Analytical determination of intrinsic permeability of synthetic nonwoven filter fabrics

In this paper an analytical method for determining the permeability of nonwoven filter fabrics is presented. The derived formula shows that the intrinsic permeability, fully characterizing the porous medium, depends on fabric porosity, n, fibre diameter, d, and a shape factor determined experimentally.     

Review: tailoring the properties of macroporous carbon foams

Carbon foams are non-toxic, highly porous, light materials which demonstrate a wide range of properties. That fact allows carbon foams to be applied in many areas of life, ranging from electronics industry, through machinery, car and construction industry, to environmental protection. The properties of carbon foams are closely connected with their density, and its value is especially influenced by their internal structure, i.e. mainly size and number of pores, pore wall thickness and structural order of solid matrix. That is why it is possible to design the properties of carbon foams by controlling their growth. The main control factors are selecting the suitable raw material, the process parameters (temperature and pressure) and the suitable production method. Additionally, the properties of carbon foams may be modified by doping them with carbon or mineral fillers. The second method is the enrichment of carbon matrix with heteroatoms, mainly of boron and nitrogen. This paper presents the review of the possibilities of tailoring the structure and properties of carbon foams, based on the current level of knowledge available in the literature.     

Testing of explosive welding and welded joints: joint mechanism and properties of explosive welded joints

In this study physical mechanism of explosive welding joint was analysed. The mechanism refers to wavy joint with interpass and without one. Plastic strain, viscosity and acoustic waves were applied to explain the problem. The own model of the mechanism of oxide removal for the direct joint and test results confirming the bonding mechanism were showed.     

Structure and electrochemical reactivity of new sulphur–silicon podands adsorbed on silver or gold surfaces

By the self-assembly monolayer (SAM) organization, three new podands belonging to silylpropanethiols have been tested as to their ability to form nanolayers protecting the noble metal surface (gold or silver) and to form complexes with monovalent metal cations on the metal surfaces. The stable self-assembled chemisorbed layers, providing protection to metal surface against electrooxidation and capable of blocking propylene carbonate (PC) electroreduction and Li electrodeposition were produced. Reflection-absorption infrared spectroscopy (RAIRS) indicated cleavage of the S–H bond upon adsorption of species 1–3 with the formation of S–Ag bonds on the metal surface. By cyclic voltammetry, it was found that the primary adsorbate formed on a Au electrode at E _ad (between −0.2 and −1.2 V vs. SCE) underwent reductive desorption at E < −1.3 V vs. SCE. The structures of 1–3 and their complexes with Na⁺ cations on the Ag surfaces were calculated and visualized by the AM1d semi-empirical method.     

Comparative Studies of the Mixing Effect on the Thermal Effusivity,Compressibility, and Molar Volume for Aqueous Solutions of Alcohols

Concentration dependences of the thermal effusivity, isentropic compressibility coefficient, and molar volume were investigated experimentally for aqueous solutions of ethanol, 1-propanol, and 2-propanol. The thermal effusivity was determined using a photoacoustic method. The excess molar volume was found from measured densities, while the isentropic compressibility coefficient was calculated based on density and ultrasound velocity measurements. It has been shown that the dependence of the effusivity on concentration, expressed in mass fraction units, is nonlinear in the case of all the alcohols used. Moreover, the location of extreme deviations from linearity for the thermal effusivity, Δe, agrees well with that of characteristic points for the isentropic compressibility coefficient, κ _S , and the excess molar volume, V_m^E{V_{\rm m}^{\rm E}}, as a function of the concentration.     

Vibrational Relaxation in Several Derivatives of Benzene

Acoustical spectroscopy at frequencies up to 10 GHz gives the possibility of the investigation of liquid substances, where the relaxation process observed is caused by energy transfer between translational and vibrational degrees of freedom. The compounds presented in this article belong to this group of liquids. The acoustic investigations in the group of benzene derivatives, particularly research of the dependencies of acoustic parameters and the structure of organic liquids, demonstrated some interesting regularities in the group of these compounds in gas and liquid states. In this article, the results of research on five cyclic liquids: bromo-, chloro-, fluoro-, iodo-, and nitrobenzene as well as toluene and aniline are discussed and compared to benzene. The acoustic relaxation observed in all these compounds was found to result from Kneser’s processes (vibrational relaxation). Based on investigations reported in this article, as well as by other authors, and taking into account experimental and literature data concerning a great number of compounds, one can draw a conclusion that almost all acoustic relaxation (Kneser-type) processes in liquids can be described using a single relaxation time. It also seems that all vibrational degrees of freedom of the molecule take part in this process. It is known that the appearance of differences in transition probabilities could be caused by additional attraction in interactions of molecules having dipole moments. Halogen derivatives have higher values of dipole moments than benzene. This difference could be responsible for the difference of transition probabilities and changes in the relaxation times. However, benzene derivatives with amino, nitro, and methyl groups and halides show the other type of relaxation.     

Protection of Historical Wood against Microbial Degradation—Selection and Application of Microbiocides

The aim of this study was to select effective and safe microbiocides for the disinfection and protection of historical wooden surfaces at the former Auschwitz II-Birkenau concentration and extermination camp. We tested seven active compounds against bacteria and moulds, of which didecyldimethylammonium chloride and N-(3-aminopropyl)-N-dodecylpropane-1,3-diamine were effective even at 0.02%–2%. Subsequently, eight microbiocides containing the selected active ingredients were chosen and applied three times on the surface of wood samples colonized by bacteria and moulds. ABM-1 and ABM-2—6% solution; Rocima 101—8%; Preventol R 80—12%; Acticide 706 LV—15% and Boramon—30% were the most effective disinfectants. Under laboratory conditions, ABM-1, Boramon and Rocima 101 ensured antimicrobial protection of new wood samples for six months. In situ, 30% Boramon and 8% Rocima 101 applied by spraying effectively protected the historical wood from bacterial and mould growth for 12 and 3 months, respectively. Colour and luminance of the new wood were not altered after exposure to the biocides. Boramon and Rocima 101, applied by the spraying method, caused no significant change in the colour of the historical wood. Results from this study were used to develop a procedure for the protection of wood in historical buildings against biodeterioration.     

Some factors affecting oxygen index of polyester fibres

A simple fibre sample holder was applied to the oxygen index test to determine the relative flammability of filament yarns. This modification permitted the study of the effects of sample weight and position on the oxygen index (OI) of polyester fibres. In order to characterize these effects, extrapolation of the OI curves to a zero weight of a sample (intrinsic oxygen index [OI]) and introduction of a weight factor (wf) were suggested. For the control 3 tex poly(ethylene terephthalate) (PET) monofilament tested in a vertical and horizontal position, the obtained values were, respectively, [OI]_ver = 0.175, wf_ver = 0.06 g⁻¹ and [OI]_hor = 0.174, wf_hor = 0.002 g⁻¹. The respective parameters for the flame-retardant 3 tex Heim monofil fibres were [OI]_ver = 0.192, wf_ver = 0.11 g⁻¹, [OI]_hor = 0.198, and wf_hor = 0.10 g⁻¹; and for the 3 tex PET monofil containing 5 phr Flammex B10-, [OI]_ver = 0.189, wf_ver = 0.03 g⁻¹, [OI]_hor = 0.174, and wf_hor = 0.06 g⁻¹.     

Analysis of surface layers and wear products by Mössbauer spectral analysis

The article presents results of Mössbauer analysis conducted in order to identify structural factors which help to increase wear resistance of steel friction pairs. Wear resistance was tested in the regime of dry friction and oxidative wear using an original tribological tester. The device measured wear in conditions of a created and regulated isothermal boundary at a precisely defined distance from contact of rubbing bodies by receiving heat generated by friction. Cleaning elements were also employed to stabilise frictional resistances.Enhanced wear resistance was observed to obtain where temperature of the friction area becomes equal to the specific temperature of a given system.Mössbauer analysis was applied to surfaces of specimens made of C45, 145Cr6 counter specimens, and wear products. Application of Mössbauer analysis helped to identify composition and structures of ferrous compounds generated by friction, including oxidative secondary structures.Factors improving wear resistance in the testing included: presence of greater quantities of FeO and Fe₃O₄ combined with absence of Fe₂O₃ in the friction area of ferrous oxides, transfer of wear particles arising from ferrite, martensite and oxides between co-acting surfaces, enrichment of the specimen surface with martensite from the hard counter specimen and martensite generated in effect of diffusion impacts.