Materials Science Forum Vols. 587-588

Abstract: In the present study the distribution of nanofillers in the polyurethane matrix and the composite properties were investigated. As a nanofiller, zirconium oxide doped with 10% Eu3+ was used. The nanofiller was added at 0.1 wt%. Different ways of nanofiller incorporation were investigated. The microstructure of the obtained materials was examined by atomic force microscopy in force modulation. The size analysis of the nanofiller was investigated with HRSEM. The thermal (DSC, TGA) properties of polyurethane nanocomposites were also investigated in addition to the analysis of transmittance and luminescence of obtained materials. The results obtained indicate a possibility of fabrication of polymeric nanocomposites for optoelectronic applications via a relatively inexpensive processing route.

Abstract: The microporous titanosilicate ETS-10 was subjected to three cycles of ferricinium ion ([(η5-C5H5)2Fe]+, Fc+) exchange by using aqueous solutions of ferricinium hexafluorophosphate and microwave-assisted heating. The resultant hybrid inorganic-organometallic (ETS-10/Fc+) materials were characterised by elemental analysis, ICP-AES, FTIR and Raman spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance (DR) UV-Vis, 29Si and 23Na solid-state NMR. The results support the successful inclusion of Fc+ in the pores of the inorganic host by ion exchange of extra-framework sodium and potassium ions.

Abstract: Mesoporous silica can be modified and functionalised by immobilisation of organic substances covalently bonded to the silanol groups on the silica surface. This paper describes the modification of a SBA-15 nanostructured silica with 2-benzothiazolethiol. After derivatization the modified silica was chacacterized by elemental analysis, IR spectroscopy, thermal analysis (TG and DSC), NMR in solid phase and scanning electron microscopy.

Abstract: The removal of metallic ions from binary aqueous solutions of Fe(III)/Cr(III) and Fe(III)/Cr(VI) by an Arthrobacter viscosus biofilm supported on NaY zeolite was investigated. Experiments were repeated with suspended biomass for comparison purposes. Batch assays were performed using different concentrations (10, 25 and 40 mg/L), for both metals in solution. Results indicated that Arthrobacter viscosus is able to retain the metallic ions, although not totally. The removal efficiencies were improved when the biofilm was supported on the zeolite, for all the initial concentrations of Cr(III), for the intermediate and higher concentration of Cr(VI) and for all range of initial concentrations of Fe(III), in the presence of Cr(III). The bacteria reduce Cr(VI) to Cr(III) and, only then, this cation may be entrapped in the framework zeolite by ion exchange. Suspended bacteria had higher affinity for Fe(III), than for Cr(VI) or Cr(III), while the conjugated system was selective to Fe(III) when in the presence of Cr(VI). For solutions of Fe(III)/Cr(III), very high removals were achieved by the supported system, ranging from 94 to 100 % for Cr(III) and from 98 to 100 % for Fe(III). The conjugated system also reached the highest removal ratio of Cr(VI), 36 %, for the initial concentration of 40 mg/L. The materials in study were characterized by techniques such as FTIR, SEM and chemical analyses.

Abstract: Nickel powder was dry-milled using a high-energy disc-oscillating mill. The average particle size increases and the specific surface area diminishes with milling time. Crystallite size decreases and microstrains increase, under the same conditions, as shown by X-ray analysis. At 120 min milling time, the crystallite size has a value of 17 nm, i.e., a nanostructured powder, with a perturbed lattice, is obtained. The above results have been compared with published data about the effects of milling on a ceramic powder. There is, in both cases, a general agreement concerning the changes produced in crystallite size. Nevertheless, opposite results are reached regarding particle size and specific surface area.

Abstract: Mesoporous titanosilicates were directly synthesised at ambient temperature and pressure, considering a wide range of metal content (0.01≤Ti/Si≤0.5) and using cationic surfactants of different alkyl chain length. It is shown that the use of tetradecyl-, hexadecyl- and octadecyltrimethylammonium bromide as structure-directing agents provide higher quality Ti-MCM-41 materials, than those prepared with surfactants of shorter alkyl chain. The pore volume and surface areas are gradually reduced by the increase of Ti content but up to Ti/Si=0.02 the alterations in the pore structural properties are negligible as compared with pure silica grades, becoming more noticeable for Ti/Si≥0.1. Nevertheless, for Ti/Si=0.1 the directly synthesised materials still have high pore volumes as well as high regularity and uniformity of the hexagonal pore array, with superior pore structural properties to those of materials prepared by post synthesis deposition of titanium on silica MCM-41, which did not provide a valid alternative for minimising the disruptive effect of high metal content on the hexagonal porous structure.

Abstract: It has been generally accepted that a nanostructured material exhibits better properties than conventional ones. Nanostructured ceramic coatings fabricated by plasma spray have been developed for a wide variety of applications where a surface protection is required. Alumina - titania coatings are usually used as protective layers in many industrial applications requiring a high wear resistance during dry sliding contact. In this work, nanostructured and conventional Al2O3 – 13% TiO2 coatings deposited via atmospheric plasma spray were compared. Mechanical characterization was carried out using depth sensing indentation to determine hardness and Young´s modulus of the coatings. Size independent properties can be determined after considering geometrical factors such as tip rounding and indenter deformation. Nanostructured coatings show slightly better mechanical properties than conventional coatings.

Abstract: Nanocrystalline metals demonstrate a broad range of fascinating mechanical properties at the nanoscale, namely a significant increase in hardness and superior yield stress. In this regard, understanding grain growth in nanocrystalline metals is crucial, particularly because nano size grains are characterized by a high curvature, which results in a high driving force for grain growth. In this work, the effect of annealing conditions on grain size of copper nanocrystalline thin films was investigated. The nanocrystalline copper thin films were first deposited by d.c. magnetron sputtering on a copper substrate. The specimens were then annealed in vacuum at 100, 300 and 500°C from 10 minutes to 5 hours. Transmission electron microscopy observations revealed that the as-deposited thin films have a bimodal grain size distribution; an average grain size of 43±2nm and the presence of nanotwins. Abnormal grain growth was observed for some samples annealed. Increasing the annealing time induced significant grain growth and promoted twin formation in the larger grains. Finally, the hardness of these nanocrystalline Cu thin films was determined using atomic force microscope. The relation between mechanical properties, annealing conditions and grain size was analyzed.

Abstract: Successful solid state bonding of titanium aluminides requires the use of high temperature and pressure. In previous works, authors have demonstrated that the use of Ti/Al multilayer thin film as an interlayer, deposited by d.c. magnetron sputtering onto the joining surfaces, can effectively lower the bonding temperature. The enhanced diffusivity of these nanometric layers and the heat evolved by the formation of γ-TiAl improves the joinability of titanium aluminide by solid-state diffusion bonding. In the present work, further improvement of the process was pursued by doping the interlayer with 2.8 at.% of Ag; previous studies have confirmed that silver favours the transformation Ti+Al→γ-TiAl. The solid-state diffusion bonding experiments were performed in vacuum by applying 50 MPa at 900°C for 1 h. The effect of the third element on the microstructure and chemical composition along the bonding interface has been analyzed. Microstructural characterisation of the interface was performed by scanning and transmission electron microscopy. Chemical compositions were analysed by energy dispersive X-ray spectroscopy. No defects were observed at the interface and sound bonding was achieved between the interlayers and base γ-TiAl. The bonding interface shows a fine-grained microstructure, slightly coarser than the one formed at the same temperature with the undoped Ti/Al multilayer.

Abstract: Nanostructured CuO powders have been synthesized using chemical methods in the current study. Ammonium oxalate and copper nitrate were used as the precursor materials. The weight ratios of the raw materials (ammonium oxalate/copper nitrate) were 1.1, 1.2, 1.3, and 1.4. As a result of chemical reaction (between them), copper oxalate was synthesized. Produced samples were analyzed by XRD and SEM. The results show that the best ratio (for ammonium oxalate/copper nitrate) is 1.2. Produced copper oxalate powder was heated at 600, 700 and 800oC. The final product was CuO nanopowder. XRD studies indicate that the highest ratio of Cu2O to CuO was observed in the specimen heated at 700oC.