Browsing by Subject "Nanocomposite"

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  • Vu, T. H. Y.; Dufour, C.; Khomenkov, V.; Leino, A. A.; Djurabekova, F.; Nordlund, K.; Coulon, P. -E.; Rizza, G.; Hayoun, M. (2019)
    The elongation process under swift heavy ion irradiation (74 MeV Kr ions) of gold NPs, with a diameter in the range 10-30 nm, and embedded in a silica matrix has been investigated by combining experiment and simulation techniques: three-dimensional thermal spike (3DTS), molecular dynamics (MD) and a phenomenological simulation code specially developed for this study. 3DTS simulations evidence the formation of a track in the host matrix and the melting of the NP after the passage of the impinging ion. MD simulations demonstrate that melted NPs have enough time to expand after each ion impact. Our phenomenological simulation relies on the expansion of the melted NP, which flows in the track in silica with modified (lower) density, followed by its recrystallization upon cooling. Finally, the elongation of the spherical NP into a cylindrical one, with a length proportional to its initial size and a width close to the diameter of the track, is the result of the superposition of the independent effects of each expansion/recrystallization process occurring for each ion impact. In agreement with experiment, the simulation shows the gradual elongation of spherical NPs in the ion-beam direction until their widths saturate in the steady state and reach a value close to the track diameter. Moreover, the simulations indicate that the expansion of the gold NP is incomplete at each ion impact.
  • Song, Jianzhi; Srivastava, Varsha; Kohout, Tomas; Sillanpää, Mika; Sainio, Tuomo (2021)
    The treatment of stormwater to remove and recover nutrients has received increasing interest. The objective of this study was to develop a novel adsorbent that is easy to handle, has good adsorption capacity, and is economical to use. A novel nanocomposite of montmorillonite (MT)-anchored magnetite (Fe3O4) was synthesised by co-precipitation as an adsorbent for ammonium. The MT/Fe3O4 nanocomposite had pore sizes (3–13 nm) in the range of narrow mesopores. The dispersion of the anchored Fe3O4 was confirmed by transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The nanocomposite exhibited higher affinity towards ammonium than the original MT. The Langmuir isotherm model was found to be the most suitable model to explain the ammonium adsorption behaviour of the nanocomposite. The maximum adsorption capacity for ammonium was 10.48 mg/g. The adsorption mechanism was a combination of ion exchange and electrostatic interaction. In an authentic stormwater sample, the synthesised adsorbent removed 64.2% of ammonium and reduced the amount of heavy metal contaminants including Mn, Ni, Cu and Zn. Furthermore, the ammonium loading on MT/Fe3O4 during adsorption functionalised the adsorbent surface. Additionally, the spent nanocomposite showed potential for rare earth elements (REEs) adsorption as a secondary application, especially for the selective adsorption of Sc3+. The versatile application of montmorillonite-anchored magnetite nanocomposite makes it a promising adsorbent for water treatment. Graphic abstract: [Figure not available: see fulltext.].
  • Oleyaei, Seyed Amir; Razavi, Seyed Mohammad Ali; Mikkonen, Kirsi S. (2018)
    Sage seed gum (SSG) is a promising biopolymer candidate for utilization and substitution prevalent galactomannan gels of interest in soft biomaterial applications. Herein, physicochemical and rheo-mechanical properties of SSG matrix reinforced by various titanium dioxide (TiO2) nanoparticles loading (0-25wt%) were monitored. Particle size and density of the nanocomposite increased with raising TiO2 content, due to the creation of more compact agglomerated and aggregated microstructure. Increasing the particle size resulted in lower electrophoretic mobility of SSG-TiO2 systems upon nanoparticles addition, confirmed the adsorption of TiO2 on the SSG macromolecule. Mechanical spectra of the SSG-based nanocomposites demonstrated a more solid-like behavior by lower frequency-dependent viscoelastic moduli, suggested a structural decoration of the nanohybrid gels discussed in terms of polymer bridging effect and formation of percolated matrix-particle superstructure. Crucial textural parameters improved with increasing TiO2 until a critical level (15 wt%), after which further increments in filler resulted in a reduction of hardness, adhesiveness and apparent modulus of elasticity. Deformation of rod-like junction zones acting as physical crosslinks in the system and fracture theory were used to explain the strain-stiffening and adhesive behavior of SSG-based gels, respectively. The nanocomposite gels with tunable functional properties might be ideal candidates for biomaterial industry. (C) 2018 Elsevier B.V. All rights reserved.
  • Ramos, Flavio James Humberto Tommasini Vieira; da Silva, Marcelo Henrique Prado; Monteiro, Sergio Neves; Grafov, Andriy; Grafova, Iryna (2020)
    The objective of this work is the processing of recycled polypropylene (rPP) matrix and geopolymer concrete waste (GCW) to develop novel sustainable nanocomposites for engineering applications. Specimens of these nanocomposites were produced from GCW added in proportions of 20, 40 and 50 wt% to rPP. The pulverized waste, with nanometric particles, was used as neat, GCW, or as surface functionalized with vinyl trimethoxy silane (GCW/VTS). Separately, both GCW and GCW/VTS were mixed with rPP by means of extrusion reactive extrusion and injection processing before final molding of specimens. The composition microstructure, thermal stability and tensile properties of the specimens were studied by wide angle X-ray diffraction, thermogravimetry, differential scanning calorimetry, water absorption, tensile tests, and field emission gun scanning electron microscopy with energy dispersive spectroscopy. The main findings were an increased thermal stability and enhanced elastic modulus with incorporation of both GCW and GCW/VTS. A high degree of interaction between GCW filler and rPP matrix, including the first time observed mechanism of PP nanofilaments adhesion, is responsible for a negligible water absorption. A decrease in the crystallinity suggests an interference of GCW in the rPP arrangement of macromolecular chains. (C) 2020 Published by Elsevier B.V.