Change search
Refine search result
12 1 - 50 of 61
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Baghaei, Behnaz
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Berglin, Lena
    University of Borås, Swedish School of Textiles.
    Hybrid natural fibre reinforcements and prepregs for thermoplastic composites with improved performance and properties2014Conference paper (Other academic)
  • 2.
    Bakare, Fatimat
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Bashir, Tariq
    University of Borås, School of Engineering.
    Ingman, Petri
    Srivastava, Rajiv
    Synthesis and characterization of unsaturated lactic acid based thermoset bio-resins2014In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 67, p. 570-582Article in journal (Refereed)
    Abstract [en]

    Bio-based thermoset resins have been synthesized using lactic acid oligomers, which were functionalized with carbon–carbon double bonds, in order to allow their crosslinking by a free radical mechanism. Two different resin structures were synthesized. One resin was composed of an allyl alcohol terminated lactic acid oligomer, which was end-functionalized with methacrylic anhydride (MLA resin). The second resin was a mixture of the same allyl alcohol-lactic acid oligomer, and penthaerythritol. This mixture was end-functionalized with methacrylic anhydride, in order to get a methacrylate functionalized lactic acid oligomer, and methacrylate functionalized penthaerythritol (PMLA resin). The synthesized resins were characterized using FT-IR, 1H NMR and 13C NMR spectroscopy, differential scanning calorimetry as well as dynamic mechanical analysis to confirm the resin structure and reactivity. The flow viscosities were also measured in order to evaluate the suitability of the resins to be used as a matrix in composite applications. The results showed that the PMLA resin has better mechanical, thermal and rheological properties than the MLA resin, and both had properties which were comparable with a commercial unsaturated polyester resin. The high biobased content of 90% and the high glass transition temperature at 100 °C for the PMLA resin makes it an attractive candidate for composite applications where crude oil based unsaturated polyester resins are normally used.

  • 3.
    Barghi, Hamidreza
    University of Borås, School of Engineering.
    Functionalization of Synthetic Polymers for Membrane Bioreactors2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Membrane bioreactors (MBRs) show great promise for productivity improvement and energy conservation in conventional bioprocesses for wastewater reclamation. In order to attain high productivity in a bioprocess, it is crucial to retain the microorganisms in the bioreactors by preventing wash out. This enables recycling of the microorganisms, and is consequently saving energy. The main feature of MBRs is their permeable membranes, acting as a limitative interface between the medium and the microorganisms. Permeation of nutrients and metabolites through the membranes is thus dependent on the membrane characteristics, i.e. porosity, hydrophilicity,and polarity. The present thesis introduces membranes for MBRs to be used in a continuous feeding process, designed in the form of robust, durable, and semi-hydrophilic films that constitute an effective barrier for the microorganisms, while permitting passage of nutrients and metabolites. Polyamide 46 (polytetramethylene adipamide), a robust synthetic polymer, holds the desired capabilities, with the exception of porosity and hydrophilicity. In order to achieve adequate porosity and hydrophilicity, bulk functionalization of polyamide 46 with different reagents was performed. These procedures changed the configuration from dense planar to spherical, resulting in increased porosity. Hydroxyethylation of the changed membranes increased the surface tension from 11.2 to 44.6 mJ/m2. The enhanced hydrophilicity of PA 46 resulted in high productivity of biogas formation in a compact MBR, due to diminished biofouling. Copolymerization of hydrophilized polyamide 46 with hydroxymethyl 3,4-ethylenedioxythiophene revealed electroconductivity and hydrophilic properties, adequate for use in MBRs. To find either the maximal pH stability or the surface charge of the membranes having undergone carboxymethylation, polarity and the isoelectric point (pI) of the treated membranes were studied by means of a Zeta analyzer. The hydroxylated PA 46 was finally employed in a multilayer membrane bioreactor and compared with hydrophobic polyamide and PVDF membranes. The resulting biogas production showed that the hydroxylated PA 46 membrane was, after 18 days without regeneration, fully comparable with PVDF membranes.

  • 4.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Persson, Nils-Krister
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Smart Textiles: A novel concept of functionalizing textile materials2013Conference paper (Refereed)
    Abstract [en]

    Electrically conductive textile materials are the key components in smart and interactive textile applications. In our research, we introduced functionalities in commercially available textile substrates (fibers and fabrics) by coating them with conjugated polymer, such as poly (3,4-ethylenedioxythiophene) (PEDOT) [1-2]. In order to get conductivities that are of use, an efficient technique, chemical vapor deposition (CVD), was used. The obtained coated fibers and fabrics exhibited good electro-mechanical properties and can be utilized for a number of electronic applications, such as stretch sensors, anti-static air filters and electrodes for bio-fuel cells.

  • 5.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Persson, Nils-Krister
    [external].
    Production of PEDOT Coated Conductive Fibers for Smart & Interactive Textile Applications2012Conference paper (Refereed)
  • 6.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Ramamoorthy, Sunil Kumar
    Persson, Nils-Krister
    University of Borås, School of Engineering.
    All-organic conductive fibers for smart and interactive textile applications2013Conference paper (Other academic)
  • 7.
    Bazooyar, Faranak
    et al.
    University of Borås, School of Engineering.
    Momany, Frank A.
    Bolton, Kim
    University of Borås, School of Engineering.
    Validating Empirical Force Fields for Molecular-level Simulation of Cellulose Dissolution2012In: Computational and Theoretical Chemistry, ISSN 2210-271X, E-ISSN 2210-2728, Vol. 984, p. 119-127Article in journal (Refereed)
    Abstract [en]

    The calculations presented here, which include dynamics simulations using molecular mechanics forcefields and first principles studies, indicate that the COMPASS forcefield is preferred over the Dreiding and Universal forcefields for studying dissolution of large cellulose structures. The validity of these forcefields was assessed by comparing structures and energies of cellobiose, which is the shortest cellulose chain, obtained from the forcefields with those obtained from MP2 and DFT methods. In agreement with the first principles methods, COMPASS is the only forcefield of the three studied here that favors the anti form of cellobiose in the vacuum. This forcefield was also used to compare changes in energies when hydrating cellobiose with 1–4 water molecules. Although the COMPASS forcefield does not yield the change from anti to syn minimum energy structure when hydrating with more than two water molecules – as predicted by DFT – it does predict that the syn conformer is preferred when simulating cellobiose in bulk liquid water and at temperatures relevant to cellulosedissolution. This indicates that the COMPASS forcefield yields valid structures of cellulose under these conditions. Simulations based on the COMPASS forcefield show that, due to entropic effects, the syn form of cellobiose is energetically preferred at elevated temperature, both in vacuum and in bulk water. This is also in agreement with DFT calculations.

  • 8.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Satyanarayana, Kavitha Chelakara
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational Studies of Poly(vinylidene fluoride)-Single Wall Carbon Nanotube Systems2013In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 10, no 6, p. 1317-1325Article in journal (Refereed)
    Abstract [en]

    First principles and molecular mechanics methods have been used to study poly(vinylidene fluoride)—single wall carbon nanotube systems. First principles calculations (Møller-Plesset second order perturbation theory and density functional theory with B3LYP exchange correlation functional with and without dispersion correction) using short poly(vinylidene fluoride) segments and short hydrogen-capped single wall carbon nanotubes show that the polymer segments prefer to have the β-rather than the β-conformation both in the absence and presence of the single wall carbon nanotube. The lowest energy structure is obtained when the poly(vinylidene fluoride) has an β-conformation and is located parallel to the single wall carbon nanotube wall. In contrast to the Dreiding and Universal force fields, the COMPASS force field predicts the structures containing the β-conformation of poly(vinylidene fluoride) to be the lowest in energy in agreement with first principles results. The COMPASS force field was consequently used in preliminary studies of a longer poly(vinylidene fluoride) chain and a longer single wall carbon nanotube using molecular dynamics.

  • 9.
    Bolton, Kim
    University of Borås, School of Engineering.
    Modelling carbon nanotube growth2008Conference paper (Other academic)
  • 10.
    Bolton, Kim
    University of Borås, School of Engineering.
    Simulations of water, metal and carbon clustering2008Conference paper (Other academic)
  • 11.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Computational studies of single-walled carbon nanotube growth2011In: SNIC Progress Report (2008-2009), p. 40-46Article in journal (Other academic)
    Abstract [en]

    Allocation of time on the Swedish national supercomputing facilities since 2000, as well as support from other sources, has allowed us to perform computational studies on a wide variety of systems. These include properties and growth of carbon nanotubes [1–36], icecatalysed reactions of importance to stratospheric ozone depletion[37], calculations of vapour-liquid, liquid-liquid and vapour-liquid-liquid phase equilibrium of single, binary and ternary component systems[38], and, more recently, carbonaceous polymer nanocomposites and cellulose decomposition. More details of these projects are available at the web page given above.

  • 12.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Ding, F.
    Börjesson, Arne
    Zhu, W.M.
    Duan, H.M.
    Harutyunyan, A.R.
    Curtarlo, S.
    Computational Studies of Catalytic Particles for Carbon Nanotube Growth2009In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 6, no 1, p. 1-15Article in journal (Refereed)
    Abstract [en]

    We review our computational studies of the melting temperatures and mechanisms of iron and iron-carbide clusters. Both isolated and supported clusters have been considered, and substrates with different shapes or pores have been simulated. It has been seen, for example, that the surface curvature—or local surface curvature—of the particle plays a dominant role in the melting mechanism and temperature. It has also been observed that the melting mechanism for small clusters is different to that of larger clusters.

  • 13.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Zhu, Wuming
    Börjesson, Anders
    Progress in understanding controlled single-wall carbon nanotube growth from computer simulations2012In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 9, no 6, p. 819-825Article in journal (Refereed)
    Abstract [en]

    Density functional theory based on the PW91 and PBE exchange-correlation functionals was used to study processes that are expected to play a key role in single-walled carbon nanotube (SWNT) growth and continued growth. It is shown that Ni clusters adapt their shape to the shape of the SWNT end to which they are attached. The results also show that the presence of SWNTs affects Ostwald ripening of the catalyst metal clusters and that, under certain conditions, the net diffusion may be from larger to smaller clusters. Also, Ostwald ripening may affect the chiral distribution of the SWNTs.

  • 14.
    Börjesson, A.
    et al.
    University of Borås, School of Engineering.
    Zhu, W.
    Amara, H.
    Bichara, C.
    Ducastelle, F.
    Bolton, Kim
    University of Borås, School of Engineering.
    Theoretical investigation of the Nanotube-metal junction2008Conference paper (Other academic)
  • 15.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Computational Studies of Metal Clusters and Carbon Nanotubes2008Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Carbon nanotubes constitute a promising candidate material in the realisation of nanoscaled electronics. This requires the ability for systematic production of carbon nanotubes with certain properties. This is called selective carbon nanotube growth. Two important aspects related to carbon nanotube growth are investigated in order to shed some light on this issue. First the melting behaviour of nanometer sized iron particles is investigated using molec- ular dynamics simulations. The iron nanoparticles studied are mounted on a porous Al2 O3 substrate in order to mimic the experimental situation during nanotube growth with the chemical vapour deposition method. This showed that the melting temperature of a cluster on a porous substrate may be lower than the melting temperature of a cluster on a flat sub- strate. This means that the catalyst particles used for nanotube growth may be liquid. In association with these studies the role of surface curvature to melting behaviour is explored further. The second presented study concerns the docking of nickel clusters to open single wall carbon nanotube ends. The motivation for this study was the possibility to continue growth of a carbon nanotube by docking of catalyst particles to its end. This work may also be of importance for the creation of electric junctions between carbon nanotubes and metal elec- trodes. This study showed that independent of whether the metal was gently put on the nanotube end or brutally forced to the end, it is the metal that adapts to the nanotube and not vice versa. For forced docking it was seen that carbon might dissolve in to the metal. This was not seen for the gently docked clusters. Carbon dissolution might affect the electronic properties of the metal (carbide) and nanotube-metal junction.

  • 16.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    First Principles Studies of the Effect of Nickel Carbide Catalyst Composition on Carbon Nanotube Growth2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 42, p. 18045-18050Article in journal (Refereed)
    Abstract [en]

    Density functional theory calculations were used to investigate the stability of single-walled carbon nanotubes (CNTs) attached to nanoparticles. The total energies and the adhesion energies between the CNTs and the nanoparticles were calculated for systems where the nanoparticles were either pure Ni or Ni carbide. It was found that the adhesion between the CNT and a pure Ni cluster is stronger than between the same CNT and a Ni carbide cluster although the energy difference was small compared to the total adhesion energies. This adhesion strength implies that CNTs are likely to remain attached to both pure Ni and Ni carbide clusters and that either pure Ni or Ni carbide clusters may be docked onto the open CNT ends to achieve continued growth or electronic contacts between CNTs and electrode materials. The system with a CNT attached to a pure Ni cluster was found to be energetically favored compared to a system containing the same CNT attached to a Ni carbide. The difference in total energy implies that a CNT should act as a sink for C atoms dissolved in the Ni carbide cluster, which means that the dissolved C atoms will be drained from the cluster, yielding a pure metal in the zero Kelvin thermodynamic limit. It is argued that this draining procedure is likely to occur even if carbon is added to the cluster at a proper rate, for example, during CNT growth.

  • 17.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering. University of Borås, Swedish School of Textiles.
    Modelling of Ostwald ripening of metal clusters attached to carbon nanotubes2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 50, p. 24454-24462Article in journal (Refereed)
    Abstract [en]

    We present a model of Ostwald ripening of nanosized clusters and apply it to study the time evolution of metal particles attached to carbon nanotubes. The Ostwald ripening of metal clusters attached to carbon nanotubes differs from that of free metal clusters. While free clusters experience a rapid broadening in the size dispersion, this may be delayed by the nanotubes, which may therefore limit the ripening. The diameter and chirality of the carbon nanotubes were also seen to affect the Ostwald ripening of the catalyst particles. For a collection of carbon nanotubes that contains different diameters and chiralities, the clusters attached to carbon nanotubes with large diameters and strong carbon–metal adhesion are the most likely to survive the Ostwald ripening.

  • 18.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Erdtman, Edvin
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Berlin, Mikael
    Andersson, Thorbjörn
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular modelling of oxygen and water permeation in polyethylene2013In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 54, no 12, p. 2988-Article in journal (Refereed)
    Abstract [en]

    Monte Carlo and molecular dynamics simulations were performed to calculate solubility, S, and diffusion, D, coefficients of oxygen and water in polyethylene, and to obtain a molecular-level understanding of the diffusion mechanism. The permeation coefficient, P, was calculated from the product of S and D. The AMBER force field, which yields the correct polymer densities under the conditions studied, was used for the simulations, and it was observed that the results were not sensitive to the inclusion of atomic charges in the force field. The simulated S for oxygen and water are higher and lower than experimental data, respectively. The calculated diffusion coefficients are in good agreement with experimental data. Possible reasons for the discrepancy in the simulated and experimental solubilities, which results in discrepancies in the permeation coefficients, are discussed. The diffusion of both penetrants occurs mainly by large amplitude, infrequent jumps of the molecules through the polymer matrix.

  • 19.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Harutyunyan, Avetik R.
    Curtarolo, Stefano
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational study of the thermal behavior of iron clusters on a porous substrate2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 11Article in journal (Refereed)
  • 20.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Zhu, Wuming
    Amara, Hakim
    Bichara, Christophe
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational studies of metal-carbon nanotube interfaces for regrowth and electronic transport2009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 3, p. 1117-1120Article in journal (Refereed)
    Abstract [en]

    First principles and tight binding Monte Carlo simulations show that junctions between single-walled carbon nanotubes (SWNTs) and nickel clusters are on the cluster surface, and not at subsurface sites, irrespective of the nanotube chirality, temperature, and whether the docking is gentle or forced. Gentle docking helps to preserve the pristine structure of the SWNT at the metal interface, whereas forced docking may partially dissolve the SWNT in the cluster. This is important for SWNT-based electronics and SWNT-seeded regrowth.

  • 21. Chalapati, Sachin
    et al.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Toluene mediated fluid catalytic cracking of low density polyethylene using ionic liquids2014Conference paper (Other academic)
  • 22. Chelakara Satyanarayana, Kavitha
    et al.
    Bohlén, Martin
    University of Borås, School of Engineering.
    Lund, Anja
    Rychwalski, Rodney
    Bolton, Kim
    University of Borås, School of Engineering.
    Analysis of the torsion angle distribution of poly(vinylidene fluoride) in the melt2012In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 53, no 4, p. 1109-1114Article in journal (Refereed)
    Abstract [en]

    Analysis of the torsionangledistribution of poly(vinylidene fluoride) (PVDF) structures at temperatures above its melting point is addressed by combining first principles methods, atomistic simulations and laboratory experiments. Amorphous, α- and β-conformations of PVDF structures have been considered. The results from the atomistic simulations as well as the experiments show that there is a larger probability of the PVDF torsions to be near ±180° at temperatures above the melting point, which is associated more with the β-conformation than the α-conformation.

  • 23. Chelakara Satyanarayana, Kavitha
    et al.
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular dynamics simulations of α- to β-poly (vinylidene fluoride) phase change by stretching and poling2012In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 53, no 14, p. 2927-2934Article in journal (Refereed)
    Abstract [en]

    The mechanism of inducing a phase change from α-poly(vinylidene fluoride) (α-PVDF) to β-PVDF is addressed using molecular dynamics simulations based on a molecular mechanics force field. The effect of applying a strain to the α-PVDF crystal along the axis of the molecules is investigated, as well as poling the crystal before or after stretching. Rather large (at least 1010 V/m) electric fields that are perpendicular to the axis of the PVDF molecules are required to induce α- to β-PVDF phase change when no strain is applied to the α-PVDF crystal. However, at a strain of 1.0475 (i.e., when the crystal is stretched by 4.75%) α-PVDF changes to a β-PVDF like structure, where the β-PVDF molecules orientate anti-parallel relative to each other. Transformation of the anti-parallel β-PVDF to β-PVDF can be induced by poling (even at the lowest electric field of 105 V/m studied here) or by thermal annealing.

  • 24. Curtarolo, S.
    et al.
    Awasthi, N.
    Setyawan, W.
    Jiang, A.
    Bolton, Kim
    University of Borås, School of Engineering.
    Tokune, T.
    Harutyunyan, A. R.
    Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for singlewalled carbon nanotube growth2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 5Article in journal (Refereed)
  • 25. Curtarolo, Stefano
    et al.
    Awasthi, Neha
    Setyawan, Wahyu
    Mora, Elena
    Tokune, Toshio
    Bolton, Kim
    University of Borås, School of Engineering.
    Harutyunyan, Avetik R.
    The role of carbon solubility in Fe-C nano-clusters on the growth of small single-walled carbon nanotubes2008Conference paper (Other academic)
  • 26. Curtarolo, Stefano
    et al.
    Awasthi, Neha
    Setyawan, Wahyu
    Tokune, Toshio
    Mora, Elena
    Kuznetsov, O.
    Harutyunyan, Avetik R.
    Bolton, Kim
    University of Borås, School of Engineering.
    The apparent paradox of the Gibbs-Thompson phenomenon is the thermodynamic limit for the activity of Fe anf Fe:Mo catalysts for carbon nanotubes growth2008Conference paper (Other academic)
  • 27. Cutrarolo, Stefano
    et al.
    Awastahi, Neha
    Setyawan, Wahyu
    Li, Na
    Jiang, Aiqin
    Mora, Elena
    Bolton, Kim
    University of Borås, School of Engineering.
    Harutyunyan, Avetik R.
    Thermodynamics of carbon in iron nanoparticles at low temperature: reduced solubility and size-induced nucleation of cementite2010In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 6, p. 16-26Article in journal (Refereed)
    Abstract [en]

    In this manuscript we present the thermodynamics of iron-carbon nano particles at low temperature. By combining classical molecular dynamics simulations, ab initio calculations, finite temperature thermodynamics modeling, and the “size/pressure approximation”, we address carbon-induced fluidization, size-induced eutectic point shift, and reduced solubility at the nanoscale. The results are used to describe, as functions of particle size, three scenarios in the catalytic chemical vapor deposition growth of single single-walled carbon nanotubes, corresponding to steady state-, limitedand no-growth.

  • 28. Ding, Feng
    et al.
    Larsson, Peter
    Larsson, Andreas J.
    Ahuja, Rajeev
    Duan, Haiming
    Rosén, Arne
    Bolton, Kim
    University of Borås, School of Engineering.
    The importance of strong carbon-metal adhesion for catalytic nucleation of single-walled carbon nanotubes2008In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 2, p. 463-468Article in journal (Refereed)
    Abstract [en]

    Density functional theory is used to show that the adhesion between single-walled carbon nanotubes (SWNTs) and the catalyst particles from which they grow needs to be strong to support nanotube growth. It is found that Fe, Co, and Ni, commonly used to catalyze SWNT growth, have larger adhesion strengths to SWNTs than Cu, Pd, and Au and are therefore likely to be more efficient for supporting growth. The calculations also show that to maintain an open end of the SWNT it is necessary that the SWNT adhesion strength to the metal particle is comparable to the cap formation energy of the SWNT end. This implies that the difference between continued and discontinued SWNT growth to a large extent depends on the carbon-metal binding strength, which we demonstrate by molecular dynamics (MD) simulations. The results highlight that first principles computations are vital for the understanding of the binding strength's role in the SWNT growth mechanism and are needed to get accurate force field parameters for MD.

  • 29. Duan, Haiming
    et al.
    Rosén, Arne
    Harutyunyan, Avetik
    Curtarolo, Stefano
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational studies of small carbon and iron-carbon systems relevant to carbon nanotube growth2008In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 8, no 11, p. 6170-6177Article in journal (Refereed)
    Abstract [en]

    Density functional theory (DFT) calculations show that dimers and longer carbon strings are more stable than individual atoms on Fe(111) surfaces. It is therefore necessary to consider the formation of these species on the metal surfaces and their effect on the mechanism of single-walled nanotube (SWNT) growth. The good agreement between the trends (energies and structures) obtained using DFT and those based on the Brenner and AIREBO models indicate that these analytic models provide adequate descriptions of the supported carbon systems needed for valid molecular dynamics simulations of SWNT growth. In contrast, the AIREBO model provides a better description of the relative energies for isolated carbon species, and this model is preferred over the Brenner potential when simulating SWNT growth in the absence of metal particles. However, the PM3 semiempirical model appears to provide an even better description for these systems and, given sufficient computer resources, direct dynamics methods based on this model may be preferred.

  • 30. Dural-Erem, Aysin
    et al.
    Erem, Hasan
    Ozcan, Gulay
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Anatase titanium dioxide loaded polylactide membranous films: preparation, characterization, and antibacterial activity assessment2015In: Journal of the Textile Institute, ISSN 0040-5000, E-ISSN 1754-2340, Vol. 106, no 6Article in journal (Refereed)
    Abstract [en]

    In this study, the preparation method and characteristics of anatase titanium dioxide (TiO2) nanoparticle-loaded polylactide (PLA) films and their antibacterial efficacy against Klebsiella pneumoniae (ATCC 4352) and Staphylococcus aureus (ATCC 6538) bacterium were studied. A series of PLA nanocomposites containing, respectively, 0, 1, and 5% (wt.) titanium dioxide (TiO2) nanoparticles were prepared by melt intercalation method. The effect of TiO2 nanoparticles on the thermal and mechanical characteristics of the films was determined. Thermal analysis showed that the glass transition temperature, crystallization temperature, melting temperature, and decomposition temperatures (Td0.5 and Td0.05) decreased with the filler content. The results obtained from tensile tests showed that TiO2 nanoparticles reduced the mechanical properties and moduli of the PLA films. On the other hand, the water absorption properties of the nanocomposite films increased with the addition of nanoparticles and nanocomposite films exhibited bacteriostatic and limited bactericidal efficacy according to AATCC 147. Consequently, nanocomposite films may be good materials for medical applications due to their membranous properties.

  • 31. Erdtman, Edvin
    et al.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Berlin, Mikael
    Andersson, Thorbjörn
    Gkourmpis, Thomas
    Bolton, Kim
    University of Borås, School of Engineering.
    Penetration and absorption of small molecules in polymers2014Conference paper (Refereed)
  • 32.
    Erdtman, Edvin
    et al.
    University of Borås, School of Engineering.
    Chelakara Satyanarayana, Kavitha
    Bolton, Kim
    University of Borås, School of Engineering.
    Simulation of α- and β-PVDF melting mechanisms2012In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 53, no 14, p. 2919-2926Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics (MD) simulations have been used to study the melting of α- and β-poly (vinylidene fluoride) (α- and β-PVDF). It is seen that melting at the ends of the polymer chains precedes melting of the bulk crystal structure. Melting of α-PVDF initially occurs via transitions between the two gauche dihedral angles (G ↔ G′) followed by transitions between trans and gauche dihedral angles (T ↔ G/G′). Melting of β-PVDF initially occurs via T → G/G′ transitions and via transitions of complete β- (TTTT) to α- (TGTG') quartets. The melting point of β-PVDF is higher than that of α-PVDF, and the simulated melting points of both phases depend on the length of the polymer chains used in the simulations. Since melting starts at the chain ends, it is important to include these in the simulations, and simulations of infinitely long chains yield melting points far larger than the experimental values (at least for periodic cells of the size used in this work), especially for β-PVDF. The simulated heats of fusion are in agreement with available experimental data.

  • 33.
    Fazelinejad, Samaneh
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mechanical Recycling of Polylactic Acid Reinforced with Calcium Carbonate2014Conference paper (Other academic)
    Abstract [en]

    Biopolymers are becoming increasingly popular and may help reduce oil dependency. As a result, industries’ attentions have been directed towards polylactic acid (PLA) which combines the advantages of being renewable and biodegradable resources at the same time. The upward trend of the bioplastics and biocomposites usage among consumers could have great consequence for the recycled plastics industry in the next few decades. While the mechanical recycling of many of the traditional, petro-based polymers have been studied in detail, bio-based polymers still need to be better characterized. The mechanical recycling of neat PLA has previously studied and tests show that it is possible to process PLA several times without significant loss of mechanical properties. However, commercial plastics are often used with some kind of filler. Due to the low production cost of chalk (mainly consisting of CaCO3) it is often added to commercial polymers. PLA can be filled with chalk and other fillers in order to improve the toughness and lowering the cost. The purpose of this project was to investigate the mechanical recycling of PLA compounded with chalk. PLA was compounded with 30 wt-% chalk and 5 wt-% plasticizer using a twin screw extruder. The mechanical recycling was simulated by multiple extrusion. Samples for mechanical testing were prepared by compress molding. The prepared compound was recycled up to 6 times by multiple extrusion. The mechanical and thermal properties were characterized after each cycle by TGA, DSC, DMTA, FTIR and tensile tests.

  • 34. Fazelinejad, Samaneh
    et al.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Recycling of Poly Lactic Acid Reinforced with Calcium Carbonate by Multiple Processing2014Conference paper (Other academic)
    Abstract [en]

    The upward trend of the bioplastics and biocomposites usage among consumers could have great consequence for the recycled plastics industry in the next few decades. As a result,industries’ attentions have been directed towards Poly Lactic Acid (PLA) which combines the advantages of renewable and biodegradable resources at the same time. Since PLA is more environmentally friendly compared to traditional petroleum-based commodity polymers, it has benefited from an upturned trend of interest in different markets, like the packaging, textile, and automotive industries. However, it is not applicable in many fields due to its inherent brittleness; even though it is very beneficial as the result of high strength and high modulus. Due to the low production cost of Nano calcium carbonate (nano-CaCO3) (NCC) which is useful to improve the toughness of PLA, it has reached a wide market in such industries as plastics, paints, and inks. By adding Nano calcium carbonate to polymer, thermal,crystallization, mechanical, biodegradability and melt rheological properties will be improved. The mechanical recycling of neat PLA has previously studied as well as some research on blend PLA/NCC by Sabzi et al. However, the purpose of this project is to investigate the characterization of PLA blend with Chalk (CaCo3) and Plasticizer by focusing on thermaland mechanical properties. The filler, which is 30% calcium carbonate, and 5% plasticizer compound with PLA in a two screws extruder. Plasticizer is added to composite to make it softer and it is consider constant in all samples. Multiple extrusions and compress molding are methods which can help in studying the recyclability of polymeric materials containing bioplastic and its derivatives and in figuring out the stability or service life respectively. In addition, these methods make it possible to determine the impacts of thermal and thermo mechanical degradation. Bio composite was recycled up to 6 times by using extruder equipment and crushing. The mechanical and thermal properties were characterized after each cycle by TGA, DSC,DMTA, FTIR, tensile machine and flexural test. The study represents that by introducing 30% calcium carbonate to PLA, it can be recycled up to 6 times without meeting any significant change in the mechanical and thermal properties.

  • 35. Harutyunyan, A. R.
    et al.
    Awasthi, N.
    Jiang, A.
    Setyawan, W.
    Mora, E.
    Tokune, T.
    Bolton, Kim
    University of Borås, School of Engineering.
    Curtarolo, S.
    Reduced carbon solubility in Fe nanocatalysts and implications for the growth of single walled carbon nanotubes2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 19Article in journal (Refereed)
  • 36.
    Hatamvand, Mohammad
    et al.
    Yazd University.
    Mirjalili, Seyed Abbas
    Yazd University.
    Sharzehee, Maryam
    Yazd University.
    Behjat, Abbas
    Yazd University.
    Jabbari, Mostafa
    University of Borås, Faculty of Textiles, Engineering and Business.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Fabrication parameters of low-temperature ZnO-based hole-transport-free perovskite solar cells2017In: Optik (Stuttgart), ISSN 0030-4026, E-ISSN 1618-1336, Vol. 40, p. 443-450Article in journal (Refereed)
    Abstract [en]

    Perovskite solar cells (PSCs) are a new generation solar cells. Low-Temperature techniques are used for fabrication PSCs on a flexible substrate that has a low thermal tolerance. In this paper, low-temperature PSCs with ZnO nanoparticles were prepared as electron transport material (ETM) without hole transport material (HTM). Effects of some of the fabrication parameters of low-temperature ZnO based PSCs without HTM, on their principal characteristics and performance, were investigated. Parameters such as the concentration of ZnO nanoparticles (NPs) dispersion, spin coating speed of ZnO NPs, and concentration of CH3NH3I on characteristics and performance of fabricated low-temperature PSCs were studied. The study shows that by changing these parameters, the performance of the fabricated PSCs changes considerably.

  • 37.
    Johansson, Erik
    et al.
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular simulation of the effect of ionic impurities and external electric fields on rod-like water clusters in polyethylene2008In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 49, no 24, p. 5357-5362Article in journal (Refereed)
    Abstract [en]

    Monte Carlo methods have been combined with end-bridging methods to study the solubility and structure of water in polyethylene, where the polyethylene contains a pair of oppositely charged ionic impurities. The water in the polymer is in equilibrium with pure liquid water. Both the polymer and pure water phases are exposed to an external electric field. The ions dramatically increase the solubility of water in polyethylene and induce the formation of a stable, rod-like water cluster between the ions. The solubility, the hydrogen-bond ordering of the water molecules in the cluster and the size of the cluster increase in the presence of an external field that enhances the local electric field between the ions. When the direction of the external field is reversed, and when it has the same magnitude as the local ionic field, the rod-like structure is broken up and a smaller cluster forms around each ion. (C) 2008 Elsevier Ltd. All rights reserved.

  • 38.
    Johansson, Erik
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Simulations of Water Clustering in Vapour, Hydrocarbons and Polymers2008Conference paper (Other academic)
  • 39.
    Kalantar Mehrjerdi, Adib
    et al.
    University of Borås, School of Engineering.
    Abebe Mengistu, Bemnet
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Effects of a titanate coupling agent on the mechanical and thermo-physical properties of talc-reinforced polyethylene compounds2014In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 13, p. 40449-40449Article in journal (Refereed)
    Abstract [en]

    An experimental study was carried out to investigate the effects of a titanate coupling agent on the mechanical properties, moisture absorption, and thermal conductivity of talc-filled high-density polyethylene (HDPE). Talc (0–35 wt %) was used as reinforcement particulate filler in an HDPE matrix and samples were prepared in a micro-compounder and an injection molding machine. Isopropyl tri(dioctyl)phosphate titanate (0.5 wt %) was used as coupling agent. Composites with and without coupling agent were evaluated for changes in mechanical and thermo-physical properties, morphology, and void content. Addition of the titanate coupling agent most often resulted in an increase in stiffness and tensile strength. Furthermore, both the void content and the elongation at break of composites were reduced. Results also showed that the coupling agent had no effects on the thermal conductivity, thermal diffusivity, and specific heat capacity of the composites. In addition, it was observed that the coupling agent was more effective at low concentrations of filler. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40449.

  • 40. Kasaini, Henry
    et al.
    Kekana, Paul Thabo
    Saghti, Amirali Alizadeh
    Bolton, Kim
    University of Borås, School of Engineering.
    Adsorption Characteristics of Cobalt and Nickel on Oxalate-Treated Activated Carbons in Sulphate Media2013Conference paper (Refereed)
  • 41. Lasich, Matthew
    et al.
    Mohammadi, Amir H.
    Bolton, Kim
    University of Borås, School of Engineering.
    Vrabec, Jadran
    Ramjugernath, Deresh
    Influence of unlike dispersion interactions in modeling methane clathrate hydrate2014In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 381, p. 108-115Article in journal (Refereed)
    Abstract [en]

    Studies of the thermodynamic stability of clathrate hydrates of natural gas (mostly methane) is important in fields such as offshore gas exploitation and energy storage. Two approaches were used to study the effect of unlike dispersion interactions on methane clathrate hydrates: grand canonical Monte Carlo simulations (which yield adsorption data directly and can be used to infer phase equilibria), and estimation of the heat of dissociation coupled with the Clausius–Clapeyron equation (to calculate the phase equilibria, at the expense of providing no information about the adsorption behavior). It was found that the adsorption isotherm parameters change monotonically with respect to unlike dispersion interactions, although a perfect fit to experimentally-derived values may not be possible, at least using the force fields considered in this study. The heat of dissociation changes monotonically due to changes in the unlike dispersion interaction, and a best fit value of the Berthelot correction factor is achieved.

  • 42. Lasich, Matthew
    et al.
    Mohammadi, Amir H.
    Bolton, Kim
    University of Borås, School of Engineering.
    Vrabec, Jadran
    Ramjugernath, Deresh
    Lennard-Jones Corrections Applied to Lattice Distortion Calculations for Methane Clathrate Hydrate2014Conference paper (Refereed)
  • 43.
    Lasich, Matthew
    et al.
    University of Borås, School of Engineering.
    Mohammadi, Amir H.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Vrabec, Jadran
    University of Borås, School of Engineering.
    Ramjugernath, Deresh
    University of Borås, School of Engineering.
    Rapid Determination of Phase Equilibria of Clathrate Hydrates Using Molecular Simulations2014Conference paper (Refereed)
  • 44. Lee, Tae-Hyung
    et al.
    Jeon, Sera
    Kim, Hyun-Joong
    Cho, Sung-Woo
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Evaluation of mechanical properties and interfacial adhesion of PLA/Lyocell composite with silane coupling agent2014Conference paper (Other academic)
  • 45. Mahboubi Soufiani, Arman
    et al.
    Salehi, Massoud
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Persson, Maria
    Cho, Sung-Woo
    Thermomechanical properties of poly(lactic acid) films reinforced with hydroxyapatite and regenerated cellulose microfibers2014In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 20Article in journal (Refereed)
    Abstract [en]

    Novel composite films constituted of poly(lactic acid) (PLA), hydroxyapatite (HAp), and two types of regenerated cellulose fillers—particulate and fibrous type—were produced by melt extrusion in a twin-screw micro-compounder. The effect of the film composition on the tensile and dynamic mechanical behavior and the HAp dispersion in the PLA matrix were investigated thoroughly. Appearance of crazed regions and prevention of HAp aggregation in the PLA matrix were elucidated in the composites with up to 15 wt % particulate cellulose content, which was the main reason for only slight reduction in the tensile properties, and consequently trivial degradation of their pre-failure energy absorption as compared to neat PLA films. Superior dynamical energy storage capacities were obtained for the particulate cellulose modified composites, while their fibrous counterparts had not as good properties. Additionally, the anisotropic mechanical behavior obtained for the extruded composites should be favorable for use as biomaterials aimed at bone tissue engineering applications.

  • 46. Moodley, S.
    et al.
    Johansson, E.
    Bolton, Kim
    University of Borås, School of Engineering.
    Ramjugernath, D.
    Gibbs ensemble Monte Carlo simulations of binary vapour-liquid-liquid equilibrium: application to n-hexane/water and ethane/ethanol systems2010In: Molecular Simulation, ISSN 0892-7022, E-ISSN 1029-0435, Vol. 36, no 10, p. 758-762Article in journal (Refereed)
    Abstract [en]

    Gibbs ensemble Monte Carlo (GEMC) simulations in the isochoric-isothermal (NVT) ensemble were used to simulate vapour-liquid-liquid equilibrium (VLLE) for binary n-hexane-water and ethane-ethanol mixtures. The GEMC simulation of binary VLLE data proved to be extremely difficult and that is probably the reason why the open literature is so sparse with simulations for these types of systems. The results presented in this paper are to our knowledge the first successful binary three-phase GEMC simulations of non-idealised fluid systems. This paper also shows that the isobaric-isothermal (NPT) ensemble is unsuitable for the simulation of phase equilibria of binary three-phase systems.

  • 47. Moodley, Suren
    et al.
    Bolton, Kim
    University of Borås, School of Engineering.
    Ramjugernath, Deresh
    Monte Carlo simulations of vapor-liquid-liquid epuilibrium of ternary petrochemical mixtures2010In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 299, no 1, p. 24-31Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to determine the capability and accuracy of Monte Carlo simulations to predict ternary vapor-liquid-liquid equilibrium (VLLE) for some industrial systems. Hence, Gibbs ensemble Monte Carlo simulations in the isobaric-isothermal (NpT) and isochoric-isothermal (NVT) ensembles were performed to determine vapor-liquid-liquid equilibrium state points for three ternary petrochemical mixtures: methane/n-heptane/water (1), n-butane/1-butene/water (2) and n-hexane/ethanol/water (3). Since mixture (1) exhibits a high degree of mutual insolubility amongst its components, and hence has a large three-phase composition region, simulations in the NpT ensemble were successful in yielding three distinct and stable phases at equilibrium. The results were in very good agreement with experimental data at 120kPa, but minor deviations were observed at 2000 kPa. Obtaining three phases for mixture (2) with the NpT ensemble is very difficult since it has an extremely narrow three-phase region at equilibrium, and hence the NVT ensemble was used to simulate this mixture. The simulated results were, once again, in excellent agreement with experimental data. We succeeded in obtaining three-phase equilibrium in the NpT ensemble only after knowing, a priori, the correct three-phase pressure (corresponding to the force fields that were implemented) from NVT simulations. The success of the NVT simulation, compared to NpT, is due to the fact that the total volume can spontaneously partition itself favorably amongst the three boxes and only one intensive variable (T) is fixed, whereas the pressure and the temperature are fixed in an NpT simulation. NpT simulations yielded three distinct phases for mixture (3), but quantitative agreement with experimental data was obtained at very low ethanol concentrations only.

  • 48. Mphahlele, R. C. J.
    et al.
    Bolton, Kim
    University of Borås, School of Engineering.
    Kasaini, H.
    Computational Studies of Binding Energies and Structures of Methylamine on Functionalized Activated Carbon Surfaces2010Conference paper (Refereed)
    Abstract [en]

    Empirical force fields and density functional theory (DFT) were used to study the binding energies and structures of methylamine on the surface of activated carbon (ACs). This is a first step in studying the adsorption of alkyl amines on the surface of functionalized ACs. The force fields used were Dreiding (DFF), Universal (UFF) and Compass (CFF) models. The generalized gradient approximation with Perdew Wang 91 (PW91) functional was used for DFT calculations. In addition to obtaining the amine-carboxylic acid adsorption energies, the results were used to establish reliability of the empirical models for these systems. CFF predicted a binding energy of (-9.227 kcal/mol) which agreed with PW91 at (-13.17 kcal/mol), compared to DFF (0 kcal/mol) and UFF (-0.72 kcal/mol). However, the CFF binding energies for the amine to ester and ketone disagreed with PW91 results. The structures obtained from all models agreed with PW91 results.

  • 49.
    Nierstrasz, Vincent
    University of Borås, Swedish School of Textiles.
    Surface modification and functionalisation of textile materials: Digital finishing for functional and smart textile materials2013Conference paper (Refereed)
  • 50.
    Nierstrasz, Vincent
    et al.
    University of Borås, Swedish School of Textiles.
    Yu, Junchun
    University of Borås, Swedish School of Textiles.
    Seipel, Sina
    University of Borås, Swedish School of Textiles.
    Agnhage, Tove
    University of Borås, Swedish School of Textiles.
    Functionalization of textile materials using inkjet technology2014In: 53rd DORNBIRN MAN-MADE FIBERS CONGRESS, Dornbirn MFC , 2014, Vol. 60911PM1330, p. 1-8Conference paper (Other academic)
12 1 - 50 of 61
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf