having all the necessary characteristics e.g. low density, high specific surface area and resistance to attrition.

Testing of biological aerated filter (BAF) media

The cost of filter media contributes a significant proportion of the initial capital outlay in wastewater treatment by biological aerated filters (BAFs). Media characteristics also affect day to day running costs such as those involved in backwashing. To allow an informed choice relating to filter media and their prospective uses a number of standards have been produced, most recently the British Effluent and Water Association (BEWA) standard. The aim of this study was to investigate a number of granular media using the BEWA standard in order to determine their suitability for BAFs. All the media samples investigated appear suitable for use as BAF media with one in particular having all the necessary characteristics e.g. low density, high specific surface area and resistance to attrition.

Error in determining the specific surface resistance

Error in determining the specific surface resistance

Lamp-black for carbon products

Specific surface, Blaine-surface and electrical resistance of two lamp-black grades were measured. As only a small part of the surface is wetted by pitch-binders the first method is not suitable determining the required amount of binder. The two latter methods give useful relations.