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  • 751.
    Zhou, Xiaojian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sethi, Jatin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Geng, Shiyu
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Berglund, Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Frisk, Nikolina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Aitomäki, Yvonne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sain, Mohini
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dispersion and reinforcing effect of carrot nanofibers on biopolyurethane foams2016Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 110, s. 526-531Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, carrot nanofibers (CNF) were used to enhance the performance of biobased castor oil polyol polyurethane nanocomposite foams. A method of dispersing CNF in the polyol was developed and the foam characteristics and CNF reinforcing effect were studied. Co-solvent-assisted mixing resulted in well-dispersed CNF in the polyol, and foams with 0.25, 0.5 and 1 phr CNF content were prepared. The reinforced nanocomposite foams displayed a narrow cell size distribution and the compressive strength and modulus were significantly elevated and the best compressive strength and modulus were reached with 0.5 phr CNF. Similarly, the modulus of the solid material was also significantly increased based on theoretical calculations. When comparing the foam performance, compressive strength and stiffness as a function of the density, the nanocomposite foams performs as commercial rigid PU foam with a closed cell structure. These results are very promising and we believe that these foams are excellent core materials for lightweight sandwich composites.

  • 752.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ryden, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adsorption Behavior of Cellulose and Its Derivatives toward Ag(I) in Aqueous Medium: An AFM, Spectroscopic, and DFT Study2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 45, s. 12390-12400Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to develop a fundamental understanding of the adsorption behavior of metal ions on cellulose surfaces using experimental techniques supported by computational modeling, taking Ag(I) as an example. Force interactions among three types of cellulose microspheres (native cellulose and its derivatives with sulfate and phosphate groups) and the silica surface in AgNO3 solution were studied with atomic force microscopy (AFM) using the colloidal probe technique. The adhesion force between phosphate cellulose microspheres (PCM) and the silica surface in the aqueous AgNO3 medium increased significantly with increasing pH while the adhesion force slightly decreased for sulfate cellulose microspheres (SCM), and no clear adhesion force was observed for native cellulose microspheres (CM). The stronger adhesion enhancement for the PCM system is mainly attributed to the electrostatic attraction between Ag(I) and the negative silica surface. The observed force trends were in good agreement with the measured zeta potentials. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses confirmed the presence of silver on the surface of cellulose microspheres after adsorption. This study showed that PCM with a high content of phosphate groups exhibited a larger amount of adsorbed Ag(I) than CM and SCM and possible clustering of Ag(I) to nanoparticles. The presence of the phosphate group and a wavenumber shift of the P−OH vibration caused by the adsorption of silver ions on the phosphate groups were further confirmed with computational studies using density functional theory (DFT), which gives support to the above findings regarding the adsorption and clustering of Ag(I) on the cellulose surface decorated with phosphate groups as well as IR spectra.

  • 753.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Morphology and surface interactions studies of nanocellulose using Atomic Force Microscopy2015Konferansepaper (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Force interactions between native cellulose microsphere (CM), sulfate cellulose microsphere (SCM), phosphate cellulose microsphere (PCM) and glass substrate under the effect of silver ions in the model solution were investigated using atomic force microscopy (AFM). The special interest was the influence of Ag+ ions and pH on the interaction between the probe and glass substrate. The probe was functionalized with above three types of cellulose microspheres by gluing method using contact mode with AFM. Functionalized probe and glass substrate were immersed in aqueous Ag+ solutions (50mg/L) at various pH value (4.25, 5.07, 5.62 and 6.63). Zeta potential studies showed negatively charged surfaces for CM, SCM, PCM and silica powders in model Ag+ solutions. The analysis revealed a decrease of adhesion force for CM and SCM system but an increase of adhesion force for PCM system with the increase of pH. The possible mechanism of the interaction under the effects of Ag+ ions, pH, and functional group contents as well as the shape of the cellulose microspheres was discussed. The SEM and SEM-EDS analysis confirmed the presence of silver ions on the surface of the cellulose microspheres after adsorption and force measurements.

  • 754.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji p.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adsorption behavior of cellulose and its derivatives for Ag+ in aqueous medium: An AFM and spectroscopy study2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cellulose particles in micro and nano scales has shown excellent potential to adsorb water pollutants such as dyes, pesticides, bacteria and virus, and a wide range of heavy metal ions, including Ag(Ⅰ), U(Ⅱ), Fe(Ⅲ), Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅲ) and Zn(Ⅱ) 1, 2. However, mechanisms of adsorption and desorption the contaminants to/from cellulose micro or nano particles are largely unknown. The aim of the study was to develop fundamental understanding about the interaction and adsorption behavior of silver ions on cellulose surfaces using colloidal probe and spectroscopy techniques. Force interactions between three types of cellulose microspheres viz. native cellulose microspheres (CM), sulfate cellulose microspheres (SCM), phosphate cellulose microspheres (PCM) and silica surface in AgNO3 solution were studied with atomic force microscopy (AFM). The AFM results were further elaborated by extensive spectroscopy investigations.

  • 755.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University.
    Advanced microscopy and spectroscopy reveal the adsorption and clustering of Cu(II) onto TEMPO-oxidized cellulose nanofibers2017Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, nr 22, s. 7419-7428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    TEMPO (2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidation nanofibers (TOCNF), as a biocompatible and bioactive material, have opened up a new application of nanocellulose for the removal of water contaminants. This development demands extremely sensitive and accurate methods to understand the surface interactions between water pollutants and TOCNF. In this report, we investigated the adsorption of metal ions on TOCNF surfaces using experimental techniques atthe nano and molecular scales with Cu(II) as the target pollutant in both aqueous and dry forms. Imaging with in situ atomic force microscopy (AFM), together with a study of the physiochemical properties of TOCNF caused by adsorption with Cu(II) in liquid, were conducted using the PeakForce Quantitative NanoMechanics (PF-QNM) mode at the nano scale. The average adhesion force between the tip and the target single TOCNF almost tripled after adsorption with Cu(II) from 50 pN to 140 pN. The stiffness of the TOCNF was also enhanced because the Cu(II) bound to the carboxylate groups and hardened the fiber. AFM topography, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) mapping and X-ray photoelectron spectroscopy (XPS) indicated that the TOCNF were covered by copper nanolayers and/or nanoparticles after adsorption. The changes in the molecular structure caused by the adsorption were demonstrated by Raman and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). This methodology will be of great assistance to gain qualitative and quantitative information on the adsorption process and interaction between charged entities in aqueous medium.

  • 756.
    Zimmermann, Tanja
    et al.
    Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Tingaut, P.
    Eyholzer, Christian
    Richter, Klaus
    Applications of nanofibrillated cellulose in polymer composites2012Konferansepaper (Fagfellevurdert)
  • 757. Oksman, Kristiina ()
    Wood based composites: Proceedings from Nordic research course at Lövånger 22-27 March 19921992Rapport (Annet vitenskapelig)
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