Materials Science Forum Vols. 587-588

Abstract: The reactors used for Selective Catalytic Reduction (SCR) of NOx require low pressure drop structured catalyst packing. Structured packings, such as ceramic foams, are gaining increasing interest for application in low pressure drop reactors, membrane reactors and catalytic distillation units. In this work, cobalt ion exchanged mordenite (Co-HMOR)-coated cordierite-based foams produced by the replication method were evaluated for catalytic reduction of NOx with methane. The addition of 0.3 wt.% Pd to 2 wt.% Co-HMOR leads to a material that can convert 50 % NOx to N2 at 450 °C in a reaction mixture containing 2000 ppm CH4, 1000 ppm NOx, 5 % O2 and balance helium, at GHSV=17000 h-1. Although in an early stage of development, an efficient coating procedure was explored and different ways of exchange of Co and Pd cations into mordenite (Si/Al=10) were studied. Additions of 2 wt.% fumed silica enhanced adhesion of the zeolite onto the ceramic foam. Pd-exchanged Co-HMOR showed to be very sensitive to steam. A 50 % decrease in NOx conversion to N2 was observed after Pd/Co-HMOR samples were exposed at 450 °C to a reaction mixture containing 2 vol% H2O. Although further research is needed to ascertain the mechanism of this deactivation behaviour, agglomeration of Pd forming PdO particles is envisaged.

Abstract: Ni+W+Si composite coatings were prepared by nickel deposition from a bath containing suspension of tungsten and silicon powders. These coatings were obtained under galvanostatic conditions, at the current density of jdep. = 0.100 A cm-2 and at the temperature of 338 K. A scanning electron microscope was used for surface morphology characterization of the coatings. Chemical composition of the coatings was determined by EDS method and phase composition investigations were conducted by X-ray diffraction. Thermal treatment of obtained coatings was conducted in the air and nitrogen atmosphere. Electrochemical corrosion resistance investigations were carried out in the 5 M KOH, using potentiodynamic method. It was found that Ni+W+Si coatings after thermal treatment in the air are more corrosion resistant in alkaline solution than Ni+W+Si coatings after thermal treatment in the nitrogen atmosphere and as-deposited coatings. The main reason of this is presence of new phases, in particular NiWO4 and SiO2.

Abstract: Ni-Ti Shape Memory Alloy thin films are suitable materials for microelectromechanical devices. During the deposition of Ni-Ti thin films on Si substrates, there exist interfacial diffusion and chemical interactions at the interface due to the high temperature processing necessary to crystallize the film. For the present study, Ni-Ti thin films were prepared by magnetron cosputtering from Ni-Ti and Ti targets in a specially designed chamber mounted on the 6-circle goniometer of the ROssendorf BeamLine (ROBL-CRG) at ESRF, Grenoble (France). The objective of this study has been to investigate the interfacial structure resulting from depositions (at a temperature of ≈ 470°C) on different substrates: naturally oxidized Si(100), Si(111) and poly-Si substrates. A detailed High-Resolution TEM analysis of the interfacial structure has been performed. When Ni-Ti is deposited on Si(100) substrate, a considerable diffusion of Ni into the substrate takes place, resulting in the growth of semi-octaeder A-NiSi2 silicide. In the case of Ni-Ti deposited on Si(111), there appears an uniform thickness plate, due to the alignment between substrate orientation and the [111]-growth front. For Ni-Ti deposited on poly-Si, the diffusion is inhomogeneous. Preferential diffusion is found along the columnar grains of poly-Si, which are favourably aligned for Ni diffusion. These results show that for the Ni-Ti/Si system, the morphology of the diffusion interface is strongly dependent on the type of substrates.

Abstract: TiO2 films were prepared using radio frequency (RF) magnetron sputtering and were deposited on glass and Si substrates. We varied deposition time at room temperature with RF density of 3.7 W/cm2 and argon flow rate of 4 sccm. The morphological, structural, optical and electrical properties were studied by Atomic Force Microscope (AFM), X ray Diffractometer (XRD) and UV-VIS-NIR spectrophotometer. The transmittance is maintained in the range of 70- 90% in the visible and near-infrared range, high refractive index of 2.4 and large direct band gap of about 3.5 eV are obtained. These films are annealed at 300°C during 2 hours. The annealing effect is investigated in this work. The results of this study suggest that the variation of the deposition time allow the control of the structural, optical and electrical properties of the films.

Abstract: For silver plating, mainly silver cyanide solutions are used and this is extensively treated in the literature. Yet, in view of the growing concern for environmental problems, they will have to be replaced because of their toxic properties. In the present work, the appropriateness of thiosulphate ) O S ( 2 3 2 − , a complexing agent for silver of common use in photographic applications, as an alternative for cyanide in electroplating baths is investigated. The kinetic characteristics of the reduction are determined, since they fix at which rate the plating can proceed. Prior to the kinetic study, requiring measurements in solutions of varying composition, the thermodynamic data on complex formation between Ag+ and − 2 3 2O S ions are analysed. And finally, the composition and the morphology of the silver deposits are examined as a function of the plating conditions. Electrochemical and analytical physical techniques are used.

Abstract: Transparent conducting Al doped ZnO films have been deposited by dc magnetron sputtering on glass and polymer substrates at room temperature. Depositions have been carried out from an AZOY (contains a small amount of Y2O3 in addition to Al2O3 and ZnO) target under different conditions such as working pressure, substrate bias voltage and oxygen flow rate. The crystallinity of the Al doped ZnO films has been improved by using low-energy-ion bombardment. Likewise, the use of either the rotation or the static mode of the substrate during deposition influences the crystallinity and therefore the optical parameters and the electrical resistance of the films. Increasing the thickness of the films reduces the threshold strain at which the films can be deformed without provoking significant changes on their electrical properties.

Abstract: In this work, Si-doped DLC films were deposited on stainless steel (316SS) and polycarbonate (PC) substrates by RF-PACVD in gas mixtures of SiH4+CH4, with 2, 5 and 10 vol.% SiH4. The increase of the Si content in the films led to a progressive drop in the hardness from 30 GPa down to 23 GPa whereas the elastic modulus increased from 124 GPa up to 146 GPa, as measured in the SS coated substrates. In the case of coated PC samples pop-in was observed in the loading curve which was interpreted by finite element simulation and nanoscratching techniques.

Abstract: Activated carbons are materials extensively used to remove a variety of pollutants in different media. The porous structure, the surface chemistry and the type of adsorptive determine the potential of activated carbons as an adsorbent material. However, in a more global perspective it is necessary to consider other factors such as the economical viability of production and reuse. This last factor depends on the capacity of regeneration of the activated carbons after each application. Following this guideline, the objective of this work was to evaluate the capacity of regeneration of some specific activated carbons prepared from cork oak wastes, used in the adsorption of phenolic compounds in the liquid phase. Simultaneously, the performance of our carbons are compared with the behaviour of a commercial carbon (Norit SX plus). The experimental procedure consists in the adsorption of one phenolic compound, followed by the regeneration of the adsorbent, succeeding a series of adsorption/regeneration processes. The methods of regeneration used were simple washing with distilled water under magnetic stirring, washing with ultrasound and thermal regeneration under inert atmosphere. The performance of the activated carbons was strongly dependent on their nature and the regeneration method applied.

Abstract: Carbon nanotube-TiO2 composites and pure TiO2 are prepared by a modified sol-gel method. The nanoscaled materials obtained are extensively characterized by spectroscopic, microscopic and calorimetric techniques. Their photoactivity is tested in the degradation of phenol under visible illumination. A correlation between the CNT content and the changes in the UV–vis absorption properties was found. The effect induced by CNT on the composite catalysts is explained in terms of an interphase interaction between CNT and TiO2 in the composite catalysts.

Abstract: This paper presents an innovative technology for soil reinforced structures. The technology is based on the use of pre-tensioned geogrids reinforcements and face panels reinforced with fiber glass. Main technology advantages are: i) the very light face with great variety of geometries, size, color and surface textures; ii) either the face and the reinforcements are corrosion free; iii) the good behavior under seismic actions; iv) reduction of structure horizontal strains due to the pre-tension. First, the state of art on reinforced soil structures is done and then the constituents of the new technology are presented followed by the reference to the main theoretical principles considered in its conception. Secondly, numerical data from the behavior, in static conditions, of geogrid reinforced soil structures with and without pre-tensioned reinforcements are presented. In the numerical study the FLAC program, based on the differences finites method, will be used. The construction of the structures will be modeled considering the sequential placement of soil layers and reinforcements, enhancing the deformation behavior of the structures. Thirdly, the advantages of the new technology against the traditional ones are quantified, based on the results of the numerical studies. Special relevance will be given to face horizontal deformations and reinforcements strains. Finally, the main conclusions about the new technology will be put forward and its main advantages towards traditional technologies will be listed. Application fields where the technology is competitiveness will be identified.