Raman studies of coals

Raman spectra were used to estimate the sizes of microcrystalline regions in coal. A variety of different Polish coals were investigated by means of the laser Raman technique. To prevent decomposition of the coals in the laser beam, the rotating disc technique was used to obtain the spectra. Some i.r. spectra of the coals under investigation were also considered. The aromatic carbon content was determined by the method of Oelert. The results of both spectroscopic techniques were compared and found to lead to the same order of magnitude of microcrystalline regions. The Tuingstra and Koenig method used for evaluation of microcrystalline regions in coal was found to be applicable if infrared studies indicate a high value of the aromaticity coefficient, i.e. if aromatic bonds are predominant in the coal under investigation.     

Investigations of the passive layer cracking by means of Dynamic Electrochemical Impedance Spectroscopy

The Dynamic Electrochemical Impedance Spectroscopy has been applied for stress corrosion cracking (SCC) investigations. The effect of applied potential and tensile stresses on the stress corrosion cracking behaviour of type 304L stainless steel (SS) immersed in 0.5 M NaCl solution of room temperature has been examined. This paper presents impedance spectra obtained for 304L stainless steel samples at the different potential values. The results obtained proved the possibility of providing new details about the dynamics of the initiation and propagation of the crack path compared to classical electrochemical techniques.     

An Attempt to Decompose the Impact of Land Use and Climate Change on Annual Runoff in a Small Agricultural Catchment

Water Resources Management - The aims of this study are: i) to better understand the coupled interactions between land use changes, climate change and the aquatic ecosystem in a small agricultural...     

Damage detection of composite milling process by recurrence plots and quantifications analysis

We study the dynamics of a milling process of carbon fiber reinforced plastic based on experimental time series of cutting force with help of recurrence plots and recurrence quantifications methods. The two cases of composite machining are analyzed in detail. The first case is a milling of undamaged material, while the second is a milling of damaged material. The detailed recurrence analysis shows interesting results, and additionally some of all quantifications can be used to damage detection.     

Applicability of selected methods and sorbents to simultaneous removal of siloxanes and other impurities from biogas

This paper critically reviews and discusses the state-of-the-art technologies for the removal of siloxanes from biogas, which could be used to simultaneously remove other contaminants. The reasons for purifying biogas, the scope of this purification and the recommended (depending on the biogas utilization equipment) concentrations of volatile silicon-organic compounds are presented. Established and new promising methods of removing typical methylsiloxanes from biogases from municipal landfills and sewage sludge are characterized and analyzed. Their suitability for the simultaneous removal of other trace biogas impurities and possibilities of regenerating the spent sorbent are assessed. It is shown that the commonly used activated carbon is not suitable for comprehensive biogas treatment. On the basis of the analysis, an adsorption method using halloysite (a natural zeolite mineral) as an inexpensive, universal and regenerable adsorbent is proposed. The method can be used after physicochemical treatment to comprehensively purify biogas from methylsiloxanes, hydrogen sulfide, ammonia, halides and other technically and environmentally burdensome impurities. Some directions for further research in this regard and possible environmentally safe ways of utilizing the spent sorbent are indicated.     

Multispectral impedance quality testing of coil-coating system using principal component analysis

The task of quality checking of the coil-coated system was undertaken using impedance spectroscopy. In order to properly characterize the system the new impedance spectrum was calculated as an averaged result of 12 experimental spectra obtained from 12 different places of the sample at the same time of immersion in 3% of NaCl. The experimental spectra were recorded for a 24-h period at 1 h intervals between starting points of each measurement. Averaged impedance at each frequency point of the calculated spectrum was characterized by standard deviation. Impedance analysis using two-time constant equivalent electrical circuit was conducted showing the permissible parameter scatter for the checked system. A new classification method of obtained parameters using principal component analysis was presented. This approach enables to identify samples of low quality.     

Application of impedance imaging to evaluation of organic coating degradation at a local scale

A new approach for evaluating the local electrical properties of organic coatings has been proposed. It was performed with contact mode atomic force microscopy (AFM). A current response signal was measured when a single-frequency voltage perturbation was applied between AFM tip and coated metal. Suitability of the proposed technique has been presented on the representative acrylic coating degraded by two different factors—UV radiation and electrolyte exposure. It was possible to disclose the early stages of the coating deterioration, to spatially localize defective regions, and to observe distinctly different modes of the coating degradation as a result of exposure to various degradation factors.     

Application of the dynamic EIS to investigation of transport within organic coatings

The paper presents results of an investigation on rapid degradation of organic coating using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). For 60 s, polyvinyl coating has been subjected to the impact of 0.01 M solution of tetraethylammonium tetrafluoroborate in methylene chloride. During that time instantaneous impedance spectra have been determined allowing tracing the dynamics of a degradation process. Usefulness of the DEIS technique in the investigation of non-stationary phenomena has been proved in the field of coating research.