Interaction of Chrysosporium merdarium with titanium oxide surface

The growth of Chrysosporium merdarium on TiO₂ (rutile, anatase) and its possibility to deteriorate the surface were investigated. Treated with fungi and untreated samples of deteriorated TiO₂ surfaces were studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Microbial deterioration of TiO₂ is also discussed. The attachment to the TiO₂ surface via metabolic products resulted in the formation of cryptand [2,2,2] complex with Ca²⁺ ions. According to water contact angle (CA) measurements microbial growth increases the wettability of TiO₂ film surfaces. A much more intensive fungal action during microbial treatment on rutile in comparison with that of anatase was observed. A chemical deterioration product, the volatile trimethyl borate, on rutile in exudation of C. merdarium was detected by gas chromatographic–mass spectrometric analysis.     

Decontamination of Zincate Solutions Using Calcium Hydroxide in a Fluidised Bed Reactor

This article deals with the decontamination and utilisation of waste water. The effectiveness and conditions for the removal of Zn(II) from diluted alkali zinc electroplating bath solutions in flow-rate regime have been investigated. A cheap and simple decontamination route is proposed using the fluidised bed reactor with Ca(OH)₂. The advantage of this method is that up to 98% of Zn(II) can be precipitated as a fine crystalline recyclable material—CaZn₂ (OH) ₆ 2H₂O with small amount of ZnO. The industrial scheme of this process using lime is proposed.     

Selective transfer phenomenon in lubricated sliding surfaces with copper and its alloy coatings made by electro-pulse spraying

The decrease of the coefficient of friction and wear are characteristics of the selective transfer phenomenon caused by the self-formation of a non-oxidising metal film in the friction zone. In this paper, the possibility of providing the selective transfer phenomenon by electro-pulse spraying (EPS) will be discussed. The analysed copper and brass coatings were manufactured by an electric pulse at 5 kV and an energy density of about 4.7-5 MJ/kg. EPS manufactured coatings have a fine-grained, multi-layer structure with a small share of voids and non-metal inclusions. The analysis (tribological test, microscopy) of such conditioned friction pairings has shown that a protecting metal film will be formed by itself, even at marginal lubricated test conditions. As a consequence, a low coefficient of friction (f = 0.003-0.004) occurs in the contact zone, which is similar to those, which indicate viscous friction.     

Microbially influenced corrosion of zinc and aluminium - Two-year subjection to influence of Aspergillus niger

Aspergillus niger. Tiegh., a filamentous ascomycete fungus, was isolated from the metal samples exposed to marine, rural and urban sites in Lithuania. Al and Zn samples were subjected to two-year influence of A. niger under laboratory conditions in humid atmosphere. Electrochemical impedance spectroscopy (EIS) ascertained microbially influenced corrosion acceleration (MICA) of Zn and inhibition (MICI) of Al. EIS data indicated a two-layer structure of corrosion products on Zn. The microorganisms reduced the thickness of the inner layer, whose passivating capacity was much higher when compared to that of the outer layer. An increase in aluminium oxide layer resistance but decrease in the layer thickness implied that MICI affected primarily the sites of localized corrosion of Al (pores, micro-cracks, etc.). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies indicated that bioproducts (i.e. organic acids) did not form crystalline phases with corrosion products of zinc. The study suggested a hypothesis that microorganisms could be used as corrosion protectors instead of toxic chemicals, application of which tends to be increasingly restricted.     

Influence of wild strain Bacillus mycoides on metals: From corrosion acceleration to environmentally friendly protection

Aluminium, zinc and mild steel were subjected to influence of wild strain Bacillus mycoides for 2 years under laboratory conditions at controlled temperature and humidity. The microorganisms were isolated from the metal samples exposed under outdoor conditions in different regions of Lithuania. Electrochemical impedance measurements performed for both biotic and abiotic samples indicated microbially influenced corrosion inhibition for aluminium, corrosion acceleration for zinc and indifference for steel. The microbiological corrosion inhibition implied an environmentally friendly alternative of corrosion protection to toxic chemicals, application of which due to stricter environmental regulations tends to be increasingly restricted.     

Effect of Aspergillus niger Tiegh. L-10 on the physical and chemical properties of a polyaniline coating in the growth substrate

The influence of the growth of Aspergillus niger Tiegh. fungi on the morphological, chemical and electrochemical properties of the polyaniline (PANI) modified Ni surface has been investigated. The strain of Aspergillus niger Tiegh. L-10 was cultivated on the malt extract agar (DIFCO OXOID). A PANI film was synthesized by potentiodynamic polymerization in an aqueous 0.3 M H₂C₂O₄ solution containing 0.1 M aniline on the Ni electrode. The electrochemical behaviour of polymer films was determined in a 0.05 M H₂SO₄ solution by the cyclic voltammetry method. The composition of PANI and Aspergillus niger Tiegh. treated PANI surfaces have been characterized using X-ray photoelectron spectroscopy (XPS). The morphology has been studied using scanning electron microscopy (SEM). The attachment of a polymer film via the metabolic product resulted in oxidation of the surface. It was estimated that at the PANI/microorganism interface, a Ca-complexed carboxylate interfacial reaction product was formed.