Materials Science Forum Vol. 752

Abstract: In this paper a special effect of aluminium and nickel on the spectral lines of alkaline-earth metals being present in low concentration was studied. During the study a sharp difference could be obtained in the behaviour of atomic and ionic lines, therefore among the lines investigated both atomic and ionic ones were included. The effect of Ni and Al was investigated in a wide concentration range in case of Be, Mg, Ca and Sr. In case of each of the four alkaline-earth element a significant difference in the depression of the signal could be observed with increasing Al or Ni concentration among atomic and ion lines.

Abstract: Based on the previously published sodium and Ag, Cu, Zn ion-exchange and re-excange experiments we took an attempt to modeling its structure. We also took in account the ion release experimental results and the rigorous survey of the literature data when we positioned the ions in zeolite crystal structure. Therefore the current study aimed to modeling the ion distribution of single, binary and ternary ion-exchanged zeolite systems used for antimicrobial purposes, where the variation of silver, copper and zinc is incorporated into the zeolite structure. The tool of modelling was “CrystalMaker6” developed by CrystalMaker Software Ltd.

Abstract: Fine balance between active galvanic and passive barrier corrosion protection by zinc-rich hybrid paints is explored depending on the absolute and relative amounts of the electrically semi-conducting particles, viz. polypyrrole (PPy) modified alumina hydrate and multi-walled carbon nanotubes (MWCNTs) and the zinc pigments. The former was varied between 3.21 and 1.75 wt.%, the latter was altered from 70 to 80 wt.% in the primers. The coating with less zinc indicated firm and stable barrier nature in a 254 h immersion test whereas the primer with greater zinc content afforded superior galvanic corrosion prevention in salt-mist test over 142 days. Different nature of the coatings are expounded on the basis of structure and 3D arrangement of the nano-size inhibitor particles in the epoxy vehicle besides interpreted considering varied grain contents caused changing electrical percolation and electrolytic conductivity of the primers.

Abstract: Small batches of two oxide powders falling in the particle size range of about 30-230 μm were received from industrial sources and were electroless nickel (EN) coated in order to prepare properly modified reinforcing particles for further laboratory experiments with the Laser Melt Injection (LMI) technique to produce particle reinforced steel composite surface layers. The partially calcined alumina (Al2O3) as well as the hydrothermally recycled crystalline iron(III) oxide precipitate were characterized first to check their exact size ranges, specific surface areas and major chemical contaminants so that the best possible EN plating technique would be selected and applied. It was revealed soon that the sensitization and activation pre-treatment steps could not be omitted and after their proper adjustment, also the composition and pH of a relatively commonly used hypophosphite reducing type bath had to be modified to the given purpose. Eventually a slightly alkaline EN bath was successfully prepared with which both industrial oxide powders surface could be nickel coated soundly, which final result was demonstrated also by several metallographic testing techniques showing the microstructure of the quite evenly and fully coated oxide particles.

Abstract: A flexible and efficient process of tin electrorefining has been devised, using aqueous solutions of relatively low HCl and tin chloride concentrations. Any additives have been avoided, which enhances purity but also incurs the difficulty of obtaining compact cathode deposits. This feature is however assisted by the natural inhibition in complexing chloride solutions and the modulation of the current. Due to the rough dendritic crystal growth, special provisions are required to avoid short circuiting. Using short pulses in the 50-250 μs range of periodically reversed or interrupted currents, the lengths of the usually large dendrites can be moderated. The periodic current with extremely short cycle times and special electrode arrangement can be utilized for averting short circuits and for achieving better coverage of the cathode surface. This technique can be applied efficiently to obtain pure tin from soldering waste materials.

Abstract: Scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) has been used to characterize the elemental composition of diesel soot samples. The STEM employed in this investigation is the Vacuum Generators Microscope HB603, with a microanalytical resolution approaching 1 nm, allowing the analysis of individual soot particles and aggregates. Quantification of the EDX spectra is accomplished after background and absorption corrections. This information can then be used to pinpoint the fuels and combustion process from which the soot originated. Six diesel soots were analyzed in this study including three from a U.S. Bureau of Mines diesel test engine, two from a West Virginia University diesel test engine, and one from an Orion diesel bus engine. This research showed that soot impurities were found throughout the aggregates, and that only one or two soot particles were necessary to obtain a chemical fingerprint. Some of these elements may be traced to the fuel and lubricant. Other elements were components of the engine itself that combined with the soot particulates during the combustion process. The concept of using a ‘Truth Table’ for the purpose of source attribution is also introduced.